Determinants of vulnerability and recovery after trauma to the developing brain

发育中大脑创伤后脆弱性和恢复的决定因素

• 批准号: 8870454
• 负责人: LINDA J. NOBLE
• 金额: $ 36.2万
• 依托单位: UNIVERSITY OF CALIFORNIA, SAN FRANCISCO
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-07-01 至 2016-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8870454
• 关键词: Address; Adult; Adverse effects; Age; Animals; Behavioral; Behavioral Assay; Biological Assay; Brain; Brain Injuries; Cause of Death; Cells; Child; Childhood Injury; Chronic; Clinical Research; Cognitive; Cognitive deficits; Cytoplasmic Granules; Data; Dependency; Development; Endopeptidases; Environment; Enzymes; Event; Extracellular Matrix Degradation; Flow Cytometry; Foundations; Gelatinase B; Genetic; Goals; Hand; Hippocampus (Brain); Impaired cognition; Infection; Infiltration; Inflammatory; Inflammatory Response; Injury; Kinetics; Knock-out; Knockout Mice; Lead; Leukocyte Elastase; Leukocytes; Magnetic Resonance Imaging; Measures; Mediating; Mediator of activation protein; Modeling; Morbidity - disease rate; Mus; Neurological status; Neuronal Injury; Neurons; Neutrophil Activation; Neutrophil Infiltration; Outcome; Oxidative Stress; Pathogenesis; Peptide Hydrolases; Permeability; Positioning Attribute; Process; Protease Inhibitor; Proteins; Proteolysis; Recovery; Serine Protease; Signal Transduction; Signal Transduction Pathway; Specificity; Structure; Substrate Specificity; Testing; Therapeutic; Tissues; Toxic effect; Trauma; Traumatic Brain Injury; Up-Regulation; Western Blotting; Wound Healing; Zinc; base; behavior measurement; brain volume; cell injury; clinically relevant; cognitive development; cognitive recovery; disability; human SYK protein; improved; indexing; inhibitor/antagonist; injured; microorganism; nerve injury; neuroprotection; neutrophil; neutrophil elastase inhibitor; novel; postnatal; social; social skills; therapeutic target; therapy development; trafficking

DESCRIPTION (provided by applicant): Traumatic brain injury (TBI) in children is the leading cause of death and disability. Although clinical studies have shown that the developing brain is particularly vulnerable to injury, the basis for this vulnerability remains unclear. TBI to the developing murine brain results in prolonged trafficking of neutrophils into cortical and subcortical structures. We hypothesize that neutrophil elastase (NE) is a determinant of cell injury and a self-propagating inflammatory loop that is driven by an imbalance between NE and its inhibitor, A1- protease inhibitor (A1-PI). With broad substrate specificity and in the absence f adequate local inhibition, excessive NE activity may lead to degradation of the extracellular matrix and exert direct toxic effects on resident cells, events that signal further recruitment of leukocytes into the damaged tissue. We will examine the mechanism underlying proteolytic imbalance, focusing on matrix metalloproteinase-9 (MMP-9). Like NE, MMP-9 is released from activated neutrophils, thus positioning it in proximity to NE. Here we will determine if excessive NE activity arises from inactivation of A1-PI by neutrophil-derived MMP-9. Our general hypothesis is that unopposed NE activity is a key mediator of cell injury after TBI and that strategies to reduce or eliminate its activity will confer neuroprotection and establish an environment that is favorable to brain development and cognitive recovery. Specific Aim 1 will test the hypothesis that unopposed proteolytic activity of NE contributes to a self-propagating inflammatory response. Specific Aim 2 will test the hypothesis that NE, released from activated neutrophils, contributes to cell injury and oxidative stress. Specific Aim 3 will determine if MMP-9 inactivates a1-PI thus allowing NE to produce neural injury and further neutrophil recruitment. Specific Aim 4 will test the hypothesis that pharmacologic blockade of NE will result in long-term structural and behavioral recovery. To address these aims we will use a murine model of TBI at postnatal day 21 and complimentary pharmacologic and genetic strategies to modulate NE activity. We will compare indices of tissue damage in brain injured wildtype (WT) and NE knockout (KO) mice and WT mice treated with a specific inhibitor of NE. To determine the dependency of NE-directed pathogenesis on the over-all activational state of neutrophils, we will study neutrophil-specific SYK-conditional KOs that show a reduced activational state while still retaining NE activity. With state-of-the-art magnetic resonance imaging and a comprehensive battery of behavioral assays, we will further determine if pharmacologic blockage of NE activity supports structural recovery and improves long-term cognitive outcomes. Together, these studies provide an important foundation for understanding the unique vulnerability of the young brain to TBI and for developing the therapies that are specifically tailored to the brain-injured child.

描述（由申请人提供）：儿童创伤性脑损伤（TBI）是导致死亡和残疾的主要原因。尽管临床研究表明发育中的大脑特别容易受到伤害，但这种脆弱性的基础仍不清楚。对发育中的小鼠大脑的 TBI 会导致中性粒细胞长时间运输到皮质和皮质下结构。我们假设中性粒细胞弹性蛋白酶 (NE) 是细胞损伤和自我传播炎症循环的决定因素，该循环是由 NE 及其抑制剂 A1-蛋白酶抑制剂 (A1-PI) 之间的不平衡驱动的。由于具有广泛的底物特异性，并且在缺乏足够的局部抑制的情况下，过度的 NE 活性可能导致细胞外基质降解并对驻留细胞产生直接毒性作用，这些事件标志着白细胞进一步募集到受损组织中。我们将研究蛋白水解失衡的潜在机制，重点关注基质金属蛋白酶-9 (MMP-9)。与 NE 一样，MMP-9 是从活化的中性粒细胞中释放出来的，因此将其定位在靠近 NE 的位置。在这里，我们将确定过度的 NE 活性是否是由于中性粒细胞衍生的 MMP-9 使 A1-PI 失活所致。我们的一般假设是，不受对抗的 NE 活性是 TBI 后细胞损伤的关键介质，减少或消除其活性的策略将提供神经保护并建立有利于大脑发育和认知恢复的环境。具体目标 1 将检验以下假设：NE 不受对抗的蛋白水解活性有助于自我传播的炎症反应。具体目标 2 将检验以下假设：活化的中性粒细胞释放的 NE 会导致细胞损伤和氧化应激。具体目标 3 将确定 MMP-9 是否使 a1-PI 失活，从而使 NE 产生神经损伤并进一步招募中性粒细胞。具体目标 4 将检验 NE 的药物阻断将导致长期结构和行为恢复的假设。为了实现这些目标，我们将使用出生后第 21 天的 TBI 小鼠模型以及补充药理学和遗传策略来调节 NE 活性。我们将比较脑损伤的野生型 (WT) 和 NE 敲除 (KO) 小鼠以及用 NE 特异性抑制剂治疗的 WT 小鼠的组织损伤指数。为了确定 NE 导向的发病机制对中性粒细胞总体激活状态的依赖性，我们将研究中性粒细胞特异性 SYK 条件 KO，这些 KO 表现出较低的激活状态，同时仍保留 NE 活性。借助最先进的磁共振成像和全面的行为分析，我们将进一步确定药物阻断 NE 活性是否支持结构恢复并改善长期认知结果。总之，这些研究为了解年轻大脑对 TBI 的独特脆弱性以及开发专门针对脑损伤儿童的疗法提供了重要基础。