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Age-Dependent Paraoxonase 1 (PON1) Activity and LDL Oxidation in Wistar Rats during Their Entire Lifespan

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The Scientific World Journal

Hindawi Publishing Corporation

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      Abstract

      Paraoxonase 1 (PON1) is an HDL bound enzyme which plays a key role in the protection of LDL and HDL from oxidation by hydrolyzing activated phospholipids and lipid peroxide products. Oxidative stress plays a crucial role in the development of atherosclerosis by oxidation of LDL. This study was conducted to determine age-dependent changes in plasma PON1 arylesterase activity and LDL oxidation in rats during their entire lifespan. 48 Wistar strain rats were grouped in six different age groups (1, 4, 8, 12, 18, and 24 months). We observe a significant (P < 0.001) age-dependent decrease in plasma PON1 arylesterase activity correlating with increase in susceptibility of LDL oxidation and increase in plasma MDA level concomitantly with a significant (P < 0.001) decrease in plasma radical scavenging activity after 8 months. The reduction of PON1 and free radical scavenging activity with age could have a considerable impact on the increased incidence of atherosclerosis with age. Our observation of a significant decline in PON1 activity which correlates with increased LDL oxidation after 8 months of age is an interesting observation and needs further investigation.

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      Most cited references 40

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      Oxidants, oxidative stress and the biology of ageing.

       N. Holbrook,  T Finkel (2000)
      Living in an oxygenated environment has required the evolution of effective cellular strategies to detect and detoxify metabolites of molecular oxygen known as reactive oxygen species. Here we review evidence that the appropriate and inappropriate production of oxidants, together with the ability of organisms to respond to oxidative stress, is intricately connected to ageing and life span.
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        Determination of aldehydic lipid peroxidation products: malonaldehyde and 4-hydroxynonenal.

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          Paraoxonase inhibits high-density lipoprotein oxidation and preserves its functions. A possible peroxidative role for paraoxonase.

          HDL levels are inversely related to the risk of developing atherosclerosis. In serum, paraoxonase (PON) is associated with HDL, and was shown to inhibit LDL oxidation. Whether PON also protects HDL from oxidation is unknown, and was determined in the present study. In humans, we found serum HDL PON activity and HDL susceptibility to oxidation to be inversely correlated (r2 = 0.77, n = 15). Supplementing human HDL with purified PON inhibited copper-induced HDL oxidation in a concentration-dependent manner. Adding PON to HDL prolonged the oxidation lag phase and reduced HDL peroxide and aldehyde formation by up to 95%. This inhibitory effect was most pronounced when PON was added before oxidation initiation. When purified PON was added to whole serum, essentially all of it became HDL-associated. The PON-enriched HDL was more resistant to copper ion-induced oxidation than was control HDL. Compared with control HDL, HDL from PON-treated serum showed a 66% prolongation in the lag phase of its oxidation, and up to a 40% reduction in peroxide and aldehyde content. In contrast, in the presence of various PON inhibitors, HDL oxidation induced by either copper ions or by a free radical generating system was markedly enhanced. As PON inhibited HDL oxidation, two major functions of HDL were assessed: macrophage cholesterol efflux, and LDL protection from oxidation. Compared with oxidized untreated HDL, oxidized PON-treated HDL caused a 45% increase in cellular cholesterol efflux from J-774 A.1 macrophages. Both HDL-associated PON and purified PON were potent inhibitors of LDL oxidation. Searching for a possible mechanism for PON-induced inhibition of HDL oxidation revealed PON (2 paraoxonase U/ml)-mediated hydrolysis of lipid peroxides (by 19%) and of cholesteryl linoleate hydroperoxides (by 90%) in oxidized HDL. HDL-associated PON, as well as purified PON, were also able to substantially hydrolyze (up to 25%) hydrogen peroxide (H2O2), a major reactive oxygen species produced under oxidative stress during atherogenesis. Finally, we analyzed serum PON activity in the atherosclerotic apolipoprotein E-deficient mice during aging and development of atherosclerotic lesions. With age, serum lipid peroxidation and lesion size increased, whereas serum PON activity decreased. We thus conclude that HDL-associated PON possesses peroxidase-like activity that can contribute to the protective effect of PON against lipoprotein oxidation. The presence of PON in HDL may thus be a major contributor to the antiatherogenicity of this lipoprotein.
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            Author and article information

            Affiliations
            Department of Biochemistry, University of Allahabad, Allahabad, Uttar Pradesh 211002, India
            Author notes
            *Syed Ibrahim Rizvi: sirizvi@ 123456gmail.com

            Academic Editor: Alfons López-Soto

            Journal
            ScientificWorldJournal
            ScientificWorldJournal
            TSWJ
            The Scientific World Journal
            Hindawi Publishing Corporation
            2356-6140
            1537-744X
            2014
            22 May 2014
            : 2014
            4055568
            10.1155/2014/538049
            Copyright © 2014 D. Kumar and S. I. Rizvi.

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

            Funding
            Funded by: SERB DST, New Delhi
            Award ID: SR/SO/HS-1467/2010
            Funded by: Department of Science and Technology, Government of India
            Categories
            Research Article

            Uncategorized

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