Involvement of MAPK pathway in TNF-α-induced MMP-9 expression in human trophoblastic cells

The aim of this article was to investigate the signalling pathways involved in metalloproteinase-9 (MMP-9) expression induced by tumour necrosis factor-alpha (TNF-alpha) in first-trimester trophoblastic cells. TNF-alpha-induced MMP-9 expression, secretion and activity were completely blocked by stress-activated protein kinase/jun kinase (SAPK/JNK) and Erk inhibitors (SP600 125 and U0126 respectively) but not by p38 mitogen-activated protein kinase (MAPK) inhibitors (SB203 580 and SB202 190). Stimulation of HIPEC 65 cells with TNF-alpha caused phosphorylation of JNK and extracellular signal-regulated kinase 1/2 (Erk1/2), with a peak after 20 min of treatment. Transcription factors nuclear factor-kappa B (NF-kappa B) and activator protein 1 (AP-1)-binding site were identified as the cis-elements involved in TNF-alpha activation as determined by electromobility shift assays. TNF-alpha-induced transactivation of NF-kappa B was inhibited by U0126, whereas TNF-alpha-induced transactivation of AP-1 was inhibited by SP600 125. Taken together, these results indicate that in trophoblastic cells, TNF-alpha probably activates two different pathways leading to MMP-9 expression: (a) Erk1/2 pathway which in turn initiates NF-kappa B activation and (b) SAPK/JNK pathway that activates AP-1.