Luteolytic effect of prostaglandin F 2 alpha on bovine corpus luteum depends on cell composition and contact

Luteotropic and Luteolytic Factors Modulate the Expression of Nuclear Receptor Coregulators in Bovine Luteal Cells Independently of Histone Acetyltransferase and Histone Deacetylase Activities

The aims of this study were to examine the effect of luteotropic and luteolytic factors on the mRNA and protein expression of the coactivators HAT: histone acetyltransferase p300 (P300), cyclic adenosine monophosphate response element-binding protein (CREB), and steroid receptor coactivator-1 (SRC-1) and the corepressor: nuclear receptor corepressor-2 (NCOR-2) in bovine luteal cells on days 6-10 and 16-20. HAT and HDAC activities were also measured. The obtained results showed that luteotropic and luteolytic factors influence changes in the mRNA and protein levels of the coregulators of PGRs. However, they did not affect the activity of related HAT and HDAC, respectively. Therefore, it is possible that these factors, through changes in the expression of nuclear receptor coactivators and corepressors, may affect the functioning of the nuclear receptors, including PGRs, in the bovine CL.

The Role of Peroxisome Proliferator-Activated Receptors in PGF2α-Induced Luteolysis in the Bovine Corpus Luteum

Simple Summary

The corpus luteum (CL) is responsible for progesterone (P₄) secretion. In the absence of pregnancy, luteolysis occurs, which leads to a reduction in P₄ production, followed by the structural regression of the CL. In cows, prostaglandin F_2α (PGF_2α) is the main luteolytic factor. It is also an endogenous ligand for peroxisome proliferator-activated receptors (PPARs), which are important factors regulating mammalian reproductive function. However, the mechanisms of action of PPAR isoforms, i.e., PPARα, PPARδ and PPARγ, in the luteolytic pathways in cattle are still not fully understood. The aim of this in vitro study was to determine the expression of PPAR isoforms in the bovine CL throughout the estrous cycle, and their involvement in PGF_2α-induced processes related to luteolysis. The obtained results indicate that the expression of PPARs changes in the bovine CL throughout the estrous cycle; moreover, PGF_2α affects its expression. This study provides evidence that PPARγ, among all examined PPAR isoforms, could be involved in the regulation of PGF_2α-induced luteolysis in cattle, and PPARs may affect CL regression at multiple sites. These results help to widen the knowledge of the mechanisms of luteal regression in the bovine CL.

Abstract

The participation of peroxisome proliferator-activated receptors (PPARs) in ovarian function in cattle is still not fully understood. The aim of this in vitro study was to determine: (i) the immunolocalization, mRNA expression and tissue concentration of PPARα, PPARδ and PPARγ in the bovine corpus luteum (CL) (n = 40) throughout the estrous cycle, and (ii) the involvement of PPAR in PGF_2α-induced processes related to luteolysis. CL (n = 9) explants were cultured in the presence of PPAR antagonists (10⁻⁵ M) in combination with or without PGF_2α receptor antagonist (10⁻⁵ M) and PGF_2α (10⁻⁶ M). The mRNA and protein expression of PPARs was evaluated through qPCR, IHC, and ELISA, respectively. The results showed that PPAR mRNA and protein expression differed according to the luteal stages. PGF_2α upregulated PPARδ and PPARγ mRNA expression in the bovine CL in vitro, whereas PPARγ increased the inhibitory effect of PGF_2α by decreasing progesterone secretion and the mRNA expression of hydroxy-delta-5-steroid dehydrogenase, 3 β- and steroid delta-isomerase 1 (HSD3B1) in the CL explants; mRNA transcription of tumor necrosis factor α (TNFα) and inducible nitric oxide synthase (iNOS) was increased. The obtained results indicate that the mRNA and protein expression of PPARs changes in the bovine CL throughout the estrous cycle and under the influence of PGF_2α. We suggest that isoform γ, among all examined PPARs, could be a factor involved in the regulation of PGF_2α-induced processes related to luteolysis in the bovine CL. Further studies are needed to understand the role of PPAR in luteal regression in the CL of cattle.

Cloprostenol, a synthetic analog of prostaglandin F2α induces functional regression in cultured luteal cells of felids†

In the present study, we investigated the effect of the synthetic analog of prostaglandin F2α (PGF2α)-cloprostenol-on cultured steroidogenic luteal cells of selected felid species over a 2-day culture period. The changes induced by cloprostenol were measured based on progesterone concentration and mRNA expression analysis of selected genes. Cloprostenol significantly reduced concentration of progesterone in cell culture medium of small luteal cells isolated from domestic cat corpora lutea (CL) at the development/maintenance stage (P < 0.05), but did not influence progesterone production in cultured cells from the regression stage. A decrease or complete silencing of progesterone production was also measured in cultured luteal cells of African lion (formation stage) and Javan leopard (development/maintenance stage). Gene-expression analysis by real-time PCR revealed that treatment with cloprostenol did not have an influence on expression of selected genes coding for enzymes of steroidogenesis (StAR, HSD3B, CYP11A1) or prostaglandin synthesis (PTGS2, PGES), nor did it effect hormone receptors (AR, ESR1, PGR, PTGER2), an anti-oxidative enzyme (SOD1) or factors of cell apoptosis (FAS, CASP3, TNFRSF1B, BCL2) over the studied period. Significant changes were measured only for expressions of luteinizing hormone (P < 0.05), prolactin (P < 0.05) and PGF2α receptors (P < 0.005) (LHCGR, PRLR, and PTGFR). The obtained results confirm that PGF2α/cloprostenol is a luteolytic agent in CL of felids and its impact on progesterone production depends on the developmental stage of the CL. Cloprostenol short-term treatment on luteal cells was associated only with functional but not structural changes related to luteal regression.

Prostaglandin F2 Alpha Triggers the Disruption of Cell Adhesion with Cytokeratin and Vimentin in Bovine Luteal Theca Cells

Simple Summary

Luteolysis is an important event in the control of the corpus luteum function in bovines. However, some aspects of the luteolytic mechanism remain unclear. We evaluated changes in cell adhesion in luteal cells during regression of corpus luteum. Bovine luteal theca cells (LTCs) were treated in vitro with Prostaglandin F2 alpha (PGF2α). Cytokeratin, vimentin and desmoplakin proteins in LTCs were disrupted by PGF2α, affecting cell adhesion. These results suggest that PGF2α plays an important function in cell adhesion during the regression of corpus luteum.

Abstract

Intermediate filaments (IFs) maintain cell–cell adhesions and are involved in diverse cellular processes such as cytokinesis, cell migration and the maintenance of cell structure. In this study, we investigated the influence of prostaglandin F2 alpha (PGF2α) on cytokeratin and vimentin IFs, Rho-associated protein kinase (ROCK), and cell-cell adhesion in bovine luteal theca cells (LTCs). The luteal cells were isolated from bovine corpus luteum (CL), and the LTCs were treated with 0, 0.01, 0.1 and 1.0 mM PGF2α. Cytokeratin, vimentin and desmoplakin proteins were disrupted and the ROCK protein was significantly increased in PGF2α-treated LTCs. In addition, cell–cell adhesion was significantly (p < 0.05) decreased in the PGF2α-induced LTCs compared to control group (0 mM PGF2α). In conclusion, PGF2α affected the adhesion of cell to cell via disruption of desmoplakin, cytokeratin and vimentin, additionally increasing ROCK in bovine LTCs. These results may provide a better understanding of the mechanism of bovine CL regression.

The effect of basic fibroblast growth factor 2 on the bovine corpus luteum depends on the stage of the estrous cycle and modulates prostaglandin F2α action

The roles of fibroblast growth factor 2 (FGF2) in the corpus luteum (CL) function and its modulatory effect on prostaglandin (PG) F_2α during the bovine estrous cycle were studied using the following design of in vivo and in vitro experiments: (1) effects of FGF2 and FGF receptor 1 inhibitor (PD173074) on bovine CL function in the early (PGF_2α-resistant) and mid (PGF_2α-responsive) luteal stage in vivo, (2) the modulatory effect of FGF2 on PGF_2α action during the luteal phase in vivo and (3) effects of FGF2 and PD173074 on bovine CL secretory function in vitro. Cows were treated by injection into the CL with: (1) saline (control), (2) FGF2, (3) PD173074, (4) FGF2 followed by intramuscular (i.m.) PGF_2α, (5) PD173074 followed by i.m. PGF_2α and (6) i.m. PGF_2α as a positive control. For in vitro experiments, CL explants were treated with the aforementioned factors. Progesterone (P₄) concentrations of blood samples or culture media were determined by radioimmunoassay. Relative mRNA expressions of the genes involved in angiogenesis and steroidogenesis were determined by quantitative real-time PCR. Although FGF2 treatment on day 4 of the estrous cycle did not change the cycle length, FGF2 with PGF_2α decreased the P₄ concentrations observed during the estrous cycle compared to the control group (P < 0.001). Moreover, FGF2 treatment on day 10 prolonged CL function as indicated by a significantly greater concentration of P₄ on day 21 compared to the control group. In the in vitro study, FGF2 decreased cytochrome P450 family 11 subfamily A member 1 (CYP11A1) and hydroxy-delta-5-steroid dehydrogenase (HSD3B1) mRNA expression (P < 0.01) and decreased P₄ production in the early-stage CL (P < 0.001). However, FGF2 + PGF_2α or PGF_2α alone resulted in an elevation of steroidogenic acute regulatory protein and CYP11A1 mRNA expression and P₄ secretion in the early-stage CL (P < 0.01). In the mid-luteal phase, FGF2 upregulated CYP11A1 and HSD3B1 mRNA expression (P < 0.01), while FGF2 + PGF_2α increased only HSD3B1 mRNA expression (P < 0.001). In conclusion, FGF2 seems to play a modulatory role in CL development or luteolysis, differentially regulating steroidogenesis and angiogenic factors as well as PGF_2α actions.

Effects of prostaglandin F2α (PGF2α) on cell-death pathways in the bovine corpus luteum (CL)

BACKGROUND

Prostaglandin F_2α (PGF_2α) may differentially affect viability of luteal cells by inducing either proliferation or cell death (via apoptosis or necroptosis). The diverse effects of PGF_2α may depend on its local vs. systemic actions. In our study, we determined changes in expression of genes related to: (i) apoptosis: caspase (CASP) 3, CASP8, BCL2 associated X (BAX), B-cell lymphoma 2 (BCL2) and (ii) necroptosis: receptor-interacting protein kinase (RIPK) 1, RIPK3, cylindromatosis (CYLD), and mixed lineage kinase domain-like (MLKL) in the early and mid-stage corpus luteum (CL) that accompany local (intra-CL) vs. systemic (i.m.) analogue of PGF_2α (aPGF_2α) actions. Cows at day 4 (n = 24) or day 10 (n = 24) of the estrous cycle were treated by injections as follows: (1) systemic saline, (2) systemic aPGF_2α (25 mg; Dinoprost), (3) local saline, (4) local aPGF_2α (2.5 mg; Dinoprost). After 4 h, CLs were collected by ovariectomy. Expression levels of mRNA and protein were investigated by RT-q PCR, Western blotting and immunohistochemistry, respectively.

RESULTS

We found that local and systemic administration of aPGF_2α in the early-stage CL resulted in decreased expression of CASP3 (P < 0.01), but CASP8 mRNA expression was up-regulated (P < 0.05). However, the expression of CASP3 was up-regulated after local aPGF_2α treatment in the middle-stage CL, whereas systemic aPGF_2α administration increased both CASP3 and CASP8 expression (P < 0.01). Moreover, we observed that both local and systemic aPGF_2α injections increased RIPK1, RIPK3 and MLKL expression in the middle-stage CL (P < 0.05) while CYLD expression was markedly higher after i.m. aPGF_2α injections (P < 0.001). Moreover, we investigated the localization of necroptotic factors (RIPK1, RIPK3, CYLD and MLKL) in bovine CL tissue after local and systemic aPGF_2α injections in the bovine CL.

CONCLUSION

Our results demonstrated for the first time that genes related to cell death pathways exhibit stage-specific responses to PGF_2α administration depending on its local or systemic actions. Locally-acting PGF_2α plays a luteoprotective role by inhibiting apoptosis and necroptosis in the early CL. Necroptosis is a potent mechanism responsible for structural CL regression during PGF_2α-induced luteolysis in cattle.

Receptor interacting protein kinases-dependent necroptosis as a new, potent mechanism for elimination of the endothelial cells during luteolysis in cow

Necroptosis is an alternative form of programmed cell death regulated by receptor-interacting protein kinase (RIPK) 1 and 3-dependent. In the present study, to clarify if necroptosis in luteal endothelial cells (LECs) participates and contributes for bovine luteolysis, we investigated RIPK1 and RIPK3 localization in luteal tissue and their expression in cultured LECs after treatment with selected immune factors - mediators of luteolytic action of prostaglandin F2α (PGF). In addition, effects of tumor necrosis factor α (TNF; 2.3 nM) in combination with interferon γ (IFNG; 2.5 nM), and/or nitric oxide donor - NONOate (100 μM) on viability and CASP3 activity in the cultured LECs were investigated. Furthermore, effects of a RIPK1 inhibitor (necrostatin-1, Nec-1; 50 μM) on RIPKs and CASPs expression, were evaluated. Localization of RIPK1 and RIPK3 protein in the cultured LECs were determined. In cultured LECs, expression of RIPKs mRNA were up-regulated by TNF + IFNG at 12 h, and by PGF (1 μM) or NONOate at 24 h, respectively (P < 0.05). Although NONOate decreased cell viability, it prevented TNF + IFNG-stimulated CASP3 activity in cultured LECs. Nec-1 prevented TNF + IFNG-induced RIPK1 and CASP3 mRNA expression at 12 h and prevented RIPK3 mRNA expression. These findings suggest that RIPKs-dependent necroptosis which are induced by TNF + IFNG, PGF or NO could be potent mechanism responsible for LECs cell death and disappearance of luteal capillaries in regressing bovine CL.

Isolation of luteal endothelial cells and functional interactions with T lymphocytes

The objectives of this study were to optimize the isolation of luteal endothelial cells (LEC) and examine their functional interactions with autologous T lymphocytes. Analysis by flow cytometry showed that the purity of LEC isolated by filtration was nearly 90% as indicated by Bandeiraea simplicifolia (BS)-1 lectin binding. LEC expressed mRNA for progesterone receptor (PGR), prostaglandin receptors (PTGFR, PTGER2 and 4, and PTGIR), tumor necrosis factor receptors (TNFRSF1A&B) and interleukin (IL) 1B receptors (IL1R1&2). LEC were pretreated with either vehicle, progesterone (P₄; 0-20 µM), prostaglandin (PG) E₂ or PGF_2α (0-0.2 µM), and further treated with or without TNF and IL1B (50 ng/mL each). LEC were then incubated with autologous T lymphocytes in an adhesion assay. Fewer lymphocytes adhered to LEC after exposure to high compared to low P₄ concentrations (cubic response; P < 0.05). In contrast, 0.2 µM PGE₂ and PGF_2α each increased T lymphocyte adhesion in the absence of cytokines (P < 0.05). LEC induced IL2 receptor alpha (CD25) expression and proliferation of T lymphocytes. In conclusion, filtration is an effective way of isolating large numbers of viable LEC. It is proposed that PGs and P₄ modulate the ability of endothelial cells to bind T lymphocytes, potentially regulating extravasation, and that LEC activate T lymphocytes migrating into or resident in the CL.

Programmed necrosis - a new mechanism of steroidogenic luteal cell death and elimination during luteolysis in cows

Programmed necrosis (necroptosis) is an alternative form of programmed cell death that is regulated by receptor-interacting protein kinase (RIPK) 1 and 3-dependent, but is a caspase (CASP)-independent pathway. In the present study, to determine if necroptosis participates in bovine structural luteolysis, we investigated RIPK1 and RIPK3 expression throughout the estrous cycle, during prostaglandin F2α (PGF)-induced luteolysis in the bovine corpus luteum (CL), and in cultured luteal steroidogenic cells (LSCs) after treatment with selected luteolytic factors. In addition, effects of a RIPK1 inhibitor (necrostatin-1, Nec-1; 50 μM) on cell viability, progesterone secretion, apoptosis related factors and RIPKs expression, were evaluated. Expression of RIPK1 and RIPK3 increased in the CL tissue during both spontaneous and PGF-induced luteolysis (P < 0.05). In cultured LSCs, tumor necrosis factor α (TNF; 2.3 nM) in combination with interferon γ (IFNG; 2.5 nM) up-regulated RIPK1 mRNA and protein expression (P < 0.05). TNF + IFNG also up-regulated RIPK3 mRNA expression (P < 0.05), but not RIPK3 protein. Although Nec-1 prevented TNF + IFNG-induced cell death (P < 0.05), it did not affect CASP3 and CASP8 expression. Nec-1 decreased both RIPK1 and RIPK3 protein expression (P < 0.05). These findings suggest that RIPKs-dependent necroptosis is a potent mechanism responsible for bovine structural luteolysis induced by pro-inflammatory cytokines.

Luteotropic and luteolytic factors regulate mRNA and protein expression of progesterone receptor isoforms A and B in the bovine endometrium

The aim of the present study was to examine the effects of luteotropic and luteolytic factors on the mRNA and protein levels of progesterone receptor isoforms A (PGRA) and B (PGRB) in the bovine endometrium. Endometrial slices from Days 6–10 and 17–20 of the oestrous cycle were treated with LH (100 ng mL–1), oestradiol (E2; 1 × 10–8 M), prostaglandin (PG) E2 (1 × 10–6 M) and PGF2α (1 × 10–6 M) and the nitric oxide donor NONOate (1 × 10–4 M); these treatments lasted for 6 h for mRNA expression analysis and 24 h for protein expression analysis. On Days 6–10 of the oestrous cycle PGRAB (PGRAB; the entire PGRA mRNA sequence is common to the PGRB mRNA sequence) mRNA expression in endometrial slices was enhanced by E2 treatment (P < 0.001), whereas PGRB mRNA expression was increased by LH (P < 0.001), E2 (P < 0.05) and NONOate (P < 0.05) treatment. On Days 17–20, PGRAB mRNA expression increased after E2 (P < 0.001) and PGE2 (P < 0.05) treatment; PGRB mRNA expression was increased by PGE2 (P < 0.05) and PGF2α (P < 0.01) treatment, but decreased by LH (P < 0.05). On Days 6–10 protein levels of PGRA were stimulated by E2 (P < 0.01), whereas PGRB protein levels were increased by LH (P < 0.05) and E2 (P < 0.05). On Days 17–20 of the oestrous cycle, PGRA protein levels were enhanced by E2 (P < 0.05) and PGF2α (P < 0.05), whereas PGRB protein levels were stimulated by PGE2 (P < 0.05) and PGF2α (P < 0.001). These data suggest that luteotropic and luteolytic factors affect PGRA and PGRB mRNA and protein levels, and this may regulate the effects of progesterone on endometrial cells.

Profiling of luteal transcriptome during prostaglandin F2-alpha treatment in buffalo cows: analysis of signaling pathways associated with luteolysis

In several species including the buffalo cow, prostaglandin (PG) F2α is the key molecule responsible for regression of corpus luteum (CL). Experiments were carried out to characterize gene expression changes in the CL tissue at various time points after administration of luteolytic dose of PGF2α in buffalo cows. Circulating progesterone levels decreased within 1 h of PGF2α treatment and evidence of apoptosis was demonstrable at 18 h post treatment. Microarray analysis indicated expression changes in several of immediate early genes and transcription factors within 3 h of treatment. Also, changes in expression of genes associated with cell to cell signaling, cytokine signaling, steroidogenesis, PG synthesis and apoptosis were observed. Analysis of various components of LH/CGR signaling in CL tissues indicated decreased LH/CGR protein expression, pCREB levels and PKA activity post PGF2α treatment. The novel finding of this study is the down regulation of CYP19A1 gene expression accompanied by decrease in expression of E2 receptors and circulating and intra luteal E2 post PGF2α treatment. Mining of microarray data revealed several differentially expressed E2 responsive genes. Since CYP19A1 gene expression is low in the bovine CL, mining of microarray data of PGF2α-treated macaques, the species with high luteal CYP19A1 expression, showed good correlation between differentially expressed E2 responsive genes between both the species. Taken together, the results of this study suggest that PGF2α interferes with luteotrophic signaling, impairs intra-luteal E2 levels and regulates various signaling pathways before the effects on structural luteolysis are manifest.

Influence of prostaglandin F₂α analogues on the secretory function of bovine luteal cells and ovarian arterial contractility in vitro

Although prostaglandin (PG) F2α analogues are routinely used for oestrus synchronisation in cattle, their effects on the function of the bovine corpus luteum (CL), and on ovarian arterial contractility, may not reflect the physiological effects of endogenous PGF2α. In the first of two related experiments, the effects of different analogues of PGF2α (aPGF2α) on the secretory function and apoptosis of cultured bovine cells of the CL were assessed. Enzymatically-isolated bovine luteal cells (from between days 8 and 12 of the oestrous cycle), were stimulated for 24h with naturally-occurring PGF2α or aPGF2α (dinoprost, cloprostenol or luprostiol). Secretion of progesterone (P4) was determined and cellular [Ca(2+)]i mobilisation, as well as cell viability and apoptosis were measured. Naturally-occurring PGF2α and dinoprost stimulated P4 secretion (P<0.05), whereas cloprostenol and luprostiol did not influence P4 synthesis. The greatest cytotoxic and pro-apoptotic effects were observed in the luprostiol-treated cells, at 37.3% and 202%, respectively (P<0.001). The greatest effect on [Ca(2+)]i mobilisation in luteal cells was observed post-luprostiol treatment (200%; P<0.001). In a second experiment, the influence of naturally-occurring PGF2α and aPGF2α on ovarian arterial contraction in vitro, were examined. No differences in the effects of dinoprost or naturally-occurring PGF2α were found across the studied parameters. The effects of cloprostenol and luprostiol on luteal cell death, in addition to their effects on ovarian arterial contractility, were much greater than those produced by treatment with naturally-occurring PGF2α.

Physiology and Endocrinology Symposium: role of immune cells in the corpus luteum

The immune system is essential for optimal function of the reproductive system. The corpus luteum (CL) is an endocrine organ that secretes progesterone, which is responsible for regulating the length of the estrous cycle, and for the establishment and maintenance of pregnancy in mammals. This paper reviews literature that addresses 2 areas; i) how immune cells are recruited to the CL, and ii) how immune cells communicate with luteal cells to affect the formation, development, and regression of the CL. Immune cells, primarily recruited to the ovulatory follicle from lymphoid organs after the LH surge, facilitate ovulation and populate the developing CL. During the luteal phase, changes in the population of macrophages, eosinophils, neutrophils, and T lymphocytes occur at critical functional stages of the CL. In addition to their role in facilitating ovulation, immune cells may have an important role in luteal function. Evidence shows that cytokines secreted by immune cells modulate both luteotropic and luteolytic processes. However, the decision to pursue either function may depend on the environment provided by luteal cells. It is suggested that understanding the role immune cells play could lead to identification of new strategies to improve fertility in dairy cattle and other species.

Life or death decisions in the corpus luteum

The corpus luteum (CL) is an ephemeral endocrine organ. During its lifespan, it undergoes a period of extremely rapid growth that involves hypertrophy, proliferation and differentiation of the steroidogenic cells, as well as extensive angiogenesis. The growth phase is followed by a period in which remodelling of the tissue ceases, but it engages in unparalleled production of steroids, resulting in extraordinarily high metabolic activity within the tissue. It is during this stage that a critical juncture occurs. In the non-fertile cycle, uterine release of prostaglandin (PG)F(2α) initiates a cascade of events that result in rapid loss of steroidogenesis and destruction of the luteal tissue. Alternatively, if a viable embryo is present, signals are produced that result in rescue of the CL. This review article summarizes the major concepts related to the fate of the CL, with particular focus on recent insights into the mechanisms associated with the ability of PGF(2α) to bring about complete luteolysis. It has become clear that the achievement of luteolysis depends on repeated exposure to PGF(2α) and involves coordinated actions of heterogeneous cell types within the CL. Together, these components of the process bring about not only the loss in progesterone production, but also the rapid demise of the structure itself.

Leukotrienes are auto-/paracrine factors in the bovine corpus luteum: an in vitro study

The aim of this study was to determine leukotrienes (LTs) functions in the bovine corpus luteum (BCL) during the oestrous cycle. In steroidogenic CL cells we examined the effect of luteotropic [LH, prostaglandin E(2) (PGE(2))] and luteolytic (PGF(2α), cytokines) factors on: the levels of LTB(4) and C(4), the expression of 5-lipoxygenase (LO), LT receptors type I (LTR-I) and LTR-II, and the effects of LTB(4) and C(4) stimulations on the levels of progesterone (P4), PGE(2), F(2α) and nitric oxide (NO) metabolites. Both luteolytic and luteotropic factors stimulated 5-LO expression on days 2-4 and 17-19 of the cycle. Leukotriene receptors type I expression increased after PGE(2) and tumour necrosis factor α with interferon γ (TNF/IFN) stimulation on days 2-4 of the cycle. Leukotriene receptor type II expression increased after PGE(2α) and TNF/IFN stimulation on days 2-4 and 17-19 of the cycle, and LTR-II expression on days 8-10 of the cycle was unchanged after cell stimulation with any factor. Leukotriene B(4) level increased after BSC incubation with luteotropic factors during all examined days of the cycle and after cytokine stimulation at early- and mid-luteal stages, whereas luteolytic factors stimulated LTC(4) secretion over the entire cycle. Leukotriene B(4) stimulated P4 secretion at the mid-luteal stage and stimulated NO secretion during all examined phases. Leukotriene B(4) stimulated PGE(2) secretion at the early- and mid-luteal stage. Leukotriene C(4) inhibited P4 secretion at the mid- and regressing-luteal stage, stimulated NO (entire cycle) and PGF(2α) at mid- and regressing-luteal phases. Leukotrienes modulate steroidogenic cells functions, depending on the stage of the cycle. Leukotriene B(4) plays a luteotropic role stimulating P4 and PGE(2) secretions; LTC(4) stimulates the secretion of luteolytic factors and enhances the luteolytic cascade within BCL.

Tumor necrosis factor-α inhibits the stimulatory effect of luteinizing hormone and prostaglandin E(2) on progesterone secretion by the bovine corpus luteum

Tumor necrosis factor-α (TNF-α) is involved in the tissue remodeling that occurs in the corpus luteum (CL) during its development and regression. This cytokine is also implicated in the regulation of reproduction by its actions on ovarian steroidogenic cells. The aim of this study was to examine the influence of TNF-α on (1) progesterone (P(4)) output by the bovine CL and on (2) the responsiveness of the CL to LH or prostaglandin E(2) (PGE(2)) in vitro. In experiment 1, CL (days 8 to 10 of the estrous cycle) were perfused by using an in vitro microdialysis system with TNF-α (0.1, 0.5, or 1 μg/mL) alone or with TNF-α (1 μg/mL) followed by LH (1000 ng/mL) or PGE(2) (2 × 10(-5) M). Basal P(4) release (P < 0.05) was increased by TNF-α (0.5 or 1 μg/mL). Moreover, TNF-α (1 μg/mL) inhibited the stimulatory effect of LH or PGE(2) on P(4) output (P < 0.05). In experiment 2, 4 h after intrauterine infusion of TNF-α (0.01 μg/mL or 1 μg/mL), CL (days 8 to 10 of the estrous cycle) were collected by colpotomy, cultured, and stimulated with LH (10 ng/mL) or PGE(2) (10(-6) M). Intrauterine infusion of TNF-α at a concentration of 1 μg/mL increased basal P(4) output by CL (P < 0.05). Moreover, the intrauterine infusion of TNF-α at a concentration of 0.01 μg/mL inhibited the stimulatory effect of LH or PGE(2) on P(4) output (P < 0.05). These results indicate that TNF-α (1) does not have an effect on the autonomous, pulsatile release of P(4); (2) increases P(4) secretion by bovine CL with increasing doses, and (3) reduces in a dose-dependent manner the responsiveness of CL to luteotropic factors both directly (after infusion to CL) and indirectly (after intrauterine infusion).

Leukotrienes modulate secretion of progesterone and prostaglandins during the estrous cycle and early pregnancy in cattle: an in vivo study

Recently, we showed that leukotrienes (LTs) regulate ovarian cell function in vitro. The aim of this study was to examine the role of LTs in corpus luteum (CL) function during both the estrous cycle and early pregnancy in vivo. mRNA expression of LT receptors (BLT for LTB(4) and CYSLT for LTC(4)), and 5-lipoxygenase (5-LO) in CL tissue and their localization in the ovary were studied during the estrous cycle and early pregnancy. Moreover, concentrations of LTs (LTB(4) and C(4)) in the CL tissue and blood were measured. 5-LO and BLT mRNA expression increased on days 16-18 of the cycle, whereas CYSLT mRNA expression increased on days 16-18 of the pregnancy. The level of LTB(4) was evaluated during pregnancy compared with the level of LTC(4), which increased during CL regression. LT antagonists influenced the duration of the estrous cycle: the LTC(4) antagonist (azelastine) prolonged the luteal phase, whereas the LTB(4) antagonist (dapsone) caused earlier luteolysis in vivo. Dapsone decreased progesterone (P(4)) secretion and azelastine increased P(4) secretion during the estrous cycle. In summary, LT action in the bovine reproductive tract is dependent on LT type: LTB(4) is luteotropic during the estrous cycle and supports early pregnancy, whereas LTC(4) is luteolytic, regarded as undesirable in early pregnancy. LTs are produced/secreted in the CL tissue, influence prostaglandin function, and serve as important factors during the estrous cycle and early pregnancy in cattle.

The relationship between the production and the anti-gonadotrophic action of prostaglandin F 2 alpha in luteal cells from the marmoset monkey (Callithrix jacchus) in the early and mid-luteal phase

To address the potential luteolytic role for prostaglandin F(2 alpha) (PGF(2 alpha)) in the corpus luteum of the common marmoset monkey (Callithrix jacchus), the ability of marmoset luteal cells, maintained in monolayer culture, to produce PGF(2 alpha) was determined in vitro in the presence and absence of human chorionic gonadotrophin (hCG) and other established pharmacological modulators of PGF(2 alpha) synthesis. We also assessed the effects of the PGF(2 alpha) analogue, cloprostenol, on progesterone output from luteal cells isolated in the early luteal phase versus the mid-luteal phase (days 3 and 14 post ovulation, respectively). Cloprostenol had no effect on progesterone output from luteal cells isolated on day 3 of the luteal phase, whereas it significantly inhibited both basal and hCG-stimulated progesterone synthesis by day 14 luteal cells during the culture period 48-72 h (P<0.001). Intra-luteal PGF(2 alpha) concentrations were 5-fold higher in luteal cells isolated in the early luteal phase than in mid-luteal phase cells (16.5+/-3.5 versus 3.5+/-0.6 pmol/10(5) cells). While PGF(2 alpha) production was unaffected by hCG in vitro, it was decreased by indomethacin (1000 ng/ml) (P<0.05) and stimulated by the calcium ionophore A23187 (10 micromol/l) (P<0.05) in luteal cells from both stages of the luteal phase. Phospholipase A(2) did not influence PGF(2 alpha) production by day 3 luteal cells whereas at 10 IU/ml, it significantly stimulated PGF(2 alpha) production by day 14 luteal cells (P<0.05). Hence, the timing of luteolysis in the common marmoset monkey appears to involve changes in both the luteal cell response to and production of PGF(2 alpha).

Species Comparison of the Role of p38 MAP Kinase in the Female Reproductive System

The p38 mitogen-activated protein kinases (MAPKs) are members of discrete signal transduction pathways that have significant regulatory roles in a variety of biological processes, depending on the cell, tissue and organ type. p38 MAPKs are involved in inflammation, cell growth and differentiation and cell cycle. In the female reproductive system, p38 MAPKs are known to regulate various aspects of the reproductive process such as mammalian estrous and menstrual cycles as well as early pregnancy and parturition. p38 MAPKs have also been implicated in alterations and pathologies observed in the female reproductive system. Therefore, pharmacologic modulation of p38 MAPKs, and inter-connected signaling pathways (e.g., estrogen receptor signaling, c-fos, c-jun), may influence reproductive physiology and function. This article provides a critical, comparative review of available data on the roles of p38 MAPKs in the mammalian female reproductive system and in reproductive pathophysiology in humans and preclinical species. We first introduce fundamental differences and similarities of the mammalian female reproductive system that should be considered by toxicologists and toxicologic pathologists when assessing the effects of new pharmacologic agents on the female reproductive system. We then explore in detail the known roles for p38 MAPKs and related molecules in female reproduction. This foundation is then extended to pathological conditions in which p38 MAPKs are thought to play an integral role.