Decreased vascular H2S production is associated with vascular oxidative stress in rats fed a high-fat western diet

Protective role of 3-mercaptopyruvate sulfurtransferase (MPST) in the development of metabolic syndrome and vascular inflammation

Metabolic syndrome (MetS) is a cluster of metabolic abnormalities that occur concurrently and increase the risk of cardiovascular disease. 3-mercaptopyruvate sulfurtransferase (MPST) is a cysteine-catabolizing enzyme that yields pyruvate and hydrogen sulfide (H2S) and plays a central role in the regulation of energy homeostasis. Herein, we seek to investigate the role of MPST/H2S in MetS and its cardiovascular consequences using a mouse model of the disease. Mice were fed a high-fat diet (HFD) for 15 weeks to induce obesity and hyperglycemia and administrated a nitric oxide synthase inhibitor, during the last 5 weeks to induce hypertension and MetS. This model caused a mild left ventricular (LV) diastolic dysfunction and vascular endothelial dysfunction. Free H2S and sulfane-sulfur levels were decreased in the aorta, but unaltered in the heart. Also, downregulation of MPST and thiosulfate sulfuretransferase (TST) were observed in the aorta. Global deletion of Mpst (Mpst-/-) resulted in increased body weight and greater glucose intolerance in mice with MetS, without affecting their blood pressure, and caused an upregulation of genes involved in immune responses in the vasculature suggestive of T-cell infiltration and activation. Pharmacological restoration of H2S levels ameliorated the comorbidities of MetS; GYY4137 administration reduced body weight and blood pressure, attenuated cardiac fibrosis and improved glucose handling and endothelium-dependent relaxation. In conclusion, this study found that reduced MPST/H2S exacerbates the pathological changes associated with MetS and contributes to vascular inflammation. H2S supplementation emerges as a potential therapeutic approach to treat the abnormalities associated with MetS.

Hydrogen Sulfide and Irisin, Potential Allies in Ensuring Cardiovascular Health

Irisin is a myokine secreted under the influence of physical activity and exposure to low temperatures and through different exogenous stimuli by the cleavage of its precursor, fibronectin type III domain-containing protein 5 (FNDC5). It is mainly known for maintaining of metabolic homeostasis, promoting the browning of white adipose tissue, the thermogenesis process, and glucose homeostasis. Growing experimental evidence suggests the possible central role of irisin in the regulation of cardiometabolic pathophysiological processes. On the other side, hydrogen sulfide (H2S) is well recognized as a pleiotropic gasotransmitter that regulates several homeostatic balances and physiological functions and takes part in the pathogenesis of cardiometabolic diseases. Through the S-persulfidation of cysteine protein residues, H2S is capable of interacting with crucial signaling pathways, exerting beneficial effects in regulating glucose and lipid homeostasis as well. H2S and irisin seem to be intertwined; indeed, recently, H2S was found to regulate irisin secretion by activating the peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α)/FNDC5/irisin signaling pathway, and they share several mechanisms of action. Their involvement in metabolic diseases is confirmed by the detection of their lower circulating levels in obese and diabetic subjects. Along with the importance of metabolic disorders, these modulators exert favorable effects against cardiovascular diseases, preventing incidents of hypertension, atherosclerosis, heart failure, myocardial infarction, and ischemia-reperfusion injury. This review, for the first time, aims to explore the role of H2S and irisin and their possible crosstalk in cardiovascular diseases, pointing out the main effects exerted through the common molecular pathways involved.

Metabolic changes with the occurrence of atherosclerotic plaques and the effects of statins

Atherosclerosis is a common cardiovascular disease caused by the abnormal expression of multiple factors and genes influenced by both environmental and genetic factors. The primary manifestation of atherosclerosis is plaque formation, which occurs when inflammatory cells consume excess lipids, affecting their retention and modification within the arterial intima. This triggers endothelial cell (EC) activation, immune cell infiltration, vascular smooth muscle cell (VSMC) proliferation and migration, foam cell formation, lipid streaks, and fibrous plaque development. These processes can lead to vascular wall sclerosis, lumen stenosis, and thrombosis. Immune cells, ECs, and VSMCs in atherosclerotic plaques undergo significant metabolic changes and inflammatory responses. The interaction of cytokines and chemokines secreted by these cells leads to the onset, progression, and regression of atherosclerosis. The regulation of cell- or cytokine-based immune responses is a novel therapeutic approach for atherosclerosis. Statins are currently the primary pharmacological agents utilised for managing unstable plaques owing to their ability to enhance endothelial function, regulate VSMC proliferation and apoptosis by reducing cholesterol levels, and mitigate the expression and activity of inflammatory cytokines. In this review, we provide an overview of the metabolic changes associated with atherosclerosis, describe the effects of inflammatory responses on atherosclerotic plaques, and discuss the mechanisms through which statins contribute to plaque stabilisation. Additionally, we examine the role of statins in combination with other drugs in the management of atherosclerosis.

Effect of consumption of whole egg and egg fractions on cardiovascular disease factors in adult rats

BACKGROUND

While eggs are a low-cost source of protein, rich in macro- and micronutrients, the association of egg intake and cardiovascular disease (CVD) remains controversial. This study investigated the effect of egg consumption on CVD parameters. Eggs were boiled, separated into four fractions (whole egg, 50% yolk-reduced whole egg, egg yolk and egg white) and then freeze-dried. The different egg fractions or distilled water (control) were orally gavaged to adult male Wistar rats at 1 g kg^-1 rat body weight, each day for 8 weeks, following which basal blood pressure, heart rate, complete blood cell count, blood biochemistry, body fat and liver cell lipid accumulation were determined. The vascular functions of isolated thoracic aorta were studied using classical pharmacological techniques.

RESULTS

In comparison to the control group, none of the egg fractions affected body weight, food intake, plasma glucose or lipid profile. The yolk group experienced increased plasma alkaline phosphatase and creatinine levels, while egg white caused decreased plasma cholesterol and blood urea nitrogen. Whole egg and egg yolk increased blood pressure and mean hemoglobin concentration and the yolk increased liver lipid accumulation. Egg white decreased the white blood cell count and body fat lipids. No changes were found in basal heart rate or vascular functions in any of the groups.

CONCLUSIONS

Consumption of whole egg or egg yolk at the dosage given caused hypertension, with impairment of liver and kidney functions following the intake of yolk alone. However, egg white is beneficial for the cardiovascular system as it decreased plasma cholesterol and body fat accumulation. © 2020 Society of Chemical Industry.

High metabolic substrate load induces mitochondrial dysfunction in rat skeletal muscle microvascular endothelial cells

The influence of glucose and palmitic acid (PA) on mitochondrial respiration and emission of hydrogen peroxide (H2 O2 ) was determined in skeletal muscle-derived microvascular endothelial cells. Measurements were assessed in intact and permeabilized (cells treated with 0.025% saponin) low passage endothelial cells with acute-or prolonged (3 days) incubation with regular (1.7 mM) or elevated (2.2 mM) PA concentrations and regular (5 mM) or elevated (11 mM) glucose concentrations. In intact cells, acute incubation with 1.7 mM PA alone or with 1.7 mM PA + 5 mM glucose (p < .001) led to a lower mitochondrial respiration (p < 0.01) and markedly higher H2 O2 /O2 emission (p < 0.05) than with 5 mM glucose alone. Prolonged incubation of intact cells with 1.7 mM PA +5 mM glucose led to 34% (p < 0.05) lower respiration and 2.5-fold higher H2 O2 /O2 emission (p < 0.01) than incubation with 5 mM glucose alone. Prolonged incubation of intact cells with elevated glucose led to 60% lower (p < 0.05) mitochondrial respiration and 4.6-fold higher H2 O2 /O2 production than incubation with 5 mM glucose in intact cells (p < 0.001). All effects observed in intact cells were present also in permeabilized cells (State 2). In conclusion, our results show that acute and prolonged lipid availability, as well as prolonged hyperglycemia, induces mitochondrial dysfunction as evidenced by lower mitochondrial respiration and enhanced H2 O2/ O2 emission. Elevated plasma substrate availability may lead to microvascular dysfunction in skeletal muscle by impairing endothelial mitochondrial function.

Diet and Hydrogen Sulfide Production in Mammals

Significance: In recent times, it has emerged that some dietary sulfur compounds can act on mammalian cell signaling systems via their propensity to release hydrogen sulfide (H₂S). H₂S plays important biochemical and physiological roles in the heart, gastrointestinal tract, brain, kidney, and immune systems of mammals. Reduced levels of H₂S in cells and tissues correlate with a spectrum of pathophysiological conditions, including heart disease, diabetes, obesity, and altered immune function. Recent Advances: In the last decade, researchers have now begun to explore the mechanisms by which dietary-derived sulfur compounds, in addition to cysteine, can act as sources of H₂S. This research has led to the identified several compounds, organic sulfides, isothiocyanates, and inorganic sulfur species including sulfate that can act as potential sources of H₂S in mammalian cells and tissues. Critical Issues: We have summarised progress made in the identification of dietary factors that can impact on endogenous H₂S levels in mammals. We also describe current research focused on how some sulfur molecules present in dietary plants, and associated chemical analogues, act as sources of H₂S, and discuss the biological properties of these molecules as studied in a range of in vitro and in vivo systems. Future Directions: The identification of sulfur compounds in edible plants that can act as novel H₂S releasing molecules is intriguing. Research in this area could inform future studies exploring the impact of diet on H₂S levels in mammalian systems. Despite recent progress, additional work is needed to determine the mechanisms by which H₂S is released from these molecules following ingestions of dietary plants in humans, whether the amounts of H₂S produced is of physiological significance following the metabolism of these compounds in vivo, and if diet could be used to manipulated H₂S levels in humans. Importantly, this will lead to a better understanding of the biological significance of H₂S generated from dietary sources, and this information could be used in the development of plant breeding initiatives to increase the levels of H₂S releasing sulfur compounds in crops, or inform dietary intervention strategies that could be used to alter the levels of H₂S in humans.

Metabolism of vascular smooth muscle cells in vascular diseases

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

Sodium Tanshinone IIA Sulfonate Attenuates Erectile Dysfunction in Rats with Hyperlipidemia

Hyperlipidemia is considered one of the most important risk factors for erectile dysfunction (ED). To determine the effect of sodium tanshinone IIA sulfonate (STS) as an antioxidant agent on ED in high-fat diet- (HFD-) induced hyperlipidemia in rats and to investigate if STS administration could improve erectile function via hydrogen sulfide (H₂S) production by inhibition of oxidative stress. Hyperlipidemia was induced in Sprague-Dawley rats by feeding HFD for 16 weeks. The rats were randomly divided into 3 groups: control, HFD, and HFD treated with STS (10 mg/kg/day for 12 weeks, intraperitoneal injection). Erectile function including intracavernosal pressure (ICP), H₂S production, and antioxidant capacity was assessed. In addition, cavernosal smooth muscle cells (CSMC) isolated from SD rats were pretreated with STS in vitro and exposed to H₂O₂. Expressions of nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1), activity of antioxidant enzymes, and H₂S-generating enzymes within CSMC were examined. ICP was significantly decreased in HFD rats compared with control. In addition, decreased H₂S production and expression of cystathionine ɣ-lyase (CSE) and cystathionine β-synthase (CBS) associated with increased oxidative stress were observed in the penile tissue of HFD rats. However, all these changes were reversed by 16 weeks after STS administration. STS also increased antioxidant defense as evidenced by increased expression of Nrf2/HO-1 in the penile tissue of HFD rats. In CSMC, pretreatment with STS attenuated the decreased expression of CSE and CBS and H₂S production by H₂O₂. STS exerted similar protective antioxidative effect as shown in the in vivo hyperlipidemia model. The present study demonstrated the redox effect of STS treatment on ED via increased H₂S production in HFD-induced hyperlipidemia rat model by increased antioxidant capacity via activation of the Nrf2/HO-1 pathway, which provides STS potential clinical application in the treatment of hyperlipidemia-related ED.

Gut microbiota and neuroinflammation in pathogenesis of hypertension: A potential role for hydrogen sulfide

Inflammation and gut dysbiosis are hallmarks of hypertension (HTN). Hydrogen sulfide (H2S) is an important freely diffusing molecule that modulates the function of neural, cardiovascular and immune systems, and circulating levels of H2S are reduced in animals and humans with HTN. While most research to date has focused on H₂S produced endogenously by the host, H2S is also produced by the gut bacteria and may affect the host homeostasis. Here, we review an association between neuroinflammation and gut dysbiosis in HTN, with special emphasis on a potential role of H2S in this interplay.

Application of high-fat cell model in steady-state regulation of vascular function

In order to effectively apply the high-fat cell model to the regulation of vascular homeostasis and the repair of vascular endothelial cell injury, and to provide a new theoretical basis for the treatment of vascular homeostasis imbalance in the future, in this study, the mouse thoracic aorta tissue is extracted by using mouse endothelial cells. Western blotting and immunofluorescence resonance energy transfer (Immuno-FRET) are then used to verify the distribution and physical coupling properties of TRPV4 and Nox2 in cells. Finally, mouse mesenteric endothelial cells are isolated and cultured to induce FFA high-fat cell model. The results show that the nucleic acid expression levels of TRPV4 and Nox2 in RNA are significantly different from those of TRPV4 and Nox2 in protein. The relative values of TRPV4 and Nox2 in the control group are relatively low (0.8 ± 0.11). However, the relative values of TRPV4 and Nox2 are higher in the FFA high-fat cell model induced by the experimental group, and the values are (1.7 ± 0.8). Obviously, the relative values of TRPV4 and Nox2 in the experimental group are higher than those in the control group. The expression of reactive oxygen species (ROS) in vascular endothelial cells of control group is (1.0 ± 0.16), and that in FFA group is (2.5 ± 0.46). The expression of ROS in FFA cell model with HC067047A inhibitor is (1.5 ± 0.38). In the FFA cell model with apo inhibitor, ROS expression is (1.2 ± 0.23). Thus, in the FFA high-fat cell model induced successfully, the physical coupling of TRPV4 and Nox2 increases in primary endothelial cells, and the increase of physical coupling of TRPV4 and Nox2 results in the increase of ROS expression, which also means the imbalance of ROS homeostasis in vascular endothelial cells and the change of vascular endothelial cell permeability. The expression levels of TRPV4 and Nox2 are used as indicators of whether the vascular function is stable or unbalanced, thus providing a new theoretical basis for the treatment of cardiovascular diseases.

[PYRIDOXAL-5-PHOSPHATE RESTORES HYDROGEN SULFIDE SYNTHES AND REDOX STATE OF HEART AND BLOOD VESSELS TISSUE IN OLD ANIMALS]

It was shown the alterations in hydrogen sulfide (H(2)S) metabolism and the development of oxidative and nitrozative stress in cardiovascular system by aging. The administration of pyridoxal-5-phosphate as cofactor of H(2)S synthesizing enzymes restored endogenous H(2)S level and redox state in the heart and aorta tissues. Under these conditions, the following indicators of oxidative stress were significantly decreased in heart and aorta tissues: superoxide generation rate (·0(2)(-)) and hydroxyl (·OH) anion radicals, compared with significantly elevated levels of these parameters in old animals. We also found the reduction of non-enzymatic (diene conjugates and malonic dialdehyde) and enzymatic (uric acid, LTC(4) and TxB(2)) lipid oxidation products levels in old rats under H(2)S synthesis stimulation that confirms the restriction of oxidative stress. An important consequence of endogenous synthesis stimulation of hydrogen sulfide during aging is a decrease of nitrozative stress, such as iNOS activity and nitrate reductase, as well as recovery of constitutive NO synthase activity, indicating the importance of this gas transmitter in cardiovascular system. Thus, stimulation of hydrogen sulfide endogenous synthesis contributed to reduced production of reactive oxygen species (oxidative stress) and nitrogen (nitrozative stress) in heart and aorta tissues with aging. The presence of a pronounced antioxidant effect and modulating influence of pyridoxal-5- phosphate in the redox state of heart tissue and blood vessels during aging suggests cardioprotective properties of the substance and prospects for future research.

Dietary and Endocrine Regulation of Endogenous Hydrogen Sulfide Production: Implications for Longevity

SIGNIFICANCE

Hydrogen sulfide (H₂S) at the right concentration is associated with numerous health benefits in experimental organisms, ranging from protection from ischemia/reperfusion injury to life span extension. Given the considerable translation potential, two major strategies have emerged: supplementation of exogenous H₂S and modulation of endogenous H₂S metabolism. Recent Advances: Recently, it was reported that hepatic H₂S production capacity is increased in two of the best-characterized mammalian models of life span extension, dietary restriction, and hypopituitary dwarfism, leading to new insights into dietary and hormonal regulation of endogenous H₂S production together with broader changes in sulfur amino acid (SAA) metabolism with implications for DNA methylation and redox status.

CRITICAL ISSUES

Here, we discuss the role of dietary SAAs and growth hormone (GH)/thyroid hormone (TH) signaling in regulation of endogenous H₂S production largely via repression of H₂S generating enzymes cystathionine γ-lyase (CGL) and cystathionine β-synthase (CBS) on the level of gene transcription, as well as reciprocal regulation of GH and TH signaling by H₂S itself. We also discuss plasticity of CGL and CBS gene expression in response to environmental stimuli and the potential of the microbiome to impact overall H₂S levels.

FUTURE DIRECTIONS

The relative contribution of increased H₂S to health span or lifespan benefits in models of extended longevity remains to be determined, as does the mechanism by which such benefits occur. Nonetheless, our ability to control H₂S levels using exogenous H₂S donors or by modifying the endogenous H₂S production/consumption equilibrium has the potential to improve health and increase "shelf-life" across evolutionary boundaries, including our own. Antioxid. Redox Signal. 28, 1483-1502.

Reduced adipose tissue H2S in obesity

Hydrogen sulfide (H₂S) is an endogenously produced signaling molecule synthesized by cystathionine γ-lyase (CSE), cystathionine β-synthase (CBS) and 3-mercaptopyruvate sulfurtransferase (3-MST). Given that H₂S exerts significant effects on bioenergetics and metabolism, the goal of the current study was to determine the expression of H₂S-producing enzymes in adipose tissues in models of obesity and metabolic disruption. Mice fed a western diet expressed lower mRNA levels of all three enzymes in epididymal fat (EWAT), while only CSE and 3-MST were reduced in brown adipose tissue (BAT). At the protein level 3-MST was reduced in all fat depots studied. Using db/db mice, a genetic model of obesity, we found that CSE, CBS and 3-MST mRNA were reduced in white fat, while only CSE was reduced in BAT. CBS and CSE protein levels were suppressed in all three fat depots. In a model of age-related weight gain, no reduction in the mRNA of any of the enzymes was noted. Smaller amounts of 3-MST protein were found in EWAT, while both CSE and 3-MST were reduced in BAT. Tissue levels of H₂S were lower in WAT in HFD mice; both WAT and BAT contained lower H₂S amounts in db/db animals. Taken together, our data suggest that obesity is associated with a decreased expression of H₂S-synthesizing enzymes and reduced H₂S levels in adipose tissues of mice. We propose that the reduction in H₂S may contribute to the metabolic response associated with obesity. Further work is needed to determine whether restoring H₂S levels may have a beneficial effect on obesity-associated metabolic alterations.

Tocotrienol-Rich Tocomin Attenuates Oxidative Stress and Improves Endothelium-Dependent Relaxation in Aortae from Rats Fed a High-Fat Western Diet

We have previously reported that tocomin, a mixture high in tocotrienol content and also containing tocopherol, acutely preserves endothelial function in the presence of oxidative stress. In this study, we investigated whether tocomin treatment would preserve endothelial function in aortae isolated from rats fed a high-fat diet known to cause oxidative stress. Wistar hooded rats were fed a western diet (WD, 21% fat) or control rat chow (standard diet, 6% fat) for 12 weeks. Tocomin (40 mg/kg/day sc) or its vehicle (peanut oil) was administered for the last 4 weeks of the feeding regime. Aortae from WD rats showed an impairment of endothelium-dependent relaxation that was associated with an increased expression of the NADPH oxidase Nox2 subunit and an increase in the vascular generation of superoxide measured using L-012 chemiluminescence. The increase in vascular oxidative stress was accompanied by a decrease in basal NO release and impairment of the contribution of NO to ACh-induced relaxation. The impaired relaxation is likely contributed to by a decreased expression of eNOS, calmodulin, and phosphorylated Akt and an increase in caveolin. Tocotrienol rich tocomin, which prevented the diet-induced changes in vascular function, reduced vascular superoxide production and abolished the diet-induced changes in eNOS and other protein expression. Using selective inhibitors of nitric oxide synthase (NOS), soluble guanylate cyclase (sGC) and calcium-activated potassium (K_Ca) channels we demonstrated that tocomin increased NO-mediated relaxation, without affecting the contribution of endothelium-dependent hyperpolarization type relaxation to the endothelium-dependent relaxation. The beneficial actions of tocomin in this diet-induced model of obesity suggest that it may have potential to be used as a therapeutic agent to prevent vascular disease in obesity.