Oxygen doi: 10.3390/oxygen6020014

Authors: Biswadev Mitra Jackson Catalano Paul Jennings John Moloney Simon Savage Natasha Jennings Gerard O’Reilly

Background: The aim of this study was to assess the effectiveness of supplemental low-flow oxygen on emergency clinicians in improving their quality and length of performance of external chest compressions (ECCs) on a resuscitation manikin. Methods: This was a double-blinded randomized crossover trial. Participants were emergency medicine doctors, nurses, or paramedics working at large emergency departments or ambulance services in Victoria, Australia. The intervention was oxygen and air via nasal cannula during external cardiac compressions. The primary outcome measure was ‘time to inadequate CPR’. Secondary outcome measures included compression rate and compression depth and global rating on a 10-point ordinal scale reporting their ‘comfort’ and ‘convenience’ ratings. Results: There was no statistical or clinical difference between the three study arms with respect to time to inadequate CPR or compression rates per minute. There was a statistically significant difference in the median depth of compression between the control (51.5 mm; IQR 43–58) and air study arms (48.0 mm; IQR 40–55; p = 0.015). Conclusions: Administration of supplemental oxygen (or air) to clinicians performing ECC on a manikin does not improve their performance when measured against internationally accepted guidelines. Supplemental oxygen or air to rescuers performing ECC was not supported.

Oxygen doi: 10.3390/oxygen6020013

Authors: Elisa Morales Jeremy Brown Chloe Runge Madeline York Genesis Dennis Cole Johnson Anthony Baudino Norman Paz-Ramirez Lily Samson John Rey A. Romal Kari L. Stone Sarah E. Shaner

This study explores the potential of utilizing biogenic manganese oxides (BMOs) produced by Mn-oxidizing Pseudomonas putida MnB1 to facilitate metal cation uptake for rare earth element (REE) sequestration and the synthesis of novel materials. Previous studies have shown that P. putida MnB1 efficiently oxidizes environmental Mn(II) to Mn(IV)-oxides, producing BMOs with unique physicochemical properties. Unlike their abiotic counterparts, BMOs exhibit high surface area, reactivity, and amorphous, poorly crystalline structures, making them promising platforms for adsorbing metal cations. This research study, building on the prior work, demonstrates the incorporation of ten different main group, transition, and rare earth metals into the BMO material, with structural characterization conducted via scanning electron microscopy and powder X-ray diffraction. Compositional characterization was determined by inductively coupled plasma optical emission spectroscopy and energy dispersive X-ray spectroscopy via scanning electron microscopy. Following the initial screening of these ten cations, batch adsorption studies were performed for a representative light REE, heavy REE, and transition metal-spiked sample prepared with real wastewater effluent indicating that the BMO material in this study is promising for sequestering REEs from real water streams. These findings advance the understanding of biologically mediated metal adsorption and open pathways for designing new functional materials with potential applications in rare earth sequestration and catalysis. To highlight this later point, the BMO materials with an incorporated main group (Al3+, Ca2+) or transition metal cation (Fe3+, Cu2+) were tested electrochemically for their ability to act as water oxidation catalysts, and each of these materials’ activity was comparable to BMO except for the material with incorporated iron, which showed significantly enhanced activity.

Oxygen doi: 10.3390/oxygen6020012

Authors: Enrique A. Martinez Mosqueira Pierrick Martinez Manuel Aparicio-Alonso Antonio Vega-Galvez

Chlorine dioxide (ClO2) is a neutral oxidant molecule with a short lifespan once in contact with electron donors (organic matter). ClO2 solutions have antiviral, antibacterial, antifungal, anti-protozoan, anti-inflammatory, anticancer, and wound-healing activity and it was used at safe concentrations on patients from different countries during the COVID-19 pandemic. In Mexico, 1067 COVID-19 patients received compassionate treatments with ClO2 during the 2020/2021 pandemic years. We describe the treatments and clinical reports of these patients, as it concerns the oxygen saturation (SpO2) recovery, and provide a biochemical explanation. The number of healed patients was 1057, >99% of the total and SpO2 showed a hyperbolic fast increase. This might happen because ClO2 attracts one electron from the organic matter and produces a chlorite anion (ClO2−). This new molecule is known to exhibit metabolic activity in the blood stream. On the one hand, it will perform the aforementioned antibiotic and healing properties. On the other hand, it will also allow the production of oxygen (O2) to be transported by the Oxyhemoglobin. This reaction is mediated by an intermediate state of a ferryl molecule (Fe=O) in the allosteric heme site of methemoglobin, which behaves as a reductase enzyme. This reaction can explain the rapid and steady increase in O2 saturation in healed patients.

Oxygen doi: 10.3390/oxygen6020011

Authors: Valery M. Dembitsky Alexander O. Terent’ev Sergey V. Baranin

Catechol (benzene-1,2-diol) is a highly versatile chemical motif that plays a central role in both terrestrial and marine systems, where its reactivity is governed by a combination of enzymatic oxidation and non-enzymatic interactions. This review examines the diverse enzymatic pathways responsible for catechol oxidation, including polyphenol oxidases, laccases, peroxidases, and microbial dioxygenases, and highlights how these conserved systems are adapted to distinct ecological functions such as plant defense, carbon cycling, bioadhesion, and material formation. A key focus is placed on the non-enzymatic formation of boron–catechol complexes, which can significantly modulate catechol reactivity. These complexes, formed through reversible interactions between boron species and the 1,2-diol group, can act as inhibitors of catechol oxidation by limiting substrate availability and altering redox behavior. Importantly, the extent of this inhibition is strongly dependent on pH, which governs both the speciation of boron (e.g., boric acid vs. borate) and the stability of borate esters, as well as the activity of oxidative enzymes. In terrestrial systems, variable pH conditions and soil chemistry influence the balance between oxidation, complexation, and degradation, whereas in marine environments, relatively stable and slightly alkaline conditions favor distinct modes of regulation. By integrating enzymatic and non-enzymatic perspectives, this review underscores the importance of boron–catechol interactions as a previously underappreciated control on catechol oxidation across ecosystems, with implications for biogeochemical cycling and the design of bioinspired materials.

Oxygen doi: 10.3390/oxygen6020010

Authors: Qin Wu Huan Yang Junyu Chen Zhixin Chai Hongwen Zhao Zhijuan Wu

The yak (Bos grunniens), a unique bovine species that is endemic to the Qinghai–Tibet Plateau and adjacent mountainous regions, exhibits remarkable adaptations to chronic high-altitude hypoxia. However, the molecular mechanisms underlying yaks’ adaptation to this extreme environment remain poorly understood. This study aimed to elucidate the spatiotemporal expression dynamics of hypoxia-inducible factor 1α (HIF-1α) and 2α (HIF-2α) in major tissues of yaks across developmental stages (0.5, 1.5, 2.5, and 4.5 years; n = 3 per group). The tissues (heart, liver, spleen, lungs, kidneys, blood vessels and skeletal muscles) were analyzed using hematoxylin and eosin (H&E) staining and immunohistochemistry. The results revealed significant differences in the expression levels of HIF-1α and HIF-2α between tissues and at different ages. In cardiac tissue, both HIF-1α and HIF-2α are localized to the myocardial interstitium, with HIF-1α expression peaking at 1.5–2.5 years and HIF-2α expression reaching its maximum at 2.5 years. Hepatic HIF-1α showed perivenous hepatocytes enrichment and peaked at 2.5 years (p < 0.01 vs. other ages), while HIF-2α was uniformly distributed across lobules without age-related changes. Splenic HIF-1α and HIF-2α levels increased progressively with age, both peaking at 4.5 years (p < 0.01), and age was strongly correlated with expression levels (HIF-1α: r = 0.430; HIF-2α: r = 0.493). In pulmonary tissues, HIF-1α in bronchial smooth muscle peaked at 2.5 years, whereas alveolar septal HIF-2α peaked at 1.5 years (p < 0.05). In the kidney, HIF-1α was primarily localized to tubular epithelial cells and HIF-2α was diffusely distributed in the glomerular interstitium; neither factor showed significant variation across ages. In vascular tissues, HIF-1α expression remained stable across all ages and was predominantly observed in the smooth muscle layer, while HIF-2α exhibited a significant peak in endothelial cells at 2.5 years (p < 0.01). These findings suggest that HIF-1α predominates during early development stages, while HIF-2α becomes dominant as yaks approach maturity.

Oxygen doi: 10.3390/oxygen6020009

Authors: Sruthi Tatavarthi Valentina Vanos Abigail Lepsch Combs Alvina Pan Mahita Saini Mostafa A. Borahay

Uterine fibroids (leiomyomas) are common benign smooth muscle tumors that impose substantial symptom burden and healthcare costs worldwide. Although uterine fibroid (leiomyoma) pathogenesis is multifactorial, hypoxia has emerged as a key feature of the uterine fibroid (leiomyoma) microenvironment, particularly within poorly perfused tumor cores. Hypoxia-inducible factor-1α (HIF-1α) is a central transcriptional regulator of cellular adaptation to low oxygen and coordinates downstream programs that support angiogenesis, metabolic reprogramming, cell survival, and extracellular matrix (ECM) remodeling. In uterine fibroids (leiomyomas), these HIF-1α–dependent processes intersect with steroid hormone signaling, growth factor pathways, inflammatory mediators, and redox imbalance, together promoting tumor persistence and progressive fibrosis. This review synthesizes the molecular regulation of HIF-1α, highlights major HIF-linked effector pathways relevant to uterine fibroid (leiomyoma) biology, and emphasizes mechanistic crosstalk with estrogen- and progesterone-responsive signaling, TGF-β/SMAD-driven fibrosis, NF-κB-mediated inflammation, and metabolic checkpoint pathways including mTOR and AMPK. Finally, we evaluate emerging therapeutic strategies that target HIF-1α directly or indirectly through upstream regulators.

Oxygen doi: 10.3390/oxygen6020008

Authors: Devi Sasikumar Rajimol Raju Vidya Viswanad

Pneumonia, an acute inflammatory condition of the lung tissue, imposes a significant burden on global health and is characterized by a high rate of illness and death. The pathogenesis of the disease extends beyond infection to breakdown of redox hemostasis, where the excessive reactive oxygen species produced during the immune response inflict damage on the alveolar tissues and hence promote varying complications. This dual role of oxygen and oxidative mechanisms makes the management of pneumonia challenging, as the very oxygen that is vital for host defense, when not regulated, imposes severe lung damage. Antioxidant administration and oxygen therapy offer limited efficacy, mostly due to their non-specific action and iatrogenic harm from oxygen oversupply. These limitations are overcome by the use of emerging therapeutic strategies, which primarily focus on precision-targeted approaches. These include inhalable antioxidants, nanoparticle-based systems and biomaterials that are engineered to respond to local ROS concentrations, which aim to deliver the therapeutic agent directly to the inflamed regions of the lung. Calcium peroxide- and manganese dioxide-incorporating materials are being designed to modulate the oxygen levels, either by releasing it in hypoxic zones or scavenging it in hyperoxic microenvironments. This approach simultaneously addresses hypoxia and oxidative stress. Despite showing promising results in experimental and preclinical studies, complications related to product stability, regulatory compliance, and manufacturing scalability need to be addressed. Personalized treatment protocols, guided by biomarkers, involve the future generation of treatments, aiming to achieve a delicate recalibration of the lung’s oxidative environment for improved patient outcomes.

Oxygen doi: 10.3390/oxygen6020007

Authors: Gustavo Zubieta-Calleja Felipe de Jesús Montelongo Manuel Gabriel Romo Sanchez Michele Samaja Natalia Zubieta-DeUrioste

Background: Severe lung compromise from COVID-19, ARDS, and recently AH3N2 can progress to life-threatening hypoxia. Past experience led to standardized protocols that assumed similarity to SARS-CoV. Methods: COVID-19 pathophysiology and histopathological lung biopsy photomicrographs are analyzed. Results: Pneumolysis is defined as progressive alveolar–capillary destruction resulting from SARS-CoV-2 attack on pneumocytes. In the final stages preceding pneumolysis, molecular mechanisms in the lungs include apoptosis in alveolar epithelial type I and II cells, compromising alveolar regeneration, and necrosis, resulting in leakage of intracellular contents and amplifying inflammation. Pyroptosis, driven by inflammasome activity, further disrupts alveolar integrity in ARDS. Histopathological findings include Masson bodies, alveolar-coating cells with nuclear atypia, reactive pneumocytes and reparative fibrosis, intra-alveolar hemorrhage, moderate inflammatory infiltrates and abscesses, microthrombi, hyaline membrane remnants, and emphysema. The three theoretical pathophysiological stages of progressive hypoxemia (silent hypoxemia, gasping, and death zone) are shown. Conclusions: Silent hypoxemia rapidly progresses to critical hypoxemia. This progression results from progressive pneumolysis, inflammation, immune overexpression, autoimmunity, and HAPE-type edema, leading to acute pulmonary insufficiency. Long-lasting COVID-19 can result in fibrosis and, as a compensatory mechanism, polierythrocythemia. The proposed treatment (based on tolerance to hypoxia and the hemoglobin factor) includes prompt oxygen administration, control of inflammatory and immune responses, antibiotics, rehydration, erythropoietin and platelet aggregation inhibitors.

Oxygen doi: 10.3390/oxygen6020006

Authors: Vandana Blossom Sheetal Dinkar Ullal Rajalakshmi Rai Anupama Hegde Sharada Rai Anita Sherly A

Systemic inflammation leading to neuroinflammation is a matter of concern in recent years because of its implication with neurological disorders. Selective peroxisome proliferator-activated receptor gamma (PPAR-γ) agonists have shown promising anti-inflammatory effects in various neurodegenerative diseases. With pioglitazone being one such PPAR-γ agonist, our study was aimed at investigating the role of pioglitazone on oxidative stress and cognitive changes against LPS-induced neuroinflammation in rats. In-house-bred male Wistar rats, about six weeks old, were utilized for the present study. They were categorized as A (preventive) and B (curative) groups, each with five subgroups: control (1A and 1B), neuro-inflammatory (2A and 2B), and three different dosages of pioglitazone treatment (3A, 3B, 4A, 4B, and 5A, 5B). After the experimental period, cognitive changes were examined by behavioral tests. Brain homogenate was used for biochemical parameters. Deteriorated memory, superoxide dismutase activity and increase in lipid peroxidation in the brain tissue induced by LPS exposure were substantially alleviated (p < 0.001) by pioglitazone treatment. These results suggest that pioglitazone may be neuroprotective against LPS-induced neuroinflammation.

Oxygen doi: 10.3390/oxygen6010005

Authors: Mostafa Ahmed Sally I. Abd-El Fatah Abdulrhman Sayed Shaker Zoltán Tóth Kincső Decsi

The authors have requested to replace the Molecular Operating Environment (MOE) mentioned in the main text with AutoDock (SWISS Dock, (version 1 [...]

Oxygen doi: 10.3390/oxygen6010004

Authors: Philip I. Aaronson Jeremy P. T. Ward Asuncion Rocher Jesus Prieto-Lloret

Hypoxic pulmonary vasoconstriction (HPV) is a rapid and reversible constrictor response of the pulmonary vasculature, and especially its small muscular precapillary arteries, which is initiated by episodes of local alveolar hypoxia. Acting as a protective homeostatic vasomotor mechanism, HPV enables maximal gas exchange by diverting blood from poorly ventilated alveoli into those rich in oxygen, thereby optimizing oxygen uptake and the ventilation–perfusion (V/Q) ratio so as to maintain the arterial oxygen partial pressure (PaO2) within the physiological range. HPV is an intrinsic mechanism of pulmonary artery smooth muscle cells (PASMCs), and requires an O2 sensor which acts through mediator(s) to trigger effector mechanisms within these cells to evoke constriction. Whereas HPV effector mechanisms are reasonably well defined, the nature of the O2 sensor and mediators remains in dispute, and a number of proposals have been developed to account for these. Some (but not all) of these share a focus on the concept that hypoxia activates effector mechanisms by inducing a change in the PASMC cytoplasmic redox state. Of these, the Redox Theory, first proposed by Kenneth Weir and Stephen Archer in 1995, proposes that hypoxia inhibits mitochondrial production of reactive oxygen species (ROS), thereby causing the cytoplasm to become more reduced. This inhibits ongoing vasorelaxation maintained by the opening of voltage-gated K+ channels. In contrast, according to the Mitochondrial ROS hypothesis, introduced by Paul Schumacker and Naveen Chandel in 2001, hypoxia increases mitochondrial ROS production, causing an oxidizing shift in the cytoplasmic redox state that activates several vasoconstricting pathways. In a third redox-based scenario, developed by Michael Wolin and Sachin Gupte, hypoxia evokes contraction by causing a fall in H2O2 production by NADPH oxidase and by activating the pentose phosphate pathway. These effects inhibit basal vasorelaxation maintained by the guanylate cyclase and protein kinase G and also stimulate vasoconstricting mechanisms. In this comprehensive review, we first provide a detailed summary of the key studies contributing to the development of these proposals and then subject the evidence supporting them to a critical appraisal, based in part on how well they accord with the wider literature and recent developments in our understanding of how cells shape and deploy redox mechanisms in order to regulate cell function.

Oxygen doi: 10.3390/oxygen6010003

Authors: Panagiotis Theodosis-Nobelos Georgios Papagiouvannis Maria Fesatidou Gabriel Marc Athina Geronikaki Boris Lichitsky Victor Kartsev Andrey Komogortsev Samvel Sirakanyan

Oxidative stress seems to be part of many deranged processes in the organism, affecting multiple degenerative conditions at a cellular and tissue level. Coumarins and flavonoids comprise two main categories of naturally derived compounds with multiple effects and applications. Our aim in this paper is the design of compounds with increased antioxidant activity with the conjugation of two moieties with highly antioxidant potency in the frame of one molecule. A series of novel derivatives, comprising fusion of 7-hydroxycoumarin (Umbelliferone) and Quercetin (flavonol) have been synthesized using classical organic chemistry methods. Additionally, one novel flavone derivative was prepared for comparison. The novel compounds were tested for their radical, reactive oxygen and nitrogen species (ROS and RNS) scavenging, their reductive activity, and their labile metal chelating potency, as well as with in silico tools. All of them were more active, in most cases, than reference molecules Trolox and vitamin C. The most active compound 2 reached IC50 of 4.03 and 43.75 μM for ABTS and DPPH, respectively (up to three times lower than that of Trolox). Compound 1 was of equal to vitamin C activity in H2O2 scavenging, whilst compound 3 was up to 6.4 times more active than Trolox in NO scavenging. Since our designed compounds seem to exhibit high antioxidant potential, scavenging reactive nitrogen and oxygen species, which are accumulated and promote the progression of inflammatory conditions, and have reductive and metal chelating abilities, they can be considered as potential candidates for protection in cases of oxidative stress derived toxicity.

Oxygen doi: 10.3390/oxygen6010002

Authors: Mostafa Ahmed Sally I. Abd-El Fatah Abdulrhman Sayed Shaker Zoltán Tóth Kincső Decsi

Salt stress is a major agricultural issue. A promising modern agriculture method is the foliar treatment of zinc oxide nanoparticles (ZnONPs). This approach has shown promise in boosting challenged tomato yields, fruit quality, and leaf extract antibacterial activity against pathogens. A greenhouse experiment was conducted. The previously synthesized and characterized ZnONPs were used to alleviate the harmful effects of NaCl stress. Tomato fruit weight from different treatments was determined, and the gas–liquid chromatography device was used to observe the changes in fatty acid production. The antimicrobial activities of the aqueous and diethyl ether extracts from tomato leaves were determined against six bacterial and six fungal strains. The plants that were salinity-stressed and sprayed with 0.075 and 0.15 g/L ZnONPs showed a better improvement compared to the salinity-stressed plants. Also, the sprayed plants that were not stressed at all showed promising results compared to the control and the other different treatments. Through the process of molecular docking, it was shown that caffeic acid, ferulic acid, p-coumaric acid, sinapic acid, and apigenin-7-glucoside are essential chemicals that possess antibacterial and antifungal effects against the DNA Gyrase inhibitor and the sterol 14-alpha demethylase (CYP51) enzyme, respectively. It is concluded that salt stress can negatively affect the growth, quality, and variant plant features. However, the foliar application of ZnONPs is able to overcome those adverse effects in the stressed plants, and enhance the non-stressed as well.

Oxygen doi: 10.3390/oxygen6010001

Authors: Rinko Aso Kohei Shibusawa Sogo Aoki Kiyoshi Sato Hiroyoshi Kawakami

Age-related macular degeneration (AMD) is an age-associated disease characterized by damage to the central retina and represents a leading cause of acquired blindness, with increasing prevalence in aging populations. However, effective therapeutic options remain limited. The accumulation of dysfunctional mitochondria in retinal pigment epithelial (RPE) cells leads to excessive production of reactive oxygen species (ROS), triggering cellular senescence and cell death that contribute to the pathogenesis of AMD. Therefore, removal of accumulated dysfunctional mitochondria in senescent RPE cells is expected to treat AMD. Herein, we investigated transferrin (Trf)-modified mitophagy-inducing dual-drug nanocarriers (Trf-M-NCs) for the treatment of a senescent RPE cell. To evaluate efficacy, we used sodium iodate-treated ARPE-19 cells. The Trf-M-NCs exhibited significantly higher uptake by ARPE-19 cells than the unmodified M-NCs. Importantly, Trf-M-NC treatment alleviated cellular senescence by restoring the mitochondrial functions. Furthermore, Trf-M-NC treatment not only restored the production of α-ketoglutarate, an essential energy source for photoreceptor cells, but also reduced the secretion of IL-6, a key inflammatory cytokine. These findings suggest that improving mitochondrial quality in RPE cells is a novel and promising therapeutic approach for AMD.

Oxygen doi: 10.3390/oxygen5040027

Authors: Dario Vrdoljak Colin D. Hubbard Geoff B. Coombs Andrew T. Lovering Ivan Drvis Nikola Foretic Joseph W. Duke Željko Dujić

Background: During an apnea, oxygen depletion occurs at all tissue levels, so apnea duration is influenced by the mammalian dive reflex, which includes a bradycardia resulting in reduced cardiac oxygen consumption. This study aimed to examine the relationships between heart rate (HR), peripheral estimation of O2 (SpO2), deltoid and respiratory muscle oxygenation (SmO2), and apnea duration. Methods: The study included 10 breath-hold divers (BHD), 39 ± 10 years of age, with body height of 184.3 ± 3.5 cm, body mass of 84.0 ± 9.2 kg, and 16.2 ± 9.7 years of apnea experience. The BHD performed three preparatory apneas followed by three maximal apneas with 5 min of supine rest between each apnea. During all apneas (duration, 115–323 s; involuntary breathing movements (IBMs), 7–35), SmO2 (measured via NIRS on intercostals (respiratory) and deltoid (locomotor) muscles), heart rate, and SpO2 (measured via forehead sensor) were obtained. Results: The smallest disagreement in oxygen levels was between intercostal SmO2 and SpO2 during the easy-going phase (no IBMs), whereas deltoid desaturation values were more variable. During the struggle phase, Intercostal SmO2, moderately, and Deltoid SmO2, strongly, differed from SpO2. Correlations between apnea duration and O2 saturation showed that only Intercostal SmO2 (r = −0.71; p = 0.03) was significantly related to apnea duration. There was also a significant correlation between HR and SpO2 in the struggle phase (r = −0.58; p = 0.05). Conclusions: These findings suggest that during the struggle phase, SpO2 and SmO2 are not highly connected and that local and systemic oxygen levels in the blood are depleted at different rates. Furthermore, the HR response during the struggle phase affected only SpO2, which indicates that lowering the heart rate may help prevent more rapid deoxygenation. Lastly, the intercostal trend of deoxygenation could be interpreted as respiratory muscle work, suggesting that the increased work of respiratory muscles may prolong apnea duration.

Oxygen doi: 10.3390/oxygen5040026

Authors: Matthew G. Mercurio Lawrence A. Lavery Animesh Agarwal Alisha Oropallo

The purpose of this analysis is to report on the clinical efficacy of Continuous Diffusion of Oxygen (CDO) therapy in real-world clinical practice and compare those results to data published in controlled clinical studies. For the real-world clinical results, a Prospective Patients Database (PPD) of 764 patients treated using CDO therapy in a broad range of clinical practices across a wide range of wound types and wound locations was analyzed. The objectives included analyzing the clinical efficacy of CDO therapy across multiple wound types and anatomical locations, testing the data for robustness, and comparing the efficacy to results from controlled clinical studies for CDO and NPWT. The PPD data is also analyzed for efficacy among the sexes and by age for older patients in the Medicare population. The robustness of the PPD data is tested using various non- and semi-parametric statistical tools, including the Kaplan–Meier and Cox proportional hazard (PH) models, among others. The results show that CDO therapy is highly efficacious with an average healing success rate of 76.3% in real-world application, ranging from 71.2% to 84.1% for different wound types. The Medicare age population had an average age of 78 years old and similar healing rates to the overall population, with slightly better results for pressure ulcers in the older patient population. The PPD data proved to be extremely robust in every test method, demonstrating substantially equivalent efficacy in various wound types and locations, as well as between men and women. The PPD results for CDO compared favorably to clinical trial results for CDO and NPWT. Both clinical trial and PPD data for CDO exhibited better healing rates when compared to NPWT. Kaplan–Meier analysis shows that CDO use in clinical practice has 79.2% full closure in 112 days, as compared to NPWT, which has 43.2% full closure in the same timeframe for similar wound sizes and severity. These results demonstrate not only that CDO is highly efficacious in clinical practice, but that the efficacy is also similar across all wound types and locations in the body. CDO also compares very favorably to NPWT.

Oxygen doi: 10.3390/oxygen5040025

Authors: Jonas Haferanke Lisa Baumgartner Maximilian Dettenhofer Stefanie Huber Frauke Mühlbauer Tobias Engl Renate Oberhoffer Thorsten Schulz Sebastian Freilinger

Maximal aerobic power (V̇O2peak) in youth depends on hemoglobin (Hb)—mediated oxygen transport. While sex- and age-specific patterns are established in untrained cohorts, further research is needed in competitive adolescent athletes. We studied 124 young athletes matched by age and sex (62 boys, 62 girls; 10–16 years). Hb was measured from fasting blood samples, and V̇O2peak was determined via cardiopulmonary exercise testing (CPET). Boys showed higher Hb than girls (14.43 ± 0.85 g/dL vs. 13.6 ± 0.74 g/dL; p < 0.001) and a significant age-related increase (B = 0.29, p < 0.001), whereas girls remained stable. V̇O2peak was also higher in boys (50.03 ± 6.18 mL/min/kg, p < 0.001). Regression analysis identified Hb as a strong predictor of V̇O2peak (β = 0.40, p < 0.001). These findings demonstrate that classical developmental Hb trajectories persist in highly trained youth and confirm Hb as a key determinant of aerobic power. Monitoring hematological status, particularly in female athletes, is essential for optimizing performance and development.

Oxygen doi: 10.3390/oxygen5040024

Authors: Masaru Sakamoto Takahiro Suzuki

Root pruning has been proposed as a practical method to regulate growth and metabolite accumulation in horticultural crops, yet its physiological and metabolic consequences in hydroponically grown lettuce remain poorly understood. In this study, we examined the effects of root pruning, applied two days before harvest, on biomass production, oxidative stress responses, and metabolite accumulation in red leaf lettuce. Root pruning suppressed root growth and reduced root water content in a severity-dependent manner. Shoot fresh weight also declined, whereas shoot dry weight was significantly reduced only under severe pruning. Young leaves of pruned plants exhibited transient reddish coloration, which was most pronounced under severe pruning. Quantitative analyses revealed that anthocyanin content increased up to 4.5-fold compared with the control, while total phenolic content also rose significantly. These metabolic changes were accompanied by pronounced oxidative stress, as indicated by elevated hydrogen peroxide accumulation and enhanced lipid peroxidation. In addition, leaf nitrate concentration decreased significantly in both moderate and severe pruning treatments. Collectively, these findings demonstrate that root pruning acts as a controllable stressor that triggers oxidative stress signaling, enhances antioxidant metabolite accumulation, and reduces nitrate content, highlighting its potential as a pre-harvest strategy for improving the nutritional and functional quality of hydroponic lettuce.

Oxygen doi: 10.3390/oxygen5040023

Authors: Abdul-Rhman H. Muhammad Diaa Attia Marrez Mostafa Ahmed Abdulrhman S. Shaker Rasha S. Mohamed Olfat S. Barakat

This review indicates that microalgae may serve as a sustainable supply of bioactive compounds and lipids over the long run. It also discusses the significance of lactic acid bacteria (LAB) and Saccharomyces cerevisiae in biotransformation processes. Microalgae contribute to food security and environmental sustainability due to their rapid growth and diverse applications, including food, feed, and biofuels. Fermentation with LAB and S. cerevisiae enhances the nutritional and functional properties of microalgal biomass, rendering it more digestible, bioactive, and palatable. This review discusses the metabolic characteristics of LAB and S. cerevisiae, their ability to modify microalgal components through enzymatic action, and the resultant products, including enhanced fatty acid profiles and bioactive compounds. Furthermore, the biotransformation of pigments during LAB fermentation is examined, revealing significant alterations in the hue and bioactivity of the pigments, hence enhancing the appeal of microalgal products. Future perspectives emphasize the necessity for further investigation to identify optimal fermentation conditions and to explore the synergistic interactions between LAB and S. cerevisiae in the production of novel beneficial components from microalgae using both microbes.

Oxygen doi: 10.3390/oxygen5040022

Authors: Grace Sliwinski Emily Lessard Lisa M. Landino

Photosensitized excitation of molecular oxygen generates singlet oxygen, a reactive oxygen species that has been studied in biological systems, synthetic methods and in aquatic ecosystems. The reaction of singlet oxygen with tertiary amines is important because they are widely used as electron donors in photochemical reactions. Herein we studied the reaction of singlet oxygen with multiple tertiary amines including ethylenediamine tetraacetic acid (EDTA), triethanolamine (TEOA) and triethylamine (TEA). Singlet oxygen was generated using the photosensitizers methylene blue or chlorin e6 and red light with output at 660 nm. TEOA and TEA generated more hydrogen peroxide (H2O2), the stable end product, than EDTA at all pH values tested and regardless of the photosensitizer used. Both histidine and imidazole scavenged singlet oxygen and decreased H2O2 yield. The extent of histidine scavenging was pH-dependent for the combination of methylene blue and EDTA but not for TEOA or TEA. The combination of chlorin e6 and EDTA generated less H2O2 because both contain multiple negative charges that limit their interaction. Multiple tertiary amines that are used as biochemical buffers produced similar quantities of H2O2 as EDTA, TEOA and TEA. However, these sulfonic acid-containing tertiary amines did not function as electron donors in a benzoquinone photoreduction assay.

Oxygen doi: 10.3390/oxygen5040021

Authors: Sedolfo Carrasquero-Ferrer Gabriel Vaca-Suárez Grace Viteri-Guzmán Gilberto Colina-Andrade

Swine effluents require effective treatment due to their high pollutant load, particularly nitrogen and phosphorus, which can cause eutrophication of water bodies. This study focused on monitoring nutrient removal in a sequential biological reactor through online measurements of parameters such as dissolved oxygen (DO), pH, oxidation-reduction potential (ORP), and total alkalinity during the treatment of effluents from a pig slaughterhouse. A laboratory-scale reactor was used, operated with timer switches in an anaerobic–aerobic–anoxic sequence, a sludge retention time (SRT) of 25 days, and an operational cycle time of 16 h. The reactor demonstrated notable efficiency in contaminant removal, with an average organic matter removal of 87.1% measured as chemical oxygen demand (COD) and 95.5% as biochemical oxygen demand (BOD). Regarding nitrogen and phosphorus removal, a 69.4% reduction in total nitrogen (TN) and a 53.2% reduction in total phosphorus (TP) were observed. The pH, ORP, and DO profiles showed a clear correlation with the nutrient removal processes, allowing optimization of the phase durations in the reactor to enhance treatment efficiency.

Oxygen doi: 10.3390/oxygen5040020

Authors: Valera-Arévalo Gemma Paula Jara Caro María del Mar Rodríguez-San Pedro Claudia Yuste María Gabriela Ortiz-Diaz Rafael Ramírez Matilde Alique Natalia Guerra-Pérez Julia Carracedo Enrique Morales

Chronic kidney disease is closely associated with an increased risk of cardiovascular disease. Although kidney transplantation represents the treatment of choice for patients with end-stage chronic kidney disease, it is also linked to significant cardiovascular risk. This study aimed to evaluate the relationship between cardiovascular pathology and oxidative status in kidney transplant recipients, while also assessing the influence of disease etiology and humoral immune response on oxidative imbalance. A cross-sectional analysis was conducted in individuals with advanced chronic kidney disease (n = 36) and kidney transplant recipients (n = 40). A total of 18 healthy subjects were included. The enzymatic activities of xanthine oxidase, superoxide dismutase, and glutathione peroxidase, and levels of lipid peroxidation products, oxidized glutathione, and reduced glutathione were measured using spectrophotometry in plasma and mononuclear and polymorphonuclear leukocytes isolated using Ficoll density gradients. Individual oxidative status was evaluated using OXYSCORE. Kidney transplantation was associated with a higher incidence of cardiovascular disease (p < 0.01) and increased levels of both prooxidant (p < 0.01) and antioxidant parameters (p < 0.01). Elevated OXYSCORE values were observed particularly in patients with nephroangiosclerosis, diabetic kidney disease, polycystic kidney disease (p < 0.05), and cardiovascular comorbidities (p < 0.001). Additionally, the presence of anti-graft antibodies correlated with higher oxidative scores. These findings suggest that OXYSCORE may serve as a potential indicator of cardiovascular damage in kidney transplant recipients.

Oxygen doi: 10.3390/oxygen5030019

Authors: Waqas Ahmad Muhammad Yasin Tipu Muti ur Rehman Khan Haroon Akbar Aftab Ahmad Anjum Muhammad Ovais Omer

Background/Objectives: Trypanosoma evansi (T. evansi) is an etiological agent of surra, and it causes significant economic losses in livestock. Rising trypanocide resistance demands alternatives that control parasitemia while mitigating oxidative and genotoxic damage. Therefore, the present study was designed to explore both the in vivo and in silico potential of Zingiber officinale (Z. officinale) as a novel phytotherapy to counter growing resistance against conventional trypanocides. Methods: Methanolic extract of Z. officinale (MZ) was orally administered at dosages of 200 mg/kg (MZ 200), 400 mg/kg (MZ 400), and 800 mg/kg (MZ 800) on a daily basis to the experimentally infected mice and compared against treated control (TC) and untreated control (UC) groups. After the infection, different parameters such as parasitemia counts, body weight changes, and the survival of infected mice were monitored for up to 7 days post-infection, while hematobiochemical parameters, oxidative stress profiles (catalase, malondialdehyde, and superoxide dismutase), and genotoxicity in brain tissues were compared at the end of the trial. Moreover, computational tools were used to predict the affinities of key bioactive compounds with twenty-one essential proteins of T. evansi. Results: The findings showed that the administration of MZ significantly (p < 0.05) reduced parasitemia and improved the survival rates in the experimentally infected mice in a dose-dependent manner. Noteworthy, significant (p < 0.05) improvements in hematological parameters and liver enzyme profiles were also recorded in MZ-treated groups. Compared to the untreated control, MZ-treated groups showed a significant amelioration in oxidative stress and genotoxicity in brain tissue in a dose-dependent fashion. The current study’s findings suggest that MZ potentially inhibits various essential proteins of T. evansi, including adenosine transporter-1, casein kinase, leucyl-tRNA synthetase, and multidrug resistance E protein. Among its constituents, 6-Isoshogaol and 6-Gingerol showed the most stable interactions in the molecular dynamics simulation. Conclusions: MZ efficiently reduced parasitemia, oxidative stress, and genotoxicity, and increased the survival rate in infected mice, suggesting it as a promising natural trypanicidal agent.

Oxygen doi: 10.3390/oxygen5030018

Authors: Riko Siewert Artemiy A. Samarov Sergey V. Vostrikov Karsten Müller Peter Wasserscheid Sergey P. Verevkin

Compounds known as liquid organic hydrogen carriers (LOHCs) offer a promising pathway for storing hydrogen. Beyond the use of pure hydrocarbons, the incorporation of oxygen atoms offers a way to modify thermodynamic properties and potentially improve suitability for hydrogen storage. This study explores the effect of oxygen functionalization in aromatic ethers and lactones on the reaction equilibrium of reversible hydrogenation. To address this question, reaction enthalpies and entropies are calculated using both experimental and theoretically determined pure substance data. The equilibrium position shift in the hydrogenation of furan derivatives has been shown to follow a similar trend to that of their hydrocarbon counterparts upon the addition of aromatic rings. This shift is, however, more pronounced in the case of the furan-based systems. The effect is reflected in increasing Gibbs reaction energies during the dehydrogenation process. Both the formation of lactones and the addition of a second ring to the furan core leads to a further increase in the Gibbs reaction energy. The highest value is observed for dibenzofuran, with a Gibbs reaction energy of 36.6 kJ∙mol−1 at 500 K. These findings indicate that, from a thermodynamic perspective, hydrogen release is feasible at temperatures below 500 K, which is an important feature for the potential application as a hydrogen storage system.

Oxygen doi: 10.3390/oxygen5030017

Authors: Panoraia Bousdouni Eleni Dalaka Aikaterini Kandyliari Vasileios Gkalpinos Nikolaos Parisis Andreas G. Tzakos Georgios Theodorou Maria Kapsokefalou Antonios E. Koutelidakis

Experimental evidence indicates that aqueous extracts of the Cistus genus have significant antioxidant properties, suggesting their potential as food fortifiers. In the present study, the antioxidant capacity and total phenolic content of lyophilized Cistus creticus extract were examined before and after in vitro digestion. Three concentrations of Cistus creticus extract were evaluated before and after in vitro gastrointestinal digestion, along with yogurt products fortified with these extracts, examined after digestion. Biochemical and cellular analyses were performed to assess these properties. The results showed statistically significant differences in total antioxidant capacity and total phenolic content, with values increasing from the lowest to the highest concentration studied, for both the lyophilized extracts and fortified yogurts after digestion. Additionally, cellular antioxidant activity after digestion was concentration-dependent (p < 0.05) within the range 25–500 mg/mL for both the extracts and fortified yogurts. In conclusion, based on the high phenolic content and the increased antioxidant capacity observed in epithelial cells, 250 mg of extract per 200 g of yogurt was proposed as the optimal fortification dose.

Oxygen doi: 10.3390/oxygen5030016

Authors: Konrad A. Szychowski

Amiodarone (AMD) is an effective antiarrhythmic drug whose long-term use is limited by multi-organ toxicities linked to oxidative stress. This review synthesizes current evidence on how AMD induces reactive oxygen species (ROS) generation in vitro and in vivo, and the mechanistic pathways involved. AMD promotes ROS production through both direct and indirect mechanisms. Directly, AMD accumulates in mitochondria and impairs the electron transport chain, leading to electron leakage and superoxide formation. It also undergoes redox cycling, forming radical intermediates that trigger lipid peroxidation and deplete cellular antioxidants. AMD and its metabolites inhibit antioxidant enzymes (SOD, CAT, GPx) expression and/or activities and reduce glutathione level, compounding oxidative injury. Indirectly, AMD activates signaling pathways that exacerbate ROS generation. This compound can induce pro-inflammatory mediators such as TNF-α and modulate nuclear receptors such as AhR, PXR, CAR, and PPARs, altering the expression of metabolic enzymes and endogenous antioxidants. These processes are time- and dose-dependent: short exposures at low concentrations may transiently scavenge radicals, whereas chronic or higher-dose exposures consistently lead to net ROS accumulation. The oxidative effects of AMD vary by tissue and experimental models. In chronic models, organs such as the lung and liver show pronounced ROS-mediated injury, whereas acute or cell-based systems typically exhibit subtler changes. AMD-induced toxicity arises from multifactorial oxidative stress involving mitochondrial dysfunction, increased radical formation, depletion of antioxidant defenses, and activation of pro-oxidant signaling pathways. Recognizing these pathways suggests that antioxidant and mitochondria-targeted co-therapies could ameliorate the side effects of AMD.

Oxygen doi: 10.3390/oxygen5030015

Authors: Estefani Yaquelin Hernández-Cruz Elí Juárez-Peredo Karla Alejandra Avendaño-Briseño Jorge Escutia-Martínez Karla Jaqueline Ramírez-Magaña Tania Gómez-Sierra José Pedraza-Chaverri

Cadmium (Cd) is a highly toxic heavy metal that disrupts development and reproduction, primarily through oxidative stress. In this context, sulforaphane (SFN), an antioxidant compound, may serve as a promising agent to counteract Cd-induced oxidative damage and prevent developmental and reproductive abnormalities. This study aimed to evaluate the effect of SFN on reproductive toxicity induced by cadmium chloride (CdCl2) in the nematode Caenorhabditis elegans (C. elegans). Five experimental groups were established: (I) Control: no treatment, (II) dimethyl sulfoxide (DMSO): 48 h with 0.01% DMSO, (III) CdCl2: 24 h with 4600 µM CdCl2, (IV) SFN + CdCl2: 24 h with 100 µM SFN followed by 24 h with both SFN and CdCl2, and (V) SFN: 48 h with 100 µM SFN. Co-exposure to SFN and CdCl2 prevented the reduction in the percentage of adult nematodes and increased egg-laying. It also significantly improved hatching rates, allowing more embryos to reach the larval stage, and prevented reductions in body size. However, no effects were observed on glutathione S-transferase-4 (GST-4) levels in the transgenic CL2166 strain. In conclusion, SFN substantially prevents Cd-induced reproductive toxicity in C. elegans. Future studies should investigate the molecular mechanisms by which SFN enhances egg-laying and offspring viability in this model.

Oxygen doi: 10.3390/oxygen5030014

Authors: Maria Cristina Porcu Daniele Sanna

Seven lager beers and seven non-alcoholic counterparts, marketed by the same producers, were analyzed for their total phenolic content (TPC), radical scavenging activity (RSA) towards the DPPH radical and ThioBarbituric Index (TBI). All beers were also subjected to spin trapping experiments at 60 °C in the presence of PBN. To our knowledge, this is the first time that non-alcoholic beers (NABs) have been subjected to spin trapping experiments coupled with Electron Spin Resonance (ESR) spectroscopy. The evolution of the intensity of the PBN radical adducts during the first 150 min was represented graphically and the intensity at 150 min (I150) and the area under the curve (AUC), were measured. The I150 and the AUC of lagers and NABs are significantly different, whereas the TPC, the EC50 of the DPPH assay, and the TBI of the two groups are superimposed. A relationship, previously proposed by us, to correlate ESR spectroscopy parameters with others obtained from UV-Vis spectrophotometry, was also applied, demonstrating its practicability. Multivariate analysis shows that clustering in two separate groups occurs only if I150 and AUC are included in the model. Based on these results, ESR spectroscopy can be applied to study the oxidative stability of NABs.

Oxygen doi: 10.3390/oxygen5030013

Authors: Clive Kelly Shireen Saxena Kieran Kelly

Introduction: Rapid ascent to altitudes of over 5000 m above sea level are associated with dramatic changes in adaptive physiology. The effects of a gradual ascent on symptoms, oximetry, and heart rate are described and compared with the effects of a rapid ascent to the same altitude by a comparable cohort. Methods: A group of 13 individuals (six females) representing 10 countries from five continents ascended gradually from Lukla (2300 m) to Everest Base Camp (5300 m) in Nepal over an 8-day period, then descended over a further 4 days. All symptoms and medication were recorded, along with pulse oximetry (SpO2) and heart rate (HR) every 500 m of ascent. The results were then compared with those obtained at equivalent altitudes using similar methodology from a fast ascent of Mount Kilimanjaro to an equivalent altitude by a comparable cohort over 4 days. Results: The gradual ascent group had a median age of 33 years (range 25–66), and all successfully completed the trek. No severe headache, vomiting, orthopnoea, or productive cough occurred, although minor nausea and mild headache were common. Baseline oximetry fell from a median of 96% (93–97%) to a median of 78% (53–86%) at 8 days but recovered to 94% (89–99%) inside 4 days. Corresponding HR rose from a baseline median of 72 bpm (57–85) to a median of 103 bpm (78–115) at 8 days, then recovered to 80 bpm (54–94) after 4 days. Neither age nor gender correlated with outcomes. Individually, HR correlated inversely with oximetry, but there was no group correlation between these two variables. By contrast, a more rapid 4-day ascent from the same starting height, with similar baseline values for HR and oximetry, to the same final altitude was associated with more severe headache, breathlessness, and vomiting. Fast ascent was associated with a significantly more marked reduction in oximetry to a median of 71% (52–76) and an increase in HR to a median of 110 bpm (88–140). The fast ascent group also required significantly more medication, rated their experience as less enjoyable, and had a 100% incidence of acute mountain sickness compared to 0% in the slow ascent group. Discussion: Oxygen desaturation and tachycardia are inevitable consequences of ascending above 5000 m, but the degree to which this occurs can be reduced by slowing ascent times and taking rest days every 1000 m of ascent. This practice is associated with fewer symptoms and greater safety, with less need for either prophylactic or therapeutic medication. Careful consideration should be given to rates of ascent when climbing to altitudes at or above 5000 m.

Oxygen doi: 10.3390/oxygen5030012

Authors: John T. Hancock

As aerobic organisms, we cannot live without molecular oxygen (O2), but we also have to work hard to live with it [...]

Oxygen doi: 10.3390/oxygen5030011

Authors: Margot Evelin Bernedo-Itusaca Kely Melina Vilca-Coaquira Ángel Gabriel Calisaya-Huacasi Madeleyne Rosmery Cosi-Cupi Stanley Rivaldo Leqque-Santi Shantal Cutipa-Tinta Alberto Salazar-Granara Yony Martin-Pino Vanegas Alcides Flores-Paredes Shihui Guo William Li Moua Yang Ginés Viscor Ivan Hancco Zirena

(1) Background: Previous studies indicate that individuals who engage in regular physical activity have a higher pain threshold than those who do not exercise. However, it remains unclear how this phenomenon behaves in individuals exposed to chronic hypoxia. This study evaluates pain perception at high altitude between high-altitude natives who exercised regularly and those who did not practice physical activity. (2) Methods: Eighty-four healthy volunteers aged 20 to 30 years old with a body mass index (BMI) within the normal range (18.5–24.9) residing in the city of Puno (3825 m) were recruited. The unilateral ischemia pain provocation test was used, applying pressure with a manual sphygmomanometer to generate transient ischemia in the arm while the patient opens and closes their hand. Onset, peak, and resolution times of pain, heart rate, and oxygen saturation were recorded. (3) Results: The average time to pain onset in the right arm was 30.2 s ± 14.1 during light physical activity, whereas, during moderate physical activity, it increased to 32.5 s ± 15.4. In the left arm, the average time until pain sensation was 27.9 s ± 16.8 during light physical activity and increased to 34.6 s ± 18.5 with moderate physical activity. Regarding the progression of pain intensity, the average time to reach unbearable pain in the right arm was 54.1 s ± 16.4 during light physical activity and 53.8 s ± 19.6 during moderate physical activity; in the left arm, it was 53.0 s ± 19.6 during light physical activity, increasing to 59.3 s ± 24.5 during moderate physical activity. (4) Conclusions: A more stable and slightly higher pain tolerance in the dominant arm was observed.

Oxygen doi: 10.3390/oxygen5030010

Authors: Amisha Beniwal Hariom Gurjar Khushabu Shekhawat Ashima Bagaria Dinesh Bhalothia

Platinum-based catalysts remain the benchmark for the oxygen reduction reaction (ORR) in fuel cells, owing to their exceptional catalytic activity in the harsh chemical environment. However, optimizing Pt utilization and improving performance through support engineering are essential for commercial viability. In this study, we synthesized carbon-supported binary Pt-M (M = Ni, Cu, Co) electrocatalysts to investigate the influence of metal–support interactions on ORR activity. The Pt-M nanoparticles were fabricated on carbon supports, enabling the systematic screening of electronic and structural interactions. Among all compositions, Pt@Co exhibited the highest ORR mass activity, delivering 817 mA mgPt−1 at 0.85 V and 464 mA mgPt−1 at 0.90 V vs. RHE, surpassing both commercial Pt/C (J.M. 20 wt.%) and its Pt@Ni, Pt@Cu, and Pt@CNT counterparts. Structural and spectroscopic analyses reveal a strong electronic interaction between Pt and Co, leading to localized electron transfer from Co to Pt domains. This electronic modulation facilitates an optimal surface binding energy, enhancing oxygen adsorption–desorption kinetics and ORR activity. These findings highlight the critical role of transition metal–support synergy in the rational design of high-performance Pt-based electrocatalysts for next-generation fuel cell applications.

Oxygen doi: 10.3390/oxygen5030009

Authors: Melissa S. Totten Precious K. Wondzi

Fibromyalgia is a syndrome that causes chronic musculoskeletal pain accompanied by symptoms such as fatigue, sleep disorders, headaches, anxiety, and depression. People diagnosed with fibromyalgia usually have higher levels of reactive oxygen species and lower antioxidant capacity compared to healthy individuals. This condition can contribute to elevated oxidative stress in the body, especially within the lipid-rich nervous system. Treatment with antioxidants through diet or supplements is one method being investigated to reduce the symptoms of fibromyalgia. This narrative review focuses on the latest research, specifically peer-reviewed publications within the last 10 years, on potential antioxidant treatments for patients with fibromyalgia. Relevant micronutrients, such as vitamin B12, vitamin D, and iron, and supplements such as melatonin, coenzyme Q, alpha-lipoic acid, and palmitoylethanolamide are discussed. Based on the current evidence, many of these antioxidants show potential for the management of fibromyalgia symptoms as standalone treatments or in combination with other antioxidants or pharmacological agents. More clinical research is required to understand the long-term efficacy and safety of these micronutrients and supplements, as well as their overall health impact.

Oxygen doi: 10.3390/oxygen5020008

Authors: Oumaima Ammar Marwa Ben Ali Gannoun Tesnim Ajina Assila Hadj Ali Manel Boussabbeh Amira Sallem Zohra Haouas Mariarosaria Di Tommaso Meriem Mehdi

Oxidative stress (OS) contributes to poor sperm parameters and increased sperm DNA fragmentation (sDF), yet effective therapeutic strategies remain limited. This study aimed to evaluate the in vitro efficacy of pentoxifylline (PTX) in improving sperm motility and reducing OS and sDF in men with isolated asthenozoospermia. Thirty semen samples from patients with asthenozoospermia were processed using density gradient centrifugation. Each sample was divided into two aliquots: one treated with PTX at a dose of 3.6 mM and the other without PTX treatment. The sperm viability and motility were assessed at 30 min, 1 h, 2 h, and 24 h post-treatment. OS was evaluated using nitro blue tetrazolium staining and a chemiluminescence assay. sDF was assessed using the alkaline Comet assay. The sperm samples treated with PTX, compared to the controls, exhibited a significant increase in total sperm motility (71.8 ± 23.03% versus 47.47 ± 4.88%, respectively; p < 0.0001). However, no significant difference was observed in the sperm viability. PTX treatment significantly reduced ROS production and sDF levels compared to controls (p < 0.01). These findings suggest that in vitro PTX supplementation enhances sperm motility and reduces the nuclear sperm injury associated with seminal ROS production. Therefore, PTX supplementation in vitro may be beneficial in assisted reproductive technology procedures involving men with asthenozoospermia.

Oxygen doi: 10.3390/oxygen5020007

Authors: Amisha Parekh Parker Knotts Amol V. Janorkar Michael D. Roach

With humans living longer and the median age of the population increasing, there is an ever-increasing demand for better biomedical implants. Titanium implants have a long history of successful use, but their naturally forming amorphous oxide surfaces are not ideal to promote bone growth. Therefore, titanium surfaces are often modified to improve bioactivity through electrochemical processes such as anodization which can crystallize the oxide into more bioactive titanium oxide phases, form hierarchical micro- and nano-scale roughness profiles, and incorporate beneficial bone chemistry into the oxide layer to improve interactions with bone cells. We have recently developed three innovative anodization electrolytes based on combinations of citrus fruit juices and commercially available calcium compounds. Anodization in these electrolytes produced citrus-based oxides exhibiting surface Ca/P ratios within the range of human bone, unique cauliflower-like hierarchical micro- and nano-scale surface roughness profiles, and the formation of titanate compounds which have been shown to be precursors for subsequent apatite formation. Thus, our titanate-containing citrus-based oxides show much promise for improving future osseointegration.

Oxygen doi: 10.3390/oxygen5020006

Authors: Kalyan Annamalai

The biology literature addresses two puzzles: (i) the increase in specific metabolic rate of organs (SOrMR, W/kg of organ) with a decrease in body mass (MB) of biological species (BS), and (ii) how the organs recognize they are in a smaller or larger body and adjust metabolic rates of the body (q˙B) accordingly. These puzzles were answered in the author’s earlier work by linking the field of oxygen-deficient combustion (ODC) of fuel particle clouds (FC) in engineering to the field of oxygen-deficient metabolism (ODM) of cell clouds (CC) in biology. The current work extends the ODM hypothesis to predict the whole-body metabolic rates of 114 BS and demonstrates Kleiber’s power law {q˙B =  a  MBb}. The methodology is based on the postulate of Lindstedt and Schaeffer that “150 ton blue whale. and the 2 g Etruscan shrew.. share the same.. biochemical pathways” and involve the following steps: (i) extension of the effectiveness factor relation, expressed in terms of the dimensionless group number G (=Thiele Modulus2), from engineering to the organs of BS, (ii) modification of G as GOD for the biology literature as a measure of oxygen deficiency (OD), (iii) collection of data on organ and body masses of 116 species and prediction of SOrMRk of organ k of 114 BS (from 0.0076 kg Shrew to 6650 kg elephant) using only the SOrMRk and organ masses of two reference species (Shrew, 0.0076 kg: RS-1; Rat Wistar, 0.390 kg: RS-2), (iv) estimation of q˙B for 114 species versus MB and demonstration of Kleiber’s law with a = 2.962, b = 0.747, and (v) extension of ODM to predict the allometric law for maximal metabolic rate (under exercise, {q˙B,MMR =  aMMR  MBbMMR}) and validate the approach for MMR by comparing bMMR with the literature data. A method of detecting hypoxic condition of an organ as a precursor to cancer is suggested for use by medical personnel

Oxygen doi: 10.3390/oxygen5020005

Authors: Bernard A. Hauser Ya-Ying Wang Kenneth J. Boote Prachee Chaturvedi Eric S. McLamore Leon H. Allen

In a previous Arabidopsis investigation, three ovule-specific cell-wall peroxidases decreased seed abortion rates. These peroxidases were expressed in soybean plants. Because cell wall peroxidases alter extensibility, possible effects on seed size and plant yield were evaluated. Since the effects of these peroxidases in Arabidopsis were dependent on environmental stress, soybean plants were grown in controlled environment greenhouse rooms under four temperature treatments; the daily temperature averages were 26, 30, 34, and 38 °C. In this experiment in vivo oxygen levels during seed growth were 25-fold below ambient, which could affect peroxidase activities. Consequently, soybeans were grown at atmospheric (21%) and elevated (32%) O2 to evaluate peroxidase activities at higher O2. Chambers were maintained at 700 ppm CO2 in an attempt to minimize photorespiration in elevated O2. Individual seed weight decreased with increasing temperature to zero at 38 °C. In elevated O2 rooms, the oxygen concentration in developing seeds increased, but, due to leaf photorespiration, plant biomass and seed yield decreased. Seed size and shelling percentage declined equally with temperature at both O2 concentrations. Expression of all three cell-wall peroxidases reduced seed abortion; however, that did not increase yields at ambient or elevated O2. While O2 concentration is less than 1% in developing seeds, increased O2 levels in seeds were not beneficial for soybean reproduction.

Oxygen doi: 10.3390/oxygen5020004

Authors: Pwint Phoo Wai Hisateru Yamaguchi Keisuke Hitachi Kunihiro Tsuchida Setsuko Komatsu

Because soybean is sensitive to salt stress, it is necessary to improve their stress tolerance. Titanium-oxide nanoparticles (TiO2 NPs) enhanced the growth of soybean under salt stress. To elucidate the promotive effects of TiO2 NPs on soybean growth under salt stress, a gel-free/label-free proteomic analysis was carried out. The principal component analysis of proteins showed that TiO2 NPs affected proteins in roots grown under salt stress. The differentially changed proteins were associated with protein metabolism and transport in the biological process, the nucleus in the cellular component, and nucleic acid binding activity in the molecular function. Proteins identified with proteomics were verified using immunoblot analysis. The abundance of V-ATPase decreased in soybean under salt stress and increased with additional TiO2 NPs under stress, whereas xyloglucan endotransglucosylase/hydrolase did not change with any treatment. The abundance of peroxiredoxin increased under salt stress but decreased with additional TiO2 NPs under stress. These results suggest that TiO2 NPs confer salt tolerance in soybean plants at the early growth stage by regulating vacuole transport and reactive oxygen scavenging systems.

Oxygen doi: 10.3390/oxygen5020003

Authors: Francesca Cascone Antonio Minni Marco de Vincentiis Christian Barbato Federica Zoccali

Pharyngocutaneous fistulas (PCF) are a common postoperative complication following head and neck surgery, particularly after total laryngectomy. These types of fistulas represent a challenge for both patients and clinicians due to their persistence and resistance to conventional healing methods. Hyperbaric Oxygen Therapy (HBOT) has been proposed as an adjunctive treatment to enhance healing and closure of PCF. While many studies report positive outcomes, the results are not universally consistent. This comprehensive review aimed to examine the clinical evidence supporting the efficacy of HBOT in the management of pharyngocutaneous fistulas, focusing on fistula closure rates, infection control, and overall healing improvement. All publications without the restriction of time and published in the English language were included. Searches were performed in the PubMed, MEDLINE, Scopus, and Embase databases. Ten articles were included in this review. The evaluation of our clinical experience with this method of treating PCF showed results comparable to those found in the literature and analyzed among the studies reviewed. Several studies indicate that HBOT promotes fistula closure, reduces healing time, and enhances the local immune response, but further investigation is required to optimize protocols and patients’ selections.

Oxygen doi: 10.3390/oxygen5010002

Authors: Jadwiga Inglot Joanna Katarzyna Strzelczyk Jakub Tylutki Dorota Bartusik-Aebisher David Aebisher

Photodynamic therapy (PDT) is an effective method of preventing the progression of cancer. The PDT method guarantees localized generation of singlet oxygen (1O2), which is toxic to the cells. Therefore, this treatment, also called light-activated chemotherapy, is particularly useful for tumors whose location is difficult to access but needs to be known. Therefore, PDT may be an alternative method to the surgical removal of the tumor by replacing the scalpel tool with three factors, i.e., light, a photosensitizer and oxygen, to generate singlet oxygen in the cell. Herein, primary brain tumors that probably originate from neuroglial stem or progenitor cells are discussed. In this review, we have included current information on the use of PDT in the treatment of gliomas in the context of genetics. We have mainly focused on the study of the use of PDT in patients with genetic syndromes that are associated with an increased risk of glioma. The review also uses information on genetic syndromes that are important for the diagnosis and treatment of patients with glioma. We discuss the association between brain tumors and a few genetic abnormalities. In this review, we highlight the molecular mechanism of human cell response to PDT based on the literature data. In treated samples, significant changes in gene expression were noted after PDT.

Oxygen doi: 10.3390/oxygen5010001

Authors: Kely Melina Vilca-Coaquira Angel Gabriel Calisaya-Huacasi Jeancarlo Tejada-Flores Henry Oscar Tintaya-Ramos Mariela Mercedes Quispe-Trujillo Solanyela Anny Quispe-Humpiri Rossela Alejandra Rojas-Chambilla Gilberto Félix Peña-Vicuña Alberto Salazar Granara Luis F. Lens Sardón Alcides Flores-Paredes Moua Yang Ginés Viscor Ivan Hancco Zirena

Previous studies indicate that individuals at high altitudes have a lower pain threshold than those living at sea level. This study evaluates the differences in pain perception among young people living at an altitude of 3800 m and after acute exposure to a severe hypoxic environment at more than 5100 m. Fourteen people (BMI of 22.6 ± 1.2 and age of 23.3 ± 1.9 years) residing in the city of Puno (3825 m) participated in an ascent to the Populated Center of La Rinconada (>5100 m). The unilateral ischemia pain provocation test was used, applying pressure with a manual sphygmomanometer to generate transient ischemia in the arm while the patient opens and closes their hand. Onset, peak, and resolution times of pain, heart rate, and oxygen saturation were recorded. At their residence altitude of 3828 m, the mean hemoglobin was 16.16 ± 2.29, while at 5100 m, mean hemoglobin increased to 17.57 ± 1.74. The average time to pain onset in the right arm was 30.43 s ± 14.15 at 3828 m, whereas at 5100 m above sea level, the pain perception was at 31.00 s ± 19.01. At 3828 m, the average time until pain sensation in the left arm was 19.93 s ± 9.44 and increased to 23.07 s ± 10.83 at 5100 m. During exposure to a severe hypoxic environment, the pain perception threshold was similar between 3828 m and 5100 m above sea level.

Oxygen doi: 10.3390/oxygen4040028

Authors: Ian Shuttleworth

Nanoparticles are a mainstay of heterogeneous catalysis. This is in part due to their mesoscopic structure; they can be grown to have large available surface areas which can be both regenerative and durable in reaction. Their utility is possible by the alloys used in their production—however, analysis of their operation is generally at the DFT or molecular dynamics level. This review will present an overview of the post-DFT methods relevant to materials supporting the ORR and OER reactions. Pt-bearing alloys will then be highlighted with a focus on their application in heterogeneous catalysis and the ORR/OER reactions. The current computational approaches to accurately predicting the band properties of the alloys will then be discussed and both the fundamental and applied importance of this modelling will be highlighted.

Oxygen doi: 10.3390/oxygen4040027

Authors: Lisa M. Landino Emily E. Lessard

Alterations in cellular energy metabolism are a hallmark of cancer and lactate dehydrogenase (LDH) enzymes are overexpressed in many cancers regardless of sufficient oxygen and functional mitochondria. Further, L-lactate plays signaling roles in multiple cell types. We evaluated the effect of singlet oxygen and hypochlorous acid (HOCl) on pig heart LDH-B, which shares 97% homology with human LDH-B. Singlet oxygen was generated photochemically using methylene blue or the chlorophyll metabolites, pheophorbide A and chlorin e6. Singlet oxygen induced protein crosslinks observed by SDS-PAGE under reducing conditions and inhibited LDH-B activity. Ascorbate, hydrocaffeic acid, glutathione and sodium azide were employed as singlet oxygen scavengers and shown to protect LDH-B. Using fluorescein-modified maleimide, no changes in cysteine availability as a result of singlet oxygen damage were observed. This was in contrast to HOCl, which induced the formation of disulfides between LDH-B subunits, thereby decreasing LDH-B labeling with fluorescein. HOCl oxidation inhibited LDH-B activity; however, disulfide reduction did not restore it. LDH-B cysteines were resistant to millimolar H2O2, chloramines and Angeli’s salt. In the absence of pyruvate, LDH-B enhanced NADH oxidation in a chain reaction initiated by singlet oxygen that resulted in H2O2 formation. Once damaged by either singlet oxygen or HOCl, NADH oxidation by LDH-B was impaired.

Oxygen doi: 10.3390/oxygen4040026

Authors: David A. Winkler

Noble gases are a valuable but overlooked source of effective and safe therapeutics. Being monoatomic and chemically inert, they nonetheless have a surprisingly wide range of biochemical and medically valuable properties. This mini review briefly summarizes these properties for the most widely used noble gases and focuses and research gaps and missed opportunities for wider use of these intriguing ‘atomic’ drugs. The main research gaps and opportunities lie firstly in the application of advanced computational modelling methods for noble gases and recent developments in accurate predictions of protein structures from sequence (AlphaFold), and secondly in the use of very efficient and selective drug delivery technologies to improve the solubility, efficacy, and delivery of noble gases to key targets, especially for the lighter, poorly soluble gases.

Oxygen doi: 10.3390/oxygen4040025

Authors: Catherine L. Bruni Haden A. Johnson Aya Ali Amisha Parekh Mary E. Marquart Amol V. Janorkar Michael D. Roach

Bacteria-related infections remain a leading cause of dental implant failures. Despite the successful history of titanium implants, naturally forming oxides lack antibacterial properties. Crystalline oxides, modified through anodization processes, have shown photocatalytic-induced antibacterial properties when exposed to sufficient energy sources such as UVA light. Chemically doping these oxides with some metallic and non-metallic elements has been shown to enhance their photocatalytic activity (PCA). The present study’s objectives were to assess the relative UVA and violet-light-irradiated PCA levels, bacterial attachment levels, and pre-osteoblast early cell viability levels of phosphorus-doped and phosphorus-and-silver-doped anatase-phase oxides. Each oxide revealed similar surface topographies and surface porosity levels. However, the phosphorus-and-silver-doped oxides exhibited significantly higher PCA levels compared to the phosphorus-doped oxide counterpart after irradiation with 365 nm UVA (p < 0.0001) or 410 nm violet (p = 0.007 and 0.03) light. The phosphorus-doped oxides and phosphorus-and-silver-doped oxides revealed similar Staphylococcus aureus attachment levels after 60 min of UVA irradiation. The phosphorus-and-silver-doped oxides exhibited significantly increased 7-day cell viability compared to their phosphorus-doped oxide counterparts. Thus, it was concluded that the silver doping additions to the oxides show much promise for biomaterials applications and warrant further exploration.

Oxygen doi: 10.3390/oxygen4040024

Authors: Jiri Käser Kai Töpfer Markus Meuwly

The diffusional dynamics and vibrational spectroscopy of molecular hydrogen (H2) in myoglobin (Mb) is characterized. Hydrogen has been implicated in a number of physiologically relevant processes, including cellular aging or inflammation. Here, the internal diffusion through the protein matrix was characterized, and the vibrational spectroscopy was investigated using conventional empirical energy functions and improved models able to describe higher-order electrostatic moments of the ligand. Depending on the energy function used, H2 can occupy the same internal defects as already found for Xe or CO (Xe1 to Xe4 and B-state). Furthermore, four additional sites were found, some of which had been discovered in earlier simulation studies. Simulations using a model based on a Morse oscillator and distributed charges to correctly describe the molecular quadrupole moment of H2 indicate that the vibrational spectroscopy of the ligand depends on the docking site it occupies. This is consistent with the findings for CO in Mb from experiments and simulations. For H2, the maxima of the absorption spectra cover ∼20 cm−1 which are indicative of a pronounced Stark effect of the surrounding protein matrix on the vibrational spectroscopy of the ligand. Electronic structure calculations show that H2 forms a stable complex with the heme iron (stabilized by ∼−12 kcal/mol), but splitting of H2 is unlikely due to a high activation energy (∼50 kcal/mol).

Oxygen doi: 10.3390/oxygen4040023

Authors: Omer A. Idris Alexandra L. Uridge Syann Hollins Kyle Ver Steeg

Skin grafting is a critical procedure for treating skin defects from burns, trauma, and surgical interventions, yet complications such as ischemia, necrosis, and infection can limit graft success. Hyperbaric Oxygen Therapy (HBOT) has emerged as a promising adjunctive treatment that enhances skin graft viability through mechanisms including enhanced oxygenation, angiogenesis, reduced inflammation, and anti-infective effects. This review synthesizes findings from clinical studies, comparative analyses, and case reports to clarify HBOT’s efficacy in improving skin graft outcomes. Methods include a comprehensive analysis of HBOT’s impact on graft take rates, healing times, and complication rates. Results indicate that HBOT significantly improves graft survival by mitigating ischemia and infection, while comparative studies show a reduction in major amputations and improved healing in complex cases, such as diabetic foot ulcers and traumatic injuries. These findings suggest that HBOT can serve as a valuable adjunct to standard grafting procedures, offering a multifaceted approach to improve graft viability, especially in high-risk cases. This review highlights HBOT’s potential for integration into wound management protocols, providing a foundation for further exploration into its efficacy and applications in reconstructive surgery.

Oxygen doi: 10.3390/oxygen4040022

Authors: Nancy E. Gomez Silvia Granata

The success of heated tobacco products (HTPs) and electronic cigarettes (e-cigs) has been largely attributed to their ability to mimic the gestural experience of traditional cigarette smoking, while being perceived as a safer alternative due to the absence of combustion, as well as to their appeal, particularly among younger populations. Despite the initial idea that these new devices were harmless, recent literature reveals a concerning expanding body of evidence on their potential toxicity. Thus, this literature review aims to elucidate the mechanisms by which reactive oxygen species generated by HTPs and e-cigs induce oxidative stress and inflammation and the subsequent biological and health consequences, in order to raise awareness on the significance of addressing the potential toxicological effects associated with these devices, which are commonly believed to be safe.

Oxygen doi: 10.3390/oxygen4030021

Authors: Evan Los George Ford Dawn Tuell Demetrio Macariola William Stone

Evidence suggests that COVID-19 infection increases the risk of type 1 (T1D) and type 2 diabetes (T2D). Diabetes, in turn, increases COVID-19 susceptibility and contributes to increased COVID-19 morbidity and mortality. Oxidative stress has emerged as a common factor driving the pathogenesis of diabetes and COVID-19 caused by the severe acute respiratory syndrome coronavirus. The mechanistic links between oxidative stress, diabetes, and COVID-19 have primarily been studied in adults and will be summarized in this review. However, we suggest that studying these interconnections in children and young adults is critical since early intervention is optimal for improving outcomes. At the height of the pandemic, COVID-19 was a leading cause of death in children and young people, and people in this age group are as susceptible to COVID-19 as adults and the elderly. Glutathione is the primary water-soluble intracellular antioxidant and can be deficient in both diabetes and COVID-19. Glutathione is a tripeptide containing cysteine, glutamic acid, and glycine. Strategies to increase glutathione levels may be beneficial in helping to manage COVID-19-induced diabetes and diabetes-induced COVID-19 risk. Dietary supplementation with glycine plus n-acetyl-l-cysteine may be optimal since it contains two metabolic glutathione precursors.

Oxygen doi: 10.3390/oxygen4030020

Authors: Grace Russell Alexander Nenov

Cancer remains one of the leading causes of death despite advancements in research and treatment, with traditional therapies often causing significant side effects and resistance. Oxyhydrogen gas, a mixture of 66% molecular hydrogen (H2) and 33% molecular oxygen (O2) has shown exceptional promise as a novel therapeutic agent due to its ability to modulate oxidative stress, inflammation, and apoptosis. H2, a key component of oxyhydrogen gas, neutralises reactive oxygen and nitrogen species, enhancing existing treatments and reducing harmful oxidative states in cancer cells. H2 also lowers proinflammatory mediators including chemokines, cytokines, and interleukins, inhibiting cancer cell proliferation and boosting the effectiveness of conventional therapies. Additionally, hydrogen can induce apoptosis in cancer cells by modulating pathways such as MAPK and inhibiting the PI3K/Akt phosphorylation cascade. Preclinical and clinical evidence supports oxyhydrogen gas’s potential in treating various cancers. In lung cancer models, it inhibits cell proliferation, induces apoptosis, and enhances chemotherapy sensitivity. Similar results have been observed in breast cancer, where patients reported improved quality of life. In colorectal cancer, oxyhydrogen gas suppresses tumour growth, induces apoptosis, and improves intestinal microflora dysbiosis. The unique properties of oxyhydrogen gas make it a promising adjunctive or standalone cancer treatment. However, further research is needed to understand H2s’ mechanisms, optimise treatment protocols, and evaluate long-term safety and efficacy in human patients.

Oxygen doi: 10.3390/oxygen4030019

Authors: Ana Salomé Correia Nuno Vale

Oxidative stress, characterized by an imbalance between the production of reactive oxygen species and the body’s antioxidant defenses, plays an important role in the pathogenesis of various health conditions, including cancer and neurological disorders. For example, excessive ROS can lead to mutations, genomic instability, and uncontrolled cell proliferation in cancer. In neurological disorders, oxidative stress contributes to neuronal damage, inflammation, and the progression of diseases such as Alzheimer’s and Parkinson’s diseases. Adenosine, a nucleoside involved in energy transfer and signal transduction, is crucial to maintaining cellular homeostasis. Its role extends to modulating oxidative stress. Adenosine receptors are implicated in various physiological processes and in the pathophysiology of diseases. The interplay between oxidative stress and adenosine signaling is complex and critical. Adenosine can modulate oxidative stress responses, providing therapeutic potential for conditions where oxidative stress is a key player. Understanding this connection opens up avenues for novel therapeutic strategies targeting adenosine receptors to mitigate oxidative damage.

Oxygen doi: 10.3390/oxygen4030018

Authors: Dimitrios Kalompatsios Alexandra-Ioana Ionescu Vassilis Athanasiadis Theodoros Chatzimitakos Martha Mantiniotou Konstantina Kotsou Eleni Bozinou Stavros I. Lalas

This study explored the use of mandarin peels as an important source of health-promoting compounds by utilizing green methods (i.e., pulsed electric field and ultrasound-assisted extraction), along with conventional stirring. The impact of several extraction parameters, such as extraction duration, temperature, and solvent composition, on the recovery of bioactive compounds was evaluated through a response surface methodology. To identify the most effective conditions for all assays, a partial least-squares analysis was implemented. It was revealed that a combination of the above techniques was optimal at 80 °C for 30 min, with 75% v/v of ethanol in water as the extraction solvent. The concentration of bioactive compounds in the optimum extract had a total polyphenol content of 18.69 mg of gallic acid equivalents (GAE) per gram of dry weight (dw), and an ascorbic acid concentration of 18.25 mg/g dw. However, correlation analyses revealed a rather negative relationship between these bioactive compounds. The chromatographic analysis of optimum extracts supported this result by quantifying 20.53 mg/g dw of total individual polyphenols, with hesperidin being the dominant compound (13.98 mg/g dw). The antioxidant assays, including ferric-reducing antioxidant power and DPPH• inhibition activity, were measured at 123.21 and 65.12 μmol of ascorbic acid equivalents (AAE) per gram of dw, respectively. This research enhances the valorization of mandarin peels as a renewable source of bioactive compounds, providing the opportunity to generate high-added-value products from food waste in the food and pharmaceutical sectors.

Oxygen doi: 10.3390/oxygen4030017

Authors: Efstathios Kaloudis

This study focuses on post-harvest pest management in agriculture, in particular the transition to modified atmospheres as a sustainable alternative to conventional pesticide methods. Using Computational Fluid Dynamics (CFD) simulations, we analysed the dynamics of oxygen distribution within a pest control chamber. We tested four different configurations of nitrogen inlet and outlet positions to determine the most effective setup. The simulations used the twoLiquidMixingFoam solver in OpenFOAM to model gas mixing and diffusion. Our results show that the configuration with the nitrogen inlet at the top and the outlet at the bottom (Case D) was the most efficient. This configuration reached the target oxygen concentration of 1.5% in 4.4 h, significantly faster than the other configurations. These results highlight the importance of inlet and outlet positioning in improving the efficiency of oxygen reduction and ensuring a consistent low oxygen level throughout the chamber. Optimising the placement of nitrogen inlets and outlets has significant potential to improve the effectiveness of modified atmosphere treatments for pest control. Future research should consider additional environmental factors, different storage conditions and insect mortality models to further refine these methods.

Oxygen doi: 10.3390/oxygen4030016

Authors: Dario Vrdoljak Željko Dujić Nikola Foretić

Lower limb muscle fatigue is the main reason for withdrawal from diving. Therefore, this study aimed to determine the local muscle oxygen saturation and hemoglobin concentration in the vastus lateralis muscle during different freediving disciplines. One freediver participated in this study, and his chronological age was 40 years, body mass 75.0 kg, body height 184.0 cm, and body fat 13.7%. The participant has been practicing freediving for 6 years. The variables in this study included anthropometric indices, heart rate, and muscle oxygen dynamics parameters (SmO2 (oxygen muscle saturation) and tHb (total hemoglobin)). The variables were measured during five diving disciplines: static apnea, bifin, dynamic no fins (DNF), monofin, and sneaking. Measurements were performed during intensive training/competition during the diving season in August 2023. The results of this study showed that when oxygen starts to decrease during the dive, the tHb increases. Furthermore, the times at which maximal tHb and minimal SmO2 were achieved are also shown. These parameters occurred at almost the same time across all disciplines: static (SmO2, 142; tHb, 150 s), bifin (SmO2, 153; tHb, 148 s), DNF (SmO2, 162; tHb, 178 s), monofin (SmO2, 96; tHb, 94 s), and sneaking (SmO2, 212; tHb, 228 s). Also, differences in tHb and SmO2 were present between diving disciplines. In particular, the highest increase in tHb was present in bifin (0.0028 AU/s), whereas monofin showed a decrease (−0.0009 AU/s). On the other hand, the highest desaturation was seen in bifin (−0.87%/s) and the lowest in sneaking (−0.29%/s) These findings emphasize the physiological characteristics of freedivers engaging in different freediving disciplines that influence muscles during the dive. Such responses could be observed through a concurrent hypoxia/hypercapnia and a transient reduction in the Fahraeus effect.

Oxygen doi: 10.3390/oxygen4030015

Authors: Sergey P. Verevkin Artemiy A. Samarov Sergey V. Vostrikov

Liquid organic hydrogen carriers (LOHCs) are aromatic molecules that are being considered for the safe storage and release of hydrogen. The thermodynamic properties of a range of aromatic ethers were investigated using various experimental and theoretical methods to assess their suitability as LOHC materials. The absolute vapour pressures were measured for benzyl phenyl ether, dibenzyl ether and 2-methoxynaphthalene using the transpiration method. The standard molar enthalpies and entropies of vaporisation/sublimation were derived from the temperature dependence of the vapour pressures. The combustion energies of benzyl phenyl ether and dibenzyl ether were measured using high-precision combustion calorimetry, and their standard molar enthalpies of formation were derived from these data. High-level quantum chemical calculations were used to calculate the standard molar enthalpies of formation in the gas phase for benzyl phenyl ether, dibenzyl ether and 2-methoxynaphthalene. The latter values agreed very well with the experimental results obtained in this work. The thermodynamic properties of the hydrogenation/dehydrogenation reactions in liquid phase in LOHC systems based on methoxy–benzene, diphenyl ether, benzyl phenyl ether, dibenzyl ether and 2-methoxynaphthalene were derived and compared with the data for similarly structured hydrogen carriers based on benzene, diphenylmethane, 1,2-diphenylethane, 1,3-diphenylpropane and naphthalene. The influence of the oxygen functionality on the thermodynamic properties of the hydrogenation/dehydrogenation reactions was evaluated.

Oxygen doi: 10.3390/oxygen4030014

Authors: Stavroula Ioannidou Athanasia Tsiakalidou Konstantina Kazeli Argyrios Ginoudis Ariadne Fouza Maria Daoudaki Evgenia Lymperaki

Rheumatoid arthritis (RA) is a well-known autoimmune inflammatory disease that affects the diarthrodial joints. Inflammation increases the production of reactive oxygen species (ROS), which may explain why RA is one of the diseases that induce oxidative stress. This study aimed to evaluate the potential differences in biochemical, hematological, and oxidative stress markers in the early stages of RA and after different treatment regimens. The study involved 111 patients, 28 men and 83 women aged 34 to 59 years, who were divided based on their c-reactive protein (CRP) levels into inactive RA patients (IRA) with CRP < 1.3 (n = 57, 22 men and 35 women) and active RA patients (ARA) with CRP ≥ 1.3 (n = 54, 6 men and 48 women). The study participants were divided into two groups, A and B, based on their treatment regimen. Group A, 90% of which were IRA patients, received methotrexate (MTX) monotherapy. Group B, which comprised 90% ARA patients, received a combination of leflunomide, a conventional disease-modifying antirheumatic drug (DMARD), and a biologic DMARD. The hematological, biochemical, oxidative stress, and RA-specific biomarkers were measured twice in groups A and B in the early stage of the disease, before and 3 months post-treatment, using conventional colorimetric, fluorometric, and immunological assays. According to the results of our study, glutathione peroxidase (GPx), ROS, calcium (Ca) and phosphorus (P) ions, vitamin C and D, and lipid profiles could serve as potential diagnostic markers in the early stages of the disease. Both treatment options were equally effective at improving the overall health of the patients. However, treatment resulted in a further increase in ROS levels and a decrease in antioxidant markers.

Oxygen doi: 10.3390/oxygen4020013

Authors: Sydney L. Olson Razeen J. Akbar Adrianna Gorniak Laura I. Fuhr Mostafa A. Borahay

Uterine fibroids are the most common tumors in females, affecting up to 70% of women worldwide, yet targeted therapeutic options are limited. Oxidative stress has recently surfaced as a key driver of fibroid pathogenesis and provides insights into hypoxia-induced cell transformation, extracellular matrix pathophysiology, hypoxic cell signaling cascades, and uterine biology. Hypoxia drives fibroid tumorigenesis through (1) promoting myometrial stem cell proliferation, (2) causing DNA damage propelling the transformation of stem cells to tumor-initiating cells, and (3) driving excess extracellular matrix (ECM) production. Common fibroid-associated DNA mutations include MED12 mutations, HMGA2 overexpression, and fumarate hydratase loss of function. Evidence suggests an interaction between hypoxia signaling and these mutations. Fibroid development and growth are promoted by hypoxia-triggered cell signaling via various pathways including HIF-1, TGFβ, and Wnt/β-catenin. Fibroid-associated hypoxia persists due to antioxidant imbalance, ECM accumulation, and growth beyond adequate vascular supply. Current clinically available fibroid treatments do not take advantage of hypoxia-targeting therapies. A growing number of pre-clinical and clinical studies identify ROS inhibitors, anti-HIF-1 agents, Wnt/β-catenin inhibition, and TGFβ cascade inhibitors as agents that may reduce fibroid development and growth through targeting hypoxia.

Oxygen doi: 10.3390/oxygen4020012

Authors: Valery M. Dembitsky

This review explores the unique structural and functional characteristics of natural products featuring highly oxygenated cyclobutane rings, with a specific focus on oxetane and 1,2-dioxetane motifs. It presents the structures and biological activities of compounds containing these rings, highlighting their contribution to molecular stability and pharmacological potency. Through detailed case studies and recent research findings, it has been demonstrated that these oxygen-rich rings enhance the molecular diversity and biological efficacy of natural products, potentially offering new avenues for drug development. Notably, these compounds are predominantly synthesized by microorganisms and can also be found in extracts from fungi, plants, and certain marine invertebrates. Compounds with oxetane and 1,2-dioxetane rings are primarily noted for their strong antineoplastic properties, among other biological activities. In contrast, most 1,2-dioxetanes exhibit potent antiprotozoal effects. It is important to note that 1,2-dioxetanes often serve as intermediate products in oxidation reactions, characterized by their instability and propensity to decompose into new compounds.

Oxygen doi: 10.3390/oxygen4020011

Authors: Inês João Ferreira Ana Rita C. Duarte Mário Diniz Ricardo Salgado

Halophyte plants and seaweed are described in the literature as rich sources of antioxidant compounds that can be used in the pharmaceutical and food industries. In this work, we studied the antioxidant composition of five species of halophytic plants (Suaeda vera Forssk, Halimione portulacoides L., Inula crithmoides L., Salicornia ramosissima (Hook.f.) J. Woods and Sarcocornia perennis (Mill.) A.J.Scott) and three seaweeds (Gracilaria gracilis (Stackhouse) Steentoft, L.Irvine and Farnham, Fucus spiralis L. and Ulva rigida C. Agardh) collected in Sado Estuary, Portugal. In the case of the plants, different parts of the plant were also assessed. Various extraction procedures were also performed to understand which methods were most suitable for extracting the various antioxidant compounds. Therefore, the aim of this study was to characterize the antioxidant compounds in halophytes and seaweed using various methods (ABTS, DPPH and FRAP), as well as the phenolic (TPC) and flavonoid (TFC) contents in the different extracts obtained. The amount of soluble protein in each extract was also determined. The results show that methanolic extracts generally have a higher antioxidant capacity, while the highest soluble protein content was observed in aqueous extracts. The seaweed Fucus Spiralis showed the highest antioxidant content, while in halophytic plants the highest antioxidant content was detected in the leaves. In general, this work confirms the potential of halophytes and seaweed as sources of antioxidant compounds for use in the food and pharmaceutical industries.

Oxygen doi: 10.3390/oxygen4020010

Authors: Andrea Collettini Federica Zoccali Christian Barbato Antonio Minni

Background: In otorhinolaryngology and head and neck surgery, oxygen is a therapeutic tool used for various pathologies. Oxidative stress is the imbalance between the production of free radicals (ROS) and the antioxidant capacity of the body, which can represent the pathogenesis of several pathologies or contribute to their worsening. This narrative review aims to analyze the benefits, indications, and side effects of hyperbaric oxygen therapy (HBOT) in different head and neck disorders. Methods: The search was carried out on multiple electronic databases such as PubMed and Google Scholar, and prospective, randomized, and reviewed studies were analyzed from January 1982 to February 2024. Results and Conclusions: The most common tools used to manage oxidative stress in the ear, nose, and throat (ENT) field are continuous positive airway pressure (CPAP) and HBOT. A common ENT pathology, while the latter can be used for osteoradionecrosis treatment in head and neck cancer patients, infections, malignant external otitis, head and neck reconstruction, facial cosmetic surgery, and among patients with sudden sensorineural hearing loss. From our analysis, it emerged that HBOT is a currently used effective therapy in various ENT pathologies’ treatment, alone or in association with other treatments; it can guarantee functional recovery and healing depending on the type of pathology for which it is used and on its severity.

Oxygen doi: 10.3390/oxygen4020009

Authors: Raphaël Serreau Ammar Amirouche Amine Benyamina Sabine Berteina-Raboin

In this review, in addition to the potential cardiovascular applications of β-blockers and, more specifically, propranolol, we wanted to list the more recent applications in psychiatry as well as current knowledge on the impact of oxidative stress on propranolol hydrochloride and the oxidative stress that could be limited by the latter. In fact, a number of studies show that this molecule is modified by oxidative stress but is also able to limit it. Mention is also made to studies on the increasingly important problem of eliminating drug waste and its impact on the environment, particularly the marine environment. Given the increase in the consumption of medicines, more rigorous waste management is needed to avoid impacting biodiversity.

Oxygen doi: 10.3390/oxygen4020008

Authors: David Mantle Hannah Rowbottom Jacob Jones Indiia Margarita Potts Nadia Turton Mollie Dewsbury Guillermo Lopez-Lluch Iain P. Hargreaves

The generation of energy within cells is a fundamental process enabling cell survival, and as such it represents a potential target in cancer therapy. In this article, we therefore review the relative contributions of glycolysis and oxidative phosphorylation/mitochondrial function to cancer cell energy generation, and we highlight their respective potential value as chemotherapeutic targets. This article is particularly focussed on the potential role of coenzyme Q10 in the prevention and treatment of cancer.

Oxygen doi: 10.3390/oxygen4010007

Authors: John T. Hancock

Oxygen (O2) was discovered approximately 250 years ago (Contribution 1), a breakthrough accredited to at least three people: Antoine-Laurent de Lavoisier in France (Antoine Lavoisier), Carl Wilhelm Scheele in Sweden, and Joseph Priestley in England [...]

Oxygen doi: 10.3390/oxygen4010006

Authors: Luke A. Borchardt Zachariah P. G. Olufs Philip G. Morgan David A. Wassarman Misha Perouansky

The mitochondrial electron transport chain (mETC) contains molecular targets of volatile general anesthetics (VGAs), which places individuals with mETC mutations at risk for anesthetic complications, as exemplified by patients with Leigh syndrome (LS). The Drosophila melanogaster homozygous mutant for ND-23, which encodes a subunit of mETC Complex I, replicates numerous characteristics of LS, including neurodegeneration, shortened lifespan, behavioral anesthetic hypersensitivity, and toxicity. The anesthetic phenotype of toxicity (lethality) is also observed in flies homozygous for mutations in other Complex I subunits. By contrast, mutations conferring sensitivity have not yet been identified for subunits of Complexes II–V. Furthermore, anesthetic phenotypes are thought to be recessive; that is, risk is not conferred by heterozygous mutations. However, at older ages, exposure of heterozygous mutant ND-23 flies to the VGA isoflurane in 75% oxygen (hyperoxia) results in toxicity. It is also unknown whether combinations of heterozygous mutations in different subunits of the mETC can result in anesthetic toxicity. Here, we show that, following exposure to isoflurane in hyperoxia, flies carrying heterozygous mutations in two Complex I subunits, ND-23 and ND-SGDH (NADH dehydrogenase (ubiquinone) SGDH subunit), had a level of anesthetic toxicity that exceeded the added toxicities of the individual heterozygous mutations. In addition, we show that flies heterozygous for two different alleles of the Complex II gene SdhB were susceptible to isoflurane/hyperoxia-induced anesthetic toxicity. Finally, a mutation in the SdhC subunit of Complex II of Caenorhabditis elegans resulted in isoflurane-induced mortality, supporting the role of Complex II in anesthetic toxicity. These data expand the landscape of mutations in the mETC that increase sensitivity to anesthetic toxicity.

Oxygen doi: 10.3390/oxygen4010005

Authors: Dimitrios Palaiogiannis Vassilis Athanasiadis Theodoros Chatzimitakos Martha Mantiniotou Eleni Bozinou Dimitris P. Makris Stavros I. Lalas

The objective of this study was to determine the optimal conditions for the recovery of bioactive and antioxidant compounds in aqueous solutions of Cistus creticus leaves and then employ the optimal extract for the enrichment of yogurt samples. The optimal conditions were established by a response surface methodology and were determined to be a liquid-to-solid ratio of 48 mL/g at 76 °C for 41 min. The optimum extract yielded TPC 157.17 mg GAE/g dw and TFC 2.38 mg QE/g dw, while FRAP and DPPH values were 1258.52 and 933.67 μmol AAE/g dw, respectively. HPLC-DAD was utilized to identify and quantify specific polyphenols, like myricetin rhamnoside, in the extract. The optimal extract was then added to yogurt desserts during their preparation at three different concentrations to study how the physicochemical characteristics of the yogurt, as well as the antioxidant capacity added during enrichment, were affected. Statistical analysis of the results was carried out in order to obtain more valid data. It seems that the most suitable concentration for yogurt fortification was 0.1% w/v of the extract as, at this concentration, the yogurts exhibited higher antioxidant capacity, and their physicochemical characteristics were improved.

Oxygen doi: 10.3390/oxygen4010004

Authors: Asuncion Rocher Philip I. Aaronson

On the thirty-fifth anniversary of the first description of O2-sensitive K+ channels in the carotid body chemoreceptors O2 sensing remains a salient issue in the literature. Whereas much has been learned about this subject, important questions such as the identity of the specific K+ channel subtype(s) responsible for O2 sensing by chemoreceptors and the mechanism(s) by which their activities are altered by hypoxia have not yet been definitively answered. O2 sensing is a fundamental biological process necessary for the acute and chronic responses to varying environmental O2 levels which allow organisms to adapt to hypoxia. Whereas chronic responses depend on the modulation of hypoxia-inducible transcription factors which determine the expression of numerous genes encoding enzymes, transporters and growth factors, acute responses rely mainly on the dynamic modulation of ion channels by hypoxia, causing adaptive changes in cell excitability, contractility and secretory activity in specialized tissues. The most widely studied oxygen-sensitive ion channels are potassium channels, but oxygen sensing by members of both the calcium and sodium channel families has also been demonstrated. Given the explosion of information on this topic, in this review, we will focus on the mechanisms of physiological oxygen chemotransduction by PO2-dependent K+ channels, with particular emphasis on their function in carotid body chemoreceptor cells (CBCC) and pulmonary artery smooth muscle cells (PASMC), highlighting areas of consensus and controversy within the field. We will first describe the most well-established concepts, those reproduced in multiple laboratories, and then discuss selected observations or questions that remain unresolved, and that limit our progress in this field.

Oxygen doi: 10.3390/oxygen4010003

Authors: Grace Russell Jennifer May John T. Hancock

Produced by photosynthesis, oxygen (O2) is a fundamentally important gas in biological systems, playing roles as a terminal electron receptor in respiration and in host defence through the creation of reactive oxygen species (ROS). Hydrogen (H2) plays a role in metabolism for some organisms, such as at thermal vents and in the gut environment, but has a role in controlling growth and development, and in disease states, both in plants and animals. It has been suggested as a medical therapy and for enhancing agriculture. However, the exact mode of action of H2 in biological systems is not fully established. Furthermore, there is an interrelationship between O2 and H2 in organisms. These gases may influence each other’s presence in solution, and may both interact with the same cellular components, such as haem prosthetic groups. It has also been suggested that H2 may affect the structures of some proteins, such as globins, with possible effects on O2 movement in organisms. Lastly, therapies may be based on supplying O2 and H2 together, such as with oxyhydrogen. Therefore, the relationship regarding how biological systems perceive and respond to both O2 and H2, and the interrelationship seen are worth considering, and will be discussed here.

Oxygen doi: 10.3390/oxygen4010002

Authors: Amin M. Ektesabi Julia Simone Chirag Vaswani Greaton W. Tan Yanbo Wang Jacqueline L. Pavelick Xiao Wu Janice Tai Sahil Gupta James N. Tsoporis Claudia C. dos Santos

Background: Sepsis is a severe and life-threatening condition triggered by a dysregulated response to infection, leading to organ failure and, often, death. The syndrome is expensive to treat, with survivors frequently experiencing reduced quality of life and enduring various long-term disabilities. The increasing understanding of RNA, RNA biology, and therapeutic potential offers an unprecedented opportunity to develop innovative therapy. Objective: This study is a scoping review focusing on pre-clinical studies of microRNA (miRNA)-based therapies for sepsis. Methodology: A scoping review. The search strategy identified papers published in PubMed until 15 October 2023, using the keywords (microRNA) AND (sepsis) AND (animal model). Inclusion criteria included papers that used either gain- or loss-of-function approaches, excluding papers that did not focus on microRNAs as therapy targets, did not include animal models, did not show organ failure-specific assessments, and focused on microRNAs as biomarkers. The PRISMA-ScR guideline was used in this study. Results: A total of 199 articles were identified that featured the terms “microRNA/miRNA/miR”, “Sepsis”, and “animal model”. Of these, 51 articles (25.6%) employed miRNA-based therapeutic interventions in animal models of sepsis. Of these, 15 studies extended their inquiry to include or reference human clinical data. Key microRNAs of interest and their putative mechanisms of action in sepsis are highlighted. Conclusions: The body of work examined herein predominantly addresses various dimensions of sepsis-induced organ dysfunction, supporting the emerging role of miRNAs as potential therapeutic candidates. However, nearly 5% of papers on miR-based therapy have been retracted over the past 5 years, raising important concerns regarding the quality and complexity of the biology and models for assessing therapeutic potential.

Oxygen doi: 10.3390/oxygen4010001

Authors: Vassilis Athanasiadis Theodoros Chatzimitakos Ioannis Makrygiannis Dimitrios Kalompatsios Eleni Bozinou Stavros I. Lalas

A member of the Verbenaceae family, Aloysia citrodora, or lemon verbena, is a medicinal herb with antioxidant compounds. The aim of this study was to develop a green, optimized method for the bioactive compound (carotenoids, ascorbic acid, and polyphenols) extraction from lemon verbena leaves through response surface methodology (RSM). The bioactive compound recovery was shown to be significantly affected by the extraction technique (both with pulsed electric field and ultrasound-assisted extraction), along with an extraction solvent, based on partial least squares analysis. Consequently, the maximum polyphenol yield required a double-assisted extraction with a relatively low extraction duration (60 min) at a high temperature (80 °C), with a moderate-polarity extraction solvent (50% v/v ethanol). With the optimized method, the total polyphenol content (TPC) was measured at 175.03 mg gallic acid equivalents/g, whereas chromatographic analysis revealed that verbascoside was the most prevalent polyphenol (132.61 mg/g). The optimum extract provided a high antioxidant capacity through the measurements of FRAP (1462.17 μmol ascorbic acid equivalents (AAE)/g), DPPH (1108.91 μmol AAE/g), and H2O2 (1662.93 μmol AAE/g). Total carotenoids were measured at 499.61 μg/g, with ascorbic acid at 8.36 μg/g. Correlation analyses revealed a negative correlation of the latter compound with color coordinates. This study highlights the potential of lemon verbena leaves to be used in pharmaceutical and food industries.

Oxygen doi: 10.3390/oxygen3040027

Authors: Yoshio Nosaka

Addressing the global environmental problem of water splitting to produce hydrogen fuel by solar energy is receiving so much attention. In water splitting, the essential problem to solve is the development of efficient catalysts for oxygen production. In this paper, having the prospect for a practical application of photocatalysts to artificial photosynthesis, molecular mechanisms in the current literature are briefly reviewed. At first, recent progress in the function of the Mn cluster at the natural photosystem II is briefly described. The kinds of devices in which oxygen evolution reaction (OER) catalysts are used were designated: water electrolyzers, photoelectrodes, and photocatalysts. Some methods for analyzing molecular mechanisms in OER catalysis, emphasized by the FTIR method, are shown briefly. After describing common OER mechanisms, the molecular mechanisms are discussed for TiO2 and BiVO4 photoelectrodes with our novel data, followed by presenting OER co-catalysts of IrO2, RuO2, NiO2, and other metal oxides. Recent reports describing OER catalysts of perovskites, layered double hydroxides (LDH), metal–organic frameworks (MOF), single-atom catalysts, as well as metal complexes are reviewed. Finally, by comparing with natural photosystem, the required factors to improve the activity of the catalysts for artificial photosynthesis will be discussed.

Oxygen doi: 10.3390/oxygen3040026

Authors: Kiyoshi Sato Hiroyoshi Kawakami

Mitochondrial dysfunction significantly contributes to the pathogenesis and progression of chronic obstructive pulmonary disease (COPD). To treat mitochondrial dysfunction in COPD, novel drug delivery systems (DDS) are needed. In this review, we provide a brief overview of the current understanding of the factors in COPD and highlight the trends in novel nanocarriers/nanoparticles for targeting mitochondrial dysfunction. These drug-encapsulated nanoparticles are still in the early stages of clinical application but represent the most promising system for COPD therapy.

Oxygen doi: 10.3390/oxygen3040025

Authors: Konstantinos Kourtidis Michel Vorenhout

Atmospheric electric fields (AEFs) have recently been proposed to link to biogeochemical processes below the Earth’s surface by means of a charge separation. Despite the potential importance of such a process, up to now we almost completely lack the relevant measurements. Here, we extend the database with 2 months of concurrent soil redox and atmospheric electric field measurements. It appears that the changes that occur in the order of days in soil redox are at periods anticorrelated with the logarithm of the positive values of the AEF. However, weather conditions might be driving the anticorrelation rather than a direct link, as the synoptic weather conditions appear to influence soil redox. Soil redox does not respond to changes in the AEF that are of shorter duration, either minutes or several hours, except in some cases of very negative AEFs or very high field strengths in the presence of moderate rainfall. In such a case, the variation in soil redox could be associated with a mechanism that transfers charge to the ground or brings ions towards the ground’s surface. To reach firmer conclusions on the effect of the AEF on soil redox, we need to extend the range of collocated soil redox and AEF measurements so that they cover at least one year.

Oxygen doi: 10.3390/oxygen3040024

Authors: Ekaterina A. Yurchenko Olga O. Khmel Liliana E. Nesterenko Dmitry L. Aminin

Marine fungal metabolites often exhibit antioxidant activity, but their effects on the Keap1/Nrf2 cellular system are rarely studied, possibly due to insufficient isolated amounts. In this work, we used a bioinformatics approach to evaluate the ability of some promising cytoprotective compounds to bind Kelch domain of Keap1 protein, and thus inhibit its interaction with Nrf2. The molecular docking data suggested that gliorosein, niveoglaucin A, 6-hydroxy-N-acetyl-β-oxotryptamine, 4-hydroxyscytalone and 4-hydroxy-6-dehydroxyscytalone can form the hydrogen building with Arg415 or Arg483 amino acid residues of P1-P2 sub-pockets in the Nrf2 binding site of Keap1′s Kelch domain. These positions of the small molecules in the Kelch domain of Keap1 can inhibit the interaction of Keap1 with Nrf2 and enhance the nuclear translocation of Nrf2 from cytosol that can result in overexpression of relative genes. This assumption, based on virtual screening of a number of low molecular weight metabolites of marine fungi, makes them promising for further studies.

Oxygen doi: 10.3390/oxygen3030023

Authors: Daniel Rojas-Valverde Aldo A. Vasquez-Bonilla Rafael Timón Joan M. Feliu-Ilvonen Ismael Martínez-Guardado Guillermo Olcina

Background: Emerging evidence suggests that the outcomes of hypoxia training may be influenced by various factors, contingent upon the chosen method, such as chamber, tent, or mask. This study aimed to examine how different training methods influence the effects of Repeated Sprints in Hypoxia (RSH) training. Methods: Sixteen well-trained cyclists were divided into two groups, experimental (tent; n = 8) and control (mask; n = 8), and carried out eight RSH sessions for four weeks. Training sessions consisted of three bouts of high-intensity sprints using a cycle ergometer. The indoor ambient conditions (CO2, temperature, and humidity), performance variables (power and relative power output), arterial oxygen saturation, local muscle oxygen of vastus lateralis, heart rate, core temperature, and physiological variables (perception of effort) were measured in each training session. Results: The experimental group reported significantly higher CO2 (p < 0.001 ES = 0.784), humidity levels (p < 0.001 ES = 0.750), thermal discomfort (p = 0.003 ES = 0.266), dehydration (p 0.025 ES = 0.097), heart rate (p = 0.017 ES = 0.113), and lower muscle oxygen amplification (p = 0.002 ES = 0.181) than the control group. Conclusion: According to the responses observed, interval training performed under hypoxic conditions inside a chamber induces a more severe physiological response.

Oxygen doi: 10.3390/oxygen3030022

Authors: Maria Rosaria Miranda Vincenzo Vestuto Ornella Moltedo Michele Manfra Pietro Campiglia Giacomo Pepe

The pathogenesis of various gastrointestinal (GI) disorders, including gastritis, ulcers, inflammatory bowel disease (IBD) and cancer, can be linked to oxidative stress. It is known that reactive species carry out a crucial role in the genesis and progression of these pathologies; however, the contribution of ionic channels in their development is still under discussion. The function of ion channels in the gastrointestinal tract influences a variety of cellular processes. Acid-base balance, mucus layer, microbiota and mucosal blood flow are only some of the essential features for maintaining the mucosal integrity of the cellular barrier in the intestine, allowing for the preservation of proper permeability and ensuring tissue homeostasis. As the functional modulation of several ion channels is altered during oxidative stress conditions associated with gastrointestinal inflammation, this review focuses on contributing new insight into the roles of and the relationship between ion channels and oxidative stress in GI diseases. The association between ion channels and oxidative stress conditions could be used in diagnostics and the development of new pharmacological treatments for major gastrointestinal diseases.

Oxygen doi: 10.3390/oxygen3030021

Authors: Fritz Boehm Ruth Edge T. George Truscott

Molecular mechanisms based on photo-physical processes involving dietary carotenoids, their radicals, and the role of oxygen are discussed and used to suggest explanations of the poorly understood and often contradictory results related to mainly skin and vision. Differing and conflicting efficiencies of singlet oxygen reactions with carotenoids of biological importance are discussed in environments from ‘simple’ organic solvents to single He La cells. A range of free radical reactions with carotenoids, and the corresponding radicals of the carotenoids themselves, are compared and used to explain the switch from beneficial to deleterious processes involving dietary carotenoids and to unravel their differing functions; of particular interest is a possible role for vitamin C.

Oxygen doi: 10.3390/oxygen3030020

Authors: Verónica Miguel Alba Rojo

Chronic kidney disease (CKD) affects 10% of the population. Fibrosis is the hallmark of CKD, which is marked by the deposit of extracellular matrix (ECM). This response is the final outcome of an unbalanced reaction to inflammation and wound healing and can be induced by a variety of insults, including hypoxia. Vascular damage results in an impaired tissue oxygen supply, inducing immune cell infiltration, tubule injury and the activation of ECM-secreting myofibroblasts. In turn, tubulointerstitial fibrosis development worsens oxygen diffusion. Hypoxia-inducible factor (HIF) is the primary transcriptional regulator of hypoxia-associated responses, such as oxidative stress and metabolic reprogramming, triggering a proinflammatory and profibrotic landscape. In this review, we discuss hypoxia-driven reprogramming in CKD as well as potential therapeutic approaches to target chronic hypoxia.

Oxygen doi: 10.3390/oxygen3030019

Authors: Klemens Hocke

Atmospheric oxygen is produced and consumed by life on Earth, and the ozone layer protects life on Earth from harmful solar UV radiation. The research on oxygen in the Earth system is of interest to many different geoscientific communities, from paleoclimatology to aeronomy. I provide a brief overview of the research activities and their motivations. In situ measurements and remote sensing of atmospheric oxygen are described. The global evolution, distribution, and trends of atmospheric oxygen are discussed.

Oxygen doi: 10.3390/oxygen3030018

Authors: Dimitrios Palaiogiannis Theodoros Chatzimitakos Vassilis Athanasiadis Eleni Bozinou Dimitris P. Makris Stavros I. Lalas

The aim of this study was to evaluate the efficiency of successive extraction (using solvents of increasing polarity, namely hexane, ethyl acetate, acetone, ethanol, and water) of polyphenols from Cistus creticus L. The results were compared with the ones obtained from a single-solvent extraction (ethanol, water, and 50% ethanol: water). According to the results, each solvent used for extraction had a significant effect on the yield of extracted polyphenols and the antioxidant activity of the extracts. The highest extraction yield for successive extraction was achieved with ethanol (95.33 mg GAE/g), whereas a comparable amount could also be extracted with 50% ethanol: water mixture single-solvent extraction (96.51 mg GAE/g). The ethanolic and aqueous extracts had the highest antioxidant activity as indicated by their lowest IC50 values in the DPPH assay, specifically 350.99 μg/mL for ethanolic extract of successive extraction and 341.18 μg/mL for 50% ethanol: water mixture of single-solvent extraction, followed by the extract produced using acetone. However, the acetone extract contained more flavonoids than the other two extracts up to 28.03 mg QE/g. The results obtained were in line with those for the single-solvent extraction. It is concluded that using a range of solvents in succession is a more efficient way of extracting higher amounts of antioxidant compounds with varying antioxidant activity.

Oxygen doi: 10.3390/oxygen3020017

Authors: Despina Chatziharalambous Chrysoula Kaloteraki Panagiota Potsaki Olga Papagianni Konstantinos Giannoutsos Danai I. Koukoumaki Dimitris Sarris Konstantinos Gkatzionis Antonios E. Koutelidakis

Wheat-flour crackers represent a staple snack option, although they lack nutritional value. Agricultural by-products such as olive and grape seeds, cereals such as barley and legumes such as lupine and chickpea are rich in bioactive compounds; therefore, flours obtained from those could represent a better option for bakery products fortification. The purpose of the present study was the investigation of total phenolic content and antioxidant activity before and after the baking of wheat crackers enriched with 10–30% olive seed, 10–30% grape seed, 10–40% lupine, 10–30% barley and 20–60% and 80% chickpea flours and the evaluation of the predicted bioavailability after in vitro digestion of crackers demonstrating the highest values. Crackers and doughs were processed and analyzed using Folin–Ciocâlteu and ferric reducing antioxidant power (FRAP) assays, respectively. Crackers with the highest properties were subjected to in vitro gastrointestinal digestion. Baking resulted in an increase in total phenolics and antioxidant activity in the majority of crackers. Olive and grape seed flour crackers demonstrated the highest antioxidant properties. Following in vitro digestion, 30% olive seed flour crackers retained the majority of polyphenols and antioxidant activity. Crackers enriched with 30% olive seed flour could represent a healthy functional bakery snack regarding their increased antioxidant properties.

Oxygen doi: 10.3390/oxygen3020016

Authors: Beatriz Jávega Guadalupe Herrera Alicia Martínez-Romero José-Enrique O’Connor

Reactive oxygen species (ROS) are unstable and highly reactive molecular forms that play physiological roles in cell signaling and immune defense. However, when ROS generation is not properly balanced by antioxidant defenses, a pathological condition known as oxidative stress arises, in association with the onset and progression of many diseases and conditions, including degeneration and aging. Biomarkers of oxidative stress in biomedicine are actively investigated using different approaches, among which flow cytometry (FCM) and other single-cell, fluorescence-based techniques are most frequent. FCM is an analytical method that measures light scattering and emission of multiple fluorescences by single cells or microscopic particles at a very fast rate. To assess the specific role of ROS in oxidative stress, it is essential to detect and characterize these species accurately. However, the detection and quantitation of individual intracellular ROS and parameters of oxidative stress using fluorogenic substrates and fluorescent probes are still a challenge, because of biological and methodological issues. In this review, we present and discuss a series of complementary strategies to detect ROS or to focus on other endpoints of oxidative stress. Based on our results, we propose some recommendations for proper design of cytometric studies of oxidative stress in order to prevent or minimize the limitations and experimental errors of such approaches.

Oxygen doi: 10.3390/oxygen3020015

Authors: Monoj Kumar Das Neelu Singh Paulraj Rajamani

Globally, among different types of cancers, breast cancer is identified as the chief cause of mortality among females, and it is a challenge to find new effective treatment strategies with minimal side effects and increased efficacy. Plants are an integral part of the traditional indigenous healthcare system and are becoming the concrete source of new drug discovery. Thus, there is a need to obtain a scientific basis for applying traditionally used plants in cancer treatments that may harbour novel phytochemicals. Therefore, this study aims to investigate the antioxidant and anticancer potential of selected plants of ethnobotanical importance. Five plants of ethnobotanical importance were selected and screened to determine their antioxidant potential through various in vitro free radical scavenging assays (such as DPPH, ABTS, hydroxyl, and superoxide radical scavenging), ferric chelation, and total antioxidant potential, and the total phenolic and flavonoid content was estimated for the selected plants. In contrast, the anticancer potential of crude plant extracts was assessed using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) against different breast cancer (MCF-7, MDA-MB-231, and MDA-MB-435S) and hepatic cancer cell lines (HepG2), and human PBMCs (peripheral blood mononuclear cells) were used for toxicity studies. The MTT results showed that among all of the crude plant extracts (CAN = Etlingera linguiformis, SES = Sesbania grandiflora, LEX = Smilax ovalifolia, DES = Desmodium triflorum, and CA = Chenopodium album), it was CAN and LEX that showed the best cytotoxic potential on exposed breast cancer cell lines in contrast to SES, DES, and CA. In addition, at the selected dosages that were exposed to breast cancer cells, none of the extracts from any of the five plants showed any cytotoxicity against human PBMCs. Thus, the crude extracts can be explored further for chemopreventive and anticancer activity on murine models to understand their underlying mechanism for effective cancer management.

Oxygen doi: 10.3390/oxygen3020014

Authors: Steven B. Machek Dillon R. Harris Jeffery L. Heileson Dylan T. Wilburn Jeffrey S. Forsse Darryn S. Willoughby

Blood flow restriction (BFR) may become ineffective or potentially dangerous without sufficient standardization. The purpose of this investigation was therefore to (1) assess the viability of multiple sizes of a novel BFR cuff to determine arterial occlusion pressure (AOP) and (2) compare resting arterial, venous and calf muscle pump (cMP)-mediated blood flow between the aforementioned conditions and a commonly employed wide-rigid, tourniquet-style cuff. In randomized, counter-balanced, and crossover fashion, 20 apparently healthy males (18–40 years) donned a widely employed wide-rigid (WR) cuff, along with the largest (NE) and manufacturer-recommended sizes (NER) of a novel narrow-elastic cuff. Participants subsequently assessed AOP, as well as (at 80%AOP) arterial, venous, and venous cMP flow relative to baseline values via ultrasound. All analyses were performed at a significance level of p < 0.05. Analyses revealed a significant condition effect for AOP (p < 0.001; ηp2 = 0.907) whereby WR was significantly lower than both NE and NER; in addition, the latter two did not differ. Compared with baseline, there were no statistically significant differences between cuffs for either arterial or cMP-mediated blood flow. Unsurprisingly, no participants demonstrated venous blood flow at 80% AOP. These findings support the viability of a novel narrow-elastic BFR product, evidenced by consistent AOP acquisition and equivocal blood flow parameters.

Oxygen doi: 10.3390/oxygen3020013

Authors: Eva Tvrdá Július Árvay Michal Ďuračka Miroslava Kačániová

Propolis is a natural honeybee product, which is known for its beneficial pharmacological effects and use in traditional medicine. This study aspired to investigate the chemical and antioxidant properties of five propolis specimens, followed by the analysis of their in vitro impact on bovine spermatozoa vitality and oxidative profile. Semen samples from 10 breeding bulls were incubated in the absence or presence of 50 µg/mL propolis extracts, and selected sperm quality parameters including motility, mitochondrial activity, cAMP concentration, NAD+/NADH ratio, reactive oxygen species (ROS) and superoxide production were assessed at 2 h and 24 h. Sperm motion behavior and mitochondrial function were stabilized particularly in the presence of propolis collected from Hrabské and Litpovský Hrádok, Slovakia. At the same time, all propolis specimens acted as significant ROS quenchers and stabilized the oxidative milieu of the sperm cultures. Our data suggest that propolis may stabilize the mitochondrial function of spermatozoa while preventing excessive oxidative insults, thereby showing the potential to sustain the sperm motility of extended semen.

Oxygen doi: 10.3390/oxygen3020012

Authors: Andrew Nguyen Anjali B. Patel Ivelina P. Kioutchoukova Michael J. Diaz Brandon Lucke-Wold

Mitochondrial oxidative stress has been implicated in various forms of brain injury, both traumatic and non-traumatic. Due to its oxidative demand, the brain is intimately dependent on its mitochondrial functioning. However, there remains appreciable heterogeneity in the development of these injuries regarding ROS and their effect on the sequelae. These include traumatic insults such as TBIs and intracranial hemorrhaging secondary to this. In a different vein, such injuries may be attributed to other etiologies such as infection, neoplasm, or spontaneous hemorrhage (strokes, aneurysms). Clinically, the manner of treatment may also be adjusted in relation to each injury and its unique progression in the context of ROS. In the current review, then, the authors highlight the role of mitochondrial ROS in various forms of brain injury, emphasizing both the collective and unique elements of each form. Lastly, these narratives are met with the current therapeutic landscape and the role of emerging therapies in treating reactive oxygen species in brain injuries.

Oxygen doi: 10.3390/oxygen3010011

Authors: Tyler W. LeBaron Kinji Ohno John T. Hancock

Over 2000 publications including more than 100 human studies seem to indicate that humans have only recently benefited from or known about the medical effects of H2 within the past 15 years. However, we have unknowingly benefited from H2 since the dawn of time, from H2-producing bacteria to the use of naturally occurring hydrogen-rich waters. Moreover, the first writings on the therapeutic effects of H2 date to around 1793. Since then, papers appeared sporadically in the literature every few decades but never exploded until Ohsawa et al. again demonstrated hydrogen’s therapeutic effects in 2007. This landmark paper appears to have been the spark that ignited the medical interest in hydrogen. Although H2 was used in the 1880s to locate intestinal perforations, in the 1940s in deep sea diving, and in the 1960s to measure blood flow, H2 was largely viewed as biologically inert. This review highlights the history of hydrogen in the genesis/evolution of life and its medicinal and non-medicinal use in humans. Although hydrogen medicine has a long and erratic history, perhaps future history will show that, this time around, these 15 years of ignited interest resulted in a self-sustaining explosion of its unique medical effects.

Oxygen doi: 10.3390/oxygen3010010

Authors: Mary V. Raymond Taylor M. Yount Rebecca R. Rogers Christopher G. Ballmann

Red spinach extract is high in inorganic nitrate/nitrite (NO3/NO2) which has been shown to enhance vascular function, cognition, and physical performance. To date, there have been no investigations as to whether red spinach extract serves as an effective strategy to improve repeated exercise performance, which is applicable to many sports and activities. The purpose of this study was to investigate the effect of acute red spinach extract ingestion on repeated sprint ability in female athletes. Eleven Division I NCAA female athletes (ages 18–24) were recruited. In a double-blinded, randomized, counterbalanced design, participants completed two separate visits each with a different treatment: placebo (placebo; tomato juice) or red spinach extract (~400 mg nitrate). For each trial, participants consumed their respective treatment two hours before exercise. Following a warm-up, participants completed 3 × 15 s Wingate Anaerobic Tests (WAnTs) separated by 2 min of recovery. A capillary blood sample was obtained pre-exercise to measure NO2 concentrations. Performance outcomes, heart rate (heart rate), and rate of perceived exertion were measured following each WAnT. Blood lactate (La-) was obtained prior to exercise (PRE) and after the completion of the repeated sprints (POST). Each visit was separated by a minimal recovery period of 72 h. Mean power (p = 0.204), peak power (p = 0.067), heart rate (p = 0.151), and rate of perceived exertion (p = 0.379) were not significantly different between treatments. POST La- concentration was significantly higher with red spinach extract when compared to the placebo (p = 0.030). Furthermore, the fatigue index (p = 0.018) was significantly lower with red spinach extract. The results do not support the use of red spinach extract for the enhancement of power output during repeated anaerobic exercise. However, it may result in improved La-/H+ removal from the muscle, thereby combating physical fatigue.

Oxygen doi: 10.3390/oxygen3010009

Authors: Setsuko Komatsu Natsuru Nishiyama Azzahrah Diniyah

Flooding induces low-oxygen stress, which reduces plant growth. The activity of the γ-aminobutyric acid (GABA) shunt is crucial for plant stress adaptation, in which it acts by changing cytosolic pH, limiting reactive oxygen species production, regulating nitrogen metabolism, and bypassing steps in the tricarboxylic acid cycle. GABA accumulates under osmotic stress as well as flooding stress. To clarify the dynamic roles of GABA accumulation in wheat under flooding stress, biochemical and enzymatic analyses were performed using a plant-derived smoke solution (PDSS), which rescued wheat growth from flooding stress. Alcohol dehydrogenase abundance increased under flooding stress; however, under the same conditions, pyruvic acid content increased only following PDSS application. Glutamic acid content increased under flooding stress, but decreased following the application of PDSS after 2 days of flooding. Glutamate decarboxylase abundance and GABA content increased under flooding stress, and further increased after 1 day of application of PDSS. Succinyl semialdehyde dehydrogenase accumulated after 2 days of flooding. These results suggest that flooding stress increases GABA content along with the increase and decrease of glutamate decarboxylase and succinyl semialdehyde dehydrogenase, respectively. Additionally, PDSS increased GABA content along with the increase of glutamate decarboxylase abundance at the initial stage of application.

Oxygen doi: 10.3390/oxygen3010008

Authors: John T. Hancock Tyler W. LeBaron

In 2007 a paper in Nature Medicine sparked a new wave of interest in the use of molecular hydrogen (H2) for medical treatments. Since then there has been a flurry of papers looking at a range of medical aspects, from neurodegenerative disease to sports injuries. Several methods of application have been developed, including breathing the gas, or making a hydrogen-rich solution that can be ingested, or administered as saline. H2 treatments are deemed to be safe and can be used in agricultural practice as well as in the biomedical arena. However, the first studies to investigate the use of H2 in medicine were carried out by those interested in the use of a range of gases and how this may affect respiration in humans. Beddoes was published in 1793 and Cavallo in 1798, with Davy following shortly after in 1800. With so many papers now appearing on H2 in biological systems, it seems timely, and interesting, to revisit the early papers, to humbly remind us of what these pioneers of respiratory research did.

Oxygen doi: 10.3390/oxygen3010007

Authors: Igor A. Lavrinenko Gennady A. Vashanov José L. Hernández Cáceres Yury D. Nechipurenko

Oxygen binds to hemoglobin cooperatively, and a correct description of this binding is relevant not only for understanding the mechanisms of involved molecular processes but also for clinical purposes. Hill’s equation, derived over a hundred years ago, is still the simplest and most efficient way to perform this description. However, in terms of accuracy, it is inferior to Adair´s equation, which contains more parameters. We proposed to use a modified Hill equation and showed that it allows a more accurate description of the binding of oxygen to hemoglobin than Adair’s equation. At the same time, unlike Adair’s equation, our model retains the physical meaning given to the original Hill equation. We considered and analyzed the influence of the equation parameters on the course of the oxygenation curve and presented the relationship between the fitting parameters and other parameters derived from them in the form of a diagram-graph, which, in our opinion, simplifies the perception of these estimates and can be useful in solving a number of problems for which the traditional way of analyzing the degree of cooperative interaction was via the Hill equation. We suggest that the newly proposed parameter hmax introduced in our model should be regarded as crucial for a better description of the oxygenation curve.

Oxygen doi: 10.3390/oxygen3010006

Authors: Michal Szczepanczyk Lea Paul Tautgirdas Ruzgas Sebastian Björklund

Catalase is a key antioxidative enzyme, and a deficiency or malfunction of catalase is hypothesized to be related to various diseases. To investigate catalase activity, it is important to use reliable methods and experimental protocols enabling consistent fallouts. One major problem, however, is that the activity values obtained with different techniques and procedures can vary to a large extent. The aim of this work was to identify experimental conditions that provide similar catalase activity values with two different methods based on either spectrophotometry or chronoamperometry. The investigated parameters include the concentration of catalase and its substrate (H2O2), as well as the effect of deoxygenation of the catalase medium by nitrogen (N2). Within the frame of investigated conditions, we show that spectrophotometry is strongly affected by the catalase concentration, whereas chronoamperometry is shown to be more dependent on the substrate concentration. Deoxygenation leads to elevated catalase activity values in the case of chronoamperometry, whereas it shows no influence on the results obtained with spectrophotometry. In particular, in the case of low substrate concentrations (i.e., low catalase reaction rates), higher and more accurate results are obtained with deoxygenation in the case of chronoamperometry measurements due to minimized oxygen escape. The effect of deoxygenation, giving rise to elevated catalase activity values, however, is not statistically significant at high substrate concentrations, implying that the protocol can be simplified by excluding this step as long as the other parameters are optimized. Finally, by comparing the two methods at different experimental conditions, we identified protocols resulting in similar results, i.e., 10 mM H2O2 and catalase activity of 4–5 U/mL. Based on this work, improved consistency of catalase activity data obtained with different methodologies and in different labs is expected.

Oxygen doi: 10.3390/oxygen3010005

Authors: Kayla J. Steinberger Timothy D. Eubank

Low tissue oxygenation, termed hypoxia, is a characteristic of solid tumors with negative consequences. Tumor-associated macrophages (TAMs) accumulate in hypoxic tumor regions and correlate with worse outcomes in cancer patients across several tumor types. Thus, the molecular mechanism in which macrophages respond to low oxygen tension has been increasingly investigated in the last decade. Hypoxia stabilizes a group of hypoxia-inducible transcription factors (HIFs) reported to drive transcriptional programs involved in cell survival, metabolism, and angiogenesis. Though both tumor macrophage HIF-1α and HIF-2α correlate with unfavorable tumor microenvironments, most research focuses on HIF-1α as the master regulator of hypoxia signaling, because HIF-1α expression was originally identified in several cancer types and correlates with worse outcome in cancer patients. The relative contribution of each HIFα subunit to cell phenotypes is poorly understood especially in TAMs. Once thought to have overlapping roles, recent investigation of macrophage HIF-2α has demonstrated a diverse function from HIF-1α. Little work has been published on the differential role of hypoxia-dependent macrophage HIF-2α when compared to HIF-1α in the context of tumor biology. This review highlights cellular HIF-2α functions and emphasizes the gap in research investigating oxygen-dependent functions of tumor macrophage HIF-2α.

Oxygen doi: 10.3390/oxygen3010004

Authors: Valentina Membrino Alice Di Paolo Sonila Alia Giulio Papiri Arianna Vignini

Autism spectrum disorder (ASD) is a multifaceted neurodevelopmental disorder that comprises a complex aetiology, where a genetic component has been suggested, together with multiple environmental risk factors. Because of its increasing incidence in the paediatric population and the lack of successful curative therapies, ASD is one of the most puzzling disorders for medicine. In the last two decades and more, the relationship between oxidative stress (OS) and ASD has been recurrently documented. For this reason, the former hypothesis, according to which reactive oxygen and nitrogen species (ROS and RNS) play an important role in ASD, is now a certainty. Thus, in this review, we will discuss many aspects of the role of OS in ASD. In addition, we will describe, in the context of the most recent literature, the possibility that free radicals promote lipid peroxidation, as well as an increase in other OS biomarkers. Finally, we will outline the possibility of novel nutritional interventions aimed at counteracting ROS production in people with ASD. In fact, new strategies have investigated the possibility that ASD symptoms, as well behavioral anomalies, may be improved after interventions using antioxidants as supplements or included in foods.

Oxygen doi: 10.3390/oxygen3010003

Authors: Oxygen Editorial Office Oxygen Editorial Office

High-quality academic publishing is built on rigorous peer review [...]

Oxygen doi: 10.3390/oxygen3010002

Authors: Ekaterina A. Golenkina Svetlana I. Galkina Galina M. Viryasova Galina F. Sud’ina

Synthetic CpG oligonucleotides are promising components of immunomodulatory drugs for the treatment and prophylaxis of infectious diseases, cancers, and allergies. Phosphorothioate modification stabilizes these compounds, contributing to the achievement of a clinical effect, but at the same time changes their immunomodulatory properties. We used the diffusible fluorescent dye dihydroethidium and the non-diffusible 6-carboxy-2′,7′dihydrochlorofluorescein diacetate and cytochrome c probes to demonstrate that it is the phosphorothioate backbones that determine the pronounced nonspecific pro-oxidant effect of CpG ODN on neutrophils. At the same time, as was shown using diaminofluorescein diacetate, the potentiation of nitric oxide synthesis in these leucocytes by CpG ODN class A strictly depends on the presence of CpG motifs and a palindromic “hairpin”. The results obtained will contribute to a more complete understanding of the physiological action of therapeutic agents based on synthetic CpG oligonucleotides.

Oxygen doi: 10.3390/oxygen3010001

Authors: Ekaterina A. Savinova Tatiana A. Salimova Elena V. Proskurnina Ivan V. Rodionov Olga A. Kraevaya Pavel A. Troshin Larisa V. Kameneva Elena M. Malinovskaya Olga A. Dolgikh Natalia N. Veiko Svetlana V. Kostyuk

The development of novel biologically active nanopharmaceuticals is a topical problem of medicine. Water-soluble fullerene derivatives are of particular interest due to their ability to regulate intracellular metabolism of reactive oxygen species (ROS) by direct oxidation or effects on oxidative and signaling enzymes. Here, we studied the effect of a water-soluble chlorine-containing derivative of C60 fullerene on human embryonic lung fibroblasts. MTT tests, intracellular ROS visualization, detection of the ROS-associated gene and protein expression, repair, cell proliferation and cell cycle regulation, and quantitation of oxidative DNA damage were used. Within the first three hours after exposure, antioxidant effects were revealed. Later, oxidative damage appeared. Thus, the studied compound had an ambiguous effect on ROS metabolism associated with a switch in the regulatory effect, which must be taken into account when assessing its biological activity and toxicity.

Oxygen doi: 10.3390/oxygen2040042

Authors: Manoel Rios Victor Machado Reis Susana Soares Daniel Moreira-Gonçalves Ricardo J. Fernandes

The current study aimed to evidence the strengths and weaknesses of two indirect methods for assessing the anaerobic alactic contribution to a specific CrossFit® workout. Thirty experienced crossfitters performed the Fran workout at maximal intensity, and ventilatory data were collected during the recovery period using a telemetric portable gas analyser to assess the oxygen uptake (VO2) of the off-kinetics fast component (Anarecovery). The kinetics of maximal phosphocreatine splitting (AnaPCr) were determined based on the literature. No differences between the two methods were observed (31.4 ± 4.0 vs. 30.4 ± 4.1 kJ for Anarecovery and AnaPCr, respectively). Despite the existence of some caveats (e.g., errors derived from a delay at the onset of VO2 recovery and the assumption of given values in the concentration of phosphocreatine per kilogram of wet muscle, respectively) in both methods, the data indicate that they yield similar results and allow for estimations of alactic energy contribution from a short-duration and high intensity CrossFit® routine. The current data contributes to CrossFit® workout evaluations and training strategies, helping researchers to evaluate crossfitters more accurately. The advantage of the two methods used in the current study is that they are non-invasive, which differs greatly from muscle biopsies.

Oxygen doi: 10.3390/oxygen2040041

Authors: Vincenzo Zanon Silvia Magri Giulia Bonera Enrico Camporesi

Gas embolism is a potentially fatal occurrence in which bubbles are introduced into the arterial/venous circulation. A multifocal ischemia could be the life-threatening scenario of that and occurring after diving-related activities, or pulmonary barotrauma, or even iatrogenic procedure capable to cause an accidental introduction of gas into the vasculature. The case here reported concerns the good outcome of one of these rare occurrences thanks to a prompt diagnosis and proper management of the ongoing gaseous lesion. Unfortunately, it remains ethically and technically complex to consider feasible Randomized Clinical Trials (RCTs) in hyperbaric medicine in general, and even more so in this type of eventuality. We are happy to share this further favorable result as we believe it is just thanks to growing documented clinical evidence that now anyone, if ever had to be suffering from gas embolism, in presence of a RCT would widely prefer to be included in the arm that can take advantage of oxygen hyperbaric (HBO) therapy.

Oxygen doi: 10.3390/oxygen2040040

Authors: Maria Cristina Porcu Angela Fadda Daniele Sanna

The beers’ lag time measured with the PBN (N-t-Butyl-α-phenylnitrone) spin trapping experiments coupled with EPR spectroscopy is related to their antioxidant capacity and shelf life. The effect on the lag time of the alcohol content of the beer (starting values, 9 and 13%) and PBN concentration (50 or 200 mM) was analyzed on three samples, a pilsner, a strong lager, and a blonde Ale heated at 60 °C to trigger the production of the 1-hydroxyethyl radical. The lag time was determined only for the strong lager beer, with the values depending on the experimental conditions, being higher when PBN had a lower concentration. The antioxidant activity of the three beers gave the following values: 0.9089 mL pilsner beer/mg DPPH, 0.8510 mL strong lager beer/mg DPPH, and 0.7184 mL blonde Ale beer/mg DPPH, indicating that the unsuccessful determination of the lag time was not due to stale beers. The EPR intensity of the PBN adduct after 150 min (I150) and the area under the curve (AUC) were also measured and related to the oxidative stability of beers. Further studies are needed to verify the influence of the heating temperature in samples that do not show a lag time at 60 °C.

Oxygen doi: 10.3390/oxygen2040039

Authors: Antony V. Samrot Sanjay Preeth Ram Singh Rajalakshmi Deenadhayalan Vinod Vincent Rajesh Sathiyamoorthy Padmanaban Kamalakannan Radhakrishnan

The usage of nanoparticles became inevitable in medicine and other fields when it was found that they could be administered to hosts to act as oxidants or antioxidants. These oxidative nanoparticles act as pro-oxidants and induce oxidative stress-mediated toxicity through the generation of free radicals. Some nanoparticles can act as antioxidants to scavenge these free radicals and help in maintaining normal metabolism. The oxidant and antioxidant properties of nanoparticles rely on various factors including size, shape, chemical composition, etc. These properties also help them to be taken up by cells and lead to further interaction with cell organelles/biological macromolecules, leading to either the prevention of oxidative damage, the creation of mitochondrial dysfunction, damage to genetic material, or cytotoxic effects. It is important to know the properties that make these nanoparticles act as oxidants/antioxidants and the mechanisms behind them. In this review, the roles and mechanisms of nanoparticles as oxidants and antioxidants are explained.