Changing ratios of omega-6 to omega-3 fatty acids can differentially modulate polychlorinated biphenyl toxicity in endothelial cells

Exposure to persistent organic pollutants, such as polychlorinated biphenyls (PCBs) can cause endothelial cell (EC) activation by inducing pro-inflammatory signaling pathways. Our previous studies indicated that linoleic acid (LA, 18:2), a major omega-6 unsaturated fatty acid in the American diet, can potentiate PCB77-mediated inflammatory responses in EC. In addition, omega-3 fatty acids (such as α-linolenic acid, ALA and 18:3) are known for their anti-inflammatory properties. We tested the hypothesis that mechanisms of PCB-induced endothelial cell activation and inflammation can be modified by different ratios of omega-6 to omega-3 fatty acids. EC were pretreated with LA, ALA, or different ratios of these fatty acids, followed by exposure to PCB77. PCB77-induced oxidative stress and activation of the oxidative stress sensitive transcription factor nuclear factor κB (NF-κB) were markedly increased in the presence of LA and diminished by increasing the relative amount of ALA to LA. Similar protective effects by increasing ALA were observed by measuring NF-κB-responsive genes, such as vascular cell adhesion molecule-1 (VCAM-1) and cyclooxygenase-2 (COX-2). COX-2 catalyzes the rate limiting step of the biosynthesis of prostaglandin E₂ (PGE₂). PCB77 exposure also increased PGE₂ levels, which were down-regulated with relative increasing amounts of ALA to LA. The present studies suggest that NF-κB is a critical player in the regulation of PCB-induced inflammatory markers as modulated by omega-6 and omega-3 fatty acids.