INHIBITORY EFFECTS OF OXIDIZED LOW-DENSITY-LIPOPROTEIN ON THE ACTIVITY OF PLASMA LECITHIN - CHOLESTEROL ACYLTRANSFERASE

Lecithin:cholesterol acyltransferase (LCAT) is an enzyme that is impor tant in the cholesterol reverse-transport system by converting the sur face cholesterol of high-density lipoprotein (HDL) to cholesterol este r inside HDL. We have investigated changes in plasma LCAT activity ind uced by oxidized low-density lipoiprotein(ox-LDL), (i) LCAT activity w as inhibited by the addition of even a smalt amount of ox-LDL, (ii) Th is inhibitory effect was dose-dependent and was related to the degree of oxidation of LDL, (iii) As this inhibitory effect was not prevented by antioxidants, it is suggested that it does not occur via oxidation of substrate HDL. These results suggest that cholesterol reverse-tran sport via HDL may be affected by ox-LDL and they are noteworthy in sug gesting a new physiological function for ox-LDL.