Ethanol induces vascular relaxation via redox-sensitive and nitric oxide-dependent pathways

AbstractWe investigated the role of reactive oxygen species (ROS) and nitric oxide (NO) in ethanol-induced relaxation. Vascular reactivity experiments showed that ethanol (0.03–200mmol/L) induced relaxation in endothelium-intact and denuded rat aortic rings isolated from male Wistar rats. Pre-incubation of intact or denuded rings with l-NAME (non selective NOS inhibitor, 100μmol/L), 7-nitroindazole (selective nNOS inhibitor, 100μmol/L), ODQ (selective inhibitor of guanylyl cyclase enzyme, 1μmol/L), glibenclamide (selective blocker of ATP-sensitive K+ channels, 3μmol/L) and 4-aminopyridine (selective blocker of voltage-dependent K+ channels, 4-AP, 1mmol/L) reduced ethanol-induced relaxation. Similarly, tiron (superoxide anion (O2−) scavenger, 1mmol/L) and catalase (hydrogen peroxide (H2O2) scavenger, 300U/mL) reduced ethanol-induced relaxation to a similar extent in both endothelium-intact and denuded rings. Finally, prodifen (non-selective cytochrome P450 enzymes inhibitor, 10μmol/L) and 4-methylpyrazole (selective alcohol dehydrogenase inhibitor, 10μmol/L) reduced ethanol-induced relaxation. In cultured aortic vascular smooth muscle cells (VSMCs), ethanol stimulated generation of NO, which was significantly inhibited by l-NAME. In endothelial cells, flow cytometry studies showed that ethanol increased cytosolic Ca2+ concentration ([Ca2+]c), O2- and cytosolic NO concentration ([NO]c). Tiron inhibited ethanol-induced increase in [Ca2+]c and [NO]c. The major new finding of this work is that ethanol induces relaxation via redox-sensitive and NO–cGMP-dependent pathways through direct effects on ROS production and NO signaling. These findings identify putative molecular mechanisms whereby ethanol, at pharmacological concentrations, influences vascular reactivity