Monocytes/macrophages| Volume 241, ISSUE 1, e79-e80, July 2015

Eicosapentaenoic acid (EPA) membrane incorporation impaired ABCA1-dependent cholesterol efflux through a PKA pathway in primary human macrophages

      Dietary polyunsaturated fatty acids (PUFA) affect the cellular phospholipids composition which may influence the function of membrane proteins. We investigated the impact of the incorporation of several PUFA on the ABCA1-mediated cholesterol efflux, an anti-atherogenic process. The arachidonic acid (AA) (C20:4 n-6) and docosahexaenoic acid (DHA) (C22:6 n-3) supplementation decreased or increased cholesterol efflux from J774 mouse macrophages, respectively, whereas they had no effect on efflux from human monocyte-derived macrophages (HMDM). Importantly, the membrane incorporation of eicosapentaenoic acid (EPA) (C20:5 n-3) induced a dose-dependent reduction of ABCA1 functionality in both cellular models (-28% for 70 μM of EPA in HMDM). The EPA addition did not alter the ABCA1 expression (mRNA or protein) in mouse or human macrophages. The EPA-treated HMDM exhibited strong phospholipids composition changes with high levels of both EPA and its elongation product docosapentaenoic acid (DPA) (C22:5 n-3) associated to a decreased level of AA. In human macrophages, cellular ATP was required for the effect of EPA. In addition, we observed that addition of forskolin, a direct activator of adenylate cyclase, and isobutylmethylxanthine, an inhibitor of cAMP phosphodiesterase restored ABCA1 cholesterol efflux in EPA-treated human macrophages. Moreover, the cyclooxygenase inhibition by indomethacin abolished the impact of EPA whereas the lipoxygenase inhibition by nordihydroguaiaretic acid (NGDA) had no consequence in HMDM. In conclusion, our results suggest that EPA membrane incorporation may be deleterious by reducing the ABCA1 function from human macrophages through a PKA-dependent mechanism, likely by altering the balance of the cellular eicosanoids produced from AA or EPA.
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