Reversible inhibitory effects of apo-B-carrying lipoproteins on acid lipase activity of mononuclear leukocytes from cholesterol-fed rabbits.

Abstract

Acid lipase (AL) activity of mixed mononuclear leukocytes from cholesterol-fed rabbits exhibited reduced values when compared with that of normolipidemic rabbits. The observed suppression of the AL activity was reversed commensurate with a fall in the plasma concentrations of cholesterol and lipid peroxides (LPO) after the rabbits were returned to a basal diet. The AL activity was negatively correlated with both plasma cholesterol and LPO levels in rabbits. This reversible inhibition was caused by apo-B-carrying lipoproteins from the hypercholesterolemic rabbits, and protective effects were produced by preincubation of lipoproteins with anti apo-B serum. The increase in plasma LPO in the hypercholesterolemic rabbits suggests that the observed reversible inhibition of the AL activity might be due to an increase in free radicals produced in the process of lipid peroxidation in the hypercholesterolemic state. The current findings also suggest that, through the combined effects of suppression of lysosomal hydrolysis and stimulation of microsomal synthesis of esterified cholesterol, β-migrating very low density lipoprotein in cholesterol-fed rabbits accelerates hypercholesterolemia and causes accumulation of esterified cholesterol in cells.