VEGF-induced relaxation of pulmonary arteries is mediated by endothelial cytochrome P-450 hydroxylase

The cytochrome P-450 metabolite 20-HETE induces calcium-, endothelial-, and nitric oxide (NO)-dependent relaxation of bovine pulmonary arteries (PA). VEGF is an NO-dependent dilator of systemic arteries and plays a key role in maintaining the integrity of the pulmonary vasculature. We tested the effect of VEGF on PA diameter and tone and the contribution of cytochrome P-450 family 4 (CYP4) to vasoactive effects of VEGF. Bovine PA rings (1 mm in diameter) relaxed with VEGF (0.1 -10 nM) in an endothelial-and eNOS-dependent manner. This response was blunted by pretreatment with the CYP4 inhibitor dibromododecynyl methyl sulfonamide (DDMS) as well as a mechanistically different CYP4 inhibitor N-hydroxy-N'-(4-butyl-2-methylphenyl) formamidine. PAs also increased in diameter by 6 -12% in the presence of VEGF (10 nM), and this increase was attenuated by DDMS. In contrast to that shown in PAs, 20-HETE constricted bovine renal arteries and did not increase intracellular Ca2+ in renal artery endothelial cells as observed in bovine pulmonary artery endothelial cells (BPAECs). VEGF-evoked increases in intracellular Ca2+ concentration ([Ca2+] i) in BPAECs were blunted by treatment with DDMS. Both VEGF (10 nM) and 20-HETE (1-5 mu M) stimulated NO release from cultured BPAECs, and once again VEGF-induced increases were attenuated by pretreating the cells with DDMS. We conclude that CYP4/ 20-HETE contributes to VEGF-stimulated NO release and vasodilation in bovine PAs. Given the unique expression of 20-HETE-forming CYP4 in BPAECs vs. systemic arterial endothelial cells, CYP4 may be an important mediator of endothelial-dependent vasoreactivity in PAs.