Elsevier

Journal of Hepatology

Volume 59, Issue 5, November 2013, Pages 978-983
Journal of Hepatology

Research Article
Oxidative albumin damage in chronic liver failure: Relation to albumin binding capacity, liver dysfunction and survival

https://doi.org/10.1016/j.jhep.2013.06.013Get rights and content

Background & Aims

Impaired binding function of albumin has been demonstrated in end-stage liver disease. This and other functional disturbances of albumin may be related to oxidative stress which is believed to play an important role in the pathogenesis of liver failure as well as sepsis. The aim of the present study was to relate oxidative modification of albumin to loss of albumin binding function in advanced chronic liver failure and in sepsis.

Methods

Patients with decompensated cirrhosis or sepsis and healthy controls were investigated. Three fractions of albumin were separated by chromatography according to the redox state of cysteine-34: non-oxidized human mercaptalbumin, reversibly oxidized human non-mercaptalbumin-1, and irreversibly oxidized human non-mercaptalbumin-2 (HNA2). Binding properties of albumin site II were measured using dansylsarcosine as a ligand.

Results

Both in cirrhotic and septic patients, fractions of oxidized albumin were increased and binding capacity for dansylsarcosine was decreased. Mass spectroscopy confirmed specific oxidation of cysteine-34. In cirrhotic patients, dansylsarcosine binding correlated strongly with liver function parameters and moderately with HNA2. Baseline levels of HNA2 accurately predicted 30-day and 90-day survival in cirrhotic patients and this was confirmed in an external validation cohort.

Conclusions

Our results suggest that oxidative damage impairs binding properties of albumin. In advanced liver disease, reduced binding capacity of albumin site II is mainly related to impaired liver function. The plasma level of HNA2 is closely related to survival and may represent a novel biomarker for liver failure.

Introduction

Albumin, a 66.5 kDa protein (Fig. 1), is the most abundant plasma protein, the main determinant of colloid osmotic pressure and an important carrier for endogenous and exogenous substances [1]. Among its most important functions are fatty acid transport (on several binding areas), drug binding and transport, metal chelation, and free radical scavenging which is mediated by the anti-oxidant properties of its thiol moiety at cysteine-34 (reviewed in [2]).

Albumin is the major extracellular source of reduced sulfhydryl groups, which are potent scavengers of reactive oxygen and nitrogen species [3]. Depending on the redox state, there are three major fractions of albumin: human mercaptalbumin (HMA), the non-oxidized form with a free thiol group on cysteine-34, and two different oxidized forms: (i) human non-mercaptalbumin-1 (HNA1) with cysteine, homocysteine or glutathione bound to cysteine-34 by a disulfide bond and (ii) human non-mercaptalbumin-2 (HNA2) with cysteine-34 irreversibly oxidized to sulfinic or sulfonic acid [4], [5]. Oxidative stress is believed to play an important role in advanced liver failure [6] and may be reflected in oxidative modification of albumin. Decreased HMA and/or elevated HNA levels have been reported in chronic liver disease and these changes have been shown to correlate with its severity as estimated by the Child-Pugh score [7], [8]. Recently, we demonstrated a 4-fold increase of the irreversibly oxidized albumin fraction, HNA2, indicating a marked alteration in the redox state of circulating albumin, in patients with advanced liver disease [9].

Albumin harbours two specific binding sites described by Sudlow: site I, which binds large heterocyclic compounds and dicarboxylic acids (such as bilirubin), and site II, which binds aromatic carboxylic compounds (such as benzodiazepines) [10]. Oxidized albumin shows altered binding capacities for several substances used to assess albumin function [11], [12]. Decreased binding of dansylsarcosine – a model ligand for the benzodiazepin binding site II – was found in patients with end-stage liver disease [13], [14]. The pathogenesis of this impaired binding capacity and, specifically, its relation to oxidative albumin damage remain unknown.

Several disturbances of albumin binding function are known to occur in cirrhotic patients [9], [14], [15]. Based on these pathophysiologic changes, albumin infusions are being used therapeutically to normalize the serum albumin level and/or restore albumin function in various conditions such as prevention and treatment of hepatorenal syndrome, prevention of postparacentesis circulatory dysfunction, and extracorporeal albumin dialysis for removal of potentially toxic substances accumulating in liver failure (reviewed in [16]). These beneficial effects are believed to be mediated at least in part by improved toxin binding and transport following infusion of fresh albumin or, in case of albumin dialysis, regeneration of toxin-laden albumin.

Acute-on-chronic liver failure (ACLF), i.e., acute exacerbation of chronic liver failure, is frequently triggered by infection and its clinical features such as end-organ failure resemble those of sepsis [17]. Since ACLF is believed to be mediated by oxidative stress [6], oxidation of albumin is likely to occur. The specific aims of the present study were (i) to assess oxidative modification of albumin in these clinical conditions, (ii) to relate these changes to albumin dysfunction, specifically the disturbance of site II specific binding, and (iii) to determine the prognostic significance of the observed changes in chronic liver failure.

Section snippets

Patients

The study population comprised 67 consecutive cirrhotic patients hospitalized for acute decompensation at the Medical University of Graz, including 16 patients requiring ICU treatment, and 18 consecutive non-cirrhotic patients with sepsis without evidence for cirrhosis or underlying hematologic disease admitted at our ICU. In addition, 15 age- and sex-matched blood donors served as healthy controls. Patients with hepatocellular carcinoma, recent gastrointestinal bleeding (<7 days before

Results

The characteristics of the study population including the external validation set are shown in Table 1. Within the cirrhosis cohort, the main reasons for admission were ascites (40%), acute kidney injury (22%), gastrointestinal bleeding (19%), and hepatic encephalopathy (8%). As expected, both in cirrhotic and septic patients, bilirubin and CRP were increased and albumin decreased compared to controls. Septic patients presented with the highest leukocyte counts and CRP values while bilirubin

Discussion

In the present study, we observed marked alterations of the redox state of albumin and significant impairment of albumin binding capacity (site II) in patients with chronic liver failure as well as in septic patients without liver failure. This is in line with our previous finding of decreased binding of bilirubin to the oxidized albumin fractions, HNA1 and HNA2 [9]. Univariate analysis showed correlations of DS binding with liver functions parameters as well as HNA2 in cirrhotic but not in

Financial support

This study was supported by the Franz Lanyar Stiftung (project # 314) and by BioPersMed (COMET K-project 825329), which is funded by the Austrian Federal Ministry of Transport, Innovation and Technology (BMVIT) and the Austrian Federal Ministry of Economics and Labour/the Federal Ministry of Economy, Family and Youth (BMWA/BMWFJ) and the Styrian Business Promotion Agency (SFG).

V.S. was the recipient of an Erwin-Schrödinger fellowship (J2547) from the Austrian Science Foundation.

Conflict of interest

The authors who have taken part in this study declared that they do not have anything to disclose regarding funding or conflict of interest with respect to this manuscript.

Acknowledgements

The technical assistance of Martina Brtnik, Doris Payerl, and Stefan Spoerk is gratefully acknowledged.

References (31)

  • Y.A. Gryzunov et al.

    Binding of fatty acids facilitates oxidation of cysteine-34 and converts copper-albumin complexes from antioxidants to prooxidants

    Arch Biochem Biophys

    (2003)
  • P.A. Zunszain et al.

    Crystallographic analysis of human serum albumin complexed with 4Z,15E-bilirubin-IXalpha

    J Mol Biol

    (2008)
  • K. Oettl et al.

    Redox state of human serum albumin in terms of cysteine-34 in health and disease

    Methods Enzymol

    (2010)
  • M.A. Rothschild et al.

    Serum albumin

    Hepatology

    (1988)
  • T.W. Evans

    Review article: albumin as a drug-biological effects of albumin unrelated to oncotic pressure

    Aliment Pharmacol Ther

    (2002)
  • Cited by (150)

    • Posttranslational-modifications of human-serum-albumin analysis by a top-down approach validated by a comprehensive bottom-up analysis

      2023, Journal of Chromatography B: Analytical Technologies in the Biomedical and Life Sciences
    View all citing articles on Scopus
    View full text