H2 S donor improves heart function and vascular relaxation in diabetes.

BACKGROUND AND AIMS: Diabetes dramatically increases the risk of cardiovascular complications and mortality. Hydrogen sulphide plays an important role in reducing oxidative stress. Several studies demonstrated that hydrogen sulphide protects islet beta cells from oxidant stress damage and decreases apoptosis. The aim of the work is to investigate the effect of hydrogen sulphide donor on heart functions and endothelium-dependent relaxation of aortic smooth muscle in diabetes. MATERIALS AND METHODS: Rats were divided into control and diabetic groups. Diabetes mellitus was induced with a single intraperitoneally injection of streptozotocin (60 mg kg-1 ). The functional cardiohemodynamic indicators were registered via microcatheter and Pressure-Volume System. The sodium hydrosulphide NaHS (15.8 mg kg-1 ) was administered intraperitoneally. The contractile activity of the muscle preparations of the thoracic aorta was recorded using a strain gauge. RESULTS: We demonstrate that the NaHS improves pumping function and restores diastolic heart function in streptozotocin-induced (STZ) diabetes rats. We show that pretreatment with NaHS increased the stroke volume by 43.1%, and the ejection fraction increased by 48.64%. NaHS improves the ventriculo-arterial coupling and increases by 3.4 times acetylcholine-induced relaxation of the aorta in diabetic rats. The inhibition of NOS activity by blocker L-NAME abolished NaHS-mediated vasodilatation in the intact endothelium of the aorta in diabetes. It indicates that the NaHS caused vasodilatation by a NOS-dependent mechanism. CONCLUSION: The exogenous hydrogen sulphide can improve pumping function and restore diastolic heart function in diabetes. The pretreatment with NaHS can prevent endothelial dysfunction in diabetes due to the NOS-dependent mechanism.

The quest for endothelial atypical cannabinoid receptor: BKCa channels act as cellular sensors for cannabinoids in in vitro and in situ endothelial cells.

Endothelium-dependent component of cannabinoid-induced vasodilation has been postulated to require G-protein-coupled non-CB1/CB2 endothelial cannabinoid (eCB) receptor. GPR18 was proposed as a candidate for eCBR. To address the hypothesis that the effects attributed to eCBR are mediated by G-protein-coupled receptor (GPCR)-independent targets, we studied the electrical responses in endothelial cells, focusing on BKCa channels. In patches excised from endothelial-derived EA.hy926 cells, N-arachidonoyl glycine (NAGly) and abnormal cannabidiol (abn-cbd), prototypical agonists for eCB receptor, stimulate single BKCa activity in a concentration- and Ca2+-dependent manner. The postulated eCB receptor inhibitors rimonabant and AM251 were found to inhibit basal and stimulated by NAGly- and abn-cbd BKCa activity in cell-free patches. In isolated mice aortas, abn-cbd and NAGly produced endothelial cell hyperpolarization that was sensitive to paxilline, a selective BKCa inhibitor, but not to GPR18 antibody, and mimicked by NS1619, a direct BKCa opener. In excised patches from mice aortic endothelium, single channel activity with characteristics similar to BKCa was established by the addition of abn-cbd and NAGly. We conclude that the two cannabinoids abn-cbd and NAGly initiate a GPR18-independent activation of BKCa channels in mice aortic endothelial cells that might contribute to vasodilation to cannabinoids.

N-Arachidonoyl glycine suppresses Na⁺/Ca²âº exchanger-mediated Ca²âº entry into endothelial cells and activates BK(Ca) channels independently of GPCRs.

BACKGROUND AND PURPOSE: N-Arachidonoyl glycine (NAGly) is a lipoamino acid with vasorelaxant properties. We aimed to explore the mechanisms of NAGly's action on unstimulated and agonist-stimulated endothelial cells. EXPERIMENTAL APPROACH: The effects of NAGly on endothelial electrical signalling were studied in combination with vascular reactivity. KEY RESULTS: In EA.hy926 cells, the sustained hyperpolarization to histamine was inhibited by the non-selective Na⁺/Ca²âº exchanger (NCX) inhibitor bepridil and by an inhibitor of reversed mode NCX, KB-R7943. In cells dialysed with Cs⁺-based Na⁺-containing solution, the outwardly rectifying current with typical characteristics of NCX was augmented following histamine exposure, further increased upon external Na⁺ withdrawal and inhibited by bepridil. NAGly (0.3-30 µM) suppressed NCX currents in a URB597- and guanosine 5'-O-(2-thiodiphosphate) (GDPßS)-insensitive manner, [Ca²âº]i elevation evoked by Na⁺ removal and the hyperpolarization to histamine. In rat aorta, NAGly opposed the endothelial hyperpolarization and relaxation response to ACh. In unstimulated EA.hy926 cells, NAGly potentiated the whole-cell current attributable to large-conductance Ca²âº-activated K⁺ (BK(Ca)) channels in a GDPßS-insensitive, paxilline-sensitive manner and produced a sustained hyperpolarization. In cell-free inside-out patches, NAGly stimulated single BK(Ca) channel activity. CONCLUSION AND IMPLICATIONS: Our data showed that NCX is a Ca²âº entry pathway in endothelial cells and that NAGly is a potent G-protein-independent modulator of endothelial electrical signalling and has a dual effect on endothelial electrical responses. In agonist pre-stimulated cells, NAGly opposes hyperpolarization and relaxation via inhibition of NCX-mediated Ca²âº entry, while in unstimulated cells, it promotes hyperpolarization via receptor-independent activation of BK(Ca) channels.