LDL-Induced Cell Injury. An Effect Of LDL Independent Of Specific Binding And Uptake Of LDL

LDL can injure endothelial cells in culture. HDL can inhibit this injurious effect of DDL. This effect of LDL seems to be independent of the LDL-receptor pathway since LDL-receptor negative cells were also injured. Ehdocytotic uptake of LDL appear not to be necessary for the DDL- induced cell injury to occur because LDL can injure both endothelial cells and erythrocytes at 4°C. By using radioactive ¹²⁵I-DDL an increasing amount of ¹²⁵I-LDL was shown to be associated with the cell with increasing concentrations of ¹²⁵I-LDL in the incubation medium. A corresponding increase in cell injury as measured by ⁵¹Cr-release was observed. Presence of HDL in the incubation medium reduced both the cell associated radioactivity and the ⁵¹Cr-release. Thus, a relationship between the amount of ¹²⁵I-DDL associated with the cell and the degree of cell injury was present.

In conclusion, association of DDL to the cell surface seems to be closely related to the mechanism by which DDL can induce cell injury. Any kind of endocytotic uptake of DDL is not a prerequisite for the occurrence of DDL-mediated cell injury.