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

免疫荧光染色、Western blot和RT-PCR检测表明，大鼠脑微血管内皮细胞（RBECs）表达HGF受体c-Met，利用原代培养的血脑屏障（BBB）体外模型，研究HGF对血脑屏障功能的影响。HGF可降低红细胞单层对荧光素钠和伊文思蓝白蛋白的通透性，并呈剂量依赖性增加跨内皮电阻（TEER）。认为HGF通过最初靶向TJ对BBB功能具有保护作用。免疫荧光染色和Western blot分析显示，HGF处理后，红细胞紧密连接蛋白claudin-3、claudin-5、occludin和ZO-1的表达无明显变化。相比之下，作为粘附连接蛋白的E-钙粘蛋白通过HGF处理而增加。肝细胞生长因子减少皮质肌动蛋白带和增加应力纤维密度的F-肌动蛋白带。HGF改变了F-actin的免疫组化染色模式。HGF作用于血脑屏障，增强血脑屏障的完整性，但其作用机制与紧密连接蛋白的变化无关。此外，在红细胞与血脑屏障的紧密连接功能方面，TGF-β的作用与HGF相反。

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.