TAK1 activation for cytokine synthesis and proliferation of endometriotic cells.

Endometriosis causes pelvic pain and infertility in women of reproductive age. We explored TNFalpha-induced specific signaling pathways and gene expressions in endometriotic stromal cells (ESCs). Based on the data of the pathway specific cDNA array, we analyzed the role of TAK1, which is believed to work as a common mediator for NF-kappaB and MAPK pathways. Using the NF-kappaB pathway array, we found that TNFalpha upregulated ICAM-3, IL-6, IL-8, TAK1, JNK2, RelA, and TLR4 expressions. TNFalpha augmented the phosphorylation of TAK1. By transfection of TAK1 siRNA, TNFalpha-induced phosphorylation of IkappaBalpha, JNK1/2, and p38MAPK, as well as IL-6 or IL-8 expression, were repressed. TAK1 silencing in TNFalpha-pretreated ESCs caused a decrease in the proportion of cells in S-phase, and reduced TNFalpha-promoted BrdU incorporation. We provide the first evidence that TNFalpha and its downstream TAK1, which are key mediators for NF-kappaB and MAPK pathways, may be involved in the pathogenesis of endometriosis.