Paraoxonase-2 Is a Ubiquitously Expressed Protein with Antioxidant Properties and Is Capable of Preventing Cell-mediated Oxidative Modification of Low Density Lipoprotein

Abstract

The oxidation of apolipoprotein B-containing lipoproteins and cell membrane lipids is believed to play an integral role in the development of fatty streak lesions, an initial step in atherogenesis. We have previously shown that two antioxidant-like enzymes, paraoxonase (PON)-1 and PON3, are high density lipoprotein-associated proteins capable of preventing the oxidative modification of low density lipoprotein (LDL) (Reddy, S. T., Wadleigh, D. J., Grijalva, V., Ng, C., Hama, S., Gangopadhyay, A., Shih, D. M., Lusis, A. J., Navab, M., and Fogelman, A. M. (2001) Arterioscler. Thromb. Vasc. Biol. 21, 542-547). In the present study, we demonstrate that PON2 (i) is not associated with high density lipoprotein; (ii) has antioxidant properties; and (iii) prevents LDL lipid peroxidation, reverses the oxidation of mildly oxidized LDL (MM-LDL), and inhibits the ability of MM-LDL to induce monocyte chemotaxis. The PON2 protein was overexpressed in HeLa cells using the tetracyclineinducible ("Tet-On") system, and its antioxidant capacity was measured in a fluorometric assay. Cells that overexpressed PON2 showed significantly less intracellular oxidative stress following treatment with hydrogen peroxide or oxidized phospholipid. Moreover, cells that overexpressed PON2 were also less effective in oxidizing and modifying LDL and, in fact, were able to reverse the effects of preformed MM-LDL. Our results suggest that PON2 possesses antioxidant properties similar to those of PON1 and PON3. However, in contrast to PON1 and PON3, PON2 may exert its antioxidant functions at the cellular level, joining the host of intracellular antioxidant enzymes that protect cells from oxidative stress. Oxidation of low density lipoproteins (LDL)1 trapped in the arterial subendothelial space is a key process in atherosclerotic lesion development. High density lipoprotein (HDL) inhibits LDL oxidation (1-4) and prevents the synthesis and secretion of monocyte chemotactic protein-1 by artery wall cells, thereby blocking the recruitment and transmigration of monocytes though the arterial endothelial layer (5). The anti-atherogenic properties associated with HDL are due, at least in part, to the activity of HDL-associated enzymes, which interact with LDL and prevent and/or reverse its oxidation (6). The calcium-dependent ester hydrolase paraoxonase (PON)-1 (EC 3.1.8.1) is one of several such enzymes and is found tightly associated with apoA-I in the HDL particle (7). Purified PON1 not only prevents LDL oxidation (8), but also blocks the ability of mildly oxidized LDL (MM-LDL) to induce monocyte chemotaxis and binding to endothelial cells (9). Epidemiological studies have shown that PON1 polymorphisms are correlated with variations in plasma lipoprotein levels (10) and coronary artery disease in some populations (11-15). In addition, Mackness et al. (16) showed that alloenzymes of PON1 determine the effectiveness of HDL in the protection of LDL from lipid peroxidation. Two other members of the PON gene family, termed PON2 and PON3, have been identified...

The CD16−CD56bright NK Cell Subset Is Resistant to Reactive Oxygen Species Produced by Activated Granulocytes and Has Higher Antioxidative Capacity Than the CD16+CD56dim Subset

“…Several genes found to be differentially expressed between CD56 dim and CD56 bright NK cells may be candidate antioxidants, as inferred from this study. In particular, paraoxonase 2, which has antioxidant ability (45), and lysozyme, which has been shown to be protective against oxidative stress by H 2 O 2 and other oxidants (46), are two factors that were up-regulated at least 6-fold in CD56 bright NK cells (paraoxonase 2 expression was below the limit of detection in CD56 dim cells). Furthermore, glutathione peroxidase 1, an enzyme that catalyzes the reduction of H 2 O 2 and organic hydroperoxides using glutathione, was found to be expressed to a higher extent in CD56 bright cells (2.5-fold).…”

Negative association between paraoxonase 2, anthropometric markers and metabolic syndrome

“…Unlike Paraoxonase 1 (PON1) and PON3 that are associated with high-density lipoproteins (HDL) in plasma [4], PON2 is not linked to HDL being an intracellular enzyme expressed ubiquitously [5,6]. All three PONs are antioxidant enzymes and lactonases, but PON2 displays the highest activity hydrolyzing a number of acylhomoserine lactones [7,8].…”

Estudo das paraoxonases 1, 2 e 3 em pacientes portadores de anemia falciforme"

“…O estresse oxidativo é um potente precursor do estado inflamatório e muitos marcadores têm sido sugeridos como bons preditores de prognóstico para as doenças inflamatórias, como a PCR, DHL, ICAM, VCAM, haptoglobina, entre outros (Zulet et al, 2007). A PCR é sintetizada pelos hepatócitos sob estimulo primário da interleucina-6 (IL-6), e tem sido considerada um marcador da inflamação sistêmica, podendo estar elevada em processos inflamatórios e infecciosos (Denardi et al,2008 Ainda são poucas as informações sobre o gene PON2, no entanto os polimorfismos nas posições 148 (A/G) e 311 (C/S) desse gene têm sido associados a numerosas condições fisiopatológicas como a variações no metabolismo e níveis plasmáticos de lipoproteínas e glicose (Li et al, 2003;Ng et al, 2005). Há ainda estudos que associam uma combinação entre polimorfismos do gene PON2, com os do gene PON1 a uma maior predisposição a doença coronariana (Sanghera et al, 1998;Leus et al, 2001).…”

“…Além disso, esses mesmos polimorfismos associam-se com inúmeras condições patofisiológicas (Goswami et al, 2009;Hussein et al, 2011;Rajković et al, 2011 (Ng et al, 2005).…”

“…As consequências funcionais desses dois polimorfismos ainda não foram descritas (Ng et al, 2005;Précourt et al 2011). …”