Eicosapentaenoic Acid Potentiates the Production of Nitric Oxide Evoked by lnterleukin-1β in Cultured Vascular Smooth Muscle Cells

Abstract

Experiments were designed to determine whether the ω3-unsaturated fatty acid eicosapentaenoic acid affects the production of nitric oxide evoked by interleukin-lβ in cultured vascular smooth muscle cells. Incubation of cultured rat or human aortic smooth muscle cells with interleukin-1β evoked a time- and concentration-dependent release of nitrite, an oxidation product of nitric oxide. The exposure of cells to interleukin-1β in combination with eicosapentaenoic acid caused a significantly larger production of nitrite than that evoked by the cytokine alone. The potentiation by eicosapentaenoic acid was concentration-dependent. The production of nitrite evoked by equieffective concentrations of interleukin-1β in the presence and absence of eicosapentaenoic acid were inhibited to a similar extent by nitro L-arginine (an inhibitor of nitric oxide synthase), transforming growth factor β₁ platelet-derived growth factor_AB and thrombin. The addition of interleukin-1β -activated smooth muscle cells to suspensions of washed and indomethacin-treated platelets inhibited the aggregation caused by thrombin. The inhibitory effect was enhanced when the smooth muscle cells were exposed to the cytokine in the presence of eicosapentaenoic acid prior to the experiment. Smooth muscle cells exposed to interleukin-1β and eicosapentaenoic acid did not affect platelet aggregation in the presence of oxyhemoglobin or methylene blue. Untreated cells or cells exposed to the fatty acid alone did not have such effects. These observations suggest that eicosapentaenoic acid potentiates the production of nitric oxide evoked by interleukin-1β in vascular smooth muscle.