TY - JOUR
T1 - Progesterone receptor plays a major antiinflammatory role in human myometrial cells by antagonism of nuclear factor-κB activation of cyclooxygenase 2 expression
AU - Hardy, Daniel B.
AU - Janowski, Bethany A.
AU - Corey, David R.
AU - Mendelson, Carole R.
PY - 2006/11
Y1 - 2006/11
N2 - Spontaneous labor in women and in other mammals is likely mediated by a concerted series of biochemical events that negatively impact the ability of the progesterone receptor (PR) to regulate target genes that maintain myometrial quiescence. In the present study, we tested the hypothesis that progesterone/PR inhibits uterine contractility by blocking nuclear factor κB (NF-κB) activation and induction of cyclooxygenase-2 (COX-2), a contractile gene that is up-regulated in labor. To uncover mechanisms for regulation of uterine COX-2, immortalized human fundal myometrial cells were treated with IL-1β ± progesterone. IL-1β alone caused a marked up-regulation of COX-2 mRNA, whereas treatment with progesterone suppressed this induction. This was also observed in human breast cancer (T47D) cells. In both cell lines, this inhibitory effect of progesterone was blocked by RU486. Using chromatin immunoprecipitation, we observed that IL-1β stimulated recruitment of NF-κB p65 to both proximal and distal NF-κB elements of the COX-2 promoter; these effects were diminished by coincubation with progesterone. The ability of progesterone to inhibit COX-2 expression in myometrial cells was associated with rapid induction of mRNA and protein levels of inhibitor of κBα, a protein that blocks NF-κB transactivation. Furthermore, small interfering RNA-mediated ablation of both PR-A and PR-B isoforms in T47D cells greatly enhanced NF-κB activation and COX-2 expression. These effects were observed in the absence of exogenous progesterone, suggesting a ligand-independent action of PR. Based on these findings, we propose that PR may inhibit NF-κB activation of COX-2 gene expression and uterine contractility via ligand-dependent and ligand-independent mechanisms.
AB - Spontaneous labor in women and in other mammals is likely mediated by a concerted series of biochemical events that negatively impact the ability of the progesterone receptor (PR) to regulate target genes that maintain myometrial quiescence. In the present study, we tested the hypothesis that progesterone/PR inhibits uterine contractility by blocking nuclear factor κB (NF-κB) activation and induction of cyclooxygenase-2 (COX-2), a contractile gene that is up-regulated in labor. To uncover mechanisms for regulation of uterine COX-2, immortalized human fundal myometrial cells were treated with IL-1β ± progesterone. IL-1β alone caused a marked up-regulation of COX-2 mRNA, whereas treatment with progesterone suppressed this induction. This was also observed in human breast cancer (T47D) cells. In both cell lines, this inhibitory effect of progesterone was blocked by RU486. Using chromatin immunoprecipitation, we observed that IL-1β stimulated recruitment of NF-κB p65 to both proximal and distal NF-κB elements of the COX-2 promoter; these effects were diminished by coincubation with progesterone. The ability of progesterone to inhibit COX-2 expression in myometrial cells was associated with rapid induction of mRNA and protein levels of inhibitor of κBα, a protein that blocks NF-κB transactivation. Furthermore, small interfering RNA-mediated ablation of both PR-A and PR-B isoforms in T47D cells greatly enhanced NF-κB activation and COX-2 expression. These effects were observed in the absence of exogenous progesterone, suggesting a ligand-independent action of PR. Based on these findings, we propose that PR may inhibit NF-κB activation of COX-2 gene expression and uterine contractility via ligand-dependent and ligand-independent mechanisms.
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U2 - 10.1210/me.2006-0112
DO - 10.1210/me.2006-0112
M3 - Article
C2 - 16772530
AN - SCOPUS:33751531210
SN - 0888-8809
VL - 20
SP - 2724
EP - 2733
JO - Molecular Endocrinology
JF - Molecular Endocrinology
IS - 11
ER -