Abstract 704: The Omega-3 Fatty Acid Docosahexaenoate Attenuates Vascular Inflammation Reducing Endothelial Cyclooxygenase-2 Induction through the Inhibition of Both NADP(H) Oxidase and PKCε
Background and Aims. A high intake of the omega-3 fatty acid docosahexaenoate (DHA) has been associated with systemic anti-inflammatory effects and cardiovascular protection, but the molecular basis responsible for these effects remains incompletely defined. Cyclooxygenase (COX)-2 is responsible for the overproduction of prostaglandins (PG) at inflammatory sites and its expression is increased in human atheroma. We here investigated the effects of DHA on COX-2 expression and activity in human saphenous vein endothelial (HSVEC) cells challenged with proinflammatory stimuli, and explored underlying molecular mechanisms.
Methods and Results. A long-term (24 –72 h) exposure of HSVEC to DHA (10 –25 μmol/L) significantly reduced IL1α- and PMA-stimulated PG production, as well as COX-2 protein (by 50%, at Western analysis) and mRNA (by 70%, Northern analysis). Analysis of COX-2 promoter activity showed that DHA effect was dependent on the Nuclear Factor (NF)-κB binding sites in the COX-2 promoter, and electrophoretic mobility shift assays (EMSA) confirmed that DHA attenuated NF-κB activation. Since mitogen-activated protein kinases, protein kinase-C (PKC), and NAD(P)H oxidase all participate in IL-1-mediated COX-2 expression, we tested whether these enzymatic activities were affected by DHA. Western analysis and immunofluorescence showed that DHA blocked nuclear p65 NF-κB subunit translocation by decreasing cytokine-stimulated reactive oxygen species release (by 50%, at a DCF assay) and ERK1/2 activation (by 50%, at Western analysis) via the reduction of both NAD(P)H oxidase and PKCε activities. Because COX-2 overexpression in atherosclerosis appears linked to plaque inflammation and instability, these studies provide a valuable mechanistic explanation for the observed anti-inflammatory and plaque-stabilizing effects of DHA.