Protective Roles of Hydrogen Sulfide in Alzheimer's Disease and Traumatic Brain Injury

Recent advances in the role of gasotransmitters in necroptosis

Necroptosis is a finely regulated programmed cell death process involving complex molecular mechanisms and signal transduction networks. Among them, receptor-interacting protein kinase 1 (RIPK1), receptor-interacting protein kinase 3 (RIPK3) and mixed lineage kinase domain-like protein are the key molecules regulating this process. In recent years, gasotransmitters such as nitric oxide, carbon monoxide and hydrogen sulfide have been suggested to play a regulatory role in necroptosis. This paper reviews the evidence that these gasotransmitters are involved in the regulation of necroptosis by influencing the production of reactive oxygen species, regulating the modification of S subunits of RIPK1 and RIPK3, regulating inflammatory mediators, and signal transduction. In addition, this review explores the potential therapeutic applications of these gasotransmitters in pathological conditions such as cardiovascular disease and ischemia-reperfusion injury. Although some studies have revealed the important role of gasotransmitters in necroptosis, the specific mechanism of action is still not fully understood. Future research is needed to further elucidate the molecular mechanisms of gasotransmitters in precisely regulating necroptosis, which will help develop new therapeutic strategies to prevent and treat related diseases.

Hydrogen Sulfide (H2S- or H2Sn-Polysulfides) in Synaptic Plasticity: Modulation of NMDA Receptors and Neurotransmitter Release in Learning and Memory

Hydrogen sulfide (H2S) has emerged as a pivotal gaseous transmitter in the central nervous system, influencing synaptic plasticity, learning, and memory by modulating various molecular pathways. This review examines recent evidence regarding how H2S regulates NMDA receptor function and neurotransmitter release in neuronal circuits. By synthesizing findings from animal and cellular models, we investigate the impacts of enzymatic H2S production and exogenous H2S on excitatory synaptic currents, long-term potentiation, and intracellular calcium signaling. Data suggest that H2S interacts directly with NMDA receptor subunits, altering receptor function and modulating neuronal excitability. Simultaneously, H2S promotes the release of neurotransmitters such as glutamate and GABA, shaping synaptic dynamics and plasticity. Furthermore, reports indicate that disruptions in H2S metabolism contribute to cognitive impairments and neurodegenerative disorders, underscoring the potential therapeutic value of targeting H2S-mediated pathways. Although the precise mechanisms of H2S-induced changes in synaptic strength remain elusive, a growing body of evidence positions H2S as a significant regulator of memory formation processes. This review calls for more rigorous exploration into the molecular underpinnings of H2S in synaptic plasticity, paving the way for novel pharmacological interventions in cognitive dysfunction.

Homogeneous dual-mode ECL-FL sensor for sensitive hydrogen sulfide detection: Mechanistic insights and applications in environmental and bioanalytical monitoring

A dual-mode electrochemiluminescence (ECL) and fluorescence (FL) probe was developed based on functionalized metal-organic framework nanosheets (RuMOFNSs) and (3-((2,4-dinitrophenyl)thio)phenyl)methanol (DNB) for the highly sensitive detection of hydrogen sulfide (H₂S) in homogeneous systems. Compared to conventional heterogeneous detection strategies, the homogeneous nature of this probe eliminates signal loss associated with solid-phase immobilization, thereby enhancing the interaction efficiency between the probe and target molecules. The developed sensing platform exhibited exceptional sensitivity, achieving detection limits of 0.18 pM in ECL and 0.4 nM in FL, with recovery rates ranging from 96.1 % to 101.7 %. Moreover, the probe demonstrated high selectivity against potential interfering metal ions and proved effective for monitoring food spoilage and dynamic H₂S fluctuations in rat brain tissue. Compared to existing detection approaches, this dual-mode probe offers superior sensitivity, selectivity, and broader applicability, underscoring its potential for environmental and biomedical analyse.

NaHS alters synaptic plasticity proteins and enhances dendritic arborization to improve cognitive and motor deficits after traumatic brain injury in mice

BACKGROUND AND PURPOSE

Traumatic brain injury (TBI) is a complex medical condition affecting people globally. Hydrogen sulfide (H2S) is a recently discovered gaseous mediator and is dysregulated in the brain after TBI. Sodium hydrogen sulfide (NaHS), a known donor of H2S, is beneficial in various biological processes involving aging and diseases, including injury. It is neuroprotective against oxidative stress, neuroinflammation, and other secondary injury processes. However, the NaHS-H2S system has not been investigated as a regulator of injury-mediated synaptic plasticity proteins and the underlying mechanisms after TBI.

EXPERIMENTAL APPROACH

We developed a model of TBI in Swiss albino mice to study the effects of exogenous H2S, administered as NaHS. We assessed cognitive function (Barnes maze and novel object recognition) and motor function (rotarod). Brain tissue was analysed with ELISA, qRT-PCR, immunoblotting, Golgi-cox staining, and immunofluorescence.

KEY RESULTS

NaHS administration restored the injury-caused decline in H2S levels. Injury-mediated oxidative stress parameters were improved following NaHS. It down-regulated TBI biomarkers, ameliorated the synaptic marker proteins, and improved cognitive and motor deficits. These changes were accompanied by enhanced dendritic arborization and spine number. Restoration of N-methyl D-aspartate receptor subunits and diminished glutamate and calcium levels, along with marked changes in microtubule-associated protein 2 A and calcium/calmodulin-dependent protein kinase II, formed the basis of the underlying mechanism(s).

CONCLUSION AND IMPLICATIONS

Our findings suggest that NaHS could have therapeutic activity against TBI, as it ameliorated cognitive and motor deficits caused by changes in synaptic plasticity proteins and dendritic arborisation, in our model.

Hydrogen Sulfide Alleviates Schizophrenia-Like Behavior Through Regulating Apoptosis by S-Sulfhydrylation Modification

BACKGROUND

We initiated an exploration of the relationship between hydrogen sulfide (H2S) and Schizophrenia (SZ) as well as its mechanism at the three levels of population study, cellular investigation, and animal model.

MATERIALS AND METHODS

Clinical data and peripheral blood samples from 78 patients with SZ and 83 healthy controls (HC) were collected for the detection of H2S levels (ChiCTR (Chinese Clinical Trial Registry) 900026776). MK801 (Dizocilpine) was used to establish SZ models in cells and rats, with sodium hydrosulfide (NaHS) serving as an exogenous H2S donor. H2S levels in plasma and hippocampal tissue of rats were measured using Enzyme Linked Immunosorbent Assay (ELISA). Terminal dUTP Nick End Labeling (TUNEL) staining was employed to detect apoptosis, enzyme activity was determined to assess apoptotic protease activity, neuron damage was identified by Nissl staining, and the protein S-sulfhydrylation test was utilized to evaluate alterations in apoptosis-associated protein S-sulfhydrylation.

RESULTS

H2S content significantly decreased in the plasma of SZ patients and in the plasma and hippocampal tissue of SZ model rats. NaHS pretreatment reduced MK801-induced apoptosis in SH-SY5Y cells. SZ model rats exhibited increased behavioral abnormalities, hippocampal apoptosis, and reduced S-sulfhydrylation of an apoptosis-related protein, both restored after NaHS pretreatment.

CONCLUSIONS

H2S content is significantly reduced in SZ, and supplementation of H2S can alleviate SZ-like behavior by inducing S-sulfhydration of apoptotic proteins.

Critical role of hydrogen sulfide in the management of neurodegenerative disease

Hydrogen sulfide has been known to humans for about 300 years and the previous studies emphasize only on its toxic side effects. In the last two decennium, researchers have varied their perspectives and insights towards H2S biology based on experimental findings. It has been found that H2S is an endogenic gaseous signaling molecule in many organisms and plays a crucial role in many systems and diseases. Early reports suggest that H2S as a neuromodulator influences calcium levels within the brain cells which ultimately control memory, learning, and cognition. It has also been observed that some complications in the pathogenesis of neurodegenerative diseases are due to anomalies in the biosynthesis and metabolism of H2S. This review focuses on the role of H2S in the pathophysiology of major neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, Huntington's disease and Vascular dementia. H2S was observed to have a protective role in the above-mentioned neurological conditions and the H2S donor therapy may help in disease management. The H2S gas displays a neuroprotective role and protects against cellular damage thereby declining the neurological conditions. Some studies have revealed that treatment with H2S donors has improved neuronal damage, restored memory and cognition in animal models. In this review, we have discussed the role of H2S donors as neuroprotective agents with examples of some of the natural and synthetic H2S donors, and also briefly enumerated the molecules used to detect H2S in neurodegenerative diseases.

Fecal Microbiota Transplantation Improves Cognitive Function of a Mouse Model of Alzheimer's Disease

BACKGROUND

A growing body of evidence suggests a link between the gut microbiota and Alzheimer's disease (AD), although the underlying mechanisms remain elusive. This study aimed to investigate the impact of fecal microbiota transplantation (FMT) on cognitive function in a mouse model of AD.

METHODS

Four-month-old 5 × FAD (familial Alzheimer's disease) mice underwent antibiotic treatment to deplete their native gut microbiota. Subsequently, they received FMT either weekly or every other day. After 8 weeks, cognitive function and β-amyloid (Aβ) load were assessed through behavioral testing and pathological analysis, respectively. The composition of the gut microbiota was analyzed using 16S rRNA sequencing.

RESULTS

Initial weekly FMT failed to alleviate memory deficits or reduce brain Aβ pathology in 5 × FAD mice. In contrast, FMT administered every other day effectively restored gut dysbiosis in 5 × FAD mice and decreased Aβ pathology and lipopolysaccharide levels in the colon and hippocampus. Mechanistically, FMT reduced the expression of amyloid β precursor protein, β-site APP cleaving enzyme 1, and presenilin-1, potentially by inhibiting the Toll-like receptor 4/inhibitor of kappa B kinase β/nuclear factor kappa-B signaling pathway. However, the cognitive benefits of FMT on 5 × FAD mice diminished over time.

CONCLUSION

These findings demonstrate the dose- and time-dependent efficacy of FMT in mitigating AD-like pathology, underscoring the potential of targeting the gut microbiota for AD treatment.

Sodium Thiosulfate: An Innovative Multi-Target Repurposed Treatment Strategy for Late-Onset Alzheimer's Disease

Late-onset Alzheimer's disease (LOAD) is a chronic, multifactorial, and progressive neurodegenerative disease that associates with aging and is highly prevalent in our older population (≥65 years of age). This hypothesis generating this narrative review will examine the important role for the use of sodium thiosulfate (STS) as a possible multi-targeting treatment option for LOAD. Sulfur is widely available in our environment and is responsible for forming organosulfur compounds that are known to be associated with a wide range of biological activities in the brain. STS is known to have (i) antioxidant and (ii) anti-inflammatory properties; (iii) chelation properties for calcium and the pro-oxidative cation metals such as iron and copper; (iv) donor properties for hydrogen sulfide production; (v) possible restorative properties for brain endothelial-cell-derived bioavailable nitric oxide. Thus, it becomes apparent that STS has the potential for neuroprotection and neuromodulation and may allow for an attenuation of the progressive nature of neurodegeneration and impaired cognition in LOAD. STS has been successfully used to prevent cisplatin oxidative-stress-induced ototoxicity in the treatment of head and neck and solid cancers, cyanide and arsenic poisoning, and fungal skin diseases. Most recently, intravenous STS has become part of the treatment plan for calciphylaxis globally due to vascular calcification and ischemia-induced skin necrosis and ulceration. Side effects have been minimal with reports of metabolic acidosis and increased anion gap; as with any drug treatment, there is also the possibility of allergic reactions, possible long-term osteoporosis from animal studies to date, and minor side-effects of nausea, headache, and rhinorrhea if infused too rapidly. While STS poorly penetrates the intact blood-brain barrier(s) (BBBs), it could readily penetrate BBBs that are dysfunctional and disrupted to deliver its neuroprotective and neuromodulating effects in addition to its ability to penetrate the blood-cerebrospinal fluid barrier of the choroid plexus. Novel strategies such as the future use of nano-technology may be helpful in allowing an increased entry of STS into the brain.

Electron transfer in biological systems

Examples of how metalloproteins feature in electron transfer processes in biological systems are reviewed. Attention is focused on the electron transport chains of cellular respiration and photosynthesis, and on metalloproteins that directly couple electron transfer to a chemical reaction. Brief mention is also made of extracellular electron transport. While covering highlights of the recent and the current literature, this review is aimed primarily at introducing the senior undergraduate and the novice postgraduate student to this important aspect of bioinorganic chemistry.

New insight on the potential detrimental effect of metabolic syndrome on the Alzheimer disease neuropathology: Mechanistic role

The metabolic syndrome or syndrome X is a clustering of different components counting insulin resistance (IR), glucose intolerance, visceral obesity, hypertension and dyslipidemia. It has been shown that IR and dysregulation of insulin signalling play a critical role in the development of metabolic syndrome by initiating the pathophysiology of metabolic syndrome through induction of glucolipotoxicity, impairment of glucose disposal and triggering of pro-inflammatory response. Furthermore, metabolic syndrome unfavourably affects the cognitive function and the development of different neurodegenerative diseases such as Alzheimer disease (AD) by inducing oxidative stress, neuroinflammation and brain IR. These changes together with brain IR impair cerebrovascular reactivity leading to cognitive impairment. In addition, metabolic syndrome increases the risk for the development of AD. However, the central mechanisms by which metabolic syndrome amplify AD risk are not completely elucidated. Consequently, this narrative review aims to revise from published articles the association between metabolic syndrome and AD regarding cellular and subcellular pathways. In conclusion, metabolic syndrome is regarded as a potential risk factor for the induction of AD neuropathology by different signalling pathways such as initiation of brain IR, activation of inflammatory signalling pathways and neuroinflammation.

Role of Microbiota-Derived Hydrogen Sulfide (H2S) in Modulating the Gut-Brain Axis: Implications for Alzheimer's and Parkinson's Disease Pathogenesis

Microbiota-derived hydrogen sulfide (H2S) plays a crucial role in modulating the gut-brain axis, with significant implications for neurodegenerative diseases such as Alzheimer's and Parkinson's. H2S is produced by sulfate-reducing bacteria in the gut and acts as a critical signaling molecule influencing brain health via various pathways, including regulating inflammation, oxidative stress, and immune responses. H2S maintains gut barrier integrity at physiological levels and prevents systemic inflammation, which could impact neuroinflammation. However, as H2S has a dual role or a Janus face, excessive H2S production, often resulting from gut dysbiosis, can compromise the intestinal barrier and exacerbate neurodegenerative processes by promoting neuroinflammation and glial cell dysfunction. This imbalance is linked to the early pathogenesis of Alzheimer's and Parkinson's diseases, where the overproduction of H2S exacerbates beta-amyloid deposition, tau hyperphosphorylation, and alpha-synuclein aggregation, driving neuroinflammatory responses and neuronal damage. Targeting gut microbiota to restore H2S homeostasis through dietary interventions, probiotics, prebiotics, and fecal microbiota transplantation presents a promising therapeutic approach. By rebalancing the microbiota-derived H2S, these strategies may mitigate neurodegeneration and offer novel treatments for Alzheimer's and Parkinson's diseases, underscoring the critical role of the gut-brain axis in maintaining central nervous system health.

A unique near-infrared fluorescent probe based on dual-DNP binding sites for rapid monitoring of hydrogen sulfide in food samples and living cells

A new NIR fluorescent probe (DCIQ-2DNP), which combined the thiolysis of dinitrophenyl (DNP) ether and DNP-marked electron-deficient quaternary carbon, was reported for the first time for detection of H2S. The DCIQ-2DNP probe showed an NIR emission signal (740 nm), a large Stokes shift (128 nm), and rapid monitoring of hydrogen sulfide (within 60 s) in food samples and living cells.

Novelties on Neuroinflammation in Alzheimer's Disease-Focus on Gut and Oral Microbiota Involvement

Recent studies underscore the role of gut and oral microbiota in influencing neuroinflammation through the microbiota-gut-brain axis, including in Alzheimer's disease (AD). This review aims to provide a comprehensive synthesis of recent findings on the involvement of gut and oral microbiota in the neuroinflammatory processes associated with AD, emphasizing novel insights and therapeutic implications. This review reveals that dysbiosis in AD patients' gut and oral microbiota is linked to heightened peripheral and central inflammatory responses. Specific bacterial taxa, such as Bacteroides and Firmicutes in the gut, as well as Porphyromonas gingivalis in the oral cavity, are notably altered in AD, leading to significant changes in microglial activation and cytokine production. Gut microbiota alterations are associated with increased intestinal permeability, facilitating the translocation of endotoxins like lipopolysaccharides (LPS) into the bloodstream and exacerbating neuroinflammation by activating the brain's toll-like receptor 4 (TLR4) pathways. Furthermore, microbiota-derived metabolites, including short-chain fatty acids (SCFAs) and amyloid peptides, can cross the blood-brain barrier and modulate neuroinflammatory responses. While microbial amyloids may contribute to amyloid-beta aggregation in the brain, certain SCFAs like butyrate exhibit anti-inflammatory properties, suggesting a potential therapeutic avenue to mitigate neuroinflammation. This review not only highlights the critical role of microbiota in AD pathology but also offers a ray of hope by suggesting that modulating gut and oral microbiota could represent a novel therapeutic strategy for reducing neuroinflammation and slowing disease progression.

Lactobacillus Eats Amyloid Plaque and Post-Biotically Attenuates Senescence Due to Repeat Expansion Disorder and Alzheimer's Disease

Patients with Alzheimer's disease and related dementia (ADRD) are faced with a formidable challenge of focal amyloid deposits and cerebral amyloid angiopathy (CAA). The treatment of amyloid deposits in ADRD by targeting only oxidative stress, inflammation and hyperlipidemia has not yielded significant positive clinical outcomes. The chronic high-fat diet (HFD), or gut dysbiosis, is one of the major contributors of ADRD in part by disrupted transport, epigenetic DNMT1 and the folate 1-carbon metabolism (FOCM) cycle, i.e., rhythmic methylation/de-methylation on DNA, an active part of epigenetic memory during genes turning off and on by the gene writer (DNMT1) and eraser (TET2/FTO) and the transsulfuration pathway by mitochondrial 3-mercaptopyruvate sulfur transferase (3MST)-producing H2S. The repeat CAG expansion and m6A disorder causes senescence and AD. We aim to target the paradigm-shift pathway of the gut-brain microbiome axis that selectively inhibits amyloid deposits and increases mitochondrial transsulfuration and H2S. We have observed an increase in DNMT1 and decreased FTO levels in the cortex of the brain of AD mice. Interestingly, we also observed that probiotic lactobacillus-producing post-biotic folate and lactone/ketone effectively prevented FOCM-associated gut dysbiosis and amyloid deposits. The s-adenosine-methionine (SAM) transporter (SLC25A) was increased by hyperhomocysteinemia (HHcy). Thus, we hypothesize that chronic gut dysbiosis induces SLC25A, the gene writer, and HHcy, and decreases the gene eraser, leading to a decrease in SLC7A and mitochondrial transsulfuration H2S production and bioenergetics. Lactobacillus engulfs lipids/cholesterol and a tri-directional post-biotic, folic acid (an antioxidant and inhibitor of beta amyloid deposits; reduces Hcy levels), and the lactate ketone body (fuel for mitochondria) producer increases SLC7A and H2S (an antioxidant, potent vasodilator and neurotransmitter gas) production and inhibits amyloid deposits. Therefore, it is important to discuss whether lactobacillus downregulates SLC25A and DNMT1 and upregulates TET2/FTO, inhibiting β-amyloid deposits by lowering homocysteine. It is also important to discuss whether lactobacillus upregulates SLC7A and inhibits β-amyloid deposits by increasing the mitochondrial transsulfuration of H2S production.

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.

Modulation of gut microbiome in the treatment of neurodegenerative diseases: A systematic review

BACKGROUND AND AIMS

Microbiota plays an essential role in maintaining body health, through positive influences on metabolic, defensive, and trophic processes and on intercellular communication. Imbalance in intestinal flora, with the proliferation of harmful bacterial species (dysbiosis) is consistently reported in chronic illnesses, including neurodegenerative diseases (ND). Correcting dysbiosis can have a beneficial impact on the symptoms and evolution of ND. This review examines the effects of microbiota modulation through administration of probiotics, prebiotics, symbiotics, or prebiotics' metabolites (postbiotics) in patients with ND like multiple sclerosis (MS), Alzheimer's disease (AD), Parkinson's disease (PD) and amyotrophic lateral sclerosis (ALS).

METHODS

PubMed, Web of Science, Medline databases and ClinicalTrials.gov registry searches were performed using pre-/pro-/postbiotics and ND-related terms. Further references were obtained by checking relevant articles.

RESULTS

Although few compared to animal studies, the human studies generally show positive effects on disease-specific symptoms, overall health, metabolic parameters, on oxidative stress and immunological markers. Therapy with probiotics in various forms (mixtures of bacterial strains, fecal microbiota transplant, diets rich in fermented foods) exert favorable effects on patients' mental health, cognition, and quality of life, targeting pathogenetic ND mechanisms and inducing reparatory mechanisms at the cellular level. More encouraging results have been observed in prebiotic/postbiotic therapy in some ND.

CONCLUSIONS

The effects of probiotic-related interventions depend on the patients' ND stage and pre-existing allopathic medication. Further studies on larger cohorts and long term comprehensive neuropsychiatric, metabolic, biochemical testing, and neuroimaging monitoring are necessary to optimize therapeutic protocols in ND.

Hydrogen sulfide (H2S) metabolism: Unraveling cellular regulation, disease implications, and therapeutic prospects for precision medicine

Hydrogen sulfide (H2S), traditionally recognized as a noxious gas with a pungent odor, has emerged as a fascinating metabolite originating from proteinaceous foods. This review provides a comprehensive examination of H2S regulatory metabolism in cell. Dysregulation of cellular processes plays a pivotal role in the pathogenesis of numerous diseases. Recent development explores the chemistry of biosynthesis and degradation of H2S in cells. The consequences of dysregulation causing diseases and the emerging role of hydrogen sulfide (H2S) modulation as a promising therapeutic platform has not been explored much. These disturbances can manifest as oxidative stress, inflammation, and aberrant cellular signaling pathways, contributing to the development and progression of diseases such as cancer, cardiovascular disorders, neurodegenerative diseases, and diabetes. Hydrogen sulfide has gained recognition as a key player in cellular regulation. H2S is involved in numerous physiological processes, including vasodilation, inflammation control, and cytoprotection. Recent advances in research have focused on modulating H2S levels to restore cellular balance and mitigate disease progression. This approach involves both exogenous H2S donors and inhibitors of H2S -producing enzymes. By harnessing the versatile properties of H2S, researchers and clinicians may develop innovative therapies that address the root causes of dysregulation-induced diseases. As our understanding of H2S biology deepens, the potential for precision medicine approaches tailored to specific diseases becomes increasingly exciting, holding the promise of improved patient outcomes and a new era in therapeutics.

A novel polymer-based probe for fluorescently ratiometric sensing of hydrogen sulfide with multiple applications

Hydrogen sulfide (H2S) as an endogenous signaling molecule, plays an irreplaceable role in many important physiological activities. It is also closely related to sewage treatment, wine quality evaluation, and food spoilage. Herein, we have successfully synthesized a novel polymer-based probe P1 for fluorescently ratiometric sensing of H2S with a high selectivity and sensitivity. By virtue of ring-opening metathesis polymerization (ROMP), P1 was prepared with the disulfide bond linked coumarin-norbornene dyad NB-SS-COU as energy donor, the aggregation-induced emission (AIE) fluorophore anchored norbornene NB-TPE as energy receptor, and the polyethylene glycol (PEG) attached norbornene NB-PEG as a hydrophilic chain. At the 400 nm excitation, P1 displays a bright red emission at 615 nm due to the efficient fluorescence resonance energy transfer (FRET) from energy donor COU to energy acceptor TPE. Upon addition of H2S, it shows strong COU-based blue emission at 473 nm for cleavage of the disulfide bond. We also constructed a smartphone sensing platform to conduct visual quantitative detection of H2S by calculating the B/R (blue/red) emission ratio values. Moreover, P1 can be successfully employed in evaluating the level fluctuations of endogenous and exogenous H2S in living cells, testing water samples/wine samples, and monitoring food freshness.

Slow Release of Hydrogen Sulfide in CA1 Hippocampal Neurons Rescues Long-Term Synaptic Plasticity and Associativity in an Amyloid-β Induced Model of Alzheimer's Disease

Background

Impairment of synaptic plasticity along with the formation of amyloid-β (Aβ) plaques and tau-protein neurofibrillary tangles have been associated with Alzheimer's disease (AD). Earlier studies with rat and mouse hippocampal slices have revealed the association of AD with the absence of synthesis of memory related proteins leading to impairment in cognitive functions. The role of hydrogen sulfide (H2S), a gaseous neurotransmitter, has been gaining attention as a neuroprotective agent. However, its role in AD-like conditions has not been studied so far.

Objective

To study the neuroprotective role of H2S in AD conditions using rat hippocampal slices and the organic molecule GYY4137, a slow releasing H2S donor.

Methods

Electrophysiological recordings were carried out in rat hippocampal slices to look into the impairment of LTP, a cellular correlate of memory. The Aβ42 peptide was bath-applied to mimic AD-like conditions and checked for both late-LTP and synaptic tagging and capture (STC) mechanisms of the synapses. GYY4137 was applied to look into its neuroprotective role at different stages during the recording of fEPSP.

Results

There has been a steady decline in the plasticity properties of the synapses, in the form of late-LTP and STC, after the application of Aβ42 peptide in the hippocampal slices. However, application of GYY4137 rescued these conditions in vitro.

Conclusions

GYY4137, with its slow release of H2S, could possibly act as a therapeutic agent in cognitive dysfunctions of the brain, mainly AD.

The Role of TNF-α in Alzheimer's Disease: A Narrative Review

This review analyzes the role of TNF-α and its increase in biological fluids in mild cognitive impairment, and Alzheimer's disease (AD). The potential inhibition of TNF-α with pharmacological strategies paves the way for preventing AD and improving cognitive function in people at risk for dementia. We conducted a narrative review to characterize the evidence in relation to the involvement of TNF-α in AD and its possible therapeutic inhibition. Several studies report that patients with RA and systemic inflammatory diseases treated with TNF-α blocking agents reduce the probability of emerging dementia compared with the general population. Animal model studies also showed interesting results and are discussed. An increasing amount of basic scientific data and clinical studies underscore the importance of inflammatory processes and subsequent glial activation in the pathogenesis of AD. TNF-α targeted therapy is a biologically plausible approach for cognition preservation and further trials are necessary to investigate the potential benefits of therapy in populations at risk of developing AD.

Mitochondrial Targeting against Alzheimer's Disease: Lessons from Hibernation

Alzheimer's disease (AD) is the most common cause of dementia worldwide and yet remains without effective therapy. Amongst the many proposed causes of AD, the mitochondrial cascade hypothesis is gaining attention. Accumulating evidence shows that mitochondrial dysfunction is a driving force behind synaptic dysfunction and cognitive decline in AD patients. However, therapies targeting the mitochondria in AD have proven unsuccessful so far, and out-of-the-box options, such as hibernation-derived mitochondrial mechanisms, may provide valuable new insights. Hibernators uniquely and rapidly alternate between suppression and re-activation of the mitochondria while maintaining a sufficient energy supply and without acquiring ROS damage. Here, we briefly give an overview of mitochondrial dysfunction in AD, how it affects synaptic function, and why mitochondrial targeting in AD has remained unsuccessful so far. We then discuss mitochondria in hibernation and daily torpor in mice, covering current advancements in hibernation-derived mitochondrial targeting strategies. We conclude with new ideas on how hibernation-derived dual mitochondrial targeting of both the ATP and ROS pathways may boost mitochondrial health and induce local synaptic protein translation to increase synaptic function and plasticity. Further exploration of these mechanisms may provide more effective treatment options for AD in the future.

Positive association of acetylcholinesterase (AChE) with the neutrophil-to-lymphocyte ratio and HbA1c, and a negative association with hydrogen sulfide (H2S) levels among healthy African Americans, and H2S-inhibition and high-glucose-upregulation of AChE in cultured THP-1 human monocytes

The incidence of Alzheimer's disease (AD) is higher in people over the age of 65 and in African Americans (AA). Elevated acetylcholinesterase (AChE) activity has been considered a major player in the onset of AD symptoms. As a result, many FDA-approved AD drugs target AChE inhibition to treat AD patients. Hydrogen sulfide (H2S) is a signaling molecule known to downregulate oxidative stress and inflammation. The neutrophil-to-lymphocyte ratio (NLR) in the blood is widely used as a biomarker to monitor inflammation and immunity. This study examined the hypothesis that plasma AChE levels have a negative association with H2S levels and that a positive association exists between levels of NLR, HbA1c, and ROS with the AChE in the peripheral blood. The fasting blood sample was taken from 114 African Americans who had provided written informed consent approved by the IRB. The effect of H2S and high-glucose treatment on AChE activity levels was also investigated in THP-1 human monocytes. There was a significant negative relationship between AChE and the levels of H2S (r = -0.41, p = 0.001); a positive association between the levels of AChE with age (r = 0.26, p = 0.03), NLR (r = 0.23, p = 0.04), ROS (r = 0.23, p = 0.04) and HbA1c levels (r = 0.24, p = 0.04), in AA subjects. No correlation was seen between blood levels of AChE and acetylcholine (ACh). Blood creatinine had a negative correlation (r = -0.23, p = 0.04) with ACh levels. There was a significant effect of H2S on AChE inhibition and of high glucose in upregulating AChE activity in cultured monocytes. This study suggests hyperglycemia and lower H2S status can contribute to an increase in the AChE activity levels. Future clinical studies are needed to examine the potential benefits of supplementation with hydrogen sulfide pro-drugs/compounds in reducing the AChE and the cognitive dysfunctions associated with AD.

Mechanistic Intimate Insights into the Role of Hydrogen Sulfide in Alzheimer's Disease: A Recent Systematic Review

In the rapidly evolving field of Alzheimer's Disease (AD) research, the intricate role of Hydrogen Sulfide (H2S) has garnered critical attention for its diverse involvement in both pathological substrates and prospective therapeutic paradigms. While conventional pathophysiological models of AD have primarily emphasized the significance of amyloid-beta (Aβ) deposition and tau protein hyperphosphorylation, this targeted systematic review meticulously aggregates and rigorously appraises seminal contributions from the past year elucidating the complex mechanisms of H2S in AD pathogenesis. Current scholarly literature accentuates H2S's dual role, delineating its regulatory functions in critical cellular processes-such as neurotransmission, inflammation, and oxidative stress homeostasis-while concurrently highlighting its disruptive impact on quintessential AD biomarkers. Moreover, this review illuminates the nuanced mechanistic intimate interactions of H2S in cerebrovascular and cardiovascular pathology associated with AD, thereby exploring avant-garde therapeutic modalities, including sulfurous mineral water inhalations and mud therapy. By emphasizing the potential for therapeutic modulation of H2S via both donors and inhibitors, this review accentuates the imperative for future research endeavors to deepen our understanding, thereby potentially advancing novel diagnostic and therapeutic strategies in AD.

Reactive Sulfur Species in Biology and Medicine

Hydrogen sulfide (H2S) has emerged as a third small-molecule bioactive signaling agent, along with nitric oxide (NO) and carbon monoxide (CO) [...].

Hydrogen Sulfide: An Emerging Regulator of Oxidative Stress and Cellular Homeostasis-A Comprehensive One-Year Review

Hydrogen sulfide (H2S), traditionally recognized as a toxic gas, has emerged as a critical regulator in many biological processes, including oxidative stress and cellular homeostasis. This review presents an exhaustive overview of the current understanding of H2S and its multifaceted role in mammalian cellular functioning and oxidative stress management. We delve into the biological sources and function of H2S, mechanisms underlying oxidative stress and cellular homeostasis, and the intricate relationships between these processes. We explore evidence from recent experimental and clinical studies, unraveling the intricate biochemical and molecular mechanisms dictating H2S's roles in modulating oxidative stress responses and maintaining cellular homeostasis. The clinical implications and therapeutic potential of H2S in conditions characterized by oxidative stress dysregulation and disrupted homeostasis are discussed, highlighting the emerging significance of H2S in health and disease. Finally, this review underscores current challenges, controversies, and future directions in the field, emphasizing the need for further research to harness H2S's potential as a therapeutic agent for diseases associated with oxidative stress and homeostatic imbalance. Through this review, we aim to emphasize H2S's pivotal role in cellular function, encouraging further exploration into this burgeoning area of research.

The Role of Hydrogen Sulfide (H2S) in Epigenetic Regulation of Neurodegenerative Diseases: A Systematic Review

This review explores the emerging role of hydrogen sulfide (H2S) in modulating epigenetic mechanisms involved in neurodegenerative diseases. Accumulating evidence has begun to elucidate the multifaceted ways in which H2S influences the epigenetic landscape and, subsequently, the progression of various neurodegenerative disorders, including Alzheimer's, Parkinson's, and Huntington's disease. H2S can modulate key components of the epigenetic machinery, such as DNA methylation, histone modifications, and non-coding RNAs, impacting gene expression and cellular functions relevant to neuronal survival, inflammation, and synaptic plasticity. We synthesize recent research that positions H2S as an essential player within this intricate network, with the potential to open new therapeutic avenues for these currently incurable conditions. Despite significant progress, there remains a considerable gap in our understanding of the precise molecular mechanisms and the potential therapeutic implications of modulating H2S levels or its downstream targets. We conclude by identifying future directions for research aimed at exploiting the therapeutic potential of H2S in neurodegenerative diseases.

Effect of exogenous hydrogen sulfide in the nucleus tractus solitarius on gastric motility in rats

BACKGROUND

Hydrogen sulfide (H2S) is a recently discovered gaseous neurotransmitter in the nervous and gastrointestinal systems. It exerts its effects through multiple signaling pathways, impacting various physiological activities. The nucleus tractus solitarius (NTS), a vital nucleus involved in visceral sensation, was investigated in this study to understand the role of H2S in regulating gastric function in rats.

AIM

To examine whether H2S affects the nuclear factor kappa-B (NF-κB) and transient receptor potential vanilloid 1 pathways and the neurokinin 1 (NK1) receptor in the NTS.

METHODS

Immunohistochemical and fluorescent double-labeling techniques were employed to identify cystathionine beta-synthase (CBS) and c-Fos co-expressed positive neurons in the NTS during rat stress. Gastric motility curves were recorded by inserting a pressure-sensing balloon into the pylorus through the stomach fundus. Changes in gastric motility were observed before and after injecting different doses of NaHS (4 nmol and 8 nmol), physiological saline, Capsazepine (4 nmol) + NaHS (4 nmol), pyrrolidine dithiocarbamate (PDTC, 4 nmol) + NaHS (4 nmol), and L703606 (4 nmol) + NaHS (4 nmol).

RESULTS

We identified a significant increase in the co-expression of c-Fos and CBS positive neurons in the NTS after 1 h and 3 h of restraint water-immersion stress compared to the expressions observed in the control group. Intra-NTS injection of NaHS at different doses significantly inhibited gastric motility in rats (P < 0.01). However, injection of saline, first injection NF-κB inhibitor PDTC or transient receptor potential vanilloid 1 (TRPV1) antagonist Capsazepine or NK1 receptor blockers L703606 and then injection NaHS did not produce significant changes (P > 0.05).

CONCLUSION

NTS contains neurons co-expressing CBS and c-Fos, and the injection of NaHS into the NTS can suppress gastric motility in rats. This effect may be mediated by activating TRPV1 and NK1 receptors via the NF-κB channel.

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.