Examining reasons that patients discard cryopreserved oocytes

PURPOSE

Assess the rate, rationale, and characteristics of patients who cryopreserved and subsequently discarded their oocytes, and compare their characteristics to patients with continued cryopreservation of oocytes.

METHODS

All patients who disposed of cryopreserved oocytes between 2009 and 2022 reported their reason for discarding their oocytes. This was a retrospective cohort study.

RESULTS

Of 5,010 patients who underwent oocyte cryopreservation (OC) cycles, 201 (4%) patients elected to discard their oocytes and 751 (15%) thawed oocytes for clinical use. The average ages of OC and disposal were 35 and 39 years old, respectively. Of the 201 patients who discarded their oocytes, 71 patients (35%) requested disposal after having a child. Twenty-six (13%) discarded oocytes because of worsening cancer and three (1.4%) discarded because of death. 16 (8%) discarded oocytes due to cost of cryopreservation and eight (4%) due to low oocyte yield. Ten (5%) patients underwent new IVF cycles and discarded previously stored oocytes. Sixty-seven patients (33%) discarded oocytes for unspecified reasons. When comparing patients who discarded oocytes with those who did not, the former had lower AMH (2.7 vs 3.5 ng/ml, p < 0.001) but otherwise comparable age and number of cryopreserved oocytes. The mean age for those with continued cryopreservation was 35.4 years at time of OC and 40 years at time of data collection in June 2023.

CONCLUSION

Childbirth was the most common reason to dispose of oocytes followed by unspecified reasons. Larger studies of oocyte disposal may better define clinical characteristics of patients most likely to use, maintain or discard their oocytes.

Public reporting of IVF outcomes influences medical decision-making and physician training

Background

Since 1992 ART clinics have been required to report outcome data. Our objective was to assess practitioners’ opinions of the impact of public reporting of assisted reproductive technology (ART) outcomes on treatment strategies, medical decision-making, and fellow training.

Methods

Survey study performed in an academic medical center. Members of the Society of Reproductive Endocrinology and Infertility and the Society of Reproductive Surgery were recruited to participate in an online survey in April 2012.: Categorical survey responses were expressed as percentages. Written responses were categorized according to common themes regarding effects of reporting on participants’ medical management of patients. The study was primarily qualitative and was not powered to make statistical conclusions.

Results

Of 1019 surveys sent, 323 participants (31.7%) responded from around the United States, and 275 provided complete data. Nearly all (273 of 282; 96.8%) participants responded that public reporting sometimes or always affected other providers’ practices, and 264 of 281 (93.9%) responded that other practitioners were motivated to deny care to poor-prognosis patients to improve reported success rates. However, only 121 of 282 (42.9%) indicated that public reporting influenced their own medical management. The majority of respondents agreed that public reporting may hinder adoption of single embryo transfer practices (194 of 299; 64.9%) and contribute to the persistent rate of twinning in in vitro fertilization (187 of 279; 67%). A small majority (153 of 279; 54.8%) felt that public reporting did not benefit fellow training, and 58 (61.7%) of the 94 participants who trained fellows believed that having fellows perform embryo transfers reduced pregnancy rates. A small majority (163 of 277; 58.8%) of respondents reported their ART success rates on clinical websites. However, the majority (200 of 275; 72.7%) of respondents compared their success rates with those of other clinics. Finally, most respondents (211 of 277; 76%) believed that most centers that advertised their success rates did so in ways that were misleading to patients.

Conclusions

Public reporting of ART clinical outcomes is intended to drive improvement, promote trust between patients and providers, and inform consumers and payers. However, providers reported that they modified their practices, felt others denied care to poor-prognosis patients, and limited participation of trainees in procedures in response to public reporting of ART outcomes.

Myeloid-specific deletion of Zfp36 protects against insulin resistance and fatty liver in diet-induced obese mice

Obesity is associated with adipose tissue inflammation that contributes to insulin resistance. Zinc finger protein 36 (Zfp36) is an mRNA-binding protein that reduces inflammation by binding to cytokine transcripts and promoting their degradation. We hypothesized that myeloid-specific deficiency of Zfp36 would lead to increased adipose tissue inflammation and reduced insulin sensitivity in diet-induced obese mice. As expected, wild-type (Control) mice became obese and diabetic on a high-fat diet, and obese mice with myeloid-specific loss of Zfp36 [knockout (KO)] demonstrated increased adipose tissue and liver cytokine mRNA expression compared with Control mice. Unexpectedly, in glucose tolerance testing and hyperinsulinemic-euglycemic clamp studies, myeloid Zfp36 KO mice demonstrated improved insulin sensitivity compared with Control mice. Obese KO and Control mice had similar macrophage infiltration of the adipose depots and similar peripheral cytokine levels, but lean and obese KO mice demonstrated increased Kupffer cell (KC; the hepatic macrophage)-expressed Mac2 compared with lean Control mice. Insulin resistance in obese Control mice was associated with enhanced Zfp36 expression in KCs. Compared with Control mice, KO mice demonstrated increased hepatic mRNA expression of a multitude of classical (M1) inflammatory cytokines/chemokines, and this M1-inflammatory hepatic milieu was associated with enhanced nuclear localization of IKKβ and the p65 subunit of NF-κB. Our data confirm the important role of innate immune cells in regulating hepatic insulin sensitivity and lipid metabolism, challenge-prevailing models in which M1 inflammatory responses predict insulin resistance, and indicate that myeloid-expressed Zfp36 modulates the response to insulin in mice.

Lipid Synthesis Is Required to Resolve Endoplasmic Reticulum Stress and Limit Fibrotic Responses in the Lung

Endoplasmic reticulum (ER) stress is evident in the alveolar epithelium of humans and mice with pulmonary fibrosis, but neither the mechanisms causing ER stress nor the contribution of ER stress to fibrosis is understood. A well-recognized adaptive response to ER stress is that affected cells induce lipid synthesis; however, we recently reported that lipid synthesis was downregulated in the alveolar epithelium in pulmonary fibrosis. In the present study, we sought to determine whether lipid synthesis is needed to resolve ER stress and limit fibrotic remodeling in the lung. Pharmacologic and genetic manipulations were performed to assess whether lipid production is required for resolving ER stress and limiting fibrotic responses in cultured alveolar epithelial cells and whole-lung tissues. Concentrations of ER stress markers and lipid synthesis enzymes were also measured in control and idiopathic pulmonary fibrosis lung tissues. We found that chemical agents that induce ER stress (tunicamycin or thapsigargin) enhanced lipid production in cultured alveolar epithelial cells and in the mouse lung. Moreover, lipid production was found to be dependent on the enzyme stearoyl-coenzyme A desaturase 1, and when pharmacologically inhibited, ER stress persisted and lung fibrosis ensued. Conversely, lipid production was reduced in mouse and human fibrotic lung, despite there being an increase in the magnitude of ER stress. Furthermore, augmenting lipid production effectively reduced ER stress and mitigated fibrotic remodeling in the mouse lung after exposure to silica. Augmenting lipid production reduces ER stress and attenuates fibrotic remodeling in the mouse lung, suggesting that similar approaches might be effective for treating human fibrotic lung diseases.

Obesity-Induced Endoplasmic Reticulum Stress Causes Lung Endothelial Dysfunction and Promotes Acute Lung Injury

RETRACTED: Obesity is a significant risk factor for acute respiratory distress syndrome. The mechanisms underlying this association are unknown. We recently showed that diet-induced obese mice exhibit pulmonary vascular endothelial dysfunction, which is associated with enhanced susceptibility to LPS-induced acute lung injury. Here, we demonstrate that lung endothelial dysfunction in diet-induced obese mice coincides with increased endoplasmic reticulum (ER) stress. Specifically, we observed enhanced expression of the major sensors of misfolded proteins, including protein kinase R-like ER kinase, inositol-requiring enzyme α, and activating transcription factor 6, in whole lung and in primary lung endothelial cells isolated from diet-induced obese mice. Furthermore, we found that primary lung endothelial cells exposed to serum from obese mice, or to saturated fatty acids that mimic obese serum, resulted in enhanced expression of markers of ER stress and the induction of other biological responses that typify the lung endothelium of diet-induced obese mice, including an increase in expression of endothelial adhesion molecules and a decrease in expression of endothelial cell-cell junctional proteins. Similar changes were observed in lung endothelial cells and in whole-lung tissue after exposure to tunicamycin, a compound that causes ER stress by blocking N-linked glycosylation, indicating that ER stress causes endothelial dysfunction in the lung. Treatment with 4-phenylbutyric acid, a chemical protein chaperone that reduces ER stress, restored vascular endothelial cell expression of adhesion molecules and protected against LPS-induced acute lung injury in diet-induced obese mice. Our work indicates that fatty acids in obese serum induce ER stress in the pulmonary endothelium, leading to pulmonary endothelial cell dysfunction. Our work suggests that reducing protein load in the ER of pulmonary endothelial cells might protect against acute respiratory distress syndrome in obese individuals.

A pneumocyte-macrophage paracrine lipid axis drives the lung toward fibrosis

Lipid-laden macrophages, or "foam cells," are observed in the lungs of patients with fibrotic lung disease, but their contribution to disease pathogenesis remains unexplored. Here, we demonstrate that fibrosis induced by bleomycin, silica dust, or thoracic radiation promotes early and sustained accumulation of foam cells in the lung. In the bleomycin model, we show that foam cells arise from neighboring alveolar epithelial type II cells, which respond to injury by dumping lipids into the distal airspaces of the lungs. We demonstrate that oxidized phospholipids accumulate within alveolar macrophages (AMs) after bleomycin injury and that murine and human AMs treated with oxidized phosphatidylcholine (oxPc) become polarized along an M2 phenotype and display enhanced production of transforming growth factor-β1. The direct instillation of oxPc into the mouse lung induces foam cell formation and triggers a severe fibrotic reaction. Further, we show that reducing pulmonary lipid clearance by targeted deletion of the lipid efflux transporter ATP-binding cassette subfamily G member 1 increases foam cell formation and worsens lung fibrosis after bleomycin. Conversely, we found that treatment with granulocyte-macrophage colony-stimulating factor attenuates fibrotic responses, at least in part through its ability to decrease AM lipid accumulation. In summary, this work describes a novel mechanism leading to foam cell formation in the mouse lung and suggests that strategies aimed at blocking foam cell formation might be effective for treating fibrotic lung disorders.

Direct effects of leptin and adiponectin on peripheral reproductive tissues: a critical review

Obesity is a risk factor for infertility and adverse reproductive outcomes. Adipose tissue is an important endocrine gland that secretes a host of endocrine factors, called adipokines, which modulate diverse physiologic processes including appetite, metabolism, cardiovascular function, immunity and reproduction. Altered adipokine expression in obese individuals has been implicated in the pathogenesis of a host of health disorders including diabetes and cardiovascular disease. It remains unclear whether adipokines play a significant role in the pathogenesis of adverse reproductive outcomes in obese individuals and, if so, whether the adipokines are acting directly or indirectly on the peripheral reproductive tissues. Many groups have demonstrated that receptors for the adipokines leptin and adiponectin are expressed in peripheral reproductive tissues and that these adipokines are likely, therefore, to exert direct effects on these tissues. Many groups have tested for direct effects of leptin and adiponectin on reproductive tissues including the testis, ovary, uterus, placenta and egg/embryo. The hypothesis that decreased fertility potential or adverse reproductive outcomes may result, at least in part, from defects in adipokine signaling within reproductive tissues has also been tested. Here, we present a critical analysis of published studies with respect to two adipokines, leptin and adiponectin, for which significant data have been generated. Our evaluation reveals significant inconsistencies and methodological limitations regarding the direct effects of these adipokines on peripheral reproductive tissues. We also observe a pervasive failure to account for in vivo data that challenge observations made in vitro. Overall, while leptin and adiponectin may directly modulate peripheral reproductive tissues, existing data suggest that these effects are minor and non-essential to human or mouse reproductive function. Current evidence suggests that direct effects of leptin or adiponectin on peripheral reproductive tissues are unlikely to factor significantly in the adverse reproductive outcomes observed in obese individuals.

Chronic alcohol ingestion in rats alters lung metabolism, promotes lipid accumulation, and impairs alveolar macrophage functions

Chronic alcoholism impairs pulmonary immune homeostasis and predisposes to inflammatory lung diseases, including infectious pneumonia and acute respiratory distress syndrome. Although alcoholism has been shown to alter hepatic metabolism, leading to lipid accumulation, hepatitis, and, eventually, cirrhosis, the effects of alcohol on pulmonary metabolism remain largely unknown. Because both the lung and the liver actively engage in lipid synthesis, we hypothesized that chronic alcoholism would impair pulmonary metabolic homeostasis in ways similar to its effects in the liver. We reasoned that perturbations in lipid metabolism might contribute to the impaired pulmonary immunity observed in people who chronically consume alcohol. We studied the metabolic consequences of chronic alcohol consumption in rat lungs in vivo and in alveolar epithelial type II cells and alveolar macrophages (AMs) in vitro. We found that chronic alcohol ingestion significantly alters lung metabolic homeostasis, inhibiting AMP-activated protein kinase, increasing lipid synthesis, and suppressing the expression of genes essential to metabolizing fatty acids (FAs). Furthermore, we show that these metabolic alterations promoted a lung phenotype that is reminiscent of alcoholic fatty liver and is characterized by marked accumulation of triglycerides and free FAs within distal airspaces, AMs, and, to a lesser extent, alveolar epithelial type II cells. We provide evidence that the metabolic alterations in alcohol-exposed rats are mechanistically linked to immune impairments in the alcoholic lung: the elevations in FAs alter AM phenotypes and suppress both phagocytic functions and agonist-induced inflammatory responses. In summary, our work demonstrates that chronic alcohol ingestion impairs lung metabolic homeostasis and promotes pulmonary immune dysfunction. These findings suggest that therapies aimed at reversing alcohol-related metabolic alterations might be effective for preventing and/or treating alcohol-related pulmonary disorders.

mRNA-binding protein TIA-1 reduces cytokine expression in human endometrial stromal cells and is down-regulated in ectopic endometrium

BACKGROUND

Cytokines and growth factors play important roles in endometrial function and the pathogenesis of endometriosis. mRNAs encoding cytokines and growth factors undergo rapid turnover; primarily mediated by adenosine- and uridine-rich elements (AREs) located in their 3'-untranslated regions. T-cell intracellular antigen (TIA-1), an mRNA-binding protein, binds to AREs in target transcripts, leading to decreased gene expression.

OBJECTIVE

The purpose of this article was to determine whether TIA-1 plays a role in the regulation of endometrial cytokine and growth factor expression during the normal menstrual cycle and whether TIA-1 expression is altered in women with endometriosis.

METHODS

Eutopic endometrial tissue obtained from women without endometriosis (n = 30) and eutopic and ectopic endometrial tissues from women with endometriosis (n = 17) were immunostained for TIA-1. Staining intensities were evaluated by histological scores (HSCOREs). The regulation of endometrial TIA-1 expression by immune factors and steroid hormones was studied by treating primary cultured human endometrial stromal cells (HESCs) with vehicle, lipopolysaccharide, TNF-α, IL-6, estradiol, or progesterone, followed by protein blot analyses. HESCs were engineered to over- or underexpress TIA-1 to test whether TIA-1 regulates IL-6 or TNF-α expression in these cells.

RESULTS

We found that TIA-1 is expressed in endometrial stromal and glandular cells throughout the menstrual cycle and that this expression is significantly higher in the perimenstrual phase. In women with endometriosis, TIA-1 expression in eutopic and ectopic endometrium was reduced compared with TIA-1 expression in eutopic endometrium of unaffected control women. Lipopolysaccharide and TNF-α increased TIA-1 expression in HESCs in vitro, whereas IL-6 or steroid hormones had no effect. In HESCs, down-regulation of TIA-1 resulted in elevated IL-6 and TNF-α expression, whereas TIA-1 overexpression resulted in decreased IL-6 and TNF-α expression.

CONCLUSIONS

Endometrial TIA-1 is regulated throughout the menstrual cycle, TIA-1 modulates the expression of immune factors in endometrial cells, and downregulation of TIA-1 may contribute to the pathogenesis of endometriosis.

mRNA-binding protein ZFP36 is expressed in atherosclerotic lesions and reduces inflammation in aortic endothelial cells

OBJECTIVE

We studied the expression and function of an mRNA-binding protein, zinc finger protein-36 (ZFP36), in vascular endothelial cells in vivo and in vitro. We tested the hypotheses that ZFP36 regulates inflammation in vascular endothelial cells and that it functions through direct binding to target cytokine mRNAs. We also tested whether ZFP36 inhibits nuclear factor-κB-mediated transcriptional responses in vascular endothelial cells.

APPROACH AND RESULTS

ZFP36 was minimally expressed in healthy aorta but was expressed in endothelial cells overlying atherosclerotic lesions in mice and humans. The protein was also expressed in macrophage foam cells of atherosclerosis. ZFP36 was expressed in human aortic endothelial cells in response to bacterial lipopolysaccharide, glucocorticoid, and forskolin, but not oxidized low-density lipoproteins or angiotensin II. Functional studies demonstrated that ZFP36 reduces the expression of inflammatory cytokines in target cells by 2 distinct mechanisms: ZFP36 inhibits nuclear factor-κB transcriptional activation and also binds to cytokine mRNAs, leading to reduced transcript stability.

CONCLUSIONS

ZFP36 is expressed in vascular endothelial cells and macrophage foam cells where it inhibits the expression of proinflammatory mRNA transcripts. The anti-inflammatory effects of ZFP36 in endothelial cells occur via both transcriptional and posttranscriptional mechanisms. Our data suggest that enhancing vascular ZFP36 expression might reduce vascular inflammation.

The mRNA-binding protein Zfp36 is upregulated by β-adrenergic stimulation and represses IL-6 production in 3T3-L1 adipocytes

Obesity produces a chronic inflammatory state that contributes to the development of diabetes and atherosclerosis. In obese humans, fat depot adipocytes and macrophages produce inflammatory cytokines and other factors which exert unfavorable local and systemic immune responses. The expression of many cytokines is modulated at the post-transcriptional level by mRNA-binding proteins which recognize AU-rich elements (AREs) in the 3'-untranslated regions (3'-UTR) of these transcripts. One such protein, zinc finger protein 36 (Zfp36), is known to destabilize target mRNAs leading to decreased cytokine expression. Few regulators of Zfp36 expression in adipocytes have been described and mRNA targets of Zfp36 in adipocytes are largely unknown. We found that macrophage-derived inflammatory stimuli enhanced endogenous Zfp36 expression in 3T3-L1 adipocytes. Furthermore, the β-adrenergic receptor agonist isoproterenol (Iso) and the glucocorticoid dexamethasone (Dex) each enhanced Zfp36 expression in adipocytes, the former most likely via a cyclic adenosine monophosphate (cAMP)-dependent pathway. By contrast, Zfp36 expression in murine macrophages (RAW 264.7) was not enhanced by exposure to Dex but was stimulated by retinoic acid (RA). Zfp36 inhibited basal and lipopolysaccharide (LPS)-stimulated interleukin-6 (IL-6) expression in adipocytes. These data reveal important and cell type-specific modulators of Zfp36 expression in adipocytes and macrophages and identify Zfp36 as a potent repressor of adipocyte-derived IL-6. Furthermore, this work identifies new factors that stimulate adipocyte Zfp36 expression that are neither classically inflammatory nor mitogenic. Upregulating an mRNA-binding protein for therapeutic purposes may provide a novel mechanistic approach with which to treat diverse inflammatory disorders including common conditions associated with obesity.

Abstract B66: Characterization of bis-phenazine compounds that inhibit estrogen signaling through direct interaction with estrogen response elements

Hormone therapies interfere with estrogen signaling by targeting Estrogen Receptors (ERs) and are routinely used for the prevention and treatment of ER-expressing breast cancers. However, current therapies have significant limitations related to inherent or acquired resistance. Thus, there is a need to develop therapeutic compounds that do not depend on competitive binding to the ER or on depleting cells of endogenous estrogen. Previous data suggested that certain bis-phenazines, such as our lead compound XR5944, possess potent antiestrogenic properties through a novel mechanism of action: they inhibit gene transcription via direct intercalation with DNA at estrogen response elements (EREs) which are located in estrogen-responsive gene promoters. While these studies have demonstrated the potent antiestrogenic activity of XR5944, they have also demonstrated its capacity to bind to alternative DNA motifs. In order to improve upon ERE target specificity, we have identified XR5944 derivatives that retain potent antiestrogenic properties but may have greater specificity for ERE sequences, to be developed as new therapies for the treatment of estrogen-driven cancers. Such compounds may also be effective in overcoming resistance to current antiestrogen therapies. Here, we characterize DNA sequence interactions and transcriptional effects of five XR5944 derivatives that differ from the parent compound in the composition of their linker chains (compounds 26357 and 26373), cyclic side rings (26576), or both (26536 and 27402). We utilized 1D 1H NMR titration experiments to monitor compound:DNA binding properties to a canonical ERE (AGGTCAcggTGACCT) containing a CGG trinucleotide spacer (ERECGG), electrophoretic mobility shift assays (EMSA) to assess the ability of the derivatives to disrupt ER:ERECGG interactions, and luciferase reporter assays to evaluate their potency in blocking estrogen-dependent transactivation through ERECGG. Our NMR results indicated that alteration of either linker chain or side ring structures of XR5944 reduced the affinity and specificity of compound:ERECGG interactions. These findings correlated with the ability of the compounds to inhibit ER:ERECGG binding in the order of XR5944&gt;26576&gt;26536&gt;26373&gt;26357&gt;27402, as evaluated by EMSA. To further determine the effects of the compounds on ERECGG-driven transactivation, we performed luciferase reporter assays utilizing ERα-expressing MCF-7 breast cancer cells transfected with an ERECGG-luciferase reporter construct. Unlike the EMSA results, there was not a strict concordance between the compound-dependent potency in inhibiting estrogen-driven transcriptional responses and the specificity of interaction with DNA as determined by NMR. Specifically, inhibition of reporter activity was more potent with compounds that had the same cyclic side rings but altered linker chains as XR5944 (26373 and 26357) and was less effective with compounds possessing altered side rings (26576, 26536, and 27402). Together, our findings indicate that the cyclic side chain structures appear to be the most important components of bis-phenazines in disrupting the transcriptional potential of ER:ERE interactions. NMR can be useful for predicting the relative potency of XR5944 derivatives in blocking ER binding to EREs in vitro, but fails to predict their efficacy in inhibiting ERE-mediated transactivation. This information should prove valuable for the rational drug design of new antiestrogenic compounds with improved specificity for ERE sequences.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the Second AACR International Conference on Frontiers in Basic Cancer Research; 2011 Sep 14-18; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2011;71(18 Suppl):Abstract nr B66.

Intercalation of XR5944 with the estrogen response element is modulated by the tri-nucleotide spacer sequence between half-sites

DNA-intercalating molecules can impair DNA replication, DNA repair, and gene transcription. We previously demonstrated that XR5944, a DNA bis-intercalator, specifically blocks binding of estrogen receptor-α (ERα) to the consensus estrogen response element (ERE). The consensus ERE sequence is AGGTCAnnnTGACCT, where nnn is known as the tri-nucleotide spacer. Recent work has shown that the tri-nucleotide spacer can modulate ERα-ERE binding affinity and ligand-mediated transcriptional responses. To further understand the mechanism by which XR5944 inhibits ERα-ERE binding, we tested its ability to interact with consensus EREs with variable tri-nucleotide spacer sequences and with natural but non-consensus ERE sequences using one dimensional nuclear magnetic resonance (1D (1)H NMR) titration studies. We found that the tri-nucleotide spacer sequence significantly modulates the binding of XR5944 to EREs. Of the sequences that were tested, EREs with CGG and AGG spacers showed the best binding specificity with XR5944, while those spaced with TTT demonstrated the least specific binding. The binding stoichiometry of XR5944 with EREs was 2:1, which can explain why the spacer influences the drug-DNA interaction; each XR5944 spans four nucleotides (including portions of the spacer) when intercalating with DNA. To validate our NMR results, we conducted functional studies using reporter constructs containing consensus EREs with tri-nucleotide spacers CGG, CTG, and TTT. Results of reporter assays in MCF-7 cells indicated that XR5944 was significantly more potent in inhibiting the activity of CGG- than TTT-spaced EREs, consistent with our NMR results. Taken together, these findings predict that the anti-estrogenic effects of XR5944 will depend not only on ERE half-site composition but also on the tri-nucleotide spacer sequence of EREs located in the promoters of estrogen-responsive genes.

β-Catenin independent cross-control between the estradiol and Wnt pathways in osteoblasts

Osteoblasts are controlled by the individual and combined effects of systemic and local growth regulators. Here we show functional and physical interactions between estradiol (17βE) and Wnt activated pathways in osteoblasts. 17βE increased gene promoter activity by the Wnt pathway transcriptional effector T cell factor (TCF) in an estrogen receptor (ER) dependent way. This occurred independently of its activity through traditional estrogen response elements and was not replicated by androgen receptor activation. 17βE also increased the stimulatory effect of LiCl on TCF activity, LiCl increased the stimulatory effect of 17βE through estrogen response elements, and both were further enhanced by a noncanonical Wnt receptor agonist (WAg) that functions independently of β-catenin stabilization. In contrast to LiCl, WAg increased DNA synthesis and reduced relative collagen synthesis and alkaline phosphatase activity in otherwise untreated or 17βE stimulated cells. In addition, WAg suppressed Runx2, osterix, and alkaline phosphatase mRNA levels, and potently induced osteoprotegerin mRNA, whereas LiCl was ineffective alone and inhibitory in combination with 17βE. A definitive intersection between the 17βE and Wnt pathways occurred at the protein level, where ERα physically associated with TCF-4 independently of its β-catenin binding domain. This interaction required ligand-dependent exposure of a TCF binding region that mapped to ERα domain E and was further enhanced by Wnt pathway activation. Our studies reveal highly focused co-regulatory effects between the 17βE and Wnt pathways in osteoblasts that involve activated ERα and TCF-4 and downstream changes in gene expression, osteoblast proliferation, and differentiated cell function.

The mRNA-binding protein HuR is regulated in the menstrual cycle and repressed in ectopic endometrium

Cytokines modulate turnover of the endometrium during the menstrual cycle and contribute to the pathogenesis of endometriosis. Gene expression for cytokines is often regulated by proteins that bind to adenosine- and uridine-rich elements (AREs) in their transcripts to stabilize or destabilize bound messenger RNAs (mRNAs). HuR/ELAVL1 is an RNA-binding protein that stabilizes ARE-containing mRNAs. We hypothesized that HuR might play a role in regulating cytokine expression during the menstrual cycle and in endometriosis and characterized the expression and regulation of HuR in eutopic and ectopic human endometrium. Tissue sections obtained from normal (n = 23) and ectopic (n = 16) endometrium were immunostained for HuR, and staining intensity was evaluated by HSCORE. Cultured stromal cells isolated from normal endometrium were treated with vehicle, estradiol (E2), progesterone (P), E2 + P, tumor necrosis factor-α (TNF-α), and interleukin 1β (IL-1β) for 24 hours, and HuR expression was determined by Western blot. HuR immunoreactivity was significantly lower in the early proliferative and late secretory phases (157.5 ± 11.08 and 190.0 ± 15.2, respectively), compared to the mid-late proliferative (270.0 ± 8.0) and early-mid secretory phases (256.6 ± 20.2; P < .01, analysis of variance [ANOVA]). Furthermore, HuR expression was significantly lower in ectopic endometrial cells compared to normal endometrium in mid-late proliferative and early-mid-secretory phases (P < .01). Estrogen, P, or cytokines did not alter HuR expression in cultured endometrial stromal cells. Increased HuR levels in the mid-menstrual phases are likely to contribute to reduced mid-cycle cytokine expression and enhanced cellular survival in eutopic endometrium. In ectopic endometrium, elevated cytokine levels associated with endometriosis likely reduce HuR expression.

The tri-nucleotide spacer sequence between estrogen response element half-sites is conserved and modulates ERalpha-mediated transcriptional responses

The estrogen response element (ERE) consensus sequence is AGGTCAnnnTGACCT, where nnn is known as the tri-nucleotide spacer sequence. Studying 1017 high-confidence ERalpha-bound loci, we found that genomic EREs are enriched for spacers composed of C(A/T)G, suggesting that the spacer may influence receptor binding and transcriptional responses. We designed consensus EREs containing variable spacer sequences and compared ERalpha binding in gel shift assays and enhancer function in reporter assays. We found that ERalpha-ERE binding affinity is modulated by the tri-nucleotide spacer sequence and is favored by spacer sequences of CTG>GCC>TTT. Similarly, luciferase reporter assays indicated that the estrogen-stimulated transcriptional response is modulated by the spacer and parallels the gel shift data: CTG>GCC>TTT. Reporter assays demonstrated that the spacer sequence also modulates the sensitivity of EREs to repression engendered by the receptor antagonist hydroxytamoxifen. These experiments indicate that the sequence of the tri-nucleotide spacer is non-random at receptor-bound genomic loci, influences ERalpha-DNA-binding affinity, and modulates transactivation potential of the receptor-ligand-DNA complex. This work has implications for understanding which genomic EREs are targeted by ERalpha, should improve computational prediction of functional EREs within genomic sequences, and describes novel sequence determinants of the estrogen response.

Location analysis for the estrogen receptor-alpha reveals binding to diverse ERE sequences and widespread binding within repetitive DNA elements

Location analysis for estrogen receptor-α (ERα)-bound cis-regulatory elements was determined in MCF7 cells using chromatin immunoprecipitation (ChIP)-on-chip. Here, we present the estrogen response element (ERE) sequences that were identified at ERα-bound loci and quantify the incidence of ERE sequences under two stringencies of detection: <10% and 10–20% nucleotide deviation from the canonical ERE sequence. We demonstrate that ∼50% of all ERα-bound loci do not have a discernable ERE and show that most ERα-bound EREs are not perfect consensus EREs. Approximately one-third of all ERα-bound ERE sequences reside within repetitive DNA sequences, most commonly of the AluS family. In addition, the 3-bp spacer between the inverted ERE half-sites, rather than being random nucleotides, is C(A/T)G-enriched at bona fide receptor targets. Diverse ERα-bound loci were validated using electrophoretic mobility shift assay and ChIP-polymerase chain reaction (PCR). The functional significance of receptor-bound loci was demonstrated using luciferase reporter assays which proved that repetitive element ERE sequences contribute to enhancer function. ChIP-PCR demonstrated estrogen-dependent recruitment of the coactivator SRC3 to these loci in vivo. Our data demonstrate that ERα binds to widely variant EREs with less sequence specificity than had previously been suspected and that binding at repetitive and nonrepetitive genomic targets is favored by specific trinucleotide spacers.

Clinical assessment of fracture risk and novel therapeutic strategies to combat osteoporosis

OBJECTIVE

To review the latest tools in the clinical assessment of fracture risk and to review new and emerging options for osteoporosis therapy.

DESIGN

Retrospective analysis of published studies regarding the diagnosis and treatment of osteoporosis.

RESULT(S)

Large-scale epidemiologic data were recently assembled by the World Health Organization to produce a Web-based clinical assessment tool, FRAX, which uses clinical and historical data to provide prompt assessment and quantitation of fracture risk. The FRAX models were developed from studying population-based cohorts in Europe, North America, Asia, and Australia. The FRAX algorithms indicate the 10-year probability of hip fracture and the 10-year probability of a major osteoporotic fracture (at the clinical spine, forearm, hip, or shoulder) on which to base treatment decisions. Recent progress in the study of bone metabolism including anabolic pathways that enhance bone maintenance, is anticipated to improve the ways in which skeletal health can be maintained and osteoporosis can be treated.

CONCLUSION(S)

Using FRAX, fracture risk in now easily assessed in the clinical setting. New and emerging treatment strategies for bone maintenance are reviewed. Improved assessment of fracture risk, combined with tailored therapies for at-risk patients, will increase the number of patients who receive appropriate bone-sparing therapies.

Two estrogen response element sequences near the PCNA gene are not responsible for its estrogen-enhanced expression in MCF7 cells

Background

The proliferating cell nuclear antigen (PCNA) is an essential component of DNA replication, cell cycle regulation, and epigenetic inheritance. High expression of PCNA is associated with poor prognosis in patients with breast cancer. The 5′-region of the PCNA gene contains two computationally-detected estrogen response element (ERE) sequences, one of which is evolutionarily conserved. Both of these sequences are of undocumented cis-regulatory function. We recently demonstrated that estradiol (E2) enhances PCNA mRNA expression in MCF7 breast cancer cells. MCF7 cells proliferate in response to E2.

Methodology/Principal Findings

Here, we demonstrate that E2 rapidly enhanced PCNA mRNA and protein expression in a process that requires ERα as well as de novo protein synthesis. One of the two upstream ERE sequences was specifically bound by ERα-containing protein complexes, in vitro, in gel shift analysis. Yet, each ERE sequence, when cloned as a single copy, or when engineered as two tandem copies of the ERE-containing sequence, was not capable of activating a luciferase reporter construct in response to E2. In MCF7 cells, neither ERE-containing genomic region demonstrated E2-dependent recruitment of ERα by sensitive ChIP-PCR assays.

Conclusion/Significance

We conclude that E2 enhances PCNA gene expression by an indirect process and that computational detection of EREs, even when evolutionarily conserved and when near E2-responsive genes, requires biochemical validation.

Ovarian hyperstimulation after a short course of an oral contraceptive in a patient with premature ovarian failure

OBJECTIVE

To report a patient with premature ovarian failure who, after discontinuing a short course of therapy with an oral contraceptive, demonstrated clinical and biochemical evidence of ovarian hyperstimulation.

DESIGN

Case report.

SETTING

Reproductive Center at a university hospital.

PATIENT(S)

31-year-old woman with premature ovarian failure.

INTERVENTION(S)

Triggered ovulation using recombinant human chorionic gonadotropin (hCG).

MAIN OUTCOME MEASURE(S)

Follicle sizes documented by transvaginal ultrasound and corresponding serum estradiol levels.

RESULT(S)

Hyperstimulated ovaries, documented by pelvic ultrasound, demonstrated lead follicles of 16, 22, 27, and 46 mm in average diameters. The serum estradiol level was 979 pg/mL with a serum progesterone of 0.87 ng/mL. Five days after triggered ovulation with recombinant hCG, serum progesterone levels rose to 13.8 ng/mL.

CONCLUSION(S)

Ovarian hyperstimulation may occur after brief gonadotropin suppression in women with premature ovarian failure.

Steroid hormone synthesis in pregnancy

The goal of this article is to summarize what is known about the pathways of steroid hormone synthesis and metabolism in human pregnancy. Emphasis is placed on the distinctions between steroidogenic pathways in adults and those that are operative during human pregnancy.

Immune testing in fertility practice: truth or deception?

PURPOSE OF REVIEW

Much attention has been paid to the role of immunology in reproductive success or failure. Every step in the establishment of normal pregnancy has been implicated as a possible site of immune-mediated reproductive failure. The widespread testing of antiphospholipid, antinuclear, antithyroid, and antisperm antibodies, as well as generalized immune testing, have thus been employed to diagnose patients with otherwise unexplained infertility or recurrent pregnancy loss. Controversial data surrounding the widespread and variable use of immune testing in current fertility practice is reviewed to determine which tests are warranted based on sound scientific evidence. Because it is postulated that early miscarriage, when occult, could represent a failure of embryo implantation indistinguishable from unexplained infertility, this analysis of immune testing includes a discussion of patients with recurrent pregnancy loss.

RECENT FINDINGS

Despite the increased prevalence of abnormal immune testing associated with early reproductive failure, the most rigorous studies have not proven a cause and effect between these phenomena. There is wide variation and inconsistency regarding this association, depending upon which test(s) are employed, the study methodology used, and the patient population under study. The significance of selected immunological test abnormalities associated with early reproductive failure is uncertain.

SUMMARY

Great variability exists in identifying candidates for immune testing, determining which tests to order, interpreting the test results, and offering immunologic treatments. This review argues that the use of widespread immune testing in clinical practice can not be supported by existing data. The resulting therapies are similarly of unconfirmed benefit and may cause harm.

The steroidogenic acute regulatory protein (StAR): a window into the complexities of intracellular cholesterol trafficking

Stimulation of steroid-producing cells of the gonads and adrenals with tropic hormone results in a marked increase in steroid hormone synthesis within minutes. The rate-limiting step in this acute steroidogenic response is the transport of cholesterol from the outer to the inner mitochondrial membrane, where the first committed step in steroid synthesis is performed by the side-chain cleavage enzyme system. This process of cholesterol translocation is blocked by inhibitors of protein synthesis, suggesting that the effect of trophic hormones, acting through the intermediacy of cAMP, most likely involves the de novo synthesis of a protein that is rapidly inactivated. The recently identified steroidogenic acute regulatory (StAR) protein appears to be the most likely candidate for the "labile" protein, based on the following observations: 1) Expression of StAR in COS-1 cells engineered to contain the cholesterol side-chain cleavage system substantially augments pregnenolone formation; 2) StAR protein is expressed almost exclusively in steroid-producing cells, except the trophoblast of the human placenta, and its presence is correlated with steroid hormone production; 3) StAR mRNA increases in response to cAMP; 4) StAR is a target for serine phosphorylation mediated by protein kinase A, a process that is essential for maximizing StAR activity; and 5) lack of functional StAR causes the autosomal recessive disease, congenital lipoid adrenal hyperplasia, characterized by markedly impaired gonadal and adrenal steroid hormone synthesis. Studies on the mechanism of action of StAR revealed that import into mitochondria is not essential to its steroidogenesis-enhancing activity and more likely represents a means of rapidly inactivating StAR. Truncation mutations and site-directed mutations established that the C-terminus of the StAR protein contains the functionally important domains. The demonstration of steroidogenic activity of recombinant StAR protein on isolated mitochondria from bovine corpus luteum using protein that lacks the mitochondrial targeting sequence confirmed that StAR import is not essential for its steroidogenic activity and suggested that StAR acts directly on the outer mitochondrial membrane in the absence of intermediary cytosolic factors. Evidence that StAR functions as a cholesterol transfer protein raises the possibility that StAR acts directly on lipids of the outer mitochondrial membrane, probably stimulating cholesterol desorption from the sterol-rich outer membrane and its movement to the relatively sterol-poor inner membrane.

Induction of matrix metalloproteinases and collagenolysis in chick embryonic membranes before hatching

The membranes surrounding the chick embryo undergo striking morphological changes before hatching, which include structural degradation of the allantoic membrane. The fibrillar collagen content of the membranes declined by embryonic day (ED) 20 (the day of hatching). By ED 19, a 55-kDa matrix metalloproteinase (MMP) activity appeared in the extraembryonic fluid, and by ED 20 there was substantial 55-kDa MMP activity in embryonic membrane extracts. Reverse transcription-polymerase chain reaction was employed to clone a partial cDNA representing the chicken homologue of MMP-13, a 55- to 57-kDa enzyme. MMP-13 mRNA dramatically increased in abundance in embryonic membranes by ED 19, reaching a peak on ED 20. Introduction of the MMP inhibitor batimastat into the extraembryonic fluid prevented the structural changes in the embryonic membranes before hatching. We conclude that, like mammalian fetal membranes, chick embryonic membranes undergo terminal remodeling before hatching, in part as a result of increased MMP activity. The chicken egg system represents a novel in vivo model for exploring biochemical events leading to embryonic membrane remodeling prior to birth and to test inhibitors of MMPs for their ability to prevent collagenolysis and fetal membrane rupture.

Unveiling the mechanism of action and regulation of the steroidogenic acute regulatory protein

Stimulation of steroid-producing cells of the gonads and adrenals with trophic hormone (LH, and ACTH, respectively) produces a marked increase in steroid hormone synthesis within minutes. The rate-limiting step in this acute steroidogenic response is the transport of cholesterol from the outer to the inner mitochondrial membrane, where the first committed step in steroid synthesis is performed by the side-chain cleavage enzyme system (P450scc), resulting in the production of pregnenolone. This process of cholesterol translocation is blocked by inhibitors of protein synthesis (i.e. cycloheximide) indicating that the effect of trophic hormones, acting through the intermediacy of cAMP, most likely involves the de novo synthesis of a protein that is rapidly inactivated. The recently identified steroidogenic acute regulatory protein (StAR) appears to be the most likely candidate for the labile protein: (1) StAR is synthesized in response to cAMP and the StAR preprotein disappears rapidly in the presence of inhibitors of protein synthesis; (2) StAR has an N-terminal targeting sequence that directs the protein to the mitochondria; and (3) StAR protein is expressed almost exclusively in steroid-producing cells, its presence is correlated with steroid hormone production, and lack of functional StAR causes the autosomal recessive disease congenital lipoid adrenal hyperplasia (lipoid CAH), characterized by markedly impaired gonadal and adrenal steroid hormone synthesis. We have demonstrated that StAR is a target for serine phosphorylation mediated by protein kinase A (PKA), a process that is essential to maximizing StAR activity. StAR import by mitochondria is not essential to its steroidogenesis enhancing activity, and more likely, represents a means of rapidly inactivating StAR. Truncation mutations and site-directed mutations in StAR demonstrated that the C-terminus of the protein contains the functionally important domains. Further, we have demonstrated potent steroidogenic activity of recombinant StAR protein on isolated mitochondria from bovine corpus luteum using protein that lacks the mitochondrial targeting sequence. These observations confirm that StAR import is not essential for its steroidogenic activity and suggest that StAR acts directly on the outer mitochondrial membrane in the absence of intermediary cytosolic factors. More recently, we have found that StAR functions as a cholesterol transfer protein that does not require a protein receptor or co-factor, suggesting that StAR acts directly on lipids of the outer mitochondrial membrane to promote cholesterol translocation.

Steroidogenic acute regulatory protein (StAR) is a sterol transfer protein

Steroidogenic acute regulatory protein (StAR) plays a critical role in steroidogenesis by enhancing the delivery of substrate cholesterol from the outer mitochondrial membrane to the cholesterol side chain cleavage enzyme system on the inner membrane. A recombinant StAR protein lacking the first N-terminal 62 amino acid residues that includes the mitochondrial targeting sequence was shown to stimulate the transfer of cholesterol and beta-sitosterol from liposomes to heat-treated mitochondria in a dose-, time-, and temperature-dependent manner. A recombinant mutant StAR protein that cannot stimulate steroidogenesis by isolated mitochondria did not promote sterol transfer. Unlike the more promiscuous lipid transfer protein, sterol carrier protein 2 (SCP2), StAR did not stimulate phosphatidylcholine transfer in our assay system. The recombinant StAR protein increased cholesterol transfer to heat-treated microsomes as well as to heat- and trypsin-treated mitochondria. These observations demonstrate that StAR has sterol transfer activity, which may reflect an ability to enhance desorption of cholesterol from sterol-rich donor membranes. We suggest that the ability of StAR to promote sterol transfer explains its steroidogenic activity.

Steroidogenic acute regulatory protein (StAR) acts on the outside of mitochondria to stimulate steroidogenesis

Steroidogenic acute regulatory protein (StAR) facilitates delivery of cholesterol to the inner mitochondrial membranes. StAR is imported into mitochondria and processed to a mature form by cleavage of the N-terminal mitochondrial targeting sequence. We produced His-tagged (His-tag StAR) constructs lacking the N-terminal 62 amino acids that encode the mitochondrial targeting sequence and examined their steroidogenic activity in intact cells and on isolated mitochondria. His-tag StAR proteins stimulated pregnenolone synthesis to the same extent as wild-type StAR when expressed in COS-1 cells transfected with the cholesterol side-chain cleavage system. His-tag StAR was diffusely distributed in the cytoplasm of transfected COS-1 cells, whereas wild-type StAR was localized to mitochondria. There was no evidence at the light or electron microscope levels for selective localization of His-tag StAR protein to mitochondrial membranes. We established an assay system using mitochondria isolated from bovine corpora lutea and purified recombinant His-tag StAR proteins expressed in E. coli. Recombinant His-tag StAR stimulated pregnenolone production in a dose- and time-dependent manner, functioning at nanomolar concentrations. A point mutant of StAR (A218V) that causes lipoid congenital adrenal hyperplasia was incorporated into the His-tag protein. This mutant was steroidogenically inactive in COS-1 cells and on isolated mitochondria. Our observations conclusively document that StAR acts on the outside of mitochondria, independent of mitochondrial import.

The mechanism of action of steroidogenic acute regulatory protein (StAR). StAR acts on the outside of mitochondria to stimulate steroidogenesis

Steroidogenic acute regulatory protein (StAR) plays an essential role in steroidogenesis, facilitating delivery of cholesterol to cytochrome P450scc on the inner mitochondrial membrane. StAR is synthesized in the cytoplasm and is subsequently imported by mitochondria and processed to a mature form by cleavage of the NH2-terminal mitochondrial targeting sequence. To explore the mechanism of StAR action, we produced 6-histidine-tagged N-62 StAR (His-tag StAR) constructs lacking the NH2-terminal 62 amino acids that encode the mitochondrial targeting sequence and examined their steroidogenic activity in intact cells and on isolated mitochondria. His-tag StAR proteins stimulated pregnenolone synthesis to the same extent as wild-type StAR when expressed in COS-1 cells transfected with the cholesterol side-chain cleavage system. His-tag StAR was diffusely distributed in the cytoplasm of transfected COS-1 cells whereas wild-type StAR was localized to mitochondria. There was no evidence at the light or electron microscope levels for selective localization of His-tag StAR protein to mitochondrial membranes. In vitro import assays demonstrated that wild-type StAR preprotein was imported and processed to mature protein that was protected from subsequent trypsin treatment. In contrast, His-tag StAR was not imported and protein associated with mitochondria was sensitive to trypsin. Using metabolically labeled COS-1 cells transfected with wild-type or His-tag StAR constructs, we confirmed that wild-type StAR preprotein was imported and processed by mitochondria, whereas His-tag StAR remained largely cytosolic and unprocessed. To determine whether cytosolic factors are required for StAR action, we developed an assay system using washed mitochondria isolated from bovine corpora lutea and purified recombinant His-tag StAR proteins expressed in Escherichia coli. Recombinant His-tag StAR stimulated pregnenolone production in a dose- and time-dependent manner, functioning at nanomolar concentrations. A point mutant of StAR (A218V) that causes lipoid congenital adrenal hyperplasia was incorporated into the His-tag protein. This mutant was steroidogenically inactive in COS-1 cells and on isolated mitochondria. Our observations conclusively document that StAR acts on the outside of mitochondria, independent of mitochondrial import, and in the absence of cytosol. The ability to produce bioactive recombinant StAR protein paves the way for refined structural studies of StAR and StAR mutants.

Phosphorylation of steroidogenic acute regulatory protein (StAR) modulates its steroidogenic activity

Steroidogenic acute regulatory protein (StAR) plays a critical role in steroid hormone synthesis. StAR is thought to increase the delivery of cholesterol to the inner mitochondrial membrane where P450scc resides. Tropic hormones acting through the intermediacy of cAMP rapidly increase pregnenolone synthesis, and this rapid steroidogenic response is believed to be due to StAR's action. The StAR protein contains two consensus sequences for phosphorylation catalyzed by protein kinase A that are conserved across all species in which the amino acid sequence of the StAR protein has been determined. We demonstrated that human StAR expressed in COS-1 cells exists in at least four species detectable by two-dimensional gel electrophoresis followed by Western blotting. The two more acidic species disappeared after treatment of the cell extracts with alkaline phosphatase. 32P was incorporated into StAR protein immunoprecipitated from COS-1 cell extracts, and a 10-min treatment with 8-bromo-cAMP increased 32P incorporation into the StAR preprotein. StAR protein generated by in vitro transcription/translation was phosphorylated by the protein kinase A catalytic subunit in the presence of [gamma-32P]ATP. Mutation of potential sites for protein kinase A-mediated phosphorylation at serine 57 and serine 195 to alanines, individually, reduced 32P incorporation from labeled ATP into StAR preprotein produced by in vitro transcription/translation when incubated with protein kinase A catalytic subunit. 32P labeling of StAR protein expressed in COS-1 cells was also reduced when serine 57 or serine 195 were mutated to alanines. A double mutant in which both serine 57 and serine 195 were changed to alanines displayed markedly reduced 32P incorporation. To determine the functional significance of StAR phosphorylation, we tested the steroidogenic activity of the wild-type StAR and mutated StAR proteins in COS-1 cells expressing the human cholesterol side chain cleavage enzyme system. Mutation of the conserved protein kinase A phosphorylation site at serine 57 had no effect on pregnenolone synthesis. However, mutation of the serine residue at 195 resulted in an approximately 50% reduction in pregnenolone production. The S195A mutant construct did not yield the more acidic species of StAR detected in two-dimensional Western blots, indicating that the mutation affected the ability of the protein to be post-translationally modified. Mutation of the corresponding serine residues in murine StAR (Ser56 and Ser194) to alanines yielded results that were similar to those obtained with human StAR; the S56A mutant displayed a modest reduction in steroidogenic activity, whereas the S194A mutant had approximately 40% of the activity of murine wild-type StAR. In contrast to the human S195A mutation, conversion of serine 195 to an aspartic acid residue had no effect on steroidogenic activity, consistent with the idea that a negative charge at this site modulates StAR function. Our observations suggest that phosphorylation of serine 194/195 increases the biological activity of StAR and that this post- or co-translational event accounts, in part, for the immediate effects of cAMP on steroid production.

Localization of the steroidogenic acute regulatory protein in human tissues

The rate-limiting step in steroid hormone production in the adrenal cortex and gonads, the translocation of cholesterol from the outer to the inner mitochondrial membranes, is mediated by the steroidogenic acute regulatory protein (StAR). Heretofore, the localization of StAR in human adult and fetal tissues has not been defined. To this end, expression of StAR was detected in formalin-fixed, paraffin-embedded specimens using a polyclonal antiserum raised against recombinant human StAR. Primordial follicles of adult ovaries did not contain StAR, whereas antral follicles stained intensely in the thecal layer, with occasional staining of granulosa cells. Corpora lutea were intensely stained, but with a patchy distribution. Corpora albicantia did not stain. A luteoma of pregnancy stained with patches of moderate intensity. Ovaries with hyperthecosis contained areas of intense thecal staining. An ovarian Leydig cell tumor stained intensely, whereas granulosa cell tumors were negative. Ovarian adenocarcinomas, borderline tumors, teratomas, cystadenomas, and a Brenner tumor displayed no specific StAR immunostaining. Testicular Leydig cells stained moderately to intensely, as did a testicular Leydig cell tumor. Sertoli cells stained weakly in some specimens. Seminomas and testicular germ cell tumors were negative. There was minimal to moderate staining in the adrenal glomerulosa and faciculata and minimal staining in the reticularis, while the medulla was negative. Adrenal cortical adenomas, hyperplasias, and carcinomas all contained areas of StAR staining. The renal distal tubules stained with moderate to marked intensity. Renal carcinomas had occasional modest staining. No immunostaining was found in the placenta. Fetal ovaries contained sporadic stromal cells displaying intense StAR staining, particularly in the hilar region. Oocytes from a 32-week fetal ovary showed moderate to intense staining. Fetal testes displayed intense Leydig cell staining. The neocortex of the fetal adrenal glands displayed only minimal StAR staining, whereas moderate to intense staining was found in the fetal zone. The fetal kidneys had moderate StAR staining of the distal convoluted tubules. We conclude that StAR is localized to normal and neoplastic cells in the gonads and adrenal cortex, which produce large amounts of pregnenolone. StAR protein was not detected in the placenta, documenting that placental progestin synthesis occurs through StAR-independent mechanisms. The presence of StAR in cells that do not express cholesterol side-chain cleavage enzyme cytochrome P450, including renal distal tubules, Sertoli cells, and fetal oocytes, suggests that StAR has roles in metabolic processes in addition to stimulating pregnenolone synthesis.

MLN64 contains a domain with homology to the steroidogenic acute regulatory protein (StAR) that stimulates steroidogenesis

MLN64 is a protein that is highly expressed in certain breast carcinomas. The C terminus of MLN64 shares significant homology with the steroidogenic acute regulatory protein (StAR), which plays a key role in steroid hormone biosynthesis by enhancing the intramitochondrial translocation of cholesterol to the cholesterol side-chain cleavage enzyme. We tested the ability of MLN64 to stimulate steroidogenesis by using COS-1 cells cotransfected with plasmids expressing the human cholesterol side-chain cleavage enzyme system and wild-type and mutant MLN64 proteins. Wild-type MLN64 increased pregnenolone secretion in this system 2-fold. The steroidogenic activity of MLN64 was found to reside in the C terminus of the protein, because constructs from which the C-terminal StAR homology domain was deleted had no steroidogenic activity. In contrast, removal of N-terminal sequences increased MLN64's steroidogenesis-enhancing activity. MLN64 mRNA was found in many human tissues, including the placenta and brain, which synthesize steroid hormones but do not express StAR. Western blot analysis revealed the presence of lower molecular weight immunoreactive MLN64 species that contain the C-terminal sequences in human tissues. Homologs of both MLN64 and StAR were identified in Caenorhabditis elegans, indicating that the two proteins are ancient. Mutations that inactivate StAR were correlated with amino acid residues that are identical or similar among StAR and MLN64, indicating that conserved motifs are important for steroidogenic activity. We conclude that MLN64 stimulates steroidogenesis by virtue of its homology to StAR.

Multiple steroidogenic factor 1 binding elements in the human steroidogenic acute regulatory protein gene 5'-flanking region are required for maximal promoter activity and cyclic AMP responsiveness

A proximal element from the human StAR gene promoter, containing the sequence (-105)TATCCTTGAC(-95), was shown to confer responsiveness to 8-Br-cAMP in the presence of steroidogenic factor 1 (SF-1) when placed behind a minimal thymidine kinase promoter or an SV40 promoter and transfected into BeWo cells which normally lack StAR and SF-1. This element was also transactivated by SF-1 in a yeast one-hybrid system. The -105 to -95 sequence was protected by SF-1 in footprint analysis and a double-stranded oligonucleotide containing the element bound SF-1 specifically in electrophoretic mobility shift assays. Another SF-1-binding sequence 35 bp upstream of the transcription start site ((-42)CAGCCTTC(-35)) was identified in the DNase 1 footprint analysis and, when mutated, markedly reduced SF-1-dependent and 8-Br-cAMP-stimulated StAR promoter activity in BeWo cells. The two proximal SF-1 response elements were shown to be critical for StAR promoter function in human granulosalutein cells, which express SF-1 and respond to cAMP with increased transcription of the StAR gene. Mutation of either element substantially reduced basal and forskolin-stimulated promoter activity, although mutation of the -105 to -95 element had more pronounced effects. Mutation of a third, more distal, SF-1-binding site at -926 to -918 also reduced basal but not forskolin-stimulated promoter activity in the granulosa-lutein cells. These findings demonstrate that multiple SF-1 response elements are required for maximal StAR promoter activity and regulation by cAMP.

Antidiabetic thiazolidinediones inhibit leptin (ob) gene expression in 3T3-L1 adipocytes

Lack of leptin (ob) protein causes obesity in mice. The leptin gene product is important for normal regulation of appetite and metabolic rate and is produced exclusively by adipocytes. Leptin mRNA was induced during the adipose conversion of 3T3-L1 cells, which are useful for studying adipocyte differentiation and function under controlled conditions. We studied leptin regulation by antidiabetic thiazolidinedione compounds, which are ligands for the adipocyte-specific nuclear receptor peroxisome proliferator-activated receptor gamma (PPARgamma) that regulates the transcription of other adipocyte-specific genes. Remarkably, leptin gene expression was dramatically repressed within a few hours after thiazolidinedione treatment. The ED50 for inhibition of leptin expression by the thiazolidinedione BRL49653 was between 5 and 50 nM, similar to its Kd for binding to PPARgamma. The relatively weak, nonthiazolidinedione PPAR activator WY 14,643 also inhibited leptin expression, but was approximately 1000 times less potent than BRL49653. These results indicate that antidiabetic thiazolidinediones down-regulate leptin gene expression with potencies that correlate with their abilities to bind and activate PPARgamma.

Differential activation of peroxisome proliferator-activated receptors by eicosanoids

Peroxisome proliferator-activated receptors (PPARs) are nuclear hormone receptors that regulate gene transcription in response to peroxisome proliferators and fatty acids. PPARs also play an important role in the regulation of adipocyte differentiation. It is unclear, however, what naturally occurring compounds activate each of the PPAR subtypes. To address this issue, a screening assay was established using heterologous fusions of the bacterial tetracycline repressor to several members of the peroxisome proliferator-activated receptor (PPAR) family. This assay was employed to compare the activation of PPAR family members by known PPAR activators including peroxisome proliferators and fatty acids. Interestingly, the activation of PPARs by fatty acids was partially inhibited by the cyclooxygenase inhibitor indomethacin, which prevents prostaglandin synthesis. Indeed, prostaglandins PGA1 and 2, PGD1 and 2, and PGJ2-activated PPARs, while a number of other prostaglandins had no effect. We also screened a variety of hydroxyeicosatetraenoic acids (HETEs) for the ability to activate PPARs. 8(S)-HETE, but not other (S)-HETEs, was a strong activator of PPAR alpha. Remarkably, PPAR activation by 8(S)-HETE was stereoselective. In addition, 8(S)-HETE was able to induce differentiation of 3T3-L1 preadipocytes. These results indicate that PPARs are differentially activated by naturally occurring eicosanoids and related molecules.

Cloning and expression of a cDNA encoding human sterol carrier protein 2

We report the cloning and expression of a cDNA encoding human sterol carrier protein 2 (SCP2). The 1.3-kilobase (kb) cDNA contains an open reading frame which encompasses a 143-amino acid sequence which is 89% identical to the rat SCP2 amino acid sequence. The deduced amino acid sequence of the polypeptide reveals a 20-residue amino-terminal leader sequence in front of the mature polypeptide, which contains a carboxyl-terminal tripeptide (Ala-Lys-Leu) related to the peroxisome targeting sequence. The expressed cDNA in COS-7 cells yields a 15.3-kDa polypeptide and increased amounts of a 13.2-kDa polypeptide, both reacting with a specific rabbit antiserum to rat liver SCP2. The cDNA insert hybridizes with 3.2- and 1.8-kb mRNA species in human liver poly(A)+ RNA. In human fibroblasts and placenta the 1.8-kb mRNA was most abundant. Southern blot analysis suggests either that there are multiple copies of the SCP2 gene in the human genome or that the SCP2 gene is very large. Coexpression of the SCP2 cDNA with expression vectors for cholesterol side-chain cleavage enzyme and adrenodoxin resulted in a 2.5-fold enhancement of progestin synthesis over that obtained with expression of the steroidogenic enzyme system alone. These findings are concordant with the notion that SCP2 plays a role in regulating steroidogenesis, among other possible functions.

Regulation of human trophoblast function by glucocorticoids: dexamethasone promotes increased secretion of chorionic gonadotropin

Steroid hormones are thought to play a role in controlling placental endocrine function. Since maternal free cortisol levels increase during gestation, and glucocorticoid receptors have been identified in placental tissue, we examined the effects of glucocorticoids on the production of CG by cultured human cytotrophoblasts. Treatment of cytotrophoblasts with 1 microM dexamethasone increased CG secretion by 6- to 10-fold over a 72-h period, whereas progesterone (1 microM) had no effect. The stimulatory effects of dexamethasone were blocked by the glucocorticoid antagonist RU 486, indicating a requirement for the glucocorticoid receptor. Intracellular accumulation of the CG alpha-subunit in response to dexamethasone was demonstrated by immunocytochemistry, and Northern blot analyses revealed that dexamethasone treatment increases CG alpha- and beta-subunit mRNA levels. Dexamethasone also enhanced the stimulatory effects of 8-bromo-cAMP on CG secretion. We conclude that glucocorticoids as well as cAMP modulate human trophoblast endocrine functions.