Expression of ACAT-1 protein in human atherosclerotic lesions and cultured human monocytes-macrophages.
The acyl coenzyme A:cholesterol acyltransferase (ACAT) gene was first cloned in 1993 (Chang et al, J Biol Chem. 1993;268:20747-20755; designated ACAT-1). Using affinity-purified antibodies raised against the N-terminal portion of human ACAT-1 protein, we performed immunohistochemical localization studies and showed that the ACAT-1 protein was highly expressed in atherosclerotic lesions of the human aorta. We also performed cell-specific localization studies using double immunostaining and showed that ACAT-1 was predominantly expressed in macrophages but not in smooth muscle cells. We then used a cell culture system in vitro to monitor the ACAT-1 expression in differentiating monocytes-macrophages. The ACAT-1 protein content increased by up to 10-fold when monocytes spontaneously differentiated into macrophages. This increase occurred within the first 2 days of culturing the monocytes and reached a plateau level within 4 days of culturing, indicating that the increase in ACAT-1 protein content is an early event during the monocyte differentiation process. The ACAT-1 protein expressed in the differentiating monocytes-macrophages was shown to be active by enzyme assay in vitro. The high levels of ACAT-1 present in macrophages maintained in culture can explain the high ACAT-1 contents found in atherosclerotic lesions. Our results thus support the idea that ACAT-1 plays an important role in differentiating monocytes and in forming macrophage foam cells during the development of human atherosclerosis.
Department of Biochemistry, Dartmouth Medical School, Hanover, NH, USA, the Second Department of Pathology and the Department of Biochemistry Kumamoto University School of Medicine, Kumamo, Japan.
A
A
Miyazaki
N
N
Sakashita
O
O
Lee
K
K
Takahashi
S
S
Horiuchi
H
H
Hakamata
P M
PM
Morganelli
C C
CC
Chang
T Y
TY
Chang
D000328:Adult; D000368:Aged; D000818:Animals; D001161:Arteriosclerosis / Q000201:enzymology* / Q000473:pathology; D002478:Cells, Cultured; D005260:Female; D006801:Humans; D008264:Macrophages / Q000201:enzymology*; D008297:Male; D008875:Middle Aged; D009000:Monocytes / Q000201:enzymology*; D011817:Rabbits; D002785:Sterol O-Acyltransferase / Q000378:metabolism*
D002785:Sterol O-Acyltransferase