Nox4型NADPH氧化酶在调节内皮细胞动静脉表型转化过程中的作用及机制研究

Vascular endothelial cells play cardinal roles in modulating vascular function and vascular system stability. Endothelial cells are genetically determined to differentiate into arterial and venous endothelial cells identified with respective arterial-venous markers. EphrinB2 is mainly found in arterial endothelial cells, while EphB4 specifically expressed in venous endothelial cells. Notch signaling, PI3K-Akt and ERK1/2 pathways are involved in the process of arterial-venous differentiation. Arterial-venous differentiation is not only a key segment in embryogenesis, but its disturbance also influences normal physical function afterwards. Endothelial cells remain phenotypic plasticity in adulthood. NADPH oxidase-mediated redox signaling pathway regulates differentiation of embryonic stem cell and progenitor cells, but whether redox mechanism affects arterial-venous phenotypic switch of adult endothelial cells remains to be clarified. Our preliminary study demonstrated that Nox4 has dual impacts on regulating apoptosis of endothelial cells and redox signaling can also modulate arterial-venous phenotypic switch. In this study, we will investigate the roles of endogenous and exogenous Nox4 in arterial-venous phenotypic switch and elucidate the underlying mechanisms. Vein graft arterialization occurs in the course of autogenous vein graft implantation, and it is companied by decreased EphB4 expression, that is indicated to be related with intimal hyperplasia. We also carry out animal experiment to explore the effect of Nox4 on the process of vein graft arterialization, and maybe provide theoretical basis for prevention of vein graft stenosis.

血管内皮细胞在调节血管功能和维持血管稳态中发挥重要作用。内皮细胞受基因调控分化为动脉或静脉表型，分别表达特异性的动静脉标志物。EphrinB2主要在动脉内皮细胞表达，而EphB4特异性在静脉内皮细胞表达。Notch、PI3K-Akt和ERK1/2信号通路参与内皮细胞的动静脉分化。动静脉分化不仅是胚胎发育的重要环节，成年内皮细胞动静脉表型仍具有可塑性。NADPH氧化酶对干细胞分化具有重要的调控作用，但目前在内皮细胞动静脉转化中的作用未见报道。我们前期研究发现Nox4在调节内皮细胞凋亡中具有双刃剑的作用，同时还发现氧化还原机制调节内皮细胞动静脉转化，本课题将研究内源性与外源性Nox4在内皮细胞动静脉转化中的作用及机制。自体静脉移植过程中发生静脉桥动脉化，伴随EphB4表达减少，与静脉桥内膜增生有关。我们在整体水平研究干预Nox4是否对静脉桥动脉化产生影响，为寻找静脉桥狭窄防治措施提供理论依据。

血管内皮细胞在调节血管功能和维持血管稳态中发挥重要作用。内皮细胞受基因调控分化为动脉或静脉表型，分别表达特异性的动静脉标志物。EphrinB2主要在动脉内皮细胞表达，而EphB4特异性在静脉内皮细胞表达。Notch、PI3K-Akt和ERK1/2信号通路参与内皮细胞的动静脉分化。自体静脉移植过程中发生静脉桥动脉化，伴随EphB4表达减少，与静脉桥内膜增生有关。在本课题中我们研究了内源性与外源性Nox4在内皮细胞动静脉转化中的作用及机制。我们发现内源性Nox4和外源性Nox4在成熟静脉内皮细胞的动静脉表型转化中扮演着双面的角色，外源性Nox4增加动脉标志物EphrinB2的表达，而内源性Nox4促进静脉标志物EphB4的基因和蛋白表达。内源性Nox4和外源性Nox4不仅在成熟静脉内皮细胞中对动静脉表型转化发挥不同的作用，而且在内皮祖细胞中也具有相似的作用，即外源性Nox4促进内皮祖细胞向动脉内皮细胞转化，而内源性Nox4促进其向静脉内皮细胞转化。相关的机制研究发现，内源性及外源性Nox4均能激活p38和JNK通路。外源性Nox4激活Notch信号通路，而内源性Nox4激活Akt通路。我们发现Notch和PI3K-Akt信号通路是内源性及外源性Nox4影响静脉内皮细胞动静脉表型作用不同的关键通路。在大鼠自体颈静脉移植动物实验中，我们发现静脉桥动脉化过程中，Nox4表达减少，EphB4逐渐减少，而EphrinB2表达变化不大。而尾静脉注射Nox4慢病毒能减轻EphB4减少趋势，使静脉桥内膜增生减轻，平滑肌细胞增殖及迁移减少，炎症因子TNF-α、IL-1β和PDGF-β水平有所下降。说明Nox4可能通过EphB4影响静脉桥动脉化过程。我们的研究结果，为将来防治冠心病患者冠状动脉旁路移植术后静脉桥狭窄问题提供了新的思路和理论依据。