International Conference: Paraoxonases - Basic and Clinical Directions of Current Research (1st) Held in Ann Arbor, Michigan on April 22-24, 2004

摘要

Human serum paraoxonase (PON1) is physically associated with high density lipoprotein (HDL) and the activity of PON 1 was shown to be inversely associated with the risk for atherosclerosis development (which is enhanced under oxidative stress). We thus questioned whether this is related to the ability of PON 1 to protect against lipids peroxidation in lipoproteins and in arterial cells. PON 1 hydrolyzed cholesteryl linoleate hydroperoxides (CL-OOH) in oxidized LDL, HDL and macrophages and in human and mice atherosclerotic coronary or carotid lesions, yielding in the formation of linoleic acid hydroperoxides (L-OOH) and linoleic acid hydroxide (L-OH). This indicates esterase- and peroxidse-like activities for PON1. The PONlQ isoform was 50% more potent than PON1R in this respect. Using site-directed mutagenesis technique, the PON 1's free sulfhydryl group at cysteine - 284 was found to be the enzyme active site. Macrophage foam cell formation is the hallmark of early atherogenesis and hence we questioned the effect of PON 1 on macrophage atherogenicity. PON 1 hydrolyzed macrophage lipid peroxides (PD) resulting in a 40% decreased content of PD, which was associated with a 36% reduced macrophage mediated oxidation of LDL and also in a 44% decreased cellular uptake of oxidized LDL (secondary to a decrease in the expression of the scavenger receptor CD-36). On using PON 1 - deficient mice (PON1/E), a 42% increased atherosclerotic lesion size was shown in comparison to control E mice and this was associated with increased (40-60%) oxidative stress in their serum, as well as in their macrophages (peritoneal and arterial). In macrophages from PON 1 mice, NADPH oxidase activation was evident, resulting in enhanced cell- mediated oxidation of LDL. PON 1 action on macrophages reversed cellular oxidative stress toward normal levels.