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)-κB signaling was analyzed by Western blot analysis and electrophoretic mobility shift assay (EMSA). RESULTS. Stimulation of hRVECs with VEGF₁₆₅, TNFα, or IL-1β 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 μM of BSA-bound DHA_22:6n3 for 24 hours remarkably inhibited cytokine-induced CAM expression. IL-1β, TNFα, and VEGF₁₆₅ induced nuclear translocation and binding of p65 and p50 NF-κB isoforms to the VCAM-1 promoter. DHA_22:6n3 pretreatment inhibited cytokine-induced NF-κB binding by 25% to 40%. Moreover, DHA _22:6n3 diminished IL-1β induced phosphorylation of the inhibitor of nuclear factor (NF)-κB (I-κBα), thus preventing its degradation. CONCLUSIONS. IL-1β, TNFα, and VEGF₁₆₅ induced CAM expression in hRVECs through activation of the NF-κB pathway. DHA_22:6n3 inhibited cytokine induced CAM expression through suppression of NF-κB nuclear translocation and upstream I-κBα 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.