EFFECT OF 7-BETA-HYDROXYCHOLESTEROL ON ASTROCYTE PRIMARY CULTURES AND DERIVED SPONTANEOUSLY TRANSFORMED-CELL LINES - CYTOTOXICITY AND CHOLESTEROGENESIS

The correlation between the lethal effect of 7-beta-hydroxycholesterol (7-beta-OH-CH) on spontaneously transformed cell lines derived from rat astrocyte primary cultures (normal cells) and de novo cholesterogenesis was investigated. Both 7-beta-OH-CH and 7-keto-CH were not cytotoxic on normal cells but 7-beta-OH-CH affected markedly the viability of the transformed cells. The use of [C-14]acetate or [C-14]mevalonate indicated that 7-keto-CH inhibits de novo cholesterogenesis upstream of 3-hydroxy-3-methylglutaryl CoA reductase (HMGR) in both cell types whereas 7-beta-OH-CH also inhibits downstream of HMGR. The accumulation of two radiolabelled products X1 and X2 between mevalonate and CH was found in unsaponifiable neutral lipids extracted from 7-beta-OH-CH treated transformed cells. HPLC and GC-MS revealed that X1 and X2 are not lanosterol and 24,25-epoxylanosterol, respectively. Incubation of the transformed cells with X1 and X2 did not affect their viability. Our data demonstrate that, under our experimental conditions, 7-beta-OH-CH cytotoxicity is not linked to the inhibition of de novo cholesterogenesis in cultured glial transformed cells.