Brain injury due to transcranial versus transthoracic blast exposure

描述（由申请人提供）： 爆炸引起的创伤性脑损伤（爆炸-TBI）是参与最近中东战争的士兵和退伍军人以及暴露于恐怖行为的平民死亡和残疾的主要原因。一般认为冲击波可以通过“直接经颅”和“间接经胸/经血管”两种途径影响大脑，但对每种途径的细胞和分子机制知之甚少。我们假设，直接与间接冲击伤的神经后果将显着不同，蛛网膜下腔 出血和中缝神经元损伤诱发创伤后应激障碍（PTSD）样症状，主要是直接损伤，而水肿和血管周围炎症主要是间接损伤。我们最近开发了一种独特的设备，旨在提供专门的冲击波到颅骨-颅骨爆炸损伤装置（COBIA），允许研究冲击波对大脑的影响，而不受经胸/经血管机制的影响。从这项工作中出现的最重要的见解是，冲击颅骨的冲击波往往会损伤密度边界处的组织，特别是脑脊液（CSF）-脑密度边界，诱发蛛网膜下腔出血和室周神经元损伤，中缝背核（5-HT）神经支配前脑结构的重要来源）的显著参与。该提案的新的初步工作包括开发仅胸部爆炸损伤装置（TOBIA），以允许研究这种损伤机制，并探索血管系统的具体参与及其在改变BBB渗透性和血管周围炎症中的作用。该提议的初步数据显示，磺酰脲受体1（SUR 1）调节的NC（Ca-ATP）通道，我们发现它在非冲击波诱导的创伤性和缺血性CNS损伤中起着核心作用，在大鼠暴露于COBIA和TOBIA的冲击波后上调。在这里，在具体目标1中，我们将阐明和比较大脑对以下的反应：（i）通过颅骨暴露直接向大脑传递冲击波与（ii）间接传递冲击波。 冲击波通过经胸/经血管暴露到大脑vs.（iii）通过全身暴露的组合递送。我们将使用qPCR、原位杂交、免疫印迹和免疫组织化学确定机械敏感性转录因子、特异性蛋白1（Sp1）和核因子kappaB（p65）的早期激活，以及细胞死亡分子、SUR 1、瞬时受体电位melastatin 4（TRPM 4）和caspase- 3的时程和细胞定位。在具体目标2中，我们将评估SUR 1选择性阻断剂格列本脲对涉及SUR 1的爆炸诱导继发性损伤的影响。我们将评估损伤后1小时给予格列本脲对早期前庭功能和后期认知和神经心理功能的影响，以及对前脑结构中细胞死亡、神经变性、炎症和5-HT神经支配的组织标志物的影响。迫切需要为爆炸-TBI的受害者开发有效的药物疗法，以阻断由冲击波诱导的继发性损伤反应，包括蛛网膜下腔出血诱导的皮质炎症、改变的BBB通透性和延迟的神经心理障碍。我们预计，成功完成拟定研究将促进我们对冲击波诱导脑损伤的病理生理学机制的理解，将确立格列本脲在冲击波-TBI中的治疗潜力，并将阐明可能将冲击波- TBI与PTSD样症状联系起来的新发现。

DESCRIPTION (provided by applicant): Blast-induced traumatic brain injury (blast-TBI) is a leading cause of death and disability in soldiers and veterans involved in recent wars in the Middle East, and in civilians exposed to terrorist acts. It is generally accepted that a blast wave can affect the brain via both a "direct transcranial" path and by an "indirect transthoracic/transvascular" path. Cellular and molecular mechanisms involved in each path are poorly understood. We hypothesize that the neurological consequences of direct vs. indirect blast injury will be significantly different, with subarachnoid hemorrhage and injury to raphe neurons predisposing to post- traumatic stress disorder (PTSD)-like symptoms predominating with direct injury, versus edema and perivascular inflammation predominating with indirect injury. We recently developed a unique device designed to deliver a blast wave exclusively to the cranium - a Cranium Only Blast Injury Apparatus (COBIA), allowing study of the effects of a blast wave on the brain independent of the effects due to the transthoracic/transvascular mechanism. The most important insight to emerge from this work is that a blast wave that impacts the cranium tends to injure tissues at density boundaries, especially the cerebrospinal fluid (CSF)-brain density boundaries, predisposing to subarachnoid hemorhage and to injury to periventicular neurons, with significant involvement of the dorsal raphe nucleus, a critical source of serotoninergic (5-HT) innervation in forebrain structures. New preliminary work for this proposal included the development of a Thoracic Only Blast Injury Apparatus (TOBIA) to allow study of this mechanism of injury, and to explore specific involvement of the vasculature and its role in altered BBB permeability and perivascular inflammation. Preliminary data for this proposal show that the sulfonylurea receptor 1 (SUR1)-regulated NC(Ca-ATP) channel, which we discovered plays a central role in non-blast-induced traumatic and ischemic CNS injuries, is upregulated after exposure of rats to blasts from COBIA and TOBIA. Here, in Specific Aim 1, we will elucidate and compare responses of the brain to: (i) direct delivery of the blast wave to the brain via cranial exposure vs. (ii) indirect delivery of a blast wave to the brain via transthoracic/transvascular exposure vs. (iii) combined delivery via total body exposure. We will determine the early activation of the mechano-sensitive transcription factors, specificity protein 1 (Sp1) and nuclear factor kappaB (p65), and the time-course and cellular localization for the cell death molecules, SUR1, transient receptor potential melastatin 4 (TRPM4) and caspase- 3, using qPCR, in situ hybridization, immunoblots and immunohistochemistry. In Specific Aim 2, we will evaluate the effect of the SUR1-selective blocker, glibenclamide, on blast-induced secondary injury involving SUR1. We will assess the effect of glibenclamide, administered 1 hour after injury, on early vestibulomotor and later cognitive and neuropsychological function, and on tissue markers of cell death, neurodegeneration, inflammation and 5-HT innervation in forebrain structures. There is an urgent need to develop effective pharamacotherapies for victims of blast-TBI, to block secondary injury responses that are induced by a blast wave, including subarachnoid hemorrhage-induced inflammation of the cortex, altered BBB permeability, and delayed neuropsychological disorders. We anticipate that the successful completion of the proposed studies will advance our understanding of pathophysiological mechanisms of brain injury induced by blast, will establish the therapeutic potential of glibenclamide in blast-TBI, and will elucidate novel findings that may link blast- TBI to PTSD-like symptoms.