Hydrogen sulfide-releasing peptide hydrogel limits the development of intimal hyperplasia in human vein segments

Endothelium-Mimicking Bilayer Vascular Grafts with Dual-Releasing of NO/H2S for Anti-Inflammation and Anticalcification

Vascular complications caused by diabetes impair the activities of endothelial nitric oxide synthase (eNOS) and cystathionine γ-lyase (CSE), resulting in decreased physiological levels of nitric oxide (NO) and hydrogen sulfide (H2S). The low bioavailability of NO and H2S hinders the endothelialization of vascular grafts. In this study, endothelium-mimicking bilayer vascular grafts were designed with spatiotemporally controlled dual releases of NO and H2S for in situ endothelialization and angiogenesis. Keratin-based H2S donor was synthesized and electrospun with poly(l-lactide-co-ε-caprolactone) (PLCL) as the outer layer of the graft to release H2S. Hyaluronic acid, one of the major glycosaminoglycans in endothelial glycocalyx, was complexed with Cu ions as the inner layer to mimic glutathione peroxidase (GPx) and maintain long-term physiological NO flux. The synergistic effects of NO and H2S of bilayer grafts selectively promoted the regeneration and migration of human umbilical vascular endothelial cells (HUVECs), while inhibiting the overproliferation of human umbilical artery smooth muscle cells (HUASMCs). Bilayer grafts could effectively prevent vascular calcification, reduce inflammation, and alleviate endothelial dysfunction. The in vivo study in a rat abdominal aorta replacement model for 1 month showed that the graft had a good patency rate and had potential for vascular remodeling in situ.

Bilayer vascular grafts with on-demand NO and H2S release capabilities

Nitric oxide (NO) and hydrogen sulfide (H2S) gasotransmitters exhibit potential therapeutic effects in the cardiovascular system. Herein, biomimicking multilayer structures of biological blood vessels, bilayer small-diameter vascular grafts (SDVGs) with on-demand NO and H2S release capabilities, were designed and fabricated. The keratin-based H2S donor (KTC) with good biocompatibility and high stability was first synthesized and then electrospun with poly (l-lactide-co-caprolactone) (PLCL) to be used as the outer layer of grafts. The electrospun poly (ε-caprolactone) (PCL) mats were aminolyzed and further chelated with copper (II) ions to construct glutathione peroxidase (GPx)-like structural surfaces for the catalytic generation of NO, which acted as the inner layer of grafts. The on-demand release of NO and H2S selectively and synergistically promoted the proliferation and migration of human umbilical vein endothelial cells (HUVECs) while inhibiting the proliferation and migration of human umbilical artery smooth muscle cells (HUASMCs). Dual releases of NO and H2S gasotransmitters could enhance their respective production, resulting in enhanced promotion of HUVECs and inhibition of HUASMCs owing to their combined actions. In addition, the bilayer grafts were conducive to forming endothelial cell layers under flow shear stress. In rat abdominal aorta replacement models, the grafts remained patency for 6 months. These grafts were capable of facilitating rapid endothelialization and alleviating neointimal hyperplasia without obvious injury, inflammation, or thrombosis. More importantly, the grafts were expected to avoid calcification with the degradation of the grafts. Taken together, these bilayer grafts will be greatly promising candidates for SDVGs with rapid endothelialization and anti-calcification properties.

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

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

Clinical Potential of Hydrogen Sulfide in Peripheral Arterial Disease

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

Cystathionine-γ-lyase overexpression modulates oxidized nicotinamide adenine dinucleotide biosynthesis and enhances neovascularization

Objective

Hydrogen sulfide is a proangiogenic gas produced primarily by the transsulfuration enzyme cystathionine-γ-lyase (CGL). CGL-dependent hydrogen sulfide production is required for neovascularization in models of peripheral arterial disease. However, the benefits of increasing endogenous CGL and its mechanism of action have not yet been elucidated.

Methods

Male whole body CGL-overexpressing transgenic (CGLTg) mice and wild-type (WT) littermates (C57BL/6J) were subjected to the hindlimb ischemia model (age, 10-12 weeks). Functional recovery was assessed via the treadmill exercise endurance test. Leg perfusion was measured by laser Doppler imaging and vascular endothelial-cadherin immunostaining. To examine the angiogenic potential, aortic ring sprouting assay and postnatal mouse retinal vasculature development studies were performed. Finally, comparative metabolomics analysis, oxidized/reduced nicotinamide adenine dinucleotide (NAD+/NADH) analysis, and quantitative real-time polymerase chain reaction were performed on CGLWT and CGLTg gastrocnemius muscle.

Results

The restoration of blood flow occurred more rapidly in CGLTg mice. Compared with the CGLWT mice, the median ± standard deviation running distance and time were increased for the CGLTg mice after femoral artery ligation (159 ± 53 m vs 291 ± 74 m [P < .005] and 17 ± 4 minutes vs 27 ± 5 minutes [P < .05], respectively). Consistently, in the CGLTg ischemic gastrocnemius muscle, the capillary density was increased fourfold (0.05 ± 0.02 vs 0.20 ± 0.12; P < .005). Ex vivo, the endothelial cell (EC) sprouting length was increased in aorta isolated from CGLTg mice, especially when cultured in VEGFA (vascular endothelial growth factor A)-only media (63 ± 2 pixels vs 146 ± 52 pixels; P < .05). Metabolomics analysis demonstrated a higher level of niacinamide, a precursor of NAD+/NADH in the muscle of CGLTg mice (61.4 × 106 ± 5.9 × 106 vs 72.4 ± 7.7 × 106 area under the curve; P < .05). Similarly, the NAD+ salvage pathway gene expression was increased in CGLTg gastrocnemius muscle. Finally, CGL overexpression or supplementation with the NAD+ precursor nicotinamide mononucleotide improved EC migration in vitro (wound closure: control, 35% ± 9%; CGL, 55% ± 11%; nicotinamide mononucleotide, 42% ± 13%; P < .05).

Conclusions

Our results have demonstrated that CGL overexpression improves the neovascularization of skeletal muscle on hindlimb ischemia. These effects correlated with changes in the NAD pathway, which improved EC migration.

Vascular smooth muscle cells in intimal hyperplasia, an update

Arterial occlusive disease is the leading cause of death in Western countries. Core contemporary therapies for this disease include angioplasties, stents, endarterectomies and bypass surgery. However, these treatments suffer from high failure rates due to re-occlusive vascular wall adaptations and restenosis. Restenosis following vascular surgery is largely due to intimal hyperplasia. Intimal hyperplasia develops in response to vessel injury, leading to inflammation, vascular smooth muscle cells dedifferentiation, migration, proliferation and secretion of extra-cellular matrix into the vessel's innermost layer or intima. In this review, we describe the current state of knowledge on the origin and mechanisms underlying the dysregulated proliferation of vascular smooth muscle cells in intimal hyperplasia, and we present the new avenues of research targeting VSMC phenotype and proliferation.

Intelligent polymeric hydrogen sulfide delivery systems for therapeutic applications

Hydrogen sulfide (H₂S) plays an important role in regulating various pathological processes such as protecting mammalian cell from harmful injuries, promoting tissue regeneration, and regulating the process of various diseases caused by physiological disorders. Studies have revealed that the physiological effects of H₂S are highly associated with its concentrations. At relatively low concentration, H₂S shows beneficial functions. However, long-time and high-dose donation of H₂S would inhibit regular biological process, resulting in cell dysfunction and apoptosis. To regulate the dosage of H₂S delivery for precision medicine, H₂S delivery systems with intelligent characteristics were developed and a variety of biocompatibility polymers have been utilized to establish intelligent polymeric H₂S delivery systems, with the abilities to specifically target the lesions, smartly respond to pathological microenvironments, as well as real-timely monitor H₂S delivery and lesion conditions by incorporating imaging-capable moieties. In this review, we focus on the design, preparation, and therapeutic applications of intelligent polymeric H₂S delivery systems in cardiovascular therapy, inflammatory therapy, tissue regenerative therapy, cancer therapy and bacteria-associated therapy. Strategies for precise H₂S therapies especially imaging-guided H₂S theranostics are highlighted. Since H₂S donors with stimuli-responsive characters are vital components for establishing intelligent H₂S delivery systems, the development of H₂S donors is also briefly introduced.

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H₂S is an endogenous gasotransmitter that plays important role in regulating various physiological and pathological pathways.

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Controlled H₂S delivery is vital since the therapeutic effects of H₂S are highly associated with its concentrations.

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Intelligent polymeric H₂S delivery systems possess specific targeting, stimuli responsive and imaging guided capabilities, representing a strategic option for next generation of therapies.

Recent development of hydrogen sulfide-releasing biomaterials as novel therapies: a narrative review

Hydrogen sulfide (H₂S) has been reported as an endogenous gasotransmitter that contributes to the modulation of a myriad of biological signalling pathways, which includes maintaining homeostasis in living organisms at physiological concentrations, controlling protein sulfhydration and persulfidation for signalling processes, mediating neurodegeneration, and regulating inflammation and innate immunity, etc. As a result, researchers are actively exploring effective approaches to evaluate the properties and the distribution of H₂S in vivo. Furthermore, the regulation of the physiological conditions of H₂S in vivo introduces the opportunity to further study the molecular mechanisms by which H₂S regulates cellular functions. In recent years, many H₂S-releasing compounds and biomaterials that can deliver H₂S to various body systems have been developed to provide sustained and stable H₂S delivery. Additionally, various designs of these H₂S-releasing biomaterials have been proposed to aid in the normal conduction of physiological processes, such as cardioprotection and wound healing, by modulating different signalling pathways and cell functionalities. Using biomaterials as a platform to control the delivery of H₂S introduces the opportunity to fine tune the physiological concentration of H₂S in vivo, a key to many therapeutic applications. In this review, we highlight recent research works concerning the development and application of H₂S-releasing biomaterials with a special emphasis to different release triggering conditions in in vivo studies. We believe that the further exploration of the molecular mechanisms underlying H₂S donors and their function when incorporated with various biomaterials will potentially help us understand the pathophysiological mechanisms of different diseases and assist the development of H₂S-based therapies.

On-demand therapeutic delivery of hydrogen sulfide aided by biomolecules

Hydrogen sulfide (H₂S), known as the third gasotransmitter, exerts various physiological functions including cardiac protection, angiogenesis, anti-inflammatory, and anti-cancer capability. Given its promising therapeutic potential as well as severe perniciousness if improper use, the sustained and tunable H₂S delivery systems are highly required for H₂S-based gas therapy with enhanced bioactivity and reduced side effects. To this end, a series of stimuli-responsive compounds capable of releasing H₂S (termed H₂S donors) have been designed over the past two decades to mimic the endogenous generation of H₂S and elucidate the biological functions. Further to improve the stability of H₂S donors and achieve the targeted delivery, various delivery systems have been constructed. In this review, we focus on the recent advances of an emerging subset, biomolecular-based H₂S delivery systems, which combine H₂S donors with biomolecular vectors including polysaccharide, peptide, and protein. We demonstrated their basic structures, building strategies, and therapeutic applications respectively to unfold their inherent merits endued by biomolecules including biocompatibility, biodegradability as well as expansibility. The varied development potentials of biomolecular-based H₂S delivery systems based on their specific properties are also discussed. At the end, brief future outlooks and upcoming challenges are presented as well.

The Role of Hydrogen Sulfide in Plaque Stability

Atherosclerosis is the greatest contributor to cardiovascular events and is involved in the majority of deaths worldwide. Plaque rapture or erosion precipitates life-threatening thrombi, resulting in the obstruction blood flow to the heart (acute coronary syndrome), brain (ischemic stroke) or low extremities (peripheral vascular diseases). Among these events, major causation dues to the plaque rupture. Although the initiation, procession, and precise time of controlling plaque rupture are unclear, foam cell formation and apoptosis, cell death, extracellular matrix components, protease expression and activity, local inflammation, intraplaque hemorrhage, and calcification contribute to the plaque instability. These alterations tightly associate with the function regulation of intraplaque various cell populations. Hydrogen sulfide (H₂S) is gasotransmitter derived from methionine metabolism and exerts a protective role in the genesis of atherosclerosis. Recent progress also showed H₂S mediated the plaque stability. In this review, we discuss the progress of endogenous H₂S modulation on functions of vascular smooth muscle cells, monocytes/macrophages, and T cells, and the molecular mechanism in plaque stability.

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

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

Pharmacological prevention of intimal hyperplasia: A state-of-the-art review

Intimal hyperplasia (IH) occurs in a considerable number of cases of blood vessel reconstruction by stenting or balloon angioplasty, venous bypass grafting, and arteriovenous dialysis accesses. It is triggered by endothelial injury during the vascular intervention and leads to vessel restenosis with life-threatening consequences for patients. To date, the drugs used for IH prevention in clinics-paclitaxel and rapalog drugs-have been focusing primarily on the vascular smooth muscle cell (VSMC) proliferation pathway of IH development. Limitations, such as endothelial toxicity and inappropriate drug administration timing, have spurred the search for new and efficient pharmacological approaches to control IH. In this state-of-the-art review, we present the pathways of IH development, focusing on the key events and actors involved in IH. Subsequently, we discuss different drugs and drug combinations interfering with these pathways based on their effect on peripheral circulation IH models in animal studies, or on clinical reports. The reports were obtained through an extensive search of peer-reviewed publications in Pubmed, Embase, and Google Scholar, with search equations composed based on five concepts around IH and their various combinations. To improve vascular intervention outcomes, rethinking of conventional therapeutic approaches to IH prevention is needed. Exploring local application of drugs and drug combinations acting on different pathophysiological pathways of IH development has the potential to provide effective and safe restenosis prevention.

SM22α-lineage niche cells regulate intramembranous bone regeneration via PDGFRβ-triggered hydrogen sulfide production

Bone stromal cells are critical for bone homeostasis and regeneration. Growing evidence suggests that non-stem bone niche cells support bone homeostasis and regeneration via paracrine mechanisms, which remain to be elucidated. Here, we show that physiologically quiescent SM22α-lineage stromal cells expand after bone injury to regulate diverse processes of intramembranous bone regeneration. The majority of SM22α-lineage cells neither act as stem cells in vivo nor show their expression patterns. Dysfunction of SM22α-lineage niche cells induced by loss of platelet-derived growth factor receptor β (PDGFRβ) impairs bone repair. We further show that PDGFRβ-triggered hydrogen sulfide (H₂S) generation in SM22α-lineage niche cells facilitates osteogenesis and angiogenesis and suppresses overactive osteoclastogenesis. Collectively, these data demonstrate that non-stem SM22α-lineage niche cells support the niche for bone regeneration with a PDGFRβ/H₂S-dependent regulatory mechanism. Our findings provide further insight into non-stem bone stromal niche cell populations and niche-regulation strategy for bone repair.

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

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

Clinical Use of Hydrogen Sulfide to Protect Against Intimal Hyperplasia

Arterial occlusive disease is the narrowing of the arteries via atherosclerotic plaque buildup. The major risk factors for arterial occlusive disease are age, high levels of cholesterol and triglycerides, diabetes, high blood pressure, and smoking. Arterial occlusive disease is the leading cause of death in Western countries. Patients who suffer from arterial occlusive disease develop peripheral arterial disease (PAD) when the narrowing affects limbs, stroke when the narrowing affects carotid arteries, and heart disease when the narrowing affects coronary arteries. When lifestyle interventions (exercise, diet…) fail, the only solution remains surgical endovascular and open revascularization. Unfortunately, these surgeries still suffer from high failure rates due to re-occlusive vascular wall adaptations, which is largely due to intimal hyperplasia (IH). IH develops in response to vessel injury, leading to inflammation, vascular smooth muscle cells dedifferentiation, migration, proliferation and secretion of extra-cellular matrix into the vessel’s innermost layer or intima. Re-occlusive IH lesions result in costly and complex recurrent end-organ ischemia, and often lead to loss of limb, brain function, or life. Despite decades of IH research, limited therapies are currently available. Hydrogen sulfide (H₂S) is an endogenous gasotransmitter derived from cysteine metabolism. Although environmental exposure to exogenous high H₂S is toxic, endogenous H₂S has important vasorelaxant, cytoprotective and anti-inflammatory properties. Its vasculo-protective properties have attracted a remarkable amount of attention, especially its ability to inhibit IH. This review summarizes IH pathophysiology and treatment, and provides an overview of the potential clinical role of H₂S to prevent IH and restenosis.

Sodium thiosulfate acts as a hydrogen sulfide mimetic to prevent intimal hyperplasia via inhibition of tubulin polymerisation

Background

Intimal hyperplasia (IH) remains a major limitation in the long-term success of any type of revascularisation. IH is due to vascular smooth muscle cell (VSMC) dedifferentiation, proliferation and migration. The gasotransmitter Hydrogen Sulfide (H₂S), mainly produced in blood vessels by the enzyme cystathionine- γ-lyase (CSE), inhibits IH in pre-clinical models. However, there is currently no H₂S donor available to treat patients. Here we used sodium thiosulfate (STS), a clinically-approved source of sulfur, to limit IH.

Methods

Low density lipoprotein receptor deleted (LDLR^−/−), WT or Cse-deleted (Cse^−/−) male mice randomly treated with 4 g/L STS in the water bottle were submitted to focal carotid artery stenosis to induce IH. Human vein segments were maintained in culture for 7 days to induce IH. Further in vitro studies were conducted in primary human vascular smooth muscle cells (VSMCs).

Findings

STS inhibited IH in WT mice, as well as in LDLR^−/− and Cse^−/− mice, and in human vein segments. STS inhibited cell proliferation in the carotid artery wall and in human vein segments. STS increased polysulfides in vivo and protein persulfidation in vitro, which correlated with microtubule depolymerisation, cell cycle arrest and reduced VSMC migration and proliferation.

Interpretation

STS, a drug used for the treatment of cyanide poisoning and calciphylaxis, protects against IH in a mouse model of arterial restenosis and in human vein segments. STS acts as an H₂S donor to limit VSMC migration and proliferation via microtubule depolymerisation.

Funding

This work was supported by the Swiss National Science Foundation (grant FN-310030_176158 to FA and SD and PZ00P3-185927 to AL); the Novartis Foundation to FA; and the Union des Sociétés Suisses des Maladies Vasculaires to SD, and the Fondation pour la recherche en chirurgie vasculaire et thoracique.

Hydrogen Sulfide Releasing Hydrogel for Alleviating Cardiac Inflammation and Protecting Against Myocardial Ischemia-Reperfusion Injury

Myocardial infarction is one of the leading causes of death worldwide. Thus, protection against myocardial ischemia-reperfusion injury is particularly important to improve the prognosis of myocardial infarction. Recently, hydrogen sulfide...

Recent strategies for improving hemocompatibility and endothelialization of cardiovascular devices and inhibition of intimal hyperplasia

Cardiovascular diseases have become one of the leading causes of mortality worldwide. Stents and artificial grafts have been used to treat cardiovascular diseases. Thrombosis and restenosis seriously impact clinical outcome...

Hydrogen Sulphide Release via the Angiotensin Converting Enzyme Inhibitor Zofenopril Prevents Intimal Hyperplasia in Human Vein Segments and in a Mouse Model of Carotid Artery Stenosis

OBJECTIVE

Hypertension is a major risk factor for intimal hyperplasia (IH) and re-stenosis following vascular and endovascular interventions. Preclinical studies suggest that hydrogen sulphide (H₂S), an endogenous gasotransmitter, limits re-stenosis. While there is no clinically available pure H₂S releasing compound, the sulfhydryl containing angiotensin converting enzyme inhibitor zofenopril is a source of H₂S. Here, it was hypothesised that zofenopril, due to H₂S release, would be superior to other non-sulfhydryl containing angiotensin converting enzyme inhibitors (ACEi) in reducing intimal hyperplasia.

METHODS

Spontaneously hypertensive male Cx40 deleted mice (Cx40^-/-) or wild type (WT) littermates were randomly treated with enalapril 20 mg or zofenopril 30 mg. Discarded human vein segments and primary human smooth muscle cells (SMCs) were treated with the active compound enalaprilat or zofenoprilat. IH was evaluated in mice 28 days after focal carotid artery stenosis surgery and in human vein segments cultured for seven days ex vivo. Human primary smooth muscle cell (SMC) proliferation and migration were studied in vitro.

RESULTS

Compared with control animals (intima/media thickness 2.3 ± 0.33 μm), enalapril reduced IH in Cx40^-/- hypertensive mice by 30% (1.7 ± 0.35 μm; p = .037), while zofenopril abrogated IH (0.4 ± 0.16 μm; p < .002 vs. control and p > .99 vs. sham operated Cx40^-/- mice). In WT normotensive mice, enalapril had no effect (0.9665 ± 0.2 μm in control vs. 1.140 ± 0.27 μm; p > .99), while zofenopril also abrogated IH (0.1623 ± 0.07 μm; p < .008 vs. control and p > .99 vs. sham operated WT mice). Zofenoprilat, but not enalaprilat, also prevented IH in human vein segments ex vivo. The effect of zofenopril on carotid and SMCs correlated with reduced SMC proliferation and migration. Zofenoprilat inhibited the mitogen activated protein kinase and mammalian target of rapamycin pathways in SMCs and human vein segments.

CONCLUSION

Zofenopril provides extra beneficial effects compared with non-sulfhydryl ACEi in reducing SMC proliferation and re-stenosis, even in normotensive animals. These findings may hold broad clinical implications for patients suffering from vascular occlusive diseases and hypertension.

Engineering macromolecular nanocarriers for local delivery of gaseous signaling molecules

In addition to being notorious air pollutants, nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H₂S) have also been known as endogenous gaseous signaling molecules (GSMs). These GSMs play critical roles in maintaining the homeostasis of living organisms. Importantly, the occurrence and development of many diseases such as inflammation and cancer are highly associated with the concentration changes of GSMs. As such, GSMs could also be used as new therapeutic agents, showing great potential in the treatment of many formidable diseases. Although clinically it is possible to directly inhale GSMs, the precise control of the dose and concentration for local delivery of GSMs remains a substantial challenge. The development of gaseous signaling molecule-releasing molecules provides a great tool for the safe and convenient delivery of GSMs. In this review article, we primarily focus on the recent development of macromolecular nanocarriers for the local delivery of various GSMs. Learning from the chemistry of small molecule-based donors, the integration of these gaseous signaling molecule-releasing molecules into polymeric matrices through physical encapsulation, post-modification, or direct polymerization approach renders it possible to fabricate numerous macromolecular nanocarriers with optimized pharmacokinetics and pharmacodynamics, revealing improved therapeutic performance than the small molecule analogs. The development of GSMs represents a new means for many disease treatments with unique therapeutic outcomes.

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.

Mechanisms underlying the vasorelaxant effect of hydrogen sulfide on human saphenous vein

Hydrogen sulfide (H₂ S) represents the third and the youngest member of the gaseous transmitters family. The dominant effect of H₂ S on isolated vessels is vasodilation. As the mechanism of H₂ S-induced relaxation in human vessels remains unclear, the present study aimed to investigate the effects of H₂ S donor, sodium hydrosulfide (NaHS), on isolated human saphenous vein (HSV) and to determine the mechanism of action. Our results showed that NaHS (1 µM-3 mM) induced a concentration-dependent relaxation of endothelium-intact HSV rings pre-contracted by phenylephrine. Pre-treatment with L-NAME, ODQ and KT5823 significantly inhibited NaHS-induced relaxation, while indomethacin induced partial inhibition. Among K⁺ channel blockers, the combination of apamin and TRAM-34 significantly affected the relaxation produced by NaHS, while iberiotoxin and glibenclamide only reduced maximal relaxation of HSV. NaHS partially relaxed endothelium-intact rings pre-contracted by high K⁺ , as well as phenylephrine-contracted rings in the presence of nifedipine. Additionally, the incubation of HSV rings with NaHS increased NO production. These results demonstrate that NaHS produces the concentration- and endothelium-dependent relaxation of isolated HSV. Vasorelaxation to NaHS probably involves activation of NO/cGMP/PKG pathway and partially prostacyclin. In addition, different K⁺ channels subtypes, especially SK_Ca and IK_Ca , as well as BK_Ca and K_ATP channels in high concentrations of NaHS, probably participate in the NaHS-induced vasorelaxation.

Supramolecular Biopolymers for Tissue Engineering

Supramolecular biopolymers (SBPs) are those polymeric units derived from macromolecules that can assemble with each other by noncovalent interactions. Macromolecular structures are commonly found in living systems such as proteins, DNA/RNA, and polysaccharides. Bioorganic chemistry allows the generation of sequence-specific supramolecular units like SBPs that can be tailored for novel applications in tissue engineering (TE). SBPs hold advantages over other conventional polymers previously used for TE; these materials can be easily functionalized; they are self-healing, biodegradable, stimuli-responsive, and nonimmunogenic. These characteristics are vital for the further development of current trends in TE, such as the use of pluripotent cells for organoid generation, cell-free scaffolds for tissue regeneration, patient-derived organ models, and controlled delivery systems of small molecules. In this review, we will analyse the 3 subtypes of SBPs: peptide-, nucleic acid-, and oligosaccharide-derived. Then, we will discuss the role that SBPs will be playing in TE as dynamic scaffolds, therapeutic scaffolds, and bioinks. Finally, we will describe possible outlooks of SBPs for TE.

Periprocedural Hydrogen Sulfide Therapy Improves Vascular Remodeling and Attenuates Vein Graft Disease

Background Failure rates after revascularization surgery remain high, both in vein grafts (VG) and arterial interventions. One promising approach to improve outcomes is endogenous upregulation of the gaseous transmitter-molecule hydrogen sulfide, via short-term dietary restriction. However, strict patient compliance stands as a potential translational barrier in the vascular surgery patient population. Here we present a new therapeutic approach, via a locally applicable gel containing the hydrogen sulfide releasing prodrug (GYY), to both mitigate graft failure and improve arterial remodeling. Methods and Results All experiments were performed on C57BL/6 (male, 12 weeks old) mice. VG surgery was performed by grafting a donor-mouse cava vein into the right common carotid artery of a recipient via an end-to-end anastomosis. In separate experiments arterial intimal hyperplasia was assayed via a right common carotid artery focal stenosis model. All mice were harvested at postoperative day 28 and artery/graft was processed for histology. Efficacy of hydrogen sulfide was first tested via GYY supplementation of drinking water either 1 week before VG surgery (pre-GYY) or starting immediately postoperatively (post-GYY). Pre-GYY mice had a 36.5% decrease in intimal/media+adventitia area ratio compared with controls. GYY in a 40% Pluronic gel (or vehicle) locally applied to the graft/artery had decreased intimal/media area ratios (right common carotid artery) and improved vessel diameters. GYY-geltreated VG had larger diameters at both postoperative days 14 and 28, and a 56.7% reduction in intimal/media+adventitia area ratios. Intimal vascular smooth muscle cell migration was decreased 30.6% after GYY gel treatment, which was reproduced in vitro. Conclusions Local gel-based treatment with the hydrogen sulfide-donor GYY stands as a translatable therapy to improve VG durability and arterial remodeling after injury.

A combined experimental and computational approach reveals how aromatic peptide amphiphiles self-assemble to form ion-conducting nanohelices

Reported here is a combined experimental-computational strategy to determine structure-property-function relationships in persistent nanohelices formed by a set of aromatic peptide amphiphile (APA) tetramers with the general structure K S XEK S , where KS= S-aroylthiooxime modified lysine, X = glutamic acid or citrulline, and E = glutamic acid. In low phosphate buffer concentrations, the APAs self-assembled into flat nanoribbons, but in high phosphate buffer concentrations they formed nanohelices with regular twisting pitches ranging from 9-31 nm. Coarse-grained molecular dynamics simulations mimicking low and high salt concentrations matched experimental observations, and analysis of simulations revealed that increasing strength of hydrophobic interactions under high salt conditions compared with low salt conditions drove intramolecular collapse of the APAs, leading to nanohelix formation. Analysis of the radial distribution functions in the final self-assembled structures led to several insights. For example, comparing distances between water beads and beads representing hydrolysable KS units in the APAs indicated that the KS units in the nanohelices should undergo hydrolysis faster than those in the nanoribbons; experimental results verified this hypothesis. Simulation results also suggested that these nanohelices might display high ionic conductivity due to closer packing of carboxylate beads in the nanohelices than in the nanoribbons. Experimental results showed no conductivity increase over baseline buffer values for unassembled APAs, a slight increase (0.4 × 102 μS/cm) for self-assembled APAs under low salt conditions in their nanoribbon form, and a dramatic increase (8.6 × 102 μS/cm) under high salt conditions in their nanohelix form. Remarkably, under the same salt conditions, these self-assembled nanohelices conducted ions 5-10-fold more efficiently than several charged polymers, including alginate and DNA. These results highlight how experiments and simulations can be combined to provide insight into how molecular design affects self-assembly pathways; additionally, this work highlights how this approach can lead to discovery of unexpected properties of self-assembled nanostructures.

Alleviating Cellular Oxidative Stress through Treatment with Superoxide-Triggered Persulfide Prodrugs

Overproduction of superoxide anion (O2.- ), the primary cellular reactive oxygen species (ROS), is implicated in various human diseases. To reduce cellular oxidative stress caused by overproduction of superoxide, we developed a compound that reacts with O2.- to release a persulfide (RSSH), a type of reactive sulfur species related to the gasotransmitter hydrogen sulfide (H2 S). Termed SOPD-NAC, this persulfide donor reacts specifically with O2.- , decomposing to generate N-acetyl cysteine (NAC) persulfide. To enhance persulfide delivery to cells, we conjugated the SOPD motif to a short, self-assembling peptide (Bz-CFFE-NH2 ) to make a superoxide-responsive, persulfide-donating peptide (SOPD-Pep). Both SOPD-NAC and SOPD-Pep delivered persulfides/H2 S to H9C2 cardiomyocytes and lowered ROS levels as confirmed by quantitative in vitro fluorescence imaging studies. Additional in vitro studies on RAW 264.7 macrophages showed that SOPD-Pep mitigated toxicity induced by phorbol 12-myristate 13-acetate (PMA) more effectively than SOPD-NAC and several control compounds, including common H2 S donors.

Metabolism of vascular smooth muscle cells in vascular diseases

Vascular smooth muscle cells (VSMCs) are the fundamental component of the medial layer of arteries and are essential for arterial physiology and pathology. It is becoming increasingly clear that VSMCs can alter their metabolism to fulfill the bioenergetic and biosynthetic requirements. During vascular injury, VSMCs switch from a quiescent "contractile" phenotype to a highly migratory and proliferative "synthetic" phenotype. Recent studies have found that the phenotype switching of VSMCs is driven by a metabolic switch. Metabolic pathways, including aerobic glycolysis, fatty acid oxidation, and amino acid metabolism, have distinct, indispensable roles in normal and dysfunctional vasculature. VSMCs metabolism is also related to the metabolism of endothelial cells. In the present review, we present a brief overview of VSMCs metabolism and how it regulates the progression of several vascular diseases, including atherosclerosis, systemic hypertension, diabetes, pulmonary hypertension, vascular calcification, and aneurysms, and the effect of the risk factors for vascular disease (aging, cigarette smoking, and excessive alcohol drinking) on VSMC metabolism to clarify the role of VSMCs metabolism in the key pathological process.

The evolving landscape for cellular nitric oxide and hydrogen sulfide delivery systems: A new era of customized medications

Nitric oxide (NO) and hydrogen sulfide (H2S) are industrial toxins or pollutants; however, both are produced endogenously and have important biological roles in most mammalian tissues. The recognition that these gasotransmitters have a role in physiological and pathophysiological processes has presented opportunities to harness their intracellular effects either through inhibition of their production; or more commonly, through inducing their levels and or delivering them by various modalities. In this review article, we have focused on an array of NO and H2S donors, their hybrids with other established classes of drugs, and the various engineered delivery platforms such a fibers, polymers, nanoparticles, hydrogels, and others. In each case, we have reviewed the rationale for their development.

Molecular-Level Control over Plasmonic Properties in Silver Nanoparticle/Self-Assembling Peptide Hybrids

The plasmonic properties of silver nanoparticle (AgNP) arrays are directly controlled by AgNP size, shape, and spatial arrangement. Reported here is a strategy to prepare chiral AgNP arrays templated by two constitutionally isomeric aromatic peptide amphiphiles (APAs), KSC'EKS and C'EKSKS (KS = S-aroylthiooxime-modified lysine, C' = citrulline, and E = glutamic acid). In phosphate buffer, both APAs initially self-assembled into nanoribbons with a similar geometry. However, in the presence of silver ions and poly(sodium 4-styrenesulfonate) (PSSS), one of the nanoribbons (KSC'EKS) turned into nanohelices with a regular twisting pitch, while the other (C'EKSKS) remained as nanoribbons. Both were used as templates for synthesis of arrays of ∼8 nm AgNPs to understand how small changes in molecular structure affect the plasmonic properties of these chiral AgNP/APA hybrids. Both hybrids showed improved colloidal stability compared to pure AgNPs, and both showed enhanced sensitivity as surface-enhanced Raman spectroscopy (SERS) substrates for model analytes, with nanohelices showing better SERS performance compared to their nanoribbon counterparts and pure AgNPs.

H2S-releasing amphiphilic dipeptide hydrogels are potent S. aureus biofilm disruptors

As a gasotransmitter, hydrogen sulfide (H2S) has been studied to treat wounds and inflammation, but its potential antimicrobial effects in this context have not been evaluated. An H2S-releasing dipeptide hydrogel (S-FE), and several non-H2S-releasing control dipeptides, (C-FE, C-GE, FBA-FE, and FE where S = S-aroylthiooxime, an H2S donor; C = control, an oxime incapable of H2S release; FBA = 4-formylbenzamide, also incapable of H2S release; and E, F, G = glutamic acid, phenylalanine, and glycine, respectively), were studied to correlate differences in their chemical structures and H2S-releasing abilities with their antimicrobial effects on Staphylococcus aureus bacteria. Dipeptides with Phe (S-FE, C-FE, and FE) self-assembled into nanoribbons in water and displayed β-sheet formation and enhanced fluorescence, while the other two dipeptides (FBA-FE and C-GE) did not form assemblies in water. In vitro experiments with Staphylococcus aureus, which is a commonly found bacterium associated with wounds, showed significant antimicrobial effects from some of the dipeptides. Dipeptide S-FE inhibited bacterial growth more effectively than any of the controls, thereby limiting biofilm formation or disrupting established biofilms. These antimicrobial H2S-releasing dipeptide hydrogels provide a promising new approach to treat wound infections.

Linker-Regulated H2S Release from Aromatic Peptide Amphiphile Hydrogels

Controlled release is an essential requirement for delivery of hydrogen sulfide (H₂S) because of its reactive nature, short half-life in biological fluids, and toxicity at high concentrations. In this context, H₂S delivery via hydrogels may be beneficial as they can deliver H₂S locally at the site of interest. Herein, we employed hydrogels based on aromatic peptide amphiphiles (APAs) with tunable mechanical properties to modulate the rates of H₂S release. The APAs contained an aromatic S-aroylthiooxime (SATO) H₂S donor attached with a linker to a short IAVEEE hexapeptide. Linker units included carbonyl, substituted O-methylenes, alkenyl, and alkyl segments with the goal of evaluating the role of linker structure on self-assembly, capacity for hydrogelation, and H₂S release rate. We studied each peptide by transmission electron microscopy, circular dichroism spectroscopy, and rheology, and we measured H₂S release rates from each gel, triggering SATO decomposition and release of H₂S by addition of cysteine (Cys). Using an H₂S-selective electrode probe as well as a turn-on fluorescent H₂S probe in the presence of H9C2 cardiomyocytes, we found that the rate of H₂S release from the hydrogels depended on the rate of Cys penetration into the nanofiber core with stiffer gels showing longer overall release.

Autonomous Temporal Control of Hydrogen Sulfide Delivery

Hydrogen sulfide (H₂S) is dichotomous in nature as it is lethal at higher concentrations, but at lower concentrations it shows a more cytoprotective nature. Due to its involvement in many physiological processes, it has recently risen to significance as a gasotransmitter alongside carbon monoxide (CO) and nitric oxide (NO). Experimentation using H₂S is thus important to generate in vitro and in vivo models for this ubiquitous gasotransmitter. However, laboratory studies involving H₂S are challenging due to the special handling conditions required to work with such a toxic gas. The use of chemical donors in the cell culture also show temporally varying release profiles, which are not optimal when trying to control H₂S in cell cultures lasting several days. Previously we applied microfluidics to deliver stable concentrations of H₂S, and in this work, we demonstrate a novel experimental method incorporating feedback control to precisely deliver H₂S that accounts for donor solution concentration decay.

Imbalance of Homocysteine and H2S: Significance, Mechanisms, and Therapeutic Promise in Vascular Injury

While the role of hyperhomocysteinemia in cardiovascular pathogenesis continuously draws attention, deficiency of hydrogen sulfide (H₂S) has been growingly implicated in cardiovascular diseases. Generation of H₂S is closely associated with the metabolism of homocysteine via key enzymes such as cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE). The level of homocysteine and H₂S is regulated by each other. Metabolic switch in the activity of CBS and CSE may occur with a resultant operating preference change of these enzymes in homocysteine and H₂S metabolism. This paper presented an overview regarding (1) linkage between the metabolism of homocysteine and H₂S, (2) mutual regulation of homocysteine and H₂S, (3) imbalance of homocysteine and H₂S in cardiovascular disorders, (4) mechanisms underlying the protective effect of H₂S against homocysteine-induced vascular injury, and (5) the current status of homocysteine-lowering and H₂S-based therapies for cardiovascular disease. The metabolic imbalance of homocysteine and H₂S renders H₂S/homocysteine ratio a potentially reliable biomarker for cardiovascular disease and development of drugs or interventions targeting the interplay between homocysteine and H₂S to maintain the endogenous balance of these two molecules may hold an even bigger promise for management of vascular disorders than targeting homocysteine or H₂S alone.

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.

Supramolecular nanostructures with tunable donor loading for controlled H2S release

Hydrogen sulfide (H₂S), an endogenously generated and regulated signaling gas, plays a vital role in a variety of (patho)physiological processes. In the past few years, different kinds of H₂S-releasing compounds (often referred to as H₂S donors) have been developed for H₂S delivery, but it is still challenging to make H₂S donors with tunable payloads in a simple and efficient manner. Herein, a series of peptide-H₂S donor conjugates (PHDCs) with tunable donor loadings are designed for controlled H₂S release. The PHDCs self-assemble into nanoribbons with different geometries in aqueous solution. Upon addition of cysteine, these nanostructures release H₂S, delivering their payload into H9C2 cells, as visualized using an H₂S-selective fluorescent probe. Beyond imaging, in vitro studies show that the ability of PHDCs to mitigate doxorubicin-induced cardiotoxicity in H9C2 cardiomyocytes depends on their nanostructures and H₂S release profiles. This strategy may enable the development of sophisticated H₂S-releasing biomaterials for drug delivery and regenerative medicine.

Hydrogels Based Drug Delivery Synthesis, Characterization and Administration

Hydrogels represent 3D polymeric networks specially designed for various medical applications. Due to their porous structure, they are able to swollen and to entrap large amounts of therapeutic agents and other molecules. In addition, their biocompatibility and biodegradability properties, together with a controlled release profile, make hydrogels a potential drug delivery system. In vivo studies have demonstrated their effectiveness as curing platforms for various diseases and affections. In addition, the results of the clinical trials are very encouraging and promising for the use of hydrogels as future target therapy strategies.