Liu Hai-Xiang, Zhao Hua, Xi Cong, Li Shuang, Ma Li-Ping, Lu Xue, Yan Juan, Tian Xue-Lei, Gao Ling, Tian Mei, Liu Qing-Jie
China CDC Key Laboratory of Radiological Protection and Nuclear Emergency, National Institute for Radiological Protection, Chinese Center for Disease Control and Prevention, Beijing, People's Republic of China.
Radiat Res. 2022 Aug 17. doi: 10.1667/21-00174.1.
The intestinal compensatory proliferative potential is a key influencing factor for susceptibility to radiation-induced intestinal injury. Studies indicated that the carnitine palmitoyltransferase 1 (CPT1) mediated fatty acid β-oxidation (FAO) plays a crucial role in promoting the survival and proliferation of tumor cells. Here, we aimed to explore the effect of 60Co gamma rays on CPT1 mediated FAO in the radiation-induced intestinal injury models, and investigate the role of CPT1 mediated FAO in the survival and proliferation of intestinal cells after irradiation. We detected the changed of FAO in the plasma and small intestine of Sprague Dawley (SD) rats at 24 h after 60Co gamma irradiation (0, 5 and 10 Gy), using target metabolomics, qRT-PCR, immunohistochemistry (IHC), western blot (WB) and related enzymatic activity kits. We then analyzed the FAO changes in radiation-induced intestinal injury models regardless of ex vivo (mice enteroids), or in vitro (normal human intestinal epithelial cell lines, HIEC-6). HIEC-6 cells were transduced with lentivirus vector GV392 and treated with puromycin for obtaining CPT1 stable knockout cell lines, named CPT1 KO. CPT1 enzymatic activities of HIEC-6 cells and mice enteroids were also inhibited by pharmaceutical inhibitor ST1326 and Etomoxir (ETO), to study the function of CPT1 in the survival and proliferation of HIEC-6 cells after 60Co gamma irradiation. We found that CPT1 mediated FAO was altered in the small intestine of the SD rats after irradiation, especially, the expression level and enzymatic activity of CPT1 were significantly increased. Similarly, the expression levels of CPT1 were also remarkably enhanced in mice enteroids and HIEC-6 cells after irradiation. CPT1 inhibition decreased the proliferation of the HIEC-6 cells and mice enteroids after irradiation partially by reducing the extracellular signal-regulated kinase (ERK1/2) and c-Jun N-terminal kinase (JNK) pathways activation, CPT1 inhibition also reduced the proliferation of mice enteroids after irradiation partially by down-regulating the Wnt/β-catenin signaling activity. In conclusion, our study indicated that CPT1 plays a crucial role in promoting intestinal epithelial cell proliferation after irradiation.
肠道代偿性增殖潜能是影响辐射诱导的肠道损伤易感性的关键因素。研究表明，肉碱棕榈酰转移酶1（CPT1）介导的脂肪酸β氧化（FAO）在促进肿瘤细胞存活和增殖中起关键作用。在此，我们旨在探讨60Coγ射线对辐射诱导的肠道损伤模型中CPT1介导的FAO的影响，并研究CPT1介导的FAO在照射后肠道细胞存活和增殖中的作用。我们使用靶向代谢组学、qRT-PCR、免疫组织化学（IHC）、蛋白质免疫印迹（WB）和相关酶活性试剂盒，检测了60Coγ射线照射（0、5和10 Gy）后24小时Sprague Dawley（SD）大鼠血浆和小肠中FAO的变化。然后，我们分析了辐射诱导的肠道损伤模型中FAO的变化，无论在体外（小鼠肠类器官）还是在体内（正常人肠道上皮细胞系，HIEC-6）。用慢病毒载体GV392转导HIEC-6细胞并用嘌呤霉素处理，以获得CPT1稳定敲除细胞系，命名为CPT1 KO。还使用药物抑制剂ST1326和依托莫昔芬（ETO）抑制HIEC-6细胞和小鼠肠类器官的CPT1酶活性，以研究CPT1在60Coγ射线照射后HIEC-6细胞存活和增殖中的功能。我们发现，照射后SD大鼠小肠中CPT1介导的FAO发生改变，特别是CPT1的表达水平和酶活性显著增加。同样，照射后小鼠肠类器官和HIEC-6细胞中CPT1的表达水平也显著增强。CPT1抑制通过降低细胞外信号调节激酶（ERK1/2）和c-Jun氨基末端激酶（JNK）途径的激活，部分降低了照射后HIEC-6细胞和小鼠肠类器官的增殖，CPT1抑制还通过下调Wnt/β-连环蛋白信号活性，部分降低了照射后小鼠肠类器官的增殖。总之，我们的研究表明，CPT1在促进照射后肠道上皮细胞增殖中起关键作用。
