Hydrogen sulfide depletion contributes to microvascular remodeling in obesity

A novel, microvascular evaluation method and device for early diagnosis of peripheral artery disease and chronic limb-threatening ischemia in individuals with diabetes

Objective

A novel transdermal arterial gasotransmitter sensor (TAGS) has been tested as a diagnostic tool for lower limb microvascular disease in individuals with and without diabetes mellitus (DM).

Methods

The TAGS system noninvasively measures hydrogen sulfide (H2S) emitted from the skin. Measurements were made on the forearm and lower limbs of individuals from three cohorts, including subjects with DM and chronic limb-threatening ischemia, to evaluate skin microvascular integrity. These measurements were compared with diagnosis of peripheral artery disease (PAD) using the standard approach of the toe brachial index. Other measures of vascular health were made in some subjects including fasting blood glucose, hemoglobin A1c, plasma lipids, blood pressure, estimated glomerular filtration, and body mass index.

Results

The leg:arm ratio of H2S emissions correlated with risk factors for microvascular disease (ie, high-density lipoprotein levels, estimated glomerular filtration rate, systolic blood pressure, and hemoglobin A1c). The ratios were significantly lower in symptomatic DM subjects being treated for chronic limb-threatening ischemia (n = 8, 0.48 ± 0.21) compared with healthy controls (n = 5, 1.08 ± 0.30; P = .0001) and with asymptomatic DM subjects (n = 4, 0.79 ± 0.08; P = .0086). The asymptomatic DM group ratios were also significantly lower than the healthy controls (P = .0194). Using ratios of leg:arm transdermal H2S measurement (17 subjects, 34 ratios), the overall accuracy to identify limbs with severe PAD had an area under the curve of the receiver operating curve of 0.93.

Conclusions

Ratios of transdermal H2S measurements are lower in legs with impaired microvascular function, and the decrease in ratio precedes clinically apparent severe microvascular disease and diabetic ulcers. The TAGS instrument is a novel, sensitive tool that may aid in the early detection and monitoring of PAD complications and efforts for limb salvage.

Guidelines on Models of Diabetic Heart Disease

Diabetes is a major risk factor for cardiovascular diseases, including diabetic cardiomyopathy, atherosclerosis, myocardial infarction, and heart failure. As cardiovascular disease represents the number one cause of death in people with diabetes, there has been a major emphasis on understanding the mechanisms by which diabetes promotes cardiovascular disease, and how antidiabetic therapies impact diabetic heart disease. With a wide array of models to study diabetes (both type 1 and type 2), the field has made major progress in answering these questions. However, each model has its own inherent limitations. Therefore, the purpose of this guidelines document is to provide the field with information on which aspects of cardiovascular disease in the human diabetic population are most accurately reproduced by the available models. This review aims to emphasize the advantages and disadvantages of each model, and to highlight the practical challenges and technical considerations involved. We will review the preclinical animal models of diabetes (based on their method of induction), appraise models of diabetes-related atherosclerosis and heart failure, and discuss in vitro models of diabetic heart disease. These guidelines will allow researchers to select the appropriate model of diabetic heart disease, depending on the specific research question being addressed.

H2S alleviates aortic aneurysm and dissection: Crosstalk between transforming growth factor 1 signaling and NLRP3 inflammasome

BACKGROUND

Vascular remodeling and inflammation are involved in aortic aneurysm (AA) and aortic dissection (AD). TGF-β1 signaling is involved in tissue fibrosis, extracellular matrix remodeling and inflammation, which are linked with AA and AD. The inhibition of NLRP3 inflammasome suppresses AA and AD. Hydrogen sulfide (H₂S) exerts anti-vascular remodeling and anti-inflammatory properties, but little is known about its action on AA and AD progression.

METHODS

The effect of H₂S on AA and AD formation was investigated in Sprague-Dawley (SD) rat fed a normal diet supplemented with 0.25% β-aminopropionitrile (BAPN). HE staining, Masson's trichrome staining, Picrosirius red staining and EVG staining were to evaluate vascular remodeling in the aortic wall. Western blotting and IHC were to detect the expression of TGF-β1 and matrix metalloproteinases (MMPs) and NLRP3 inflammasome-associated proteins. The interaction between TGF-β1 signaling and NLRP3 inflammasome was explored in Human aortic vascular smooth muscle cells (HA-VSMCs).

RESULTS

H₂S alleviated AA and AD progression. Specifically, it improved irregular tissue arrangement and vascular fibrosis, increased the expression of elastin fibers, decreased collagen deposition and the expression of TGF-β1 and matrix metalloproteinases (MMP-2/9). In addition, H₂S inhibited the expression of proteins involved in NLRP3 inflammasome. Furthermore, H₂S down-regulated TGF-β1 signaling and then ameliorated vascular fibrosis by preventing NLRP3 inflammasome activation. Finally, H₂S inhibited NLRP3 inflammasome activation and decreased the level of IL-1β by disrupting TGF-β1 signaling.

CONCLUSIONS

These data support a crosstalk between TGF-β1 signaling and NLRP3 inflammasome. H₂S inhibits AA and AD progression via blocking the crosstalk.

Oxidative Stress and Vascular Damage in the Context of Obesity: The Hidden Guest

The vascular system plays a central role in the transport of cells, oxygen and nutrients between different regions of the body, depending on the needs, as well as of metabolic waste products for their elimination. While the structure of different components of the vascular system varies, these structures, especially those of main arteries and arterioles, can be affected by the presence of different cardiovascular risk factors, including obesity. This vascular remodeling is mainly characterized by a thickening of the media layer as a consequence of changes in smooth muscle cells or excessive fibrosis accumulation. These vascular changes associated with obesity can trigger functional alterations, with endothelial dysfunction and vascular stiffness being especially common features of obese vessels. These changes can also lead to impaired tissue perfusion that may affect multiple tissues and organs. In this review, we focus on the role played by perivascular adipose tissue, the activation of the renin-angiotensin-aldosterone system and endoplasmic reticulum stress in the vascular dysfunction associated with obesity. In addition, the participation of oxidative stress in this vascular damage, which can be produced in the perivascular adipose tissue as well as in other components of the vascular wall, is updated.

Selenium-Binding Protein 1 (SELENBP1) Supports Hydrogen Sulfide Biosynthesis and Adipogenesis

Hydrogen sulfide (H₂S), a mammalian gasotransmitter, is involved in the regulation of a variety of fundamental processes including intracellular signaling, cellular bioenergetics, cell proliferation, and cell differentiation. Cystathionine γ-lyase (CSE), cystathionine β-synthase (CBS), and 3-mercaptopyruvate sulfurtransferase (3-MST) are currently considered the three principal mammalian H₂S-generating enzymes. However, recently, a fourth H₂S-producing enzyme, selenium-binding-protein 1 (SELENBP1), has also been identified. The cellular regulatory role(s) of SELENBP1 are incompletely understood. The current study investigated whether SELENBP1 plays a role in the regulation of adipocyte differentiation in vitro. 3T3-L1 preadipocytes with or without SELENBP1 knock-down were subjected to differentiation-inducing conditions, and H₂S production, cellular lipid accumulation, cell proliferation, and mitochondrial activity were quantified. Adipocyte differentiation was associated with an upregulation of H₂S biosynthesis. SELENBP1 silencing decreased cellular H₂S levels, suppressed the expression of the three “classical” H₂S-producing enzymes (CBS, CSE, and 3-MST) and significantly suppressed adipocyte differentiation. Treatment of SELENBP1 knock-down cells with the H₂S donor GYY4137 partially restored lipid accumulation, increased cellular H₂S levels, and exerted a bell-shaped effect on cellular bioenergetics (enhancement at 1 and 3 mM, and inhibition at 6 mM). We conclude that SELENBP1 in adipocytes (1) contributes to H₂S biosynthesis and (2) acts as an endogenous stimulator of adipocyte differentiation.

Bioenergetic effects of hydrogen sulfide suppress soluble Flt-1 and soluble endoglin in cystathionine gamma-lyase compromised endothelial cells

Endothelial dysfunction is a hallmark of preeclampsia, a life-threatening complication of pregnancy characterised by hypertension and elevated soluble Fms-Like Tyrosine Kinase-1 (sFlt-1). Dysregulation of hydrogen sulfide (H₂S) by inhibition of cystathionine γ-lyase (CSE) increases sFlt-1 and soluble endoglin (sEng) release. We explored whether compromise in CSE/H₂S pathway is linked to dysregulation of the mitochondrial bioenergetics and oxidative status. We investigated whether these effects were linked to CSE-induced sFlt-1 and sEng production in endothelial cells. Here, we demonstrate that CSE/H₂S pathway sustain endothelial mitochondrial bioenergetics and loss of CSE increases the production of mitochondrial-specific superoxide. As a compensatory effect, low CSE environment enhances the reliance on glycolysis. The mitochondrial-targeted H₂S donor, AP39, suppressed the antiangiogenic response and restored the mitochondrial bioenergetics in endothelial cells. AP39 revealed that upregulation of sFlt-1, but not sEng, is independent of the mitochondrial H₂S metabolising enzyme, SQR. These data provide new insights into the molecular mechanisms for antiangiogenic upregulation in a mitochondrial-driven environment. Targeting H₂S to the mitochondria may be of therapeutic benefit in the prevention of endothelial dysfunction associated with preeclampsia.

Reversal of prolonged obesity-associated cerebrovascular dysfunction by inhibiting microglial Tak1

Prolonged obesity is associated with cerebrovascular dysfunction; however, the underlying mechanisms remain largely unclear. In the present study, using a prolonged obesity mouse model that suffers from basilar artery (BA) abnormalities, we find that microglial transforming growth factor β-activated kinase 1 (Tak1) is over-activated in the brainstem. Both pharmacological inhibition primarily in the brainstem and genetic microglia-selective deletion of Tak1 ameliorated BA vascular dysfunction. Conversely, microglia-specific activation of Tak1 in the brainstem was sufficient to cause an impairment in BA function in chow-fed mice. Mechanistically, Tak1 activation leads to increased interleukin-18 (IL-18) production, whereas blockade of IL-18 receptor in the brain helped protect against cerebrovascular dysfunction despite prolonged obesity. Microglia-selective deletion of Tak1 also protects against ischemic stroke in prolonged obesity. Taken together, these findings provide evidence that microglial Tak1 in the brain, and particularly the brainstem, contributes to the pathogenesis of obesity-associated cerebrovascular dysfunction.

Immunomodulatory Effects of Glutathione, Garlic Derivatives, and Hydrogen Sulfide

Glutathione and aged garlic extract are sulfur-containing products that play important protective and regulatory roles within the immune system and in oxidative processes. Hydrogen sulfide (H₂S), an endogenous, gaseous, signaling transmitter, has also been shown to be involved in the regulation of inflammation. Recent studies have shown that sulfur-containing compounds from garlic have beneficial effects in attenuating outcomes associated with cardiovascular disease and inflammation by a mechanism that may be related to the H₂S signaling pathway. In this review, we summarize the main functions of glutathione (GSH), garlic derivatives and H₂S and their role in the immune response and impact on health and disease.

A Postmortem Study of Frontal and Temporal Gyri Thickness and Cell Number in Human Obesity

OBJECTIVE

This study aimed to compare cortex thickness and neuronal cell density in postmortem brain tissue from people with overweight or obesity and normal weight.

METHODS

The cortex thickness and neuron density of eight donors with overweight or obesity (mean = 31.6 kg/m² ; SD = 4.35; n = 8; 6 male) and eight donors with normal weight (mean = 21.8 kg/m² ; SD = 1.5; n = 8; 5 male) were compared. All participants were Mexican and lived in Mexico City. Randomly selected thickness measures of different cortex areas from the frontal and temporal lobes were analyzed based on high-resolution real-size photographs. A histological analysis of systematic-random fields was used to quantify the number of neurons in postmortem left and right of the first, second, and third gyri of frontal and temporal lobe brain samples.

RESULTS

No statistical difference was found in cortical thickness between donors with overweight or obesity and individuals with normal weight. A smaller number of neurons was found among the donors with overweight or obesity than the donors with normal weight at different frontal and temporal areas.

CONCLUSIONS

A lower density of neurons is associated with overweight or obesity. The morphological basis for structural brain changes in obesity requires further investigation.

Cystathionine gamma-lyase/hydrogen sulfide system is essential for adipogenesis and fat mass accumulation in mice

Hydrogen sulfide (H₂S) has been recognized as an important gasotransmitter analogous to nitric oxide and carbon monoxide. Cystathionine gamma-lyase (CSE)-derived H₂S is implicated in the regulation of insulin resistance and glucose metabolism, but the involvement of CSE/H₂S system in energy homeostasis and fat mass has not been extensively explored. In this study, a potential functional role of the CSE/H₂S system in in vitro adipocyte differentiation and in vivo adipogenesis and the underlying mechanism was investigated. CSE expression and H₂S production were increased during adipocyte differentiation, and that the pattern of CSE mRNA expression was similar to that of CCAAT/enhancer-binding protein (C/EBP) β and δ, two key regulators for adipogenesis. C/EBPβ and γ bind to the CCAAT box in CSE promoter and stimulate CSE gene transcription. H₂S induced PPARγ transactivation activity by S-sulfhydrating all the cysteine residues in the DNA binding domain and stimulated adipogenesis. High fat diet-induced fat mass was lost in CSE deficient mice, and exogenously applied H₂S promoted fat mass accumulation in fruit flies. In conclusion, CSE/H₂S system is essential for adipogenesis and fat mass accumulation through enhancement of PPARγ function in adipocytes. This study suggests that the CSE/H₂S system is involved in the pathogenesis of obesity in mice.

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.

Microvascular Endothelial Dysfunction in Obesity Is Driven by Macrophage-Dependent Hydrogen Sulfide Depletion

Objective—

The function of perivascular adipose tissue as an anticontractile mediator in the microvasculature is lost during obesity. Obesity results in inflammation and recruitment of proinflammatory macrophages to the perivascular adipose tissue that is paralleled by depletion of the vasorelaxant signaling molecule hydrogen sulfide (H 2 S) in the vessel. The current objective was to assess the role of macrophages in determining vascular [H 2 S] and defining how this impinged on vasodilation.

Approach and Results—

Contractility and [H 2 S] were measured in mesenteric resistance arterioles from lean and obese mice by using pressure myography and confocal microscopy, respectively. Vasodilation was impaired and smooth muscle and endothelial [H 2 S] decreased in vessels from obese mice compared with those from lean controls. Coculturing vessels from lean mice with macrophages from obese mice, or macrophage-conditioned media, recapitulated obese phenotypes in vessels. These effects were mediated by low molecular weight species and dependent on macrophage inducible nitric oxide synthase activity.

Conclusions—

The inducible nitric oxide synthase activity of perivascular adipose tissue–resident proinflammatory macrophages promotes microvascular endothelial dysfunction by reducing the bioavailability of H 2 S in the vessel. These findings support a model in which vascular H 2 S depletion underpins the loss of perivascular adipose tissue anticontractile function in obesity.

Perivascular adipose tissue as a regulator of vascular disease pathogenesis: identifying novel therapeutic targets

Adipose tissue (AT) is an active endocrine organ with the ability to dynamically secrete a wide range of adipocytokines. Importantly, its secretory profile is altered in various cardiovascular disease states. AT surrounding vessels, or perivascular AT (PVAT), is recognized in particular as an important local regulator of vascular function and dysfunction. Specifically, PVAT has the ability to sense vascular paracrine signals and respond by secreting a variety of vasoactive adipocytokines. Due to the crucial role of PVAT in regulating many aspects of vascular biology, it may constitute a novel therapeutic target for the prevention and treatment of vascular disease pathogenesis. Signalling pathways in PVAT, such as those using adiponectin, H₂ S, glucagon-like peptide 1 or pro-inflammatory cytokines, are among the potential novel pharmacological therapeutic targets of PVAT.

LINKED ARTICLES

This article is part of a themed section on Molecular Mechanisms Regulating Perivascular Adipose Tissue - Potential Pharmacological Targets? To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.20/issuetoc.

H2S biosynthesis and catabolism: new insights from molecular studies

Hydrogen sulfide (H₂S) has profound biological effects within living organisms and is now increasingly being considered alongside other gaseous signalling molecules, such as nitric oxide (NO) and carbon monoxide (CO). Conventional use of pharmacological and molecular approaches has spawned a rapidly growing research field that has identified H₂S as playing a functional role in cell-signalling and post-translational modifications. Recently, a number of laboratories have reported the use of siRNA methodologies and genetic mouse models to mimic the loss of function of genes involved in the biosynthesis and degradation of H₂S within tissues. Studies utilising these systems are revealing new insights into the biology of H₂S within the cardiovascular system, inflammatory disease, and in cell signalling. In light of this work, the current review will describe recent advances in H₂S research made possible by the use of molecular approaches and genetic mouse models with perturbed capacities to generate or detoxify physiological levels of H₂S gas within tissues.