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      Evaluation of Paraoxonase Activity in Children With Nephrotic Syndrome

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          Abstract

          Background

          It has been proposed that reactive oxygen species (ROS) is involved in the pathogenesis of various diseases. Paraoxonase, a high-density lipoprotein associated enzyme, prevents low-density lipoproteins from oxidation.

          Objectives

          The aim of the present study was to investigate the serum activities of paraoxonase-1 (PON-1), and aryleterase (ARE) as well as total antioxidant capacity (TAC) in children with nephrotic syndrome in acute and remission phase.

          Patients and Methods

          The study consisted of 20 patients in acute and remission phases and 23 healthy controls. PON-1 and ARE activities were determined spectrophotometrically using paraoxone and phenyacetate as substrate, respectively. TAC was measured using ferric reducing ability of plasma (FRAP).

          Results

          The levels of PON, ARE, and TAC were significantly lower in acute phase of nephrotic syndrome compared with the remission phase. The levels of PON, ARE and TAC increased in remission phase.

          Conclusions

          Our results revealed that the determination of paraoxonase activity might be a biomarker for responses to nephrotic syndrome treatment, which needs to be fully clarified.

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          Most cited references30

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          The evolution of free radicals and oxidative stress.

          The superoxide free radical has come to occupy an amazingly central role in a wide variety of diseases. Our metabolic focus on aerobic energy metabolism in all cell types, coupled with some chemical peculiarities of the oxygen molecule itself, contribute to the phenomenon. Superoxide is not, as we once thought, just a toxic but unavoidable byproduct of oxygen metabolism. Rather it appears to be a carefully regulated metabolite capable of signaling and communicating important information to the cell's genetic machinery. Redox regulation of gene expression by superoxide and other related oxidants and antioxidants is beginning to unfold as a vital mechanism in health and disease.
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            Paraoxonase polymorphism Met-Leu54 is associated with modified serum concentrations of the enzyme. A possible link between the paraoxonase gene and increased risk of cardiovascular disease in diabetes.

            Paraoxonase was identified as a genetic risk factor for cardiovascular disease (CVD) in recent studies focusing on a polymorphism affecting position 191. A second polymorphism of the paraoxonase gene affects position 54 and involves a methionine (M allele) to leucine (L allele) change. It was investigated in diabetic patients (n = 408) with and without vascular disease. There were highly significant differences in plasma concentrations and activities of paraoxonase between genotypes defined by the 54 polymorphism: MMAA, MLAA, LLAA; protein, 65.3+/-18.0, 77.9+/-18.0, 93.5+/-26.0 microg/ml; P < 0.0001: activity (phenylacetate), 48.6+/-13.5, 64.1+/-14.5, 68.1+/-13.0 U/ml; P < 0.0001. The 191 variant had little impact on paraoxonase concentrations. Homozygosity for the L allele was an independent risk factor for CVD (odds ratio 1.98 (1.07-3.83); P = 0.031). A linkage disequilibrium (P < 0.0001) was apparent between the mutations giving rise to leucine and arginine at positions 54 and 191, respectively. The study underlines that susceptibility to CVD correlates with high activity paraoxonase alleles. The 54 polymorphism would appear to be of central importance to paraoxonase function by virtue of its association with modulated concentrations. The latter could explain the association between both the 54 and 191 polymorphisms and CVD.
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              Human serum paraoxonases (PON1) Q and R selectively decrease lipid peroxides in human coronary and carotid atherosclerotic lesions: PON1 esterase and peroxidase-like activities.

              Human serum paraoxonase (PON1) exists in two polymorphic forms: one that differs in the amino acid at position 192 (glutamine and arginine, Q and R, respectively) and the second one that differs in the amino acid at position 55 (methionine and leucine, M and L, respectively). PON1 protects LDL from oxidation, and during LDL oxidation, PON1 is inactivated. The present study compared PON1 isoforms Q and R for their effect on lipid peroxide content in human coronary and carotid lesions. After 24 hours of incubation with PON1Q or PON1R (10 arylesterase units/mL), lipid peroxides content in both coronary and carotid lesion homogenates (0.1 g/mL) was reduced up to 27% and 16%, respectively. The above incubation was associated with inactivation of PON1Q and PON1R by 15% and 45%, respectively. Lesion cholesteryl linoleate hydroperoxides and cholesteryl linoleate hydroxides were hydrolyzed by PON1 to yield linoleic acid hydroperoxides and linoleic acid hydroxides. Furthermore, lesion and pure linoleic acid hydroperoxides were reduced to yield linoleic acid hydroxides. These results thus indicate that PON1 demonstrates esterase-like and peroxidase-like activities. Recombinant PON1 mutants in which the PON1-free sulfhydryl group at cysteine-284 was replaced with either alanine or serine were no longer able to reduce lipid peroxide content in carotid lesions. We conclude that PON1 may be antiatherogenic because it hydrolyzes lipid peroxides in human atherosclerotic lesions.
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                Author and article information

                Journal
                Nephrourol Mon
                Nephrourol Mon
                10.5812/numonthly
                Kowsar
                Nephro-urology Monthly
                Kowsar
                2251-7006
                2251-7014
                13 November 2013
                November 2013
                : 5
                : 5
                : 978-982
                Affiliations
                [1 ]Cellular and Molecular Research Center, Zahedan University of Medical Sciences, Zahedan, IR Iran
                [2 ]Department of Clinical Biochemistry, School of Medicine, Zahedan University of Medical Sciences, Zahedan, IR Iran
                [3 ]Research Center for Children and Adolescents Health, Zahedan University of Medical Sciences, Zahedan, IR Iran
                [4 ]Department of Pediaterics, School of Medicine, Zahedan University of Medical Sciences, Zahedan, IR Iran
                Author notes
                [* ]Corresponding author: Mohammad Hashemi, Department of Clinical Biochemistry, School of Medicine, Zahedan University of Medical Sciences, Zahedan, IR Iran. Tel: +541-3414573, E-mail: hashemim@ 123456zaums.ac.ir .
                Article
                10.5812/numonthly.12606
                3955290
                24693505
                4637776e-e4f6-408e-897b-b501ca4f718a
                Copyright © 2013, Nephrology and Urology Research Center; Published by Kowsar Corp.

                This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 31 May 2013
                : 17 July 2013
                : 17 August 2013
                Categories
                Research Article

                nephrotic syndrome,aryldialkylphosphatase,antioxidants

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