Hydrogen sulfide improves diabetic wound healing in ob/ob mice via attenuating inflammation

Role of hydrogen sulfide in dermatological diseases

Hydrogen sulfide (H2S), together with carbon monoxide (CO) and nitric oxide (NO), is recognized as a vital gasotransmitter. H2S is biosynthesized by enzymatic pathways in the skin and exerts significant physiological effects on a variety of biological processes, such as apoptosis, modulation of inflammation, cellular proliferation, and regulation of vasodilation. As a major health problem, dermatological diseases affect a large proportion of the population every day. It is urgent to design and develop effective drugs to deal with dermatological diseases. Dermatological diseases can arise from a multitude of etiologies, including neoplastic growth, infectious agents, and inflammatory processes. The abnormal metabolism of H2S is associated with many dermatological diseases, such as melanoma, fibrotic diseases, and psoriasis, suggesting its therapeutic potential in the treatment of these diseases. In addition, therapies based on H2S donors are being developed to treat some of these conditions. In the review, we discuss recent advances in the function of H2S in normal skin, the role of altering H2S metabolism in dermatological diseases, and the therapeutic potential of diverse H2S donors for the treatment of dermatological diseases.

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.

Hydrogen sulfide dysfunction in metabolic syndrome-associated vascular complications involves cGMP regulation through soluble guanylyl cyclase persulfidation

Here, by using in vitro and ex vivo approaches, we elucidate the impairment of the hydrogen sulfide (H2S) pathway in vascular complications associated with metabolic syndrome (MetS). In the in vitro model simulating hyperlipidemic/hyperglycemic conditions, we observe significant hallmarks of endothelial dysfunction, including eNOS/NO signaling impairment, ROS overproduction, and a reduction in CSE-derived H2S. Transitioning to an ex vivo model using db/db mice, a genetic MetS model, we identify a downregulation of CBS and CSE expression in aorta, coupled with a diminished L-cysteine-induced vasorelaxation. Molecular mechanisms of eNOS/NO signaling impairment, dissected using pharmacological and molecular approaches, indicate an altered eNOS/Cav-1 ratio, along with reduced Ach- and Iso-induced vasorelaxation and increased L-NIO-induced contraction. In vivo treatment with the H2S donor Erucin ameliorates vascular dysfunction observed in db/db mice without impacting eNOS, further highlighting a specific action on smooth muscle component rather than the endothelium. Analyzing the NO signaling pathway in db/db mice aortas, reduced cGMP levels were detected, implicating a defective sGC/cGMP signaling. In vivo Erucin administration restores cGMP content. This beneficial effect involves an increased sGC activity, due to enzyme persulfidation observed in sGC overexpressed cells, coupled with PDE5 inhibition. In conclusion, our study demonstrates a pivotal role of reduced cGMP levels in impaired vasorelaxation in a murine model of MetS involving an impairment of both H2S and NO signaling. Exogenous H2S supplementation through Erucin represents a promising alternative in MetS therapy, targeting smooth muscle cells and supporting the importance of lifestyle and nutrition in managing MetS.

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

BACKGROUND

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

AIM OF REVIEW

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

KEY SCIENTIFIC CONCEPTS OF REVIEW

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

H2S donor S-propargyl-cysteine for skin wound healing improvement via smart transdermal delivery

Hydrogen sulfide for wound healing has drawn a lot of attention recently. In this research, the S-propargyl-cysteine (SPRC), an endogenous H2S donor, was loaded on carbomer hydrogel, and a copper sheet rat burn model was developed. Pathological changes in rat skin tissue were examined using hematoxylin-eosin (HE) and Masson staining. The immunohistochemistry (IHC) staining was performed to detect the expression of Collagen I (Col I) and Collagen III (Col III). The mRNA levels of interleukin (IL)-6, Col Iα2, Col IIIα1, tissue inhibitors of metalloproteinase (TIMP)-1, matrix metalloproteinase (MMP)-9, vascular endothelial growth factor (VEGF), and transforming growth factor (TGF)-β1 were examined by quantitative real-time chain polymerase reaction. The findings demonstrated that the collagen layer was thicker in the SPRC group during the proliferative phase, SPRC hydrogel promoted VEGF expression. In the late stage of wound healing, the expression of IL-6, TIMP-1, MMP-9, and TGF-β1 was inhibited, and the Col I content was closer to that of normal tissue. These results surface that SPRC hydrogel can promote wound healing and play a positive role in reducing scar formation. Our results imply that SPRC can facilitate wound healing and play a positive role in reducing scar formation.

Enhancing diabetic wound healing: advances in electrospun scaffolds from pathogenesis to therapeutic applications

Diabetic wounds are a significant subset of chronic wounds characterized by elevated levels of inflammatory cytokines, matrix metalloproteinases (MMPs), and reactive oxygen species (ROS). They are also associated with impaired angiogenesis, persistent infection, and a high likelihood of hospitalization, leading to a substantial economic burden for patients. In severe cases, amputation or even mortality may occur. Diabetic foot ulcers (DFUs) are a common complication of diabetes, with up to 25% of diabetic patients being at risk of developing foot ulcers over their lifetime, and more than 70% ultimately requiring amputation. Electrospun scaffolds exhibit a structural similarity to the extracellular matrix (ECM), promoting the adhesion, growth, and migration of fibroblasts, thereby facilitating the formation of new skin tissue at the wound site. The composition and size of electrospun scaffolds can be easily adjusted, enabling controlled drug release through fiber structure modifications. The porous nature of these scaffolds facilitates gas exchange and the absorption of wound exudate. Furthermore, the fiber surface can be readily modified to impart specific functionalities, making electrospinning nanofiber scaffolds highly promising for the treatment of diabetic wounds. This article provides a concise overview of the healing process in normal wounds and the pathological mechanisms underlying diabetic wounds, including complications such as diabetic foot ulcers. It also explores the advantages of electrospinning nanofiber scaffolds in diabetic wound treatment. Additionally, it summarizes findings from various studies on the use of different types of nanofiber scaffolds for diabetic wounds and reviews methods of drug loading onto nanofiber scaffolds. These advancements broaden the horizon for effectively treating diabetic wounds.

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.

Gas Therapy: Generating, Delivery, and Biomedical Applications

Oxygen (O2 ), nitric oxide (NO), carbon monoxide (CO), hydrogen sulfide (H2 S), and hydrogen (H2 ) with direct effects, and carbon dioxide (CO2 ) with complementary effects on the condition of various diseases are known as therapeutic gases. The targeted delivery and in situ generation of these therapeutic gases with controllable release at the site of disease has attracted attention to avoid the risk of gas poisoning and improve their performance in treating various diseases such as cancer therapy, cardiovascular therapy, bone tissue engineering, and wound healing. Stimuli-responsive gas-generating sources and delivery systems based on biomaterials that enable on-demand and controllable release are promising approaches for precise gas therapy. This work highlights current advances in the design and development of new approaches and systems to generate and deliver therapeutic gases at the site of disease with on-demand release behavior. The performance of the delivered gases in various biomedical applications is then discussed.

Hydrogen sulfide releasing poly(γ-glutamic acid) biocomposite hydrogel with monitoring, antioxidant, and antibacterial properties for diabetic wound healing

Adverse factors such as high levels of glucose, oxidative stress, inflammation, and bacterial infection impede diabetic wound healing and even worsen wounds. Owing to its outstanding anti-inflammatory and antioxidant properties as well as the potential to promote cell migration and proliferation, hydrogen sulfide(H2S) gas therapy is promising for chronic diabetic wound recovery. In this work, a multifunctional poly(γ-glutamic acid)(PGA) hydrogel encapsulated with keratin-based H2S donor(KTC), ciprofloxacin(Cip), and anthocyanins(Ant) was developed. The resultant hydrogel was capable of releasing H2S, thereby promoting cell proliferation and enhancing anti-inflammation and antioxidant activity. The release of antibiotic Cip was accelerated under a diabetic wound microenvironment, thereby enhancing the antibacterial activity of the hydrogel. The encapsulated Ant could serve as a pH monitor, sensitively indicating wound pH conditions in situ and indirectly reflecting wound infection. In vivo results in diabetic wound healing suggested that PGA/Ant/KTC/Cip hydrogel reduced inflammation and promoted angiogenesis and collagen deposition, thereby accelerating wound healing.

Reactive Sulfur Species in Human Diseases

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

Study of hydrogen sulfide biosynthesis in synovial tissue from diabetes-associated osteoarthritis and its influence on macrophage phenotype and abundance

Type 2 diabetes (DB) is an independent risk factor for osteoarthritis (OA). However, the mechanisms underlying the connection between both diseases remain unclear. Synovial macrophages from OA patients with DB present a marked pro-inflammatory phenotype. Since hydrogen sulphide (H₂S) has been previously described to be involved in macrophage polarization, in this study we examined H₂S biosynthesis in synovial tissue from OA patients with DB, observing a reduction of H₂S-synthetizing enzymes in this subset of individuals. To elucidate these findings, we detected that differentiated TPH-1 cells to macrophages exposed to high levels of glucose presented a lower expression of H₂S-synthetizing enzymes and an increased inflammatory response to LPS, showing upregulated expression of markers associated with M1 phenotype (i.e., CD11c, CD86, iNOS, and IL-6) and reduced levels of those related to M2 fate (CD206 and CD163). The co-treatment of the cells with a slow-releasing H₂S donor, GYY-4137, attenuated the expression of M1 markers, but failed to modulate the levels of M2 indicators. GYY-4137 also reduced HIF-1α expression and upregulated the protein levels of HO-1, suggesting their involvement in the anti-inflammatory effects of H₂S induction. In addition, we observed that intraarticular administration of H₂S donor attenuated synovial abundance of CD68⁺ cells, mainly macrophages, in an in vivo model of OA. Taken together, the findings of this study seem to reinforce the key role of H₂S in the M1-like polarization of synovial macrophages associated to OA and specifically its metabolic phenotype, opening new therapeutic perspectives in the management of this pathology.

A Theranostic Probe for Promotion of Skin Wound Healing by Exudate-Triggered H2S Release with Self-Monitoring Ability

Hydrogen sulfide (H₂S) as an endogenous gasotransmitter plays a critical role in promotion of wound healing. However, the current H₂S release system lacks the in situ monitoring ability, which may lead to insufficient or overdose release of H₂S and serious side effects. Herein, we develop a self-monitoring theranostic probe TPATCF-S, which can quickly release H₂S under water stimuli associated with a self-monitoring ability by a color change from colorless to deep blue. With a full thickness dermal defect as a model, the TPATCF-S absorbed on alginate dressings can be used for wound exudate-responsive release of H₂S to efficiently promote skin wound healing.

Bilayer dressing based on aerogel/electrospun mats with self-catalytic hydrogen sulfide generation and enhanced antioxidant ability

Hydrogen sulfide (H₂S) releasing wound dressings have attracted much attention for their ability to promote cell proliferation, stimulate angiogenesis, and resist inflammation. Mimicking the skin structure, a bilayer wound dressing based on aerogel/mats with H₂S release capability was designed and fabricated. A bio-macromolecular H₂S donor based on a keratin-TA conjugate (KTC) was first synthesized through a thiol-disulfide exchange reaction. As an inner layer, KTC was then loaded into a gelatin hydrogel with large pores to absorb the wound exudates and generate H₂S self-catalytically. Subsequently, polyurethane was electrospun with glutathione (GSH) to be used as an outer layer with small pores, which provided mechanical support, supplied GSH, and prevented bacterial invasion. The bilayer dressing was capable of generating H₂S self-catalytically, achieving a controlled and sustained release. The dressing could also promote cell proliferation and migration. In addition, the dress possessed enhanced antioxidant ability and reactive oxygen species (ROS) scavenging capability. The bilayer dressing on promoting wound healing was investigated in a full-thickness excisional cutaneous wound model in rats. The results demonstrated that it could reduce inflammation, promote vascularization, and facilitate hair follicle regeneration, thereby accelerating wound healing. Overall, the bilayer dressing has great potential applications in the field of the wound dressing.

Salen, salan and salalen zinc(II) complexes in the interaction with HS-: time-resolved fluorescence applications

In the current work we investigate the route of interaction of a newly synthesized family of zinc complexes with HS^- by a plethora of different spectroscopic techniques. A computational analysis on the time dependent density functional theory (TD-DFT) level explored the overall fluorescence properties of the title complexes and their different fluorescence responses to HS^-. Time-resolved fluorescence experiments were also performed and highlight the great potential of the current systems to be implemented as HS^- fluorescent sensors.

Hydrogen Sulfide in Diabetic Complications Revisited: The State of the Art, Challenges, and Future Directions

Significance: Diabetes and its related complications are becoming an increasing public health problem that affects hundreds of millions of people globally. Increased disability and mortality rate of diabetic individuals are closely associated with various life-threatening complications, such as atherosclerosis, nephropathy, retinopathy, and cardiomyopathy. Recent Advances: Conventional treatments for diabetes are still limited because of undesirable side effects, including obesity, hypoglycemia, and hepatic and renal toxicity. Studies have shown that hydrogen sulfide (H₂S) plays a critical role in the modulation of glycolipid metabolism, pancreatic β cell functions, and diabetic complications. Critical Issues: Preservation of endogenous H₂S systems and supplementation of H₂S donors are effective in attenuating diabetes-induced complications, thus representing a new avenue to treat diabetes and its associated complications. Future Directions: This review systematically recapitulates and discusses the most recent updates regarding the therapeutic effects of H₂S on diabetes and its various complications, with an emphasis on the molecular mechanisms that underlie H₂S-mediated protection against diabetic complications. Furthermore, current clinical trials of H₂S in diabetic populations are highlighted, and the challenges and solutions to the clinical transformation of H₂S-derived therapies in diabetes are proposed. Finally, future research directions of the pharmacological actions of H₂S in diabetes and its related complications are summarized. Antioxid. Redox Signal. 38, 18-44.

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.

Signaling pathways in cutaneous wound healing

Wound healing is a very complex process, where variety of different pathways is activated, depending on the phase of healing. Improper or interrupted healing might result in development of chronic wounds. Therefore, novel approaches based on detailed knowledge of signalling pathways that are activated during acute or chronic cutaneous wound healing enables quicker and more effective healing. This review outlined new possibilities of cutaneous wound healing by modulation of some signalling molecules, e.g., gasotransmitters, or calcium. Special focus is given to gasotransmitters, since these bioactive signalling molecules that can freely diffuse into the cell and exert antioxidative effects. Calcium is an important booster of immune system and it can significantly contribute to healing process. Special interest is given to chronic wounds caused by diabetes mellitus and overcoming problems with the inflammation.

Hydrogen Sulfide Improves Angiogenesis by Regulating the Transcription of pri-miR-126 in Diabetic Endothelial Cells

Introduction: Diabetes mellitus results in high rates of cardiovascular disease, such as microcirculation disorder of the lower limbs, with angiogenesis impairment being the main factor. The endothelium functions as a barrier between blood and the vessel wall. Vascular endothelial cell dysfunction caused by hyperglycemia is the main factor leading to angiogenesis impairment. Hydrogen sulfide (H₂S) and miR-126-3p are known for their pro-angiogenesis effects; however, little is known about how H₂S regulates miR-126-3p to promote angiogenesis under high-glucose conditions. Objectives: The main objective of this research was to explore how H₂S regulates the miR-126-3p levels under high-glucose conditions. Methods: We evaluated the pro-angiogenesis effects of H₂S in the diabetic hindlimb of an ischemia mice model and in vivo Matrigel plugs. Two microRNA datasets were used to screen microRNAs regulated by both diabetes and H₂S. The mRNA and protein levels were detected through real-time PCR and Western blot, respectively. Immunofluorescent staining was also used to assess the capillary density and to evaluate the protein levels in vascular endothelial cells. Human umbilical vein endothelial cells (HUVECs) were used in in vitro experiments. A scratch wound-healing assay was applied to detect the migration ability of endothelial cells. Methylated DNA immunoprecipitation combined with real-time PCR was chosen to identify the DNA methylation level in the HUVECs. Results: Exogenous H₂S improved angiogenesis in diabetic mice. miR-126-3p was regulated by both diabetes and H₂S. Exogenous H₂S up-regulated the miR-126-3p level and recovered the migration rate of endothelial cells via down-regulating the DNMT1 protein level, which was increased by high glucose. Furthermore, DNMT1 upregulation in the HUVECs increased the methylation levels of the gene sequences upstream of miR-126-3p and then inhibited the transcription of primary-miR-126, thus decreasing the miR-126-3p level. CSE overexpression in the HUVECs rescued the miR-126-3p level, by decreasing the methylation level to improve migration. Conclusion: H₂S increases the miR-126-3p level through down-regulating the methylation level, by decreasing the DNMT1 protein level induced by high glucose, thus improving the angiogenesis originally impaired by high glucose.

Hydrogen Sulfide Suppresses Skin Fibroblast Proliferation via Oxidative Stress Alleviation and Necroptosis Inhibition

Keloid is a common dermatofibrotic disease with excessive skin fibroblast proliferation. Hydrogen sulfide (H₂S) as the third gasotransmitter improves fibrosis of various organs and tissues. Our study is aimed at investigating the effects and possible mechanisms of H₂S on skin fibroblast proliferation. Scar tissues from six patients with keloid and discarded skin tissue from six normal control patients were collected after surgery, respectively. Plasma H₂S content and skin H₂S production in patients with keloid were measured. Keloid fibroblasts and transforming growth factor-β₁- (TGF-β₁, 10 ng/mL) stimulated normal skin fibroblasts were pretreated with H₂S donor as NaHS (50 μM) for 4 h. Cell migration after scratch was assessed. The expressions of α-smooth muscle actin (α-SMA), proliferating cell nuclear antigen (PCNA), collagen I, and collagen III were detected by immunofluorescence, real-time PCR, and/or Western blot. Intracellular superoxide anion and mitochondrial superoxide were evaluated by dihydroethidium (DHE) and MitoSOX staining, respectively. Mitochondrial membrane potential was detected by JC-1 staining. Apoptotic cells were detected by TDT-mediated dUTP nick end labeling (TUNEL). The expressions of receptor interacting protein kinase 1 (RIPK1), RIPK3, and mixed lineage kinase domain-like protein (MLKL) were measured by Western blot. We found that H₂S production was impaired in both the plasma and skin of patients with keloid. In keloid fibroblasts and TGF-β₁-stimulated normal skin fibroblasts, exogenous H₂S supplementation suppressed the expressions of α-SMA, PCNA, collagen I, and collagen III, reduced intracellular superoxide anion and mitochondrial superoxide, improved the mitochondrial membrane potential, decreased the positive rate of TUNEL staining, and inhibited RIPK1 and RIPK3 expression as well as MLKL phosphorylation. Overall, H₂S suppressed skin fibroblast proliferation via oxidative stress alleviation and necroptosis inhibition.

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.

Small-molecule antagonism of the interaction of the RAGE cytoplasmic domain with DIAPH1 reduces diabetic complications in mice

The macro- and microvascular complications of type 1 and 2 diabetes lead to increased disease severity and mortality. The receptor for advanced glycation end products (RAGE) can bind AGEs and multiple proinflammatory ligands that accumulate in diabetic tissues. Preclinical studies indicate that RAGE antagonists have beneficial effects on numerous complications of diabetes. However, these antagonists target the extracellular domains of RAGE, which bind distinct RAGE ligands at diverse sites in the immunoglobulin-like variable domain and two constant domains. The cytoplasmic tail of RAGE (ctRAGE) binds to the formin, Diaphanous-1 (DIAPH1), and this interaction is important for RAGE signaling. To comprehensively capture the breadth of RAGE signaling, we developed small-molecule antagonists of ctRAGE-DIAPH1 interaction, termed RAGE229. We demonstrated that RAGE229 is effective in suppressing RAGE-DIAPH1 binding, Förster resonance energy transfer, and biological activities in cellular assays. Using solution nuclear magnetic resonance spectroscopy, we defined the molecular underpinnings of the interaction of RAGE229 with RAGE. Through in vivo experimentation, we showed that RAGE229 assuaged short- and long-term complications of diabetes in both male and female mice, without lowering blood glucose concentrations. Last, the treatment with RAGE229 reduced plasma concentrations of TNF-α, IL-6, and CCL2/JE-MCP1 in diabetic mice, in parallel with reduced pathological and functional indices of diabetes-like kidney disease. Targeting ctRAGE-DIAPH1 interaction with RAGE229 mitigated diabetic complications in rodents by attenuating inflammatory signaling.

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.

Hydrogen Sulfide Is a Novel Protector of the Retinal Glycocalyx and Endothelial Permeability Barrier

Significantly reduced levels of the anti-inflammatory gaseous transmitter hydrogen sulfide (H₂S) are observed in diabetic patients and correlate with microvascular dysfunction. H₂S may protect the microvasculature by preventing loss of the endothelial glycocalyx. We tested the hypothesis that H₂S could prevent or treat retinal microvascular endothelial dysfunction in diabetes. Bovine retinal endothelial cells (BRECs) were exposed to normal (NG, 5.5 mmol/L) or high glucose (HG, 25 mmol/L) ± the slow-release H₂S donor NaGYY4137 in vitro. Glycocalyx coverage (stained with WGA-FITC) and calcein-labeled monocyte adherence were measured. In vivo, fundus fluorescein angiography (FFA) was performed in normal and streptozotocin-induced (STZ) diabetic rats. Animals received intraocular injection of NaGYY4137 (1 μM) or the mitochondrial-targeted H₂S donor AP39 (100 nM) simultaneously with STZ (prevention) or on day 6 after STZ (treatment), and the ratio of interstitial to vascular fluorescence was used to estimate apparent permeability. NaGYY4137 prevented HG-induced loss of BREC glycocalyx, increased monocyte binding to BRECs (p ≤ 0.001), and increased overall glycocalyx coverage (p ≤ 0.001). In rats, the STZ-induced increase in apparent retinal vascular permeability (p ≤ 0.01) was significantly prevented by pre-treatment with NaGYY4137 and AP39 (p < 0.05) and stabilized by their post-STZ administration. NaGYY4137 also reduced the number of acellular capillaries (collagen IV + /IB4-) in the diabetic retina in both groups (p ≤ 0.05). We conclude that NaGYY4137 and AP39 protected the retinal glycocalyx and endothelial permeability barrier from diabetes-associated loss of integrity and reduced the progression of diabetic retinopathy (DR). Hydrogen sulfide donors that target the glycocalyx may therefore be a therapeutic candidate for DR.

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.

TNFα regulates the expression of the CSE gene in HUVEC

The hydrogen sulfide (H₂S)/cystathionine γ-lyase (CSE) signaling pathway is involved in several inflammatory conditions, where tumor necrosis factor-α (TNFα) is one of the inflammatory cytokines activated during sepsis. Therefore, the present study investigated the role of the NF-κB transcription factor binding site in the transcriptional regulation of the CSE gene in 293T cells following treatment with TNFα using luciferase assays, as well as using western blotting and reverse transcription-quantitative PCR to examine the effect of TNFα on CSE expression in HUVECs. After transfected 293T cells were incubated with various concentrations of TNFα for 1, 3, and 6 h, the wild-type promoter of the CSE gene increased significantly at 1 h compared to 0 h. By contrast, after the transfected 293T cells were incubated with various concentrations of TNFα for 1 h, the mutant-type promoter activity of the CSE gene decreased significantly compared to the wild-type. These results revealed that the DNA sequence GGGACATTCC on the CSE gene promoter was directly associated with the transcriptional regulation of the CSE gene in Human cells (293T cells) that's were treated with TNFα. This suggests that TNFα affects CSE gene expression, such that vascular endothelial cells respond to TNFα in the blood by regulating CSE expression. The regulatory mechanisms associated with the effects of TNFα on the transcriptional regulation of the CSE gene in HUVECs and the NF-κB pathway warrant further investigation.

Relationship Between Endogenous Hydrogen Sulfide and Pulmonary Vascular Indexes on High-Resolution Computed Tomography in Patients with Chronic Obstructive Pulmonary Disease

Objective

To explore the relationship between endogenous hydrogen sulfide (H₂S) and high-resolution computed tomography (HRCT) indexes in pulmonary vascular remodeling.

Methods

A total of 94 stable chronic obstructive pulmonary disease (COPD) patients were recruited for the study．Plasma H₂S levels were measured using fluorescence probe. Fluorescence quantitative polymerase chain reaction was used to measure H₂S synthase cystathionine-γ-lyase (CSE) mRNA and cystathionine-β-synthesis enzyme (CBS) mRNA. The main pulmonary artery diameter (mPAD), axial diagonal mPAD, coronal mPAD, sagittal mPAD, right pulmonary artery diameter (RPAD), left pulmonary artery diameter (LPAD), and ascending aortic diameter (AAD) and the percentage of total cross-sectional area of vessels less than 5 mm² of total lung area (%CSA <5) on HRCT were measured. Pulmonary arterial systolic pressure (PASP) of echocardiography, blood gas analysis, and routine blood tests were performed. Correlation analysis and multivariate linear regression were performed using SPSS 22.0.

Results

H₂S was negatively correlated with mPAD, axial diagonal mPAD, and sagittal mPAD (r = -0.25~-0.32) and positively correlated with PaO₂ (r = 0.35). Relative expression of CSE mRNA was positively correlated with PASP, coronal mPAD, sagittal mPAD, white blood cell count (WBC), and neutrophil count (N) (r = 0.30~0.44). The relative expression of CBS mRNA was positively correlated with PASP, WBC, and N (r = 0.34~0.41). In separate models predicting pulmonary vascular indexes, a 1μmol/L increase in H₂S predicted lower pulmonary artery diameter (for axial diagonal mPAD, 0.76mm lower; for mPAD/AAD, 0.68mm lower). All P values were less than 0.05.

Conclusion

Endogenous H₂S may be involved in pulmonary vascular remodeling, providing a new method for the diagnosis and treatment of COPD. The generation of H₂S may be inhibited by hypoxia, inflammation, etc.

Limited Treatment Options for Diabetic Wounds: Barriers to Clinical Translation Despite Therapeutic Success in Murine Models

Significance: Millions of people worldwide suffer from diabetes mellitus and its complications, including chronic diabetic wounds. To date, there are few widely successful clinical therapies specific to diabetic wounds beyond general wound care, despite the vast number of scientific discoveries in the pathogenesis of defective healing in diabetes. Recent Advances: In recent years, murine animal models of diabetes have enabled the investigation of many possible therapeutics for diabetic wound care. These include specific cell types, growth factors, cytokines, peptides, small molecules, plant extracts, microRNAs, extracellular vesicles, novel wound dressings, mechanical interventions, bioengineered materials, and more. Critical Issues: Despite many research discoveries, few have been translated from their success in murine models to clinical use in humans. This massive gap between bench discovery and bedside application begs the simple and critical question: what is still missing? The complexity and multiplicity of the diabetic wound makes it an immensely challenging therapeutic target, and this lopsided progress highlights the need for new methods to overcome the bench-to-bedside barrier. How can laboratory discoveries in animal models be effectively translated to novel clinical therapies for human patients? Future Directions: As research continues to decipher deficient healing in diabetes, new approaches and considerations are required to ensure that these discoveries can become translational, clinically usable therapies. Clinical progress requires the development of new, more accurate models of the human disease state, multifaceted investigations that address multiple critical components in wound repair, and more innovative research strategies that harness both the existing knowledge and the potential of new advances across disciplines.

Hydrogen sulfide alleviates the anxiety-like and depressive-like behaviors of type 1 diabetic mice via inhibiting inflammation and ferroptosis

Studies reported that sodium hydrosulfide (NaHS) can remit the depressive-like and anxiety-like behaviors induced by type 1 diabetes mellitus (T1DM). However, the mechanism is still unclear. In this study, we aimed to investigate the mechanism of NaHS on T1DM. Mice were randomly divided into four groups, including the control group (CON group), DM group, DM + 5.6 mg/kg NaHS group, and CON + 5.6 mg/kg NaHS group. Data showed that NaHS did attenuate the depressive-like and anxiety-like behaviors by OFT, EPM test, FST, and TST. Results suggest that NaHS markedly alleviated the ferroptosis in the prefrontal cortex (PFC) of diabetic mice by reducing iron deposition and oxidative stress, increasing the expression of GPX4 and SLC7A11. Moreover, NaHS could dampen the activation of microglias and the release of pro-inflammatory cytokines, enhance the protein expression of sirtuin 6 (Sirt6) and the interaction between Sirt6 and the acetylation of histoneH3 lysine9 (H3K9ac), and decrease the protein expressions of the Notch1 receptor and H3K9ac. In vitro experiment, NaHS ameliorated the ferroptosis via increasing the protein expressions of SLC7A11, glutathione peroxidase 4 (GPX4), and cystathionine β-synthase (CBS), reducing the pro-inflammatory cytokines, decreasing the levels of Fe²⁺, MDA, ROS, and lipid ROS. In conclusion, our results suggested that NaHS did alleviate anxiety-like and depressive-like behaviors. It can inhibit inflammation via modulating Sirt6 and was able to decrease the ferroptosis in the PFC of type 1 diabetic mice and the BV2 cells.

Hydrogen Sulfide in Skin Diseases: A Novel Mediator and Therapeutic Target

Together with nitric oxide (NO) and carbon monoxide (CO), hydrogen sulfide (H₂S) is now recognized as a vital gaseous transmitter. The ubiquitous distributions of H₂S-producing enzymes and potent chemical reactivities of H₂S in biological systems make H₂S unique in its ability to regulate cellular and organ functions in both health and disease. Acting as an antioxidant, H₂S can combat oxidative species such as reactive oxygen species (ROS) and reactive nitrogen species (RNS) and protect the skin from oxidative stress. The aberrant metabolism of H₂S is involved in the pathogenesis of several skin diseases, such as vascular disorders, psoriasis, ulcers, pigment disorders, and melanoma. Furthermore, H₂S donors and some H₂S hybrids have been evaluated in many experimental models of human disease and have shown promising therapeutic results. In this review, we discuss recent advances in understanding H₂S and its antioxidant effects on skin pathology, the roles of altered H₂S metabolism in skin disorders, and the potential value of H₂S as a therapeutic intervention in skin diseases.

Endothelium as a Source and Target of H2S to Improve Its Trophism and Function

The vascular endothelium consists of a single layer of squamous endothelial cells (ECs) lining the inner surface of blood vessels. Nowadays, it is no longer considered as a simple barrier between the blood and vessel wall, but a central hub to control blood flow homeostasis and fulfill tissue metabolic demands by furnishing oxygen and nutrients. The endothelium regulates the proper functioning of vessels and microcirculation, in terms of tone control, blood fluidity, and fine tuning of inflammatory and redox reactions within the vessel wall and in surrounding tissues. This multiplicity of effects is due to the ability of ECs to produce, process, and release key modulators. Among these, gasotransmitters such as nitric oxide (NO) and hydrogen sulfide (H₂S) are very active molecules constitutively produced by endotheliocytes for the maintenance and control of vascular physiological functions, while their impairment is responsible for endothelial dysfunction and cardiovascular disorders such as hypertension, atherosclerosis, and impaired wound healing and vascularization due to diabetes, infections, and ischemia. Upregulation of H₂S producing enzymes and administration of H₂S donors can be considered as innovative therapeutic approaches to improve EC biology and function, to revert endothelial dysfunction or to prevent cardiovascular disease progression. This review will focus on the beneficial autocrine/paracrine properties of H₂S on ECs and the state of the art on H₂S potentiating drugs and tools.

Direct Comparison of Triggering Motifs on Chemiluminescent Probes for Hydrogen Sulfide Detection in Water

Hydrogen sulfide (H2S) is an important biomolecule and significant efforts have focused on developing chemical tools to aid different biological investigations. Of such tools, there are relatively few chemiluminescent or bioluminescent methods for H2S detection. Here we report two dioxetane-based chemiluminescent probes for H2S detection. With these probes, we directly compare the probe response to H2S-mediated azide reduction and nucleophilic displacement of 2,4-dinitrophenyl motifs and demonstrate that the SNAr cleavage of the DNP group results in a larger response and greater stability in water.

Hydrogen sulfide: Recent progress and perspectives for the treatment of dermatological diseases

•

Three hydrogen sulfide (H₂S) production enzymes including CSE, CBS and 3-MST exist in the skin.

•

H₂S regulates burn, diabetic skin wound, psoriasis, systemic sclerosis, melanoma, and pruritus.

•

H₂S regulates oxidative stress, inflammation, angiogenesis and apoptosis in skin diseases.

•

Some ideal characteristics of H₂S-based therapeutics for topical delivery are preferred.

•

Therapeutic potential of H₂S for skin disorders will be further proposed in clinical trials.

Background

Hydrogen sulfide (H₂S) is now recognized as a vital endogenous gasotransmitter with a variety of biological functions in different systems. Recently, studies have increasingly focused on the role of H₂S in the skin.

Aim of Review

This review summarizes recent progress and provides perspectives on H₂S in the treatment of dermatological diseases.

Key Scientific Concepts of Review

Three H₂S production enzymes, cystathionine-γ-lyase (CSE), cystathionine-β-synthase (CBS) and 3-mercaptopyruvate sulfur transferase (3-MST), are all present in the skin, and it is likely that different cell types in the skin express them differently. Previous studies have demonstrated that H₂S protects against several dermatological diseases, such as burns, diabetic skin wounds, psoriasis, skin flap transplantation, systemic sclerosis, melanoma, and pruritus. The mechanism might be related to the regulation of oxidative stress, inflammation, angiogenesis, apoptosis, and allergic reactions. H₂S-based therapeutics require certain characteristics for topical delivery, for example, controlled release, appropriate physicochemical properties, good storage stability, acceptable odor, and advanced delivery systems. H₂S-induced S-sulfhydration on proteins are potential novel targets for therapeutic intervention and drug design for the skin, which may lead to the development and application of H₂S-related drugs for dermatological diseases.

The role of hydrogen sulphide signalling in macrophage activation

Hydrogen sulphide (H₂S) is the latest identified small gaseous mediator enabled by its lipophilic nature to freely permeate the biological membranes. Initially, H₂S was recognized by its roles in neuronal activity and vascular relaxation, which makes it an important molecule involved in paracrine signalling pathways. Recently, the immune regulatory function of gasotransmitters, H₂S in particular, is increasingly being appreciated. Endogenous H₂S level has been linked to macrophage activation, polarization and inflammasome formation. Mechanistically, H₂S‐induced protein S‐sulphydration suppresses several inflammatory pathways including NF‐κB and JNK signalling. Moreover, H₂S serves as a potent cellular redox regulator to modulate epigenetic alterations and to promote mitochondrial biogenesis in macrophages. Here in this review, we intend to summarize the recent advancements of H₂S studies in macrophages, and to discuss with focus on the therapeutic potential of H₂S donors by targeting macrophages. The feasibility of H₂S signalling component as a macrophage biomarker under disease conditions would be also discussed.

Electrospun nanofiber-based drug delivery platform: advances in diabetic foot ulcer management

INTRODUCTION

Electrospinning is a facile and viable method for the fabrication of nanofibers. Electrospun nanofiber has a great potential in providing local drug or therapeutic molecule delivery to the wound site. The versatile nature of this technique ensures a broad scope of material used in the fabrication of nanofibers.

AREA COVERED

A brief introduction to diabetic foot ulcer (DFU) is covered with its pathogenesis, followed by the role of electrospun nanofibers in DFU. This review covers the evolution of the electrospinning technique over the past few years, various types of electrospun nanofibers reported for DFU or chronic diabetic wounds, the challenges associated with the preparation of nanofibers, and various methods to evaluate their efficacy and performance in diabetic wound healing.

EXPERT OPINION

Electrospinning-based nanofibers provide a safe, effective, and multifunctional system for effective management of DFU.

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.

Systematic review and meta-analysis of mouse models of diabetes-associated ulcers

Mouse models are frequently used to study diabetes-associated ulcers, however, whether these models accurately simulate impaired wound healing has not been thoroughly investigated. This systematic review aimed to determine whether wound healing is impaired in mouse models of diabetes and assess the quality of the past research. A systematic literature search was performed of publicly available databases to identify original articles examining wound healing in mouse models of diabetes. A meta-analysis was performed to examine the effect of diabetes on wound healing rate using random effect models. A meta-regression was performed to examine the effect of diabetes duration on wound healing impairment. The quality of the included studies was also assessed using two newly developed tools. 77 studies using eight different models of diabetes within 678 non-diabetic and 720 diabetic mice were included. Meta-analysis showed that wound healing was impaired in all eight models. Meta-regression suggested that longer duration of diabetes prior to wound induction was correlated with greater degree of wound healing impairment. Pairwise comparisons suggested that non-obese diabetic mice exhibited more severe wound healing impairment compared with db/db mice, streptozotocin-induced diabetic mice or high-fat fed mice at an intermediate stage of wound healing (p<0.01). Quality assessment suggested that the prior research frequently lacked incorporation of key clinically relevant characteristics. This systematic review suggested that impaired wound healing can be simulated in many different mouse models of diabetes but these require further refinement to become more clinically relevant.

A hydrogen sulfide-releasing alginate dressing for effective wound healing

For wounds with heavy exudate levels, a dressing that can help to absorb wound exudate and improve the wound healing process is highly desired. Hydrogen sulfide (H₂S) has been recognized as an important gasotransmitter that can improve angiogenesis which is crucial for wound healing. In this study, a functional sodium alginate (SA) dressing with H₂S-releasing property (SA/JK-1) was fabricated by incorporating JK-1 molecule, a pH-dependent H₂S donor, into SA sponge. The resultant SA/JK-1 sponge provided a moist and protective healing environment and was capable of releasing H₂S consistently under acidic pH condition by absorbing exudate at the wound interface. The H₂S release of JK-1 donor was prolonged by the SA sponge compared with JK-1 in solution. Cell study in vitro indicated that SA/JK-1 not only exhibited good cyto-compatibility, but also improved fibroblast proliferation and migration. In addition, the effects of the SA/JK-1 dressing on wound healing was evaluated using an in vivo full thickness dermal defect model, which revealed that SA/JK-1 can significantly improve wound healing process with enhanced granulation tissue formation, re-epithelialization, collagen deposition and angiogenesis, due to the H₂S released from JK-1. Taken together, our results showed that SA dressing doped with H₂S donor could potentially serves as an effective wound healing strategy. STATEMENT OF SIGNIFICANCE: The gasotransmitter H₂S has been proven to improve the wound healing process in nanofibrous dressing due to its biological functions on angiogenesis. However, for non-healing wounds with heavy exudates, a wound dressing that can absorb wound exudates and controlled gasotransmitter release to improve the wound healing process is still in urgent need. Here we fabricated a sodium alginate (SA) sponge incorporated with H₂S donor JK-1 (SA/JK-1), which showed strong water uptake capability, and released H₂S under acidic condition. The SA/JK-1 sponge exhibited biocompatibility to fibroblasts and promoted cell migration in vitro, and exhibited obviously positive influence on wound healing in vivo. This H₂S donor doped alginate wound dressing represents a promising strategy for treatment of non-healing wound.

Role of Endothelial Dysfunction in Cardiovascular Diseases: The Link Between Inflammation and Hydrogen Sulfide

Endothelial cells are important constituents of blood vessels that play critical roles in cardiovascular homeostasis by regulating blood fluidity and fibrinolysis, vascular tone, angiogenesis, monocyte/leukocyte adhesion, and platelet aggregation. The normal vascular endothelium is taken as a gatekeeper of cardiovascular health, whereas abnormality of vascular endothelium is a major contributor to a plethora of cardiovascular ailments, such as atherosclerosis, aging, hypertension, obesity, and diabetes. Endothelial dysfunction is characterized by imbalanced vasodilation and vasoconstriction, elevated reactive oxygen species (ROS), and proinflammatory factors, as well as deficiency of nitric oxide (NO) bioavailability. The occurrence of endothelial dysfunction disrupts the endothelial barrier permeability that is a part of inflammatory response in the development of cardiovascular diseases. As such, abrogation of endothelial cell activation/inflammation is of clinical relevance. Recently, hydrogen sulfide (H₂S), an entry as a gasotransmitter, exerts diverse biological effects through acting on various targeted signaling pathways. Within the cardiovascular system, the formation of H₂S is detected in smooth muscle cells, vascular endothelial cells, and cardiomyocytes. Disrupted H₂S bioavailability is postulated to be a new indicator for endothelial cell inflammation and its associated endothelial dysfunction. In this review, we will summarize recent advances about the roles of H₂S in endothelial cell homeostasis, especially under pathological conditions, and discuss its putative therapeutic applications in endothelial inflammation-associated cardiovascular disorders.

A Novel Liposomal S-Propargyl-Cysteine: A Sustained Release of Hydrogen Sulfide Reducing Myocardial Fibrosis via TGF-β1/Smad Pathway

Purpose

S-propargyl-cysteine (SPRC; alternatively known as ZYZ-802) is a novel modulator of endogenous tissue H₂S concentrations with known cardioprotective and anti-inflammatory effects. However, its rapid metabolism and excretion have limited its clinical application. To overcome these issues, we have developed some novel liposomal carriers to deliver ZYZ-802 to cells and tissues and have characterized their physicochemical, morphological and pharmacological properties.

Methods

Two liposomal formulations of ZYZ-802 were prepared by thin-layer hydration and the morphological characteristics of each liposome system were assessed using a laser particle size analyzer and transmission electron microscopy. The entrapment efficiency and ZYZ-802 release profiles were determined following ultrafiltration centrifugation, dialysis tube and HPLC measurements. LC-MS/MS was used to evaluate the pharmacokinetic parameters and tissue distribution profiles of each formulation via the measurements of plasma and tissues ZYZ-802 and H₂S concentrations. Using an in vivo model of heart failure (HF), the cardio-protective effects of liposomal carrier were determined by echocardiography, histopathology, Western blot and the assessment of antioxidant and myocardial fibrosis markers.

Results

Both liposomal formulations improved ZYZ-802 pharmacokinetics and optimized H₂S concentrations in plasma and tissues. Liposomal ZYZ-802 showed enhanced cardioprotective effects in vivo. Importantly, liposomal ZYZ-802 could inhibit myocardial fibrosis via the inhibition of the TGF-β1/Smad signaling pathway.

Conclusion

The liposomal formulations of ZYZ-802 have enhanced pharmacokinetic and pharmacological properties in vivo. This work is the first report to describe the development of liposomal formulations to improve the sustained release of H₂S within tissues.

The role of nitric oxide during embryonic wound healing

Background

The study of the mechanisms controlling wound healing is an attractive area within the field of biology, with it having a potentially significant impact on the health sector given the current medical burden associated with healing in the elderly population. Healing is a complex process and includes many steps that are regulated by coding and noncoding RNAs, proteins and other molecules. Nitric oxide (NO) is one of these small molecule regulators and its function has already been associated with inflammation and angiogenesis during adult healing.

Results

Our results showed that NO is also an essential component during embryonic scarless healing and acts via a previously unknown mechanism. NO is mainly produced during the early phase of healing and it is crucial for the expression of genes associated with healing. However, we also observed a late phase of healing, which occurs for several hours after wound closure and takes place under the epidermis and includes tissue remodelling that is dependent on NO. We also found that the NO is associated with multiple cellular metabolic pathways, in particularly the glucose metabolism pathway. This is particular noteworthy as the use of NO donors have already been found to be beneficial for the treatment of chronic healing defects (including those associated with diabetes) and it is possible that its mechanism of action follows those observed during embryonic wound healing.

Conclusions

Our study describes a new role of NO during healing, which may potentially translate to improved therapeutic treatments, especially for individual suffering with problematic healing.

Hydrogen Sulfide in Bone Tissue Regeneration and Repair: State of the Art and New Perspectives

The importance of hydrogen sulfide (H₂S) in the regulation of multiple physiological functions has been clearly recognized in the over 20 years since it was first identified as a novel gasotransmitter. In bone tissue H₂S exerts a cytoprotective effect and promotes bone formation. Just recently, the scientific community has begun to appreciate its role as a therapeutic agent in bone pathologies. Pharmacological administration of H₂S achieved encouraging results in preclinical studies in the treatment of systemic bone diseases, such as osteoporosis; however, a local delivery of H₂S at sites of bone damage may provide additional opportunities of treatment. Here, we highlight how H₂S stimulates multiple signaling pathways involved in various stages of the processes of bone repair. Moreover, we discuss how material science and chemistry have recently developed biomaterials and H₂S-donors with improved features, laying the ground for the development of H₂S-releasing devices for bone regenerative medicine. This review is intended to give a state-of-the-art description of the pro-regenerative properties of H₂S, with a focus on bone tissue, and to discuss the potential of H₂S-releasing scaffolds as a support for bone repair.

Hydrogen sulfide and dermatological diseases

Skin diseases constitute a major health problem affecting a high proportion of the population every day and have different aetiologies that include inflammation, infections, and tumours. Hydrogen sulfide (H₂ S) is a gaseous signalling molecule recognized as a gasotransmitter together with NO and carbon monoxide. Under physiological conditions, H₂ S is produced in the skin by enzymic pathways and plays a physiological role in a variety of functions, such as vasodilatation, cell proliferation, apoptosis, and inflammation. Alterations of H₂ S production are implicated in a variety of dermatological diseases, such as psoriasis, melanoma, and other dermatoses. On the other hand, H₂ S-releasing-based therapies based on H₂ S donor compounds are being developed to treat some of these situations. In this review, we provide an up-to-date overview of the role of H₂ S in the normal skin and its clinical and pathological significance, as well as the therapeutic potential of different H₂ S donors for treatment of skin diseases. 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.

In vivo comparison of wound healing and scar treatment effect between curcumin-oligochitosan nanoparticle complex and oligochitosan-coated curcumin-loaded-liposome

This study aimed to compare the in vivo effectiveness between curcumin-oligochitosan nanoplexes (CUR-OCH nanoplexes) and oligochitosan-coated curcumin-encapsulated liposomes (OCH-Lip-CUR) with respect to wound healing and scar treatment. Firstly, CUR-OCH nanoplexes was prepared by drug-polysaccharide complexation method and OCH-Lip-CUR was prepared by a combining method of lipid-film hydration and sonication. Their in vitro cytotoxicity and in vivo wound healing and scar treatment effectiveness were evaluated using 3T3 cells and mice Mus musculus var. Albino, respectively. The resutls indicated that both of them were in nanosize with a moderate PDI (less than 0.3), and exhibited negligible cytotoxicity at low CUR concentration (0.01 mg/mL). Moreover, their application onto wounds resulted in faster healing and higher scar treatment effectiveness than control samples. Interestingly, OCH-Lip-CUR exhibited higher in vivo effectiveness than CUR-OCH nanoplexes. However, based on their own advantages, both of them were good candidates for a commercial formulation for wound healing and scar treatment.

Exogenous hydrogen sulphide supplement accelerates skin wound healing via oxidative stress inhibition and vascular endothelial growth factor enhancement

Hydrogen sulphide (H₂ S) is an important gasotransmitter with several physiological functions. However, the roles and the detailed mechanisms of H₂ S on skin wound healing are not known well. In the present study, 129S1/SvImJ mice were intraperitoneally injected with NaHS (50 μmol/kg/d) for 2 weeks. Then, a round wound of 6 mm diameter with depth into the dermis was made. The skin wound area, blood perfusion, superoxide production, malondialdehyde (MDA) levels, total antioxidant capacity (T-AOC), expression of vascular endothelial growth factor (VEGF), dynamin-related protein 1 (DRP1) and optic atrophy 1 (OPA1) were measured. After NaHS (50 μmol/L) pre-administration for 4 hours, cell migration rate, DRP1, OPA1 and α-smooth muscle actin (α-SMA) expression, superoxide production and mitochondrial membrane potential in primary skin fibroblasts were measured. Tube formation in human umbilical vein endothelial cells (HUVECs) and cell migration in human keratinocytes were also measured. The results showed that NaHS pretreatment significantly accelerated wound healing and improved blood flow in the wound after operation. NaHS increased VEGF expression in the wound and promoted tube formation in HUVECs. Meanwhile, NaHS attenuated reactive oxygen species (ROS) production, suppressed MDA level but restored T-AOC in the wound. NaHS also promoted skin fibroblasts migration and α-SMA expression after scratch. Moreover, NaHS alleviated ROS, increased mitochondrial membrane potential, decreased DRP1 but enhanced OPA1 expression in skin fibroblasts after scratch. NaHS also accelerated human keratinocytes migration after scratch. Taken together, exogenous H₂ S supplementary accelerated the skin wound healing, which might be related to oxidative stress inhibition and VEGF enhancement.

The Dynamics of the Skin's Immune System

The skin is a complex organ that has devised numerous strategies, such as physical, chemical, and microbiological barriers, to protect the host from external insults. In addition, the skin contains an intricate network of immune cells resident to the tissue, crucial for host defense as well as tissue homeostasis. In the event of an insult, the skin-resident immune cells are crucial not only for prevention of infection but also for tissue reconstruction. Deregulation of immune responses often leads to impaired healing and poor tissue restoration and function. In this review, we will discuss the defensive components of the skin and focus on the function of skin-resident immune cells in homeostasis and their role in wound healing.

Mechanisms by which hydrogen sulfide attenuates muscle function following ischemia-reperfusion injury: effects on Akt signaling, mitochondrial function, and apoptosis

Ischemia–reperfusion injury is caused by a period of ischemia followed by massive blood flow into a tissue that had experienced restricted blood flow. The severity of the injury is dependent on the time the tissue was restricted from blood flow, becoming more severe after longer ischemia times. This can lead to many complications such as tissue necrosis, cellular apoptosis, inflammation, metabolic and mitochondrial dysfunction, and even organ failure. One of the emerging therapies to combat ischemic reperfusion injury complications is hydrogen sulfide, which is a gasotransmitter that diffuses across cell membranes to exert effects on various signaling pathways regulating cell survival such as Akt, mitochondrial activity, and apoptosis. Although commonly thought of as a toxic gas, low concentrations of hydrogen sulfide have been shown to be beneficial in promoting tissue survival post-ischemia, and modulate a wide variety of cellular responses. This review will detail the mechanisms of hydrogen sulfide in affecting the Akt signaling pathway, mitochondrial function, and apoptosis, particularly in regards to ischemic reperfusion injury in muscle tissue. It will conclude with potential clinical applications of hydrogen sulfide, combinations with other therapies, and perspectives for future studies.

Is there a role of H2S in mediating health span benefits of caloric restriction?

Caloric restriction (CR) is a dietary regimen that aims to reduce the intake of total calories while maintaining adequate supply of key nutrients so as to avoid malnutrition. CR is one of only a small number of interventions that show promising outcomes on health span and lifespan across different species. There is growing interest in the development of compounds that might replicate CR-related benefits without actually restricting food intake. Hydrogen sulfide (H₂S) is produced inside the bodies of many animals, including humans, by evolutionarily conserved H₂S synthesizing enzymes. Endogenous H₂S is increasingly recognized as an important gaseous signalling molecule involved in diverse cellular and molecular processes. However, the specific role of H₂S in diverse biological processes remains to be elucidated and not all its biological effects are beneficial. Nonetheless, recent evidence suggests that the biological functions of H₂S intersect with the network of evolutionarily conserved nutrient sensing and stress response pathways that govern organismal responses to CR. Induction of H₂S synthesizing enzymes appears to be a conserved and essential feature of the CR response in evolutionarily distant organisms, including nematodes and mice. Here we review the evidence for a role of H₂S in CR and lifespan modulation. H₂S releasing drugs, capable of controlled delivery of exogenous H₂S, are currently in clinical development. These findings suggest such H₂S releasing drugs as a promising novel avenue for the development of CR mimetic compounds.

H2S-Induced Sulfhydration: Biological Function and Detection Methodology

At appropriate concentrations, hydrogen sulfide, a well-known gasotransmitter, plays important roles in both physiology and pathophysiology. Increasing evidence suggests that modifying thiol groups of specific cysteines in target proteins via sulfhydration or persulfidation is one of the important mechanisms responsible for the biological functions of hydrogen sulfide. A variety of key proteins of different cellular pathways in mammals have been reported to be sulfhydrated by hydrogen sulfide to participate and regulate the processes of cell survival/death, cell differentiation, cell proliferation/hypertrophy, cellular metabolism, mitochondrial bioenergetics/biogenesis, endoplasmic reticulum stress, vasorelaxtion, inflammation, oxidative stress, etc. Moreover, S-sulfhydration also exerts many biological functions through the cross-talk with other post-translational modifications including phosphorylation, S-nitrosylation and tyrosine nitration. This review summarizes recent studies of hydrogen sulfide-induced sulfhydration as a posttranslational modification, an important biological function of hydrogen sulfide, and sulfhydrated proteins are introduced. Additionally, we discuss the main methods of detecting sulfhydration of proteins.