Interleukin-1 beta is a potent stimulator of prostaglandin synthesis in bovine luteal cells.

Interleukin-1 (IL-1) is a polypeptide that has both local and systemic effects on numerous tissues, including endocrine cells. To evaluate the effect of IL-1 on luteal function, bovine luteal cells were cultured for 5 days with increasing concentrations (0.1, 0.5, 1.0, 2.5, 5.0, 10.0 ng/ml) of recombinant bovine interleukin-1 beta (rbIL-1 beta). IL-1 beta increased the production of luteal 6-keto-prostaglandin-F1 alpha (6-keto-PGF1 alpha), prostaglandin E2 (PGE2), and prostaglandin F2 alpha (PGF2 alpha) in a dose-dependent manner, but had no effect on progesterone (P4) production. Treatment with the cyclooxygenase inhibitor, indomethacin (5 micrograms/ml), inhibited basal, as well as rbIL-1 beta-stimulated prostaglandin production. Addition of Iloprost (a synthetic analogue of prostacyclin, 5 ng/ml) suppressed basal production of PGF2 alpha and PGE2, but did not reduce the stimulatory effect of rbIL-1 beta. Similarly, PGF2 alpha suppressed basal, but not IL-1 beta-stimulated, production of 6-keto-PGF1 alpha. PGE2 had no effect on the synthesis of either PGF2 alpha or 6-keto-PGF1 alpha. P4 (1.75 micrograms/ml) reduced basal as well as rbIL-1 beta-stimulated production of 6-keto-PGF1 alpha, PGE2, and PGF2 alpha. These results indicate that IL-1 beta could serve as an endogenous regulator of luteal prostaglandin production. It appears that IL-1 beta action is not modified by exogenous prostaglandins, but is at least partially regulated by elevated P4. It is possible that the role of IL-1 beta in stimulation of luteal prostaglandin production may be confined to a period characterized by low P4 levels, such as during luteal development or regression.     

Production of prostaglandin f(2alpha) by cultured bovine endometrial cells in response to tumor necrosis factor alpha: cell type specificity and intracellular mechanisms

Tumor necrosis factor alpha (TNFalpha) has been shown to be a potent stimulator of prostaglandin (PG) F(2alpha) secretion in the bovine endometrium. The aims of the present study were to determine the cell types in the endometrium (epithelial or stromal cells) responsible for the secretion of PGF(2alpha) in response to TNFalpha, and the intracellular mechanisms of TNFalpha action. Cultured bovine epithelial and stromal cells were exposed to TNFalpha (0.006-6 nM) or oxytocin (100 nM) for 4 h. TNFalpha resulted in a dose-dependent increase of PGF(2alpha) production in the stromal cells (P < 0.001) but not in the epithelial cells. On the other hand, oxytocin stimulated PGF(2alpha) output in the epithelial cells but not in the stromal cells. When the stromal cells were incubated for 24 h with TNFalpha and inhibitors of phospholipase (PL) C or PLA(2), only PLA(2) inhibitor completely stopped the actions of TNFalpha (P < 0.001). When the stromal cells were exposed to TNFalpha and arachidonic acid, the action of TNFalpha was augmented (P < 0.001). When the stromal cells were incubated for 24 h with a nitric oxide (NO) donor (S-NAP), S-NAP stimulated the PGF(2alpha) production dose-dependently. Although an NO synthase (NOS) inhibitor (L-NAME) reduced TNFalpha-stimulated PGF(2alpha) production, an inhibitor of phosphodiesterase augmented the actions of TNFalpha and S-NAP (P < 0. 05). The overall results indicate that the target of TNFalpha for stimulation of PGF(2alpha) production in cattle is the endometrial stromal cells, and that the actions of TNFalpha are mediated via the activation of PLA(2) and arachidonic acid conversion. Moreover, TNFalpha may exert a stimulatory effect on PGF(2alpha) production via the induction of NOS and the subsequent NO-cGMP formation.     

Prostaglandin E and E2 alpha secretion by glandular and stromal cells of the pig endometrium in vitro: effects of estradiol-17 beta, progesterone, and day of pregnancy.

Prostaglandins (PGs) are believed to play important roles in the establishment of pregnancy. Glandular and stromal cells were isolated from pig endometrium on days 11 through 19 of pregnancy and cultured in the presence of estradiol-17 beta (E2) and progesterone (P4) to determine the effect of day of pregnancy and steroids on the secretion of PGE and PGF2 alpha. Estradiol at concentrations between .01 and 1 microM did not affect PGE and PGF2 alpha secretion into the medium by glandular and stromal cells. Progesterone (.1 microM) suppressed (P less than .001) PGE and PGF2 alpha production from both cell types. Glandular cells secreted more (P less than .01) PGF2 alpha than PGE, whereas stromal cells collected on days 11, 12, 13, and 19 secreted more (P less than .05) PGE than PGF2 alpha. Stromal cells isolated from tissues collected on day 13 of pregnancy produced PGs with higher (P less than .01) PGE:PGF2 alpha ratio than those from tissues harvested on other days of pregnancy. Glandular cells isolated from tissues collected on days 13 and 19 and stromal cells isolated from tissue collected on day 13 of pregnancy secreted more (P less than .05) PGE and PGF2 alpha than cells isolated on other days of pregnancy. We conclude that: 1) P4 has a suppressing effect on PG secretion; 2) endometrial glandular and stromal cells each produce a unique profile of PGs; and 3) endometrial cells harvested on different days of pregnancy secrete different amounts of PGE and PGF2 alpha.     

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

Prostaglandins (PGs) are known to modulate the proper cyclicity of bovine reproductive organs. The main luteolytic agent in ruminants is PGF2alpha, whereas PGE2 has luteotropic actions. Estradiol 17beta (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 PGF2alpha and PGE2 synthesis 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, PGF2alpha synthesis by both kinds of cells was greater stimulated than PGE2 synthesis. Moreover, epithelial cells treated with phytoestrogens synthesized more PGF2alpha than stromal cells, increasing the PGF2alpha to PGE2 ratio. The epithelial and stromal cells were preincubated with an estrogen-receptor (ER) antagonist (i.e., ICI), a translation 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 PGF2alpha 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 E2 action, phytoestrogens did not cause intracellular calcium mobilization in either epithelial or stromal cells. Phytoestrogens stimulate both PGF2alpha and PGE2 in both cell types of bovine endometrium via an ER-dependent genomic pathway. However, because phytoestrogens preferentially stimulated PGF2alpha synthesis in epithelial cells of bovine endometrium, they may disrupt uterus function by altering the PGF2alpha to PGE2 ratio.     

Regulation of prostaglandin secretion from epithelial and stromal cells of the bovine endometrium by interleukin-1 beta, interleukin-2, granulocyte-macrophage colony stimulating factor and tumor necrosis factor-alpha.

Bovine endometrium was obtained on day 16 of pregnancy (estrus = 0) and separated into epithelial and stromal cell populations. When confluent, the two cell populations were treated for 24 h with cytokines at 1, 10 and 100 ng/ml. Prostaglandin (PG) E2 was the major prostaglandin produced by both cell types. For control cultures, more PGE2 was secreted into medium by stromal cells than by epithelial cells, whereas secretion of PGF was similar for epithelial and stromal cells. Interleukin-1 beta had no effect on prostaglandin production by stromal cell cultures but increased epithelial production of PGE2 and, to a lesser extent, PGF. Conversely, granulocyte-macrophage colony stimulating factor had no effect on epithelial cells but reduced secretion of PGE2 and PGF from stromal cells. There were no effects of interleukin-2 or tumor necrosis factor-alpha on prostaglandin secretion. Results indicate that certain cytokines can regulate endometrial prostaglandin secretion in a cell type-restricted manner.     

Separation and culture of ovine endometrial epithelial and stromal cells: evidence of morphological and functional polarity.

Epithelial and stromal cells from endometria of ovariectomized estradiol-treated Corriedale ewes were separated and purified after collagenase digestion. The separation method utilized differences in the speed and ease of detachment of cultured epithelial and stromal cells attached to plastic in response to brief trypsin exposure. Cells were characterized according to morphological, growth, and histochemical criteria. Contamination of each cell type with the other was less than 1%. Separated cells were grown on plastic or on Matrigel-coated Millicell inserts with nitrocellulose membranes. Transmission and scanning electron microscope analyses demonstrated the existence of tight junctions and prominent microvilli in the epithelial cultures on inserts but not on plastic. Asymmetrical secretion of prostaglandin F2 alpha (PGF2 alpha) and prostaglandin E (PGE) by epithelial cells provided further evidence of polarization. Epithelial cell secretion of PGF2 alpha was greater than that by stromal cells whereas PGE secretion by stromal cells was greater than that by epithelial cells. Epithelial secretion in the basal direction was approximately 4 and 3 times that of apical secretion for PGF2 alpha and PGE, respectively. The separation protocol provides pure populations of ovine endometrial epithelial and stromal cells and the cultured epithelial cells exhibit characteristics of in vivo morphology and polarized function.     

Expression of tenascin-C in stromal cells of the murine uterus during early pregnancy: induction by interleukin-1 alpha, prostaglandin E(2), and prostaglandin F(2 alpha)

Tenascin-C (TN-C), an extracellular matrix glycoprotein, is known to be expressed in uterine stroma in the peri-implantation period. Examination of the spatiotemporal pattern during early pregnancy using immunohistochemistry and in situ hybridization revealed TN-C expression in the stroma beneath the luminal epithelia of the murine endometrium on Days 0 and 1 of pregnancy, subsequent disappearance, and reappearance on Day 4. After decidualization, tissue around the deciduoma was positive. In situ hybridization demonstrated TN-C production by the stromal cells adjacent to the epithelia. To investigate the regulation of TN-C expression in vitro, murine uterine stromal and epithelial cells were isolated and cultured. Addition of interleukin-1 alpha (IL-1 alpha) and prostaglandin E(2) (PGE(2)) and F(2 alpha) (PGF(2 alpha)) induced TN-C expression in the stromal cells at both protein and mRNA levels, while the sex steroid hormones, progesterone and ss-estradiol, exerted little effect. Immunohistochemistry using anti-IL-1 alpha antibody showed epithelial cells to be positive on Days 2-4 of pregnancy, and addition of progesterone but not ss-estradiol enhanced IL-1 alpha expression in epithelial cells in vitro. In a culture insert system, TN-C expression by stromal cells cocultured with epithelial cells was induced by addition of progesterone alone that was blocked by additions of anti-IL-1 alpha antibody. Collectively, these findings indicate that TN-C expression in the preimplantation period is under the control of progesterone, but not directly, possibly by the paracrine and autocrine intervention of IL-1 alpha secreted by epithelial cells and PGE(2) and PGF(2 alpha) secreted by stromal cells.     

Phytoestrogen metabolites are much more active than phytoestrogens themselves in increasing prostaglandin F(2alpha) synthesis via prostaglanin F(2alpha) synthase-like 2 stimulation in bovine endometrium

Phytoestrogens have recently been suggested to be the cause of infertility by stimulating luteolytic prostaglandin (PG) F(2alpha) secretion from endometrium in cattle. The purpose of this study was to examine the enzymatic and molecular mechanisms involved in the preferential induction of PGF(2alpha) synthesis by phytoestrogens, and whether phytoestrogens influence endometrial cell viability. Cultured bovine endometrial epithelial and stromal cells were exposed to phytoestrogens (daidzein and genistein) and their metabolites (equol and p-ethyl phenol) for 24h. Prostaglandin F(2alpha) and PGE2 were stimulated by phytoestrogens in both stromal and epithelial cells, with a preference for PGF(2alpha) synthesis in epithelial cells (P<0.001). Although RT-PCR and Western Blot analyses did not reveal the influence of phytoestrogens on either gene expression or protein level of cyclooxygenase-2 (COX-2) and PGE2 synthase (PGES) in stromal and epithelial cells (P>0.05), the stimulative effects of equol and p-ethyl phenol on PGF(2alpha) synthase-like 2 (PGFSL2) gene expression and protein level were observed only in epithelial cells (P<0.05). The same compounds did not affect PGFSL2 gene expression and protein in stromal cells (P>0.05). Exposure to phytoestrogens and their metabolites decreased cell viability in both stromal and epithelial cells. Stromal cell viability decreased to 50% of the control and was more evident than that in epithelial cells (P<0.001). The overall results suggest that infertility in cattle, caused by phytoestrogen-dependent preferential stimulation of luteolytic PGF(2alpha) synthesis, is caused by increasing PGFSL2 in epithelial cells, and by decreasing stromal cell viability, which are the main source of luteotropic PGE2 production.     

Prostaglandin synthesis by isolated cells of rat uterus: production rates, and effects of indomethacin and histamine

Luminal epithelial and residual cells (mainly of the endometrial stromal tissue) of proestrous rat uteri have been isolated and cultured in defined medium. The prostaglandins produced during a short-term incubation (2 h) in the presence of 10 microM arachidonic acid (to optimize PG production) were determined by direct assay of the culture medium. For the epithelial cells, PGF2 alpha was produced in greatest amounts, followed by 6-keto PGF1 alpha and PGE, while low levels were synthesized by the residual cells. The synthesis of PGF2 alpha by the epithelial cells was inhibited by incorporating indomethacin into the medium and an IC50 value of 2.3 microM was obtained. Incubations performed with histamine in the absence of exogenous arachidonic acid indicated that the pathways for the production of individual prostaglandins were followed to different relative extents, with the production of 6-keto PGF1 alpha being enhanced for both groups of cells when compared to incubations with arachidonic acid.     

Interferon-tau blocks the stimulatory effect of tumor necrosis factor-alpha on prostaglandin F2alpha synthesis by bovine endometrial stromal cells

Tumor necrosis factor-alpha (TNFalpha) has been shown to be a potent stimulator of prostaglandin (PG) F2alpha synthesis in bovine endometrial stromal cells. The aims of the present study were to determine the effect of interferon-tau (IFNtau) on TNFalpha-stimulated PGF2alpha synthesis and the intracellular mechanisms of TNFalpha and IFNtau action in the stromal cells. When cultured bovine stromal cells were exposed to TNFalpha (0.006-0.6 nM) for 24 h, the production of PGF2alpha and cyclooxygenase (COX)-2 gene expression were stimulated by TNFalpha (0.06-0.6 nM, P < 0.05). Moreover, a specific COX-2 inhibitor (NS-398; 5 nM) blocked the stimulatory effect of TNFalpha on PGF2alpha production (P < 0.05). Although IFNtau (0.03-30 ng/ml) did not stimulate basal PGF2alpha production in the stromal cells, it suppressed TNFalpha action in PGF2alpha production dose dependently (P < 0.05). Moreover, the stimulatory effect of TNFalpha (0.6 nM) on COX-2 gene expression was completely blocked by IFNtau (30 ng/ml; P < 0.05), although the gene expression of COX-2 was not influenced by IFNtau. The overall results indicate that the stimulatory effect of TNFalpha on PGF2alpha production is mediated by the up-regulation of COX-2 gene expression and suggest that one of the mechanisms of the inhibitory effect of IFNtau on luteolysis is the inhibition of TNFalpha action in PGF2alpha production in the stromal cells by the down-regulation of COX-2 gene expression stimulated by TNFalpha.     

The effects of Arcanobacterium pyogenes on endometrial function in vitro, and on uterine and ovarian function in vivo

Uterine bacterial infection after parturition causes endometritis, perturbs ovarian function and leads to infertility in cattle. Although endometritis is caused by mixed infections, endometrial pathology is associated with the presence of Arcanobacterium pyogenes. The aims of the present study were to determine the effects of A. pyogenes on endometrial function in vitro, and on uterine and ovarian function in vivo. Heat-killed A. pyogenes did not affect the production of prostaglandin F2alpha (PGF) or prostaglandin E(2) (PGE) from endometrial explants, or purified populations of endometrial epithelial or stromal cells. However, the explants produced more PGF and PGE than controls when treated with a bacteria-free filtrate (BFF) cultured from A. pyogenes. Similarly, BFF stimulated PGF and PGE production by epithelial and stromal cells, respectively. So, BFF or control PBS was infused into the uterus of heifers (n=7 per group) for 8 days, starting the day after estrus. Emergence of the follicle wave, dominant follicle or corpus luteum diameter, and peripheral plasma FSH, LH, estradiol, progesterone, PGFM, or acute phase protein concentrations were unaffected by the BFF infusion. In the live animal it is likely that the intact uterine mucosa limits the exposure of the endometrial cells to the exotoxin of A. pyogenes, whereas the cells are readily exposed to the toxin in vitro.     

Effects of tumor necrosis factor-alpha on secretion of prostaglandins E2 and F2alpha in bovine endometrium throughout the estrous cycle

To determine the physiological significance of tumor necrosis factor-alpha (TNFalpha) in the regulation of endometrial prostaglandin (PG) release in cattle, we investigated the effects of TNFalpha on the secretion of PGE2 and PGF2alpha by bovine endometrium during the estrous cycle. Bovine uteri were classified into six stages (estrus: Day 0, early luteal 1: Days 2 to 3, early luteal 11: Days 5 to 6, mid-luteal: Days 8 to 12, late luteal: Days 15 to 17 and follicular: Days 19 to 21). After 1 h of pre-incubation, endometrial tissues (20 to 30 mg) were exposed to 0 or 0.6 nM TNFalpha for 4 h. The PGE2 concentrations in the medium were higher in the luteal stages than in the follicular stage and in estrus. In contrast, PGF2alpha concentrations were higher in the follicular stage and in estrus than in the luteal stages. The ratio of the basal concentrations of PGE2 and PGF2alpha (PGE2/PGF2alpha ratio) was higher in the luteal stages than in the follicular stage and in estrus. Although TNFalpha stimulated both PGE2 and PGF2alpha secretion during the entire period of the estrous cycle, the level of stimulation of TNFalpha on PGE2 output by the bovine endometrium does not show the same cyclical changes as that shown on PGF2alpha output. The stimulation of TNFalpha resulted in a decrease in the PGE2/PGF2alpha ratio only in the late luteal stage. Furthermore, TNFalpha stimulated PGE2 secretion in stromal, but not epithelial cells. The overall results suggest that TNFalpha is a potent regulator of endometrial PGE2 secretion as well as PGF2alpha secretion during the entire period of estrous cycle, and that TNFalpha plays different roles in the regulation of secretory function of bovine endometrium at different phases of the estrous cycle.     

Cell-type specific responses in prostaglandin secretion by glandular and stromal cells from pig endometrium treated with catecholestrogens, methoxyestrogens and progesterone.

The pig conceptus and endometrium possess the ability to convert estrogens into catecholestrogens and catecholestrogens into methoxyestrogens. Experiments were carried out to evaluate the effect of catecholestrogens, methoxyestrogens and progesterone on the secretion of prostaglandin (PG) E and F2 alpha by porcine endometrial glandular and stromal cells in vitro. Both 2-hydroxyestradiol (2-OH-E2, 0-20 microM) and 4-hydroxyestradiol (4-OH-E2, 0-20 microM) increased (P less than .05) PGE and PGF2 alpha secretion by stromal cells in a dose response manner. Two-hydroxyestradiol tended (P less than .1) to decrease PGF2 alpha production by glandular cells. Two-methoxyestradiol (20 microM) suppressed (P less than .05) PGF2 alpha secretion by glandular and stromal cells. Four-methoxyestradiol (20 microM) stimulated (P less than .05) PGE production and PGE:PGF2 alpha ratio. Progesterone (.1 microM) suppressed (P less than .05) PG secretion in both cell types. We conclude that catecholestrogens, methoxyestrogens, and progesterone may participate in the establishment of pregnancy by modulating PG production in the endometrium.     

Expression and action of hepatocyte growth factor in bovine endometrial stromal and epithelial cells in vitro.

Hepatocyte growth factor (HGF) is a pleiotropic growth factor that acts on various epithelial cells. The objectives of this study were to determine whether HGF altered the proliferation and prostaglandin (PG) secretion of bovine endometrial stromal and epithelial cells in vitro. We also observed HGF and HGF receptor (c-met) mRNA expression in cultured bovine endometrial stromal and epithelial cells by RT-PCR. Stromal and epithelial cells obtained from cows in early stage of the estrous cycle (days 2-5) were cultured in DMEM/Ham's F-12 supplemented with 10% calf serum. The cells were exposed to HGF (0-10 ng/ml) for 2, 4, or 6 days. HGF significantly increased the total DNA in epithelial (P < 0.05), but not stromal cells. In another experiment, when the cells reached confluence, the culture medium was replaced with fresh medium with 0.1% BSA containing HGF 0-100 ng/ml and the cells were cultured for 24 hr. The HGF stimulated PGF2alpha secretion in epithelial, but not stromal cells. RT-PCR revealed that mRNA of HGF is expressed only in stromal cells, and that c-met mRNA is expressed in both stromal and epithelial cells. These results suggest that HGF plays roles in the proliferation and the regulation of secretory function of bovine endometrial epithelial cells in a paracrine fashion.     

Human endometrial stromal interleukin-1 beta: autocrine secretion and inhibition by interleukin-1 receptor antagonist

Decidualization of human endometrial stromal cells is suppressed by endometrial IL-1 in an autocrine or paracrine manner, indicating that constant suppression of stromal decidualization by IL-1 requires a neutralizing mechanism for IL-1 action to accept embryo implantation. Since production of IL-1ra in human endometrium is reported to be 10- to 30-fold higher than that of IL-1 alpha/beta, we investigated whether endogenous IL-1 beta secreted from human endometrial stromal cells can be inhibited by IL-1ra by using an in vitro decidualization culture. Human stromal cells were cultured with 8-Br-cAMP to induce decidualization, and concentrations of IL-1 beta, IL-8, and prolactin in the culture supernatants were assayed before and after decidualization. There was no significant difference in mean IL-1 beta concentrations measured before and after decidualization. Addition of IL-1ra to endometrial stromal cell cultures strongly inhibited endogenous IL-8 secretion from the cells. Although IL-1 beta showed a biphasic effect on cell proliferation and a suppressive effect on decidualization of stromal cells, these effects were completely inhibited by IL-1ra. The results imply that a high in vivo concentration of IL-1ra in human endometrial tissues may regulate IL-1 effects on decidualization and cell proliferation of human endometrial stromal cells.     

Inhibition of cAMP-mediated decidualization in human endometrial stromal cells by IL-1beta and laminin.

Both IL-1 and laminin are reported to inhibit progesterone receptor-mediated decidualization signals in endometrial stromal cells, but the effects of these two inhibitors on cAMP-mediated decidualization signals remain unknown. Furthermore, the interaction between IL-1-stimulated and laminin-stimulated signals has not been analyzed yet. In this study, interactions between these two decidualization-inhibitory signals and their effects on 8-Br-cAMP-mediated decidualization in human endometrial stromal cells were investigated. Prolactin release from decidualized stromal cells was measured by enzyme immunoassay in order to quantitate in vitro decidualization. Both IL-1beta and laminin were found to inhibit 8-Br-cAMP-induced decidualization in vitro in human endometrial stromal cells. IL-1beta dose-dependently inhibited decidualization of stromal cells cultured on both laminin-coated and collagen-coated dishes, while laminin inhibited the decidualization of stromal cells cultured both with and without IL-1beta. These results indicate that IL-1beta and laminin additively and mutually inhibit cAMP-mediated decidualization signals, and that they may inhibit these signals through different mechanisms.