Induction of human beta-defensin 2 (HBD-2) by interleukin-1beta (IL-1beta) in epithelial cells has been reported. However, the mechanism by which IL-1beta up-regulates HBD-2 remains poorly understood. In this study, we investigated the effect of IL-1beta on induction of HBD-2 in A549 cells. IL-1beta markedly increased HBD-2 mRNA expression in concentration- and time-dependent manners. HBD-2 mRNA expression in response to IL-1beta was attenuated by pretreatment of GF109203X, Go6976, and staurosporine [inhibitors of protein kinase C (PKC)], SB203580 [an inhibitor of p38 mitogen-activated protein kinase (MAPK)], SP600125 [an inhibitor of c-Jun N-terminal kinase (JNK)], and LY294002 [an inhibitor of phosphatidylinositol-3-kinase (PI3K)], but not PD98059 [an inhibitor of extracellular signal-regulated kinase (ERK)], suggesting involvement of PKC, p38 MAPK, JNK, and PI3K in this response. Interestingly, IL-1beta induced nuclear factor-kappaB (NF-kappaB) activation in A549 cells, which was shown by increased nuclear translocation of p65 NF-kappaB and degradation of IkappaB-alpha. Importantly, IL-1beta-induced HBD-2 mRNA expression was inhibited by blockage of NF-kappaB activation using NF-kappaB inhibitors, including pyrrolidine dithiocarbamate and MG132. Specifically, IL-1beta-induced nuclear translocation of NF-kappaB was in part attenuated by LY294002, but not by GF109203X, SB203580, and SP600125, suggesting PI3K-dependent nuclear translocation of NF-kappaB in response to IL-1beta. Together, these results suggest that IL-1beta induces HBD-2 mRNA expression in A549 cells, and the induction seems to be at least in part mediated through activation of NF-kappaB transcription factor as well as activation of signaling proteins of PKC, p38 MAPK, JNK, and PI3K, but not ERK.