Crosstalk between ERα and NFκB transcription factors on E2 induced leptin expression in placental cells

Abstract

Objectives: Leptin is a key hormone in placental physiology. It regulates trophoblast proliferation, inhibits apoptosis, stimulates protein synthesis, and regulates fetal growth and development. It plays an important role in reproduction mainly because it has been suggested to have function in the placenta during the gestation, where leptin and leptin receptors expression were detected. Previous results from our lab demonstrated that estradiol (E2) regulates leptin expression involving genomic and nongenomic effects. In the present work, we analysed the crosstalk between estrogen receptor alpha (ERa) and NFkB transcription factors on E2 induced leptin expression in human trophoblast cells. Methods: BeWo cells, cultured and human term placental explants were used. Western blot, immunocytochemistry, co-immunoprecipitation and transfection assays were carried out. Ethical review committee at the Alejandro Posadas National Hospital approved all procedures. Results: We found that E2 treatment significantly enhanced the NFkB member p65 expression both in BeWo cells and human term placental explants. Moreover E2 increased IkBa phosphorylation and NFkB transcriptional activity determined by reporter analysis. We also evaluated the localization of ERa and p65 NFkB subunit in BeWo cells by immunofluorescence assay. We found that both proteins are located in the cytoplasm and migrate to the nucleus when they are overexpressed. Besides ERa and p65 form a complex determined by co-immunoprecipitation, as previously seen. These findings suggest that the transcription factor NFkB, might be affecting estradiol leptin induction. Finally through transient transfection analysis we observed that the overexpression of RelA (p65) and HEGO (ERa) increases basal transcriptional activity of leptin promoter. Conclusion: These results suggest that leptin expression is tightly regulated and help to comprehend the mechanisms where E2 regulated leptin expression possibly involving the cooperation between ERa and NFkB transcription factors.