Deficiency of Antioxidative Paraoxonase 2 (Pon2) Leads to Increased Number of Phenotypic LT-HSCs and Disturbed Erythropoiesis.

BACKGROUND: Long-term hematopoietic stem cells (LT-HSCs) reside in bone marrow niches with tightly controlled reactive oxygen species (ROS) levels. ROS increase results into LT-HSC differentiation and stem cell exhaustion. Paraoxonase 2 (PON2) has been shown to be important for ROS control. OBJECTIVES: We investigate the effects of inactivation of the PON2 gene on hematopoietic cell differentiation and activity. METHODS AND RESULTS: In young mice with inactivated Pon2 gene (Pon2 -/-, <3 months), we observed an increase of LT-HSCs and a reduced frequency of progenitor cells. In competitive transplantations, young Pon2-/- BM outcompeted WT BM at early time points. ROS levels were significantly increased in Pon2-/- whole BM, but not in Pon2-/- LT-HSCs. In more differentiated stages of hematopoiesis, Pon2 deficiency led to a misbalanced erythropoiesis both in physiologic and stress conditions. In older mice (>9 months), Pon2 depletion caused an increase in LT-HSCs as well as increased levels of granulocyte/macrophage progenitors (GMPs) and myeloid skewing, indicating a premature aging phenotype. No significant changes in ROS levels in old Pon2-/- LT- and short-term (ST-) HSCs were observed, but a significant reduction of spontaneous apoptotic cell death was measured. RNA-seq analysis in Pon2 -/- LT-HSCs identified overrepresentation of genes involved in the C-X-C chemokine receptor type 4 (Cxcr4) signaling, suggesting compensatory mechanisms to overcome ROS-mediated accelerated aging in hematopoietic progenitor cells. CONCLUSIONS: In summary, our current data indicate that PON2 is involved in the regulation of HSC functions.

Chemokine (C-C motif) ligand 2 gene ablation protects low-density lipoprotein and paraoxonase-1 double deficient mice from liver injury, oxidative stress and inflammation.

The risk of non-alcoholic fatty liver disease increases with obesity. Vulnerability to oxidative stress and/or inflammation represents a crucial step in non-alcoholic fatty liver disease progression through abnormal metabolic responses. In this study, we investigated the role of CCL2 gene ablation in mice that were double deficient in low density lipoprotein receptor and in paraoxonase-1. Mass spectrometry methods were used to assess the liver metabolic response in mice fed either regular chow or a high-fat diet. Dietary fat caused liver steatosis, oxidative stress and the accumulation of pro-inflammatory macrophages in the livers of double deficient mice. We observed alterations in energy metabolism-related pathways and in metabolites associated with the methionine cycle and the glutathione reduction pathway. This metabolic response was associated with impaired autophagy. Conversely, when we established CCL2 deficiency, histologic features of fatty liver disease were abrogated, hepatic liver oxidative stress decreased, and anti-inflammatory macrophage marker expression levels increased. These changes were associated with the normalization of metabolic disturbances and increased lysosome-associated membrane protein 2, expression, which suggests enhanced chaperone-mediated autophagy. This study demonstrates that CCL2 is a key molecule for the development of metabolic and histological alterations in the liver of mice sensitive to the development of hyperlipidemia and hepatic steatosis, a finding with potential to identify new therapeutic targets in liver diseases.

Paraoxonase 2 protects against acute myocardial ischemia-reperfusion injury by modulating mitochondrial function and oxidative stress via the PI3K/Akt/GSK-3ß RISK pathway.

OBJECTIVE: To investigate the novel role of Paraoxonase 2 (PON2) in modulating acute myocardial ischemia-reperfusion injury (IRI). APPROACH: IRI was induced both in vivo and ex vivo in male, C57BL6/J (WT) and PON2-deficient (PON-def) mice. In addition, in vitro hypoxia-reoxygenation injury (HRI) was induced in H9c2 cells expressing empty vector (H9c2-EV) or human PON2 (H9c2-hPON2) ±â€¯LY294002 (a potent PI3K inhibitor). Infarct size, PON2 gene expression, mitochondrial calcium retention capacity (CRC), reactive oxygen species (ROS) generation, mitochondrial membrane potential, CHOP and pGSK-3ß protein levels, and cell apoptosis were evaluated. RESULTS: PON2 gene expression is upregulated in WT mice following in vivo IRI. PON2-def mice exhibit a 2-fold larger infarct, increased CHOP levels, and reduced pGSK-3ß levels compared to WT controls. Global cardiac mitochondria isolated from PON2-def mice exhibit reduced CRC and increased ROS production. Cardiomyocytes isolated from PON2-def mice subjected to ex vivo IRI have mitochondria with reduced CRC (also seen under non-IRI conditions), and increased ROS generation and apoptosis compared to WT controls. PON2 knockdown in H9c2 cells subjected to HRI leads to an increase in mitochondrial membrane depolarization. H9c2-hPON2 cells exhibit i) improvement in mitochondrial membrane potential, pGSK-3ß levels and mitochondrial CRC, and ii) decrease in CHOP levels, mitochondrial ROS generation and cell apoptosis, when compared to H9c2-EV controls. Treatment with LY294002 resulted in a decrease of mitochondrial CRC and increase in mitochondrial ROS production and cell apoptosis in the H9c2-hPON2 group versus H9c2-EV controls. CONCLUSION: PON2 protects against acute myocardial IRI by reducing mitochondrial dysfunction and oxidative stress in cardiomyocytes via activation of the PI3K/Akt/GSK-3ß RISK pathway.

Paraoxonases-1, -2 and -3: What are their functions?

Paraoxonase-1 (PON1), an esterase/lactonase primarily associated with plasma high-density lipoprotein (HDL), was the first member of this family of enzymes to be characterized. Its name was derived from its ability to hydrolyze paraoxon, the toxic metabolite of the insecticide parathion. Related enzymes PON2 and PON3 were named from their evolutionary relationship with PON1. Mice with each PON gene knocked out were generated at UCLA and have been key for elucidating their roles in organophosphorus (OP) metabolism, cardiovascular disease, innate immunity, obesity, and cancer. PON1 status, determined with two-substrate analyses, reveals an individual's functional Q192R genotype and activity levels. The three-dimensional structure for a chimeric PON1 has been useful for understanding the structural properties of PON1 and for engineering PON1 as a catalytic scavenger of OP compounds. All three PONs hydrolyze microbial N-acyl homoserine lactone quorum sensing factors, quenching Pseudomonas aeruginosa's pathogenesis. All three PONs modulate oxidative stress and inflammation. PON2 is localized in the mitochondria and endoplasmic reticulum. PON2 has potent antioxidant properties and is found at 3- to 4-fold higher levels in females than males, providing increased protection against oxidative stress, as observed in primary cultures of neurons and astrocytes from female mice compared with male mice. The higher levels of PON2 in females may explain the lower frequency of neurological and cardiovascular diseases in females and the ability to identify males but not females with Parkinson's disease using a special PON1 status assay. Less is known about PON3; however, recent experiments with PON3 knockout mice show them to be susceptible to obesity, gallstone formation and atherosclerosis. Like PONs 1 and 2, PON3 also appears to modulate oxidative stress. It is localized in the endoplasmic reticulum, mitochondria and on HDL. Both PON2 and PON3 are upregulated in cancer, favoring tumor progression through mitochondrial protection against oxidative stress and apoptosis.

Hyperhomocysteinemia: a missing link to dysfunctional HDL via paraoxanase-1.

Paraoxanase-1 (PON1) is an HDL-associated enzyme that contributes to the antioxidant and antiatherosclerotic properties of HDL. Lack of PON1 results in dysfunctional HDL. HHcy is a risk factor for cardiovascular disorders, and instigates vascular dysfunction and ECM remodeling. Although studies have reported HHcy during atherosclerosis, the exact mechanism is unclear. Here, we hypothesize that dysfunctional HDL due to lack of PON1 contributes to endothelial impairment and atherogenesis through HHcy-induced ECM re-modeling. To verify this hypothesis, we used C57BL6/J and PON1 knockout mice (KO) and fed them an atherogenic diet. The expression of Akt, ADMA, and DDAH, as well as endothelial gap junction proteins such as Cx-37 and Cx-40 and eNOS was measured for vascular dysfunction and inflammation. We observed that cardiac function was decreased and plasma Hcy levels were increased in PON1 KO mice fed the atherogenic diet compared with the controls. Expression of Akt, eNOS, DDAH, Cx-37, and Cx-40 was decreased, and the expression of MMP-9 and ADMA was increased in PON1 KO mice fed an atherogenic diet compared with the controls. Our results suggest that HHcy plays an intricate role in dysfunctional HDL, owing to the lack of PON1. This contributes to vascular endothelial impairment and atherosclerosis through MMP-9-induced vascular remodeling.

PON3 knockout mice are susceptible to obesity, gallstone formation, and atherosclerosis.

We report the engineering and characterization of paraoxonase-3 knockout mice (Pon3KO). The mice were generally healthy but exhibited quantitative alterations in bile acid metabolism and a 37% increased body weight compared to the wild-type mice on a high fat diet. PON3 was enriched in the mitochondria-associated membrane fraction of hepatocytes. PON3 deficiency resulted in impaired mitochondrial respiration, increased mitochondrial superoxide levels, and increased hepatic expression of inflammatory genes. PON3 deficiency did not influence atherosclerosis development on an apolipoprotein E null hyperlipidemic background, but it did lead to a significant 60% increase in atherosclerotic lesion size in Pon3KO mice on the C57BL/6J background when fed a cholate-cholesterol diet. On the diet, the Pon3KO had significantly increased plasma intermediate-density lipoprotein/LDL cholesterol and bile acid levels. They also exhibited significantly elevated levels of hepatotoxicity markers in circulation, a 58% increase in gallstone weight, a 40% increase in hepatic cholesterol level, and increased mortality. Furthermore, Pon3KO mice exhibited decreased hepatic bile acid synthesis and decreased bile acid levels in the small intestine compared with wild-type mice. Our study suggests a role for PON3 in the metabolism of lipid and bile acid as well as protection against atherosclerosis, gallstone disease, and obesity.

Paraoxonase-1 deficiency is associated with severe liver steatosis in mice fed a high-fat high-cholesterol diet: a metabolomic approach.

Oxidative stress is a determinant of liver steatosis and the progression to more severe forms of disease. The present study investigated the effect of paraoxonase-1 (PON1) deficiency on histological alterations and hepatic metabolism in mice fed a high-fat high-cholesterol diet. We performed nontargeted metabolomics on liver tissues from 8 male PON1-deficient mice and 8 wild-type animals fed a high-fat, high-cholesterol diet for 22 weeks. We also measured 8-oxo-20-deoxyguanosine, reduced and oxidized glutathione, malondialdehyde, 8-isoprostanes and protein carbonyl concentrations. Results indicated lipid droplets in 14.5% of the hepatocytes of wild-type mice and in 83.3% of the PON1-deficient animals (P < 0.001). The metabolomic assay included 322 biochemical compounds, 169 of which were significantly decreased and 16 increased in PON1-deficient mice. There were significant increases in lipid peroxide concentrations and oxidative stress markers. We also found decreased glycolysis and the Krebs cycle. The urea cycle was decreased, and the pyrimidine cycle had a significant increase in orotate. The pathways of triglyceride and phospholipid synthesis were significantly increased. We conclude that PON1 deficiency is associated with oxidative stress and metabolic alterations leading to steatosis in the livers of mice receiving a high-fat high-cholesterol diet.

Macrophage paraoxonase 2 regulates calcium homeostasis and cell survival under endoplasmic reticulum stress conditions and is sufficient to prevent the development of aggravated atherosclerosis in paraoxonase 2 deficiency/apoE-/- mice on a Western diet.

Paraoxonase 2 deficiency (PON2-def) alters mitochondrial function and exacerbates the development of atherosclerosis in mice. PON2 overexpression protects against ER stress in cell culture. In this paper, we examined the role of PON2 in the unexplored link between ER stress and mitochondrial dysfunction and tested whether restoration of PON2 in macrophages is sufficient to reduce aggravated atherosclerosis in PON2-def/apoE(-/-) mice on a Western diet. ER stress response genes, intracellular calcium levels, and apoptotic nuclei were significantly elevated in PON2-def/apoE(-/-) macrophages compared to apoE(-/-) macrophages in response to ER stressors, but not at the basal level. In contrast, PON2-def/apoE(-/-) macrophages exhibited greater mitochondrial stress at the basal level, which was further worsened in response to ER stressors. There was no difference in ER stress response genes and apoptotic nuclei between apoE(-/-) and PON2-def/apoE(-/-) macrophages when pretreated with xestospongin (which blocks the release of calcium from ER) suggesting that PON2 modulates cell survival and ER stress by maintaining calcium homeostasis. Treatment with a mitochondrial calcium uptake inhibitor, RU360, attenuated ER stressor mediated mitochondrial dysfunction in PON2-def/apoE(-/-) macrophages. CHOP expression (ER stress marker) and apoptotic nuclei were significantly higher in aortic lesions of PON2-def/apoE(-/-) mice compared to apoE(-/-) mice fed a Western diet. Restoration of PON2 in macrophages reduced ER stress, mitochondrial dysfunction and apoptosis in response to ER stressors. Furthermore, restoration of PON2 in macrophages reduced lesional apoptosis and atherosclerosis in PON2-def/apoE(-/-) mice on a Western diet. Our data suggest that macrophage PON2 modulates mechanisms that link ER stress, mitochondrial dysfunction and the development of atherosclerosis.

The antioxidant HDL-associated paraoxonase-1 (PON1) attenuates diabetes development and stimulates ß-cell insulin release.

OBJECTIVE: To analyze the direct effects of paraoxonase-1 (PON1) on diabetes development and on ß-cell insulin release. METHODS AND RESULTS: Injection of rePON1 to mice, prior to STZ-induced diabetes, resulted in reduced incidence of diabetes, as well as, in higher serum insulin levels. Incubation of ß-cells with PON1 also dose-dependently increased insulin secretion and its cellular content. PON1 increased cell survival under high glucose levels, but not under high STZ concentrations. The addition of the PON1 carrier in the circulation - HDL, to ßTC3 cell line, had an additive effect on PON1-induced insulin secretion. PON1 administration to mice or incubation with ß-cells was associated with a substantial decreased oxidative stress. Just like PON1, the dietary anti-oxidants, pomegranate juice, punicalagin (major polyphenol in pomegranate) or vitamin E, also increased insulin release from ßTC3, but unlike PON1, failed to increase insulin cellular content, suggesting a possible role for PON1 in insulin biosynthesis, separately from PON1 antioxidative effect. Both, PON1 catalytic activity and PON1 association to HDL, were not required for PON1 stimulation of insulin release from ß-cells. However, the PON1 free sulfhydryl group was shown to be essential for insulin release by PON1, as blocking the PON1 SH group, abolished PON1 stimulatory effect on insulin secretion. CONCLUSION: PON1 is a potent anti-diabetic enzyme that exerts this protection against diabetes through its antioxidative, as well as via its insulin stimulation properties on ß-cells.

Paraoxonase 1 (PON1) inhibits monocyte-to-macrophage differentiation.

OBJECTIVE: To analyze paraoxonase 1 (PON1) effect on monocyte-to-macrophage differentiation. METHODS AND RESULTS: THP-1 monocytic cell-line and mouse peritoneal macrophages (MPM) were studied. Markers for monocytes differentiation included: morphological changes, CD11b and CD36 expression, and cellular oxidative stress. PON1KO MPM were more differentiated than control C57BL/6 MPM. Intraperitoneal injection of recombinant PON1 (rePON1) to C57BL/6 or to PON1KO mice significantly increased serum, MPM, and tissues PON1 activities. These effects were associated with a significant decrease in CD11b in C57BL/6 and PON1KO MPM (by 21% and 35%, respectively), in CD36 (by 35% and 38%, respectively), and in cellular total peroxides content (by 18% and 20%, respectively). rePON1 also significantly inhibited CD11b and CD36 expression, and cellular total peroxides during PMA-induced THP-1 monocytes differentiation, by 68%, 56% and 53%, respectively. Similar effects were observed upon using reconstituted HDL (rHDL) +rePON1, or human HDL +rePON1, in comparison to rHDL or to human HDL, as well as, HDL from C57BL/6 vs. PON1KO mice. Inhibition of monocyte-to-macrophage differentiation was demonstrated also by several dietary antioxidants such as vitamin E, gallic acid, or punicalagin (the major polyphenol in pomegranate). Whereas NADPH oxidase was not involved in PON1 anti-differentiation effect, mitochondrial complex I could be involved, as rotenone (complex I inhibitor) significantly decreased (by 77%) the expression of CD11b during THP-1 differentiation. Finally, blocking PON1 sulfhydryl group with N-ethylmalemide significantly attenuated PON1 inhibitory effect on THP-I monocyte-to-macrophage differentiation. CONCLUSION: HDL-associated PON1 inhibits monocyte-to-macrophage differentiation, and this effect could be related to PON1 peroxidase-like activity which involves its free sulfhydryl group.

Paraoxonase 2 deficiency alters mitochondrial function and exacerbates the development of atherosclerosis.

Increased production of reactive oxygen species (ROS) as a result of decreased activities of mitochondrial electron transport chain (ETC) complexes plays a role in the development of many inflammatory diseases, including atherosclerosis. Our previous studies established that paraoxonase 2 (PON2) possesses antiatherogenic properties and is associated with lower ROS levels. The aim of the present study was to determine the mechanism by which PON2 modulates ROS production. In this report, we demonstrate that PON2-def mice on the hyperlipidemic apolipoprotein E(-/-) background (PON2-def/apolipoprotein E(-/-)) develop exacerbated atherosclerotic lesions with enhanced mitochondrial oxidative stress. We show that PON2 protein is localized to the inner mitochondrial membrane, where it is found associated with respiratory complex III. Employing surface-plasmon-resonance, we demonstrate that PON2 binds with high affinity to coenzyme Q(10), an important component of the ETC. Enhanced mitochondrial oxidative stress in PON2-def mice was accompanied by significantly reduced ETC complex I + III activities, oxygen consumption, and adenosine triphosphate levels in PON2-def mice. In contrast, overexpression of PON2 effectively protected mitochondria from antimycin- or oligomycin-mediated mitochondrial dysfunction. Our results illustrate that the antiatherogenic effects of PON2 are, in part, mediated by the role of PON2 in mitochondrial function.

Paraoxonase 1 deficiency in mice is associated with reduced steroid biosynthesis: effects on HDL binding, cholesteryl ester accumulation and scavenger receptor type BI expression.

OBJECTIVE: Selective uptake of high density lipoprotein (HDL) cholesteryl ester (CE) is considered as the major source of cholesterol for production of steroids in the adrenal gland in rodents. As paraoxonase 1 (PON1) is an HDL-associated lipo-lactonase that has been shown to increase binding of HDL to macrophages, we used PON1 knock-out (PON1KO) mice to test the possible role of PON1 in corticosterone (CS) biosynthesis. METHODS AND RESULTS: PON1 deficiency was associated with reduced serum CS concentration. Adrenal glands obtained from PON1KO mice had significantly lower CE content compared to adrenals from C57Bl6 control mice. Binding of HDL obtained from PON1KO mice to human adrenocortical carcinoma cell line was found to be significantly lower than that of control HDL, and was associated with decreased CS biosynthesis. Addition of purified PON1 to HDL from PON1KO mice increased HDL binding and CS synthesis. Furthermore, the expression of the HDL receptor, SR-BI, protein and mRNA, was reduced in adrenals from PON1KO mice compared to control mice. When challenged with low salt diet, PON1KO mice demonstrated an increase in adrenal SR-BI gene expression and in serum corticosterone which reached levels similar to those obtained in control mice. CONCLUSION: PON1 regulates adrenal CS biosynthesis at two levels: (a) via an accessory role in HDL binding properties, and (b) a supportive role in SR-BI expression and CE supply to the cells.

Paraoxonase 1 (PON1) deficiency in mice is associated with reduced expression of macrophage SR-BI and consequently the loss of HDL cytoprotection against apoptosis.

BACKGROUND: Paraoxonase 1 (PON1) was shown to stimulate HDL binding and HDL-mediated cholesterol efflux from macrophages. This study examined the role of PON1 in the expression of proteins that enhance macrophage HDL binding, i.e. ABCA1 and SR-BI. METHODS AND RESULTS: ABCA1 expression was similar, whereas SR-BI expression (mRNA and protein determined by FACS, Western blot, or immunocytochemistry) was significantly decreased in peritoneal macrophages from PON1 deficient (MPM-PON1(0)) in comparison to C57Bl/6 (MPM-Control) mice. PON1 deficiency correction with HDL-control, recombinant PON1 (rePON1), or by transfection with a plasmid containing the rePON1 gene, increased SR-BI expression in MPM-PON1(0), whereas rePON1/H115Gln mutant, or the H115Q/H134Q double mutant, which lack catalytic activity, did not stimulate SR-BI expression. Lysophosphatidyl choline (LPC) resulting from PON1 action on macrophage PC, upregulated SR-BI expression in MPM-PON1(0) via activation of ERK1/2 and PI3K. Functionally, HDL bound to MPM-PON1(0) significantly less than to MPM-Control, and failed to inhibit tunicamycin-induced apoptosis, but had no significant effect on HDL-mediated cholesterol efflux from macrophages. CONCLUSIONS: PON1 deficiency in mice is associated with decreased macrophage SR-BI expression, decreased cellular HDL binding, and consequently the loss of HDL-mediated cytoprotection against apoptosis, which may contribute to the accelerated atherosclerosis observed in PON1(0) mice. These findings add new insights into the function of SR-BI in macrophages, and define the potential role of PON1 in regulating SR-BI-mediated HDL protection against macrophages apoptosis.

Paraoxonase-2 deficiency enhances Pseudomonas aeruginosa quorum sensing in murine tracheal epithelia.

Pseudomonas aeruginosa is an important cause of nosocomial infections and is frequently present in the airways of cystic fibrosis patients. Quorum sensing mediates P. aeruginosa's virulence and biofilm formation through density-dependent interbacterial signaling with autoinducers. N-3-oxododecanoyl homoserine lactone (3OC12-HSL) is the major autoinducer in P. aeruginosa. We have previously shown that human airway epithelia and paraoxonases (PONs) degrade 3OC12-HSL. This study investigated the role of PON1, PON2, and PON3 in airway epithelial cell inactivation of 3OC12-HSL. All three PONs were present in murine tracheal epithelial cells, with PON2 and PON3 expressed at the highest levels. Lysates of tracheal epithelial cells from PON2, but not PON1 or PON3, knockout mice had impaired 3OC12-HSL inactivation compared with wild-type mice. In contrast, PON1-, PON2-, or PON3-targeted deletions did not affect 3OC12-HSL degradation by intact epithelia. Overexpression of PON2 enhanced 3OC12-HSL degradation by human airway epithelial cell lysates but not by intact epithelia. Finally, using a quorum-sensing reporter strain of P. aeruginosa, we found that quorum sensing was enhanced in PON2-deficient airway epithelia. In summary, these results show that loss of PON2 impairs 3OC12-HSL degradation by airway epithelial cells and suggests that diffusion of 3OC12-HSL into the airway cells can be the rate-limiting step for degradation of the molecule.

Decreased macrophage paraoxonase 2 expression in patients with hypercholesterolemia is the result of their increased cellular cholesterol content: effect of atorvastatin therapy.

OBJECTIVE: To analyze paraoxonase2 (PON2) expression in human monocyte-derived macrophages (HMDM) from patients with hypercholesterolemia in relation to cellular cholesterol and oxidative stress. METHODS AND RESULTS: Ten healthy subjects (controls) and 10 patients with hypercholesterolema who received 20-mg/d atorvastatin participated in the study. The patients' versus controls' HMDM demonstrated increased cholesterol content (270%) and oxidative stress (30% to 45%). Atorvastatin therapy reduced these parameters (59% and 25%, respectively). The patients' versus controls' macrophage-PON2 mRNA expression and PON2 activity were lower (100% and 40%, respectively), and atorvastatin therapy increased these parameters (76% and 200%, respectively). Untreated patient HMDM incubation with atorvastatin (0 to 10 micromol/L) resulted in a dose-dependent reduction in cellular cholesterol content and in cell-mediated low-density lipoprotein (LDL) oxidation up to 79% and 66%, respectively. In parallel, PON2 mRNA expression and PON2 activity increased dose-dependently up to 3.6- and 2.1-fold, respectively. On incubation of control HMDM with acetylated-LDL or aggregated-LDL, cellular cholesterol content increased (77% and 100%), and macrophage-PON2 activity decreased (49% and 22%), respectively. In contrast, oxidized LDL increased both cellular oxidative stress and PON2 expression. CONCLUSIONS: HMDM-PON2 expression is reduced in patients with hypercholesterolemia as a result of their increased cellular cholesterol content. Atorvastatin therapy reduced both macrophage oxidative stress and cholesterol content, and upregulated PON2 expression, thus contributing to attenuation of foam cells formation.