A review of hydrogen sulfide (H2S) donors: Chemistry and potential therapeutic applications

Multifunctional injectable hydrogel with self-supplied H2S release and bacterial inhibition for the wound healing with enhanced macrophages polarization via interfering with PI3K/Akt pathway

Hydrogen sulfide (H2S) gas therapy is beneficial for accelerating wound healing and alleviating the inflammatory process, but is seriously hindered by insufficient delivery and unsustainable release in vivo. This study presents a multifunctional injectable hydrogel, OC@ε-PL-SATO, composed of oxidized hyaluronic acid and N-acetylcysteine (NAC) as an initiator, carboxymethyl chitosan and S-aroylthiooxime modified ε-Poly-(l-lysine) (ε-PL-SATO). ε-PL-SATO is a NAC-responsive H2S donor. OC@ε-PL-SATO hydrogel is designed for the desired wound healing process, with rapid gelation (<30 s) and a sustained H2S release. After mixing and gelling, H2S could be long-term released from the hydrogel and effectively drives macrophages toward M2 polarization, thereby ameliorating the inflammatory response. Revealed by transcriptome analysis, the underlying mechanism is that OC@ε-PL-SATO hydrogel releasing H2S inhibits LPS-mediated inflammatory responses in RAW264.7 cells by interfering with phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) signaling and NF-κB activation. Furthermore, the OC@ε-PL-SATO hydrogel effectively eliminates the bacterial burden and alleviates the accompanying inflammation in a rat model of cutaneous wound infection. Importantly, the sustained generation of H2S gas significantly promotes angiogenesis and collagen deposition, ultimately accelerating the wound repair. In conclusion, this study provides a multifunctional injectable hydrogel with rapid gelatinization and continuous H2S release for accelerating the infected wound healing.

Exploring medical gas therapy in hemorrhagic stroke treatment: A narrative review

Hemorrhagic stroke (HS) is a neurological disorder caused by the rupture of cerebral blood vessels, resulting in blood seeping into the brain parenchyma and causing varying degrees of neurological impairment, including intracerebral hemorrhage (ICH) and subarachnoid hemorrhage (SAH). Current treatment methods mainly include hematoma evacuation surgery and conservative treatment. However, these methods have limited efficacy in enhancing neurological function and prognosis. The current challenge in treating HS lies in inhibiting the occurrence and progression of secondary brain damage after bleeding, which is a key factor affecting the prognosis of HS patients. Studies have shown that medical gas therapy is gaining more attention and has demonstrated various levels of neuroprotective effects on central nervous system disorders, such as hyperbaric oxygen, hydrogen sulfide, nitric oxide, carbon monoxide, and other inhalable gas molecules. These medical gas molecules primarily improve brain tissue damage and neurological dysfunction by regulating inflammation, oxidative stress, apoptosis, and other processes. However, many of these medical gasses also possess neurotoxic properties. Therefore, the use of medical gases in HS deserves further exploration and research. In this review, we will elucidate the therapeutic effects and study the advances in medical gas molecules in HS.

Hydrogen sulfide mechanism of action in plants; from interaction with regulatory molecules to persulfidation of proteins

Hydrogen sulfide (H2S), previously known as a toxic gas, is currently considered one of the most important gaseous transmitters in plants. This novel signaling molecule has been determined to play notable roles in plant growth, development, and maturation. In addition, pharmacological and genetic evidence indicated that this regulatory molecule effectively ameliorates various plant stress conditions. H2S is involved in these processes by changing gene expression, enzyme activities, and metabolite concentrations. During its regulatory function, H2S interacts with other signaling pathways such as hydrogen peroxide (H2O2), nitric oxide (NO), Ca2+, carbon monoxide (CO), phosphatidic acid (PA), phytohormones, etc. The H2S mechanism of action may depend on the persulfidation post-translational modification (PTM), which attacks the cysteine (Cys) residues on the target proteins and changes their structure and activities. This review summarized H2S biosynthesis pathways, its role in sulfide state, and its donors in plant biology. We also discuss recent progress in the research on the interactions of H2S with other signaling molecules, as well as the role of persulfidation in modulating various plant reactions.

The new perspective of gasotransmitters in cancer metastasis

Cancer metastasis is the leading cause of death in cancer patients, which renders heavy burdens to family and society. Cancer metastasis is a complicated process in which a large variety of biological molecules, cells and signaling pathways are involved. Nitric oxide (NO), carbon monoxide (CO) and hydrogen sulfide (H2S) are common air pollutants which are harmful to human bodies and environments. However, recent studies show that these gases, which are collectively termed gasotransmitters, play significant roles in physiological homeostasis and pathogenesis including immunological responses, neuronal regulations, respiratory as well as cardiovascular diseases, metabolic disorders and cancers. These gases are abnormally expressed in cancer cells or tissues, along with the gas-producing enzymes. They have been demonstrated to participate in cancer metastasis intensively by modulating diverse signaling axes. This review introduces the nature of gasotransmitters, summaries novel research progression in gasotransmitters-induced cancer metastasis and elucidates multifaceted mechanisms how the process is modulated, with an effort to bring new therapeutic targets for cancer management in the future.

Intramolecular Thiol-Promoted Decomposition of Cysteine Ester (ITPDC): A General Platform for Controllable Release of Reactive Sulfur Species

Endogenously generated reactive sulfur species (RSS) play critical roles in various physiological processes. RSS donors can enhance our understanding of RSS chemical biology and open new avenues for treating RSS-associated diseases. Nevertheless, general strategies for the controllable release of distinct RSS remain lacking. Herein, we present the first general platform for controllable release of RSS with sulfur oxidation states ranging from -2 to +4, based on the intramolecular thiol-promoted decomposition of cysteine ester (ITPDC). We first rationally designed ITPDC-based hydrogen sulfide (H2S) donors that avoid electrophilic byproducts and exhibit high H2S release efficiencies (>50%). Mechanistic investigations and density functional theory calculations elucidated the detailed pathways of pH-controllable H2S release from ITPDC, and computational studies also predicted other H2S-related RSS release from the ITPDC-based motifs. Importantly, we developed a series of ITPDC-based donors capable of releasing various RSS, including persulfide, hydrogen persulfide, sulfenic acid, sulfinic acid, and sulfur dioxide (SO2). Moreover, fluorescent imaging demonstrated the successful cellular delivery of H2S, persulfide, and SO2 from these donors, and the ITPDC-based motif was employed to create a light-triggered donor. We anticipate that these innovative chemistries will provide valuable tools for studying sulfur biology and for developing new RSS donors and bio-orthogonal cleavage techniques.

Stimuli-responsive hydrogel with spatiotemporal co-delivery of FGF21 and H₂S for synergistic diabetic wound repair

Chronic diabetic wounds pose significant clinical challenges due to persistent inflammation, impaired angiogenesis, and disrupted cellular homeostasis. To address these multifactorial barriers, we engineered an injectable, biodegradable, and biocompatible methylated silk fibroin (SilMA) hydrogel system co-loaded with cobalt sulfide (CoS) and fibroblast growth factor 21 (FGF21), designed for on-demand therapeutic release. In the acidic microenvironment characteristic of the inflammatory phase of diabetic wounds, the hydrogel rapidly releases hydrogen sulfide (H₂S) and Co2+ ions, mitigating inflammation and exerting antibacterial effects. Subsequently, during the proliferative and remodeling phases, sustained release of FGF21 promotes cellular proliferation, angiogenesis, and enzymatic homeostasis, thereby accelerating wound healing. Mechanistic studies reveal that the hydrogel facilitates M2 macrophage polarization and activates the JAK/STAT signaling pathway, leading to upregulation of vascular endothelial growth factor (VEGF). Additionally, it enhances antioxidant enzyme activities (superoxide dismutase, catalase, glutathione) while suppressing pro-oxidant enzymes (NADPH oxidase, lipoxygenase, cyclooxygenase). In vivo studies using a diabetic mouse model demonstrate that this dual-functional hydrogel significantly improves wound closure rates and tissue regeneration. These findings suggest that the SilMA-FGF21/CoS hydrogel represents a promising therapeutic strategy for the management of diabetic wounds.

Aminopeptidase N-Activated Self-immolative Hydrogen Sulfide Donor for Inflammatory Response-Specific Wound Healing

Hydrogen sulfide (H2S) plays crucial inflammatory modulating roles, representing a promising candidate for anti-inflammatory therapies. However, current H2S delivery approaches lack sufficient specificity against inflammatory response. Herein, regarding the overexpressed aminopeptidase N (APN) at the inflammation sites, an APN-activated self-immolative carbonyl sulfide (COS)/H2S donor (AlaCOS) was developed for inflammatory response-specific H2S delivery. The compound showed sustained H2S generation upon APN activation in the presence of carbonic anhydrase (CA), and the responsiveness could be well regulated by modulating the amino acid sequence. Due to the inflammatory response-specific sustained H2S delivery, AlaCOS provided potent anti-inflammatory capability, which was further validated by RNA sequencing. In vivo experiments on a full-thickness cutaneous wound murine model also showed the strong promoting effect on wound healing, mainly due to the regulation of the inflammatory response by AlaCOS. By introducing a caged coumarin fluorophore to the molecular architecture, self-reporting fluorescence could be generated accompanied with APN-mediated COS/H2S release, which achieved the visualization of H2S delivery in vitro and in vivo. This work not only offers a useful tool for studying the bioactivity of H2S on inflammation, but also provides new insights for developing novel therapies to cope with inflammation-associated diseases.

Genetic variation in the INMT gene strongly impacts the production of trimethylsulfonium in humans

We previously identified the trimethylsulfonium ion (TMS) in human urine and highlighted its potential as a novel H2S biomarker but observed significant inter-individual variability in its urinary excretion. In this work we investigate the contribution of genetic factors to this variability in a group of European subjects (n = 100) from the BioPersMed cohort. Urinary TMS concentrations displayed two clusters within 5.0-20 nM and 100-400 nM. Genotyping revealed that this clustering is linked to a single nucleotide polymorphism (rs6970396) in the INMT gene, P < 0.001. We found strong contrast in the effects of rs6970396 between TMS and the selenium analogue TMSe which is one of many other detoxification products of the poorly recognized chalcogen-methylation activity of the INMT enzyme. Genetic variability in INMT has wide implications not only for the detoxification of H2S, both inhaled and naturally produced, but also for that of other volatile sulfur compounds in humans which may serve as substrates including xenobiotics.

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.

Sustained-Release H2S Nanospheres Regulate the Inflammatory Microenvironment of Wounds, Promote Angiogenesis and Collagen Deposition, and Accelerate Diabetic Wound Healing

Diabetic wounds are blocked in the inflammatory stage, growth factors are degraded, and blood vessels are difficult to regenerate, leading to continuous necrosis and nonhealing of the wound. Hydrogen sulfide (H2S) plays an important role in the pathophysiological process of wound healing and has a long history of treating skin diseases. Although the sulfide salt solution is the preferred donor of exogenous H2S, its rapid release rate, excess production, and difficulty in accurately controlling the dose limit its use. Herein, we developed H2S sustained-release nanospheres NaHS@MS@LP for the treatment of diabetic wounds. NaHS@MS@LP nanosphere was composed of a NaHS-loaded mesoporous silicon core and a DSPE-PEG liposome outer membrane. When NaHS@MS@LP nanospheres were used to treat the wound of diabetic rats, mesoporous silicon was delivered into the cells and the loaded NaHS slowly released H2S through hydrolysis, participating in all stages of wound healing. In conclusion, NaHS@MS@LP nanospheres regulated the inflammatory microenvironment of wound skin by inducing the transformation of macrophages into M2 type and promoted angiogenesis and collagen deposition to accelerate wound healing in diabetic rats. Our findings provide strategies for the treatment of chronic wounds, including but not limited to diabetic wounds.

Mercapto-NSAIDs generate a non-steroidal anti-inflammatory drug (NSAID) and hydrogen sulfide

Non-steroidal anti-inflammatory drugs (NSAIDs) are among the frontline treatments for inflammation and pain. Hydrogen sulfide (H2S) and related persulfide (RS-SH) are important mediators of antioxidant response and protect cells from oxidative stress. Hybrids of these pharmacological agents have shown promise in clinical trials and are superior to the parent NSAID. Here, we report a new class of NSAID-H2S hybrids, where a strategic placement of a sulfhydryl group adjacent to a carbonyl of a NSAID facilitates the enzymatic generation of H2S. We show that α-mercapto-nabumetone, a derivative of the clinical drug nabumetone, is a substrate for 3-mercaptopyruvate sulfurtransferase (3-MST), an enzyme involved in H2S biosynthesis. The key step of 3-MST catalysis is the cleavage of a C-S bond adjacent to a carbonyl group, which generates an enolate and 3-MST persulfide, which in turn is cleaved under reducing conditions to generate H2S. Guided by a molecular docking study with 3-MST, we prepared two mercapto-nabumetone derivatives, protected as their thioacetates. In the presence of 3-MST, both mercapto-nabumetone derivatives generated H2S and the NSAID in a nearly quantitative yield, produced glutathione persulfide (GS-SH), an important mediator of cellular antioxidant response, and permeated cells to generate H2S. Lastly, to gain insights into the scope of this strategy, we prepared mercapto-NSAID derivatives containing a carboxylic acid. We found that the propensity to generate H2S depended on the nature of the enol that is produced during the transformation of the mercapto-NSAID into the parent NSAID. This offers new insights into 3-MST catalysis and how reaction outcomes can be modulated by the keto-enol equilibrium. Taken together, the atom economical transformation of a clinical NSAID with one strategically placed sulfhydryl group to generate H2S presents new opportunities to enhance the properties of NSAIDs through participation in endogenous H2S biosynthesis.

Structure-activity-relationships of the Stability of Six Pentathiepins Towards Glutathione: Possible Correlations with Biological Activities

The biological properties of pentathiepins have been intensively studied in recent years. Although the proposed mechanism of action requires activation by intracellular thiols, the dependence of activity on the stability of pentathiepins towards glutathione (GSH) has not been directly investigated. Here, we determined the structure-related stability of six different pentathiepins with four different scaffolds in the presence of GSH by using reversed-phase high-performance liquid chromatography (RP-HPLC) and UV-vis spectroscopy over a wide range of GSH concentrations. We found significant differences in compound stability depending on the pentathiepin scaffold; these differences were reflected in their cytotoxic activities. However, we found no substantial differences in their inhibition of glutathione peroxidase 1 (GPx-1). While the intact pentathiepin ring is necessary for the antiproliferative activity of pentathiepins, the depletion of intracellular GSH content with dl-buthionine-(S,R)-sulfoximine (BSO) led to a significant increase in cytotoxicity of the tested substances. In view of the increased cytotoxicity following artificial GSH depletion, this calls into question the sole role of GSH in the intracellular activation mechanism.

In Situ Slow-Release Hydrogen Sulfide Therapeutics for Advanced Disease Treatments

Hydrogen sulfide (H2S) gas therapygarners significant attention for its potential to improve outcomes in various disease treatments. The quantitative control of H2S release is crucial for effective the rapeutic interventions; however, traditional researchon H2S therapy frequently utilizes static release models and neglects the dynamic nature of blood flow. In this study, we propose a novel slow-release in-situ H2S release model that leverages the dynamic hydrolysis of H2S donorswithin the bloodstream. Calcium sulfide nanoparticles (CaS NPs) withmicrosolubility characteristics exhibit continuous H2S release, surpassing 24 h at normal blood flow velocities. The extended-release profile demonstrates superior potential in aligning with the bell-shapedpharmacological effect of H2S, compared to NaHS. Moreover, we synthesisedrare earth-doped CaS NPs (CaS: Eu2+, Sm3+ NPs) tha texhibit persistent luminescence, enabling visualisation of the continuous H2S release in trials. Our results demonstrate that lowdose CaS: Eu2+, Sm3+ NPs significantly reduces seizureduration to 1.2 ± 0.7 minutes, while high dose effectively suppresses colontumor growth with a tumor inhibition rate of 54%. Remarkably, these findings closely resemble endogenous H2S levels in treating epilepsy and tumors. This innovative slow-release, in-situ H2S the rapeutic approach via hydrolysis rejuvenates the development of H2S-basedtherapeutics.

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.

A Bioluminescent Probe for H2S Detection in Tumor Microenvironment

Hydrogen sulfide (H2S) is an endogenous gaseous signaling molecule that regulates various physiological functions, and its abnormal levels have been closely linked to the onset and progression of numerous diseases including renal cell carcinoma (RCC). RCC is the most common malignant tumor of the kidney, accounting for 85-90% of all kidney cancer cases. However, studies using H2S as a biomarker for monitoring RCC progression at the molecular level remain relatively limited. Most current H2S luminescent probes suffer from low sensitivity and often need external stimuli, such as cysteine, to artificially elevate H2S levels, thereby reducing their effectiveness in detecting H2S in cells or in vivo. Although bioluminescent imaging probes are gaining attention for their specificity and high signal-to-noise ratio, no existing probes are specifically designed for detecting H2S in RCC. Additionally, many bioluminescent probes face challenges such as short emission wavelengths or dependence on complex conditions such as external adenosine triphosphate (ATP). Herein, through "caging" the luciferin substrate QTZ with H2S recognition groups, a H2S-sensitive bioluminescent probe QTZ-N3 with good sensitivity (∼0.19 μM) and selectivity was prepared. QTZ-N3 can effectively detect endogenous H2S in 786-O-Nluc renal cancer cells and sensitively monitor H2S levels in the RCC xenograft nude mouse model without requiring stimuli like cysteine. Furthermore, QTZ-N3 allows for the real-time monitoring of H2S during tumor progression. This work lays a solid foundation for future understanding of the biological functions of H2S in vivo.

Current Approaches and Innovations in Managing Preeclampsia: Highlighting Maternal Health Disparities

Preeclampsia (PE) is a major cause of maternal mortality and morbidity, affecting 3-6% of pregnancies worldwide and ranking among the top six causes of maternal deaths in the U.S. PE typically develops after 20 weeks of gestation and is characterized by new-onset hypertension and/or end-organ dysfunction, with or without proteinuria. Current management strategies for PE emphasize early diagnosis, blood pressure control, and timely delivery. For prevention, low-dose aspirin (81 mg/day) is recommended for high-risk women between 12 and 28 weeks of gestation. Magnesium sulfate is also advised to prevent seizures in preeclamptic women at risk of eclampsia. Emerging management approaches include antiangiogenic therapies, hypoxia-inducible factor suppression, statins, and supplementation with CoQ10, nitric oxide, and hydrogen sulfide donors. Black women are at particularly high risk for PE, potentially due to higher rates of hypertension and cholesterol, compounded by healthcare disparities and possible genetic factors, such as the APOL1 gene. This review explores current and emerging strategies for managing PE and addresses the underlying causes of health disparities, offering potential solutions to improve outcomes.

Analysis of the protective effect of hydrogen sulfide over time in ischemic rat skin flaps

BACKGROUND

Hydrogen sulfide (H2S) is a widely studied gasotransmitter, and its protective effect against ischemia-reperfusion damage has been explored in several studies. Therefore, a requirement exists for a comprehensive study about H2S effects on ischemia-reperfusion damage in flap surgery. The aim of this study is to examine the effect of hydrogen sulfide by creating ischemia-reperfusion injury in the vascular-stemmed island flap prepared from the rat groin area.

MATERIALS AND METHODS

"Wistar albino" rats weighing between 250 and 300 grams were divided into 4 groups (group 1, group 2, group 3, group 4). Each group was divided into 2 subgroups: subgroup A (control) and subgroup B (H2S). In each group, skin flaps were elevated as an island flap with a superficial epigastric artery pedicle, 6 × 4cm from the groin area. In subgroup B (H2S), liquid hydrogen sulfide was injected through the tail vein 20minutes before ischemia at a final concentration of 10μM. Femoral artery and vein blood flows were stopped with separate microclips and left in ischemia, according to the planned ischemia hours of the flaps: group 1 as 1 hour, group 2 as 2hours, group 3 as 3hours, and group 4 as 6hours. Later, microclips were removed, and blood flow restored again. After 12hours of reperfusion, the rats were sacrificed by cervical dislocation, and tissue samples were taken. From the samples taken, neutrophil count in ischemic tissue, MDA (malondialdehyde) measurement, and damage in the tissue were evaluated by electron microscopy.

RESULTS

On electron microscopy inspection at all hours (1, 2, 3, and 6), hydrogen sulfide was found to provide protection against ischemia, reperfusion damage, and apoptosis at the cellular level. There was a statistically significant (P=0.035) decrease in the tissue neutrophil count at the 1st, 2nd, and 3rd hours. In the tissue MDA measurement, a statistically significant (P=0.026) decrease in hydrogen sulfide was detected at the first hour. There was no statistically significant difference in the 6th hour tissue neutrophil count and 2nd, 3rd, and 6th hour tissue MDA measurement.

CONCLUSION

Electron microscopy results in this study showed that hydrogen sulfide had antiapoptotic effects on reperfusion damage in skin flaps at all hours. However, the neutrophil counts showed it had cytoprotective and anti-inflammatory properties during the 1st, 2nd, and 3rd hours following ischemia, but not during the 6th hour. Tissue MDA levels indicate that H2S mitigates significant I/R injury during the 1st hour but not in the subsequent 2nd, 3rd, and 6th hours. These results led to the hypothesis that, in order to offer a strong enough protective effect against I/R damage, H2S should be administered repeatedly or at varying concentrations. After more research on how H2S affects skin flaps, we believe that it can be used in plastic surgery practices.

Synthesis, H2S releasing properties, antiviral and antioxidant activities and acute cardiac effects of nucleoside 5'-dithioacetates

Hydrogen sulfide (H2S) is an endogenous gasotransmitter with cardioprotective and antiviral effects. In this work, new cysteine-selective nucleoside-H2S-donor hybrid molecules were prepared by conjugating nucleoside biomolecules with a thiol-activatable dithioacetyl group. 5'-Dithioacetate derivatives were synthesized from the canonical nucleosides (uridine, adenosine, cytidine, guanosine and thymidine), and the putative 5'-thio metabolites were also produced from uridine and adenosine. According to our measurements made with an H2S-specific sensor, nucleoside dithioacetates are moderately fast H2S donors, the guanosine derivative showed the fastest kinetics and the adenosine derivative the slowest. The antioxidant activity of 5'-thionucleosides is significantly higher than that of trolox, but lower than that of ascorbic acid, while intact dithioacetates have no remarkable antioxidant effect. In human Calu cells, the guanosine derivative showed a moderate anti-SARS-CoV-2 effect which was also confirmed by virus yield reduction assay. Dithioacetyl-adenosine and its metabolite showed similar acute cardiac effects as adenosine, however, it is noteworthy that both 5'-thio modified adenosines increased left ventricular ejection fraction or stroke volume, which was not observed with native adenosine.

The double face of licorice-kansui herb pair: Cure or curse, depending on the combining ratio and mediated by hydrogen sulfide

BACKGROUND

The safety and efficacy of herbal medicines including traditional Chinese medicine (TCM) has been one of the major scientific problems in the medical field. In TCM prescriptions, reasonable herbal combinations bring stronger efficacy and low risk of toxicity. However, the rules and mechanisms for herbal combinations are far from complete understood yet.

PURPOSE

In this study, we investigated the efficacy-toxicity transformation of the licorice-kansui herbal combination under clinical equivalent doses, and study the inside mechanisms.

STUDY DESIGN

Licorice-kansui or glycyrrhetinic acid-kansuinine A combinations of different combining ratio were given to malignant pleural effusion mice as well as the IEC-6 and S-180 cells.

METHODS

The therapeutic and toxic effects were characterized by various indicators; the chemical changes were analyzed by LC-MS method; the role of H2S was also studied through its inhibitors.

RESULTS

Low-proportion of licorice combined with kansui exerted comparable therapeutic effects to cisplatin, by reducing pleural effusion, promoting respiration, increasing urine volume, protecting lung tissue, and inhibiting tumor cells by inducing oxidative stress and apoptosis. On the other hand, high-proportion of licorice combined with kansui had poor therapeutic effect but induced oxidative stress, inflammation and tissue damages, especially to the small intestine. This efficacy-toxicity transformation was also reproduced by the glycyrrhetinic acid-kansuinine A combination on IEC-6 epithelial cells and S-180 tumor cells. The transformation was not simply caused by the in-solution solubilization effects of licorice during co-decocted with kansui. Furthermore, the therapeutic and toxic effects were both highly related to the hydrogen sulfide level and its anabolic enzymes, cystathionine-gamma-lyase (CSE) or cystathionine beta-synthase (CBS), either in tissues or in-vitro cells. By inhibiting CSE or CBS, all the therapeutic or toxic effects were abolished both in-vivo and in-vitro. Moreover, the intestinal sulfide-reducing bacteria Desulfovibrio and body drug-metabolism were also important variants influencing the efficacy-toxicity transformation of licorice-kansui herbal combination.

CONCLUSION

This study comprehensively uncovered the rules of licorice-kansui herbal combination, and for the first time confirmed that H2S plays a crucial role in mediating its efficacy-toxicity transformation. Our study not only supports the reasonable clinical usage of these two herbs but also provide ideas and methods for the study of other herb pairs in TCM prescriptions.

A new era of cancer phototherapy: mechanisms and applications

The past decades have witnessed great strides in phototherapy as an experimental option or regulation-approved treatment in numerous cancer indications. Of particular interest is nanoscale photosensitizer-based phototherapy, which has been established as a prominent candidate for advanced tumor treatment by virtue of its high efficacy and safety. Despite considerable research progress on materials, methods and devices in nanoscale photosensitizing agent-based phototherapy, their mechanisms of action are not always clear, which impedes their practical application in cancer treatment. Hence, from a new perspective, this review elaborates the working mechanisms, involving impairment and moderation effects, of diverse phototherapies on cells, organelles, organs, and tissues. Furthermore, the most current available phototherapy modalities are categorized as photodynamic, photothermal, photo-immune, photo-gas, and radio therapies in this review. A comprehensive understanding of the inferiority and superiority of various phototherapies will facilitate the advent of a new era of cancer phototherapy.

Excessive hydrogen sulfide-induced activation of NMDA receptors in the colon participates in anxiety- and compulsive-like behaviors in a rodent model of hemorrhagic shock and resuscitation

OBJECTIVE

Hemorrhagic shock and resuscitation (HSR) cause inflammatory responses in the gastrointestinal tract and is associated with substantial morbidity and mortality rates. Hydrogen sulfide (H2S), a gasotransmitter with pleiotropic activity, exhibits anti-inflammatory benefits at physiological levels. However, deleterious effects are observed when its concentration increases. In this investigation, we employed a mouse model of HSR to examine the effects of an H2S scavenger on the gastrointestinal tract and brain, with emphasis on N-Methyl-d-Aspartate (NMDA) receptor function.

METHODS

Mice were immediately administered dl-propargylglycine (PAG) intragastrically as an H2S scavenger after HSR exposure. The O-maze and buried beads tests were used to assess compulsive- and anxiety-like behaviors. Pathological changes in the intestine were evaluated at 24 and 30 days after HSR. Subsequently, at 30 days after HSR, we examined electrophysiological and pathological changes in the amygdala.

RESULTS

Within 24 h of HSR exposure, animals treated with PAG showed significantly lower colonic injury. Additionally, compared to the HSR-treated mice 30 days after HSR, the PAG-treated mice displayed reduced buried beads, increased open-arm time, lower blood levels of Diamine Oxidase (DAO) and considerably improved ZO-1 intensity, a stronger association between the delta rhythm phase and beta activity amplitude, and lower neuroinflammatory response in the amygdala. MK-801, an NMDA receptor inhibitor, significantly reversed H2S-induced intestinal and cerebral injury.

CONCLUSION

This experimental data suggests that H2S-induced excessive activation of NMDA receptors contributes to anxiety- and compulsive-like behaviors caused by HSR.

Hydrogen sulfide mitigates mitochondrial dysfunction and cellular senescence in diabetic patients: Potential therapeutic applications

Diabetes induces a pro-aging state characterized by an increased abundance of senescent cells in various tissues, heightened chronic inflammation, reduced substance and energy metabolism, and a significant increase in intracellular reactive oxygen species (ROS) levels. This condition leads to mitochondrial dysfunction, including elevated oxidative stress, the accumulation of mitochondrial DNA (mtDNA) damage, mitophagy defects, dysregulation of mitochondrial dynamics, and abnormal energy metabolism. These dysfunctions result in intracellular calcium ion (Ca2+) homeostasis disorders, telomere shortening, immune cell damage, and exacerbated inflammation, accelerating the aging of diabetic cells or tissues. Hydrogen sulfide (H2S), a novel gaseous signaling molecule, plays a crucial role in maintaining mitochondrial function and mitigating the aging process in diabetic cells. This article systematically explores the specific mechanisms by which H2S regulates diabetes-induced mitochondrial dysfunction to delay cellular senescence, offering a promising new strategy for improving diabetes and its complications.

FGF2 Functions in H2S's Attenuating Effect on Brain Injury Induced by Deep Hypothermic Circulatory Arrest in Rats

Deep hypothermic circulatory arrest (DHCA) can protect the brain during cardiac and aortic surgery by cooling the body, but meanwhile, temporary or permanent brain injury may arise. H2S protects neurons and the central nervous system, especially from secondary neuronal injury. We aim to unveil part of the mechanism of H2S's attenuating effect on brain injury induced by DHCA by exploring crucial target genes, and further promote the clinical application of H2S in DHCA. Nine SD rats were utilized to provide histological and microarray samples, and further the differential expression analysis. Then we conducted GO and KEGG pathway enrichment analyses on candidate genes. The protein-protein interaction (PPI) networks were performed by STRING and GeneMANIA. Crucial target genes' expression was validated by qRT-PCR and western blot. Histological study proved DHCA's damaging effect and H2S's repairing effect on brain. Next, we got 477 candidate genes by analyzing differentially expressed genes. The candidate genes were enriched in 303 GO terms and 28 KEGG pathways. Then nine genes were selected as crucial target genes. The function prediction by GeneMANIA suggested their close relation to immunity. FGF2 was identified as the crucial gene. FGF2 plays a vital role in the pathway when H2S attenuates brain injury after DHCA. Our research provides more information for understanding the mechanism of H2S attenuating brain injury after DHCA. We infer the process might probably be closely associated with immunity.

Development and evaluation of nanostructured systems for cutaneous delivery of H2S-releasing corticosteroids for skin inflammatory diseases

Psoriasis is an immune-mediated chronic inflammatory disease that causes major psychosocial impact. Topical corticosteroids represent the standard pharmacological treatment for mild-to-moderate disease, but their local and systemic adverse effects reinforce the need for treatment innovations. Here we developed lamellar phase-based formulations for topical delivery of a hybrid dexamethasone and hydrogen sulfide (H2S) donor molecule (Dexa-TBZ), aiming to potentiate the effects of the glucocorticoid with H2S. They offer the possibility to obtain precursor formulations free of water that originate lamellar phases upon water addition, preventing drug hydrolysis during storage. Two groups of formulations were developed varying the surfactants and oil phase types and content. Systems containing 20 and 70 % of water formed, respectively, bulk lamellar phase and a more fluid formulation consisting of dispersed droplets (< 1000 nm) stabilized by lamellar phase. Both presented pseudoplastic behavior. Dexa-TBZ was incorporated at 1 %, remaining stable for 8 h. Drug content decreased to ∼80 % after 1 week in precursor formulations free of water, but remained stable after that. Without causing changes to the cutaneous barrier function ex vivo or to the histological structure of the skin in vivo, the formulation containing phosphatidylcholine as surfactant and 70 % of water promoted 1.8- and 2.7-fold increases in Dexa-TBZ penetration in the stratum corneum and epidermis+dermis, respectively, compared to a control solution, demonstrating their potential applicability as topical delivery systems.

A meta-analysis of animal studies evaluating the effect of hydrogen sulfide on ischemic stroke: is the preclinical evidence sufficient to move forward?

Hydrogen sulfide (H2S) is a gasotransmitter that has been studied for its potential therapeutic effects, including its role in the pathophysiology and treatment of stroke. This systematic review and meta-analysis aimed to determine the sufficiency of overall preclinical evidence to guide the initiation of clinical stroke trials with H2S and provide tailored recommendations for their design. PubMed, Web of Science, Scopus, EMBASE, and MEDLINE were searched for studies evaluating the effect of any H2S donor on in vivo animal models of regional ischemic stroke, and 34 publications were identified. Pooling of the effect sizes using the random-effect model revealed that H2S decreased the infarct area by 34.5% (95% confidence interval (CI) 28.2-40.8%, p < 0.0001), with substantial variability among the studies (I2 = 89.8%). H2S also caused a 37.9% reduction in the neurological deficit score (95% CI 29.0-46.8%, p < 0.0001, I2 = 63.8%) and in the brain water content (3.2%, 95% CI 1.4-4.9%, p = 0.0014, I2 = 94.6%). Overall, the studies had a high risk of bias and low quality of evidence (median quality score 5/15, interquartile range 4-9). The majority of the included studies had a "high" or "unclear" risk of bias, and none of the studies overall had a "low" risk. In conclusion, H2S significantly improves structural and functional outcomes in in vivo animal models of ischemic stroke. However, the level of evidence from preclinical studies is not sufficient to proceed to clinical trials due to the low external validity, high risk of bias, and variable design of existing animal studies.

Thio-ProTide strategy: A novel H2S donor-drug conjugate (DDC) alleviates hepatic injury via innate lysosomal targeting

Hydrogen sulfide (H2S) is a gas signaling molecule with versatile bioactivities; however, its exploitation for disease treatment appears challenging. This study describes the design and characterization of a novel type of H2S donor-drug conjugate (DDC) based on the thio-ProTide scaffold, an evolution of the ProTide strategy successfully used in drug discovery. The new H2S DDCs achieved hepatic co-delivery of H2S and an anti-fibrotic drug candidate named hydronidone, which synergistically attenuated liver injury and resulted in more sufficient intracellular drug exposure. The potent hepatoprotective effects were also attributed to the H2S-mediated multipronged intervention in lipid peroxidation both at the whole cellular and lysosomal levels. Lysosomal H2S accumulation and H2S DDC activation were facilitated by the hydrolysis through the specific lysosomal hydrolase, representing a distinct mechanism for lysosomal targeting independent of the classical basic moieties. These findings provided a novel pattern for the design of optimally therapeutic H2S DDC and organelle-targeting functional molecules.

Insufficient S-sulfhydration of serum and glucocorticoid-regulated kinase 1 participates in hyperhomocysteinemia-induced liver injury

BACKGROUND & AIMS

Previous studies have established that hyperhomocysteinemia (HHcy) significantly contributes to the development of non-alcoholic steatohepatitis (NASH). Conversely, hydrogen sulfide (H2S) has shown potential in mitigating NASH. Despite these findings, it remains uncertain whether H2S can serve as a therapeutic agent against HHcy-induced liver damage.

METHODS

Mice were fed a high-methionine diet to induce HHcy and HepG2 cells were exposed to homocysteine (Hcy). In both models, we assessed liver injury, H2S concentration, and autophagy levels. For rescue, sodium hydrosulfide (NaHS), an H2S donor, was used to test its potential in reversing hepatic pathological features induced by HHcy.

RESULTS

1) Hcy accumulation led to liver damage and increased autophagy. This was linked to insufficient S-sulfhydration of serum and glucocorticoid-regulated kinase 1 (SGK1) at Cys244 and Cys282, a crucial autophagy regulator. The deficiency in S-sulfhydration was resulted from downregulation of cystathionine-γ-lyase (CSE) and subsequent H2S decrease, leading to SGK1 inactivation. 2) Administration of NaHS reduced the liver damage caused by high Hcy levels and restored H2S levels, promoting the S-sulfhydration and activation of SGK1. 3) Pharmacological inhibition of SGK1 induced autosis, a specific type of cell death caused by overactivation of autophagy. Conversely, a constitutively active mutant of SGK1 (SGK1S422D) significantly decreased autophagy and improved cell viability.

CONCLUSIONS

NaHS supplementation mitigates HHcy-induced liver injury by downregulating hepatic autophagy through the S-sulfhydration and activation of SGK1. This post-translational modification by H2S holds promise as a therapeutic approach for HHcy-induced liver injury.

Mixed H2S and H2O Clusters─New Insights into Dispersion-Dominated Hydrogen Bonding

Here, we report the results of an IR spectroscopy study on heteroclusters of H2S and H2O and several of their isotopomers using mass-selective IR spectroscopy in superfluid helium nanodroplets in the range of 2560-2800 cm-1. Based on DFT calculations on the B3LYP-D3/6-311++G(d,p) level of theory, we were able to assign the experimentally observed O-D stretching bands to heterodimer and heterotrimer clusters. Since no bands of the S-H-bound conformer HSH···OH2 could be observed, we were able to determine the O-H-bound conformer HOH···SH2 to be the global minimum structure. A trapping of the local minima in helium nanodroplets was not observed. This is in line with the weaker hydrogen bond expected for H2S complexes. In these clusters, the interaction energy is expected to be more dominated by dispersion and less dictated by highly directional electrostatic forces.

Phototriggered Hydrogen Persulfide Donors via Hydrosulfide Radical Formation Enhancing the Reactive Sulfur Metabolome in Cells

Hydrogen persulfide (H2S2) is an important sulfur-containing signaling molecule that plays a crucial role in the homeostasis of various organ systems, such as the renal, cardiovascular, liver, and gastrointestinal systems. However, research on H2S2 in biological settings is still challenging due to its instability and high reactivity. Compounds that can controllably release H2S2 (also known as donors) are thus crucial research tools. Currently, available H2S2 donors are still very limited, with most of them relying on modified disulfide templates. These templates possess an unavoidable limitation of being susceptible to cellular disulfide exchange which can compromise their efficacy. In this work, we explored nondisulfide-based and nonoxidation-dependent templates for the design of H2S2 donors. We found that tertiary naphthacyl thiols could undergo phototriggered C-S homolytic cleavage to form H2S2 via hydrosulfide (HS) radicals. In addition, the release of H2S2 was associated with the formation of a product with strong blue fluorescence, which allowed for real-time monitoring of the release process. This reaction was demonstrated to proceed effectively in both buffers and cells, with the ability to enhance intracellular production of persulfides, including GSSH, CysSSH, H2S2, H2S3, etc. It provides a unique photocontrolled H2S2 donor system with distinct advantages compared to known H2S2 donors due to its good stability and spatiotemporal control ability.

A fluorogenic ROS-triggered hydrogen sulfide donor for alleviating cerebral ischemia-reperfusion injury

Rationale: Cerebral ischemia-reperfusion injury is a severe neurovascular disease that urgently requires effective therapeutic interventions. Recently, hydrogen sulfide (H2S) has garnered significant attention as a potential treatment for stroke; however, the precise and targeted delivery of H2S remains a considerable challenge for its clinical application. Methods: We have developed HSDF-NH2, a novel H2S donor characterized by high selectivity, self-reporting capabilities, and the ability to penetrate the blood-brain barrier (BBB). Results: HSDF-NH2 effectively scavenges reactive oxygen species (ROS) while generating H2S, with emitted fluorescence facilitating the visualization and quantification of H2S release. This compound has demonstrated protective effects against cerebral ischemia-reperfusion (I/R) injury and contributes to the reconstruction of brain structure and function in a rat stroke model (tMCAO/R). Conclusion: As a ROS-responsive, self-reporting, and fluorescent H2S donor, HSDF-NH2 holds considerable promise for the treatment of ischemic diseases beyond stroke.

Exploring the Reactivity of Electrophilic Organic Carbonates and Thiocarbonates as Vehicles to Convert Hydrosulfide into COS and CS2

Hydrogen sulfide (H2S) and other reactive sulfur species are important small molecules with biological significance. In addition to common reactive sulfur species like H2S, polysulfides, and persulfides, both carbonyl sulfide (COS) and carbon disulfide (CS2) have been postulated to be potential sources of reduced sulfur. To better understand this possible connection, we demonstrate that H2S can be converted to COS and CS2 by reaction with simple organic carbonate and thiocarbonate electrophiles, respectively.

Hydrogen sulfide donor NaHS inhibits formaldehyde-induced epithelial-mesenchymal transition in human lung epithelial cells via activating TGF-β1/Smad2/3 and MAPKs signaling pathways

Formaldehyde (FA) long term exposure leads to abnormal pulmonary function and small airway obstruction of the patients. Hydrogen sulfide (H2S) is one of the recognized gaseous transmitters involved in a wide range of cellular functions. It is unknown the involvement of H2S in FA-induced lung injury. The purpose of this study is to investigate the therapeutic potential and mechanism of H2S on FA-induced epithelial-mesenchymal transition (EMT) of human lung epithelial cells. The cell viability of Beas2B and A549 cells after FA treatment were assessed using MTT assay. The endogenous H2S was visualized by fluorescence microscopy using of the 7-azido-4-methylcoumarin (AzMC). Cell morphology was observed under phase contrast microscope. The mRNAs and proteins level were evaluated by reverse transcription-polymerase chain reaction and western blotting assays. FA treatment downregulated the endogenous H2S levels and the mRNAs and proteins level of H2S synthesizing enzymes, such as cystathionine-β-synthase (CBS), cystathionine-γ-lyase (CSE), and 3-mercaptopyruvate sulfurtransferase (3-MST) in Beas2B and A549 cells. FA treatment changed the cell morphology of Beas2B cells from cuboid to a spindle-shape, while declined the protein level of E-cadherin and increased the protein level of Vimentin. Moreover, FA treatment increased the proteins level of transforming growth factor-β1 (TGF-β1), phosphorylated-Smad2 (p-Smad2), phosphorylated-Smad3 (p-Smad3), phosphorylated-extracellular signal-regulated kinase (p-ERK), phosphorylated-c-Jun N-terminal kinase (p-JNK), and phosphorylated-P38 (p-P38). Furthermore, the inhibitors of TGF-β receptor type 1 (TGFβRI) and mitogen-activated protein kinases (MAPKs) signaling pathways reversed FA-induced decrease in E-cadherin expression and increase in Vimentin expression in Beas2B cells. Sodium hydrogen sulfide (NaHS) increased the level of H2S, while reversed FA-induced the low expression of E-cadherin and the high expression of Vimentin, TGF-β1, p-Smad2, p-Smad3, p-ERK, p-JNK, and p-P38. These findings indicates FA treatment downregulating the endogenous H2S in human lung epithelial cells. NaHS may inhibit FA-induced EMT in human lung epithelial cells via modulating TGF-β1/Smad2/3 and MAPKs signaling pathways. Therefore, we demonstrated that supplementation of exogenous H2S may inhibit FA-induced lung injury.

Regulating H2S release from self-assembled peptide H2S-donor conjugates using cysteine derivatives

Self-assembled peptides provide a modular and diverse platform for drug delivery, and innovative delivery methods are needed for delivery of hydrogen sulfide (H2S), an endogenous signaling molecule (gasotransmitter) with significant therapeutic potential. Of the available types of H2S donors, peptide/protein H2S donor conjugates (PHDCs) offer significant versatility. Here we discuss the design, synthesis, and in-depth study of a PHDC containing three covalently linked components: a thiol-triggered H2S donor based on an S-aroylthiooxime (SATO), a GFFF tetrapeptide, and a tetraethylene glycol (TEG) dendron. Conventional transmission electron microscopy showed that the PHDC self-assembled into spherical structures without heat or stirring, but it formed nanofibers with gentle heat (37 °C) and stirring. Circular dichroism (CD) spectroscopy data collected during self-assembly under nanofiber-forming conditions suggested an increase in β-sheet character and a decrease in organization of the SATO units. Release of H2S from the nanofibers was studied through triggering with various thiols. The release rate and total amount of H2S released over both short (5 h) and long (7 d) time scales varied with the charge state: negatively charged and zwitterionic thiols (e.g., Ac-Cys-OH and H-Cys-OH) triggered release slowly while a neutral thiol (Ac-Cys-OMe) showed ∼10-fold faster release, and a positively charged thiol (H-Cys-OMe) triggered H2S release nearly 50-fold faster than the negatively charged thiols. CD spectroscopy studies monitoring changes in secondary structure over time during H2S release showed similar trends. This study sheds light on the driving forces behind self-assembling nanostructures and offers insights into tuning H2S release through thiol charge state modulation.

Discovery of SIRT1-Activating Hydrogen Sulfide Donating Derivatives for Efficient Resistant of Myocardial Ischemic Injury

Activating SIRT1 or promoting SIRT1 expression are both protective against myocardial ischemia. Combining these approaches would be an effective strategy for treating ischemic heart disease. Herein, we identified lead compounds with SIRT1 activation activity through screening the natural product library, and five series of H2S donating derivatives were designed and synthesized. Among them, compound 17 exerted an effective cardioprotective effect in vitro and in vivo. The addition of H2S scavenger attenuated the protective activity, emphasizing the critical involvement of H2S in the myocardial ischemia process. Interestingly, 17 exhibited stronger direct SIRT1 activative ability and induced higher SIRT1 expression capability compared to the lead. Furthermore, 17 attenuates oxidative stress-induced cardiomyocytes apoptosis by activating the SIRT1-PGC1α signaling pathway. Our study validated the promising potential of activating SIRT1 and promoting SIRT1 expression through H2S to improve cardiomyocytes function, providing novel insights into the protective mechanisms during the progression of ischemic heart disease.

Sodium Hydrosulfide Protects Rats from Hypobaric-Hypoxia-Induced Acute Lung Injury

Hydrogen sulfide (H2S), as a key gas signaling molecule, plays an important role in regulating various diseases, with appropriate concentrations providing antioxidative, anti-inflammatory, and anti-apoptotic effects. The specific role of H2S in acute hypoxic injury remains to be clarified. This study focuses on the H2S donor sodium hydrosulfide (NaHS) and explores its protective effects and mechanisms against acute hypoxic lung injury. First, various mouse hypoxia models were established to evaluate H2S's protection in hypoxia tolerance. Next, a rat model of acute lung injury (ALI) induced by hypoxia at 6500 m above sea level for 72 h was created to assess H2S's protective effects and mechanisms. Evaluation metrics included blood gas analysis, blood routine indicators, lung water content, and lung tissue pathology. Additionally, LC-MS/MS and bioinformatic analyses were combined in performing quantitative proteomics on lung tissues from the normoxic control group, the hypoxia model group, and the hypoxia model group with NaHS treatment to preliminarily explore the protective mechanisms of H2S. Further, enzyme-linked immunosorbent assays (ELISA) were used to measure oxidative stress markers and inflammatory factors in rat lung tissues. Lastly, Western blot analysis was performed to detect Nrf2, HO-1, P-NF-κB, NF-κB, HIF-1α, Bcl-2, and Bax proteins in lung tissues. Results showed that H2S exhibited significant anti-hypoxic effects in various hypoxia models, effectively modulating blood gas and blood routine indicators in ALI rats, reducing pulmonary edema, improving lung tissue pathology, and alleviating oxidative stress, inflammatory responses, and apoptosis levels.

Real-time detection of enzymatically formed hydrogen sulfide by pathogenic variants of cystathionine beta-synthase using hemoglobin I of Lucina pectinata as a biosensor

Classical homocystinuria is a rare disease caused by mutations in cystathionine β-synthase (CBS) gene (OMIM 613381). CBS catalyzes the first step of the transsulfuration pathway that converts homocysteine (Hcy) into cystathionine (Cysta) via a number of co-substrates and mechanisms. Formation of Cysta by condensation of Hcy and cysteine (Cys) produces a molar equivalent of hydrogen sulfide (H2S). H2S plays important roles in cognitive and vascular functions. Clinically, patients with CBS deficiency present with vascular, ocular, neurological and skeletal impairments. Biochemically, CBS deficiency manifests with elevated Hcy and reduced concentration of Cysta in plasma and urine. A number of pathogenic variants of human CBS have been characterized by their residual enzymatic activity, but very few studies have examined H2S production by pathogenic CBS variants, possibly due to technical hurdles in H2S detection and quantification. We describe a method for the real-time, continuous quantification of H2S formed by wild-type and pathogenic variants of human recombinant CBS, as well as by fibroblast extracts from healthy controls and patients diagnosed with CBS deficiency. The method takes advantage of the specificity and high affinity of hemoglobin I of the clam Lucina pectinata toward H2S and is based on UV-visible spectrophotometry. Comparison with the gold-standard, end-point H2S quantification method employing monobromobimane, as well as correlations with CBS enzymatic activity determined by LC-MS/MS showed agreement and correlation, and permitted the direct, time-resolved determination of H2S production rates by purified human recombinant CBS and by CBS present in fibroblast extracts. Rates of H2S production were highest for wild-type CBS, and lower for pathogenic variants. This method enables the examination of structural determinants of CBS that are important for H2S production and its possible relevance to the clinical outcome of patients.

Neuroprotective Actions of Hydrogen Sulfide-Releasing Compounds in Isolated Bovine Retinae

Background: We have evidence that hydrogen sulfide (H2S)-releasing compounds can reduce intraocular pressure in normotensive and glaucomatous rabbits by increasing the aqueous humor (AH) outflow through the trabecular meshwork. Since H2S has been reported to possess neuroprotective actions, the prevention of retinal ganglion cell loss is an important strategy in the pharmacotherapy of glaucoma. Consequently, the present study aimed to investigate the neuroprotective actions of H2S-releasing compounds against hydrogen peroxide (H2O2)-induced oxidative stress in an isolated bovine retina. Materials and Methods: The isolated neural retinae were pretreated with a substrate for H2S biosynthesis called L-cysteine, with the fast H2S-releasing compound sodium hydrosulfide, and with a mitochondrial-targeting H2S-releasing compound, AP123, for thirty minutes before a 30-min oxidative insult with H2O2 (100 µM). Lipid peroxidation was assessed via an enzyme immunoassay by measuring the stable oxidative stress marker, 8-epi PGF2α (8-isoprostane), levels in the retinal tissues. To determine the role of endogenous H2S, studies were performed using the following biosynthesis enzyme inhibitors: aminooxyacetic acid (AOAA, 30 µM); a cystathione-β-synthase/cystathionine-γ-lyase (CBS/CSE) inhibitor, α-ketobutyric acid (KBA, 1 mM); and a 3-mercaptopyruvate-s-sulfurtransferase (3-MST) inhibitor, in the absence and presence of H2S-releasing compounds. Results: Exposure of the isolated retinas to H2O2 produced a time-dependent (10-40 min) and concentration-dependent (30-300 µM) increase in the 8-isoprostane levels when compared to the untreated tissues. L-cysteine (10 nM-1 µM) and NaHS (30 -100 µM) significantly (p < 0.001; n = 12) prevented H2O2-induced oxidative damage in a concentration-dependent manner. Furthermore, AP123 (100 nM-1 µM) attenuated oxidative H2O2 damage resulted in an approximated 60% reduction in 8-isoprostane levels compared to the tissues treated with H2O2 alone. While AOAA (30 µM) and KBA (1 mM) did not affect the L-cysteine evoked attenuation of H2O2-induced oxidative stress, KBA reversed the antioxidant responses caused by AP123. Conclusions: In conclusion, various forms of H2S-releasing compounds and the substrate, L-cysteine, can prevent H2O2-induced lipid peroxidation in an isolated bovine retina.

Signaling Paradigms of H2S-Induced Vasodilation: A Comprehensive Review

Hydrogen sulfide (H2S), a gas traditionally considered toxic, is now recognized as a vital endogenous signaling molecule with a complex physiology. This comprehensive study encompasses a systematic literature review that explores the intricate mechanisms underlying H2S-induced vasodilation. The vasodilatory effects of H2S are primarily mediated by activating ATP-sensitive potassium (K_ATP) channels, leading to membrane hyperpolarization and subsequent relaxation of vascular smooth muscle cells (VSMCs). Additionally, H2S inhibits L-type calcium channels, reducing calcium influx and diminishing VSMC contraction. Beyond ion channel modulation, H2S profoundly impacts cyclic nucleotide signaling pathways. It stimulates soluble guanylyl cyclase (sGC), increasing the production of cyclic guanosine monophosphate (cGMP). Elevated cGMP levels activate protein kinase G (PKG), which phosphorylates downstream targets like vasodilator-stimulated phosphoprotein (VASP) and promotes smooth muscle relaxation. The synergy between H2S and nitric oxide (NO) signaling further amplifies vasodilation. H2S enhances NO bioavailability by inhibiting its degradation and stimulating endothelial nitric oxide synthase (eNOS) activity, increasing cGMP levels and potent vasodilatory responses. Protein sulfhydration, a post-translational modification, plays a crucial role in cell signaling. H2S S-sulfurates oxidized cysteine residues, while polysulfides (H2Sn) are responsible for S-sulfurating reduced cysteine residues. Sulfhydration of key proteins like K_ATP channels and sGC enhances their activity, contributing to the overall vasodilatory effect. Furthermore, H2S interaction with endothelium-derived hyperpolarizing factor (EDHF) pathways adds another layer to its vasodilatory mechanism. By enhancing EDHF activity, H2S facilitates the hyperpolarization and relaxation of VSMCs through gap junctions between endothelial cells and VSMCs. Recent findings suggest that H2S can also modulate transient receptor potential (TRP) channels, particularly TRPV4 channels, in endothelial cells. Activating these channels by H2S promotes calcium entry, stimulating the production of vasodilatory agents like NO and prostacyclin, thereby regulating vascular tone. The comprehensive understanding of H2S-induced vasodilation mechanisms highlights its therapeutic potential. The multifaceted approach of H2S in modulating vascular tone presents a promising strategy for developing novel treatments for hypertension, ischemic conditions, and other vascular disorders. The interaction of H2S with ion channels, cyclic nucleotide signaling, NO pathways, ROS (Reactive Oxygen Species) scavenging, protein sulfhydration, and EDHF underscores its complexity and therapeutic relevance. In conclusion, the intricate signaling paradigms of H2S-induced vasodilation offer valuable insights into its physiological role and therapeutic potential, promising innovative approaches for managing various vascular diseases through the modulation of vascular tone.

Hydrogen Sulfide-Releasing Carbonic Anhydrase Inhibitors Effectively Suppress Cancer Cell Growth

This study proposes a novel therapeutic strategy for cancer management by combining the antitumor effects of hydrogen sulfide (H2S) and inhibition of carbonic anhydrases (CAs; EC 4.2.1.1), specifically isoforms IV, IX, and XII. H2S has demonstrated cytotoxicity against various cancers at high concentrations. The inhibition of tumor-associated CAs leads to lethal intracellular alkalinization and acidification of the extracellular tumor microenvironment and restores tumor responsiveness to the immune system, chemotherapy, and radiotherapy. The study proposes H2S donor-CA inhibitor (CAI) hybrids for tumor management. These compounds effectively inhibit the target CAs, release H2S consistently, and exhibit potent antitumor effects against MDA-MB-231, HCT-116, and A549 cancer cell lines. Notably, some compounds display high cytotoxicity across all investigated cell lines. Derivative 30 shows a 2-fold increase in cytotoxicity (0.93 ± 0.02 µM) under chemically induced hypoxia in HCT-116 cells. These compounds also disturb the cell cycle, leading to a reduction in cell populations in G0/G1 and S phases, with a notable increase in G2/M and Sub-G1. This disruption is correlated with induced apoptosis, with fold increases of 37.2, 24.5, and 32.9 against HCT-116 cells and 14.2, 13.1, and 19.9 against A549 cells compared to untreated cells. These findings suggest the potential of H2S releaser-CAI hybrids as effective and versatile tools in cancer treatment.

Gas Delivery Relevant to Human Health using Porous Materials

Gases are essential for various applications relevant to human health, including in medicine, biomedical imaging, and pharmaceutical synthesis. However, gases are significantly more challenging to safely handle than liquids and solids. Herein, we review the use of porous materials, such as metal-organic frameworks (MOFs), zeolites, and silicas, to adsorb medicinally relevant gases and facilitate their handling as solids. Specific topics include the use of MOFs and zeolites to deliver H2S for therapeutic applications, 129Xe for magnetic resonance imaging, O2 for the treatment of cancer and hypoxia, and various gases for use in organic synthesis. This Perspective aims to bring together the organic, inorganic, medicinal, and materials chemistry communities to inspire the design of next-generation porous materials for the storage and delivery of medicinally relevant gases.

Diallyl Trisulfide and Cardiovascular Health: Evidence and Potential Molecular Mechanisms

Traditionally, garlic has a valuable role in preventing and reducing the incidence of many diseases and pathophysiological disorders. Consequently, some researchers have focused on the beneficial cardiovascular properties of diallyl trisulfide (DATS), the most potent polysulfide isolated from garlic. Therefore, in this review, we collected the available data on DATS, its biochemical synthesis, metabolism and pharmacokinetics, and gathered the current knowledge and the role of DATS in cardiovascular diseases. Overall, this review summarizes the cardioprotective effects of DATS and brings together all previous findings on its protective molecular mechanisms, which are mainly based on the potent anti-apoptotic, anti-inflammatory, and antioxidant potential of this polysulfide. Our review is an important cornerstone for further basic and clinical research on DATS as a new therapeutic agent for the treatment of numerous heart diseases.

Role of hydrogen sulfide in health and disease

In the past, hydrogen sulfide (H2S) was recognized as a toxic and dangerous gas; in recent years, with increased research, we have discovered that H2S can act as an endogenous regulatory transmitter. In mammals, H2S-catalyzing enzymes, such as cystathionine-β-synthase, cystathionine-γ-lyase, and 3-mercaptopyruvate sulfurtransferase, are differentially expressed in a variety of tissues and affect a variety of biological functions, such as transcriptional and posttranslational modification of genes, activation of signaling pathways in the cell, and metabolic processes in tissues, by producing H2S. Various preclinical studies have shown that H2S affects physiological and pathological processes in the body. However, a detailed systematic summary of these roles in health and disease is lacking. Therefore, this review provides a thorough overview of the physiological roles of H2S in different systems and the diseases associated with disorders of H2S metabolism, such as ischemia-reperfusion injury, hypertension, neurodegenerative diseases, inflammatory bowel disease, and cancer. Meanwhile, this paper also introduces H2S donors and novel release modes, as well as the latest preclinical experimental results, aiming to provide researchers with new ideas to discover new diagnostic targets and therapeutic options.

The functions of hydrogen sulfide on the urogenital system of both males and females: from inception to the present

Hydrogen sulfide (H2S) is known as a chemical gas in nature with both enzymatic and non-enzymatic biosynthesis in different human organs. A couple of studies have demonstrated the function of H2S in regulating the homeostasis of the human body. Additionally, they have shown its synthesis, measurement, chemistry, protective effects, and interaction in various aspects of scientific evidence. Furthermore, many researches have demonstrated the beneficial impacts of H2S on genital organs and systems. According to various studies, it is recognized that H2S-producing enzymes and the endogenous production of H2S are expressed in male and female reproductive systems in different mammalian species. The main goal of this comprehensive review is to assess the potential therapeutic impacts of this gasotransmitter in the male and female urogenital system and find underlying mechanisms of this agent. This narrative review investigated the articles that were published from the 1970s to 2022. The review's primary focus is the impacts of H2S on the male and female urogenital system. Medline, CINAHL, PubMed, and Google scholar databases were searched. Keywords used in this review were "Hydrogen sulfide," "H2S," "urogenital system," and "urogenital tract". Numerous studies have demonstrated the therapeutic and protective effects of sodium hydrosulfide (Na-HS) as an H2S donor on male and female infertility disorders. Furthermore, it has been observed that H2S plays a significant role in improving different diseases such as ameliorating sperm parameters. The specific localization of H2S enzymes in the urogenital system provides an excellent opportunity to comprehend its function and role in various disorders related to this system. It is noteworthy that H2S has been demonstrated to be produced in endocrine organs and exhibit diverse activities. Moreover, it is important to recognize that alterations in H2S biosynthesis are closely linked to endocrine disorders. Therefore, hormones can be pivotal in regulating H2S production, and H2S synthesis pathways may aid in establishing novel therapeutic strategies. H2S possesses pharmacological effects on essential disorders, such as anti-inflammation, anti-apoptosis, and anti-oxidant activities, which render it a valuable therapeutic agent for human urogenital disease. Furthermore, this agent shows promise in ameliorating the detrimental effects of various male and female diseases. Despite the limited clinical research, studies have demonstrated that applying H2S as an anti-oxidant source could ameliorate adverse effects of different conditions in the urogenital system. More clinical studies are required to confirm the role of this component in clinical settings.

Progress in the Pathogenesis of Diabetic Encephalopathy: The Key Role of Neuroinflammation

Diabetic encephalopathy (DE) is a severe complication that occurs in the central nervous system (CNS) and leads to cognitive impairment. DE involves various pathophysiological processes, and its pathogenesis is still unclear. This review summarised current research on the pathogenesis of diabetic encephalopathy, which involves neuroinflammation, oxidative stress, iron homoeostasis, blood-brain barrier disruption, altered gut microbiota, insulin resistance, etc. Among these pathological mechanisms, neuroinflammation has been focused on. This paper summarises some of the molecular mechanisms involved in neuroinflammation, including the Mammalian Target of Rapamycin (mTOR), Lipocalin-2 (LCN-2), Pyroptosis, Advanced Glycosylation End Products (AGEs), and some common pro-inflammatory factors. In addition, we discuss recent advances in the study of potential therapeutic targets for the treatment of DE against neuroinflammation. The current research on the pathogenesis of DE is progressing slowly, and more research is needed in the future. Further study of neuroinflammation as a mechanism is conducive to the discovery of more effective treatments for DE in the future.

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.

Self-immolative poly(thiocarbamate) with localized H2S signal amplification for precise cancer imaging and therapy

Hydrogen sulfide is essential in numerous physiological and pathological processes and has emerged as a promising cancer imaging and signaling molecule and a potentially versatile therapeutic agent. However, the endogenous levels of hydrogen sulfide remain insufficient to perform its biological functions, and thus, developing novel strategies that amplify hydrogen sulfide signals at lesion sites is of increasing interest. In this work, a nanoplatform (SNP) based on hydrogen sulfide-responsive self-immolative poly(thiocarbamate) with localized hydrogen sulfide signal amplification capability is developed to encapsulate a hydrogen sulfide-responsive fluorescent probe (e.g., hemicyanine dye; p-Cy) or an anticancer prodrug (e.g., doxorubicin; p-DOX) to form a nanoprobe (SNPp-Cy) or nanomedicine (SNPp-DOX) for cancer imaging and therapy, respectively. SNPp-Cy exhibits a low detection limit for hydrogen sulfide, enabling ultrasensitive detection of small (<2 mm) tumors in female mice. In addition, SNPp-DOX can effectively inhibit the growth of DOX-resistant human breast cancer xenograft, lung metastasis, and patient-derived xenograft tumors in female mice.

Hydrogen Sulfide Modulation of Matrix Metalloproteinases and CD147/EMMPRIN: Mechanistic Pathways and Impact on Atherosclerosis Progression

Atherosclerosis is a chronic inflammatory condition marked by endothelial dysfunction, lipid accumulation, inflammatory cell infiltration, and extracellular matrix (ECM) remodeling within arterial walls, leading to plaque formation and potential cardiovascular events. Key players in ECM remodeling and inflammation are matrix metalloproteinases (MMPs) and CD147/EMMPRIN, a cell surface glycoprotein expressed on endothelial cells, vascular smooth muscle cells (VSMCs), and immune cells, that regulates MMP activity. Hydrogen sulfide (H₂S), a gaseous signaling molecule, has emerged as a significant modulator of these processes including oxidative stress mitigation, inflammation reduction, and vascular remodeling. This systematic review investigates the mechanistic pathways through which H₂S influences MMPs and CD147/EMMPRIN and assesses its impact on atherosclerosis progression. A comprehensive literature search was conducted across PubMed, Scopus, and Web of Science databases, focusing on studies examining H₂S modulation of MMPs and CD147/EMMPRIN in atherosclerosis contexts. Findings indicate that H₂S modulates MMP expression and activity through transcriptional regulation and post-translational modifications, including S-sulfhydration. By mitigating oxidative stress, H₂S reduces MMP activation, contributing to plaque stability and vascular remodeling. H₂S also downregulates CD147/EMMPRIN expression via transcriptional pathways, diminishing inflammatory responses and vascular cellular proliferation within plaques. The dual regulatory role of H₂S in inhibiting MMP activity and downregulating CD147 suggests its potential as a therapeutic agent in stabilizing atherosclerotic plaques and mitigating inflammation. Further research is warranted to elucidate the precise molecular mechanisms and to explore H₂S-based therapies for clinical application in atherosclerosis.

Recent Developments On Activatable Turn-On Fluorogenic Donors of Hydrogen Sulfide (H2S)

Hydrogen sulfide (H2S) is considered the third member of the gasotransmitter family, along with nitric oxide (NO) and carbon monoxide (CO). Besides its role in physiological and pathophysiological conditions, the promising therapeutic potential of this small-molecule makes it advantageous for various pharmaceutical applications. The endogenous production of H2S at a lower concentration is crucial in maintaining redox balance and cellular homeostasis, and the dysregulation leads to various disease states. In the event of H2S deficiency, the exogenous donation of H2S could help maintain the optimal cellular concentration of H2S and cellular homeostasis. Over the last several years, researchers have developed numerous small-molecule non-fluorogenic organosulfur compounds as H2S donors and investigated their pharmacological potentials. However, reports on stimuli-responsive turn-on fluorogenic donors of H2S have appeared recently. Interestingly, the fluorogenic H2S donors offer additional advantages with the non-invasive real-time monitoring of the H2S release utilizing the simultaneous turn-on fluorogenic processes. The review summarizes the recent developments in turn-on fluorogenic donors of H2S and the potential biological applications that have developed over the years.

Pharmacology of Hydrogen Sulfide and Its Donors in Cardiometabolic Diseases

Cardiometabolic diseases (CMDs) are major contributors to global mortality, emphasizing the critical need for novel therapeutic interventions. Hydrogen sulfide (H2S) has garnered enormous attention as a significant gasotransmitter with various physiological, pathophysiological, and pharmacological impacts within mammalian cardiometabolic systems. In addition to its roles in attenuating oxidative stress and inflammatory response, burgeoning research emphasizes the significance of H2S in regulating proteins via persulfidation, a well known modification intricately associated with the pathogenesis of CMDs. This review seeks to investigate recent updates on the physiological actions of endogenous H2S and the pharmacological roles of various H2S donors in addressing diverse aspects of CMDs across cellular, animal, and clinical studies. Of note, advanced methodologies, including multiomics, intestinal microflora analysis, organoid, and single-cell sequencing techniques, are gaining traction due to their ability to offer comprehensive insights into biomedical research. These emerging approaches hold promise in characterizing the pharmacological roles of H2S in health and diseases. We will critically assess the current literature to clarify the roles of H2S in diseases while also delineating the opportunities and challenges they present in H2S-based pharmacotherapy for CMDs. SIGNIFICANCE STATEMENT: This comprehensive review covers recent developments in H2S biology and pharmacology in cardiometabolic diseases CMDs. Endogenous H2S and its donors show great promise for the management of CMDs by regulating numerous proteins and signaling pathways. The emergence of new technologies will considerably advance the pharmacological research and clinical translation of H2S.

An Examination of Chemical Tools for Hydrogen Selenide Donation and Detection

Hydrogen selenide (H2Se) is an emerging biomolecule of interest with similar properties to that of other gaseous signaling molecules (i.e., gasotransmitters that include nitric oxide, carbon monoxide, and hydrogen sulfide). H2Se is enzymatically generated in humans where it serves as a key metabolic intermediate in the production of selenoproteins and other selenium-containing biomolecules. However, beyond its participation in biosynthetic pathways, its involvement in cellular signaling or other biological mechanisms remains unclear. To uncover its true biological significance, H2Se-specific chemical tools capable of functioning under physiological conditions are required but lacking in comparison to those that exist for other gasotransmitters. Recently, researchers have begun to fill this unmet need by developing new H2Se-releasing compounds, along with pioneering methods for selenide detection and quantification. In combination, the chemical tools highlighted in this review have the potential to spark groundbreaking explorations into the chemical biology of H2Se, which may lead to its branding as the fourth official gasotransmitter.