Oxidative damage of cells and components in living bodies is one of the possible means of damage that can take place in vivo. [1][2][3] Recognition and phagocytic removal of damaged components or cells is an important function of macrophages in maintaining homeostasis.4) It is known that macrophages avidly bind and take up oxidized low density lipoprotein through the scavenger receptors on the cell surface, which may lead to the accumulation of lipid-laden foam cells in the artery wall in atherosclerotic lesions. [5][6][7][8][9][10] We have found that macrophages bind oxidatively damaged erythrocytes, [11][12][13][14] polymorphonuclear leukocytes, 15) and T-lymphoid cell line Jurkat cells, [16][17][18] and this recognition is due to the lectin-like receptors on the macrophage cell surface for sialylated poly-N-acetyllactosaminyl sugar chains on the oxidized cells. 13,[15][16][17][18][19][20] Upon oxidation of these cells, band 3 or CD43 glycoproteins bearing sialylated poly-N-acetyllactosaminyl sugar chains on the cell surface aggregate and the sugar chains in a higher density are more readily recognized by macrophages in the absence of serum. The presence of the lectin-like receptors on macrophages has been demonstrated. 14,16,18) In the previous study, we have demonstrated that antioxidants at relatively high concentrations inhibited macrophage functions, i.e., binding of oxidized low density lipoprotein, foam cell formation and accumulation of cholesterol, and suggested that the scavenger receptor activity of macrophages is exerted by oxidative mechanisms. 21) In the present study, whether oxidative mechanisms were also involved in macrophage recognition of oxidized erythrocytes through the lectin-like receptors was examined by preincubation of macrophages with water-soluble antioxidants. It was found that the recognition of macrophages for oxidized erythrocytes was inhibited by ascorbic acid-related compounds, catechin compounds and thiol-related compounds, suggesting the involvement of oxidative mechanisms in the macrophage lectin-like receptor recognition for these erythrocytes.
MATERIALS AND METHODSMaterials Hanks' balanced salt solution (HBSS) and N-2-hyroxyethyl-piperazine-NЈ-2-ethanesulfonic acid (HEPES) (pH 7.2) were obtained from Nissui Pharmaceutical Co., Tokyo, and Dojindo Laboratories, Kumamoto, respectively. Thioglycollate medium was obtained from Difco Laboratories, Detroit, MI, U.S.A. RPMI 1640 medium and penicillinstreptomycin solution were obtained from Gibco Laboratories, Grand Island, NY, U.S.A. Glutathione (GSH), oxidized glutathione (GSSG) and L-buthionine-[S,R]-sulfoximine (buthionine sulfoximine, BSO) were obtained from Sigma Chemical Company, St. Louis, MO, U.S.A. Epicatechin (EC), epigallocatechin (EGC), epicatechin gallate (ECg), and epigallocatechin gallate (EGCg) were obtained from Funakoshi, Tokyo. Dehydroascorbic acid (DHA) was from Aldrich Chemical, Milwaukee, MI, U.S.A. N-Acetylcysteine (NAC), L-ascorbic acid (ascorbic acid, ASA), erythorbic acid (ERA), Mayer's hematoxylin solu...
