Macrophage paraoxonase 2 (PON2) expression is upregulated by unesterified cholesterol through activation of the phosphatidylinositol 3-kinase (PI3K) pathway.
Advanced atherosclerotic lesions are characterized by a progressive increase in the unesterified cholesterol (UC) content and a decrease in its cholesteryl ester (CE) content. In the present study, we examined mechanisms involved in the effect of UC and CE on the expression of paraoxonase 2 (PON2) in macrophages. J774A.1 macrophages were enriched with CE or UC by incubation for 14-48 h with 50 microg acetylated low-density lipoprotein in the absence or presence of the acyl-CoA:cholesterol acyltransferase (ACAT) inhibitor 58035 (50 microg/ml), respectively. Macrophage PON2 mRNA expression, protein abundance and activity were increased only in the UC-enriched cells. In UC-enriched cells, inhibition of phosphatidylinositol 3-kinase (PI(3)K; using wortmannin or LY294002) attenuated the increase in PON2 mRNA expression by 50%, compared to untreated cells. In addition, we evidenced an increased phosphorylation of Akt in UC-enriched cells. Thus, we conclude from our data that macrophage PON2 expression is upregulated in UC-enriched macrophages through activation of the PI(3)K signal pathway.
Shiner
Maayan
M
Lipid Research Laboratory, Technion Faculty of Medicine, The Rappaport Family Institute for Research in the Medical Sciences and Rambam Medical Center, Haifa 31096, Israel.
Fuhrman
Bianca
B
Aviram
Michael
M
D000818:Animals; D043303:Aryldialkylphosphatase / Q000096:biosynthesis* / Q000235:genetics*; D015153:Blotting, Western; D002784:Cholesterol / Q000494:pharmacology*; D008078:Cholesterol, LDL / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D007202:Indicators and Reagents; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D018613:Microscopy, Confocal; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics* / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects; D015854:Up-Regulation / Q000187:drug effects
D008078:Cholesterol, LDL; D007202:Indicators and Reagents; D002784:Cholesterol; D019869:Phosphatidylinositol 3-Kinases; D043303:Aryldialkylphosphatase; C468411:PON2 protein, human