Mitochondria as a target for protection against hypoxic-ischemic brain injury

描述(申请人提供)：据估计，每年有120万婴儿死于出生窒息及其并发症--缺氧缺血性脑损伤。在美国，新生儿缺氧脑损伤仍然是导致儿童终生神经残疾的主要原因之一。这表明迫切需要在更好地了解发育中大脑的缺氧损伤机制的基础上制定治疗策略。线粒体功能障碍是导致本病神经元损伤的最基本的生物学事件。虽然线粒体复合体-I(C-I)受到缺氧损伤的严重抑制，但在复氧/再灌流后，C-I的能量生成功能迅速恢复。这种再灌流驱动的C-I重新激活与活性氧物种(ROS)的产生密切相关。我们推测，抑制再灌注时线粒体C-I的恢复代表了一种防止再灌注早期氧化爆发的治疗策略。我们发现，与对照组相比，暴露于C-I抑制剂的小鼠，尽管C-I连接的线粒体呼吸恢复缓慢，但脑损伤明显减轻。从这些暴露于灭鼠灵的HI小鼠中分离出的线粒体显示，在再灌流期间ROS的产生有限地加速。提示在缺血再灌流过程中，心肌细胞电子传递流的恢复不仅有助于细胞的恢复，而且对细胞的损伤也有一定的作用。目的1，抑制再灌流期间的C-I恢复是否减轻对线粒体基质的氧化损伤，从而增加线粒体对钙诱导的通透性转换孔(PTP)开放的耐受性。和目标2，再灌流期间的低氧血症是否减缓线粒体C-I的重新激活，以及这是否保护大脑免受再灌注驱动的氧化应激。因此，该项目旨在建立两者的机制基础和临床翻译，以创新的治疗概念，即针对再灌注驱动的氧化应激，逐步代谢恢复C-I。 公共卫生相关性：这项提案的重点是开发一种新的治疗概念，以保护缺血大脑免受再灌流驱动的氧化应激的影响。这项研究的潜在意义非常广泛，因为缺血性脑损伤(中风、缺氧缺血性脑病)是成人和儿童神经障碍的主要原因。

DESCRIPTION (provided by applicant): It is estimated that 1.2 million infants die annually from birth asphyxia and its complication, hypoxic- ischemic (HI) brain injury. In U.S. neonatal HI-brain injury remains one of the major causes for a life-long neurological disability in children. This indicates an urgent need to develop therapeutic strategies based on a better understanding the mechanisms of HI injury in the developing brain. Mitochondrial dysfunction is the most fundamental biological event leading to neuronal injury in this disease. Although, mitochondrial complex-I (C-I) is severely inhibited by a HI insult, upon re-oxygenation/reperfusion the energy-generating function of C-I rapidly recovers. This reperfusion-driven re-activation of C-I is tightly linked to the generation of reactive oxygen species (ROS). We hypothesize that the inhibition of mitochondrial C-I recovery upon reperfusion represents a therapeutic strategy against an oxidative burst during early reperfusion. We show that compared to controls, mice exposed to C-I inhibitor, pyridaben exhibited significant attenuation of cerebral injury, despite a sluggish recovery of the C-I linked mitochondrial respiration. Mitochondria isolated from these pyridaben-exposed HI-mice demonstrated a limited acceleration in ROS production during reperfusion. This suggests that during reperfusion post-HI restoration of electron transport flow in the C-I contributes not only to cellular recovery, but also to cellular injury. Specific aims are designed to determine; Aim 1, whether an inhibition of the C-I recovery during reperfusion attenuates oxidative damage to mitochondrial matrix and as a result, increases mitochondrial tolerance to Ca++ induced opening of permeability transition pore (PTP). and Aim 2, whether hypoxemia during reperfusion slow down reactivation of mitochondrial C-I and whether this protects brain against reperfusion-driven oxidative stress Thus, the project is designed to establish both, mechanistic rationale and a clinical translation for an innovative therapeutic concept of a gradual metabolic recovery of the C-I directed against reperfusion-driven oxidative stress. PUBLIC HEALTH RELEVANCE: This proposal is focused to develop a novel therapeutic concept for protection of the ischemic brain against reperfusion-driven oxidative stress. Potential implication of this research is very broad, because an ischemic brain injury (stroke, hypoxic-ischemic encephalopathy) is a leading cause for neurological handicap in adults and children.