Characterization of the role of Activator Protein 1 signaling pathway on extracellular matrix deposition in uterine leiomyoma

Objective: To characterize the role Activator Protein 1 (AP 1) family members play in mediating extracellular matrix deposition in uterine leiomyoma. Design: Laboratory study. Setting: University research laboratory. Intervention(s): Exposure of leiomyoma and myometrial cell lines to either an AP 1 inhibitor alone, AP 1 inhibitor plus transforming growth factor (TGF)ß3, or TGFß3 alone. Main Outcome Measure(s): Western immunoblot analysis was performed to assess for changes in AP 1 family member protein expression. Result(s): In patient-matched myometrial and leiomyoma cell lines, the only AP 1 member found to be elevated significantly in leiomyoma compared with myometrium was FOSB (3.47 ± 0.12-fold), whereas others were decreased significantly: FRA1 (0.67 ± 0.02-fold), FRA2 (0.45 ± 0.01-fold), c FOS (0.37 ± 0.01-fold), Phos c FOS (0.19 ± 0.02-fold), Phos c JUN (0.75 ± 0.02-fold), JUNB (0.81 ± 0.04-fold), and JUND (0.65 ± 0.03-fold). c JUN (0.93 ± 0.03-fold) concentration was reduced but at nonsignificant levels. Following stimulation with TGF ß 3, fibronectin (2.16 ± 0.14-fold) and versican (4.71 ± 0.15-fold) protein concentrations were increased at 24 hours. Collagen 1A demonstrated a time-dependent significant increased concentration beginning at 6 hours (1.32 ± 0.01-fold) and increased to (6.49 ± 0.02-fold) at 24 hours. Following treatment with AP 1 inhibitor (SR11302), there were significant reductions in Collagen 1A concentration at 4 hours (0.59 ± 0.03-fold) and 6 hours (0.42 ± 0.05-fold). Activator Protein 1 inhibition did not reduce significantly versican concentration until 6 hours of treatment (0.84 ± 0.04-fold). SR11302 also decreased significantly fibronectin concentration (0.68 ± 0.05-fold) at 8 hours of treatment. Conclusion(s): Activator Protein 1 signaling is well described in fibrotic diseases, and, herein, we demonstrated that signaling via AP 1 family members promotes extracellular matrix deposition in leiomyoma.