Ethanol administration impairs pancreatic repair after injury.

OBJECTIVES: Alcohol abuse is one of the most common factors associated with acute and chronic pancreatitis. Although it is evident that alcohol abuse can have an important role in the development of pancreatitis, it does not seem that alcohol abuse alone is responsible for this disease. We investigated the involvement of ethanol in the impairment of pancreatic repair after induction of pancreatitis. METHODS: A biologically relevant mouse model of alcoholic pancreatitis, combining long-term ethanol consumption and coxsackievirus infection, was used to investigate the effects of ethanol on pancreatic regeneration. Tissues were harvested and analyzed by reverse transcription-polymerase chain reaction and immunoblot. RESULTS: These studies demonstrate that long-term ethanol consumption impairs the structural repair of the exocrine pancreas. This is accompanied by a delay in the restitution of lipase expression. In addition, impaired expression of the critical pancreatic transcription factors, PDX1 and PTF1, and the mediator of Notch signaling, HES1, was observed. CONCLUSIONS: Long-term ethanol consumption impairs the structural repair and functional restitution of the pancreas after severe injury. These impairments may, in part, be explained by the impaired expression of factors important in the development and maintenance of the exocrine pancreas. Impaired pancreatic regeneration may have a role in the pathogenesis of alcoholic pancreatitis.

Ethanol metabolism activates cell cycle checkpoint kinase, Chk2.

Chronic ethanol abuse results in hepatocyte injury and impairs hepatocyte replication. We have previously shown that ethanol metabolism results in cell cycle arrest at the G2/M transition, which is partially mediated by inhibitory phosphorylation of the cyclin-dependent kinase, Cdc2. To further delineate the mechanisms by which ethanol metabolism mediates this G2/M arrest, we investigated the involvement of upstream regulators of Cdc2 activity. Cdc2 is activated by the phosphatase Cdc25C. The activity of Cdc25C can, in turn, be regulated by the checkpoint kinase, Chk2, which is regulated by the kinase ataxia telangiectasia mutated (ATM). To investigate the involvement of the regulators of Cdc2 activity, VA-13 cells, which are Hep G2 cells modified to efficiently express alcohol dehydrogenase, were cultured in the presence or absence of 25 mM ethanol. Immunoblots were performed to determine the effects of ethanol metabolism on the activation of Cdc25C, Chk2, and ATM. Ethanol metabolism increased the active forms of ATM and Chk2, as well as the phosphorylated form of Cdc25C. Additionally, inhibition of ATM resulted in approximately 50% of the cells being rescued from the G2/M cell cycle arrest and ameliorated the inhibitory phosphorylation of Cdc2. Our findings demonstrated that ethanol metabolism activates ATM. ATM can activate the checkpoint kinase Chk2, resulting in phosphorylation of Cdc25C and ultimately in the accumulation of inactive Cdc2. This may, in part, explain the ethanol metabolism-mediated impairment in hepatocyte replication, which may be important in the initiation and progression of alcoholic liver injury.