Scutellarin is a flavonoid extracted from a traditional Chinese herb, Erigeron breviscapus. The present study investigated the effect of scutellarin on MUC5AC mucin production and the possible mechanism. Human bronchial epithelial 16 (HBE16) cells were pretreated with scutellarin for 60 min, and then exposed to human neutrophil elastase (HNE) or interleukin (IL)-13 for 12 hr. RT-PCR and ELISA were performed to measure the amount of MUC5AC mucin production. The results showed that scutellarin inhibited MUC5AC expression both in mRNA and protein level induced by HNE in a concentration-dependent manner. However, scutellarin failed to inhibit MUC5AC mucin production induced by IL-13. To investigate the intracellular mechanisms associated with the effect of scutellarin on MUC5AC mucin production, western blotting was carried out to examine the phosphorylation of protein kinase C (PKC), signal transducer and activator of transcription 6 (STAT6) and extracellular signal-regulated kinase 1/2 (ERK1/2). The phosphorylation of PKC and ERK1/2 was attenuated after treatment with scutellarin, whereas STAT6 was not significantly affected. Therefore, it is suggested that scutellarin down-regulates MUC5AC mucin production on HBE16 cells via ERK-dependent and PKC-dependent pathways.
Apigenin/chemistry/*pharmacology ; Cells, Cultured ; Dose-Response Relationship, Drug ; Down-Regulation ; Epithelial Cells/*drug effects/metabolism ; Erigeron/chemistry ; Glucuronic Acids/chemistry/*pharmacology ; Humans ; Interleukin-13/*pharmacology ; Leukocyte Elastase/*pharmacology ; Mitogen-Activated Protein Kinase 1/metabolism ; Mitogen-Activated Protein Kinase 3/metabolism ; Mucin 5AC/genetics/*metabolism ; Phosphorylation ; Protein Kinase C/metabolism ; Respiratory Mucosa/drug effects/*metabolism ; STAT6 Transcription Factor/metabolism ; Signal Transduction

<p>OBJECTIVETo investigate the effect of interleukin-13 (IL-13) on mucus secretion in vivo and the possible mechanism.p><p>METHODSThe SD rats were randomly divided into control group, IL-13 group and IL-13 plus SP600125 group. The phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2), c-Jun N-terminal kinase 1/2 (JNK1/2) and the level of MUC5AC in the lung tissues were examined using Western blotting. RT-PCR was performed to examine the mRNA level of STAT4 and STAT6, and electrophoretic mobility shift assays (EMSA) was used to detect the DNA-binding activities of Forkhead box a2 (FOXA2) and activator protein-1 (AP-1).p><p>RESULTSIL-13 caused a significant increase in MUC5AC and p-JNK1/2 expression, but did not affect the phosphorylation of ERK1/2. The expression of MUC5AC was attenuated after treatment with SP600125. A significant increase in STAT6 was observed in IL-13 group compared with that in the control group, whereas the expression of STAT4 mRNA was not significantly affected. The DNA-binding activity of FOXA2 was down-regulated after IL-13 exposure, which did not affect the DNA-binding activity of AP-1.p><p>CONCLUSIONIL-13 down-regulates mucus secretion via STAT6-FOXA2 pathway in vitro.p>
Animals ; Bronchi ; secretion ; Female ; Hepatocyte Nuclear Factor 3-beta ; genetics ; metabolism ; Interleukin-13 ; pharmacology ; Male ; Mucin 5AC ; metabolism ; Mucus ; secretion ; RNA, Messenger ; genetics ; metabolism ; Random Allocation ; Rats ; Rats, Sprague-Dawley ; STAT6 Transcription Factor ; genetics ; metabolism ; Signal Transduction ; drug effects

To explore the role of cortical actin-binding protein (cortactin) in shear stress-induced mucin (MUC) 5AC secretion in human airway epithelial cells and the effect of phosphorylation of cortactin at different sites.
 Methods: HBE16 airway epithelial cells were cultured, and then transfected with mutation carrier, such as pEGFP-N1-cortactin (Cort), pEGFP-N1-Cort-Y421A, pEGFP-N1-Cort-Y470A and pEGFP-N1-Cort-Y486A. The cells were divided into a normal control group, a shear stress group, a shear stress + pEGFP-N1 group, a shear stress + PEGFP-N1-Cort group, a shear stress + pEGFP-N1-Cort-Y421A group, a shear stress + pEGFP-N1-Cort-Y470A group, and a shear stress + pEGFP-N1-Cort-Y486A group. The shear stress were set at 4 dynes/cm2. The levels of MUC5AC protein and mRNA in cells and culture supernatant were assayed with enzyme-linked immunosorbent assay (ELISA) and real-time PCR. The cortactin and phosphorylated cortactin were detected by Western blot. F-actin was stained by fluorescein isothiocyanate (FITC)-phalloidin.
 Results: There was an obvious increase of phosphorylated cortactin in cells exposed to 4 dynes/cm2 of shear stress for 30 min, which reached climax at 2 hours concomitant with elevation of MUC5AC protein production and mRNA expression in the different experiment groups (all P<0.05). Compared with single shear stress-stimulated group, MUC5AC in supernatant was increased obviously, and the distribution of F-actin in cytomembrane was also increased in the pEGFP-N1-Cort group (both P<0.05), while there were no changes in the MUC5AC protein and mRNA levels in cytoplasm. Compared with the shear stress+pEGFP-N1-Cort group, the MUC5AC protein in the culture supernatant was decreased, and the polymerization of F-actin at cell membranes were also attenuated in the shear stress+pEGFP-N1-Cort-Y421A group and the shear stress + pEGFP-N1-Cort-Y470A group (both P<0.05), while there was no significant effect in the shear stress + pEGFP-N1-Cort-Y486A group (P>0.05).
 Conclusion: Cortactin is involved in shear stress-mediated MUC5AC secretion in human airway epithelial cells, and the phosphorylated site of Tyr421 and Tyr470 may play an important role in it.
Cortactin ; Epithelial Cells ; Humans ; Mucin 5AC ; Mucus ; Phosphorylation