Pitavastatin inhibits remnant lipoprotein-induced macrophage foam cell formation through apoB48 receptor-dependent mechanism

Objective - Atherogenic remnant lipoproteins (RLPs) are known to induce foam cell formation in macrophages in vitro and in vivo. We examined the involvement of apoB48 receptor (apoB48R), a novel receptor for RLPs, in that process in vitro and its potential regulation by pitavastatin. Methods and Results - THP-1 macrophages were incubated in the presence of RLPs ( 20 mg cholesterol/ dL, 24 hours) isolated from hypertriglyceridemic subjects. RLPs significantly increased intracellular cholesterol ester (CE) and triglyceride (TG) contents (4.8-fold and 5.8-fold, respectively) in the macrophages. Transfection of THP-1 macrophages with short interfering RNA ( siRNA) against apoB48R significantly inhibited RLP-induced TG accumulation by 44%. When THP-1 macrophages were pretreated with pitavastatin ( 5 mumol/L, 24 hours), the expression of apoB48R was significantly decreased and RLP-induced TG accumulation was reduced by 56%. ApoB48R siRNA also inhibited TG accumulation in THP-1 macrophage induced by beta-very-low-density lipoprotein derived from apoE -/- mice by 58%, supporting the notion that apoB48R recognizes and takes-up RLPs in an apoE-independent manner. Conclusions - RLPs induce macrophage foam cell formation via apoB48R. Pitavastatin inhibits RLP-induced macrophage foam cell formation. The underlying mechanism involves, at least in part, inhibition of apoB48R-dependent mechanism. Our findings indicate a potential role of apoB48R in atherosclerosis.