Plasma membrane hydroxyethyl radical adducts cause antibody-dependent cytotoxicity in rat hepatocytes exposed to alcohol

Synergistic and Detrimental Effects of Alcohol Intake on Progression of Liver Steatosis

Nonalcoholic fatty liver disease (NAFLD) and alcoholic liver disease (ALD) are the most common liver disorders worldwide and the major causes of non-viral liver cirrhosis in the general population. In NAFLD, metabolic abnormalities, obesity, and metabolic syndrome are the driving factors for liver damage with no or minimal alcohol consumption. ALD refers to liver damage caused by excess alcohol intake in individuals drinking more than 5 to 10 daily units for years. Although NAFLD and ALD are nosologically considered two distinct entities, they show a continuum and exert synergistic effects on the progression toward liver cirrhosis. The current view is that low alcohol use might also increase the risk of advanced clinical liver disease in NAFLD, whereas metabolic factors increase the risk of cirrhosis among alcohol risk drinkers. Therefore, special interest is now addressed to individuals with metabolic abnormalities who consume small amounts of alcohol or who binge drink, for the role of light-to-moderate alcohol use in fibrosis progression and clinical severity of the liver disease. Evidence shows that in the presence of NAFLD, there is no liver-safe limit of alcohol intake. We discuss the epidemiological and clinical features of NAFLD/ALD, aspects of alcohol metabolism, and mechanisms of damage concerning steatosis, fibrosis, cumulative effects, and deleterious consequences which include hepatocellular carcinoma.

Advanced glycation end products (AGEs) and other adducts in aging-related diseases and alcohol-mediated tissue injury

Advanced glycation end products (AGEs) are potentially harmful and heterogeneous molecules derived from nonenzymatic glycation. The pathological implications of AGEs are ascribed to their ability to promote oxidative stress, inflammation, and apoptosis. Recent studies in basic and translational research have revealed the contributing roles of AGEs in the development and progression of various aging-related pathological conditions, such as diabetes, cardiovascular complications, gut microbiome-associated illnesses, liver or neurodegenerative diseases, and cancer. Excessive chronic and/or acute binge consumption of alcohol (ethanol), a widely consumed addictive substance, is known to cause more than 200 diseases, including alcohol use disorder (addiction), alcoholic liver disease, and brain damage. However, despite the considerable amount of research in this area, the underlying molecular mechanisms by which alcohol abuse causes cellular toxicity and organ damage remain to be further characterized. In this review, we first briefly describe the properties of AGEs: their formation, accumulation, and receptor interactions. We then focus on the causative functions of AGEs that impact various aging-related diseases. We also highlight the biological connection of AGE-alcohol-adduct formations to alcohol-mediated tissue injury. Finally, we describe the potential translational research opportunities for treatment of various AGE- and/or alcohol-related adduct-associated disorders according to the mechanistic insights presented.

Lipid peroxidation derived reactive aldehydes in alcoholic liver disease

Lipid peroxidation is a known consequence of oxidative stress and is thought to play a key role in numerous disease pathologies, including alcoholic liver disease (ALD). The overaccumulation of lipid peroxidation products during chronic alcohol consumption results in pathogenic lesions on protein, DNA, and lipids throughout the cell. Molecular adducts due to secondary end products of lipid peroxidation impact a host of biochemical processes, including inflammation, antioxidant defense, and metabolism. The aggregate burden of lipid peroxidation which occurs due to chronic alcohol metabolism, including downstream signaling events, contributes to the development and progression of ALD. In this current opinion we highlight recent studies and approaches relating cellular mechanisms of lipid peroxidation to the pathogenesis of alcoholic liver disease.

CYP2E1 autoantibodies in liver diseases

Autoimmune reactions involving cytochrome P4502E1 (CYP2E1) are a feature of idiosyncratic liver injury induced by halogenated hydrocarbons and isoniazid, but are also detectable in about one third of the patients with advanced alcoholic liver disease (ALD) and chronic hepatitis C (CHC). In these latter the presence of anti-CYP2E1 auto-antibodies is an independent predictor of extensive necro-inflammation and fibrosis and worsens the recurrence of hepatitis following liver transplantation, indicating that CYP2E1-directed autoimmunity can contribute to hepatic injury. The molecular characterization of the antigens recognized by anti-CYP2E1 auto-antibodies in ALD and CHC has shown that the targeted conformational epitopes are located in close proximity on the molecular surface. Furthermore, these epitopes can be recognized on CYP2E1 expressed on hepatocyte plasma membranes where they can trigger antibody-mediated cytotoxicity. This does not exclude that T cell-mediated responses against CYP2E1 might also be involved in causing hepatocyte damage. CYP2E1 structural modifications by reactive metabolites and molecular mimicry represent important factors in the breaking of self-tolerance against CYP2E1 in, respectively, ALD and CHC. However, genetic or acquired interferences with the mechanisms controlling the homeostasis of the immune system are also likely to contribute. More studies are needed to better characterize the impact of anti-CYP2E1 autoimmunity in liver diseases particularly in relation to the fact that common metabolic alterations such as obesity and diabetes stimulates hepatic CYP2E1 expression.

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CYP2E1 is a frequent autoimmune target in alcoholic liver disease and hepatitis C.

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Anti-CYP2E1 auto-antibodies mainly target conformational epitopes.

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Molecular mimicry contribute to anti-CYP2E1 autoimmunity during HCV infection.

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Anti-CYP2E1 autoimmunity contributes to the evolution of liver damage.

Brief alcohol exposure alters transcription in astrocytes via the heat shock pathway

Astrocytes are critical for maintaining homeostasis in the central nervous system (CNS), and also participate in the genomic response of the brain to drugs of abuse, including alcohol. In this study, we investigated ethanol regulation of gene expression in astrocytes. A microarray screen revealed that a brief exposure of cortical astrocytes to ethanol increased the expression of a large number of genes. Among the alcohol-responsive genes (ARGs) are glial-specific immune response genes, as well as genes involved in the regulation of transcription, cell proliferation, and differentiation, and genes of the cytoskeleton and extracellular matrix. Genes involved in metabolism were also upregulated by alcohol exposure, including genes associated with oxidoreductase activity, insulin-like growth factor signaling, acetyl-CoA, and lipid metabolism. Previous microarray studies performed on ethanol-treated hepatocyte cultures and mouse liver tissue revealed the induction of almost identical classes of genes to those identified in our microarray experiments, suggesting that alcohol induces similar signaling mechanisms in the brain and liver. We found that acute ethanol exposure activated heat shock factor 1 (HSF1) in astrocytes, as demonstrated by the translocation of this transcription factor to the nucleus and the induction of a family of known HSF1-dependent genes, the heat shock proteins (Hsps). Transfection of a constitutively transcriptionally active Hsf1 construct into astrocytes induced many of the ARGs identified in our microarray study supporting the hypothesis that HSF1 transcriptional activity, as part of the heat shock cascade, may mediate the ethanol induction of these genes. These data indicate that acute ethanol exposure alters gene expression in astrocytes, in part via the activation of HSF1 and the heat shock cascade.

The importance of CYP2E1 in the pathogenesis of alcoholic liver disease and drug toxicity and the role of the proteasome

The chapter discusses about the critical role of CYP2E1 in ethanol mediated liver injury and its association with NASH. Ethanol metabolism by CYP2E1 generates hydroxyethyl radicals which promote ethanol hepatotoxicity. Greater induction of CYP2E1 and hence greater liver injury occurs with co-administration of ethanol and drugs. Induction of CYP2E1 leads to prominent epigenetic effects and CYP2E1 polymorphism may be associated with alcoholic liver disease. These are some aspects of CYP2E1, amongst many others which account for its importance in the context of drug metabolism and disease development and have been reviewed in the chapter.

Cytochrome P450 2E1: its clinical aspects and a brief perspective on the current research scenario

Research on Cytochrome P450 2E1 (CYP2E1), a key enzyme in alcohol metabolism has been very well documented in literature. Besides the involvement of CYP2E1 in alcohol metabolism as illustrated through the studies discussed in the chapter, recent studies have thrown light on several other aspects of CYP2E1 i.e. its extrahepatic expression, its involvement in several diseases and pathophysiological conditions; and CYP2E1 mediated carcinogenesis and modulation of drug efficacy. Studies involving these interesting facets of CYP2E1 have been discussed in the chapter focusing on the recent observations or ongoing studies illustrating the crucial role of CYP2E1 in disease development and drug metabolism.

Increased immunogenicity to P815 cells modified with malondialdehyde and acetaldehyde

Aldehyde modified proteins have been associated with the development and/or progression of alcoholic liver disease (ALD). These protein adducts are capable of initiating many immunological responses that are harmful to the normal homeostasis of organism function. Previous studies have shown that malondialdehyde (MDA) and acetaldehyde (AA) synergistically form a unique adduct (MAA) with soluble proteins, which are capable of inducing cytokine release, T-cell proliferation, and antibody production. The purpose of this study was to determine whether MAA adduction can elicit similar responses to cells using a well-defined tumor model. The mouse mastocytoma P815 tumor cell line was modified with MAA (P815-MAA) or left unmodified (P815) and 10(6) irradiated cells were injected into DBA/2 mice once a week for 5 weeks. Serum was collected and tested for antibody responses to P815 cells and the MAA epitope. Immunization of MAA adducted P815 cells into syngeneic DBA/2 mice induced a strong antibody response to the MAA epitope as determined by ELISA on Alb and MAA-Alb (508 microg/ml and 1092 microg/ml, respectively). In addition, antibody to unmodified P815 cells was detected by fluorescent technique. Mice immunized with P815 cells or PBS showed little or no reactivity to the MAA epitope or P815 cells. Studies to assess IL-12 stimulation showed that peritoneal macrophages from P815 and PBS immunized animals produced modest amounts of IL-12 (20 and 35 pg/ml) when stimulated with Alb or MAA-Alb. However, macrophage from P815-MAA immunized mice responded to soluble MAA adduct (142 pg/ml). Finally, in tumor survival studies the mean survival was 14.25 days in PBS treated mice; 15.75 days with P815 immunized mice and 18.25 days with P815-MAA immunized mice. Therefore, these data strongly suggest that antibody responses are induced by P815 cells modified with MAA adducts. This may be a possible tool to begin looking at how alcohol metabolites potentially modify cells and/or cellular components making them recognizable to the immune system as foreign. It is thought that these studies define a model system that will be useful in assessing antibody and potentially T-cell responses to cells that are modified by MAA.

Protective effect of some vitamins against the toxic action of ethanol on liver regeneration induced by partial hepatectomy in rats

AIM

To investigate the effects of vitamins (A, C and E) on liver injury induced by ethanol administration during liver regeneration in rats.

METHODS

Male Wistar rats subjected to 70% partial hepatectomy were divided into five groups (groups 1-5). During the experiment, animals of Group 1 drank only water. The other four groups (2-5) drank 30 mL of ethanol/L of water. Group 3 additionally received vitamin A, those of group 4 vitamin C and those of group 5 received vitamin E. Subsequently serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), albumin and bilirubin were measured colorimetrically. Lipid peroxidation (thiobarbituric-acid reactive substances, TBARS) both in plasma and liver was measured, as well as liver mass gain assessment and total DNA.

RESULTS

Compared with sham group, serum AST and ALT increased significantly under ethanol treatment (43% and 93%, respectively, with P < 0.05). Vitamin C and vitamin E treatment attenuated the ethanol-induced increases in ALT and AST activity. Ethanol treatment also decreased serum albumin concentration compared to sham group (3.1 +/- 0.4 g/dL vs 4.5 +/- 0.2 g/dL; P < 0.05). During liver regeneration vitamins C and E significantly ameliorated liver injury for ethanol administration in hepatic lipid peroxidation (4.92 nmol/mg and 4.25 nmol/mg vs 14.78 nmol/mg, respectively, with P < 0.05). In association with hepatic injury, ethanol administration caused a significant increase in both hepatic and plasma lipid peroxidation. Vitamins (C and E) treatment attenuated hepatic and plasma lipid peroxidation.

CONCLUSION

Vitamins C and E protect against liver injury and dysfunction, attenuate lipid peroxidation, and thus appear to be significantly more effective than vitamin A against ethanol-mediated toxic effects during liver regeneration.

Detection of auto-antibodies against cytochrome P4502E1 (CYP2E1) in chronic hepatitis C

BACKGROUND/AIMS

Chronic hepatitis C (CHC) is often associated with auto-immune reactions. In the light of the role of alcohol in promoting CHC progression, we have investigated the possible presence of auto-reactivity against the ethanol-inducible cytochrome P4502E1 (CYP2E1) in CHC patients with and without alcohol consumption.

METHODS

The IgG reactivity against recombinant human CYP2E1 was evaluated by solid-phase immunoassays in 102 CHC patients with different alcohol consumption and 59 HCV-free controls.

RESULTS

Auto-antibodies against CYP2E1 were significantly (p<0.0001) increased in CHC patients as compared to controls. Anti-CYP2E1 IgG above the 97th percentile in the controls were evident in 41 (40%) CHC patients. Competition experiments revealed that CYP2E1 recognition was not due to the cross-reactivity with CYP2D6. The detection of anti-CYP2E1 IgG was unrelated to alcohol consumption and no difference in gender, age, aminotransferase levels and virus genotype was evident among the patients with or without anti-CYP2E1 auto-antibodies. However, anti-CYP2E1 auto-reactivity was significantly (p=0.025) associated with the severity of periportal/periseptal interface hepatitis. Moreover, confocal microscopy demonstrated that anti-CYP2E1 IgG associated with CHC recognized CYP2E1 exposed on the outer side of hepatocyte plasma membranes.

CONCLUSIONS

HCV infection favours the breaking of self-tolerance against CYP2E1 that might contribute to hepatocyte injury.

Alcohol, oxidative stress and free radical damage

The involvement of free radical mechanisms in the pathogenesis of alcoholic liver disease (ALD) is demonstrated by the detection of lipid peroxidation markers in the liver and the serum of patients with alcoholism, as well as by experiments in alcohol-feed rodents that show a relationship between alcohol-induced oxidative stress and the development of liver pathology. Ethanol-induced oxidative stress is the result of the combined impairment of antioxidant defences and the production of reactive oxygen species by the mitochondrial electron transport chain, the alcohol-inducible cytochrome P450 (CYP) 2E1 and activated phagocytes. Furthermore, hydroxyethyl free radicals (HER) are also generated during ethanol metabolism by CYP2E1. The mechanisms by which oxidative stress contributes to alcohol toxicity are still not completely understood. The available evidence indicates that, by favouring mitochondrial permeability transition, oxidative stress promotes hepatocyte necrosis and/or apoptosis and is implicated in the alcohol-induced sensitization of hepatocytes to the pro-apoptotic action of TNF-alpha. Moreover, oxidative mechanisms can contribute to liver fibrosis, by triggering the release of pro-fibrotic cytokines and collagen gene expression in hepatic stellate cells. Finally, the reactions of HER and lipid peroxidation products with hepatic proteins stimulate both humoral and cellular immune reactions and favour the breaking of self-tolerance during ALD. Thus, immune responses might represent the mechanism by which alcohol-induced oxidative stress contributes to the perpetuation of chronic hepatic inflammation. Together these observations provide a rationale for the possible clinical application of antioxidants in the therapy for ALD.

Review article: alcoholic liver disease--pathophysiological aspects and risk factors

BACKGROUND

Alcoholic liver disease has a known aetiology but a complex and incompletely known pathogenesis. It is an extremely common disease with significant morbidity and mortality, but the reason why only a relatively small proportion of heavy drinkers progress to advanced disease remains elusive.

AIM

To recognize the factors responsible for the development and progression of alcoholic liver disease, in the light of current knowledge on this matter.

METHODS

We performed a structured literature review identifying studies focusing on the complex pathogenetic pathway and risk factors of alcoholic liver disease. Results In addition to the cumulative amount of alcohol intake and alcohol consumption patterns, factors such as gender and ethnicity, genetic background, nutritional factors, energy metabolism abnormalities, oxidative stress, immunological mechanisms and hepatic co-morbid conditions play a key role in the genesis and progression of alcoholic liver injury.

CONCLUSIONS

Understanding the pathogenesis and risk factors of alcoholic liver disease should provide insight into the development of therapeutic strategies.

Acute alcoholic hepatitis

Acute alcoholic hepatitis (AAH) is a frequent inflammatory liver disease with high short-term mortality rate. In this review, relationships between alcohol abuse and the epidemiology and the outcomes of AAH are discussed, as well as AAH pathogenesis. The role of endotoxins, tumor necrosis factor alpha, fibroblasts, and immune response to altered hepatocyte proteins is discussed. The need of a careful prognosis, supported by the use of Maddrey score, by the model for end-stage liver disease [Mayo end-stage liver disease (MELD)] score or by the Glasgow alcoholic hepatitis score, is outlined, as the use of the most effective drugs (glucocorticoids and anti-tumor necrosis factor alpha infliximab) is recommended only in severe AAH cases. The problems of liver transplant in severe AAH, and the need of a 6-month alcohol abstinence before transplant, are discussed, as well as the need of a careful psychologic assessment before the transplant.

Peroxidases: a role in the metabolism and side effects of drugs

Current safety screening of drug candidates or new chemical entities for reactive metabolite formation focuses on the role of cytochrome P450. However, peroxidases also have a major role in drug metabolism, and peroxidase-catalyzed drug oxidation could lead to reactive metabolite formation, resulting in oxidative stress and cytotoxicity. Here, the different classes of human peroxidases are summarized and the molecular mechanisms of peroxidase-catalyzed drug metabolism are discussed. In addition, evidence is presented that indicates a role of these enzymes in drug toxicity.

"In vitro" effect of lipid peroxidation metabolites on elongation factor-2

Elongation Factor-2 (eEF-2) is the protein that catalyzes the translocation of the ribosome through mRNA. Not all oxidants affect eEF-2, which is extremely sensitive to oxidative stress caused mainly by lipid peroxidant compounds such as cumene hydroperoxide and t-butyl hydroperoxide. Lipid peroxides constitute a potential hazard to living organisms because of their direct reactivity with a variety of biomolecules and the ability to decompose into free radicals and reactive aldehydes. In this "in vitro" study, we show the effect of three of these aldehydes on the levels of hepatic eEF-2. The results suggest that the toxicity associated with prooxidant-mediated hepatic lipid peroxidation on protein synthesis can originate from the interaction of the aldehydic end products of lipid peroxidation with eEF-2.

Effects of N-acetylcysteine on ethanol-induced hepatotoxicity in rats fed via total enteral nutrition

The effects of the dietary antioxidant N-acetylcysteine (NAC) on alcoholic liver damage were examined in a total enteral nutrition (TEN) model of ethanol toxicity in which liver pathology occurs in the absence of endotoxemia. Ethanol treatment resulted in steatosis, inflammatory infiltrates, occasional foci of necrosis, and elevated ALT in the absence of increased expression of the endotoxin receptor CD 14, a marker of Kupffer cell activation by LPS. In addition, ethanol treatment induced CYP 2 E1 and increased TNFalpha and TGFbeta mRNA expression accompanied by suppressed hepatic IL-4 mRNA expression. Ethanol treatment also resulted in the hepatic accumulation of malondialdehyde (MDA) and hydroxynonenal (HNE) protein adducts, decreased antioxidant capacity, and increased antibody titers toward serum hydroxyethyl radical (HER), MDA, and HNE adducts. NAC treatment increased cytosolic antioxidant capacity, abolished ethanol-induced lipid peroxidation, and inhibited the formation of antibodies toward HNE and HER adducts without interfering with CYP 2 E1 induction. NAC also decreased ethanol-induced ALT release and inflammation and prevented significant loss of hepatic GSH content. However, the improvement in necrosis score and reduction of TNFalpha mRNA elevation did not reach statistical significance. Although a direct correlation was observed among hepatic MDA and HNE adduct content and TNFalpha mRNA expression, inflammation, and necrosis scores, no correlation was observed between oxidative stress markers or TNFalpha and steatosis score. These data suggest that ethanol-induced oxidative stress can contribute to inflammation and liver injury even in the absence of Kupffer cell activation by endotoxemia.

Ciprofloxacin suppresses bacterial overgrowth, increases fasting insulin but does not correct low acylated ghrelin concentration in non-alcoholic steatohepatitis

BACKGROUND

Insulin resistance and oxidative stress induced by products of small intestinal bacterial activity are putative factors in the pathogenesis of non-alcoholic steatohepatitis. Acylated ghrelin is the biologically active form of an orexigenic gastric hormone that modifies insulin sensitivity and body composition.

AIM

To investigate the effect of ciprofloxacin on small intestinal bacterial activity, ethanol, ghrelin and insulin in non-alcoholic steatohepatitis patients.

METHODS

Twelve non-alcoholic steatohepatitis patients and 11 controls were studied before and after ciprofloxacin 500 mg b.d. for 5 days. After an overnight fast, 75 g glucose was ingested and blood was sampled every 20 min for 120 min. Acylated and total ghrelin, ethanol and insulin were measured. Small intestinal bacterial activity was detected by glucose hydrogen breath test.

RESULTS

Mean (range) integrated plasma acylated ghrelin which was 102 (21-241) and 202 (88-366) pg/mL . 2 h in non-alcoholic steatohepatitis and controls respectively (P = 0.015). This difference persisted after correction for body mass index and was unaffected by ciprofloxacin treatment. One of six non-alcoholic steatohepatitis patients positive for small intestinal bacterial activity remained positive after ciprofloxacin. In contrast, the one healthy control positive for small intestinal bacterial activity remained positive after ciprofloxacin (P = 0.025). Ethanol was detected in two subjects in each group, becoming immeasurable after ciprofloxacin. In non-alcoholic steatohepatitis patients median (range) fasting insulin increased from 113 (10-223) to 152 (32-396) pmol/L (P < 0.02), after ciprofloxacin. This was accompanied by similar changes in insulin resistance.

CONCLUSIONS

Small intestinal bacterial activity is common in non-alcoholic steatohepatitis. Low acylated ghrelin in non-alcoholic steatohepatitis cannot be attributed to small intestinal bacterial activity. Changes in fasting insulin and ethanol following ciprofloxacin suggest that these parameters may be influenced by small intestinal bacterial activity.

Serum antibodies against the hepatitis C virus E2 protein mediate antibody-dependent cellular cytotoxicity (ADCC)

BACKGROUND/AIMS

The role of antibody dependent cellular cytotoxicity (ADCC) in HCV infection is unclear at present. Antibodies mediating ADCC are usually directed against viral envelope proteins. As cell surface expression of the HCV envelope E2 protein has been shown, the HCV E2 protein is an especially promising candidate target for ADCC.

METHODS

Sera from patients with acute (n=6), self-limited (n=11) and chronic (n=19) HCV infection were analyzed in this study. Sera reacting with cell-bound HCV antigens were examined in a flowcytometric cytotoxicity assay using antigen-coated JOK-1 cells as targets.

RESULTS

We found that sera from all stages of HCV infection reacted with cells loaded with HCV E2. E2-specific ADCC was observed in patients with acute (n=3/6), self-limited (n=5/11) and chronic (n=13/19) hepatitis C and was closely related to fluorescence intensity in the E2-binding assay (r=0.67, P<0.001).

CONCLUSIONS

We conclude that E2-antibodies from all stages of HCV infection can mediate ADCC. Thus, the role of this process in the pathogenesis of chronic hepatitis C should be further elucidated.

Immunology of alcoholic liver disease

Alcohol-induced liver injury is a reflection of the immunologic response of the liver to this stimulus. Reported studies of immunologic abnormalities in alcoholic liver disease (ALD) patients suggest that immunologic response plays a key role in the pathogenesis of chronic liver disease in alcoholics, and have contributed to the understanding of how some patients with ALD progress into alcoholic liver cirrhosis. The immunologic response of the liver is reflected in alcoholic fatty liver disease, hyaline necrosis, and cirrhosis, promoted by the role of neutrophils in damaging liver cells through cytotoxicity, and lymphocytes through cytotoxicity, inducing fibrogenesis of the liver and formation of immune complexes responsible for immune complex-mediated cytotoxicity, in addition to the role of different chemokines in attracting leucocytes, inducing fibrogenesis and liver cell apoptosis, with the established mechanism by which Mallory bodies evoke both cellular and humoral immunity contributing to the process of alcoholic liver cirrhosis, which plays a key role in transformation of alcoholic hepatitis to cirrhosis. At present, research is underway to find modalities to correct the induced immunologic changes, so at this time, it is necessary to avoid alcoholism, with the use of social and educational programs to stop alcoholism.

Treatment of alcoholic hepatitis

Cirrhosis and its sequelae are responsible for close to 2% of all causes of death in the United States. Some studies have suggested that the costs of liver disease may account for as much as 1% of all health care spending, with alcohol-related liver disease (ALD) representing a major portion. It accounts for between 40% to 50% of all deaths due to cirrhosis, with an accompanying rate of progression of up to 60% in patients with pure alcoholic fatty liver over 10 years, and a 5-year survival rate as low as 35% if patients continue to drink. A subset of patients with ALD will develop an acute, virulent form of injury, acute alcoholic hepatitis, which has a substantially worse prognosis. Despite enormous progress in understanding the physiology of this disease, much remains unknown, and therefore, a consensus regarding effective therapy for ALD is lacking. Conventional therapy is still based largely on abstinence from alcohol, as well as general supportive and symptomatic care. Unfortunately, hepatocellular damage may progress despite these measures. Multiple treatment interventions for both the short- and long-term morbidity and mortality of this disease have been proposed, but strong disagreement exists among experts regarding the value of any of the proposed specific therapeutic interventions.

Use of molecular simulation for mapping conformational CYP2E1 epitopes

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 alpha helices and beta 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.

Oxidative stress as a trigger for cellular immune responses in patients with alcoholic liver disease

Serum antibodies reactive with neo-antigens generated during ethanol metabolism have been identified in patients with alcoholic liver disease (ALD), although their role in the pathogenesis of disease remains unclear. In this study, we characterized peripheral blood mononuclear cell (PBMC) T-cell and antibody responses to human serum albumin (HAS) adducted with acetaldehyde under reducing conditions (AcA-HSA) or with malondialdehyde (MDA-HSA) in patients with advanced ALD (AALD, n = 28), heavy drinkers with no liver disease (NALD, n = 14), and mild/moderate drinking controls (n = 22). Peak proliferative responses of PBMC were assessed in vitro by tritiated thymidine incorporation after the addition of optimized concentrations of antigen or OKT3. Antibody titers were determined by enzyme-linked immunosorbent assay (ELISA). MDA-HSA induced PBMC T-cell proliferation was significantly higher in ALD than in NALD or control patients. Moreover, 10 of 28 (36%) of ALD patients had significant T-cell proliferative responses to MDA-HSA compared to 0 of 14 (0%, P =.02) of the NALD group and 2 of 22 (9%, P <.05) of controls. No significant difference in PBMC T-cell response to Aca-HSA was seen between subject groups. Patients with positive cellular responses to MDA had higher serum anti-MDA antibody titers than those not exhibiting a positive cellular response (P <.005). In conclusion, the pattern of cellular and humoral responses to MDA adducts suggests that the development of these responses may be a susceptibility factor for the development of advanced alcoholic liver disease. The apparent importance of T-cell responses to MDA adducts suggests that oxidative stress may represent an important stimulus for the development of cellular immune responses associated with advanced ALD.

T cell proliferative responses to malondialdehyde-acetaldehyde haptenated protein are scavenger receptor mediated

Malondialdehyde-acetaldehyde (MAA) haptenated proteins have been described in disease processes related to prolonged oxidative stress (via malondialdehyde production), such as alcohol liver disease (ALD), non-alcoholic non-steatohepatitis (NASH) and atherosclerosis. Experimentally, high titer IgG1 antibody responses are seen after immunization without adjuvant; however, T cell proliferative responses and the role of scavenger receptors in this immunogenicity has not previously been described. In this study, T cell proliferative responses to the carrier protein, but not the MAA hapten itself, were identified in vitro. Moreover, these T proliferative responses were inhibited when MAA-hen egg lysozyme (HEL) was co-immunized with excess scavenger receptor ligand polyG (poly-guanylic acid), implicating the role of (a) scavenger receptor(s) in initiating the T helper cell response. Activated B cells were unable to process and present MAA-HEL preferentially to T cells, while thioglycollate-elicited (but not Con A-elicited) macrophages and dendritic cells (DC) did so with approximately 32-fold less MAA-HEL than native antigen necessary to initiate equal proliferative responses. While this preferential processing and presentation may be related to several factors, preferential binding of MAA haptenated proteins mediated by scavenger receptors may be one mechanism. IL-4 was absent from the supernatants of T proliferative assays despite a strong IgG1 response in vivo, although the TH2 cytokines IL-6 and IL-10 were expressed. Since the modification of proteins by the MAA have previously been shown to occur after ethanol consumption in vivo, the ability of MAA haptens to experimentally enhance immune responses, specifically humoral and T cell responses, may represent mechanisms by which autoimmune phenomena found in ALD occur.

Iron-induced oxidant stress in alcoholic liver fibrogenesis

Iron is an essential micronutrient. However, because human beings have no means to control iron excretion, excess iron, regardless of the route of entry, accumulates in parenchymal organs and threatens cell viability. Indeed, when iron-buffering capability is overwhelmed, oxidative stress-induced cell damage and fibrogenesis may arise, mainly in the liver, the main storage site for iron in the body. Results of recent studies have clearly shown that these pathologic events are induced by iron-generated reactive oxygen species and lipid peroxidation by-products. Hepatic fibrosis, characterized by excessive accumulation of extracellular matrix components in the liver, is a dynamic process, from chronic liver damage to end-stage liver cirrhosis. Iron-induced oxidant stress is involved in this process (1) as the primary cause of parenchymal cell necrosis or (2) as activator of cells that are effectors [e.g., hepatic stellate cells, (myo)fibroblasts] or key mediators (e.g., Kupffer cells) of hepatic fibrogenesis (or through both mechanisms). Beyond their effect as direct cytotoxic agents, iron and free radicals may trigger increased synthesis of collagen in myofibroblast-like cells as well as activate granulocytes and Kupffer cells, resulting in an increased formation of cytokines and eicosanoids and further reactive oxygen species. This may constitute a cascade of amplifying loops, which perpetuate the fibrogenic process. The fibrogenic potential of iron is even more dramatic when iron acts in concert with other hepatotoxins such as alcohol. In this instance, even if tissue iron levels are only slightly elevated, the toxic effect of alcohol or its metabolites may be amplified and propagated with rapid acceleration of the liver disease. At the molecular level, the presence of catalytically active "free iron" may (1) contribute directly to the hepatotoxicity of alcohol or (2) enhance the generation of cytokine and fibrogenic mediators from resident Kupffer cells (or be involved in both ways). A challenge for future research is to develop therapeutic tools able to block "redox-active" free iron in the cell.

The generation of free radicals by nitric oxide synthase

Nitric oxide synthase (NOS) is an example of a family of heme-containing monooxygenases that, under the restricted control of a specific substrate, can generate free radicals. While the generation of nitric oxide (NO*) depends solely on the binding of L-arginine, NOS produces superoxide (O(2)*(-)) and hydrogen peroxide (H(2)O(2)) when the concentration of the substrate is low. Not surprisingly, effort has been put forth to understand the pathway by which NOS generates NO*, O(2)*(-) and H(2)O(2), including the role of substrate binding in determining the pathways by which free radicals are generated. By binding within the distal heme pocket near the sixth coordination position of the NOS heme iron, L-arginine alters the coordination properties of the heme iron that promotes formation of the perferryl complex NOS-[Fe(5+)=O](3+). This reactive iron intermediate has been shown to abstract a hydrogen atom from a carbon alpha to a heteroatom and generate carbon-centered free radicals. The ability of NOS to produce free radicals during enzymic cycling demonstrates that NOS-[Fe(5+)=O](3+) behaves like an analogous iron-oxo complex of cytochrome P-450 during aliphatic hydroxylation. The present review discusses the mechanism(s) by which NOS generates secondary free radicals that may initiate pathological events, along with the cell signaling properties of NO*, O(2)*(-) and H(2)O(2).

Genetic and epigenetic factors in autoimmune reactions toward cytochrome P4502E1 in alcoholic liver disease

Autoimmune reactions are often associated with alcoholic liver disease; however, the mechanisms responsible are largely unknown. This study investigates the potential role of the immune response against hydroxyethyl free radical (HER)-derived antigens and of polymorphisms in immunoregulatory genes in the development of anti-cytochrome P4502E1 (CYP2E1) autoantibodies in alcohol abusers. Immunoglobulin G (IgG) recognizing human CYP2E1 and HER-derived epitopes were measured by microplate immunosorbent assay in the sera of 90 patients with alcoholic fibrosis/cirrhosis (ALD), 37 heavy drinkers without liver disease or steatosis only (HD), and 59 healthy subjects. Single nucleotide polymorphisms in the interleukin 10 (IL-10) promoter and in exon 1 of the cytotoxic T-lymphocyte antigen-4 (CTLA-4) gene were genotyped by polymerase chain reaction-restriction fragment length polymorphism analysis. The titers and frequency of anti-CYP2E1 autoantibodies were significantly higher in ALD than in HD subjects or controls. ALD patients with anti-HER IgG had higher titers and a 4-fold increased risk (OR: 4.4 [1.8-10.9]) of developing anti-CYP2E1 autoantibodies than subjects without anti-HER antibodies. The mutant CTLA-4 G allele, but not the IL-10 polymorphism, was associated with an enhanced risk of developing anti-CYP2E1 IgG (OR: 3.8 [1.4-10.3]). CTLA-4 polymorphism did not influence antibody formation toward HER-antigens. ALD patients with concomitant anti-HER IgG and the CTLA-4 G allele had a 22-fold higher (OR: 22.9 [4.2-125.6]) risk of developing anti-CYP2E1 autoreactivity than subjects negative for these factors. In conclusion, antigenic stimulation by HER-modified CYP2E1 combined with an impaired control of T-cell proliferation by CTLA-4 mutation promotes the development of anti-CYP2E1 autoantibodies that might contribute to alcohol-induced liver injury.

Alcohol metabolism: role in toxicity and carcinogenesis

This article contains the proceedings of a symposium at the 2002 RSA Meeting in San Francisco, organized and co-chaired by Thomas M. Badger, Paul Shih-Jiun Yin, and Helmut Seitz. The presentations were (1) First-pass metabolism of ethanol: Basic and clinical aspects, by Charles Lieber; (2) Intracellular CYP2E1 transport, oxidative stress, cytokine release, and ALD, by Magnus Ingelman-Sundberg; (3) Pulsatile ethanol metabolism in intragastric infusion models: Potential role in toxic outcomes, by Thomas M. Badger and Martin J.J. Ronis; (4) Free radicals, adducts, and autoantibodies resulting from ethanol metabolism: Role in ethanol-associated toxicity, by Emanuele Albano; and (5) Gastrointestinal metabolism of ethanol and its possible role in carcinogenesis, by Helmut Seitz.

Alcohol abstinence does not offset the strong negative effect of lifetime alcohol consumption on the outcome of interferon therapy

Heavy alcohol consumption has been reported to negatively affect the outcome of interferon therapy. We studied the impact of lifetime alcohol consumption in patients with chronic hepatitis C treated with interferon after 6 months of alcohol withdrawal. Alcohol intake was measured when patients with chronic hepatitis C were referred to us for the first time, and from that moment complete abstinence was recommended. After 6 months of abstinence, 150 patients with persistent elevated serum alanine aminotransferase (ALT) have been treated with interferon (IFN)-alpha, 3 or 6 microU three times per week for 12 months. Univariate and multivariate analysis were performed to identify the predictors of treatment response. Carbohydrate-deficient transferrin was employed to assess alcoholic abstinence. The sustained response rate felt from 33% in nondrinkers to 20% of mild-drinkers and to only 9% in heavy drinkers. Drinker patients showed a relapse rate twice as high as that of nondrinkers. According to the multivariate analysis, the strongest independent predictors of nonresponse were genotype 1b infection, age of the patients and their lifetime alcohol intake. Carbohydrate-deficient transferrin detected at baseline, at 3 months of therapy and at the end of follow-up gave a positive result only in eight determinations (1.77%), confirming the compliance of patients to our recommendation of alcohol abstinence. Lifetime alcohol consumption has a strong negative effect on the outcome of interferon treatment, mainly in heavy drinkers. A 6-month period of abstinence may not be sufficient to offset this negative effect on treatment outcome.

Quantitative analysis of transforming growth factor beta 1 mRNA in patients with alcoholic liver disease

AIM: To investigate the expression of the transforming growth factor beta 1 (TGF- beta 1) mRNA in different stages of alcoholic liver disease (ALD) and its clinical value.

METHODS: One hundred and seven male alcoholics were grouped by clinical findings into four groups: Alcohol abusers without liver impairment (n = 22), alcoholic steatosis (n = 30); alcoholic hepatitis (n = 31); and alcoholic cirrhosis (n = 24). Using peripheral blood mononuclear cells (PBMC) as samples the gene expression of TGF-beta 1 was examined quantitatively by reverse transcription polymerase chain reaction (RT-PCR) and dot blot. There are 34 healthy subjects served as control.

RESULTS: The expression of TGF-beta 1 from all ALD patients was significantly greater than that in controls (1.320 ± 1.162 vs 0.808 ± 0.276, P < 0.001). The differences of the expressions were significant between the patients from each groups (alcoholic steatosis, alcoholic hepatitis and alcoholic cirrhosis) and the controls (1.168 ± 0.852, 1.462 ± 1.657, 1.329 ± 0.610 vs 0.808 ± 0.276, P < 0.050). No significant differences of TGF-beta 1 mRNA expression were observed between alcohol abusers without liver impairment and controls. The expressions in patients with alcoholic hepatitis and alcoholic cirrhosis were significantly greater than that in alcohol abusers respectively (1.462 ± 1.657, 1.329 ± 0.610 vs 0.841 ± 0.706, P < 0.050). No significant differences of TGF-beta 1 mRNA expression were observed between alcoholic fatty liver men and alcohol abusers.

CONCLUSION: TGF-beta 1 expression level can be a risk factor for alcoholic liver disease and might be related to the inflammatory activity and fibrosis of the liver in patients.

Free radical mechanisms in immune reactions associated with alcoholic liver disease

Immune reactions toward the liver have been implicated in the pathogenesis of alcoholic liver disease (ALD), however the antigens involved are still poorly characterized. The contribution of free radical mechanisms to the immune reactions associated with ALD first emerged from the observation that the binding of hydroxyethyl free radicals (HER) to hepatic proteins, including cytochrome P4502E1 (CYP2E1), stimulates the production of specific antibodies in both alcohol-fed rats and alcoholic patients. We have subsequently observed that ALD patients have increased titers of antibodies directed against protein adducts with different lipid peroxidation products and antigens derived from the combination of malonildialdehyde and acetaldehyde. Free radical mechanisms can also contribute in promoting the autoimmune reactions often associated with ALD. Indeed, we have observed that antiphospholipid antibodies present in more than 50% of ALD patients recognize oxidized cardiolipin complexed with beta2-glycoprotein 1. Furthermore, a strict association between anti-HER IgG and the development of autoantibodies against CYP2E1 indicates that CYP2E1 modification by HER might promote anti-CYP2E1 autoreactivity in subjects with alcoholic cirrhosis. Altogether, these observations suggest the importance of ethanol-induced oxidative stress in stimulating immune reactions towards both liver allo-and self-antigens.

[Peripheral markers, future perspectives]

Four of the recently described peripheral markers of alcohol abuse have been reviewed. The acetaldehyde adducts allow to detect an alcohol abuse lasting for several weeks, even after a recent alcohol withdrawal. Inversely, 5-hydroxytryptophol (5-HTOL) reflects the alcohol consumption of the last 24 hours. Its detection is possible after the blood alcohol concentration has disappeared. Its measurement is run in urine samples, thus without invasive sampling. The hyaluronic acid and the activity of beta-hexosaminidase are markers of hepatobiliary alcohol induced disorders more than direct markers of alcohol intake. Acetaldehyde adducts could be used as markers of long term alcohol abuse, CDT as a marker of the recent alcohol abuse, and 5-HTOL the detection of alcohol abuse of the past day.

Alcoholic liver disease: new insights into mechanisms and preventative strategies

Alcoholic liver disease has a known aetiology but a complex pathogenesis. It is an extremely common disease with a high mortality, but the reason why only a relatively small proportion of heavy drinkers progress to advanced disease remains elusive. Accumulating evidence points towards an elaborate interplay between metabolism, inflammation and immunity in the development of steatosis, hepatitis and fibrosis. These complex pathways leading to liver injury offer many potential susceptibility loci, as well as sites for potential therapeutic intervention.

Cytochrome P450 2E1 (CYP2E1)-dependent production of a 37-kDa acetaldehyde-protein adduct in the rat liver

Ethanol-inducible cytochrome P450 2E1 (CYP2E1) has been shown to be involved in the metabolism of both ethanol and acetaldehyde. Acetaldehyde, produced from ethanol metabolism, is highly reactive and can form various protein adducts. In this study, we investigated the role of CYP2E1 in the production of a 37-kDa acetaldehyde-protein adduct. Rats were pairfed an isocaloric control or an alcohol liquid diet with and without cotreatment of YH439, an inhibitor of CYP2E1 gene transcription, for 4 weeks. The soluble proteins from rat livers of each group were separated on SDS-polyacrylamide gels followed by immunoblot analysis using specific antibodies against the 37-kDa protein acetaldehyde adduct. In addition, catalytic activities of the enzymes involved in alcohol and acetaldehyde metabolism were measured and compared with the adduct level. Immunoblot analysis revealed that the 37-kDa adduct, absent in the pair-fed control, was evident in alcohol-fed rats but markedly reduced by YH439 treatment. Immunohistochemical analysis also showed that the 37-kDa adduct is predominantly localized in the pericentral region of the liver where CYP2E1 protein is mainly expressed. This staining disappeared in the pericentral region after YH439 treatment. The levels of alcohol dehydrogenase (ADH) and aldehyde dehydrogenase isozymes were unchanged after YH439 treatment. However, the level of the 37-kDa protein adduct positively correlated with the hepatic content of P4502E1. These data indicate that the 37-kDa adduct could be produced by CYP2E1-mediated ethanol metabolism in addition to the ADH-dependent formation.

Human microsomal epoxide hydrolase is the target of germander-induced autoantibodies on the surface of human hepatocytes

Germander, a plant used in folk medicine, caused an epidemic of cytolytic hepatitis in France. In about half of these patients, a rechallenge caused early recurrence, suggesting an immunoallergic type of hepatitis. Teucrin A (TA) was found responsible for the hepatotoxicity via metabolic activation by CYP3A. In this study, we describe the presence of anti-microsomal epoxide hydrolase (EH) autoantibodies in the sera of patients who drank germander teas for a long period of time. By Western blotting and immunocytochemistry, human microsomal EH was shown to be present in purified plasma membranes of both human hepatocytes and transformed spheroplasts and to be exposed on the cell surface where affinity-purified germander autoantibodies recognized it as their autoantigen. Immunoprecipitation of EH activity by germander-induced autoantibodies confirmed this finding. These autoantibodies were not immunoinhibitory. The plasma membrane-located EH was catalytically competent and may act as target for reactive metabolites from TA. To test this hypothesis CYP3A4 and EH were expressed with human cytochrome P450 reductase and cytochrome b(5) in a "humanized" yeast strain. In the absence of EH only one metabolite was formed. In the presence of EH, two additional metabolites were formed, and a time-dependent inactivation of EH was detected, suggesting that a reactive oxide derived from TA could alkylate the enzyme and trigger an immune response. Antibodies were found to recognize TA-alkylated EH. Recognition of EH present at the surface of human hepatocytes could suggest an (auto)antibody participation in an immune cell destruction.

Detection of circulating antibodies against malondialdehyde-acetaldehyde adducts in patients with alcohol-induced liver disease

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 malonildialdehyde-derived antigens and mainly recognized a specific, cyclic MAA epitope. Some degree of immune reactivity towards MAA adducts was also observed in patients with non-alcohol-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.

Interaction of 1-hydroxyethyl radical with antioxidant enzymes

There is considerable interest in the role of the 1-hydroxyethyl radical (HER) in the toxic effects of ethanol. The goal of this study was to evaluate the effects of HER on classical antioxidant enzymes. The interaction of acetaldehyde with hydroxylamine-o-sulfonic acid has been shown to produce 1, 1'-dihydroxyazoethane (DHAE); this compound appears to be highly unstable, and its decomposition leads to the generation of HER. Addition of DHAE into a solution of PBN led to the appearance of the typical EPR spectra of PBN/HER adduct. No PBN/HER spin adduct was detected when DHAE was incubated with 0.1 M PBN in the presence of GSH. In the absence of PBN, DHAE oxidized ascorbic acid to semidehydroascorbyl radical, presumably via an ascorbate-dependent one-electron reduction of HER back to ethanol. Catalase was progressively inactivated by exposure to DHAE-generated HER in a time and HER concentration-dependent manner. Ascorbic acid and PBN gave full protection to catalase against HER-dependent inactivation. The antioxidants 2-tert-butyl-4-methylphenol, propylgallate, and alpha-tocopherol-protected catalase against inactivation by 84, 88, and 39%, respectively. Other antioxidant enzymes were also sensitive to exposure to HER. Glutathione reductase, glutathione peroxidase, and superoxide dismutase were inactivated by 46, 36, and 39%, respectively, by HER. The results reported here plus previous results showing HER interacts with GSH, ascorbate, and alpha-tocopherol suggest that prolonged generation of HER in cells from animals chronically exposed to ethanol may lower the antioxidant defense status, thereby contributing to mechanisms by which ethanol produces a state of oxidative stress and produces toxicity.

4-Hydroxynonenal and malondialdehyde hepatic protein adducts in rats treated with carbon tetrachloride: immunochemical detection and lobular localization

The metabolism of CCl(4) initiates the peroxidation of polyunsaturated fatty acids producing alpha,beta-unsaturated aldehydes, such as 4-hydroxynonenal (4-HNE) and malondialdehyde (MDA). The facile reactivity of these electrophilic aldehydic products suggests they play a role in the toxicity of compounds like CCl(4). To determine the rate at which CCl(4)-initiated lipid peroxidation results in the formation of 4-HNE and/or MDA hepatic protein adducts, rats were given an intragastric dose of CCl(4) (1.0 ml/kg) and euthanized 0-72 h after administration. Rabbit polyclonal antisera directed toward 4-HNE- or MDA-protein epitopes were employed in immuno-histochemical and immuno-precipitation/Western analyses to detect 4-HNE and MDA-protein adducts in paraffin-embedded liver sections and liver homogenates. As early as 6 h post CCl(4) exposure, 4-HNE and MDA adducts were detected immuno-histochemically in hepatocytes localized to zone 2 of the hepatic acinus. Liver injury was progressive to 24 h as lipid peroxidation and hepatocellular necrosis increased. The hallmark of CCl(4) hepatotoxicity, zone 3 necrosis, was observed 24 h after CCl(4) administration and immuno-positive hepatocytes were observed in zone 2 as well as zone 3. Immuno-positive cells were no longer visible by 36 to 72 h post CCl(4) administration. From 6 to 48 h after CCl(4) administration, at least four adducted proteins were immuno-precipitated from liver homogenates with the anti-MDA or anti-4HNE serum, which corresponded to molecular weights of 80, 150, 205, and greater than 205 kDa. These results demonstrate that 4-HNE and MDA alkylate specific hepatic proteins in a time-dependent manner, which appears to be associated with hepatocellular injury following CCl(4) exposure.

Nutritional and metabolic effects of alcoholism: their relationship with alcoholic liver disease

Excessive alcohol ingestion disturbs the metabolism of most nutrients. Although alcohol can lead to severe hypoglycemia, alcoholics are usually glucose intolerant, probably due to a inhibition of glucose-stimulated insulin secretion. Ethanol intake also leads to negative nitrogen balance and an increased protein turnover. Alcohol also alters lipid metabolism, causing a profound inhibition of lipolysis. Looking for an association between alcohol intake, nutrition, and alcoholic liver disease, we have observed a higher prevalence of subclinical histologic liver damage among obese alcoholics. Multivariate analysis in a large group of alcoholics has shown that obesity is an independent predictor of alcoholic liver disease. Other authors have reported that alcoholics with a history of obesity have a two to three times higher risk of having alcoholic liver disease than non-obese alcoholics. The possible explanation for this association is that the microsomal system, which plays an important pathogenic role in alcoholic liver disease, is induced in non-alcoholic obese subjects and alcoholics. Also, peripheral blood monocyte cells of obese alcoholics produce higher levels of interleukin-1, a cytokine that can contribute to liver damage. The ingestion of polyunsaturated fatty acids can also increase the damaging effects of alcohol on the liver, as has been demonstrated in rats subjected to continuous intragastric infusion of alcohol. Observations in human alcoholics have shown that liver damage is associated with a higher ratio of C:18:1/C:18:0 and a lower ratio of C:22:4/C:18:2 in liver lipids, consistent with an induction of delta 9 desaturase and an increased peroxidation of C:22:4.

Cytotoxicity of short-chain alcohols

Ethanol and other short-chain alcohols elicit a number of cellular responses that are potentially cytotoxic and, to some extent, independent of cell type. Aberrations in phospholipid and fatty acid metabolism, changes in the cellular redox state, disruptions of the energy state, and increased production of reactive oxygen metabolites have been implicated in cellular damage resulting from acute or chronic exposure to short-chain alcohols. Resulting disruptions of intracellular signaling cascades through interference with the synthesis of phosphatidic acid, decreases in phosphorylation potential and lipid peroxidation are mechanisms by which solvent alcohols can affect the rate of cell proliferation and, consequently, cell number. Nonoxidative metabolism of short-chain alcohols, including phospholipase D-mediated synthesis of alcohol phospholipids, and the synthesis of fatty acid alcohol esters are additional mechanisms by which alcohols can affect membrane structure and compromise cell function.

Alcohol abuse, alcoholism, and damage to the immune system--a review

Chronic alcohol abuse exacts a major social and medical toll in the United States and other Western countries. One of the least appreciated medical complications of alcohol abuse is altered immune regulation leading to immunodeficiency and autoimmunity. The consequences of the immunodeficiency include increased susceptibility to bacterial pneumonia, tuberculosis, and other infectious diseases. In addition, the chronic alcoholic often has circulating autoantibodies, and recent investigations indicate that the most destructive complications of alcoholism, such as liver disease and liver failure, may have a component of autoimmunity. Current research on altered cytokine balance produced by alcohol is leading to new insights on the regulation of the immune system in the chronic alcoholic. There is also recent development of exciting new techniques designed to improve or restore immune function by manipulation of cytokine balance. Although much remains to be learned, both in the abnormalities produced by alcohol and in the techniques to reverse those abnormalities, current progress reflects a rapidly improving understanding of the basic immune disorders of the alcoholic.

The inheritance of alcoholic liver disease

Available evidence supports the concept that alcoholic liver disease (ALD) is a multifactorial disease with a heritable component. A number of polymorphic genes with small and additive effects will thus encode susceptibilty to this 'polygenic' disease. Molecular genetic studies of ALD are in their infancy, and methods available for the genetic dissection of complex traits are discussed. Some candidate genes have been identified, and studies have been undertaken to test for association between specific alleles and ALD susceptibility. There is evidence to support a role for alleles of two genes encoding enzymes involved in the oxidative metabolism of alcohol (acetaldehyde dehydrogenase2*2 and cytochrome P4502E1 c2 allele) in susceptibility to ALD. More recently, attention has focused on cytokines, and there are now data showing association of specific alleles of both tumour necrosis factor alpha and interleukin-10 with predisposition to ALD. These candidate genes need to be subjected to rigorous evaluation in different populations. Such research should help to define more precisely the molecular mechanisms underlying the development of ALD in a sub-population (< 20%) of alcoholics, thereby improving the hepatologist's ability to develop rational treatments.