Izabela Woclawek-Potocka

Progesterone Is a Suppressor of Apoptosis in Bovine Luteal Cells

Abstract Progesterone is suggested to be a suppressor of apoptosis in bovine luteal cells. Fas antigen (Fas) is a cell surface receptor that triggers apoptosis in sensitive cells. Furthermore, apoptosis is known to be controlled by the bcl-2 gene/protein family and caspases. This study was undertaken to determine whether intraluteal progesterone (P4) is involved in Fas L–mediated luteal cell death in the bovine corpus luteum (CL) in vitro. Moreover, we studied whether an antagonist of P4 influences gene expression of the bcl-2 family and caspase-3 and the activity of caspase-3 in the bovine CL. Luteal cells obtained from the cows in the midluteal phase of the estrous cycle (Days 8–12 of the cycle) were exposed to a specific P4 antagonist (onapristone [OP], 10−4 M) with or without 100 ng/ml Fas L. Although Fas L alone did not show a cytotoxic effect, treatment of the cells with OP alone or in combination with Fas L resulted in killing of 30% and 45% of the cells, respectively (P < 0.05). DNA fragmentation was observed in the cells treated with Fas L in the presence of OP. The inhibition of P4 action by OP increased the expression of Fas mRNA (P < 0.01); however, it did not affect bax or bcl-2 mRNA expression (P > 0.05). Moreover, OP stimulated expression of caspase-3 mRNA (P < 0.01). The overall results indirectly show that intraluteal P4 suppresses apoptosis in bovine luteal cells through the inhibition of Fas and caspase-3 mRNA expression and inhibition of caspase-3 activation.

Roles of Tumor Necrosis Factor-α of the Estrous Cycle in Cattle: An In Vivo Study

Abstract We have suggested in a previous in vitro study that tumor necrosis factor-α (TNFα) plays a role in the initiation of luteolysis in cattle. The aim of the present study was to examine the influence of different doses of TNFα on the estrous cycle in cattle by observing the standing behavior and measuring peripheral concentrations of progesterone (P4) during the estrous cycle. Moreover, we evaluated the secretion of P4, oxytocin (OT), nitric oxide (NO), and luteolytic (prostaglandin F2α [PGF2α] and leukotriene C4 [LTC4]) and luteotropic (PGE2) metabolites of arachidonic acid in peripheral blood plasma as parameters of TNFα actions. Mature Holstein/Polish black and white heifers (n = 36) were treated on Day 14 of the estrous cycle (Day 0 = estrus) by infusion into the aorta abdominalis of saline (n = 8), an analogue of PGF2α (cloprostenol, 100 μg; n = 3) or saline with TNFα at doses of 0.1 (n = 3), 1 (n = 8), 10 (n = 8), 25 (n = 3), or 50 μg (n = 3) per animal. Peripheral blood samples were collected frequently before, during, and up to 4 h after TNFα treatment. After Day 15 of the estrous cycle, blood was collected once daily until Day 22 following the first estrus. Lower doses of TNFα (0.1 and 1 μg) decreased the P4 level during the estrous cycle and consequently resulted in shortening of the estrous cycle (18.8 ± 0.9 and 18.0 ± 0.7 days, respectively) compared with the control (22.3 ± 0.3 days, P < 0.05). One microgram of TNFα increased the PGF2α (P < 0.001) and NO (P < 0.001) concentrations and decreased OT secretion (P < 0.01). Higher doses of TNFα (10, 25, 50 μg) stimulated synthesis of P4 (P < 0.001) and PGE2 (P < 0.001), inhibited LTC4 secreton (P < 0.05), and consequently resulted in prolongation of the estrous cycle (throughout 30 days, P < 0.05). Altogether, the results suggest that low concentrations of TNFα cause luteolysis, whereas high concentrations of TNFα activate corpus luteum function and prolong the estrous cycle in cattle.

Soybean-derived phytoestrogens regulate prostaglandin secretion in endometrium during cattle estrous cycle and early pregnancy.

Phytoestrogens acting as endocrine disruptors may induce various pathologies in the female reproductive tract. The purpose of this study was to determine whether phytoestrogens present in the soybean and/or their metabolites are detectable in the plasma of cows fed a diet rich in soy and whether these phytoestrogens influence reproductive efficiency and prostaglandin (PG) synthesis during the estrous cycle and early pregnancy in the bovine endometrium. In in vivo Experiment 1, we found significant levels of daidzein and genistein in the fodder and their metabolites (equol and p-ethyl-phenol) in bovine serum and urine. The mean number of artificial inseminations (Als) and pregnancy rates in two kinds of herds, control and experimental (cows fed with soybean 2.5 kg/day), were almost double in the soy-diet herd in comparison with the control animals. In in vivo Experiment 2, three out of five heifers fed soybean (2.5 kg/day) became pregnant whereas four out of five heifers in the control group became pregnant. The concentrations of a metabolite of PGF2α (PGFM) were significantly higher in the blood plasma of heifers fed a diet rich in soybean than those in the control heifers throughout the first 21 days after ovulation and AI. The higher levels of PGFM were positively correlated with equol and p-ethyl phenol concentrations in the blood. In in vitro experiments, the influence of isoflavones on PG secretion in different stages of the estrous cycle was studied. Although all phytoestrogens augmented the output of both PGs throughout the estrous cycle, equol and p-ethyl-phenol preferentially stimulated PGF2α output. The results obtained lead to the conclusion that soy-derived phytoestrogens and their metabolites disrupt reproductive efficiency and uterus function by modulating the ratio of PGF2α to PGE2, which leads to high, nonphysiological production of luteolytic PGF2α in cattle during the estrous cycle and early pregnancy.

The influence of tumor necrosis factor α (TNF) on the secretory function of bovine corpus luteum: TNF and its receptors expression during the estrous cycle

Tumor necrosis factor alpha (TNF) inversely regulates the function of bovine corpus luteum (CL). Whereas the low doses of TNF induce luteolysis, the high doses prolong CL lifespan and prevent luteolysis in vivo. We suggest that the varying effects of TNF may be caused by its action exerted on CL via multiple signaling pathways involving two distinct receptors: TNFR-I (responsible for induction of the cell death) and TNFR-II (implicated in cell proliferation). In the study, we determined CL expressions of TNF, TNFR-I and TNFR-II mRNAs during the bovine estrous cycle using semi-quantitative RT-PCR. Specific transcripts for TNF, TNFR-I and TNFR-II were found in the CL with the highest (p<0.05) expression in the regressed CL. We also examined the TNF influence on the bovine CL function in vivo. On Day 15 of the estrous cycle, cows were infused (via aorta abdominalis) with saline, TNF (1 or 10 microg) or analogue of prostaglandin (PG)F(2alpha) (aPGF(2alpha) , 500 microg; a positive control). Four hours after infusions, CLs were collected by colpotomy and luteal contents of progesterone (P(4)), stable metabolites of nitric oxide (NO; nitrite/nitrate), leukotriene (LT)C(4), luteolytic PGF(2alpha),and luteotropic PGE(2) were determined. Moreover, caspase-3 activity was measured in the CLs as an indicator of apoptosis induction. The luteal content of P(4) decreased (p<0.05) after infusion of 1 microg of TNF. TNF inversely affected PGs content in CL: the low dose increased (p<0.01) the PGF(2alpha) level and the high dose increased (p<0.05) PGE(2) level. Contents of LTC(4) and nitrite/nitrate increased (p<0.01) after the low dose of TNF. Moreover, 1 microg of TNF induced apoptosis and increased (p<0.05) caspase-3 activity in the CLs collected during the late luteal phase. In conclusion, the high expressions of TNF and TNF receptors mRNAs were observed during or just after the luteolysis. A low concentration of TNF stimulated in vivo luteolytic factors such as PGF(2alpha), LTC(4) and NO as well as induced apoptosis; whereas the high concentration of TNF stimulated a survival pathway in the bovine CL increasing luteal content of P(4) and PGE(2).

Lysophosphatic acid modulates prostaglandin secretion in the bovine uterus.

Lysophosphatidic acid (LPA) modulates prostaglandin (PG) synthesis via LPA receptor 3 (LPAR3) in the murine endometrium. The lack of functional LPAR3 in mice may lead to embryo mortality. In the present study, we examined the role of LPA in the bovine uterus. We confirmed that LPA is locally produced and released from the bovine endometrium. Moreover, there are enzymes involved in LPA synthesis (phospholipase (PL) D(2) and PLA2G1B) in the bovine endometrium during estrous cycle and early pregnancy. Expression of the receptor for LPA (LPAR1) was positively correlated with the expression of PGE(2) synthase (PGES) and negatively correlated with the expression of PGF(2alpha) synthase (aldose reductase with 20 alpha-hydroxysteroid dehydrogenase activity - PGFS) during early pregnancy. In vivo LPA induced P4 and PGE(2) secretion was inhibited by LPAR1 antagonist (Ki16425). The overall results indicate that LPA is locally produced and released from the bovine endometrium. Moreover, LPAR1 gene expression in the endometrium during the estrous cycle and early pregnancy indicates that LPA may play autocrine and/or paracrine roles in the bovine uterus. LPAR1 gene expression is positively correlated with the expression of the enzyme responsible for luteotropic PGE(2) production (PGES) in endometrium. In cow, LPA stimulates P4 and PGE(2) secretion. Thus, LPA in the bovine reproductive tract may indirectly (via endometrium) or directly support corpus luteum action via the increase of P4 synthesis and the increase of PGE(2)/PGF(2)(alpha) ratio. It suggests that LPA may serve as an important factor in the maintenance of early pregnancy in cow.

Phytoestrogens modulate prostaglandin production in bovine endometrium: cell type specificity and intracellular mechanisms.

Prostaglandins (PGs) are known to modulate the proper cycllcity of bovine reproductive organs. The main luteolytlc agent in ruminants Is PGF2α, whereas PGE2 has luteotropic actions. Estradiol 17ß (E2) regulates uterus function by influencing PG synthesis. Phytoestrogens structurally resemble E2 and possess estrogenic activity; therefore, they may mimic the effects of E2 on PG synthesis and influence the reproductive system. Using a cell-culture system of bovine epithelial and stromal cells, we determined cell-specific effects of phytoestrogens (i.e., daidzein, genistein), their metabolites (i.e., equol and para-ethyl-phenol, respectively), and E2 on PGF2α and PGE2synthesis and examined the intracellular mechanisms of their actions. Both PGs produced by stromal and epithelial cells were significantly stimulated by phytoestrogens and their metabolites. However, PGF2α synthesis by both kinds of cells was greater stimulated than PGE2 synthesis. Moreover, epithelial cells treated with phytoestrogens synthesized more PGF2α than stromal cells, increasing the PGF2α, to PGE2 ratio. The epithelial and stromal cells were prelncubated with an estrogen-receptor (ER) antagonist (i.e., ICI), a transiation inhibitor (i.e., actinomycin D), a protein kinase A inhibitor (i.e., staurosporin), and a phospholipase C inhibitor (i.e., U73122) for 0.5 hrs and then stimulated with equol, para-ethyl-phenol, or E2- Although the action of E2 on PGF2α synthesis was blocked by all reagents, the stimulatory effect of phytoestrogens was blocked only by ICI and actinomycin D in both cell types. Moreover, in contrast to E2action, phytoestrogens did not cause Intracellular calcium mobilization in either epithelial or stromal cells. Phytoestrogens stimulate both PGF2α and PGE2 in both cell types of bovine endometrium via an ER-dependent genomic pathway. However, because phytoestrogens preferentially stimulated PGF2α synthesis in epithelial cells of bovine endometrium, they may disrupt uterus function by altering the PGF2α to PGE2 ratio.

Lysophosphatidic acid stimulates prostaglandin E2 production in cultured stromal endometrial cells through LPA1 receptor.

Lysophosphatidic acid (LPA) has been shown to be a potent modulator of prostaglandin (PG) secretion during the luteal phase of the estrous cycle in the bovine endometrium in vivo. The aims of the present study were to determine the cell types of the bovine endometrium (epithelial or stromal cells) responsible for the secretion of PGs in response to LPA, the cellular, receptor, intracellular, and enzymatic mechanisms of LPA action. Cultured bovine epithelial and stromal cells were exposed to LPA (10−5–10−9 M), tumor necrosis factor α (TNFα; 10 ng/mL) or oxytocin (OT; 10−7 M) for 24 h. LPA treatment resulted in a dose-dependent increase of PGE2 production in stromal cells, but not in epithelial cells. LPA did not influence PGF2α production in stromal or epithelial cells. To examine which type of LPA G-protein–coupled receptor (LP-GPCR; LPA1, LPA2, or LPA3) is responsible for LPA action, stromal cells were preincubated with three selected blockers of LPA receptors: NAEPA, DGPP, and Ki16425 for 0.5 h, and then stimulated with LPA. Only Ki16425 inhibited the stimulatory effect of LPA on PGE2 production and cell proliferation in the stromal cells. LPA-induced intracellular calcium ion mobilization was also inhibited only by Ki16425. Finally, we examined whether LPA-induced PGE2 synthesis in stromal cells is via the influence on mRNA expression for the enzymes responsible for PGE2 synthesis—PGE 2 synthase (PGES) and PG-endoperoxide synthase 2 (PTGS2). We demonstrated that the stimulatory effect of LPA on PGE2 production in stromal cells is via the stimulation of PTGS2 and PGES mRNA expression in the cells. The overall results indicate that LPA stimulates PGE2 production, cell viability, and intracellular calcium ion mobilization in cultured stromal endometrial cells via Ki16425-sensitive LPA1 receptors. Moreover, LPA exerts a stimulatory effect on PGE2 production in stromal cells via the induction of PTGS2 and PGES mRNA expression.

Interferon-τ Blocks the Stimulatory Effect of Tumor Necrosis Factor-α on Prostaglandin F2α Synthesis by Bovine Endometrial Stromal Cells

Abstract Tumor necrosis factor-α (TNFα) has been shown to be a potent stimulator of prostaglandin (PG) F2α synthesis in bovine endometrial stromal cells. The aims of the present study were to determine the effect of interferon-τ (IFNτ) on TNFα-stimulated PGF2α synthesis and the intracellular mechanisms of TNFα and IFNτ action in the stromal cells. When cultured bovine stromal cells were exposed to TNFα (0.006–0.6 nM) for 24 h, the production of PGF2α and cyclooxygenase (COX)-2 gene expression were stimulated by TNFα (0.06–0.6 nM, P < 0.05). Moreover, a specific COX-2 inhibitor (NS-398; 5 nM) blocked the stimulatory effect of TNFα on PGF2α production (P < 0.05). Although IFNτ (0.03–30 ng/ml) did not stimulate basal PGF2α production in the stromal cells, it suppressed TNFα action in PGF2α production dose dependently (P < 0.05). Moreover, the stimulatory effect of TNFα (0.6 nM) on COX-2 gene expression was completely blocked by IFNτ (30 ng/ml; P < 0.05), although the gene expression of COX-2 was not influenced by IFNτ. The overall results indicate that the stimulatory effect of TNFα on PGF2α production is mediated by the up-regulation of COX-2 gene expression and suggest that one of the mechanisms of the inhibitory effect of IFNτ on luteolysis is the inhibition of TNFα action in PGF2α production in the stromal cells by the down-regulation of COX-2 gene expression stimulated by TNFα.

Infusion of Exogenous Tumor Necrosis Factor Dose Dependently Alters the Length of the Luteal Phase in Cattle: Differential Responses to Treatment with Indomethacin and L-NAME, a Nitric Oxide Synthase Inhibitor

Abstract We examined whether prostaglandins (PGs) and nitric oxide (NO) mediate tumor necrosis factor (TNF) actions in the estrus cycle. On Day 14 of the cycle, the following solutions were infused into the aorta abdominalis of a total of 51 heifers (Experiments 1 and 2): saline; 1 or 10 μg of TNF; 480 mg indomethacin (INDO), an inhibitor of prostaglandin H synthase; 800 mg L-NAME, an inhibitor of NO synthase; and TNF (1 or 10 μg) in combination with INDO or L-NAME. TNF at 1 μg infused directly into aorta abdominalis increased the level of PGF2alpha and decreased the level of progesterone (P4) in the peripheral blood and shortened the estrus cycle. The high TNF dose stimulated P4 and PGE2 and prolonged the corpus luteum (CL) lifespan. INDO blocked the effects of both TNF doses on the CL lifespan and hormone output. L-NAME completely blocked the effects of the luteolytic TNF dose, whereas the effects of the luteotropic TNF dose were not inhibited. In Experiment 3 (Day 14), saline or different TNF doses were infused into the jugular vein (n = 9) or into the uterine lumen (n = 18). The CL lifespans of the different groups were not different when TNF was infused into the jugular vein. Although high TNF doses (1 and 10 μg) infused into the uterine lumen prolonged the CL lifespan, low doses (0.01 and 0.1 μg) induced premature luteolysis. We suggest that the actions of exogenous TNF on the CL lifespan depend on PG synthesis stimulated by TNF in the uterus. TNF at low concentrations initiates a positive cascade between uterine PGF2alpha and various luteolytic factors, including NO, to complete premature luteolysis. PGE2 is a good candidate mediator of the luteotropic actions of exogenous TNF action.

Diverse Effects of Phytoestrogens on the Reproductive Performance: Cow as a Model

Phytoestrogens, polyphenolic compounds derived from plants, are more and more common constituents of human and animal diets. In most of the cases, these chemicals are much less potent than endogenous estrogens but exert their biological effects via similar mechanisms of action. The most common source of phytoestrogen exposure to humans as well as ruminants is soybean-derived foods that are rich in the isoflavones genistein and daidzein being metabolized in the digestive tract to even more potent metabolites—para-ethyl-phenol and equol. Phytoestrogens have recently come into considerable interest due to the increasing information on their adverse effects in human and animal reproduction, increasing the number of people substituting animal proteins with plant-derived proteins. Finally, the soybean becomes the main source of protein in animal fodder because of an absolute prohibition of bone meal use for animal feeding in 1995 in Europe. The review describes how exposure of soybean-derived phytoestrogens can have adverse effects on reproductive performance in female adults.