Transactivation of Src, PDGF receptor, and Akt is involved in IL-1β-induced ICAM-1 expression in A549 cells

In previous study, interleukin-1 beta (IL-1 beta) has been shown to induce ICAM-I expression through MAPKs and NF-kappa B in A549 cells. In addition to these pathways, transactivation of non-receptor tyrosine kinase (Src), PDGF receptors (PDGFRs), and phosphatidylinositol 3-kinase (Pl3K)/Akt has been implicated in the expression of inflammatory genes. Here, we further investigated whether these different mechanisms participating in IL-1 beta induced ICAM-I expression in A549 cells. We initially observed that IL-1 beta-induced ICAM-I promoter activity was attenuated by the inhibitors of Src (PPI), PDGFR (AGI296), Pl3-K (LY294002 and wortmannin), and Akt (SH-5), revealed by reporter gene assay, Western blotting, and RT-PCR analyses. The involvement of Src and Pl3-K/Akt in IL-1 beta-induced ICAM-I expression was significantly attenuated by transfection of A549 cells with dominant negative plasmids of Src, p85 and Akt, respectively. Src, PDGFR, and Pl3K/Akt mediated the effects of IL-1 beta because pretreatment with PPI, AGI296, and wortmannin also abrogated IL-1 beta-stimulated Src, PDGFR, and Akt phosphorylation, respectively. Moreover, pretreatment with p300 inhibitor (curcumin) also blocked ICAM-I expression. We further confirmed that p300 was associated with ICAM-I promoter which was dynamically linked to histone H4 acetylation stimulated by IL-1 beta, determined by chromatin immunoprecipitation assay. Association of p300 and histone-H4 to ICAM-I promoter was inhibited by LY294002. Up-regulation of ICAM-I enhanced the adhesion of neutrophils onto A549 cell monolayer exposed to IL-1 beta, which was inhibited by PPI, AGI296, LY294002, wortmannin, and helenalin. These results suggested that Akt phosphorylation mediated through transactivation of Src/PDGFR promotes the transcriptional p300 activity and eventually leads to ICAM-I expression induced by IL-1 beta.