Impaired Hydrogen Sulfide-Mediated Vasodilation Contributes to Microvascular Endothelial Dysfunction in Hypertensive Adults

Oxidative Stress Contributes to Microvascular Endothelial Dysfunction in Men and Women With Major Depressive Disorder

RATIONALE

In rodent models of depression, oxidative stress-induced reductions in NO bioavailability contribute to impaired endothelium-dependent dilation. Endothelial dysfunction is evident in major depressive disorder (MDD); however, the molecular mediators remain undefined.

OBJECTIVE

We sought to translate preclinical findings to humans by testing the role of oxidative stress in mediating microvascular endothelial dysfunction, including potential modulatory influences of sex, in MDD.

METHODS AND RESULTS

Twenty-four treatment-naive, otherwise healthy, young adults with MDD (14 women; 18-23 years) and 20 healthy adults (10 women; 19-30 years) participated. Red blood cell flux (laser Doppler flowmetry) was measured during graded intradermal microdialysis perfusion of the endothelium-dependent agonist acetylcholine, alone and in combination with an NO synthase inhibitor (L-NAME), a superoxide scavenger (Tempol), and an NADPH oxidase inhibitor (apocynin), as well as during perfusion of the endothelium-independent agonist sodium nitroprusside. Tissue oxidative stress markers (eg, nitrotyrosine abundance, superoxide production) were also quantified. Endothelium-dependent dilation was blunted in MDD and mediated by reductions in NO-dependent dilation. Endothelium-independent dilation was likewise attenuated in MDD. In MDD, there were no sex differences in either NO-mediated endothelium-dependent dilation or endothelium-independent dilation. Acute scavenging of superoxide or inhibition of NADPH oxidase improved NO-dependent dilation in MDD. Expression and activity of oxidative stress markers were increased in MDD. In a subset of adults with MDD treated with a selective serotonin reuptake inhibitor for their depressive symptoms and in remission (n=8; 7 women; 19-37 years), NO-mediated endothelium-dependent dilation was preserved, but endothelium-independent dilation was impaired, compared with healthy adults.

CONCLUSIONS

Oxidative stress-induced reductions in NO-dependent dilation, as well as alterations in vascular smooth muscle function, directly contribute to microvascular dysfunction in MDD. Strategies targeting vascular oxidative stress may be viable therapeutic options for improving NO-mediated endothelial function and reducing cardiovascular risk in MDD.

Historical reviews of the assessment of human cardiovascular function: interrogation and understanding of the control of skin blood flow

Several techniques exist for the determination of skin blood flow that have historically been used in the investigation of thermoregulatory control of skin blood flow, and more recently, in clinical assessments or as an index of global vascular function. Skin blood flow measurement techniques differ in their methodology and their strengths and limitations. To examine the historical development of techniques for assessing skin blood flow by describing the origin, basic principles, and important aspects of each procedure and to provide recommendations for best practise. Venous occlusion plethysmography was one of the earliest techniques to intermittently index a limb’s skin blood flow under conditions in which local muscle blood flow does not change. The introduction of laser Doppler flowmetry provided a method that continuously records an index of skin blood flow (red cell flux) (albeit from a relatively small skin area) that requires normalisation due to high site-to-site variability. The subsequent development of laser Doppler and laser speckle imaging techniques allows the mapping of skin blood flow from larger surface areas and the visualisation of capillary filling from the dermal plexus in two dimensions. The use of iontophoresis or intradermal microdialysis in conjunction with laser Doppler methods allows for the local delivery of pharmacological agents to interrogate the local and neural control of skin blood flow. The recent development of optical coherence tomography promises further advances in assessment of the skin circulation via three-dimensional imaging of the skin microvasculature for quantification of vessel diameter and vessel recruitment.

Aqueous garlic extract supresses experimental gentamicin induced renal pathophysiology mediated by oxidative stress, inflammation and Kim-1

BACKGROUND

Gentamicin (Gent) has rapid & high bactericidal action in addition to its cheap price. Nevertheless, 30% of gentamicin-treated patients develop nephrotoxicity.

OBJECTIVE

To explore the probable nephroprotective effects of the aqueous garlic extract (AGE) & to elucidate its underlying mechanisms via monitoring proinflammatory cytokines as tumer necrosis factor (TNF-α), interleukin 6 (IL-6) and interferon-γ (INF-γ), oxidative stess markers as malondialdehyde (MDA) & superoxide dismutase (SOD) & kidney injury molecule (Kim-1) as a promising early specific biomarker of renal dysfunction.

METHODS

32 adult male rats were divided into 4 equal groups treated for 21 days as: normal control group received normal saline orally, AGE-treated group received AGE at 250 mg/kg/day orally, Gent-treated group received Gent-sulphate intraperitoneal injection at 80 mg/kg /day, and AGE & Gent cotreated group received AGE and Gent concomitantly in the same previous doses. Serum urea, creatinine, glomerular filteration rate (GFR), systolic (SBP) and diastolic blood pressure (DBP), TNF-α, IL-6, INF-γ, MDA and SOD and Kim-1 mRNA expression were evaluated in kidney tissue homogenate. Renal cortex sections stained with Haematoxylin & eosin (H&E) were examined.

RESULTS

AGE is nephroprotective through significantly reducing serum urea, creatinine, SBP and DBP, TNF-α, IL-6, INF-γ and MDA (the main product of lipid peroxidation), decreasing expression of Kim-1 mRNA in renal tissue and increasing level of GFR, the natural antioxidant SOD and improving renal histological features of Gent-treated rats.

CONCLUSION

AGE normalizes Gent-induced renal dysfunction. Their co-administration is a plausible advice, although the therapeutic efficiency of Gent was not investigated.

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.

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.

A small-molecule probe for ratiometric photoacoustic imaging of hydrogen sulfide in living mice

A small molecule ratiometric photoacoustic probe was developed for real-time monitoring of hydrogen sulfide in living mice.

Controllable thioester-based hydrogen sulfide slow-releasing donors as cardioprotective agents

Hydrogen sulfide (H₂S) is an important signaling molecule with promising protective effects in many physiological and pathological processes.

Garlic (Allium sativum) exhibits a cardioprotective effect in experimental chronic renal failure rat model by reducing oxidative stress and controlling cardiac Na+/K+-ATPase activity and Ca2+ levels

Gentamicin (GNT)-induced nephrotoxicity culminates into renal failure with a possible cardiovascular impact. Garlic extract (GE) is a cardiovascular protectant with limited mechanistic data. Therefore, we assessed the disturbance in specific cardiac parameters and the potential protective effect of GE supplementation against them in a rat model of GNT-induced chronic renal failure (CRF). Adult male rats (n = 24) were randomly assigned into four groups (n = 6 each): normal controls (CON), garlic extract controls (GE; 250 mg kg-1, orally), GNT-induced CRF (GNT; 100 mg kg-1, i.p.), and GNT + GE (GNT and GE in the same previous doses) groups. GNT and GE were given daily for 3 weeks. Animals co-treated with GNT and GE exhibited improved renal functions, body weight (BW), and heart weight (HW)/BW ratio; declined blood pressure; lowered plasma levels of lactate dehydrogenase (LDH), creatine kinase-MB (CK-MB), and total peroxides (TP); and elevated total antioxidant capacity (TAC) levels. Moreover, the heart tissue contained raised levels of TAC and Na+/K+-ATPase activity and lowered levels of TP and Ca2+. Findings provide evidence that administration of GE in experimental CRF model helped protect the heart through reducing oxidative stress and controlling cardiac Na+/K+-ATPase activity and Ca2+ levels.

Increases in placental nitric oxide, but not nitric oxide-mediated relaxation, underlie the improvement in placental efficiency and antihypertensive effects of hydrogen sulphide donor in hypertensive pregnancy

Dysregulation of hydrogen sulphide (H₂ S) producing enzymes has been related to hypertensive pregnancy, and H₂ S donor, sodium hydrosulphide (NaHS) exerts antihypertensive effects, modulates angiogenic factors production and acts as an antioxidant. Moreover, reduction in nitric oxide (NO) bioavailability is related to hypertensive pregnancy and H₂ S may interact with NO, modulating its production. We aimed to investigate the NaHS effects in hypertension-in-pregnancy and also in feto-placental parameters. Female Wistar rats (200-250 g) were mated and desoxycorticosterone acetate injections followed by replacement of water by 0.9% saline solution were used to induce hypertensive pregnancy. Rats were divided into four groups: normal pregnant (Norm-Preg), pregnant + NaHS (Preg+NaHS), hypertensive pregnant (HTN-Preg) and HTN-Preg+NaHS. Systolic blood pressure was increased in HTN-Preg and this increase was blunted in HTN-Preg+NaHS. Fetal and placental weights were decreased in HTN-Preg animals, while fetal growth restriction was improved in HTN-Preg+NaHS. Placental weight was lower in HTN-Preg+NaHS than in HTN-Preg; however, placental efficiency was re-established in HTN-Preg+NaHS rats. We observed that a partial contribution of placental NO, but not changes in anti-angiogenic factors may mediate the increases in placental efficiency in HTN-Preg+NaHS. HTN-Preg presented thoracic aorta hyperreactivity to phenylephrine while NaHS treatment blunted this hyperreactivity, which seems not to be related to NO-mediated relaxation induced by acetylcholine. Therefore, changes in vascular responsiveness promoted by NaHS treatment may underlie the beneficial effects in systolic blood pressure and feto-placental parameters in our study.

The Increased Endogenous Sulfur Dioxide Acts as a Compensatory Mechanism for the Downregulated Endogenous Hydrogen Sulfide Pathway in the Endothelial Cell Inflammation

Endogenous hydrogen sulfide (H₂S) and sulfur dioxide (SO₂) are regarded as important regulators to control endothelial cell function and protect endothelial cell against various injuries. In our present study, we aimed to investigate the effect of endogenous H₂S on the SO₂ generation in the endothelial cells and explore its significance in the endothelial inflammation in vitro and in vivo. The human umbilical vein endothelial cell (HUVEC) line (EA.hy926), primary HUVECs, primary rat pulmonary artery endothelial cells (RPAECs), and purified aspartate aminotransferase (AAT) protein from pig heart were used for in vitro experiments. A rat model of monocrotaline (MCT)-induced pulmonary vascular inflammation was used for in vivo experiments. We found that endogenous H₂S deficiency caused by cystathionine-γ-lyase (CSE) knockdown increased endogenous SO₂ level in endothelial cells and enhanced the enzymatic activity of AAT, a major SO₂ synthesis enzyme, without affecting the expressions of AAT1 and AAT2. While H₂S donor could reverse the CSE knockdown-induced increase in the endogenous SO₂ level and AAT activity. Moreover, H₂S donor directly inhibited the activity of purified AAT protein, which was reversed by a thiol reductant DTT. Mechanistically, H₂S donor sulfhydrated the purified AAT1/2 protein and rescued the decrease in the sulfhydration of AAT1/2 protein in the CSE knockdown endothelial cells. Furthermore, an AAT inhibitor l-aspartate-β-hydroxamate (HDX), which blocked the upregulation of endogenous SO₂/AAT generation induced by CSE knockdown, aggravated CSE knockdown-activated nuclear factor-κB pathway in the endothelial cells and its downstream inflammatory factors including ICAM-1, TNF-α, and IL-6. In in vivo experiment, H₂S donor restored the deficiency of endogenous H₂S production induced by MCT, and reversed the upregulation of endogenous SO₂/AAT pathway via sulfhydrating AAT1 and AAT2. In accordance with the results of the in vitro experiment, HDX exacerbated the pulmonary vascular inflammation induced by the broken endogenous H₂S production in MCT-treated rat. In conclusion, for the first time, the present study showed that H₂S inhibited endogenous SO₂ generation by inactivating AAT via the sulfhydration of AAT1/2; and the increased endogenous SO₂ generation might play a compensatory role when H₂S/CSE pathway was downregulated, thereby exerting protective effects in endothelial inflammatory responses in vitro and in vivo.

Clinical and Experimental Evidences of Hydrogen Sulfide Involvement in Lead-Induced Hypertension

Lead- (Pb-) induced hypertension has been shown in humans and experimental animals and cardiovascular effects of hydrogen sulfide (H₂S) have been reported previously. However, no studies examined involvement of H₂S in Pb-induced hypertension. We found increases in diastolic blood pressure and mean blood pressure in Pb-intoxicated humans followed by diminished H₂S plasmatic levels. In order to expand our findings, male Wistar rats were divided into four groups: Saline, Pb, NaHS, and Pb + NaHS. Pb-intoxicated animals received intraperitoneally (i.p.) 1st dose of 8 μg/100 g of Pb acetate and subsequent doses of 0.1 μg/100 g for seven days and sodium hydrosulfide- (NaHS-) treated animals received i.p. NaHS injections (50 μmol/kg/twice daily) for seven days. NaHS treatment blunted increases in systolic blood pressure, increased H₂S plasmatic levels, and diminished whole-blood lead levels. Treatment with NaHS in Pb-induced hypertension seems to induce a protective role in rat aorta which is dependent on endothelium and seems to promote non-NO-mediated relaxation. Pb-intoxication increased oxidative stress in rats, while treatment with NaHS blunted increases in plasmatic MDA levels and increased antioxidant status of plasma. Therefore, H₂S pathway may be involved in Pb-induced hypertension and treatment with NaHS exerts antihypertensive effect, promotes non-NO-mediated relaxation, and decreases oxidative stress in rats with Pb-induced hypertension.

Regulation of vascular tone homeostasis by NO and H2S: Implications in hypertension

Nitric oxide (NO) and hydrogen sulfide (H2S) are two gasotransmitters that are produced in the vasculature and contribute to the regulation of vascular tone. NO and H2S are synthesized in both vascular smooth muscle and endothelial cells; NO functions primarily through the sGC/cGMP pathway, and H2S mainly through activation of the ATP-dependent potassium channels; both leading to relaxation of vascular smooth muscle cells. A deficit in the NO/H2S homeostasis is involved in the pathogenesis of various cardiovascular diseases, especially hypertension. It is now becoming increasingly clear that there are important interactions between NO and H2S and that have a profound impact on vascular tone and this may provide insights into the new therapeutic interventions. The aim of this review is to provide a better understanding of individual and interactive roles of NO and H2S in vascular biology. Overall, available data indicate that both NO and H2S contribute to vascular (patho)physiology and in regulating blood pressure. In addition, boosting NO and H2S using various dietary sources or donors could be a hopeful therapeutic strategy in the management of hypertension.

Endothelium-Dependent Hyperpolarization (EDH) in Hypertension: The Role of Endothelial Ion Channels

Upon stimulation with agonists and shear stress, the vascular endothelium of different vessels selectively releases several vasodilator factors such as nitric oxide and prostacyclin. In addition, vascular endothelial cells of many vessels regulate the contractility of the vascular smooth muscle cells through the generation of endothelium-dependent hyperpolarization (EDH). There is a general consensus that the opening of small- and intermediate-conductance Ca2+-activated K⁺ channels (SKCa and IKCa) is the initial mechanistic step for the generation of EDH. In animal models and humans, EDH and EDH-mediated relaxations are impaired during hypertension, and anti-hypertensive treatments restore such impairments. However, the underlying mechanisms of reduced EDH and its improvement by lowering blood pressure are poorly understood. Emerging evidence suggests that alterations of endothelial ion channels such as SKCa channels, inward rectifier K⁺ channels, Ca2+-activated Cl- channels, and transient receptor potential vanilloid type 4 channels contribute to the impaired EDH during hypertension. In this review, we attempt to summarize the accumulating evidence regarding the pathophysiological role of endothelial ion channels, focusing on their relationship with EDH during hypertension.

Hydrogen Sulfide Preserves Endothelial Nitric Oxide Synthase Function by Inhibiting Proline-Rich Kinase 2: Implications for Cardiomyocyte Survival and Cardioprotection

Hydrogen sulfide (H₂S) exhibits beneficial effects in the cardiovascular system, many of which depend on nitric oxide (NO). Proline-rich tyrosine kinase 2 (PYK2), a redox-sensitive tyrosine kinase, directly phosphorylates and inhibits endothelial NO synthase (eNOS). We investigated the ability of H₂S to relieve PYK2-mediated eNOS inhibition and evaluated the importance of the H₂S/PYK2/eNOS axis on cardiomyocyte injury in vitro and in vivo. Exposure of H9c2 cardiomyocytes to H₂O₂ or pharmacologic inhibition of H₂S production increased PYK2 (Y402) and eNOS (Y656) phosphorylation. These effects were blocked by treatment with Na₂S or by overexpression of cystathionine γ-lyase (CSE). In addition, PYK2 overexpression reduced eNOS activity in a H₂S-reversible manner. The viability of cardiomyocytes exposed to Η₂Ο₂ was reduced and declined further after the inhibition of H₂S production. PYK2 downregulation, l-cysteine supplementation, or CSE overexpression alleviated the effects of H₂O₂ on H9c2 cardiomyocyte survival. Moreover, H₂S promoted PYK2 sulfhydration and inhibited its activity. In vivo, H₂S administration reduced reactive oxygen species levels, as well as PYK2 (Y402) and eNOS (Y656) phosphorylation. Pharmacologic blockade of PYK2 or inhibition of PYK2 activation by Na₂S reduced myocardial infarct size in mice. Coadministration of a PYK2 inhibitor and Na₂S did not result in additive effects on infarct size. We conclude that H₂S relieves the inhibitory effect of PYK2 on eNOS, allowing the latter to produce greater amounts of NO, thereby affording cardioprotection. Our results unravel the existence of a novel H₂S-NO interaction and identify PYK2 as a crucial target for the protective effects of H₂S under conditions of oxidative stress.

Diurnal Fluctuations in Plasma Hydrogen Sulfide of the Mice

Circadian rhythms are essential in a myriad of physiological processes to maintain homeostasis, especially the redox homeostasis. However, little is known about whether plasma H₂S exhibits the physiological diurnal variation. The present study was performed to investigate the diurnal fluctuations of plasma H₂S and explore the potential mechanisms. We found that the plasma H₂S of the C57BL/6J mice was significantly higher at 19 o’clock than those at 7 o’clock which was not affected by the blood-collecting sequence and the concentrations of plasma cysteine (a precursor of H₂S). No significant differences in mRNA or protein expression of the CSE, CBS, or MPST were observed between 7: 00 and 19: 00. There were also no significant differences in the CSE and CBS activities, while the activities of MPST in tissues were significantly higher at 19 o’clock. After treatment with AOAA (a CBS inhibitor) or PPG (a CSE inhibitor) for 14 days, plasma H₂S concentrations at 19 o’clock were still significantly higher than those at 7 o’clock, although they were both significantly decreased as compared with controls. Identical findings were also observed in CSE KO mice. We also found the plasma H₂O₂ concentrations were significantly higher at 19 o’clock than those at 7 o’clock. However, H₂O₂ concentrations were significantly decreased at 19 o’clock than those at 7 o’clock when mice were exposed to continuous light for 24 h. Meanwhile, the diurnal fluctuations of plasma H₂S levels and MPST activities in tissues were disappeared. After treatment with DTT for 14 days, there was no significant difference in plasma H₂O₂ concentrations between 7 o’clock and 19 o’clock. Meanwhile, the diurnal fluctuations of plasma H₂S levels and MPST activities in tissues were disappeared. Identical findings were also observed in SOD^2+/- mice. When heart tissues were incubated with increasing concentrations of H₂O₂in vitro, H₂O₂ could dose-dependently increase the activity of MPST within a certain concentration range. In conclusion, our studies revealed that plasma H₂S concentration and tissue MPST activity exhibited diurnal fluctuations. Modulated by plasma H₂O₂ concentration, changes of MPST activity probably led to the diurnal fluctuations of plasma H₂S.

Hydrogen sulfide ameliorated L-NAME-induced hypertensive heart disease by the Akt/eNOS/NO pathway

Reductions in hydrogen sulfide (H₂S) production have been implicated in the pathogenesis of hypertension; however, no studies have examined the functional role of hydrogen sulfide in hypertensive heart disease. We hypothesized that the endogenous production of hydrogen sulfide would be reduced and exogenous hydrogen sulfide would ameliorate cardiac dysfunction in N^ω-nitro- L-arginine methyl ester ( L-NAME)-induced hypertensive rats. Therefore, this study investigated the cardioprotective effects of hydrogen sulfide on L-NAME-induced hypertensive heart disease and explored potential mechanisms. The rats were randomly divided into five groups: Control, Control + sodium hydrosulfide (NaHS), L-NAME, L-NAME + NaHS, and L-NAME + NaHS + glibenclamide (Gli) groups. Systolic blood pressure was monitored each week. In Langendorff-isolated rat heart, cardiac function represented by ±LV dP/dt_max and left ventricular developing pressure was recorded after five weeks of treatment. Hematoxylin and Eosin and Masson's trichrome staining and myocardium ultrastructure under transmission electron microscopy were used to evaluate cardiac remodeling. The plasma nitric oxide and hydrogen sulfide concentrations, as well as nitric oxide synthases and cystathionine-γ-lyase activity in left ventricle tissue were determined. The protein expression of p-Akt, Akt, p-eNOS, and eNOS in left ventricle tissue was analyzed using Western blot. After five weeks of L-NAME treatment, there was a time-dependent hypertension, cardiac remodeling, and dysfunction accompanied by a decrease in eNOS phosphorylation, nitric oxide synthase activity, and nitric oxide concentration. Meanwhile, cystathionine-γ-lyase activity and hydrogen sulfide concentration were also decreased. NaHS treatment significantly increased plasma hydrogen sulfide concentration and subsequently promoted the Akt/eNOS/NO pathway which inhibited the development of hypertension and attenuated cardiac remodeling and dysfunction. The cardioprotective effects of NaHS were counteracted by Gli which inhibited the Akt/eNOS/NO pathway. This suggests that the effects of hydrogen sulfide were mediated by the activation of the K_ATP channels. In conclusion, hydrogen sulfide ameliorated L-NAME-induced hypertensive heart disease via the activation of the Akt/eNOS/NO pathway, which was mediated by K_ATP channels. Impact statement 1. We found that H₂S ameliorated L-NAME-induced cardiac remodeling and dysfunction, and played a protective role in L-NAME-induced hypertensive heart disease, which the existing studies have not reported. 2. H₂S activated the Akt/eNOS/NO pathway, thereby playing a cardioprotective role in L-NAME-induced hypertensive heart disease. 3. The cardioprotective effect of H₂S was mediated by ATP-sensitive potassium channels.

International Union of Basic and Clinical Pharmacology. CII: Pharmacological Modulation of H2S Levels: H2S Donors and H2S Biosynthesis Inhibitors

Over the last decade, hydrogen sulfide (H2S) has emerged as an important endogenous gasotransmitter in mammalian cells and tissues. Similar to the previously characterized gasotransmitters nitric oxide and carbon monoxide, H2S is produced by various enzymatic reactions and regulates a host of physiologic and pathophysiological processes in various cells and tissues. H2S levels are decreased in a number of conditions (e.g., diabetes mellitus, ischemia, and aging) and are increased in other states (e.g., inflammation, critical illness, and cancer). Over the last decades, multiple approaches have been identified for the therapeutic exploitation of H2S, either based on H2S donation or inhibition of H2S biosynthesis. H2S donation can be achieved through the inhalation of H2S gas and/or the parenteral or enteral administration of so-called fast-releasing H2S donors (salts of H2S such as NaHS and Na2S) or slow-releasing H2S donors (GYY4137 being the prototypical compound used in hundreds of studies in vitro and in vivo). Recent work also identifies various donors with regulated H2S release profiles, including oxidant-triggered donors, pH-dependent donors, esterase-activated donors, and organelle-targeted (e.g., mitochondrial) compounds. There are also approaches where existing, clinically approved drugs of various classes (e.g., nonsteroidal anti-inflammatories) are coupled with H2S-donating groups (the most advanced compound in clinical trials is ATB-346, an H2S-donating derivative of the non-steroidal anti-inflammatory compound naproxen). For pharmacological inhibition of H2S synthesis, there are now several small molecule compounds targeting each of the three H2S-producing enzymes cystathionine-β-synthase (CBS), cystathionine-γ-lyase, and 3-mercaptopyruvate sulfurtransferase. Although many of these compounds have their limitations (potency, selectivity), these molecules, especially in combination with genetic approaches, can be instrumental for the delineation of the biologic processes involving endogenous H2S production. Moreover, some of these compounds (e.g., cell-permeable prodrugs of the CBS inhibitor aminooxyacetate, or benserazide, a potentially repurposable CBS inhibitor) may serve as starting points for future clinical translation. The present article overviews the currently known H2S donors and H2S biosynthesis inhibitors, delineates their mode of action, and offers examples for their biologic effects and potential therapeutic utility.

Edward F. Adolph Distinguished Lecture: Skin-deep insights into vascular aging

The skin is an accessible model circulation for studying vascular function and dysfunction across the lifespan. Age-related changes, as well as those associated with disease progression, often appear first in the cutaneous circulation. Furthermore, impaired vascular signaling and attendant endothelial dysfunction, the earliest indicators of cardiovascular pathogenesis, occur in a similar fashion across multiple tissue beds throughout the body, including the skin. Because microvascular dysfunction is a better predictor of long-term outcomes and adverse cardiovascular events than is large vessel disease, an understanding of age-associated changes in the control of the human cutaneous microcirculation is important. This review focuses on 1) the merits of using skin-specific methods and techniques to study vascular function, 2) microvascular changes in aged skin (in particular, the role of the endothelial-derived dilator nitric oxide), and 3) the impact of aging on heat-induced changes in skin vasodilation. While skin blood flow is controlled by multiple, often redundant, mechanisms, our laboratory has used a variety of distinct thermal provocations of this model circulation to isolate specific age-associated changes in vascular function. Skin-specific approaches and techniques, such as intradermal microdialysis coupled with laser-Doppler flowmetry (in vivo) and biochemical analyses of skin biopsy samples (in vitro), have allowed for the targeted pharmacodissection of the mechanistic pathways controlling skin vasoreactivity and study of the impact of aging and disease states. Aged skin has an attenuated ability to vasodilate in response to warm stimuli and to vasoconstrict in response to cold stimuli.