U18666A inhibits intracellular cholesterol transport and neurotransmitter release in human neuroblastoma cells

To determine if neurochemical function might be impaired in cell models wit h altered cholesterol balance, we studied the effects of U18666A (3 -beta-[ (2-diethyl-amino)ethoxy] androst-5-en-17-one) on intracellular cholesterol metabolism in three human neuroblastoma cell lines (SK-N-SH, SK-N-MC, and S H-SY5Y). U18666A (less than or equal to 0.2 mu g/ml) completely inhibited l ow density lipoprotein (LDL)-stimulated cholesterol esterification in SK-N- SH cells, while cholesterol esterification stimulated by 25-hydroxycholeste rol or bacterial sphingomyelinase was unaffected or partially inhibited, re spectively. U18666A also blocked LDL-stimulated downregulation of LDL recep tor and caused lysosomal accumulation of cholesterol as measured by filipin staining. U18666A treatment for 18 h resulted in 70% inhibition of K+-evok ed norepinephrine release in phorbol ester-differentiated SH-SY5Y cells, wh ile release stimulated by the calcium ionophore A23187 was only slightly af fected. These results suggest that U18666A may preferentially block a volta ge-regulated Ca2+ channel involved in norepinephrine release and that alter ations in neurotransmitter secretion might be a feature of disorders such a s Niemann-Pick Type C, in which intracellular cholesterol transport and dis tribution are impaired.