Dietary restriction transforms the mammalian protein persulfidome in a tissue-specific and cystathionine γ-lyase-dependent manner

Polyphenols reverse hyperglycemia-induced adipocyte dysfunction: A Metabolomic and Lipidomic study of efficacy

Hyperglycemia leads to metabolic dysfunction in human adipocytes, characterized by decreased AKT phosphorylation, downregulation of glycolysis, TCA cycle, and amino acid metabolism, as well as altered lipid profiles. This study aimed to elucidate these metabolic alterations and evaluate the potential therapeutic effects of selected polyphenols. Comprehensive metabolic profiling revealed profound disruptions, including impaired carbon metabolism, amino acids, and lipids associated with obesity. Importantly, treatment with polyphenols, particularly verbascoside and ferulic acid, effectively mitigated these metabolic disturbances, restoring adipocyte homeostasis. The polyphenols increased metabolites from carbon metabolism and amino acids, improving glycolysis, the TCA cycle, and related pathways. They also modulated lipid profiles that are negatively associated with obesity and related diseases. These findings provide valuable insights into the metabolic pathways underlying adipocyte dysfunction in hyperglycemia and highlight the therapeutic potential of polyphenols in ameliorating metabolic disorders.

Hydrogen sulfide and ferroptosis inhibition underlies the dietary restriction-induced protection against cyclophosphamide cystitis

Dietary restriction (DR) has emerged as a potential therapeutic intervention for various pathological conditions. This study investigated the effects of DR on cyclophosphamide-induced cystitis in mice. Animals were subjected to controlled food restriction for 1 week prior to cyclophosphamide administration. We evaluated changes in body weight, bladder pathology, redox status, and ferroptotic parameters. DR significantly attenuated cyclophosphamide-induced cystitis severity, as evidenced by reduced bladder weight, decreased lipid peroxidation, and diminished ferroptotic markers in bladder tissue. Mechanistic investigations revealed that DR upregulated hepatic hydrogen sulfide (H2S)-synthesizing enzymes and enhanced H2S production. Inhibition of H2S-synthesizing enzymes with DL-propargylglycine (PAG) and aminooxyacetic acid (AOAA) exacerbated cyclophosphamide-induced cystitis, whereas administration of diallyl trisulfide (DATS), an H2S donor, markedly ameliorated bladder pathology. In vitro studies demonstrated that H2S donors, NaHS and DATS, protected against cyclophosphamide metabolite acrolein (ACR)-induced urothelial cell death by suppressing oxidative stress, as indicated by reduced p38 MAPK activation and protein carbonylation. These findings suggest that DR confers protection against cyclophosphamide-induced cystitis through the induction of endogenous H2S production and inhibition of ferroptosis. Our study provides additional evidence supporting the health-promoting effects of DR as well as novel mechanistic insights into the beneficial effects of DR. Given H2S has anti-inflammatory and anti-oxidative properties and that oxidative stress and ferroptosis underlie various diseases, our finding could have broader implications.

Association of Kidney Graft Long-term Outcome With Recipient Cystathionine Gamma-lyase Polymorphisms and Hydrogen Sulfide Levels: A Cohort Study

Background

Hydrogen sulfide (H2S) produced endogenously by the CTH gene-encoded cystathionine gamma-lyase protects from renal ischemia-reperfusion injury in preclinical models. Here, we hypothesized that CTH gene polymorphisms (single nucleotide polymorphism [SNP]) and recipient H2S serum levels influence kidney graft outcomes after transplantation.

Methods

We included all consecutive recipients of a first kidney transplant in the Swiss Transplant Cohort Study and with available genotyping. In addition, 192 deceased-donor kidney transplant recipients were randomly selected to measure baseline serum H2S levels. The primary endpoint was graft loss during follow-up.

Results

CTH SNPs were identified in up to 50% of the patients. During median follow-up (6.4 y, interquartile range: 3.9-9.8), graft loss was observed in 247 (9.8%) of 2518 patients. The incidence of graft loss was associated with the presence or absence of CTH SNPs. Specifically, rs672203 and rs10458561, increased the risk of graft loss (hazard ratio [HR]: 1.36, 95% confidence interval [CI]: 1.04-1.78, P = 0.02; and HR: 1.29, 95% CI: 1.0-1.66, P = 0.05; respectively), whereas rs113285275 was protective (HR: 0.78, 95% CI: 0.6-1.01, P = 0.05). Interestingly, rs672203 was associated with an increased risk of acute rejection (P = 0.05), whereas rs113285275 was associated with a lower risk of acute rejection (P = 0.01). Finally, in patients with delayed graft function, serum H2S levels correlated with lower graft dysfunction (defined as estimated glomerular filtration rate <30 mL/min/1.73 m2) (P = 0.05).

Conclusions

Graft outcome after kidney transplantation was associated with CTH genotype and, to some extent, H2S serum levels. Further research is needed to define the underlying protective mechanisms.

Sulfhydrated albumin transmits H2S signaling and ameliorates DOX-induced multiorgan injuries

Hydrogen sulfide (H2S) is a vital signaling molecule involved in various physiological processes; however, the mechanisms underlying its systemic signaling remain poorly understood. We hypothesized that albumin, the predominant plasma protein and a vital sulfhydryl carrier, mediated systemic H2S signaling, which could potentially treat H2S-deficient diseases. This study aimed to investigate this hypothesis. Our results showed the presence of sulfhydrated proteins in normal mouse serum, with albumin being particularly enriched. The level of sulfhydration was influenced by H2S availability and the redox environment. In vitro incubation of albumin with NaHS resulted in an increased number of sulfhydrated groups. Under reductive conditions, this sulfhydrated albumin (-SSH-Alb) released substantial amounts of H2S. When -SSH-Alb was added to cultured endothelial cells, it activated the cAMP signaling pathway, upregulated cystathionine γ-lyase (CSE) expression, and enhanced intracellular H2S levels. In an in vitro inflammatory model involving macrophages and endothelial cells, -SSH-Alb inhibited macrophage adhesion, reduced LPS-induced expression of adhesion molecules, and suppressed cytokine production and inflammasome activation. These effects correlated with improved cellular redox status. Furthermore, in vivo administration of -SSH-Alb protected mice from doxorubicin (DOX)-induced cardiotoxicity and intestinal damage. It improved mouse mortality, and alleviated ferroptotic cardiac injury and gut barrier dysfunction. These therapeutic benefits were associated with rebalanced local and systemic redox status. In summary, our study reveals that -SSH-Alb reserves, transmits, and amplifies H2S signals and exhibits significant anti-inflammatory and antioxidant properties. This characteristic of -SSH-Alb holds promise for preventing and treating a wide range of diseases.

The Janus Face of Oxidative Stress and Hydrogen Sulfide: Insights into Neurodegenerative Disease Pathogenesis

Oxidative stress plays an essential role in neurodegenerative pathophysiology, acting as both a critical signaling mediator and a driver of neuronal damage. Hydrogen sulfide (H2S), a versatile gasotransmitter, exhibits a similarly "Janus-faced" nature, acting as a potent antioxidant and cytoprotective molecule at physiological concentrations, but becoming detrimental when dysregulated. This review explores the dual roles of oxidative stress and H2S in normal cellular physiology and pathophysiology, focusing on neurodegenerative disease progression. We highlight potential therapeutic opportunities for targeting redox and sulfur-based signaling systems in neurodegenerative diseases by elucidating the intricate balance between these opposing forces.

Multi-omics reveal an overlooked pathway for H2S production induced by bacterial biogenesis from composting

Sulfate reduction has long been considered a leading cause of hydrogen sulfide (H2S) emissions from composting, causing serious air pollution and health threats. H2S biogenesis through cysteine cleavage is a known pathway for bacteria to resist oxidative stress. However, whether the biogenesis pathway exacerbates H2S emission during composting with dramatic temperature changes and oxidative stress is largely unknown. Here, we used DL-propargylglycine (PAG), an inhibitor of cysteine lyase (cystathionine γ-lyase), to explore the contribution of biogenesis pathway to H2S production during composting with different aeration rates. We found that PAG addition significantly inhibited H2S emission by 45.52 % and 19.74 % at high and low aeration rates, respectively. PAG addition reduced the diversity of core bacteria associated with H2S production. Metagenomic and metaproteomic analysis further revealed that PAG decreased the abundance of sulfate reduction genes, down-regulated the expression of cysteine lyases, and up-regulated the catalase expression. Therefore, both sulfate reduction and biosynthesis contributed to the H2S production, and PAG inhibited both pathways. Finally, microbial pure culture experiment further verified the effectiveness of PAG in reducing H2S emission of composting. This work reveals an overlooked pathway for H2S production during composting, which fills the research gap in the role of the biogenesis pathway in composting H2S emission. This provides breakthrough guidance for future environmental management and pollution control at source.

Harshly Oxidized Activated Charcoal Enhances Protein Persulfidation with Implications for Neurodegeneration as Exemplified by Friedreich's Ataxia

Harsh acid oxidation of activated charcoal transforms an insoluble carbon-rich source into water-soluble, disc structures of graphene decorated with multiple oxygen-containing functionalities. We term these pleiotropic nano-enzymes as "pleozymes". A broad redox potential spans many crucial redox reactions including the oxidation of hydrogen sulfide (H2S) to polysulfides and thiosulfate, dismutation of the superoxide radical (O2-*), and oxidation of NADH to NAD+. The oxidation of H2S is predicted to enhance protein persulfidation-the attachment of sulfur to cysteine residues. Persulfidated proteins act as redox intermediates, and persulfidation protects proteins from irreversible oxidation and ubiquitination, providing an important means of signaling. Protein persulfidation is believed to decline in several neurological disorders and aging. Importantly, and consistent with the role of persulfidation in signaling, the master antioxidant transcription factor Nrf2 is regulated by Keap1's persulfidation. Here, we demonstrate that pleozymes increased overall protein persulfidation in cells from apparently healthy individuals and from individuals with the mitochondrial protein mutation responsible for Friedreich's ataxia. We further find that pleozymes specifically enhanced Keap1 persulfidation, with subsequent increased accumulation of Nrf2 and Nrf2's antioxidant targets.

Deficiency of thiosulfate sulfurtransferase mediates the dysfunction of renal tubular mitochondrial fatty acid oxidation in diabetic kidney disease

One of the main characteristics of diabetic kidney disease (DKD) is abnormal renal tubular fatty acid metabolism, especially defective fatty acid oxidation (FAO), accelerating tubular injury and tubulointerstitial fibrosis. Thiosulfate sulfurtransferase (TST), a mitochondrial enzyme essential for sulfur transfer, is reduced in metabolic diseases like diabetes and obesity. However, the potential role of TST in regulating fatty acid metabolic abnormalities in DKD remains unclear. Here, our data revealed decreased TST expression in the renal cortex of DKD patients. TST deficiency exacerbated tubular impairment in both diabetic and renal fibrosis mouse models, while sodium thiosulfate treatment or TST overexpression mitigated renal tubular injury with high-glucose exposure. TST downregulation mediated the decrease in S-sulfhydration of very long-chain specific acyl-CoA dehydrogenase, resulting in mitochondrial FAO dysfunction. This sequence of events exacerbates the progression of tubulointerstitial injury in DKD. Together, our findings demonstrate TST as a regulator of renal tubular injury in DKD.

Asynchronous changes of hydrogen sulfide and its generating enzymes in most tissues with the aging process

Aging is an inevitable and irreversible biological process that gradually heightens the risks of various diseases and death. As a newly discovered endogenous gasotransmitter, hydrogen sulfide (H2S) has been identified to exert multiple beneficial impacts on the regulation of aging and age-related pathologies. This study was aimed at systematically exploring the relationship between asynchronous aging processes and H2S concentrations in various tissues of aging mice. Samples of plasma and 13 tissues were collected from four cross-sectional age groups (3, 6, 12 and 18 months of age) covering the lifespan of male C57BL/6J mice. The H2S concentration was quantified by a reported liquid chromatography-tandem mass spectrometry (LC-MS/MS) method with monobromobimane derivatization. Additionally, the expressions of cystathionine γ-lyase (CSE), cystathionine β-synthase and 3-mercaptopyruvate sulfurtransferase, in those tissues were analyzed by Western blotting. We discovered that the H2S concentrations decreased asynchronously with the aging process in plasma, heart, liver, kidney, spleen, subcutaneous fat and brown fat and increased in brain and lung. At least one of the three H2S-generating enzymes expressions was compensatorily up-regulated with the aging process in most tissues, among which the up-regulation of CSE was the most prominent.

Metabolic regulation of the host-fungus interaction: from biological principles to therapeutic opportunities

Fungal infections present a significant global public health concern, impacting over 1 billion individuals worldwide and resulting in more than 3 million deaths annually. Despite considerable progress in recent years, the management of fungal infections remains challenging. The limited development of novel diagnostic and therapeutic approaches is largely attributed to our incomplete understanding of the pathogenetic mechanisms involved in these diseases. Recent research has highlighted the pivotal role of cellular metabolism in regulating the interaction between fungi and their hosts. In response to fungal infection, immune cells undergo complex metabolic adjustments to meet the energy demands necessary for an effective immune response. A comprehensive understanding of the metabolic circuits governing antifungal immunity, combined with the integration of individual host traits, holds the potential to inform novel medical interventions for fungal infections. This review explores recent insights into the immunometabolic regulation of host-fungal interactions and the infection outcome and discusses how the metabolic repurposing of immune cell function could be exploited in innovative and personalized therapeutic approaches.

Persulfidome of Sweet Pepper Fruits during Ripening: The Case Study of Leucine Aminopeptidase That Is Positively Modulated by H2S

Protein persulfidation is a thiol-based oxidative posttranslational modification (oxiPTM) that involves the modification of susceptible cysteine thiol groups present in peptides and proteins through hydrogen sulfide (H2S), thus affecting their function. Using sweet pepper (Capsicum annuum L.) fruits as a model material at different stages of ripening (immature green and ripe red), endogenous persulfidated proteins (persulfidome) were labeled using the dimedone switch method and identified using liquid chromatography and mass spectrometry analysis (LC-MS/MS). A total of 891 persulfidated proteins were found in pepper fruits, either immature green or ripe red. Among these, 370 proteins were exclusively present in green pepper, 237 proteins were exclusively present in red pepper, and 284 proteins were shared between both stages of ripening. A comparative analysis of the pepper persulfidome with that described in Arabidopsis leaves allowed the identification of 25% of common proteins. Among these proteins, glutathione reductase (GR) and leucine aminopeptidase (LAP) were selected to evaluate the effect of persulfidation using an in vitro approach. GR activity was unaffected, whereas LAP activity increased by 3-fold after persulfidation. Furthermore, this effect was reverted through treatment with dithiothreitol (DTT). To our knowledge, this is the first persulfidome described in fruits, which opens new avenues to study H2S metabolism. Additionally, the results obtained lead us to hypothesize that LAP could be involved in glutathione (GSH) recycling in pepper fruits.

Mining proteomes for zinc finger persulfidation

Hydrogen sulfide (H2S) is an endogenous gasotransmitter that signals via persulfidation. There is evidence that the cysteine residues of certain zinc finger (ZF) proteins, a common type of cysteine rich protein, are modified to persulfides by H2S. To determine how frequently ZF persulfidation occurs in cells and identify the types of ZFs that are persulfidated, persulfide specific proteomics data were evaluated. 22 datasets from 16 studies were analyzed via a meta-analysis approach. Persulfidated ZFs were identified in a range of eukaryotic species, including Homo sapiens, Mus musculus, Rattus norvegicus, Arabidopsis thaliana, and Emiliania huxley (single-celled phytoplankton). The types of ZFs identified for each species encompassed all three common ZF ligand sets (4-cysteine, 3-cysteine-1-histidine, and 2-cysteine-2-hisitidine), indicating that persulfidation of ZFs is broad. Overlap analysis between different species identified several common ZFs. GO and KEGG analysis identified pathway enrichment for ubiquitin-dependent protein catabolic process and viral carcinogenesis. These collective findings support ZF persulfidation as a wide-ranging PTM that impacts all classes of ZFs.

Redox Regulation of Xenobiotics by Reactive Sulfur and Supersulfide Species

Significance: Routine exposure to xenobiotics is unavoidable during our lifetimes. Certain xenobiotics are hazardous to human health, and are metabolized in the body to render them less toxic. During this process, several detoxification enzymes cooperatively metabolize xenobiotics. Glutathione (GSH) conjugation plays an important role in the metabolism of electrophilic xenobiotics. Recent Advances: Recent advances in reactive sulfur and supersulfide (RSS) analyses showed that persulfides and polysulfides bound to low-molecular-weight thiols, such as GSH, and to protein thiols are abundant in both eukaryotes and prokaryotes. The highly nucleophilic nature of hydropersulfides and hydropolysulfides contributes to cell protection against oxidative stress and electrophilic stress. Critical Issues: In contrast to GSH conjugation to electrophiles that is aided by glutathione S-transferase (GST), persulfides and polysulfides can directly form conjugates with electrophiles without the catalytic actions of GST. The polysulfur bonds in the conjugates are further reduced by perthioanions and polythioanions derived from RSS to form sulfhydrated metabolites that are no longer electrophilic but rather nucleophilic, and differ from metabolites that are formed via GSH conjugation. Future Directions: In view of the abundance of RSS in cells and tissues, metabolism of xenobiotics that is mediated by RSS warrants additional investigations, such as studies of the impact of microbiota-derived RSS on xenobiotic metabolism. Metabolites formed from reactions between electrophiles and RSS may be potential biomarkers for monitoring exposure to electrophiles and for studying their metabolism by RSS. Antioxid. Redox Signal. 40, 679-690.

Apoptosis releases hydrogen sulfide to inhibit Th17 cell differentiation

Over 50 billion cells undergo apoptosis each day in an adult human to maintain immune homeostasis. Hydrogen sulfide (H2S) is also required to safeguard the function of immune response. However, it is unknown whether apoptosis regulates H2S production. Here, we show that apoptosis-deficient MRL/lpr (B6.MRL-Faslpr/J) and Bim-/- (B6.129S1-Bcl2l11tm1.1Ast/J) mice exhibit significantly reduced H2S levels along with aberrant differentiation of Th17 cells, which can be rescued by the additional H2S. Moreover, apoptotic cells and vesicles (apoVs) express key H2S-generating enzymes and generate a significant amount of H2S, indicating that apoptotic metabolism is an important source of H2S. Mechanistically, H2S sulfhydrates selenoprotein F (Sep15) to promote signal transducer and activator of transcription 1 (STAT1) phosphorylation and suppress STAT3 phosphorylation, leading to the inhibition of Th17 cell differentiation. Taken together, this study reveals a previously unknown role of apoptosis in maintaining H2S homeostasis and the unique role of H2S in regulating Th17 cell differentiation via sulfhydration of Sep15C38.

Diet-Modifiable Redox Alterations in Ageing and Cancer

With ageing comes some of life's best and worst moments. Those lucky enough to live out into the seventh, eighth, and nineth decades and perhaps beyond have more opportunities to experience the wonders and joys of the world. As the world's population shifts towards more and more of these individuals, this is something to be celebrated. However, it is not without negative consequences. Advanced age also ushers in health decline and the burden of non-communicable diseases such as cancer, heart disease, stroke, and organ function decay. Thus, alleviating or at least dampening the severity of ageing as a whole, as well as these individual age-related disorders will enable the improvement in lifespan and healthspan. In the following chapter, we delve into hypothesised causes of ageing and experimental interventions that can be taken to slow their progression. We also highlight cellular and subcellular mechanisms of ageing with a focus on protein thiol oxidation and posttranslational modifications that impact cellular homeostasis and the advent and progression of ageing-related cancers. By having a better understanding of the mechanisms of ageing, we can hopefully develop effective, safe, and efficient therapeutic modalities that can be used prophylactically and/or concurrent to the onset of ageing.

Global approaches for protein thiol redox state detection

Due to its nucleophilicity, the thiol group of cysteine is chemically very versatile. Hence, cysteine often has important functions in a protein, be it as the active site or, in extracellular proteins, as part of a structural disulfide. Within the cytosol, cysteines are typically reduced. But the nucleophilicity of its thiol group makes it also particularly prone to post-translational oxidative modifications. These modifications often lead to an alteration of the function of the affected protein and are reversible in vivo, e.g. by the thioredoxin and glutaredoxin system. The in vivo-reversible nature of these modifications and their genesis in the presence of localized high oxidant levels led to the paradigm of thiol-based redox regulation, the adaptation, and modulation of the cellular metabolism in response to oxidative stimuli by thiol oxidation in regulative proteins. Consequently, the proteomic study of these oxidative posttranslational modifications of cysteine plays an indispensable role in redox biology.

Untargeted polysulfide omics analysis of alternations in polysulfide production during the germination of broccoli sprouts

Higher consumption of broccoli (Brassica oleracea var. italica) is associated with a reduced risk of cardiometabolic diseases, neurological disorders, diabetes, and cancer. Broccoli is rich in various phytochemicals, including glucosinolates, and isothiocyanates. Moreover, it has recently reported the endogenous production of polysulfides, such as cysteine hydropersulfide (CysS2H) and glutathione hydropersulfide (GS2H), in mammals including humans, and that these bioactive substances function as potent antioxidants and important regulators of redox signaling in vivo. However, few studies have focused on the endogenous polysulfide content of broccoli and the impact of germination on the polysulfide content and composition in broccoli. In this study, we investigated the alternations in polysulfide biosynthesis in broccoli during germination by performing untargeted polysulfide omics analysis and quantitative targeted polysulfide metabolomics through liquid chromatography-electrospray ionization-tandem mass spectrometry. We also performed 2,2-diphenyl-1-picrylhydrazyl radical-scavenging assay to determine the antioxidant properties of the polysulfides. The results revealed that the total polysulfide content of broccoli sprouts significantly increased during germination and growth; CysS2H and cysteine hydrotrisulfide were the predominant organic polysulfide metabolites. Furthermore, we determined that novel sulforaphane (SFN) derivatives conjugated with CysS2H and GS2H were endogenously produced in the broccoli sprouts, and the novel SFN conjugated with CysS2H exhibited a greater radical scavenging capacity than SFN and cysteine. These results suggest that the abundance of polysulfides in broccoli sprouts contribute to their health-promoting properties. Our findings have important biological implications for the development of novel pharmacological targets for the health-promoting effects of broccoli sprouts in humans.

Expanded bioinformatic analysis of Oximouse dataset reveals key putative processes involved in brain aging and cognitive decline

The theory that aging is driven by the damage produced by reactive oxygen species (ROS) derived from oxidative metabolism dominated geroscience studies during the second half of the 20th century. However, increasing evidence that ROS also plays a key role in the physiological regulation of numerous processes through the reversible oxidation of cysteine residues in proteins, has challenged this notion. Currently, the scope of redox signaling has reached proteomic dimensions through mass spectrometry techniques. Here, we perform a comprehensive bioinformatics analysis of cysteine oxidation changes during mouse brain aging, using the quantitative data provided in the Oximouse dataset. Interestingly, our unbiased analysis identified hundreds of putative cysteine redox switches covering several pathways previously associated with aging. These include the ubiquitin-proteasome pathway and one-carbon metabolism (folate cycle, methionine cycle, transsulfuration and polyamine pathways). Surprisingly, cysteine oxidation changes are enriched in synaptic proteins in a highly asymmetric distribution: while postsynaptic proteins tend to increase cysteine oxidation with age, the opposite occurs for presynaptic proteins. Additionally, cysteine oxidation changes during aging are associated with proteins involved in the regulation of the mitochondrial transition pore opening and synaptic calcium homeostasis. Our analysis reinforces the concept that brain aging is associated with selective changes in the oxidation state of key proteins, rather than an overall trend toward increased oxidation. Also, we provide a prioritized list of specific cysteine residues with putative impact in aging processes for future experimental validation.

Emerging Chemical Biology of Protein Persulfidation

Significance: Protein persulfidation (the formation of RSSH), an evolutionarily conserved oxidative posttranslational modification in which thiol groups in cysteine residues are converted into persulfides, has emerged as one of the main mechanisms through which hydrogen sulfide (H2S) conveys its signaling. Recent Advances: New methodological advances in persulfide labeling started unraveling the chemical biology of this modification and its role in (patho)physiology. Some of the key metabolic enzymes are regulated by persulfidation. RSSH levels are important for the cellular defense against oxidative injury, and they decrease with aging, leaving proteins vulnerable to oxidative damage. Persulfidation is dysregulated in many diseases. Critical Issues: A relatively new field of signaling by protein persulfidation still has many unanswered questions: the mechanism(s) of persulfide formation and transpersulfidation and the identification of "protein persulfidases," the improvement of methods to monitor RSSH changes and identify protein targets, and understanding the mechanisms through which this modification controls important (patho)physiological functions. Future Directions: Deep mechanistic studies using more selective and sensitive RSSH labeling techniques will provide high-resolution structural, functional, quantitative, and spatiotemporal information on RSSH dynamics and help with better understanding how H2S-derived protein persulfidation affects protein structure and function in health and disease. This knowledge could pave the way for targeted drug design for a wide variety of pathologies. Antioxid. Redox Signal. 39, 19-39.

3-Mercaptopyruvate sulfur transferase is a protein persulfidase

Protein S-persulfidation (P-SSH) is recognized as a common posttranslational modification. It occurs under basal conditions and is often observed to be elevated under stress conditions. However, the mechanism(s) by which proteins are persulfidated inside cells have remained unclear. Here we report that 3-mercaptopyruvate sulfur transferase (MPST) engages in direct protein-to-protein transpersulfidation reactions beyond its previously known protein substrates thioredoxin and MOCS3/Uba4, associated with H₂S generation and transfer RNA thiolation, respectively. We observe that depletion of MPST in human cells lowers overall intracellular protein persulfidation levels and identify a subset of proteins whose persulfidation depends on MPST. The predicted involvement of these proteins in the adaptation to stress responses supports the notion that MPST-dependent protein persulfidation promotes cytoprotective functions. The observation of MPST-independent protein persulfidation suggests that other protein persulfidases remain to be identified.

A long-term obesogenic high-fat diet in mice partially dampens the anti-frailty benefits of late-life intermittent fasting

The global obesity pandemic coupled with ever-growing life expectancies equates to hundreds of millions of individuals with potentially longer but not healthier lives. Aging is one of the risk factors for numerous maladies such as metabolic disorder and frailty, which are exacerbated under obesity. Thus, therapeutic approaches that address obesity to ultimately improve affected individuals' quality of life and extend their lifespan are needed. We previously reported that the every other day (EOD) fasting initiated late-life improved metabolic, musculoskeletal, and cognitive endpoints in standard rodent diet-fed mice. In the present study, using the same dietary intervention methodology, we tested if 2.5 months of EOD fasting could improve metabolic, physiological, and cognitive endpoints in mice after an 18 month obesogenic high-fat diet (HFD). The positive effects of EOD fasting were generally consistent across the endpoints; EOD fasting decreased total body mass, maintained more %lean mass, improved glucose tolerance and utilization, and improved neuromuscular function. In contrast to our previous study, grip strength, hippocampal-dependent memory, and renal hydrogen sulfide (H₂S) production were not improved by the HFD EOD fasting. Thus, efficacy for late-life initiated intermittent fasting to improve specific frailty markers may be partially dependent on nutritional compositions of the diet.

Reactive sulfur species and their significance in health and disease

Reactive sulfur species (RSS) have been recognized in the last two decades as very important molecules in redox regulation. They are involved in metabolic processes and, in this way, they are responsible for maintenance of health. This review summarizes current information about the essential biological RSS, including H₂S, low molecular weight persulfides, protein persulfides as well as organic and inorganic polysulfides, their synthesis, catabolism and chemical reactivity. Moreover, the role of RSS disturbances in various pathologies including vascular diseases, chronic kidney diseases, diabetes mellitus Type 2, neurological diseases, obesity, chronic obstructive pulmonary disease and in the most current problem of COVID-19 is presented. The significance of RSS in aging is also mentioned. Finally, the possibilities of using the precursors of various forms of RSS for therapeutic purposes are discussed.

Hydrogen sulfide: the gas that fuels longevity

The molecular determinants of lifespan can be examined in animal models with the long-term objective of applying what is learned to the development of strategies to enhance longevity in humans. Here, we comment on a recent publication examining the molecular mechanisms that determine lifespan in worms, Caenorhabditis elegans (C. elegans), where it was shown that inhibiting protein synthesis increased levels of the transcription factor, ATF4. Gene expression analyses showed that ATF4 increased the expression of genes responsible for the formation of the gas, hydrogen sulfide (H₂S). Further examination showed that H₂S increased longevity in C. elegans by modifying proteins in ways that stabilize their structures and enhance their functions. H₂S has been shown to improve cardiovascular performance in mouse models of heart disease, and clinical trials are underway to test the effects of H₂S on cardiovascular health in humans. These findings support the concept that nutrient deprivation, which slows protein synthesis and leads to ATF4-mediated H₂S production, may extend lifespan by improving the function of the cardiovascular system and other systems that influence longevity in humans.

Recent Advances in Molecular Research on Hydrogen Sulfide (H2S) Role in Diabetes Mellitus (DM)-A Systematic Review

Abundant experimental data suggest that hydrogen sulfide (H₂S) is related to the pathophysiology of Diabetes Mellitus (DM). Multiple molecular mechanisms, including receptors, membrane ion channels, signalingmolecules, enzymes, and transcription factors, are known to be responsible for the H₂S biological actions; however, H₂S is not fully documented as a gaseous signaling molecule interfering with DM and vascular-linked pathology. In recent decades, multiple approaches regarding therapeutic exploitation of H₂S have been identified, either based on H₂S exogenous apport or on its modulated endogenous biosynthesis. This paper aims to synthesize and systematize, as comprehensively as possible, the recent literature-related data regarding the therapeutic/rehabilitative role of H₂S in DM. This review was conducted following the “Preferred reporting items for systematic reviews and meta-analyses” (PRISMA) methodology, interrogating five international medically renowned databases by specific keyword combinations/“syntaxes” used contextually, over the last five years (2017–2021). The respective search/filtered and selection methodology we applied has identified, in the first step, 212 articles. After deploying the next specific quest steps, 51 unique published papers qualified for minute analysis resulted. To these bibliographic resources obtained through the PRISMA methodology, in order to have the best available information coverage, we added 86 papers that were freely found by a direct internet search. Finally, we selected for a connected meta-analysis eight relevant reports that included 1237 human subjects elicited from clinical trial registration platforms. Numerous H₂S releasing/stimulating compounds have been produced, some being used in experimental models. However, very few of them were further advanced in clinical studies, indicating that the development of H₂S as a therapeutic agent is still at the beginning.

Dietary intervention improves health metrics and life expectancy of the genetically obese Titan mouse

Suitable animal models are essential for translational research, especially in the case of complex, multifactorial conditions, such as obesity. The non-inbred mouse (Mus musculus) line Titan, also known as DU6, is one of the world’s longest selection experiments for high body mass and was previously described as a model for metabolic healthy (benign) obesity. The present study further characterizes the geno- and phenotypes of this non-inbred mouse line and tests its suitability as an interventional obesity model. In contrast to previous findings, our data suggest that Titan mice are metabolically unhealthy obese and short-lived. Line-specific patterns of genetic invariability are in accordance with observed phenotypic traits. Titan mice also show modifications in the liver transcriptome, proteome, and epigenome linked to metabolic (dys)regulations. Importantly, dietary intervention partially reversed the metabolic phenotype in Titan mice and significantly extended their life expectancy. Therefore, the Titan mouse line is a valuable resource for translational and interventional obesity research.

This study further characterizes the non-inbred Titan (also known as DU6) mouse line, which could be a useful model for obesity research.

Sulfur Amino Acid Supplementation Abrogates Protective Effects of Caloric Restriction for Enhancing Bone Marrow Regrowth Following Ionizing Radiation

Radiation therapy damages and depletes total bone marrow (BM) cellularity, compromising safety and limiting effective dosing. Aging also strains total BM and BM hematopoietic stem and progenitor cell (HSPC) renewal and function, resulting in multi-system defects. Interventions that preserve BM and BM HSPC homeostasis thus have potential clinical significance. Here, we report that 50% calorie restriction (CR) for 7-days or fasting for 3-days prior to irradiation improved mouse BM regrowth in the days and weeks post irradiation. Specifically, one week of 50% CR ameliorated loss of total BM cellularity post irradiation compared to ad libitum-fed controls. CR-mediated BM protection was abrogated by dietary sulfur amino acid (i.e., cysteine, methionine) supplementation or pharmacological inhibition of sulfur amino acid metabolizing and hydrogen sulfide (H₂S) producing enzymes. Up to 2-fold increased proliferative capacity of ex vivo-irradiated BM isolated from food restricted mice relative to control mice indicates cell autonomy of the protective effect. Pretreatment with H₂S in vitro was sufficient to preserve proliferative capacity by over 50% compared to non-treated cells in ex vivo-irradiated BM and BM HSPCs. The exogenous addition of H₂S inhibited Ten eleven translocation 2 (TET2) activity in vitro, thus providing a potential mechanism of action. Short-term CR or fasting therefore offers BM radioprotection and promotes regrowth in part via altered sulfur amino acid metabolism and H₂S generation, with translational implications for radiation treatment and aging.

Dopamine 1 receptors inhibit apoptosis via activating CSE/H2 S pathway in high glucose-induced vascular endothelial cells

High glucose (HG) induced dysfunction of vascular endothelial cells plays a crucial role in the development of diabetic vascular complications. Inhibition of cystathionine γ-synthase/hydrogen sulfide (CSE/H₂ S) pathway is one of the causes of vascular endothelial cells injury induced by HG. Dopamine D1 receptors (DR1) are widely expressed and regulate important physiological functions in the vascular system. However, the effect of DR1 inhibition on HG-induced vascular endothelial apoptosis by regulating CSE/H₂ S pathway is unclear. Therefore, we aimed to determine if DR1 can regulate the CSE/H₂ S pathway and the effect of DR1 on HG-induced apoptosis in human umbilical vein endothelial cells (HUVECs). In this study, we found that HG treatment significantly decreased the expression of DR1 and CSE and the endogenous content of H₂ S, DR1 agonist SKF 38393 reversed these effect, while NaHS only increased CSE expression and the endogenous H₂ S production and had no effect on DR1 expression. Meanwhile, HG significantly raised intracellular calcium concentration ([Ca²⁺ ]_i ), SKF 38393 further increased HG-induced [Ca²⁺ ]_i . In addition, HG increased LDH activity, MDA and ROS contents, apoptotic rate, the expression of cleaved caspase-3, -9 and Cytochrome C and the activity of phosphorylated-IκBα (p-IκBα) and phosphorylated-NF-κB (p-NF-κB), reduced cell viability, SOD activity and Bcl-2 expressions. SKF 38393 and NaHS markedly reversed the effect of HG. The effect of SKF 38393 was similar to NAC (an inhibitor of oxidative stress) or PDTC (a NF-kB inhibitor). Taken together, DR1 up-regulate CSE/H₂ S pathway by increasing [Ca²⁺ ]_i , which inhibits HG-induced apoptosis via down-regulating NF-κB/IκBα pathway in vascular endothelial cells. This article is protected by copyright. All rights reserved.

Cysteine as a Multifaceted Player in Kidney, the Cysteine-Related Thiolome and Its Implications for Precision Medicine

In this review encouraged by original data, we first provided in vivo evidence that the kidney, comparative to the liver or brain, is an organ particularly rich in cysteine. In the kidney, the total availability of cysteine was higher in cortex tissue than in the medulla and distributed in free reduced, free oxidized and protein-bound fractions (in descending order). Next, we provided a comprehensive integrated review on the evidence that supports the reliance on cysteine of the kidney beyond cysteine antioxidant properties, highlighting the relevance of cysteine and its renal metabolism in the control of cysteine excess in the body as a pivotal source of metabolites to kidney biomass and bioenergetics and a promoter of adaptive responses to stressors. This view might translate into novel perspectives on the mechanisms of kidney function and blood pressure regulation and on clinical implications of the cysteine-related thiolome as a tool in precision medicine.

Hydrogen Sulfide and the Kidney: Physiological Roles, Contribution to Pathophysiology, and Therapeutic Potential

Significance: Hydrogen sulfide (H₂S), the third member of the gasotransmitter family, has a broad spectrum of biological activities, including antioxidant and cytoprotective actions, as well as vasodilatory, anti-inflammatory and antifibrotic effects. New, significant aspects of H₂S biology in the kidney continue to emerge, underscoring the importance of this signaling molecule in kidney homeostasis, function, and disease. Recent Advances: H₂S signals via three main mechanisms, by maintaining redox balance through its antioxidant actions, by post-translational modifications of cellular proteins (S-sulfhydration), and by binding to protein metal centers. Important renal functions such as glomerular filtration, renin release, or sodium reabsorption have been shown to be regulated by H₂S, using either exogenous donors or by the endogenous-producing systems. Critical Issues: Lower H₂S levels are observed in many renal pathologies, including renal ischemia-reperfusion injury and obstructive, diabetic, or hypertensive nephropathy. Unraveling the molecular targets through which H₂S exerts its beneficial effects would be of great importance not only for understanding basic renal physiology, but also for identifying new pharmacological interventions for renal disease. Future Directions: Additional studies are needed to better understand the role of H₂S in the kidney. Mapping the expression pattern of H₂S-producing and -degrading enzymes in renal cells and generation of cell-specific knockout mice based on this information will be invaluable in the effort to unravel additional roles for H₂S in kidney (patho)physiology. With this knowledge, novel targeted more effective therapeutic strategies for renal disease can be designed. Antioxid. Redox Signal. 36, 220-243.

One-Carbon Metabolism: Pulling the Strings behind Aging and Neurodegeneration

One-carbon metabolism (OCM) is a network of biochemical reactions delivering one-carbon units to various biosynthetic pathways. The folate cycle and methionine cycle are the two key modules of this network that regulate purine and thymidine synthesis, amino acid homeostasis, and epigenetic mechanisms. Intersection with the transsulfuration pathway supports glutathione production and regulation of the cellular redox state. Dietary intake of micronutrients, such as folates and amino acids, directly contributes to OCM, thereby adapting the cellular metabolic state to environmental inputs. The contribution of OCM to cellular proliferation during development and in adult proliferative tissues is well established. Nevertheless, accumulating evidence reveals the pivotal role of OCM in cellular homeostasis of non-proliferative tissues and in coordination of signaling cascades that regulate energy homeostasis and longevity. In this review, we summarize the current knowledge on OCM and related pathways and discuss how this metabolic network may impact longevity and neurodegeneration across species.

The DR1‑CSE/H2S system inhibits renal fibrosis by downregulating the ERK1/2 signaling pathway in diabetic mice

Glomerular mesangial cell (MC) proliferation and extracellular matrix deposition are the main pathological changes in diabetic nephropathy. Hydrogen sulfide (H2S) inhibits the proliferation of MCs. Dopamine 1 receptors (DR1) are expressed in MCs and serve important physiological roles. However, it is unclear whether DR1 activation inhibits MC proliferation by increasing endogenous H2S. The present study found that the production of H2S and the expression of DR1 and cystathionine‑γ‑lyase (CSE) were decreased in the renal tissues of diabetic mice and high glucose (HG)‑induced MCs. SKF38393 (a DR1 agonist) increased the production of H2S and the expression of DR1 and CSE and NaHS (an exogenous H2S donor) only increased H2S production and CSE expression but not DR1 expression. HG increased the thickness of the glomerular basement membrane, cell viability and proliferation, the expression of cyclin D1, PCNA, collagen 1 and α‑smooth muscle actin and the activity of phosphorylated ERK1/2 and decreased the expression of P21 and MMP9. SKF38393 and NaHS reversed the effects of HG. PPG (a CSE inhibitor) abolished the beneficial effects of SKF38393. The beneficial effects of SKF38393 were similar to those of PD98059 (an ERK1/2 inhibitor). Taken together, the findings suggested that the DR1‑CSE/H2S pathway activation attenuated diabetic MC proliferation and extracellular matrix deposition by downregulating the ERK1/2 signaling pathway.

Expanding the Reactive Sulfur Metabolome: Intracellular and Efflux Measurements of Small Oxoacids of Sulfur (SOS) and H2S in Human Primary Vascular Cell Culture

Hydrogen sulfide (H2S) is an endogenous signaling molecule which is important for cardiovascular health, but its mechanism of action remains poorly understood. Here, we report measurements of H2S as well as its oxidized metabolites, termed small oxoacids of sulfur (SOS = HSOH and HOSOH), in four human primary vascular cell lines: smooth muscle and endothelial cells derived from both human arterial and coronary tissues. We use a methodology that targets small molecular weight sulfur species; mass spectrometric analysis allows for species quantification to report cellular concentrations based on an H2S calibration curve. The production of H2S and SOS is orders of magnitude higher in smooth muscle (nanomolar) as compared to endothelial cell lines (picomolar). In all the primary lines measured, the distributions of these three species were HOSOH >H2S > HSOH, with much higher SOS than seen previously in non-vascular cell lines. H2S and SOS were effluxed from smooth muscle cells in higher concentrations than endothelial cells. Aortic smooth muscle cells were used to examine changes under hypoxic growth conditions. Hypoxia caused notable increases in HSOH and ROS, which we attribute to enhanced sulfide quinone oxidase activity that results in reverse electron transport.

Plasma Hydrogen Sulfide Is Positively Associated With Post-operative Survival in Patients Undergoing Surgical Revascularization

Objective: Hydrogen sulfide (H₂S) is a gaseous signaling molecule and redox factor important for cardiovascular function. Deficiencies in its production or bioavailability are implicated in atherosclerotic disease. However, it is unknown if circulating H₂S levels differ between vasculopaths and healthy individuals, and if so, whether H₂S measurements can be used to predict surgical outcomes. Here, we examined: (1) Plasma H₂S levels in patients undergoing vascular surgery and compared these to healthy controls, and (2) the association between H₂S levels and mortality in a cohort of patients undergoing surgical revascularization.

Methods: One hundred and fifteen patients undergoing carotid endarterectomy, open lower extremity revascularization or lower leg amputation were enrolled at a single institution. Peripheral blood was also collected from a matched control cohort of 20 patients without peripheral or coronary artery disease. Plasma H₂S production capacity and sulfide concentration were measured using the lead acetate and monobromobimane methods, respectively.

Results: Plasma H₂S production capacity and plasma sulfide concentrations were reduced in patients with PAD (p < 0.001, p = 0.013, respectively). Patients that underwent surgical revascularization were divided into high vs. low H₂S production capacity groups by median split. Patients in the low H₂S production group had increased probability of mortality (p = 0.003). This association was robust to correction for potentially confounding variables using Cox proportional hazard models.

Conclusion: Circulating H₂S levels were lower in patients with atherosclerotic disease. Patients undergoing surgical revascularization with lower H₂S production capacity, but not sulfide concentrations, had increased probability of mortality within 36 months post-surgery. This work provides insight on the role H₂S plays as a diagnostic and potential therapeutic for cardiovascular disease.

Hydrogen sulfide in ageing, longevity and disease

Hydrogen sulfide (H₂S) modulates many biological processes, including ageing. Initially considered a hazardous toxic gas, it is now recognised that H₂S is produced endogenously across taxa and is a key mediator of processes that promote longevity and improve late-life health. In this review, we consider the key developments in our understanding of this gaseous signalling molecule in the context of health and disease, discuss potential mechanisms through which H₂S can influence processes central to ageing and highlight the emergence of novel H₂S-based therapeutics. We also consider the major challenges that may potentially hinder the development of such therapies.

Hydrogen sulfide operates as a glioblastoma suppressor and is lost under high fat diet

Glioblastoma (GBM) is one of the deadliest and aggressive forms of brain cancer. Environmental and intrinsic factors such as Western Diet and advanced age can function as powerful accelerants to the progression of GBM. Recently, we discovered that pre-clinical GBM models subject to an obesogenic and age-accelerating high fat diet (HFD) presented with hyperaggressive GBM phenotypes, including treatment-refractory cancer stem cell (CSC) enrichment. Mechanistically, HFD suppressed production of the gasotransmitter hydrogen sulfide (H₂S) and its downstream sulfhydration signaling in the brain. Likewise, we observed dramatic loss of sulfhydration in brains of GBM patients. Importantly, we showed the tumor suppressive effects of H₂S against GBM in cell culture and in vivo. Here, we discuss these recent findings and provide insight into how they can be leveraged to improve treatment modalities, prognosis, and quality of life for GBM patients.

Peripubertal Bisphenol A Exposure Imparts Detrimental Age-Related Changes in Body Composition, Cognition, and Hydrogen Sulfide Production Capacities

Aims: Peripubertal endocrine disruption has immediate and lifelong consequences on health, cognition, and lifespan. Disruption comes from dietary, environmental, and pharmaceutical sources. The plasticizer Bisphenol A (BPA) is one such endocrine disrupting chemical. However, it is unclear whether peripubertal BPA exposure incites long-lasting physiological, neuro-cognitive, and/or longevity-related metabolic impairments. Catabolism of cysteine via transsulfuration enzymes produces hydrogen sulfide (H2S), a redox-modulating gasotransmitter causative to endocrine and metabolic homeostasis and improved cognitive function with age. As thyroid hormone (TH) regulates hepatic H2S production and BPA is a TH receptor antagonist, we hypothesized that BPA exposure during peripubertal development impairs metabolic and neuro-cognitive/behavioral endpoints in aged mice, in part, due to altered peripheral and/or localized H2S production and redox status. Results: To test this, male C57BL/6J mice at 5 weeks of age were orally exposed daily for 5 weeks to 250 μg BPA/kg, defined as low dose group (LD BPA), or 250 mg BPA/kg, defined as high dose group (HD BPA). Both LD and HD BPA exposure decreased lean mass and increased fat mass accompanied by decreased serum total TH at advanced ages. In addition, LD BPA had an anxiogenic effect whereas HD BPA caused cognitive deficits. Notably, HD BPA disrupted tissue-specific H2S production capacities and/or protein persulfidation, with the former negatively correlated with memory deficits and oxidative stress. Innovation and Conclusion: These findings provide a potential mechanism of action for acute and long-term health impacts of BPA-induced peripubertal endocrine disruption and bolster the need for improved monitoring and limitation of adolescent BPA exposure.

Severe consequences of a high-lipid diet include hydrogen sulfide dysfunction and enhanced aggression in glioblastoma

Glioblastoma (GBM) remains among the deadliest of human malignancies, and the emergence of the cancer stem cell (CSC) phenotype represents a major challenge to durable treatment response. Because the environmental and lifestyle factors that impact CSC populations are not clear, we sought to understand the consequences of diet on CSC enrichment. We evaluated disease progression in mice fed an obesity-inducing high-fat diet (HFD) versus a low-fat, control diet. HFD resulted in hyper-aggressive disease accompanied by CSC enrichment and shortened survival. HFD drove intracerebral accumulation of saturated fats, which inhibited the production of the cysteine metabolite and gasotransmitter, hydrogen sulfide (H2S). H2S functions principally through protein S-sulfhydration and regulates multiple programs including bioenergetics and metabolism. Inhibition of H2S increased proliferation and chemotherapy resistance, whereas treatment with H2S donors led to death of cultured GBM cells and stasis of GBM tumors in vivo. Syngeneic GBM models and GBM patient specimens present an overall reduction in protein S-sulfhydration, primarily associated with proteins regulating cellular metabolism. These findings provide clear evidence that diet modifiable H2S signaling serves to suppress GBM by restricting metabolic fitness, while its loss triggers CSC enrichment and disease acceleration. Interventions augmenting H2S bioavailability concurrent with GBM standard of care may improve outcomes for GBM patients.

Harnessing the Benefits of Endogenous Hydrogen Sulfide to Reduce Cardiovascular Disease

Cardiovascular disease is the leading cause of death in the U.S. While various studies have shown the beneficial impact of exogenous hydrogen sulfide (H₂S)-releasing drugs, few have demonstrated the influence of endogenous H₂S production. Modulating the predominant enzymatic sources of H₂S-cystathionine-β-synthase, cystathionine-γ-lyase, and 3-mercaptopyruvate sulfurtransferase-is an emerging and promising research area. This review frames the discussion of harnessing endogenous H₂S within the context of a non-ischemic form of cardiomyopathy, termed diabetic cardiomyopathy, and heart failure. Also, we examine the current literature around therapeutic interventions, such as intermittent fasting and exercise, that stimulate H₂S production.