Novel Angiogenic Activity and Molecular Mechanisms of ZYZ-803, a Slow-Releasing Hydrogen Sulfide-Nitric Oxide Hybrid Molecule

Codelivery of Gaseous Signaling Molecules for Biomedical Applications

Gaseous signaling molecules (GSMs) including nitric oxide (NO), carbon monoxide (CO) and hydrogen sulfide (H2S) have presented excellent therapeutic efficacy such as anti-inflammatory, anti-microbial and anti-cancer effects and multiple biomedical applications in recent years. As the three most vital signaling molecules in human physiology, these three GSMs show so intertwined and orchestrated interactions that the synergy of multiple gases may demonstrate a more complex therapeutic potential than single gas delivery. Consequently, researchers have been devoted to developing codelivery systems of GSMs by synthesizing a single molecule as a dual donor to maximize the gaseous therapeutic efficacy. In this minireview, we summarize the recent developments of molecules or materials enabling codelivery of GSMs for biomedical applications. It appears that compared with the abundant cases of codelivery of NO and H2S, research on codelivery of CO and the other two GSMs separately remains to be explored.

Gelatin-based biomaterials and gelatin as an additive for chronic wound repair

Disturbing or disrupting the regular healing process of a skin wound may result in its progression to a chronic state. Chronic wounds often lead to increased infection because of their long healing time, malnutrition, and insufficient oxygen flow, subsequently affecting wound progression. Gelatin-the main structure of natural collagen-is widely used in biomedical fields because of its low cost, wide availability, biocompatibility, and degradability. However, gelatin may exhibit diverse tailored physical properties and poor antibacterial activity. Research on gelatin-based biomaterials has identified the challenges of improving gelatin's poor antibacterial properties and low mechanical properties. In chronic wounds, gelatin-based biomaterials can promote wound hemostasis, enhance peri-wound antibacterial and anti-inflammatory properties, and promote vascular and epithelial cell regeneration. In this article, we first introduce the natural process of wound healing. Second, we present the role of gelatin-based biomaterials and gelatin as an additive in wound healing. Finally, we present the future implications of gelatin-based biomaterials.

Long noncoding RNA KCNQ1OT1 aggravates cerebral infarction by regulating PTBT1/SIRT1 via miR-16-5p

Cerebral infarction (CI) is one of the leading causes of disability and death. LncRNAs are key factors in CI progression. Herein, we studied the function of long noncoding RNA KCNQ1OT1 in CI patient plasma samples and in CI models. Quantitative real-time PCR and Western blotting tested gene and protein expressions. The interactions of KCNQ1OT1/PTBP1 and miR-16-5p were analyzed using dual-luciferase reporter and RNA immunoprecipitation assays; MTT assays measured cell viability. Cell migration and angiogenesis were tested by wound healing and tube formation assays. Pathological changes were analyzed by triphenyltetrazolium chloride and routine staining. We found that KCNQ1OT1 and PTBP1 were overexpressed and miR-16-5p was downregulated in CI patient plasma and in oxygen-glucose deprived (OGD) induced mouse brain microvascular endothelial (bEnd.3) cells. KCNQ1OT1 knockdown suppressed pro-inflammatory cytokine production and stimulated angiogenic responses in OGD-bEnd.3 cells. KCNQ1OT1 upregulated PTBP1 by sponging miR-16-5p. PTBP1 overexpression or miR-16-5p inhibition attenuated the effects of KCNQ1OT1 knockdown. PTBP1 silencing protected against OGD-bEnd.3 cell injury by enhancing SIRT1. KCNQ1OT1 silencing or miR-16-5p overexpression also alleviated ischemic injury in a mice middle cerebral artery occlusion model. Thus, KCNQ1OT1 silencing alleviates CI by regulating the miR-16-5p/PTBP1/SIRT1 pathway, providing a theoretical basis for novel therapeutic strategies targeting CI.

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.

Chemical Strategies Toward Prodrugs and Fluorescent Probes for Gasotransmitters

Three gaseous molecules are widely accepted as important gasotransmitters in mammalian cells, namely NO, CO and H2S. Due to the pharmacological effects observed in preclinical studies, these three gasotransmitters represent promising drug candidates for clinical translation. Fluorescent probes of the gasotransmitters are also in high demand; however, the mechanisms of actions or the roles played by gasotransmitters under both physiological and pathological conditions remain to be answered. In order to bring these challenges to the attention of both chemists and biologists working in this field, we herein summarize the chemical strategies used for the design of both probes and prodrugs of these three gasotransmitters.

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

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

Role of RIPK3‑CaMKII‑mPTP signaling pathway‑mediated necroptosis in cardiovascular diseases (Review)

Necroptosis, which is distinct from apoptosis and necrosis, serves a crucial role in ontogeny and the maintenance of homeostasis. In the last decade, it has been demonstrated that the pathogenesis of cardiovascular diseases is also linked to necroptosis. Receptor interaction protein kinase (RIPK) 1, RIPK3 and mixed lineage kinase domain‑like protein serve vital roles in necroptosis. In addition to the aforementioned necroptosis‑related components, calcium/calmodulin‑dependent protein kinase II (CaMKII) has been identified as a novel substrate for RIPK3 that promotes the opening of the mitochondrial permeability transition pore (mPTP), and thus, mediates necroptosis of myocardial cells through the RIPK3‑CaMKII‑mPTP signaling pathway. The present review provides an overview of the current knowledge of the RIPK3‑CaMKII‑mPTP‑mediated necroptosis signaling pathway in cardiovascular diseases, focusing on the role of the RIPK3‑CaMKII‑mPTP signaling pathway in acute myocardial infarction, ischemia‑reperfusion injury, heart failure, abdominal aortic aneurysm, atherosclerosis, diabetic cardiomyopathy, hypertrophic cardiomyopathy, atrial fibrillation, and the cardiotoxicity associated with antitumor drugs and other chemicals. Finally, the present review discusses the research status of drugs targeting the RIPK3‑CaMKII‑mPTP signaling pathway.

Hydrogen sulfide: Recent development of its dual donors and hybrid drugs

Hydrogen sulfide (H2 S) is an important gaseous signalling molecule known to be critically involved in regulating cellular redox homeostasis. As the beneficial and therapeutic effects of H2 S in pathophysiology, such as in cardiovascular and neurodegenerative diseases, have emerged, so too has the drive for the development of H2 S-releasing compounds (aka donors) and their therapeutic applications. Most reported donor compounds singularly release H2 S through biocompatible triggers. An emerging area in the field is the development of compounds that can co-deliver H2 S with other drugs or biologically relevant species, such as reactive oxygen and nitrogen species (ROS and RNS, respectively). These H2 S-based dual donors and hybrid drugs are expected to offset negative side effects from individual treatments or achieve synergistic effects rendering them more clinically effective. Additionally, considering that molecules exist and interact physiologically, dual donors may more accurately mimic biological systems as compared to single donors and allow for the elucidation of fundamental chemistry and biology. This review focuses on the recent advances in the development of H2 S-based dual donors and hybrid drugs along with their design principles and synergistic effects.

Gasotransmitter-Induced Therapeutic Angiogenesis: A Biomaterial Prospective

Gasotransmitters such as NO, H₂S, and CO have emerged as key players in the regulation of various pathophysiological functions, prompting the development of gas therapy for various pathogeneses. Deficient production of gasotransmitters has been linked to various diseases such as hypertension, endothelial dysfunction, myocardial infarction, ischemia, and impaired wound healing, as they are involved in the regulatory action of angiogenesis. A better understanding of the regulatory mechanisms has given new hope to address the vascular impairment caused by the breakthroughs in gasotransmitters as therapeutics. However, the unstable nature and poor target specificity of gas donors limit the full efficacy of drugs. In this regard, biomaterials that possess excellent biocompatibility and porosity are ideal drug carriers to deliver the gas transmitters in a tunable manner for therapeutic angiogenesis. This review article provides a comprehensive discussion of biomaterial-based gasotransmitter delivery approaches for therapeutic angiogenesis. The critical role of gasotransmitters in modulating angiogenesis during tissue repair as well as their challenges and future directions are demonstrated.

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.

Hydrogen sulfide-releasing polyurethane/gelatin/keratin-TA conjugate mats for wound healing

Hydrogen sulfide (H₂S) has indispensable effects on wound healing promotion, such as anti-inflammatory, cell proliferation enhancement, and angiogenesis improvement. However, small-molecular donors have drawbacks of burst release and low biocompatibility. In this study, a novel bio-macromolecular donor of H₂S based on a keratin-thiobenzoic acid conjugate (KTC) was first synthesized by a thiol-disulfide exchange reaction. Then, the KTC was incorporated into polyurethane and gelatin to fabricate nanofibrous mats by electrospinning. Interestingly, both the KTC donor and biocomposite mats were capable of releasing H₂S triggered by glutathione (GSH) under physiological conditions. These mats had excellent water absorption capacity, demonstrating their great ability to absorb tissue exudate. In addition, these mats possessed a notable antioxidant ability, thereby protecting cell membranes from oxidation. Cell assays in vitro demonstrated that these mats could promote cell proliferation and migration. Furthermore, the in vivo full-thickness defect model verified that these H₂S-releasing wound dressing mats could accelerate granulation tissue formation, enhance collagen deposition, and promote angiogenesis. Based on these advantages, these wound dressing mats had great potential applications for wound healing.

Hydrogen Sulfide Biomedical Research in China-20 Years of Hindsight

Hydrogen sulfide (H2S) is an important gasotransmitter that is produced by mammalian cells and performs profound physiological and pathophysiological functions. Biomedical research on H2S metabolism and function in China began 20 years ago, which pioneered the examination of the correlation of abnormal H2S metabolism and cardiovascular diseases. Over the last two decades, research teams in China have made numerous breakthrough discoveries on the effects of H2S metabolism on hypertension, atherosclerosis, pulmonary hypertension, shock, angiogenesis, chronic obstructive pulmonary disease, pain, iron homeostasis, and testicle function, to name a few. These research developments, carried by numerous research teams all over China, build nationwide research network and advance both laboratory study and clinical applications. An integrated and collaborative research strategy would further promote and sustain H2S biomedical research in China and in the world.

Nitric Oxide-Releasing Platforms for Treating Cardiovascular Disease

Cardiovascular disease (CVD) is the first leading cause of death globally. Nitric oxide (NO) is an important signaling molecule that mediates diverse processes in the cardiovascular system, thereby providing a fundamental basis for NO-based therapy of CVD. At present, numerous prodrugs have been developed to release NO in vivo. However, the clinical application of these prodrugs still faces many problems, including the low payloads, burst release, and non-controlled delivery. To address these, various biomaterial-based platforms have been developed as the carriers to deliver NO to the targeted tissues in a controlled and sustained manner. This review aims to summarize recent developments of various therapeutic platforms, engineered to release NO for the treatment of CVD. In addition, two potential strategies to improve the effectiveness of existing NO therapy are also discussed, including the combination of NO-releasing platforms and either hydrogen sulfide-based therapy or stem cell therapy. Hopefully, some NO-releasing platforms may provide important therapeutic benefits for CVD.

Discovery of 1,3,4-oxadiazole derivatives containing a bisamide moiety as a novel class of potential cardioprotective agents

Myocardial injury is a nonnegligible problem in cardiovascular diseases and cancer therapy. The functional feature of N-containing heterocycles in the cardiovascular field has attracted much attention in recent years. Herein, we discovered a lead compound 12a containing 1,3,4-oxadiazole by extensive screening of anticancer derivatives containing nitrogen-heterocycle, which exhibited potential protective activity against oxidative stress in cardiomyocytes. Follow-up structure-activity relationship (SAR) studies also highlighted the role of substitution sites and bisamide moiety in enhancing the protective activity against oxidative stress. Specifically, compound 12d exhibited low cytotoxicity under high concentration and potent myocardial protection against oxidative stress in H9c2 cells. Preliminary mechanistic studies showed compound 12d could decrease the expression of cardiac hypertrophy and oxidative stress-related proteins/genes and reduce mitochondria-mediated cell apoptosis, thereby enhancing the cell vitality of injured cardiomyocytes. In this study, 1,3,4-oxadiazole may represent a novel pharmacophore that possesses potential myocardial protection and provides more choices for future optimization of cardiovascular drugs, especially for the treatment of onco-cardiology.

Enzyme-responsive hybrid prodrug of nitric oxide and hydrogen sulfide for heart failure therapy

A hybrid prodrug was synthesized to realize the combined delivery of nitric oxide and hydrogen sulfide. The NO-H₂S donor can release nitric oxide and hydrogen sulfide step by step in response to the endogenous enzymes β-galactosidase and carbonic anhydrase, providing potent therapeutic efficacy for heart failure post- myocardial infarction.

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.

H2S Donors and Their Use in Medicinal Chemistry

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

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.

Enhanced NO-induced angiogenesis via NO/H2S co-delivery from self-assembled nanoparticles

Nitric oxide (NO) and hydrogen sulfide (H2S) have been the focus of research as therapeutic agents because of their biological functions. The controlled release of NO and H2S can enhance NO-induced angiogenesis by H2S inhibiting PDE5A. Polymeric carriers have been researched to deliver gasotransmitters and used as therapeutic agents because of their important ability to help control the concentration of NO and H2S. Here, NO/H2S-releasing nanoparticles were self-assembled from carboxyl-functionalized mPEG-PLGH-thiobenzamide [(methoxy poly (ethylene glycol-b-lactic-co-glycolic-co-hydroxymethyl propionic acid)-thiobenzamide)], PTA copolymer and encapsulated diethylenetriamine NONOate (DETA NONOate). The PTA copolymers were characterized by FT-IR and 1H NMR, and the PTA-NO nanoparticles (PTA-NO-NPs) were confirmed to have core-shell structures with a size of about 140 nm. The PTA-NO-NPs were demonstrated to be biocompatible with viabilities above 100% in various cell types, with a sustained NO and H2S releasing behavior over 72 h. Co-releasing NO and H2S accelerated tube formation by HUVECs compared to the only NO- or H2S-releasing groups in vitro. Also, PTA-NO-NPs performed enhanced angiogenesis compared to the control groups with statistically significant differences ex vivo. These results indicate the feasibility of medical applications through NO and H2S crosstalk.

Trends in H2S-Donors Chemistry and Their Effects in Cardiovascular Diseases

Hydrogen sulfide (H₂S) is an endogenous gasotransmitter recently emerged as an important regulatory mediator of numerous human cell functions in health and in disease. In fact, much evidence has suggested that hydrogen sulfide plays a significant role in many physio-pathological processes, such as inflammation, oxidation, neurophysiology, ion channels regulation, cardiovascular protection, endocrine regulation, and tumor progression. Considering the plethora of physiological effects of this gasotransmitter, the protective role of H₂S donors in different disease models has been extensively studied. Based on the growing interest in H₂S-releasing compounds and their importance as tools for biological and pharmacological studies, this review is an exploration of currently available H₂S donors, classifying them by the H₂S-releasing-triggered mechanism and highlighting those potentially useful as promising drugs in the treatment of cardiovascular diseases.

The vasodilatory mechanism of nitric oxide and hydrogen sulfide in the human mesenteric artery in patients with colorectal cancer

Recent studies have focused on the role of gasotransmitters in cancer progression and prevention. Therefore, the current study was designed to explore the vasodilator activity of NO and H₂S in the human mesenteric arteries of patients with colorectal cancer (CRC) via the activation of K⁺ channels. A total of two sets of experiments were established for the current investigation. Blood samples from patients with CRC were obtained to detect serum levels of endocan and malondialdehyde (MDA). The role of K⁺ channels in mediating the vasodilation of the human mesenteric artery in response to sodium nitroprusside (SNP) and sodium disulfide (Na₂S) was assessed. The level of serum endocan was indicated to be decreased in patients with CRC compared with healthy individuals, while the level of serum MDA remained unaltered between groups. The arterial rings pre-contracted with norepinephrine were first relaxed by the cumulative addition of increasing concentrations of either SNP (30 nM-30 µM) or (1-6 mM). Maximal relaxation rates were then calculated at 15 min intervals for 60 min. Pre-incubation of arterial rings for 20 min with individual K⁺ channel blockers was indicated to significantly reduce SNP- and Na₂S-induced relaxation at different time points. Pre-treatment of L-nitro-arginine methyl ester did not alter vasodilation that was induced by Na₂S. Furthermore, vasodilation of the CRC mesenteric artery was not altered by the synergistic application of SNP and Na₂S, while pre-incubation of arterial rings with D,L-propargylglycine significantly enhanced vasodilation induced by SNP. These results indicated that endothelial dysfunction and oxidative stress do not serve roles in the pathogenesis of CRC. The dilatory mechanisms of NO and H₂S in mesenteric arteries of patients with CRC were K⁺ channel- and time-dependent, and the activity of cystathionine γ-lyase enzyme inhibited the ability of exogenous NO in vasodilation processes.

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.

Hydrogen Sulfide and Carnosine: Modulation of Oxidative Stress and Inflammation in Kidney and Brain Axis

Emerging evidence indicates that the dysregulation of cellular redox homeostasis and chronic inflammatory processes are implicated in the pathogenesis of kidney and brain disorders. In this light, endogenous dipeptide carnosine (β-alanyl-L-histidine) and hydrogen sulfide (H₂S) exert cytoprotective actions through the modulation of redox-dependent resilience pathways during oxidative stress and inflammation. Several recent studies have elucidated a functional crosstalk occurring between kidney and the brain. The pathophysiological link of this crosstalk is represented by oxidative stress and inflammatory processes which contribute to the high prevalence of neuropsychiatric disorders, cognitive impairment, and dementia during the natural history of chronic kidney disease. Herein, we provide an overview of the main pathophysiological mechanisms related to high levels of pro-inflammatory cytokines, including interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and neurotoxins, which play a critical role in the kidney–brain crosstalk. The present paper also explores the respective role of H₂S and carnosine in the modulation of oxidative stress and inflammation in the kidney–brain axis. It suggests that these activities are likely mediated, at least in part, via hormetic processes, involving Nrf2 (Nuclear factor-like 2), Hsp 70 (heat shock protein 70), SIRT-1 (Sirtuin-1), Trx (Thioredoxin), and the glutathione system. Metabolic interactions at the kidney and brain axis level operate in controlling and reducing oxidant-induced inflammatory damage and therefore, can be a promising potential therapeutic target to reduce the severity of renal and brain injuries in humans.

Advances in the Protective Mechanism of NO, H2S, and H2 in Myocardial Ischemic Injury

Myocardial ischemic injury is among the top 10 leading causes of death from cardiovascular diseases worldwide. Myocardial ischemia is caused mainly by coronary artery occlusion or obstruction. It usually occurs when the heart is insufficiently perfused, oxygen supply to the myocardium is reduced, and energy metabolism in the myocardium is abnormal. Pathologically, myocardial ischemic injury generates a large number of inflammatory cells, thus inducing a state of oxidative stress. This sharp reduction in the number of normal cells as a result of apoptosis leads to organ and tissue damage, which can be life-threatening. Therefore, effective methods for the treatment of myocardial ischemic injury and clarification of the underlying mechanisms are urgently required. Gaseous signaling molecules, such as NO, H₂S, H₂, and combined gas donors, have gradually become a focus of research. Gaseous signaling molecules have shown anti-apoptotic, anti-oxidative and anti-inflammatory effects as potential therapeutic agents for myocardial ischemic injury in a large number of studies. In this review, we summarize and discuss the mechanism underlying the protective effect of gaseous signaling molecules on myocardial ischemic injury.

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.

A Novel Rhynchophylline Analog, Y396, Inhibits Endothelial Dysfunction Induced by Oxidative Stress in Diabetes Through Epidermal Growth Factor Receptor

Aims: Endothelial dysfunction appears in early diabetes mellitus partially because of epidermal growth factor receptor (EGFR) abnormal activation and downstream oxidative stress. The aim of this study was to determine whether Y396, a synthesized analog of rhynchophylline, could protect against endothelial dysfunction in diabetes and the underlying molecular mechanism. Results: Y396 could directly target the EGFR and inhibit its phosphorylation induced by high glucose and EGF, downstream translocation to the nucleus of E2F1, and its transcriptional activity and expression of Nox4. Diabetes-induced endothelium malfunction was ameliorated by Y396 treatment through EGFR inhibition. Downstream oxidative stress was decreased by Y396 in the aortas of type 1 diabetes mellitus mice and primary rat aorta endothelial cells (RAECs). Y396 could also ameliorate tunicamycin-induced oxidative stress in the aorta and RAECs. In addition, we again determined the protective effects of Y396 on high-fat diet/streptozotocin-induced type 2 diabetes mellitus. Innovation: This is the first study to demonstrate that Y396, a novel rhynchophylline analog, suppressed high-glucose-induced endothelial malfunction both in vivo and in vitro by inhibiting abnormal phosphorylation of EGFR. Our work uncovered EGFR as a novel therapeutic target and Y396 as a potential therapy against diabetes-induced complication. Conclusion: Y396 could directly bind with EGFR, and inhibit its phosphorylation and downstream E2F1 transcriptional activity. It could also preserve tunicamycin-evoked endothelial dysfunction and oxidative stress. It could protect against diabetes-induced endothelium malfunction in vivo through EGFR inhibition and downstream oxidative stress. Antioxid. Redox Signal. 32, 743-765.

ZYZ-803, a novel hydrogen sulfide-nitric oxide conjugated donor, promotes angiogenesis via cross-talk between STAT3 and CaMKII

Endothelial angiogenesis plays a vital role in recovery from chronic ischemic injuries. ZYZ-803 is a hybrid donor of hydrogen sulfide (H2S) and nitric oxide (NO). Previous studies showed that ZYZ-803 stimulated endothelial cell angiogenesis both in vitro and in vivo. In this study, we investigated whether the signal transducer and activator of transcription 3 (STAT3) and Ca2+/CaM-dependent protein kinase II (CaMKII) signaling was involved in ZYZ-803-induced angiogenesis. Treatment with ZYZ-803 (1 μM) significantly increased the phosphorylation of STAT3 (Tyr705) and CaMKII (Thr286) in human umbilical vein endothelial cells (HUVECs), these two effects had a similar time course. Pretreatment with WP1066 (STAT3 inhibitor) or KN93 (CAMKII inhibitor) blocked ZYZ-803-induced STAT3/CAMKII activation and significantly suppressed the proliferation and migration of HUVECs. In addition, pretreatment with the inhibitors significantly decreased ZYZ-803-induced tube formations along with the outgrowths of branch-like microvessels in aortic rings. In the mice with femoral artery ligation, administration of ZYZ-803 significantly increased the blood perfusion and vascular density in the hind limb, whereas co-administration of WP1066 or KN93 abrogated ZYZ-803-induced angiogenesis. By using STAT3 siRNA, we further explored the cross-talk between STAT3 and CaMKII in ZYZ-803-induced angiogenesis. We found that STAT3 knockdown suppressed ZYZ-803-induced HUVEC angiogenesis and affected CaMKII expression. ZYZ-803 treatment markedly enhanced the interaction between CaMKII and STAT3. ZYZ-803 treatment induced the nuclear translocation of STAT3. We demonstrated that both STAT3 and CaMKII functioned as positive regulators in ZYZ-803-induced endothelial angiogenesis and STAT3 was important in ZYZ-803-induced CaMKII activation, which highlights the beneficial role of ZYZ-803 in STAT3/CaMKII-related cardiovascular diseases.

A concise review of recent advances in anti-heart failure targets and its small molecules inhibitors in recent years

Heart failure is a disease with high mortality and the risk of heart failure increases in magnitude with age. The patients of heart failure is increasing year by year. Hence, Pharmaceutical researchers have to develop new drugs with better pharmacological effects to coping with this phenomenon. In this article, we reviewed the small molecule compounds for heart failure that have been marketed in recent years or are promising to enter clinical research. We also reviewed the SAR (structure activity relationship) of these molecules, such as renin inhibitors, ROMK inhibitors, a kind of new diuretics, and some dual-targets inhibitors. These small molecules proven to be beneficial effect on heart failure patients. Which may provide ideas for the design of novel anti-heart failure therapeutic drugs.

An Appraisal of Developments in Allium Sulfur Chemistry: Expanding the Pharmacopeia of Garlic

Alliums and allied plant species are rich sources of sulfur compounds that have effects on vascular homeostasis and the control of metabolic systems linked to nutrient metabolism in mammals. In view of the multiple biological effects ascribed to these sulfur molecules, researchers are now using these compounds as inspiration for the synthesis and development of novel sulfur-based therapeutics. This research has led to the chemical synthesis and biological assessment of a diverse array of sulfur compounds representative of derivatives of S-alkenyl-l-cysteine sulfoxides, thiosulfinates, ajoene molecules, sulfides, and S-allylcysteine. Many of these synthetic derivatives have potent antimicrobial and anticancer properties when tested in preclinical models of disease. Therefore, the current review provides an overview of advances in the development and biological assessment of synthetic analogs of allium-derived sulfur compounds.

Evolution of Hydrogen Sulfide Therapeutics to Treat Cardiovascular Disease

Hydrogen sulfide (H₂S)-a potent gaseous signaling molecule-has emerged as a critical regulator of cardiovascular homeostasis. H₂S is produced enzymatically by 3 constitutively active endogenous enzymes in all mammalian species. Within the past 2 decades, studies administering H₂S-donating agents and the genetic manipulation of H₂S-producing enzymes have revealed multiple beneficial effects of H₂S, including vasodilation, activation of antiapoptotic and antioxidant pathways, and anti-inflammatory effects. More recently, the heightened enthusiasm in this field has shifted to the development of novel H₂S-donating agents that exert favorable pharmacological profiles. This has led to the discovery of novel H₂S-mediated signaling pathways. This review will discuss recently developed H₂S therapeutics, introduce signaling pathways that are influenced by H₂S-dependent sulfhydration, and explore the dual-protective effect of H₂S in cardiorenal syndrome.

Gasotransmitters in health and disease: a mitochondria-centered view

Gasotransmitters fulfill important roles in cellular homeostasis having been linked to various pathologies, including inflammation and cardiovascular diseases. In addition to the known pathways mediating the actions of gasotransmitters, their effects in regulating mitochondrial function are emerging. Given that mitochondria are key organelles in energy production, formation of reactive oxygen species and apoptosis, they are important mediators in preserving health and disease. Preserving or restoring mitochondrial function by gasotransmitters may be beneficial, and mitigate pathogenetic processes. In this review we discuss the actions of gasotransmitters with focus on their role in mitochondrial function and their therapeutic potential.

ZYZ-803 Mitigates Endoplasmic Reticulum Stress-Related Necroptosis after Acute Myocardial Infarction through Downregulating the RIP3-CaMKII Signaling Pathway

Acute myocardial infarction (AMI) is a leading cause of morbidity and mortality worldwide, and both cardiac necroptosis and endoplasmic reticulum stress (ERS) have been involved in the pathophysiology of AMI. ZYZ-803 is a hybrid molecule of a dual donor for gasotransmitters H₂S and NO. The aim of the present study is to investigate the antinecroptosis role and potential mechanisms of ZYZ-803 in the setting of ERS during AMI injury. In vivo, ZYZ-803 preserves cardiac function and reduces infarct size significantly after 24-hour left coronary artery ligation through revising H₂S and NO imbalance. In addition, ZYZ-803 relieves ERS and necroptosis in an AMI heart. In vitro, ZYZ-803 ameliorates ERS-related necroptosis induced by tunicamycin, and such effect has been depending on the receptor-interacting protein 3- (RIP3-) Ca²⁺-calmodulin-dependent protein kinase (CaMKII) signaling pathway. These findings have identified a novel antinecroptosis potential of ZYZ-803, providing a valuable candidate for cardioprotection in acute myocardial ischemia.

Buyang Huanwu Decoction Targets SIRT1/VEGF Pathway to Promote Angiogenesis After Cerebral Ischemia/Reperfusion Injury

Background: Ischemia stroke is known as the major cause of morbidity and mortality. Buyang Huanwu Decoction (BHD), a classical traditional Chinese medicine (TCM) formula, has been used to prevent and treat stoke for hundreds of years. The purpose of present study is to investigate the effects of BHD on angiogenesis in rats after cerebral ischemia/reperfusion (I/R) injury targeting Silent information regulator 1 (SIRT1) / Vascular endothelial growth factor (VEGF) pathway.

Methods: The cerebral I/R injury model was induced by middle cerebral artery occlusion (MCAO). Adult Sprag-Dawley (SD) rats were randomly divided into five groups: sham group, normal saline (NS) group, BHD group, BHD+EX527 (SIRT1 specific inhibitor) group, and NS+EX527 group. Each group was divided into the subgroups according to 1, 3, 7, or 14 days time-point after cerebral ischemia/reperfusion, respectively. Neurological function score (NFS) was evaluated by the Rogers scale; microvascular density (MVD) in brain tissue around infarction area was observed by immunofluorescence; and the expression of SIRT1 and VEGF was assessed by Western Blot and Quantitative Real-time-PCR.

Results: BHD can significantly improve NFS (P < 0.05), increase the MVD in the boundary ischemic area (P < 0.01) and elevate the expression of protein and mRNA of SIRT1 and VEGF following I/R injury (P < 0.01). In contrast, treatment with EX527 reversed the BHD-induced improvements in NFS (P < 0.01) and decreased the MVD (P < 0.01) and the expression of SIRT1 and VEGF (P < 0.05).

Conclusion: BHD exerts neuroprotection targeting angiogenesis through the up-regulation of SIRT1/VEGF pathway against cerebral ischemic injury in rats.

An Update on Hydrogen Sulfide and Nitric Oxide Interactions in the Cardiovascular System

Hydrogen sulfide (H₂S) and nitric oxide (NO) are now recognized as important regulators in the cardiovascular system, although they were historically considered as toxic gases. As gaseous transmitters, H₂S and NO share a wide range of physical properties and physiological functions: they penetrate into the membrane freely; they are endogenously produced by special enzymes, they stimulate endothelial cell angiogenesis, they regulate vascular tone, they protect against heart injury, and they regulate target protein activity via posttranslational modification. Growing evidence has determined that these two gases are not independent regulators but have substantial overlapping pathophysiological functions and signaling transduction pathways. H₂S and NO not only affect each other's biosynthesis but also produce novel species through chemical interaction. They play a regulatory role in the cardiovascular system involving similar signaling mechanisms or molecular targets. However, the natural precise mechanism of the interactions between H₂S and NO remains unclear. In this review, we discuss the current understanding of individual and interactive regulatory functions of H₂S and NO in biosynthesis, angiogenesis, vascular one, cardioprotection, and posttranslational modification, indicating the importance of their cross-talk in the cardiovascular system.

The Drug Developments of Hydrogen Sulfide on Cardiovascular Disease

The recognition of hydrogen sulfide (H₂S) has been evolved from a toxic gas to a physiological mediator, exhibiting properties similar to NO and CO. On the one hand, H₂S is produced from L-cysteine by enzymes of cystathionine γ-lyase (CSE) and cystathionine β-synthase (CBS), 3-mercaptopyruvate sulfurtransferase (3MST) in combination with aspartate aminotransferase (AAT) (also called as cysteine aminotransferase, CAT); on the other hand, H₂S is produced from D-cysteine by enzymes of D-amino acid oxidase (DAO). Besides sulfide salt, several sulfide-releasing compounds have been synthesized, including organosulfur compounds, Lawesson's reagent and analogs, and plant-derived natural products. Based on garlic extractions, we synthesized S-propargyl-L-cysteine (SPRC) and its analogs to contribute our endeavors on drug development of sulfide-containing compounds. A multitude of evidences has presented H₂S is widely involved in the roles of physiological and pathological process, including hypertension, atherosclerosis, angiogenesis, and myocardial infarcts. This review summarizes current sulfide compounds, available H₂S measurements, and potential molecular mechanisms involved in cardioprotections to help researchers develop further applications and therapeutically drugs.

Use of gasotransmitters for the controlled release of polymer-based nitric oxide carriers in medical applications

Nitric Oxide (NO) is a small molecule gasotransmitter synthesized by nitric oxide synthase in almost all types of mammalian cells. NO is synthesized by NO synthase by conversion of l-arginine to l-citrulline in the human body. NO then stimulates soluble guanylate cyclase, from which various physiological functions are mediated in a concentration-dependent manner. High concentrations of NO induce apoptosis or antibacterial responses whereas low NO circulation leads to angiogenesis. The bidirectional effect of NO has attracted considerable attention, and efforts to deliver NO in a controlled manner, especially through polymeric carriers, has been the topic of much research. This naturally produced signaling molecule has stood out as a potentially more potent therapeutic agent compared to exogenously synthesized drugs. In this review, we will focus on past efforts of using the controlled release of NO via polymer-based materials to derive specific therapeutic results. We have also added studies and our future suggestions on co-delivery methods with other gasotransmitters as a step towards developing multifunctional carriers.

Nitric oxide signalling in cardiovascular health and disease

Nitric oxide (NO) signalling has pleiotropic roles in biology and a crucial function in cardiovascular homeostasis. Tremendous knowledge has been accumulated on the mechanisms of the nitric oxide synthase (NOS)-NO pathway, but how this highly reactive, free radical gas signals to specific targets for precise regulation of cardiovascular function remains the focus of much intense research. In this Review, we summarize the updated paradigms on NOS regulation, NO interaction with reactive oxidant species in specific subcellular compartments, and downstream effects of NO in target cardiovascular tissues, while emphasizing the latest developments of molecular tools and biomarkers to modulate and monitor NO production and bioavailability.

Novel H2S-NO hybrid molecule (ZYZ-803) promoted synergistic effects against heart failure

Therapeutic strategies that increase hydrogen sulfide (H₂S) or nitric oxide (NO) are cytoprotective in various models of cardiovascular injury. However, the nature of interaction between H₂S and NO in heart failure and the underlying mechanisms for the protective effects remain undefined. The present study tested the cardioprotective effect of ZYZ-803, a novel synthetic H₂S-NO hybrid molecule that decomposed to release H₂S and NO. ZYZ-803 dose dependently improved left ventricular remodeling and preserved left ventricular function in the setting of isoprenaline-induced heart failure. The cardioprotective effect of ZYZ-803 is significantly more potent than that of H₂S and/or NO donor alone. ZYZ-803 stimulated the expression of cystathionine γ-lyase (CSE) for H₂S generation and the activity of endothelial NO synthase (eNOS) for NO production. Blocking CSE and/or eNOS suppressed ZYZ-803-induced H₂S and NO production and cardioprotection. ZYZ-803 increased vascular endothelial growth factor (VEGF) concentration and cyclic guanosine 5′-monophosphate (cGMP) level. Moreover, ZYZ-803 upregulated the endogenous antioxidants, glutathione peroxidase (GPx) and heme oxygenase 1 (HO-1). These findings indicate that H₂S and NO cooperatively attenuates left ventricular remodeling and dysfunction during the development of heart failure through VEGF/cGMP pathway and ZYZ-803 provide expanding insight into strategies for treatment of heart failure.

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.

Redox regulation of gasotransmission in the vascular system: A focus on angiogenesis

Reactive oxygen species have emerged as key participants in a broad range of physiological and pathophysiological processes, not least within the vascular system. Diverse cellular functions which have been attributed to some of these pro-oxidants within the vasculature include the regulation of blood pressure, neovascularisation and vascular inflammation. We here highlight the emerging roles of the enzymatically-generated reaction oxygen species, O₂^- and H₂O₂, in the regulation of the functions of the gaseous signalling molecules: nitric oxide (NO), carbon monoxide (CO), and hydrogen sulphide (H₂S). These gasotransmitters are produced on demand from distinct enzymatic sources and in recent years it has become apparent that they are capable of mediating a number of homeostatic processes within the cardiovascular system including enhanced vasodilation, angiogenesis, wound healing and improved cardiac function following myocardial infarction. In common with O₂^- and/or H₂O₂ they signal by altering the functions of target proteins, either by the covalent modification of thiol groups or by direct binding to metal centres within metalloproteins, most notably haem proteins. The regulation of the enzymes which generate NO, CO and H₂S have been shown to be influenced at both the transcriptional and post-translational levels by redox-dependent mechanisms, while the activity and bioavailability of the gasotransmitters themselves are also subject to oxidative modification. Within vascular cells, the family of nicotinamide adenine dinucleotide phosphate oxidases (NAPDH oxidases/Noxs) have emerged as functionally significant sources of regulated O₂^- and H₂O₂ production and accordingly, direct associations between Nox-generated oxidants and the functions of specific gasotransmitters are beginning to be identified. This review focuses on the current knowledge of the redox-dependent mechanisms which regulate the generation and activity of these gases, with particular reference to their roles in angiogenesis.

New method for quantification of gasotransmitter hydrogen sulfide in biological matrices by LC-MS/MS

Hydrogen sulfide exists widely in mammalian tissues and plays a vital role in physiological and pathophysiological processes. However, striking differences with orders of magnitude were observed for the detected hydrogen sulfide concentrations in biological matrices among different measurements in literature, which lead to the uncertainty for examination the biological relevance of hydrogen sulfide. Here, we developed and validated a liquid chromatography- mass spectrometry (LC-MS/MS) method for the determination of hydrogen sulfide in various biological matrices by determination of a derivative of hydrogen sulfide and monobromobimane named sulfide dibimane (SDB). ³⁶S-labeled SDB was synthesized and validated for using as an internal standard. This method has been successfully used to measure hydrogen sulfide levels in a broad range of biological matrices, such as blood, plasma, tissues, cells, and enzymes, across different species. Moreover, a novel mode that hydrogen sulfide could loosely and non-covalently bind to human serum protein (HSA) and hemoglobin (HB) was revealed by using the developed method.

H2S regulates endothelial nitric oxide synthase protein stability by promoting microRNA-455-3p expression

The aims of the present study are to determine whether hydrogen sulfide (H₂S) is involved in the expression of endothelial nitric oxide synthase (eNOS) and nitric oxide (NO) production, and to identify the role of microRNA-455-3p (miR-455-3p) during those processes. In cultured human umbilical vein endothelial cells (HUVECs), the expression of miR-455-3p, eNOS protein and the NO production was detected after administration with 50 μM NaHS. The results indicated that H₂S could augment the expression of miR-455-3p and eNOS protein, leading to the increase of NO level. We also found that overexpression of miR-455-3p in HUVECs increased the protein levels of eNOS whereas inhibition of miR-455-3p decreased it. Moreover, H₂S and miR-455-3p could no longer increase the protein level of eNOS in the presence of proteasome inhibitor, MG-132. In vivo, miR-455-3p and eNOS expression were considerably increased in C57BL/6 mouse aorta, muscle and heart after administration with 50 μmol/kg/day NaHS for 7 days. We also identified that H₂S levels and miR-455-3p expression increased in human atherosclerosis plaque while H₂S levels decreased in plasma of atherosclerosis patients. Our data suggest that the stability of eNOS protein and the NO production could be regulated by H₂S through miR-455-3p.

H2S biosynthesis and catabolism: new insights from molecular studies

Hydrogen sulfide (H₂S) has profound biological effects within living organisms and is now increasingly being considered alongside other gaseous signalling molecules, such as nitric oxide (NO) and carbon monoxide (CO). Conventional use of pharmacological and molecular approaches has spawned a rapidly growing research field that has identified H₂S as playing a functional role in cell-signalling and post-translational modifications. Recently, a number of laboratories have reported the use of siRNA methodologies and genetic mouse models to mimic the loss of function of genes involved in the biosynthesis and degradation of H₂S within tissues. Studies utilising these systems are revealing new insights into the biology of H₂S within the cardiovascular system, inflammatory disease, and in cell signalling. In light of this work, the current review will describe recent advances in H₂S research made possible by the use of molecular approaches and genetic mouse models with perturbed capacities to generate or detoxify physiological levels of H₂S gas within tissues.

Hydrogen sulfide, an enhancer of vascular nitric oxide signaling: mechanisms and implications

Nitric oxide (NO) vascular signaling has long been considered an independent, self-sufficient pathway. However, recent data indicate that the novel gaseous mediator, hydrogen sulfide (H₂S), serves as an essential enhancer of vascular NO signaling. The current article overviews the multiple levels at which this enhancement takes place. The first level of interaction relates to the formation of biologically active hybrid S/N species and the H₂S-induced stimulation of NO release from its various stable "pools" (e.g., nitrite). The next interactions occur on the level of endothelial calcium mobilization and PI3K/Akt signaling, increasing the specific activity of endothelial NO synthase (eNOS). The next level of interaction occurs on eNOS itself; H₂S directly interacts with the enzyme: sulfhydration of critical cysteines stabilizes it in its physiological, dimeric state, thereby optimizing eNOS-derived NO production and minimizing superoxide formation. Yet another level of interaction, further downstream, occurs at the level of soluble guanylate cyclase (sGC): H₂S stabilizes sGC in its NO-responsive, physiological, reduced form. Further downstream, H₂S inhibits the vascular cGMP phosphodiesterase (PDE5), thereby prolonging the biological half-life of cGMP. Finally, H₂S-derived polysulfides directly activate cGMP-dependent protein kinase (PKG). Taken together, H₂S emerges an essential endogenous enhancer of vascular NO signaling, contributing to vasorelaxation and angiogenesis. The functional importance of the H₂S/NO cooperative interactions is highlighted by the fact that H₂S loses many of its beneficial cardiovascular effects when eNOS is inactive.

Restoration of Hydrogen Sulfide Production in Diabetic Mice Improves Reparative Function of Bone Marrow Cells

BACKGROUND

Bone marrow cell (BMC)-based treatment for critical limb ischemia in diabetic patients yielded a modest therapeutic effect resulting from cell dysfunction. Therefore, approaches that improve diabetic stem/progenitor cell functions may provide therapeutic benefits. Here, we tested the hypothesis that restoration of hydrogen sulfide (H₂S) production in diabetic BMCs improves their reparative capacities.

METHODS

Mouse BMCs were isolated by density-gradient centrifugation. Unilateral hind limb ischemia was conducted in 12- to 14-week-old db/+ and db/db mice by ligation of the left femoral artery. The H₂S level was measured by either gas chromatography or staining with florescent dye sulfidefluor 7 AM.

RESULTS

Both H₂S production and cystathionine γ-lyase (CSE), an H₂S enzyme, levels were significantly decreased in BMCs from diabetic db/db mice. Administration of H₂S donor diallyl trisulfide (DATS) or overexpression of CSE restored H₂S production and enhanced cell survival and migratory capacity in high glucose (HG)-treated BMCs. Immediately after hind limb ischemia surgery, the db/+ and db/db mice were administered DATS orally and/or given a local intramuscular injection of green fluorescent protein-labeled BMCs or red fluorescent protein-CSE-overexpressing BMCs (CSE-BMCs). Mice with hind limb ischemia were divided into 6 groups: db/+, db/db, db/db+BMCs, db/db+DATS, db/db+DATS+BMCs, and db/db+CSE-BMCs. DATS and CSE overexpression greatly enhanced diabetic BMC retention in ischemic hind limbs followed by improved blood perfusion, capillary/arteriole density, skeletal muscle architecture, and cell survival and decreased perivascular CD68⁺ cell infiltration in the ischemic hind limbs of diabetic mice. It is interesting to note that DATS or CSE overexpression rescued high glucose-impaired migration, tube formation, and survival of BMCs or mature human cardiac microvascular endothelial cells. Moreover, DATS restored nitric oxide production and decreased endothelial nitric oxide synthase phosphorylation at threonine 495 levels in human cardiac microvascular endothelial cells and improved BMC angiogenic activity under high glucose condition. Last, silencing CSE by siRNA significantly increased endothelial nitric oxide synthase phosphorylation at threonine 495 levels in human cardiac microvascular endothelial cells.

CONCLUSIONS

Decreased CSE-mediated H₂S bioavailability is an underlying source of BMC dysfunction in diabetes mellitus. Our data indicate that H₂S and overexpression of CSE in diabetic BMCs may rescue their dysfunction and open novel avenues for cell-based therapeutics of critical limb ischemia in diabetic patients.