The mechanism of diffuse axonal injury development

弥漫性轴索损伤发生的机制

• 批准号: 09670460
• 负责人: TANAKA Noriyuki
• 金额: $ 1.79万
• 依托单位: University of Occupational and Environmental Health
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1997
• 资助国家: 日本
• 起止时间: 1997 至 1998
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09670460/
• 关键词: Traumatic head injury; Diffuse axonal injury; Tumor necrosis factor-alpha; beta-amyloid precursor protein; Fluid percussion device; Glial cell; MRI

We approach to show the immunolocalization of TNF a after diffuse axonal injury (DAI) by midline fluid percussion rat model (moderate brain injury of lOOOmmHg was generated) and the effects of TNF alpha on the axolemmal permeability using horseradish peroxidase as a tracer. Add to this, we investigate the accumulation of beta -amyloid precursor protein (beta -APP), which has recently been shown to be reliable marker for the functional damage of axons associated with fatal head injury. TNF alpha levels of brain tissues, which was impact cortex site including the corpus callosum, gradually increased during the first 1h, rose to a maximal elevation at 3h and gradually decresed at 6h and more decreased to 24h. Horseradish peroxidase (HRP) tracer experiments revealed that primary axonal damage appeared as early as 15min after impact, but rapidly recovered and 1h after impact secondary axonal damage occurred in the corpus callosum nd the brain stem. By theimmunoelectron microscopy, beta -APP accumulated in the axon at 1h after impact and this revealed functional axonal damage. TNF alpha reactions were detected in the lysosomes of microglia at the 3Omin after impact, and 1h after impact these reactions were mainly detected at the glial cells (such as microglia, astrocytes and oligodendrocytes) in the corpus callosum and the brain stem. It is widely accepted that TNF alpha induces primary demyelination and oligodendrocyte apoptosis. Therefore the delayed axonal damage observed in these sites may be induced by TNF a which is synthesized mainly by glial cells. The present study suggests that TNF alpha conveyed from the glial cells is one cofactor contributing to the DAI formation by the fluid percussive brain injury.

本实验采用大鼠中线液压冲击脑损伤模型，观察了脑弥漫性轴索损伤（DAI）后TNF-α的免疫定位，并以辣根过氧化物酶为示踪剂，观察了TNF-α对轴膜通透性的影响。除此之外，我们还研究了β-淀粉样前体蛋白（β-APP）的积累，该蛋白最近被证明是与致命性头部损伤相关的轴突功能损伤的可靠标志物。伤后1h内，包括胼胝体在内的皮质区脑组织TNF-α水平逐渐升高，3 h达高峰，6 h后逐渐下降，24 h后逐渐下降。辣根过氧化物酶（HRP）示踪实验显示，撞击后15 min，胼胝体和脑干出现了初级轴突损伤，但很快恢复，撞击后1h，胼胝体和脑干出现了次级轴突损伤。免疫电镜观察发现，β-APP在撞击后1h即在轴突内聚集，提示轴突功能性损伤。撞击后30 min，小胶质细胞溶酶体内可见TNF-α反应，撞击后1h主要见于胼胝体和脑干内的胶质细胞（如小胶质细胞、星形胶质细胞和少突胶质细胞）。广泛认为TNF α诱导原发性脱髓鞘和少突胶质细胞凋亡。因此，在这些部位观察到的迟发性轴突损伤可能是由主要由胶质细胞合成的TNF α诱导的。提示胶质细胞分泌的TNF-α可能是液体性脑损伤后DAI形成的辅助因子。