Endometrial receptivity defects and impaired implantation in diabetic NOD mice

Implantation failure is a major hurdle to a successful pregnancy. The high rate of postimplantation fetal loss in nonobese diabetic (NOD) mice is believed to be related to an abnormal decidual production of interferon (IFN)gamma. To address whether diabetes alters the natural events associated with successful implantation, certain morphological and molecular features of uterine receptivity in diabetic NOD (dNOD) mice were examined in normally mated pregnancy and in concanavalin A (ConA)-induced pseudopregnancy. As opposed to normoglycemic NOD (cNOD) mice, dNOD mice expressed retarded maturation of their uterine pinopodes and overexpressed MUC1 mucin at implantation sites (P < 0.001). Uterine production of leukemia inhibitory factor (LIF) and phosphorylation of uterine NFkappaBp65 and STAT3-Ty705 were found to be low (P < 0.01) during Day 4.5 postcoitum, whereas IFNgamma was aberrantly overexpressed. Loss of temporal regulation of progesterone receptor A (PR A) and PR B, together with aberrantly increased expression of the protein inhibitor of activated STAT-y (PIASy) (P < 0.01) and reduced recruitment (P < 0.01) of the latter to nuclear progesterone receptor sites were prominent features of decidualization failure occurring at peri-implantation in dNOD mice. In conclusion, the aberrant expression of endometrial IFNgamma in dNOD mice is associated with a nonreceptive endometrial milieu contributing to peri-implantation embryo loss in type 1 diabetes.     

Transforming growth factor-beta1 attenuates expression of both the progesterone receptor and Dickkopf in differentiated human endometrial stromal cells

TGFbeta1 is thought to be intimately involved in cyclic tissue remodeling and inflammatory events associated with menstruation. Menstruation is initiated by progesterone withdrawal; however, the underlying mechanisms are not well understood. In the present study, we have tested the hypothesis that locally produced TGFbeta1 may influence expression of progesterone receptor (PR) or the Wnt antagonist Dickkopf-1 (DKK) with consequential impact on regulation of menstruation. Endometrial stromal cells (ESC) were isolated from endometrial biopsy samples collected from patients undergoing gynecological procedures for benign indications. Treatment of differentiated ESC with TGFbeta1 (10 ng/ml) significantly inhibited the expression of mRNAs encoding PR and DKK. TGFbeta1 also attenuated the protein expression of PR and secretion of DKK proteins in culture supernatants. Neutralization of endogenous TGFbeta1 signaling abolished the TGFbeta1-induced effects, significantly increased expression of PR, and increased DKK protein release levels to that of differentiated ESCs, confirming the specificity of the TGFbeta1 effect. Additionally, in vitro decidualization of ESCs significantly augmented DKK protein release. Moreover, although TGFbeta1 was capable of signaling via the Sma- and mothers against decapentaplegic (MAD)-related protein (SMAD) pathway, the inhibitory effect on DKK was SMAD independent. Conversely, the inhibitory effect of TGFbeta1 on PR was dependent on SMAD signal transduction. In conclusion, these results suggest that local TGFbeta1 signaling can potentiate progesterone withdrawal by suppressing expression of PR and may coordinate tissue remodeling associated with menstruation by inducing Wnt-signaling via inhibition of DKK, which we found to be up-regulated as a consequence of decidualization of ESCs.     

5'-AMP-activated protein kinase (AMPK) regulates progesterone receptor transcriptional activity in breast cancer cells

The steroid hormone progesterone is an essential regulator of the cellular processes that are required for the development and maintenance of reproductive function. The diverse effects of progesterone are mediated by the progesterone receptor (PR). The functions of the PR are regulated not only by ligands but also by modulators of various cell signaling pathways. However, it is not clear which energy state regulates PR activity. AMP-activated protein kinase (AMPK), a serine/threonine protein kinase, is a key modulator of energy homeostasis. Once activated by an increasing cellular AMP:ATP ratio, AMPK switches off ATP-consuming processes and switches on ATP-producing processes. We found that both 5-aminoimidazole-4-carboxamide 1-β-d-ribofuranoside (AICAR) and metformin, traditional pharmacological activators of AMPK, inhibited the PR pathway, as evidenced by progesterone response element (PRE)-driven luciferase activity and PR target gene expression. Compound C, an inhibitor of AMPK, partly but significantly reversed the anti-PR effects of AICAR and metformin. The downregulation of endogenous AMPK by small interfering RNAs (siRNAs) stimulated PR activity. AMPK activation by AICAR decreased the progesterone-induced phosphorylation of PR at serine 294 and inhibited the recruitment of PR to an endogenous PRE. Taken together, our data suggest that AMPK, an energy sensor, is involved in the regulation of PR signaling.