PARENT SESSION

(147) ACTIVATION OF NUCLEAR FACTOR KAPPA B DURING THE OPENING OF THE IMPLANTATION WINDOW IN THE PIG.

Ross, Jason¹, Ashworth, Morgan¹, Stein, Daniel¹, Geisert, Rodney¹, ¹ Oklahoma State University, Stillwater, OK

ABSTRACT- Establishment and maintenance of pregnancy in the pig involves intricate communication between the developing conceptuses and maternal endometrium. This process occurs during trophoblast elongation concomitant with conceptus synthesis and release of estrogen and interleukin-1 (IL-1) on d 12 of gestation. The transient synthesis and release of conceptus IL-1 is associated with pregnancy specific endometrial up-regulation of IL-1 receptors, indicating the potential for activation of the transcription factor, NF-B. The objective of the current investigation was to determine changes in NF-B expression and cellular localization during the estrous cycle and early pregnancy in the pig. Uterine endometrium was collected from gilts during the estrous cycle (d 0, 5, 7.5, 10, 12, 13, 15 and 17) and early pregnancy (d 10, 12, 13, 15, 17). Quantitative RT-PCR assayed gene expression changes for NF-B subunits p65 and p50, inhibitors of NF-B (IB and IB), receptor activator of NF-B (RANK), and cyclooxygenase-2 (COX-2; a product of NF-B activation). Western blot analysis evaluated endometrial COX-2 protein expression while immunohistochemistry was used to measure and localize NF-B p65 protein expression in uterine endometrium. Gene expression for p50 and p65 was affected by a day x status interaction (P < 0.03 and 0.05, respectively), with basal expression for both genes occurring on d 5 and increasing nearly 3-fold by d 17 in both pregnant and cyclic animals. RANK and IB gene expression did not change although IB was slightly higher in pregnant gilts. Cellular localization identified NF-B p65 expression in the cytoplasm of epithelial and glandular endometrium on all days. Nuclear translocation of p65 occurred by d 10 in stromal endometrium of the estrous cycle and pregnancy. Epithelial translocation of p65 was initiated between d 10 and 13 in cyclic and pregnant gilts, yet appears more extensive during gestation. Basal COX-2 gene expression occurred on d 5 and increased over 100-fold by d 15 in both pregnant and cyclic animals. Activation and translocation of NF-B is temporally associated with the loss of progesterone receptor in the uterine endometrium and may regulate both cyclicity and the opening of the implantation window. This work supported in part by NRICGP/USDA grant 2002-35203-12262 to RDG.

KEY WORDS: NF-B, Implantation, Pig, Pregnancy