Anti-fibrosis activity of quercetin attenuates rabbit tracheal stenosis via the TGF-β/AKT/mTOR signaling pathway

This study aimed to explore the possible mechanism of trauma-induced laryngotracheal stenosis and potential protective and therapeutic efficacy of quercetin on trauma-induced laryngotracheal stenosis.The expression and activity of fibrotic factors [interleukin (IL)-6, IL-8, autophagy related 5 (ATG5), collagen (COL)-1, tumor growth factor (TGF)-β COL-3, microtubule-associated proteins 1A/1B light chain 3A (LC3), and vascular endothelial growth factor (VEGF)] and fibrotic signaling mediators [mammalian target of rapamycin (mTOR) and phosphorylated AKT (pAKT)] were detected by real-time quantitative PCR (qRT-PCR), ELISA, Western blot, and immunohistochemical staining, respectively, in the lipopolysaccharide (LPS)-induced WI-38 (a human embryonic lung fibroblast cell line) cellular fibrotic model and a trauma-induced rabbit tracheal stenosis model, with and without quercetin treatment.Pre-treatment with quercetin significantly reversed the LPS-induced upregulation of pro-fibrotic factors (IL-6, IL-8, COL-1, COL-3, LC3) and fibrotic signaling mediators (mTOR and AKT), and it induced the downregulation of ATG5 in the WI-38 cells. Furthermore, the anti-fibrotic activity of quercetin was confirmed in the trauma-induced rabbit tracheal stenosis model. Thus, the nasogastric administration of quercetin attenuated the tracheal stenosis of the rabbit tracheal stenosis model, in addition to effectively reversing an increase in pro-fibrotic factors (VEGF, IL-6, TGF-β, COL-1, and COL-3) and fibrotic signaling mediators (mTOR and AKT), as well as downregulating ATG5 of the rabbit tracheal stenosis model.Quercetin exhibits anti-fibrotic activity by inhibiting pro-fibrotic factors and AKT/mTOR signaling pathway, in addition to activating autophagy activity. This study provided experimental evidence supporting the application of quercetin in tracheal stenosis, clinically.