Up-regulation of the progesterone receptor (PR)-C isoform in laboring myometrium by activation of nuclear factor-κB may contribute to the onset of labor through inhibition of PR function

Jennifer C. Condon, Daniel B. Hardy, Kelly Kovaric, Carole R. Mendelson

Research output: Contribution to journalArticle

213 Scopus citations

Abstract

Progesterone acting via the progesterone receptor (PR) plays a critical role in maintaining uterine quiescence during pregnancy. In the present study, we tested the hypothesis that the transactivating capability of the PR is down-regulated in the myometrium at term by a change in uterine PR isoform ratio resulting from local activation of the nuclear factor (NF)-κB pathway. Overexpression of the truncated PR-C isoform in human myometrial cells inhibited PR-B transactivation. Expression of PR isoforms, PR-A, PR-B, and PR-C, was characterized by immunoblotting and quantitative PCR (Q-PCR) in fundal and lower uterine segment myometrium from pregnant women in labor and not in labor and in the pregnant mouse uterus during late gestation. We observed a marked increase in levels of PR-C and transcriptionally active PR-B specifically in fundal myometrium of women in labor. In pregnant mouse uterus, levels of PR-B and PR-C also increased between 15 days post coitum and term, whereas expression of PR-A was dramatically up-regulated at 19 days post coitum. In studies of uterine tissues of mice injected intraamniotically with surfactant protein A and of human myometrial and T47D breast cancer cells in culture, up-regulation of PR isoform expression was observed in response to activation of the NF-κB pathway. Chromatin immunoprecipitation analysis revealed IL-1β induced binding of NF-κB to the PR promoter. Collectively, these findings suggest that up-regulation of inhibitory PR isoform expression by NF-κB activation in both laboring human fundus and pregnant mouse uterus near term may inhibit PR transactivation and thereby lead to a loss of uterine quiescence and the onset of labor.

Original languageEnglish (US)
Pages (from-to)764-775
Number of pages12
JournalMolecular Endocrinology
Volume20
Issue number4
DOIs
StatePublished - Apr 1 2006

ASJC Scopus subject areas

  • Molecular Biology
  • Endocrinology

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