Nrf2信号通路对脑梗死后血管内皮细胞损伤与再生的研究

The blood-brain barrier (BBB) is present at the level of the brain capillaries and is critical for microenvironment homeostasis in the central nervous system. Impermeability of the BBB is maintained by microvascular endothelial cells through their tight junctions and basal lamina. When this barrier integrity is lost, inflammatory cells and fluid penetrate the brain, causing edema and cell death, which play an important role in propagation of injury and providing a promising therapeutic target. Our previous findings proved that activation of Nrf2 pathways after stroke decreased vasogenic edema and protected neurons against ischemic injury. However whether Nrf2 contribute to remodeling and homeostasis maintenance of cerebral vascular function after stroke is still unknown. In this project, an evaluation system of microvascular homeostasis using two-photon microscope, bone marrow transplantation and transgenic mice produced by Cre-LoxP recombination system, and other biological technique was set up to test the effect of Nrf2 signaling pathway in maintaining BBB function and cerebral vascular remodeling after stroke. We also aim to test whether and how Nrf2 signaling pathways regulate angiogenesis, neurovascular unit remodeling and bone marrow stem cell differentiation and migration after stroke, and to test whether homeostasis maintenance of cerebral vascular function induced by Nrf2 signaling pathway is a promising therapeutic target in future study.

脑血管功能障碍是脑梗死后继发性脑损伤的重要原因，改善缺血区血液循环、减轻继发性脑损伤一直是临床医学的重点和难点。申请人前期研究证实Nrf2信号通路对脑梗死后继发性脑损伤及脑水肿具有显著改善作用（文章发表在Brain Res. 2009;1282:133-141, 被引证203次），并具有促进微血管再生的现象，推测Nrf2信号通路可能在脑梗死后血管功能调控及重构中起重要作用。本项目拟通过应用细胞特异性Nrf2基因敲除、Nrf2基因敲除小鼠、活体荧光成像、骨髓移植等关键技术，动态观察脑梗死后活体微血管三维重构过程。重点研究Nrf2信号通路是否参与脑梗死后血脑屏障保护与内皮细胞新生及血管重构，以及调控Nrf2信号通路是否是预防和治疗脑梗死的重要手段和方法，Nrf2信号通路是否参与骨髓干细胞介导的血管再生过程。以期为脑梗死的预防和治疗提供一种新的靶点。

脑血管病是世界范围内严重危害人类健康的主要疾病之一，但是在临床上有效的治疗手段仍然有限。目前，研究认为在急性期 3-4.5 小时内采用重组组织型纤溶酶原激活物（ recombinant tissue-type plasminogen activator， rt-PA） 进行静脉溶栓是唯一有效而可行的缺血性脑卒中的治疗措施，但是由于急性期治疗时间窗过窄， 并且存在发生颅内出血的风险，在临床上，发生脑卒中的患者往往因为就医不及时不能接受此项治疗，能从中获益的患者十分有限。因此需要进一步寻找更有效的治疗措施。本研究项目应用叔丁基对苯二酚 （tert-butylhydroquinone, tBHQ）（Nrf2的诱导剂，能够延缓 Nrf2 的降解速率，促进 Nrf2 核转位及其下游的抗氧化酶的表达，具有强力抗氧化能力）。发现①Nrf2诱导剂叔丁基对苯二酚对实验性脑梗死小鼠的神经保护作用； ②Nrf2诱导剂叔丁基对苯二酚促进实验性脑梗死小鼠血管再生；③Nrf2诱导剂Nrf2诱导剂叔丁基对苯二酚促进Nrf2核转位；④发现益母草就能够通过激活Nrf2通路促进脑梗死后血管再生。