BACKGROUND AND PURPOSE Interleukin (IL)-1β-induced matrix metalloproteinase (MMP-9) expression is regulated by mitogen activated protein kinases (MAPKs) and NF-κB. IL-1β also stimulates transactivation of growth factor receptors and phosphatidylinositol 3-kinase (PI3K)/Akt., leading to the expression of inflammatory proteins. Here, we investigated whether these transactivation mechanisms participated in IL-1β-induced MMP-9 expression in A549 cells.
EXPERIMENTAL APPROACH A549 cells were treated with/without pharmacological inhibitors and neutralizing antibody or transfected with dominant negative mutants and siRNA of particular protein kinases before stimulation with IL-1β. Cell migration was measured by in vitro scratch assay. Expression and enzymatic activity of MMP-9 were analysed by Western blot and gelatin zymography. Transcriptional activity of MMP-9 was analysed by RT-PCR, chromatin immunoprecipitation and promoter assays.
KEY RESULTS Inhibition of MMP-9 expression by inhibitors of Src (PP1), platelet-derived growth factor (PDGF) receptor and epithelial growth factor (EGF) receptor or transfection with siRNA for Src and Akt prevented IL-1β-induced migration of A549 cells. These tyrosine kinases were involved through phosphorylation of Src, PDGF, or EGF receptors (EGFRs) via the formation of Src/PDGFR or Src/EGFR complexes, attenuated by PP1. IL-1β-induced MMP-9 expression through EGFR transactivation was diminished by inhibitors of MMPs and heparin-binding EGF-like factor (HB-EGF), or a neutralizing HB-EGF antibody. IL-1β-stimulated activation and translocation of Akt and NF-κB (p65); the recruitment of activated NF-κB (p65) to the MMP-9 promoter region was attenuated by LY294002.
CONCLUSIONS AND IMPLICATIONS IL-1β-induced MMP-9 expression and cell migration was mediated through c-Src-dependent transactivation of EGFR/PDGFR/PI3K/Akt linking to the NF-κB pathway in A549 cells.