Chen Rui, Wang Bin, Chen Ling, Cai Dunpeng, Li Bing, Chen Chuanxiang, Huang Enping, Liu Chao, Lin Zhoumeng, Xie Wei-Bing, Wang Huijun
Department of Forensic Medicine, School of Basic Medical Science, Southern Medical University, Guangzhou 510515, People's Republic of China; Department of Forensic Medicine, Guangdong Medical University, Dongguan 523808, People's Republic of China.
Department of Forensic Medicine, School of Basic Medical Science, Southern Medical University, Guangzhou 510515, People's Republic of China.
Toxicol Appl Pharmacol. 2016 Mar 15;295:1-11. doi: 10.1016/j.taap.2016.01.017. Epub 2016 Jan 26.
Methamphetamine (METH) is an amphetamine-like psychostimulant that is commonly abused. Previous studies have shown that METH can induce damages to the nervous system and recent studies suggest that METH can also cause adverse and potentially lethal effects on the cardiovascular system. Recently, we demonstrated that DNA damage-inducible transcript 4 (DDIT4) regulates METH-induced neurotoxicity. However, the role of DDIT4 in METH-induced cardiotoxicity remains unknown. We hypothesized that DDIT4 may mediate METH-induced autophagy and apoptosis in cardiomyocytes. To test the hypothesis, we examined DDIT4 protein expression in cardiomyocytes and in heart tissues of rats exposed to METH with Western blotting. We also determined the effects on METH-induced autophagy and apoptosis after silencing DDIT4 expression with synthetic siRNA with or without pretreatment of a mTOR inhibitor rapamycin in cardiomyocytes using Western blot analysis, fluorescence microscopy and TUNEL staining. Our results showed that METH exposure increased DDIT4 expression and decreased phosphorylation of mTOR that was accompanied with increased autophagy and apoptosis both in vitro and in vivo. These effects were normalized after silencing DDIT4. On the other hand, rapamycin promoted METH-induced autophagy and apoptosis in DDIT4 knockdown cardiomyocytes. These results suggest that DDIT4 mediates METH-induced autophagy and apoptosis through mTOR signaling pathway in cardiomyocytes.
甲基苯丙胺（METH）是一种类似苯丙胺的精神兴奋剂，常被滥用。先前的研究表明，METH可诱导对神经系统的损害，最近的研究表明，METH对心血管系统也可产生不良和潜在的致命影响。最近，我们证明DNA损伤诱导转录物4（DDIT4）调节METH诱导的神经毒性。然而，DDIT4在METH诱导的心脏毒性中的作用仍然未知。我们假设DDIT4可能介导METH诱导的心肌细胞自噬和凋亡。为了验证这一假设，我们用蛋白质印迹法检测了暴露于METH的大鼠心肌细胞和心脏组织中DDIT4蛋白的表达。我们还使用蛋白质印迹分析、荧光显微镜和TUNEL染色，在心肌细胞中用合成的小干扰RNA沉默DDIT4表达，在有或没有mTOR抑制剂雷帕霉素预处理的情况下，确定其对METH诱导的自噬和凋亡的影响。我们的结果表明，METH暴露增加了DDIT4的表达，并降低了mTOR的磷酸化，这在体外和体内均伴随着自噬和凋亡的增加。沉默DDIT4后，这些影响恢复正常。另一方面，雷帕霉素在DDIT4敲低的心肌细胞中促进了METH诱导的自噬和凋亡。这些结果表明，DDIT4通过mTOR信号通路介导METH诱导的心肌细胞自噬和凋亡。
