Interactions of C-reactive protein with low-density lipoproteins: Implications for an active role of modified C-reactive protein in atherosclerosis

The interaction of C-reactive protein with low-density lipoprotein is considered to be one of the key properties that link C-reactive protein with atherosclerosis. However the data obtained to date are controversial, and hence make it difficult to conclude actual physiological or pathological impact of such interaction. The incompatible findings could be ascribed to the different structural state of C-reactive protein and/or low-density lipoprotein. We investigated in detail the interaction of various C-reactive protein isoforms with native and modified low-density lipoprotein. Our data showed "C-reactive protein" could indeed interact with each of native low-density lipoprotein, oxidized or enzymatically modified low-density lipoprotein, but that interaction occurs primarily when C-reactive protein is conformed in a modified form and not pentameric structure. Low level of modified C-reactive protein "contaminant" could confer C-reactive protein obvious low-density lipoprotein binding capacity. Interaction of modified C-reactive protein and low-density lipoprotein was mediated synergistically by both electrostatic association with ApoB and hydrophobic insertion into lipid layer. When complexed with modified C-reactive protein, macrophage binding/uptake of native and oxidized low-density lipoprotein was either increased 150% or decreased 35%, respectively. Thus the interaction of modified C-reactive protein with low-density lipoprotein may contribute to the regulation of low-density lipoprotein metabolism and foam cell formation in arterial wall. These results highlight an active role of modified C-reactive protein in atherosclerotic process.