Jennifer Dedes

S‐adenosylmethionine prevents mallory denk body formation in drug‐primed mice by inhibiting the epigenetic memory

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 (SAMe; 4 g/kg of body weight). The livers were studied for evidence of oxidative stress and changes in gene expression with microarray analysis. SAMe prevented Mallory Denk body formation in vivo. The molecular cellular memory induced by DDC refeeding lasted for 4 months after drug withdrawal and was not manifest when SAMe was added to the diet in the in vivo experiment. Liver cells from drug‐primed mice spontaneously formed Mallory Denk bodies in primary tissue cultures. SAMe prevented Mallory Denk bodies when it was added to the culture medium. Conclusion: SAMe treatment prevented Mallory Denk body formation in vivo and in vitro by preventing the expression of a molecular cellular memory induced by prior DDC feeding. No evidence for the involvement of oxidative stress in induction of the memory was found. The molecular memory included the up‐regulation of the expression of genes associated with the development of liver cell preneoplasia. (HEPATOLOGY 2007.) (This is a corrected version of the abstract first published online on 20 December 2007 — the corrected version appears in print.)

Chronic Ethanol Feeding Alters Hepatocyte Memory Which is not Altered by Acute Feeding

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. METHODS To test this hypothesis, gene microarray analysis was performed on the livers of rats (n = 3) fed an acute binge dose of ethanol (6 g/kg body wt) and killed at 3 and 12 hours after ethanol by gavage. The gene microarrays were compared with those made on the liver of rats from a previous study, in which the rats were fed ethanol by intragastric tube for 1 month (36% of calories derived from ethanol). RESULTS Microarray analysis data varied between the acute and chronic models in several important respects. Growth factors increased mainly in the chronic alcohol fed rat. Changes in enzymes involved in oxidative stress were noted only with chronic ethanol feeding. Gene expression of fat metabolism was increased only with chronic ethanol feeding. Most importantly, epigenetic related enzymes and acetylation and methylation of histones changed only after chronic ethanol feeding. CONCLUSIONS The results support the concept that chronic ethanol ingestion induces altered gene expression as a result of changes in epigenetic mechanisms, where acetylation and methylation of histones were altered.

Epigenetic mechanisms regulate Mallory Denk body formation in the livers of drug-primed mice.

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 4 months after withdrawal from the DDC diet. In the present study, mice were fed a diet containing DDC or a diet containing DDC and S-adenosylmethionine (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 ubiquitinylation. 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 provides 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.

The effect of propranolol on gene expression during the blood alcohol cycle of rats fed ethanol intragastrically.

Propranolol, a beta adrenergic blocker prevents the blood alcohol (BAL) cycle in rats fed ethanol intragastrically at a constant rate by preventing the cyclic changes in the metabolic rate caused by fluctuating levels of norepinephrine released into the blood. The change in the rate of metabolism changes the rate of alcohol elimination in the blood which causes the BAL to cycle. Microarray analysis of the livers from the rats fed ethanol and propranolol showed similar changes in clusters of functionally related gene expressions. The controls and the trough of the cycle differed dramatically from the cluster pattern seen in the rats at the peaks of the blood alcohol cycle. The changes in gene expression induced by ethanol were similar when propranolol was fed without ethanol especially with the changes in the kinases and phosphatases, Toll-like receptor signaling and cytokine-cytokine receptor interaction were also changed. The changes in gene expression caused by ethanol and propranolol feeding are alike probably because both drugs induce beta adrenergic receptor desensitization.