Hydrogen sulfide stimulates ischemic vascular remodeling through nitric oxide synthase and nitrite reduction activity regulating hypoxia-inducible factor-1α and vascular endothelial growth factor-dependent angiogenesis

NaHS protects brain, heart, and lungs as remote organs from renal ischemia/reperfusion-induced oxidative stress in male and female rats

Acute Kidney Injury (AKI) is frequently observed in hospitalized patients in intensive care units, often caused by renal ischemia-reperfusion injury (IRI). IRI disrupts the function of various 'remote organs' such as the lungs, pancreas, intestine, liver, heart, and brain through inflammation, oxidative stress, apoptosis, leukocyte infiltration, and increased urea and creatinine levels. Gender differences in renal IRI-induced injury are noted. H2S, an endogenous gaseous modulator, shows potential in vasodilation, bronchodilation, and hypotension and can regulate apoptosis, inflammation, angiogenesis, metabolism, and oxidative stress. This study aims to investigate the protective effects of NaHS on brain, heart, and lung injuries following renal IR and to assess the oxidative system status as a potential mechanism in male and female rats.Forty-eight Wistar rats were randomly divided into eight groups (n = 6): Control/Saline, Sham/Saline, IR/Saline, and IR/NaHS in both sexes. Forty-five minutes of bilateral renal ischemia followed by 24-hour reperfusion was induced in the IR groups. NaHS (100µM/Kg, IP) was administered 10 min before clamp release in treated groups. BUN, SCr, BUN/SCr, albuminuria, histopathology, and oxidative stress biomarkers of the brain, heart, and lung were assessed as remote organs. IR increased serum markers of renal function, albuminuria, malondialdehyde levels, and tissue injury scores while reducing nitrite levels and superoxide dismutase and glutathione peroxidase activities. NaHS treatment reversed the adverse effects of IR in remote organs in both sexes, although it showed limited improvement in renal function. Our findings demonstrate that NaHS has a beneficial effect on remote organ injury following renal IR by mitigating oxidative stress, with noted tissue-specific and gender-specific differences in response. These findings suggest NaHS as a potential therapeutic agent for mitigating multi-organ injury after renal IR, with effects varying by tissue and gender.

Hydrogen sulfide and its potential as a possible therapeutic agent in male reproduction

Hydrogen sulfide (H2S) is an endogenously produced signaling molecule that belongs to the group of gasotransmitters along with nitric oxide (NO) and carbon monoxide (CO). H2S plays a pivotal role in male reproductive processes. It is produced in various tissues and cells of the male reproductive system, including testicular tissue, Leydig and Sertoli cells, epididymis, seminal plasma, prostate, penile tissues, and sperm cells. This review aims to summarize the knowledge about the presence and effects of H2S in male reproductive tissues and outline possible therapeutic strategies in pathological conditions related to male fertility, e. g. spermatogenetic disorders and erectile dysfunction (ED). For instance, H2S supports spermatogenesis by maintaining the integrity of the blood-testicular barrier (BTB), stimulating testosterone production, and providing cytoprotective effects. In spermatozoa, H2S modulates sperm motility, promotes sperm maturation, capacitation, and acrosome reaction, and has significant cytoprotective effects. Given its vasorelaxant effects, it supports the erection of penile tissue. These findings suggest the importance and therapeutic potential of H2S in male reproduction, paving the way for further research and potential clinical applications.

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.

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.

Recent advances in the mechanism of hydrogen sulfide in wound healing in diabetes

Wound healing difficulties in diabetes continue to be a clinical challenge, posing a considerable burden to patients and society. Recently, exploration of the mechanism of wound healing and associated treatment options in diabetes has become topical. Of note, the positive role of hydrogen sulfide in promoting wound healing has been demonstrated in recent studies. Hydrogen sulfide is a confirmed gas transmitter in mammals, playing an essential role in pathology and physiology. This review describes the mechanism underlying the role of hydrogen sulfide in the promotion of diabetic wound healing and the potential for hydrogen sulfide supplementation as a therapeutic application.

Hypoxia increases persulfide and polysulfide formation by AMP kinase dependent cystathionine gamma lyase phosphorylation

Hydropersulfide and hydropolysulfide metabolites are increasingly important reactive sulfur species (RSS) regulating numerous cellular redox dependent functions. Intracellular production of these species is known to occur through RSS interactions or through translational mechanisms involving cysteinyl t-RNA synthetases. However, regulation of these species under cell stress conditions, such as hypoxia, that are known to modulate RSS remain poorly understood. Here we define an important mechanism of increased persulfide and polysulfide production involving cystathionine gamma lyase (CSE) phosphorylation at serine 346 and threonine 355 in a substrate specific manner, under acute hypoxic conditions. Hypoxic phosphorylation of CSE occurs in an AMP kinase dependent manner increasing enzyme activity involving unique inter- and intramolecular interactions within the tetramer. Importantly, both cellular hypoxia and tissue ischemia result in AMP Kinase dependent CSE phosphorylation that regulates blood flow in ischemic tissues. Our findings reveal hypoxia molecular signaling pathways regulating CSE dependent persulfide and polysulfide production impacting tissue and cellular response to stress.

Paper-assisted ratiometric fluorescent sensors for on-site sensing of sulfide based on the target-induced inner filter effect

Dissolved sulfide tends to species transformation and loss upon leaving the matrix, thus the development of a practical on-site determination of sulfide is crucial for environmental monitoring and human health. In this work, a novel paper-based ratiometric fluorescence sensor was developed for the field analysis of sulfide, which system was constructed by the inner filter effect (IFE) of CdS quantum dots (QDs) toward carbon dots (C-dots). Instead of an aqueous phase system, the conversion of sulfide to its hydride would induce the in-situ formation of CdS QDs on the paper, which acted as an energy acceptor to quench the emission of C-dots, leading to a variation of ratiometric fluorescence from blue to yellow with the increasing concentration of sulfide. Moreover, we proposed a smartphone-based fluorescence capture device integrated with a programmed Python program, accomplishing both color recognition and accurate detection of sulfide. Under the optimal condition, this ratiometric fluorescence sensor allowed for the on-site analysis of sulfide with a limit of detection of 0.05 μM. The accuracy of the sensor was validated via the successful field analysis of environmental water samples with satisfactory recoveries. Compared to other fluorescence methods used for sulfide analysis, this developed system retains the advantages of label-free, low-cost, ease of operation, and miniaturization, showing great potential for the measurement of sulfide on-site, as well as environmental monitoring.

Modulation of the nitric oxide/cGMP pathway in cardiac contraction and relaxation: Potential role in heart failure treatment

Evidence exists that heart failure (HF) has an overall impact of 1-2 % in the global population being often associated with comorbidities that contribute to increased disease prevalence, hospitalization, and mortality. Recent advances in pharmacological approaches have significantly improved clinical outcomes for patients with vascular injury and HF. Nevertheless, there remains an unmet need to clarify the crucial role of nitric oxide/cyclic guanosine 3',5'-monophosphate (NO/cGMP) signalling in cardiac contraction and relaxation, to better identify the key mechanisms involved in the pathophysiology of myocardial dysfunction both with reduced (HFrEF) as well as preserved ejection fraction (HFpEF). Indeed, NO signalling plays a crucial role in cardiovascular homeostasis and its dysregulation induces a significant increase in oxidative and nitrosative stress, producing anatomical and physiological cardiac alterations that can lead to heart failure. The present review aims to examine the molecular mechanisms involved in the bioavailability of NO and its modulation of downstream pathways. In particular, we focus on the main therapeutic targets and emphasize the recent evidence of preclinical and clinical studies, describing the different emerging therapeutic strategies developed to counteract NO impaired signalling and cardiovascular disease (CVD) development.

The Triple Crown: NO, CO, and H2S in cancer cell biology

Nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2S) are three endogenously produced gases with important functions in the vasculature, immune defense, and inflammation. It is increasingly apparent that, far from working in isolation, these three exert many effects by modulating each other's activity. Each gas is produced by three enzymes, which have some tissue specificities and can also be non-enzymatically produced by redox reactions of various substrates. Both NO and CO share similar properties, such as activating soluble guanylate cyclase (sGC) to increase cyclic guanosine monophosphate (cGMP) levels. At the same time, H2S both inhibits phosphodiesterase 5A (PDE5A), an enzyme that metabolizes sGC and exerts redox regulation on sGC. The role of NO, CO, and H2S in the setting of cancer has been quite perplexing, as there is evidence for both tumor-promoting and pro-inflammatory effects and anti-tumor and anti-inflammatory activities. Each gasotransmitter has been found to have dual effects on different aspects of cancer biology, including cancer cell proliferation and apoptosis, invasion and metastasis, angiogenesis, and immunomodulation. These seemingly contradictory actions may relate to each gas having a dual effect dependent on its local flux. In this review, we discuss the major roles of NO, CO, and H2S in the context of cancer, with an effort to highlight the dual nature of each gas in different events occurring during cancer progression.

Dose-Dependent Effect of Hydrogen Sulfide in Cyclophosphamide-Induced Hepatotoxicity in Rats

BACKGROUND

Cyclophosphamide is a commonly used anticancer and immunosuppressive agent; however, hepatotoxicity is one of its severe toxicities. Hydrogen sulfide is a gaseous signaling molecule that plays crucial regulatory roles in various physiological functions. This study aimed to evaluate the hepatoprotective effect of hydrogen sulfide against cyclo phosp hamid e-ind uced hepatic damage in rats.

METHODS

Hepatotoxicity was induced by the single intraperitoneal administration of cyclophosphamide (200 mg/kg). Sprague-Dawley rats were treated by hydrogen sulfide donor, sodium hydrosulfide (25, 50, and 100 μmol/kg, intraperitoneal) 7 days before and 7 days after the administration of a single intraperitoneal injection of cyclophosphamide (200 mg/kg). Cyclo phosp hamide-ind uced hepatotoxicity was evaluated by serum and tissue biochemical and histopathological assessments. The levels of hydrogen sulfide, nitric oxide, cyclic guanosine monophosphate, interleukin 6, and interleukin 10 in liver homogenates were also determined by ELISA. One-way analysis of variance and Kruskal-Wallis tests were used as statistical analyses.

RESULTS

Cyclophosphamide increased liver function enzymes (alanine aminotransferase and aspartate aminotransferase), immunoreactivity to caspase-3 and Apaf-1, and proinflammatory cytokines. Cyclophosphamide also induced histopathological alterations including pycnotic nucleus with eosinophilic cytoplasm, increased sinusoidal dilatation, congestion, and edema. Hydrogen sulfide cotreatment significantly reduced cyclo phosp hamid e-ind uced inflammation, histological alterations, and apoptosis in the liver. 50 mg/kg sodium hydrosulfide was more effective against cyclo phosp hamid e-ind uced hepatotoxicity.

CONCLUSION

In conclusion, hydrogen sulfide with its anti-inflammatory and anti-apoptotic effects seems to be beneficial as an adjunct to cyclophosphamide treatment to reduce cyclo phosp hamid e-ind uced hepatotoxicity and thereby can be suggested as a promising agent to increase the therapeutic efficacy of cyclophosphamide.

A novel, microvascular evaluation method and device for early diagnosis of peripheral artery disease and chronic limb-threatening ischemia in individuals with diabetes

Objective

A novel transdermal arterial gasotransmitter sensor (TAGS) has been tested as a diagnostic tool for lower limb microvascular disease in individuals with and without diabetes mellitus (DM).

Methods

The TAGS system noninvasively measures hydrogen sulfide (H2S) emitted from the skin. Measurements were made on the forearm and lower limbs of individuals from three cohorts, including subjects with DM and chronic limb-threatening ischemia, to evaluate skin microvascular integrity. These measurements were compared with diagnosis of peripheral artery disease (PAD) using the standard approach of the toe brachial index. Other measures of vascular health were made in some subjects including fasting blood glucose, hemoglobin A1c, plasma lipids, blood pressure, estimated glomerular filtration, and body mass index.

Results

The leg:arm ratio of H2S emissions correlated with risk factors for microvascular disease (ie, high-density lipoprotein levels, estimated glomerular filtration rate, systolic blood pressure, and hemoglobin A1c). The ratios were significantly lower in symptomatic DM subjects being treated for chronic limb-threatening ischemia (n = 8, 0.48 ± 0.21) compared with healthy controls (n = 5, 1.08 ± 0.30; P = .0001) and with asymptomatic DM subjects (n = 4, 0.79 ± 0.08; P = .0086). The asymptomatic DM group ratios were also significantly lower than the healthy controls (P = .0194). Using ratios of leg:arm transdermal H2S measurement (17 subjects, 34 ratios), the overall accuracy to identify limbs with severe PAD had an area under the curve of the receiver operating curve of 0.93.

Conclusions

Ratios of transdermal H2S measurements are lower in legs with impaired microvascular function, and the decrease in ratio precedes clinically apparent severe microvascular disease and diabetic ulcers. The TAGS instrument is a novel, sensitive tool that may aid in the early detection and monitoring of PAD complications and efforts for limb salvage.

Comparative Study of Different H2S Donors as Vasodilators and Attenuators of Superoxide-Induced Endothelial Damage

In the last years, research proofs have confirmed that hydrogen sulfide (H₂S) plays an important role in various physio-pathological processes, such as oxidation, inflammation, neurophysiology, and cardiovascular protection; in particular, the protective effects of H₂S in cardiovascular diseases were demonstrated. The interest in H₂S-donating molecules as tools for biological and pharmacological studies has grown, together with the understanding of H₂S importance. Here we performed a comparative study of a series of H₂S donor molecules with different chemical scaffolds and H₂S release mechanisms. The compounds were tested in human serum for their stability and ability to generate H₂S. Their vasorelaxant properties were studied on rat aorta strips, and the capacity of the selected compounds to protect NO-dependent endothelium reactivity in an acute oxidative stress model was tested. H₂S donors showed different H₂S-releasing kinetic and produced amounts and vasodilating profiles; in particular, compound 6 was able to attenuate the dysfunction of relaxation induced by pyrogallol exposure, showing endothelial protective effects. These results may represent a useful basis for the rational development of promising H₂S-releasing agents also conjugated with other pharmacophores.

Sulfide regulation of cardiovascular function in health and disease

Hydrogen sulfide (H2S) has emerged as a gaseous signalling molecule with crucial implications for cardiovascular health. H2S is involved in many biological functions, including interactions with nitric oxide, activation of molecular signalling cascades, post-translational modifications and redox regulation. Various preclinical and clinical studies have shown that H2S and its synthesizing enzymes - cystathionine γ-lyase, cystathionine β-synthase and 3-mercaptosulfotransferase - can protect against cardiovascular pathologies, including arrhythmias, atherosclerosis, heart failure, myocardial infarction and ischaemia-reperfusion injury. The bioavailability of H2S and its metabolites, such as hydropersulfides and polysulfides, is substantially reduced in cardiovascular disease and has been associated with single-nucleotide polymorphisms in H2S synthesis enzymes. In this Review, we highlight the role of H2S, its synthesizing enzymes and metabolites, their roles in the cardiovascular system, and their involvement in cardiovascular disease and associated pathologies. We also discuss the latest clinical findings from the field and outline areas for future study.

Role of hydrogen sulphide in physiological and pathological angiogenesis

The role of hydrogen sulphide (H₂ S) in angiogenesis has been widely demonstrated. Vascular endothelial growth factor (VEGF) plays an important role in H₂ S-induced angiogenesis. H₂ S promotes angiogenesis by upregulating VEGF via pro-angiogenic signal transduction. The involved signalling pathways include the mitogen-activated protein kinase pathway, phosphoinositide-3 kinase pathway, nitric oxide (NO) synthase/NO pathway, signal transducer and activator of transcription 3 (STAT3) pathway, and adenosine triphosphate (ATP)-sensitive potassium (K_ATP ) channels. H₂ S has been shown to contribute to tumour angiogenesis, diabetic wound healing, angiogenesis in cardiac and cerebral ischaemic tissues, and physiological angiogenesis during the menstrual cycle and pregnancy. Furthermore, H₂ S can exert an anti-angiogenic effect by inactivating Wnt/β-catenin signalling or blocking the STAT3 pathway in tumours. Therefore, H₂ S plays a double-edged sword role in the process of angiogenesis. The regulation of H₂ S production is a promising therapeutic approach for angiogenesis-associated diseases. Novel H₂ S donors and/or inhibitors can be developed in the treatment of angiogenesis-dependent diseases.

Methamphetamine causes cardiovascular dysfunction via cystathionine gamma lyase and hydrogen sulfide depletion

Methamphetamine (METH) is an addictive illicit drug used worldwide that causes significant damage to blood vessels resulting in cardiovascular dysfunction. Recent studies highlight increased prevalence of cardiovascular disease (CVD) and associated complications including hypertension, vasospasm, left ventricular hypertrophy, and coronary artery disease in younger populations due to METH use. Here we report that METH administration in a mouse model of 'binge and crash' decreases cardiovascular function via cystathionine gamma lyase (CSE), hydrogen sulfide (H2S), nitric oxide (NO) (CSE/H2S/NO) dependent pathway. METH significantly reduced H2S and NO bioavailability in plasma and skeletal muscle tissues co-incident with a significant reduction in flow-mediated vasodilation (FMD) and blood flow velocity revealing endothelial dysfunction. METH administration also reduced cardiac ejection fraction (EF) and fractional shortening (FS) associated with increased tissue and perivascular fibrosis. Importantly, METH treatment selectively decreased CSE expression and sulfide bioavailability along with reduced eNOS phosphorylation and NO levels. Exogenous sulfide therapy or endothelial CSE transgenic overexpression corrected cardiovascular and associated pathological responses due to METH implicating a central molecular regulatory pathway for tissue pathology. These findings reveal that therapeutic intervention targeting CSE/H2S bioavailability may be useful in attenuating METH mediated cardiovascular disease.

Sodium Thiosulphate-Loaded Liposomes Control Hydrogen Sulphide Release and Retain Its Biological Properties in Hypoxia-like Environment

Hypoxia, or insufficient oxygen availability is a common feature in the development of a myriad of cardiovascular-related conditions including ischemic disease. Hydrogen sulphide (H2S) donors, such as sodium thiosulphate (STS), are known for their cardioprotective properties. However, H2S due to its gaseous nature, is released and cleared rapidly, limiting its potential translation to clinical settings. For the first time, we developed and characterised liposome formulations encapsulating STS and explored their potential for modulating STS uptake, H2S release and the ability to retain pro-angiogenic and biological signals in a hypoxia-like environment mirroring oxygen insufficiency in vitro. Liposomes were prepared by varying lipid ratios and characterised for size, polydispersity and charge. STS liposomal encapsulation was confirmed by HPLC-UV detection and STS uptake and H2S release was assessed in vitro. To mimic hypoxia, cobalt chloride (CoCl2) was administered in conjunction with formulated and non-formulated STS, to explore pro-angiogenic and metabolic signals. Optimised liposomal formulation observed a liposome diameter of 146.42 ± 7.34 nm, a polydispersity of 0.22 ± 0.19, and charge of 3.02 ± 1.44 mV, resulting in 25% STS encapsulation. Maximum STS uptake (76.96 ± 3.08%) from liposome encapsulated STS was determined at 24 h. Co-exposure with CoCl2 and liposome encapsulated STS resulted in increased vascular endothelial growth factor mRNA as well as protein expression, enhanced wound closure and increased capillary-like formation. Finally, liposomal STS reversed metabolic switch induced by hypoxia by enhancing mitochondrial bioenergetics. These novel findings provide evidence of a feasible controlled-delivery system for STS, thus H2S, using liposome-based nanoparticles. Likewise, data suggests that in scenarios of hypoxia, liposomal STS is a good therapeutic candidate to sustain pro-angiogenic signals and retain metabolic functions that might be impaired by limited oxygen and nutrient availability.

Sodium thiosulfate, a source of hydrogen sulfide, stimulates endothelial cell proliferation and neovascularization

Therapies to accelerate vascular repair are currently lacking. Pre-clinical studies suggest that hydrogen sulfide (H₂S), an endogenous gasotransmitter, promotes angiogenesis. Here, we hypothesized that sodium thiosulfate (STS), a clinically relevant source of H₂S, would stimulate angiogenesis and vascular repair. STS stimulated neovascularization in WT and LDLR receptor knockout mice following hindlimb ischemia as evidenced by increased leg perfusion assessed by laser Doppler imaging, and capillary density in the gastrocnemius muscle. STS also promoted VEGF-dependent angiogenesis in matrigel plugs in vivo and in the chorioallantoic membrane of chick embryos. In vitro, STS and NaHS stimulated human umbilical vein endothelial cell (HUVEC) migration and proliferation. Seahorse experiments further revealed that STS inhibited mitochondrial respiration and promoted glycolysis in HUVEC. The effect of STS on migration and proliferation was glycolysis-dependent. STS probably acts through metabolic reprogramming of endothelial cells toward a more proliferative glycolytic state. These findings may hold broad clinical implications for patients suffering from vascular occlusive diseases.

Progress and perspective on hydrogen sulfide donors and their biomedical applications

Following the discovery of nitric oxide (NO) and carbon monoxide (CO), hydrogen sulfide (H₂ S) has been identified as the third gasotransmitter in humans. Increasing evidence have shown that H₂ S is of preventive or therapeutic effects on diverse pathological complications. As a consequence, it is of great significance to develop suitable approaches of H₂ S-based therapeutics for biomedical applications. H₂ S-releasing agents (H₂ S donors) play important roles in exploring and understanding the physiological functions of H₂ S. More importantly, accumulating studies have validated the theranostic potential of H₂ S donors in extensive repertoires of in vitro and in vivo disease models. Thus, it is imperative to summarize and update the literatures in this field. In this review, first, the background of H₂ S on its chemical and biological aspects is concisely introduced. Second, the studies regarding the H₂ S-releasing compounds are categorized and described, and accordingly, their H₂ S-donating mechanisms, biological applications, and therapeutic values are also comprehensively delineated and discussed. Necessary comparisons between related H₂ S donors are presented, and the drawbacks of many typical H₂ S donors are analyzed and revealed. Finally, several critical challenges encountered in the development of multifunctional H₂ S donors are discussed, and the direction of their future development as well as their biomedical applications is proposed. We expect that this review will reach extensive audiences across multiple disciplines and promote the innovation of H₂ S biomedicine.

Medical Gas Therapy for Tissue, Organ, and CNS Protection: A Systematic Review of Effects, Mechanisms, and Challenges

Gaseous molecules have been increasingly explored for therapeutic development. Here, following an analytical background introduction, a systematic review of medical gas research is presented, focusing on tissue protections, mechanisms, data tangibility, and translational challenges. The pharmacological efficacies of carbon monoxide (CO) and xenon (Xe) are further examined with emphasis on intracellular messengers associated with cytoprotection and functional improvement for the CNS, heart, retina, liver, kidneys, lungs, etc. Overall, the outcome supports the hypothesis that readily deliverable "biological gas" (CO, H2 , H2 S, NO, O2 , O3 , and N2 O) or "noble gas" (He, Ar, and Xe) treatment may preserve cells against common pathologies by regulating oxidative, inflammatory, apoptotic, survival, and/or repair processes. Specifically, CO, in safe dosages, elicits neurorestoration via igniting sGC/cGMP/MAPK signaling and crosstalk between HO-CO, HIF-1α/VEGF, and NOS pathways. Xe rescues neurons through NMDA antagonism and PI3K/Akt/HIF-1α/ERK activation. Primary findings also reveal that the need to utilize cutting-edge molecular and genetic tactics to validate mechanistic targets and optimize outcome consistency remains urgent; the number of neurotherapeutic investigations is limited, without published results from large in vivo models. Lastly, the broad-spectrum, concurrent multimodal homeostatic actions of medical gases may represent a novel pharmaceutical approach to treating critical organ failure and neurotrauma.

Physiological roles of hydrogen sulfide in mammalian cells, tissues and organs

H2S belongs to the class of molecules known as gasotransmitters, which also includes nitric oxide (NO) and carbon monoxide (CO). Three enzymes are recognized as endogenous sources of H2S in various cells and tissues: cystathionine g-lyase (CSE), cystathionine β-synthase (CBS) and 3-mercaptopyruvate sulfurtransferase (3-MST). The current article reviews the regulation of these enzymes as well as the pathways of their enzymatic and non-enzymatic degradation and elimination. The multiple interactions of H2S with other labile endogenous molecules (e.g. NO) and reactive oxygen species are also outlined. The various biological targets and signaling pathways are discussed, with special reference to H2S and oxidative posttranscriptional modification of proteins, the effect of H2S on channels and intracellular second messenger pathways, the regulation of gene transcription and translation and the regulation of cellular bioenergetics and metabolism. The pharmacological and molecular tools currently available to study H2S physiology are also reviewed, including their utility and limitations. In subsequent sections, the role of H2S in the regulation of various physiological and cellular functions is reviewed. The physiological role of H2S in various cell types and organ systems are overviewed. Finally, the role of H2S in the regulation of various organ functions is discussed as well as the characteristic bell-shaped biphasic effects of H2S. In addition, key pathophysiological aspects, debated areas, and future research and translational areas are identified A wide array of significant roles of H2S in the physiological regulation of all organ functions emerges from this review.

The Role of Amino Acids in Endothelial Biology and Function

The vascular endothelium acts as an important component of the vascular system. It is a barrier between the blood and vessel wall. It plays an important role in regulating blood vessel tone, permeability, angiogenesis, and platelet functions. Several studies have shown that amino acids (AA) are key regulators in maintaining vascular homeostasis by modulating endothelial cell (EC) proliferation, migration, survival, and function. This review summarizes the metabolic and signaling pathways of AAs in ECs and discusses the importance of AA homeostasis in the functioning of ECs and vascular homeostasis. It also discusses the challenges in understanding the role of AA in the development of cardiovascular pathophysiology and possible directions for future research.

Xanthine Oxidase Inhibitor, Febuxostat Is Effective against 5-Fluorouracil-Induced Parotid Salivary Gland Injury in Rats Via Inhibition of Oxidative Stress, Inflammation and Targeting TRPC1/CHOP Signalling Pathway

The current research aimed to examine the ameliorative role of febuxostat (FEB), a highly potent xanthine oxidase inhibitor, against 5-fluorouracil (5-FU)-induced parotid salivary gland damage in rats, as FEB is a pleiotropic drug that has multiple pharmacological effects. A total of 32 Wistar adult male rats were randomly arranged into four groups. Group 1: the control group; given only the vehicle for 14 days, then given a saline i.p. injection from the 10th to the 14th day. Group 2: the FEB group; rats received FEB (10 mg/kg) once daily po for 14 days before receiving a saline i.p. injection from the 10th to the 14th day. Group 3: the 5-FU group; from the 10th to the 14th day, rats received an intraperitoneal injection of 5-FU (35 mg/kg/day). Group 4: the FEB/5-FU group; rats were pre-treated with FEB po for 14 days before receiving 5-FU i.p injections for five consecutive days from the 10th to the 14th day. Parotid gland damage was detected histologically and biochemically by the evaluation of oxidative stress markers (malondialdehyde (MDA) and nitric oxide levels (NOx)), oxidant defences (reduced glutathione (GSH) and superoxide dismutase (SOD)), inflammatory markers (tumour necrosis factor-alpha (TNF-α), interleukin-1β (IL-1β)), and transient receptor potential canonical1 (TRCP1) and C/EBP homologous protein (CHOP). FEB pre-treatment reduced MDA, TNF-, and IL-1 while increasing SOD, GSH, and NOx. FEB also significantly increased TRPC1 and decreased CHOP in parotid gland tissue. In conclusion, FEB pre-treatment reduced 5-FU-induced parotid salivary gland damage not only through its powerful anti-inflammatory and antioxidant effects, but also through its effect on the TRPC1/CHOP signalling pathway.

Stimulation of mitochondrial hydrogen sulfide and glutathione production improves the Frank-Starling response of the rat heart via a nitric oxide-dependent pathway

The Frank-Starling response of the heart is known to be mediated by nitric oxide (NO) signaling, which is regulated by reduced glutathione (GSH) and hydrogen sulfide (H2S). We hypothesized that stimulation of endogenous H2S or GSH synthesis would improve the Frank-Starling response. Wistar male rats were injected with propargylglycine (PAG; 11.3 mg/kg, 40 min, n = 12), an inhibitor of H2S-producing enzyme (cystationine-γ-lyase), and l-cysteine (121 mg/kg, 30 min, n = 20), a precursor of H2S and GSH. Pretreatment with PAG or l-cysteine separately slightly improved the pressure-volume (P-V) dependence of the isolated rat heart, but the combination of PAG and l-cysteine (n = 12) improved heart contractile activity. H2S content, Ca2+-dependent NOS activity (cNOS) activity, nitrate reductase activity, and nitrite content increased by 2, 3.83, 2.5, and 1.3 times in cardiac mitochondria, and GSH and oxidized glutathione (GSSG) levels increased by 2.24 and 1.86 times in the heart homogenates of the PAG + l-cysteine group compared with the control (all P < 0.05). Inhibition of glutathione with DL-buthionine-sulfoximine (BSO; 22.2 mg/kg, 40 min, n = 6) drastically decreased Frank-Starling response of the heart and prevented PAG + l-cysteine-induced increase of GSH and GSSG levels (BSO + PAG + l-cysteine, n = 9). Inhibition of NOS, N-nitro-l-arginine-methylester hydrochloride (l-NAME; 40 min, 27 mg/kg) abolished positive inotropy induced by PAG+l-cysteine pretreatment (l-NAME + PAG + l-cysteine, n = 7). Thus, PAG + l-cysteine administration improves the Frank-Starling response by upregulating mitochondrial H2S, glutathione, and NO synthesis, which may be a promising approach in the treatment of myocardial dysfunction.

Hydrogen sulfide: A new therapeutic target in vascular diseases

Hydrogen sulfide (H₂S) is one of most important gas transmitters. H₂S modulates many physiological and pathological processes such as inflammation, oxidative stress and cell apoptosis that play a critical role in vascular function. Recently, solid evidence show that H₂S is closely associated to various vascular diseases. However, specific function of H₂S remains unclear. Therefore, in this review we systemically summarized the role of H₂S in vascular diseases, including hypertension, atherosclerosis, inflammation and angiogenesis. In addition, this review also outlined a novel therapeutic perspective comprising crosstalk between H₂S and smooth muscle cell function. Therefore, this review may provide new insight inH₂S application clinically.

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

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

Vascular Dysfunction in Preeclampsia

Preeclampsia is a life-threatening pregnancy-associated cardiovascular disorder characterized by hypertension and proteinuria at 20 weeks of gestation. Though its exact underlying cause is not precisely defined and likely heterogenous, a plethora of research indicates that in some women with preeclampsia, both maternal and placental vascular dysfunction plays a role in the pathogenesis and can persist into the postpartum period. Potential abnormalities include impaired placentation, incomplete spiral artery remodeling, and endothelial damage, which are further propagated by immune factors, mitochondrial stress, and an imbalance of pro- and antiangiogenic substances. While the field has progressed, current gaps in knowledge include detailed initial molecular mechanisms and effective treatment options. Newfound evidence indicates that vasopressin is an early mediator and biomarker of the disorder, and promising future therapeutic avenues include mitigating mitochondrial dysfunction, excess oxidative stress, and the resulting inflammatory state. In this review, we provide a detailed overview of vascular defects present during preeclampsia and connect well-established notions to newer discoveries at the molecular, cellular, and whole-organism levels.

Emerging Nitric Oxide and Hydrogen Sulfide Releasing Carriers for Skin Wound Healing Therapy

Nitric oxide (NO) and hydrogen sulfide (H₂ S) have been recognized as important signalling molecules involved in multiple physiological functions, including wound healing. Their exogenous delivery has been established as a new route for therapies, being the topical application the nearest to commercialization. Nevertheless, the gaseous nature of these therapeutic agents and their toxicity at high levels imply additional challenges in the design of effective delivery systems, including the tailoring of their morphology and surface chemistry to get controllable release kinetics and suitable lifetimes. This review highlights the increasing interest in the use of these gases in wound healing applications by presenting the various potential strategies in which NO and/or H₂ S are the main therapeutic agents, with focus on their conceptual design, release behaviour and therapeutic performance. These strategies comprise the application of several types of nanoparticles, polymers, porous materials, and composites as new releasing carriers of NO and H₂ S, with characteristics that will facilitate the application of these molecules in the clinical practice.

Human and rodent red blood cells do not demonstrate xanthine oxidase activity or XO-catalyzed nitrite reduction to NO

A number of molybdopterin enzymes, including xanthine oxidoreductase (XOR), aldehyde oxidase (AO), sulfite oxidase (SO), and mitochondrial amidoxime reducing component (mARC), have been identified as nitrate and nitrite reductases. Of these enzymes, XOR has been the most extensively studied and reported to be a substantive source of nitric oxide (NO) under inflammatory/hypoxic conditions that limit the catalytic activity of the canonical NOS pathway. It has also been postulated that XOR nitrite reductase activity extends to red blood cell (RBCs) membranes where it has been immunohistochemically identified. These findings, when combined with countervailing reports of XOR activity in RBCs, incentivized our current study to critically evaluate XOR protein abundance/enzymatic activity in/on RBCs from human, mouse, and rat sources. Using various protein concentrations of RBC homogenates for both human and rodent samples, neither XOR protein nor enzymatic activity (xanthine → uric acid) was detectable. In addition, potential loading of RBC-associated glycosaminoglycans (GAGs) by exposing RBC preparations to purified XO before washing did not solicit detectable enzymatic activity (xanthine → uric acid) or alter NO generation profiles. To ensure these observations extended to absence of XOR-mediated contributions to overall RBC-associated nitrite reduction, we examined the nitrite reductase activity of washed and lysed RBC preparations via enhanced chemiluminescence in the presence or absence of the XOR-specific inhibitor febuxostat (Uloric®). Neither addition of inhibitor nor the presence of the XOR substrate xanthine significantly altered the rates of nitrite reduction to NO by RBC preparations from either human or rodent sources confirming the absence of XO enzymatic activity. Furthermore, examination of the influence of the age (young cells vs. old cells) of human RBCs on XO activity also failed to demonstrate detectable XO protein. Combined, these data suggest: 1) that XO does not contribute to nitrite reduction in/on human and rodent erythrocytes, 2) care should be taken to validate immuno-detectable XO by demonstrating enzymatic activity, and 3) XO does not associate with human erythrocytic glycosaminoglycans or participate in nonspecific binding.

Hydrogen Sulfide Actions in the Vasculature

Hydrogen sulfide (H2 S) is a small, gaseous molecule with poor solubility in water that is generated by multiple pathways in many species including humans. It acts as a signaling molecule in many tissues with both beneficial and pathological effects. This article discusses its many actions in the vascular system and the growing evidence of its role to regulate vascular tone, angiogenesis, endothelial barrier function, redox, and inflammation. Alterations in some disease states are also discussed including potential roles in promoting tumor growth and contributions to the development of metabolic disease. © 2021 American Physiological Society. Compr Physiol 11:1-22, 2021.

Sodium hydrosulfide has no additive effects on nitrite-inhibited renal gluconeogenesis in type 2 diabetic rats

OBJECTIVE

Increased renal and hepatic gluconeogenesis are important sources of fasting hyperglycemia in type 2 diabetes (T2D). The inhibitory effect of co-administration of sodium nitrite and sodium hydrosulfide (NaSH) on hepatic but not renal gluconeogenesis has been reported in rats with T2D. The present study aimed to determine the effects of co-administration of sodium nitrite and NaSH on the expression of genes involved in renal gluconeogenesis in rats with T2D.

METHODS

T2D was induced by a combination of a high-fat diet and low-dose streptozotocin (30 mg/kg). Male Wistar rats were divided into 5 groups (n = 6/group): Control, T2D, T2D + nitrite, T2D + NaSH, and T2D + nitrite+NaSH. Nitrite and NaSH were administered for nine weeks at a dose of 50 mg/L (in drinking water) and 0.28 mg/kg (daily intraperitoneal injection), respectively. Serum levels of urea and creatinine, and mRNA expressions of PEPCK, G6Pase, FBPase, PC, PI3K, AKT, PGC-1α, and FoxO1 in the renal tissue, were measured at the end of the study.

RESULTS

Nitrite decreased mRNA expression of PEPCK by 39%, G6Pase by 43%, FBPase by 41%, PC by 63%, PGC-1α by 45%, and FoxO1 by 27% in the renal tissue of rats with T2D; co-administration of nitrite and NaSH further decreases FoxO1, while had no additive effects on the tissue expression of the other genes. In addition, nitrite+NaSH decreased elevated serum urea levels by 58% and creatinine by 37% in rats with T2D.

CONCLUSION

The inhibitory effect of nitrite on gluconeogenesis in T2D rats is at least in part due to decreased mRNA expressions of renal gluconeogenic genes. Unlike effects on hepatic gluconeogenesis, co-administration of nitrite and NaSH has no additive effects on genes involved in renal gluconeogenesis in rats with T2D.

CoenzymeQ in cellular redox regulation and clinical heart failure

Coenzyme Q (CoQ) is ubiquitously embedded in lipid bilayers of various cellular organelles. As a redox cycler, CoQ shuttles electrons between mitochondrial complexes and extramitochondrial reductases and oxidases. In this way, CoQ is crucial for maintaining the mitochondrial function, ATP synthesis, and redox homeostasis. Cardiomyocytes have a high metabolic rate and rely heavily on mitochondria to provide energy. CoQ levels, in both plasma and the heart, correlate with heart failure in patients, indicating that CoQ is critical for cardiac function. Moreover, CoQ supplementation in clinics showed promising results for treating heart failure. This review provides a comprehensive view of CoQ metabolism and its interaction with redox enzymes and reactive species. We summarize the clinical trials and applications of CoQ in heart failure and discuss the caveats and future directions to improve CoQ therapeutics.

The Potential of Hydrogen Sulfide Donors in Treating Cardiovascular Diseases

Hydrogen sulfide (H2S) has long been considered as a toxic gas, but as research progressed, the idea has been updated and it has now been shown to have potent protective effects at reasonable concentrations. H2S is an endogenous gas signaling molecule in mammals and is produced by specific enzymes in different cell types. An increasing number of studies indicate that H2S plays an important role in cardiovascular homeostasis, and in most cases, H2S has been reported to be downregulated in cardiovascular diseases (CVDs). Similarly, in preclinical studies, H2S has been shown to prevent CVDs and improve heart function after heart failure. Recently, many H2S donors have been synthesized and tested in cellular and animal models. Moreover, numerous molecular mechanisms have been proposed to demonstrate the effects of these donors. In this review, we will provide an update on the role of H2S in cardiovascular activities and its involvement in pathological states, with a special focus on the roles of exogenous H2S in cardiac protection.

Nitrite and myocardial ischaemia reperfusion injury. Where are we now?

Cardiovascular disease remains the leading cause of death worldwide despite major advances in technology and treatment, with coronary heart disease (CHD) being a key contributor. Following an acute myocardial infarction (AMI), it is imperative that blood flow is rapidly restored to the ischaemic myocardium. However, this restoration is associated with an increased risk of additional complications and further cardiomyocyte death, termed myocardial ischaemia reperfusion injury (IRI). Endogenously produced nitric oxide (NO) plays an important role in protecting the myocardium from IRI. It is well established that NO mediates many of its downstream functions through the 'canonical' NO-sGC-cGMP pathway, which is vital for cardiovascular homeostasis; however, this pathway can become impaired in the face of inadequate delivery of necessary substrates, in particular L-arginine, oxygen and reducing equivalents. Recently, it has been shown that during conditions of ischaemia an alternative pathway for NO generation exists, which has become known as the 'nitrate-nitrite-NO pathway'. This pathway has been reported to improve endothelial dysfunction, protect against myocardial IRI and attenuate infarct size in various experimental models. Furthermore, emerging evidence suggests that nitrite itself provides multi-faceted protection, in an NO-independent fashion, against a myriad of pathophysiologies attributed to IRI. In this review, we explore the existing pre-clinical and clinical evidence for the role of nitrate and nitrite in cardioprotection and discuss the lessons learnt from the clinical trials for nitrite as a perconditioning agent. We also discuss the potential future for nitrite as a pre-conditioning intervention in man.

A Common Molecular Switch for H2S to Regulate Multiple Protein Targets

Hydrogen sulfide, a small molecule, produced by endogenous enzymes, such as CTH, CBS, and MPST using L-cysteine as substrates, has been reported to have numerous protective effects. However, the key problem that the target of H₂S and how it can affect the structure and activity of biological molecules is still unknown. Till now, there are two main theories of its working mechanism. One is that H₂S can modify the free thiol in cysteine to produce the persulfide state of the thiol and the sulfhydration of cysteine can significantly change the structure and activity of target proteins. The other theory is that H₂S, as an antioxidant molecule, can directly break the disulfide bond in target proteins, and the persulfide state of thiol can be an intermediate product during the reaction. Both phenomena exit for no doubt since they are both supported by large amounts of experiments. Here, we will summarize both theories and try to discuss which one is the more effective or direct mechanism for H₂S and what is the relationship between them. Therefore, we will discover more protein targets of H₂S with the mechanism and understand more about the effect of this small molecule.

Interaction among Hydrogen Sulfide and Other Gasotransmitters in Mammalian Physiology and Pathophysiology

Hydrogen sulfide (H₂S), nitric oxide (NO), carbon monoxide (CO), and sulfur dioxide (SO₂) were previously considered as toxic gases, but now they are found to be members of mammalian gasotransmitters family. Both H₂S and SO₂ are endogenously produced in sulfur-containing amino acid metabolic pathway in vivo. The enzymes catalyzing the formation of H₂S are mainly CBS, CSE, and 3-MST, and the key enzymes for SO₂ production are AAT1 and AAT2. Endogenous NO is produced from L-arginine under catalysis of three isoforms of NOS (eNOS, iNOS, and nNOS). HO-mediated heme catabolism is the main source of endogenous CO. These four gasotransmitters play important physiological and pathophysiological roles in mammalian cardiovascular, nervous, gastrointestinal, respiratory, and immune systems. The similarity among these four gasotransmitters can be seen from the same and/or shared signals. With many studies on the biological effects of gasotransmitters on multiple systems, the interaction among H₂S and other gasotransmitters has been gradually explored. H₂S not only interacts with NO to form nitroxyl (HNO), but also regulates the HO/CO and AAT/SO₂ pathways. Here, we review the biosynthesis and metabolism of the gasotransmitters in mammals, as well as the known complicated interactions among H₂S and other gasotransmitters (NO, CO, and SO₂) and their effects on various aspects of cardiovascular physiology and pathophysiology, such as vascular tension, angiogenesis, heart contractility, and cardiac protection.

Amelioration of testosterone-induced benign prostatic hyperplasia using febuxostat in rats: The role of VEGF/TGFβ and iNOS/COX-2

Benign prostatic hyperplasia (BPH) is a common male disorder. Febuxostat is a non-purine, selective inhibitor of xanthine oxidase (XO), which has a strong antioxidant capacity and pleiotropic pharmacological properties. This study's objective was to explore the potential ameliorative effects of febuxostat against testosterone-induced BPH in rats. Febuxostat (10 mg/kg/day, per os [p.o.]) prevented increased prostate index levels, serum levels of prostate-specific antigen (PSA), and testosterone levels compared to animals treated with testosterone alone, when administered for 28 days. Histological examination indicated that febuxostat dramatically ameliorated pathological changes in the prostate architecture compared to the testosterone group. Similarly, febuxostat markedly improved testosterone-induced oxidative stress by inhibiting the increase in lipid peroxide and nitrite content, and by reducing the level of depletion of reduced glutathione (GSH) and superoxide dismutase (SOD) activity, which significantly reduced the prostate content of pro-inflammatory cytokines, including tumor necrosis factor α (TNF-α) and interleukin 6 (IL-6). Furthermore, febuxostat significantly reduced the prostatic content, both in terms of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) messenger ribonucleic acid (mRNA) levels, and of protein levels. Moreover, compared to the testosterone group, febuxostat's beneficial effects prevented the increase in growth factors, comprising vascular endothelial cell growth factor A (VEGF-A) and transforming growth factor beta (TGF-β) protein levels. Its ameliorating effects were equal to those of finasteride, which is the most widely used remedy for BPH. In conclusion, this study provides novel evidence that febuxostat experimentally attenuates testosterone-induced BPH in rats, at least in part by inhibiting iNOS/COX-2 and VEGF/TGF-β pathways.

H2S promotes developmental brain angiogenesis via the NOS/NO pathway in zebrafish

Background

Hydrogen sulphide (H₂S) is considered as the third member of the gasotransmitter family, along with nitric oxide (NO) and carbon monoxide. H₂S has been reported to induce angiogenesis by promoting the growth, migration and tube-like structure formation of endothelial cells. Those studies were conducted in conditions of cell culture, mouse Matrigel plug assay model, rat wound healing model or rat hindlimb ischaemia model. Recent in vivo studies showed the physiological importance of H₂S in muscle angiogenesis. However, the importance of endogenous H₂S for brain angiogenesis during development remains unknown. We therefore aimed at determining the role of H₂S in brain vascular development.

Methods and results

Both knockdown and knockout of H₂S-producing enzymes, cystathionine β-synthase (cbs) and cystathionine γ-lyase (cth), using morpholino oligonucleotides and clustered regularly interspaced short palindromic repeats/Cas9-mediated mutation, impaired brain vascular development of larval zebrafish. Incubation with the slow-releasing H₂S donor GYY4137 alleviated the defects of brain vascular development in cbs and cth morphants. Quantitative analysis of the midbrain vascular network showed that H₂S enhances angiogenesis without affecting the topological structure of the brain vasculature. Mechanically, nitric oxide synthase 2a (nos2a) expression and NO production were decreased in both cbs and cth morphants. Overexpression of nos2a by coinjection of cbs or cth MO with full-length zebrafish nos2a mRNA alleviated the brain vascular developmental defects in cbs and cth morphants.

Conclusion

We conclude that H₂S promotes brain developmental angiogenesis via the NOS/NO pathway in zebrafish.

Long-term co-administration of sodium nitrite and sodium hydrosulfide inhibits hepatic gluconeogenesis in male type 2 diabetic rats: Role of PI3K-Akt-eNOS pathway

OBJECTIVE

A deficiency in hydrogen sulfide (H₂S) and nitric oxide (NO) contributes to the development of type 2 diabetes (T2D). An inhibitory effect on liver gluconeogenesis has been reported in rats with T2D with co-administration of sodium nitrite and sodium hydrosulfide (NaSH); the underlying mechanisms have however not yet been elucidated. The aim of this study is to determine the long-term effects of co-administering sodium nitrite and NaSH on expression of genes involved in liver gluconeogenesis in rats with T2D.

METHODS

T2D was induced using a high fat diet combined with low-dose of streptozotocin (30 mg/kg). Rats were divided into 5 groups (n = 7/group): Control, T2D, T2D + nitrite, T2D + NaSH, and T2D + nitrite+NaSH. Nitrite (50 mg/L) and NaSH (0.28 mg/kg) were administered for 9 weeks. Intraperitoneal pyruvate tolerance test (PTT) was performed at the end of the ninth week and mRNA expressions of PI3K, Akt, eNOS, PEPCK, G6Pase, and FBPase were measured in the liver.

RESULTS

Co-administration of nitrite and NaSH decreased elevated serum glucose concentrations during PTT. Compared to T2D + nitrite, co-administration of nitrite and NaSH resulted in significant increases in mRNA expression of PI3K, Akt, and eNOS and significant decreases in mRNA expression of G6Pase and FBPase but had no effect on PEPCK expression.

CONCLUSION

Long-term NaSH administration at low-dose, potentiated the inhibitory effects of nitrite on mRNA expression of key liver gluconeogenic enzymes in rats with T2D. This inhibitory effect of nitrite and NaSH co-administration on gluconeogenesis were associated with increased gene expression of PI3K, Akt, and eNOS in the liver.

Potential role of hydrogen sulfide in diabetes-impaired angiogenesis and ischemic tissue repair

Diabetes is one of the most prevalent metabolic disorders and is estimated to affect 400 million of 4.4% of population worldwide in the next 20 year. In diabetes, risk to develop vascular diseases is two-to four-fold increased. Ischemic tissue injury, such as refractory wounds and critical ischemic limb (CLI) are major ischemic vascular complications in diabetic patients where oxygen supplement is insufficient due to impaired angiogenesis/neovascularization. In spite of intensive studies, the underlying mechanisms of diabetes-impaired ischemic tissue injury remain incompletely understood. Hydrogen sulfide (H₂S) has been considered as a third gasotransmitter regulating angiogenesis under physiological and ischemic conditions. Here, the underlying mechanisms of insufficient H₂S-impaired angiogenesis and ischemic tissue repair in diabetes are discussed. We will primarily focuses on the signaling pathways of H₂S in controlling endothelial function/biology, angiogenesis and ischemic tissue repair in diabetic animal models. We summarized that H₂S plays an important role in maintaining endothelial function/biology and angiogenic property in diabetes. We demonstrated that exogenous H₂S may be a theraputic agent for endothelial dysfunction and impaired ischemic tissue repair in diabetes.

Hydrogen sulfide stimulates xanthine oxidoreductase conversion to nitrite reductase and formation of NO

Cardiovascular disease is the leading cause of death and disability worldwide with increased oxidative stress and reduced NO bioavailability serving as key risk factors. For decades, elevation in protein abundance and enzymatic activity of xanthine oxidoreductase (XOR) under hypoxic/inflammatory conditions has been associated with organ damage and vascular dysfunction. Recent reports have challenged this dogma by identifying a beneficial function for XOR, under similar hypoxic/acidic conditions, whereby XOR catalyzes the reduction of nitrite (NO2-) to nitric oxide (NO) through poorly defined mechanisms. We previously reported that hydrogen sulfide (H2S/sulfide) confers significant vascular benefit under these same conditions via NO2- mediated mechanisms independent of nitric oxide synthase (NOS). Here we report for the first time the convergence of H2S, XOR, and nitrite to form a concerted triad for NO generation. Specifically, hypoxic endothelial cells show a dose-dependent, sulfide and polysulfide (diallyl trisulfide (DATS)-induced, NOS-independent NO2- reduction to NO that is dependent upon the enzymatic activity of XOR. Interestingly, nitrite reduction to NO was found to be slower and more sustained with DATS compared to H2S. Capacity for sulfide/polysulfide to produce an XOR-dependent impact on NO generation translates to salutary actions in vivo as DATS administration in cystathionine-γ-lyase (CSE) knockout mice significantly improved hindlimb ischemia blood flow post ligation, while the XOR-specific inhibitor, febuxostat (Febx), abrogated this benefit. Moreover, flow-mediated vasodilation (FMD) in CSE knockout mice following administration of DATS resulted in greater than 4-fold enhancement in femoral artery dilation while co-treatment with Febx completely completely abrogated this effect. Together, these results identify XOR as a focal point of convergence between sulfide- and nitrite-mediated signaling, as well as affirm the critical need to reexamine current dogma regarding inhibition of XOR in the context of vascular dysfunction.

The Effect of a Fast-Releasing Hydrogen Sulfide Donor on Vascularization of Subcutaneous Scaffolds in Immunocompetent and Immunocompromised Mice

Islet transplantation into subcutaneous polymer scaffolds has shown to successfully induce normoglycemia in type 1 diabetes models. Vascularization of these scaffolds is imperative for optimal control of glucose levels. We studied the effect of the vascular stimulator hydrogen sulfide (H₂S) on the degree of vascularization of a scaffold and the role of the immune system in this process. Scaffolds were subcutaneously implanted in immunocompetent C57BL/6 and immunocompromised nude mice. Mice received twice-daily intraperitoneal injections of the fast-releasing H₂S donor sodium hydrosulfide (NaHS, 25 or 50 μmol/kg) or saline for 28 days. After 63 days the vascular network was analyzed by histology and gene expression. Here we showed that the vascularization of a subcutaneous scaffold in nude mice was significantly impaired by H₂S treatment. Both the CD31 gene and protein expression were reduced in these scaffolds compared to the saline-treated controls. In C57BL/6 mice, the opposite was found, the vascularization of the scaffold was significantly increased by H₂S. The mRNA expression of the angiogenesis marker CD105 was significantly increased compared to the controls as well as the number of CD31 positive blood vessels. In conclusion, the immune system plays an important role in the H₂S mediated effect on vascularization of subcutaneous scaffolds.

Evaluation of combined therapeutic effects of hydrogen sulfide donor sodium hydrogen sulfide and phosphodiesterase type-5 inhibitor tadalafil on erectile dysfunction in a partially bladder outlet obstructed rat model

AIMS

To evaluate the impacts of hydrogen sulfide (H₂ S) donor, sodium hydrogen sulfide (NaHS), and phosphodiesterase type-5 inhibitor (PDE5i), tadalafil per se and their combination treatment on partial bladder outlet obstruction (PBOO)-induced erectile dysfunction (ED).

METHODS

Sprague-Dawley rats were equally divided into five groups: (a) sham-operated control; (b) PBOO; (c) PBOO-treated with NaHS (5.6 mg/kg/day, ip); (d) PBOO-treated with tadalafil (2 mg/kg/day, oral); and (e) PBOO-treated with combination of NaHS and tadalafil. The obstruction was created by urethral ligation for 6 weeks. In vivo erectile responses, in vitro relaxant and contractile responses in penile tissue as well as protein expression of nitric oxide synthases (NOS), H₂ S synthesis enzymes, oxidative stress, hypoxia, fibrosis markers, and the smooth muscle/collagen ratio and apoptosis were analyzed.

RESULTS

Combined treatment entirely returned increased bladder mass, reduced erectile responses, relaxation responses to acetylcholine, and electrical field stimulation in obstructed rats, while partial amelioration was observed after mono-treatment. Decreased neuronal NOS and 3-mercaptopiruvate transferase enzyme expressions in penile tissue from obstructed rats were also entirely restored by the combined treatment. Mono-treatment partially improved increased hypoxia, oxidative stress, fibrosis markers, decreased smooth muscle mass, and H₂ S levels, while combined therapy completely recovered.

CONCLUSIONS

The combination therapy with H₂ S donor and PDE5i had positive effects on erectile responses through the improvement of ischemia-induced morphological and functional penile alterations in obstruction. H₂ S and NO may likely play a synergistic role in the regulation of erectile function and have constructive effects on clinical outcomes in male patients with ED and benign prostatic hyperplasia/lower urinary tract symptoms.

Signalling by hydrogen sulfide and polysulfides via protein S-sulfuration

Hydrogen sulfide (H2 S) is a signalling molecule that regulates neuronal transmission, vascular tone, cytoprotection, inflammatory responses, angiogenesis, and oxygen sensing. Some of these functions have recently been ascribed to its oxidized form polysulfides (H2 Sn ), which can be produced by 3-mercaptopyruvate sulfurtransferase (MPST), also known as a H2 S-producing enzyme. H2 Sn activate ion channels, tumour suppressors, transcription factors, and protein kinases. H2 Sn S-sulfurate (S-sulfhydrate) cysteine residues of these target proteins to modify their activity by inducing conformational changes through the formation of a disulfide bridge between the two cysteine residues involved. The chemical interaction between H2 S and NO also generates H2 Sn , which may be a chemical entity that exerts the synergistic effect of H2 S and NO. MPST also produces redox regulators cysteine persulfide (CysSSH), GSH persulfide (GSSH), and persulfurated proteins. In addition to MPST, haemoproteins such as haemoglobin, myoglobin, neuroglobin, and catalase as well as SOD can produce H2 Sn , and sulfide quinone oxidoreductase and cysteinyl tRNA synthetase can make GSSH and CysSSH. This review focuses on the recent progress in the study of the production and physiological roles of these persulfurated and polysulfurated molecules. LINKED ARTICLES: This article is part of a themed section on Hydrogen Sulfide in Biology & Medicine. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.4/issuetoc.

Regulation of carbohydrate metabolism by nitric oxide and hydrogen sulfide: Implications in diabetes

Nitric oxide (NO) and hydrogen sulfide (H₂S) are two gasotransmitters that are produced in the human body and have a key role in many of the physiological activities of the various organ systems. Decreased NO bioavailability and deficiency of H₂S are involved in the pathophysiology of type 2 diabetes and its complications. Restoration of NO levels have favorable metabolic effects in diabetes. The role of H₂S in pathophysiology of diabetes is however controversial; H₂S production is decreased during development of obesity, diabetes, and its complications, suggesting the potential therapeutic effects of H₂S. On the other hand, increased H₂S levels disturb the pancreatic β-cell function and decrease insulin secretion. In addition, there appear to be important interactions between NO and H₂S at the levels of both biosynthesis and signaling pathways, yet clear an insight into this relationship is lacking. H₂S potentiates the effects of NO in the cardiovascular system as well as NO release from its storage pools. Likewise, NO increases the activity and the expression of H₂S-generating enzymes. Inhibition of NO production leads to elimination/attenuation of the cardioprotective effects of H₂S. Regarding the increasing interest in the therapeutic applications of NO or H₂S-releasing molecules in a variety of diseases, particularly in the cardiovascular disorders, much is to be learned about their function in glucose/insulin metabolism, especially in diabetes. The aim of this review is to provide a better understanding of the individual and the interactive roles of NO and H₂S in carbohydrate metabolism.

Hydrogen sulfide regulation of renal and mesenteric blood flow

Hydrogen sulfide (H₂S) dilates isolated arteries, and knockout of the H₂S-synthesizing enzyme cystathionine γ-lyase (CSE) increases blood pressure. However, the contributions of endogenously produced H₂S to blood flow regulation in specific vascular beds are unknown. Published studies in isolated arteries show that CSE production of H₂S influences vascular tone more in small mesenteric arteries than in renal arteries or the aorta. Therefore, the goal of this study was to evaluate H₂S regulation of blood pressure, vascular resistance, and regional blood flows using chronically instrumented rats. We hypothesized that during whole animal CSE inhibition, vascular resistance would increase more in the mesenteric than the renal circulation. Under anesthesia, CSE inhibition [β-cyanoalanine (BCA), 30 mg/kg bolus + 5 mg·kg^-1·min^-1 for 20 min iv) rapidly increased mean arterial pressure (MAP) more than saline administration (%Δ: saline -1.4 ± 0.75 vs. BCA 7.1 ± 1.69, P < 0.05) but did not change resistance (MAP/flow) in either the mesenteric or renal circulation. In conscious rats, BCA infusion similarly increased MAP (%Δ: saline -0.8 ± 1.18 vs. BCA 8.2 ± 2.6, P < 0.05, n = 7) and significantly increased mesenteric resistance (saline 0.9 ± 3.1 vs. BCA 15.6 ± 6.5, P < 0.05, n = 12). The H₂S donor Na₂S (50 mg/kg) decreased blood pressure and mesenteric resistance ,but the fall in resistance was not significant. Inhibiting CSE for multiple days with dl-proparglycine (PAG, 50 mg·kg^-1·min^-1 iv bolus for 5 days) significantly increased vascular resistance in both mesenteric (ratio of day 1: saline 0.86 ± 0.033 vs. PAG 1.79 ± 0.38) and renal circulations (ratio of day 1: saline 1.26 ± 0.22 vs. 1.98 ± 0.14 PAG). These results support our hypothesis that CSE-derived H₂S is an important regulator of blood pressure and vascular resistance in both mesenteric and renal circulations. Furthermore, inhalation anesthesia diminishes the effect of CSE inhibition on vascular tone.NEW & NOTEWORTHY These results suggest that CSE-derived H₂S has a prominent role in regulating blood pressure and blood flow under physiological conditions, which may have been underestimated in prior studies in anesthetized subjects. Therefore, enhancing substrate availability or enzyme activity or dosing with H₂S donors could be a novel therapeutic approach to treat cardiovascular diseases.

Hydrogen sulfide potentiates the favorable metabolic effects of inorganic nitrite in type 2 diabetic rats

OBJECTIVE

Decreased nitric oxide (NO) bioavailability and hydrogen sulfide (H₂S) deficiency have been linked with the pathophysiology of type 2 diabetes (T2D). Restoration of NO levels by nitrite have been associated with favorable metabolic effects in T2D. Moreover, H₂S can potentiate the effects of NO in the cardiovascular system. The aim of this study was to determine the effects of long-term co-administration of sodium nitrite and sodium hydrosulfide (NaSH) on carbohydrate metabolism in type 2 diabetic rats.

METHODS

T2D was induced using chronic high fat diet (HFD) feeding combined with low dose streptozotocin (STZ) regimen. Rats were divided into 5 groups (N = 10/group): Control, T2D, T2D + nitrite, T2D + NaSH, and T2D + nitrite + NaSH. Nitrite (50 mg/L in drinking water) and NaSH (0.28 mg/kg, daily i. p. injection) were administered for 9 weeks. Fasting serum glucose, insulin, lipid profile, liver function tests, and oxidative stress indices were measured. Intraperitoneal glucose tolerance test (GTT) was performed at the end of the eighth week, and three days later, intraperitoneal pyruvate tolerance test (PTT) was done. Protein levels and mRNA expression of glucose transporter type 4 (GLUT4) in soleus muscle and epididymal adipose tissue as well as mRNA expression of H₂S-producing enzymes in the liver, soleus muscle, and epididymal adipose tissue were measured at the end of the study.

RESULTS

Compared to the controls, HFD and STZ treated rats developed metabolic dysfunction. Nitrite treatment improved carbohydrate metabolism, liver function, and oxidative stress indices whereas NaSH treatment per se had no significant effects. However, co-administration of NaSH and nitrite resulted in further improvement in serum insulin level, GTT, PTT, liver function, oxidative stress, protein level and mRNA expression of GLUT4, as well as mRNA expression of H₂S-producing enzymes in diabetic rats.

CONCLUSION

Low dose of NaSH per se had no effect on carbohydrate metabolism while it potentiated the favorable metabolic effects of inorganic nitrite in type 2 diabetic rats. These favorable effects were associated with decreased oxidative stress and increased GLUT4 expression in insulin-sensitive tissues as well as improvement of liver function.

A Review of Hydrogen Sulfide Synthesis, Metabolism, and Measurement: Is Modulation of Hydrogen Sulfide a Novel Therapeutic for Cancer?

Significance: Hydrogen sulfide (H2S) has been recognized as the third gaseous transmitter alongside nitric oxide and carbon monoxide. In the past decade, numerous studies have demonstrated an active role of H2S in the context of cancer biology. Recent Advances: The three H2S-producing enzymes, namely cystathionine γ-lyase (CSE), cystathionine β-synthase (CBS), and 3-mercaptopyruvate sulfurtransferase (3MST), have been found to be highly expressed in numerous types of cancer. Moreover, inhibition of CBS has shown anti-tumor activity, particularly in colon cancer, ovarian cancer, and breast cancer, whereas the consequence of CSE or 3MST inhibition remains largely unexplored in cancer cells. Intriguingly, H2S donation at high amounts or a long time duration has also been observed to induce cancer cell apoptosis in vitro and in vivo while sparing noncancerous fibroblast cells. Therefore, a bell-shaped model has been proposed to explain the role of H2S in cancer development. Specifically, endogenous H2S or a relatively low level of exogenous H2S may exhibit a pro-cancer effect, whereas exposure to H2S at a higher amount or for a long period may lead to cancer cell death. This indicates that inhibition of H2S biosynthesis and H2S supplementation serve as two distinct ways for cancer treatment. This paradoxical role of H2S has stimulated the enthusiasm for the development of novel CBS inhibitors, H2S donors, and H2S-releasing hybrids. Critical Issues: A clear relationship between H2S level and cancer progression remains lacking. The possibility that the altered levels of these byproducts have influenced the cell viability of cancer cells has not been excluded in previous studies when modulating H2S producing enzymes. Future Directions: The consequence of CSE or 3MST inhibition in cancer cells need to be examined in the future. Better portrayal of the crosstalk among these gaseous transmitters may not only lead to an in-depth understanding of cancer progression but also shed light on novel strategies for cancer therapy.

Nitric Oxide and Hydrogen Sulfide Regulation of Ischemic Vascular Growth and Remodeling

Ischemic vascular remodeling occurs in response to stenosis or arterial occlusion leading to a change in blood flow and tissue perfusion. Altered blood flow elicits a cascade of molecular and cellular physiological responses leading to vascular remodeling of the macro- and micro-circulation. Although cellular mechanisms of vascular remodeling such as arteriogenesis and angiogenesis have been studied, therapeutic approaches in these areas have had limited success due to the complexity and heterogeneous constellation of molecular signaling events regulating these processes. Understanding central molecular players of vascular remodeling should lead to a deeper understanding of this response and aid in the development of novel therapeutic strategies. Hydrogen sulfide (H₂ S) and nitric oxide (NO) are gaseous signaling molecules that are critically involved in regulating fundamental biochemical and molecular responses necessary for vascular growth and remodeling. This review examines how NO and H₂ S regulate pathophysiological mechanisms of angiogenesis and arteriogenesis, along with important chemical and experimental considerations revealed thus far. The importance of NO and H₂ S bioavailability, their synthesis enzymes and cofactors, and genetic variations associated with cardiovascular risk factors suggest that they serve as pivotal regulators of vascular remodeling responses. © 2019 American Physiological Society. Compr Physiol 9:1213-1247, 2019.