Pru J K, Rueda B R, Austin K J, Thatcher W W, Guzeloglu A, Hansen T R
Department of Animal Science, University of Wyoming, Laramie, Wyoming 82071-3684, USA.
Biol Reprod. 2001 Mar;64(3):965-73. doi: 10.1095/biolreprod64.3.965.
Pregnancy is established in ruminants through inhibitory actions of interferon (IFN)-tau on the release of prostaglandin F2alpha (PGF), which allows the corpus luteum to survive and continue to produce progesterone. Experiments were designed to 1) delineate the signal transduction pathway coordinating the synthesis of PGF, 2) determine how rapidly recombinant bovine (rb) IFN-tau attenuated phorbol ester (PDBu)-induced secretion of PGF, and 3) establish the site at which rbIFN-tau attenuates the secretion of PGF in cultured bovine endometrial (BEND) cells. BEND cells were untreated (control) or treated for 5, 10, 60, 180, or 300 min with PDBu (100 ng/ml), rbIFN-tau (50 or 500 ng/ml), PDBu + rbIFN-tau, or PDBu + PD98059 (MEK-1 inhibitor; 50 microM). Secretion of PGF was induced (P < 0.0001) by PDBu within 180 min, but induction was inhibited 74% by the addition of rbIFN-tau (P < 0.0001) and was ablated completely by PD98059. Parallel results were obtained for cyclooxygenase (COX)-2 protein expression. PDBu induced (P < 0.05) activation of the Raf-1/MEK-1/ERK-1/2 pathway, which was obligatory for the expression of COX-2 and secretion of PGF but was not altered by cotreatment with rbIFN-tau. PDBu induced (P < 0.05) transcription of c-jun and c-fos mRNAs within 30 min; induction was inhibited (P < 0.05) by cotreatment with PD98059 but not by cotreatment with rbIFN-tau. Treatment of BEND cells with rbIFN-tau also did not attenuate PDBu-induced degradation of IkappaBalpha, suggesting that the IkappaBalpha/NFkappaB pathway is not a site of IFN-tau inhibition of PGF. However, rbIFN-tau did block transcription of the COX-2 gene induced by PDBu within 30 min. In conclusion, COX-2 expression and PGF secretion induced by PDBu is mediated through the Raf-1/MEK-1/ERK-1/2 pathway, but this pathway is not disrupted by rbIFN-tau. Because rbIFN-tau inhibits COX-2 mRNA within 30 min, we hypothesized that transcription factors activated by rbIFN-tau rapidly and directly attenuate COX-2 gene expression, thereby suppressing secretion of PGF.
在反刍动物中，妊娠是通过干扰素（IFN）-τ对前列腺素F2α（PGF）释放的抑制作用来建立的，这使得黄体得以存活并继续产生孕酮。实验旨在：1）描绘协调PGF合成的信号转导途径；2）确定重组牛（rb）IFN-τ多快能减弱佛波酯（PDBu）诱导的PGF分泌；3）确定rbIFN-τ在培养的牛子宫内膜（BEND）细胞中减弱PGF分泌的位点。BEND细胞未处理（对照）或用PDBu（100 ng/ml）、rbIFN-τ（50或500 ng/ml）、PDBu + rbIFN-τ或PDBu + PD98059（MEK-1抑制剂；50 μM）处理5、10、60、180或300分钟。PDBu在180分钟内诱导PGF分泌增加（P < 0.0001），但添加rbIFN-τ后诱导作用减弱74%（P < 0.0001），而PD98059则完全消除了这种诱导作用。环氧合酶（COX）-2蛋白表达也得到了类似结果。PDBu诱导（P < 0.05）Raf-1/MEK-1/ERK-1/2途径激活，这是COX-2表达和PGF分泌所必需的，但与rbIFN-τ共同处理并未改变该途径。PDBu在30分钟内诱导（P < 0.05）c-jun和c-fos mRNA转录；与PD98059共同处理可抑制（P < 0.05）这种诱导作用，但与rbIFN-τ共同处理则无此作用。用rbIFN-τ处理BEND细胞也未减弱PDBu诱导的IκBα降解，这表明IκBα/NFκB途径不是IFN-τ抑制PGF的作用位点。然而，rbIFN-τ确实在30分钟内阻断了PDBu诱导的COX-2基因转录。总之，PDBu诱导的COX-2表达和PGF分泌是通过Raf-1/MEK-1/ERK-1/2途径介导的，但该途径未被rbIFN-τ破坏。由于rbIFN-τ在30分钟内抑制COX-2 mRNA，我们推测rbIFN-τ激活的转录因子迅速且直接减弱COX-2基因表达，从而抑制PGF分泌。
