Interactions between macrophages and oxidized low density lipoprotein in the presence of type I collagen.

In order to investigate the influence of collagen on the interactions between macrophages and oxidatively modified low density lipoprotein (ox-LDL), type I collagen was isolated from rat tail tendon and prepared as a gel. The binding of 125I-ox-LDL, 125I-malondialdehyde (MDA)-LDL and 125I-acetyl-LDL to collagen was higher but the binding of 125I-4-hydroxynonenal (HNE)-LDL was lower than that of native 125I-LDL. When mouse peritoneal macrophages were cultivated on this collagen gel, most of the modified LDL was bound to the collagen gel rather than taken up by macrophages. The amount of modified 125I-LDL degraded by the macrophages decreased in the presence of the collagen gel. In the absence of gel a similar degree of reduction in degradation of modified 125I-LDL by macrophages was obtained when the cells were treated with cytochalasin D, an inhibitor of non-specific phagocytosis. However, the treatment of the macrophages cultivated on the collagen gel with cytochalasin D did not influence the degradation of 125I-ox-LDL and 125I-HNE-LDL. These results suggest that the uptake of ox-LDL by macrophages grown on collagen gel is primarily mediated via the scavenger receptors pathway, whereas in the absence of collagen also other mechanisms of uptake are operating.