title: The nuclear factor-κB pathway is involved in matrix metalloproteinase-9 expression in RU486-induced endometrium breakdown in mice.
abstract: BACKGROUND
  Progesterone-withdrawal (WP)-induced endometrial breakdown occurs in both physiological and pathological processes such as menstruation and abortion. However, the underlying mechanisms are not clearly understood. As the nuclear factor-κB (NF-κB) pathway has been proposed to play a role in endometrial breakdown, we tested this hypothesis using RU486-induced mouse menstruation-like model.
  
  
  METHODS
  The activation of NF-κB was evaluated by immunohistochemistry, western blot and immunofluorescence. The expression of matrix metalloproteinase-9 (MMP9) was analyzed by real-time PCR and its proteins by gelatin zymography and western blot. Chromatin immunoprecipitation was used to investigate the direct binding of NF-κB to MMP9 gene promoter. Inhibitors of NF-κB were used to block its signal in vivo and in vitro to analyze the function of NF-κB in the tissue breakdown process.
  
  
  RESULTS
  Administration of RU486 resulted in increased phospho-IκB levels and nuclear translocation of p65 in decidual stromal cells, accompanied by the up-regulation of NF-κB inducing kinase and IκB kinase β mRNA. The NF-κB inhibitor, 'pyrrolidine dithiocarbamate' partially suppressed the RU486-induced endometrial breakdown, thus verifying the role of this pathway in vivo. MMP9 was up- and down-regulated following the NF-κB activation and inhibition, respectively. RU486 stimulated recruitment of NF-κB p65 to the MMP9 promoter and further increased its expression. Effects of NF-κB activation and inactivation on MMP9 expression were further explored in human stromal cells in vitro. A similar MMP9 expression pattern was observed in cultured human, as well as mouse, decidual stromal cells following RU486 treatment.
  
  
  CONCLUSIONS
  The activation of the NF-κB pathway induces downstream target genes, including MMP9 from stromal cells to facilitate tissue breakdown in mouse uterus, highlighting the likelihood that this regulatory pattern exists in the human endometrium.
authors.affiliation: Graduate School of Peking Union Medical College, Beijing 100730,  People's Republic of China.
authors.forename: Yun-Feng
authors.initials: YF
authors.lastname: Li
authors.forename: Xiang-Bo
authors.initials: XB
authors.lastname: Xu
authors.forename: Xi-Hua
authors.initials: XH
authors.lastname: Chen
authors.forename: Gang
authors.initials: G
authors.lastname: Wei
authors.forename: Bin
authors.initials: B
authors.lastname: He
authors.forename: Jie-Dong
authors.initials: JD
authors.lastname: Wang
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D004717:Endometrium / Q000378:metabolism* / Q000473:pathology; D005260:Female; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008856:Microscopy, Fluorescence / Q000379:methods; D015735:Mifepristone / Q000494:pharmacology*; D023421:Models, Animal; D016328:NF-kappa B / Q000378:metabolism*; D011374:Progesterone / Q000378:metabolism; D011401:Promoter Regions, Genetic; D017154:Stromal Cells / Q000166:cytology; D014599:Uterus / Q000187:drug effects
chemical_list: D016328:NF-kappa B; D015735:Mifepristone; D011374:Progesterone; D020780:Matrix Metalloproteinase 9