MicroRNA-21-5p regulates autophagy and apoptosis via the activation of the PI3K/AKT/mTOR signaling pathway and reducing HO-induced damage in primary AEC-II.

OBJECTIVE

We examined whether miR-21-5p activates the PI3K/AKT/mTOR signaling pathway, thereby inhibiting autophagy and apoptosis induced by HO in AEC II cells.

INTRODUCTION

MicroRNA and autophagy play crucial roles in important biological processes during hyperoxia-induced acute lung injury. Located on chromosome 17q23.1, miR-21-5p, as a critical component of the miRNAs family, significantly contributes to the regulation of cell growth, apoptosis, and autophagy. However, the underlying mechanism through which miR-21-5p suppresses HO-induced autophagy and apoptosis of primary AEC-II in vitro remains to be fully elucidated.

METHODS

To investigate the regulatory role of miR-21-5p in autophagy, primary type II alveolar epithelial cells (AEC-II) were isolated from rat lung tissue and subjected to 0.5 mmol/L HO in a cell culture environment to simulate hyperoxia-induced acute lung injury. Cell viability was detected by cell counting Kit 8. Reactive oxygen species and apoptosis were detected by flow cytometry. Autophagy levels in AEC-II were evaluated by autophagic double marker method. The expressions of apoptosis and autophagy related proteins were detected by Western blotting.

RESULTS

We found that in the process of HO injury of AEC-II, the level of autophagy flow was up-regulated and the expression of miR-21-5p was down-regulated. Overexpression of miR-21-5p can significantly reduce the level of autophagy flow, inhibit apoptosis, and activate the AKT/mTOR signaling pathway.We pretreated with rapamycin, an mTOR inhibitor, to block the biological effects of miR-21-5p. In addition, pretreatment with MHY1485, an mTOR activator, inhibited AEC-II autophagy flow levels and increased apoptosis.

CONCLUSION

In summary, miR-21-5p can inhibit HO-induced AEC-II apoptosis and autophagy flow, which is partially mediated by the AKT/mTOR signaling pathway.MiR-21-5p could be used as both a clinical biomarker and a promising molecular target in patients with HALI.