Blood-brain barrier (BBB) disruption is a serious pathological consequence of traumatic brain injury (TBI), for which there are limited therapeutic strategies. Tissue inhibitor of metalloproteinase-2 (TIMP2), a molecule with dual functions of inhibiting MMP activity and displaying cytokine-like activity through receptor binding, has been reported to inhibit VEGF-induced vascular hyperpermeability. Here, we investigate the ability of TIMP2 to ameliorate BBB disruption in TBI and the underlying molecular mechanisms. Both TIMP2 and AlaTIMP2, a TIMP2 mutant without MMP-inhibiting activity, attenuated neurological deficits and BBB leakage in TBI mice; they also inhibited junctional protein degradation and translocation to reduce paracellular permeability in human brain microvascular endothelial cells (ECs) exposed to hypoxic plus inflammatory insult. Mechanistic studies revealed that TIMP2 interacted with α3β1 integrin on ECs, inhibiting Src activation-dependent VE-cadherin phosphorylation, VE-cadherin/catenin complex destabilization, and subsequent VE-cadherin internalization. Notably, localization of VE-cadherin on the membrane was critical for TIMP2-mediated EC barrier integrity. Furthermore, TIMP2-mediated increased membrane localization of VE-cadherin enhanced the level of active Rac1, thereby inhibiting stress fiber formation. All together, our studies have identified an MMP-independent mechanism by which TIMP2 regulates EC barrier integrity after TBI. TIMP2 may be a therapeutic agent for TBI and other neurological disorders involving BBB breakdown.

中文翻译：

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TIMP2 通过抑制 Src 依赖性 VE-钙粘蛋白内化来改善创伤性脑损伤中的血脑屏障破坏。


血脑屏障（BBB）破坏是创伤性脑损伤（TBI）的严重病理后果，目前治疗策略有限。金属蛋白酶组织抑制剂 2 (TIMP2) 是一种具有抑制 MMP 活性和通过受体结合显示细胞因子样活性双重功能的分子，据报道可以抑制 VEGF 诱导的血管通透性过高。在这里，我们研究了 TIMP2 改善 TBI 中 BBB 破坏的能力及其潜在的分子机制。 TIMP2 和 AlaTIMP2（一种不具有 MMP 抑制活性的 TIMP2 突变体）均可减轻 TBI 小鼠的神经功能缺陷和 BBB 渗漏；它们还抑制连接蛋白降解和易位，以降低暴露于缺氧和炎症损伤的人脑微血管内皮细胞（EC）的细胞旁通透性。机制研究表明，TIMP2 与 EC 上的 α3β1 整合素相互作用，抑制 Src 激活依赖性 VE-钙粘蛋白磷酸化、VE-钙粘蛋白/连环蛋白复合物不稳定以及随后的 VE-钙粘蛋白内化。值得注意的是，VE-钙粘蛋白在膜上的定位对于 TIMP2 介导的 EC 屏障完整性至关重要。此外，TIMP2介导的VE-钙粘蛋白膜定位增加增强了活性Rac1的水平，从而抑制应力纤维的形成。总之，我们的研究已经确定了一种独立于 MMP 的机制，TIMP2 通过该机制在 TBI 后调节 EC 屏障完整性。 TIMP2 可能是 TBI 和其他涉及 BBB 破坏的神经系统疾病的治疗剂。