STAT3 knockdown alleviates the effects of miR-4485 inhibition on H1N1-induced A549 cell injury. (A) Western blotting demonstrated STAT3 knockdown in A549 cells following transfection with si-STAT3. (B) Phosphorylated and total protein levels of STAT3, PI3K, AKT and mTOR and the ratio of p-STAT3/STAT3, p-PI3K/PI3K, p-AKT/AKT and p-mTOR/mTOR in A549 cells. (C) Cell Counting Kit-8 cell viability assay, (D) TUNEL apoptosis detection (magnification ×200), (E) protein expression levels of Bax and Bcl-2, and (F) production of IL-6, TNF-α and IL-1β in A549 cells infected with or without H1N1 following co-transfection with miR-4485 inhibitor and/or si-STAT3. The experiments were performed three times and the data are presented as the mean ± SD. **P<0.05 vs. control group; ##P<0.05 vs. H1N1 + si-NC + inhibitor NC group; ΔΔP<0.01 vs. H1N1 + si-NC + miR-4485 inhibitor group. miR-4485, microRNA-4485; Mut, mutant; NC, negative control; OD, optical density; p-, phosphorylated; si, small interfering RNA.