Hepatic paraoxonase 1 ameliorates dysfunctional high-density lipoprotein and atherosclerosis in scavenger receptor class B type I deficient mice.

Abstract

Background\nHigh-density lipoprotein (HDL) plays an antiatherogenic role by mediating reverse cholesterol transport (RCT), antioxidation, anti-inflammation, and endothelial cell protection. Recently, series of evidence have shown that HDL can also convert to proatherogenic HDL under certain circumstances. Plasma paraoxonase 1 (PON1) as an HDL-bound esterase, is responsible for most of the antioxidant properties of HDL. However, whether PON1 can serve as a therapeutic target of dysfunctional HDL-related atherosclerosis remains unclear.\n\n\nMethods\nIn this study, scavenger receptor class B type I deficient (Scarb1-/- ) mice were used as the animal model with dysfunctional HDL and increased atherosclerotic susceptibility. Hepatic PON1 overexpression and secretion into circulation were achieved by lentivirus injection through the tail vein. We monitored plasma lipids levels and lipoprotein profiles in Scarb1-/- mice, and measured the levels and activities of proteins associated with HDL function. Meanwhile, lipid deposition in the liver and atherosclerotic lesions was quantified. Hepatic genes relevant to HDL metabolism and inflammation were analyzed.\n\n\nResults\nThe results showed the relative levels of PON1 in liver and plasma were increased by 1.1-fold and 1.6-fold, respectively, and mean plasma PON1 activity was increased by 63%. High-level PON1 increased the antioxidative and anti-inflammatory properties, promoted HDL maturation and macrophage cholesterol efflux through increasing HDL functional proteins components apolipoprotein A1 (APOA1), apolipoprotein E (APOE), and lecithin-cholesterol acyltransferase (LCAT), while decreased inflammatory protein markers, such as serum amyloid A (SAA), apolipoprotein A4 (APOA4) and alpha 1 antitrypsin (A1AT). Furthermore, hepatic PON1 overexpression linked the effects of antioxidation and anti-inflammation with HDL metabolism regulation mainly through up-regulating liver X receptor alpha (LXRα) and its downstream genes. The pleiotropic effects involved promoting HDL biogenesis by raising the level of APOA1, increasing cholesterol uptake by the liver through the APOE-low density lipoprotein receptor (LDLR) pathway, and increasing cholesterol excretion into the bile, thereby reducing hepatic steatosis and aorta atherosclerosis in Western diet-fed mice.\n\n\nConclusions\nOur study reveals that high-level PON1 improved dysfunctional HDL and alleviated the development of atherosclerosis in Scarb1-/- mice. It is suggested that PON1 represents a promising target of HDL-based therapeutic strategy for HDL-related atherosclerotic cardiovascular disease.