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.
Miyazaki
A
A
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.
Sakashita
N
N
Lee
O
O
Takahashi
K
K
Horiuchi
S
S
Hakamata
H
H
Morganelli
P M
PM
Chang
C C
CC
Chang
T Y
TY
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