TNF-α plays a critical mediator in the pathogenesis of chronic heart failure contributing to cardiac remodeling and peripheral vascular disturbances. The implication of TNF-α in inflammatory responses has been shown to be mediated through up-regulation of inflammatory genes, including matrix metalloproteinase-9 (MMP-9). However, the detailed mechanisms of TNF-α-induced MMP-9 expression are largely unclear in the heart cells. Here, we demonstrated that in rat embryonic-heart derived H9c2 cells, TNF-α could induce MMP-9 mRNA expression associated with an increase in the secretion of MMP-9, determined by real-time PCR, zymography, and promoter activity assays. TNF-α-mediated responses were attenuated by pretreatment with the inhibitor of c-Src (PP1), EGFR (AG1478), PDGFR (AG1296), PI3K (LY294002), Akt (SH-5), MEK1/2 (U0126), p38 MAPK (SB202190), JNK1/2 (SP600125), or AP-1 (Tanshinone IIA) and transfection with siRNA of c-Src, EGFR, PDGFR, p110, Akt, or c-Jun. TNF-α stimulated c-Src, PDGFR, and EGFR phosphorylation, which were reduced by PP1. In addition, TNF-α-stimulated Akt phosphorylation was inhibited by PP1, AG1478, AG1296, or LY294002. We further demonstrated that TNF-α markedly stimulated p38 MAPK, p42/p44 MAPK, and JNK1/2 phosphorylation via a c-Src/EGFR, PDGFR/PI3 K/Akt pathway. Finally, we showed that, in H9c2 cells, TNF-α-stimulated AP-1 promoter activity, c-Jun mRNA expression, and c-Jun phosphorylation were attenuated by PP1, AG1478, AG1296, LY294002, SB202190, SP600125, or U0126. These results suggested that TNF-α-induced MMP-9 expression is mediated through a c-Src/EGFR, PDGFR/PI3K/Akt/MAPKs/AP-1 cascade in H9c2 cells. Consequently, MMP-9 induction may contribute to cell migration and cardiovascular inflammation.
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