日本血吸虫虫卵蛋白诱导肝星状细胞衰老的分子机制研究

Senescence of activated hepatic stellate cells is considered to be one of the important mechanisms in reversing liver fibrosis. However, we wonder to know whether the senescence of activated hepatic stellate cells also plays a key role in reversing the liver fibrosis caused by the infection of Schistosoma japonicum. Furthermore, the mechanism of the senescence of activated hepatic stellate cells and the clearance of senescent stellate cells remains unclear. In our previous study, we found that the number of the senescent stellate cells around the hepatic egg gralunomas increased in the mice with advanced schistosomiasis, resulting in the reversion of liver fibrosis. And the egg proteins could induce the senescence of activated hepatic stellate cells and upregulate the expression of related proteins in signal transduction pathway, such as p53, p21. To define the effect of egg proteins on senescence of hepatic stellate cells and the mechanism of senescence of hepatic stellate cells, the hepatic stellate cell, p53-/- mouse model with liver fibrosis and so on could be utilized. We will observe the effect of egg proteins on senescence of hepatic stellate cells and screen the egg protein molecules which can induce senescence of hepatic stellate cells. And then we confirm whether the egg proteins induced-senescence of hepatic stellate cells is associated with p53-p21-pRb signaling pathway and explore the mechanism of the clearance of activated hepatic stellate cells through some experiments in vivo and in vitro. Desired outcomes will provide the potential target that could prevent liver fibrosis in the infection of Schistosoma japonicum.

活化的肝星状细胞衰老是肝纤维化逆转的重要机制之一。在日本血吸虫病肝纤维化逆转过程中，是否存在肝星状细胞衰老？其中肝星状细胞衰老及衰老肝星状细胞清除的机制是什么？目前尚未见报道。本项目的前期实验表明在晚期血吸虫病小鼠肝脏肉芽肿周围衰老的肝星状细胞增加，肝纤维化出现逆转。虫卵蛋白可以诱导活化的肝星状细胞衰老，信号转导相关分子p53和p21等表达上调。为了明确日本血吸虫虫卵蛋白对肝星状细胞衰老的作用及机制，本项目将运用肝星状细胞和p53-/-基因敲除小鼠肝纤维化模型等，观察日本血吸虫虫卵蛋白在体内外对肝星状细胞衰老的作用，筛选能诱导肝星状细胞衰老的虫卵蛋白分子，确定p53-p21-pRb信号通路是否参与促进肝星状细胞衰老，探讨衰老的肝星状细胞清除的分子机制。预期结果将为日本血吸虫病肝纤维化的防治提供新的潜在靶点。

血吸虫感染晚期出现肝纤维化减轻现象，活化的肝星状细胞（HSCs）衰老可能是肝纤维化负性调节的重要环节之一。为了探明血吸虫病进程中活化的HSCs衰老及其分子机制，本项目首先利用动物模型观察了小鼠肝纤维化进程中HSCs衰老情况，随后通过体外实验观察了日本血吸虫可溶性虫卵抗原（SEA）对活化的HSCs衰老的影响，并进一步从 SEA中筛选了抑制HSCs活化以及诱导活化的HSCs发生细胞衰老的主要成分，确认重组日本血吸虫虫卵P40（rSjP40）蛋白对HSCs衰老的作用，进而深入探讨rSjP40促进HSCs衰老的信号通路以及衰老的HSCs的清除途径。研究结果表明，晚期日本血吸虫病肝纤维化减轻与HSCs 衰老相关；SEA可能主要通过TLR4/STAT3/SOCS3/p53/p21以及FoxO3a/SKP2/p27通路诱导活化的HSCs发生细胞衰老；SjP40作为SEA的主要成分之一，其重组蛋白rSjP40不仅能够通过活化BMP-7信号通路以及抑制TGF-β1信号通路从而抑制HSCs活化，还能够通过TLR4/STAT3/p53/p21以及SKP2/p27诱导活化的HSCs发生细胞衰老，而SEA的其他组分的重组蛋白，包括重组日本血吸虫 T2 核糖核酸酶蛋白和重组日本血吸虫Y-box 结合蛋白1 (YB1), 仅能够部分抑制HSCs活化。同时，本项目中还发现，rSjP40能够通过诱导细胞间的黏附、受体配体活化从而增强NK细胞对衰老HSCs的清除作用。此外，在研究中我们还发现，SEA能够通过抑制TNF-α处理的肝星状细胞中NF-κB信号通路从而抑制IL-34表达，该作用可能与SEA抑制肝星状细胞活化密切相关。这些研究结果提示，日本血吸虫虫卵蛋白能够促进HSCs衰老，该项目成果既从理论上深化对晚期血吸虫病肝纤维化负调控机制的认识，也在实践上为各种因素所致肝纤维化的治疗提供新的潜在靶点。