Neonatal Stroke: the Role of Microglia

描述（由申请人提供）：动脉缺血性卒中在足月婴儿中的发生率与老年人一样高，但不成熟影响缺血性损伤和恢复的机制。新生儿脑对缺氧缺血性、单纯缺血性和兴奋性毒性损伤敏感，并伴有广泛的神经元凋亡。与调节细胞凋亡的分子事件的广泛知识相比，对负责凋亡神经元的清除和细胞碎片的降解的过程知之甚少。未能通过巨噬细胞快速去除凋亡神经元允许垂死细胞经历凋亡后坏死并导致损伤恶化。小胶质细胞可以通过清除死亡细胞来保护大脑，但也可以在正常的出生后大脑发育过程中导致损伤甚至引起神经元凋亡。在新生儿中风的动物模型中，未成熟啮齿动物的局灶性短暂大脑中动脉（MCA）闭塞，小胶质细胞活化迅速，这些细胞产生许多有毒物质，但吞噬凋亡神经元的能力很差。使用我们的体内模型和体外模型的原代小胶质细胞培养的凋亡神经元，我们将确定清道夫受体CD 36介导的新生儿中风后凋亡神经元的去除的影响，并评估参与CD 36介导的识别，吞噬和吞噬凋亡神经元的小胶质细胞的信号转导机制。将使用药理学方法和具有缺失的CD 36和半胱天冬酶-3的小鼠以及源自缺陷小鼠的细胞。我们将测试的假设，即小胶质细胞加剧急性缺血再灌注损伤新生儿脑细胞凋亡的神经元清除不足。我们将确定小胶质细胞的消融是否保护新生儿脑免于中风（Aim 1），新生儿中风后小胶质细胞对凋亡神经元的有限吞噬是否由清道夫受体CD 36调节（Aim 2），炎性细胞因子是否不利地影响以半胱天冬酶-3依赖性方式死亡的神经元的CD 36介导的吞噬（Aim 3），以及通过CD 36去除凋亡神经元是否依赖于半胱天冬酶-3活化（Aim 4）。与公共卫生的相关性：新生儿卒中是一种严重且常见的疾病。了解新生儿脑损伤的机制是确定保护新生儿免受中风终身后果的治疗靶点的重要一步。

DESCRIPTION (provided by applicant): Arterial ischemic stroke occurs as frequently in term babies as in the elderly but immaturity affects mechanisms of ischemic injury and recovery. The neonatal brain is preferentially susceptible to hypoxic-ischemic, pure ischemic and excitotoxic injury with widespread neuronal apoptosis. Compared to the extensive knowledge of the molecular events regulating apoptosis, relatively little is known about the processes responsible for clearance of apoptotic neurons and degradation of cellular debris. Failure to rapidly remove apoptotic neurons by macrophages allows dying cells to undergo post-apoptotic necrosis and leads to injury exacerbation. Microglial cells can protect the brain by removing dying cells but can also contribute to injury or even provoke neuronal apoptosis during normal postnatal brain development. In an animal model of neonatal stroke, focal transient middle cerebral artery (MCA) occlusion in immature rodents, microglial activation is rapid, these cells produce a number of toxic species but poorly phagocytose apoptotic neurons. Using our in vivo model and in vitro models of primary microglial cells cultured with apoptotic neurons, we will determine the effects of the scavenger receptor CD36 in mediating removal of apoptotic neurons after neonatal stroke and evaluate signaling mechanisms involved in CD36-mediated recognition, engulfment and phagocytosis of apoptotic neurons by microglial cells. Pharmacological approaches and mice with deleted CD36 and caspase-3 and cells derived from deficient mice will be used. We will test the hypothesis that microglial cells exacerbate acute ischemia-reperfusion injury to the neonatal brain by insufficient clearance of apoptotic neurons. We will determine if ablation of microglia protects the neonatal brain from stroke (Aim 1), if limited phagocytosis of apoptotic neurons by microglial cells after neonatal stroke is modulated by the scavenger receptor CD36 (Aim 2), if inflammatory cytokines adversely affect CD36-medated phagocytosis of neurons dying in a caspase-3 dependent manner (Aim 3), and if removal of apoptotic neurons via CD36 depends on caspase-3 activation (Aim 4). RELEVANCE TO PUBLIC HEALTH: Neonatal stroke is an existing serious and frequent disorder. Understanding the mechanisms of brain injury in the neonatal brain is an important step in the identification of therapeutic targets that protect the newborn from the lifelong consequences of stroke.