The role of endoplasmic reticulum stress response in the regulation of endometrial interferon beta production in decidualized versus non-decidualized endometrial cells

Endoplasmic reticulum (ER) stress response has been associated with the induction of sterile inflammation in varied disease contexts like atherosclerosis, cancer, diabetes, obesity etc. ER stress induced by implantation also elevates the pro inflammatory cytokine Interferon b (IFN b), with cytokine signaling pathways participating as mediators of these communications to promote healthy pregnancy. Careful regulation of ER stress is crucial for mammalian reproduction by allowing decidualization and placentation to occur and the maintenance of uterine quiescence. However, prolonged or elevated ER stress can also lead to apoptosis and autophagy, which in turn could pose adverse effects on pregnancy outcomes and placentation. In support of this hypothesis, in vitro fertilization (IVF) patients with recurrent implantation failure have been established to have significantly lower concentrations of intrauterine IFNb. Therefore, we investigated the expression of IFNb in response to ER stress in decidualized and non-decidualized cells in vitro, to gain an understating of the role of IFN b in the implantation process. Human Endometrial Stromal Cells (HESC) were cultured until they reached 70% confluence. Then they were treated with Medroxyprogesterone (10_7 M), dibutryl cAMP (2,5 10-3 M) and Beta estradiol, for 8 days, renewing the stimuli every 48 hours. Non-decidualized cells were cultured similarly in the absence of decidualization stimuli. Then, both decidualized and non-decidualized HESC were treated with Tunicamycin (a chemical ER stress inducer) in a dose (0, 5, 10 and 20 μg) and time dependent fashion (24 and 48 hours). The levels of IFNb and other cytoplasmic and nuclear enzymes in response to increasing levels of ER stress were measured. Experiments were performed in triplicate; statistical analysis was performed using Chi-square test. There was a distinct difference in the response between decidualized cells versus non-decidualized cells, with decidualized cells exhibiting a 4 fold rise in IFNb in response to stress as opposed to non-decidualized cells. Other stress response proteins such as Immunoglobulin heavy chain-binding protein (BiP), Cleaved caspase 3 level were elevated with higher doses and longer treatments of Tunicamycin but they were no different between decidualized and non-decidualized cells. Collectively, our data suggests that there is a signaling pathway controlling the expression and function of IFNb in the decidualized cells in response to stress and that this is distinctly different from the non-decidualized cells.