SUMO Conjugation and Deep Hypothermia-Induced Organ Protection

描述（由申请人提供）：各种儿科和成人心血管手术涉及需要循环停搏一段时间的体外循环（CPB）程序。儿童和成人患者的主要心血管手术会引起围手术期器官损伤，因此与显著的脑、肾和心血管不良结局相关。为了保护器官免受缺血性损伤，手术通常在深度低温条件下进行（深度低温循环停止，DHCA）。虽然深低温的保护潜力是毋庸置疑的，但人们对其保护器官的机制或如何最大化其功效知之甚少。因此，阐明深层低温保护器官的机制具有巨大的临床意义。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，从而诱导耐受状态，而不会冒着与深度低温相关的副作用的风险。我们假设深低温通过激活小泛素样修饰物（SUMO）偶联途径保护器官免受缺血性损伤。蛋白质summoylation显著影响转录因子和其他细胞内蛋白的稳定性、定位和活性。因此，深度低温诱导的SUMO偶联的变化可能在决定细胞暴露于短暂DHCA的最终结果中起关键作用。我们发现，在深度低温期间，SUMO结合蛋白的水平显著增加，并且SUMO结合的激活已被证明可以保护细胞免受缺血样条件引起的损伤。我们有以下具体目的：1)研究低温程度和持续时间与SUMO偶联通路激活之间的关系；2)识别

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.