β-Migrating very low density lipoproteins induce foam cell formation in mouse mesangial cells

To elucidate whether β-migrating very low density lipoproteins (β-VLDL) induce foam cell formation in mesangial cells or not, surface binding and foam cell formation with β-VLDL were studied in mouse mesangial cells. Specific binding kinetics for β-VLDL and low density lipoproteins (LDL) on the mesangial cells were observed with Kd = 3.8 and 13.7 μg/ml, and Bmax = 65.9 and 71.9 ng/mg cell protein at 4 °C, respectively. The binding of β-VLDL was inhibited by excess amounts of LDL or β-VLDL, but not by acetyl-low density lipoproteins. Ligand blotting using β-VLDL or LDL and immunoblotting using anti-human LDL receptor monoclonal antibody detected the same apparent single protein (approx. 130 kDa). Incorporation of [14C]oleate into cholesteryl ester in mouse mesangial cells was enhanced by β-VLDL to 3-fold higher than that by LDL, and it was inhibited by chloroquine or anti-human LDL receptor monoclonal antibody. The light microscopic findings also demonstrated that cholesteryl ester deposition increased in these cells incubated with β-VLDL, but not with LDL. In conclusion, β-VLDL was specifically taken up by receptor-mediated endocytosis in mouse mesangial cells through LDL receptors, resulting in foam cell formation.