高压氧抑制创伤性脑损伤后 TRAF6 介导的神经炎症反应机制

Studies show that hyperbaric oxygen (HBO) inhibits neuroinflammation after traumatic brain injury (TBI). We have reported that the expressions of chemokine C-C motif ligand 2 (CCL2) and chemokine C-X-C motif ligand 1 (CXCL1) were elevated in brain tissue and blood following severe TBI in patients and mainly co-localized in astrocytes in brain tissue. Our preliminary studies from our project suggested that HBO therapy can promote the recovery of neurological function following TBI in rats. This may be partially attributed to the attenuation of astrocytes activation and the down regulation of the CCL2, CXCL1 and TNF receptor associated factor 6 (TRAF6) in injured cortex following TBI. However, the neuroinflammation signaling pathways mediated by TRAF6 after TBI and the effects of HBO on the signaling pathways have not been reported for now. Base on our preliminary data, our project will establish the model of rat with TBI and clarify whether the TRAF6 downstream signaling pathways induce the expressions of CCL2 and CXCL1 after TBI and then investigate the effects of HBO on the neuroinflammation pathways mediated by TRAF6 and neurological function. We will further build up the astrocyte injury model and explore the role of TRAF6-MAPKs/NF-κB-CCL2/CXCL1 signaling pathways in astrocytes on neurons injury and reveal the effects of HBO on the signaling pathways. In conclusion, this project will not only systematically elucidate the mechanism of HBO to inhibit neuroinflammation after TBI, but also provide theoretical basis for HBO therapy of TBI in clinic.

研究表明高压氧（HBO）有助于减轻创伤性脑损伤（TBI）后神经炎症。我们研究显示重度TBI患者脑组织和血液中趋化因子CCL2和CXCL1表达上调，在脑组织主要表达在星形胶质细胞。预实验发现HBO治疗后TBI大鼠神经功能改善与抑制星形胶质细胞激活、损伤区皮层TRAF6、CCL2和CXCL1表达下调有关，但TBI后TRAF6介导的神经炎症通路及HBO对该通路的作用均未见报道。基于预实验结果，本项目建立大鼠脑损伤模型，明确TBI后TRAF6的下游信号通路诱导CCL2和CXCL1表达；研究HBO对TBI后TRAF6介导的神经炎症抑制作用及对神经功能的影响。建立星形胶质细胞损伤模型，探讨胞内TRAF6-MAPKs/NF-κB-CCL2/CXCL1信号通路对神经元的损伤作用；揭示HBO对该通路的抑制作用。本研究不但系统阐明HBO抑制TBI后神经炎症反应的机制，也为临床HBO治疗TBI提供理论依据。

创伤性脑损伤（TBI）后TRAF6介导的神经炎症通路及高压氧（HBO）对该通路的作用均未见报道。本项目建立大鼠TBI模型，结果发现：TBI后大鼠神经功能减退，损伤皮层区神经细胞凋亡增加；TRAF6、MAPKs、p-NF-κB、CCL2、CCR2、CXCL1和CXCR2表达均增高，TRAF6主要表达在星形胶质细胞和神经元中，CCL2和CXCL1主要表达在星形胶质细胞中，而CCR2和CXCR2主要表达在神经元中。应用CCR2或CXCR2拮抗剂后神经细胞凋亡减少的同时神经功能改善；应用ERK、JNK、p38和NF-κB抑制剂均可降低大鼠CCL2、CCR2、CXCL1和CXCR2的表达；腺病毒干扰脑皮层中TRAF6的表达后，TBI大鼠神经功能好转，损伤区皮层神经细胞凋亡减少，p-NF-κB、p-JNK、p-ERK、p-p38、CCL2、CXCL1、CCR2和CXCR2表达均下降。我们进一步研究发现HBO治疗可以改善TBI后大鼠的神经功能，神经细胞凋亡减少；同时损伤区皮层中TRAF6、p-ERK、p-JNK、p38、p-NF-κB、CCL2、CCR2、CXCL1和CXCR2均明显降低。综上所述，TRAF6-NF-κB/MAPKs-CCL2/CXCL1信号通路在TBI后神经炎症中发挥着重要作用，HBO治疗可以通过调控TRAF6-NF-κB/MAPKs（REK、JNK和p38）-CCL2/CXCL1炎性通路来调控TBI后神经炎症而发挥神经保护作用。体外实验用LPS刺激分化成熟的原代星形胶质细胞，结果显示：LPS刺激后TRAF6、pNF-κB、p-ERK、p-JNK、p-p38、CXCL1和CCL2含量均明显增加；抑制NF-κB、ERK、JNK信号传导通路可下调星形胶质细胞内CXCL1和CCL2的表达；星形胶质细胞转染TRAF6的siRNA后，pNF-κB、p-ERK、p-JNK、p-p38、CCL2和CXCL1含量均下调；而HBO治疗后能下调TRAF6、p-NF-κB、p-ERK、p-JNK、p-p38、CXCL1和CCL2的表达。上述结果表明HBO治疗通过抑制LPS诱导的TRAF6-NF-κB/MAPKs（REK和JNK）- CCL2/CXCL1信号通路而发挥调控神经炎症的作用。本研究不但系统阐明HBO抑制TBI后神经炎症反应的机制，也为临床上HBO治疗TBI提供理论依据。