Search Results (366)

Oxidative stress and mitochondrial dysfunction are heavily implicated in all forms of Parkinson’s disease; however, antioxidant administration has largely failed in clinical trials. Among the likely causes of failure are brain bioavailability and cellular redox state. We have administered two manganese porphyrin compounds with different bioavailability, MnTE-2-PyP⁵⁺ and MnTnBuOE-2-PyP⁵⁺, to parkin-null Drosophila food and found that the more bioavailable one, with higher brain and mitochondrial availability, MnTnBuOE-2-PyP⁵⁺, improves developmental deficits and motivated behavior in female flies. Using highly sensitive redox reporters, we further found that MnTnBuOE-2-PyP⁵⁺ reduces hydrogen peroxide levels in mitochondria of dopaminergic neurons that are functionally homologous to the mammalian substantia nigra and facilitates motivated behavior in female flies. Interestingly, both compounds reduce an oxidative stress marker at the whole-brain level and extend lifespan in control flies. Neither compound improves lifespan in parkin-null flies. Thus, additional studies, changing the timing and/or dosage of compound administration, are warranted. Full article

Parkinson’s disease (PD) is a common neurodegenerative disorder caused by progressive loss of dopaminergic neurons in the substantia nigra and the presence of Lewy bodies. While PD is most recognized by its motor symptoms (resting tremor, rigidity, bradykinesia, and postural instability), cognitive decline (CD) may become apparent as PD progresses, leading to Parkinson’s disease dementia (PDD). Type 2 diabetes mellitus (T2DM) and insulin resistance (IR) are risk factors for dementia, especially Alzheimer’s disease; however, their influence on dementia in PD is underexplored. Therefore, we sought to determine the effect of T2DM and IR on dementia in PD. A systematic search of articles from 2005 to March 2025 was undertaken using Embase, PubMed, Scopus, Web of Science, and citation searching. Case–control, cross-sectional, longitudinal, and non-human population studies assessing cognitive outcomes in individuals with PD, with and without T2DM and IR, were included (PROSPERO registration number CRD420251013367). In total, 27 studies met the inclusion criteria, with clinical sample sizes ranging from 23 to 544,162 participants. Among the 23 clinical studies, 15 identified T2DM as a contributor to cognitive decline (CD) in PD, and 4 specifically examined insulin resistance (IR). Elevated HbA1c was consistently associated with poorer cognitive performance and increased risk of Parkinson’s disease dementia (PDD); HbA1c ≥ 7% independently predicted cognitive impairment (OR = 4.25, 95% CI: 1.59–11.34). Vascular and inflammatory markers, including elevated LDL-C, fibrinogen, and hs-CRP, further exacerbated CD. MoCA and MMSE scores were the most common cognitive measures, consistently showing worse outcomes in PD patients with T2DM. Preclinical studies supported these associations, showing that high-fat-diet-induced T2DM and IR aggravated dopaminergic neuronal loss by 38–45%, increased α-synuclein by 35%, and heightened microglial activation, providing mechanistic evidence for the observed clinical associations. This systematic review, the first to examine the impact of T2DM and IRs on the occurrence and advancement of CD in PD patients, demonstrates a possible association between the two. However, these results demonstrate the need for larger sample sizes and the inclusion of additional clinical variables, such as HbA1c levels and pharmacological interventions, providing further information about the link between metabolic dysfunction and CD in PD. To further strengthen this link, longitudinal studies with systematic follow-ups are essential to establish causal links and avoid misdiagnosis in clinical practice. Full article

Pituitary pars intermedia dysfunction (PPID) is a common, slowly progressive, neurodegenerative disorder of the older horse. Oxidative damage to the hypothalamic periventricular neurons results in loss of dopaminergic inhibition of the pars intermedia region of the pituitary gland. Consequently, there is increased production of the pro-opiomelanocortin (POMC)-derived hormones normally produced by this region, as well as initial melanocyte hypertrophy and hyperplasia, followed by adenomatous change. Clinical signs that are highly suggestive of the disease are generalised and regional hypertrichosis and delayed/abnormal coat shedding. Numerous clinical signs provide a moderate clinical suspicion, including hyperhidrosis, abnormal fat distribution/regional adiposity, epaxial muscle atrophy/loss of topline, laminitis, weight loss, recurrent infections, behavioural changes/lethargy, polyuria and polydipsia, a pot-bellied appearance, bulging supraorbital fat pads, reduced wound healing, lordosis and infertility. In all animals, a diagnosis of PPID is made based on the signalment, clinical signs and results of further diagnostic tests, with age being a crucial factor to consider. Currently recommended further diagnostic tests are measurement of basal adrenocorticotrophic hormone (ACTH) concentrations (all year) and evaluation of the ACTH response to thyrotrophin-releasing hormone (TRH) using seasonally adjusted references intervals (non-autumn). Animals should also be tested for insulin dysregulation, as laminitis risk in PPID is associated with hyperinsulinaemia. PPID can be managed but not cured; it is a lifelong condition. The individual clinical signs can be managed, e.g., clipping the excessive haircoat and providing unrestricted access to water for individuals with polydipsia. Alternatively, pharmacological management can be employed, and the dopamine-2 receptor agonist pergolide is licensed/approved for the treatment of equine PPID. This should be prescribed in combination with dietary recommendations based on the body condition score and insulin sensitivity status of the individual animal. Full article

Sleep is a vital biological function governed by neuronal networks in the brainstem, hypothalamus, and thalamus. Disruptions in these circuits contribute to the sleep disturbances observed in neurodegenerative disorders, including Parkinson’s disease, epilepsy, Huntington’s disease, and Alzheimer’s disease. Oxidative stress, mitochondrial dysfunction, neuroinflammation, and abnormal protein accumulation adversely affect sleep architecture in these conditions. The interaction among these pathological processes is believed to modify sleep-regulating circuits, consequently worsening clinical symptoms. This review examines the cellular and molecular mechanisms that impair sleep regulation in experimental models of these four disorders, emphasizing how oxidative stress, neuroinflammation and synaptic dysfunction contribute to sleep fragmentation and alterations in rapid eye movement (REM) sleep and slow-wave sleep (SWS) phases. In Parkinson’s disease models (6-OHDA and MPTP), dopaminergic degeneration and damage to sleep-regulating nuclei result in daytime somnolence and disrupted sleep patterns. Epilepsy models (kainate, pentylenetetrazole, and kindling) provoke hyperexcitability and oxidative damage, compromising both REM and SWS. Huntington’s disease models (R6/2 and 3-NP) demonstrate reduced sleep duration, circadian irregularities, and oxidative damage in the hypothalamus and suprachiasmatic nucleus. In Alzheimer’s disease (AD) models (APP/PS1, 3xTg-AD, and Tg2576), early sleep problems include diminished SWS and REM sleep, increased awakenings, and circadian rhythm disruption. These changes correlate with β-amyloid and tau deposition, glial activation, chronic inflammation, and mitochondrial damage in the hypothalamus, hippocampus, and prefrontal cortex. Sleep disturbances across these neurodegenerative disease models share common underlying mechanisms like oxidative stress, neuroinflammation, and mitochondrial dysfunction. Understanding these pathways may reveal therapeutic targets to improve both motor symptoms and sleep quality in neurodegenerative disorders. Full article

The study objectives were to investigate the role of ferroptosis, the mechanism linking iron accumulation, oxidative stress, and dopaminergic dysfunction, in restless legs syndrome (RLS), and to explore its connection with circadian regulation, a key feature of RLS and a known modulator of ferroptosis. We conducted pathway and gene expression analyses in 17 RLS patients and 39 controls, focusing on pathways related to ferroptosis, oxidative stress, iron metabolism, dopaminergic signaling, circadian rhythms, and immune responses. Enrichment analysis, differential gene expression, and cross-pathway gene overlaps were assessed. Ferroptosis and efferocytosis pathways were significantly upregulated in RLS, while oxidative phosphorylation, phosphatidylinositol signaling, PI3K-Akt, FoxO, and adipocytokine pathways were downregulated. The circadian rhythm pathway was markedly suppressed, with 12 circadian genes downregulated, suggesting that circadian disruption may drive ferroptosis activation. Decreased expression of protective pathways, including antioxidant responses and autophagy, was associated with increased iron accumulation, oxidative stress, and inflammation. Dopaminergic synapse genes were upregulated, possibly as a compensatory response to neuronal damage. Several genes overlapped across ferroptosis, circadian, and dopaminergic pathways, indicating a shared pathogenic mechanism. Our findings support a model in which circadian disruption promotes ferroptosis in RLS, contributing to iron overload, oxidative damage, and dopaminergic dysfunction. This pathogenic cascade may also enhance immune activation and inflammation. Circadian regulation and ferroptosis emerge as promising therapeutic targets in RLS. Further studies in larger cohorts are warranted to validate these mechanistic insights. Full article

The etiology of obsessive–compulsive disorder (OCD) remains incompletely understood, but it is widely recognized as the result of a complex interplay among multiple contributing mechanisms, often emerging during childhood. This narrative review synthesizes current evidence on the etiology of childhood-onset OCD, with particular focus on whether GM alterations are involved in the pathophysiological mechanisms underlying the disorder. Specifically, the review first examines both biological and psychosocial determinants of OCD, and then explores the role of the gut microbiome (GM), including the potential of psychobiotics as a novel therapeutic approach. OCD has a strong hereditary component, involving both common polygenic variants and rare mutations. Epigenetic mechanisms such as DNA methylation and microRNA play a role in mediating gene–environment interactions and influencing OCD risk. Dysfunction and hyperactivity within cortico-striato-thalamo-cortical circuits underlie one of the neurobiological bases of OCD. Infections and autoimmune reactions can trigger or exacerbate OCD, particularly in pediatric populations. A range of psychosocial factors have been implicated in the onset of OCD, often in interaction with underlying neurobiological vulnerabilities. Current evidence indicates that GM alterations may also contribute to OCD pathophysiology through immune-mediated neuroinflammation, disrupted gut–brain signaling, and neurotransmitter imbalance. Individuals with OCD present reduced microbial diversity and lower abundance of butyrate-producing taxa, as well as altered IgA levels and increased infection susceptibility. These shifts may affect dopaminergic, glutamatergic, and serotonergic pathways, particularly via tryptophan metabolism and compromised gut integrity. Thus, the GM plays a pivotal role in OCD, constituting a promising approach for understanding its etiology and highlighting the significant clinical potential of microbial-based treatments such as psychobiotics. Nevertheless, despite progress, gaps remain in understanding childhood-onset OCD determinants, including limited longitudinal studies, incomplete characterization of the GM, scarce psychobiotic trials, and a need for integrated multidisciplinary approaches. Moreover, epidemiological evidence is compromised by reliance on lay diagnoses, questionable assessment validity, and insufficient distinction from related disorders. Full article

Parkinson’s disease (PD) is a progressive, multisystemic α-synucleinopathy, recognized as the second most prevalent neurodegenerative disorder globally. Its neuropathology is characterized by the degeneration of dopaminergic neurons, particularly in the substantia nigra pars compacta (SNpc), and the intraneuronal accumulation of α-synuclein-forming Lewy bodies. Oxidative stress is a key contributor to PD pathogenesis. Thioredoxin-interacting protein (TXNIP) is a crucial regulator of cellular redox balance, inhibiting the antioxidant function of thioredoxin. This pilot study aimed to investigate the protein expression and localization of TXNIP in the SNpc of PD patients compared to healthy controls. We performed immunohistochemical analyses on 12 post-mortem human brain sections (formalin-fixed, paraffin-embedded) from six subjects with PD and six healthy controls. The study was performed on PD subjects with Braak stage 6. Our findings revealed that in control samples, TXNIP protein was distinctly and closely associated with neuromelanin (NM) pigment within the cytoplasm of SNpc dopaminergic neurons. Conversely, in PD samples, there was a markedly weak cytoplasmic expression of TXNIP, and critically, this association with NM pigment was absent. Furthermore, PD samples exhibited a significant reduction in both dopaminergic neurons and NM content, consistent with advanced disease. These findings, which mirror previous transcriptomic data showing TXNIP gene under-expression in the same subjects, suggest that altered TXNIP expression and localization in SNpc dopaminergic neurons are features of late-stage PD, potentially reflecting neuronal dysfunction and loss. Full article

Allicin (ALC), a naturally occurring organosulfur compound derived from garlic (Allium sativum), exhibits potential neuroprotective properties. Parkinson’s disease (PD) is a progressive neurodegenerative disease characterized by degeneration of dopaminergic neurons and motor dysfunction. This study utilized bioinformatics and network pharmacology methods to predict the anti-PD mechanism of ALC and established in vivo and in vitro PD models using 6-hydroxydopamine (6-OHDA) for experimental verification. Network pharmacological analysis indicates that apoptosis regulation and the PKA/p-CREB/BDNF signaling pathway are closely related to the anti-PD effect of ALC, and protein kinase A (PKA) and dopamine transporter (DAT) are key molecular targets. The experimental results show that ALC administration can alleviate the cytotoxicity of SH-SY5Y induced by 6-OHDA and simultaneously improve the motor dysfunction and dopaminergic neuron loss in PD mice. In addition, ALC can also activate the PKA/p-CREB/BDNF signaling pathway and increase the DAT level in brain tissue, regulate the expression of BAX and Bcl-2, and reduce neuronal apoptosis. These results indicate that ALC can exert anti-PD effects by up-regulating the PKA/p-CREB/BDNF/DAT signaling pathway and inhibiting neuronal apoptosis, providing theoretical support for the application of ALC in PD. Full article

Mitochondrial dysfunction is a key contributor to neurodegeneration, particularly in Parkinson’s disease (PD), where dopaminergic neurons being highly metabolically active are vulnerable to oxidative stress and bioenergetic failure. In this study, we investigate the effects of rotenone, a Complex I inhibitor, and antimycin A, a Complex III inhibitor, on mitochondrial function in MN9D dopaminergic neuronal cells. Cells were treated with rotenone (1.5 µM) or antimycin A (10 µM) for one hour, and key biochemical parameters were assessed, including ATP levels, reactive oxygen species (ROS) production, dopamine metabolism, and neuromelanin formation. Our results indicate significant ATP depletion and ROS accumulation following treatment with both inhibitors, with antimycin A inducing a more pronounced oxidative stress response. Dysregulation of dopamine biosynthesis differed mechanistically from vesicular monoamine transporter (VMAT2) inhibition by tetrabenazine, suggesting alternative pathways of catecholamine disruption. Additionally, oxidative stress led to increased neuromelanin accumulation, indicating a possible adaptive response to mitochondrial dysfunction. These findings provide insights into the cellular mechanisms underlying dopaminergic neurotoxicity and highlight mitochondrial electron transport chain inhibition as a key driver of PD pathogenesis. Future research should explore therapeutic strategies aimed at enhancing mitochondrial function to mitigate neurodegenerative progression. Full article

Background: Parkinson’s disease (PD) involves progressive dopaminergic neuron degeneration and motor deficits. Oligodendrocyte dysfunction contributes to PD pathogenesis through impaired myelination. Methods: Single-nucleus RNA sequencing (snRNA-seq) of PD mice revealed compromised oligodendrocyte differentiation and STAT5B downregulation. Pseudotemporal trajectory analysis via Monocle2 demonstrated impaired oligodendrocyte maturation in PD oligodendrocytes, correlating with reduced myelin-related gene expression (Sox10, Plp1, Mbp, Mog, Mag, Mobp). DoRothEA-predicted regulon activity identified STAT5B as a key transcriptional regulator. Results: Oligodendrocyte-specific STAT5B activation improved myelin integrity, as validated by Luxol Fast Blue staining and transmission electron microscopy; attenuated dopaminergic neuron loss; and improved motor function. Mechanistically, STAT5B binds the MBP promoter to drive transcription, a finding confirmed by the luciferase assay, while the DNMT3A-mediated hypermethylation of the STAT5B promoter epigenetically silences its expression, as verified by MethylTarget sequencing and methylation-specific PCR. Conclusions: DNMT3A inhibited the expression of STAT5B by affecting its methylation, which reduced the transcription of MBP, caused oligodendrocyte myelin damage, and eventually led to dopamine neuron damage and motor dysfunction in an MPTP-induced mouse model. This DNMT3A-STAT5B-MBP axis underlies PD-associated myelin damage, connecting epigenetic dysregulation with oligodendrocyte dysfunction and subsequent PD pathogenesis. Full article

Parkinson’s disease (PD) is a progressive neurodegenerative disorder characterized by the selective loss of dopaminergic neurons in the substantia nigra, resulting in motor symptoms such as bradykinesia, tremor, rigidity, and postural instability, as well as a wide variety of non-motor manifestations. Branched-chain amino acids (BCAAs)—leucine, isoleucine, and valine—are essential nutrients involved in neurotransmitter synthesis, energy metabolism, and cellular signaling. Emerging evidence suggests that BCAA metabolism is intricately linked to the pathophysiology of PD. Dysregulation of BCAA levels has been associated with energy metabolism, mitochondrial dysfunction, oxidative stress, neuroinflammation, and altered neurotransmission. Furthermore, the branched-chain ketoacid dehydrogenase kinase (BCKDK), a key regulator of BCAA catabolism, has been implicated in PD through its role in modulating neuronal energetics and redox homeostasis. In this review, we synthesize current molecular, genetic, microbiome, and clinical evidence on BCAA dysregulation in PD to provide an integrative perspective on the BCAA–PD axis and highlight directions for future translational research. We explored the dualistic role of BCAAs as both potential neuroprotective agents and metabolic stressors, and critically examined the therapeutic prospects and limitations of BCAA supplementation and BCKDK targeting. Full article

Parkinson’s disease (PD) is a progressive neurodegenerative disorder marked by dopaminergic neuronal loss, α-synuclein aggregation, and chronic neuroinflammation. Recent evidence suggests that exosomal microRNAs (miRNAs)—small, non-coding RNAs encapsulated in extracellular vesicles—are key regulators of PD pathophysiology and promising candidates for biomarker development and therapeutic intervention. Exosomes facilitate intercellular communication, cross the blood–brain barrier, and protect miRNAs from degradation, rendering them suitable for non-invasive diagnostics and targeted delivery. Specific exosomal miRNAs modulate neuroinflammatory cascades, oxidative stress, and synaptic dysfunction, and their altered expression in cerebrospinal fluid and plasma correlates with disease onset, severity, and progression. Despite their translational promise, challenges persist, including methodological variability in exosome isolation, miRNA profiling, and delivery strategies. This review integrates findings from preclinical models, patient-derived samples, and systems biology to delineate the functional impact of exosomal miRNAs in PD. We propose mechanistic hypotheses linking miRNA dysregulation to molecular pathogenesis and present an interactome model highlighting therapeutic nodes. Advancing exosomal miRNA research may transform the clinical management of PD by enabling earlier diagnosis, molecular stratification, and the development of disease-modifying therapies. Full article

Zebrafish (Danio rerio) combine accessible behavioral phenotypes with conserved neurochemical pathways and molecular features of vertebrate brain function, positioning them as a powerful model for investigating early neurodegenerative processes and screening neuroprotective strategies. In this context, integrated behavioral and proteomic analyses provide valuable insights into the initial pathophysiological events shared by conditions such as Parkinson’s disease and related disorders—including mitochondrial dysfunction, oxidative stress, and synaptic impairment—which emerge before overt neuronal loss and offer a crucial window to understand disease progression and evaluate therapeutic candidates prior to irreversible damage. To investigate this early window of dysfunction, zebrafish larvae were exposed to 500 μM 1-methyl-4-phenylpyridinium (MPP⁺) from 1 to 5 days post-fertilization and evaluated through integrated behavioral and label-free proteomic analyses. MPP⁺-treated larvae exhibited hypokinesia, characterized by significantly reduced total distance traveled, fewer movement bursts, prolonged immobility, and a near-complete absence of light-evoked responses—mirroring features of early Parkinsonian-like motor dysfunction. Label-free proteomic profiling revealed 40 differentially expressed proteins related to mitochondrial metabolism, redox regulation, proteasomal activity, and synaptic organization. Enrichment analysis indicated broad molecular alterations, including pathways such as mitochondrial translation and vesicle-mediated transport. A focused subset of Parkinsonism-related proteins—such as DJ-1 (PARK7), succinate dehydrogenase (SDHA), and multiple 26S proteasome subunits—exhibited coordinated dysregulation, as visualized through protein–protein interaction mapping. The upregulation of proteasome components and antioxidant proteins suggests an early-stage stress response, while the downregulation of mitochondrial enzymes and synaptic regulators reflects canonical PD-related neurodegeneration. Together, these findings provide a comprehensive functional and molecular characterization of MPP⁺-induced neurotoxicity in zebrafish larvae, supporting its use as a relevant in vivo system to investigate early-stage Parkinson’s disease mechanisms and shared neurodegenerative pathways, as well as for screening candidate therapeutics in a developmentally responsive context. Full article

Parkinson’s disease (PD) is the second most prevalent neurodegenerative disease. It is characterized by mitochondrial dysfunction, increased reactive oxygen species (ROS), α-synuclein (α-syn) and phosphorylated-tau protein (p-tau) aggregation, and dopaminergic neuron cell death. Current drug therapies only provide temporary symptomatic relief and fail to stop or reverse disease progression due to the severe side effects or the blood–brain barrier. This study aimed to investigate the neuroprotective effects of an intermittent heating approach, thermal cycling-hyperthermia (TC-HT), in an in vitro PD model using rotenone (ROT)-induced human neural SH-SY5Y cells. Our results revealed that TC-HT pretreatment conferred neuroprotective effects in the ROT-induced in vitro PD model using human SH-SY5Y neuronal cells, including reducing ROT-induced mitochondrial apoptosis and ROS accumulation in SH-SY5Y cells. In addition, TC-HT also inhibited the expression of α-syn and p-tau through heat-activated pathways associated with sirtuin 1 (SIRT1) and heat-shock protein 70 (Hsp70), involved in protein chaperoning, and resulted in the phosphorylation of Akt and glycogen synthase kinase-3β (GSK-3β), which inhibit p-tau formation. These findings underscore the potential of TC-HT as an effective treatment for PD in vitro, supporting its further investigation in in vivo models with focused ultrasound (FUS) as a feasible heat-delivery approach. Full article

The common gardening herbicides and fertilizers are crucial for weed control and plant growth, yet they may have potentially harmful impacts on neurological health. This review explored the possible effects of these chemicals on neurodegenerative disorders, especially Alzheimer’s disease (AD) and Parkinson’s disease (PD). The mode of action of several frequently used gardening chemicals (paraquat, glyphosate, 2,4-dichlorophenoxyacetic acid: 2,4-D, and ammonium chloride) in AD and PD has been highlighted. The mechanisms involved are glutamate excitotoxicity, dopaminergic pathway disruption, oxidative stress, mitochondrial dysfunction, neuroinflammation, synaptic dysfunction, and gut–brain-axis dysregulation, crucial in the pathophysiology of AD and PD. Although the links between these substances and neurodegenerative conditions remained to be seen, growing evidence indicated their detrimental effects on brain health. This highlights the need for further research to understand their long-term consequences and develop effective interventions to mitigate the adverse effects of commonly used chemicals on human health and the environment. Full article