Matrix metalloproteinases (MMPs), in particular MMP-9, is induced by cytokines including IL-1 beta and contributes to airway injury and remodeling. However, the mechanisms underlying IL-1 beta-induced MMP-9 expression and cell migration in human A549 cells remain unclear. Here, we report that the IL-1 beta-induced MMP-9 gene expression was mediated through the activation of p42/p44 MAPK, p38 MAPK, and JNK1/2 in A549 cells, determined by zymographic, RT-PCR, and Western blotting. The involvement of MAPKs in the IL-1beta-induced responses was further ensured by transfection with siRNA of MEK1, p42, p38, or JNK2. Moreover, the IL-1 beta-induced MMP-9 gene expression was also mediated through the translocation of NF-kappaB (p65) into the nucleus and the degradation of I kappaB alpha. In addition, the IL-1 beta-induced c-Jun phosphorylation was reduced by pretreatment with U0126 or SP600125. IL-1 beta stimulated the transcriptional activity of wild-type MMP-9 promoter in A549 cells, which was inhibited by U0126, SB203580, SP600125, and helenalin. In contrast, IL-1 beta had no effect on the cells transfected with a NF-kappaB-mutated MMP-9 promoter construct, suggesting that NF-kappaB is required for this response. Finally, the IL-1 beta-induced MMP-9 expression led to cell migration which was attenuated by pretreatment with U0126, SB203580, SP600125, helenalin, or MMP-2/9 inhibitor. These results suggested that in A549 cells, the activation of p42/p44 MAPK, p38 MAPK, JNK1/2, NF-kappaB, and AP-1 are essential for the IL-1 beta-induced MMP-9 gene expression and cell migration.