Anti-inflammatory effect of docosahexaenoic acid on cytokine-induced adhesion molecule expression in human retinal vascular endothelial cells

PURPOSE. Docosahexaenoic acid (DHA(22: 6n3)), the principal n3-polyunsaturated fatty acid (PUFA) in the retina, has been shown to have a pronounced anti-inflammatory effect in numerous in vivo and in vitro studies. Despite the importance of vascular inflammation in diabetic retinopathy, the anti-inflammatory role of DHA(22: 6n3) in cytokine-stimulated human retinal vascular endothelial cells (hRVECs) has not been addressed. METHODS. Cytokine-induced expression of cell adhesion molecules (CAMs) was assessed by Western blot. The effect of DHA(22: 6n3) on cytokine-induced nuclear factor (NF)-kappa B signaling was analyzed by Western blot analysis and electrophoretic mobility shift assay ( EMSA). RESULTS. Stimulation of hRVECs with VEGF(165), TNF alpha, or IL-1 beta for 6 to 24 hours caused significant induction of intracellular adhesion molecule ( ICAM)-1 and vascular cell adhesion molecule ( VCAM)-1 expression. Pretreatment of the cells with 100 mu M of BSA-bound DHA(22: 6n3) for 24 hours remarkably inhibited cytokine-induced CAM expression. IL-1 beta, TNF alpha, and VEGF(165) induced nuclear translocation and binding of p65 and p50 NF-kappa B isoforms to the VCAM-1 promoter. DHA(22: 6n3) pretreatment inhibited cytokine-induced NF-kappa B binding by 25% to 40%. Moreover, DHA(22: 6n3) diminished IL-1 beta induced phosphorylation of the inhibitor of nuclear factor (NF)-kappa B (I-kappa B alpha), thus preventing its degradation. CONCLUSIONS. IL-1 beta, TNF alpha, and VEGF(165) induced CAM expression in hRVECs through activation of the NF-kappa B pathway. DHA(22: 6n3) inhibited cytokine induced CAM expression through suppression of NF-kappa B nuclear translocation and upstream I-kappa B alpha phosphorylation and degradation. DHA(22: 6n3) could be an important anti-inflammatory agent in the face of increased cytokine production and CAM expression in the diabetic retina.