Mucus hypersecretion and goblet cell hyperplasia are common features that characterize asthma. IL-13 increases mucin (MUC) 5AC, the major component of airway mucus, in airway epithelial cells. According to the literature, IL-13 receptor activation leads to STAT6 activation and consequent induction of chloride channel accessory 1 (CLCA1) gene expression, associated with the induction of MUC5AC. Heme oxygenase-1 (HO-1) is an enzyme that catalyzes oxidation of heme to biliverdin, and has anti-inflammatory and anti-oxidant properties. We examined the effects of HO-1 on mucin production and goblet cell hyperplasia induced by IL-13. Moreover, we assessed the cell signaling intermediates that appear to be responsible for mucin production. Normal human bronchial epithelial (NHBE) cells were grown at air liquid interface (ALI) in the presence or absence of IL-13 and hemin, a HO-1 inducer, for 14 days. Protein concentration was analyzed using ELISA, and mRNA expression was examined by real-time PCR. Histochemical analysis was performed using HE staining, and Western blotting was performed to evaluate signaling transduction pathway. Hemin (4 μM) significantly increased HO-1 protein expression (p < 0.01) and HO-1 mRNA expression (p < 0.001). IL-13 significantly increased goblet cells, MUC5AC protein secretion (p < 0.01) and MUC5AC mRNA (p < 0.001), and these were decreased by hemin by way of HO-1. Tin protoporphyrin (SnPP)-IX, a HO-1 inhibitor, blocked the effect of hemin restoring MUC5AC protein secretion (p < 0.05) and goblet cell hyperplasia. Hemin decreased the expression of CLCA1 mRNA (p < 0.05) and it was reversed by SnPP-IX, but could not suppress IL-13-induced phosphorylation of STAT6 or SAM pointed domain-containing ETS transcription factor (SPDEF) and Forkhead box A2 (FOXA2) mRNA expression.
In summary, HO-1 overexpression suppressed IL-13-induced goblet cell hyperplasia and MUC5AC production, and involvement of CLCA1 in the mechanism was suggested.