Acetaldehyde and malonildialdehyde can form hybrid protein adducts, named MAA adducts that have strong immunogenic properties. The formation of MAA adducts in the liver of chronic alcohol-fed rats is associated with the development of circulating antibodies that specifically recognized these adducts. The aim of this study was to examine whether MAA adducts might participate in the immune response associated with human alcohol-induced liver disease. Circulating antibodies against MAA adducts were evaluated in 50 patients with alcohol-induced hepatitis or cirrhosis, in 40 patients with non-alcohol-induced liver disease, in 15 heavy drinkers without liver damage and in 40 healthy controls by enzyme-linked immunosorbent assays (ELISA). Immunoglobulin G (IgG) reacting with MAA-modified proteins were significantly increased in the patients with alcohol-induced cirrhosis or hepatitis. The individual levels of anti-MAA IgG in those patients were associated with the severity of liver damage. Anti-MAA antibodies were also positively correlated with the levels of IgG recognizing epitopes generated by acetaldehyde and malonildialdehyde. However, competitive inhibition experiments indicated that the anti-MAA antibodies were unrelated to those against acetaldehyde-or malonildialdehydederived antigens and mainly recognized a specific, cyclic MAA epitope. Some degree of immune reactivity towards MAA adducts was also observed in patients with nonalcohol-induced liver injury. However, competitive ELISA showed that the antigens recognized by these sera were not the cyclic MAA adducts. Altogether, these results showed the formation of MAA antigens during alcohol-induced liver disease and suggest their possible contribution to the development of immunologic reactions associated with alcohol-related liver damage. (HEPATOLOGY 2000;31:878-884.)

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SummaryThe mechanisms responsible for the progression of nonalcoholic fatty liver disease (NAFLD) to more severe liver injury are still poorly understood. Data from animal models suggest that oxidative stress contributes to steatohepatitis and an increase of lipid peroxidation has been documented in human NAFLD. By measuring the titers of circulating antibodies against lipid peroxidation products as markers of oxidative stress we have observed that NAFLD patients have titers of these antibodies significantly higher than in controls. Moreover, the titers of lipid peroxidation‐related antibodies are associated with a 3‐fold increase in the risk of developing advanced fibrosis/cirrhosis. Although the mechanisms causing oxidative stress in NAFLD have not been elucidated, these results support the involvement of lipid peroxidation in the processes leading to liver fibrosis associated with NAFLD.

The mechanisms by which alcohol consumption worsens the evolution of chronic hepatitis C (CHC) are poorly understood. We have investigated the possible interaction between hepatitis C virus (HCV) and ethanol in promoting oxidative stress. Circulating IgG against human serum albumin (HSA) adducted with malondialdehyde (MDA-HSA), 4-hydroxynonenal (HNE-HSA), or arachidonic acid hydroperoxide (AAHP-HSA) and against oxidized cardiolipin (Ox-CL) were evaluated as markers of oxidative stress in 145 CHC patients with different alcohol consumption, 20 HCV-free heavy drinkers (HD) without liver disease, and 50 healthy controls. Anti-MDA IgG was increased in CHC patients irrespective of alcohol intake as well as in the HD group. CHC patients with moderate alcohol intake (<50 g ethanol/d), but not HD, also had significantly higher values of anti-AAHP-HSA, anti-HNE-HSA, and anti-Ox-CL IgG (P < .05) than controls. A further elevation (P < .001) of these antibodies was evident in CHC patients with heavy alcohol intake (>50 g ethanol/d). Anti-AAHP and anti-Ox-CL IgG above the 95th percentile in the controls were observed in 24% to 26% of moderate and 58% to 63% of heavy drinkers but only in 6% to 9% of the abstainers. The risk of developing oxidative stress during CHC was increased 3-fold by moderate and 13-to 24-fold by heavy alcohol consumption. Heavy drinking CHC patients had significantly more piecemeal necrosis and fibrosis than abstainers. Diffuse piecemeal necrosis was 4-fold more frequent among alcohol-consuming patients with lipid peroxidation-related antibodies than among those without these antibodies. In conclusion, even moderate alcohol consumption promotes oxidative stress in CHC patients, suggesting a role for oxidative injury in the worsening of CHC evolution by alcohol. (HEPATOLOGY 2003; 38:42-49.)

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The identification of the epitopes recognized by autoantibodies against cytochrome P450s (CYPs) associated with drug-induced hepatotoxicity is difficult because of their conformational nature. In the present investigation, we used a novel approach based on the analysis of the whole molecule antigenic capacity following single amino acid substitutions to identify the conformational epitopes on CYP2E1. A molecular model of CYP2E1 was generated based on the CYP2C5 crystal structure, and potential motifs for amino acid exchanges were selected by computer simulation in the surface of ␣ helices and ␤ sheets. Fourteen modified, apparently correctly folded CYP2E1 variants were produced in Escherichia coli and evaluated in immunoprecipitation experiments using sera with anti-CYP2E1 autoreactivity from 10 patients with halothane hepatitis and 12 patients with alcoholic liver disease. Ala substitution of Glu-248 and Lys-251 as well as of Lys-324, Lys-342, Lys-420, and Phe-421 severely decreased or abolished CYP2E1 recognition by the majority of both the halothane hepatitis and alcoholic liver disease sera, whereas the other substitutions had only minor effects. Based on the structural model, these substitutions identified two distinct epitopes on the CYP2E1 surface corresponding to the G-helix and an area formed by juxtaposition of the J and K؆ helices, respectively. The combined use of molecular modeling and single amino acid mutagenesis is thus a useful approach for the characterization of conformational epitopes recognized by autoantibodies.

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