Human scavenger receptor class B type I is expressed with cell-specific fashion in both initial and terminal site of reverse cholesterol transport.
The reverse cholesterol transport (RCT) is one of the major protective systems against atherosclerosis, in which high-density lipoprotein (HDL) removes cholesterol from lipid-laden cells and delivers it to the liver. Scavenger receptor class B type I (SR-BI) is a HDL receptor in the liver and adrenal glands and is involved in the selective uptake of cholesteryl ester from HDL, which has been extensively, analyzed using rodent models. However, the expression and regulation of the human homologue of this receptor are not known yet. We previously reported that this receptor is expressed in in vitro differentiated macrophages and its expression is up-regulated by the addition of modified lipoproteins into the medium [Hirano K, Yamashita S, Nakagawa Y, et al. Expression of human scavenger receptor class B type I in cultured human monocyte-derived macrophages and atherosclerotic lesions. Circ Res 1999;85:108-16]. In order to further investigate the physiological significance of this receptor in humans, we have performed extensive immunohistochemical analyses with specimens of the liver and adrenal glands as well as arteries with different stages of atherosclerotic lesions. In human liver and adrenal glands, a positive SR-BI immunoreactivity was detected in both hepatic and adrenal parenchymal cells as well as Kupffer cells. These parenchymal cells had a strong signal on the cell surface, whereas Kupffer cells showed a heterogeneous and punctate pattern. In human aorta and coronary arteries, SR-BI was highly expressed in atherosclerotic plaques, but not in non-atherosclerotic lesions. Double immunostaining revealed that SR-BI was expressed in a subpopulation of macrophages, of which staining pattern was similar to that observed in Kupffer cells. These data clearly demonstrated that SR-BI was expressed with cell-specific fashions in both the initial and terminal step of RCT in humans. Thus, SR-BI might be physiologically relevant and have distinct tissue-specific functions.
Nakagawa-Toyama
Yumiko
Y
Department of Internal Medicine and Molecular Science, Graduate School of Medicine, B5, Osaka University, 2-2 Yamada-oka, Suita, Osaka 565-0871, Japan.
Hirano
Ken-ichi
K
Tsujii
Ken-ichi
K
Nishida
Makoto
M
Miyagawa
Jun-ichiro
J
Sakai
Naohiko
N
Yamashita
Shizuya
S
D000311:Adrenal Glands / Q000737:chemistry / Q000378:metabolism*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001011:Aorta / Q000737:chemistry / Q000378:metabolism*; D001018:Aortic Diseases / Q000378:metabolism / Q000473:pathology; D050197:Atherosclerosis / Q000378:metabolism* / Q000473:pathology; D001692:Biological Transport; D002784:Cholesterol / Q000378:metabolism*; D002788:Cholesterol Esters / Q000378:metabolism; D008076:Cholesterol, HDL / Q000378:metabolism; D005260:Female; D005487:Foam Cells / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D007728:Kupffer Cells / Q000737:chemistry / Q000378:metabolism; D008099:Liver / Q000737:chemistry / Q000378:metabolism*; D008264:Macrophages / Q000737:chemistry / Q000378:metabolism; D008297:Male; D008856:Microscopy, Fluorescence; D008875:Middle Aged; D009928:Organ Specificity; D051122:Scavenger Receptors, Class B / Q000032:analysis* / Q000502:physiology; D017539:Tunica Intima / Q000737:chemistry / Q000378:metabolism
D002788:Cholesterol Esters; D008076:Cholesterol, HDL; C495124:SCARB1 protein, human; D051122:Scavenger Receptors, Class B; D002784:Cholesterol