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      Age-Related Changes in Hepatic Activity and Expression of Detoxification Enzymes in Male Rats

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          Abstract

          Process of aging is accompanied by changes in the biotransformation of xenobiotics and impairment of normal cellular functions by free radicals. Therefore, this study was designed to determine age-related differences in the activities and/or expressions of selected drug-metabolizing and antioxidant enzymes in young and old rats. Specific activities of 8 drug-metabolizing enzymes and 4 antioxidant enzymes were assessed in hepatic subcellular fractions of 6-week-old and 21-month-old male Wistar rats. Protein expressions of carbonyl reductase 1 (CBR1) and glutathione S-transferase (GST) were determined using immunoblotting. Remarkable age-related decrease in specific activities of CYP2B, CYP3A, and UDP-glucuronosyl transferase was observed, whereas no changes in activities of CYP1A2, flavine monooxygenase, aldo-keto reductase 1C, and antioxidant enzymes with advancing age were found. On the other hand, specific activity of CBR1 and GST was 2.4 folds and 5.6 folds higher in the senescent rats compared with the young ones, respectively. Interindividual variability in CBR1 activity increased significantly with rising age. We suppose that elevated activities of GST and CBR1 may protect senescent rats against xenobiotic as well as eobiotic electrophiles and reactive carbonyls, but they may alter metabolism of drugs, which are CBR1 and especially GSTs substrates.

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          A simple method for determination of serum catalase activity and revision of reference range.

          L Góth (1991)
          A rapid, cost-efficient, spectrophotometric assay for serum catalase activity was developed. It was a combination of optimized enzymatic conditions and the spectrophotometric assay of hydrogen peroxide based on formation of its stable complex with ammonium molybdate. Lipemic and icteric sera increased the absorbance without influencing the catalase assay. Due to the high catalase activity in erythrocytes artificial hemolysis increased serum catalase activity. The imprecision of the method was CV less than 5.8% within run as well and day-to-day. The catalase assay performed using polarographic and spectrophotometric determination of hydrogen peroxide yielded a good correlation (r = 0.9602, b = 1.011, a = -0.648, n = 440). In 742 healthy individuals the mean and SD values of serum catalase were 50.5 +/- 18.1 kU/l with 17.7% higher activity in males than in females. Between 14-60 yr the serum catalase increased with age.
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            Oxidative stress and oxidative damage in carcinogenesis.

            James Klaunig, Lisa Kamendulis, Barbara Hocevar (2010)
            Carcinogenesis is a multistep process involving mutation and the subsequent selective clonal expansion of the mutated cell. Chemical and physical agents including those that induce reative oxygen species can induce and/or modulate this multistep process. Several modes of action by which carcinogens induce cancer have been identified, including through production of reactive oxygen species (ROS). Oxidative damage to cellular macromolecules can arise through overproduction of ROS and faulty antioxidant and/or DNA repair mechanisms. In addition, ROS can stimulate signal transduction pathways and lead to activation of key transcription factors such as Nrf2 and NF-kappaB. The resultant altered gene expression patterns evoked by ROS contribute to the carcinogenesis process. Recent evidence demonstrates an association between a number of single nucleotide polymorphisms (SNPs) in oxidative DNA repair genes and antioxidant genes with human cancer susceptibility. These aspects of ROS biology will be discussed in the context of their relationship to carcinogenesis.
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              Glutathione peroxidase-1 regulates mitochondrial function to modulate redox-dependent cellular responses.

              Jane A. Leopold, Yi Zhang, Matthew Galbraith … (2009)
              Glutathione peroxidase-1 (GPx-1) is a selenocysteine-containing enzyme that plays a major role in the reductive detoxification of peroxides in cells. In permanently transfected cells with approximate 2-fold overexpression of GPx-1, we found that intracellular accumulation of oxidants in response to exogenous hydrogen peroxide was diminished, as was epidermal growth factor receptor (EGFR)-mediated Akt activation in response to hydrogen peroxide or EGF stimulation. Knockdown of GPx-1 augmented EGFR-mediated Akt activation, whereas overexpression of catalase decreased Akt activation, suggesting that EGFR signaling is regulated by redox mechanisms. To determine whether mitochondrial oxidants played a role in these processes, cells were pretreated with a mitochondrial uncoupler prior to EGF stimulation. Inhibition of mitochondrial function attenuated EGF-mediated activation of Akt in control cells but had no additional effect in GPx-1-overexpressing cells, suggesting that GPx-1 overexpression decreased EGFR signaling by decreasing mitochondrial oxidants. Consistent with this finding, GPx-1 overexpression decreased global protein disulfide bond formation, which is dependent on mitochondrially produced oxidants. GPx-1 overexpression, in permanently transfected or adenovirus-treated cells, also caused overall mitochondrial dysfunction with a decrease in mitochondrial potential and a decrease in ATP production. GPx-1 overexpression also decreased EGF- and serum-mediated [(3)H]thymidine incorporation, indicating that alterations in GPx-1 can attenuate cell proliferation. Taken together, these data suggest that GPx-1 can modulate redox-dependent cellular responses by regulating mitochondrial function.
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                Author and article information

                Journal
                Journal ID (nlm-ta): Biomed Res Int
                Journal ID (iso-abbrev): Biomed Res Int
                Journal ID (publisher-id): BMRI
                Title: BioMed Research International
                Publisher: Hindawi Publishing Corporation
                ISSN (Print): 2314-6133
                ISSN (Electronic): 2314-6141
                Publication date (Print): 2013
                Publication date (Electronic): 22 July 2013
                Volume: 2013
                Electronic Location Identifier: 408573
                Affiliations
                Department of Biochemical Sciences, Charles University in Prague, Faculty of Pharmacy in Hradec Králové, Heyrovského 1203, CZ-500 05 Hradec Králové, Czech Republic
                Author notes

                Academic Editor: Michael Kalafatis

                Author information
                http://orcid.org/0000-0003-2863-717X
                Article
                DOI: 10.1155/2013/408573
                PMC ID: 3736498
                PubMed ID: 23971034
                SO-VID: afaaf23c-a700-4f10-991f-56e5cd028305
                Copyright © Copyright © 2013 Erika Vyskočilová et al.
                License:

                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.

                History
                Date received : 4 April 2013
                Date accepted : 2 July 2013
                Categories
                Subject: Research Article

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