EICOSAPENTAENOIC ACID INHIBITS LIPOPOLYSACCHARIDE (LPS)-INDUCED MACROPHAGE ACTIVATION THROUGH A POTENTIAL CYCLOOXYGENASE PATHWAY

Abstract

<h3>BACKGROUND</h3> Activated macrophages, characterized by increased inducible nitric oxide synthase (iNOS) expression, participate in atherosclerosis and its complications. Cyclooxygenase (COX) regulates iNOS activity. As both a substrate for and potential inhibitor of COX, the omega-3 fatty acid, eicosapentaenoic acid (EPA), may reduce iNOS activity. Icosapent ethyl is an ethyl ester of EPA, and was shown to reduce ischemic events in high-risk patients (REDUCE-IT). We tested the effects of EPA on iNOS activity in lipopolysaccharide (LPS)-activated macrophages. <h3>METHODS AND RESULTS</h3> Murine J774 macrophages were pretreated with vehicle, EPA (10, 20, 40 µM), (10 µM) for 2 h, then challenged with LPS (1.0 µg/ml). After 24 h, iNOS activity was measured by nitrite production using the Griess assay. As a positive control, the COX inhibitor diclofenac was tested (1.0 µg/ml). Treatment with LPS increased nitrite production by 465% (p < 0.001). EPA treatment reduced nitrite production in a significant, dose-dependent manner by 40-77% at 10-40 µM, respectively, compared to LPS-alone. EPA at the lowest concentration tested produced an effect similar to diclofenac, which reduced nitrite levels by 40% (p < 0.01). <h3>CONCLUSION</h3> EPA reduced LPS-induced macrophage activation in a dose-dependent manner that was reproduced to a lesser extent by diclofenac. These findings indicate a novel effect of EPA on both COX and iNOS activity. The ability of EPA to reduce macrophage activity may contribute to limiting atherothrombotic risk as evidenced in REDUCE-IT.