Polyamine metabolism in heart and kidney ischemic injury

描述（由申请人提供）：与缺血/再灌注损伤（IRI）相关的疾病，如心肌梗死和急性缺血性肾衰竭，是发病率和死亡率的主要原因。IRI的病理生理学在心脏和肾脏中惊人地相似，再灌注后毒性代谢物（即H2 O2）的产生增强、细胞凋亡增加和细胞死亡增加，这提高了相同途径可能介导IRI中两个器官中的细胞损伤和功能障碍的可能性。为了鉴定IRI的病理生理学中涉及的因素，对来自正常大鼠肾脏和经受30分钟缺血（肾动脉结扎）随后12小时再灌注的动物肾脏的RNA进行抑制性消减杂交。结果表明，亚精胺/精胺N-1乙酰转移酶（SSAT）的表达增强，SSAT是参与多胺催化的限速酶。有趣的是，30分钟的缺血（左前降支动脉结扎）随后6-12小时的再灌注导致心肌损伤区中SSAT的诱导，其中SSAT表达在正常心肌中几乎检测不到，并且在6小时的再灌注时增加>50倍。增强SSAT表达在肾脏和心脏IRI与腐胺的浓度增加，细胞凋亡的介质和一种现象，表明增加的活动SSAT。SSAT在培养细胞中的条件性过表达导致细胞生长降低。 本提案中概述的研究将检验以下假设：SSAT是细胞损伤的生物标志物，其表达增加反映了心脏和肾脏中与IRI相关的组织损伤程度。我们进一步假设肾脏或心脏中SSA T的表达增强通过多胺的耗尽、有毒代谢物（例如H2 O2、腐胺和各种醛）的产生和细胞凋亡的诱导导致细胞损伤。为了验证这些假设，我们建议：1。检测SSAT和多胺通路在肾脏和心脏IRI中的表达和调节。确定SSAT过表达在肾和心脏IRI中对细胞存活和损伤易感性的作用，以及3.探讨SSAT介导的肾和心脏IRI细胞损伤机制。深入了解SSAT和其他参与多胺代谢的酶在IRI中的表达和调节，将为IRI在心脏和肾脏中的病理生理学提供新的线索，并可能为针对缺血性心脏病发作和急性缺血性肾功能衰竭的早期检测、预防或治疗的新型诊断测试和治疗选择提供基础。

DESCRIPTION (provided by applicant): Conditions associated with ischemia/reperfusion injury (IRI) such as myocardial infarction and acute ischemic renal failure are among the major causes of morbidity and mortality. The pathophysiology of IRI is strikingly similar in heart and kidney, with enhanced production of toxic metabolites (i.e. H202), increased apoptosis, and cell death following reperfusion, raising the possibility that identical pathway(s) may mediate cell injury and dysfunction in both organs in IRI. In an attempt to identify the factors involved in the pathophysiology of IRI, suppression subtractive hybridization on RNA from normal rat kidneys and kidneys of animals subjected to 30 min of ischemia (renal artery ligation) followed by 12 hrs of reperfusion was performed. The results identified enhanced expression of Spermidine/Spermine N-1 acetyltransferase (SSAT), the rate limiting enzyme involved in the catabolism of polyamines, in IRI. Interestingly, thirty (30) min of ischemia (left anterior descending artery ligation) followed by 6-12 hrs of reperfusion resulted in the induction of SSAT in the injury zone in myocardium, with SSAT expression being almost undetectable in normal myocardium and increasing by >50-fold at 6 hrs of reperfusion. Enhanced SSAT expression in kidney and heart in IRI was associated with increased concentrations of putrescine, a mediator of apoptosis and a phenomenon indicative of increased activity of SSAT. Conditional overexpression of SSAT in cultured cells resulted in decreased cell growth. The studies outlined in this proposal will test the hypothesis that SSAT is a biomarker of cell injury and its increased expression reflects the extent of tissue damage associated with IRI in heart and kidney. We further hypothesize that enhanced expression of SSA T in kidney or heart leads to cell damage through depletion of polyamines, production of toxic metabolites (e.g. H202, putrescine and various aldehydes) and induction of apoptosis. To test these hypotheses, we propose to: 1. Examine the expression and regulation of SSAT and polyamine pathway in renal and heart IRI, 2. Ascertain the role of SSAT over expression on cell survival and susceptibility to injury in renal and cardiac IRI, and 3. Ascertain the mechanism of SSAT-mediated cell injury in renal and cardiac IRI. Insight into the expression and regulation of SSAT and other enzymes involved in polyamine metabolism in IRI will shed new lights into the pathophysiology of IRI in heart and kidney and may provide basis for novel diagnostic tests and therapeutic options targeted at early detection, prevention or treatment of ischemic heart attack and acute ischemic renal failure.