SMO去泛素化激活NLRP3炎症小体介导巨噬细胞焦亡在放射性心肌损伤中的作用机制研究

随着长期存活的肿瘤患者逐渐增多，放射性心肌损伤(radiation induced myocardial damage, RIMD)成为目前研究热点。课题组前期发现心肌巨噬细胞辐射后出现焦亡现象，Caspase-1 mRNA和蛋白表达水平与动物模型中辐射后心肌纤维化的进程具有时间吻合性，且下游IL-1β与心肌成纤维细胞TGF-β1/p38的变化具有相似性，鉴于辐射可以引起多种组织的“焦亡”，因此首次提出焦亡可能在RIMD中发挥作用。进一步发现巨噬细胞辐射后Hedgehog(Hh)信号通路也被激活，其中SMO与焦亡炎症小体NLRP3变化趋势相同，加入去泛素化抑制剂MG132后，NLRP3 mRNA无明显变化，但蛋白水平明显下降。故课题组首次提出辐射通过巨噬细胞SMO去泛素化激活NLRP3炎症小体，进一步介导巨噬细胞焦亡发生导致放射性心肌损伤，为RIMD的免疫机制提供了一条崭新的信号通路。

With a progressive improvement in cancer treatment, increasing population of cancer-survivor is developing radiotherapy related late side effects, in which radiation induced myocardial damage (RIMD) is drawing growing attention. In our preliminary experiment, quantitative reverse transcriptase polymerase chain reaction revealed expression of Capspase-1 mRNA and its protein level in macrophage of heart coordinated with process of myocardial fibrosis in animal model with C57BL/6 rats exposed to 12Gy. Meanwhile, ELISA test showed the change curve of downstream plasma IL-1β of macrophage and TGF-β1/p38 of cardiac fibroblast cell also fitted the severity of myocardial fibrosis. As caspase-1-dependent innate immunity pyroptosis is a form of programmed cell death and can be induced by ionizing radiation, we hypothesized pyroptosis mediated radiation-induced myocardial fibrosis by infammatory classical caspase-1-pathway activation. Further exploratory research revealed Hedgehog (Hh) signal transduction pathway was also activated. The Levels of Smoothened (SMO), marker of Hh pathway, and NLRP3 of macrophage had similar changing trends. After cultivated with MG132, an inhibitor of deubiquitination, the protein level of NLRP3 significantly reduced while the mRNA level was not affected. Combined with previous report that TGF-β1/p38/MAPK is considered the main promoting pathway of myofibroblast-induced extracellular matrix accumulation, we first propose a new pathway of irradiation-induced myocardial fibrosis: macrophage pyroptosis activated by irradiaton via deubiquitination of NLRP3 by SMO was an important mechanism in RIMD. This application will elucidate the role of pyroptosis in mediating radiation-induced myocardial fibrosis via deubiquitination of NLRP3 by SMO. This study help promotes explore new therapeutic strategies of RIMD with experimental envidence.