Apolipoprotein M regulates the uptake and efflux of cholesterol in Ana-1 cells

Abstract

Objective To understand the role of apolipoprotein M(apoM) in the uptake and efflux of cholesterol. Methods Ana-1 cells were incubated with different concentrations of NBD-cholesterol to observe the effect of cholesterol concentration and incubation time on cholesterol uptake. The peritoneal macrophages from diverse genotypes of mice were harvested and the efficiencies of cholesterol intake were detected. After incubated with 10μmol/L NBD-cholesterol for 4 hours, the Ana-1 cells were then dealt with different inducing fluid, respectively, supplemented with or without apoM. NBD-cholesterol uptake and efflux rate were reflected by fluorescent intensity. Results Uptake of NBD-cholesterol in Ana-1 cells was concentration dependent in vitro. The peak of cholesterol uptake by macrophages appeared at 6 hours, and it was not associated with the concentration of cholesterol or macrophage genotype. In platform stage, the uptake rate of cholesterol in ApoM-/-SR-BⅠ-/- mice was significantly lower than that of the SR-BⅠ-/- mice and ApoM-/- mice(t=6.8、13.66, P<0.05). ApoM+ HDL enhanced cholesterol efflux from Ana-1 cells compared with apoM-HDL(24.65%±0.93% vs 10.85%±0.64%, P=0.000 3). In vitro, apoM recombinant proteins could inhibit apoM-HDL induced cholesterol efflux comparing with apoM-HDL group. Conclusion In vitro, apoM involved in the uptake of cholesterol by peritoneal macrophages and might regulate HDL-mediated cholesterol efflux. (Chin J Endocrinol Metab, 2017, 33: 135-140) Key words: Apolipoproteins; High density lipoprotein; Cholesterol; Scavenger receptor class B type I