The Effect Of Caveolin-1on Cigarette Smoke Extract-induced MUC5AC Hypersecretion

Airway mucus hypersecretion is an important regulator for the pathological progress in many chronic airway inflammatory diseases. MUC5AC is the main secretory mucin in the airway. Recent experiments showed that EGFR-PI3K cell signaling pathway plays a significant role in lipopolysaccharide or neutrophil elastase-induced MUC5AC hypersecret-ion in airway epithelial cell. Smoking is a crucial cause of airway hypersecretion in chronic obstructive pulmonary disease (COPD). We speculated that mucus hypersecretion caused by cigarette smoke extract in airway epithelial may be closely related to EGFR-PI3K signaling pathway. Caveolin-1is a membrane marker protein of caveolae, invaginations in cell membrane, which was widely expressed in a variety of cells and involved as the hub of many cell signaling pathways mediated cell physiology or pathological processes. In recent years, Caveolin-1was considered to be an important modulator of the development of airway inflammation. There was no related report about the function of caveolin-1in airway mucus hypersecretion yet. In this study we investigate the mechanism of cigarette smoke extract (CSE)-induced airway MUC5AC hypersecretion, and explore the role of caveolin-1in CSE-induced MUC5AC hyper-secretion.Objectives:To explore the effects of CSE on MUC5AC hypersecretion in airway epithelial cells. To examine the effects of caveolin-1on CSE-induced MUC5AC hypersecretion, and to investigate its molecular mechanism in CSE-induced MUC5AC hypersecretion.Methods:(1)The well cultured airway epithelial cells, HBE16cell lines, were exposed to CSE to establish mucus hypersecretion model in vitro. HBE16cell lines were pretreated by EGFR inhibitor (AG1478)10μ M for30mins or PI3K inhibitor (LY294002)10M for lh before exposure to CSE. The level of MUC5AC mRNA and protein in each were detected by RT-PCR and ELISA respectively; the level of protein for EGFR, p-EGFR, Akt and p-Akt were measured by Western Blotting.(2) HBE16cell lines were transfected with caveolin-1cDNA overexpression plasmid or pretreated by Methyl-β-cyclodextrin (MβCD)10μM for30mins before exposure to CSE. The level of MUC5AC mRNA and protein in each were detected by RT-PCR and ELISA respectively; the level of protein for caveolin-1, EGFR, p-EGFR, Akt and p-Akt were measured by Western Blotting. HBE16cells were pretreated with AG1478and LY294002respectively, and factors mentioned above were detected by related methods.Results:(1) Mucus hypersecretion model was successfully established by CSE.10%CSE treatment for24h significantly increased MUC5AC mRNA and protein in dose-and time-dependent way. P-EGFR and p-Akt protein were upregulated after CSE treatment (p<0.05). AG1478inhibited CSE induced MUC5AC hypersecretion and p-EGFR and p-Akt activation. LY294002inhibited CSE induced MUC5AC hypersecretion and p-Akt activation, but no significant changes in p-EGFR protein activation.(2) The transfection of caveolin-1cDNA plasmid increased the expression of caveolin-1and CSE-induced MUC5AC, p-EGFR, p-Akt expression. M β CD could effectively decrease the expression of caveolin-1and CSE-induced MUC5AC, p-EGFR, p-Akt expression. AG1478inhibited MUC5AC hypersecretion, p-EGFR and p-Akt activation. LY294002inhibited MUC5AC hypersecretion and p-Akt activation, but no significant changes in p-EGFR protein activation.Conclusions:(1) CSE can induce MUC5AC hypersecretion through a signaling pathway involving EGFR-PI3K-Akt.(2) Caveolin-1can promote CSE induced MUC5AC expression via EGFR-PI3K-Akt signaling pathway.