Role of intra-pancreatic trypsinogen activation in alcoholic pancreatitis ABSTRACT Pancreatitis is an inflammatory disease of the pancreas associated with significant morbidity and mortality and is most commonly associated with alcohol abuse. However, the mechanism of alcoholic pancreatitis is not clear. It is believed that alcohol sensitizes the pancreas to genetic or environmental predisposing factors. A challenge remains to identify sensitization factors, to define their contribution to the injury and to understand the mechanisms of ethanol sensitizing effects. There is therefore an inarguable need to better understand the patho-physiological mechanism of alcoholic pancreatitis to develop a targeted therapy for the disease. Existing studies in non-alcoholic models of pancreatitis suggest a role for trypsinogen activation within the pancreas in the pathogenesis of the disease. Alcohol exposure is known to enhance activation of trypsinogen in acinar cells. Pancreatic juice of human alcoholics was found to have increased levels of trypsinogens. These changes are thought to make acinar cells more prone to injury. These findings suggest that trypsinogen activation in the pancreas might be the central event in the pathogenesis of alcoholic pancreatitis, although there is no direct experimental evidence to prove this. Ethanol exposure has several other deleterious effects like altered NFkB activation and perturbed endoplasmic reticulum stress response, which have the potential to cause pancreatic damage. Recently, we have developed knockout mice lacking trypsinogen 7, the mouse cationic trypsinogen. These mice do not show pathological activation of trypsinogen. Cathepsin B activity is required for intra-acinar activation of trypsinogen and the mice with cathepsin B gene deletion also lack pathological trypsinogen activation. Our access to these two strains of mice places us in a unique position to define the role of trypsinogen activation in the pathogenesis of alcoholic pancreatitis. In the absence of trypsinogen activation, we will also be able to understand if other ethanol exposure-induced deleterious events have any role in pathogenesis of the disease. In this grant proposal, we will be testing the hypothesis that intra-acinar activation of trypsinogen is the critical early event in alcoholic pancreatitis leading to acinar cll injury and activation of inflammatory pathways which result in acute pancreatitis and when prolonged, these events leads to fibrosis and chronic inflammatory response of alcoholic pancreatitis. Completion of these studies, while clearly defining the role of trypsinogen activatio in alcohol abuse induced sensitization, will lay the foundation for future investigations focused on understanding the role of other ethanol induced events in the pancreas and the searching for potential therapeutic targets in alcoholic pancreatitis.
Alcohol abuse is the common factor associated with pancreatitis but the mechanism of alcoholic pancreatitis is not clear. There is inarguable need to understand key events in the pathogenesis of the disease in order to identify novel therapeutic targets. Alcohol exposure is believed to enhance trypsinogen activation in acinar cells making pancreas susceptible to injury. However, the role of active trypsin in alcoholic pancreatitis is no clear. This project application aims at understanding the role of intra-pancreatic activation of trypsinogen in pancreatic acinar cell injury and inflammatory response using newly generated mice with trypsinogen 7 gene deletion and mice with cathepsin B deletion, both of which do not demonstrate pathologic trypsin activation.
