title: Regulation of cholesterol biosynthesis and esterification by 25-hydroxycholesterol in a macrophage-like cell line: uncoupling by progesterone.
abstract: The coordinated control of cholesterol biosynthesis and esterification by 25-hydroxycholesterol was studied in the macrophage-like cell line P388D1. Since 25-hydroxycholesterol rapidly stimulated incorporation of [3H]oleate into the cholesteryl ester fraction of these cells, we have tested the possibility that the well-known inhibition of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA reductase) by 25-hydroxycholesterol might be the indirect consequence of an increased cholesterol esterification rather than a direct effect on HMG-CoA reductase. The experimental results show that progesterone, an inhibitor of acyl-CoA:cholesterol acyltransferase (ACAT), when added together with 25-hydroxycholesterol, abolished the increased cholesterol esterification without affecting the inhibition of HMG-CoA reductase by 25-hydroxycholesterol. Thus, uncoupling cholesterol esterification had no effect on 25-hydroxycholesterol's ability to inhibit HMG-CoA reductase. Unexpectedly, pretreatment of P388D1 cells with 25-hydroxycholesterol resulted in no elevation of ACAT activity as measured in broken cell preparations. Therefore, the possibility that 25-hydroxycholesterol stimulated cholesteryl ester formation by increasing the amount of cholesterol available for esterification, rather than by acting directly on ACAT activity, was considered. Labeling experiments using [14C]-cholesterol have provided evidence for this assumption.
mesh_terms: D000085:Acetates / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D002784:Cholesterol / Q000096:biosynthesis*; D002788:Cholesterol Esters / Q000378:metabolism*; D006888:Hydroxycholesterols / Q000378:metabolism*; D006903:Hydroxymethylglutaryl CoA Reductases / Q000378:metabolism; D007941:Leukemia P388 / Q000378:metabolism; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D008811:Mice, Inbred DBA; D019301:Oleic Acid; D009829:Oleic Acids / Q000378:metabolism; D011374:Progesterone / Q000494:pharmacology*; D002785:Sterol O-Acyltransferase / Q000378:metabolism; D013997:Time Factors
chemical_list: D000085:Acetates; D002788:Cholesterol Esters; D006888:Hydroxycholesterols; D009829:Oleic Acids; D019301:Oleic Acid; D011374:Progesterone; C007997:25-hydroxycholesterol; D002784:Cholesterol; D006903:Hydroxymethylglutaryl CoA Reductases; D002785:Sterol O-Acyltransferase