CYP epoxygenase-derived HO is involved in the endothelium-derived hyperpolarization (EDH) and relaxation of intrarenal arteries.

Reactive oxygen species (ROS) like hydrogen peroxide (HO) are involved in the in endothelium-derived hyperpolarization (EDH)-type relaxant responses of coronary and mesenteric arterioles. The role of ROS in kidney vascular function has mainly been investigated in the context of harmful ROS generation associated to kidney disease. The present study was sought to investigate whether HO is involved in the endothelium-dependent relaxations of intrarenal arteries as well the possible endothelial sources of ROS generation involved in these responses. Under conditions of cyclooxygenase (COX) and nitric oxide (NO) synthase inhibition, acetylcholine (ACh) induced relaxations and stimulated HO release that were reduced by catalase and by the glutathione peroxidase (GPx) mimetic ebselen in rat renal interlobar arteries, suggesting the involvement of HO in the endothelium-dependent responses. ACh relaxations were also blunted by the CYP2C inhibitor sulfaphenazole and by the NADPH oxidase inhibitor apocynin. Acetylcholine stimulated both superoxide (O) and HO production that were reduced by sulfaphenazole and apocynin. Expression of the antioxidant enzyme CuZnSOD and of the HO reducing enzymes catalase and GPx-1 was found in both intrarenal arteries and renal cortex. On the other hand, exogenous HO relaxed renal arteries by decreasing vascular smooth muscle (VSM) intracellular calcium concentration [Ca] and markedly enhanced endothelial K currents in freshly isolated renal endothelial cells. CYP2C11 and CYP2C23 epoxygenases were highly expressed in interlobar renal arteries and renal cortex, respectively, and were co-localized with eNOS in renal endothelial cells. These results demonstrate that HO is involved in the EDH-type relaxant responses of renal arteries and that CYP 2C epoxygenases are physiologically relevant endothelial sources of vasodilator HO in the kidney.