Mechanisms of Docosahexaenoic Acid Neuroprotection after Rat Pup TBI

二十二碳六烯酸对幼鼠TBI后神经保护的机制

• 批准号: 8968061
• 负责人: Michelle Elena Schober
• 金额: $ 23.6万
• 依托单位: UNIVERSITY OF UTAH
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-08-01 至 2017-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8968061
• 关键词: Address; Adult; Affect; Agonist; Animal Model; Anti-Inflammatory Agents; Anti-inflammatory; Antioxidants; Autoradiography; Benefits and Risks; Blood; Brain; Cause of Death; Child; Childhood; Clinical; Clinical Trials; Clinical Trials Design; Cognitive; Data; Development; Diet; Dietary Intervention; Docosahexaenoic Acids; Dose; Fish Oils; Fostering; Free Radicals; Future; Gene Expression; Histologic; Histology; Image; Impaired cognition; Impairment; Inflammation; Inflammatory; Injury; Knowledge; Lead; Lesion; Life; Lipids; Measures; Mediating; Messenger RNA; Microglia; Modeling; Neurologic; Neurologic Dysfunctions; Neurological outcome; Neuroprotective Agents; Nutrient; Operative Surgical Procedures; Outcome; Oxidative Stress; PPAR gamma; Pathway interactions; Patient Selection; Peroxisome Proliferator-Activated Receptors; Phenotype; Play; Preclinical Testing; Production; Rattus; Reactive Oxygen Species; Relative (related person); Role; Safety; Sum; Testing; Time; Traumatic Brain Injury; cognitive function; cognitive testing; controlled cortical impact; disability; feeding; improved; in vivo; innovation; macrophage; mature animal; neuroprotection; novel; oxidation; pediatric traumatic brain injury; preclinical study; public health relevance; pup; research clinical testing; response; response to injury; risk benefit ratio; therapy duration; transcription factor; Address; Adult; Affect; Agonist; Animal Model; Anti-Inflammatory Agents; Anti-inflammatory; Antioxidants; Autoradiography; Benefits and Risks; Blood; Brain; Cause of Death; Child; Childhood; Clinical; Clinical Trials; Clinical Trials Design; Cognitive; Data; Development; Diet; Dietary Intervention; Docosahexaenoic Acids; Dose; Fish Oils; Fostering; Free Radicals; Future; Gene Expression; Histologic; Histology; Image; Impaired cognition; Impairment; Inflammation; Inflammatory; Injury; Knowledge; Lead; Lesion; Life; Lipids; Measures; Mediating; Messenger RNA; Microglia; Modeling; Neurologic; Neurologic Dysfunctions; Neurological outcome; Neuroprotective Agents; Nutrient; Operative Surgical Procedures; Outcome; Oxidative Stress; PPAR gamma; Pathway interactions; Patient Selection; Peroxisome Proliferator-Activated Receptors; Phenotype; Play; Preclinical Testing; Production; Rattus; Reactive Oxygen Species; Relative (related person); Role; Safety; Sum; Testing; Time; Traumatic Brain Injury; cognitive function; cognitive testing; controlled cortical impact; disability; feeding; improved; in vivo; innovation; macrophage; mature animal; neuroprotection; novel; oxidation; pediatric traumatic brain injury; preclinical study; public health relevance; pup; research clinical testing; response; response to injury; risk benefit ratio; therapy duration; transcription factor

 DESCRIPTION (provided by applicant): Traumatic brain injury (TBI) is the leading cause of death and disability in children, resulting in life-long neurologic dysfunction for which there is o specific therapy. Dietary docosahexaenoic acid (DHA) improved neurologic outcome after severe TBI in adult rats and in our pediatric TBI model. However, the mechanism of DHA's neuroprotection is not understood. TBI activates microglia, the brain's resident macrophages, into a spectrum ranging between M1 and M2 activation. M1 promotes oxidative stress, while M2 decreases oxidative stress. In adult animals, M2 activation is associated with improved outcome. It is not known if M2 activation after TBI is associated with improved outcome in the immature brain, nor how such "polarization" may be fostered. Our preliminary data suggests that DHA decreases microglial activation in our pediatric TBI model, controlled cortical impact (CCI) in rat pups. Our DHA diet increases brain gene expression downstream of a microglial transcription factor that regulates polarization, the Peroxisome Proliferator Activated Receptor (PPARγ). PPARγ agonists polarize microglia towards M2. Our results led us to ask if DHA's neuroprotection depends on promoting microglial M2 polarization via a PPARγ-dependent pathway. Of concern, DHA is readily oxidized. Large amounts of oxidized DHA could cause oxidative injury by depleting the immature brain's limited antioxidant reserve. On the other hand, DHA could decrease oxidative injury by directly absorbing reactive oxygen species and decreasing microglial free radical production. Oxidative injury may be assessed using total antioxidant capacity (TAC). In sum, mechanistic preclinical studies of DHA safety and mechanism are needed. We hypothesize that DHA will polarize activated microglia towards the M2 phenotype and increase brain TAC in rat pups after experimental TBI, via a PPARγ-dependent mechanism, associated with improved neurologic outcome. To test this, we will expose rat pups to DHA or regular (REG) diet after CCI or SHAM surgery and inject them daily with either a PPARγ antagonist or vehicle. We will use imaging and gene expression to characterize M2 activation, TAC to assess oxidation, and histology/cognitive function testing to assess outcome. We anticipate that DHA will increase M2 polarization and TAC in rat pup brains after TBI, abrogated by PPARγ antagonism and associated with decreased lesion volume and cognitive impairment. Our proposal will provide new knowledge on the time course, and functional importance, of M2 microglial polarization in the immature brain after TBI, and whether these are modified by DHA. While the availability and apparent safety of DHA make it an appealing candidate therapy for children after severe TBI, its clinical use is hindered by important knowledge deficits regarding its mechanism of action and safety in the immature brain after TBI. Our proposal will lead to focused pre-clinical studies that will guide clinical trials o DHA in children after severe TBI and potentially decrease the burden of neurologic disability after childhood TBI.

 描述（由适用提供）：创伤性脑损伤（TBI）是儿童死亡和残疾的主要原因，导致终生的神经功能障碍，有特定的治疗。成年大鼠和我们的小儿TBI模型中严重的TBI后，饮食二十二碳六烯酸（DHA）改善了神经系统结局。但是，DHA神经保护的机制尚不清楚。 TBI将小胶质细胞（大脑的居民巨噬细胞）激活成M1和M2激活之间的光谱。 M1促进氧化应激，而M2降低了氧化应激。在成年动物中，M2激活与预后改善有关。尚不清楚TBI后M2激活是否与未成熟大脑的预后改善相关，也不知道如何促进这种“偏光化”。我们的初步数据表明，DHA在我们的小儿TBI模型中降低小胶质细胞激活，即大鼠幼崽中的皮质影响（CCI）。我们的DHA饮食增加了调节极化的小胶质细胞转录因子下游的脑基因表达，即过氧化物组增殖物激活受体（PPARγ）。 PPARγ激动剂将小胶质细胞偏向M2。我们的结果使我们询问DHA的神经保护是否取决于通过PPARγ依赖性途径促进小胶质细胞M2极化。令人担忧的是，DHA容易被氧化。大量氧化DHA可能会通过耗尽未成熟大脑的有限抗氧化剂储备来造成氧化损伤。另一方面，DHA可以通过直接吸收活性氧并降低小胶质性自由基生产来减少氧化损伤。可以使用总抗氧化能力（TAC）评估氧化损伤。总而言之，DHA安全性和机制的机械临床前研究假设，DHA将通过PPARγ依赖性机制对M2表型的活化小胶质细胞两极化，并增加大鼠幼崽的大鼠TAC，并与改善的神经学结果相关。为了进行测试，我们将在CCI或假手术后将大鼠幼崽暴露于DHA或常规（Reg）饮食中，并每天将它们注入PPARγ拮抗剂或媒介物。我们将使用成像和基因表达来表征M2激活，评估氧化的TAC以及组织学/认知功能测试以评估结果。我们预计DHA将在TBI后增加大鼠幼崽大脑中的M2极化和TAC，并通过PPARγ拮抗作用，并与病变的体积减少和认知障碍有关。我们的建议将提供有关TBI后未成熟大脑中M2小胶质细胞极化的时间过程和功能重要性的新知识，以及它们是否通过DHA进行了修改。尽管DHA的可用性和明显的安全性使其成为严重TBI后儿童的外观候选疗法，但其临床用途受到有关其在TBI后未成熟大脑中其动作和安全机制的重要知识定义的阻碍。我们的建议将导致重点临床前研究，该研究将指导严重TBI后儿童的临床试验O DHA，并有可能减少儿童期TBI后神经系统疾病的伯宁。