Inhibition of endogenous hydrogen sulfide formation reduces the organ injury caused by endotoxemia

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.

Role of Gasotransmitters in Inflammatory Edema

Significance: Nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2S) are, to date, the identified members of the gasotransmitter family, which consists of gaseous signaling molecules that play central roles in the regulation of a wide variety of physiological and pathophysiological processes, including inflammatory edema. Recent Advances: Recent studies show the potential anti-inflammatory and antiedematogenic effects of NO-, CO-, and H2S-donors in vivo. In general, it has been observed that the therapeutical effects of NO-donors are more relevant when administered at low doses at the onset of the inflammatory process. Regarding CO-donors, their antiedematogenic effects are mainly associated with inhibition of proinflammatory mediators (such as inducible NO synthase [iNOS]-derived NO), and the observed protective effects of H2S-donors seem to be mediated by reducing some proinflammatory enzyme activities. Critical Issues: The most recent investigations focus on the interactions among the gasotransmitters under different pathophysiological conditions. However, the biochemical/pharmacological nature of these interactions is neither general nor fully understood, although specifically dependent on the site where the inflammatory edema occurs. Future Directions: Considering the nature of the involved mechanisms, a deeper knowledge of the interactions among the gasotransmitters is mandatory. In addition, the development of new pharmacological tools, either donors or synthesis inhibitors of the three gasotransmitters, will certainly aid the basic investigations and open new strategies for the therapeutic treatment of inflammatory edema. Antioxid. Redox Signal. 40, 272-291.

Pharmacological Inhibition and Genetic Deletion of Cystathionine Gamma-Lyase in Mice Protects against Organ Injury in Sepsis: A Key Role of Adhesion Molecules on Endothelial Cells

Hydrogen sulfide (H2S), synthesized by cystathionine gamma-lyase (Cth), contributes to the inflammatory response observed in sepsis. This study examines the effect of Cth-derived H2S in adhesion molecules on endothelial cells of vital organs in mice in a cecal ligation puncture (CLP)-induced model of sepsis, using two different and complementary approaches: Cth gene deletion and pharmacological inhibition. Our findings revealed a decreased level of H2S-synthesizing activity (via Cth) in both Cth-/- mice and PAG-treated wild-type (WT) mice following CLP-induced sepsis. Both treatment groups had reduced MPO activity and expression of chemokines (MCP-1 and MIP-2α), adhesion molecules (ICAM-1 and VCAM-1), ERK1/2 phosphorylation, and NF-κB in the liver and lung compared with in CLP-WT mice. Additionally, we found that PAG treatment in Cth-/- mice had no additional effect on the expression of ERK1/2 phosphorylation, NF-κB, or the production of chemokines and adhesion molecules in the liver and lung compared to Cth-/- mice following CLP-induced sepsis. The WT group with sepsis had an increased immunoreactivity of adhesion molecules on endothelial cells in the liver and lung than the WT sham-operated control. The Cth-/-, PAG-treated WT, and Cth-/- groups of mice showed decreased immunoreactivity of adhesion molecules on endothelial cells in the liver and lung following sepsis. Inhibition of H2S production via both approaches reduced adhesion molecule expression on endothelial cells and reduced liver and lung injury in mice with sepsis. In conclusion, this study demonstrates that H2S has an important role in the pathogenesis of sepsis and validates PAG use as a suited tool for investigating the Cth/H2S-signalling axis in sepsis.

Supersulphides provide airway protection in viral and chronic lung diseases

Supersulphides are inorganic and organic sulphides with sulphur catenation with diverse physiological functions. Their synthesis is mainly mediated by mitochondrial cysteinyl-tRNA synthetase (CARS2) that functions as a principal cysteine persulphide synthase (CPERS). Here, we identify protective functions of supersulphides in viral airway infections (influenza and COVID-19), in aged lungs and in chronic lung diseases, including chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF). We develop a method for breath supersulphur-omics and demonstrate that levels of exhaled supersulphides increase in people with COVID-19 infection and in a hamster model of SARS-CoV-2 infection. Lung damage and subsequent lethality that result from oxidative stress and inflammation in mouse models of COPD, IPF, and ageing were mitigated by endogenous supersulphides production by CARS2/CPERS or exogenous administration of the supersulphide donor glutathione trisulphide. We revealed a protective role of supersulphides in airways with various viral or chronic insults and demonstrated the potential of targeting supersulphides in lung disease.

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.

Mitochondria-targeted cyclometalated iridium (III) complex for H2S-responsive intracellular redox regulation as potent photo-oxidation anticancer agent

Owing to the safety and low toxicity, photodynamic therapy (PDT) for cancer treatment has received extensive attention. However, the excess H₂S in cancer cells reduces the PDT efficiency, because H₂S indirectly depletes the reactive oxygen species (ROS). To improve anticancer efficiency, a mitochondria-targeted iridium(III) complex Ir-MMB has been developed as H₂S consumer and photo-oxidation anticancer agent. On the one hand, complex Ir-MMB can consume H₂S with sensitive phosphorescence turn-on, which has been successfully applied to exogenous and endogenous H₂S response imaging in living cells. On the other hand, Ir-MMB can enhance its anticancer activity and cause photo-oxidation damage via catalyzing the oxidation of reduced form of nicotinamide-adenine dinucleotide (NADH) to NAD⁺ and producing H₂O₂ under light, and ultimately results in cell apoptosis through mitochondrial depolarization and ROS production.

Heart and kidney H2S production is reduced in hypertensive and older rats

The prevalence of hypertension increases with age, but the mechanisms linking this phenomenon are not well understood. Hydrogen sulfide (H₂S) may be involved in this process, as it plays a role in the cardiovascular system, affecting blood pressure and heart and kidney functions. The aim of this study was to evaluate the influence of hypertension and aging on sulfur-containing compounds metabolism in the hearts and kidneys of Wistar Kyoto (WKY) and Spontaneously Hypertensive Rats (SHR) of different age groups. We determined the expression and activity of four enzymes participating in H₂S production: cystathionine beta-synthase (CBS), cystathionine gamma-lyase (CTH), 3-mercaptopyruvate sulfurtransferase (MPST), and thiosulfate sulfurtransferase (TST). The levels of reduced/oxidized glutathione, cysteine, cystine, and cystathionine, and the ability of tissues to form hydrogen sulfide were also investigated. Tissues obtained from younger WKY rats produced the highest amounts of H₂S. The effect of hypertension on the metabolism of sulfur-containing compounds was manifested by a decrease in sulfane sulfur concentrations in heart homogenates and a decrease in CTH activity in the kidneys. The hearts and kidneys of older WKY rats were characterized by lower MPST or CTH gene expression, respectively, compared to younger animals. Our study demonstrates that hypertension and aging influence cardiac and renal sulfur-containing compounds metabolism and reduce H₂S production. Furthermore, we showed that MPST plays a major role in the production of hydrogen sulfide in the heart and CTH in the kidneys of rats.

CBS-H2S axis preserves the intestinal barrier function by inhibiting COX-2 through sulfhydrating human antigen R in colitis

INTRODUCTION

Lipopolysaccharide (LPS) causes lesions of the epithelial barrier, which allows translocation of pathogens from the intestinal lumen to the host's circulation. Hydrogen sulfide (H₂S) regulates multiple physiological and pathological processes in colonic epithelial tissue, and CBS-H₂S axis involved in multiple gastrointestinal disorder. However, the mechanism underlying the effect of the CBS-H₂S axis on the intestinal and systemic inflammation in colitis remains to be illustrated.

OBJECTIVES

To investigate the effect of CBS-H₂S axis on the intestinal and systematic inflammation related injuries in LPS induced colitis and the underlying mechanisms.

METHODS

Wild type and CBS^-/+ mice were used to evaluate the effect of endogenous and exogenous H₂S on LPS-induced colitis in vivo. Cytokine quantitative antibody array, western blot and real-time PCR were applied to detect the key cytokines in the mechanism of action. Biotin switch of S-sulfhydration, CRISPR/Cas9 mediated knockout, immunofluorescence and ActD chase assay were used in the in vitro experiment to further clarify the molecular mechanisms.

RESULTS

H₂S significantly alleviated the symptoms of LPS-induced colitis in vivo and attenuated the increase of COX-2 expression. The sulfhydrated HuR increased when CBS express normally or GYY4137 was administered. While after knocking kown CBS, the expression of COX-2 in mice colon increased significantly, and the sulfhydration level of HuR decreased. The results in vitro illustrated that HuR can increase the stability of COX-2 mRNA, and the decrease of COX-2 were due to increased sulfhydration of HuR rather than the reduction of total HuR levels.

CONCLUSION

These results indicated that CBS-H₂S axis played an important role in protecting intestinal barrier function in colitis. CBS-H₂S axis increases the sulfhydration level of HuR, by which reduces the binding of HuR with COX-2 mRNA and inhibited the expression of COX-2.

Effects of Exogenous Hydrogen Sulfide in the Hypothalamic Paraventricular Nucleus on Gastric Function in Rats

Background: Hydrogen sulfide (H₂S) is a new type of gas neurotransmitter discovered in recent years. It plays an important role in various physiological activities. The hypothalamus paraventricular nucleus (PVN) is an important nucleus that regulates gastric function. This study aimed to clarify the role of H₂S in the paraventricular nucleus of the hypothalamus on the gastric function of rats.

Methods: An immunofluorescence histochemistry double-labelling technique was used to determine whether cystathionine-beta-synthase (CBS) and c-Fos neurons are involved in PVN stress. Through microinjection of different concentrations of NaHS, physiological saline (PS), D-2-Amino-5-phosphonovaleric acid (D-AP5), and pyrrolidine dithiocarbamate (PDTC), we observed gastric motility and gastric acid secretion.

Results: c-Fos and CBS co-expressed the most positive neurons after 1 h of restraint and immersion, followed by 3 h, and the least was at 0 h. After injection of different concentrations of NaHS into the PVN, gastric motility and gastric acid secretion in rats were significantly inhibited and promoted, respectively (p < 0.01); however, injection of normal saline, D-AP5, and PDTC did not cause any significant change (p > 0.05). The suppressive effect of NaHS on gastrointestinal motility and the promotional effect of NaHS on gastric acid secretion could be prevented by D-AP5, a specific N-methyl-D-aspartic acid (NMDA) receptor antagonist, and PDTC, an NF-κB inhibitor.

Conclusion: There are neurons co-expressing CBS and c-Fos in the PVN, and the injection of NaHS into the PVN can inhibit gastric motility and promote gastric acid secretion in rats. This effect may be mediated by NMDA receptors and the NF-κB signalling pathway.

Hydrogen Sulfide: An Emerging Precision Strategy for Gas Therapy

Advances in nanotechnology have enabled the rapid development of stimuli-responsive therapeutic nanomaterials for precision gas therapy. Hydrogen sulfide (H₂ S) is a significant gaseous signaling molecule with intrinsic biochemical properties, which exerts its various physiological effects under both normal and pathological conditions. Various nanomaterials with H₂ S-responsive properties, as new-generation therapeutic agents, are explored to guide therapeutic behaviors in biological milieu. The cross disciplinary of H₂ S is an emerging scientific hotspot that studies the chemical properties, biological mechanisms, and therapeutic effects of H₂ S. This review summarizes the state-of-art research on H₂ S-related nanomedicines. In particular, recent advances in H₂ S therapeutics for cancer, such as H₂ S-mediated gas therapy and H₂ S-related synergistic therapies (combined with chemotherapy, photodynamic therapy, photothermal therapy, and chemodynamic therapy) are highlighted. Versatile imaging techniques for real-time monitoring H₂ S during biological diagnosis are reviewed. Finally, the biosafety issues, current challenges, and potential possibilities in the evolution of H₂ S-based therapy that facilitate clinical translation to patients are discussed.

Profiling Cystathionine β/γ-Lyase in Complex Biosamples Using Novel Activatable Fluorogens

Cystathionine lyase, the key enzyme in transsulfuration and reverse transsulfuration pathways, is involved in a wide array of physiological and pathophysiological processes in both mammals and nonmammals. Though the biological significance of the hydrogen sulfide/cystathionine lyase system in disease states is extensively discussed, the absence of molecular methods for direct monitoring of cystathionine lyase in complex biosamples renders the result unreliable and perplexing. Here, we present the first attempt at designing and developing effective activatable fluorescent probes for cystathionine lyase based on the naphthylamide scaffold. CBLP and CSEP were designed based on the catalytic preference of cystathionine β-lyase (CBL) and cystathionine γ-lyase (CSE). Briefly, incorporation of cysteine/homocysteine as the recognition moiety and a carbamate ethyl sulfide group as a self-immolated linker proved to be an effective strategy for cystathionine lyase fluorescence reporting. CBLP exhibits high selectivity and sensitivity in vitro in semiquantifying CBL levels in roots of wild-type Arabidopsis thaliana and cbl mutants (cbl knockout: SALK_014740C, overexpressed: OE-CBL). Meanwhile, CSEP successfully detected CSE levels in HCC-LM3 cells, zebrafish models, and upregulated CSE in frozen section slides from the liver tissue of cecal ligation and puncture (CLP)-induced septic rats, which was also validated by Western blotting and immunohistochemical analysis. In summary, the practical design strategy facilitates profiling of cystathionine lyase activity in biological processes. It may pave the way for the development of accurate and efficient methods for the direct estimation of cystathionine lyase.

Mitochondria-targeted phosphorescent cyclometalated iridium(III) complex for bioimaging of H2S

The selective visualization of H₂S in mitochondria is still a challenge, but it correlates closely with mitochondrial damage and some related diseases. In this work, a cyclometalated iridium complex Ir-DNB, [Ir(ppy)₂(N^N)](PF₆) (ppy = 2-phenylpyridine, N^N = (4'-methyl-[2,2'-bipyridin]-4-yl)methyl 2-((2,4-dinitrophenyl) thio)benzoate) has been explored for the detection of mitochondrial H₂S. Adding H₂S to a solution of complex Ir-DNB results in a clearly luminescence enhancement, and displays high selectivity and sensitivity. Moreover, this complex displays negligible toxicity and good mitochondrial localization to HeLa cells, and has also been successfully used for endogenous and exogenous H₂S imaging in vitro and in vivo.

Hydrogen Sulfide and the Immune System

Hydrogen sulfide (H₂S) is the "third gasotransmitter" recognized alongside nitric oxide (NO) and carbon monoxide (CO). H₂S exhibits an array of biological effects in mammalian cells as revealed by studies showing important roles in the cardiovascular system, in cell signalling processes, post-translational modifications and in the immune system. Regarding the latter, using pharmacological and genetic approaches scientists have shown this molecule to have both pro- and anti-inflammatory effects in mammalian systems. The anti-inflammatory effects of H₂S appeared to be due to its inhibitory action on the nuclear factor kappa beta signalling pathway; NF-kB representing a transcription factor involved in the regulation pro-inflammatory mediators like nitric oxide, prostaglandins, and cytokines. In contrast, results from several animal model describe a more complicated picture and report on pro-inflammatory effects linked to exposure to this molecule; linked to dosage used and point of administration of this molecule. Overall, roles for H₂S in several inflammatory diseases spanning arthritis, atherosclerosis, sepsis, and asthma have been described by researchers. In light this work fascinating research, this chapter will cover H₂S biology and its many roles in the immune system.

Hydrogen Sulfide in Inflammation: A Novel Mediator and Therapeutic Target

Significance: Inflammation is a normal response to injury, but uncontrolled inflammation can lead to several diseases. In recent years, research has shown endogenously synthesized hydrogen sulfide (H₂S) to be a novel mediator of inflammation. This review summarizes the current understanding and recent advances of H₂S role with respect to inflammation in different diseases. Recent Advances: Promising early results from clinical studies suggest an important role of H₂S in human inflammatory disease. Critical Issues: Defining the precise mechanism by which H₂S contributes to inflammation is a complex challenge, and there is active ongoing research that is focused on addressing this question. Most of this work has been conducted on animal models of human disease and isolated/cultured cells, and its translation to the clinic is another challenge in the area of H₂S research. Future Directions: Defining the mechanism by which H₂S acts as an inflammatory mediator will help us better understand different inflammatory diseases and help develop novel therapeutic approaches for these diseases.

Hypertension and Aging Affect Liver Sulfur Metabolism in Rats

Hypertension and age are key risk factors for cardiovascular morbidity and mortality. Hydrogen sulfide (H2S), a gaseous transmitter, contributes significantly to regulating arterial blood pressure and aging processes. This study evaluated the effects of hypertension and aging on the hepatic metabolism of sulfur-containing compounds, the activity of the enzymes involved in sulfur homeostasis, and the liver's ability to generate H2S. Livers isolated from 16- and 60-week-old normotensive Wistar Kyoto rats (WKY) and Spontaneously Hypertensive Rats (SHR) were used to evaluate gene expression using RT-PCR, and the activity of enzymes participating in H2S metabolism, including thiosulfate sulfurtransferase (rhodanese; TST), cystathionine gamma-lyase (CTH), and 3-mercaptopyruvate sulfurtransferase (MPST). The levels of cysteine, cystine, reduced and oxidized glutathione were measured using RP-HPLC. SHR livers from both age groups showed a higher capacity to generate H2S than livers from WKY. The gene expression and activity of enzymes involved in sulfur metabolism differed between WKY and SHR, and between the age groups. For example, 16-week-old SHR had significantly higher activity of TST than 16-week-old WKY. Furthermore, differences between younger and older WKY rats in the expression and/or activity of TST and MPST were present. In conclusion, our study shows that arterial hypertension and aging affect hepatic sulfur metabolism and H2S production in rats. These findings pave the way for interventional studies evaluating a potential causal relation between liver sulfur metabolism, hypertension and aging.

Hydrogen sulfide as a novel biomarker of asthma and chronic obstructive pulmonary disease

Hydrogen sulfide (H₂S) has recently been recognised as the third important gas-signalling molecule, besides nitric oxide and carbon monoxide. H₂S has been reported to be produced by many cell types in mammalian tissues and organs throughout the actions of H₂S-generating enzymes or redox reactions between the oxidation of glucose and element of sulfur. Although the pathological role of H₂S has not yet been fully elucidated, accumulative data suggest that H₂S may have biphasic effects. Briefly, it mainly has anti-inflammatory and antioxidant roles, although it can also have pro-inflammatory effects under certain conditions where rapid release of H₂S in tissues occur, such as sepsis. To date, there have been several clinical studies published on H₂S in respiratory disorders, including asthma and chronic obstructive pulmonary disease (COPD). According to previous studies, H₂S is detectable in serum, sputum, and exhaled breath, although a gold standard method for detection has not yet been established. In asthma and COPD, H₂S levels in serum and sputum can vary depending on the underlying conditions such as an acute exacerbation. Furthermore, sputum H₂S in particular correlates with sputum neutrophils and the degree of airflow limitation, indicating that H₂S has potential as a novel promising biomarker for neutrophilic airway inflammation for predicting current control state as well as future risks of asthma. In the future, concurrent measures of H₂S with conventional inflammatory biomarkers (fractional exhaled nitric oxide, eosinophils etc) may provide more useful information regarding the identification of inflammatory phenotypes of asthma and COPD for personalised treatment.

Effects of gut microbiota on atherosclerosis through hydrogen sulfide

Cardiovascular diseases are the leading cause of death and morbidity worldwide. Atherosclerotic cardiovascular disease (ASCVD) is affected by both environmental and genetic factors. Microenvironmental disorders of the human gut flora are associated with a variety of health problems, not only gastrointestinal diseases, such as inflammatory bowel disease, but also extralintestinal organs. Hydrogen sulfide (H₂S) is the third gas signaling molecule other than nitric oxide and carbon monoxide. In the cardiovascular system, H₂S plays important roles in the regulation of blood pressure, angiogenesis, smooth muscle cell proliferation and apoptosis, anti-oxidative stress, cardiac functions. This review is aiming to explore the potential role of gut microbiota in the development of atherosclerosis through hydrogen sulfide production as a novel therapeutic direction for atherosclerosis.

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

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

Enzymatic Regulation and Biological Functions of Reactive Cysteine Persulfides and Polysulfides

Cysteine persulfide (CysSSH) and cysteine polysulfides (CysSS_nH, n > 1) are cysteine derivatives that have sulfane sulfur atoms bound to cysteine thiol. Advances in analytical methods that detect and quantify persulfides and polysulfides have shown that CysSSH and related species such as glutathione persulfide occur physiologically and are prevalent in prokaryotes, eukaryotes, and mammals in vivo. The chemical properties and abundance of these compounds suggest a central role for reactive persulfides in cell-regulatory processes. CysSSH and related species have been suggested to act as powerful antioxidants and cellular protectants and may serve as redox signaling intermediates. It was recently shown that cysteinyl-tRNA synthetase (CARS) is a new cysteine persulfide synthase. In addition, we discovered that CARS is involved in protein polysulfidation that is coupled with translation. Mitochondrial activity in biogenesis and bioenergetics is supported and upregulated by CysSSH derived from mitochondrial CARS. In this review article, we discuss the mechanisms of the biosynthesis of CysSSH and related persulfide species, with a particular focus on the roles of CARS. We also review the antioxidative and anti-inflammatory actions of persulfides.

Hydrogen sulfide: An endogenous regulator of the immune system

Hydrogen sulfide (H₂S) is now recognized as an endogenous signaling gasotransmitter in mammals. It is produced by mammalian cells and tissues by various enzymes - predominantly cystathionine β-synthase (CBS), cystathionine γ-lyase (CSE) and 3-mercaptopyruvate sulfurtransferase (3-MST) - but part of the H₂S is produced by the intestinal microbiota (colonic H₂S-producing bacteria). Here we summarize the available information on the production and functional role of H₂S in the various cell types typically associated with innate immunity (neutrophils, macrophages, dendritic cells, natural killer cells, mast cells, basophils, eosinophils) and adaptive immunity (T and B lymphocytes) under normal conditions and as it relates to the development of various inflammatory and immune diseases. Special attention is paid to the physiological and the pathophysiological aspects of the oral cavity and the colon, where the immune cells and the parenchymal cells are exposed to a special "H₂S environment" due to bacterial H₂S production. H₂S has many cellular and molecular targets. Immune cells are "surrounded" by a "cloud" of H₂S, as a result of endogenous H₂S production and exogenous production from the surrounding parenchymal cells, which, in turn, importantly regulates their viability and function. Downregulation of endogenous H₂S producing enzymes in various diseases, or genetic defects in H₂S biosynthetic enzyme systems either lead to the development of spontaneous autoimmune disease or accelerate the onset and worsen the severity of various immune-mediated diseases (e.g. autoimmune rheumatoid arthritis or asthma). Low, regulated amounts of H₂S, when therapeutically delivered by small molecule donors, improve the function of various immune cells, and protect them against dysfunction induced by various noxious stimuli (e.g. reactive oxygen species or oxidized LDL). These effects of H₂S contribute to the maintenance of immune functions, can stimulate antimicrobial defenses and can exert anti-inflammatory therapeutic effects in various diseases.

Immune Dysfunction in Uremia 2020

Cardiovascular disease and infections are major causes for the high incidence of morbidity and mortality of patients with chronic kidney disease. Both complications are directly or indirectly associated with disturbed functions or altered apoptotic rates of polymorphonuclear leukocytes, monocytes, lymphocytes, and dendritic cells. Normal responses of immune cells can be reduced, leading to infectious diseases or pre-activated/primed, giving rise to inflammation and subsequently to cardiovascular disease. This review summarizes the impact of kidney dysfunction on the immune system. Renal failure results in disturbed renal metabolic activities with reduced renin, erythropoietin, and vitamin D production, which adversely affects the immune system. Decreased kidney function also leads to reduced glomerular filtration and the retention of uremic toxins. A large number of uremic toxins with detrimental effects on immune cells have been identified. Besides small water-soluble and protein-bound compounds originating from the intestinal microbiome, several molecules in the middle molecular range, e.g., immunoglobulin light chains, retinol-binding protein, the neuropeptides Met-enkephalin and neuropeptide Y, endothelin-1, and the adipokines leptin and resistin, adversely affect immune cells. Posttranslational modifications such as carbamoylation, advanced glycation products, and oxidative modifications contribute to uremic toxicity. Furthermore, high-density lipoprotein from uremic patients has an altered protein profile and thereby loses its anti-inflammatory properties.

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

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

Hydrogen sulfide biosynthesis is impaired in the osteoarthritic joint

Osteoarthritis (OA) is the most common form of arthritis and it is a leading cause of disability in the elderly. Its complete etiology is not known although there are several metabolic, genetic, epigenetic, and local contributing factors involved. At the moment, there is no cure for this pathology and treatment alternatives to retard or stop its progression are intensively being sought. Hydrogen sulfide (H₂S) is a small gaseous molecule and is present in sulfurous mineral waters as its active component. Data from recent clinical trials shows that balneotherapy (immersion in mineral and/or thermal waters from natural springs) in sulfurous waters can improve OA symptoms, in particular, pain and function. Yet, the underlying mechanisms are poorly known. Hydrogen sulfide is also considered, with NO and CO, an endogenous signaling gasotransmitter. It is synthesized endogenously with the help of three enzymes, cystathionine gamma-lyase (CTH), cystathionine beta-synthase (CBS), and 3-mercaptopyruvate sulfurtransferase (3-MPST). Here, the expression of these three enzymes was demonstrated by quantitative real-time polymerase chain reaction (qRT-PCR) and their protein abundance [by immunohistochemistry and Western blot (WB)] in human articular cartilage. No significant differences were found in CBS or CTH expression or abundance, but mRNA and protein levels of 3-MPST were significantly reduced in cartilage form OA donors. Also, the biosynthesis of H₂S from OA cartilage, measured with a specific microelectrode, was significantly lower than in OA-free tissue. Yet, no differences were found in H₂S concentration in serum from OA patients and OA-free donors. The current results suggest that reduced levels of the mitochondrial enzyme 3-MPST in OA cartilage might be, at least in part, responsible for a reduction in H₂S biosynthesis in this tissue and that impaired H₂S biosynthesis in the joint might be a contributing factor to OA. This could contribute to explain why exogenous supplementation of H₂S, for instance with sulfurous thermal water, has positive effects in OA patients.

Protective effects of pharmacological agents against aminoglycoside-induced nephrotoxicity: A systematic review

Introduction: Aminoglycosides have been long used for antibacterial treatment and are still commonly used in clinical practice. Despite their extensive application and positive effects, drug-related toxicity is considered as the main obstacle for aminoglycosides. Aminoglycosides induce nephrotoxicity through the endocytosis and accumulation of the antibiotics in the epithelial cells of proximal tubule. Most importantly, however, a number of pharmacological agents were demonstrated to have protective activities against nephrotoxicity in experimental animals.Areas covered: In the present systematic review, the authors provide and discuss the mechanisms and epidemiological features of aminoglycoside-induced nephrotoxicity, and focus mainly on recent discoveries and key features of pharmacological interventions. In total, 39 articles were included in this review.Expert opinion: The majority of studies investigated gentamicin-induced nephrotoxicity in animal models. Antioxidants, chemicals, synthetic drugs, hormones, vitamins, and minerals showed potential values to prevent gentamicin-induced nephrotoxicity. Indicators used to evaluate the effectiveness of nephroprotection included antioxidative indexes, inflammatory responses, and apoptotic markers. Among the nephroprotective agents studied, herbs and natural antioxidant agents showed excellent potential to provide a protective strategy against gentamicin-induced nephrotoxicity.

Hydrogen sulfide impacts on inflammation-induced adipocyte dysfunction

A dual role of hydrogen sulfide (H₂S) in inflammation is well-reported and recent studies demonstrated adipogenic effects of H₂S in 3T3-L1 cells. Here, we aimed to investigate the effects of H₂S on adipocyte differentiation and inflammation. H₂S concentration in 3T3-L1 culture media was increased during adipocyte differentiation in parallel to adipogenic and Cth gene expression, and its inhibition using DL-Propargyl Glycine (PPG) impaired 3T3-L1 differentiation. GYY4137 and Na₂S administration only in the first or in the last stage of adipocyte differentiation resulted in a significant increased expression of adipogenic genes. However, when GYY4137 or Na₂S were administrated during all process no significant effects on adipogenic gene expression were found, suggesting that excessive H₂S administration might exert negative effects on adipogenesis. In fact, continuous addition of Na₂S, which resulted in Na₂S excess, inhibited adipogenesis, whereas time-expired Na₂S had no effect. In inflammatory conditions, GYY4137, but not Na₂S, administration attenuated the negative effects of inflammation on adipogenesis and insulin signaling-related gene expression during adipocyte differentiation. In inflamed adipocytes, Na₂S administration enhanced the negative effects of inflammatory process. Altogether these data showed that slow-releasing H₂S improved adipocyte differentiation in inflammatory conditions, and that H₂S proadipogenic effects depend on dose, donor and exposure time.

Hydrogen Sulfide Affects Radical Formation in the Hippocampus of LPS Treated Rats and the Effect of Antipsychotics on Hydrogen Sulfide Forming Enzymes in Human Cell Lines

Objectives: Psychiatric disorders, such as schizophrenia and other neuroinflammatory diseases are accompanied by an increase in the oxidative stress and changes in the immune system and in the metabolic, hormonal and neurological components of the central nervous system (CNS). Hydrogen sulfide (H2S) is a gaseous molecule that is endogenously produced in the peripheral and central nervous system through cysteine by the following major H2S producing enzymes in the brain: cystathionine-γlyase (CSE), cystathionine ß-synthase (CBS) and 3-mercaptopyruvate sulfurtransferase (MPST). The physiological effects of H2S are broad, with antioxidative properties being a major role in the body. The aims of our investigation were to analyze the central nervous antioxidant, metabolic and neuronal effects in the hippocampus of the rat after inflammatory peripheral lipopolysaccharide (LPS) treatment; and to examine the effects of antipsychotics on the expression of these enzymes in human cell lines. Material and Methods: Male Lewis rats (250 g) received an i.p. LPS injection (1 mg/kg) 24 h before microdialysis experiments. Conscious rats were infused via these probes (1.5 μl/min) with a radical scavenger 1-hydroxy-3-methoxycarbonyl-2,2,5,5-tetramethylpyrrolidine (CMH) in Krebs-Ringer solution. Sodiumhydrogensulfide (NaHS, 10 μg/min) was infused after a 2- h baseline for 1 h. Corticosterone, glutamate, glucose and lactate were measured by Elisa. Reactive oxygen species (ROS) were detected by electron spin resonance spectroscopy (ESR). The impact of the antipsychotics haloperidol, clozapine, olanzapine and risperidone on the expression of genes encoding the key enzymes of H2S synthesis was studied at the human neuroblastoma SH-SY5Y and monocytic U-937 cell lines. The cells were incubated for 24 h with 30 μM antipsychotic following which mRNA levels were measured by polymerase chain reaction. Results: Microdialysate glucose and lactate levels dramatically increased in the hippocampus of LPS untreated rats by local application of NaHS. By contrast, in the LPS pretreated rats, there was no effect of NaHS infusion on glucose but a further significant increase in microdialysate lactate was found. It was LPS pretreatment alone that particularly enhanced lactate levels. There was a marked increase in hippocampal microdialysate glutamate levels after local NaHS infusion in LPS untreated animals. In LPS treated rats, no change was observed by NaHS, but LPS itself had the strongest effect on microdialysate glutamate levels. Microdialysate corticosterone levels were reduced by NaHS in both LPS pretreated and untreated rats. The formation of free radicals in the hippocampus significantly reduced in LPS pretreated rats, while in LPS untreated rats a significant increase was observed after NaHS infusion. In human SH-SY5Y and U-937 cells, all three major enzymes of H2S-Synthesis, namely cystathionine-γ-lyase, cystathione ß-synthase and 3-mercaptopyruvate sulfurtransferase, could be detected by PCR. The antipsychotics haloperidol, clozapine, olanzapine and risperidone affected all three enzymes in different ways; with haloperidol and risperidone showing major effects that led to reductions in CBS or CSE expression. Discussion: The local application of NaHS in the hippocampus of the rat strongly affected glucose, lactate and glutamate release. Contrastingly, in LPS pretreated rats, a decreased radical formation was the only effect found. H2S synthetizing enzymes may be involved in antipsychotic mechanisms, although no clear common mechanism could be found.

Gasotransmitters and the immune system: Mode of action and novel therapeutic targets

Gasotransmitters are a group of gaseous molecules, with pleiotropic biological functions. These molecules include nitric oxide (NO), hydrogen sulfide (H₂S), and carbon monoxide (CO). Abnormal production and metabolism of these molecules have been observed in several pathological conditions. The understanding of the role of gasotransmitters in the immune system has grown significantly in the past years, and independent studies have shed light on the effect of exogenous and endogenous gasotransmitters on immune responses. Moreover, encouraging results come from the efficacy of NO-, CO- and H₂S -donors in preclinical animal models of autoimmune, acute and chronic inflammatory diseases. To date, data on the influence of gasotransmitters in immunity and immunopathology are often scattered and partial, and the scarcity of clinical trials using NO-, CO- and H₂S -donors, reveals that more effort is warranted. This review focuses on the role of gasotransmitters in the immune system and covers the evidences on the possible use of gasotransmitters for the treatment of inflammatory conditions.

Sputum-to-serum hydrogen sulphide ratio as a novel biomarker of predicting future risks of asthma exacerbation

BACKGROUND

Increased level of hydrogen sulphide (H₂ S) in sputum is reported to be a new biomarker of neutrophilic airway inflammation in chronic airway disorders. However, the relationship between H₂ S and disease activity remains unclear.

OBJECTIVE

We investigated whether H₂ S levels could vary during different conditions in asthma.

METHOD

H₂ S levels in sputum and serum were measured using a sulphide-sensitive electrode in 47 stable asthmatic subjects (S-BA), 21 uncontrolled asthmatic subjects (UC-BA), 26 asthmatic subjects with acute exacerbation (AE-BA) and 15 healthy subjects. Of these, H₂ S levels during stable, as well as exacerbation states, were obtained in 13 asthmatic subjects.

RESULTS

Sputum H₂ S levels were significantly higher in the AE-BA subjects compared to the UC-BA and healthy subjects (P < .05). However, serum H₂ S levels in the AE-BA subjects were lower than in the S-BA subjects (P < .001) and similar to those in healthy subjects. Thus, the sputum-to-serum ratio of H₂ S (H₂ S ratio) in the AE-BA subjects was significantly higher than in the S-BA, UC-BA and healthy subjects (P < .05). Among all subjects, sputum H₂ S levels showed a trend to decrease with FEV₁ %predicted and significantly positive correlations with sputum neutrophils (%), sputum IL-8 and serum IL-8. A multiple linear regression analysis showed that sputum H₂ S was independently associated with increased sputum neutrophils (%) and decreased FEV₁ %predicted (P < .05). The cut-off level of H₂ S ratio to indicate an exacerbation was ≥0.34 (area under the curve; 0.88, with a sensitivity of 81.8% and specificity of 72.7%, P < .001). Furthermore, half of the asthmatic subjects with H₂ S ratios higher than the cut-off level experienced asthma exacerbations over the following 3 months after enrolment.

CONCLUSIONS

The H₂ S ratio may provide useful information on predicting future risks of asthma exacerbation, as well as on obstructive neutrophilic airway inflammation as one of the non-Th2 biomarkers, in asthma.

Resolution of inflammation pathways in preeclampsia-a narrative review

Preeclampsia (PE) is one of the leading causes of maternal morbidity and mortality worldwide. This disease is believed to occur in two stages with placental dysfunction in early pregnancy leading to maternal clinical findings after 20 weeks of gestation, as consequence of systemic inflammation, oxidative stress, and endothelial dysfunction. Much evidence suggests that PE women display an overshooting inflammatory response throughout pregnancy due to an unbalanced regulation of innate and adaptive immune responses. Recently, it has been suggested that dysregulation of endogenous protective pathways might be associated with PE etiopathogenesis. Resolution of inflammation is an active process coordinated by mediators from diverse nature that regulate key cellular events to restore tissue homeostasis. Inadequate or insufficient resolution of inflammation is believed to play an important role in the development of chronic inflammatory diseases, like PE. In this narrative review, we discuss possible pro-resolution pathways that might be compromised in PE women, which could be targets to novel therapeutic strategies in this disease.

Endogenous peripheral hydrogen sulfide is propyretic: its permissive role in brown adipose tissue thermogenesis in rats

NEW FINDINGS

What is the central question of this study? In fever, the most striking response in the acute phase reaction of systemic inflammation, plasma H₂ S concentration increases. However, the role of endogenous peripheral H₂ S in fever is unknown. What is the main finding and its importance? Endogenous peripheral H₂ S is permissive for increased brown adipose tissue thermogenesis to maintain thermal homeostasis in cold environments as well as to mount fever. This finding expands the physiological role of the gaseous modulator as a key regulator of thermal control in health (thermal homeostasis) and disease (fever in systemic inflammation).

ABSTRACT

In recent years, hydrogen sulfide (H₂ S) has been reported as a gaseous modulator acting in several tissues in health and disease. In animal models of systemic inflammation, the plasma H₂ S concentration increases in response to endotoxin (bacterial lipopolysaccharide, LPS). The most striking response in the acute phase reaction of systemic inflammation is fever, but we found no reports of the peripheral action of H₂ S on this thermoregulatory response. We aimed at investigating whether endogenous systemic H₂ S modulates LPS-induced fever. A temperature datalogger capsule was inserted in the abdominal cavity of male Wistar rats (220-270 g) to record body core temperature. These animals received an i.p. injection of a systemic H₂ S inhibitor (propargylglycine; 50 or 75 mg kg^-1 ), immediately followed by an i.p. injection of LPS (50 or 2500 μg kg^-1 ), and were exposed to different ambient temperatures (16, 22 or 27°C). At 22°C, but not at 27°C, propargylglycine at 75 mg kg^-1 significantly attenuated (P < 0.0001) the fever induced by LPS (50 μg kg^-1 ), indicating a modulatory (permissive) action of endogenous peripheral H₂ S on brown adipose tissue (BAT) thermogenesis. Evidence on the modulatory role of peripheral H₂ S in BAT thermogenesis was strengthened when we discarded (i) the possible influence of the gas on febrigenic signalling (when measuring plasma cytokines), and (ii) its interaction with the nitric oxide pathway, and mainly when (iii) we carried out physiological and pharmacological activations of BAT. Endogenous peripheral H₂ S modulates (permits) BAT activity not only in fever but also during maintenance of thermal homeostasis in cold environments.

International Union of Basic and Clinical Pharmacology. CII: Pharmacological Modulation of H2S Levels: H2S Donors and H2S Biosynthesis Inhibitors

Over the last decade, hydrogen sulfide (H2S) has emerged as an important endogenous gasotransmitter in mammalian cells and tissues. Similar to the previously characterized gasotransmitters nitric oxide and carbon monoxide, H2S is produced by various enzymatic reactions and regulates a host of physiologic and pathophysiological processes in various cells and tissues. H2S levels are decreased in a number of conditions (e.g., diabetes mellitus, ischemia, and aging) and are increased in other states (e.g., inflammation, critical illness, and cancer). Over the last decades, multiple approaches have been identified for the therapeutic exploitation of H2S, either based on H2S donation or inhibition of H2S biosynthesis. H2S donation can be achieved through the inhalation of H2S gas and/or the parenteral or enteral administration of so-called fast-releasing H2S donors (salts of H2S such as NaHS and Na2S) or slow-releasing H2S donors (GYY4137 being the prototypical compound used in hundreds of studies in vitro and in vivo). Recent work also identifies various donors with regulated H2S release profiles, including oxidant-triggered donors, pH-dependent donors, esterase-activated donors, and organelle-targeted (e.g., mitochondrial) compounds. There are also approaches where existing, clinically approved drugs of various classes (e.g., nonsteroidal anti-inflammatories) are coupled with H2S-donating groups (the most advanced compound in clinical trials is ATB-346, an H2S-donating derivative of the non-steroidal anti-inflammatory compound naproxen). For pharmacological inhibition of H2S synthesis, there are now several small molecule compounds targeting each of the three H2S-producing enzymes cystathionine-β-synthase (CBS), cystathionine-γ-lyase, and 3-mercaptopyruvate sulfurtransferase. Although many of these compounds have their limitations (potency, selectivity), these molecules, especially in combination with genetic approaches, can be instrumental for the delineation of the biologic processes involving endogenous H2S production. Moreover, some of these compounds (e.g., cell-permeable prodrugs of the CBS inhibitor aminooxyacetate, or benserazide, a potentially repurposable CBS inhibitor) may serve as starting points for future clinical translation. The present article overviews the currently known H2S donors and H2S biosynthesis inhibitors, delineates their mode of action, and offers examples for their biologic effects and potential therapeutic utility.

Hydrogen sulfide prevents diaphragm weakness in cecal ligation puncture-induced sepsis by preservation of mitochondrial function

Mitochondrial dysfunction plays an important role in the pathogenesis of diaphragm weakness during sepsis. Recently, hydrogen sulfide (H₂S), a gaseous transmitter endogenously generated by cystathionine-β-synthase (CBS), cystathionine-γ-lyase (CSE) and 3-mercaptopyruvate sulfurtransferase (3-MST), is found to improve mitochondrial function. The present study aimed to examine whether H₂S synthases are expressed in the diaphragm, and investigated the effect of H₂S donor in sepsis-induced diaphragm weakness and its relationship with mitochondrial function. Immunohistochemical staining of the rat diaphragm revealed that positive immunoreactivity for CBS, CSE as well as 3-MST was predominately localized to muscle cells. Using a cecal ligation and puncture (CLP)-induced sepsis model, it was found that CBS and CSE, but not 3-MST, was significantly down-regulated in the diaphragm at 24 h post-CLP compared with sham group. To determine the effect of H₂S on sepsis-induced diaphragm weakness, H₂S donor NaHS was intraperitoneally administered 30 min after CLP operation. NaHS at a dose of 50 μmol/kg significantly decreased the mortality in septic rats. CLP markedly reduced diaphragm-specific force generation (force/cross-sectional area and maximal titanic force), which was improved by NaHS treatment. In addition, CLP caused mitochondrial damage in the diaphragm tissues as evidenced by increased mitochondrial superoxide production, decreased mitochondrial membrane potential and ATP production, as well as mitochondrial ultrastructural abnormalities, which was also attenuated by NaHS treatment. These findings indicate that H₂S donor may prevent sepsis-induced diaphragm weakness by preservation of mitochondrial function, suggesting that modulation of H₂S levels may be considered as a potential therapeutic approach for diaphragm dysfunction during sepsis.

Significance of hydrogen sulfide in sepsis-induced myocardial injury in rats

Sepsis-induced myocardial injury is a detrimental disorder for intensive care medicine due to its high rates of morbidity and mortality. Data suggest that nuclear factor (NF)-κB serves a critical role in the pathogenesis of myocardial injury. Hydrogen sulfide (H₂S) serves an important role in the physiology and pathophysiology of regulatory mechanisms, particularly during an inflammatory reaction. However, the relationship between NF-κB and H₂S in sepsis-induced myocardial injury is not well understood, and the underlying mechanisms remain unclear. In the present study, 60 male Sprague Dawley rats were randomly divided into the following six groups: A sham group, cecal ligation and puncture (CLP) group, sham + propargylglycine (PAG) group, CLP + PAG group, sham + sodium hydrosulfide (NaHS) group and CLP + NaHS group, with 10 rats in each group. The rats in all groups were sacrificed 12 h after surgery for sample collection. Compared with the sham group, it was observed that the concentrations of Creatine Kinase-MB (CK-MB) and cardiac troponin I (cTnI) in the serum, and pathological scores of myocardial tissue were significantly increased in the CLP, CLP + NaHS and CLP + PAG groups (P<0.05). The pathological scores and concentrations of CK-MB and cTnI were significantly higher in the CLP + PAG group (P<0.05) and significantly lower in the CLP + NaHS group (P<0.05) when compared with the CLP group. The expression of cystathionine-γ-lyase (CSE) mRNA and content of interleukin (IL)-10 were significantly higher in the CLP group compared with the CLP + PAG group (P<0.05), while the expression of myocardial NF-κB and content of tumor necrosis factor (TNF)-α in the CLP group were significantly lowered compared with the CLP + PAG group (P<0.05). The expression of NF-κB and content of TNF-α were significantly increased in the CLP group when compared with the CLP + NaHS group (P<0.05), while the content of myocardial IL-10 in the CLP group was significantly lower than in the CLP + NaHS group (P<0.05). In conclusion, H₂S acted as an anti-inflammatory cytokine and biomarker in sepsis-induced myocardial injury. Furthermore, H₂S may downregulate the NF-κB subunit p65 to mediate inflammatory responses. The present data suggest that myocardial injury in sepsis may be relieved through the regulation of H₂S expression, and provide an experimental basis for the treatment of sepsis patients presenting with myocardial injury. In addition, myocardial injury in sepsis may be identified by monitoring changes in the expression of H₂S.

Hydrogen Sulfide Prevents and Partially Reverses Ozone-Induced Features of Lung Inflammation and Emphysema in Mice

Hydrogen sulfide (H2S), a novel signaling gasotransmitter in the respiratory system, may have antiinflammatory properties in the lung. We examined the preventive and therapeutic effects of H2S on ozone-induced features of lung inflammation and emphysema. C57/BL6 mice were exposed to ozone or filtered air over 6 weeks. Sodium hydrogen sulfide (NaHS), an H2S donor, was administered to the mice either before ozone exposure (preventive effect) or after completion of 6 weeks of ozone exposure (therapeutic effect). The ozone-exposed mice developed emphysema, measured by micro-computed tomography and histology, airflow limitation, measured by the forced maneuver system, and increased lung inflammation with augmented IL-1β, IL-18, and matrix metalloproteinase-9 (MMP-9) gene expression. Ozone-induced changes were associated with increased Nod-like receptor pyrin domain containing 3 (NLRP3)-caspase-1 activation and p38 mitogen-activated protein kinase phosphorylation and decreased Akt phosphorylation. NaHS both prevented and reversed lung inflammation and emphysematous changes in alveolar space. In contrast, NaHS prevented, but did not reverse, ozone-induced airflow limitation and bronchial structural remodeling. In conclusion, NaHS administration prevented and partially reversed ozone-induced features of lung inflammation and emphysema via regulation of the NLRP3-caspase-1, p38 mitogen-activated protein kinase, and Akt pathways.

Cystathionine-gamma-lyase deficient mice are protected against the development of multiorgan failure and exhibit reduced inflammatory response during burn

Considering the role of H₂S in critical illness, the aim of this study was to compare the outcome of burn in wild-type mice and in mice deficient in CSE, one of the principal mammalian H₂S-generating enzymes. Animals were subjected to scald burn. Outcome variables included indices of organ injury, clinical chemistry parameters and plasma levels of inflammatory mediators. Plasma levels of H₂S significantly increased in response to burn in wild-type mice, but remained unchanged in CSE^-/- mice. Expression of the three H₂S-producing enzymes (CSE, CBS and 3-MST) in the lung and liver, and the capacity of tissue homogenates to produce H₂S, however, was not affected by burn. In CSE deficient mice there was a significant amelioration of burn-induced accumulation of myeloperoxidase levels in heart, lung, liver and kidney and significantly lower degree of malon dialdehyde accumulation in the heart, lung and kidney than in wild-type mice. CSE deficient mice, compared to wild-type mice, showed a significant attenuation of the burn-induced elevation in circulating alkaline aminotransferase and blood urea nitrogen and creatinine levels, indicative of protective effects of CSE deficiency against burn-induced hepatic, and renal functional impairment. Multiple burn-induced inflammatory mediators (TNF-α, IL-1β, IL-4, IL-6, IL-10 and IL-12) were significantly lower in the plasma of CSE^-/- animals after burn than in the plasma of wild-type controls subjected to burns. In conclusion, CSE deficiency improves organ function and attenuates the inflammatory response in a murine model of burn.

Hydrogen sulfide prevents postoperative adhesion in a rat uterine horn model

OBJECTIVE

Abdominal adhesions are primarily severe postoperative complications that can cause gynecological problems such as infertility and chronic pelvic pain. Inflammatory mediators are significantly related to adhesion formation, and hydrogen sulfide plays a significant anti-inflammatory role in multiple physiological processes. Therefore, the effect of NaHS, a hydrogen sulfide donor, on postoperative adhesion formation was examined in a rat uterine horn model.

MATERIALS AND METHODS

A rat uterine horn model was created to evaluate whether NaHS, a hydrogen sulfide donor, could decrease postoperative adhesion formation. Rats were randomly grouped and administrated with different doses of NaHS, where DL-propargylglycine and low-molecular-weight heparin acted as negative and positive controls, respectively. The extent and severity of adhesions were assessed on the 14^th postoperative day. Serum of rats was sampled for the determination of 27 cytokines using a chip.

RESULTS

The severity and total scores of adhesion in rats given 112μM/kg and 56μM/kg NaHS were significantly less compared with those of the control group (p<0.01). Scores for the extent of adhesion re-formation in the DL-propargylglycine and control groups did not differ (p>0.05). At least six cytokines were involved in the procedures for the prevention of adhesion formation, as they varied significantly among different groups.

CONCLUSION

Administration of NaHS could apparently reduce postoperative adhesion in the rat uterine horn model. This preventive effect may be associated with the variation of cytokine that is related to inflammatory.

Cystathionine-γ-lyase gene silencing with siRNA in monocytes/ macrophages attenuates inflammation in cecal ligation and puncture-induced sepsis in the mouse

Hydrogen sulphide is an endogenous inflammatory mediator produced by cystathionine-γ-lyase (CSE) in macrophages. To determine the role of H2S and macrophages in sepsis, we used small interference RNA (siRNA) to target the CSE gene and investigated its effect in a mouse model of sepsis. Cecal ligation puncture (CLP)-induced sepsis is characterized by increased levels of myeloperoxidase (MPO) activity, morphological changes in liver and pro-inflammatory cytokines and chemokines in the liver and lung. SiRNA treatment attenuated inflammation in the liver and lungs of mice following CLP-induced sepsis. Liver MPO activity increased in CLP-induced sepsis and treatment with siRNA significantly reduced this. Similarly, lung MPO activity increased following induction of sepsis with CLP while siRNA treatment significantly reduced MPO activity. Liver and lung cytokine and chemokine levels in CLP-induced sepsis reduced following treatment with siRNA. These findings show a crucial pro-inflammatory role for H2S synthesized by CSE in macrophages in sepsis and suggest CSE gene silencing with siRNA as a potential therapeutic approach for this condition.

Time-Gated Detection of Cystathionine γ-Lyase Activity and Inhibition with a Selective, Luminogenic Hydrogen Sulfide Sensor

Herein, we report the design, synthesis, and characterization of a lanthanide^III complex-based probe for the time-gated luminescence detection of hydrogen sulfide (H₂ S) in aqueous media. The probe's unique sensing mechanism relies on the selective reduction of azide to amine by sulfide, followed by intramolecular cyclization to form a quinolinone. The quinolinone is a sensitizer that absorbs near-UV light and transfers excitation energy to coordinated Tb^III or Eu^III ions to trigger a strong "turn-on" luminescence response with ms-scale lifetimes characteristic of lanthanide complexes. Using this probe, we developed a robust, high throughput screening (HTS) assay for detecting H₂ S generated by cystathionine γ-lyase (CSE), one of the main producers of H₂ S in mammalian cells. In a 240-compound screen to identify potential CSE inhibitors, the Eu^III analogue of the sensor showed a low false-positive rate and high Z'-factor (>0.7).

Effect of endotoxemia in mice genetically deficient in cystathionine-γ-lyase, cystathionine-β-synthase or 3-mercaptopyruvate sulfurtransferase

Hydrogen sulfide (H₂S) has been proposed to exert pro- as well as anti-inflammatory effects in various models of critical illness. In this study, we compared bacterial lipopolysaccharide (LPS)-induced changes in inflammatory mediator production, indices of multiple organ injury and survival in wild-type (WT) mice and in mice with reduced expression of one of the three H₂S-producing enzymes, cystathionine-γ-lyase (CSE), cystathionine-β-synthase (CBS) or 3-mercaptopyruvate sulfurtransferase (3MST). Mice were injected intraperitoneally (i.p.) with LPS (10 mg/kg). After 6 h, the animals were sacrificed, blood and organs were collected and the following parameters were evaluated: blood urea nitrogen (BUN) levels in blood, myeloperoxidase (MPO) and malondialdehyde (MDA) in the lung, cytokine levels in plasma and the expression of the three H₂S-producing enzymes (CBS, CSE and 3MST) in the spleen, lung, liver and kidney. LPS induced a tissue-dependent upregulation of some of the H₂S-producing enzymes in WT mice (upregulation of CBS in the spleen, upregulation of 3MST in the liver and upregulation of CBS, CSE and 3MST in the lung). Moreover, LPS impaired glomerular function, as evidenced by increased BUN levels. Renal impairment was comparable in the CSE^−/− and Δ3MST mice after LPS challenge; however, it was attenuated in the CBS^+/− mice. MPO levels (an index of neutrophil infiltration) and MDA levels (an index of oxidative stress) in lung homogenates were significantly increased in response to LPS; these effects were similar in the WT, CBS^+/−, CSE^−/− and Δ3MST mice; however, the MDA levels tended to be lower in the CBS^+/− and CSE^−/− mice. LPS induced significant increases in the plasma levels of multiple cytokines [tumor necrosis factor (TNF)α, interleukin (IL)-1β, IL-6, IL-10, IL-12 and interferon (IFN)γ] in plasma; TNFα, IL-10 and IL-12 levels tended to be lower in all three groups of animals expressing lower levels of H₂S-producing enzymes. The survival rates after the LPS challenge did not show any significant differences between the four animal groups tested. Thus, the findings of this study indicate that a deficiency in 3MST does not significantly affect endotoxemia, while a deficiency in CBS or CSE slightly ameliorates the outcome of LPS-induced endotoxemia in vivo.

Fragment-based de novo design of a cystathionine γ-lyase selective inhibitor blocking hydrogen sulfide production

Hydrogen sulfide is an essential catabolite that intervenes in the pathophysiology of several diseases from hypertension to stroke, diabetes and pancreatitis. It is endogenously synthesized mainly by two pyridoxal-5′-phosphate-dependent enzymes involved in L-cysteine metabolism: cystathionine-ß-synthase (CBS) and cystathionine-γ-lyase (CSE). Research in this field is currently impaired by the lack of pharmacological tools such as selective enzymatic inhibitors that could target specifically only one of these pathways. We used a novel approach based on a hybrid method that includes drug design, synthetic biology, metabolomics and pharmacological assays to rationally design a new inhibitor selective for the CSE enzyme. The identification of this compound opens new frontiers towards a better understanding of the role of CSE over CBS in the pathophysiology of diseases where a role for the H₂S pathway has been proposed and the development of new lead compounds that could target the CSE enzyme.

Both the H2S biosynthesis inhibitor aminooxyacetic acid and the mitochondrially targeted H2S donor AP39 exert protective effects in a mouse model of burn injury

Hydrogen sulfide (H₂S) exerts beneficial as well as deleterious effects in various models of critical illness. Here we tested the effect of two different pharmacological interventions: (a) inhibition of H₂S biosynthesis using the cystathionine-beta-synthase (CBS)/cystathionine-gamma-lyase (CSE) inhibitor aminooxyacetic acid (AOAA) and the mitochondrially targeted H₂S donor [10-oxo-10-[4-(3-thioxo-3H-1,2-dithiol-5-yl)phenoxy]decyl]triphenyl-phosphonium (AP39). A 30% body surface area burn injury was induced in anesthetized mice; animals were treated with vehicle, AOAA (10mg/kg i.p. once or once a day for 6days), or AP39 (0.3mg/kg/day once or once a day for 6days). In two separate groups, animals were sacrificed, at 24h post-burn or on Day 7 post-burn, blood and lungs were collected and the following parameters were evaluated: myeloperoxidase (MPO) and malondialdehyde (MDA) in lung homogenates, plasma cytokines (Luminex analysis) and circulating indicators of organ dysfunction (Vetscan analysis). Lung MPO levels (an index of neutrophil infiltration) and MDA levels (an index of oxidative stress) were significantly increased in response to burn injury both at 24h and at 7days; both AOAA and AP39 attenuated these increases. From a panel of inflammatory cytokines (TNFα, IL-1β, IL-6, IL-10, MCP-1, MIP-2, VEGF and IFNγ) in the plasma, IL-6 and IL-10 levels were markedly elevated at 24h and VEGF was slightly elevated. IL-6 remained highly elevated at 7days post-burn while IL-10 levels decreased, but remained slightly elevated over baseline 7days post-burn. The changes in cytokine levels were attenuated both by AP39 and AOAA at both time points studied. The burn-induced increases in the organ injury markers ALP and ALT, amylase and creatinine were reduced by both AOAA and AP39. We conclude that both H₂S biosynthesis inhibition (using AOAA) and H₂S donation (using AP39) suppresses inflammatory mediator production and reduces multi-organ injury in a murine model of burn injury, both at an early time point (when systemic H₂S levels are elevated) and at a later time point (at which time systemic H₂S levels have returned to baseline). These findings point to the complex pathogenetic role of H₂S in burns.

Cystathionine-Gamma-Lyase Gene Deletion Protects Mice against Inflammation and Liver Sieve Injury following Polymicrobial Sepsis

Background

Hydrogen sulfide (H₂S), produced by the activity of cystathionine-gamma-lyase (CSE), is a key mediator of inflammation in sepsis. The liver sinusoidal endothelial cells (LSECs) are important target and mediator of sepsis. The aim of this study was to investigate the role of CSE-derived H₂S on inflammation and LSECs fenestrae in caecal-ligation and puncture (CLP)-induced sepsis using CSE KO mice.

Methods

Sepsis was induced by CLP, and mice (C57BL/6J, male) were sacrificed after 8 hours. Liver, lung, and blood were collected and processed to measure CSE expression, H₂S synthesis, MPO activity, NF-κB p65, ERK1/2, and cytokines/chemokines levels. Diameter, frequency, porosity and gap area of the liver sieve were calculated from scanning electron micrographs of the LSECs.

Results

An increased CSE expression and H₂S synthesizing activity in the liver and lung of wild-type mice following CLP-induced sepsis. This was associated with an increased liver and lung MPO activity, and increased liver and lung and plasma levels of the pro-inflammatory cytokines TNF-α, IL-6, and IL-1β, and the chemokines MCP-1 and MIP-2α. Conversely, CSE KO mice had less liver and lung injury and reduced inflammation following CLP-induced sepsis as evidenced by decreased levels of H₂S synthesizing activity, MPO activity, and pro-inflammatory cytokines/chemokines production. Extracellular-regulated kinase (ERK1/2) and nuclear factor-κB p65 (NF-κB) became significantly activated after the CLP in WT mice but not in CSE KO mice. In addition, CLP-induced damage to the LSECs, as indicated by increased defenestration and gaps formation in the LSECs compared to WT sham control. CSE KO mice showed decreased defenestration and gaps formation following sepsis.

Conclusions

Mice with CSE (an H₂S synthesising enzyme) gene deletion are less susceptible to CLP-induced sepsis and associated inflammatory response through ERK1/2-NF-κB p65 pathway as evidenced by reduced inflammation, tissue damage, and LSECs defenestration and gaps formation.

Synthesis of Amino-ADT Provides Access to Hydrolytically Stable Amide-Coupled Hydrogen Sulfide Releasing Drug Targets

As additional physiological functions of hydrogen sulfide (H2S) are discovered, developing practical methods for exogenous H2S delivery is important. In particular, nonsteroidal anti-inflammatory drugs (NSAIDs) functionalized with H2S-releasing anethole dithiolethione (ADT-OH) through ester bonds are being investigated for their combined anti-inflammatory and antioxidant potential. The chemical robustness of the connection between drug and H2S-delivery components, however, is a key and controllable linkage in these compounds. Because esters are susceptible to hydrolysis, particularly under acidic conditions such as stomach acid in oral drug delivery applications, we report here a simple synthesis of amino-ADT (ADT-NH2 ) and provide conditions for successful ADT-NH2 derivatization with the drugs naproxen and valproic acid. Using UV-vis spectroscopy and HPLC analysis, we demonstrate that amide-functionalized ADT derivatives are significantly more resistant to hydrolysis than ester-functionalized ADT derivatives.

A critical review of pharmacological significance of Hydrogen Sulfide in hypertension

In the family of gas transmitters, hydrogen sulfide (H2S) is yet not adequately researched. Known for its rotten egg smell and adverse effects on the brain, lungs, and kidneys for more than 300 years, the vasorelaxant effects of H2S on blood vessel was first observed in 1997. Since then, research continued to explore the possible therapeutic effects of H2S in hypertension, inflammation, pancreatitis, different types of shock, diabetes, and heart failure. However, a considerable amount of efforts are yet needed to elucidate the mechanisms involved in the therapeutic effects of H2S, such as nitric oxide-dependent or independent vasodilation in hypertension and regression of left ventricular hypertrophy. More than a decade of good repute among researchers, H2S research has certain results that need to be clarified or reevaluated. H2S produces its response by multiple modes of action, such as opening the ATP-sensitive potassium channel, angiotensin-converting enzyme inhibition, and calcium channel blockade. H2S is endogenously produced from two sulfur-containing amino acids L-cysteine and L-methionine by the two enzymes cystathionine γ lyase and cystathionine β synthase. Recently, the third enzyme, 3-mercaptopyruvate sulfur transferase, along with cysteine aminotransferase, which is similar to aspartate aminotransferase, has been found to produce H2S in the brain. The H2S has interested researchers, and a great deal of information is being generated every year. This review aims to provide an update on the developments in the research of H2S in hypertension amid the ambiguity in defining the exact role of H2S in hypertension because of insufficient number of research results on this area. This critical review on the role of H2S in hypertension will clarify the gray areas and highlight its future prospects.

D-Penicillamine modulates hydrogen sulfide (H2S) pathway through selective inhibition of cystathionine-γ-lyase

BACKGROUND AND PURPOSE

Hydrogen sulfide (H2S) is a gasotransmitter produced from L-cysteine through the enzymatic action of cystathionine-γ-lyase (CSE) and/or cystathionine-β-synthase. D-Penicillamine is the d isomer of a dimethylated cysteine and has been used for the treatment of rheumatoid arthritis. AsD-penicillamine is structurally very similar to cysteine, we have investigated whether D-penicillamine, as a cysteine analogue, has an effect on the H2 S pathway.

EXPERIMENTAL APPROACH

We tested the effect of D-penicillamine (0.01-1 mM) in mouse aortic rings mounted in isolated organ baths and determined whether it could affect H2 S biosynthesis. In particular, we investigated any possible inhibitor or donor behaviour by using recombinant enzyme-based assays and an in vivo approach.

KEY RESULTS

D-Penicillamine, per se, showed little or no vasodilator effect, and it cannot be metabolized as a substrate in place of l-cysteine. However, d-penicillamine significantly reduced L-cysteine-induced vasodilatation in a concentration-dependent manner through inhibition of H2 S biosynthesis, and this effect occurred at concentrations 10 times lower than those needed to induce the release of H2 S. In particular, D-penicillamine selectively inhibited CSE in a pyridoxal-5'-phosphate-dependent manner.

CONCLUSIONS AND IMPLICATIONS

Taken together, our results suggest that D-penicillamine acts as a selective CSE inhibitor, leading to new perspectives in the design and use of specific pharmacological tools for H2 S research. In addition, the inhibitory effect of D-penicillamine on CSE could account for its beneficial action in rheumatoid arthritis patients, where H2 S has been shown to have a detrimental effect.