TNF-α Induces Matrix Metalloproteinase-9 Expression in A549 Cells: Role of TNFR1/TRAF2/PKCα-Dependent Signaling Pathways

Matrix metalloproteinases (MMPs), in particular MMP-9, have been shown to be induced by cytokines, including TNF-alpha. and contributes to airway inflammation. However, the mechanisms underlying TNF-alpha-induced MMP-9 expression in human A549 cells remain unclear. Here, we report that TNF-a-induced MMP-9 gene expression was mediated through the TNFR1/TRAF2/PKC alpha-dependent signaling pathways in A549 cells, determined by zymographic, RT-PCR, and Western blotting analyses. TNF-a-induced MMP-9 expression was reduced by pretreatment with a TNFR Ab. Furthermore, TNF-alpha-induced TNFR I and TRAF2 complex formation was revealed by immunoprecipitation using an anti-TNFR1 Ab followed by Western blot analysis against an anti-TRAF2 or anti-TNFR1 Ab. In addition, TNF-alpha-induced MMP-9 expression was also reduced by pretreatment with the inhibitor of PKC alpha (Go6983), c-Src (PP I), EGFR (AG1478), or PI3K (LY294002) or transfection with siRNAs of PKC alpha, Src, EGFR, Akt, p65, p300, and c-Jun. On the other hand, TNF-alpha stimulated the phosphorylation of c-Src, EGFR, Akt, JNK1/2, and c-Jun, which were inhibited by pretreatment with Go6983. We also showed that TNF-a induced Akt translocation and the formation of an Akt/p65/p300 complex. Pretreatment with the inhibitor of JNK1/2 (SP600125) but not the inhibitor of MEK1/2 (U0126), p38 MAPK (SB202190), or PI3K (LY294002), markedly inhibited TNF-a-induced c-Jun mRNA levels. Taken together, these data suggest that in A549 cells, TNF-a induces MMP-9 expression via the TNFR1/TRAF2/PKCa-dependent JNK1/2/c-Jun and c-Src/EGFR/PI3K/Akt pathways. J. Cell. Physiol. 224: 454-464, 2010. (C) 2010 Wiley-Liss, Inc.