MITOCHONDRIAL STRUCTURAL CHANGES IN CARDIOPROTECTION

这个子项目是利用由NIH/NCRR资助的中心拨款提供的资源的许多研究子项目之一。子项目和调查员(PI)可能从另一个NIH来源获得了主要资金，因此可能会出现在其他CRISE条目中。列出的机构是针对中心的，而不一定是针对调查员的机构。缺血预适应(IPC)是目前已知的对心脏和脑内继发性脑梗塞最有效的保护机制。我们已经证明，二氮嗪，一种可能的线粒体KATP(mito-KATP)开放剂，通过以下方式模拟IPC的保护作用：1)通过最小化线粒体钙超载来防止线粒体通透性转变(MPT)和细胞死亡；2)抑制缺氧线粒体细胞c的释放[Korge等人]。PNAS 99：3312-17,2002]。最近的研究表明，线粒体结构的改变可能调节细胞色素c的释放。在细胞凋亡过程中，冠突和膜间隙之间的连接变宽，导致细胞c的释放[Korsmeyer等，发育细胞1：515-25,2001]。总之，这些观察结果支持这样的观点，即线粒体的结构和功能通过细胞凋亡(Cytoc释放)或坏死(MPT)决定细胞生命和细胞死亡之间的平衡。我们的假设是，IPC和mito-KATP通道开放剂都可以通过重塑线粒体结构，抑制细胞c的释放，促进再灌注后ATP的产生，从而保护缺血时的线粒体功能。已被公认的是，在给予能量的线粒体中加入ADP会导致线粒体瞬间去极化和基质收缩，并伴随着ATP的产生，随后在ADP被消耗后，膜电位和基质体积恢复。我们已经发现，在生理K浓度下，ADP连续加入到被激活的线粒体中，会导致线粒体收缩和膜电位耗散，这在几次ADP脉冲后是不可逆的。加入ADP后O2消耗和膜电位耗散均显著降低，表明ADP/ATP交换失败。我们有实验证据表明，这些导致ADP产生减少的功能变化与已知调节线粒体体积的离子通量之间的失衡有关。通过电子断层扫描，我们希望描述线粒体结构重构(膜间、基质和结晶区的变化)在上述功能变化中的重要性。我们推测，缺血预适应和KATP开放剂通过线粒体结构重塑保护心脏免受未来的损伤，线粒体结构重塑允许持续的ATP产生。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Ischemic preconditioning (IPC) is the most powerful protective mechanism known against subsequent infarction in both heart and brain. We have shown that diazoxide, a putative mitochondrial KATP (mito-KATP) opener, mimics the protective effects of IPC by 1) preventing mitochondrial permeability transition (MPT) and cell death by minimizing mitochondrial calcium overload and 2) inhibiting the release of cyto c from anoxic mitochondria [Korge, et al. PNAS 99:3312-17, 2002]. Recently, it has been shown that the mitochondrial structural changes may regulate cytochrome c release. The junctions between cristae and the intermembrane space widens during apoptosis, leading to cyto c release [Korsmeyer et al, Developmental Cell 1:515-25, 2001]. Together these observations support the view that mitochondrial structure and function determine the balance between cell life and cell death by either apoptosis (cyto c release) or necrosis (MPT). Our hypothesis is that both IPC and mito-KATP channel openers can preserve mitochondrial function during ischemia by inhibiting cyto c release and enhancing subsequent ATP production upon reperfusion by remodeling mitochondrial structure. It is well-accepted that addition of ADP to energized mitochondria leads to transient mitochondrial depolarization and matrix shrinkage associated with ATP production, followed by membrane potential and matrix volume recovery after ADP is consumed. We have discovered that serial additions of ADP to energized mitochondria in physiologic K concentrations lead to mitochondrial shrinkage and membrane potential dissipation that is not reversible after several ADP pulses. Both O2 consumption and membrane potential dissipation in response to ADP addition are significantly decreased, pointing to a failure of ADP/ATP exchange. We have experimental evidence that these functional changes resulting in decreased ADP production are connected to an imbalance between ion fluxes that are known to regulate mitochondrial volume. By using electron tomography, we wish to characterize the importance of mitochondrial structural remodeling (changes in intermembrane, matrix and cristal compartments) in the functional changes as described above. We postulate that ischemic preconditioning and KATP openers protect hearts against future injury by structural remodeling in mitochondria that allow for sustained ATP production.