Symposium 14 Monday Sept. 24th 1.30 pm–3.00 pm; Room: Lecture Hall 2
Progression factors in alcoholic liver disease: Chairpersons: Seitz HK (Germany), Albano E (Italy)
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Abstract |
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Presentation S14-1
Genetic factors in the progression of alcoholic liver disease
Stickel F (Switzerland)
Chronic alcohol consumption is a major cause of liver cirrhosis which, however, develops in only a minority of heavy drinkers. Evidence from twin studies indicate that genetic factors account for a large proportion of an individual's susceptibility to develop end-stage liver disease. The contribution of these so far unknown genetic factors to the development of diseases may be investigated either by means of animal experiments, through linkage studies in families of affected patients, or population based case-control studies. With regard to the latter, single nucleotide polymorphisms of genes involved in the degradation of alcohol, antioxidant defense, necroinflammation, and formation and degradation of extracellular matrix are attractive candidates for studying genotype-phenotype associations. Recently, screening for haplotypes that confer risk to liver damage have gathered increasing attention.
In spite of tremendous efforts and an avalanche of publications, no genetic risk factor has been firmly established with regard to the evolution of cirrhosis and many positive associations in early studies were found to be spurious and could not be confirmed in stringently designed subsequent investigations. Therefore, future genotype-phenotype studies in alcoholic liver disease should meet stringent requirements with regard to characterization of cases and controls, selection of candidate genes, sample size, and appropriate statistical measures in order to avoid pure chance observations due to a lack of power and false functional interpretation.
Presentation S14-2
The role of fatty liver in the development of advanced alcoholic liver disease
Cortez-Pinto H (Portugal)
Fatty liver (FL) is present in over 90% of chronic drinkers. This effect of alcohol has been linked to its metabolism through ADH, converting NAD to NADH, thereby contributing to hepatic steatosis by inhibiting lipid oxidation and promoting lipogenesis. Patients with alcoholic FL disease who continue to consume large amounts of alcohol daily have been found to have a risk of 8–30% of developing fibrosis or cirrhosis after 10 years. Although FL has an important role in the development of advanced ALD, progression beyond the FL stage requires additional risk factors, such as the severity and persistence of the underlying cause of steatosis and the sensitivity to reactive oxygen species, cytokine effects, and to very long-chain fatty-acid toxicity, among others. Alcoholic FL is associated with striking alternations of the mitochondria, accompanied by significant decrease in their level of phospholipids with a reduction in hepatic mitochondrial cytochrome oxidase activity. Chronic alcohol consumption is also associated with proliferation of the microsomes and activation of CYP2E1 that associates with the production of free radicals with resulting tissue damage due to lipid peroxidation. We demonstrated in liver biopsies from 17 patients with ASH (11 biopsied within 4 days of admission, and 6 after 1–2 weeks) that hepatic CYP2E1 induction was significantly enhanced when biopsy was done early, suggesting that CYP2E1 induction may operate only in the first stages of the disease. Recently, we have also shown that total bile acids in liver biopsies were elevated in ASH, with chenodeoxycholic and deoxycholic acids markedly elevated, and hydrofobicity of the biliary acid pool correlating with steatosis. The PPAR-
may also play an important role in the control of lipid homeostasis, metabolism of bioactive molecules, and modulation of inflammatory responses. Nakajima et al. have shown a protective role for PPAR- in ALD. The role of apoptosis is controversial; we found markedly increased apoptosis in ASH hepatocytes, not correlating with steatosis, and a remarkable expression of active NF-kB; in fact there is evidence that although the hepatocyte activates defence mechanisms against apoptosis that may still proceed.
Presentation S14-3
Immunological aspects in the progression of alcoholic liver disease
Albano E, Vidali M (Italy)
Inflammatory reactions are recognized to play an important role in the pathogenesis of alcoholic liver disease (ALD). Nonetheless the mechanisms by which alcohol maintains chronic inflammation in the liver are still incompletely characterized. The immune system is known to orchestrate inflammation associated to chronic liver diseases. Therefore a key issue is to clarify whether the modulation of immune reactions by alcohol influences liver inflammation.
The contribution of ethanol-induced oxidative stress to the development of immune responses has emerged form the detection in ALD patients of antibodies directed against protein adducts with several lipid peroxidation products as well as of auto-antibodies targeting oxidized phospholipids, such as oxidized cardiolipin and phoshatidylserine. These latter are particularly interesting because recognize apoptotic, but not to living, cells by specifically targeting oxidized phosphatidylserine on the outer layer of apoptotic bodies. Such a peculiarity suggests the possibility that they might interfere with the disposal of apoptotic hepatocytes. ALD patients also display a T-lymphocyte response toward lipid peroxidation antigens, indicating the involvement of oxidative damage in promoting both humoral and cellular immune reactions. Experimental studies in chronic alcohol-feed rats have shown that the development of IgG against lipid peroxidation-derived antigens is associated with the stimulation of hepatic TNF- mRNA expression and with the severity of inflammatory infiltration of the livers. A similar association between immune responses and circulating pro-inflammatory cytokines is also evident in ALD patients.
We propose that allo- and auto-immune reactions triggered oxidative stress might contribute to the progression hepatic inflammatory injuries associated with alcohol abuse.
Presentation S14-4
The role of epigenetic memory in the progression of experimental alcoholic liver disease
French SW, Bardag-Gorce F, French BA, Li J, Amidi F, Oliva J, Dedes J
Aims. To determine the role of epigenetic memory in alcoholic steatohepatitis (ASH). In a large VA study of ASH parameters which predicted progression, balloon degeneration with Mallory bodies (MDB) was implicated. MBDs incorporate M-30 a product of CK 18 degradation by caspase 3, a marker for apoptosis found in the serum of ASH. M-30 is associated with 8-OHdG, a marker of DNA damage. CK-18 is a major component of MDBs. MDBs are, therefore, a major marker for aepigenetic phenomenon.
Methods. To investigate the consequence of DNA damage, microarray analysis was performed on livers and cell cultures of CYP2E1 over expressing hepatocytes exposed to acute and chronic alcohol or DDC. DDC induces MDBs in mice liver and in cultures of DDC primed hepatocytes.
Results. THe expression of a large number of genes was changed in all of the models tested suggesting that alcohol and DDC treatment induced an epigenetic cellular memory change. This was based on changes in methylation of DNA and histones and acetylation of histones. There was an increase in DNA damage and a decrease in DNA repair enzyme in the rat model of chronic high blood alcohol levels (BAL).
Acetylation of H3K9 was increased at high BALs as was the level of histone acetyltransferase (HAT) protein and HAT enzyme activity. Acetylation of H3K9 was also increased in the DDC mouse model. S-adenosyl methionine (SAMe), a methyl donor, fed to DDC primed mice refed DDC prevented the changes in gene expression and MDB formation in vivo and in vetro. Methylation of H3K9 was reduced by DDC refeeding and it was increased when SAMe was fed with DDC refeeding.
Conclusions. The results support the role of epigenetic cellular memory in the progession of ASH. Supported by NIH/NIAAA grants P50-011999 and 8116.
Presentation S14-5
Hepatic fibrogenesis—a key event in the progression of alcoholic liver disease
Schuppan D (USA)
Cirrhosis is a major determinant of morbidity and mortality in patients with alcohol abuse. Even low grade alcoholic hepatitis frequently progresses to cirrhosis. Progression depends to a large extent on additional environmental factors (second hits) and genetic predisposition. After elimination of alcohol and second hits, such as obesity and hepatitis C, advanced fibrosis and even cirrhosis are (partly) reversible. Novel drugs are aimed at speeding up or inducing reversal of advanced fibrosis/cirrhosis. Numerous agents show antifibrotic efficacy in rodent models of liver fibrosis. However, their validation in patients is difficult due to the slow progression from normal to cirrhosis (10–40 years) and the unreliability of liver biopsy to quantify fibrosis (biopsy sampling error: 30 and 60% for 1 out of 4 fibrosis stages). Current serum fibrosis markers are ill validated and too insensitive to confirm antifibrotic drug effects. Transient elastography adds a new dimension of fibrosis assessment, but is again too insensitive to monitor fibrosis progression or regression. Therefore, much effort is currently invested to develop quantitative imaging of liver fibrosis and fibrogenesis by use of molecular probes that are targeted at collagen or at the fibrogenic cells, and to identify sensitive serum markers of progression and regression by use of advanced transcriptomics and proteomics. Apart from liver transplantation which is only available to a minority of patients with end stage alcoholic liver disease, future reversal therapies are anticipated that use combinations of antifibrotic agents, likley in concert with hepatocyte regenerative approaches, such as stem or progenitor cell transplantation.