The effect of hepatocyte growth factor(HGF) on the blood-brain barrier

免疫荧光染色、western blot分析和RT-PCR分析表明，大鼠脑微血管内皮细胞（RBECs）表达c-Met作为HGF受体。利用体外血脑屏障（BBB）模型和RBECs原代培养研究了HGF对屏障功能的影响。HGF通过RBECs单层降低了荧光素钠和埃文斯蓝白蛋白的通透性，并剂量依赖性地增加了跨内皮电阻（TEER）。人们认为HGF通过最初靶向TJ对血脑屏障功能具有保护作用。然而，免疫荧光染色和Western blot分析显示，HGF处理对RBECs中紧密连接蛋白claudin-3、claudin-5、occludin和ZO-1没有显著影响。相比之下，HGF处理后粘附连接蛋白E-cadherin增加。HGF减少了皮层肌动蛋白带，增加了f -肌动蛋白带的应力纤维密度。HGF改变了f -肌动蛋白条带的免疫组织化学染色模式。HGF似乎作用于血脑屏障以增强血脑屏障的完整性，但其机制不是由紧密连接蛋白的改变引起的。其他机制，例如，细胞骨架重排可能是HGF对血脑屏障影响的候选机制。此外，在RBECs血脑屏障的紧密连接功能中，表明转化生长因子-β (TGF-β)与HGF具有相反的作用。

Immunofluorescent staining, western blot analysis and RT-PCR indicated that rat brain microvascular endothelial cells(RBECs) expressed c-Met as the HGF receptor.The effect of HGF on barrier function was investigated using an in vitro model of the blood-brain barrier(BBB) with a primary culture of RBECs. HGF decreased permeability to sodium fluorescein and Evans blue albumin through the RBECs monolayer, and dose-dependently increased transendothelial electrical resistance(TEER). It was thought that HGF had a protective effect on BBB function by initially targeting the TJ. However, immunofluorescent staining and Western blot analysis indicated that HGF treatment did not significantly change the tight junction proteins claudin-3, claudin-5, occludin and ZO-1 in RBECs. In comparison, E-cadherin as adherens junction protein was increased by HGF treatment. HGF reduced cortical actin bands and increased stress fiber density in F-actin bands. HGF altered immunohistochemical staining pattern of F-actin bands. HGF seems to act on the BBB to strengthen BBB integrity, but the mechanism was not caused by changes of tight junction proteins. Other mechanisms, for example, cytoskeletal rearrangement could be a candidate mechanism for the effect of HGF on BBB.Furthermore, in the tight junctional function of BBB in RBECs, it was indicated that Transforming growth factor-beta(TGF-β) had opposite effects from HGF.