TLR9在放射性肺纤维化治疗中的作用及其机制研究

Pulmonary fibrosis is a serious adverse effect of radiotherapy for thoracic tumor, which is leading cause of morbidity and mortality.Thus, there is widespread interest to find agents to prevent the development of irradiation-induced pulmonary fibrosis. Current treatments for pulmonary fibrosis target the inflammatory cascade, but they have been widely unsuccessful, largely because the mechanisms that are involved in fibrogenesis are now know to be distinct from those involved inflammation. Recently, some reports showed that Th cells have an important role in the progression of fibrosis. In particular, the type of Th cell response that develops is crucial. Fibrogenesis is strongly linked with the imbalance of Th1 and Th2 cell response toward to Th2 cell response. CpG-oligodeoxynucleotides (ODN), unmethylated CpG dinucleotide is capable of mimicking the immunostimulatory effects of bacterial DNA. Our previous study showed that CpG-ODN could induce IFN-γ and IL-12 expression and inhibit IL-4 and IL-13 expression,suggested that administration of CpG-ODN in vivo is able to provide a signal to switch on Th1-dominated response and switch off Th2-dominated response to produce an environment favoring a Th1 immunity response. therefore, we speculated that CpG-ODN might have preventing effect on pulmonary fibrosis induced by irradiation. To demonstrate our hypothesis, this study will investigate that the function role of CpG-ODN/TLR9 signal pathway in pulmonary fibrosis development by generating mice carrying knockout (KO) genes (such asTLR9 and MyD88) that abrogate their activity, and provide a new strategy for therapeutic application of pulmonary fibrosis induced by irradiation

放射性肺纤维化是肺部大剂量受照射后常见的严重病变，目前尚未找到防治良策，死亡率高，亟需探索新的治疗途径。近年来证明Th1/Th2免疫失衡在肺纤维化发生中起着关键作用。我们前期研究发现，机体照后Th1/Th2免疫会出现显著失衡，而TLR9激动剂能够扭转这种失衡，提示调控TLR9信号传导途径在放射性肺纤维化治疗中具有重要作用，极有可能成为治疗放射性肺纤维化的新突破口。本项目将在多个层次研究激活TLR9对放射性肺纤维化形成的影响及其治疗效应；通过遗传性阻断TLR9受体和MyD88等负性调控技术，进一步论证TLR9信号通路在治疗放射性肺纤维化中的作用地位；从TLR9下游几个主要基因位点、信号途径、免疫细胞亚群和效应分子等入手，探索激活TLR9治疗放射性肺纤维化的可能作用机制。最终阐明TLR9信号通路在放射性肺纤维治疗中的重要作用及其潜在价值，揭示其作用机制，为治疗放射性肺纤维化提供新思路、新策略。

放射性肺纤维化是肺部大剂量受照射后常见的严重病变，近年来证明Th1/Th2 免疫失衡在肺纤维化发生中起着关键作用，而TLR9 激动剂能够扭转这种失衡，提示调控TLR9 信号传导途径在放射性肺纤维化治疗中具有重要作用。但是对其确切效应和分子机理仍未见系统研究，成为制约其由实验研究向临床应用转化的突出问题。本课题在国家自然科学基金资助下，根据原计划书内容，成功构建小鼠放射性肺纤维化模型，完成了通过激活TLR9对放射性肺纤维化形成的影响的研究，明确了激活TLR9对放射性肺纤维化治疗的重要作用，并探讨了激活TLR9对放射性肺纤维化影响的作用机制。在项目执行过程中，我们也开展了一些原计划没有列入的工作；比如，原花青素能显著减轻放射性肺损伤, 虎杖苷减轻电离辐射所致的急性肺炎和慢性肺纤维化等。研究发现：1. 激活TLR9治疗电离辐射诱导肺纤维化的效果好，毒副作用小。2. 筛选出与放射性肺纤维化治疗相关的TLR9下游相关重要基因及效应分子，CpG-ODN通过拮抗由电离辐射诱导的Th2型免疫反应同时促进Th1型免疫反应，下调纤维化相关的TGF-β1-Smad依赖性和Smad非依赖性通路发挥对放射性肺纤维化治疗的重要作用。3. 此外我们也发现原花青素能显著减轻放射性肺损伤, 虎杖苷减轻电离辐射所致的急性肺炎和慢性肺纤维化。以上结果表明调控TLR9信号途径可以作为治疗放射性肺纤维化的新途径，为防治放射性肺纤维化提供了新的理论基础，进一步证实了CpG-ODN调控TLR9具有重要的理论价值和应用前景。本项目总体执行情况良好，注本基金已发表论文5篇，其中影响因子5分的SCI论文2篇，后续已经成文待发表SCI论文1篇；培养了博士4名，硕士1名；获得上海市科技进步一等奖1项等奖励；受邀在国内外学术做大会报告10次，顺利圆满地完成了本项目。