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

急性胰腺炎是一种常见的、使人衰弱和危及生命的炎症性疾病。这种疾病的发病率正在迅速增加，而没有专门的治疗方法。这突出了研究急性胰腺炎机制以及在该领域工作的基础和转化研究人员之间协调的重要性。胰腺腺泡细胞储存和分泌消化酶和消化酶前体。胰腺腺泡细胞损伤是急性胰腺炎发生的重要早期事件。这种损伤可由胆汁酸和乙醇代谢物等急性胰腺炎诱导剂触发，表现为细胞内大液泡的形成，细胞内消化酶的激活，以及对本研究重要的线粒体损伤。Ca2+是调节胰腺分泌的重要第二信使。然而，过量的Ca2+积累对细胞是有毒的。我们假设，暴露于急性胰腺炎诱导剂的胰腺腺泡细胞的线粒体损伤是由于过量的Ca2+通过线粒体Ca2+单转运体（MCU）进入线粒体而产生的，并且这种MCU依赖的Ca2+过载可能是导致急性胰腺炎早期细胞损伤的机制。该项目将利用最近对MCU的分子鉴定。在我们的研究中，我们将研究MCU在急性胰腺炎中的潜在作用，确定特定的潜在细胞机制以及针对这些机制开发治疗这种疾病的潜力。我们研究的第一个目的是确定MCU与急性胰腺炎的相关性。我们期望通过描述MCU敲除（MCU KO）动物急性胰腺炎的发展特征来揭示这一点。本组在实验性急性胰腺炎方面有丰富的经验，常规评估多种模型。在MCU KO动物的实验中，我们将使用三种不同的急性胰腺炎模型（包括反复注射蓝蛋白，向胰管输注3-硫酸牛磺酸胆酸和联合注射酒精和脂肪酸）。我们对MCU KO动物分离的胰腺腺泡细胞进行的初步实验显示，Ca2+进入线粒体的数量大大减少，并且这些细胞免受Ca2+释放促分泌剂胆囊收缩素的最大浓度诱导的损伤。这些实验表明，Ca2+通过MCU进入胰腺腺泡细胞可能对急性胰腺炎的发展很重要。因此，我们的下一个目标将是确定mcu依赖性胰腺腺泡细胞损伤在急性胰腺炎发展中的具体作用。在细胞特异性MCU KO小鼠（在胰腺腺泡细胞中特异性敲除MCU）上的实验将用于该部分项目。在对转基因动物进行体内实验的同时，我们将对分离细胞进行实验。这些实验的目的将是表征Ca2+进入线粒体的腺泡细胞分离MCU敲除动物和处理的诱导剂急性胰腺炎。这对于解释涉及急性胰腺炎动物模型的实验至关重要。在分离细胞的实验中，我们还将确定mcu介导的Ca2+进入在细胞生物能量学、凋亡和坏死中的作用。这些实验需要揭示确定MCU在急性胰腺炎中的作用的细胞机制。药理抑制MCU对胰腺腺泡细胞的生物能量学、凋亡和坏死的影响将有助于我们解释转基因细胞和动物实验的结果。药理抑制MCU的实验也有助于我们评估MCU抑制剂治疗急性胰腺炎的潜力。

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.