Trapidil derivatives and low density lipoprotein metabolism by human skin fibroblasts and by human hepatoma cell line Hep G2

Is the antiatherosclerotic potency of HDL modulated by the origin of HDL?

Different HDL preparations from rabbit blood were injected intravenously (10 mg HDL protein/injection and animal) into cholesterol fed rabbits twice a week for 8 weeks. The composition of the used high density lipoprotein (HDL) was modified by dietary pretreatment. HDL-1 was taken from rabbits after 8 weeks pellet diet, HDL-2 after 8 weeks fish-oil rich diet and HDL-3 after 8 weeks of cholesterol rich diet. The animals treated with HDL-1 and HDL-2 had a significantly smaller area of intima covered with fatty streaks than the control animals (injection of saline instead of HDL). The injection of HDL-3 was without influence. These differences were correlated with changes in the level of free and esterified cholesterol (FC and CE) in kidney, liver and aorta of the rabbits, but not with the level of cholesterol in the serum lipoproteins. We investigated simultaneously the influence of the different HDL preparations on the cholesterol content in rabbit skin fibroblasts (RSF), rabbit smooth muscle cells (SMC) and human hepatoma cell line Hep G2. Additionally the influence on the proliferation of SMC was studied. HDL-1 diminished the level of FC in cholesterol enriched RSF and rabbit SMC, whereas both other HDL preparations had no effect. The level of FC in Hep G2 was not influenced. HDL-1 and HDL-3 stimulated the proliferation of rabbit SMC, whereas HDL-2 had no such influence. The data support the antiatherosclerotic role of HDL injections in cholesterol fed rabbits, but the composition of the used HDL seems to modify this influence, probably by different effects on the biochemical changes induced by the HDL.

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

27-Hydroxycholesterol**, 25-hydroxycholesterol and cholesterol suppressed LDL uptake and degradation in human extrahepatic and hepatic cell lines in 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 microM). The results support a possible role of 27-hydroxycholesterol, a physiological oxysterol, in the regulation of cellular cholesterol homeostasis in non-hepatic tissues.

Effect of trapidil derivative AR 12456 on intracellular cholesterol homeostasis in human hepatoma cell line Hep G2

The effect of trapidil derivative AR12456 on intracellular cholesterol metabolism was investigated in human hepatoma cell line HepG2. AR12456 enhanced the uptake and degradation of(125)I-LDL in a dose-dependent manner. The drug inhibited cholesterol synthesis and esterification without affecting cellular cholesterol content and bile acid synthesis; cholesterol efflux was slightly increased. These results show that the inhibition of cholesterol synthesis together with the enhanced expression of LDL receptors may partially explain the hypocholesterolemic activity of compound AR12456.