In previous studies, microarray analysis of livers from mice fed diethyl-1,4-dihydro-2,4,6-trimethyl-3,5-pyridine decarboxylate (DDC) for 10 weeks followed by 1 month of drug withdrawal (drug-primed mice) and then 7 days of drug refeeding showed an increase in the expression of numerous genes referred to here as the molecular cellular memory. This memory predisposes the liver to Mallory Denk body formation in response to drug refeeding. In the current study, drug-primed mice were refed DDC with or without a daily dose of S-adenosylmethionine M allory bodies (MBs) are an important component of chronic progressive liver injury. [1][2][3][4][5] MBs have been renamed Mallory Denk bodies (MDBs) in recognition of Dr. Denk's important contributions to the understanding of MBs. 1 Because S-adenosylmethionine (SAMe) is effective in attenuating alcoholic and nonalcoholic liver disease experimentally, 6 it has been postulated that SAMe treatment would attenuate MDB formation with the drug-primed mouse model.The questions are as follows: what is the role of molecular cellular memory and oxidative stress in the induction of MDB formation in drug-primed mice and how does SAMe treatment affect these two parameters? In the drugprimed mouse, MDB formation is induced in 7 days of drug refeeding or in 6 days of primary liver cell culture. [7][8][9][10] Microarray analysis performed on livers from drugprimed or drug-refed mice showed that the expression of a large number of genes was changed when MDBs were formed. 11 Experiments in which signal transduction cascades involving extracellular signal-regulated kinase 1/2, nuclear factor kappa B (NFB), or p38 pathways were blocked by chemical inhibitors showed that inhibition of each pathway prevented MB formation in vitro. 7,8 The

Background-Gene expression changes in the liver after acute binge drinking may differ from the changes seen in chronic ethanol feeding in the rat. The changes in gene expression after chronic ethanol feeding may sensitize the liver to alcohol-induced liver damage, which is not seen after acute binge drinking.

The mechanism of Mallory Denk body formation is still not fully understood, but growing evidence implicates epigenetic mechanisms in MDB formation. In a previous study the epigenetic memory of MDB formation remained intact for at least four months after withdrawal from the DDC diet. In the present study, mice were fed a diet containing DDC or a diet containing DDC and Sadenosylmethionine (SAMe) to investigate the epigenetic memory of MDB formation. DDC feeding caused an increase in histone 3 acetylation, a decrease in histone 3 trimethylation, and an increase in histone ubiquitination. The addition of SAMe to the DDC diet prevented the DDC induced decrease of H3K4 and H3K9 trimethylation and the increase in histone ubiquitinylation. Changes in histone modifying enzymes, (HATs and HDACs) were also found in the liver nuclear extracts of the DDC/ SAMe fed mice. Data mining of microarray analysis confirmed that gene expression changed with DDC refeeding, particularly the SAMe-metabolizing enzymes, Mat2a, AMD, AHCY and Mthfr. SAMe supplementation prevented the decrease of AHCY and GNMT, and prevented the increase in Mthfr, which provide a mechanism to explain how DDC inhibits methylation of histones. The results indicate that SAMe prevented the epigenetic cellular memory involved in the MDB formation

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Microarrays were done on the livers of mice fed DDC for 10 weeks, withdrawn 1 month (DDC primed livers) and refed 6 days, and compared with mice fed the control diet. The expression of a large number of genes changed when DDC was fed or refed. A Venn diagram analysis identified 649 genes where gene expression was changed in the same direction. The epigenetic memory of the DDC primed liver involved an increase in the expression of ubiquitin D, alpha fetoprotein, connective tissue growth factor, integrin beta 2, DNA methyl transferase 3a and DNA damage-inducible 45 gamma. DNA methyl transferase 3b was down-regulated as was Cbp/p300. When DDC was refed, DNA methyltransferase and histone deacetylase were up-regulated as shown by microarray analysis. Histone3 lysine9 acetylation was increased by DDC and DDC refeeding and DNA methyltransferases were not changed as shown by Western blot analysis. The data suggest the concept that the epigenetic memory that explains why DDC primed hepatocytes form MBs in 7 days of DDC refeeding is primarily the result of epigenetic modifications of gene expression through changes in histone acetylation and methylation, as well as DNA methylation.

AIM:To examine the effects of ethanol-induced proteasome inhibition, and the effects of proteasome inhibition in the regulation of epigenetic mechanisms. METHODS:Rats were fed ethanol for 1 mo using the Tsukamoto-French model and were compared to rats given the proteasome inhibitor PS-341 (Bortezomib, Velcade™) by intraperitoneal injection. Microarray analysis and real time PCR were performed and proteasome activity assays and Western blot analysis were performed using isolated nuclei. RESULTS:Chronic ethanol feeding caused a significant inhibition of the ubiquitin proteasome pathway in the nucleus, which led to changes in the turnover of transcriptional factors, histone-modifying enzymes, and, therefore, affected epigenetic mechanisms. Chronic ethanol feeding was related to an increase in histone acetylation, and it is hypothesized that the proteasome proteolytic activity regulated histone modifications by controlling the stability of histone modifying enzymes, and, therefore, regulated the chromatin structure, allowing easy access to chromatin by RNA polymerase, and, thus, proper gene expression. Proteasome inhibition by PS-341 increased histone acetylation similar to chronic ethanol feeding. In addition, proteasome inhibition caused dramatic changes in hepatic remethylation reactions as there was a significant decrease in the enzymes responsible for the regeneration of S-adenosylmethionine, and, in particular, a significant decrease in the betainehomocysteine methyltransferase enzyme. This suggested that hypomethylation was associated with proteasome inhibition, as indicated by the decrease in histone methylation. CONCLUSION:The role of proteasome inhibition in regulating epigenetic mechanisms, and its link to liver injury in alcoholic liver disease, is thus a promising approach to study liver injury due to chronic ethanol consumption.

Chronic ethanol ingestion, achieved by feeding ethanol at a constant rate using intragastric