Eicosapentaenoic acid inhibits cholesterol efflux pathways from cholesterol-loaded human THP-1 macrophages by reducing the hydrolysis of cholesteryl esters mediated by carboxylesterase 1

Abstract

A diet high in n-3 polyunsaturated fatty acids (PUFAs), particularly eicosapentaenoic acid (EPA) (C20:5 n-3), is cardioprotective. PUFAs integrate into membrane phospholipids, altering membrane protein function. We investigated the effects of various PUFAs on the anti-atherogenic cholesterol efflux pathways from cholesterol-loaded human THP-1 macrophages. Cells were supplemented (or not: standard cells) with 70 μM EPA, 50 μM arachidonic acid (AA) (C20:4 n-6) or 15 μM docosahexaenoic acid (DHA) (C22:6 n-3) for an extended duration to simulate a dietary strategy. EPA led to a 13 % decrease in ABCA1-mediated cholesterol efflux and to a 17 % decrease in SR-BI/ABCG1-mediated cholesterol efflux without affecting the expression of efflux proteins, while AA and DHA showed no impact. Compared to standard cells, EPA cells exhibited higher EPA levels along with reduced AA levels. EPA cells showed increased amounts of triglycerides and cholesteryl esters (CE) without a change in the acetylated LDL uptake. EPA did not influence the phenotype of macrophages according to surface markers and released cytokines. The incorporation of EPA did not disrupt efflux in macrophages loaded with free cholesterol. Conversely, EPA decreased CE hydrolysis from lipid droplets by 22 %. The diminished cholesterol efflux was not related to triglyceride accumulation or to variations in apo E secretion. EPA reduced the expression of carboxylesterase 1 (CES1) protein by 17 % without affecting the expression of neutral cholesterol ester hydrolase 1 (NCEH1). In conclusion, the membrane incorporation of EPA hinders the cholesterol efflux pathways in THP-1 foam cells likely by impairing the CE hydrolysis mediated by carboxylesterase 1.