Abstract 316: Paraoxonase 1 (PON1) Promotes the Cholesterol Efflux and Regulates the Reverse Cholesterol Transport (RCT)

Abstract

Paraoxonase 1 (PON1) is a High Density Lipoprotein (HDL) associated enzyme which contributes to the antioxidant and anti-inflammatory properties of HDL. It also stimulates cholesterol efflux mediated by HDL. The purpose of this study is to determine the mechanism by which PON1 regulates this antiatherogenic activity of HDL. The oxidized phospholipids hydrolysis by PON1 results in the formation of Lysophosphatidylcholine (LPC). The phospholipase PON1 activity effect on the cholesterol efflux and the gene and protein expression were determined in vitro on J774 macrophages cells and was also determined in vivo on C57/BL6 male mice. Our results show that due to its phospholipase activity, PON1 hydrolyzes oxidized LDL (oxLDL) and contributes to the formation of LPC, which stimulates cholesterol efflux from macrophages. Our results show that PON1 induced the expression of ABCA1 cholesterol transporters. Western blot as well as qPCR analysis show that PON1 stimulate PPARγ and LXRα nuclear receptors expression. Moreover, the use of ABCA1, PPARγ and LXRα inhibitors (respectively DIDS, GGPP and GW9662) affects the capacity of PON1 to stimulate cholesterol efflux, in particular by decreasing the proteins expression of interest (ABCA1, PPARγ and LXRα). Incubation of macrophages with purified LPC with macrophages induces a high expression of PPARγ-LXRα-ABCA1 pathway. Incubation of macrophages with PON1-oxLDL mixture and their injection to mice increase significantly the reverse cholesterol transport. Our results show that tPON1 stimulate both cholesterol efflux and RCT. via the regulation of the PPARγ-LXRα-ABCA1 pathway. This effect is attributed to the phospholipase activity of PON1 which mediates the hydrolysis of ox-LDL to form LPC.