Down-regulation of oxytocin-induced cyclooxygenase-2 and prostaglandin F synthase expression by interferon-tau in bovine endometrial cells

Oxytocin (OT) is responsible for the episodic release of luteolytic prostag landin (PC) F-2 alpha from the uterus in ruminants. The attenuation of OT-s timulated uterine PGF(2 alpha) secretion by interferon-tau (IFN-tau) is ess ential for prevention of luteolysis during pregnancy in cows. To better und erstand the mechanisms involved, the effect of recombinant bovine IFN-tau ( rbIFN-tau) on OT-induced PG production and cyclooxygenase-2 (COX-2) and PCF synthase (PGFS) expression in cultured endometrial epithelial cells was in vestigated. Cells were obtained from cows at Days 1-3 of the estrous cycle and cultured to confluence in RPMI medium supplemented with 5% steroid-free fetal calf serum. The cells were then incubated in the presence or absence of either 100 ng/ml OT or OT + 100 ng/ml rbIFN-tau for 3, 6, 12, and 24 h. OT significantly increased PGF(2 alpha) and PGE(2) secretion at all time p oints (p < 0.01), while rbIFN-tau inhibited the OT-induced PG production an d reduced OT receptor binding in a time-dependent manner. OT increased the steady-state level of COX-2 mRNA, measured by Northern blot, which was maxi mal at 3 h (9-fold increase) and then decreased with time (p < 0.01). OT al so caused an increase in COX-2 protein, which peaked at 12 h (Il-fold incre ase), as measured by Western blot. Addition of rbIFN-tau suppressed the ind uction of COX-2 mRNA (89%, p < 0.01) and COX-2 protein (50%, p < 0.01) by O T. OT also increased PGFS mRNA, and this stimulation was attenuated by rbIF N-tau (p < 0.01). To ensure that the decrease in COX-2 was not solely due t o down-regulation of the OT receptor, cells were stimulated with a phorbol ester (phorbol 12-myristate 13-acetate; PMA) in the presence and absence of rbIFN-tau. The results showed that rbIFN-tau also decreased PMA-stimulated PC production and COX-2 protein. It can be concluded that rbIFN-tau inhibi tion of OT-stimulated PC production is due to down-regulation of OT recepto r, COX-2, and PGFS.