Hydrogen sulfide and nitric oxide are mutually dependent in the regulation of angiogenesis and endothelium-dependent vasorelaxation

Sirtuins family as a target in endothelial cell dysfunction: implications for vascular ageing

The vascular endothelium is a protective barrier between the bloodstream and the vasculature that may be disrupted by different factors such as the presence of diseased states. Diseases like diabetes and obesity pose a great risk toward endothelial cell inflammation and oxidative stress, leading to endothelial cell dysfunction and thereby cardiovascular complications such as atherosclerosis. Sirtuins are NAD⁺-dependent histone deacetylases that are implicated in the pathophysiology of cardiovascular diseases, and they have been identified to be important regulators of endothelial cell function. A handful of recent studies suggest that disbalance in the regulation of endothelial sirtuins, mainly sirtuin 1 (SIRT1), contributes to endothelial cell dysfunction. Herein, we summarize how SIRT1 and other sirtuins may contribute to endothelial cell function and how presence of diseased conditions may alter their expressions to cause endothelial dysfunction. Moreover, we discuss how the beneficial effects of exercise on the endothelium are dependent on SIRT1. These mainly include regulation of signaling pathways related to endothelial nitric oxide synthase phosphorylation and nitric oxide production, mitochondrial biogenesis and mitochondria-mediated apoptotic pathways, oxidative stress and inflammatory pathways. Sirtuins as modulators of the adverse conditions in the endothelium hold a promising therapeutic potential for health conditions related to endothelial dysfunction and vascular ageing.

Surgical Preparation Reduces Hydrogen Sulfide Released from Human Saphenous Veins in Coronary Artery Bypass Grafting

The long-term patency rate of saphenous vein (SV) grafts is poor compared to arterial grafts. To investigate the effects of surgical preparation (distention) of SV on hydrogen sulfide (H2S) released from the endothelium, human SV segments were harvested from 43 patients during coronary artery bypass surgery (CABG). Acetylcholine (ACh) induced relaxation that was inhibited by NG-nitro-L-arginine + indomethacin and cysteine aminotransferase inhibitor aminooxyacetic acid in the normal SV. In contrast, ACh did not evoke relaxation in the distended SV (DSV). The concentration of H2S quantified by methylene blue assay in DSV was significantly lower than that in control. Transmission electron microscope and immunohistochemistry studies showed that the preparation destroyed the endothelium, smooth muscle, organelle, and vasa vasorum. We conclude that surgical preparation injures the endothelium and smooth muscle of the SV grafts and reduces H2S release from SV. These effects may contribute to the poor long-term patency of the SV graft.

Redox Modifications of Proteins of the Mitochondrial Fusion and Fission Machinery

Mitochondrial fusion and fission tailors the mitochondrial shape to changes in cellular homeostasis. Players of this process are the mitofusins, which regulate fusion of the outer mitochondrial membrane, and the fission protein DRP1. Upon specific stimuli, DRP1 translocates to the mitochondria, where it interacts with its receptors FIS1, MFF, and MID49/51. Another fission factor of clinical relevance is GDAP1. Here, we identify and discuss cysteine residues of these proteins that are conserved in phylogenetically distant organisms and which represent potential sites of posttranslational redox modifications. We reveal that worms and flies possess only a single mitofusin, which in vertebrates diverged into MFN1 and MFN2. All mitofusins contain four conserved cysteines in addition to cysteine 684 in MFN2, a site involved in mitochondrial hyperfusion. DRP1 and FIS1 are also evolutionarily conserved but only DRP1 contains four conserved cysteine residues besides cysteine 644, a specific site of nitrosylation. MFF and MID49/51 are only present in the vertebrate lineage. GDAP1 is missing in the nematode genome and contains no conserved cysteine residues. Our analysis suggests that the function of the evolutionarily oldest proteins of the mitochondrial fusion and fission machinery, the mitofusins and DRP1 but not FIS1, might be altered by redox modifications.

An Update on Thiol Signaling: S-Nitrosothiols, Hydrogen Sulfide and a Putative Role for Thionitrous Acid

Long considered vital to antioxidant defenses, thiol chemistry has more recently been recognized to be of fundamental importance to cell signaling. S-nitrosothiols—such as S-nitrosoglutathione (GSNO)—and hydrogen sulfide (H₂S) are physiologic signaling thiols that are regulated enzymatically. Current evidence suggests that they modify target protein function primarily through post-translational modifications. GSNO is made by NOS and other metalloproteins; H₂S by metabolism of cysteine, homocysteine and cystathionine precursors. GSNO generally acts independently of NO generation and has a variety of gene regulatory, immune modulator, vascular, respiratory and neuronal effects. Some of this physiology is shared with H₂S, though the mechanisms differ. Recent evidence also suggests that molecules resulting from reactions between GSNO and H₂S, such as thionitrous acid (HSNO), could also have a role in physiology. Taken together, these data suggest important new potential targets for thiol-based drug development.

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

AIMS

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Hydrogen Sulfide as Potential Regulatory Gasotransmitter in Arthritic Diseases

The social and economic impact of chronic inflammatory diseases, such as arthritis, explains the growing interest of the research in this field. The antioxidant and anti-inflammatory properties of the endogenous gasotransmitter hydrogen sulfide (H₂S) were recently demonstrated in the context of different inflammatory diseases. In particular, H₂S is able to suppress the production of pro-inflammatory mediations by lymphocytes and innate immunity cells. Considering these biological effects of H₂S, a potential role in the treatment of inflammatory arthritis, such as rheumatoid arthritis (RA), can be postulated. However, despite the growing interest in H₂S, more evidence is needed to understand the pathophysiology and the potential of H₂S as a therapeutic agent. Within this review, we provide an overview on H₂S biological effects, on its role in immune-mediated inflammatory diseases, on H₂S releasing drugs, and on systems of tissue repair and regeneration that are currently under investigation for potential therapeutic applications in arthritic diseases.

Cardiovascular phenotype of mice lacking 3-mercaptopyruvate sulfurtransferase

RATIONALE

Hydrogen sulfide (H₂S) is a physiological mediator that regulates cardiovascular homeostasis. Three major enzymes contribute to the generation of endogenously produced H₂S, namely cystathionine γ-lyase (CSE), cystathionine β-synthase (CBS) and 3-mercaptopyruvate sulfurtransferase (3-MST). Although the biological roles of CSE and CBS have been extensively investigated in the cardiovascular system, very little is known about that of 3-MST. In the present study we determined the importance of 3-MST in the heart and blood vessels, using a genetic model with a global 3-MST deletion.

RESULTS

3-MST is the most abundant transcript in the mouse heart, compared to CSE and CBS. 3-MST was mainly localized in smooth muscle cells and cardiomyocytes, where it was present in both the mitochondria and the cytosol. Levels of serum and cardiac H₂S species were not altered in adult young (2-3 months old) 3-MST^-/- mice compared to WT animals. No significant changes in the expression of CSE and CBS were observed. Additionally, 3-MST^-/- mice had normal left ventricular structure and function, blood pressure and vascular reactivity. Interestingly, genetic ablation of 3-MST protected mice against myocardial ischemia reperfusion injury, and abolished the protection offered by ischemic pre- and post-conditioning. 3-MST^-/- mice showed lower expression levels of thiosulfate sulfurtransferase, lower levels of cellular antioxidants and elevated basal levels of cardiac reactive oxygen species. In parallel, 3-MST^-/- mice showed no significant alterations in endothelial NO synthase or downstream targets. Finally, in a separate cohort of older 3-MST^-/- mice (18 months old), a hypertensive phenotype associated with cardiac hypertrophy and NO insufficiency was observed.

CONCLUSIONS

Overall, genetic ablation of 3-MST impacts on the mouse cardiovascular system in an age-dependent manner. Loss of 3-MST exerts a cardioprotective role in young adult mice, while with aging it predisposes them to hypertension and cardiac hypertrophy.

Signalling by hydrogen sulfide and polysulfides via protein S-sulfuration

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

From primordial gas to the medicine cabinet

LINKED ARTICLES

This article is part of a themed section on Hydrogen Sulfide in Biology & Medicine. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.4/issuetoc.

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

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

Maternal disease and gasotransmitters

The three known gasotransmitters, nitric oxide, carbon monoxide, and hydrogen sulfide are involved in key processes throughout pregnancy. Gasotransmitters are known to impact on smooth muscle tone, regulation of immune responses, and oxidative state of cells and their component molecules. Failure of the systems that tightly regulate gasotransmitter production and downstream effects are thought to contribute to common maternal diseases such as preeclampsia and preterm birth. Normal pregnancy-related changes in uterine blood flow depend heavily on gasotransmitter signaling. In preeclampsia, endothelial dysfunction is a major contributor to aberrant gasotransmitter signaling, resulting in hypertension after 20 weeks gestation. Maintenance of pregnancy to term also requires gasotransmitter-mediated uterine quiescence. As the appropriate signals for parturition occur, regulation of gasotransmitter signaling must work in concert with those endocrine signals in order for appropriate labor and delivery timing. Like preeclampsia, preterm birth may have origins in abnormal gasotransmitter signaling. We review the evidence for the involvement of gasotransmitters in preeclampsia and preterm birth, as well as mechanistic and molecular signaling targets.

Rapid and sensitive detection of nitric oxide by a BODIPY-based fluorescent probe in live cells: glutathione effects

Glutathione effects on the sensing reaction toward nitric oxide in live cells.

Molecular isomerization triggered by H2S to an NIR accessible first direct visualization of Ca2+-dependent production in living HeLa cells

Few studies determined the role of intracellular labile Ca²⁺ in H₂S homeostasis. Undoubtedly, fluorescent probes are powerful tools for exploring the question because of their unique advantages: non-destruction, visualization, and multi-levels imaging. Herein, a near-infrared (λ_em = 687 nm) and methylene blue chromophore-based fluorescent probe (MB1) for H₂S was rationally developed. Based on its high sensitivity and selectivity, MB1 was employed to image the concentration change of H₂S, upon stimulating it with ionomycin (a specific calcium ionophore). We found that the intracellular labile Ca²⁺ acted as a promotor for H₂S production in living cells. Furthermore, cystathionine γ-lyase (CSE) might have functioned as a positive mediator of Ca²⁺-dependent H₂S production. These direct and visible links for H₂S/Ca²⁺ will help us to understand the complex signaling in a better way.

Vasorelaxation elicited by endogenous and exogenous hydrogen sulfide in mouse mesenteric arteries

H₂S causes vasorelaxation however there is considerable heterogeneity in the reported pharmacological mechanism of this effect. This study examines the contribution of endogenously released H₂S in the regulation of vascular tone and the mechanism of H₂S-induced vasorelaxation in small resistance-like arteries. Mesenteric arteries from C57 and eNOS^-/- mice were mounted in myographs to record isometric force. Vasorelaxation responses to NaHS were examined in the presence of various inhibitors of vasorelaxation pathways. Expression and activity of the H₂S-producing enzyme, cystathionine-γ-lyase (CSE), were also examined. CSE was expressed in vascular smooth muscle and perivascular adipose cells from mouse mesenteric artery. The substrate for CSE, L-cysteine, caused a modest vasorelaxation (35%) in arteries from C57 mice and poor vasorelaxation (10%) in arteries from eNOS^-/- mice that was sensitive to the CSE inhibitor DL-propargylglycine. The fast H₂S donor, NaHS, elicited a full and biphasic vasorelaxation response in mesenteric arteries (EC₅₀ (1) 8.7 μM, EC₅₀ (2) 0.6 mM), which was significantly inhibited in eNOS^-/- vessels (P < 0.05), unaffected by endothelial removal, or blockers at any point in the NO via soluble guanylate cyclase and cGMP (NO-sGC-cGMP) vasorelaxation pathway. Vasorelaxation to NaHS was significantly inhibited by blocking K⁺ channels of the K_Ca and K_V subtypes and the Cl^-/HCO₃^- exchanger (P < 0.05). Further experiments showed that NaHS can significantly inhibit voltage-gated Ca²⁺ channel function (P < 0.05). The vasorelaxant effect of H₂S in small resistance-like arteries is complex, involving eNOS, K⁺ channels, Cl^-/HCO₃^- exchanger, and voltage-gated Ca²⁺ channels. CSE is present in the smooth muscle and periadventitial adipose tissue of these resistance-like vessels and can be activated to cause modest vasorelaxation under these in vitro conditions.

Hydrogen Sulfide: Emerging Role in Bladder, Kidney, and Prostate Malignancies

Hydrogen sulfide (H₂S) is the latest member of the gasotransmitter family and known to play essential roles in cancer pathophysiology. H₂S is produced endogenously and can be administered exogenously. Recent studies showed that H₂S in cancers has both pro- and antitumor roles. Understanding the difference in the expression and localization of tissue-specific H₂S-producing enzymes in healthy and cancer tissues allows us to develop tools for cancer diagnosis and treatment. Urological malignancies are some of the most common cancers in both men and women, and their early detection is vital since advanced cancers are recurrent, metastatic, and often resistant to treatment. This review summarizes the roles of H₂S in cancer and looks at current studies investigating H₂S activity and expression of H₂S-producing enzymes in urinary cancers. We specifically focused on urothelial carcinoma, renal cell carcinoma, and prostate cancer, as they form the majority of newly diagnosed urinary cancers. Recent studies show that besides the physiological activity of H₂S in cancer cells, there are patterns between the development and prognosis of urinary cancers and the expression of H₂S-producing enzymes and indirectly the H₂S levels. Though controversial and not completely understood, studying the expression of H₂S-producing enzymes in cancer tissue may represent an avenue for novel diagnostic and therapeutic strategies for addressing urological malignancies.

Hypoxia augments NaHS-induced ANP secretion via KATP channel, HIF-1α and PPAR-γ pathway

It has been reported that sodium hydrosulfide (NaHS) stimulated high stretch induced-atrial natriuretic peptide (ANP) secretion via ATP sensitive potassium (K_ATP) channel. K_ATP channel is activated during hypoxic condition as a compensatory mechanism. However, whether NaHS affects ANP secretion during hypoxia remains obscure. The purpose of the present study is to discover the impact of NaHS on ANP secretion during hypoxia and to unravel its signaling pathway. Isolated beating rat atria were perfused with buffer exposed to different O₂ tension (to 100% O₂, normoxia; to 20% O₂, hypoxia). The ANP secretion increased negatively correlated with O₂ tension. NaHS (50 μM) did not show any significant effect on low stretch induced-ANP secretion in normoxic condition but augmented low stretch induced-ANP secretion in hypoxic condition. The augmentation of NaHS-induced ANP secretion during hypoxia was blocked by the pretreatment with K_ATP channel blocker (glibenclamide) and was enhanced by the pretreatment with K_ATP channel activator (pinacidil). Hypoxia increased the expression of PPAR-γ protein but did not change the expression of HIF-1α protein and eNOS phosphorylation. The NaHS-induced ANP secretion during hypoxia was also blocked by the pretreatment with HIF-1α inhibitor (2-methoxy- estradiol), PPAR-γ inhibitor (GW9662) but not by NOS inhibitor (L-NAME) and endothelin receptor inhibitor (bosentan). The intravenous infusion of NaHS increased plasma ANP level in monocrotaline-treated rats but not in sham rats. These results suggest that hypoxia augmented NaHS-induced ANP secretion partly through K_ATP channel, HIF-1α, and PPAR-γ pathway.

Modulation of endothelium-derived nitric oxide production and activity by taurine and taurine-conjugated bile acids

Taurine is a semiessential amino acid found at high concentrations in mammalian plasma and cells, where it regulates cellular functions such as ion flux, controls cell volume and serves as a substrate for conjugated bile acids (BAs). Exogenous administration of both taurine and taurine-conjugated BAs have also been implicated in the modulation of cardiovascular functions. This brief review summarizes the role of taurine and taurine-conjugated BAs in vascular relaxation through the modulation of endothelium-derived nitric oxide (NO). The effects of taurine on vascular health are controversial. However, in the presence of cardiometabolic risk factors, it has been proposed that taurine can increase vascular NO levels by increasing eNOS expression, eNOS phosphorylation on Ser1177, NO bioavailability, the level of antioxidative defense, and the l-arginine/NOS inhibitor asymmetric dimethylarginine (ADMA) ratio. The taurine-conjugated BA-mediated activation of Farnesoid X receptor (FXR), G protein-coupled BA receptor (TGR5) and/or muscarinic 3 receptor (M3) was also reported to increase vascular NO production. FXR activation increases eNOS expression and may reduce ADMA formation, while TGR5 increases mobilization of Ca²⁺ and phosphorylation of eNOS and Akt in endothelial cells. Furthermore, taurine and taurine-conjugated BAs might regulate NO synthesis and activity by enhancing H₂S generation. Several studies have demonstrated the beneficial effects of both taurine and taurine-conjugated BAs in reversing the endothelial dysfunction associated with diabetes, atherosclerosis, hypertension, obesity, malnutrition, and smoking. In addition, taurine-conjugated BAs have emerged as a potential treatment for portal hypertension. Despite these favorable findings, there is a need to further explore the mechanisms and signaling pathways underlying the endothelial effects of taurine and taurine-conjugated BAs. Here, we summarize the main findings regarding the effects of taurine and taurine-conjugated BAs on the endothelial dysfunction associated with altered NO metabolism in cardiovascular diseases.

Dysregulation of cystathionine γ-lyase promotes prostate cancer progression and metastasis

Hydrogen sulfide (H2 S), an endogenous signaling gaseous molecule, is involved in various physiological activities, including vessel relaxation, regulation of cellular bioenergetics, inflammation, and angiogenesis. By using xenograft orthotopic implantation of prostate cancer PC3 cells and subsequently comparing bone metastatic with primary tumor-derived cancer cells, we find that H2 S-producing enzyme cystathionine γ-lyase (CTH) is upregulated in bone-metastatic PC3 cells. Clinical data further reveal that the expression of CTH is elevated in late-stage prostate cancer patients, and higher CTH expression correlates with poor survival from The Cancer Genome Atlas (TCGA) prostate cancer RNA-seq datasets. CTH promotes NF-κB nuclear translocation through H2 S-mediated sulfhydration on cysteine-38 of the NF-κB p65 subunit, resulting in increased IL-1β expression and H2 S-induced cell invasion. Knockdown of CTH in PC3 cells results in the suppression of tumor growth and distant metastasis, while overexpression of CTH in DU145 cells promotes primary tumor growth and lymph node metastasis in the orthotopic implanted xenograft mouse model. Together, our findings provide evidence that CTH generated H2 S promotes prostate cancer progression and metastasis through IL-1β/NF-κB signaling pathways.

Raw garlic consumption is inversely associated with prehypertension in a large-scale adult population

Previous studies have shown that allicin can lower blood pressure (BP) by reducing oxidative stress and inflammation. However, the association between habitual raw garlic intake (as allicin source) and prehypertension are unclear. The aim of this study was to investigate how raw garlic consumption is associated with prehypertension in an adult population. A cross-sectional study was conducted with 22,812 adults (mean [standard deviation] age: 39.4 [10.7] years; males, 47.7%) in Tianjin, China. Raw garlic consumption was assessed using a validated food frequency questionnaire. BP was measured at least twice by trained nurses using an automatic device. Prehypertension was defined as systolic BP of 120-139 mmHg and/or diastolic BP of 80-89 mmHg without taking antihypertensive medication. Multiple logistic regression models were used to assess the association between raw garlic consumption and prehypertension. The prevalence of prehypertension was 49.9%. After fully adjusting for potential confounders, the ORs (95% confidence intervals) of having prehypertension by increasing frequency of raw garlic consumption were 1.00 (reference) for ≤3 times/week, 0.96 (0.87, 1.06) for 4 times/week to 1 time/day, and 0.69 (0.52, 0.90) for ≥2 times/day (p for trend = 0.06). In contrast, no associations were observed between other kinds of allium vegetables consumption and prehypertension. In conclusion, our results suggested that a more frequent consumption of raw garlic was inversely associated with prehypertension. This is the first large-scale study on the association between raw garlic consumption and prehypertension in the general population.

Cystathionine-γ-lyase (CSE) deficiency increases erythropoiesis and promotes mitochondrial electron transport via the upregulation of coproporphyrinogen III oxidase and consequent stimulation of heme biosynthesis

BACKGROUND

Hydrogen sulfide (H₂S) is an endogenous gasotransmitter produced by mammalian cells. The current study investigated the potential role of H₂S in the regulation of heme biosynthesis using mice deficient in cystathionine gamma-lyase (CSE), one of the three major mammalian H₂S-producing enzymes.

METHODS

Wild-type and global CSE^-/- mice, as well as mitochondria prepared from their liver were used. In vivo, arterial and venous blood gases were measured, and survival of the mice to severe global hypoxia was monitored. Ex vivo, expression of various heme biosynthetic enzymes including coproporphyrinogen oxidase (CPOX) was measured, and mitochondrial function was evaluated using Extracellular Flux Analysis. Urine samples were collected to measure the oxidized porphyrinogen intermediates. The in vivo/ex vivo studies were complemented with mitochondrial bioenergetic studies in hepatocytes in vitro. Moreover, the potential effect of H₂S on the CPOX promoter was studied in cells expressing a CPOX promoter construct system.

RESULTS

The main findings are as follows: (1) CSE^-/- mice exhibit elevated red blood cell counts and red blood cell mean corpuscular volumes compared to wild-type mice; (2) these changes are associated with elevated plasma and liver heme levels and (3) these alterations are likely due to an induction of CPOX (the sixth enzyme involved in heme biosynthesis) in CSE^-/- mice. (4) Based on in vitro promoter data the promoter activation of CPOX is directly influenced by H₂S, the product of CSE. With respect to the potential functional relevance of these findings, (5) the increased circulating red blood cell numbers do not correspond to any detectable alterations in blood gas parameters under resting conditions, (6) nor do they affect the hypoxia tolerance of the animals in an acute severe hypoxia model. However, there may be a functional interaction between the CSE system and the CPOX system in terms of mitochondrial bioenergetics: (7) CSE^-/- hepatocytes and mitochondria isolated from them exhibit increased oxidative phosphorylation parameters, and (8) this increase is partially blunted after CPOX silencing. Although heme is essential for the biosynthesis of mitochondrial electron chain complexes, and CPOX is required for heme biosynthesis, (9) the observed functional mitochondrial alterations are not associated with detectable changes in mitochondrial electron transport chain protein expression.

CONCLUSIONS

The CSE system regulates the expression of CPOX and consequent heme synthesis. These effects in turn, do not influence global oxygen transport parameters, but may regulate mitochondrial electron transport.

Hydrogen sulfide-mediated endothelial function and the interaction with eNOS and PDE5A activity in human internal mammary arteries

OBJECTIVE

To investigate the role of hydrogen sulfide (H2S) in human internal mammary arteries (IMA) and its interaction with endothelial nitric oxide synthase (eNOS) and phosphodiesterase (PDE)5A activity.

METHODS

Human IMA segments from patients undergoing coronary artery bypass grafting (CABG) were studied by myography for acetylcholine and sodium hydrosulfide (NaHS)-induced relaxation. Locations of 3-mercaptopyruvate sulfurtransferase (3-MPST) and cysteine aminotransferase (CAT) were examined immunohistochemically. Levels of H2S, eNOS, phosphorylated-eNOSser1177, and PDE5A were measured.

RESULTS

In IMA segments from 47 patients, acetylcholine-induced relaxation (resistant to NG-nitro-L-arginine and indomethacin) was significantly attenuated by aminooxyacetic acid or L-aspartate (CAT inhibitors), iberiotoxin (large-conductance calcium-activated K+ channel blocker), TRAM-34 plus apamin (intermediate- and small-conductance Ca2+-activated K+ channel blockers) or glibenclamide (ATP-sensitive K+ channel blocker). 3-MPST and mitochondrial CAT were found in endothelial and smooth muscle cells while cytosolic CAT was located only in endothelial cells. Acetylcholine significantly increased the H2S levels. The H2S donor, NaHS, increased eNOS phosphorylation and down-regulated PDE5A.

CONCLUSIONS

Human conduit artery endothelium releases H2S under basal and stimulated conditions, involving the 3-MPST/CAT pathway, eNOS phosphorylation, PDE5A activity, and potassium channels. These findings may provide new therapeutic targets for treating vasospasm in CABG grafts and facilitate the development of new vasodilator drugs.

Cystathionine γ-Lyase Modulates Flow-Dependent Vascular Remodeling

Objective- Flow patterns differentially regulate endothelial cell phenotype, with laminar flow promoting vasodilation and disturbed flow promoting endothelial proinflammatory activation. CSE (cystathionine γ-lyase), a major source of hydrogen sulfide (H₂S) in endothelial cells, critically regulates cardiovascular function, by both promoting vasodilation and reducing endothelial activation. Therefore, we sought to investigate the role of CSE in the endothelial response to flow. Approach and Results- Wild-type C57Bl/6J and CSE knockout ( CSE^-/-) mice underwent partial carotid ligation to induce disturbed flow in the left carotid. In addition, endothelial cells isolated from wild-type and CSE ^-/- mice were exposed to either laminar or oscillatory flow, an in vitro model of disturbed flow. Interestingly, laminar flow significantly reduced CSE expression in vitro, and only disturbed flow regions show discernable CSE protein expression in vivo, correlating with enhanced H₂S production in wild-type C57BL/6J but not CSE^-/- mice. Lack of CSE limited disturbed flow-induced proinflammatory gene expression (ICAM-1[intercellular adhesion molecule 1], VCAM-1 [vascular cell adhesion molecular 1]) and monocyte infiltration and CSE^-/- endothelial cells showed reduced NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells) activation and proinflammatory gene expression in response to oscillatory flow in vitro. In addition, CSE^-/- mice showed reduced inward remodeling after partial carotid ligation. CSE^-/- mice showed elevated vascular nitrite levels (measure of nitric oxide [NO]) in the unligated carotids, suggesting an elevation in baseline NO production, and the NO scavenger 2-(4-carboxyphenyl)-4,5-dihydro-4,4,5,5-tetramethyl-1H-imidazolyl-1-oxy-3-oxide normalized the reduced inward remodeling, but not inflammation, of ligated carotids in CSE^-/- mice. Conclusions- CSE expression in disturbed flow regions critically regulates both endothelial activation and flow-dependent vascular remodeling, in part through altered NO availability.

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

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

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.

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

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

A computational study on H2S release and amide formation from thionoesters and cysteine

The recognition of the biological activity of H2S has drawn much attention to the development of biocompatible H2S release reactions. Thiol-, particularly cysteine-triggered systems which mimic the enzymatic conversion of cysteine or homocysteine to H2S have been intensively reported recently. Herein, a density functional theory (DFT) study was performed to address the reaction mechanism of H2S release and potential amide bond formation from thionoesters and cysteine to gain deeper mechanistic insights. Three possible mechanisms were considered and we found that the one starting from the nucleophilic addition of the ionized mercapto of cysteine on thionoester to generate a dithioester intermediate (Path A) is kinetically favored over the others starting from the nucleophilic addition of the amine of cysteine to generate thionoamide intermediates (Paths B and C). Dithioester then undergoes intramolecular nucleophilic addition of an amine group and the rate-limiting water-assisted proton transfer to generate a cyclic thiol intermediate, and finally affords H2S and dihydrothiazole via water-assisted elimination. The hydrolysis of thionoamide or dihydrothiazole to produce amide is highly difficult under neutral conditions but is operative under strong basic conditions, which explains the experimental observation that dihydrothiazole rather than amide is the major product. Meanwhile, the ring opening reaction of the cyclic thiol intermediate to form the more stable thionoamide is detrimental to H2S release and becomes competitive under basic conditions.

Crystal-facet-dependent denitrosylation: modulation of NO release from S-nitrosothiols by Cu2O polymorphs

Nitric oxide (NO), a gaseous small molecule generated by the nitric oxide synthase (NOS) enzymes, plays key roles in signal transduction. The thiol groups present in many proteins and small molecules undergo nitrosylation to form the corresponding S-nitrosothiols. The release of NO from S-nitrosothiols is a key strategy to maintain the NO levels in biological systems. However, the controlled release of NO from the nitrosylated compounds at physiological pH remains a challenge. In this paper, we describe the synthesis and NO releasing ability of Cu2O nanomaterials and provide the first experimental evidence that the nanocrystals having different crystal facets within the same crystal system exhibit different activities toward S-nitrosothiols. We used various imaging techniques and time-dependent spectroscopic measurements to understand the nature of catalytically active species involved in the surface reactions. The denitrosylation reactions by Cu2O can be carried out multiple times without affecting the catalytic activity.

Histone deacetylase 6 inhibitor tubastatin A attenuates angiotensin II-induced hypertension by preventing cystathionine γ-lyase protein degradation

Cystathionine γ-lyase (CSEγ) is a hydrogen sulfide (H₂S)-producing enzyme. Endothelial H₂S production can mediate vasodilatory effects, contributing to the alleviation of hypertension (high blood pressure). Recent studies have suggested a role of histone deacetylase 6 (HDAC6) in hypertension, although its underlying mechanisms are poorly understood. Here, we addressed the potential regulation of CSEγ by HDAC6 in angiotensin II (AngII)-induced hypertension and its molecular details focusing on CSEγ posttranslational modification. Treatment of mice with a selective HDAC6 inhibitor tubastatin A (TubA) alleviated high blood pressure and vasoconstriction induced by AngII. Cotreatment of the aorta and human aortic endothelial cells with TubA recovered AngII-mediated decreased H₂S levels. AngII treatment upregulated HDAC6 mRNA and protein expression, but conversely downregulated CSEγ protein. Notably, potent HDAC6 inhibitors and HDAC6 siRNA as well as a proteasomal inhibitor increased CSEγ protein levels and blocked the downregulatory effect of AngII on CSEγ. In contrast, other HDAC isoforms-specific inhibitors and siRNAs did not show such blocking effects. Transfected CSEγ protein levels were also reciprocally regulated by AngII and TubA, and were reduced by wild-type, but not by deacetylase-deficient, HDAC6. Moreover, TubA significantly increased both protein stability and K73 acetylation level of CSEγ. Consistent with these results, AngII induced CSEγ ubiquitination and degradation, which was inhibited by TubA. Our results indicate that AngII promoted HDAC6-dependent deacetylation of CSEγ at K73 residue, leading to its ubiquitin-mediated proteolysis, which underlies AngII-induced hypertension. Overall, this study suggests that upregulation of CSEγ and H₂S through HDAC6 inhibition may be considered as a valid strategy for preventing the progression of hypertension.

Structure-Function Changes of the Porcine Distal Outflow Tract in Response to Nitric Oxide

Purpose

To correlate outflow function and outflow tract vessel diameter changes induced by nitric oxide (NO).

Methods

In a porcine anterior segment perfusion model, the effects of a nitric oxide donor (100 μM DETA-NO) on outflow facility were compared with controls (n = 8 per group) with trabecular meshwork (TM) and after circumferential ab interno trabeculectomy (AIT). Outflow structures were assessed with spectral-domain optical coherence tomography (SD-OCT) before and after NO, or an NO synthase inhibitor (100 μM L-NAME) and the vasoconstrictor, endothelin-1 (100 pg/mL ET-1). Scans were processed with a custom macroscript and aligned for automated reslicing and quantification of cross-sectional outflow tract areas (CSA).

Results

The facility increased after DETA-NO (Δ of 0.189 ± 0.081 μL/min·mm Hg, P = 0.034) and AIT (Δ of 0.251 ± 0.094 μL/min·mm Hg, P = 0.009), respectively. Even after AIT, DETA-NO increased the facility by 61.5% (Δ of 0.190 ± 0.074 μL/min·mm Hg, P = 0.023) and CSA by 13.9% (P < 0.001). L-NAME + ET-1 decreased CSA by -8.6% (P < 0.001). NO increased the diameter of focal constrictions 5.0 ± 3.8-fold.

Conclusions

NO can dilate vessels of the distal outflow tract and increase outflow facility in a TM-independent fashion. There are short, focally constricting vessel sections that display large diameter changes and may have a substantial impact on outflow.

Oxidative stress and antioxidant treatment in patients with peripheral artery disease

Peripheral artery disease is an atherosclerotic disease of arterial vessels that mostly affects arteries of lower extremities. Effort induced cycles of ischemia and reperfusion lead to increased reactive oxygen species production by mitochondria. Therefore, the pathophysiology of peripheral artery disease is a consequence of metabolic myopathy, and oxidative stress is the putative major operating mechanism behind the structural and metabolic changes that occur in muscle. In this review, we discuss the evidence for oxidative damage in peripheral artery disease and discuss management strategies related to antioxidant supplementation. We also highlight the major pathways governing oxidative stress in the disease and discuss their implications in disease progression. Potential therapeutic targets and diagnostic methods related to these mechanisms are explored, with an emphasis on the Nrf2 pathway.

Saying NO to H2S: A Story of HNO, HSNO, and SSNO. Inorg Chem 2019;58:4039-4051. [PMID: 30883105 DOI: 10.1021/acs.inorgchem.8b02592]

Interactions between small inorganic molecules are fundamental to the understanding of basic reaction mechanisms and some of the initial processes of chemical evolution that preceded organic molecules and led to the origin of life. The kinetics of these processes are suitable for the fast generation of a variety of new chemical entities and the propagation of a cascade of chemical reactions, a property that is ideal for signaling purposes even in biological systems. NO and H₂S are such molecules that are nowadays recognized as biological gasotransmitters involved in the regulation of physiological functions through protein modifications such as S-nitrosothiol, disulfide, and persulfide formations. In this Viewpoint, we review the current understanding of interactions of NO (and organic and metal nitrosyl species) with H₂S, in both chemical and biochemical contexts. Through the formation of HNO, (H)SNO (and its isomers), (H)SSNO, and polysulfides, these two gasotransmitters initiate reaction networks with significant roles in cell signaling. The chemical reactivities and biological effects of these nitrogen and sulfur species are still unresolved, and, thus, a cross-talk between all of them represents a challenging interdisciplinary field that awaits exciting new findings. We tackle some of the intriguing and open questions and provide perspectives for future research directions.

Vasodilation Elicited by Isoxsuprine, Identified by High-Throughput Virtual Screening of Compound Libraries, Involves Activation of the NO/cGMP and H₂S/KATP Pathways and Blockade of α₁-Adrenoceptors and Calcium Channels

Recently, our research group demonstrated that uvaol and ursolic acid increase NO and H₂S production in aortic tissue. Molecular docking studies showed that both compounds bind with high affinity to endothelial NO synthase (eNOS) and cystathionine gamma-lyase (CSE). The aim of this study was to identify hits with high binding affinity for the triterpene binding-allosteric sites of eNOS and CSE and to evaluate their vasodilator effect. Additionally, the mechanism of action of the most potent compound was explored. A high-throughput virtual screening (HTVS) of 107,373 compounds, obtained from four ZINC database libraries, was performed employing the crystallographic structures of eNOS and CSE. Among the nine top-scoring ligands, isoxsuprine showed the most potent vasodilator effect. Pharmacological evaluation, employing the rat aorta model, indicated that the vasodilation produced by this compound involved activation of the NO/cGMP and H₂S/K_ATP signaling pathways and blockade of α₁-adrenoceptors and L-type voltage-dependent Ca²⁺ channels. Incubation of aorta homogenates in the presence of isoxsuprine caused 2-fold greater levels of H₂S, which supported our preliminary in silico data. This study provides evidence to propose that the vasodilator effect of isoxsuprine involves various mechanisms, which highlights its potential to treat a wide variety of cardiovascular diseases.

3-Mercaptopyruvate sulfurtransferase supports endothelial cell angiogenesis and bioenergetics

BACKGROUND AND PURPOSE

During angiogenesis, quiescent endothelial cells (ECs) are activated by various stimuli to form new blood vessels from pre-existing ones in physiological and pathological conditions. Many research groups have shown that hydrogen sulfide (H₂ S), the newest member of the gasotransmitter family, acts as a proangiogenic factor. To date, very little is known about the regulatory role of 3-mercaptopyruvate sulfurtransferase (3-MST), an important H₂ S-producing enzyme in ECs. The aim of our study was to explore the potential role of 3-MST in human EC bioenergetics, metabolism, and angiogenesis.

EXPERIMENTAL APPROACH

To assess in vitro angiogenic responses, we used EA.hy926 human vascular ECs subjected to shRNA-mediated 3-MST attenuation and pharmacological inhibition of proliferation, migration, and tube-like network formation. To evaluate bioenergetic parameters, cell respiration, glycolysis, glucose uptake, and mitochondrial/glycolytic ATP production were measured. Finally, global metabolomic profiling was performed to determine the level of 669 metabolic compounds.

KEY RESULTS

3-MST-attenuated ECs subjected to shRNA or pharmacological inhibition of 3-MST significantly reduced EC proliferation, migration, and tube-like network formation. 3-MST silencing also suppressed VEGF-induced EC migration. From bioenergetic and metabolic standpoints, 3-MST attenuation decreased mitochondrial respiration and mitochondrial ATP production, increased glucose uptake, and perturbed the entire EC metabolome.

CONCLUSION AND IMPLICATIONS

3-MST regulates bioenergetics and morphological angiogenic functions in human ECs. The data presented in the current report support the view that 3-MST pathway may be a potential candidate for therapeutic modulation of angiogenesis.

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.

Cavernosal hydrogen sulfide levels are associated with nitric oxide and hemeoxygenase levels in diabetic rats

Penile erection is a neuromuscular event modulated by psyche, hormones as well as neurotransmitters. This pre-clinical study aimed to assess hydrogen sulfide (H2S) relationship with nitric oxide (NO) and hemeoxygenase (HO) in the cavernous tissues of diabetic rats. Overall, 90 adult male rats were investigated (6 groups, n = 15 each). They were subdivided into the following groups; untreated rats, rats treated with H2S donor/inhibitor, induced diabetic rats, diabetic rats treated with H2S donor/inhibitor. At the 6th week, the rats were killed to assess cavernous tissue cGMP, NO, H2S, HO enzyme activity levels. The rats treated with H2S donor showed increased mean cavernous tissue cGMP, NO, H2S, and HO enzyme activity levels whereas induced diabetic rats and rats treated with H2S inhibitor showed significant decreases in these parameters compared with the untreated rats. On the other hands, diabetic rats treated with H2S donor showed elevated mean cavernous tissue cGMP, NO, H2S, and HO enzyme activity levels whereas diabetic rats treated with H2S inhibitor showed significant decreases in these parameters compared with diabetic rats. Cavernous tissue H2S levels exhibited significant positive correlations with the cavernous tissue levels cGMP, NO, and HO enzyme activity levels. From these results, it could be concluded that cavernous tissues H2S plays a role of male sexual health by affecting cavernous tissues NO and HO enzyme activity in general and in diabetics in particular.

Near-Infrared Light-Triggered Sulfur Dioxide Gas Therapy of Cancer

The exploitation of gas therapy platforms holds great promise as a "green" approach for selective cancer therapy, however, it is often associated with some challenges, such as uncontrolled or insufficient gas generation and unclear therapeutic mechanisms. In this work, a gas therapy approach based on near-infrared (NIR) light-triggered sulfur dioxide (SO₂) generation was developed, and the therapeutic mechanism as well as in vivo antitumor therapeutic efficacy was demonstrated. A SO₂ prodrug-loaded rattle-structured upconversion@silica nanoparticles (RUCSNs) was constructed to enable high loading capacity without obvious leakage and to convert NIR light into ultraviolet light so as to activate the prodrug for SO₂ generation. In addition, SO₂ prodrug-loaded RUCSNs showed high cell uptake, good biocompatibility, intracellular tracking ability, and high NIR light-triggered cytotoxicity. Furthermore, the cytotoxic SO₂ was found to induce cell apoptosis accompanied by the increase of intracellular reactive oxygen species levels and the damage of nuclear DNA. Moreover, efficient inhibition of tumor growth was achieved, associated with significantly prolonged survival of mice. Such NIR light-triggered SO₂ therapy may provide an effective strategy to stimulate further development of synergistic cancer therapy platforms.

Hydrogen Sulfide Protects Hyperhomocysteinemia-Induced Renal Damage by Modulation of Caveolin and eNOS Interaction

The accumulation of homocysteine (Hcy) during chronic kidney failure (CKD) can exert toxic effects on the glomeruli and tubulo-interstitial region. Among the potential mechanisms, the formation of highly reactive metabolite, Hcy thiolactone, is known to modify proteins by N-homocysteinylation, leading to protein degradation, stress and impaired function. Previous studies documented impaired nitric oxide production and altered caveolin expression in hyperhomocysteinemia (HHcy), leading to endothelial dysfunction. The aim of this study was to determine whether Hhcy homocysteinylates endothelial nitric oxide synthase (eNOS) and alters caveolin-1 expression to decrease nitric oxide bioavailability, causing hypertension and renal dysfunction. We also examined whether hydrogen sulfide (H₂S) could dehomocysteinylate eNOS to protect the kidney. WT and Cystathionine β-Synthase deficient (CBS+/-) mice representing HHcy were treated without or with sodium hydrogen sulfide (NaHS), a H₂S donor (30 µM), in drinking water for 8 weeks. Hhcy mice (CBS+/-) showed low levels of plasma H₂S, elevated systolic blood pressure (SBP) and renal dysfunction. H₂S treatment reduced SBP and improved renal function. Hhcy was associated with homocysteinylation of eNOS, reduced enzyme activity and upregulation of caveolin-1 expression. Further, Hhcy increased extracellular matrix (ECM) protein deposition and disruption of gap junction proteins, connexins. H₂S treatment reversed the changes above and transfection of triple genes producing H₂S (CBS, CSE and 3MST) showed reduction of vascular smooth muscle cell proliferation. We conclude that during Hhcy, homocysteinylation of eNOS and disruption of caveolin-mediated regulation leads to ECM remodeling and hypertension, and H₂S treatment attenuates renovascular damage.

Important roles of endothelial caveolin-1 in endothelium-dependent hyperpolarization and ischemic angiogenesis in mice

Although increased levels of reactive oxygen species (ROS) are involved in the pathogenesis of cardiovascular diseases, the importance of physiological ROS has also been emerging. We have previously demonstrated that endothelium-derived H₂O₂ is an endothelium-dependent hyperpolarization (EDH) factor and that loss of endothelial caveolin-1 reduces EDH/H₂O₂ in the microcirculation. Caveolin-1 (Cav-1) is a scaffolding/regulatory protein that interacts with diverse signaling pathways, including angiogenesis. However, it remains unclear whether endothelial Cav-1 plays a role in ischemic angiogenesis by modulating EDH/H₂O₂. In the present study, we thus addressed this issue in a mouse model of hindlimb ischemia using male endothelium-specific Cav-1 (eCav-1) knockout (KO) mice. In isometric tension experiments with femoral arteries from eCav-1-KO mice, reduced EDH-mediated relaxations to acetylcholine and desensitization of sodium nitroprusside-mediated endothelium-independent relaxations were noted ( n = 4~6). An ex vivo aortic ring assay also showed that the extent of microvessel sprouting was significantly reduced in eCav-1-KO mice compared with wild-type (WT) littermates ( n = 12 each). Blood flow recovery at 4 wk assessed with a laser speckle flowmeter after femoral artery ligation was significantly impaired in eCav-1-KO mice compared with WT littermates ( n = 10 each) and was associated with reduced capillary density and muscle fibrosis in the legs ( n = 6 each). Importantly, posttranslational protein modifications by reactive nitrogen species and ROS, as evaluated by thiol glutathione adducts and nitrotyrosine, respectively, were both increased in eCav-1-KO mice ( n = 6~7 each). These results indicate that endothelial Cav-1 plays an important role in EDH-mediated vasodilatation and ischemic angiogenesis through posttranslational protein modifications by nitrooxidative stress in mice in vivo. NEW & NOTEWORTHY Although increased levels of reactive oxygen species (ROS) are involved in the pathogenesis of cardiovascular diseases, the importance of physiological ROS has also been emerging. The present study provides a line of novel evidence that endothelial caveolin-1 plays important roles in endothelium-dependent hyperpolarization and ischemic angiogenesis in hindlimb ischemia in mice through posttranslational protein modifications by reactive nitrogen species and ROS in mice in vivo.

Effects of sulfane sulfur content in benzyl polysulfides on thiol-triggered H2S release and cell proliferation

Investigations into hydrogen sulfide (H2S) signaling pathways have demonstrated both the generation and importance of persulfides, which are reactive sulfur species that contain both reduced and oxidized sulfur. These observations have led researchers to suggest that oxidized sulfur species, including sulfane sulfur (S0), are responsible for many of the physiological phenomena initially attributed to H2S. A common method of introducing S0 to biological systems is the administration of organic polysulfides, such as diallyl trisulfide (DATS). However, prior reports have demonstrated that commercially-available DATS often contains a mixture of polysulfides, and furthermore a lack of structure-activity relationships for organic polysulfides has limited our overall understanding of different polysulfides and their function in biological systems. Advancing our interests in the chemical biology of reactive sulfur species including H2S and S0, we report here our investigations into the rates and quantities of H2S release from a series of synthetic, pure benzyl polysulfides, ranging from monosulfide to tetrasulfide. We demonstrate that H2S is only released from the trisulfide and tetrasulfide, and that this release requires thiol-mediated reduction in the presence of cysteine or reduced glutathione. Additionally, we demonstrate the different effects of trisulfides and tetrasulfides on cell proliferation in murine epithelial bEnd.3 cells.

Amino Acid Restriction Triggers Angiogenesis via GCN2/ATF4 Regulation of VEGF and H2S Production

Angiogenesis, the formation of new blood vessels by endothelial cells (ECs), is an adaptive response to oxygen/nutrient deprivation orchestrated by vascular endothelial growth factor (VEGF) upon ischemia or exercise. Hypoxia is the best-understood trigger of VEGF expression via the transcription factor HIF1α. Nutrient deprivation is inseparable from hypoxia during ischemia, yet its role in angiogenesis is poorly characterized. Here, we identified sulfur amino acid restriction as a proangiogenic trigger, promoting increased VEGF expression, migration and sprouting in ECs in vitro, and increased capillary density in mouse skeletal muscle in vivo via the GCN2/ATF4 amino acid starvation response pathway independent of hypoxia or HIF1α. We also identified a requirement for cystathionine-γ-lyase in VEGF-dependent angiogenesis via increased hydrogen sulfide (H₂S) production. H₂S mediated its proangiogenic effects in part by inhibiting mitochondrial electron transport and oxidative phosphorylation, resulting in increased glucose uptake and glycolytic ATP production.

DNA-Templated In Situ Synthesis of Highly Dispersed AuNPs on Nitrogen-Doped Graphene for Real-Time Electrochemical Monitoring of Nitric Oxide Released from Live Cancer Cells

Dispersion promotion of nanomaterials can significantly enhance their catalytic activities. With a new DNA-templated in situ synthesis approach, we report the preparation of highly dispersed AuNPs on nitrogen-doped graphene sheets (NGS) with significantly improved electrocatalytic ability for the monitoring of nitric oxide (NO) released from live cancer cells. The template DNA is adsorbed on NGS via π-π stacking, and the Au precursor chelates along the DNA lattice through dative bonding. Subsequent introduction of the reducing agent leads to in situ nucleation and growth of AuNPs, eventually resulting in highly dispersed AuNPs on NGS. Because of the synergistic enhancement of the catalytic activities of AuNPs and NGS, as well as the high dispersion of AuNPs, such a nanocomposite shows significant electro-oxidation capability toward NO, leading to a highly sensitive subnanomolar detection limit for NO in vitro. More importantly, the laminin glycoproteins can be readily adsorbed on the surface of the nanomaterials to render excellent biocompatibility for the adhesion and proliferation of live cells, enabling the biointerface for electrochemical detection of NO released from live cancer cells.

Hydrogen sulfide downregulates colonic afferent sensitivity by a nitric oxide synthase-dependent mechanism in mice

BACKGROUND

The effect of hydrogen sulfide (H₂ S) on visceral nociception is elusive. The conflicting evidence of its pro- and antinociceptive effects raises a series of questions with respect to the effect of H₂ S on colonic afferent activity and the underlying mechanism, which was further elucidated in this study.

METHODS

Colonic mesenteric afferent nerve spikes of normal male C57BL/6J mice, Cbs^+/- mice, and Wistar rats were recorded in vitro. The abdominal withdrawal reflex (AWR) induced by colorectal distension (CRD) was evaluated in Cbs^+/- mice and WT littermates.

KEY RESULTS

Sodium hydrosulfide (NaHS) significantly decreased colonic afferent spontaneous discharge, chemosensitivity to bradykinin, mechanosensitivity to ramp distention, and intraluminal pressure in mice. Reducing the relaxant action of NaHS on intestinal smooth muscle using the nonspecific K⁺ channel blocker TEA (10 mmol/L) did not block the inhibition of NaHS on afferent nerve activity. The inhibitory effects of NaHS (0.5 mmol/L) on colonic afferent sensitivity were largely eliminated by the pretreatment with nonspecific NOS inhibitor N^G -Methyl-l-arginine acetate salt (1 mmol/L), the specific nNOS inhibitor NPLA (1 μmol/L), or N-type Ca²⁺ channel blocker ω-conotoxin GVIA (1 μmol/L). Compared with WT mice, Cbs^+/- mice showed increased mesenteric afferent sensitivity to colonic distention and enhanced hyperalgesic response to CRD. Intraperitoneal administration of NaHS (60 μmol/kg) alleviated the nociception response to CRD in both Cbs^+/- and WT mice.

CONCLUSIONS AND INFERENCES

H₂ S downregulates colonic mesenteric afferent sensitivity by a nNOS-dependent mechanism in mice. Our findings may demonstrate a new mechanism for the antinociceptive effect of H₂ S in colon.

BODIPY-based hydrazine as a fluorescent probe for sensitive and selective detection of nitric oxide: a new strategy

A novel fluorescent probe 8-HB was developed with a BODIPY as a fluorophore and 8-substituted hydrazine as a reactive site for sensitive and selective detection of nitric oxide (NO), generating major fluorescent dehydrazinated BODIPY and minor non-fluorescent azide BODIPY.

A near-infrared Nile red fluorescent probe for the discrimination of biothiols by dual-channel response and its bioimaging applications in living cells and animals

Biothiols, including cysteine (Cys), homocysteine (Hcy), glutathione (GSH) and H₂S, play important roles in human physiological processes.

Acupuncture therapy for the treatment of stable angina pectoris: An updated meta-analysis of randomized controlled trials

BACKGROUND AND PURPOSE

Stable angina pectoris is a common symptom imperiling patients' life quality. The purpose of this meta-analysis is to assess the effectiveness of acupuncture alone or acupuncture plus medicine for the treatment of stable angina pectoris.

METHODS

Seven databases were searched ranging from 1959 to February 2018. Quantitative analysis of randomized controlled trials (RCTs) was performed by RevMan 5.3 software and STATA 12.0 program, and Cochrane criteria for risk-of-bias was used to assess the methodological quality of the trials.

RESULTS

A total of 12 RCTs involving 974 patients were enrolled in this study. The pooled results showed that both acupuncture group (RR: 0.35, P < 0.00001; RR: 0.49, P < 0.00001) and acupuncture plus medicine group (RR: 0.26, P < 0.00001; RR: 0.52, P = 0.03) were associated with a higher percentage of improved anginal symptoms as well as electrocardiographic (ECG) results compared to medicine group. The acupuncture plus medicine group also had a lower intake rate of nitroglycerin than medicine group (Non-event RR: 0.79, P = 0.03). However, there was no significant difference in the reduction or discontinuation of nitroglycerin intake between acupuncture group and medicine group. No acupuncture-related adverse effects were observed or reported in the included trials.

CONCLUSION

Acupuncture therapy may improve anginal symptoms and ECG results in patients with stable angina pectoris, and can serve as an adjunctive treatment for this condition.

Hydrogen Sulfide: A Therapeutic Option in Systemic Sclerosis

Systemic sclerosis (SSc) is a lethal disease that is characterized by auto-immunity, vascular injury, and progressive fibrosis of multiple organ systems. Despite the fact that the exact etiology of SSc remains unknown, oxidative stress has been associated with a large range of SSc-related complications. In addition to the well-known detrimental properties of reactive oxygen species (ROS), gasotransmitters (e.g., nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H₂S)) are also thought to play an important role in SSc. Accordingly, the diverse physiologic actions of NO and CO and their role in SSc have been previously studied. Recently, multiple studies have also shown the importance of the third gasotransmitter H₂S in both vascular physiology and pathophysiology. Interestingly, homocysteine (which is converted into H₂S through the transsulfuration pathway) is often found to be elevated in SSc patients; suggesting defects in the transsulfuration pathway. Hydrogen sulfide, which is known to have several effects, including a strong antioxidant and vasodilator effect, could potentially play a prominent role in the initiation and progression of vasculopathy. A better understanding of the actions of gasotransmitters, like H₂S, in the development of SSc-related vasculopathy, could help to create early interventions to attenuate the disease course. This paper will review the role of H₂S in vascular (patho-)physiology and potential disturbances in SSc. Moreover, current data from experimental animal studies will be reviewed. Lastly, we will evaluate potential interventional strategies.

Rho-Associated Coiled-Coil Kinase (ROCK) in Molecular Regulation of Angiogenesis

Identified as a major downstream effector of the small GTPase RhoA, Rho-associated coiled-coil kinase (ROCK) is a versatile regulator of multiple cellular processes. Angiogenesis, the process of generating new capillaries from the pre-existing ones, is required for the development of various diseases such as cancer, diabetes and rheumatoid arthritis. Recently, ROCK has attracted attention for its crucial role in angiogenesis, making it a promising target for new therapeutic approaches. In this review, we summarize recent advances in understanding the role of ROCK signaling in regulating the permeability, migration, proliferation and tubulogenesis of endothelial cells (ECs), as well as its functions in non-ECs which constitute the pro-angiogenic microenvironment. The therapeutic potential of ROCK inhibitors in angiogenesis-related diseases is also discussed.