Interferon-γ induces degradation of TβR-I in the human endometrium: Implications for endometriosis

OBJECTIVE: Progesterone action is critical for providing an appropriate endometrial environment for pregnancy. For example, progesterone induces the expression of transforming growth factor- (TGF-2), a signaling molecule involved in down-regulation of matrix metalloproteinases (MMPs).We have demonstrated that progesterone acts through TGF- signaling to limit MMP expression within the inflammatory-like environment of early pregnancy. A recent study demonstrated that interferon-� (IFN-�) related genes are down regulated in leukocytes during the secretory phase, suggesting that progesterone may limit the action of this cytokine in the endometrium. Additional studies have indicated that endometrial tissue from women with endometriosis exhibits a degree of “progesterone resistance” resulting in altered expression of multiple genes during the secretory phase. In the current study, we investigated the potential impact of IFN-� on progesterone-mediated TGF--signaling proteins in the endometrium of women with and without endometriosis. DESIGN: Randomized, controlled laboratory study. MATERIALS AND METHODS: Archived samples of proliferative and secretory phase endometrium from women with and without endometriosis were obtained from the Human Tissue Core of the Women’s Reproductive Health Research Center. Samples were analyzed by standard immunohistochemistry for TGF-1, TGF-2, the type I and type II receptors (TR-I, TR-II) and phosporylated Smad2 (Smad2P). Biopsies of proliferative phase (days 10–12) endometrium was obtained from normal women and from women with a confirmed history of endometriosis. Endometrial stromal and epithelial cells were isolated from biopsies and maintained as co-cultures in the presence of estradiol (E; 1nM), E plus progesterone (EP; 1nM, 500nM) with or without interferon-� (50, 100 or 200 pg/mL). Cells were terminated at 2, 4, 6, 8, 12 and 24 hrs following IFN-� exposure and expression of TR-I, TR-II and Smad2P was examined by Western analysis. RESULTS: Immunohistochemical studies revealed an increased expression of TGF-2, TGF-R-I, TR-II and Smad2P in normal, secretory phase endometrium, but not in similar tissue from endometriosis patients. In vitro treatments with IFN-� induced a dose dependent degradation of TR-I in exposed tissues in the absence of progesterone in all tissues studied. IFN-� effects were not observed prior to 8 hrs, indicating a likely involvement of Smad7 (an inhibitory Smad whose expression is induced 6 hrs after IFN-� treatment). Additionally, Smad2P, an indicator of cellular response to TGF-, was also reduced in both normal and endometriosis endometrium following treatment with IFN-�. CONCLUSION: In women with endometriosis, a diminished response to progesterone increases endometrial MMP expression in response to proinflammatory cytokines. In the current study, we have shown that women with endometriosis have a reduced expression of TGF-2, TR-I and Smad2P and that treatment of normal endometrium with IFN-� results in similar alterations in these molecules. In women with a reduced ability to respond to progesterone, our study suggests that IFN-� action may further reduce the expression of TR-I and prevent the normal regulation of multiple genes including MMPs.