Potential hazards to embryo implantation: A human endometrial in vitro model to identify unwanted antigestagenic actions of chemicals.

Embryo implantation is a crucial step in human reproduction and depends on the timely development of a receptive endometrium. The human endometrium is unique among adult tissues due to its dynamic alterations during each menstrual cycle. It hosts the implantation process which is governed by progesterone, whereas 17ß-estradiol regulates the preceding proliferation of the endometrium. The receptors for both steroids are targets for drugs and endocrine disrupting chemicals. Chemicals with unwanted antigestagenic actions are potentially hazardous to embryo implantation since many pharmaceutical antiprogestins adversely affect endometrial receptivity. This risk can be addressed by human tissue-specific in vitro assays. As working basis we compiled data on chemicals interacting with the PR. In our experimental work, we developed a flexible in vitro model based on human endometrial Ishikawa cells. Effects of antiprogestin compounds on pre-selected target genes were characterized by sigmoidal concentration-response curves obtained by RT-qPCR. The estrogen sulfotransferase (SULT1E1) was identified as the most responsive target gene by microarray analysis. The agonistic effect of progesterone on SULT1E1 mRNA was concentration-dependently antagonized by RU486 (mifepristone) and ZK137316 and, with lower potency, by 4-nonylphenol, bisphenol A and apigenin. The negative control methyl acetoacetate showed no effect. The effects of progesterone and RU486 were confirmed on the protein level by Western blotting. We demonstrated proof of principle that our Ishikawa model is suitable to study quantitatively effects of antiprogestin-like chemicals on endometrial target genes in comparison to pharmaceutical reference compounds. This test is useful for hazard identification and may contribute to reduce animal studies.

In vitro-Ishikawa cell test for assessing tissue-specific chemical effects on human endometrium.

The human endometrium is a fertility-determining factor. Its receptivity during the implantation window may be altered by chemicals. Since human embryo implantation is unique chemical risk assessment cannot be based solely on animal studies. We established a tissue-specific in vitro test based on human endometrial adenocarcinoma (Ishikawa) cells. Progesterone receptor (PR) was selected as primary target gene for estrogenic effects. Changes of mRNA levels were investigated by reverse transcription quantitative real-time PCR. Sigmoidal dose-response curves for up-regulation of PR mRNA and EC(50) values were established for 17beta-estradiol, diethylstilbestrol and the weak xenoestrogen bisphenol A. Nonylphenol also had a clear PR mRNA up-regulating effect. Several other chemicals were characterized as negative compounds. Among them was methoxyacetic acid which may produce false positive results in reporter gene assays. Up-regulation of PR protein by 17beta-estradiol, diethylstilbestrol, bisphenol A and nonylphenol was confirmed by Western Blotting.

mRNA expression profiles for corticotrophin-releasing hormone, urocortin, CRH-binding protein and CRH receptors in human term gestational tissues determined by real-time quantitative RT-PCR.

Increasing maternal plasma levels of corticotrophin-releasing hormone (CRH) during the last weeks of pregnancy suggest that this stress hormone plays an important role in the control of human parturition. Little is known about the quantitative contribution of gestational tissues (other than placenta) to intrauterine formation of CRH, urocortin and CRH-binding protein (CRH-BP), or about the distribution of CRH receptors within the uterus. We have investigated the mRNA expression of CRH, urocortin, CRH-BP and CRH receptors 1 and 2 (CRH-R1 and -R2) in gestational tissues by real-time RT-PCR. Placenta, myometrium and choriodecidua were collected after uncomplicated pregnancies at term, before the onset of labour. Distribution of CRH-R1 and CRH-R2 protein was also investigated by immunostaining with receptor subtype-specific antibodies. The placenta was identified as the main site of CRH and CRH-BP mRNA expression, displaying mRNA levels >1000 and >20 times higher than those found in the myometrium and choriodecidua respectively (P<0.05 in each case). mRNA expression of urocortin was low in all tissues investigated. Myometrium and choriodecidua expressed relevant amounts of both receptor subtypes, whereas the CRH receptor population in placenta consisted mainly of CRH-R2. The high expression of CRH in placenta and the substantial expression of CRH receptors in choriodecidua and myometrium suggested that CRH derived from placenta exerts direct or indirect actions on these tissues. Neither CRH produced by myometrium or choriodecidua nor urocortin from other intrauterine sources seem to play a major role in the control of labour.

Characterization and identification of cytochrome P450 metabolites of arachidonic acid released by human peritoneal macrophages obtained from the pouch of Douglas.

Cytochrome P450 metabolism of arachidonic acid (AA) was investigated in human peritoneal macrophages which play a central role in chronic pelvic diseases in women (for example in endometriosis). The formation of eicosanoids other than prostaglandins (PGs) by these cells is still unknown. In non-activated macrophages obtained from women in the reproductive age, the main [(3)H]-AA metabolites coeluted with epoxyeicosatrienoic acids, dihydroxyeicosatrienoic acids (DHETs) and hydroxyeicosatetraenoic acids (HETEs) in reverse-phase HPLC. After zymosan activation a shift to PGs pathway was observed. Treatment with low doses of 2,3,7,8-tetrachlorodibenzo- p -dioxin increased the formation of a metabolite coeluting with 5,6-DHET. By gas chromatography/mass spectrometry 5,6-DHET (after beta-naphthoflavone induction), and 14,15-DHET as well as 11,12-DHET (after AA stimulation) were identified as major epoxygenase metabolites, respectively. The enantioselective formation of 12(S)-HETE was demonstrated by chiral-phase HPLC. Our findings demonstrate that non-activated peritoneal macrophages produce substantial amounts of bioactive cytochrome P450 metabolites of AA.

Exposure of human endometrium to environmental estrogens, antiandrogens, and organochlorine compounds.

OBJECTIVE: To determine concentrations of environmental estrogens, antiandrogens, and organochlorine compounds in human endometrium and body fat. DESIGN: Cross-sectional, population-based study. SETTING: Patient recruitment was done at a university hospital; chemical analysis was performed in a specialized private laboratory. PATIENT(S): Premenopausal, unexposed women undergoing hysterectomy for uterine myoma. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Concentrations of environmental modulators in human endometrium and body fat were quantified by high-resolution gas chromatography/high-resolution mass spectrometry. RESULT(S): Among known endocrine modulators, the antiandrogenic p, p'-dichlorodiphenyl-dichloroethylene was found in the highest concentrations in endometrium (median 4.7 microg/kg wet weight) and body fat (median 446 microg/kg wet weight). Only trace amounts of the identified environmental estrogens beta-hexachlorocyclohexane, o, p'-dichlorodiphenyl-trichloroethane, bisphenol A, hydroxylated polychlorinated biphenyls, and genistein were found in the endometrium (median <1 microg/kg wet weight). As major organochlorine contaminants without endocrine activities, polychlorinated biphenyls and hexachlorobenzene were found. CONCLUSION(S): Our data demonstrate that nonchlorinated environmental estrogens do not build up cumulative tissue concentrations in the endometrium. The risk of reduced fertility because of ambient levels of environmental estrogens in the endometrium is negligible.

Cytochrome P450 metabolites of arachidonic acid in human placenta.

Little is known about the epoxygenase pathway of the arachidonic acid cascade in uterine tissues. In this paper, we describe the formation of epoxyeicosatrienoic acids (EETs) and dihydroxyeicosatrienoic acids (DHETs) in human term placenta after uncomplicated pregnancies. Metabolism of [3H]-arachidonic acid was analyzed in short term tissue cultures of placenta by reverse phase HPLC. Major metabolites coeluted with authentic EETs and DHETs. The formation of EETs was inhibited by carbon monoxide. In non-radioactive incubations with biopsies from seven different placentas, sufficient material for GC/MS analysis was obtained. The combined media were purified by solid phase extraction and reverse phase HPLC. The fraction coeluting with DHETs was derivatized with pentafluorobenzylbromide (PFB) and bis-(trimethylsilyl)-trifluoroacetylacetamide (BSTFA) and analyzed by GC/NICI/MS/MS. 11, 12-DHET and 14, 15-DHET were identified by their mass spectra displaying specific fragments at m/z 149 and m/z 189, respectively. Our results suggest that the epoxygenase pathway is active in human term placenta.

Urinary excretion of 2,3-dinor-6-keto-PGF1 alpha and 11-dehydro-TXB2 by the gravid spontaneously hypertensive rat.

Little is known about the pathophysiological processes leading to superimposed preeclampsia. We present an animal model where the uteroplacental blood flow in spontaneously hypertensive rats (SHR) was reduced by a silver clip. Thus, a superimposed preeclampsia-like syndrome could be studied under defined conditions. Urinary excretion of 2,3-dinor-6-keto PGF1 alpha and 11-dehydro-TxB2 were measured by enzyme immunoassays at day 16 and 20 of pregnancy. In gravid, sham-operated animals excretion of 2,3-dinor-6-keto-PGF1 alpha was largely elevated compared to non gravid control animals (day 16: 1259 vs. 258 ng/kg 24h; day 20: 471 vs. 269 ng/kg.24h). However, in the gravid rats with reduced uteroplacental blood flow urinary excretion of 2,3-dinor-6-keto-PGF1 alpha decreased to non gravid levels (day 16: 335 ng/kg.24h; day 20: 238 ng/kg.24h). By antihypertensive therapy with dihydralazin this effect was largely abolished. Only minor alterations were found in the excretion of 11-dehydro-TxB2. Our findings suggest, that a reduction of uteroplacental blood flow in the spontaneously hypertensive rat decreases the systemic prostacyclin synthesis.