SUMO Conjugation and Deep Hypothermia-Induced Organ Protection

描述(申请人提供)：各种儿科和成人心血管手术都需要体外循环(CPB)手术，需要一段时间的循环停搏。儿童和成人患者的大型心血管手术会导致围手术期器官损伤，因此与严重的脑、肾和心血管不良结局相关。为了保护器官免受缺血损伤，手术通常在深低温条件下进行(深低温停循环)。尽管深低温的保护潜力是毋庸置疑的，但人们对它保护器官的机制或如何最大限度地发挥其功效知之甚少。因此，阐明深低温保护器官的机制具有重要的临床意义。如果我们了解这些机制，我们将能够设计治疗策略来激活这些过程，从而诱导一种耐受状态，而不会冒着与深度低温相关的不良影响的风险。我们假设，深低温通过激活小泛素样修饰物(SUMO)结合途径来保护器官免受缺血损伤。蛋白质总和作用显著影响转录因子和其他细胞内蛋白质的稳定性、定位和活性。因此，深低温诱导的相扑结合变化可能在确定暴露于瞬时深低温下的细胞的最终结果中发挥关键作用。我们发现，在深低温过程中，相扑结合蛋白水平显著增加，激活相扑结合已被证明可以保护细胞免受类缺血条件下的损伤。我们有以下具体目标：1)检查低温程度和持续时间与相扑结合通路激活之间的关系；2)确定 3)验证是否可以通过沉默相扑表达，从而阻断深低温诱导的相扑接合通路的激活，从而改变器官对深低温的敏感性。人们普遍认为，低温诱导的保护是一种被动的过程，通过这种过程，葡萄糖代谢速度会降低，最终去极化的时间会增加。这将缩短末端去极化的时间，从而减轻在能量耗竭状态下触发的、在缺血恢复后表现出来的所有病理过程。如果我们的假设被证明是正确的，即深低温确实诱导了一个导致相扑结合蛋白水平上升的活跃过程，而相扑结合途径的激活在这个过程中确实发挥了关键作用，它可能会彻底改变我们对低温保护作用机制的理解。相扑结合可以代表一个令人兴奋的新的治疗干预目标，通过提供 一种增加器官对血液供应短暂中断的抵抗力的方法。 公共卫生相关性：各种手术都需要停循环，包括主动脉手术或矫正新生儿先天性心脏病。为了保护器官免受短暂性缺血造成的损害，在深低温条件下进行循环停搏。这一建议侧重于一种假设，即激活靶蛋白的小泛素样修饰物(SUMO)结合在深低温诱导的器官保护中起主要作用。如果我们的假设被证明是正确的，相扑结合可能被证明是一个非常令人兴奋的治疗干预的新靶点，因为它提供了一种增加器官对血液供应短暂中断的抵抗力的方法。

DESCRIPTION (provided by applicant): Various pediatric and adult cardiovascular operations involve cardiopulmonary bypass (CPB) procedures that require a period of circulatory arrest. Major cardiovascular surgery in pediatric and adult patients induces perioperative organ injury and is therefore associated with significant adverse cerebral, renal and cardiovascular outcomes. To protect organs from ischemic damage, surgery is usually performed during deep hypothermic conditions (deep hypothermic circulatory arrest, DHCA). Although the protective potential of deep hypothermia is unquestionable, little is known about the mechanisms through which it protects organs or how to maximize its efficacy. Elucidating the mechanisms underlying protection of organs by deep hypothermia is therefore of tremendous clinical interest. If we understood these mechanisms, we would be able to design therapeutic strategies to activate such processes and thus induce a state of tolerance without risking the adverse effects associated with deep hypothermia. We hypothesize that deep hypothermia protects organs from ischemic damage by activating the small ubiquitin-like modifier (SUMO) conjugation pathway. Protein sumoylation markedly influences the stability, localization and activity of transcription factors and other intracellular proteins. Deep hypothermia-induced changes in SUMO conjugation may therefore play a key role in defining the final outcome of cells exposed to transient DHCA. We found a marked increase in levels of SUMO conjugated proteins during deep hypothermia, and activation of SUMO conjugation has been shown to protect cells from damage induced by ischemia-like conditions. We have the following Specific Aims: 1) To examine the relationship between extent and duration of hypothermia and activation of the SUMO conjugation pathway; 2) To identify proteins in which SUMO conjugation is activated by hypothermia; 3) To verify whether by silencing SUMO expression and thus blocking deep hypothermia-induced activation of the SUMO conjugation pathway, it is possible to modify the sensitivity of organs to DHCA. It is widely believed that hypothermia-induced protection is a passive process whereby the rate of glucose metabolism is lowered and the time to terminal depolarization consequently increased. This would shorten the period of terminal depolarization and thus mitigate all pathological processes triggered during the state of energy depletion and manifested after recovery from ischemia. If our hypothesis proves valid, i.e. deep hypothermia does indeed induce an active process resulting in a rise in levels of SUMO conjugated proteins and activation of the SUMO conjugation pathway does play a key role in that process, it could revolutionize our understanding of the mechanisms underlying the protective effects of hypothermia. SUMO conjugation could represent an exciting new target for therapeutic intervention by providing a means of increasing the resistance of organs to a transient interruption of blood supply. PUBLIC HEALTH RELEVANCE: Circulatory arrest is required for various surgeries, including aortic surgery or correction of congenital heart defects in the neonates. To protect organs from damage caused by transient ischemia, circulatory arrest is carried out under deep hypothermic conditions. This proposal focuses on the hypothesis that activation of small ubiquitin-like modifier (SUMO) conjugation of target proteins plays a major role in deep hypothermiainduced organ protection. If our hypothesis proves valid, SUMO conjugation could prove to be a very exciting new target for therapeutic intervention by providing a means of increasing the resistance of organs to a transient interruption of blood supply.