PAI-1在TGFβ1诱导的放射性肺纤维化形成中的作用和机制研究

TGFβ1 is a key regulator in the progress of radiation induced pulmonary fibrosis (RIPF). However, the underlying mechanism remains unclear. Studies have shown that PAI-1, downstream of TGFβ1, plays an important role in pulmonary fibrosis. In our previous study, using cDNA microarray analysis to identify genes potentially involved in the development of RIPF, we showed that irradiated cell lines and murine lung tissues expressed elevated levels of PAI-1 relative to unirradiated group. In order to further clarify its role in RIPF, we did a series of experiments to verify the elevated expression of PAI-1 after radiation in vivo and in vitro. Furthermore, we found the expression of PAI-1 could be downregulated by the use of RGD peptides inhibiting the TGFβ1-integrin αv interaction. Therefore, the applicant put forward the hypothesis that PAI-1 plays an important role in TGFβ1-mediated RIPF, which may lead to the development of RIPF through the "TGFβ1 / integrin αv-PAI-1" pathway. Our project is aimed to figure out the effect of PAI-1 on TGFβ1-mediated RIPF, to disclose the effect of TGFβ1-integrin αv interaction on PAI-1 expression, and to develop a new targeting strategy for RIPF intervention.

TGFβ1作为放射性肺纤维化（RIPF）的关键调控因子，调节RIPF的具体机制仍不明。研究表明，TGFβ1下游的PAI-1在纤维化中具有重要作用。申请人前期在基因芯片、动物、人体水平均发现PAI-1与RIPF及其相关蛋白表达密切相关，利用RGD多肽抑制与TGFβ1存在交互作用的整合素αv可下调PAI-1的表达。因此申请者提出假设：PAI-1在TGFβ1诱导的RIPF中具有重要作用，可能是通过 “TGFβ1／整合素αv－PAI-1”通路导致RIPF的发生发展。本项目在细胞和动物水平上利用抑制剂及基因敲低、敲除技术，阐明PAI-1在TGFβ1诱导的放射性肺纤维化中的作用和机制，明确TGFβ1-整合素αv交互作用对PAI-1表达的调控，为以PAI-1为靶点开发全新的抗RIPF药物提供理论依据。

放射性肺纤维化（RIPF）是胸部放射治疗的常见慢性并发症，极大限制了放射治疗的剂量。研究表明，利用RGD多肽抑制与TGFβ1存在交互作用的整合素αv可下调PAI-1的表达，提示PAI-1在TGFβ1诱导的放射性肺纤维化中发挥重要作用。本课题从细胞和动物水平研究了PAI-1在TGFβ1诱导的放射性肺纤维化中的作用和机制，证明TGFβ1调控PAI-1的表达依赖于TGFβ1与整合素αv亚基交互作用。研究表明，在16Gy放疗后三个时间点进行的Micro-CT扫描显示放疗组中小鼠肺部逐渐出现弥漫性和斑片状阴影的数量增加，α-SMA和PAI-1的表达在放疗后第16周小鼠的肺组织中显着增加。给予小鼠16Gy全胸部单次照射，并每日腹腔注射15mg/kg或75mg/kg西仑吉肽，能显著抑制PAI-1的表达。表明西仑吉肽可能通过干预TGFβ1/αvβ3-PAI-1关键蛋白的表达，减弱放射性肺纤维化。本研究进一步发现了吡非尼酮以及甲状腺素在小鼠模型中能够抑制RIPF的进展，在人体样本中验证了IL-4以及HIPK2基因中单核苷酸态性位点对接受放疗肺癌患者中射损伤的发生具有预测作用。该研究阐明了以PAI-1或整合素αv 为靶点干预RIPF的可行性，为RIPF的防治提供了候选的药物；为放射性肺损伤的预测提供了新标志物，为后期建立放射性肺损伤预测模型，设计相关试剂盒提供了依据。

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