Effects of hydrogen sulfide on cognitive dysfunction and NR2B in rats

Therapeutic importance of hydrogen sulfide in cognitive impairment diseases

The brain naturally synthesizes hydrogen sulfide (H2S) via enzymes such as cystathionine-β-synthase (CBS), 3-mercaptopyruvate sulfurtransferase (3-MST), cysteine aminotransferase (CAT), and cystathionine-γ-lyase (CSE). From a physiological point of view, H2S serves as a neuromodulator with antioxidant and neuroprotective properties. Recent research suggests that H2S is crucial in regulating learning and memory, as its downregulation is commonly observed in cognitive impairment diseases. Preclinical studies suggest that external supplementation, through donors like sodium hydrosulfide (NaHS), can improve cognitive impairment in various cognitive disorder models. Moreover, numerous molecular mechanisms have been proposed to explain the effects of these H2S donors. This review aims to detail the roles of H2S in various models of cognitive impairment and in human subjects, highlighting its potential mechanisms and providing experimental support for its use as a novel therapeutic approach in treating cognitive disorders. Overall, H2S plays a significant role in the treatment of cognitive impairment diseases, but further large-scale studies are still required to support the results of current research.

Neuroprotective signaling by hydrogen sulfide and its dysregulation in Alzheimer's disease

The ancient messenger molecule hydrogen sulfide (H2S) modulates myriad signaling cascades and has been conserved across evolutionary boundaries. Although traditionally known as an environmental toxin, H2S is also synthesized endogenously to exert modulatory and homeostatic effects in a broad array of physiologic functions. Notably, H2S levels are tightly physiologically regulated, as both its excess and paucity can be toxic. Accumulating evidence has revealed pivotal roles for H2S in neuroprotection and normal cognitive function, and H2S homeostasis is dysregulated in neurodegenerative conditions. Here, we review the normal neuroprotective roles of H2S that go awry in Alzheimer's disease, the most common form of neurodegenerative disease.

Hydrogen Sulfide and Functional Therapy: Novel Mechanisms from Epigenetics

Hydrogen sulfide (H2S) is a gasotransmitter with significant physiological effects, including anti-inflammatory properties, regulation of oxidative stress, and vasodilation, thus regulating body functions. Functional therapy involves using treatments that target the underlying cause of a disease, rather than simply treating symptoms. Epigenetics refers to changes in gene expression that occur through modifications to DNA, to the proteins that package DNA, or to noncoding RNA mechanisms. Recent research advances suggest that H2S may play a role in epigenetic regulation by altering DNA methylation patterns and regulating histone deacetylases, enzymes that modify histone proteins, or modulating microRNA mechanisms. These critical findings suggest that H2S may be a promising molecule for functional therapy in various diseases where epigenetic modifications are dysregulated. We reviewed the relevant research progress in this area, hoping to provide new insights into the epigenetic mechanisms of H2S. Despite the challenges of clinical use of H2S, future research may lead to the progress of new therapeutic approaches. Antioxid. Redox Signal. 40, 110-121.

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.

Clinical Improvement in Depression and Cognitive Deficit Following Electroconvulsive Therapy

Electroconvulsive therapy (ECT) is a long-standing treatment choice for disorders such as depression when pharmacological treatments have failed. However, a major drawback of ECT is its cognitive side effects. While numerous studies have investigated the therapeutic effects of ECT and its mechanism, much less research has been conducted regarding the mechanism behind the cognitive side effects of ECT. As both clinical remission and cognitive deficits occur after ECT, it is possible that both may share a common mechanism. This review highlights studies related to ECT as well as those investigating the mechanism of its outcomes. The process underlying these effects may lie within BDNF and NMDA signaling. Edema in the astrocytes may also be responsible for the adverse cognitive effects and is mediated by metabotropic glutamate receptor 5 and the protein Homer1a.

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 Overproduction Is Involved in Acute Ischemic Cerebral Injury Under Hyperhomocysteinemia

Objectives

This study aimed to identify the involvement of hydrogen sulfide overproduction in acute brain injury under ischemia/reperfusion and hyperhomocysteinemia.

Methods

In vitro and in vivo experiments were conducted to determine: the effect of sodium hydrosulfide treatment on the human neuroblastoma cell line (SH-SY5Y) under conditions of oxygen and glucose deprivation; the changes of hydrogen sulfide levels, inflammatory factors, energetic metabolism, and mitochondrial function in the brain tissue of rats under either ischemia/reperfusion alone or a combination of ischemia/reperfusion and hyperhomocysteinemia; and the potential mechanism underlying the relationship between homocysteine and these changes through the addition of the related inhibitors. Furthermore, experimental technologies, including western blot, enzyme-linked immunosorbent assay, immunofluorescence, reverse transcription polymerase chain reaction, and flow cytometry, were used.

Results

Our study found that high concentration of sodium hydrosulfide treatment aggravated the decrease in mitochondrial membrane potential, the increase in both mitochondrial permeability transition pore and translocation of cytochrome C, as well as the accumulation of reactive oxygen species in oxygen and glucose deprived SH-SY5Y cells. As a result, neurological deficit appeared in rats with ischemia/reperfusion or ischemia/reperfusion and hyperhomocysteinemia, and a higher water content and larger infarction size of cerebral tissue appeared in rats combined ischemia/reperfusion and hyperhomocysteinemia. Furthermore, alterations in hydrogen sulfide production, inflammatory factors, and mitochondria morphology and function were more evident under the combined ischemia/reperfusion and hyperhomocysteinemia. These changes were, however, alleviated by the addition of inhibitors for CBS, CSE, Hcy, H₂S, and NF-κB, although at different levels. Finally, we observed a negative relationship between the blockage of: (a) the nuclear factor kappa-B pathway and the levels of cystathionine β-synthase and hydrogen sulfide; and (b) the hydrogen sulfide pathway and the levels of inflammatory factors.

Conclusion

Hydrogen sulfide overproduction and reactive inflammatory response are involved in ischemic cerebral injury under hyperhomocysteinemia. Future studies in this direction are warranted to provide a scientific base for targeted medicine development.

Hepatoprotective effect of sodium hydrosulfide on hepatic encephalopathy in rats

Hydrogen sulfide is well-known to exhibit anti-inflammatory and cytoprotective activities, and also has protective effects in the liver. This study aimed to examine the protective effect of hydrogen sulfide in rats with hepatic encephalopathy, which was induced by mild bile duct ligation. In this rat model, bile ducts were mildly ligated for 26 days. Rats were treated for the final 5 days with sodium hydrosulfide (NaHS). NaHS (25 µmol/kg), 0.5% sodium carboxymethyl cellulose, or silymarin (100 mg/kg) was administered intraperitoneally once per day for 5 consecutive days. Mild bile duct ligation caused hepatotoxicity and inflammation in rats. Intraperitoneal NaHS administration reduced levels of aspartate aminotransferase and alanine aminotransferase, which are indicators of liver disease, compared to levels in the control mild bile duct ligation group. Levels of ammonia, a major causative factor of hepatic encephalopathy, were also significantly decreased. Malondialdehyde, myeloperoxidase, catalase, and tumor necrosis factor-α levels were measured to confirm antioxidative and anti-inflammatory effects. N-Methyl-D-aspartic acid (NMDA) receptors with neurotoxic activity were assessed for subunit NMDA receptor subtype 2B. Based on these data, NaHS is suggested to exhibit hepatoprotective effects and guard against neurotoxicity through antioxidant and anti-inflammatory actions.

Hydrogen Sulfide as a Novel Regulatory Factor in Liver Health and Disease

Hydrogen sulfide (H₂S), a colorless gas smelling of rotten egg, has long been recognized as a toxic gas and environment pollutant. However, increasing evidence suggests that H₂S acts as a novel gasotransmitter and plays important roles in a variety of physiological and pathological processes in mammals. H₂S is involved in many hepatic functions, including the regulation of oxidative stress, glucose and lipid metabolism, vasculature, mitochondrial function, differentiation, and circadian rhythm. In addition, H₂S contributes to the pathogenesis and treatment of a number of liver diseases, such as hepatic fibrosis, liver cirrhosis, liver cancer, hepatic ischemia/reperfusion injury, nonalcoholic fatty liver disease/nonalcoholic steatohepatitis, hepatotoxicity, and acute liver failure. In this review, the biosynthesis and metabolism of H₂S in the liver are summarized and the role and mechanism of H₂S in liver health and disease are further discussed.

Dephosphorylation by calcineurin regulates translocation of dynamin-related protein 1 to mitochondria in hepatic ischemia reperfusion induced hippocampus injury in young mice

Hepatic ischemia reperfusion (HIR) has been found to induce brain injury and cognitive dysfunction. Dynamin-related protein 1 (Drp1) mediated mitochondrial fission involves oxidative stress, apoptosis and several neurological diseases. In this study, we investigated whether Drp1 translocation to mitochondria was implicated in HIR induced hippocampus injury in young mice, and further detected the role of calcineurin in the regulation of mitochondrial dynamics. 2-week C57BL/6 mice were chosen to make HIR model. Western blot was used to detect mitochondrial dynamics regulating proteins in whole hippocampal tissues and extracted mitochondria. Transmission electron microscopy was used to observe mitochondrial morphology. TUNEL staining and ELISA (serum S100β/NSE concentrations) were used to evaluate neurons apoptosis and brain injury respectively. Drp1 inhibitor Mdivi-1 and calcineurin inhibitor FK506 were utilized to further confirm the role of Drp1 and calcineurin. Results showed that HIR affected mitochondrial dynamics in a fission-dominant manner with translocation of Drp1 to mitochondria in hippocampus of young mice. HIR induced increased expression of calcineurin and dephosphorylation of Drp1 at Ser637 in hippocampus. Treatment with Mdivi-1 and FK506 upregulated the phosphorylation of Drp1, inhibited Drp1 translocation to mitochondria, and alleviated mitochondrial fragmentation after HIR. What's more, Mdivi-1 and FK506 restrained cytochrome c release and cleaved caspase-3 expression, ameliorated hippocampal neurons apoptosis, and decreased serum S100β/NSE concentrations as well. These data suggest that calcineurin mediated Drp1 dephosphorylation and translocation to mitochondria play a crucial role in HIR induced mitochondrial fragmentation and neurons apoptosis in hippocampus.

Dietary methionine restriction ameliorates the impairment of learning and memory function induced by obesity in mice

Dietary methionine restriction improves impairment of learning and memory function induced by obesity, likely by increasing H₂S production.

Surgery, neuroinflammation and cognitive impairment

Trauma experienced during surgery can contribute to the development of a systemic inflammatory response that can cause multi-organ dysfunction or even failure. Post-surgical neuroinflammation is a documented phenomenon that results in synaptic impairment, neuronal dysfunction and death, and impaired neurogenesis. Various pro-inflammatory cytokines, such as TNFα, maintain a state of chronic neuroinflammation, manifesting as post-operative cognitive dysfunction and post-operative delirium. Furthermore, elderly patients with post-operative cognitive dysfunction or delirium are three times more likely to experience permanent cognitive impairment or dementia. We conducted a narrative review, considering evidence extracted from various databases including Pubmed, MEDLINE and EMBASE, as well as journals and book reference lists. We found that further pre-clinical and well-powered clinical studies are required to delineate the precise pathogenesis of post-operative delirium and cognitive dysfunction. Despite the burden of post-operative neurological sequelae, clinical studies investigating therapeutic agents, such as dexmedetomidine, ibuprofen and statins, have yielded conflicting results. In addition, evidence supporting novel therapeutic avenues, such as nicotinic and HMGB-1 targeting and remote ischaemic pre-conditioning, is limited and necessitates further investigation.

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.

Hydrogen sulfide attenuates chronic restrain stress-induced cognitive impairment by upreglulation of Sirt1 in hippocampus

Chronic restraint stress (CRS) has detrimental effects on cognitive function. Hydrogen sulfide (H₂S), as a neuromodulator, regulates learning and memory. Hippocampus is a key structure in learning and memory. Sirt1 (silence signal regulating factor 1) plays an important role in modulating cognitive function. Therefore, our present work was to investigate whether H₂S meliorates CRS-induced damage in hippocampus and impairment in cognition, and further to explore whether the underlying mechanism is via upreglulating Sirt1. In our present work, the behavior experiments [Y-maze test, Novel object recognition (NOR) test, Morris water maze (MWM) test] showed that sodium hydrosulfide (NaHS, a donor of H₂S) blocked CRS-induced cognitive impairments in rats. NaHS inhibited CRS-induced hippocampal oxidative stress as evidenced by decrease in MDA level as well as increases in GSH content and SOD activity. NaHS rescued CRS-generated ER stress as evidenced by downregulations of CPR78, CHOP, and cleaved caspase-12. NaHS reduced CRS-exerted apoptosis as evidenced by decreases in the number of TUNEL-positive cells and Bax expression as well as increase in Bcl-2 expression. NaHS upregulated the expression of Sirt1 in the hippocampus of CRS-exposed rats. Furthermore, inhibited Sirt1 by Sirtinol reversed the protective effects of NaHS against CRS-produced cognitive dysfunction and oxidative stress, ER stress as well as apoptosis in hippocampus. Together, these results suggest that H₂S meliorates CRS-induced hippocampal damage and cognitive impairment by upregulation of hippocampal Sirt1.