Effective-compound combination inhibits the M2-like polarization of macrophages and attenuates the development of pulmonary fibrosis by increasing autophagy through mTOR signaling

Background and purpose: The M2 polarization of macrophages substantially contributes to the progression of pulmonary fibrosis (PF). Effective-compound combination (ECC), which is composed of isoliquiritigenin, icariin, nobiletin, peimine, and paeoniflorin, ameliorated bleomycin-induced PF in rats. Hence, we investigated the antiPF mechanism of ECC with a focus on the suppression of M2 polarization in macrophages in vivo and in vitro. Methods: The PF rat model was generated via the intratracheal instillation of bleomycin. Histological changes, M2 macrophages, and profibrotic mediators were detected. The M2 polarization model was generated by incubating macrophages with IL-4. Quantitative PCR and Western blotting were used to measure mRNA and protein levels, respectively. Results: ECC attenuated bleomycin-induced PF in rats, which might be associated with reduced macrophage infiltration, M2 polarization, and profibrotic mediator expression. Furthermore, ECC significantly suppressed M2 polarization in IL-4-treated macrophages, which was accompanied by the upregulation of autophagy. An autophagy inhibitor abrogated the inhibitory effect of ECC on M2 polarization. In addition, ECC decreased the levels of p-p70S6K/p-4EBP and p-AKT473/p-GSK3 ss, which are critical regulators of autophagy. Conclusion: ECC can ameliorate PF, which might be associated with the inhibition of M2 polarization through the promotion of autophagy via mTOR signaling suppression.