Effect of Glycyrrhizin on Lysosomal Enzymes in Rat Arterial Wall

It has been reported that Glycyrrhizin inhibits the elevation of plasma total cholesterol level and reduces the formation of atheroma in the lanolinloaded rabbits. To clarify the mechanisms of the antiatherosclerotic action of Glycyrrhizin, the effects of Glycyrrhizin on lysosomal enzyme activities which were involved in the lipid metabolism of rat arterial wall, were investigated.Glycyrrhizin did not affect the uptake and the hydrolysis of cholesteryl [14C]oleate-labelled LDL in smooth muscle cells. Acid cholesterol esterase (acid CEase) activity was decreased by the addition of 0.25mM Glycyrrhizin. Glycyrrhetinic acid which is the aglicone from Glycyrrhizin did not change acid CEase activity.These results suggest that Glycyrrhizin did not work on acid CEase directly.Phospholipase A2 (PLase A2) activity increased in hypercholesterolemic rat arterial wall. PLase A2-treatment of arterial lysosomal fraction increased the releases of acid phosphatase (AcPase) and acid CEase from the lysosome. By the addition of Glycyrrhizin to PLase A2-treatment of lysosomal fraction, the release of AcPase from the lysosome was suppressed.From these results, it was suggested that Glycyrrhizin may stabilize the lysosome by inhibiting PLase A2 activity.