Effect of cholesterol and 7 β-hydroxycholesterol on glutathione status and expression of Hsp70 in cultured murine peritoneal macrophages

Abstract

Using cultured murine peritoneal macrophages, the change in redox ratio (oxidized/reduced glutathione) was studied at different incubation intervals (6, 12, 18 and 24 hr) with different concentrations (2.5, 5 and 7.5 μg/ml) of cholesterol and 7 β-hydroxycholesterol (7 β-OH), using fluorimeter. The changes in the levels of heat shock protein, hsp70 was determined using ELISA. Both cholesterol/7 β-OH caused a decrease in hsp70 protein levels at all the incubation intervals in dose dependent manner but the decrease was significantly higher with 7 β-OH. Treatment with 7 β-OH also resulted in significantly increased levels of oxidized glutathione (GSSG) and decreased reduced glutathione (GSH) while cholesterol showed no effect on GSSG levels. Moreover, GSH levels were lowered only at the highest concentration (7.5 μg/ml) at longer incubation intervals (18 and 24 hr) with cholesterol exposure. This altered the redox status in both cholesterol/7 β-OH treated macrophages. These results suggest that cholesterol and more likely 7 β-OH may exert their pro-atherogenic effects by lowering hsp70 protein production and inhibiting glutathione synthesis by macrophages present in the arterial wall.