Increased oxidative stress in cirrhotic rat livers: A potential mechanism contributing to reduced nitric oxide bioavailability

Authors

  • Jorge Gracia-Sancho,

    1. Hepatic Hemodynamic Laboratory, Liver Unit, Institut de Malalties Digestives i Metabòliques (IMDiM), Hospital Clínic, Institut d'Investigacions Biomèdiques August Pi i Sunyer and Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas, University of Barcelona, Spain
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    • These authors contributed equally to this study.

  • Bàrbara Laviña,

    1. Hepatic Hemodynamic Laboratory, Liver Unit, Institut de Malalties Digestives i Metabòliques (IMDiM), Hospital Clínic, Institut d'Investigacions Biomèdiques August Pi i Sunyer and Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas, University of Barcelona, Spain
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    • These authors contributed equally to this study.

  • Aina Rodríguez-Vilarrupla,

    1. Hepatic Hemodynamic Laboratory, Liver Unit, Institut de Malalties Digestives i Metabòliques (IMDiM), Hospital Clínic, Institut d'Investigacions Biomèdiques August Pi i Sunyer and Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas, University of Barcelona, Spain
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  • Héctor García-Calderó,

    1. Hepatic Hemodynamic Laboratory, Liver Unit, Institut de Malalties Digestives i Metabòliques (IMDiM), Hospital Clínic, Institut d'Investigacions Biomèdiques August Pi i Sunyer and Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas, University of Barcelona, Spain
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  • Mercedes Fernández,

    1. Hepatic Hemodynamic Laboratory, Liver Unit, Institut de Malalties Digestives i Metabòliques (IMDiM), Hospital Clínic, Institut d'Investigacions Biomèdiques August Pi i Sunyer and Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas, University of Barcelona, Spain
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  • Jaume Bosch,

    1. Hepatic Hemodynamic Laboratory, Liver Unit, Institut de Malalties Digestives i Metabòliques (IMDiM), Hospital Clínic, Institut d'Investigacions Biomèdiques August Pi i Sunyer and Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas, University of Barcelona, Spain
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  • Joan-Carles García-Pagán

    Corresponding author
    1. Hepatic Hemodynamic Laboratory, Liver Unit, Institut de Malalties Digestives i Metabòliques (IMDiM), Hospital Clínic, Institut d'Investigacions Biomèdiques August Pi i Sunyer and Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas, University of Barcelona, Spain
    • Hepatic Hemodynamic Laboratory, Liver Unit, Hospital Clínic, Villarroel 170, 08036 Barcelona, Spain
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    • fax: (34) 93-2279856.


  • Potential conflict of interest: Nothing to report.

Abstract

In cirrhotic livers, decreased nitric oxide (NO) bioavailability is a major factor increasing intrahepatic vascular tone. In several vascular disorders, an increase in superoxide (O2) has been shown to contribute to reduced NO bioavailability through its reaction with NO to form peroxynitrite. This study was aimed to test the hypothesis that, in cirrhotic livers, increased O2, by reacting with NO, reduces NO bioavailability. In control and cirrhotic rat livers, NO bioavailability was evaluated by the measurement of cyclic guanosine monophosphate in liver tissue and by 4-amino-5-methylamino-2′,7′-difluorofluorescein diacetate (DAF-FM-DA) fluorescence in isolated sinusoidal endothelial cells (SEC); the O2 content was determined by dihydroethidium staining in fresh liver sections. In addition, the role of endothelial nitric oxide synthase (eNOS), xanthine oxidase (XO), and cyclooxygenase (COX) as possible sources of O2 and the role of superoxide dismutase (SOD) enzymatic activity as an O2 scavenger were determined in liver homogenates. Protein-nitrotyrosination, a marker of the NO-O2 reaction, was evaluated in liver homogenates. Furthermore, in control SEC and bovine aortic endothelial cells, NO modulation by O2 was evaluated. Cirrhotic livers exhibited increased O2 levels. This was due, at least in part, to increased production by COX and XO but not eNOS and to reduced scavenging by SOD. Increased O2 was associated with a significant reduction in NO bioavailability and increased nitrotyrosinated proteins. In endothelial cells, an inverse relationship between O2 levels and NO bioavailability was observed. Conclusion: Our data show that oxidative stress may contribute to reduced NO bioavailability in cirrhotic livers, supporting the evaluation of O2 reduction as a potential mechanism to restore NO content. (HEPATOLOGY 2008.)

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