Brain injury due to transcranial versus transthoracic blast exposure

描述(由申请人提供)： 冲击波诱发的创伤性脑损伤(BLAST-TBI)是最近参与中东战争的士兵和退伍军人以及暴露在恐怖主义行为中的平民死亡和残疾的主要原因。一般认为，冲击波可以通过“直接的经颅”途径和“间接的经胸/血管”途径影响大脑。涉及每条途径的细胞和分子机制还知之甚少。我们假设，直接冲击伤和间接冲击伤的神经学后果将显著不同，蛛网膜下腔。 中缝神经元出血和损伤易导致创伤后应激障碍(PTSD)样症状，以直接损伤为主，而以水肿和血管周围炎症为主，以间接损伤为主。我们最近开发了一种独特的设备，专门用于将冲击波传递到颅骨--仅限颅骨的冲击波损伤装置(COBIA)，允许研究冲击波对大脑的影响，而不依赖于经胸/经血管机制的影响。从这项工作中得出的最重要的见解是，冲击波冲击颅骨往往会损伤密度边界处的组织，特别是脑脊液(CSF)-脑密度边界处的组织，容易发生蛛网膜下腔出血和脑室周围神经元损伤，中缝背核是前脑结构中5-羟色胺(5-HT)神经支配的关键来源。这项提议的新的初步工作包括开发仅限胸部的冲击伤装置(TOBIA)，以便于研究这种损伤机制，并探索血管系统的具体参与及其在改变血脑屏障通透性和血管周围炎症中的作用。这一建议的初步数据显示，磺酰脲受体1(SUR1)调节的NC(Ca-ATP)通道在非原始性中枢神经系统损伤中起核心作用，在大鼠暴露于来自Cobia和Tobia的冲击波后上调。在这里，在特定的目标1中，我们将阐明和比较大脑对以下情况的反应：(I)通过颅骨暴露将冲击波直接传递到大脑中；(Ii)间接传递 经胸/经血管暴露对脑部的冲击波与(Iii)经全身暴露的联合传递。我们将利用定量聚合酶链式反应、原位杂交、免疫印迹和免疫组织化学的方法，检测机械敏感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SUR1、瞬时受体潜能Melastatin 4(TRPM4)和caspase-3的时程和细胞定位。在特定的目标2中，我们将评估SUR1选择性阻滞剂格列本脲对冲击波诱导的涉及SUR1的继发性损伤的影响。我们将评估损伤后1小时给予格列本脲对早期前庭运动和后来的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-羟色胺神经支配的组织标志物的影响。迫切需要为冲击波损伤的受害者开发有效的药物治疗方法，以阻止冲击波引起的继发性损伤反应，包括蛛网膜下腔出血引起的皮质炎症，血脑屏障通透性改变，以及迟发性神经心理障碍。我们预计，这些拟议研究的成功完成将促进我们对冲击性脑损伤的病理生理机制的理解，将确立格列本脲在BLAST-TBI中的治疗潜力，并将阐明BLAST-TBI与PTSD样症状之间的联系的新发现。

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.