Characterization of binding and phagocytosis of oxidatively damaged erythrocyte to macrophage.
BACKGROUND
Scavenger receptors are thought to be involved in the recognition of oxidized low-density lipoprotein (oxLDL) and oxidized erythrocyte (oxRBC). However, there are controversies about the kind of receptors and ligands related to the binding. Macrophages lacking class A scavenger receptor show identical binding of oxRBC with wild-type ones.


METHODS
RBCs were oxidized with ascorbic acid and CuSO4. Lipid oxidation was measured indirectly by measuring TBARS semiquantitatively. The binding and phagocytosis were measured by counting the number of oxRBC bound or taken up after incubation at 4 degrees C or 37 degrees C for 60 minutes to 100 macrophages differentiated from human monocytic leukemia cell line.


RESULTS
The degree of oxidation and the binding of oxRBCs were dependent on the concentration of CuSO4. The binding and phagocytosis of oxRBC were inhibited by 99% with oxLDL. Fucoidan, competing class A scavenger receptor, inhibited the binding by more than 90%. The binding of oxRBC was higher at 37 degrees C than at 4 degrees C by 3 times. The binding of oxRBCs was maximal at pH 6.5 and higher than at physiologic pH by 2.8 times. At pH 8.5 and 9.5, binding decreased by 67 and 88%, respectively.


CONCLUSIONS
OxRBCs might bind and be taken up to macrophages not mainly through class A nor B scavenger receptors, but through other scavenger receptors and/or pathways. These processes are dynamic and ionic strength might be involved.
Ko
Hong Sook
HS
Division of Cardiology, Department of Internal Medicine, College of Medicine, Chung-Ang University, Seoul, Korea.
Kim
In Seop
IS
Lee
Kwangje
K
Kim
Sang Wook
SW
Kim
Chee Jeong
CJ
Ryu
Wang Seong
WS
D018955:CD36 Antigens; D004905:Erythrocyte Aging; D004912:Erythrocytes / Q000378:metabolism*; D006801:Humans; D008077:Lipoproteins, LDL / Q000378:metabolism; D008264:Macrophages / Q000378:metabolism*; D008565:Membrane Proteins; D010084:Oxidation-Reduction; D010587:Phagocytosis / Q000502:physiology*; D011971:Receptors, Immunologic / Q000378:metabolism; D018110:Receptors, Lipoprotein; D051116:Receptors, Scavenger; D051117:Scavenger Receptors, Class A; D051122:Scavenger Receptors, Class B; D014407:Tumor Cells, Cultured / Q000378:metabolism
D018955:CD36 Antigens; D008077:Lipoproteins, LDL; D008565:Membrane Proteins; D011971:Receptors, Immunologic; D018110:Receptors, Lipoprotein; D051116:Receptors, Scavenger; C454739:Scarb1 protein, mouse; D051117:Scavenger Receptors, Class A; D051122:Scavenger Receptors, Class B