27-Hydroxycholesterol modulation of low density lipoprotein metabolism in cultured human hepatic and extrahepatic cells

27-Hydroxycholesterol1 1 Recent publications have chosen to use 27-hydroxycholesterol rather than the conventional name 26-hydroxycholesterol to indicate that the mitochondrial enzyme stereospecifically hydroxylates only the methyl group in position C-27 [22]., 25-hydroxycholesterol and cholesterol suppressed LDL uptake and degradation in human extrahepatic and hepatic cell lines hi a concentration-dependent manner. Cholesterol was the least potent, and the inhibitory effect of oxysterols was more pronounced in skin fibroblasts and in endothelial cell line EAhy 926 than in hepatoma HepG2 cells. Shorter incubations were required for oxysterols to achieve 50% inhibition of LDL uptake and degradation in all cultured cells. The inhibition of LDL catabolism in extrahepatic cells by 27-hydroxycholesterol occurred at concentrations close to those observed in human plasma (0.2-0.6 μM). The results support a possible role of 27-hydroxycholesterol, a physiological oxysterol, in the regulation of cellular cholesterol homeostasis in non-hepatic tissues.