Docosahexaenoic acid down-regulates endothelial Nox 4 through a sPLA(2) signalling pathway

We investigated the anti-inflammatory and antioxidant activities of docosahexaenoic acid (DHA) by evaluating its modulation of the two enzymes most involved in vascular inflammation, i.e. endothelial secreted phospholipase A(2) (sPLA(2)) and NADPH oxidase 4 (Nox) 4. Exposure of human aortic endothelial cells (HAECs) to DHA led to its preferential incorporation into outer leaflet phospholipids. Pre-treatment with DHA abolished HAECs stimulation induced by A23187 and Ang II, whereas the effects on IL-1 beta treatment were less pronounced. Group V sPLA2 RNA was similarly modulated by DHA supplementation. in addition, DHA decreased Nox 4 expression and activity; this effect was associated with reduced production of reactive oxygen species. Further, the use of specific inhibitors allowed demonstrating that group V sPLA2 is involved in the down-regulation of Nox 4 expression and activity by DHA. This interplay is mediated by ERK and PKC. (C) 2009 Elsevier Inc. All rights reserved.