Mitophagy: target to improve liver function after ischemia/reperfusion injury

线粒体自噬：改善缺血/再灌注损伤后肝功能的目标

• 批准号: 8295215
• 负责人: Jae-Sung Kim
• 金额: $ 31.86万
• 依托单位: UNIVERSITY OF FLORIDA
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-04-01 至 2016-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8295215
• 关键词: Abdomen; Age; Apoptosis; Attention; Attenuated; Autophagocytosis; Autophagosome; Bioenergetics; Blood flow; Calpain; Carbamazepine; Cardiovascular Surgical Procedures; Cell Death; Cell physiology; Communities; Compartment syndromes; Complement; Data; Defect; Enzymes; Excision; Experimental Models; Extracorporeal Circulation; Failure; Genes; Genetic; Goals; Hemorrhagic Shock; Hepatic; Hepatocyte; Impairment; In Vitro; Injury; Injury to Liver; Intervention; Ischemia; Life Expectancy; Liver; Liver Dysfunction; Liver Failure; Liver diseases; Mediating; Microscopy; Mitochondria; Monitor; Morbidity - disease rate; Mus; Operative Surgical Procedures; Pathway interactions; Patients; Permeability; Recovery; Recycling; Reperfusion Injury; Reperfusion Therapy; Reporter; Research; Resolution; Role; Sirolimus; Testing; Therapeutic; Tissues; Transplantation; Warm Ischemia; age related; aged; hepatic necrosis; improved; in vivo; in vivo Model; innovation; insight; liver function; mitochondrial autophagy; mitochondrial dysfunction; mortality; novel; novel therapeutic intervention; older patient; operation; overexpression; research study; restoration; translational study

DESCRIPTION (provided by applicant): An increase in life expectancy has been accompanied by a larger number of patients with liver diseases that require surgical resection. The aged liver has significantly less reparative capacity following ischemia/ reperfusion (I/R) injury associated with this operation. Innovative approaches are urgently needed to reduce the age-dependent reperfusion injury and improve liver function of elderly patients following surgery. Mitochondrial dysfunction is the major mechanism precipitating lethal I/R injury to liver. Mitochondrial autophagy (mitophagy) is the cellular process that selectively removes abnormal mitochondria. The contribution of mitophagy to the age-dependent liver injury after warm ischemia is unknown. The goal of this study is to elucidate the mechanisms underlying the age-mediated lethal I/R injury to liver and to develop therapeutic strategies to improve liver function in the elderly patients after I/R. Our preliminary data demonstrate that the increased sensitivity of liver to I/R injury with age is strongly associated with its decreased mitophagic responsiveness. Preliminary results show that calpain-2-mediated loss of Atg4B, a key enzyme catalyzing the formation and recycling of autophagosomes, contributes to the age-dependent sensitivity of liver to I/R injury and mitochondrial dysfunction. In addition, we demonstrate that overexpression of Atg4B in both in vitro and in vivo models of I/R mitigates Atg4B loss, mitochondrial dysfunction and cell death. Thus, we propose that restoration or enhancement of mitophagy in aged liver will promote the clearance of dysfunctional mitochondria and consequently ameliorate liver dysfunction and bioenergetic failure after reperfusion. Our principal hypothesis is that defective or insufficient mitophagy is responsible for the increased sensitivity of old liver to lethal I/R injury. Two experimental models will be explored in this application using three different ages of mice. First, isolated hepatocytes will be utilized to determine the mechanisms of age-dependent mitophagic defects after I/R. Second, anesthetized mice will be employed to confirm and extend our I/R findings from an in vitro to an in vivo model. Finally, we will test the potential for mitophagy enhancing agents as therapeutic strategies to improve liver function after I/R in vivo. These studies provide critical mechanistic insights into the age-dependent I/R injury to liver, and will establish novel therapeutic approaches for improving I/R-mediated liver failure in the elderly patients. PUBLIC HEALTH RELEVANCE: Impairment of blood flow causes a tissue ischemia and recovery of blood flow causes reperfusion injury to liver. Ischemia/reperfusion (I/R) injury is a causative factor of morbidity and mortality during liver resection, hemorrhagic shock, cardiovascular surgery with extracorporeal circulation, transplantation and abdominal compartment syndrome. The liver from the elderly patients has significantly less reparative capacity following I/R injury associated with these operations. To date, there is no therapeutic strategy to reduce lethal I/R injury in the elderly patients. Thus, innovative approaches are urgently needed to reduce the age-dependent reperfusion injury and improve liver function of elderly patients following surgeries. Better understanding of the mechanisms underlying I/R injury would establish novel therapeutic approaches for improving liver function after liver surgery.

描述（由申请人提供）：预期寿命的增加伴随着越来越多的肝病患者需要手术切除。与该手术相关的缺血/再灌注（I/R）损伤后，老化的肝脏的修复能力显着降低。迫切需要创新方法来减少年龄依赖性再灌注损伤并改善老年患者术后的肝功能。线粒体功能障碍是导致肝脏致命性 I/R 损伤的主要机制。线粒体自噬（mitophagy）是选择性清除异常线粒体的细胞过程。线粒体自噬对热缺血后年龄依赖性肝损伤的影响尚不清楚。本研究的目的是阐明年龄介导的致死性 I/R 肝脏损伤的机制，并制定改善肝功能的治疗策略 I/R 后的老年患者。我们的初步数据表明，随着年龄的增长，肝脏对 I/R 损伤的敏感性增加与其线粒体自噬反应性降低密切相关。初步结果表明，calpain-2 介导的 Atg4B（一种催化自噬体形成和再循环的关键酶）的丢失，导致肝脏对 I/R 损伤和线粒体功能障碍的年龄依赖性敏感性。此外，我们证明 Atg4B 在 I/R 的体外和体内模型中过度表达可减轻 Atg4B 损失、线粒体功能障碍和细胞死亡。因此，我们提出，衰老肝脏中线粒体自噬的恢复或增强将促进功能障碍的线粒体的清除，从而改善再灌注后的肝功能障碍和生物能衰竭。我们的主要假设是，线粒体自噬缺陷或不足是导致老肝脏对致命性 I/R 损伤敏感性增加的原因。本申请将使用三种不同年龄的小鼠探索两种实验模型。首先，分离的肝细胞将用于确定 I/R 后年龄依赖性线粒体自噬缺陷的机制。其次，将使用麻醉小鼠来确认并将我们的 I/R 研究结果从体外模型扩展到体内模型。最后，我们将测试线粒体自噬增强剂作为改善体内 I/R 后肝功能的治疗策略的潜力。这些研究为年龄依赖性 I/R 肝脏损伤提供了重要的机制见解，并将建立改善老年患者 I/R 介导的肝衰竭的新治疗方法。 公共卫生相关性：血流受损会导致组织缺血，血流恢复会导致肝脏再灌注损伤。缺血/再灌注（I/R）损伤是肝切除、失血性休克、体外循环心血管手术、移植和腹腔间隔室综合征期间发病和死亡的一个致病因素。老年患者的肝脏在与这些手术相关的缺血再灌注损伤后的修复能力明显较差。迄今为止，尚无减少老年患者致命性缺血再灌注损伤的治疗策略。因此，迫切需要创新方法来减少年龄依赖性再灌注损伤并改善老年患者术后的肝功能。更好地了解 I/R 损伤的机制将为肝脏手术后改善肝功能建立新的治疗方法。