Hydrogen sulfide as endothelium-derived hyperpolarizing factor sulfhydrates potassium channels

Sodium thiosulfate treatment rescues hyperglycaemia-induced pronephros damage in zebrafish by upregulating nitric oxide signalling

Sodium thiosulfate (STS) is gaining increasing attention in research for its potential therapeutic applications across a spectrum of disease processes beyond its current uses. However, the precise mechanisms of action remain incompletely understood. We investigated the efficacy of STS in treating hyperglycaemia-induced pronephros damage in zebrafish to gain further insight into the underlying mechanisms. Hyperglycaemia was induced in zebrafish by suppressing the pdx1 transcription factor, which plays a crucial role in maintaining physiological pancreatic function. STS was administered by introducing it into the medium of zebrafish larvae. The pronephros structure was analysed at 48 h post-fertilization. Metabolomic profiling and RNA sequencing were conducted on groups exposed to various experimental conditions. Our findings reveal a downregulation of nitric oxide (NO) signalling in zebrafish with a knocked-down pdx1 gene, both metabolomically and transcriptionally. Notably, treatment with STS led to a compensatory upregulation of the NO signalling, ultimately resulting in the rescue of the pronephros structure. Our study provides compelling evidence that targeting NO metabolism by the administration of STS offers a promising strategy for addressing hyperglycaemia-induced organ damage. These findings underscore the potential of STS as a promising therapeutic agent for diabetic complications and warrant further investigation of its clinical applications. KEY POINTS: Sodium thiosulfate (STS) is increasingly drawing attention in research for its potential therapeutic applications across a spectrum of disease processes. Here, we demonstrate that STS treatment rescues hyperglycaemia-induced pronephros damage in zebrafish. We identified upregulation of nitric oxide signalling as the major driver behind STS-mediated rescue. Our data suggest that STS offers a promising strategy for addressing hyperglycaemia-induced organ damage, including diabetic nephropathy.

Involvement of different K+ channel subtypes in hydrogen sulfide-induced vasorelaxation of human internal mammary artery

BACKGROUND

Changes in K+ channel expression/function are associated with disruption of vascular reactivity in several pathological conditions, including hypertension, diabetes, and atherosclerosis. Gasotransmitters achieve part of their effects in the organism by regulating ion channels, especially K+ channels. Their involvement in hydrogen sulfide (H2S)-mediated vasorelaxation is still unclear, and data about human vessels are limited.

OBJECTIVE

To determine the role of K+ channel subtypes in the vasorelaxant mechanism of H2S donor, sodium-hydrosulfide (NaHS), on isolated human internal mammary artery (HIMA).

RESULTS

NaHS (1 × 10-6-3 × 10-3 mol/L) induced a concentration-dependent relaxation of HIMA pre-contracted by phenylephrine and high K+. Among K+ channel blockers, iberiotoxin, glibenclamide, 4-aminopyridine (4-AP), and margatoxin significantly inhibited NaHS-induced relaxation of phenylephrine-contracted HIMA (P < 0.01), whereas in the presence of apamin/1-[(2-chlorophenyl) diphenylmethyl]-1H-pyrazole (TRAM-34) combination, the HIMA relaxation was partially reduced (P < 0.05). The effect of NaHS was antagonized by NO pathway inhibitors, L-NAME and KT5823, and by cyclo-oxygenase inhibitor, indomethacin (P < 0.01). Under conditions of blocked NO/prostacyclin synthesis and release, apamin/TRAM-34 and glibenclamide caused further decrease in NaHS-induced vasorelaxation (P < 0.01), while iberiotoxin, 4-AP, and margatoxin were without additional effect (P > 0.05). In the presence of nifedipine, NaHS induced partial relaxation of HIMA (P < 0.01).

CONCLUSION

Our results demonstrated that H2S donor, NaHS, induced concentration-dependent relaxation of isolated HIMA. Vasorelaxant mechanisms of H2S included direct or indirect opening of different K+ channel subtypes, KATP, BKCa, SKCa/IKCa, and KV (subtype KV1.3), in addition to NO pathway activation and interference with extracellular Ca2+ influx.

A hydrogen sulphide-releasing non-steroidal anti-inflammatory, ATB-346, significantly attenuates human myometrial contractions

BACKGROUND

Spontaneous preterm birth is the leading cause of perinatal morbidity and mortality. Tocolytics are drugs used to inhibit uterine contractions in cases of imminent preterm birth, however, few are effective in stopping labour once initiated and all have side effects. Combination approaches involving drugs that target multiple signalling pathways that regulate contractions may increase efficacy, reduce dosage and improve tolerability. Both non-steroidal anti-inflammatory drugs (NSAIDs) and hydrogen sulphide (H2S)-releasing compounds can reduce myometrial contractions. In a novel approach we evaluated the tocolytic properties of ATB-346-a H2S-releasing derivative of the NSAID naproxen, shown clinically to reduce pain and inflammation in arthritis.

METHODS

Using organ baths, paired strips of human myometrium were exposed to increasing concentrations of ATB-346, or equimolar concentrations (10µM and 30µM) of the parent drug, naproxen, or the H2S-releasing moiety, 4-hydroxy-thiobenzamide (TBZ), alone. The ability of ATB-346 versus the individual components of ATB-346 to decrease ex vivo spontaneous contractions was investigated, and the potency was compared to a known H2S donor, Na2S.

RESULTS

Acute application of Na2S produced a concentration-dependent decrease in force amplitude and force integral (area under the curve) of contraction. ATB-346 produced a more profound decrease in contraction compared to equimolar concentrations of naproxen or TZB alone and was more potent than the equivalent concentration of Na2S.

CONCLUSIONS

ATB-346 exhibits potent tocolytic properties in human myometrium. These exciting results call for further exploration of ATB-346, with a view to repurposing this or similar drugs as novel therapies for delaying preterm labour.

The interplay of hydrogen sulfide and microRNAs in cardiovascular diseases: insights and future perspectives

Hydrogen sulfide (H2S) is recognized as the third gasotransmitter, after nitric oxide (NO) and carbon monoxide (CO). It is known for its cardioprotective properties, including the relaxation of blood vessels, promotion of angiogenesis, regulation of myocardial cell apoptosis, inhibition of vascular smooth muscle cell proliferation, and reduction of inflammation. Additionally, abnormal H2S generation has been linked to the development of cardiovascular diseases (CVD), such as pulmonary hypertension, hypertension, atherosclerosis, vascular calcification, and myocardial injury. MicroRNAs (miRNAs) are non-coding, conserved, and versatile molecules that primarily influence gene expression by repressing translation and have emerged as biomarkers for CVD diagnosis. Studies have demonstrated that H2S can ameliorate cardiac dysfunction by regulating specific miRNAs, and certain miRNAs can also regulate H2S synthesis. The crosstalk between miRNAs and H2S offers a novel perspective for investigating the pathophysiology, prevention, and treatment of CVD. The present analysis outlines the interactions between H2S and miRNAs and their influence on CVD, providing insights into their future potential and advancement.

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.

Hydrogen sulfide coordinates glucose metabolism switch through destabilizing tetrameric pyruvate kinase M2

Most cancer cells reprogram their glucose metabolic pathway from oxidative phosphorylation to aerobic glycolysis for energy production. By reducing enzyme activity of pyruvate kinase M2 (PKM2), cancer cells attain a greater fraction of glycolytic metabolites for macromolecule synthesis needed for rapid proliferation. Here we demonstrate that hydrogen sulfide (H2S) destabilizes the PKM2 tetramer into monomer/dimer through sulfhydration at cysteines, notably at C326, leading to reduced PKM2 enzyme activity and increased PKM2-mediated transcriptional activation. Blocking PKM2 sulfhydration at C326 through amino acid mutation stabilizes the PKM2 tetramer and crystal structure further revealing the tetramer organization of PKM2-C326S. The PKM2-C326S mutant in cancer cells rewires glucose metabolism to mitochondrial respiration, significantly inhibiting tumor growth. In this work, we demonstrate that PKM2 sulfhydration by H2S inactivates PKM2 activity to promote tumorigenesis and inhibiting this process could be a potential therapeutic approach for targeting cancer metabolism.

Exercise Enhances Anti-contractile Effects of PVAT Through Endogenous H2S in High-Fat Diet-Induced Obesity Hypertension

PURPOSE

Hydrogen sulfide (H2S) secreted by perivascular adipose tissue (PVAT) is a critical vasodilator, which might be involved during the pathogenesis of hypertension. The present study aimed to investigate the exact role of H2S on the regulation of PVAT anti-contraction by long-term exercise in obesity hypertension.

METHODS

After the establishment of obesity hypertension (24 weeks) through a high-fat diet, male Sprague-Dawley rats were randomly assigned to control group (HC), exercise group (HE), cystathionine γ-lyase (CSE) blocking group (HCB), and exercise combined with CSE blocking group (HEB). Exercise and CSE inhibitor regimens were performed throughout 13 weeks.

RESULTS

After 13 weeks of intervention, blood pressure was significantly decreased by long-term exercise (HC vs. HE, P < 0.05) but not by exercise combined with the CSE inhibitor regimen. Meanwhile, the CSE inhibitor significantly blocked the production of H2S in PVAT even after exercise (HE vs. HEB, P < 0.05). Furthermore, long-term exercise altered the expressions of voltage-dependent K+ (Kv) channel subunits 7 (KCNQs), which were diminished by CSE inhibition in mesenteric arteries. As for vascular tension assessment, after incubation with or without KCNQ opener (retigabine), the anti-contractile effect of PVAT (with or without transferred bath solution of PVAT) was significantly enhanced by long-term exercise and eliminated by the CSE inhibitor regimen (P < 0.05); KCNQ inhibitor (XE991) blunted this effect except for HE.

CONCLUSIONS

These results collectively suggest that endogenous H2S is a strong regulator of the anti-contractile effect of PVAT in obesity hypertension by long-term exercise, and KCNQ in the resistance artery might be involved during this process but not the only target channel mediated by H2S.

Sulfide and polysulfide as pronociceptive mediators: Focus on Cav3.2 function enhancement and TRPA1 activation

Reactive sulfur species including sulfides, polysulfides and cysteine hydropersulfide play extensive roles in health and disease, which involve modification of protein functions through the interaction with metals bound to the proteins, cleavage of cysteine disulfide (S-S) bonds and S-persulfidation of cysteine residues. Sulfides over a wide micromolar concentration range enhance the activity of Cav3.2 T-type Ca2+ channels by eliminating Zn2+ bound to the channels, thereby promoting somatic and visceral pain. Cav3.2 is under inhibition by Zn2+ in physiological conditions, so that sulfides function to reboot Cav3.2 from Zn2+ inhibition and increase the excitability of nociceptors. On the other hand, polysulfides generated from sulfides activate TRPA1 channels via cysteine S-persulfidation, thereby facilitating somatic, but not visceral, pain. Thus, Cav3.2 function enhancement by sulfides and TRPA1 activation by polysulfides, synergistically accelerate somatic pain signals. The increased activity of the sulfide/Cav3.2 system, in particular, appears to have a great impact on pathological pain, and may thus serve as a therapeutic target for treatment of neuropathic and inflammatory pain including visceral pain.

Application of Quality by Design in the Development of Hydrogen Sulfide Donor Loaded Polymeric Microparticles

Hydrogen sulfide (H2S) is a multifaceted gasotransmitter molecule which has potential applications in many pathological conditions including in lowering intraocular pressure and providing retinal neuroprotection. However, its unique physicochemical properties pose several challenges for developing its efficient and safe delivery method system. This study aims to overcome challenges related to H2S toxicity, gaseous nature, and narrow therapeutic concentrations range by developing polymeric microparticles to sustain the release of H2S for an extended period. Various formulation parameters and their interactions are quantitatively identified using Quality-by-Design (QbD) approach to optimize the microparticle-based H2S donor (HSD) delivery system. Microparticles were prepared using a solvent-evaporation coacervation process by using polycaprolactone (PCL), soy lecithin, dichloromethane, Na2S.9H2O, and silicone oil as polymer, surfactant, solvent, HSD, and dispersion medium, respectively. The microparticles were characterized for size, size distribution, entrapment efficiency, and H2S release profile. A Main Effects Screening (MES) and a Response Surface Design (RSD) model-based Box-Behnken Design (BBD) was developed to establish the relationship between critical process parameters (CPPs) and critical quality attributes (CQAs) qualitatively and quantitatively. The MES model identified polymer to drug ratio and dispersion medium quantity as significant CPPs among others, while the RSD model established their quantitative relationship. Finally, the target product performance was validated by comparing predicted and experimental outcomes. The QbD approach helped in achieving overall desired microparticle characteristics with fewer trials and provided a mathematical relationship between the CPPs and the CQAs useful for further manipulation and optimization of release profile up to at least 30 days.

Generation and characterization of cytochrome P450 3A74 CRISPR/Cas9 knockout bovine foetal hepatocyte cell line (BFH12)

In human, the cytochrome P450 3A (CYP3A) subfamily of drug-metabolizing enzymes (DMEs) is responsible for a significant number of phase I reactions, with the CYP3A4 isoform superintending the hepatic and intestinal metabolism of diverse endobiotic and xenobiotic compounds. The CYP3A4-dependent bioactivation of chemicals may result in hepatotoxicity and trigger carcinogenesis. In cattle, four CYP3A genes (CYP3A74, CYP3A76, CYP3A28 and CYP3A24) have been identified. Despite cattle being daily exposed to xenobiotics (e.g., mycotoxins, food additives, drugs and pesticides), the existing knowledge about the contribution of CYP3A in bovine hepatic metabolism is still incomplete. Nowadays, CRISPR/Cas9 mediated knockout (KO) is a valuable method to generate in vivo and in vitro models for studying the metabolism of xenobiotics. In the present study, we successfully performed CRISPR/Cas9-mediated KO of bovine CYP3A74, human CYP3A4-like, in a bovine foetal hepatocyte cell line (BFH12). After clonal expansion and selection, CYP3A74 ablation was confirmed at the DNA, mRNA, and protein level. The subsequent characterization of the CYP3A74 KO clone highlighted significant transcriptomic changes (RNA-sequencing) associated with the regulation of cell cycle and proliferation, immune and inflammatory response, as well as metabolic processes. Overall, this study successfully developed a new CYP3A74 KO in vitro model by using CRISPR/Cas9 technology, which represents a novel resource for xenobiotic metabolism studies in cattle. Furthermore, the transcriptomic analysis suggests a key role of CYP3A74 in bovine hepatocyte cell cycle regulation and metabolic homeostasis.

Role of hydrogen sulfide in the male reproductive system

As an important gas signaling molecule, hydrogen sulfide (H2S) affects multiple organ systems, including the nervous, cardiovascular, digestive, and genitourinary, reproductive systems. In particular, H2S not only regulates female reproductive function but also holds great promise in the treatment of male reproductive diseases and disorders, such as erectile dysfunction, prostate cancer, varicocele, and infertility. In this review, we summarize the relationship between H2S and male reproductive organs, including the penis, testis, prostate, vas deferens, and epididymis. As lower urinary tract symptoms have a significant impact on penile erection disorders, we also address the potential ameliorative effects of H2S in erectile dysfunction resulting from bladder disease. Additionally, we discuss the regulatory role of H2S in cavernous smooth muscle relaxation, which involves the NO/cGMP pathway, the RhoA/Rho-kinase pathway, and K+ channel activation. Recently, various compounds that can alleviate erectile dysfunction have been reported to be at least partly dependent on H2S. Therefore, understanding the role of H2S in the male reproductive system may help develop novel strategies for the clinical treatment of male reproductive system diseases.

Therapeutic Potential of Hydrogen Sulfide in Reproductive System Disorders

Hydrogen sulfide (H2S), previously regarded as a toxic exhaust and atmospheric pollutant, has emerged as the third gaseous signaling molecule following nitric oxide (NO) and carbon monoxide (CO). Recent research has revealed significant biological effects of H2S in a variety of systems, such as the nervous, cardiovascular, and digestive systems. Additionally, H2S has been found to impact reproductive system function and may have therapeutic implications for reproductive disorders. This paper explores the relationship between H2S and male reproductive disorders, specifically erectile dysfunction, prostate cancer, male infertility, and testicular damage. Additionally, it examines the impact of H2S regulation on the pathophysiology of the female reproductive system, including improvements in preterm birth, endometriosis, pre-eclampsia, fetal growth restriction, unexplained recurrent spontaneous abortion, placental oxidative damage, embryo implantation, recovery of myometrium post-delivery, and ovulation. The study delves into the regulatory functions of H2S within the reproductive systems of both genders, including its impact on the NO/cGMP pathway, the activation of K+ channels, and the relaxation mechanism of the spongy smooth muscle through the ROCK pathway, aiming to broaden the scope of potential therapeutic strategies for treating reproductive system disorders in clinical settings.

Hydrogen Sulfide and Irisin, Potential Allies in Ensuring Cardiovascular Health

Irisin is a myokine secreted under the influence of physical activity and exposure to low temperatures and through different exogenous stimuli by the cleavage of its precursor, fibronectin type III domain-containing protein 5 (FNDC5). It is mainly known for maintaining of metabolic homeostasis, promoting the browning of white adipose tissue, the thermogenesis process, and glucose homeostasis. Growing experimental evidence suggests the possible central role of irisin in the regulation of cardiometabolic pathophysiological processes. On the other side, hydrogen sulfide (H2S) is well recognized as a pleiotropic gasotransmitter that regulates several homeostatic balances and physiological functions and takes part in the pathogenesis of cardiometabolic diseases. Through the S-persulfidation of cysteine protein residues, H2S is capable of interacting with crucial signaling pathways, exerting beneficial effects in regulating glucose and lipid homeostasis as well. H2S and irisin seem to be intertwined; indeed, recently, H2S was found to regulate irisin secretion by activating the peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α)/FNDC5/irisin signaling pathway, and they share several mechanisms of action. Their involvement in metabolic diseases is confirmed by the detection of their lower circulating levels in obese and diabetic subjects. Along with the importance of metabolic disorders, these modulators exert favorable effects against cardiovascular diseases, preventing incidents of hypertension, atherosclerosis, heart failure, myocardial infarction, and ischemia-reperfusion injury. This review, for the first time, aims to explore the role of H2S and irisin and their possible crosstalk in cardiovascular diseases, pointing out the main effects exerted through the common molecular pathways involved.

Novel ray of hope for diabetic wound healing: Hydrogen sulfide and its releasing agents

BACKGROUND

Diabetes mellitus (DM) is a long-term metabolic disease accompanied by difficulties in wound healing placing a severe financial and physical burden on patients. As one of the important signal transduction molecules, both endogenous and exogenous hydrogen sulfide (H2S) was found to promote diabetic wound healing in recent studies. H2S at physiological concentrations can not only promote cell migration and adhesion functions, but also resist inflammation, oxidative stress and inappropriate remodeling of the extracellular matrix.

AIM OF REVIEW

The purpose of this review is to summarize current research on the function of H2S in diabetic wound healing at all stages, and propose future directions.

KEY SCIENTIFIC CONCEPTS OF REVIEW

In this review, first, the various factors affecting wound healing under diabetic pathological conditions and the in vivo H2S generation pathway are briefly introduced. Second, how H2S may improve diabetic wound healing is categorized and described. Finally, we discuss the relevant H2S donors and new dosage forms, analyze and reveal the characteristics of many typical H2S donors, which may provide new ideas for the development of H2S-released agents to improve diabetic wound healing.

The potential role of hydrogen sulfide in cancer cell apoptosis

For a long time, hydrogen sulfide (H2S) has been considered a toxic compound, but recent studies have found that H2S is the third gaseous signaling molecule which plays a vital role in physiological and pathological conditions. Currently, a large number of studies have shown that H2S mediates apoptosis through multiple signaling pathways to participate in cancer occurrence and development, for example, PI3K/Akt/mTOR and MAPK signaling pathways. Therefore, the regulation of the production and metabolism of H2S to mediate the apoptotic process of cancer cells may improve the effectiveness of cancer treatment. In this review, the role and mechanism of H2S in cancer cell apoptosis in mammals are summarized.

Investigating the impact of protein S-sulfhydration modification on vascular diseases: A comprehensive review

The post-translational modification of cysteine through redox reactions, especially S-sulfhydration, plays a critical role in regulating protein activity, interactions, and spatial arrangement. This review focuses on the impact of protein S-sulfhydration on vascular function and its implications in vascular diseases. Dysregulated S-sulfhydration has been linked to the development of vascular pathologies, including aortic aneurysms and dissections, atherosclerosis, and thrombotic diseases. The H2S signaling pathway and the enzyme cystathionine γ-lyase (CSE), which is responsible for H2S generation, are identified as key regulators of vascular function. Additionally, potential therapeutic targets for the treatment of vascular diseases, such as the H2S donor GYY4137 and the HDAC inhibitor entinostat, are discussed. The review also emphasizes the antithrombotic effects of H2S in regulating platelet aggregation and thrombosis. The aim of this review is to enhance our understanding of the function and mechanism of protein S-sulfhydration modification in vascular diseases, and to provide new insights into the clinical application of this modification.

Use of hydroxocobalamin to treat intraoperative vasoplegic syndrome refractory to vasopressors and methylene blue during liver transplantation

INTRODUCTION

For patients with catecholamine-resistant vasoplegic syndrome (VS) during liver transplantation (LT), treatment with methylene blue (MB) and/or hydroxocobalamin (B12) has been an acceptable therapy. However, data on the effectiveness of B12 is limited to case reports and case series.

METHODS

We retrospectively reviewed records of patients undergoing LT from January 2016 through March 2022. We identified patients with VS treated with vasopressors and MB, and abstracted hemodynamic parameters, vasopressor requirements, and B12 administration from the records. The primary aim was to describe the treatment efficacy of B12 for VS refractory to vasopressors and MB, measured as no vasopressor requirement at the conclusion of the surgery.

RESULTS

One hundred one patients received intraoperative VS treatment. For the 35 (34.7%) patients with successful VS treatment, 14 received MB only and 21 received both MB and B12. Of the 21 patients with VS resolution after receiving both MB and B12, 17 (89.5%) showed immediate, but transient, hemodynamic improvements at the time of MB administration and later showed sustained response to B12.

CONCLUSION

Immediate but transient hemodynamic response to MB in VS patients during LT supports the diagnosis of VS and should prompt B12 administration for sustained treatment response.

Preeclamptic serum and soluble fms-like tyrosine kinase-1 suppress endothelial inward rectifier potassium currents

INTRODUCTION

Inward rectifier K+ (Kir) channel, a major factor determining endothelial membrane potential, regulates Ca2+ influx and vasodilator release, which is impaired in preeclamptic blood vessels. Previously, human umbilical vein endothelial cell (HUVEC) Kir currents were shown to decrease after incubating in preeclamptic plasma. We aimed to demonstrate whether sFlt-1, which is high in preeclamptic blood, could inhibit Kir channel function and expression.

METHODS

HUVECs were cultured in regular medium, regular medium with added sFlt-1, or serum from preeclampsia patients or normal pregnant women (Control, sFlt-1, PE, or NP, respectively). Using whole-cell patch clamp technique, we identified Kir currents with the Kir blocker 2 mM BaCl2 and compared the currents among groups. The expression of Kir 2.1 and 2.2 channels were determined using immunofluorescent staining.

RESULTS

sFlt-1 and PE groups exhibited similar Kir currents, while NP group possessed significantly larger currents, similar to Control group currents. Moreover, sFlt-1 and sFlt-1/PlGF ratio showed strong negative correlation with Kir currents (r = -0.71 and -0.70, respectively; P < 0.05). There were no significant differences in mean fluorescence intensity representing Kir 2.1 and 2.2 channels expression in all four groups.

DISCUSSION

This is the first report to demonstrate sFlt-1 inhibition against Kir currents, which could lead to maternal endothelial dysfunction and hypertension seen in preeclampsia. However, channel expression was unaffected by sFlt-1 incubation, suggesting dysfunctions of channel or other processes (e.g., membrane translocation). The present data could pave the way for novel therapies targeting sFlt-1 or Kir to alleviate hypertension in preeclampsia.

Comparison of colorimetric, spectroscopic and electrochemical techniques for quantification of hydrogen sulfide

Background: Hydrogen sulfide (H2S), an endogenous gasotransmitter, has potential applications in several conditions. However, its quantification in simulated physiological solutions is a major challenge due to its gaseous nature and other physicochemical properties. Aim: This study was designed to compare four commonly used H2S detection and quantification methods in aqueous solutions. Methods: The four techniques compared were one colorimetric, one chromatographic and two electrochemical methods. Results: Colorimetric and chromatographic methods quantified H2S in millimolar and micromole ranges, respectively. The electrochemical methods quantified H2S in the nanomole and picomole ranges and were less time-consuming. Conclusion: The H2S quantification method should be selected based on the specific requirements of a research project in terms of sensitivity, response time and cost-effectiveness.

Hydrogen Sulfide (H2S)/Polysulfides (H2Sn) Signalling and TRPA1 Channels Modification on Sulfur Metabolism

Hydrogen sulfide (H2S) and polysulfides (H2Sn, n ≥ 2) produced by enzymes play a role as signalling molecules regulating neurotransmission, vascular tone, cytoprotection, inflammation, oxygen sensing, and energy formation. H2Sn, which have additional sulfur atoms to H2S, and other S-sulfurated molecules such as cysteine persulfide and S-sulfurated cysteine residues of proteins, are produced by enzymes including 3-mercaptopyruvate sulfurtransferase (3MST). H2Sn are also generated by the chemical interaction of H2S with NO, or to a lesser extent with H2O2. S-sulfuration (S-sulfhydration) has been proposed as a mode of action of H2S and H2Sn to regulate the activity of target molecules. Recently, we found that H2S/H2S2 regulate the release of neurotransmitters, such as GABA, glutamate, and D-serine, a co-agonist of N-methyl-D-aspartate (NMDA) receptors. H2S facilitates the induction of hippocampal long-term potentiation, a synaptic model of memory formation, by enhancing the activity of NMDA receptors, while H2S2 achieves this by activating transient receptor potential ankyrin 1 (TRPA1) channels in astrocytes, potentially leading to the activation of nearby neurons. The recent findings show the other aspects of TRPA1 channels-that is, the regulation of the levels of sulfur-containing molecules and their metabolizing enzymes. Disturbance of the signalling by H2S/H2Sn has been demonstrated to be involved in various diseases, including cognitive and psychiatric diseases. The physiological and pathophysiological roles of these molecules will be discussed.

Cardioprotective Effects of Hydrogen Sulfide and Its Potential Therapeutic Implications in the Amelioration of Duchenne Muscular Dystrophy Cardiomyopathy

Hydrogen sulfide (H2S) belongs to the family of gasotransmitters and can modulate a myriad of biological signaling pathways. Among others, its cardioprotective effects, through antioxidant, anti-inflammatory, anti-fibrotic, and proangiogenic activities, are well-documented in experimental studies. Cardiorespiratory failure, predominantly cardiomyopathy, is a life-threatening complication that is the number one cause of death in patients with Duchenne muscular dystrophy (DMD). Although recent data suggest the role of H2S in ameliorating muscle wasting in murine and Caenorhabditis elegans models of DMD, possible cardioprotective effects have not yet been addressed. In this review, we summarize the current understanding of the role of H2S in animal models of cardiac dysfunctions and cardiac cells. We highlight that DMD may be amenable to H2S supplementation, and we suggest H2S as a possible factor regulating DMD-associated cardiomyopathy.

Improving Cardiovascular Risk in Postmenopausal Women with an (-)-Epicatechin-Based Nutraceutical: A Randomly Assigned, Double-Blind vs. Placebo, Proof-of-Concept Trial

BACKGROUND

Age-adjusted rates of cardiovascular disease (CVD) are higher in men than in women. CVD risk-factor outcomes are underrecognized, underestimated, and undertreated in women because the clinical expressions in women differ from those of men. There are no universally accepted recommendations on what to do in women when the values of fasting glucose, blood pressure, and lipids are only slightly altered or at borderline values. We reported the positive effects on CVD risk markers using cacao by-products, showing that alternative approaches can be used to prevent cardiovascular disease in women. The objective was to evaluate the changes in lipoprotein subfractions induced by three months of treatment with an epicatechin-enriched cacao supplement.

METHODS

A double-blind, placebo-controlled proof-of-concept study was developed to evaluate the effects of 3 months of treatment with an (-)-epicatechin-enriched cacao supplement on lipoprotein subfractions.

RESULTS

The usual screening workshop for postmenopausal women could be insufficient and misleading. Assessing the effect of a (-)-epicatechin-enriched cacao supplement employing a lipoprotein subfractionation profile analysis suggests a decrease in cardiovascular risk.

CONCLUSIONS

A simple, low-cost, safe (-)-epicatechin-enriched cacao supplement product can improve the cardiovascular risk in postmenopausal women.

Erucin Exerts Cardioprotective Effects on Ischemia/Reperfusion Injury through the Modulation of mitoKATP Channels

Modulation of mitochondrial K channels represents a pharmacological strategy to promote cardioprotective effects. Isothiocyanates emerge as molecules capable of releasing hydrogen sulfide (H2S), an endogenous pleiotropic gasotransmitter responsible for anti-ischemic cardioprotective effects also through the involvement of mitoK channels. Erucin (ERU) is a natural isothiocyanate resulting from the enzymatic hydrolysis of glucosinolates (GSLs) present in Eruca sativa Mill. seeds, an edible plant of the Brassicaceae family. In this experimental work, the specific involvement of mitoKATP channels in the cardioprotective effect induced by ERU was evaluated in detail. An in vivo preclinical model of acute myocardial infarction was reproduced in rats to evaluate the cardioprotective effect of ERU. Diazoxide was used as a reference compound for the modulation of potassium fluxes and 5-hydroxydecanoic acid (5HD) as a selective blocker of KATP channels. Specific investigations on isolated cardiac mitochondria were carried out to evaluate the involvement of mitoKATP channels. The results obtained showed ERU cardioprotective effects against ischemia/reperfusion (I/R) damage through the involvement of mitoKATP channels and the consequent depolarizing effect, which in turn reduced calcium entry and preserved mitochondrial integrity.

Sulfur signaling pathway in cardiovascular disease

Hydrogen sulfide (H2S) and sulfur dioxide (SO2), recognized as endogenous sulfur-containing gas signaling molecules, were the third and fourth molecules to be identified subsequent to nitric oxide and carbon monoxide (CO), and exerted diverse biological effects on the cardiovascular system. However, the exact mechanisms underlying the actions of H2S and SO2 have remained elusive until now. Recently, novel post-translational modifications known as S-sulfhydration and S-sulfenylation, induced by H2S and SO2 respectively, have been proposed. These modifications involve the chemical alteration of specific cysteine residues in target proteins through S-sulfhydration and S-sulfenylation, respectively. H2S induced S-sulfhydrylation can have a significant impact on various cellular processes such as cell survival, apoptosis, cell proliferation, metabolism, mitochondrial function, endoplasmic reticulum stress, vasodilation, anti-inflammatory response and oxidative stress in the cardiovascular system. Alternatively, S-sulfenylation caused by SO2 serves primarily to maintain vascular homeostasis. Additional research is warranted to explore the physiological function of proteins with specific cysteine sites, despite the considerable advancements in comprehending the role of H2S-induced S-sulfhydration and SO2-induced S-sulfenylation in the cardiovascular system. The primary objective of this review is to present a comprehensive examination of the function and potential mechanism of S-sulfhydration and S-sulfenylation in the cardiovascular system. Proteins that undergo S-sulfhydration and S-sulfenylation may serve as promising targets for therapeutic intervention and drug development in the cardiovascular system. This could potentially expedite the future development and utilization of drugs related to H2S and SO2.

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.

Protein Persulfidation: Recent Progress and Future Directions

Significance: Hydrogen sulfide (H2S) is considered to be a gasotransmitter along with carbon monoxide (CO) and nitric oxide (NO), and is known as a key regulator of physiological and pathological activities. S-sulfhydration (also known as persulfidation), a mechanism involving the formation of protein persulfides by modification of cysteine residues, is proposed here to explain the multiple biological functions of H2S. Investigating the properties of protein persulfides can provide a foundation for further understanding of the potential functions of H2S. Recent Advances: Multiple methods have been developed to determine the level of protein persulfides. It has been demonstrated that protein persulfidation is involved in many biological processes through various mechanisms including the regulation of ion channels, enzymes, and transcription factors, as well as influencing protein-protein interactions. Critical Issues: Some technical and theoretical questions remain to be solved. These include how to improve the specificity of the detection methods for protein persulfidation, why persulfidation typically occurs on one or a few thiols within a protein, how this modification alters protein functions, and whether protein persulfidation has organ-specific patterns. Future Directions: Optimizing the detection methods and elucidating the properties and molecular functions of protein persulfidation would be beneficial for current therapeutics. In this review, we introduce the detailed mechanism of the persulfidation process and discuss persulfidation detection methods. In addition, this review summarizes recent discoveries of the selectivity of protein persulfidation and the regulation of protein functions and cell signaling pathways by persulfidation. Antioxid. Redox Signal. 39, 829-852.

Reactive Sulfur Species in Human Diseases

Significance: Reactive sulfur species (RSS) have been recently recognized as redox molecules no less important than reactive oxygen species or reactive nitrogen species. They possess regulatory and protective properties and are involved in various metabolic processes, thereby contributing to the maintenance of human health. It has been documented that many disorders, including neurological, cardiovascular, and respiratory diseases, diabetes mellitus (DM), and cancer, are related to the disruption of RSS homeostasis. Recent Advances: There is still a growing interest in the role of RSS in human diseases. Since a decrease in hydrogen sulfide or other RSS has been reported in many disorders, safe and efficient RSS donors have been developed and tested under in vitro conditions or on animal models. Critical Issues: Cardiovascular diseases and DM are currently the most common chronic diseases worldwide due to stressful and unhealthy lifestyles. In addition, because of high prevalence and aging of the population, neurological disorders including Parkinson's disease and Alzheimer's disease as well as respiratory diseases are a formidable challenge for health care systems. From this point of view, the knowledge of the role of RSS in these disorders and RSS modulation options are important and could be useful in therapeutic strategies. Future Directions: Improvement and standardization of analytical methods used for RSS estimation are crucial for the use of RSS as diagnostic biomarkers. Finding good, safe RSS donors applicable for therapeutic purposes could be useful as primary or adjunctive therapy in many common diseases. Antioxid. Redox Signal. 39, 1000-1023.

Hydrogen sulfide donor activates AKT-eNOS signaling and promotes lymphatic vessel formation

The lymphatic network is pivotal for various physiological functions in the human body. Accumulated evidence supports the role of therapeutic lymphangiogenesis in the treatment of several pathologies. Endogenous gasotransmitter, hydrogen sulfide (H2S) has been extensively studied for its potential as a pro-angiogenic factor and vascular function modulator. However, the role of H2S in governing lymphatic vessel formation, and underlying molecular mechanisms are understudied. The present study was designed to investigate the effects of H2S donor sodium hydrogen sulfide (NaHS) on lymphatic vascularization and pro-angiogenic signaling pathways using both in vitro and in vivo approaches. In vitro dose-response experiments showed increased proliferation and tube formation by NaHS-treated human lymphatic endothelial cells (LECs) compared with control cells. Immunoblotting performed with LEC lysates prepared after time-course NaHS treatment demonstrated increased activation of ERK1/2, AKT and eNOS after 20 min of NaHS stimulation. Further, NaHS treatment induced nitric oxide production, reduced reactive oxygen species generation, and promoted cell cycle in LECs. Additional cell cycle analysis showed that NaHS treatment abrogates oxidized LDL-induced cell cycle arrest in LECs. The results of in vivo Matrigel plug assay revealed increased lymphatic vessel density in Matrigel plugs containing NaHS compared with control plugs, however, no significant differences in angiogenesis and immune cell infiltration were observed. Collectively, these findings suggest that H2S donor NaHS promotes lymphatic vessel formation both in vitro and in vivo and may be utilized to promote reparative lymphangiogenesis to alleviate lymphatic dysfunction-related disorders.

Vasodilator Responses of Perivascular Adipose Tissue-Derived Hydrogen Sulfide Stimulated with L-Cysteine in Pregnancy Hypertension-Induced Endothelial Dysfunction in Rats

Endothelium-derived nitric oxide (NO)-induced vasodilation is impaired in pregnancy hypertension. However, the role of perivascular adipose tissue (PVAT)-derived hydrogen sulfide (H2S), as an alternative for counteracting vascular dysfunction, is incompletely clear in hypertensive disorders of pregnancy. Therefore, PVAT-derived H2S-induced vasodilation was investigated in pregnancy hypertension-induced endothelial dysfunction. Non-pregnant (Non-Preg) and pregnant (Preg) rats were submitted (or not) to the deoxycorticosterone (DOCA)-salt protocol and assigned as follows (n = 10/group): Non-Preg, Non-Preg+DOCA, Preg, and Preg+DOCA groups. Systolic blood pressure (SBP), angiogenesis-related factors, determinant levels of H2S (PbS), NO (NOx), and oxidative stress (MDA) were assessed. Vascular changes were recorded in thoracic aortas with PVAT and endothelium (intact and removed layers). Vasorelaxation responses to the substrate (L-cysteine) for the H2S-producing enzyme cystathionine-γ-lyase (CSE) were examined in the absence and presence of CSE-inhibitor DL-propargylglycine (PAG) in thoracic aorta rings pre-incubated with cofactor for CSE (pyridoxal-5 phosphate: PLP) and pre-contracted with phenylephrine. Hypertension was only found in the Preg+DOCA group. Preg+DOCA rats showed angiogenic imbalances and increased levels of MDA. PbS, but not NOx, showed increased levels in the Preg+DOCA group. Pre-incubation with PLP and L-cysteine elevated determinants of H2S in PVAT and placentas of Preg-DOCA rats, whereas no changes were found in the aortas without PVAT. Aortas of Preg-DOCA rats showed that PVAT-derived H2S-dependent vasodilation was greater compared to endothelium-derived H2S, whereas PAG blocked these responses. PVAT-derived H2S endogenously stimulated with the amino acid L-cysteine may be an alternative to induce vasorelaxation in endothelial dysfunction related to pregnancy hypertension.

Cystathionine Gamma Lyase Is Regulated by Flow and Controls Smooth Muscle Migration in Human Saphenous Vein

The saphenous vein is the conduit of choice for bypass grafting. Unfortunately, the hemodynamic stress associated with the arterial environment of the bypass vein graft leads to the development of intimal hyperplasia (IH), an excessive cellular growth and collagen deposition that results in restenosis and secondary graft occlusion. Hydrogen sulfide (H2S) is a ubiquitous redox-modifying gasotransmitter that inhibits IH. H2S is produced via the reverse trans-sulfuration pathway by three enzymes: cystathionine γ-lyase (CSE), cystathionine β-synthase (CBS) and 3-mercaptopyruvate sulfurtransferase (3-MST). However, the expression and regulation of these enzymes in the human vasculature remains unclear. Here, we investigated the expression of CSE, CBS and 3-MST in segments of native human saphenous vein and large arteries. Furthermore, we evaluated the regulation of these enzymes in vein segments cultured under static, venous (7 mmHg pressure) or arterial (100 mmHg pressure) pressure. CSE was expressed in the media, neointima and intima of the vessels and was negatively regulated by arterial shear stress. Adenoviral-mediated CSE overexpression or RNA interference-mediated CSE knock-down revealed that CSE inhibited primary human VSMC migration but not proliferation. We propose that high shear stress in arteriovenous bypass grafts inhibits CSE expression in both the media and endothelium, which may contribute to increased VSMC migration in the context of IH.

Persulfidation of mitoKv7.4 channels contributes to the cardioprotective effects of the H2S-donor Erucin against ischemia/reperfusion injury

BACKGROUND

Hydrogen sulfide (H2S) is a gasotransmitter deeply involved in cardiovascular homeostasis and implicated in the myocardial protection against ischemia/reperfusion. The post-translational persulfidation of cysteine residues has been identified as the mechanism through which H2S regulates a plethora of biological targets. Erucin (ERU) is an isothiocyanate produced upon hydrolysis of the glucosinolate glucoerucin, presents in edible plants of Brassicaceae family, such as Eruca sativa Mill., and it has emerged as a slow and long-lasting H2S-donor.

AIM

In this study the cardioprotective profile of ERU has been investigated and the action mechanism explored, focusing on the possible role of the recently identified mitochondrial Kv7.4 (mitoKv7.4) potassium channels.

RESULTS

Interestingly, ERU showed to release H2S and concentration-dependently protected H9c2 cells against H2O2-induced oxidative damage. Moreover, in in vivo model of myocardial infarct ERU showed protective effects, reducing the extension of ischemic area, the levels of troponin I and increasing the amount of total AnxA1, as well as co-related inflammatory outcomes. Conversely, the pre-treatment with XE991, a blocker of Kv7.4 channels, abolished them. In isolated cardiac mitochondria ERU exhibited the typical profile of a mitochondrial potassium channels opener, in particular, this isothiocyanate produced a mild depolarization of mitochondrial membrane potential, a reduction of calcium accumulation into the matrix and finally a flow of potassium ions. Finally, mitoKv7.4 channels were persulfidated in ERU-treated mitochondria.

CONCLUSIONS

ERU modulates the cardiac mitoKv7.4 channels and this mechanism may be relevant for cardioprotective effects.

Mapping Pregnancy-dependent Sulfhydrome Unfolds Diverse Functions of Protein Sulfhydration in Human Uterine Artery

Uterine artery (UA) hydrogen sulfide (H2S) production is augmented in pregnancy and, on stimulation by systemic/local vasodilators, contributes to pregnancy-dependent uterine vasodilation; however, how H2S exploits this role is largely unknown. S-sulfhydration converts free thiols to persulfides at reactive cysteine(s) on targeted proteins to affect the entire proteome posttranslationally, representing the main route for H2S to elicit its function. Here, we used Tag-Switch to quantify changes in sulfhydrated (SSH-) proteins (ie, sulfhydrome) in H2S-treated nonpregnant and pregnant human UA. We further used the low-pH quantitative thiol reactivity profiling platform by which paired sulfhydromes were subjected to liquid chromatography tandem mass spectrometry-based peptide sequencing to generate site (cysteine)-specific pregnancy-dependent H2S-responsive human UA sulfhydrome. Total levels of sulfhydrated proteins were significantly greater in pregnant vs nonpregnant human UA and further stimulated by treatment with sodium hydrosulfide. We identified a total of 360 and 1671 SSH-peptides from 480 and 1186 SSH-proteins in untreated and sodium hydrosulfide-treated human UA, respectively. Bioinformatics analyses identified pregnancy-dependent H2S-responsive human UA SSH peptides/proteins, which were categorized to various molecular functions, pathways, and biological processes, especially vascular smooth muscle contraction/relaxation. Pregnancy-dependent changes in these proteins were rectified by immunoblotting of the Tag-Switch labeled SSH proteins. Low-pH quantitative thiol reactivity profiling failed to identify low abundance SSH proteins such as KATP channels in human UA; however, immunoblotting of Tag-Switch-labeled SSH proteins identified pregnancy-dependent upregulation of SSH-KATP channels without altering their total proteins. Thus, comprehensive analyses of human UA sulfhydromes influenced by endogenous and exogenous H2S inform novel roles of protein sulfhydration in uterine hemodynamics regulation.

Clinical Potential of Hydrogen Sulfide in Peripheral Arterial Disease

Peripheral artery disease (PAD) affects more than 230 million people worldwide. PAD patients suffer from reduced quality of life and are at increased risk of vascular complications and all-cause mortality. Despite its prevalence, impact on quality of life and poor long-term clinical outcomes, PAD remains underdiagnosed and undertreated compared to myocardial infarction and stroke. PAD is due to a combination of macrovascular atherosclerosis and calcification, combined with microvascular rarefaction, leading to chronic peripheral ischemia. Novel therapies are needed to address the increasing incidence of PAD and its difficult long-term pharmacological and surgical management. The cysteine-derived gasotransmitter hydrogen sulfide (H₂S) has interesting vasorelaxant, cytoprotective, antioxidant and anti-inflammatory properties. In this review, we describe the current understanding of PAD pathophysiology and the remarkable benefits of H₂S against atherosclerosis, inflammation, vascular calcification, and other vasculo-protective effects.

Plasma hydrogen sulfide, nitric oxide, and thiocyanate levels are lower during pregnancy compared to postpartum in a cohort of women from the Pacific northwest of the United States

AIMS

Pregnancy alters multiple physiological processes including angiogenesis, vasodilation, inflammation, and cellular redox, which are partially modulated by the gasotransmitters hydrogen sulfide (H2S) and nitric oxide (NO). In this study, we sought to determine how plasma levels of H2S, NO, and the H2S-related metabolites thiocyanate (SCN-), and methanethiol (CH3SH) change during pregnancy progression.

MATERIALS AND METHODS

Plasma was collected from 45 women at three points: 25-28 weeks gestation, 28-32 week gestation, and at ≥3 months postpartum. Plasma levels of H2S, SCN-, and CH3SH were measured following derivatization using monobromobimane followed by LC-MS/MS. Plasma NO was measured indirectly using the Griess reagent.

KEY FINDINGS

NO and SCN- were significantly lower in women at 25-28 weeks gestation and 28-32 weeks gestation than postpartum while plasma H2S levels were significantly lower at 28-32 weeks gestation than postpartum. No significant differences were observed in CH3SH.

SIGNIFICANCE

Previous reports demonstrated that the production of H2S and NO are stimulated during pregnancy, but we observed lower levels during pregnancy compared to postpartum. Previous reports on NO have been mixed, but given the related effects of H2S and NO, it is expected that their levels would be higher during pregnancy vs. postpartum. Future studies determining the mechanism for decreased H2S and NO during pregnancy will elucidate the role of these gasotransmitters during normal and pathological progression of pregnancy.

Hydroxocobalamin as Rescue Therapy in a Patient With Refractory Amlodipine-Induced Vasoplegia

Vasoplegic syndrome is a type of distributive shock characterized by mean arterial pressure of less than 65 mmHg, with normal to high cardiac output and often refractory to fluid resuscitation, high doses of intravenous vasopressors, and inotropes. It is usually observed after cardiac and solid organ transplantation surgeries. Here, we report a 56-year-old female patient who presented with a profound vasoplegia manifesting as lethargy and confusion in the setting of amlodipine toxicity. This case of severe vasoplegia was refractory to all conditional lines of medical management reported in the literature. The mainstay treatment modalities for vasoplegia include volume resuscitation, catecholamines, vasopressin, angiotensin II, and possibly methylene blue in unresponsive cases. Our patient was given hydroxocobalamin in favor of methylene blue, given the history of serotonin reuptake inhibitors use, which would have caused a life-threatening serotonin syndrome. Hydroxycobolamine resulted in a dramatic clinical recovery, suggesting its potentially significant role in refractory vasoplegia.

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.

Local delivery of gaseous signaling molecules for orthopedic disease therapy

Over the past decade, a proliferation of research has used nanoparticles to deliver gaseous signaling molecules for medical purposes. The discovery and revelation of the role of gaseous signaling molecules have been accompanied by nanoparticle therapies for their local delivery. While most of them have been applied in oncology, recent advances have demonstrated their considerable potential in diagnosing and treating orthopedic diseases. Three of the currently recognized gaseous signaling molecules, nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2S), are highlighted in this review along with their distinctive biological functions and roles in orthopedic diseases. Moreover, this review summarizes the progress in therapeutic development over the past ten years with a deeper discussion of unresolved issues and potential clinical applications.

Hydrogen sulfide in the experimental models of arterial hypertension

Hydrogen sulfide (H₂S) is the third member of gasotransmitter family together with nitric oxide and carbon monoxide. H₂S is involved in the regulation of blood pressure by controlling vascular tone, sympathetic nervous system activity and renal sodium excretion. Moderate age-dependent hypertension and endothelial dysfunction develop in mice with knockout of cystathionine γ-lyase (CSE), the enzyme involved in H₂S production in the cardiovascular system. Decreased H₂S concentration as well as the expression and activities of H₂S-producing enzymes have been observed in most commonly used animal models of hypertension such as spontaneously hypertensive rats, Dahl salt-sensitive rats, chronic administration of NO synthase inhibitors, angiotensin II infusion and two-kidney-one-clip hypertension, the model of renovascular hypertension. Administration of H₂S donors decreases blood pressure in these models but has no major effects on blood pressure in normotensive animals. H₂S donors not only reduce blood pressure but also end-organ injury such as vascular and myocardial hypertrophy and remodeling, hypertension-associated kidney injury or erectile dysfunction. H₂S level and signaling are modulated by some antihypertensive medications as well as natural products with antihypertensive activity such as garlic polysulfides or plant-derived isothiocyanates as well as non-pharmacological interventions. Modifying H₂S signaling is the potential novel therapeutic approach for the management of hypertension, however, more experimental clinical studies about the role of H₂S in hypertension are required.

Gasotransmitter modulation of hypoglossal motoneuron activity

Obstructive sleep apnea (OSA) is characterized by sporadic collapse of the upper airway leading to periodic disruptions in breathing. Upper airway patency is governed by genioglossal nerve activity that originates from the hypoglossal motor nucleus. Mice with targeted deletion of the gene Hmox2, encoding the carbon monoxide (CO) producing enzyme, heme oxygenase-2 (HO-2), exhibit OSA, yet the contribution of central HO-2 dysregulation to the phenomenon is unknown. Using the rhythmic brainstem slice preparation that contains the preBötzinger complex (preBötC) and the hypoglossal nucleus, we tested the hypothesis that central HO-2 dysregulation weakens hypoglossal motoneuron output. Disrupting HO-2 activity increased the occurrence of subnetwork activity from the preBötC, which was associated with an increased irregularity of rhythmogenesis. These phenomena were also associated with the intermittent inability of the preBötC rhythm to drive output from the hypoglossal nucleus (i.e. transmission failures), and a reduction in the input-output relationship between the preBötC and the motor nucleus. HO-2 dysregulation reduced excitatory synaptic currents and intrinsic excitability in inspiratory hypoglossal neurons. Inhibiting activity of the CO-regulated H2S producing enzyme, cystathionine-γ-lyase (CSE), reduced transmission failures in HO-2 null brainstem slices, which also normalized excitatory synaptic currents and intrinsic excitability of hypoglossal motoneurons. These findings demonstrate a hitherto uncharacterized modulation of hypoglossal activity through mutual interaction of HO-2/CO and CSE/H2S, and support the potential importance of centrally derived gasotransmitter activity in regulating upper airway control.

Exogenous H2S Attenuates Hypertension by Regulating Renin Exocytosis under Hyperglycaemic and Hyperlipidaemic Conditions

Obesity, along with type 2 diabetes mellitus (T2DM), is a major contributor to hypertension. The renin-angiotensin-aldosterone system is involved in the occurrence of diabetes and hypertension. However, the mechanism by which obesity is related to T2DM induced hypertension is unclear. In this study, we observed that blood pressure and serum renin content were increased in patients with diabetes and hypertension. Hydrogen sulfide (H₂S), as an endogenous bioactive molecule, has been shown to be a vasodilator. Db/db mice, characterized by obesity and T2DM, and juxtaglomerular (JG) cells, which line the afferent arterioles at the entrance of the glomeruli to produce renin, treated with glucose, palmitic acid (PA) and oleic acid (OA), were used as animal and cellular models. NaHS, the H₂S donor, was administered to db/db mice through intraperitoneal injection. NaHS significantly alleviated blood pressure in db/db mice, decreased the renin content in the serum of db/db mice and reduced renin secretion from JG cells. NaHS modulated renin release via cAMP and soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs), including synaptosome-associated protein 23 (SNAP23) and vesicle-associated membrane protein 2 (VAMP2), which mediate renin exocytosis. Furthermore, NaHS increased the levels of autophagy-related proteins and colocalization with EGFP-LC3 puncta with renin-containing granules and VAMP2 to consume excessive renin to maintain intracellular homeostasis. Therefore, exogenous H₂S attenuates renin release and promotes renin-vesicular autophagy to relieve diabetes-induced hypertension.

Upregulation of ATP-Sensitive Potassium Channels as the Potential Mechanism of Cardioprotection and Vasorelaxation Under the Action of Pyridoxal-5-Phosphate in Old Rats

Background: The aging process is accompanied by the weakening of the protective systems of the organism, in particular by the decrease in the expression of ATP-sensitive potassium (KATP) channels and in the synthesis of H2S. The aim of our work was to investigate the role of KATP channels in the cardioprotection induced by pyridoxal-5-phosphate (PLP) in aging. Methods: Experiments were performed on adult and old (aged 24 months) male Wistar rats, which were divided into 3 groups: adults, old, and old PLP-treated rats. PLP was administered orally once a day for 14 days at a dose of 0.7 mg/kg. The levels of mRNA expression of subunits KATP channels were determined by reverse transcription and real-time polymerase chain reaction analysis. Protein expression levels were determined by the Western blot. Cardiac tissue morphology was determined using transverse 6 μm deparaffinized sections stained with picrosirius red staining. Vasorelaxation responses of isolated aortic rings and the function of Langendorff-perfused isolated hearts during ischemia-reperfusion, H2S levels, and markers of oxidative stress were also studied. Results: Administration of PLP to old rats reduces cardiac fibrosis and improves cardiac function during ischemia-reperfusion and vasorelaxation responses to KATP channels opening. At the same time, there was a significant increase in mRNA and protein expression of SUR2 and Kir6.1 subunits of KATP channels, H2S production, and reduced markers of oxidative stress. The specific KATP channel inhibitor-glibenclamide prevented the enhancement of vasodilator responses and anti-ischemic protection in PLP-treated animals. Conclusions: We suggest that this potential therapeutic effect of PLP in old animals may be a result of increased expression of KATP channels and H2S production.

Oxidation Driven Reversal of PIP2-dependent Gating in GIRK2 Channels

Physiological activity of G protein gated inward rectifier K⁺ (GIRK, Kir3) channel, dynamically regulated by three key ligands, phosphoinositol-4,5-bisphosphate (PIP₂), Gβγ, and Na⁺, underlies cellular electrical response to multiple hormones and neurotransmitters in myocytes and neurons. In a reducing environment, matching that inside cells, purified GIRK2 (Kir3.2) channels demonstrate low basal activity, and expected sensitivity to the above ligands. However, under oxidizing conditions, anomalous behavior emerges, including rapid loss of PIP₂ and Na⁺-dependent activation and a high basal activity in the absence of any agonists, that is now paradoxically inhibited by PIP₂. Mutagenesis identifies two cysteine residues (C65 and C190) as being responsible for the loss of PIP₂ and Na⁺-dependent activity and the elevated basal activity, respectively. The results explain anomalous findings from earlier studies and illustrate the potential pathophysiologic consequences of oxidation on GIRK channel function, as well as providing insight to reversed ligand-dependence of Kir and KirBac channels.

The roles of hydrogen sulfide in renal physiology and disease states

Hydrogen sulfide (H₂S), an endogenous gaseous signaling transmitter, has gained recognition for its physiological effects. In this review, we aim to summarize and discuss existing studies about the roles of H₂S in renal functions and renal disease as well as the underlying mechanisms. H₂S is mainly produced by four pathways, and the kidneys are major H₂S–producing organs. Previous studies have shown that H₂S can impact multiple signaling pathways via sulfhydration. In renal physiology, H₂S promotes kidney excretion, regulates renin release and increases ATP production as a sensor for oxygen. H₂S is also involved in the development of kidney disease. H₂S has been implicated in renal ischemia/reperfusion and cisplatin–and sepsis–induced kidney disease. In chronic kidney diseases, especially diabetic nephropathy, hypertensive nephropathy and obstructive kidney disease, H₂S attenuates disease progression by regulating oxidative stress, inflammation and the renin–angiotensin–aldosterone system. Despite accumulating evidence from experimental studies suggesting the potential roles of H₂S donors in the treatment of kidney disease, these results need further clinical translation. Therefore, expanding the understanding of H₂S can not only promote our further understanding of renal physiology but also lay a foundation for transforming H₂S into a target for specific kidney diseases.

Updates in the Management of Perioperative Vasoplegic Syndrome

Vasoplegic syndrome occurs relatively frequently in cardiac surgery, liver transplant, major noncardiac surgery, in post-return of spontaneous circulation situations, and in pateints with sepsis. It is paramount for the anesthesiologist to understand both the pathophysiology of vasoplegia and the different treatment strategies available for rescuing a patient from life-threatening hypotension.

Regulation of blood pressure by natural sulfur compounds: Focus on their mechanisms of action

Natural sulfur compounds are emerging as therapeutic options for the management of hypertension and prehypertension. They are mainly represented by polysulfides from Alliaceae (i.e., garlic) and isothiocyanates from Brassicaceae (or crucifers). The beneficial cardiovascular effects of these compounds, especially garlic polysulfides, are well known and widely reported both in preclinical and clinical studies. However, only a few authors have linked the ability of natural sulfur compounds to induce vasorelaxation and subsequent antihypertensive effects with their ability to release hydrogen sulfide (H₂S) in biological tissue. H₂S is an endogenous gasotransmitter involved in vascular tone regulation. Some cardiovascular diseases, such as hypertension, are associated with lower plasma H₂S levels. Consequently, exogenous sources of H₂S (H₂S donors) have been designed and synthesized or identified among secondary plant metabolites as potential therapeutic options. In addition to antioxidant effects due to its chemical properties as a reducing agent, H₂S induces vasorelaxation by interacting with a range of molecular targets. The mechanisms of action accounting for H₂S-induced vasodilation include opening of vascular potassium channels (such as ATP-sensitive (K_ATP) and voltage-operated (Kv7) channels), inhibition of 5-phosphodiesterase (5-PDE), and activation of vascular endothelial growth factor receptor-2 (VEGFR-2). These effects may be attributed to H₂S-induced S-persulfidation (or S-sulfhydration), which is a posttranslational modification of cysteine residues of many types of proteins resulting in structural and functional alterations (activation/inhibition). Thus, H₂S donors, such as natural sulfur compounds, are promising antihypertensive agents with novel mechanisms of action.

Targeting hydrogen sulfide and nitric oxide to repair cardiovascular injury after trauma

The systemic cardiovascular effects of major trauma, especially neurotrauma, contribute to death and permanent disability in trauma patients and treatments are needed to improve outcomes. In some trauma patients, dysfunction of the autonomic nervous system produces a state of adrenergic overstimulation, causing either a sustained elevation in catecholamines (sympathetic storm) or oscillating bursts of paroxysmal sympathetic hyperactivity. Trauma can also activate innate immune responses that release cytokines and damage-associated molecular patterns into the circulation. This combination of altered autonomic nervous system function and widespread systemic inflammation produces secondary cardiovascular injury, including hypertension, damage to cardiac tissue, vascular endothelial dysfunction, coagulopathy and multiorgan failure. The gasotransmitters nitric oxide (NO) and hydrogen sulfide (H2S) are small gaseous molecules with potent effects on vascular tone regulation. Exogenous NO (inhaled) has potential therapeutic benefit in cardio-cerebrovascular diseases, but limited data suggests potential efficacy in traumatic brain injury (TBI). H2S is a modulator of NO signaling and autonomic nervous system function that has also been used as a drug for cardio-cerebrovascular diseases. The inhaled gases NO and H2S are potential treatments to restore cardio-cerebrovascular function in the post-trauma period.

Synthesis of 2-(2-(4-thioxo-3H-1,2-dithiole-5-yl) phenoxy)ethyl)isoindole-1,3-thione, a novel hydrogen sulfide-releasing phthalimide hybrid, and evaluation of its activity in models of inflammatory pain

Hydrogen sulfide (H₂S) is a gaseous mediator that modulates several physiological and pathological processes. Phthalimide analogues, substances that have the phthalimide ring in the structure, belong to the group of thalidomide analogues. Both H₂S donors and phthalimide analogues exhibit activities in models of inflammation and pain. As molecular hybridization is an important strategy aiming to develop drugs with a better pharmacological profile, in the present study we synthesized a novel H₂S-releasing phthalimide hybrid, 2-(2-(4-thioxo-3H-1,2-dithiole-5-yl) phenoxy)ethyl)isoindole-1,3-thione (PTD-H₂S), and evaluated its activity in models of inflammatory pain in mice. Per os (p.o.) administration of PTD-H₂S (125 or 250 mg/kg) reduced mechanical allodynia induced by carrageenan and lipopolysaccharide. Intraperitoneal (i.p.) administration of PTD-H₂S (25 mg/kg), but not equimolar doses of its precursors 5-(4-hydroxyphenyl)-3H-1,2-dithiole-3-thione (14.2 mg/kg) and 2-phthalimidethanol (12 mg/kg), reduced mechanical allodynia induced by lipopolysaccharide. The antiallodynic effect induced by PTD-H₂S (25 mg/kg, i.p.) was more sustained than that induced by the H₂S donor NaHS (8 mg/kg, i.p.). Previous administration of hydroxocobalamin (300 mg/kg, i.p.) or glibenclamide (40 mg/kg, p.o.) attenuated PTD-H₂S antiallodynic activity. In conclusion, we synthesized a novel H₂S-releasing phthalimide hybrid and demonstrated its activity in models of inflammatory pain. PTD-H₂S activity may be due to H₂S release and activation of ATP-sensitive potassium channels. The demonstration of PTD-H₂S activity in models of pain stimulates further studies aiming to evaluate H₂S-releasing phthalimide hybrids as candidates for analgesic drugs.

Pathophysiology and Outcomes of Endothelium Function in Coronary Microvascular Diseases: A Systematic Review of Randomized Controlled Trials and Multicenter Study

BACKGROUND

Coronary macrovascular disease is a concept that has been well-studied within the literature and has long been the subject of debates surrounding coronary artery bypass grafting (CABG) vs. Percutaneous Coronary Intervention (PCI). ISCHEMIA trial reported no statistical difference in the primary clinical endpoint between initial invasive management and initial conservative management, while in the ORBITA trial PCI did not improve angina frequency score significantly more than placebo, albeit PCI resulted in more patient-reported freedom from angina than placebo. However, these results did not prove the superiority of the PCI against OMT, therefore do not indicate the benefit of PCI vs. the OMT. Please rephrase the sentence. We reviewed the role of different factors responsible for endothelial dysfunction from recent randomized clinical trials (RCTs) and multicentre studies.

METHODS

A detailed search strategy was performed using a dataset that has previously been published. Data of pooled analysis include research articles (human and animal models), CABG, and PCI randomized controlled trials (RCTs). Details of the search strategy and the methods used for data pooling have been published previously and registered with Open-Source Framework.

RESULTS

The roles of nitric oxide (NO), endothelium-derived contracting factors (EDCFs), and vasodilator prostaglandins (e.g., prostacyclin), as well as endothelium-dependent hyperpolarization (EDH) factors, are crucial for the maintenance of vasomotor tone within the coronary vasculature. These homeostatic mechanisms are affected by sheer forces and other several factors that are currently being studied, such as vaping. The role of intracoronary testing is crucial when determining the effects of therapeutic medications with further studies on the horizon.

CONCLUSION

The true impact of coronary microvascular dysfunction (CMD) is perhaps underappreciated, which supports the role of medical therapy in determining outcomes. Ongoing trials are underway to further investigate the role of therapeutic agents in secondary prevention.

Utility of NO and H2S donating platforms in managing COVID-19: Rationale and promise

Viral infections are a continuing global burden on the human population, underscored by the ramifications of the COVID-19 pandemic. Current treatment options and supportive therapies for many viral infections are relatively limited, indicating a need for alternative therapeutic approaches. Virus-induced damage occurs through direct infection of host cells and inflammation-related changes. Severe cases of certain viral infections, including COVID-19, can lead to a hyperinflammatory response termed cytokine storm, resulting in extensive endothelial damage, thrombosis, respiratory failure, and death. Therapies targeting these complications are crucial in addition to antiviral therapies. Nitric oxide and hydrogen sulfide are two endogenous gasotransmitters that have emerged as key signaling molecules with a broad range of antiviral actions in addition to having anti-inflammatory properties and protective functions in the vasculature and respiratory system. The enhancement of endogenous nitric oxide and hydrogen sulfide levels thus holds promise for managing both early-stage and later-stage viral infections, including SARS-CoV-2. Using SARS-CoV-2 as a model for similar viral infections, here we explore the current evidence regarding nitric oxide and hydrogen sulfide's use to limit viral infection, resolve inflammation, and reduce vascular and pulmonary damage.

Vasoplegic Syndrome after Cardiopulmonary Bypass in Cardiovascular Surgery: Pathophysiology and Management in Critical Care

Vasoplegic syndrome (VS) is a common complication following cardiovascular surgery with cardiopulmonary bypass (CPB), and its incidence varies from 5 to 44%. It is defined as a distributive form of shock due to a significant drop in vascular resistance after CPB. Risk factors of VS include heart failure with low ejection fraction, renal failure, pre-operative use of angiotensin-converting enzyme inhibitors, prolonged aortic cross-clamp and left ventricular assist device surgery. The pathophysiology of VS after CPB is multi-factorial. Surgical trauma, exposure to the elements of the CPB circuit and ischemia-reperfusion promote a systemic inflammatory response with the release of cytokines (IL-1β, IL-6, IL-8, and TNF-α) with vasodilating properties, both direct and indirect through the expression of inducible nitric oxide (NO) synthase. The resulting increase in NO production fosters a decrease in vascular resistance and a reduced responsiveness to vasopressor agents. Further mechanisms of vasodilation include the lowering of plasma vasopressin, the desensitization of adrenergic receptors, and the activation of ATP-dependent potassium (KATP) channels. Patients developing VS experience more complications and have increased mortality. Management includes primarily fluid resuscitation and conventional vasopressors (catecholamines and vasopressin), while alternative vasopressors (angiotensin 2, methylene blue, hydroxocobalamin) and anti-inflammatory strategies (corticosteroids) may be used as a rescue therapy in deteriorating patients, albeit with insufficient evidence to provide any strong recommendation. In this review, we present an update of the pathophysiological mechanisms of vasoplegic syndrome complicating CPB and discuss available therapeutic options.