Mechanisms and Modulation of Cell Death in Traumatic Brain Injury

创伤性脑损伤中细胞死亡的机制和调节

• 批准号: 8090307
• 负责人: ALAN Ira FADEN
• 金额: $ 45.82万
• 依托单位: UNIVERSITY OF MARYLAND BALTIMORE
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-05-18 至 2013-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8090307
• 关键词: Acute; Adenosine; Apoptosis; Apoptotic; Behavioral; Bioenergetics; Biological Models; Brain Ischemia; Carrier Proteins; Caspase; Cause of Death; Cell Culture Techniques; Cell Death; Cell Nucleus; Cells; Cessation of life; Cyclophilin A; DNA Damage; Death Domain; Health; In Vitro; Injury; Knock-out; Lesion; Location; Mediating; Mitochondria; Modeling; Mus; Neurologic Dysfunctions; Neuronal Injury; Neurons; Nicotinamide adenine dinucleotide; Outcome; Pathway interactions; Phenotype; Play; Poly(ADP-ribose) Polymerases; Recovery; Relative (related person); Role; Severities; Site; Transgenic Model; Trauma; Traumatic Brain Injury; United States; Work; apoptosis inducing factor; caspase-2; caspase-3; cell injury; clinically relevant; controlled cortical impact; disability; functional outcomes; improved; in vitro Model; in vivo; inhibitor/antagonist; knockout animal; neuron apoptosis; neuron loss; tripolyphosphate

DESCRIPTION (provided by applicant): Traumatic brain injury (TBI), or traumatic neuronal injury in vitro, causes neuronal apoptosis, in part through activation of caspases. Inhibition of caspase-3, in both in vivo or in vitro trauma models, reduces post-traumatic apoptosis, and improves functional outcomes in clinically relevant TBI models. However, some of these studies indicate that improvements often reflect only a delay in cell death, which still occurs eventually without the classical apoptotic phenotype. This suggests that caspase-independent pathways might play an important role in determining the final fate of cells. Recent work supports this hypothesis, demonstrating that caspase- independent apoptosis also contributes to neuronal cell death in a variety of in vitro model systems, and that translocation of apoptosis-inducing factor (AIF) from the mitochondria to the nucleus, in association with apoptotic morphological features, occurs after acute brain ischemia or TBI. Moreover, AIF translocation can occur under low energetic conditions, in association with activation of poly-ADP-ribose polymerase I (PARP-1) and reduction of nicotinamide adenine dinucleotide (NAD+). In contrast, caspase activation is generally associated with a more preserved bioenergetic state and requires adenosine 5'-triphosphate (ATP). Thus caspase-independent apoptosis may play a greater role than caspase-mediated cell death after a more severe injury, or within more central regions of the evolving lesion - sites at which cellular bioenergetic state is substantially compromised. AIF-mediated apoptosis may be initiated either by the same mechanisms responsible for intrinsic caspase activation or through PARP-1 activation. In the former, the role played by AIF becomes visible only when caspase activation has been blocked. In the latter, AIF is the main death-inducing factor. PARP-1 inhibition or PARP knockout animals, as well as knockout of the AIF carrier protein cyclophilin A, show reduced AIF translocation. We propose to utilize a well-established, controlled cortical impact (CCI) model of TBI in mouse, as well as selected in vitro models, to compare mechanisms underlying both caspase- dependent and caspase-independent programmed cell death of neurons and their relative roles as a function of injury severity and injury localization. Specific hypotheses include: 1) both caspase-independent and caspase-dependent pathways contribute to post-traumatic cell loss and associated neurological dysfunction after TBI, as well as to apoptotic neuronal cell death in cell culture models associated with DNA damage; 2) caspase-independent apoptosis is induced to a relatively greater degree than caspase-dependent cell death after more severe insults, or at more central regions of the expanding lesion, where bioenergetic state is reduced; 3) cell specific, inducible 'functional" knockouts of AIF pro-death domains, as well as models in which AIF translocation is inhibited (PARP knockout, treatment with PARP inhibitors, or cyclophilin A knockout), show reduced apoptotic cell death after TBI or after cell injury in vitro, and; 4) inhibition of both caspase- dependent and caspase-independent cell death improves recovery after CCI in additive or synergistic fashion. We propose the following specific aims: 1) to compare the relative degree and location of caspase-dependent and caspase-independent neuronal cell death after mild, moderate or moderately-severe TBI; 2) to investigate the role of AIF in TBI-induced neuronal death and behavioral recovery by comparing two inducible, neuron-specific, pro-death domain selective AIF transgenic models versus their "non-induced" controls; 3) to evaluate the effects of cyclophilin A knockout on AIF translocation, apoptosis and behavioral outcome after TBI and in selected cell culture models and; 4) to evaluate the effects of two structurally-distinct PARP inhibitors or PARP-1 knockout on AIF translocation, apoptosis and behavioral outcome after TBI and in selected cell culture models, and determine whether such effects are additive or synergistic to that of caspase inhibition. PUBLIC HEALTH RELEVANCE: Traumatic brain injury (TBI) represents a major cause of death and disability in the United States. A better understanding of the mechanisms underlying TBI would offer the possibility of improving survival and insuring a more complete recovery.

描述（由申请人提供）：创伤性脑损伤（TBI）或体外创伤性神经元损伤，部分通过半胱天酶的激活导致神经元凋亡。在体内或体外创伤模型中，抑制caspase-3可减少创伤后细胞凋亡，并改善临床相关TBI模型的功能结局。然而，其中一些研究表明，这些改善通常只反映细胞死亡的延迟，而最终仍然发生在没有经典凋亡表型的情况下。这表明caspase非依赖性通路可能在决定细胞的最终命运中发挥重要作用。最近的研究支持了这一假设，表明在多种体外模型系统中，不依赖caspase的凋亡也有助于神经元细胞死亡，并且在急性脑缺血或TBI后，凋亡诱导因子（AIF）从线粒体向细胞核的易位与凋亡形态学特征相关。此外，AIF易位可以在低能量条件下发生，与多adp核糖聚合酶I （PARP-1）的激活和烟酰胺腺嘌呤二核苷酸（NAD+）的还原有关。相比之下，半胱天冬酶的激活通常与更保存的生物能量状态相关，并且需要腺苷5'-三磷酸（ATP）。因此，caspase不依赖的细胞凋亡可能比caspase介导的细胞死亡在更严重的损伤后发挥更大的作用，或者在病变发展的更中心的区域-细胞生物能量状态被严重损害的地方。aif介导的细胞凋亡可能通过与内在caspase激活相同的机制启动，也可能通过PARP-1激活。在前者中，AIF的作用只有在caspase激活被阻断时才可见。在后者中，AIF是主要的致死因素。PARP-1抑制或PARP敲除动物，以及敲除AIF载体蛋白亲环蛋白A，显示AIF易位减少。我们建议利用一个成熟的、可控的小鼠脑外伤皮质冲击（CCI）模型，以及选定的体外模型，来比较caspase依赖性和caspase非依赖性神经元程序性细胞死亡的机制，以及它们在损伤严重程度和损伤定位中的相对作用。具体的假设包括：1)caspase非依赖性和caspase依赖性通路都有助于创伤后细胞损失和相关的TBI后神经功能障碍，以及与DNA损伤相关的细胞培养模型中的凋亡性神经元细胞死亡；2)在更严重的损伤后，或者在扩大的病变的更中心区域，生物能量状态降低，caspase非依赖性细胞凋亡比caspase依赖性细胞死亡的诱导程度相对更大；3)细胞特异性、可诱导的AIF促死亡结构域的“功能性”敲除，以及AIF易位被抑制的模型（PARP敲除、PARP抑制剂治疗或亲环蛋白A敲除），在体外显示TBI或细胞损伤后凋亡细胞死亡减少；4) caspase依赖性和caspase非依赖性细胞死亡的抑制以加性或协同方式改善CCI后的恢复。我们提出以下具体目的：1)比较轻、中度或中重度脑外伤后caspase依赖性和caspase非依赖性神经元细胞死亡的相对程度和位置；2)通过比较两种可诱导的、神经元特异性的、亲死亡结构域选择性的AIF转基因模型与“非诱导”对照组，研究AIF在tbi诱导的神经元死亡和行为恢复中的作用；3)评价亲环蛋白A敲除对脑外伤后AIF易位、凋亡和行为结局的影响；4)评估两种结构不同的PARP抑制剂或PARP-1敲除对脑外伤后AIF易位、凋亡和行为结局的影响，以及在选定的细胞培养模型中，确定这种影响是与caspase抑制作用相加还是协同作用。公共卫生相关性：创伤性脑损伤（TBI）是美国死亡和残疾的主要原因。更好地了解创伤性脑损伤的机制将为提高生存率和确保更完全的康复提供可能性。