Search Results (968)

Glucose is the principal energy substrate for the brain. Hypo- and hyperglycemic episodes frequently occur in senescent people, contributing to functional and structural impairment of brain neurons and causing cognitive deficits in this population. In this study, we investigate whether long-term changes in the extracellular concentration of glucose affect viability and transmitter functions of septum-derived SN56 cholinergic neuronal cells through alterations in acetyl-CoA availability. Cells with low cholinergic expression (NCs) and cAMP/retinoic acid-induced high cholinergic expression (DCs) were investigated. Hypoglycemia brought about similar (approximately 20–30%) decreases in pyruvate dehydrogenase complex (PDHC) and ATP-citrate lyase (ACLY) activities and a 65% decline in lactate dehydrogenase (LDH) activity in NCs and DCs. Choline acetyltransferase (ChAT) and LDH activities in DCs were about 3–8 and 1.7–2.4 times higher than in NCs over the tested glucose concentration range, respectively. DCs appeared to be more resistant than NCs to hypoglycemia, as evidenced by lower glucose IC₅₀ values for cell count and intracellular LDH activity. On the other hand, some of functional properties of DCs, such as the cholinergic phenotype and their plasma membrane functions (trypan blue exclusion, TB+), were found to be more sensitive to hypoglycemia than those of NCs, as demonstrated by the higher IC₅₀ for glucose in DCs. Acetyl-CoA levels in DCs were 40% lower than in NCs, and decreased by about 25% with increasing hypoglycemia in both cell types. The cytotoxic effects of amyloid-β_25–35 (Aβ) and sodium nitroprusside (SNP; NO generator) were also tested. In 25 mM glucose medium, these toxic compounds exerted greater detrimental effects on DCs than on NCs. In contrast, in 1 mM glucose, more evident cytotoxicity of SNP and Aβ was observed in NCs. These data suggest that the higher rate of glycolysis in differentiated cholinergic septal neurons may be a protective mechanism against hypoglycemia. Full article

Epidermal hyperinnervation is a major cause of intractable itch in barrier dysfunction conditions such as atopic dermatitis. Keratinocyte-derived semaphorin 3A (Sema3A) suppresses epidermal hyperinnervation, but its expression is markedly reduced in barrier-disrupted skin. Although konjac ceramide (kCer) has been reported to act as a Sema3A-like ligand, the mechanisms by which it regulates Sema3A expression in keratinocytes remain unclear. Normal human epidermal keratinocytes (NHEKs) were treated with kCer, konjac glucosylceramide (kGlcCer), or C24 ceramide. Sema3A mRNA and protein levels were assessed by quantitative real-time PCR and enzyme-linked immunosorbent assay, respectively. The involvement of intracellular signaling was examined using mitogen-activated protein kinase (MAPK) inhibitors, activator protein-1 (AP-1) inhibitors, retinoic acid-related orphan receptor alpha (RORα) inverse agonists, and siRNAs targeting c-Jun, c-Fos, and RORα. kCer induced Sema3A expression in NHEKs more potently than kGlcCer or C24 ceramide and promoted Sema3A protein secretion. Pharmacological inhibition or genetic knockdown of MEK1/2, JNK, AP-1 components, or RORα significantly attenuated kCer-induced Sema3A expression, indicating involvement of the MAPK/AP-1 signaling axis and RORα. kCer upregulates Sema3A expression in human keratinocytes through MAPK/AP-1 signaling and RORα, suggesting it may represent a promising antipruritic agent for epidermal hyperinnervation associated with skin barrier dysfunction. Full article

The innate immune system, particularly the retinoic acid-inducible gene I (RIG-I)-like receptor (RLR) signaling pathway, is a major early defense barrier against influenza A virus infection. However, excessive immune responses can trigger lethal cytokine storms and severe immune-mediated pathology. In this study, we performed a genome-wide CRISPR/dCas9 gene activation screen in human lung epithelial (A549) cells by using an A/Puerto Rico/8/1934 (H1N1) reporter virus, and identified the ubiquitin-specific protease USP17L13 as a novel negative regulator of innate immunity that promotes influenza virus replication. Overexpression of USP17L13 significantly enhanced the replication of multiple subtypes of influenza viruses in A549 cells, including a human pandemic H1N1 virus, seasonal H3N2 viruses, as well as a globally circulating clade, 2.3.4.4b, of the highly pathogenic avian H5N1 virus. Transcriptomic analysis demonstrated that USP17L13 suppresses host antiviral defenses by downregulating nuclear factor kappa B (NF-κB) signaling and arachidonic acid metabolism, while upregulating pathways associated with ribosomal translation and oxidative phosphorylation to facilitate viral production. Mechanistically, USP17L13 attenuates the host interferon (IFN) response by promoting the degradation of the key viral RNA sensors, RIG-I, and melanoma differentiation-associated protein 5 (MDA5). Further analysis revealed that USP17L13 is inducible by type I and type II interferons as well as inflammatory cytokines, suggesting that it may act as a negative-feedback regulator to limit excessive inflammation. Collectively, our findings identify USP17L13 as a previously unrecognized proviral host factor and provide new insight into how host deubiquitinases shape influenza virus-host interactions, with potential implications for host-directed approaches to controlling excessive inflammation during viral infection and improving influenza vaccine production. Full article

Background/Objectives: Type 2 diabetes mellitus (T2-DM) is a continuing national and global health challenge. Retinoic acid (RA), the major transcription-regulating ligand, plays a critical role in energy metabolism, and pancreatic β-cell homeostasis. However, human data linking circulating RA levels to T2-DM and its clinical outcomes are sparse and inconsistent. In this ethically approved cross-sectional study of consented hospital-diagnosed adult T2-DM patients (n = 292) and matched healthy controls (n = 64), variation in plasma RA levels and its relationship with disease and patient characteristics were investigated. Methods: RA concentrations assayed via specific ELISA were related to glycemic control indices [fasting blood glucose (FBG) and HbA1c], the triglyceride–glucose ratio for insulin resistance (TyG-IR), treatment modalities, and complications derived from patients’ medical records. Results: RA concentrations were substantially lower in patients with T2-DM (mean ± SD 2.63 ± 1.54 ng/mL) than in controls (5.21 ± 4.3 ng/mL; p < 0.001). Within the diabetic cohort, RA was inversely correlated with indices of glycemic dysregulation and insulin resistance. Plasma RA exhibited strong discriminatory performance for distinguishing diabetic patients from healthy adults. Its AUC is 0.870 (p < 0.0001 and 95% CI = 0.832–0.902) with a sensitivity of 79.7% and a specificity of 81.3%, at an optimal cutoff of ≤3.061 ng/mL. Conclusions: Circulating RA is associated with metabolic perturbations that define T2-DM, and therefore is promising as a clinically useful biomarker. It may reflect pathophysiological processes linking nutrient signaling, energy handling and β-cell function in T2-DM that merit further evaluation. Full article

Regulation of all-trans retinoic acid (ATRA) signaling is crucial to early embryonic development. Embryonic stem (ES) cell-derived gastruloids mimic normal development in response to the Wnt/β-catenin agonist CHIR9901, and this study has examined the importance of the activities of RAR (retinoic acid receptor) α and γ to gastruloid development. Expression of retinoic acid receptor (RAR)γ within developing gastruloids was spatially restricted to primitive cells that co-expressed ES cell and early progenitor cell markers, i.e., Nanog, Sox2, and Oct4. In contrast, RARα expression was ubiquitous. mRNAs for the key enzymes involved in ATRA synthesis (Aldh1a2) and degradation (Cyp26a1) were not seen in cells that expressed RARγ. Treatment of ES cell-derived gastruloids with physiologically relevant (10 nm) levels of ATRA or with a highly selective RARγ agonist blocked normal developmental processes, preventing symmetry-breaking and axial elongation. This was not seen following treatments with an RARα agonist, where there was a tendency for enhanced axial elongation. Brachyury (TBXT) immuno-positive cells localized in the posterior end of elongated gastruloids in control- and RARα agonist-treated cultures, with Sox2 immuno-positive cells seen more widely, whilst both TBXT and Sox2 immuno-positive cells were randomly distributed throughout ATRA- and RARγ agonist-treated gastruloids. Concurrent treatment of gastruloids with 10 nm ATRA and 100 nm of an RARγ antagonist partially abrogated the ATRA-mediated block to axial elongation. Conversely, 10 nm RARγ antagonist treatments were associated with the formation of multi-axis gastruloid elongations, with comparatively little effect seen after treatments with an RARα antagonist. These findings reveal that RARγ plays a crucial role in the development of embryonic tissues. Full article

Smooth muscle (SM) dysfunction contributes to several pathological conditions, including atherosclerosis; current treatment strategies often fail to restore functional contractility. Adipose-derived stem cells (ADSCs) offer a promising cell source for regenerative medicine due to their accessibility and multipotency. Their differentiation into smooth muscle cells (SMC) is commonly driven by biochemical cues such as retinoic acid and transforming growth factor β; however, supporting this process with additional, non-invasive stimuli may enhance outcomes. Photobiomodulation (PBM) has emerged as a potential modulator of cellular metabolism, mitochondrial function and lineage commitment; however, its role in ADSCs to SMC differentiation remains insufficiently defined. ADSCs were irradiated with green (525 nm), near-infrared (825 nm) or dual wavelengths at 5 J/cm² and 10 J/cm² alongside the growth factors. Proliferation, cytotoxicity, mitochondrial membrane potential, collagen production, migration and smooth muscle marker expression were assessed. PBM induced a fluence-dependent biphasic response. 5 J/cm² fluences enhanced proliferation, mitochondrial activity, collagen deposition and organized SMC marker expression, whereas 10 J/cm² fluences lowered proliferation and membrane potential, reduced collagen and increased migration. PBM at 5 J/cm², especially greenlight, most effectively promoted ADSCs’ progression towards a SMC-like phenotype, with features consistent with a more contractile-like state. Full article

The efficacy of the host antiviral response against Influenza A virus (IAV), a leading cause of global pandemics, hinges upon the rapid recognition of the pathogen and the prompt activation of immune mechanisms. Nevertheless, the epigenetic landscape that orchestrates this antiviral response remains largely elusive. Here, we identify histone demethylase JMJD2D as a critical regulator in defense against IAV infection. A significant upregulation of JMJD2D expression was observed clinically in response to IAV infection, indicating that JMJD2D may play a role in regulating IAV infection. Indeed, JMJD2D-deficient mice exhibit increased susceptibility to IAV, characterized by elevated viral loads, severe lung tissue damage, and reduced survival rates, suggesting that JMJD2D plays an essential role in defense against IAV infection. Consistently, knockdown or pharmacological inhibition of JMJD2D in lung cells suppressed IAV replication and the IAV-triggered innate immune response. Mechanistically, JMJD2D suppressed IAV infection by removing H3K9me3 at the promoter region of retinoic acid inducible gene-I (RIG-I) and cooperating with NF-κB to enhance the expression of RIG-I, a critical sensor for IAV RNA. This study identifies JMJD2D as an epigenetic rheostat that governs RIG-I-mediated antiviral signaling, highlighting its potential as a therapeutic target for mitigating severe IAV infection. Full article

Heterotopic ossification (HO), the pathological formation of mature bone in non-skeletal soft tissues (e.g., muscles, tendons), severely impairs patient mobility and quality of life. Despite decades of research, systematic analysis of signaling networks across HO subtypes (acquired traumatic HO, hereditary Fibrodysplasia Ossificans Progressiva (FOP), Progressive Osseous Heteroplasia (POH)) remains insufficient, and clinical therapies suffer from high recurrence and severe side effects. This review synthesizes recent advances in HO pathogenesis: FOP involves gain-of-function activin A receptor type I (ACVR1) mutations (mostly R206H), disrupting bone morphogenetic protein (BMP)/Activin A signaling; POH arises from paternal guanine nucleotide-binding protein, alpha-stimulating activity polypeptide (GNAS) loss-of-function mutations, derepressing Hedgehog signaling via reduced cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) activity; tHO features trauma-induced inflammation/hypoxia activating BMP/transforming growth factor–beta (TGF-β) pathways. Key signaling crosstalk (e.g., BMP-Yes-associated protein (YAP)-Indian hedgehog (IHH)) is integrated, and novel therapies (ACVR1 inhibitors, Activin A antibodies, retinoic acid receptor gamma (RARγ) agonists, adeno-associated virus (AAV)-mediated ACVR1 silencing) are highlighted, with emphasis on subtype-specific efficacy. A stratified, mechanism-based HO management framework is proposed, aiming to accelerate precision therapy development and advance understanding of aberrant tissue regeneration. Full article

The World Health Organization (WHO) defines infertility as the inability of a couple to conceive after at least 12 months of regular, unprotected sexual intercourse. The male factor appears to be contributing, solely or in combination with other causes, to approximately 50% of all infertility cases. Several etiological factors of male infertility have been identified; however, the exact molecular mechanisms underlying sperm dysfunction are not yet fully understood. Aldehyde dehydrogenases (ALDHs) are multifaceted metabolic enzymes that catalyze the detoxification of several aldehydes, thus acting as antioxidants, while they regulate additional homeostatic functions by contributing to retinoic acid (RA) synthesis. Consequently, they have been identified as crucial factors in various pathogenetic mechanisms. ALDHs hold physiological roles in the testis through supporting the Sertoli cell function, the steroidogenesis in Leydig cells, and the maintenance of sperm integrity. Current evidence supports that dysregulation of specific ALDHs isoforms could be associated with disrupted testicular cell function, including oxidative imbalance and altered RA synthesis. These irregularities could interfere with germ cell development and, subsequently, contribute to decline in reproductive function. In this paper, we are reviewing the role of ALDHs in male reproduction and how their dysregulation could be implicated in male infertility. Unraveling the mechanisms underlying the association of ALDHs with male reproductive function could hold clinical interest regarding the development of novel approaches for enhancing male fertility. Full article

Purpose: To study the time course of the differentiation process and its regulatory networks in primary limbal epithelial cells (pLECs) using serum-free, low calcium Keratocyte growth medium 3 (KGM3) and CnT-2D differentiation medium. Methods: pLECs were isolated from corneoscleral rims from healthy donors and cultured in serum-free low calcium (0.06 mM Ca²⁺) KGM3. Differentiation was induced by supplementation with CnT-2D differentiation medium, while control cells were maintained in low-calcium KGM3 medium. Gene and protein expression analyses were performed using qPCR and Western blotting, respectively, at 72 h and at 5, 7, 10, and 14 days post-supplementation to determine the optimal time course of differentiation induction. Results: CnT-2D differentiation medium supplementation resulted in a significant upregulation of differentiation-associated markers, including desmoglein 1 (DSG1), paired box domain 6 (PAX6), keratin 3 (KRT3), fatty acid binding protein 5 (FABP5), cellular retinoic acid binding protein 2 (CRABP2), alcohol dehydrogenase 7 (ADH7), aldehyde dehydrogenase 1A1 (ALDH1A1), with the most pronounced changes observed at day 10 post-supplementation (p ≤ 0.05). Conclusions: CnT-2D differentiation medium effectively initiates differentiation of limbal epithelial cells in vitro. The gradual increase in the expression of key differentiation markers, including DSG1, KRT3, and PAX6, indicates that CnT-2D medium successfully induces differentiation in 2D cultured primary limbal epithelial cells. However, subcellular localization of these markers, epithelial barrier function, and differentiation in 3D models were not assessed and remain to be investigated. Full article

The present review discusses vitamin A/retinoid metabolism as a cross-organ axis in which hepatic clock-dependent retinoid handling may affect immune clock gene expression through the stimulation of retinoic acid 6–Janus kinase 2–signal transducer and activator of transcription 5 signaling, potentially promoting pro-inflammatory monocyte states. We further highlight mechanosensory signaling as a second convergent layer that integrates hemodynamic forces with tissue microenvironmental cues. Among these pathways, G protein-coupled receptor 68, a proton- and flow-sensitive G protein-coupled receptor, is discussed as a representative druggable node linking mechanical and inflammatory signaling in chronic kidney disease-associated cardiac injury. Finally, we outline potential therapeutic directions, including (i) circadian alignment/chronopharmacology, (ii) modulation of retinoid metabolism and signaling, and (iii) targeted inhibition of primary immune and mechanosensory effectors. Full article

The SH-SY5Y cell line is widely used as an in vitro model for pharmacological and molecular investigations of Parkinson’s disease (PD). The use of SH-SY5Y cells in PD research critically relies on their ability to differentiate into a mature, post-mitotic, dopaminergic (DAergic) neuronal phenotype. However, SH-SY5Y cells are inherently heterogeneous since they are firstly catecholaminergic cells and may express diverse phenotypic markers besides the DAergic ones. These properties seem to be determined by the differentiation protocol that is employed, thus meaning it is crucial to obtain proper cell types. This systematic review aims to discuss the main differentiation protocols used in PD research over the last 30 years. They include inducers such as retinoic acid (RA), the phorbol ester TPA, and the BDNF. Among the 514 studies that were screened, 249 employed these inducers. Then, we quantitatively report the ability of these protocols to differentiate SH-SY5Y cells in mature DAergic neurons, evaluating morphology, differentiation markers, and DAergic markers among the studies that specifically compared differentiated to undifferentiated SH-SY5Y cells (61 studies over 249). As our research shows, despite the highest usage of the RA differentiation protocol, the combination of RA with the BDNF inducer seems to increase the expression and the acquisition of a DAergic phenotype. Nevertheless, during this analysis, some limitations emerged, highlighting the intrinsic phenotypic heterogeneity of these cells, thereby limiting their suitability according to the specific biological question under investigation. A deep investigation into the literature about the molecular phenotypic features of differentiated SH-SY5Y cells may eventually help us to understand the advantages and disadvantages of each protocol that was employed, and adequately set experiments around the PD research. Full article

Graphene oxide (GO)–lipid hybrid nanostructures represent a promising class of multifunctional platforms for drug delivery and fluorescence-guided cellular imaging. In this study, we developed a graphene oxide-supported lipid bilayer system composed of rhodamine-labeled phosphatidylcholine (POPC-Rhod) for the delivery of the repurposed antispasmodic drug alverine citrate (ALV) to neuroblastoma cells. The hybrid nanostructures were assembled using two drug-loading strategies and characterized by UV–Vis spectroscopy, fluorescence analysis, dynamic light scattering, and atomic force microscopy to evaluate molecular interactions, vesicle size distribution, and nanomechanical properties. In vitro studies were performed using human neuroblastoma SH-SY5Y cells and their retinoic acid-differentiated neuronal-like counterparts. Confocal microscopy confirmed efficient cellular uptake of the fluorescent lipid–graphene hybrids, while viability and mitochondrial reactive oxygen species assays revealed differentiation-dependent cellular responses. ALV-loaded hybrids induced cytotoxic effects in proliferating neuroblastoma cells, whereas differentiated neuron-like cells exhibited greater tolerance and, at moderate concentrations, preserved viability despite increased oxidative stress. These findings demonstrate that graphene oxide–lipid hybrids can act as fluorescence-traceable drug delivery platforms and highlight the potential of alverine as a candidate for repurposing in neural cancer models. The system presented here provides a proof-of-concept framework for the development of multifunctional nanocarriers integrating therapeutic delivery with imaging capabilities. Full article

Circadian disruption represents a global health issue associated with cardiometabolic diseases, sleep disturbances, and mood disorders, driven by a pathophysiological network including clock gene dysregulation and impaired melatonin synthesis. Vitamin D exerts pleiotropic effects on metabolic regulation, immune function, neurotransmission, and possibly circadian synchronization. Emerging evidence suggests that vitamin D and its hydroxyderivatives modulate clock gene expression, influence transcriptional regulators such as retinoic acid receptor-related orphan receptors and REV-ERBs, and interact with melatonin synthesis and signaling. Vitamin D deficiency has been associated with metabolic syndrome, impaired sleep quality, and depression. Although interventional studies yield heterogeneous results, higher vitamin D status may confer protective metabolic and neurobehavioral effects. This review summarizes current evidence on the role of vitamin D in circadian disruption and evaluates its potential therapeutic relevance in circadian–metabolic dysregulation. Full article