Hydrogen-sulfide-mediated vasodilatory effect of nucleoside 5'-monophosphorothioates in perivascular adipose tissue

Perivascular Adipose Tissue and Vascular Smooth Muscle Tone: Friends or Foes?

Perivascular adipose tissue (PVAT) is a specialized type of adipose tissue that surrounds most mammalian blood vessels. PVAT is a metabolically active, endocrine organ capable of regulating blood vessel tone, endothelium function, vascular smooth muscle cell growth and proliferation, and contributing critically to cardiovascular disease onset and progression. In the context of vascular tone regulation, under physiological conditions, PVAT exerts a potent anticontractile effect by releasing a plethora of vasoactive substances, including NO, H₂S, H₂O₂, prostacyclin, palmitic acid methyl ester, angiotensin 1-7, adiponectin, leptin, and omentin. However, under certain pathophysiological conditions, PVAT exerts pro-contractile effects by decreasing the production of anticontractile and increasing that of pro-contractile factors, including superoxide anion, angiotensin II, catecholamines, prostaglandins, chemerin, resistin, and visfatin. The present review discusses the regulatory effect of PVAT on vascular tone and the factors involved. In this scenario, dissecting the precise role of PVAT is a prerequisite to the development of PVAT-targeted therapies.

Hydrogen sulfide and its donors for the treatment of cerebral ischaemia-reperfusion injury: A comprehensive review

As an endogenous gas signalling molecule, hydrogen sulfide (H₂S) is frequently present in a variety of mammals and plays a significant role in the cardiovascular and nervous systems. Reactive oxygen species (ROS) are produced in large quantities as a result of cerebral ischaemia-reperfusion, which is a very serious class of cerebrovascular diseases. ROS cause oxidative stress and induce specific gene expression that results in apoptosis. H₂S reduces cerebral ischaemia-reperfusion-induced secondary injury via anti-oxidative stress injury, suppression of the inflammatory response, inhibition of apoptosis, attenuation of cerebrovascular endothelial cell injury, modulation of autophagy, and antagonism of P2X7 receptors, and it plays an important biological role in other cerebral ischaemic injury events. Despite the many limitations of the hydrogen sulfide therapy delivery strategy and the difficulty in controlling the ideal concentration, relevant experimental evidence demonstrating that H₂S plays an excellent neuroprotective role in cerebral ischaemia-reperfusion injury (CIRI). This paper examines the synthesis and metabolism of the gas molecule H₂S in the brain as well as the molecular mechanisms of H₂S donors in cerebral ischaemia-reperfusion injury and possibly other unknown biological functions. With the active development in this field, it is expected that this review will assist researchers in their search for the potential value of hydrogen sulfide and provide new ideas for preclinical trials of exogenous H₂S.

The role of adipose tissue-derived hydrogen sulfide in inhibiting atherosclerosis

Hydrogen sulfide (H₂S) is the third gaseous signaling molecule discovered in the body after NO and CO and plays an important organismal protective role in various diseases. Within adipose tissue, related catalytic enzymes (cystathionine-β-synthetase, cystathionine-γ-lyase, and 3-mercaptopyruvate transsulfuration enzyme) can produce and release endogenous H₂S. Atherosclerosis (As) is a pathological change in arterial vessels that is closely related to abnormal glucose and lipid metabolism and a chronic inflammatory response. Previous studies have shown that H₂S can act on the cardiovascular system, exerting effects such as improving disorders of glycolipid metabolism, alleviating insulin resistance, protecting the function of vascular endothelial cells, inhibiting vascular smooth muscle cell proliferation and migration, regulating vascular tone, inhibiting the inflammatory response, and antagonizing the occurrence and development of As.

The Role of Perivascular Adipose Tissue-Derived Hydrogen Sulfide in the Control of Vascular Homeostasis

Significance: Emerging evidence suggests that perivascular adipose tissue (PVAT) has a relevant role in the control of vascular tone in physiology and pathology. Healthy PVAT has anticontractile, anti-inflammatory, and antioxidative actions. Accumulating data from both human and experimental animal models indicate that PVAT dysfunction is conceivably coupled to cardiovascular diseases, and it is associated with vascular inflammation, oxidative stress, and arterial remodeling. Therefore, "healthy" PVAT may constitute a novel therapeutic target for the prevention and treatment of cardiovascular diseases. Recent Advances: Hydrogen sulfide (H₂S) has been recognized as a vascular anti-contractile factor released from PVAT. The enzymes deputed to H₂S biosynthesis are variously expressed in PVAT and strictly dependent on the vascular bed and species. Metabolic and cardiovascular diseases can alter the morphological and secretory characteristics of PVAT, influencing also the H₂S signaling. Here, we discuss the role of PVAT-derived H₂S in healthy conditions and its relevance in alterations occurring in vascular disorders. Critical Issues: We discuss how a better understanding may help in the prevention of vascular dysfunction related to alteration in PVAT-released H₂S as well as the importance of the interplay between PVAT and H₂S. Future Directions: We propose future directions to evaluate the contribution of each enzyme involved in H₂S biosynthesis and their alteration/switch occurring in vascular disorders and the remaining challenges in investigating the role of H₂S. Antioxid. Redox Signal. 37, 84-97.

Role of Hydrogen Sulfide and Polysulfides in the Regulation of Lipolysis in the Adipose Tissue: Possible Implications for the Pathogenesis of Metabolic Syndrome

Hydrogen sulfide (H2S) and inorganic polysulfides are important signaling molecules; however, little is known about their role in the adipose tissue. We examined the effect of H2S and polysulfides on adipose tissue lipolysis. H2S and polysulfide production by mesenteric adipose tissue explants in rats was measured. The effect of Na2S and Na2S4, the H2S and polysulfide donors, respectively, on lipolysis markers, plasma non-esterified fatty acids (NEFA) and glycerol, was examined. Na2S but not Na2S4 increased plasma NEFA and glycerol in a time- and dose-dependent manner. Na2S increased cyclic AMP but not cyclic GMP concentration in the adipose tissue. The effect of Na2S on NEFA and glycerol was abolished by the specific inhibitor of protein kinase A, KT5720. The effect of Na2S on lipolysis was not abolished by propranolol, suggesting no involvement of β-adrenergic receptors. In addition, Na2S had no effect on phosphodiesterase activity in the adipose tissue. Obesity induced by feeding rats a highly palatable diet for 1 month was associated with increased plasma NEFA and glycerol concentrations, as well as greater H2S production in the adipose tissue. In conclusion, H2S stimulates lipolysis and may contribute to the enhanced lipolysis associated with obesity.

Perivascular Adipose Tissue Regulates Vascular Function by Targeting Vascular Smooth Muscle Cells

Adipose tissues are present at multiple locations in the body. Most blood vessels are surrounded with adipose tissue which is referred to as perivascular adipose tissue (PVAT). Similarly to adipose tissues at other locations, PVAT harbors many types of cells which produce and secrete adipokines and other undetermined factors which locally modulate PVAT metabolism and vascular function. Uncoupling protein-1, which is considered as a brown fat marker, is also expressed in PVAT of rodents and humans. Thus, compared with other adipose tissues in the visceral area, PVAT displays brown-like characteristics. PVAT shows a distinct function in the cardiovascular system compared with adipose tissues in other depots which are not adjacent to the vascular tree. Growing and extensive studies have demonstrated that presence of normal PVAT is required to maintain the vasculature in a functional status. However, excessive accumulation of dysfunctional PVAT leads to vascular disorders, partially through alteration of its secretome which, in turn, affects vascular smooth muscle cells and endothelial cells. In this review, we highlight the cross talk between PVAT and vascular smooth muscle cells and its roles in vascular remodeling and blood pressure regulation.

Perivascular Adipose Tissue-Enhanced Vasodilation in Metabolic Syndrome Rats by Apelin and N-Acetyl⁻l-Cysteine-Sensitive Factor(s)

Perivascular adipose tissue (PVAT) can regulate vascular tone. In mesenteric arteries of SHRSP.Z-Lepr^fa/IzmDmcr rats (SHRSP.ZF) with metabolic syndrome, vascular dysfunction is compensated by PVAT-dependent mechanisms that disappear with increasing age. In this study, we investigated the mechanisms of the age-related changes and responsible factor(s) involved in the enhancing effects of mesenteric arterial PVAT in SHRSP.ZF. Acetylcholine- and sodium nitroprusside-induced relaxations of isolated arteries were greater with PVAT than without PVAT at 17 and 20 weeks of age (wks), and as expected, this enhancement by the presence of PVAT disappeared at 23 wks. PVAT mRNA levels of angiotensin II type 1 (AT1) receptor-associated protein was less and AT1 receptor was unchanged at 23 wks when compared to 20 wks. At 20 wks, the enhanced acetylcholine-induced relaxation by the presence of PVAT was inhibited by N-acetyl-l-cysteine (NAC). Acetylcholine-induced relaxation of arteries without PVAT was increased in the presence of exogenously added apelin. PVAT mRNA level of apelin was higher in SHRSP.ZF than in control Wistar-Kyoto rats, and the level was decreased with aging. These results suggest that AT1 receptor activation in PVAT, and changes in the regulation of apelin and a NAC-sensitive factor are related to the age-dependent deterioration of the vasodilation enhancing effects of mesenteric arterial PVAT in SHRSP.ZF.

The involvement of purinergic signalling in obesity

Obesity is a growing worldwide health problem, with an alarming increasing prevalence in developed countries, caused by a dysregulation of energy balance. Currently, no wholly successful pharmacological treatments are available for obesity and related adverse consequences. In recent years, hints obtained from several experimental animal models support the notion that purinergic signalling, acting through ATP-gated ion channels (P2X), G protein-coupled receptors (P2Y) and adenosine receptors (P1), is involved in obesity, both at peripheral and central levels. This review has drawn together, for the first time, the evidence for a promising, much needed novel therapeutic purinergic signalling approach for the treatment of obesity with a 'proof of concept' that hopefully could lead to further investigations and clinical trials for the management of obesity.

Renal perivascular adipose tissue: Form and function

Renal sympathetic activity affects blood pressure in part by increasing renovascular resistance via release of norepinephrine (NE) from sympathetic nerves onto renal arteries. Here we test the idea that adipose tissue adjacent to renal blood vessels, i.e. renal perivascular adipose tissue (RPVAT), contains a pool of NE which can be released to alter renal vascular function. RPVAT was obtained from around the main renal artery/vein of the male Sprague Dawley rats. Thoracic aortic PVAT and mesenteric PVAT also were studied as brown-like and white fat comparators respectively. RPVAT was identified as a mix of white and brown adipocytes, because of expression of both brown-like (e.g. uncoupling protein 1) and white adipogenic genes. All PVATs contained NE (ng/g tissue, RPVAT:524 ± 68, TAPVAT:740 ± 16, MPVAT:96 ± 24). NE was visualized specifically in RPVAT adipocytes by immunohistochemistry. The presence of RPVAT (+RPVAT) did not alter the response of isolated renal arteries to NE compared to responses of arteries without RPVAT (-RPVAT). By contrast, the maximum contraction to the sympathomimetic tyramine was ~2× greater in the renal artery +PVAT versus -PVAT. Tyramine-induced contraction in +RPVAT renal arteries was reduced by the α₁-adrenoceptor antagonist prazosin and the NE transporter inhibitor nisoxetine. These results suggest that tyramine caused release of NE from RPVAT. Renal denervation significantly (>50%) reduced NE content of RPVAT but did not modify tyramine-induced contraction of +RPVAT renal arteries. Collectively, these data support the existence of a releasable pool of NE in RPVAT that is independent of renal sympathetic innervation and has the potential to change renal arterial function.

Role of Perivascular Adipose Tissue in Health and Disease

Perivascular adipose tissue (PVAT) is cushion of fat tissue surrounding blood vessels, which is phenotypically different from other adipose tissue depots. PVAT is composed of adipocytes and stromal vascular fraction, constituted by different populations of immune cells, endothelial cells, and adipose-derived stromal cells. It expresses and releases an important number of vasoactive factors with paracrine effects on vascular structure and function. In healthy individuals, these factors elicit a net anticontractile and anti-inflammatory paracrine effect aimed at meeting hemodynamic and metabolic demands of specific organs and regions of the body. Pathophysiological situations, such as obesity, diabetes or hypertension, induce changes in its amount and in the expression pattern of vasoactive factors leading to a PVAT dysfunction in which the beneficial paracrine influence of PVAT is shifted to a pro-oxidant, proinflammatory, contractile, and trophic environment leading to functional and structural cardiovascular alterations and cardiovascular disease. Many different PVATs surrounding a variety of blood vessels have been described and exhibit regional differences. Both protective and deleterious influence of PVAT differs regionally depending on the specific vascular bed contributing to variations in the susceptibility of arteries and veins to vascular disease. PVAT therefore, might represent a novel target for pharmacological intervention in cardiovascular disease. © 2018 American Physiological Society. Compr Physiol 8:23-59, 2018.

Purinergic P2X7 receptor functional genetic polymorphisms are associated with the susceptibility to obesity in Chinese postmenopausal women

OBJECTIVE

We conducted a case-control study to investigate the associations of functional single-nucleotide polymorphisms in the purinergic P2X7 receptor (P2X7R) gene (rs2393799, rs7958311, rs1718119, rs2230911, and rs3751143) with obesity and overweight in a population of Chinese postmenopausal women.

METHODS

Our study included 180 obese women, 179 overweight women, and 204 controls. All participants were genotyped at the P2X7R rs2393799, rs7958311, rs1718119, rs2230911, and rs3751143 loci via allele-specific polymerase chain reaction (PCR) and PCR-restriction fragment length polymorphism procedures. The relationships between P2X7R genetic polymorphisms and their associated haplotypes with obesity (body mass index [BMI] ≥30 kg/m] and overweight (25 kg/m ≤ BMI < 30 kg/m) were evaluated.

RESULTS

Our results showed that P2X7R rs2230911G and rs1718119A were associated with an increased risk of obesity; in particular, both carriers of the rs2230911G allele and GG/(CG + GG) genotypes (G vs C, P < 0.001, odds ratio [OR] 2.87, 95% confidence interval [CI] 1.98-4.16; GG vs CC, P < 0.001, OR 8.76, 95% CI 3.29-23.35; CG + GG vs CC, P < 0.001, OR 2.54, 95% CI 1.63-3.95) and carriers of the rs17181191A allele and GA/(GA + AA) genotypes (A vs G, P < 0.001, OR 2.97, 95% CI 1.86-4.74; GA vs GG, P = 0.001, OR 2.72, 95% CI 1.55-4.79; GA + AA vs GG, P < 0.001, OR 3.05, 95% CI 1.79-5.19) were at a higher risk of obesity. No association with obesity or overweight was observed for the other three P2X7R polymorphisms (rs2393799, rs7958311, and rs3751143). Haplotype analysis indicated that P2X7R rs1718119A-rs2230911G-rs3751143C appeared to be a significant risk haplotype with obesity (P = 0.0005, OR 2.37, 95% CI 1.45-3.90).

CONCLUSIONS

P2X7R functional genetic polymorphisms and their estimated haplotypes are associated with obesity in Chinese postmenopausal women.

The mechanism of action and role of hydrogen sulfide in the control of vascular tone

Our knowledge about hydrogen sulfide (H₂S) significantly changed over the last two decades. Today it is considered as not only a toxic gas but also as a gasotransmitter with diverse roles in different physiological and pathophysiological processes. H₂S has pleiotropic effects and its possible mechanisms of action involve (1) a reversible protein sulfhydration which can alter the function of the modified proteins similar to nitrosylation or phosphorylation; (2) direct antioxidant effects and (3) interaction with metalloproteins. Its effects on the human cardiovascular system are especially important due to the high prevalence of hypertension and myocardial infarction. The exact molecular targets that affect the vascular tone include the K_ATP channel, the endothelial nitric oxide synthase, the phosphodiesterase of the vascular smooth muscle cell and the cytochrome c oxidase among others and the combination of all these effects lead to the final result on the vascular tone. The relative role of each effect depends immensely on the used concentration and also on the used donor molecules but several other factors and experimental conditions could alter the final effect. The aim of the current review is to give a comprehensive summary of the current understanding on the mechanism of action and role of H₂S in the regulation of vascular tone and to outline the obstacles that hinder the better understanding of its effects.

Hydrogen Sulfide in the Adipose Tissue-Physiology, Pathology and a Target for Pharmacotherapy

Hydrogen sulfide (H₂S) is synthesized in the adipose tissue mainly by cystathionine γ-lyase (CSE). Several studies have demonstrated that H₂S is involved in adipogenesis, that is the differentiation of preadipocytes to adipocytes, most likely by inhibiting phosphodiesterases and increasing cyclic AMP concentration. The effect of H₂S on adipose tissue insulin sensitivity and glucose uptake is controversial. Some studies suggest that H₂S inhibits insulin-induced glucose uptake and that excess of H₂S contributes to adipose tissue insulin resistance in metabolic syndrome. In contrast, other studies have demonstrated that H₂S stimulates glucose uptake and its deficiency contributes to insulin resistance. Similarly, the effect of H₂S on adipose tissue lipolysis is controversial. H₂S produced by perivascular adipose tissue decreases vascular tone by activating ATP-sensitive and/or voltage-gated potassium channels in smooth muscle cells. Experimental obesity induced by high calorie diet has a time dependent effect on H₂S in perivascular adipose tissue; short and long-term obesity increase and decrease H₂S production, respectively. Hyperglycemia has been consistently demonstrated to suppress CSE-H₂S pathway in various adipose tissue depots. Finally, H₂S deficiency may contribute to adipose tissue inflammation associated with obesity/metabolic syndrome.