Endocytosis of advanced glycation end-products in bovine choriocapillaris endothelial cells.
OBJECTIVE
Age-related changes in Bruch's membrane (BM), situated between the retina and the choroid, include the accumulation of advanced glycation end-products (AGEs) and other modified macromolecules. An important clearance mechanism for such molecules is endocytosis via macrophages and specialized endothelial cells. This study examined the endocytic clearance of AGEs in choriocapillaris endothelial (CCE) cells, which are strategically located beneath the BM.


METHODS
Bovine CCE cultures were incubated with radiolabeled or fluorescently labeled AGE-modified bovine serum albumin (AGE-BSA). Cells and tissues were examined for the expression of two AGE-binding scavenger receptors, stabilin-1 and -2, by immunohistochemistry and Western blotting, and with antibody inhibition studies.


RESULTS
CCE cells effectively endocytosed AGE-BSA via a scavenger receptor-mediated pathway. A polyclonal antibody against stabilin-2 significantly inhibited endocytosis (40%). Tissue sections stained positive for stabilin-2 and -1 in the choriocapillaris layer, which was confirmed by immunoblots of cell extracts. Colocalization of stabilin-1 and -2 and internalized AGE-BSA was seen in early endosomes.


CONCLUSIONS
CCEs actively endocytose AGE-BSA and express the scavenger receptors, stabilin-1 and -2, of which at least stabilin-2 is involved in AGE-BSA uptake. Impairment of this stabilin-mediated clearance function may contribute to depositions of waste macromolecules in BM and subsequent retinopathy.
Li
Ruomei
R
Department of Cell Biology and Histology, Institute of Medical Biology, University of Tromsø, Norway. ruomei.li@uit.no
McCourt
Peter
P
Schledzewski
Kai
K
Goerdt
Sergij
S
Moldenhauer
Gerhard
G
Liu
Xipu
X
Smedsrød
Bård
B
Sørensen
Karen Kristine
KK
D000818:Animals; D016570:Bruch Membrane; D002196:Capillaries / Q000166:cytology; D002417:Cattle; D015816:Cell Adhesion Molecules, Neuronal / Q000032:analysis; D002478:Cells, Cultured; D002829:Choroid / Q000098:blood supply; D004705:Endocytosis; D042783:Endothelial Cells / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000166:cytology*; D017127:Glycation End Products, Advanced / Q000378:metabolism*; D051116:Receptors, Scavenger / Q000032:analysis
D015816:Cell Adhesion Molecules, Neuronal; D017127:Glycation End Products, Advanced; D051116:Receptors, Scavenger