Effects of baicalin on expression of mucin 5AC and cystic fibrosis transmembrane conductance regulator in airway epithelium through NF-κB signaling pathway

Objective To investigate the mechanism of baicalin in improving pathological airway mucus by regulating the expression of airway epithelial mucus regulators mucin 5AC (MUC5AC) and cystic fibrosis transmembrane conductance regulator (CFTR) through nuclear factor κB (NF-κB) signaling pathway. Methods MTT assay was used to detect the effects of different concentrations of baicalin on the viability of human lung cancer H292 cells in order to determine the proper dose of baicalin for subsequent experiments. After H292 cells were induced by IL-1β to establish in vitro inflammatory cell model of mucus hypersecretion, the cells were divided into blank control group, model group, NF-κB inhibitor group (PDTC group, 100 μmol/L) and baicalin group (200 μg/mL). After 24 h of drug intervention, the contents of MUC5AC, IL-8, and TNF-α in the culture supernatant and the levels of MUC5AC and CFTR in the cytoplasm of each group were detected by ELISA. Real-time fluorescent quantitative PCR was adopted to detect the mRNA expression of MUC5AC and CFTR. Western blotting was performed to test the expression of p65 and IκB (inhibitor of NF-κB). Results The results of MTT assay showed that 200 μg/mL was a safe concentration of baicalin for subsequent experiments, with cell viability larger than 80%. As compared with the blank control group, the protein expression of MUC5AC, IL-8, TNF-α, p65 and the mRNA level of MUC5AC in culture supernatant and cytoplasm were all significantly increased in the model group (P < 0.05), while the expression of IκB and CFTR proteins as well as the CFTR mRNA level were remarkably decreased (P < 0.05). When compared with the model group, the PDTC group presented lower level of MUC5AC secretion, declined protein levels of IL-8, TNF-α and p65, as well as MUC5AC mRNA in the culture supernatant (P < 0.05), while higher protein expression of MUC5AC, CFTR and IκB in the cytoplasm, along with elevated mRNA level of CFTR (P < 0.05). In terms of the baicalin group, the secretion levels of MUC5AC, IL-8 and TNF-α were greatly diminished in culture supernatant (P < 0.01) as compared with the model group, whereas the expression of IκB as well as the protein and mRNA levels of CFTR notably improved (P < 0.01), and there was no significant difference in MUC5AC mRNA expression. Conclusion Baicalin reduces MUC5AC secretion and increases CFTR expression by inhibiting the activity of NF-κB, and thus attenuates airway inflammation.