Regulation of macrophage apolipoprotein E gene expression by cholesterol.
The relationship between macrophage cholesterol content and apolipoprotein E (apoE) gene expression was investigated in cultured mouse peritoneal macrophages. Acetylated low density lipoprotein (ALDL) at 25 micrograms/ml led to increased macrophage messenger RNA abundance as detected by Northern blot hybridization. Incubation in a range of ALDL concentrations (0-100 microgram/ml) led to graded increases in macrophage free and esterified cholesterol, and apoE mRNA detected by slot blot hybridization. After a 2-h pulse of ALDL, with or without acyl-CoA:cholesterol acyltransferase inhibition, increased apoE mRNA was not detected until after 6 h. Removal of cholesterol from upregulated macrophages, using human high density lipoprotein, resulted in a return of apoE mRNA levels toward baseline. Nuclear run-off transcription assays demonstrated increased apoE gene transcription in macrophages incubated with ALDL. It is concluded that: a) previously reported changes in macrophage apoE content and secretion after cholesterol enrichment or depletion can be attributed to changes in apoE mRNA levels; and b) cholesterol-induced changes in apoE mRNA are associated with increased apoE gene transcription.
Mazzone
T
T
Department of Medicine, Michael Reese Hospital, University of Chicago, IL 60637.
Basheeruddin
K
K
Poulos
C
C
D000818:Animals; D001057:Apolipoproteins E / Q000096:biosynthesis* / Q000235:genetics; D015152:Blotting, Northern; D002478:Cells, Cultured; D002784:Cholesterol / Q000502:physiology*; D005786:Gene Expression Regulation; D008077:Lipoproteins, LDL / Q000378:metabolism; D008264:Macrophages / Q000378:metabolism*; D051379:Mice; D008813:Mice, Inbred ICR; D012333:RNA, Messenger / Q000378:metabolism; D002785:Sterol O-Acyltransferase / Q000378:metabolism; D014158:Transcription, Genetic
D001057:Apolipoproteins E; D008077:Lipoproteins, LDL; D012333:RNA, Messenger; C032629:acetyl-LDL; D002784:Cholesterol; D002785:Sterol O-Acyltransferase