Up-regulation of miRNA-221 inhibits hypoxia/reoxygenation-induced autophagy through the DDIT4/mTORC1 and Tp53inp1/p62 pathways

• Published in: Biochemical and biophysical research communications Vol. 474; no. 1; pp. 168 - 174
• Main Authors: Chen, Qiying, Zhou, Yue, Richards, A. Mark, Wang, Peipei
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 20.05.2016
• Subjects: Animals; Autophagy; cell viability; Cells, Cultured; Ddit4; hypoxia; Ischemia/reperfusion; Mechanistic Target of Rapamycin Complex 1; messenger RNA; microRNA; MicroRNAs - metabolism; miRNA-221; molecular cloning; Multiprotein Complexes - metabolism; myoblasts; myocardial infarction; Myocardial Reperfusion Injury - metabolism; Myocardial Reperfusion Injury - pathology; myocytes; Nuclear Proteins - metabolism; oxygen; protective effect; Rats; Signal Transduction; TOR Serine-Threonine Kinases - metabolism; Tp53inp1; Transcription Factors - metabolism; Up-Regulation; Ddit4; miRNA-221; Tp53inp1; Autophagy; Ischemia/reperfusion
• ISSN: 0006-291X; 1090-2104; 1090-2104
• DOI: 10.1016/j.bbrc.2016.04.090

Timely reperfusion in acute myocardial infarction has improved clinical outcomes but the benefits are partially offset by ischemia-reperfusion injury (I/R). MiRNA regulates mRNA of multiple effectors within injury and survival cell signaling pathways. We have previously reported the protective effects of miRNA-221 in I/R injury. The purpose of this study was to explore the mechanisms underlying cardioprotection of miR-221. Myoblast H9c2 and neonatal rat ventricular myocytes (NRVM) were subjected to 0.2% O2 hypoxia followed by 2 h of re-oxygenation (H/R). In gain-and-loss function studies through transfections of miR-221 mimic (miR-221) and inhibitor (miR-221-i), the protective effects of miR-221 were confirmed as assessed by increased cell metabolic activity (WST-1) and decreased LDH release. Autophagy was assessed by GFP-LC3 labeling of autophagosome formation, LC3 and p62 measurements. Co-immuno-precipitation and specific gene cloning and function were used to identify the pathways underpinning miR-221 effects. MiR-221 significantly reduced H/R injury in association with inhibition of autophagy. Underlying mechanisms include (1) down-regulation of Ddit4 (disinhibiting the mTORC1/p-4EBP1 pathway) which inhibits autophagosome formation (2) down-regulation of Tp53inp1 (with reduced Tp53inp1/p62 complex formation) which inhibits autophagosome degradation. In conclusion, miRNA-221 exerts cytoprotective effects in hypoxia-reoxygenation injury in association with alterations in autophagic cell injury. Mir-221 may constitute is a novel therapeutic target in the treatment of cardiac I/R injury. [Display omitted] •miRNA-221 exerts cytoprotective effects in hypoxia-reoxygenation injury (H/R).•The protective effects are due to the inhibition of H/R-induced autophagy.•The inhibition of autophagy is through regulating Ddit4/mTORC1 and Tp53inp1/p62.