Cellular Pathophysiology of Acute Renal Failure

最近，由于对线粒体渗透性转变机制的新认识和对线粒体细胞色素c释放在细胞凋亡中的作用的认识，线粒体功能障碍作为多种形式的细胞损伤的介体引起了人们的兴趣。 在缺血性和毒性形式的急性肾功能衰竭期间，近端小管中的ATP产生是损伤的主要部位，其对线粒体功能障碍特别敏感，因为根据节段，体内近端小管细胞中不存在糖酵解或糖酵解最小。 在本资助期内的研究中，我们已经确定了一种线粒体病变，其特征是复合物I中的电子传递抑制，与基质浓缩和部分脱钙有关，这是新鲜分离的兔近端小管缺氧/复氧期间线粒体损伤的一种重要功能形式，在整体细胞恢复中发挥关键作用。 病变：a）先于线粒体渗透性转变和细胞色素c释放; B）在持续的时间内抑制否则有活力的小管的能量功能;和c）非常适合于通过特定的柠檬酸循环代谢物来预防和逆转，所述柠檬酸循环代谢物促进线粒体内ATP产生和电子传递的厌氧途径，或者在有氧条件下绕过复合物I阻断。 线粒体损伤在体内缺血/再灌注期间在经受缺氧/复氧的新鲜分离的小管中表达，并且基于超微结构变化和柠檬酸循环代谢物的修饰。 我们的一般假设是，这种形式的线粒体功能障碍在肾脏缺血性损伤的结果中起着关键作用，并且其改善将有益于细胞和组织从这些损伤中恢复。 为了验证这一假设并进一步研究其对理解和治疗缺血性急性肾衰竭的意义，我们提出了以下研究：1）表征在缺氧/复氧持续时间延长期间能量不足的演变以及保护性底物在这些条件下改善其的作用。2)更好地定义损伤过程中线粒体内膜异常的机制及其对能量不足的相对贡献。 3)在体内肾脏缺血/再灌注期间评估病变的表达并测试保护性代谢物的功效。

Recently there has been a renewal of interest in mitochondrial dysfunction as a mediator of diverse forms of cell injury as a result of new insights into the mechanism for the mitochondrial permeability transition and recognition of the role of mitochondrial cytochrome c release in apoptosis. ATP production in the proximal tubule, a major site of injury during ischemic and toxic forms of acute renal failure, is especially sensitive to mitochondrial dysfunction because, depending on the segment, glcolysis is absent or minimal in proximal tubule cells in vivo. In studies during the present funding period, we have identified a mitochondrial lesion characterized by inhibition of electron transport in complex I associated with matrix condensation and partial deenergization as a functionally important form of mitochondrial injury during hypoxia/reoxygenation of freshly isolated rabbit proximal tubules that play a pivtal role in overall cellular recovery. The lesion: a) precedes the mitochondrial permeability transition and cytochrome c release; b) depresses energetic function of otherwise viable tubules for sustained periods; and c) is highly amenable to prevention and reversal by specific citric acid cycle metabolites that promote anaerobic pathways of intramitochondrial ATP production and electron transport or, under aerobic conditions, bypass the complex I block. The mitochondrial lesion is expressed both in freshly isolated tubules subjected to hypoxia/reoxygeation, and based on ultrastructural changes and modification by citric acid cycle metabolites, during ischemia/reperfusion in vivo. Our general hypothesis is that this form of mitochondrial dysfunction plays a critical role in the outcome of ischemic insults to the kidney and that its amelioration will beneficially impact on cell and tissue recovery from these insults. To test this hypothesis and further investigate its implications for understanding and treating ischemic acute renal failure we propose studies to: 1) Characterize the energetic deficit as it evolves during extended durations of hypoxia/reoxygenation and the effects of protective substrates to ameliorate it under those conditions. 2) Better define the mechanisms for the mitochondrial inner membrane abnormalities during the insult and their relative contributions to the energetic deficit. 3) Assess expression of the lesion and test efficacy of protective metabolites during ischemia/reperfusion of the kidney in vivo.