LOW-DENSITY LIPOPROTEINS BIND MORE TO TYPE-I AND TYPE-III COLLAGENS BY NEGATIVE CHARGE-DEPENDENT MECHANISMS THAN TO TYPE-IV AND TYPE-V COLLAGENS

The accumulation of low density lipoprotein (LDL) in the arterial inti ma is an important characteristic of atherosclerosis. We investigated the mechanisms by which LDL binds to different types of collagen. The binding activities of I-125-labeled human native LDL (nLDL) and copper -oxidized LDL (oxLDL) with different collagen gels prepared in type I collagen-based mixtures with types I, III, IV and V (I+I, I+III, I+IV and I+V, respectively) were examined. A concentration of 20 mu g LDL p rotein/150 mu g collagen/well was used. The diffusion of both nLDL and oxLDL into the collagen gels reached an equilibrium after 48 h. All o f the collagen gels showed the same rates of diffusion with both LDLs. The binding activities of oxLDL were significantly greater than those of nLDL (P < 0.001%), while the binding activities for both LDLs foll owed the order I+I and I+III > I+V > I+IV. However, the increased bind ing rate of oxLDL compared to nLDL was 1.66 for I+IV, 1.50 for I+V, 1. 33 for I+I and 1.19 for I+III. When a 10-fold higher dose of NaCl (1 M ) was added to the oxLDL medium, the binding rate of oxLDL was reduced (rate of reduction: 52% (I+I), 48% (I+III), 35% (I+IV), 13% (I+V)). T hese results suggest that oxLDL binds more to type I and III collagens by negative charge-dependent mechanisms than to type IV and V collage ns. Therefore, types I and III collagens may play an important role in trapping LDL, especially oxLDL. Therefore, oxidatively modified LDL m ay contribute to atherogenesis due to its longer retention in the arte rial wall.