MAP kinases mediate FGF-induced expression and release of VEGF in human airway smooth muscle cells: The role of azithromycin

Background: Fibroblast growth factors, FGF-1, FGF-2 and vascular endothelial growth factor (VEGF) are elevated in chronic inflamed airways. Airway smooth muscle (ASM) cells are known to synthesize VEGF. We investigated the contribution of FGF-1/-2 on the VEGF production in ASM cells, the involvement of mitogen-activated protein kinases (MAPK) and the modulatory effects of azithromycin and dexamethasone. Methods: Human ASM cells were treated with 10ng/ml of FGF-1 or FGF-2. Specific blockers for ERK1/2 MAPK (U0126), p38 MAPK (SB239063), JNK (curcumin), dexamethasone or azithromycin were added 30 minutes prior to stimulation. Expression of VEGF (VEGF-A, VEGF 121 and VEGF 165 ) was assessed by quantitative PCR, VEGF release by ELISA and MAPK phosphorylation by Western blotting. Results: FGF-1/-2 upregulated mRNA expression of VEGF (VEGF-A, VEGF 121 and VEGF 165 ) and its release by 1.8 fold (FGF-1) and 6.1 fold (FGF-2). Transient increase in ERK1/2 MAPK and p38 MAPK phosphorylation and subsequent release of VEGF from FGF-1/-2 treated human ASM cells was inhibited by respective blockers. Furthermore, both dexamethasone and azithromycin reduced the VEGF secretion mediated by the p38 MAPK pathway. Conclusion: Our Results demonstrate that FGF-1 and FGF-2 upregulate VEGF production via ERK1/2 MAPK and p38 MAPK pathways. The anti-angiogeneic effect of dexamethasone and azithromycin may potentially contribute to tackle VEGF-mediated vascular remodelling in chronic airway diseases.