Protective effects of valproic acid on 6-hydroxydopamine-induced neuroinjury

Unraveling the Epigenetic Landscape: Insights into Parkinson's Disease, Amyotrophic Lateral Sclerosis, and Multiple Sclerosis

Parkinson's disease (PD), multiple sclerosis (MS), and amyotrophic lateral sclerosis (ALS) are examples of neurodegenerative movement disorders (NMDs), which are defined by a gradual loss of motor function that is frequently accompanied by cognitive decline. Although genetic abnormalities have long been acknowledged as significant factors, new research indicates that epigenetic alterations are crucial for the initiation and development of disease. This review delves into the complex interactions that exist between the pathophysiology of NMDs and epigenetic mechanisms such DNA methylation, histone modifications, and non-coding RNAs. Here, we examine how these epigenetic changes could affect protein aggregation, neuroinflammation, and gene expression patterns, thereby influencing the viability and functionality of neurons. Through the clarification of the epigenetic terrain underpinning neurodegenerative movement disorders, this review seeks to enhance comprehension of the underlying mechanisms of the illness and augment the creation of innovative therapeutic strategies.

Interplay of human gastrointestinal microbiota metabolites: Short-chain fatty acids and their correlation with Parkinson's disease

Short-chain fatty acids (SCFAs) are, the metabolic byproducts of intestinal microbiota that, are generated through anaerobic fermentation of undigested dietary fibers. SCFAs play a pivotal role in numerous physiological functions within the human body, including maintaining intestinal mucosal health, modulating immune functions, and regulating energy metabolism. In recent years, extensive research evidence has indicated that SCFAs are significantly involved in the onset and progression of Parkinson disease (PD). However, the precise mechanisms remain elusive. This review comprehensively summarizes the progress in understanding how SCFAs impact PD pathogenesis and the underlying mechanisms. Primarily, we delve into the synthesis, metabolism, and signal transduction of SCFAs within the human body. Subsequently, an analysis of SCFA levels in patients with PD is presented. Furthermore, we expound upon the mechanisms through which SCFAs induce inflammatory responses, oxidative stress, abnormal aggregation of alpha-synuclein, and the intricacies of the gut-brain axis. Finally, we provide a critical analysis and explore the potential therapeutic role of SCFAs as promising targets for treating PD.

Anti-Seizure Medications on Trial Again: Accused of Parkinson's Disease!

Association Between Antiepileptic Drugs and Incident Parkinson Disease Belete D, Jacobs BM, Simonet C, Bestwick JP, Waters S, Marshall CR, Dobson R, Noyce AJ. JAMA Neurol. 2023;80(2):183-187. doi:10.1001/jamaneurol.2022.4699 Importance: Recent studies have highlighted an association between epilepsy and Parkinson disease (PD). The role of antiepileptic drugs (AEDs) has not been explored. Objective: To investigate the association between AEDs and incident PD. Design, setting, and participants: This nested case-control study started collecting data from the UK Biobank (UKB) in 2006, and data were extracted on June 30, 2021. Individuals with linked primary care prescription data were included. Cases were defined as individuals with a Hospital Episode Statistics (HES)–coded diagnosis of PD. Controls were matched 6:1 for age, sex, race and ethnicity, and socioeconomic status. Prescription records were searched for AEDs prescribed prior to diagnosis of PD. The UKB is a longitudinal cohort study with more than 500 000 participants; 45% of individuals in the UKB have linked primary care prescription data. Participants living in the UK aged between 40 and 69 years were recruited to the UKB between 2006 and 2010. All participants with UKB-linked primary care prescription data (n = 222 106) were eligible for enrollment in the study. Individuals with only a self-reported PD diagnosis or missing data for the matching variables were excluded. In total, 1477 individuals were excluded; 49 were excluded due to having only self-reported PD, and 1428 were excluded due to missing data. Exposures: Exposure to AEDs (carbamazepine, lamotrigine, levetiracetam, and sodium valproate) was defined using routinely collected prescription data derived from primary care. Main outcomes and measures: Odds ratios and 95% CIs were calculated using adjusted logistic regression models for individuals prescribed AEDs before the first date of HES-coded diagnosis of PD. Results: In this case-control study, there were 1433 individuals with an HES-coded PD diagnosis (cases) and 8598 controls in the analysis. Of the 1433 individuals, 873 (60.9%) were male, 1397 (97.5%) had their race and ethnicity recorded as White, and their median age was 71 years (IQR, 65-75 years). An association was found between AED prescriptions and incident PD (odds ratio, 1.80; 95% CI, 1.35-2.40). There was a trend for a greater number of prescription issues and multiple AEDs being associated with a greater risk of PD. Conclusions and relevance: This study, the first to systematically look at PD risk in individuals prescribed the most common AEDs, to our knowledge, found evidence of an association between AEDs and incident PD. With the recent literature demonstrating an association between epilepsy and PD, this study provides further insights.

Alpha synuclein post translational modifications: potential targets for Parkinson's disease therapy?

Parkinson's disease (PD) is the most common neurodegenerative disorder with motor symptoms. The neuropathological alterations characterizing the brain of patients with PD include the loss of dopaminergic neurons of the nigrostriatal system and the presence of Lewy bodies (LB), intraneuronal inclusions that are mainly composed of alpha-synuclein (α-Syn) fibrils. The accumulation of α-Syn in insoluble aggregates is a main neuropathological feature in PD and in other neurodegenerative diseases, including LB dementia (LBD) and multiple system atrophy (MSA), which are therefore defined as synucleinopathies. Compelling evidence supports that α-Syn post translational modifications (PTMs) such as phosphorylation, nitration, acetylation, O-GlcNAcylation, glycation, SUMOylation, ubiquitination and C-terminal cleavage, play important roles in the modulation α-Syn aggregation, solubility, turnover and membrane binding. In particular, PTMs can impact on α-Syn conformational state, thus supporting that their modulation can in turn affect α-Syn aggregation and its ability to seed further soluble α-Syn fibrillation. This review focuses on the importance of α-Syn PTMs in PD pathophysiology but also aims at highlighting their general relevance as possible biomarkers and, more importantly, as innovative therapeutic targets for synucleinopathies. In addition, we call attention to the multiple challenges that we still need to face to enable the development of novel therapeutic approaches modulating α-Syn PTMs.

Isozyme-specific histone deacetylase 1/2 inhibitor K560 attenuates oxidative stress-induced retinal cell death

Oxidative stress-induced damage is an underlying mechanism in the pathogenesis of age-related retinal diseases. Here, we examined the effects of K560, a potential candidate drug for the treatment of these diseases, on oxidative stress-induced retinal cell death. K560 is a novel isozyme-specific inhibitor of histone deacetylase 1 and 2 (HDAC1/2). Histone acetylation in retinal lysates and dissociated retinal cells was detected with a western blot analysis and cell-based enzyme-linked immunosorbent assay (ELISA), respectively. The viability of mouse retinal cells was measured with an alamarBlue assay. We used immunohistochemistry for RNA binding protein with multiple splicing (RBPMS) to visualize the retinal ganglion cells (RGCs) of mice. An ELISA analysis indicated that histone acetylation was enhanced in dissociated mouse retinal cells treated with K560. The cell viability assay indicated that K560 attenuated both exogenous hydrogen peroxide-induced and endogenous oxidative stress-induced cell death in dissociated retinal cells. Western blot analysis indicated that intravitreal K560 administration enhanced the acetylation of histones H3 and H4 in mouse retinal lysates. To examine the effect of K560 on oxidative stress-induced RGC death, we performed whole-mount immunohistochemistry for RBPMS on retinas dissected from eyes treated with K560 or vehicle on day one, and K560 or vehicle and NMDA on day two. Quantification of RBPMS-immunopositive cells indicated that K560 attenuated NMDA-induced RGC death. Taken together, our findings suggest that administration of a HDAC1/2-specific inhibitor K560 may be effective in the treatment of oxidative stress-mediated retinal degeneration and have less cytotoxicity than other known HDAC inhibitors, which are known to target a wide range of HDAC family members.

Combined cell grafting and VPA administration facilitates neural repair through axonal regeneration and synaptogenesis in traumatic brain injury

Neuronal regeneration and functional recovery are severely compromised following traumatic brain injury (TBI). Treatment options, including cell transplantation and drug therapy, have been shown to benefit TBI, although the underlying mechanisms remain elusive. In this study, neural stem cells (NSCs) are transplanted into TBI-challenged mice, together with olfactory ensheathing cells (OECs) or followed by valproic acid (VPA) treatment. Both OEC grafting and VPA treatment facilitate the differentiation of NSCs into neurons (including endogenous and exogenous neurons) and significantly attenuate neurological functional defects in TBI mice. Combination of NSCs with OECs or VPA administration leads to overt improvement in axonal regeneration, synaptogenesis, and synaptic plasticity in the cerebral cortex in TBI-challenged mice, as shown by retrograde corticospinal tract tracing, electron microscopy, growth-associated protein 43 (GAP43), and synaptophysin (SYN) analyses. However, these beneficial effects of VPA are reversed by local delivery of N-methyl-D-aspartate (NMDA) into tissues surrounding the injury epicenter in the cerebral cortex, accompanied by a pronounced drop in axons and synapses in the brain. Our findings reveal that increased axonal regeneration and synaptogenesis evoked by cell grafting and VPA fosters neural repair in a murine model of TBI. Moreover, VPA-induced neuroprotective roles are antagonized by exogenous NMDA administration and its concomitant decrease in the number of neurons of local brain, indicating that increased neurons induced by VPA treatment mediate axonal regeneration and synaptogenesis in mice after TBI operation. Collectively, this study provides new insights into NSC transplantation therapy for TBI.

Protective Effects of Jujubosides on 6-OHDA-Induced Neurotoxicity in SH-SY5Y and SK-N-SH Cells

6-hydroxydopamine (6-OHDA) is used to induce oxidative damage in neuronal cells, which can serve as an experimental model of Parkinson’s disease (PD). Jujuboside A and B confer free radical scavenging effects but have never been examined for their neuroprotective effects, especially in PD; therefore, in this study, we aimed to investigate the feasibility of jujubosides as protectors of neurons against 6-OHDA and the underlying mechanisms. 6-OHDA-induced neurotoxicity in the human neuronal cell lines SH-SY5Y and SK-N-SH, was used to evaluate the protective effects of jujubosides. These findings indicated that jujuboside A and B were both capable of rescuing the 6-OHDA-induced loss of cell viability, activation of apoptosis, elevation of reactive oxygen species, and downregulation of the expression levels of superoxide dismutase, catalase, and glutathione peroxidase. In addition, jujuboside A and B can reverse a 6-OHDA-elevated Bax/Bcl-2 ratio, downregulate phosphorylated PI3K and AKT, and activate caspase-3, -7, and -9. These findings showed that jujubosides were capable of protecting both SH-SY5Y and SK-N-SH neuronal cells from 6-OHDA-induced toxicity via the rebalancing of the redox system, together with the resetting of the PI3K/AKT apoptotic signaling cascade. In conclusion, jujuboside may be a potential drug for PD prevention.

Histone Deacetylases as Epigenetic Targets for Treating Parkinson's Disease

Parkinson's disease (PD) is a chronic progressive neurodegenerative disease that is increasingly becoming a global threat to the health and life of the elderly worldwide. Although there are some drugs clinically available for treating PD, these treatments can only alleviate the symptoms of PD patients but cannot completely cure the disease. Therefore, exploring other potential mechanisms to develop more effective treatments that can modify the course of PD is still highly desirable. Over the last two decades, histone deacetylases, as an important group of epigenetic targets, have attracted much attention in drug discovery. This review focused on the current knowledge about histone deacetylases involved in PD pathophysiology and their inhibitors used in PD studies. Further perspectives related to small molecules that can inhibit or degrade histone deacetylases to treat PD were also discussed.

Histone deacetylase in neuropathology

Neuroepigenetics, a new branch of epigenetics, plays an important role in the regulation of gene expression. Neuroepigenetics is associated with holistic neuronal function and helps in formation and maintenance of memory and learning processes. This includes neurodevelopment and neurodegenerative defects in which histone modification enzymes appear to play a crucial role. These modifications, carried out by acetyltransferases and deacetylases, regulate biologic and cellular processes such as apoptosis and autophagy, inflammatory response, mitochondrial dysfunction, cell-cycle progression and oxidative stress. Alterations in acetylation status of histone as well as non-histone substrates lead to transcriptional deregulation. Histone deacetylase decreases acetylation status and causes transcriptional repression of regulatory genes involved in neural plasticity, synaptogenesis, synaptic and neural plasticity, cognition and memory, and neural differentiation. Transcriptional deactivation in the brain results in development of neurodevelopmental and neurodegenerative disorders. Mounting evidence implicates histone deacetylase inhibitors as potential therapeutic targets to combat neurologic disorders. Recent studies have targeted naturally-occurring biomolecules and micro-RNAs to improve cognitive defects and memory. Multi-target drug ligands targeting HDAC have been developed and used in cell-culture and animal-models of neurologic disorders to ameliorate synaptic and cognitive dysfunction. Herein, we focus on the implications of histone deacetylase enzymes in neuropathology, their regulation of brain function and plausible involvement in the pathogenesis of neurologic defects.

Chemical and Biological Molecules Involved in Differentiation, Maturation, and Survival of Dopaminergic Neurons in Health and Parkinson's Disease: Physiological Aspects and Clinical Implications

Parkinson’s disease (PD) is one of the most common neurodegenerative disease characterized by a specific and progressive loss of dopaminergic (DA) neurons and dopamine, causing motor dysfunctions and impaired movements. Unfortunately, available therapies can partially treat the motor symptoms, but they have no effect on non-motor features. In addition, the therapeutic effect reduces gradually, and the prolonged use of drugs leads to a significative increase in the number of adverse events. For these reasons, an alternative approach that allows the replacement or the improved survival of DA neurons is very appealing for the treatment of PD patients and recently the first human clinical trials for DA neurons replacement have been set up. Here, we review the role of chemical and biological molecules that are involved in the development, survival and differentiation of DA neurons. In particular, we review the chemical small molecules used to differentiate different type of stem cells into DA neurons with high efficiency; the role of microRNAs and long non-coding RNAs both in DA neurons development/survival as far as in the pathogenesis of PD; and, finally, we dissect the potential role of exosomes carrying biological molecules as treatment of PD.

Protective Effects of Baicalin on Arsenic Trioxide-induced Oxidative Damage and Apoptosis in Human Umbilical Vein Endothelial Cells

BACKGROUND/AIM

Arsenic trioxide (As₂O₃) is an environmental pollutant. However, the detailed mechanisms about As₂O₃-induced loss of endothelial integrity are unknown. This study aimed at investigating how As₂O₃ causes endothelial dysfunction and whether baicalin can reverse such dysfunction.

MATERIALS AND METHODS

Human umbilical vein endothelial cells (HUVECs) were used to examine As₂O₃-induced oxidative stress, and apoptosis. The influence of baicalin on As₂O₃-induced endothelial dysfunction were investigated.

RESULTS

The viability of HUVECs was inhibited by As₂O₃ and cells underwent apoptosis. As₂O₃ treatment increased NADPH oxidase activity, and elevated the level of reactive oxygen species (ROS). Formamidopyrimidine DNA-glycosylase- and endonuclease III-digestible adducts were accumulated. Baicalin reversed As₂O₃-induced apoptosis and As₂O₃-suppressed cell viability. Baicalin caused a decrease in NADPH oxidase activity, and re-balanced the ROS level. As₂O₃-induced formamidopyrimidine DNA-glycosylase- and endonuclease III-digestible adducts were down-regulated.

CONCLUSION

Baicalin was found to have the potential capacity to protect endothelial cells from As₂O₃-induced cytotoxicity.

Oxidopamine and oxidative stress: Recent advances in experimental physiology and pharmacology

Oxidopamine (6-hydroxydopamine, 6-OHDA) is a toxin commonly used for the creation of experimental animal models of Parkinson's disease, attention-deficit hyperactivity disorder, and Lesch-Nyhan syndrome. Its exact mechanism of action is not completely understood, although there are many indications that it is related to the generation of reactive oxygen species (ROS), primarily in dopaminergic neurons. In certain experimental conditions, oxidopamine may also cause programmed cell death via various signaling pathways. Oxidopamine may also have a significant impact on chromatin structure and nuclear structural organization in some cells. Today, many researchers use oxidopamine-associated oxidative damage to evaluate different antioxidant-based pharmacologically active compounds as drug candidates for various neurological and non-neurological diseases. Additional research is needed to clarify the exact biochemical pathways associated with oxidopamine toxicity, related ROS generation and apoptosis. In this short review, we focus on the recent research in experimental physiology and pharmacology, related to the cellular and animal experimental models of oxidopamine - mediated toxicity.

Histone Deacetylases Inhibitors in Neurodegenerative Diseases, Neuroprotection and Neuronal Differentiation

Histone deacetylases (HADC) are the enzymes that remove acetyl group from lysine residue of histones and non-histone proteins and regulate the process of transcription by binding to transcription factors and regulating fundamental cellular process such as cellular proliferation, differentiation and development. In neurodegenerative diseases, the histone acetylation homeostasis is greatly impaired, shifting towards a state of hypoacetylation. The histone hyperacetylation produced by direct inhibition of HDACs leads to neuroprotective actions. This review attempts to elaborate on role of small molecule inhibitors of HDACs on neuronal differentiation and throws light on the potential of HDAC inhibitors as therapeutic agents for treatment of neurodegenerative diseases. The role of HDACs in neuronal cellular and disease models and their modulation with HDAC inhibitors are also discussed. Significance of these HDAC inhibitors has been reviewed on the process of neuronal differentiation, neurite outgrowth and neuroprotection regarding their potential therapeutic application for treatment of neurodegenerative diseases.