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: 8681563
• 负责人: LINDA J. NOBLE
• 金额: $ 37.19万
• 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/8681563
• 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 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）是死亡和残疾的主要原因。虽然临床研究表明，发育中的大脑特别容易受到伤害，但这种脆弱性的基础仍然不清楚。发育中的小鼠脑的TBI导致嗜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，并且是由NE及其抑制剂A1-蛋白酶抑制剂（A1-PI）之间的不平衡驱动的自传播炎症循环。由于广泛的底物特异性和缺乏足够的局部抑制，过度的NE活性可能导致细胞外基质的降解，并对驻留细胞产生直接的毒性作用，这些事件表明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机制，重点是基质金属蛋白酶-9（MMP-9）。与NE一样，MMP-9从活化的中性粒细胞释放，从而将其定位在NE附近。在这里，我们将确定是否过量的NE活性产生于A1-PI的失活由嗜中性粒细胞衍生的MMP-9。我们的一般假设是，未对抗NE活性是TBI后细胞损伤的关键介质，降低或消除其活性的策略将赋予神经保护作用，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NE的无对抗蛋白水解活性有助于自传播炎症反应的假设。具体目标2将检验从活化的中性粒细胞释放的NE有助于细胞损伤和氧化应激的假设。特异性目标3将确定MMP-9是否使α 1-PI失活，从而允许NE产生神经损伤和进一步的中性粒细胞募集。具体目标4将检验NE的药理学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小鼠模型和补充的药理学和遗传策略来调节NE活性。我们将比较脑损伤野生型（WT）和NE敲除（KO）小鼠和用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整体激活状态的依赖性，我们将研究嗜中性粒细胞特异性SYK条件性科斯，其显示降低的激活状态，同时仍保留NE活性。通过最先进的磁共振成像和一系列全面的行为测定，我们将进一步确定NE活性的药物阻断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治疗方法提供了重要基础。