STAT3 inhibition decreases ATP-induced MUC8 gene expression in human airway epithelial cells

Background: Contact between the human pulmonary system and bacteria, viruses, or other pathogens can induce airway diseases. Although pathogen-induced mucus oversecretion and hyperproduction are frequently observed in the human respiratory tract, the molecular mechanisms of pathogen-induced mucus hypersecretion and overproduction remain unclear. The objective of this study was to investigate the physiological signaling mechanism of adenosine triphosphate (ATP)-induced MUC8 gene expression in human airway epithelial cells. Methods: Real-time reverse transcription polymerase chain reaction, a cytokine array, and a Ca 2+ concentration assay were performed to investigate the ATP/P2Y2-induced MUC8 gene expression levels in human airway epithelial cells. Results: The ATP/P2Y2 complex robustly secreted interleukin (IL)-6 in a time-dependent manner, whereas siRNA-P2Y2 did not. More-over, ATP/P2Y2 induced MUC8 gene expression. IL-6 secreted by ATP strongly elevated ATP/P2Y2-induced MUC8 gene expression compared to ATP/P2Y2. Interestingly, a specific signal transducer and activator of transcription 3 (STAT3) inhibitor, 5,15-DPP, dramatically inhibited ATP/P2Y2/IL-6-induced STAT3 phosphorylation and resulted in an approximately 5-fold decrease in MUC8 gene expression. Conclusion: We showed that IL-6-activated STAT6 is essential for ATP/P2Y2-induced MUC8 gene expression as part of inflammatory signaling by cytokines during airway inflammation. Our results provide a new molecular understanding of the signaling mechanism of MUC8 gene expression during airway inflammation.