Lipids-induced apoptosis is aggravated by acyl-coenzyme A: cholesterol acyltransferase inhibitor.
OBJECTIVE
To investigate the role of acyl-coenzyme A: cholesterol acyltransferase inhibitor (ACATI) in apoptosis induced by lipids and whether lipids-induced apoptosis is accompanied by increase of free cholesterol in endoplasmic reticulum (ER), in order to further understand the mechanism of lipids-induced apoptosis in advanced atherosclerosis.


METHODS
Human vascular smooth muscle cells (VSMCs) and phorbol 12-myristate 13-acetate (PMA) differentiated THP-1 macrophages were used. Tritiated thymidine incorporation was applied to detect cell proliferation. Cytotoxicity was assessed by lactate dehydrogenase (LDH) release. 4',6-diamidino-2-phenylindole (DAPI) staining, caspase-3, -7 assay, and Annexin-V/propidium iodide (PI) staining were used to detect apoptosis. High performance liquid chromatography was used in intracellular free cholesterol and cholesterol ester assay. ER free cholesterol was quantified.


RESULTS
Different lipids had different effects on proliferation and cytotoxicity of VSMCs. 25-hydroxycholesterol (25OHC) had biphasic effects on the proliferation of VSMCs. At low concentration, it stimulated cell proliferation, but turned to proliferation inhibition as concentration reached 15 mug/mL. 25OHC and acetylated low density lipoprotein (AcLDL) could respectively induce apoptosis in human VSMCs and PMA differentiated THP-1 macrophages, which was aggravated by ACATI, accompanied by increase of intracellular free cholesterol content. There was also an increase of cholesterol content in ER with AcLDL-induced apoptosis in THP-1 macrophages.


CONCLUSIONS
Lipids could induce apoptosis, accompanied by increase of intracellular free cholesterol content, which could be augmented by ACATI, suggesting that insults resulting in ER free cholesterol rise might be the initiator of apoptosis.
Tao
Jian-ling
JL
Department of Nephrology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100730, China.
Ruan
Xiong-zhong
XZ
Li
Hang
H
Li
Xue-mei
XM
Li
Xue-wang
XW
D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006801:Humans; D008055:Lipids / Q000502:physiology*; D002785:Sterol O-Acyltransferase / Q000037:antagonists & inhibitors*
D004791:Enzyme Inhibitors; D008055:Lipids; D002785:Sterol O-Acyltransferase