Enhancement of low density lipoprotein binding to both low density lipoprotein receptor-positive and -negative cells by tetracycline antibiotics.

Some tetracycline (TC) antibiotics, including TC and anhydrotetracycline, have been found to enhance specific binding of low density lipoprotein (LDL) to both LDL receptor-positive and -negative cells at relatively higher concentrations. When incubated at 37 degrees C, the ability of LDL receptor-negative human fibroblasts to bind 125I-LDL was increased from < 2 to 45 ng/mg by 170 microM TC. In normal human fibroblasts and Hep G2 cells, 125I-LDL binding was elevated 1.4- to 2-fold by 113 microM TC. The 125I-LDL binding in the presence of TC was diminished by both heparin and EDTA. The enhancement by TC was not observed when 125I-LDL binding was assayed at 4 degrees C. TC enhanced LDL binding to paraformaldehyde-fixed Hep G2 cells, excluding LDL receptor induction in the mechanism. These results demonstrated that TC enhanced cellular LDL binding through a process not involving functional LDL receptors.