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Secretoneurin Induces Airway Mucus Hypersecretion by Enhancing the Binding of EGF to NRP1

Aims: Secretoneurin(SN), a neuropeptide, has been considered a reliable marker of allergenic stimulation. However, the relationship between SN and the secretion of airway mucin remains unclear. In this study, we aimed to examine the in vitro relationship between SN and airway mucin over synthesis, as well as the signaling pathways involved. Methods and Results: Exogenous SN was added to two human airway epithelial cell lines (16HBE and NCI-H292). Measured by real-time quantitative polymerase chain reaction (qPCR) and enzyme-linked immuno sorbent assay (ELISA) respectively, the intracellular mucin(MUC)5AC mRNA and MUC5AC protein of culture supernates exhibited a time- and dose-dependent increase after stimulation of SN. Based on the evidence of an increased phosphorylation of ERK1/2 induced by exogenous SN, we performed the radioactive binding assay. We failed to find direct binding of SN to either epidermal growth factor receptor (EGFR) or Neuropilin-1(NRP1), the co-receptor of EGFR. But we detected an enhanced binding of EGF to NRP1 in the two airway epithelial cell lines induced by exogenous SN. Either EGF neutralizing antibody or MEK specific inhibitor (PD-98059) could attenuate the over synthesis of MUC5AC induced by exogenous SN, indicating an endogenous EGF dependent mechanism in MUC5AC over synthesis induced by SN. Conclusions: We conclude that SN induces MUC5AC hypersecretion in a dose- and time-dependent manner; moreover, the MUC5AC over synthesis induced by SN is strongly associated with the enhanced binding of EGF to NRP1 and the activation of EGFR and ERK1/2 subsequently.