Eicosapentaenoic acid (EPA) induces Ca 2+-independent activation and translocation of endothelial nitric oxide synthase and endothelium-dependent vasorelaxation

Abstract

Eicosapentaenoic acid (EPA), but not its metabolites (docosapentaenoic acid and docosahexaenoic acid), stimulated nitric oxide (NO) production in endothelial cells in situ and induced endothelium-dependent relaxation of bovine coronary arteries precontracted with U46619. EPA induced a greater production of NO, but a much smaller and more transient elevation of intracellular Ca 2+ concentration ([Ca 2+]i), than did a Ca 2+ ionophore (ionomycin). EPA stimulated NO production even in endothelial cells in situ loaded with a cytosolic Ca 2+ chelator 1,2-bis- o-aminophenoxythamine- N′, N′, N′-tetraacetic acid, which abolished the [Ca 2+]i elevations induced by ATP and EPA. The EPA-induced vasorelaxation was inhibited by N ω -nitro- L-arginine methyl ester. Immunostaining analysis of endothelial NO synthase (eNOS) and caveolin-1 in cultured endothelial cells revealed eNOS to be colocalized with caveolin in the cell membrane at a resting state, while EPA stimulated the translocation of eNOS to the cytosol and its dissociation from caveolin, to an extent comparable to that of the eNOS translocation induced by a [Ca 2+]i-elevating agonist (10 μM bradykinin). Thus, EPA induces Ca 2+-independent activation and translocation of eNOS and endothelium-dependent vasorelaxation.