The role of pH and progesterone on bovine uterine protein secretion in response to maternal recognition, interferon-tau

Abstract Text:  Low uterine pH, associated with high dietary protein and blood urea, reduces fertility in dairy cows.  The objective of this in vitro study was to determine the direct effects of a low pH on bovine endometrial (BEND) cells expression of Mx1 and ISG-15 in response to embryonic maternal recognition, interferon-tau (IFNτ), in the presence or absence of progesterone (P₄).   In two experiments, using BEND cells as a model, the effects of a low pH environment was examined to determine the production of two IFNτ stimulated proteins, ISG-15 and Mx1. Bovine endometrial cells were grown to 80% confluency and further incubated for additional 24 h in culture media containing no P₄ (0 M; Exp. 1) or P₄ (10⁻⁷M, Exp. 2). To reduce the pH, in both experiments, cells (90% confluent) were treated with dimethyldioxirane (DMD), at final concentrations of 0, 10, 15 and 20 mM (pH of 7.35, 7.17, 6.9 and 6.76, respectively) and subsequently, challenged with 0 or 10,000 antiviral units of rIFNτ. Cells were incubated for an additional 24 h. Once harvested, BEND cells were lysed and supernatants were analyzed and quantified for Mx1 and ISG-15, using SDS-PAGE and Western Immunoblotting protocols. Based on optical density, at 0 mM DMD, regardless of P₄ treatment, IFNτ increased (P < 0.01) Mx1 and ISG-15 in both experiments. In Exp. 1(P₄ free environment), there was effect of DMD (P < 0.01) and DMD by IFNτ interaction (P < 0.01) on both Mx1 and ISG-15. The 15 and 20 mM DMD reduced (P < 0.01) IFNτ- induced Mx1 expression, whereas only 20 mM DMD reduced (P < 0.01) ISG-15 expression in response to IFNτ. In Exp 2, in presence of P₄, there was a significant effect of DMD and IFNτ by DMD interaction (P < 0.01) on Mx1 expression. However, there was no effect of DMD or DMD by IFNτ interaction on protein expression of ISG-15 (P = 0.2 and 0.4) in a P₄ environment.  These results show that in absence of P₄ and low pH, IFNτ-stimulated proteins secretion are abrogated; however P₄, overcame pH-induced decreased of ISG-15 but not Mx1. Progesterone may regulate the secretion of IFNτ- stimulated proteins in an acidic uterine environment.

Keywords: acidic pH, progesterone, interferon, bovine endometrial cells