Submission Number: THO-4-31-2

Abstract Number: 32

INTERFERON-TAU SUPPRESSES PROSTAGLANDIN F₂ RELEASE THROUGH A MAP KINASE- AND NFB-INDEPENDENT MECHANISM.

Thomas R Hansen* ¹, James K Pru* ¹, Bo R Rueda* ², Kathy J Austin* ¹, Aydin Guzeloglu ³ and William W Thatcher* ³

Department of Animal Science, University of Wyoming, Laramie, WY ¹
Vincent Center for Reproductive Biology, Massachusetts General Hospital, Boston, MA ²
Department of Dairy and Poultry Sciences, University of Florida, Gainesville, FL ³

Abstract:
Pregnancy is established in ruminants through inhibitory actions of interferon (IFN)-tau on the release of prostaglandin F₂ (PGF). Consequently, the corpus luteum survives and continues to produce progesterone. The purpose of this study was to delineate the signal transduction cascade for synthesis of PGF, and to determine if IFN-tau inhibits PGF release through Raf-1/MEK-1/MAPK-ERKs or NFB pathways in cultured bovine endometrial (BEND) cells. BEND cells were untreated (control) or treated for 0, 5, 10, 60, 180 or 300 min with PDBu (phorbol ester; 100 ng/ml), IFN-tau (50 or 500 ng/ml), PDBu & IFN-tau, or PDBu & PD098059 (MEK-1 inhibitor; 50 mM). PDBu induced (P<0.05) PGF release within 3 h. This induction of PGF by PDBu was inhibited 75% with the addition of IFN-tau (P<0.05) and was ablated completely by PD098059. Parallel results were obtained for cyclooxygenase (COX)-2 protein expression, while phospholipase A₂ remained unchanged across treatments. Thus, the site of IFN-tau action using this model excludes a direct action on oxytocin or estradiol receptors. PDBu-induced phosphorylation of MAPK was not altered by IFN-tau. Also, Raf-1 hyperphosphorylation was sustained in response to PDBu regardless of IFN-tau treatment. This is interpreted to mean that feedback on Raf-1 hyperphosphorylation via MAPK remained intact. PDBu induced (P<0.05) transcription of c-jun and c-fos mRNAs within 30 min. This was inhibited (P<0.05) by PD098059, but not by IFN-tau. Only the 500 ng/ml concentration of IFN-tau reduced (P<0.05) IB levels. However, both concentrations of IFN-tau (50 and 500 ng/ml) inhibited (P<0.05) induction of COX-2 protein by PDBu. Thus, nuclear translocation of NFB is probably not the site through which IFN-tau inhibits COX-2 gene expression. In conclusion, PGF synthesis is mediated through the MAPK pathway, but this pathway is not disrupted by IFN-tau. It is hypothesized that signal transducers and activators of transcription or IFN regulatory factors act directly to inhibit the COX-2 gene. NIH HD32475-06.

Keywords: Interferon Prostaglandin Uterus

This abstract is being presented at: 3:45 PM in session:
SESSION 5: SIGNAL TRANSDUCTION IN REPRODUCTIVE TISSUES