Epidermal growth factor induces c-fos and c-jun mRNA via Raf-1/MEK1/ERK-dependent and -independent pathways in bovine luteal cells.

Epidermal growth factor (EGF) modulates the actions of gonadotropins in the corpus luteum. The membrane-associated EGF receptors undergo rapid tyrosine phosphorylation and internalization upon ligand binding in ovarian cells, including luteal cells. However, little is known about the post-receptor signaling events induced by EGF that lead to the transcriptional regulation of EGF-responsive genes in the ovary.

Mediators of interferon gamma-initiated signaling in bovine luteal cells.

Interferon gamma (IFNgamma) has been implicated as a mediator of luteal steroidogenesis and cell fate. IFNgamma-initiated signaling events, although implied by studies in cell lines, have yet to be described in primary luteal cells. The objective of these studies was to begin to characterize IFNgamma-initiated signaling within luteal cells.

Induction of c-fos and c-jun messenger ribonucleic acid expression by prostaglandin F2alpha is mediated by a protein kinase C-dependent extracellular signal-regulated kinase mitogen-activated protein kinase pathway in bovine luteal cells.

PGF2alpha triggers the demise of the corpus luteum whereby progesterone synthesis is inhibited, the luteal structure regresses, and the estrus cycle resumes. Upon binding to its heterotrimeric G-protein-coupled receptors, PGF2alpha initiates the phospholipase C/diacylglycerol and inositol-1,4,5-trisphosphate/Ca(2+)-protein kinase C (PKC) signaling pathway. More recently, we have demonstrated that PGF2alpha activates extracellular signal-regulated kinase (ERK) mitogen-activated protein (MAP) kinase signaling through a Raf-dependent mechanism in bovine luteal cells.

Stress-induced mitogen-activated protein kinase signaling in the corpus luteum.

Current evidence suggests that stress-induced apoptosis is mediated through the activation of the mitogen-activated protein kinase (MAPK) signaling cascade. We hypothesize that stress-related signaling events documented in other cell lines may also occur in the corpus luteum. To test this, cultured bovine luteal cells were exposed to UV irradiation and harvested at different intervals (0, 30, 120, 240 and 360 min) for analysis of protein or apoptotic cell death.

Decreased progesterone levels and progesterone receptor antagonists promote apoptotic cell death in bovine luteal cells.

We tested the hypothesis that progesterone (P(4)) acts at a local level to inhibit luteal apoptosis. Initial experiments employed aminoglutethimide, a P450 cholesterol side-chain cleavage inhibitor, to inhibit steroid synthesis. Cultured bovine luteal cells were treated with aminoglutethimide (0.

Accumulation of caspase-3 messenger ribonucleic acid and induction of caspase activity in the ovine corpus luteum following prostaglandin F2alpha treatment in vivo.

Caspase-3, a vertebrate homologue of the protein encoded by the Caenorhabditis elegans cell death gene, ced-3, induces apoptosis when overexpressed in eukaryotic cells. Since apoptosis occurs during corpus luteum (CL) regression in many species, including the ewe, these studies were conducted to 1) isolate a cDNA encoding ovine caspase-3, 2) measure steady state amounts of caspase-3 mRNA in the CL during luteolysis induced by prostaglandin F2alpha (PGF2alpha) and during the time of maternal recognition of pregnancy, and 3) measure changes in caspase activity during PGF2alpha-initiated luteal regression. Oligonucleotide primers corresponding to a human caspase-3 cDNA sequence were combined with total RNA from ovine CL in a reverse transcription-polymerase chain reaction-based procedure to amplify a 640-base pair partial cDNA with a nucleotide sequence 86% and 81% identical to the human and rat caspase-3 cDNAs, respectively.

Prostaglandin F2alpha stimulates the Raf/MEK1/mitogen-activated protein kinase signaling cascade in bovine luteal cells.

Upon binding to its G protein-coupled transmembrane receptors, the actions of PGF2alpha on the corpus luteum are initiated by the phospholipase C/diacylglycerol-inositol 1,4,5-trisphosphate (InsP3)/Ca2+-protein kinase C (PKC) pathway. However, little is known about the downstream intracellular signaling events that can lead to transcriptional activation in response to PGF2alpha. The present study was conducted to examine the involvement of the mitogen-activated protein kinase (MAPK) signaling cascade in the corpus luteum.

Mechanisms of hormone and growth factor action in the bovine corpus luteum.

The binding of hormones and growth factors to their cell surface receptors leads to an orderly cascade of events leading to activation of cytoplasmic effector molecules. The mechanism of action of luteinizing hormone involves the stimulation of multiple signal transduction effector systems including adenylyl cyclase and inositol phospholipid-specific phospholipase C (PLC). This results in the formation of second messengers that activate cAMP-dependent, Ca(2+)-dependent and lipid-dependent protein kinases.

Effect of interleukin-3 on ovine trophoblast interferon during early conceptus development.

The effect of interleukin-3 (IL-3) on conceptus production of ovine interferon tau (olFNτ) was examined using two dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis (2D SDS-PAGE), western blot, northern/slot blot,in situ hybridization and immunohistochemical methodologies. Ovine conceptuses (day 17,n=14) were culturedin vitro for 24 h in Eagle's Minimum Essential Medium (MEM) containing various doses of human recombinant interleukin-3 (hIL-3). At 75 and 150 colony forming units (units)/ml hIL-3, amounts of oIFNτ released into the culture media increased 3-8-fold over controls while at 300 units/ml (60 pM), hIL-3 did not enhance oIFNτ production.