Alcohol abuse is associated with at least 70% of cases of chronic pancreatitis (CP) and 40% of acute pancreatitis. Yet, only a small percentage of those who abuse alcohol develop pancreatic disease. Clearly there are other biological factors which predispose to the development of pancreatitis and alcohol abuse is acting as a triggering mechanism. But what are these factors? Unfortunately, to date no animal model has been developed that recapitulates alcohol related CP. Therefore, it has been difficult to make progress against this disease. However, we have recently developed two novel mouse models which are sensitive to alcohol and develop severe CP without the need for additional insults. The models involve regulated pancreatic acinar cell specific expression of mutant trypsin molecules. One is an experimental construct that becomes activated upon translation (called Trypon mice). The other involves expression of the R122H trypsinogen mutant (called R122H mice) which is associated with hereditary pancreatitis. Neither of these mutant trypsin molecules induces pancreatitis or any obvious perturbations when expressed as a heterozygote. However, when R122G or Trypon mice are fed an alcohol diet; they develop profound CP. These data support a hypothesis that alcohol sensitizes the pancreas to factors that affect trypsin activation or protection from active trypsin. The goal of this proposal is to understand the mechanisms involved in these effects by pursuing three specific aims.
Aim #1 : Determine whether acute or chronic intake of alcohol is necessary to generate CP in mice expressing mutant trypsin. Alcohol has multiple effects and the effects of acute and chronic alcohol are often opposite. It will be important to understand whether alcohol is required in the short or long term to generate chronic pancreatitis in this model. We will also determine the effects of alcohol on trypsin activity to assess whether trypsin itself is the key mechanism. Together these studies will provide important basic information about the model.
Aim #2 : We will determine the form(s) of acinar cell death initiated in these animals by ethanol. We hypothesize that alcohol perturbs normal cellular mechanisms such that intracellular trypsin induces necrosis in acinar cells. We will also examine whether autophagy is involved in the effects of ethanol in this model.
Aim #3. Determine the role of metallothionein (MT) in the development of CP in alcohol treated mice expressing mutant trypsin. We have previously found that alcohol feeding causes a down-regulation of MT, which normally plays a protective role in acute pancreatitis. To understand the role of MT in alcohol related CP we will examine the effects of mutant trypsin expression in mice with high (Zn treated) or low (MT deficient) levels of MT. We will also investigate the mechanisms of alcohol reduction of MT expression. Together these novel models and approaches will provide important new information about the relationship between alcohol and pancreatic disease.
The development of new treatments for alcohol related pancreatic disease had been hindered by the lack of physiologically relevant animal models. We have developed for the first time an animal model with a modified genetic background that develops alcohol dependent chronic pancreatitis without the need for additional injurious treatments. This new model will provide an opportunity to discover important new details about the role of alcohol in pancreatic disease.
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