脊髓损伤后EGFR活化介导血脊髓屏障破坏的机制研究

Blood spinal cord barrier (BSCB) damage following spinal cord injury (SCI) is closely related to the secondary spinal cord injury. The current study has demonstrated that the epidermal growth factor receptor (EGFR) of BSCB component cells excessive activation played a key role in the BSCB destruction after SCI. However, the exact mechanism is unclear. Our previous study found that phosphorylated EGFR and phosphorylated p38 increasing abnormally after SCI were closely concomitant with BSCB damage related protein expression. Meanwhile, EGFR inhibitors could inhibit not only EGFR and p38 activation but also nuclear translocation of NF-κB. Accordingly, we propose a reasonable hypothesis: EGFR downstream p38 MAPK signaling pathways involved in regulating the NF-κB nuclear translocation that caused blood spinal cord barrier damage related proteins abnormal expression following SCI. To verify this hypothesis, a series of experiments both in vitro and in vivo will be performed to study the signaling pathways involved in EGFR activation regulating the NF-κB nuclear translocation to cause BSCB damage related proteins abnormal expression, in order to clarify the related mechanism that EGFR activation causes BSCB destruction and secondary spinal cord injury after SCI. The research findings will help us to better understand pathological mechanism of SCI and provide new theoretical evidence for the clinical application of EGFR inhibitors in the treatment of SCI.

脊髓损伤(SCI)后血脊髓屏障（BSCB）的破坏与脊髓继发性损伤密切相关。目前研究已证实SCI后BSCB组成细胞表皮生长因子受体（EGFR）过度活化在BSCB的破坏中起着关键性作用。但具体作用机制尚未明确。我们前期研究发现SCI后磷酸化EGFR和磷酸化p38异常增多与BSCB损伤相关蛋白的表达密切相关；而EGFR抑制剂不仅可抑制EGFR和p38活化而且可抑制NF-κB核转位。据此，我们提出假说：SCI后EGFR下游的p38 MAPK信号通路参与调控NF-κB的核转位而导致BSCB损伤相关蛋白的异常表达。为验证该假说，本课题拟通过体内、外实验探讨SCI后EGFR活化调控NF-κB而影响BSCB损伤相关蛋白异常表达的信号通路，阐明SCI后EGFR活化导致BSCB破坏和脊髓继发性损伤的相关机制。研究结果将进一步深化对SCI病理机制的认识，为临床应用EGFR抑制剂治疗SCI提供新的理论依据。

本课题通过应用血脊髓屏障损伤模型及脊髓损伤（SCI）模型，研究了SCI后表皮生长因子受体（EGFR）活化导致BSCB 破坏和脊髓继发性损伤的相关机制。主要结果：1. 体外血脊髓屏障（BSCB）损伤后其组成细胞EGFR活化明显增多，这导致BSCB通透性增加，白细胞趋化因子、粘附因子、致炎因子表达增加，而紧密连接蛋白表达下降。应用EGFR抑制剂PD168393可以逆转上述改变。2. 在大鼠SCI模型中，BSCB 主要组成细胞（微血管内皮细胞和星形胶质细胞）EGFR活化明显增多，这导致BSCB通透性增大，致炎因子表达增加，紧密连接蛋白表达减少，而抑制EGFR活化后BSCB通透性破坏减轻，致炎因子表达下调而紧密连接蛋白表达上调。3. 证实SCI后BSCB组成细胞EGFR的活化导致其下游的信号分子p-p38，p-NF-κb增多，而且导致NF-κb的核转位增加。而NF-κB进入核内对紧密连接蛋白及致炎因子等基因表达起调控作用而导致血脊髓屏障紧密连接蛋白的脱失。这些结果提示：SCI后BSCB组成细胞EGFR的活化在BSCB 破坏和脊髓继发性损伤中起着关键性作用，而EGFR—p38—NF-κB信号通路是调控EGFR活化导致SCI 后 BSCB 破坏及脊髓继发性损伤的重要信号通路。