Effect of dexamethasone on uterine cell death

11Beta-hydroxysteroid dehydrogenases in human endometrium

Key reproductive events, such as menstruation and implantation, are considered to be inflammatory processes and glucocorticoids act as anti-inflammatory agents. The balance of expression of types 1 and 2 11beta-hydroxysteroid dehydrogenases (11betaHSD) controls the availability of cortisol to bind to the glucocorticoid receptor (GR) and mineralocorticoid receptor (MR). Expression profiles of glucocorticoid-metabolising enzymes and their cognate receptors have been characterized in the reproductive tract. We propose that factors that peripherally promote glucocorticoid action are part of an anti-inflammatory response to tissue remodelling in human endometrium. Protein and mRNA expression in endometrium were investigated using immunohistochemistry and quantitative real-time PCR. There was up-regulated expression of 11betaHSD-1 at menstruation and in first trimester decidua. 11BetaHSD-2 and GR were expressed across the cycle. The MR expression pattern across the cycle and in decidua implies progesterone may also play a regulatory role. The precise roles and interactions of these proteins require further investigation.

Mouse uterine epithelial apoptosis is associated with expression of mitochondrial voltage-dependent anion channels, release of cytochrome C from mitochondria, and the ratio of Bax to Bcl-2 or Bcl-X

The release of cytochrome c from mitochondria, which is regulated by Bcl-2 family members and is considered to take place through voltage-dependent anion channels (VDACs) on the outer membranes of mitochondria, results in activation of effector caspases, such as caspase-3, which induce apoptosis. We studied the involvement of the mitochondrial apoptosis pathway in uterine epithelial apoptosis. Estradiol-17beta pellets were implanted into ovariectomized mice and removed 4 days later (Day 0). The apoptotic index (percentage of apoptotic cells) of the luminal epithelium increased markedly, peaking on Day 2, whereas that of the glandular epithelium increased much less. Expression of VDAC1, 2, and 3 mRNAs increased in the luminal epithelium in correlation with the apoptotic index of the luminal epithelium. No increases in VDAC1, 2, and 3 mRNA levels were observed in the stroma or muscle, where no apoptosis occurs. VDAC1 protein levels in the uterus also correlated well with the apoptotic index of the luminal epithelium. In addition, the apoptotic index showed good correlation with the release of cytochrome c from mitochondria, activation of caspase-3, which was immunohistochemically detected only in the epithelium, and the mRNA and protein ratios of Bax:Bcl-2 and Bax:Bcl-X in the uterus. The present results suggest that the release of cytochrome c from mitochondria, which is regulated by Bcl-2 family members, plays a role in uterine epithelial apoptosis after estrogen deprivation. The increase in VDAC expression may facilitate the release of cytochrome c during apoptosis.

Regulation of 11beta-hydroxysteroid dehydrogenase type 2 by steroid hormones and epidermal growth factor in the Ishikawa human endometrial cell line

The biological actions of glucocorticoids in target organs are determined at least in part by the local expression of 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2), which is responsible for the inactivation of glucocorticoids. The human endometrium is a glucocorticoid target tissue, and is known to express 11beta-HSD2. However, little is known about the function and regulation of 11beta-HSD2 in the endometrium, probably owing to the lack of in vitro model systems (i.e., cell lines) that express 11beta-HSD2. Here, we describe the characterization of 11beta-HSD expression in Ishikawa cells, a well-differentiated human endometrial adenocarcinoma cell line. The 11beta-HSD activity in intact Ishikawa cells was characteristic of 11beta-HSD2 in that it only possessed dehydrogenase activity (cortisol to cortisone) and had a high affinity for cortisol (apparent Km of 34 nM). The exclusive expression of 11beta-HSD2 in Ishikawa cells was confirmed by RT-PCR which demonstrated the presence of the mRNA for 11beta-HSD2 but not that for 11beta-HSD1. To investigate the regulation of 11beta-HSD2 in Ishikawa cells, we treated these cells with sex steroid hormones, glucocorticoids and epidermal growth factor (EGF), and determined the effects of these treatments on 11beta-HSD2 activity by an established intact cell radiometric conversion assay. Treatment with estradiol-17beta (E2, 10 nM) and medroxyprogesterone acetate (MPA, 100 nM) produced a classic sex steroid effect; the greatest increase (330% of the control) in the level of 11beta-HSD2 activity was caused by the combined treatment, followed by MPA (240% of the control) with E2 being the least effective (156% of the control). The stimulatory effect of E2 was blocked by the pure antiestrogen ICI 182,780. The synthetic glucocorticoid dexamethasone (Dex) increased 11beta-HSD2 activity in a time- and dose-dependent manner (200% of the control; 100 nM for 48 h), and the endogenous glucocorticoid cortisol was equally effective in this regard. The antiprogesterone-antiglucocorticoid RU486 did not counteract with MPA or Dex but rather acted as an agonist; increased 11beta-HSD2 activity (160% of the control; 100 nM for 72 h). By contrast, treatment with EGF caused a dose- and time-dependent decrease in 11beta-HSD2 activity (60% of the control; 10 ng/ml for 72 h). In addition, semi-quantitative RT-PCR analysis revealed that there were corresponding changes in the level of 11beta-HSD2 mRNA following the treatment of Ishikawa cells with these steroid hormones and EGF, indicating that the effects of these hormones and EGF are mediated, at least in part, at the level of 11beta-HSD2 gene transcription. In conclusion, we have demonstrated for the first time that the human Ishikawa endometrial cell line expresses exclusively the 11beta-HSD2 isozyme. Moreover, we have presented the first direct evidence that sex steroid hormones and glucocorticoids stimulate while EGF inhibit the expression of 11beta-HSD2 in Ishikawa cells, suggesting that endometrial 11beta-HSD2 is under the control of steroid hormones and EGF. Thus, the Ishikawa cell line represents an excellent model in which the function and regulation of endometrial 11beta-HSD2 may be studied.

Changes in levels of mRNAs of transforming growth factor (TGF)-beta1, -beta2, -beta3, TGF-beta type II receptor and sulfated glycoprotein-2 during apoptosis of mouse uterine epithelium

To examine the roles played by transforming growth factors (TGF)-beta1, -beta2, -beta3, and TGF-beta type II receptors in the induction of apoptosis in the mouse uterine epithelium after estrogen deprivation, we investigated the expression of their mRNAs and the mRNA of sulfated glycoprotein-2 (SGP-2). Pellets containing 100 microg estradiol-17beta (E2) were implanted into ovariectomized mice and removed four days later. Apoptotic indices (percentage of apoptotic cells) of both luminal and glandular epithelia increased after E2 pellets were removed, but administration of progesterone (P), 5alpha-dihydrotestosterone (DHT), or continued implantation of E2 pellets suppressed this increase. Levels of mRNAs of TGF-beta1, -beta2, and -beta3, and SGP-2 did not increase after estrogen deprivation. However, estrogen deprivation caused a gradual increase in the level of TGF-beta type II receptor mRNA, and its level increased about six-fold six days later. Moreover, E2, P, and DHT markedly decreased the level of TGF-beta type II receptor mRNA. In situ hybridization demonstrated that mRNAs of TGF-beta1, -beta2, -beta3 and TGF-beta type II receptor were localized to the epithelium. Exogenous administration of TGF-beta1 into the uterine stroma induced apoptosis in the epithelium, a finding that suggests that signals produced by TGF-betas can induce apoptosis. Therefore, the present results suggest that increased sensitivity of uterine epithelial cells to TGF-betas, as demonstrated by an increase in TGF-beta type II receptor mRNA, is involved in the induction of apoptosis after estrogen deprivation, although signals produced by TGF-betas do not appear sufficient to induce apoptosis.

Estradiol induces E-cadherin degradation in mouse uterine epithelium during the estrous cycle and early pregnancy

Mouse uterine epithelium is a tissue that undergoes cyclic endocrine-regulated cell dissociation and regeneration. It shows a dramatic cell loss following normal estrus. If pregnancy ensues, cell loss is averted during the first 2.5-3.5 days. However, this is followed by a precipitous loss of basal-lateral cell adhesion and apoptosis in preparation for blastocyst invasion. By comparing epithelia isolated by protease treatment, we show that a reduction of lateral cell adhesion is a primary event in these instances of normal tissue loss. It was readily induced in ovariectomized adult and immature mice by injections of estradiol (E2), and to some extent also by progesterone (P4). The reduction of lateral adhesion induced by including ethylene glycol-bis (beta-aminoethyl ether) -N,N,N',N'-tetraacetic acid (EGTA) in the isolation medium mimicked and was additive to the effect of E2 injection. However, the E2 effect was different in not being prevented by adding Ca2+. The E2 effect also was mimicked by the action on isolated epithelium of monoclonal antibody against the calcium-dependent cell adhesion molecule, E-cadherin, suggesting that inactivation of E-cadherin was induced by E2. In detergent extracts of estrous and metestrous epithelium there was an increase in 80-kDa extracellular domain of E-cadherin relative to the intact 120-kDa molecule. The loss of adhesion between 3.5 and 4.5 days of pregnancy was associated with a loss of both intact membrane-associated 120-kDa E-cadherin and cleavage products. Cleavage of 80-kDa E-cadherin was uniquely induced by E2 in ovariectomized adult and immature mice; P4 was without effect. The cleavage of E-cadherin correlated with increased basal accumulation of E-cadherin antigen in estrous and E2-injected mice and a loss of both basal and lateral antigen at 4.5 days of pregnancy. Only the E-cadherin antigen within junctional complexes appeared unaffected. The data are consistent with the hypothesis that the cyclic and pregnancy-dependent disruption of uterine epithelial integrity are promoted by E2-dependent modification of E-cadherin, including its extracellular cleavage.

Effect of chronic stress on estradiol action in the uterus of ovariectomized rats

The aim of this study was to investigate the development of estradiol (E2) effects in ovariectomized rat uterus under chronic stress. The chronically stressed rats (swimming and overcrowded cages) were treated with a single injection of E2 dipropionate (10 micrograms/ rat, i.m.) in olive oil (0.1 ml/rat). Control groups of ovariectomized rats included one group treated with the same dose of E2 but maintained in stress-free conditions, a second group subjected to the same procedure of chronic stress but injected with olive oil only, a third group treated with olive oil and maintained in stress-free conditions, and a final group which consisted of uninfluenced ovariectomized rats. E2 effects were determined by measuring activity of proliferation (mitotic index), cellular, nuclear, and nucleolar volumes (morphometry), DNA content (Feulgen's method) in luminal and glandular epithelia, stromal cells of endometrium at 24, 36 and 48 h after injection of E2 or olive oil. In chronically stressed rats treated with E2, at each time point almost all the parameters in all the structures were significantly (P < 0.05-0.001) higher, than in unstressed E2-treated rats. In E2-untreated rats, the stress did not influence uterine tissues. Thus, the chronic stress enhances strongly the E2-induced effects in the uterus of ovariectomized rats. It is likely mediated by the changes of some steps in the mechanism of estrogen action that leads to the increase in the sensitivity of uterine structures to estrogens.

Inhibitory effects of estrogen, progesterone, androgen and glucocorticoid on death of neonatal mouse uterine epithelial cells induced to proliferate by estrogen

Female newborn mice were given daily injections of estradiol-17 beta (E2; 25 micrograms/mouse/day) for 4 days from the day of birth, and uterine cell death after this E2 priming was investigated by examining the apoptotic index (percentage of apoptotic cells), and the retention of 3H-radioactivity incorporated into epithelial or stromal DNAs after injection of [3H]thymidine into the mice on the day after birth. With injections of vehicle only after E2 priming, the apoptotic index of the uterine epithelium increased markedly, being maximal on day 4 of injections, and the 3H-radioactivity retained in the epithelium decreased rapidly. Agarose gel electrophoresis of uterine epithelial DNAs on day 4 of injections showed a ladder pattern, characteristic of apoptotic cell death. However, daily injections of E2 (7.2 micrograms/g body wt) completely inhibited the increase in the apoptotic index and the loss of 3H-radioactivity in the epithelium. Daily injections of progesterone (80 micrograms/g body wt), 5 alpha-dihydrotestosterone (DHT; 8 micrograms/g body wt), and dexamethasone (2 micrograms/g body wt) also inhibited both parameters, although not completely. The inhibitory effects of DHT and progesterone were abolished by the antiandrogen, flutamide and antiprogesterone, RU 486, respectively. In contrast, no apoptotic cells and no loss of 3H-radioactivity were found in the stroma for any treatment after E2 priming. The present results suggest that discontinuation of estrogen stimulation results in apoptotic cell death in the uterine epithelium of neonatal mice, but not in the stroma, and that estrogen, progesterone, DHT and dexamethasone inhibit cell death of uterine epithelium.