Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198, USA.
Free Radic Biol Med. 2013 Jul;60:282-91. doi: 10.1016/j.freeradbiomed.2013.02.029. Epub 2013 Mar 4.
We investigate the hypothesis that oxidative damage of the cerebral vascular barrier interface (the blood-brain barrier, BBB) causes the development of mild traumatic brain injury (TBI) during a primary blast-wave spectrum. The underlying biochemical and cellular mechanisms of this vascular layer-structure injury are examined in a novel animal model of shock tube. We first established that low-frequency (123kPa) single or repeated shock wave causes BBB/brain injury through biochemical activation by an acute mechanical force that occurs 6-24h after the exposure. This biochemical damage of the cerebral vasculature is initiated by the induction of the free radical-generating enzymes NADPH oxidase 1 and inducible nitric oxide synthase. Induction of these enzymes by shock-wave exposure paralleled the signatures of oxidative and nitrosative damage (4-HNE/3-NT) and reduction of the BBB tight-junction (TJ) proteins occludin, claudin-5, and zonula occluden 1 in the brain microvessels. In parallel with TJ protein disruption, the perivascular unit was significantly diminished by single or repeated shock-wave exposure coinciding with the kinetic profile. Loosening of the vasculature and perivascular unit was mediated by oxidative stress-induced activation of matrix metalloproteinases and fluid channel aquaporin-4, promoting vascular fluid cavitation/edema, enhanced leakiness of the BBB, and progression of neuroinflammation. The BBB leakiness and neuroinflammation were functionally demonstrated in an in vivo model by enhanced permeativity of Evans blue and sodium fluorescein low-molecular-weight tracers and the infiltration of immune cells across the BBB. The detection of brain cell proteins neuron-specific enolase and S100β in the blood samples validated the neuroastroglial injury in shock-wave TBI. Our hypothesis that cerebral vascular injury occurs before the development of neurological disorders in mild TBI was further confirmed by the activation of caspase-3 and cell apoptosis mostly around the perivascular region. Thus, induction of oxidative stress and activation of matrix metalloproteinases by shock wave underlie the mechanisms of cerebral vascular BBB leakage and neuroinflammation.
我们研究了这样一个假设，即在原发性爆炸波谱中，脑血管屏障界面（血脑屏障，BBB）的氧化损伤导致轻度创伤性脑损伤（TBI）的发展。在一种新型的冲击管动物模型中，我们检查了这种血管层结构损伤的潜在生化和细胞机制。我们首先证实，低频（123kPa）单次或重复冲击波通过暴露后 6-24 小时发生的急性机械力的生化激活引起 BBB/脑损伤。这种脑血管的生化损伤是由自由基生成酶 NADPH 氧化酶 1 和诱导型一氧化氮合酶的诱导引起的。冲击波暴露诱导这些酶的表达与氧化和硝化损伤（4-HNE/3-NT）和 BBB 紧密连接（TJ）蛋白 occludin、claudin-5 和 zonula occluden 1 的减少同时发生。与 TJ 蛋白破坏平行，单次或重复冲击波暴露使血管周围单元显著减少，与动力学特征一致。血管和血管周围单元的松弛是由氧化应激诱导的基质金属蛋白酶和流体通道水通道蛋白-4 的激活介导的，促进血管内液空化/水肿、BBB 通透性增强和神经炎症的进展。在体内模型中，通过 Evans 蓝和荧光素钠低分子量示踪剂的通透性增强以及免疫细胞穿过 BBB 的渗透，证明了 BBB 的通透性增加和神经炎症。血液样本中神经元特异性烯醇化酶和 S100β 脑蛋白的检测验证了冲击性 TBI 中的神经星形胶质损伤。我们的假设是，在轻度 TBI 中神经紊乱发展之前，脑血管损伤就已经发生了，这一假设通过 caspase-3 的激活和细胞凋亡得到了进一步证实，细胞凋亡主要发生在血管周围区域。因此，冲击波诱导的氧化应激和基质金属蛋白酶的激活是导致脑血管 BBB 渗漏和神经炎症的机制。
