Hydrogen sulfide: a gasotransmitter of clinical relevance

Molecular regulation of cardiomyocyte functions by exogenous hydrogen sulphide in Atlantic salmon (Salmo salar)

Hydrogen sulphide (H2S) is known to regulate various physiological processes, but its role in fish cardiac function, especially at the molecular level, is poorly understood. This study examined the molecular functions of exogenous H2S, using sodium hydrosulphide (NaHS) as a donor, on Atlantic salmon cardiomyocytes. NaHS concentrations of 10 to 160 μM showed limited cytotoxicity and no impact on cell proliferation, though higher doses increased ATP activity. Menadione and NaHS administered separately or sequentially differentially regulated the expression of antioxidant response and sulphide detoxification genes. Transcriptomic analysis over 24, 48, 72, and 120 h revealed differential gene expression related to metabolic recovery. Enriched Gene Ontology terms at 24 h included processes like cell signalling and lipid metabolism, shifting to lipid metabolism and ribosomal processes by 48 h. By 120 h, xenobiotic metabolism and RNA synthesis were prominent. The study highlights NaHS-induced metabolic adjustments, particularly in lipid metabolism, in Atlantic salmon cardiomyocytes.

Harnessing Gasotransmitters to Combat Age-Related Oxidative Stress in Smooth Muscle and Endothelial Cells

Age-related oxidative stress is a critical factor in vascular dysfunction, contributing to hypertension and atherosclerosis. Smooth muscle cells and endothelial cells are particularly susceptible to oxidative damage, which exacerbates vascular aging through cellular senescence, chronic inflammation, and arterial stiffness. Gasotransmitters-hydrogen sulfide (H2S), nitric oxide (NO), and carbon monoxide (CO)-are emerging as promising therapeutic agents for counteracting these processes. This review synthesizes findings from recent studies focusing on the mechanisms by which H2S, NO, and CO influence vascular smooth muscle and endothelial cell function. Therapeutic strategies involving exogenous gasotransmitter delivery systems and combination therapies were analyzed. H2S enhances mitochondrial bioenergetics, scavenges ROS, and activates antioxidant pathways. NO improves endothelial function, promotes vasodilation, and inhibits platelet aggregation. CO exhibits cytoprotective and anti-inflammatory effects by modulating heme oxygenase activity and ROS production. In preclinical studies, gasotransmitter-releasing molecules (e.g., NaHS, SNAP, CORMs) and targeted delivery systems show significant promise. Synergistic effects with lifestyle modifications and antioxidant therapies further enhance their therapeutic potential. In conclusion, gasotransmitters hold significant promise as therapeutic agents to combat age-related oxidative stress in vascular cells. Their multifaceted mechanisms and innovative delivery approaches make them potential candidates for treating vascular dysfunction and promoting healthy vascular aging. Further research is needed to translate these findings into clinical applications.

Sequential Release of Ibuprofen and the Gasotransmitter Hydrogen sulfide using Oxanorbornane-Based Synthetic Lipids as Carriers

After understanding the biological signaling roles of hydrogen sulfide and its involvement in various physiological processes, there has been enormous interest in exploring its therapeutic utility in areas such as cancer, inflammation, cardiovascular diseases, etc. There is also growing interest in using suitable H2S donors in combination with other drugs to improve the treatment outcome through the modulation of multiple pathways. The premature release of H2S from small molecule donors and the difficulty in controlling its spatio-temporal distribution are the major challenges during these efforts. Hence the development of appropriate carriers that can release this gasotransmitter along with the therapeutic entity of interest in a controlled manner has high significance. In this regard, this report presents a novel drug delivery system from oxanorbornane-based synthetic lipids that carries a H2S-releasing 1,2-dithiole-3-thione moiety as part of the head group. Nanoaggregates of the resulting conjugate are not only capable of efficiently entrapping a non-steroidal anti-inflammatory drug such as ibuprofen, but also release this drug and H2S in a controlled and sequential manner.

Development of a Bioorthogonal Click-to-Release Reaction for Hydrogen Polysulfide (H2Sn) Detection

In this study, we present an innovative "click-to-release" strategy for the design of highly specific H2Sn bioorthogonal probes that undergo a specific click reaction with H2Sn and release fluorophores by a following rearrangement. A library of cyclooctyne derivatives was established and successfully demonstrated the availability of the release strategy. Then, a model probe CM-CT was synthesized, which can achieve effective fluorophore release (>80%) in the presence of a H2Sn donor. To further validate the application of this class of probes, a new probe QN-RHO-CT based on Rhodamine 110 was developed. This probe showed good water solubility (>160 μM) and fast release kinetics and can achieve selective H2Sn detection in living cells. We used this probe to study the process of H2S-mediated protein S-persulfidation and demonstrated that excess H2S would directly react with protein persulfides to generate H2S2 and reduce the persulfides to thiols. Additionally, we elucidated the click-to-release mechanism in our design through a detailed mechanistic study, confirming the generation of the key intermediate α, β-unsaturated cyclooctanethione. This bioorthogonal click-to-release reaction provides a useful tool for investigating the function of H2Sn and paves the way for biological studies on H2Sn.

Role of hydrogen sulfide in dermatological diseases

Hydrogen sulfide (H2S), together with carbon monoxide (CO) and nitric oxide (NO), is recognized as a vital gasotransmitter. H2S is biosynthesized by enzymatic pathways in the skin and exerts significant physiological effects on a variety of biological processes, such as apoptosis, modulation of inflammation, cellular proliferation, and regulation of vasodilation. As a major health problem, dermatological diseases affect a large proportion of the population every day. It is urgent to design and develop effective drugs to deal with dermatological diseases. Dermatological diseases can arise from a multitude of etiologies, including neoplastic growth, infectious agents, and inflammatory processes. The abnormal metabolism of H2S is associated with many dermatological diseases, such as melanoma, fibrotic diseases, and psoriasis, suggesting its therapeutic potential in the treatment of these diseases. In addition, therapies based on H2S donors are being developed to treat some of these conditions. In the review, we discuss recent advances in the function of H2S in normal skin, the role of altering H2S metabolism in dermatological diseases, and the therapeutic potential of diverse H2S donors for the treatment of dermatological diseases.

Transdermal Hydrogen Sulfide Delivery Enabled by Open-Metal-Site Metal-Organic Frameworks

Hydrogen sulfide (H2S) is an endogenously produced gasotransmitter involved in many physiological processes that are integral to proper cellular functioning. Due to its profound anti-inflammatory and antioxidant properties, H2S plays important roles in preventing inflammatory skin disorders and improving wound healing. Transdermal H2S delivery is a therapeutically viable option for the management of such disorders. However, current small-molecule H2S donors are not optimally suited for transdermal delivery and typically generate electrophilic byproducts that may lead to undesired toxicity. Here, we demonstrate that H2S release from metal-organic frameworks (MOFs) bearing coordinatively unsaturated metal centers is a promising alternative for controlled transdermal delivery of H2S. Gas sorption measurements and powder X-ray diffraction (PXRD) studies of 11 MOFs support that the Mg-based framework Mg2(dobdc) (dobdc4- = 2,5-dioxidobenzene-1,4-dicarboxylate) is uniquely well-suited for transdermal H2S delivery due to its strong yet reversible binding of H2S, high capacity (14.7 mmol/g at 1 bar and 25 °C), and lack of toxicity. In addition, Rietveld refinement of synchrotron PXRD data from H2S-dosed Mg2(dobdc) supports that the high H2S capacity of this framework arises due to the presence of three distinct binding sites. Last, we demonstrate that transdermal delivery of H2S from Mg2(dobdc) is sustained over a 24 h period through porcine skin. Not only is this significantly longer than sodium sulfide but this represents the first example of controlled transdermal delivery of pure H2S gas. Overall, H2S-loaded Mg2(dobdc) is an easily accessible, solid-state source of H2S, enabling safe storage and transdermal delivery of this therapeutically relevant gas.

Practical NIR Assay Derived from Cyanine to Evaluate Intracellular H2S in Living Cell Imaging

To monitor the biological function of H2S in real time, this investigation demonstrated the design and synthesis of a novel fluorescent probe integrated with cyanine and 2,4-dinitrophenol for the qualitative and quantitative detection of H2S. An NIR sensitive sensor (FS-HS-1) was provided with a straightforward process. Spectroscopy experiments elucidated that FS-HS-1 could selectively detect H2S in a PBS solution (containing 40% acetonitrile) with a 111-fold fluorescence enhancement at 715 nm (ex. 605 nm). The response towards NaHS occurred in less than 2 min, and the detection limit was confirmed to be as low as 4.47 ± 0.11 nmol/L. Furthermore, the probe is capable of monitoring changes in exogenous H2S concentrations within living cells with confocal and 2P imaging.

Effects of H2S-donor ascorbic acid derivative and ischemia/reperfusion-induced injury in isolated rat hearts

Hydrogen sulfide (H2S), a gasotransmitter, plays a crucial role in vasorelaxation, anti-inflammatory processes and mitigating myocardial ischemia/reperfusion-induced injury by regulating various signaling processes. We designed a water soluble H2S-releasing ascorbic acid derivative, BM-164, to combine the beneficial cardiovascular and anti-inflammatory effects of H2S with the excellent water solubility and antioxidant properties of ascorbic acid. DPPH antioxidant assay revealed that the antioxidant activity of BM-164 in the presence of a myocardial tissue homogenate (extract) increased continuously over the 120 min test interval due to the continuous release of H2S from BM-164. The cytotoxicity of BM-164 was tested by MTT assay on H9c2 cells, which resulted in no cytotoxic effect at concentrations of 10 to 30 μM. The possible beneficial effects of BM-164 (30 µM) was examined in isolated 'Langendorff' rat hearts. The incidence of ventricular fibrillation (VF) was significantly reduced from its control value of 79 % to 31 % in the BM-164 treated group, and the infarct size was also diminished from the control value of 28 % to 14 % in the BM-164 treated group. However, coronary flow (CF) and heart rate (HR) values in the BM-164 treated group did not show significantly different levels in comparison with the drug-free control, although a non-significant recovery in both CF and HR was observed at each time point. We attempted to reveal the mechanism of action of BM-164, focusing on the processes of autophagy and apoptosis. The expression of key autophagic and apoptotic markers in isolated rat hearts were detected by Western blot analysis. All the examined autophagy-related proteins showed increased expression levels in the BM-164 treated group in comparison to the drug-free control and/or ascorbic acid treated groups, while the changes in the expression of apoptotic markers were not obvious. In conclusion, the designed water soluble H2S releasing ascorbic acid derivative, BM-164, showed better cardiac protection against ischemia/reperfusion-induced injury compared to the untreated and ascorbic acid treated hearts, respectively.

Collective production of hydrogen sulfide gas enables budding yeast lacking MET17 to overcome their metabolic defect

Assimilation of sulfur is vital to all organisms. In S. cerevisiae, inorganic sulfate is first reduced to sulfide, which is then affixed to an organic carbon backbone by the Met17 enzyme. The resulting homocysteine can then be converted to all other essential organosulfurs such as methionine, cysteine, and glutathione. This pathway has been known for nearly half a century, and met17 mutants have long been classified as organosulfur auxotrophs, which are unable to grow on sulfate as their sole sulfur source. Surprisingly, we found that met17Δ could grow on sulfate, albeit only at sufficiently high cell densities. We show that the accumulation of hydrogen sulfide gas underpins this density-dependent growth of met17Δ on sulfate and that the locus YLL058W (HSU1) enables met17Δ cells to assimilate hydrogen sulfide. Hsu1 protein is induced during sulfur starvation and under exposure to high sulfide concentrations in wild-type cells, and the gene has a pleiotropic role in sulfur assimilation. In a mathematical model, the low efficiency of sulfide assimilation in met17Δ can explain the observed density-dependent growth of met17Δ on sulfate. Thus, having uncovered and explained the paradoxical growth of a commonly used "auxotroph," our findings may impact the design of future studies in yeast genetics, metabolism, and volatile-mediated microbial interactions.

Chemistry of Hydrogen Sulfide-Pathological and Physiological Functions in Mammalian Cells

Hydrogen sulfide (H2S) was recognized as a gaseous signaling molecule, similar to nitric oxide (-NO) and carbon monoxide (CO). The aim of this review is to provide an overview of the formation of hydrogen sulfide (H2S) in the human body. H2S is synthesized by enzymatic processes involving cysteine and several enzymes, including cystathionine-β-synthase (CBS), cystathionine-γ-lyase (CSE), cysteine aminotransferase (CAT), 3-mercaptopyruvate sulfurtransferase (3MST) and D-amino acid oxidase (DAO). The physiological and pathological effects of hydrogen sulfide (H2S) on various systems in the human body have led to extensive research efforts to develop appropriate methods to deliver H2S under conditions that mimic physiological settings and respond to various stimuli. These functions span a wide spectrum, ranging from effects on the endocrine system and cellular lifespan to protection of liver and kidney function. The exact physiological and hazardous thresholds of hydrogen sulfide (H2S) in the human body are currently not well understood and need to be researched in depth. This article provides an overview of the physiological significance of H2S in the human body. It highlights the various sources of H2S production in different situations and examines existing techniques for detecting this gas.

Detection of aqueous and gaseous hydrogen sulfide with lanthanide-macrocycle binary complexes

Two novel, discrete lanthanide-macrocycle binary complexes for the detection of hydrogen sulfide are reported. The hydrogen sulfide sensing mechanism utilises the copper sequestration at a secondary binding site, with resulting bimetallic lanthanide(III)/copper(II) complexes (Ln = Eu3+ and Tb3+) exhibiting high selectivity, good sensitivity and excellent reversibility for aqueous hydrogen sulfide. The inclusion of the DO2A macrocycle and 4-(2-pyridyl)-1,2,3-triazole dipicolinic acid ligand, results in a complex with good solubility and stability. The europium(III) complex also displayed a low limit of detection (665 ppb) with a response time of 30 seconds with gaseous hydrogen sulfide. The improved water solubility and stability over a previous complex results in these sensors having the potential for use in environmental monitoring and biological studies for various functional settings.

Biocompatible 7-nitro-2,1,3-benzoxadiazole-embedded naphthalimide for exploring endogenous H2S in living cells

Hydrogen sulfide (H₂S) is a central signaling and antioxidant biomolecule involved in various biological processes. As inappropriate levels of H₂S in the human body are closely related to various diseases, including cancer, a tool capable of detecting H₂S with high selectivity and sensitivity in living systems is urgently required. In this work, we intended to develop a biocompatible and activatable fluorescent molecular probe for detecting H₂S generation in living cells. The 7-nitro-2,1,3-benzoxadiazole-imbedded naphthalimide (1) probe presented here responds specifically to H₂S and produces readily detectable fluorescence at 530 nm. Interestingly, probe 1 exhibited significant fluorescence responses to changes in endogenous H₂S levels as well as high biocompatibility and permeability in living HeLa cells. This allowed for the real-time monitoring of endogenous H₂S generation as an antioxidant defense response in the oxidatively stressed cells.

Exogenous Hydrogen Sulfide Induces A375 Melanoma Cell Apoptosis Through Overactivation of the Unfolded Protein Response

Purpose

Melanomas are highly malignant and rapidly develop drug resistance due to dysregulated apoptosis. Therefore, pro-apoptotic agents could be effective for the management of melanoma. Hydrogen sulfide is ubiquitous in the body, and exogenous hydrogen sulfide has been reported to show inhibitory and pro-apoptotic effects on cancer cells. However, whether high concentrations of exogenous hydrogen sulfide have pro-apoptotic effects on melanoma and its mechanisms remain unknown. Hence, this study aimed to explore the pro-apoptotic effects and mechanisms of exogenous hydrogen sulfide on the A375 melanoma cell line treated with a hydrogen sulfide donor (NaHS).

Methods

The cell proliferation test, flow cytometric analysis, Hoechst 33258 staining, and Western blotting of B-cell lymphoma 2 and cleaved caspase-3 were used to explore the pro-apoptotic effects of hydrogen sulfide on A375 cells. The transcriptional profile of NaHS-treated A375 cells was further explored via high-throughput sequencing. Western blotting of phosphorylated inositol-requiring enzyme 1α (p-IRE1α), phosphorylated protein kinase R-like ER kinase (p-PERK), phosphorylated eukaryotic translation initiation factor 2α (p-eIF2α), C/EBP homologous protein, glucose-regulating protein 78, IRE1α, PERK, and eIF2α was performed to verify the changes in the transcriptional profile.

Results

NaHS inhibited A375 melanoma cell proliferation and induced apoptosis. The endoplasmic reticulum stress unfolded protein response and apoptosis-associated gene expression was upregulated in NaHS-treated A375 melanoma cells. The overactivation of the unfolded protein response and increase in endoplasmic reticulum stress was verified at the protein level.

Conclusion

Treatment with NaHS increased endoplasmic reticulum stress, which triggered the overactivation of the unfolded protein response and ultimately lead to melanoma cell apoptosis. The pro-apoptotic effect of NaHS suggests that it can be explored as a potential therapeutic agent in melanoma.

Elevated plasma sulfides are associated with cognitive dysfunction and brain atrophy in human Alzheimer's disease and related dementias

Emerging evidence indicates that vascular stress is an important contributor to the pathophysiology of Alzheimer's disease and related dementias (ADRD). Hydrogen sulfide (H2S) and its metabolites (acid-labile (e.g., iron-sulfur clusters) and bound (e.g., per-, poly-) sulfides) have been shown to modulate both vascular and neuronal homeostasis. We recently reported that elevated plasma sulfides were associated with cognitive dysfunction and measures of microvascular disease in ADRD. Here we extend our previous work to show associations between elevated sulfides and magnetic resonance-based metrics of brain atrophy and white matter integrity. Elevated bound sulfides were associated with decreased grey matter volume, while increased acid labile sulfides were associated with decreased white matter integrity and greater ventricular volume. These findings are consistent with alterations in sulfide metabolism in ADRD which may represent maladaptive responses to oxidative stress.

A bio-friendly biotin-coupled and azide-functionalized naphthalimide for real-time endogenous hydrogen sulfide analysis in living cells

Hydrogen sulfide (H₂S) is involved in various biological processes. Thereby, abnormal levels of H₂S are reported to be related to various human diseases including cancer. Currently, many fluorescent probes are pioneered to detect H₂S by taking advantages of naphthalimides' unique internal charge transfer (ICT) property. However, most probes often require a high content of organic solvents or surfactants, and are limited to the analysis of exogenous H₂S treated externally in live cell studies, and have difficulties in analyzing endogenous H₂S, thus limiting their practical use. In this study, we developed a bio-friendly biotin-coupled and azide-functionalized naphthalimide (1) as a fluorescent probe enabling real-time analysis of H₂S in living system. Probe was able to provide a fluorescence at 545 nm via H₂S-mediated azide reduction selectively without interference by biologically abundant constituents and pH effects. In a biological study using A549 cells, probe readily penetrated living cells without cytotoxicity, and unreacted probes showed almost no fluorescence, enabling real-time detection of H₂S in living cells without requiring separate washing process. More importantly, under stimulation with various H₂S inducers and inhibitors, probe was able to provide an effective fluorescence response against fluctuations in endogenous H₂S, a key requirement for H₂S studies. Probe 1 can be applied as a useful chemical tool and enables the analysis of H₂S and the study of H₂S-related cell functions in a variety of environments.

Protein persulfidation: Rewiring the hydrogen sulfide signaling in cell stress response

The past few decades have witnessed significant progress in the discovery of hydrogen sulfide (H₂S) as a ubiquitous gaseous signaling molecule in mammalian physiology, akin to nitric oxide and carbon monoxide. As the third gasotransmitter, H₂S is now known to exert a wide range of physiological and cytoprotective functions in the biological systems. However, endogenous H₂S concentrations are usually low, and its potential biologic mechanisms responsible have not yet been fully clarified. Recently, a growing body of evidence has demonstrated that protein persulfidation, a posttranslational modification of cysteine residues (RSH) to persulfides (RSSH) elicited by H₂S, is a fundamental mechanism of H₂S-mediated signaling pathways. Persulfidation, as a biological switch for protein function, plays an important role in the maintenance of cell homeostasis in response to various internal and external stress stimuli and is also implicated in numerous diseases, such as cardiovascular and neurodegenerative diseases and cancer. In this review, the biological significance of protein persulfidation by H₂S in cell stress response is reviewed providing a framework for understanding the multifaceted roles of H₂S. A mechanism-guided perspective can help open novel avenues for the exploitation of therapeutics based on H₂S-induced persulfidation in the context of diseases.

Methionine-Restricted Diet: A Feasible Strategy Against Chronic or Aging-Related Diseases

Dietary methionine restriction (MR) has been associated with multifaceted health-promoting effects. MR is conducive to prevention of several chronic diseases and cancer, and extension of lifespan. A growing number of studies on new phenotypes and mechanisms of MR have become available in the past five years, especially in angiogenesis, neurodegenerative diseases, intestinal microbiota, and intestinal barrier function. In this review, we summarize the characteristics and advantages of MR, and current knowledge on the physiological responses and effects of MR on chronic diseases and aging-associated pathologies. Potential mechanisms, in which hydrogen sulfide, fibroblast growth factor 21, gut microbiota, short-chain fatty acids, and so on are involved, are discussed. Moreover, directions for epigenetics and gut microbiota in an MR diet are presented in future perspectives. This review comprehensively summarizes the novel roles and interpretations of the mechanisms underlying MR in the prevention of chronic diseases and aging.

Research Progress of H2S Donors Conjugate Drugs Based on ADTOH

H₂S is an endogenous gas signaling molecule and its multiple biological effects have been demonstrated. The abnormal level of H₂S is closely related to the occurrence and development of many diseases, and H₂S donors has important pharmacological implications. In recent years, H₂S donors represented by ADTOH (5-(4-hydroxyphenyl)-3H-1,2-dithiole-3-thione) are often used to synthesize new 'conjugate' compounds that can release H₂S and parent drugs. These hybrids retain the pharmacological activity of the parent drugs and H₂S and have a synergistic effect. ADTOH and parent drug hybrids have become one of the important strategies for the development of H₂S donor conjugate drugs. This review summarizes molecular hybrids between ADTOH and clinical drugs to provide new ideas for the study of H₂S donor drug design.

On-demand therapeutic delivery of hydrogen sulfide aided by biomolecules

Hydrogen sulfide (H₂S), known as the third gasotransmitter, exerts various physiological functions including cardiac protection, angiogenesis, anti-inflammatory, and anti-cancer capability. Given its promising therapeutic potential as well as severe perniciousness if improper use, the sustained and tunable H₂S delivery systems are highly required for H₂S-based gas therapy with enhanced bioactivity and reduced side effects. To this end, a series of stimuli-responsive compounds capable of releasing H₂S (termed H₂S donors) have been designed over the past two decades to mimic the endogenous generation of H₂S and elucidate the biological functions. Further to improve the stability of H₂S donors and achieve the targeted delivery, various delivery systems have been constructed. In this review, we focus on the recent advances of an emerging subset, biomolecular-based H₂S delivery systems, which combine H₂S donors with biomolecular vectors including polysaccharide, peptide, and protein. We demonstrated their basic structures, building strategies, and therapeutic applications respectively to unfold their inherent merits endued by biomolecules including biocompatibility, biodegradability as well as expansibility. The varied development potentials of biomolecular-based H₂S delivery systems based on their specific properties are also discussed. At the end, brief future outlooks and upcoming challenges are presented as well.

Targeting Wnt/β-catenin signaling pathway in triple-negative breast cancer by benzylic organotrisulfides: Contribution of the released hydrogen sulfide towards potent anti-cancer activity

The potent anti-cancer activity of naturally occurring organopolysulfides has attracted wide research attention over the last two decades. Sustained donation of hydrogen sulfide (H₂S) from organopolysulfides is found to be beneficial for the treatment of several organ-specific cancers. In the present study, for the first time, the mechanism of action for the potent anti-cancer activity of bis(3,5-dimethoxybenzyl) trisulfide 4 against highly aggressive triple-negative breast cancer cells (MDA-MB-231) is described. Preliminary in vitro studies revealed potent anti-proliferative activity of the trisulfide 4 against triple-negative breast cancer cells with an IC₅₀ value of 1.0 μM. Mechanistic studies reveal that the compound exhibited anti-cancer activity, primarily by targeting and suppressing the Wnt/β-catenin signaling pathway. The inactivation of the β-catenin level was associated with the cell cycle arrest in the G2/M phase and the significant down-regulation of downstream signaling genes such as Cyclin D1 and c-Myc expression. Several control experiments with analogous organosulfur compounds and the key enzyme inhibitors reveal that the presence of a trisulfide unit in the compound is crucial for the desired inactivation of β-catenin expression, which is promoted by GSK-3β-induced phosphorylation of β-catenin and its proteasomal degradation. Moreover, the trisulfide unit or the released H₂S induced down-regulation of the p53 expression with the possible S-sulfhydration process led to p53-independent up-regulation of p21 expression. Therefore, the key results of this study highlighting the potency of synthetic benzylic organotrisulfide and the released H₂S towards the growth inhibition of triple-negative breast cancer via Wnt/β-catenin signaling pathway would certainly be helpful for further studies and developing small-molecule anti-cancer therapeutics in future.

Concentrations of nucleophilic sulfur species in small Indian mongoose (Herpestes auropunctatus) in Okinawa, Japan

Reactive sulfur species (RSS), such as hydrogen per (poly)sulfide, cysteine per (poly)sulfide, glutathione per (poly)sulfide, and protein-bound per (poly)sulfides, can easily react with environmental electrophiles such as methylmercury (MeHg), because of their high nucleophilicity. These RSS are produced by enzymes such as cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE) and are found in mammalian organs. Organs of wildlife have not been analyzed for hydrogen sulfide, cysteine, glutathione, and RSS. In this study, low molecular weight nucleophilic sulfur substances, including RSS, were quantified by stable isotope dilution assay-based liquid chromatography-mass spectrometry using β-(4-hydroxyphenyl)ethyl iodoacetamide to capture the target chemicals in the small Indian mongoose which species possesses high mercury content as same as some marine mammals. Western blotting revealed that the mongoose organs (liver, kidney, cerebrum, and cerebellum) contained proteins that cross-reacted with anti-CBS and CSE antibodies. The expression patterns of these enzymes were similar to those in mice, indicating that mongoose organs contain CBS and CSE. Moreover, bis-methylmercury sulfide (MeHg)₂S, which is a low toxic compound in comparison to MeHg, was found in the liver of this species. These results suggest that the small Indian mongoose produces RSS and monothiols associated with detoxification of electrophilic organomercury. The animals which have high mercury content in their bodies may have function of mercury detoxification involved not only Se but also RSS interactions.

Protein S-sulfhydration: Unraveling the prospective of hydrogen sulfide in the brain, vasculature and neurological manifestations

Hydrogen sulfide (H₂S) and hydrogen polysulfides (H₂S_n) are essential regulatory signaling molecules generated by the entire body, including the central nervous system. Researchers have focused on the classical H₂S signaling from the past several decades, whereas the last decade has shown the emergence of H₂S-induced protein S-sulfhydration signaling as a potential therapeutic approach. Cysteine S-persulfidation is a critical paradigm of post-translational modification in the process of H₂S signaling. Additionally, studies have shown the cross-relationship between S-sulfhydration and other cysteine-induced post-translational modifications, namely nitrosylation and carbonylation. In the central nervous system, S-sulfhydration is involved in the cytoprotection through various signaling pathways, viz. inflammatory response, oxidative stress, endoplasmic reticulum stress, atherosclerosis, thrombosis, and angiogenesis. Further, studies have demonstrated H₂S-induced S-sulfhydration in regulating different biological processes, such as mitochondrial integrity, calcium homeostasis, blood-brain permeability, cerebral blood flow, and long-term potentiation. Thus, protein S-sulfhydration becomes a crucial regulatory molecule in cerebrovascular and neurodegenerative diseases. Herein, we first described the generation of intracellular H₂S followed by the application of H₂S in the regulation of cerebral blood flow and blood-brain permeability. Further, we described the involvement of S-sulfhydration in different biological and cellular functions, such as inflammatory response, mitochondrial integrity, calcium imbalance, and oxidative stress. Moreover, we highlighted the importance of S-sulfhydration in cerebrovascular and neurodegenerative diseases.

Sensitivity and Selectivity Analysis of Fluorescent Probes for Hydrogen Sulfide Detection

Hydrogen sulfide (H₂S) is a gasotransmitter known to regulate physiological and pathological processes. Abnormal H₂S levels have been associated with a range of conditions, including Parkinson's and Alzheimer's diseases, cardiovascular and renal diseases, bacterial and viral infections, as well as cancer. Therefore, fast and sensitive H₂S detection is of significant clinical importance. Fluorescent H₂S probes hold great potential among the currently developed detection methods because of their high sensitivity, selectivity, and biocompatibility. However, many proposed probes do not provide a gold standard for proper use and selection. Consequently, issues arise when applying the probes in different conditions. Therefore, we systematically evaluated four commercially available probes (WSP‐1, WSP‐5, CAY, and P3), considering their detection range, sensitivity, selectivity, and performance in different environments. Furthermore, their capacity for endogenous H₂S imaging in live cells was demonstrated.

Cytoprotective gastric pentadecapeptide BPC 157 resolves major vessel occlusion disturbances, ischemia-reperfusion injury following Pringle maneuver, and Budd-Chiari syndrome

The stable gastric pentadecapeptide BPC 157 counteracts various venous occlusion-induced syndromes. Summarized are all these arguments, in the Robert's cytoprotection concept, to substantiate the resolution of different major vessel occlusion disturbances, in particular ischemia-reperfusion injury following the Pringle maneuver and Budd-Chiari syndrome, which was obtained by BPC 157 therapy. Conceptually, there is a new point, namely, endothelium maintenance to epithelium maintenance (the recruitment of collateral blood vessels to compensate for vessel occlusion and reestablish blood flow or bypass the occluded or ruptured vessel). In this paper, we summarize the evidence of the native cytoprotective gastric pentadecapeptide BPC 157, which is stable in the human gastric juice, is a membrane stabilizer and counteracts gut-leaky syndrome. As a particular target, it is distinctive from the standard peptide growth factors, involving particular molecular pathways and controlling VEGF and NO pathways. In the early 1990s, BPC 157 appeared as a late outbreak of the Robert's and Szabo's cytoprotection-organoprotection concept, like the previous theoretical/practical breakthrough in the 1980s and the brain-gut axis and gut-brain axis. As the time went on, with its reported effects, it is likely most useful theory practical implementation and justification. Meantime, several reviews suggest that BPC 157, which does not have a lethal dose, has profound cytoprotective activity, used to be demonstrated in ulcerative colitis and multiple sclerosis trials. Likely, it may bring the theory to practical application, starting with the initial argument, no degradation in human gastric juice for more than 24 h, and thereby, the therapeutic effectiveness (including via a therapeutic per-oral regimen) and pleiotropic beneficial effects.

Thioredoxin Reductase-triggered Fluorogenic Donor of Hydrogen Sulfide: A Model Study with Symmetrical Organopolysulfide Probe with Turn-on Near-Infrared Fluorescence Emission

We describe herein the rational development of organopolysulfide-based fluorogenic donor of hydrogen sulfide (H2S) DCI-PS, which can be activated by the antioxidant selenoenzyme thioredoxin reductase (TrxR) with concomitant release of...

A Novel Hydrogen Sulfide Donor Reduces Pilocarpine-Induced Status Epilepticus and Regulates Microglial Inflammatory Profile

Although epilepsy is one of the most common neurologic disorders, there is still a lack of effective therapeutic drugs for it. Recently, we synthesized a novel hydrogen sulfide (H₂S) donor, which is found to reduce seizures in animal models effectively. But it remains to be determined for its mechanism. In the present study, we found that the novel H₂S donor could reduce pilocarpine-induced seizures in mice. It alleviated the epileptic behavior, the hippocampal electroencephalography (EEG) activity of seizures, and the damage of hippocampal neurons in status epilepticus mice. In addition, the novel H₂S donor could reduce microglial inflammatory response. It not only reduced the upregulation of pro-inflammatory markers [inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX2)] in status epilepticus mice, but also increased the levels of microglial anti-inflammatory marker arginase-1 (Arg-1). In lipopolysaccharide-treated microglia BV2 cells, administration of the H₂S donor also significantly reduced the lipopolysaccharide-induced upregulation of the expression of the pro-inflammatory markers and increased the expression of the anti-inflammatory markers. Thus, the novel H₂S donor regulates microglial inflammatory profile in status epilepticus mice and in vitro. These results suggested that the novel H₂S donor can reduce seizures and regulate microglial inflammatory profile, which may be a novel mechanism and potential therapeutic strategy of the H₂S donor anti-seizures.

H2S Donors and Their Use in Medicinal Chemistry

Hydrogen sulfide (H2S) is a ubiquitous gaseous signaling molecule that has an important role in many physiological and pathological processes in mammalian tissues, with the same importance as two others endogenous gasotransmitters such as NO (nitric oxide) and CO (carbon monoxide). Endogenous H2S is involved in a broad gamut of processes in mammalian tissues including inflammation, vascular tone, hypertension, gastric mucosal integrity, neuromodulation, and defense mechanisms against viral infections as well as SARS-CoV-2 infection. These results suggest that the modulation of H2S levels has a potential therapeutic value. Consequently, synthetic H2S-releasing agents represent not only important research tools, but also potent therapeutic agents. This review has been designed in order to summarize the currently available H2S donors; furthermore, herein we discuss their preparation, the H2S-releasing mechanisms, and their -biological applications.

A cysteine-triggered fluorogenic donor base on native chemical ligation for tracking H2S delivery in vivo

A hydrogen sulfide (H₂S) donor is a fundamental molecular tool used as an exogenous source in biological studies and therapies. However, finding a controllable and visual fluorescent H₂S donor is difficult. We report a new H₂S donor, HSD560, the H₂S release of which is triggered by cysteine. Importantly, the H₂S generation is accompanied with enhanced green fluorescence, which could be utilized to track H₂S release in cells using microscopy. H₂S release from HSD560 undergoes a non-enzymatic native chemical ligation (NCL) process, which provides an accurate match with activated fluorescence and localization of H₂S in zebrafish.

Rational Development of Dual-Ratiometric Fluorescent Probes for Distinguishing between H2S and SO2 in Living Organisms

For better investigating the complicated relationships between H₂S and SO₂, simultaneously detecting and visualizing them with good selectivity is crucial. However, most sensing mechanisms for H₂S and SO₂ probes are based on the addition reactions with the double bonds, which have no selectivity. In this work, by introducing an active triple bond into 4-dicyanovinyl-7-diethylamino-coumarin, we construct two unique sensors for not only distinguishing between H₂S and SO₂ but also sensing H₂S and SO₂ in a dual-ratiometric manner. Moreover, the modified sensor was successfully applied in living cells and zebrafish for discriminating H₂S and SO₂.

Hydrogen Sulfide: A Robust Combatant against Abiotic Stresses in Plants

Hydrogen sulfide (H2S) is predominantly considered as a gaseous transmitter or signaling molecule in plants. It has been known as a crucial player during various plant cellular and physiological processes and has been gaining unprecedented attention from researchers since decades. They regulate growth and plethora of plant developmental processes such as germination, senescence, defense, and maturation in plants. Owing to its gaseous state, they are effectively diffused towards different parts of the cell to counterbalance the antioxidant pools as well as providing sulfur to cells. H2S participates actively during abiotic stresses and enhances plant tolerance towards adverse conditions by regulation of the antioxidative defense system, oxidative stress signaling, metal transport, Na+/K+ homeostasis, etc. They also maintain H2S-Cys-cycle during abiotic stressed conditions followed by post-translational modifications of cysteine residues. Besides their role during abiotic stresses, crosstalk of H2S with other biomolecules such as NO and phytohormones (abscisic acid, salicylic acid, melatonin, ethylene, etc.) have also been explored in plant signaling. These processes also mediate protein post-translational modifications of cysteine residues. We have mainly highlighted all these biological functions along with proposing novel relevant issues that are required to be addressed further in the near future. Moreover, we have also proposed the possible mechanisms of H2S actions in mediating redox-dependent mechanisms in plant physiology.

Nitric oxide and hydrogen sulfide: Sibling rivalry in the family of epigenetic regulators

Nitric oxide (NO) and hydrogen sulfide (H₂S) were previously only known for their toxic properties. Now they are regarded as potent gaseous messenger molecules (gasotransmitters) that rapidly transverse cell membranes and transduce cellular signals through their chemical reactions and modifications to protein targets. Both are known to regulate numerous physiological functions including angiogenesis, vascular tone, and immune response, to name a few. NO and H₂S often work synergistically and in competition to regulate each other's synthesis, target protein activity via posttranslational modifications (PTMs), and chemical interactions. In addition to their canonical modes of action, increasing evidence has demonstrated that NO and H₂S share another signaling mechanism: epigenetic regulation. This review will compare and contrast biosynthesis and metabolism of NO and H₂S, their individual and shared interactions, and the growing body of evidence for their roles as endogenous epigenetic regulatory molecules.

Novel controlled and targeted releasing hydrogen sulfide system exerts combinational cerebral and myocardial protection after cardiac arrest

BACKGROUND

Cardiac arrest (CA) is a leading cause of death worldwide. Even after successful cardiopulmonary resuscitation (CPR), the majorities of survivals are companied with permanent myocardial and cerebral injury. Hydrogen sulfide (H2S) has been recognized as a novel gasotransmitter exerting multiple organ protection; however, the lacks of ideal H2S donors which can controlled release H2S to targeted organs such as heart and brain limits its application.

RESULTS

This work utilized mesoporous iron oxide nanoparticle (MION) as the carriers of diallyl trisulfide (DATS), with polyethylene glycol (PEG) and lactoferrin (LF) modified to MIONs to acquire the prolonged circulation time and brain-targeting effects, and a novel targeted H2S releasing system was constructed (DATS@MION-PEG-LF), which exhibited excellent biocompatibility, controlled-releasing H2S pattern, heart and brain targeting features, and the ability to be non-invasive traced by magnetic resonance imaging. DATS@MION-PEG-LF presented potent protective effects against cerebral and cardiac ischemic injury after CA in both in vitro hypoxia/reoxygenation models and in vivo CA/CPR models, which mainly involves anti-apoptosis, anti-inflammatory and anti-oxidant mechanisms. Accordingly, the cardiac and cerebral functions were obviously improved after CA/CPR, with potentially improved survival.

CONCLUSIONS

The present work provides a unique platform for targeted controlled release of H2S based on MIONs, and offers a new method for combinational myocardial and cerebral protection from ischemic injury, bringing considerable benefits for CA patients.

Fetal Hypothyroidism Impairs Aortic Vasorelaxation Responses in Adulthood: Involvement of Hydrogen Sulfide and Nitric Oxide Cross talk

ABSTRACT

Thyroid hormones have a wide range of effects on growth, differentiation, evolution, metabolism, and physiological function of all tissues, including the vascular bed. In this study, the effect of fetal hypothyroidism on impairment of aortic vasorelaxation responses in adulthood was investigated with emphasis on possible involvement of hydrogen sulfide (H2S)/nitric oxide interaction. Two groups of female rats were selected. After mating and observation of vaginal plaque, one group received propylthiouracil (200 ppm in drinking water) until the end of pregnancy and another group had no propylthiouracil treatment during the fetal period. In adult rats, aortic relaxation responses to l-arginine and GYY4137 were assessed in the presence or absence of Nω-nitro-L-arginine methyl ester hydrochloride and dl-propargylglycine in addition to the biochemical measurement of thyroid hormones and some related factors. Obtained findings showed a lower vasorelaxation response for GYY4137 and l-arginine in the fetal hypothyroidism group, and preincubation with Nω-nitro-L-arginine methyl ester hydrochloride or dl-propargylglycine did not significantly aggravate this weakened relaxation response. In addition, aortic levels of sirtuin 3, endothelial nitric oxide synthase, cystathionine gamma-lyase, and H2S were significantly lower in the fetal hypothyroidism group. Meanwhile, no significant changes were obtained regarding serum levels of thyroid hormones including free triiodothyronine;, total triiodothyronine, free thyroxine, total thyroxine, and thyroid-stimulating hormone in adult rats. It can be concluded that hypothyroidism in the fetal period has inappropriate effects on the differentiation and development of vascular bed with subsequent functional abnormality that persists into adulthood, and part of this vascular abnormality is mediated through weakened interaction and/or cross talk between H2S and nitric oxide.

Naphthalimide-based a highly selective two-photon fluorescent probe for imaging of hydrogen sulfide in living cells and inflamed tissue of mouse model

Hydrogen sulfide (H₂S) is a very important third endogenously generated gaseous signaling molecule and plays a key role in physiological and pathological regulation processes of living biosystems. Although a lot of H₂S fluorescent probes have been reported, the relationship between the physiology and pathology of H₂S in inflamed tissues remains unclear. Herein, by adopting a donor-π-acceptor (D-π-A)-structured naphthalimide derivative as the two-photon (TP) fluorophore and a 4-dinitrobenzene-ether (DNB) with a strong intramolecular charge transfer (ICT) effect as the recognition moiety, we reported a novel TP bioimaging probe NP-H₂S for H₂S with improved sensitivity. The NP-H₂S exhibits very low background fluorescence in the absence of H₂S, and a significant 258-fold fluorescence intensity enhancement was observed in the presence of H₂S, resulting in a high sensitivity and selectivity to H₂S in aqueous solutions with a detection limit of 18.8 nM observed. The probe also shows a wide linear response concentration range (0-10.0 μM) to H₂S with high selectivity. All these features are favorable for direct monitoring of H₂S in complex biological samples. It was then applied for direct TP imaging of H₂S in tissues of inflammation model with satisfactory sensitivity, indicating it has the latent capability in further biological applications for investigation of the interaction H₂S with inflammation.

The Role of Host-Generated H2S in Microbial Pathogenesis: New Perspectives on Tuberculosis

For centuries, hydrogen sulfide (H₂S) was considered primarily as a poisonous gas and environmental hazard. However, with the discovery of prokaryotic and eukaryotic enzymes for H₂S production, breakdown, and utilization, H₂S has emerged as an important signaling molecule in a wide range of physiological and pathological processes. Hence, H₂S is considered a gasotransmitter along with nitric oxide (•NO) and carbon monoxide (CO). Surprisingly, despite having overlapping functions with •NO and CO, the role of host H₂S in microbial pathogenesis is understudied and represents a gap in our knowledge. Given the numerous reports that followed the discovery of •NO and CO and their respective roles in microbial pathogenesis, we anticipate a rapid increase in studies that further define the importance of H₂S in microbial pathogenesis, which may lead to new virulence paradigms. Therefore, this review provides an overview of sulfide chemistry, enzymatic production of H₂S, and the importance of H₂S in metabolism and immunity in response to microbial pathogens. We then describe our current understanding of the role of host-derived H₂S in tuberculosis (TB) disease, including its influences on host immunity and bioenergetics, and on Mycobacterium tuberculosis (Mtb) growth and survival. Finally, this review discusses the utility of H₂S-donor compounds, inhibitors of H₂S-producing enzymes, and their potential clinical significance.

Pharmacological modulation of the hydrogen sulfide (H2 S) system by dietary H2 S-donors: A novel promising strategy in the prevention and treatment of type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) represents the most common age-related metabolic disorder, and its management is becoming both a health and economic issue worldwide. Moreover, chronic hyperglycemia represents one of the main risk factors for cardiovascular complications. In the last years, the emerging evidence about the role of the endogenous gasotransmitter hydrogen sulfide (H₂ S) in the pathogenesis and progression of T2DM led to increasing interest in the pharmacological modulation of endogenous "H₂ S-system". Indeed, H₂ S directly contributes to the homeostatic maintenance of blood glucose levels; moreover, it improves impaired angiogenesis and endothelial dysfunction under hyperglycemic conditions. Moreover, H₂ S promotes significant antioxidant, anti-inflammatory, and antiapoptotic effects, thus preventing hyperglycemia-induced vascular damage, diabetic nephropathy, and cardiomyopathy. Therefore, H₂ S-releasing molecules represent a promising strategy in both clinical management of T2DM and prevention of macro- and micro-vascular complications associated to hyperglycemia. Recently, growing attention has been focused on dietary organosulfur compounds. Among them, garlic polysulfides and isothiocyanates deriving from Brassicaceae have been recognized as H₂ S-donors of great pharmacological and nutraceutical interest. Therefore, a better understanding of the therapeutic potential of naturally occurring H₂ S-donors may pave the way to a more rational use of these nutraceuticals in the modulation of H₂ S homeostasis in T2DM.

Modified cyclodextrins solubilize elemental sulfur in water and enable biological sulfane sulfur delivery

An important form of biological sulfur is sulfane sulfur, or S⁰, which is found in polysulfide and persulfide compounds as well as in elemental sulfur. Sulfane sulfur, often in the form of S₈, functions as a key energy source in the metabolic processes of thermophilic Archaean organisms found in sulfur-rich environments and can be metabolized both aerobically and anaerobically by different archaeons. Despite this importance, S₈ has a low solubility in water (∼19 nM), raising questions of how it can be made chemically accessible in complex environments. Motivated by prior crystallographic data showing S₈ binding to hydrophobic motifs in filamentous glycoproteins from the sulfur reducing Staphylothermus marinus anaerobe, we demonstrate that simple macrocyclic hydrophobic motifs, such as 2-hydroxypropyl β-cyclodextrin (2HPβ), are sufficient to solubilize S₈ at concentrations up to 2.0 ± 0.2 mM in aqueous solution. We demonstrate that the solubilized S₈ can be reduced with the common reductant tris(2-carboxyethyl)phosphine (TCEP) and reacts with thiols to generate H₂S. The thiol-mediated conversion of 2HPβ/S₈ to H₂S ranges from 80% to quantitative efficiency for Cys and glutathione (GSH). Moreover, we demonstrate that 2HPβ can catalyze the Cys-mediated reduction of S₈ to H₂S in water. Adding to the biological relevance of the developed systems, we demonstrate that treatment of Raw 264.7 macrophage cells with the 2HPβ/S₈ complex prior to LPS stimulation decreases NO₂ ^- levels, which is consistent with known activities of bioavailable H₂S and sulfane sulfur. Taken together, these investigations provide a new strategy for delivering H₂S and sulfane sulfur in complex systems and more importantly provide new insights into the chemical accessibility and storage of S⁰ and S₈ in biological environments.

Crosstalk among hydrogen sulfide (H2S), nitric oxide (NO) and carbon monoxide (CO) in root-system development and its rhizosphere interactions: A gaseous interactome

Root development in higher plants is achieved by a precise intercellular communication which determines cell fate in the primary embryonic meristem where the gasotransmitters H₂S, NO and CO participate dynamically. Furthermore, the rhizosphere interaction of these molecules with microbial and soil metabolism also affects root development. NO regulates root growth and architecture in association with several other biomolecules like auxin indole-3-acetic acid (IAA), ethylene, jasmonic acid (JA), strigolactones, alkamides and melatonin. The CO-mediated signal transduction pathway in roots is closely linked to the NO-mediated signal cascades. Interestingly, H₂S acts also as an upstream component in IAA and NO-mediated crosstalk during root development. Heme oxygenase (HO) 1 generates CO and functions as a downstream component in H₂S-mediated adventitious rooting and H₂S-CO crosstalk. Likewise, reactive oxygen species (ROS), H₂S and NO crosstalk are important components in the regulation of root architecture. Deciphering these interactions will be a potential biotechnological tool which could provide benefits in crop management in soils, especially under adverse environmental conditions. This review aims to provide a comprehensive update of the complex networks of these gasotransmitters during the development of roots.

Effects of Hydrogen Sulfide Donor NaHS on Porcine Vascular Wall-Mesenchymal Stem Cells

Hydrogen sulfide (H2S) is now considered not only for its toxicity, but also as an endogenously produced gas transmitter with multiple physiological roles, also in maintaining and regulating stem cell physiology. In the present work, we evaluated the effect of a common H2S donor, NaHS, on porcine vascular wall-mesenchymal stem cells (pVW-MSCs). pVW-MSCs were treated for 24 h with increasing doses of NaHS, and the cell viability, cell cycle, and reactive oxygen species (ROS) production were evaluated. Moreover, the long-term effects of NaHS administration on the noteworthy characteristics of pVW-MSCs were analyzed. The MTT test revealed no alteration in cell viability, however, the cell cycle analysis demonstrated that the highest NaHS dose tested (300 μM) determined a block in S phase, which did not depend on the ROS production. Moreover, NaHS (10 μM), continuously administered in culture for 21 days, was able to significantly reduce NG2, Nestin and PDGFR-β expression. The pro-angiogenic attitude of pVW-MSCs was partially reduced by NaHS: the cells maintained the ability to grow in spheroid and sprouting from that, but endothelial markers (Factor VIII and CD31) were reduced. In conclusion, NaHS can be toxic for pVW-MSCs in high doses, while in low doses, it influences cellular physiology, by affecting the gene expression with a slowing down of the endothelial lineage.

The biothiol-triggered organotrisulfide-based self-immolative fluorogenic donors of hydrogen sulfide enable lysosomal trafficking

Biothiol-reactive organotrisulfide-based self-immolative fluorogenic donors of H2S are rationally designed for the efficient monitoring of intracellular and lysosomal trafficking of H2S with a concomitant turn-on fluorescence. The non-toxic nature of the donors with a sustained release of H2S will certainly be helpful for their biomedical applications in the future.

Effect of 3-mercaptopyruvate Sulfurtransferase Deficiency on the Development of Multiorgan Failure, Inflammation, and Wound Healing in Mice Subjected to Burn Injury

The gaseous transmitter hydrogen sulfide (H2S) has been implicated in various forms of critical illness. Here, we have compared the outcome of scald burn injury in wild-type mice and in mice deficient in 3-mercaptopyruvate sulfurtransferase (3-MST), a mammalian H2S-generating enzyme. Outcome variables included indices of organ injury, clinical chemistry parameters, and plasma levels of inflammatory mediators. Plasma levels of H2S significantly increased in response to burn in wild-type mice, but remained unchanged in 3-MST-/- mice. The capacity of tissue homogenates to produce H2S from 3-mercaptopyruvate was unaffected by burn injury. In 3-MST-/- mice, compared to wild-type controls, there was a significant enhancement in the accumulation of polymorphonuclear cells (as assessed by the quantification of myeloperoxidase) in the liver (but not heart, lung, or skin) at 7 days postburn. Oxidative tissue damage (as assessed by malon dialdehyde content) was comparable between wild-type and 3-MST-deficient mice in all tissues studied. 3-MST-/- and wild-type mice exhibited comparable burn-induced elevations in circulating plasma levels of hepatic injury; however, 3-MST-/- mice exhibited a higher degree of renal injury (as reflected by elevated blood urea nitrogen levels) at 7 days postburn. Inflammatory mediators (eg, TNF-α, IL-1β, IL-2, IL-6, IL-10, and IL-12) increased in burn injury, but without significant differences between the 3-MST-/- and wild-type groups. The healing of the burn wound was also unaffected by 3-MST deficiency. In conclusion, the absence of the H2S-producing enzyme 3-MST slightly exacerbates the development of multiorgan dysfunction but does not affect inflammatory mediator production or wound healing in a murine model of burn injury.

Iron transitions during activation of allosteric heme proteins in cell signaling

Allosteric heme proteins can fulfill a very large number of different functions thanks to the remarkable chemical versatility of heme through the entire living kingdom. Their efficacy resides in the ability of heme to transmit both iron coordination changes and iron redox state changes to the protein structure. Besides the properties of iron, proteins may impose a particular heme geometry leading to distortion, which allows selection or modulation of the electronic properties of heme. This review focusses on the mechanisms of allosteric protein activation triggered by heme coordination changes following diatomic binding to proteins as diverse as the human NO-receptor, cytochromes, NO-transporters and sensors, and a heme-activated potassium channel. It describes at the molecular level the chemical capabilities of heme to achieve very different tasks and emphasizes how the properties of heme are determined by the protein structure. Particularly, this reviews aims at giving an overview of the exquisite adaptability of heme, from bacteria to mammals.

WRKY13 Enhances Cadmium Tolerance by Promoting D-CYSTEINE DESULFHYDRASE and Hydrogen Sulfide Production

Hydrogen sulfide (H2S), a plant gasotransmitter, functions in the plant response to cadmium (Cd) stress, implying a role for cysteine desulfhydrase in producing H2S in this process. Whether d -CYSTEINE DESULFHYDRASE (DCD) acts in the plant Cd response remains to be identified, and if it does, how DCD is regulated in this process is also unknown. Here, we report that DCD-mediated H2S production enhances plant Cd tolerance in Arabidopsis (Arabidopsis thaliana). When subjected to Cd stress, a dcd mutant accumulated more Cd and reactive oxygen species and showed increased Cd sensitivity, whereas transgenic lines overexpressing DCD had decreased Cd and reactive oxygen species levels and were more tolerant to Cd stress compared with wild-type plants. Furthermore, the expression of DCD was stimulated by Cd stress, and this up-regulation was mediated by a Cd-induced transcription factor, WRKY13, which bound to the DCD promoter. Consistently, the higher Cd sensitivity of the wrky13-3 mutant was rescued by the overexpression of DCD Together, our results demonstrate that Cd-induced WRKY13 activates DCD expression to increase the production of H2S, leading to higher Cd tolerance in plants.

Quinoline H2S donor decorated fluorescent carbon dots: visible light responsive H2S nanocarriers

Fluorescent carbon dots decorated by quinoline H₂S donor have been demonstrated as a photoresponsive nanocarrier for the effective release of H₂S.

Porous materials as carriers of gasotransmitters towards gas biology and therapeutic applications

This review highlights the strategies employed to load and release gasotransmitters such as NO, CO and H₂S from different kinds of porous materials, including zeolites, mesoporous silica, metal–organic frameworks and protein assemblies.