The role of mitochondrial Ca2+ uniporter in initiation and development of acute pancreatitis

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Acute pancreatitis is a frequent, debilitating and life threatening inflammatory disease. The incidence of this disease is increasing rapidly whilst specific therapy is unavailable. This highlights the importance of research into the mechanisms of acute pancreatitis and coordination between basic and translational researchers working in this area. Pancreatic acinar cells store and secrete digestive enzymes and precursors of digestive enzymes. The damage to pancreatic acinar cells is an important early event in the development of acute pancreatitis. Such damage can be triggered by the inducers of acute pancreatitis like bile acids and ethanol metabolites and is manifested by formation of large intracellular vacuoles, intracellular activation of digestive enzymes and, importantly for this study, mitochondrial damage. Ca2+ is an important second messenger regulating pancreatic secretion. However excessive Ca2+ accumulation is toxic for the cells. We hypothesise that the mitochondrial damage in pancreatic acinar cells, exposed to the inducers of acute pancreatitis, develops as a result of excessive Ca2+ entry into mitochondria via the Mitochondrial Ca2+ Uniporter (MCU) and that such MCU-dependent Ca2+ overload could be the mechanism responsible for early cell damage in acute pancreatitis. The project will capitalise on the recent molecular identification of the MCU. In our study we will examine the potential role of MCU in acute pancreatitis, determine the specific underlying cellular mechanisms and potential of targeting these mechanisms for the development of treatment against this disease. The first objective of our study will be to determine the relevance of the MCU for acute pancreatitis. We expect that this will be revealed by characterising the development of acute pancreatitis in MCU knockout (MCU KO) animals. Our group has considerable experience in experimental acute pancreatitis, routinely assessing multiple models. In experiments with MCU KO animals we will utilise three different models of acute pancreatitis (involving repeated cerulein injections, infusion of taurolithocholic acid 3-sulphate into pancreatic duct and combined injection of alcohol and fatty acids). Our preliminary experiments on isolated pancreatic acinar cells from MCU KO animals revealed strongly reduced Ca2+ entry into mitochondria and protection of these cells against damage induced by a supramaximal concentration of Ca2+- releasing secretagogue cholecystokinin. These experiments indicate that Ca2+ entry via MCU in pancreatic acinar cells could be important for the development of acute pancreatitis. Our next objective will be therefore to determine the specific role of MCU-dependent damage to pancreatic acinar cells in the development of acute pancreatitis. Experiments on cell specific MCU KO mice (MCU knocked out specifically in the pancreatic acinar cells) will be utilised in this part of the project. In parallel with in vivo experiments on transgenic animals we will conduct experiments on isolated cells. The objective of these experiments will be to characterise Ca2+ entry into mitochondria of the acinar cells isolated from MCU knockout animals and treated with the inducers of acute pancreatitis. This is essential for interpreting experiments involving animal models of acute pancreatitis. In experiments on isolated cells we will also determine the role of MCU-mediated Ca2+ entry in cellular bioenergetics, apoptosis and necrosis. These experiments are required to reveal the cellular mechanisms defining the role of MCU in acute pancreatitis. The effects of pharmacological MCU inhibition on bioenergetics, apoptosis and necrosis of pancreatic acinar cells will help us to interpret the results of experiments with genetically modified cells and animals. Experiments with pharmacological inhibition of MCU should also help us to evaluate the potential of MCU inhibitors for the development of treatment against acute pancreatitis.