Modulation by sodium ascorbate of the effect of chloroquine on low density lipoprotein retention and degradation in cultured human skin fibroblasts.

Human skin fibroblasts in culture were incubated for 48 h with 125I-labelled low density lipoprotein and chloroquine in the presence and absence of sodium ascorbate. Pretreatment of the cells for 3 days with sodium ascorbate and addition of the vitamin during incubation resulted in a decrease in cellular retention and an increase in degradation of the labelled low density lipoprotein. Similar results were obtained when the cells were pretreated for 3 days but the vitamin was not added during the final 48 h of incubation. Pretreatment of the cells with dithiothreitol, butylated hydroxy-toluene, beta-mercaptoethanol and D-alpha-tocopherol had a similar effect to that of ascorbate, i.e. reduction in low density lipoprotein retention and increase in degradation. Neither ascorbate nor the other reducing agents affected low density lipoprotein catabolism in control cells not treated with chloroquine. Sodium ascorbate pretreatment resulted also in a slight but significant alleviation of the chloroquine-induced inhibition of hydrolysis of cholesterol linoleate. It is proposed that sodium ascorbate by virtue of its reducing properties provides some protection to the intralysosomal hydrolases against the inhibitory action of chloroquine. If cholesterol accumulation in human and experimental atheroma is caused by partial inhibition of lysosomal enzymes, sodium ascorbate could play a role in the alleviation of such an inhibition.