MicroRNA-21 protects against cardiac hypoxia/reoxygenation injury by inhibiting excessive autophagy in H9c2 cells via the Akt/mTOR pathway

J Cell Mol Med. 2017 Mar;21(3):467-474. doi: 10.1111/jcmm.12990. Epub 2016 Sep 29.

Abstract

MicroRNAs and autophagy play critical roles in cardiac hypoxia/reoxygenation (H/R)-induced injury. Here, we investigated the function of miR-21 in regulating autophagy and identified the potential molecular mechanisms involved. To determine the role of miR-21 in regulating autophagy, H9c2 cells were divided into the following six groups: control group, H/R group, (miR-21+ H/R) group, (miR-21-negative control + H/R) group, (BEZ235+ H/R) group and (miR-21+ BEZ235+ H/R) group. The cells underwent hypoxia for 1 hr and reoxygenation for 3 hrs. Cell count kit-8 was used to evaluate cell function and apoptosis was analysed by Western blotting. Western blotting and transmission electron microscopy were used to investigate autophagy. We found that miR-21 expression was down-regulated, and autophagy was remarkably increased in H9c2 cells during H/R injury. Overexpression of miR-21 with a miR-21 precursor significantly inhibited autophagic activity and decreased apoptosis, accompanied by the activation of the AKT/mTOR pathway. In addition, treatment with BEZ235, a novel dual Akt/mTOR inhibitor, resulted in a significant increase in autophagy and apoptosis. However, we found that miR-21-mediated inhibition of apoptosis and autophagy was partly independent of Akt/mTOR activation, as demonstrated in cells treated with both miR-21 and BEZ235. We showed that miR-21 could inhibit H/R-induced autophagy and apoptosis, which may be at least partially mediated by the Akt/mTOR signalling pathway.

Keywords: H9c2 cells; apoptosis; autophagy; hypoxia/reoxygenation; miR-21.

MeSH terms

  • Animals
  • Apoptosis / genetics
  • Autophagy / genetics*
  • Cell Hypoxia / genetics*
  • Cell Line
  • Down-Regulation / genetics
  • MicroRNAs / genetics*
  • Myocytes, Cardiac / pathology*
  • Proto-Oncogene Proteins c-akt / genetics*
  • Rats
  • Signal Transduction / genetics
  • TOR Serine-Threonine Kinases / genetics*

Substances

  • MicroRNAs
  • mirn21 microRNA, rat
  • mTOR protein, rat
  • Proto-Oncogene Proteins c-akt
  • TOR Serine-Threonine Kinases