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.