Acyl-coenzyme A:cholesterol acyltransferase promotes oxidized LDL/oxysterol-induced apoptosis in macrophages.
7-Ketocholesterol (7KC) is a cytotoxic component of oxidized low density lipoproteins (OxLDLs) and induces apoptosis in macrophages by a mechanism involving the activation of cytosolic phospholipase A2 (cPLA2). In the current study, we examined the role of ACAT in 7KC-induced and OxLDL-induced apoptosis in murine macrophages. An ACAT inhibitor, Sandoz 58-035, suppressed 7KC-induced apoptosis in P388D1 cells and both 7KC-induced and OxLDL-induced apoptosis in mouse peritoneal macrophages (MPMs). Furthermore, compared with wild-type MPMs, ACAT-1-deficient MPMs demonstrated significant resistance to both 7KC-induced and OxLDL-induced apoptosis. Macrophages treated with 7KC accumulated ACAT-derived [14C]cholesteryl and [3H]7-ketocholesteryl esters. Tandem LC-MS revealed that the 7KC esters contained primarily saturated and monounsaturated fatty acids. An inhibitor of cPLA2, arachidonyl trifluoromethyl ketone, prevented the accumulation of 7KC esters and inhibited 7KC-induced apoptosis in P388D1 cells. The decrease in 7KC ester accumulation produced by the inhibition of cPLA2 was reversed by supplementing with either oleic or arachidonic acid (AA); however, only AA supplementation restored the induction of apoptosis by 7KC. These results suggest that 7KC not only initiates the apoptosis pathway by activating cPLA2, as we have reported previously, but also participates in the downstream signaling pathway when esterified by ACAT to form 7KC-arachidonate.
Department of Biochemistry and Molecular Biology, James H. Quillen College of Medicine, East Tennessee State University, Johnson City, TN 37614-0581, USA.
Natalie E
NE
Freeman
Antonio E
AE
Rusinol
MacRae
M
Linton
David L
DL
Hachey
Sergio
S
Fazio
Michael S
MS
Sinensky
Douglas
D
Thewke
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D016718:Arachidonic Acid / Q000037:antagonists & inhibitors / Q000494:pharmacology; D002250:Carbon Radioisotopes; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D002788:Cholesterol Esters / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004951:Esterification / Q000187:drug effects; D020287:In Situ Nick-End Labeling; D007653:Ketocholesterols / Q000378:metabolism / Q000494:pharmacology; D008077:Lipoproteins, LDL / Q000494:pharmacology*; D008264:Macrophages / Q000187:drug effects / Q000502:physiology*; D017737:Macrophages, Peritoneal / Q000187:drug effects / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D010741:Phospholipases A / Q000037:antagonists & inhibitors / Q000378:metabolism; D054467:Phospholipases A2; D002785:Sterol O-Acyltransferase / Q000037:antagonists & inhibitors / Q000502:physiology*; D014316:Tritium
D002250:Carbon Radioisotopes; D002788:Cholesterol Esters; D004791:Enzyme Inhibitors; D007653:Ketocholesterols; D008077:Lipoproteins, LDL; C099252:oxidized low density lipoprotein; D014316:Tritium; D016718:Arachidonic Acid; D002785:Sterol O-Acyltransferase; D010741:Phospholipases A; D054467:Phospholipases A2; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases; C003001:7-ketocholesterol