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: 9120429
• 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 2017-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9120429
• 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; 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; SYK gene; 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; improved; indexing; inhibitor/antagonist; injured; microorganism; mouse model; nerve injury; neuroprotection; neutrophil; neutrophil elastase inhibitor; novel; postnatal; social; social skills; targeted treatment; 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(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。脑外伤对发育中的小鼠大脑造成中性粒细胞向皮质和皮质下结构的长期运输。我们假设，中性粒细胞弹性蛋白酶(NE)是细胞损伤的决定因素，是由NE与其抑制物A1-蛋白酶抑制物(A1-PI)之间的失衡驱动的自传播性炎症循环。由于广泛的底物特异性，在没有足够的局部抑制的情况下，过量的NE活性可能会导致细胞外基质的降解，并对驻留细胞产生直接的毒性效应，这是白细胞进一步重新聚集到受损组织中的信号。我们将研究蛋白质降解失衡的机制，重点是基质金属蛋白酶-9(MMP9)。像去甲肾上腺素一样，基质金属蛋白酶-9从激活的中性粒细胞中释放出来，从而使其接近去甲肾上腺素。在这里，我们将确定过量的去甲肾上腺素活性是否源于中性粒细胞衍生的基质金属蛋白酶-9使A1-PI失活。我们的一般假设是，无对抗的NE活性是脑创伤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，并建立有利于脑发育和认知恢复的环境。特定目标1将检验这样一个假设，即去甲肾上腺素的非对抗性蛋白分解活性有助于自我传播性炎症反应。《特殊目的2》将验证这一假说，即从激活的中性粒细胞释放的去甲肾上腺素有助于细胞损伤和氧化应激。具体目标3将确定是否基质金属蛋白酶9使A1-PI失活，从而允许去甲肾上腺素产生神经损伤和进一步的中性粒细胞募集。具体目标4将验证这样的假设，即药物阻断NE将导致长期的结构和行为恢复。为了达到这些目的，我们将使用出生后第21天的小鼠脑外伤模型，并补充药物和遗传策略来调节NE的活性。我们将比较脑损伤野生型(WT)和NE基因敲除(KO)小鼠以及用NE的特定抑制剂治疗的WT小鼠的组织损伤指数。为了确定NE诱导的发病机制与中性粒细胞的全面激活状态的相关性，我们将研究中性粒细胞特异性SYK条件KO，这些KO显示出减少的激活状态，同时仍保持NE的活性。通过最先进的磁共振成像和一系列全面的行为分析，我们将进一步确定药物阻断去甲肾上腺素活动是否支持结构恢复和改善长期认知结果。总而言之，这些研究为了解年轻大脑对脑外伤的独特脆弱性以及开发专门针对脑损伤儿童的治疗方法提供了重要的基础。