U-937 monocyte-mediated c-Jun dephosphorylation and AP-1 activation in human endometrial stromal cells

Objective: To determine paracrine effects of monocytes/macrophages on c-Jun dephosphorylation and AP-1 DNA binding activity in human endometrial stromal cells. Study Design: Conditioned medium (CM) was prepared from human monocyte U-937 cells in serum-free medium. Subconfluent immortalized human endometrial stromal N5 cells were serum-starved for 24 h and cultured in the CM or the control medium for 30 min, 1, 3, 8, 16 or 24 h. Nuclear extracts were prepared and phosphorylated and dephosphorylated c-Jun isoforms were detected by Western blot analysis and the DNA binding activity was evaluated-by electrophoretic mobility shift assay. Data on protein levels and DNA binding activity were analyzed statistically by ANOVA using SAS programs. Results: c-Jun was dominantly in the phosphorylated state in N5 cells cultured in the control medium. The CM induced c-Jun accumulation and dephosphorylation and increased AP-1 DNA binding activity in a time-dependent manner. Conclusion: U-937 cells induce c-Jun dephosphorylation and AP-1 activation in human endometrial stromal cells by paracrine factors. Further investigations are needed to characterize the nature of these paracrine factors and their signaling pathways leading to AP-1 activation. (C) 2004 Elsevier Ireland Ltd. All rights reserved.