Cross-talk between bradykinin and epidermal growth factor in regulating IL-6 production in human airway smooth muscle cells.
BACKGROUND
Bradykinin (BK), a G-protein-coupled-receptor (GPCR) agonist via the B2 receptor induces interleukin (IL)-6 expression in airway smooth muscle (ASM) cells by involving the extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathway. In some cell species, GPCR agonists have been shown to activate the ERK 1/2 pathway via transactivation of epidermal growth factor (EGF) receptor (EGFR). In this study, we tested whether there is cross-talk between BK and EGF in the regulation of IL-6 gene expression in ASM cells.


METHODS
ASM cells were treated with BK, EGF, AG-1478 and genistein. IL-6 production was analyzed by enzyme-linked immunosorbent assay (ELISA). Immunoblot study was used for detection of ERK1/2 activation. Transactivation of EGFR phosphorylation was detected by immunoprecipitation.


RESULTS
ELISA showed that EGF (10 ng/ml, 18 hr) increased IL-6 secretion (from 234 +/- 35 to 923 +/- 494 pg/ml, n = 5, p > 0.05), and significantly enhanced BK-induced IL-6 secretion (from 4383 +/- 296 to 8312 +/- 1267 pg/ml, n = 5, p < 0.05) in ASM. Moreover, AG-1478 (2 microM), reduced BK-induced IL-6 secretion by 28% and abrogated the synergic induction of IL-6 induced by BK plus EGF (from 8312 +/- 1267 to 3229 +/- 597 pg/ml, n = 5, p < 0.05). AG-1478 dual effects on IL-6 secretion induced by BK alone or BK plus EGF were also observed in cells treated with genistein, a tyrosine kinase inhibitor, and AG-825, an ErbB-2 inhibitor. Immunoblot analysis demonstrated that AG-1478 had no effect on ERK1/2 activation by BK (1 microM, 10 min). Immunoprecipitation studies showed that BK (1 muM for 2, 5 and 10 min) did not directly transactivate EGFR phosphorylation.


CONCLUSIONS
These data show that BK and EGF act in concert to regulate the expression of IL-6 in ASM cells possibly via transcriptional mechanisms involving EGFR-associated key signaling molecules.
Feng
Po-Hao
PH
Department of Thoracic Medicine, Chang Gung Memorial Hospital at Linkou, Chang Gung University College of Medicine, Taoyuan, Taiwan.
Hsiung
Te-Chih
TC
Kuo
Han-Pin
HP
Huang
Chien-Da
CD
D001920:Bradykinin / Q000494:pharmacology*; D002478:Cells, Cultured; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D066246:ErbB Receptors / Q000502:physiology; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D015850:Interleukin-6 / Q000096:biosynthesis* / Q000235:genetics; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism*; D011799:Quinazolines; D014132:Trachea / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D020032:Tyrphostins / Q000494:pharmacology
D015850:Interleukin-6; D011799:Quinazolines; D020032:Tyrphostins; C101044:RTKI cpd; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D001920:Bradykinin