Effects of troglitazone on intracellular cholesterol distribution and cholesterol-dependent cell functions in MA-10 Leydig tumor cells.
Troglitazone treatment of MA-10 Leydig tumor cells resulted in cellular cholesteryl esters decreasing and cell free cholesterol increasing. This was not an effect unique to this chemical entity; rosiglitazone and pioglitazone caused these changes also. The excess free cholesterol was recovered largely in the cholesterol oxidase susceptible, plasma membrane cholesterol pool. This effect of troglitazone probably is not mediated by activation of peroxisome proliferator activated receptors since it immediately reversed with washing and did not occur at all in cells treated with the peroxisome proliferator activated receptor agonist, 15-deoxy Delta 12,14 prostaglandin J-2. Plasma membrane cholesterol esterification was inhibited by troglitazone in a dose-dependent manner. Plasma membrane cholesterol esterification was inhibited half-maximally by 14 microM troglitazone and by more than 90% by 40 microM troglitazone. This effect was not unique for MA-10 cells. Similar results were found using fibroblasts. Troglitazone was not simply inhibiting internalization of plasma membrane cholesterol. Dibutyryl-cAMP stimulation of troglitazone-treated cells resulted in more progesterone synthesis than in stimulated control cells; moreover, radioactive plasma membrane cholesterol was readily converted into progesterone in troglitazone-treated cells. Studies of LDL uptake in troglitazone-treated cells indicated that intracellular membranes were cholesterol replete. Troglitazone inhibited plasma membrane cholesterol esterification with kinetics similar to 58-035, a known inhibitor of the acyl coenzyme A: cholesterol acyltranserase (ACAT) enzyme. It is not likely an ACAT inhibitor since troglitazone did not block incorporation of exogenous free fatty acids into cholesteryl esters. Thus, it appears that troglitazone prevented presentation of free fatty acid to the ACAT enzyme.
Freeman
Dale A
DA
Department of Internal Medicine, University of Louisville School of Medicine, 800 Zorn Avenue, Louisville, KY 40206, USA. dale.freeman@med.va.gov
Romero
Angela
A
D002462:Cell Membrane / Q000187:drug effects* / Q000201:enzymology; D002784:Cholesterol / Q000378:metabolism*; D002788:Cholesterol Esters / Q000378:metabolism; D002839:Chromans / Q000494:pharmacology*; D006801:Humans; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D007984:Leydig Cell Tumor / Q000201:enzymology / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D002785:Sterol O-Acyltransferase / Q000378:metabolism; D013844:Thiazoles / Q000494:pharmacology*; D045162:Thiazolidinediones; D014157:Transcription Factors / Q000378:metabolism; D000077288:Troglitazone; D014407:Tumor Cells, Cultured
D002788:Cholesterol Esters; D002839:Chromans; D007004:Hypoglycemic Agents; D018160:Receptors, Cytoplasmic and Nuclear; D013844:Thiazoles; D045162:Thiazolidinediones; D014157:Transcription Factors; D002784:Cholesterol; D002785:Sterol O-Acyltransferase; D000077288:Troglitazone