Neuroprotective effects of lentivirus-mediated cystathionine-beta-synthase overexpression against 6-OHDA-induced parkinson's disease rats

Statistical integration of multi-omics and drug screening data from cell lines

Data integration methods are used to obtain a unified summary of multiple datasets. For multi-modal data, we propose a computational workflow to jointly analyze datasets from cell lines. The workflow comprises a novel probabilistic data integration method, named POPLS-DA, for multi-omics data. The workflow is motivated by a study on synucleinopathies where transcriptomics, proteomics, and drug screening data are measured in affected LUHMES cell lines and controls. The aim is to highlight potentially druggable pathways and genes involved in synucleinopathies. First, POPLS-DA is used to prioritize genes and proteins that best distinguish cases and controls. For these genes, an integrated interaction network is constructed where the drug screen data is incorporated to highlight druggable genes and pathways in the network. Finally, functional enrichment analyses are performed to identify clusters of synaptic and lysosome-related genes and proteins targeted by the protective drugs. POPLS-DA is compared to other single- and multi-omics approaches. We found that HSPA5, a member of the heat shock protein 70 family, was one of the most targeted genes by the validated drugs, in particular by AT1-blockers. HSPA5 and AT1-blockers have been previously linked to α-synuclein pathology and Parkinson's disease, showing the relevance of our findings. Our computational workflow identified new directions for therapeutic targets for synucleinopathies. POPLS-DA provided a larger interpretable gene set than other single- and multi-omic approaches. An implementation based on R and markdown is freely available online.

Transsulfuration pathway: a targeting neuromodulator in Parkinson's disease

The transsulfuration pathway (TSP) is a metabolic pathway involving sulfur transfer from homocysteine to cysteine. Transsulfuration pathway leads to many sulfur metabolites, principally glutathione, H2S, taurine, and cysteine. Key enzymes of the TSP, such as cystathionine β-synthase and cystathionine γ-lyase, are essential regulators at multiple levels in this pathway. TSP metabolites are implicated in many physiological processes in the central nervous system and other tissues. TSP is important in controlling sulfur balance and optimal cellular functions such as glutathione synthesis. Alterations in the TSP and related pathways (transmethylation and remethylation) are altered in several neurodegenerative diseases, including Parkinson's disease, suggesting their participation in the pathophysiology and progression of these diseases. In Parkinson's disease many cellular processes are comprised mainly those that regulate redox homeostasis, inflammation, reticulum endoplasmic stress, mitochondrial function, oxidative stress, and sulfur content metabolites of TSP are involved in these damage processes. Current research on the transsulfuration pathway in Parkinson's disease has primarily focused on the synthesis and function of certain metabolites, particularly glutathione. However, our understanding of the regulation of other metabolites of the transsulfuration pathway, as well as their relationships with other metabolites, and their synthesis regulation in Parkinson´s disease remain limited. Thus, this paper highlights the importance of studying the molecular dynamics in different metabolites and enzymes that affect the transsulfuration in Parkinson's disease.

Hydrogen sulfide signalling in neurodegenerative diseases

The gaseous neurotransmitter hydrogen sulfide (H2 S) exerts neuroprotective efficacy in the brain via post-translational modification of cysteine residues by sulfhydration, also known as persulfidation. This process is comparable in biological impact to phosphorylation and mediates a variety of signalling events. Unlike conventional neurotransmitters, H2 S cannot be stored in vesicles due to its gaseous nature. Instead, it is either locally synthesized or released from endogenous stores. Sulfhydration affords both specific and general neuroprotective effects and is critically diminished in several neurodegenerative disorders. Conversely, some forms of neurodegenerative disease are linked to excessive cellular H2 S. Here, we review the signalling roles of H2 S across the spectrum of neurodegenerative diseases, including Huntington's disease, Parkinson's disease, Alzheimer's disease, Down syndrome, traumatic brain injury, the ataxias, and amyotrophic lateral sclerosis, as well as neurodegeneration generally associated with ageing.

H2S-based fluorescent imaging for pathophysiological processes

Hydrogen sulfide (H2S), as an important endogenous signaling molecule, plays a vital role in many physiological processes. The abnormal behaviors of hydrogen sulfide in organisms may lead to various pathophysiological processes. Monitoring the changes in hydrogen sulfide is helpful for pre-warning and treating these pathophysiological processes. Fluorescence imaging techniques can be used to observe changes in the concentration of analytes in organisms in real-time. Therefore, employing fluorescent probes imaging to investigate the behaviors of hydrogen sulfide in pathophysiological processes is vital. This paper reviews the design strategy and sensing mechanisms of hydrogen sulfide-based fluorescent probes, focusing on imaging applications in various pathophysiological processes, including neurodegenerative diseases, inflammation, apoptosis, oxidative stress, organ injury, and diabetes. This review not only demonstrates the specific value of hydrogen sulfide fluorescent probes in preclinical studies but also illuminates the potential application in clinical diagnostics.

Hydrogen Sulfide (H2S) Signaling as a Protective Mechanism against Endogenous and Exogenous Neurotoxicants

In view of the significant role of H₂S in brain functioning, it is proposed that H₂S may also possess protective effects against adverse effects of neurotoxicants. Therefore, the objective of the present review is to discuss the neuroprotective effects of H₂S against toxicity of a wide spectrum of endogenous and exogenous agents involved in the pathogenesis of neurological diseases as etiological factors or key players in disease pathogenesis. Generally, the existing data demonstrate that H₂S possesses neuroprotective effects upon exposure to endogenous (amyloid β, glucose, and advanced-glycation end-products, homocysteine, lipopolysaccharide, and ammonia) and exogenous (alcohol, formaldehyde, acrylonitrile, metals, 6-hydroxydopamine, as well as 1-methyl-4-phenyl- 1,2,3,6- tetrahydropyridine (MPTP) and its metabolite 1-methyl-4-phenyl pyridine ion (MPP)) neurotoxicants. On the one hand, neuroprotective effects are mediated by S-sulfhydration of key regulators of antioxidant (Sirt1, Nrf2) and inflammatory response (NF-κB), resulting in the modulation of the downstream signaling, such as SIRT1/TORC1/CREB/BDNF-TrkB, Nrf2/ARE/HO-1, or other pathways. On the other hand, H₂S appears to possess a direct detoxicative effect by binding endogenous (ROS, AGEs, Aβ) and exogenous (MeHg) neurotoxicants, thus reducing their toxicity. Moreover, the alteration of H₂S metabolism through the inhibition of H₂S-synthetizing enzymes in the brain (CBS, 3-MST) may be considered a significant mechanism of neurotoxicity. Taken together, the existing data indicate that the modulation of cerebral H₂S metabolism may be used as a neuroprotective strategy to counteract neurotoxicity of a wide spectrum of endogenous and exogenous neurotoxicants associated with neurodegeneration (Alzheimer's and Parkinson's disease), fetal alcohol syndrome, hepatic encephalopathy, environmental neurotoxicant exposure, etc. In this particular case, modulation of H₂S-synthetizing enzymes or the use of H₂S-releasing drugs should be considered as the potential tools, although the particular efficiency and safety of such interventions are to be addressed in further studies.

Genetic Determinants of Survival in Parkinson's Disease in the Asian Population

BACKGROUND

Patients with Parkinson's disease (PD) have reduced life expectancy compared to the general population. Genetic variation was shown to play a role in the heterogeneity of survival for patients with PD, although the underlying genetic background remains poorly studied.

OBJECTIVE

The aim was to explore the genetic determinants influencing the survival of PD.

METHODS

We performed a genome-wide association analysis using a Cox proportional hazards model in a longitudinal cohort of 1080 Chinese patients with PD. Furthermore, we built a clinical-genetic model to predict the survival of patients using clinical variables combined with polygenic risk score (PRS) of survival of PD.

RESULTS

The cohort was followed up for an average of 7.13 years, with 85 incidents of death. One locus rs12628329 (RPL3) was significantly associated with reduced survival time by ~10.8 months (P = 2.72E-08, β = 1.79, standard error = 0.32). Functional exploration suggested this variant could upregulate the expression of RPL3 and induce apoptosis and cell death. In addition, adding PRS of survival in the prediction model substantially improved survival predictability (concordance index [Cindex]: 0.936) compared with the clinical model (Cindex: 0.860).

CONCLUSIONS

These findings improve the current understanding of the genetic cause of survival of PD and provide a novel target RPL3 for further research on PD pathogenesis and potential therapeutic options. Our results also demonstrate the potential utility of PRS of survival in identifying patients with shorter survival and providing personalized clinical monitoring and treatment. © 2022 International Parkinson and Movement Disorder Society.

Oxidative stress factors in Parkinson's disease

Parkinson's disease (PD) is the second most common cause of neurodegeneration. Over the last two decades, various hypotheses have been proposed to explain the etiology of PD. Among these is the oxidant-antioxidant theory, which asserts that local and systemic oxidative damage triggered by reactive oxygen species and other free radicals may promote dopaminergic neuron degeneration. Excessive reactive oxygen species formation, one of the underlying causes of pathology in the course of PD has been evidenced by various studies showing that oxidized macromolecules including lipids, proteins, and nucleic acids accumulate in brain tissues of PD patients. DNA oxidation may produce various lesions in the course of PD. Mutations incurred as a result of DNA oxidation may further enhance reactive oxygen species production in the brains of PD patients, exacerbating neuronal loss due to defects in the mitochondrial electron transport chain, antioxidant depletion, and exposure to toxic oxidized dopamine. The protein products of SNCA, PRKN, PINK1, DJ1, and LRRK2 genes are associated with disrupted oxidoreductive homeostasis in PD. SNCA is the first gene linked with familial PD and is currently known to be affected by six mutations correlated with the disorder: A53T, A30P, E46K, G51D, H50Q and A53E. PRKN encodes Parkin, an E3 ubiquitin ligase which mediates the proteasome degradation of redundant and disordered proteins such as glycosylated α-synuclein. Over 100 mutations have been found among the 12 exons of PRKN. PINK1, a mitochondrial kinase highly expressed in the brain, may undergo loss of function mutations which constitute approximately 1-8% of early onset PD cases. More than 50 PD-promoting mutations have been found in PINK1. Mutations in DJ-1, a neuroprotective protein, are a rare cause of early onset PD and constitute only 1% of cases. Around 20 mutations have been found in DJ1 among PD patients thus far. Mutations in the LRRK2 gene are the most common known cause of familial autosomal dominant PD and sporadic PD. Treatment of PD patients, especially in the advanced stages of the disease, is very difficult. The first step in managing progressive PD is to optimize dopaminergic therapy by increasing the doses of dopamine agonists and L-dopa. The next step is the introduction of advanced therapies, such as deep brain stimulation. Genetic factors may influence the response to L-dopa and deep brain stimulation therapy and the regulation of oxidative stress. Consequently, research into minimally invasive surgical interventions, as well as therapies that target the underlying etiology of PD is warranted.

Hydrogen sulfide in longevity and pathologies: Inconsistency is malodorous

Hydrogen sulfide (H₂S) is one of the biologically active gases (gasotransmitters), which plays an important role in various physiological processes and aging. Its production in the course of methionine and cysteine catabolism and its degradation are finely balanced, and impairment of H₂S homeostasis is associated with various pathologies. Despite the strong geroprotective action of exogenous H₂S in C. elegans, there are controversial effects of hydrogen sulfide and its donors on longevity in other models, as well as on stress resistance, age-related pathologies and aging processes, including regulation of senescence-associated secretory phenotype (SASP) and senescent cell anti-apoptotic pathways (SCAPs). Here we discuss that the translation potential of H₂S as a geroprotective compound is influenced by a multiplicity of its molecular targets, pleiotropic biological effects, and the overlapping ranges of toxic and beneficial doses. We also consider the challenges of the targeted delivery of H₂S at the required dose. Along with this, the complexity of determining the natural levels of H₂S in animal and human organs and their ambiguous correlations with longevity are reviewed.

Ag2S/Ag Nanoparticle Microelectrodes for In Vivo Potentiometric Measurement of Hydrogen Sulfide Dynamics in the Rat Brain

Hydrogen sulfide (H₂S) plays a pivotal role in gas signal transduction, neuroprotection, and regulation of physiological and pathological processes. However, in vivo tracking the dynamic of hydrogen sulfide in the complex brain environment still faces huge challenges. This study demonstrates a new potentiometric method to monitor in vivo the dynamics of hydrogen sulfide in the rat brain using silver nanoparticles (AgNPs)-modified carbon fiber microelectrodes (AgNPs/CFE) pretreated with Na₂S (i.e., Ag₂S/AgNPs/CFE), which acts as a solid-contact and ion-selective microelectrode. The Ag₂S/AgNPs/CFE exhibits good potential response toward hydrogen sulfide in the range of 2.5-160 μM, with a detection limit of 0.8 μM. Because of the presence of Ag₂S, the Ag₂S/AgNPs/CFE shows good selectivity to hydrogen sulfide, avoiding the interference from coexistent electroactive neurochemicals and the analogies, such as ascorbic acid and cysteine in the central nervous system. This good selectivity combined with the reversibility, protein antifouling, and biocompatibility of the microelectrode enables the Ag₂S/AgNPs/CFE to detect hydrogen sulfide in the rat brain during local microinfusion of Na₂S and the change in pH. Our study provides a reliable method to track hydrogen sulfide selectively in vivo, which will help to explore the function of hydrogen sulfide in neurophysiology and pathology.

Lentiviral mediated gene delivery as an effective therapeutic approach for Parkinson disease

Continual strategies to devise a complete therapeutic cure for neurodegenerative conditions has been a challenge, majorly due to the presence of blood brain barrier. Lack of targeted delivery in order to minimize loss of dopamine (DA) neurones has been a major challenge to overcome anomalies in Parkinson Disease (PD). PD is a neuromotor degenerative disorder deteriorating motor coordination in affected individuals. Recent research has highlighted the use of lentiviral vectors (LVs) for selective delivery of neuroprotective substance for complete halt of disease progression in PD. LVs have the ability to infect both dividing and non-dividing cells along with non-encoding capability of viral protein that might elicit an immune response. This review will mainly focus on understanding the basic mechanism of action of LVs and its therapeutic aid in PD.

Hydrogen sulfide enhances adult neurogenesis in a mouse model of Parkinson's disease

Hydrogen sulfide (H₂S) is regarded to be a protectant against diseases of the central nervous system and cardiovascular system. However, the mechanism by which H₂S elicits neuroprotective effects in the progression of Parkinson's disease (PD) remains unclear. To investigate the role of H₂S in delaying the pathological process of PD, we used the most common sodium hydrosulfide (NaHS) as an H₂S donor and established a mouse model of PD induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine/probenecid (MPTP/p) in the present study. Our results show that H₂S reduced neuronal loss during the progression of PD. Notably, we found that H₂S exhibited protective effects on dopaminergic neurons. Excitingly, H₂S also increased the proliferation of neural stem cells in the subventricular zone. Next, we evaluated whether the neuroprotective effects of H₂S on dopaminergic neurons in PD are dependent on adult nerve regeneration by treating primary adult neural stem cells cultured ex vivo with 1-methyl-4-phenylpyridine. Our results show that H₂S could prevent nerve injury induced by 1-methyl-4-phenylpyridine, promote the growth of neurospheres, and promote neurogenesis by regulating Akt/glycogen synthase kinase-3β/β-catenin pathways in adult neural stem cells. These findings confirm that H₂S can increase neurogenesis in an adult mouse model of PD by regulating the Akt/glycogen synthase kinase-3β/β-catenin signaling pathway. This study was approved by the Animal Care and Use Committee of Nanjing Medical University, China (IACUC Approval No. 1601153-3).

Hydrogen Sulfide and Carnosine: Modulation of Oxidative Stress and Inflammation in Kidney and Brain Axis

Emerging evidence indicates that the dysregulation of cellular redox homeostasis and chronic inflammatory processes are implicated in the pathogenesis of kidney and brain disorders. In this light, endogenous dipeptide carnosine (β-alanyl-L-histidine) and hydrogen sulfide (H₂S) exert cytoprotective actions through the modulation of redox-dependent resilience pathways during oxidative stress and inflammation. Several recent studies have elucidated a functional crosstalk occurring between kidney and the brain. The pathophysiological link of this crosstalk is represented by oxidative stress and inflammatory processes which contribute to the high prevalence of neuropsychiatric disorders, cognitive impairment, and dementia during the natural history of chronic kidney disease. Herein, we provide an overview of the main pathophysiological mechanisms related to high levels of pro-inflammatory cytokines, including interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and neurotoxins, which play a critical role in the kidney–brain crosstalk. The present paper also explores the respective role of H₂S and carnosine in the modulation of oxidative stress and inflammation in the kidney–brain axis. It suggests that these activities are likely mediated, at least in part, via hormetic processes, involving Nrf2 (Nuclear factor-like 2), Hsp 70 (heat shock protein 70), SIRT-1 (Sirtuin-1), Trx (Thioredoxin), and the glutathione system. Metabolic interactions at the kidney and brain axis level operate in controlling and reducing oxidant-induced inflammatory damage and therefore, can be a promising potential therapeutic target to reduce the severity of renal and brain injuries in humans.

Hydrogen sulfide signalling in the CNS - Comparison with NO

Hydrogen sulfide (H₂ S) together with polysulfides (H₂ S_n , n > 2) are signalling molecules like NO with various physiological roles including regulation of neuronal transmission, vascular tone, inflammation and oxygen sensing. H₂ S and H₂ S_n diffuse to the target proteins for S-sulfurating their cysteine residues that induces the conformational changes to alter the activity. On the other hand, 3-mercaptopyruvate sulfurtransferase transfers sulfur from a substrate 3-mercaptopyruvate to the cysteine residues of acceptor proteins. A similar mechanism has also been identified in S-nitrosylation. S-sulfuration and S-nitrosylation by enzymes proceed only inside the cell, while reactions induced by H₂ S, H₂ S_n and NO even extend to the surrounding cells. Disturbance of signalling by these molecules as well as S-sulfuration and S-nitrosylation causes many nervous system diseases. This review focuses on the signalling by H₂ S and H₂ S_n with S-sulfuration comparing to that of NO with S-nitrosylation and discusses on their roles in physiology and pathophysiology.

Hydrogen Sulfide Alleviates Anxiety, Motor, and Cognitive Dysfunctions in Rats with Maternal Hyperhomocysteinemia via Mitigation of Oxidative Stress

Hydrogen sulfide (H₂S) is endogenously produced from sulfur containing amino acids, including homocysteine and exerts neuroprotective effects. An increase of homocysteine during pregnancy impairs fetal growth and development of the offspring due to severe oxidative stress. We analyzed the effects of the H₂S donor—sodium hydrosulfide (NaHS) administered to female rats with hyperhomocysteinemia (hHcy) on behavioral impairments and levels of oxidative stress of their offspring. Rats born from females fed with control or high methionine diet, with or without H₂S donor injections were investigated. Rats with maternal hHcy exhibit increased levels of total locomotor activity and anxiety, decreased muscle endurance and motor coordination, abnormalities of fine motor control, as well as reduced spatial memory and learning. Oxidative stress in brain tissues measured by activity of glutathione peroxidases and the level of malondialdehyde was higher in rats with maternal hHcy. Concentrations of H₂S and the activity and expression of the H₂S generating enzyme—cystathionine-beta synthase—were lower compared to the control group. Administration of the H₂S donor to females with hHcy during pregnancy prevented behavioral alterations and oxidative stress of their offspring. The acquisition of behavioral together with biochemical studies will add to our knowledge about homocysteine neurotoxicity and proposes H₂S as a potential agent for therapy of hHcy associated disorders.

In vivo reduction of striatal D1R by RNA interference alters expression of D1R signaling-related proteins and enhances methamphetamine addiction in male rats

This study sought to determine if reducing dopamine D1 receptor (D1R) expression in the dorsal striatum (DS) via RNA-interference alters methamphetamine self-administration. A lentiviral construct containing a short hairpin RNA (shRNA) was used to knock down D1R expression (D1RshRNA). D1RshRNA in male rats increased responding for methamphetamine (i.v.) under a fixed-ratio schedule in an extended access paradigm, compared to D1R-intact rats. D1RshRNA also produced a vertical shift in a dose-response paradigm and enhanced responding for methamphetamine in a progressive-ratio schedule, generating a drug-vulnerable phenotype. D1RshRNA did not alter responding for sucrose (oral) under a fixed-ratio schedule compared to D1R-intact rats. Western blotting confirmed reduced D1R expression in methamphetamine and sucrose D1RshRNA rats. D1RshRNA reduced the expression of PSD-95 and MAPK-1 and increased the expression of dopamine transporter (DAT) in the DS from methamphetamine, but not sucrose rats. Sucrose density gradient fractionation was performed in behavior-naïve controls, D1RshRNA- and D1R-intact rats to determine the subcellular localization of D1Rs, DAT and D1R signaling proteins. D1Rs, DAT, MAPK-1 and PSD-95 predominantly localized to heavy fractions, and the membrane/lipid raft protein caveolin-1 (Cav-1) and flotillin-1 were distributed equally between buoyant and heavy fractions in controls. Methamphetamine increased localization of PSD-95, Cav-1, and flotillin-1 in D1RshRNA and D1R-intact rats to buoyant fractions. Our studies indicate that reduced D1R expression in the DS increases vulnerability to methamphetamine addiction-like behavior, and this is accompanied by striatal alterations in the expression of DAT and D1R signaling proteins and is independent of the subcellular localization of these proteins.

Hydrogen sulfide signaling in mitochondria and disease

Hydrogen sulfide can signal through 3 distinct mechanisms: 1) reduction and/or direct binding of metalloprotein heme centers, 2) serving as a potent antioxidant through reactive oxygen species/reactive nitrogen species scavenging, or 3) post-translational modification of proteins by addition of a thiol (-SH) group onto reactive cysteine residues: a process known as persulfidation. Below toxic levels, hydrogen sulfide promotes mitochondrial biogenesis and function, thereby conferring protection against cellular stress. For these reasons, increases in hydrogen sulfide and hydrogen sulfide-producing enzymes have been implicated in several human disease states. This review will first summarize our current understanding of hydrogen sulfide production and metabolism, as well as its signaling mechanisms; second, this work will detail the known mechanisms of hydrogen sulfide in the mitochondria and the implications of its mitochondrial-specific impacts in several pathologic conditions.-Murphy, B., Bhattacharya, R., Mukherjee, P. Hydrogen sulfide signaling in mitochondria and disease.

Increased susceptibility of mice obtained from in vitro fertilization to global cerebral ischemia-reperfusion injury: possible role of hydrogen sulphide and its biosynthetic enzymes

Aim of the Study: This study was designed to explore the relative susceptibility of in vitro fertilization (IVF)-conceived mice to global cerebral ischemic injury with the possible role of hydrogen sulphide and enzymes responsible for its production.Materials and Methods: IVF was carried to obtain pups, which were allowed to grow to the age of eight weeks. Thereafter, male mice were subjected to 20 min of global ischemia and 24 h of reperfusion. The mice obtained from other groups including normal mating, superovulation but normal mating and normal mating but embryo implantation were also subjected to global ischemia-reperfusion (I/R) injury.Results: IVF-derived mice exhibited significant more injury in response to I/R injury in comparison to other groups assessed in terms of impairment in locomotor activity, development of motor in coordination, neurological severity score, cerebral infarction and apoptosis markers (caspase-3 activity and Bcl-2 expression). Moreover, there was a relative decrease in the brain levels of hydrogen sulphide (H₂S) and its biosynthetic enzymes viz. cystathionine-β-synthase and cystathionine-γ-lyase. Interestingly, the levels of H₂S and cystathionine-γ-lyase were significantly low in IVF-derived mice in basal conditions also, i.e. before subjecting to I/R injury and these biochemical alterations were associated with the behavioural deficits in mice, even before subjecting to I/R injury.Conclusion: It is concluded that in vitro fertilization-derived mice are more susceptible to global cerebral I/R injury, which may be possibly due to decreased levels of hydrogen sulphide and its biosynthetic enzymes viz., cystathionine-β-synthase and cystathionine-γ-lyase.

A diet rich in taurine, cysteine, folate, B12 and betaine may lessen risk for Alzheimer's disease by boosting brain synthesis of hydrogen sulfide

The gaseous physiological modulator hydrogen sulfide (H₂S) has recently been shown to exert a variety of neuroprotective effects. In particular, the treatment of transgenic mouse models of Alzheimer's disease (AD) with agents that release H₂S aids preservation of cognitive function, suppresses brain production of amyloid beta, and decreases tau phosphorylation. The possible physiological relevance of these findings is suggested by the finding that brain and plasma levels of H₂S are markedly lower in AD patients than matched controls. Hence, nutraceutical strategies which boost brain synthesis or levels of H₂S may have potential for prevention of AD. The chief enzyme which synthesizes H₂S in brain parenchyma, cystathionine beta-synthase (CBS), employs cysteine as its rate-limiting substrate, and is allosterically activated by S-adenosylmethionine (SAM). Supplemental taurine has been shown to boost expression of this enzyme, as well as that of another H₂S source, cystathionine gamma-lyase, in vascular tissue, and to enhance plasma H₂S levels; in rats subjected to hemorrhagic stroke, co-administration of taurine has been shown to blunt a marked reduction in brain CBS expression. Brain levels of SAM are about half as high in AD patients as in controls, and this is thought to explain the reduction of brain H₂S in these patients. These considerations suggest that supplementation with cysteine, taurine, and agents which promote methyl group availability - such as SAM, folate, vitamin B₁₂, and betaine - may have potential for boosting brain synthesis of H₂S and thereby aiding AD prevention. Indeed, most of these agents have already demonstrated utility in mouse AD models - albeit the extent to which increased H₂S synthesis contributes to this protection remains unclear. Moreover, prospective epidemiology has associated low dietary or plasma levels of folate, B12, and taurine with increased dementia risk. Rodent studies suggest that effective nutraceutical strategies for boosting brain H₂S synthesis may in fact have broad neuroprotective utility, possibly aiding prevention and/or control not only of AD but also Parkinson's disease and glaucoma, while diminishing the neuronal damage associated with brain trauma or stroke.

Retinal α-synuclein deposits in Parkinson's disease patients and animal models

Despite decades of research, accurate diagnosis of Parkinson's disease remains a challenge, and disease-modifying treatments are still lacking. Research into the early (presymptomatic) stages of Parkinson's disease and the discovery of novel biomarkers is of utmost importance to reduce this burden and to come to a more accurate diagnosis at the very onset of the disease. Many have speculated that non-motor symptoms could provide a breakthrough in the quest for early biomarkers of Parkinson's disease, including the visual disturbances and retinal abnormalities that are seen in the majority of Parkinson's disease patients. An expanding number of clinical studies have investigated the use of in vivo assessments of retinal structure, electrophysiological function, and vision-driven tasks as novel means for identifying patients at risk that need further neurological examination and for longitudinal follow-up of disease progression in Parkinson's disease patients. Often, the results of these studies have been interpreted in relation to α-synuclein deposits and dopamine deficiency in the retina, mirroring the defining pathological features of Parkinson's disease in the brain. To better understand the visual defects seen in Parkinson's disease patients and to propel the use of retinal changes as biomarkers for Parkinson's disease, however, more conclusive neuropathological evidence for the presence of retinal α-synuclein aggregates, and its relation to the cerebral α-synuclein burden, is urgently needed. This review provides a comprehensive and critical overview of the research conducted to unveil α-synuclein aggregates in the retina of Parkinson's disease patients and animal models, and thereby aims to aid the ongoing discussion about the potential use of the retinal changes and/or visual symptoms as biomarkers for Parkinson's disease.

Pilose Antler Extracts (PAEs) Protect against Neurodegeneration in 6-OHDA-Induced Parkinson's Disease Rat Models

Parkinson's disease (PD) is one of the most common neurodegenerative diseases worldwide. Although dopamine replacement therapy mitigates motor dysfunction in PD patients, there are no therapeutics that are currently available to reverse neuronal cell death in the substantia nigra pars compacta (SNc), which is the main region for dopamine loss in PD patients. The protein concentration of the Pilose antler extracts (PAEs) was estimated using the Bradford Protein Assay Kit. Hematoxylin and eosin (HE) staining was used to evaluate the protective effect of PAEs on 6-OHDA induced cell death in PD model rats. Immunohistochemistry (IHC) was used to detect the tyrosine hydroxylase (TH) positive neuronal cell in SNc. HPLC-MS was used to detect dopamine (DA), 3,4-Dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), 5-hydroxytryptamine (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), and glutamate (Glu) levels in the striatum and cerebrospinal fluid (CSF). The amino acid level in the striatum and CSF was measured by HPLC-FLD. Protein expression of growth associated protein-43 (GAP-43) and neurofilament heavy polypeptide (NF-H) was measured using western blotting. The components of PAEs through blood vessels were detected by HPLC/MS/MS. In this study, PAEs with proteins ranging from 10 kDa to 250 kDa molecular weight was administered to 6-OHDA-induced PD rats. We found that PAEs inhibited 6-OHDA-induced neuronal cell death and TH-positive neuronal loss in SNc. PAEs administration also increased the levels of DA, DOPAC, and 5-HT, in addition to DOPAC/DA and HVA/DA indexes in the CSF and Striatum of 6-OHDA induced rats. Conversely, PAEs decreased the levels of Glu and GABA. Treatment with PAEs and Madopar increased GAP-43 and NF-H expression in the SNc and striatum. Proteomic analysis using LC/MS/MS indicated that 11 components of PAEs may have neuropharmacological effects. These results demonstrate that PAEs protects against 6-OHDA induced toxic effects in the PD rat models. Intragastric administration of PAEs may be a novel therapeutic strategy for neurodegenerative disorders like PD.

In vivo methods for acute modulation of gene expression in the central nervous system

Accurate and timely expression of specific genes guarantees the healthy development and function of the brain. Indeed, variations in the correct amount or timing of gene expression lead to improper development and/or pathological conditions. Almost forty years after the first successful gene transfection in in vitro cell cultures, it is currently possible to regulate gene expression in an area-specific manner at any step of central nervous system development and in adulthood in experimental animals in vivo, even overcoming the very poor accessibility of the brain. Here, we will review the diverse approaches for acute gene transfer in vivo, highlighting their advantages and disadvantages with respect to the efficiency and specificity of transfection as well as to brain accessibility. In particular, we will present well-established chemical, physical and virus-based approaches suitable for different animal models, pointing out their current and future possible applications in basic and translational research as well as in gene therapy.

Gasotransmitter hydrogen sulfide signaling in neuronal health and disease

Hydrogen sulfide is a gaseous signaling molecule or gasotransmitter which plays important roles in a wide spectrum of physiologic processes in the brain and peripheral tissues. Unlike nitric oxide and carbon monoxide, the other major gasotransmitters, research on hydrogen sulfide is still in its infancy. One of the modes by which hydrogen sulfide signals is via a posttranslational modification termed sulfhydration/persulfidation, which occurs on reactive cysteine residues on target proteins, where the reactive SH group is converted to an SSH group. Sulfhydration is a substantially prevalent modification, which modulates the structure or function of proteins being modified. Thus, precise control of endogenous hydrogen sulfide production and metabolism is critical for maintenance of optimal cellular function, with excess generation and paucity, both contributing to pathology. Dysregulation of the reverse transsulfuration pathway which generates hydrogen sulfide occurs in several neurodegenerative diseases such as Parkinson's disease, Huntington's disease and Alzheimer's disease. Accordingly, treatment with donors of hydrogen sulfide or stimulation of the reverse transsulfuration have proved beneficial in several neurodegenerative states. In this review we focus on hydrogen sulfide mediated neuronal signaling processes that contribute to neuroprotection.

International Union of Basic and Clinical Pharmacology. CII: Pharmacological Modulation of H2S Levels: H2S Donors and H2S Biosynthesis Inhibitors

Over the last decade, hydrogen sulfide (H2S) has emerged as an important endogenous gasotransmitter in mammalian cells and tissues. Similar to the previously characterized gasotransmitters nitric oxide and carbon monoxide, H2S is produced by various enzymatic reactions and regulates a host of physiologic and pathophysiological processes in various cells and tissues. H2S levels are decreased in a number of conditions (e.g., diabetes mellitus, ischemia, and aging) and are increased in other states (e.g., inflammation, critical illness, and cancer). Over the last decades, multiple approaches have been identified for the therapeutic exploitation of H2S, either based on H2S donation or inhibition of H2S biosynthesis. H2S donation can be achieved through the inhalation of H2S gas and/or the parenteral or enteral administration of so-called fast-releasing H2S donors (salts of H2S such as NaHS and Na2S) or slow-releasing H2S donors (GYY4137 being the prototypical compound used in hundreds of studies in vitro and in vivo). Recent work also identifies various donors with regulated H2S release profiles, including oxidant-triggered donors, pH-dependent donors, esterase-activated donors, and organelle-targeted (e.g., mitochondrial) compounds. There are also approaches where existing, clinically approved drugs of various classes (e.g., nonsteroidal anti-inflammatories) are coupled with H2S-donating groups (the most advanced compound in clinical trials is ATB-346, an H2S-donating derivative of the non-steroidal anti-inflammatory compound naproxen). For pharmacological inhibition of H2S synthesis, there are now several small molecule compounds targeting each of the three H2S-producing enzymes cystathionine-β-synthase (CBS), cystathionine-γ-lyase, and 3-mercaptopyruvate sulfurtransferase. Although many of these compounds have their limitations (potency, selectivity), these molecules, especially in combination with genetic approaches, can be instrumental for the delineation of the biologic processes involving endogenous H2S production. Moreover, some of these compounds (e.g., cell-permeable prodrugs of the CBS inhibitor aminooxyacetate, or benserazide, a potentially repurposable CBS inhibitor) may serve as starting points for future clinical translation. The present article overviews the currently known H2S donors and H2S biosynthesis inhibitors, delineates their mode of action, and offers examples for their biologic effects and potential therapeutic utility.