Phyto- and endogenous estrogens differently activate intracellular calcium ion mobilization in bovine endometrial cells

Isoflavones

Phytoestrogens are naturally occurring nonsteroidal phenolic plant compounds that, due to their molecular structure and size, resemble vertebrate steroids estrogens. This review is focused on plant flavonoids isoflavones, which are ranked among the most estrogenic compounds. The main dietary sources of isoflavones for humans are soybean and soybean products, which contain mainly daidzein and genistein. When they are consumed, they exert estrogenic and/or antiestrogenic effects. Isoflavones are considered chemoprotective and can be used as an alternative therapy for a wide range of hormonal disorders, including several cancer types, namely breast cancer and prostate cancer, cardiovascular diseases, osteoporosis, or menopausal symptoms. On the other hand, isoflavones may also be considered endocrine disruptors with possible negative influences on the state of health in a certain part of the population or on the environment. This review deals with isoflavone classification, structure, and occurrence, with their metabolism, biological, and health effects in humans and animals, and with their utilization and potential risks.

Estrous cycle stage-dependent manner of type I interferon-stimulated genes induction in the bovine endometrium

Interferon tau (IFN-τ) is a ruminant-specific type I IFN secreted by a conceptus before its attachment to the uterus. IFN-τ induces the expression of IFN-stimulated genes (ISGs) via the type I IFN receptor (IFNAR), which is composed of IFNAR1 and IFNAR2 subunits in the endometrium. However, expression patterns of IFNARs during the estrous cycle have not been reported. We hypothesized that the response to a type I IFN changes along with IFNARs and the IFN-regulatory factors (IRFs) driving transcription of IFN signal-related genes and modulating a type I IFN signal during the estrous cycle. We investigated the estrous cycle stage-dependent type I IFN induction of ISGs and expression patterns of IFN signal-related genes in bovine endometrial tissues. Endometrial tissue pieces collected from bovine uteri at each estrous stage (early, mid, and late) were cultured with or without recombinant bovine IFN-α or concentrated pregnant uterine flushing (PUF) on day 18 after confirming the presence of a conceptus. IFN-α and PUF each significantly increased the expression of ISGs in endometrial tissues. The induction levels of the typical ISGs (MX1-a and ISG15) were significantly higher at the mid stage and correlated with high expression of IRFs at the mid stage. The immunostaining of IFNARs showed strong fluorescence intensities in luminal and glandular epithelia at the early and mid stages. Collectively, these results suggest that the endometrium exhibits estrous cycle stage-dependent responsiveness to type I IFN that may be associated with the expression of IFNARs and IRFs for pregnancy recognition.

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.

The Effect of Soybean-Derived Phytoestrogens on Concentrations of Plasma Isoflavones, 15-keto-13,14-dihydroprostaglandin F2α and Progesterone in Dairy Cows

The objective of the study was to determine the effect of soybean-derived phytoestrogens and their metabolites on the activity of sex hormones during the oestrous cycle in multiparous lactating dairy cows. The experiment was carried out on 4 multiparous lactating Holstein cows in the form of replicated Latin square in double reversal design. The experiment in the total length of 168 days was divided into 4 periods of 42 days, each consisting of a 21-day preliminary period and a 21-day collecting period. Cows were divided into 2 groups of 2 cows. The control group (C) was fed a diet based on extruded rapeseed cake while the experimental group (S) was fed a diet containing extruded full-fat soya. The intake of total isoflavones was 3297 mg/d in S and 58.0 mg/d in C (P < 0.001). The concentrations of individual isoflavones, it is daidzein, genistein and equol in plasma were significantly higher in the experimental group S (49.3, 78.7 and 218.8 ng/ml, respectively) than in the control group C (13.5, 42.9 and 18.3 ng/ml, respectively, P < 0.001). Plasma concentration of progesterone throughout the oestrous cycle was not influenced by the diet used (P > 0.05). Plasma concentration of prostaglandine PGFM throughout the oestrous cycle in the experimental group (S) tended to be higher (P = 0.095) than in the control group (C). No differences in the length of the oestrous cycle between the cows fed different diets were observed.

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 alpha (TNFalpha; 10 ng/mL) or oxytocin (OT; 10(-7) M) for 24 h. LPA treatment resulted in a dose-dependent increase of PGE(2) production in stromal cells, but not in epithelial cells. LPA did not influence PGF(2alpha) 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 PGE(2) 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 PGE(2) synthesis in stromal cells is via the influence on mRNA expression for the enzymes responsible for PGE(2) synthesis-PGE(2) synthase (PGES) and PG-endoperoxide synthase 2 (PTGS2). We demonstrated that the stimulatory effect of LPA on PGE(2) production in stromal cells is via the stimulation of PTGS2 and PGES mRNA expression in the cells. The overall results indicate that LPA stimulates PGE(2) 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 PGE(2) production in stromal cells via the induction of PTGS2 and PGES mRNA expression.

Alkylphenol xenoestrogens with varying carbon chain lengths differentially and potently activate signaling and functional responses in GH3/B6/F10 somatomammotropes

BACKGROUND

Alkylphenols varying in their side-chain lengths [ethyl-, propyl-, octyl-, and nonylphenol (EP, PP, OP, and NP, respectively)] and bisphenol A (BPA) represent a large group of structurally related xenoestrogens that have endocrine-disruptive effects. Their rapid nongenomic effects that depend on structure for cell signaling and resulting functions are unknown.

OBJECTIVES

We compared nongenomic estrogenic activities of alkylphenols with BPA and 17beta-estradiol (E(2)) in membrane estrogen receptor-alpha-enriched GH3/B6/F10 pituitary tumor cells. These actions included calcium (Ca) signaling, prolactin (PRL) release, extracellular-regulated kinase (ERK) phosphorylation, and cell proliferation.

METHODS

We imaged Ca using fura-2, measured PRL release via radioimmunoassay, detected ERK phosphorylation by fixed cell immunoassay, and estimated cell number using the crystal violet assay.

RESULTS

All compounds caused increases in Ca oscillation frequency and intracellular Ca volume at 100 fM to 1 nM concentrations, although long-chain alkylphenols were most effective. All estrogens caused rapid PRL release at concentrations as low as 1 fM to 10 pM; the potency of EP, PP, and NP exceeded that of E(2). All compounds at 1 nM produced similar increases in ERK phosphorylation, causing rapid peaks at 2.5-5 min, followed by inactivation and additional 60-min peaks (except for BPA). Dose-response patterns of ERK activation at 5 min were similar for E2, BPA, and PP, whereas EP caused larger effects. Only E2 and NP increased cell number. Some rapid estrogenic responses showed correlations with the hydrophobicity of estrogenic molecules; the more hydrophobic OP and NP were superior at Ca and cell proliferation responses, whereas the less hydrophobic EP and PP were better at ERK activations.

CONCLUSIONS

Alkylphenols are potent estrogens in evoking these nongenomic responses contributing to complex functions; their hydrophobicity can largely predict these behaviors.

Characterization of the calpain/calpastatin system in human hemopoietic cell lines

As previously suggested by PCR analysis [R. DeTullio, R. Stifanese, F. Salamino, S. Pontremoli, E. Melloni, Characterization of a new p94-like calpain form in human lymphocytes, Biochem. J. 375 (2003) 689-696], a p94-like calpain was now established to be present in six different human cells resembling the various peripheral blood cell types. This protease resulted to be the predominant calpain isoforms whereas the conventional mu- and m-calpains are also expressed although at lower or almost undetectable amounts. The p94-like calpain has been identified by a specific mAb and displays unique features such as: Ca2+ requirement for half maximum activity around 30 microM; no autolytic conversion to a low Ca2+ requiring form and lower sensitivity to calpastatin inhibition. Following cell stimulation, the p94-like calpain undergoes inactivation, a process indicating that the protease is activated and participates in the cell responses to stimuli. The involvement of this protease isoform in immunocompetent cell activation is further supported by its partial recruitment on plasma membranes, the site of action of the conventional calpain forms. The amount of calpain translocated to the membranes correlates to the level of calpastatin which has been shown to control this process through the formation of a complex with calpain, which maintains the protease in the cytosol. These results provide new information on the calpain/calpastatin system expressed in immunocompetent cells and on the functional relationship between the p94-like calpain and the biological function of these cells.