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High glucose (HG)‐induced dysfunction of vascular endothelial cells plays a crucial role in the development of diabetic vascular complications. Inhibition of cystathionine γ‐synthase/hydrogen sulfide (CSE/H2S) pathway is one of the causes of vascular endothelial cell injury induced by HG. Dopamine D1 receptors (DR1) are widely expressed and regulate important physiological functions in the vascular system. However, the effect of DR1 inhibition on HG‐induced vascular endothelial apoptosis by regulating the CSE/H2S pathway is unclear. Therefore, we aimed to determine if DR1 can regulate the CSE/H2S pathway and regulate the effect of DR1 on HG‐induced apoptosis in human umbilical vein endothelial cells. In this study, we found that HG treatment significantly decreased the expression of DR1 and CSE and the endogenous content of H2S; DR1 agonist SKF 38393 reversed these effects, while sodium hydrosulfide (NaHS) only increased CSE expression and the endogenous H2S production and had no effect on DR1 expression. Meanwhile, HG significantly increased the intracellular calcium concentration ([Ca2+]i), and SKF 38393 further increased HG‐induced [Ca2+]i. In addition, HG increased the lactate dehydrogenase activity, malondialdehyde and reactive oxygen species contents, apoptotic rate, the expression of cleaved caspase‐3, caspase‐9, and cytochrome c, and the activity of phosphorylated‐inhibitor of nuclear factor‐kappaBα (NF‐κBα) (p‐IκBα) and phosphorylated‐NF‐κB (p‐NF‐κB), and reduced cell viability, superoxide dismutase activity, and Bcl‐2 expressions. SKF 38393 and NaHS markedly reversed the effect of HG. The effect of SKF 38393 was similar to N‐acetyl‐ l‐cysteine (an inhibitor of oxidative stress) or pyrrolidinedithiocarbamate ammonium (an NF‐kB inhibitor). Taken together, DR1 upregulates the CSE/H2S pathway by increasing the [Ca2+]i, which inhibits HG‐induced apoptosis via downregulating NF‐κB/IκBα pathway in vascular endothelial cells. [ABSTRACT FROM AUTHOR]

A growing body of evidence suggests that hydrogen sulfide (H2S) is a signaling molecule in mammalian cells. In the cardiovascular system, H2S enhances vasodilation and angiogenesis. H2S-induced vasodilation is hypothesized to occur through ATP-sensitive potassium channels (KATP); however, we recently demonstrated that it also increases cGMP levels in tissues. Herein, we studied the involvement of cGMP-dependent protein kinase-I in H2S-induced vasorelaxation. The effect of H2S on vessel tone was studied in phenylephrine-contracted aortic rings with or without endothelium. cGMP levels were determined in cultured cells or isolated vessel by enzyme immunoassay. Pretreatment of aortic rings with sildenafil attenuated NaHS-induced relaxation, confirming previous findings that H2S is a phosphodiesterase inhibitor. In addition, vascular tissue levels of cGMP in cystathionine gamma lyase knockouts were lower than those in wild-type control mice. Treatment of aortic rings with NaHS, a fast releasing H2S donor, enhanced phosphorylation of vasodilator-stimulated phosphoprotein in a time-dependent manner, suggesting that cGMP-dependent protein kinase (PKG) is activated after exposure to H2S. Incubation of aortic rings with a PKG-I inhibitor (DT-2) attenuated NaHS-stimulated relaxation. Interestingly, vasodilatory responses to a slowly releasing H2S donor (GYY 4137) were unaffected by DT-2, suggesting that this donor dilates mouse aorta through PKG-independent pathways. Dilatory responses to NaHS and L-cysteine (a substrate for H2S production) were reduced in vessels of PKG-I knockout mice (PKG-I-/-). Moreover, glibenclamide inhibited NaHSinduced vasorelaxation in vessels from wild-type animals, but not PKG-I-/-, suggesting that there is a cross-talk between KATP and PKG. Our results confirm the role of cGMP in the vascular responses to NaHS and demonstrate that genetic deletion of PKG-I attenuates NaHS and L-cysteine-stimulated vasodilation. [ABSTRACT FROM AUTHOR]