METTL3-mediated m6A Modification Promotes miR-221-3p Expression to Exacerbate Ischemia/Reperfusion-Induced Acute Lung Injury.

Ischemia/reperfusion (I/R)-induced acute lung injury (ALI) represents a prevalent pulmonary pathology. The N6-methyladenosine (m6A) RNA modification is integral in regulating numerous biological processes across various human diseases through the modulation of gene expression. Nevertheless, the precise role and underlying molecular mechanisms of m6A modifications in ALI remain inadequately understood. This study aimed to elucidate the impact of RNA methyltransferase 3 (METTL3)-mediated m6A modification of miR-221-3p on the progression of I/R-induced ALI. Our initial findings demonstrated an upregulation of m6A levels and METTL3 expression in I/R-induced ALI in murine models and hypoxia/reoxygenation (H/R)-induced murine lung epithelial (MLE)-12 cells. Inhibition of METTL3 was observed to reverse H/R-induced apoptotic cell death, oxidative stress, and inflammatory cytokine secretion. Furthermore, METTL3 was found to enhance the expression of miR-221-3p in an m6A-dependent manner, thereby contributing to ALI pathogenesis. In addition, miR-221-3p was shown to negatively regulate PTEN expression, while METTL3 facilitated phosphorylated AKT expression via the miR-221-3p/PTEN axis. Functional experiments further revealed that the downregulation of PTEN negated the inhibitory effects of METTL3 knockdown in H/R-treated MLE-12 cells. In conclusion, our study demonstrates that the METTL3-mediated m6A modification of miR-221-3p exacerbates ALI through modulation of the PTEN/AKT pathway. Therapeutic strategies aimed at targeting the METTL3/m6A/miR-221-3p/PTEN/AKT axis may offer a promising approach to mitigate I/R-induced ALI.