An integrative transcriptomic analysis reveals bisphenol A exposure-induced dysregulation of microRNA expression in human endometrial cells

Emerging regulatory roles of noncoding RNAs induced by bisphenol a (BPA) and its alternatives in human diseases

Bisphenols (BPs), including BPA, BPF, BPS, and BPAF, are synthetic phenolic organic compounds and endocrine-disrupting chemicals. These organics have been broadly utilized to produce epoxy resins, polycarbonate plastics, and other products. Mounting evidence has shown that BPs, especially BPA, may enter into the human body and participate in the development of human diseases mediated by nuclear hormone receptors. Moreover, BPA may negatively affect human health at the epigenetic level through processes such as DNA methylation and histone acetylation. Recent studies have demonstrated that, as part of epigenetics, noncoding RNAs (ncRNAs), including microRNAs (miRNAs), long noncoding RNAs (lncRNAs), circular RNAs (circRNAs), and small nucleolar RNAs (snoRNAs), have vital impacts on BP-related diseases, such as reproductive system diseases, nervous system diseases, digestive system diseases, endocrine system diseases, and other diseases. Moreover, based on the bioinformatic analysis, changes in ncRNAs may be relevant to normal activities and functions and BP-induced diseases. Thus, we conducted a meta-analysis to identify more promising ncRNAs as biomarkers and therapeutic targets for BP exposure and relevant human diseases. In this review, we summarize the regulatory functions of ncRNAs induced by BPs in human diseases and latent molecular mechanisms, as well as identify prospective biomarkers and therapeutic targets for BP exposure and upper diseases.

Application of the Key Characteristics of Carcinogens to Bisphenol A

The ten key characteristics (KCs) of carcinogens are based on characteristics of known human carcinogens and encompass many types of endpoints. We propose that an objective review of the large amount of cancer mechanistic evidence for the chemical bisphenol A (BPA) can be achieved through use of these KCs. A search on metabolic and mechanistic data relevant to the carcinogenicity of BPA was conducted and web-based software tools were used to screen and organize the results. We applied the KCs to systematically identify, organize, and summarize mechanistic information for BPA, and to bring relevant carcinogenic mechanisms into focus. For some KCs with very large data sets, we utilized reviews focused on specific endpoints. Over 3000 studies for BPA from various data streams (exposed humans, animals, in vitro and cell-free systems) were identified. Mechanistic data relevant to each of the ten KCs were identified, with receptor-mediated effects, epigenetic alterations, oxidative stress, and cell proliferation being especially data rich. Reactive and bioactive metabolites are also associated with a number of KCs. This review demonstrates how the KCs can be applied to evaluate mechanistic data, especially for data-rich chemicals. While individual entities may have different approaches for the incorporation of mechanistic data in cancer hazard identification, the KCs provide a practical framework for conducting an objective examination of the available mechanistic data without a priori assumptions on mode of action. This analysis of the mechanistic data available for BPA suggests multiple and inter-connected mechanisms through which this chemical can act.

Invisible Hand behind Female Reproductive Disorders: Bisphenols, Recent Evidence and Future Perspectives

Reproductive disorders are considered a global health problem influenced by physiological, genetic, environmental, and lifestyle factors. The increased exposure to bisphenols, a chemical used in large quantities for the production of polycarbonate plastics, has raised concerns regarding health risks in humans, particularly their endocrine-disrupting effects on female reproductive health. To provide a basis for future research on environmental interference and reproductive health, we reviewed relevant studies on the exposure patterns and levels of bisphenols in environmental matrices and humans (including susceptible populations such as pregnant women and children). In addition, we focused on in vivo, in vitro, and epidemiological studies evaluating the effects of bisphenols on the female reproductive system (the uterus, ovaries, fallopian tubes, and vagina). The results indicate that bisphenols cause structural and functional damage to the female reproductive system by interfering with hormones; activating receptors; inducing oxidative stress, DNA damage, and carcinogenesis; and triggering epigenetic changes, with the damaging effects being intergenerational. Epidemiological studies support the association between bisphenols and diseases such as cancer of the female reproductive system, reproductive dysfunction, and miscarriage, which may negatively affect the establishment and maintenance of pregnancy. Altogether, this review provides a reference for assessing the adverse effects of bisphenols on female reproductive health.

The potential role of miRNAs in the pathogenesis of adrenocortical carcinoma - A focus on signaling pathways interplay

Adrenocortical carcinoma (ACC) is a highly malignant infrequent tumor with a dismal prognosis. microRNAs (miRNAs, miRs) are crucial in post-transcriptional gene expression regulation. Due to their ability to regulate multiple gene networks, miRNAs are central to the hallmarks of cancer, including sustained proliferative signaling, evasion of growth suppressors, resistance to cell death, replicative immortality, induction/access to the vasculature, activation of invasion and metastasis, reprogramming of cellular metabolism, and avoidance of immune destruction. ACC represents a singular form of neoplasia associated with aberrations in the expression of evolutionarily conserved short, non-coding RNAs. Recently, the role of miRNAs in ACC has been examined extensively despite the disease's rarity. Hence, the current review is a fast-intensive track elucidating the potential role of miRNAs in the pathogenesis of ACC besides their association with the survival of ACC.

The State of Research and Weight of Evidence on the Epigenetic Effects of Bisphenol A

Bisphenol A (BPA) is a high-production-volume chemical with numerous industrial and consumer applications. BPA is extensively used in the manufacture of polycarbonate plastics and epoxy resins. The widespread utilities of BPA include its use as internal coating for food and beverage cans, bottles, and food-packaging materials, and as a building block for countless goods of common use. BPA can be released into the environment and enter the human body at any stage during its production, or in the process of manufacture, use, or disposal of materials made from this chemical. While the general population is predominantly exposed to BPA through contaminated food and drinking water, non-dietary exposures through the respiratory system, integumentary system, and vertical transmission, as well as other routes of exposure, also exist. BPA is often classified as an endocrine-disrupting chemical as it can act as a xenoestrogen. Exposure to BPA has been associated with developmental, reproductive, cardiovascular, neurological, metabolic, or immune effects, as well as oncogenic effects. BPA can disrupt the synthesis or clearance of hormones by binding and interfering with biological receptors. BPA can also interact with key transcription factors to modulate regulation of gene expression. Over the past 17 years, an epigenetic mechanism of action for BPA has emerged. This article summarizes the current state of research on the epigenetic effects of BPA by analyzing the findings from various studies in model systems and human populations. It evaluates the weight of evidence on the ability of BPA to alter the epigenome, while also discussing the direction of future research.

Re-evaluation of the risks to public health related to the presence of bisphenol A (BPA) in foodstuffs

In 2015, EFSA established a temporary tolerable daily intake (t-TDI) for BPA of 4 μg/kg body weight (bw) per day. In 2016, the European Commission mandated EFSA to re-evaluate the risks to public health from the presence of BPA in foodstuffs and to establish a tolerable daily intake (TDI). For this re-evaluation, a pre-established protocol was used that had undergone public consultation. The CEP Panel concluded that it is Unlikely to Very Unlikely that BPA presents a genotoxic hazard through a direct mechanism. Taking into consideration the evidence from animal data and support from human observational studies, the immune system was identified as most sensitive to BPA exposure. An effect on Th17 cells in mice was identified as the critical effect; these cells are pivotal in cellular immune mechanisms and involved in the development of inflammatory conditions, including autoimmunity and lung inflammation. A reference point (RP) of 8.2 ng/kg bw per day, expressed as human equivalent dose, was identified for the critical effect. Uncertainty analysis assessed a probability of 57-73% that the lowest estimated Benchmark Dose (BMD) for other health effects was below the RP based on Th17 cells. In view of this, the CEP Panel judged that an additional uncertainty factor (UF) of 2 was needed for establishing the TDI. Applying an overall UF of 50 to the RP, a TDI of 0.2 ng BPA/kg bw per day was established. Comparison of this TDI with the dietary exposure estimates from the 2015 EFSA opinion showed that both the mean and the 95th percentile dietary exposures in all age groups exceeded the TDI by two to three orders of magnitude. Even considering the uncertainty in the exposure assessment, the exceedance being so large, the CEP Panel concluded that there is a health concern from dietary BPA exposure.

Analysis of endometrial lavage microbiota reveals an increased relative abundance of the plastic-degrading bacteria Bacillus pseudofirmus and Stenotrophomonas rhizophila in women with endometrial cancer/endometrial hyperplasia

The pathogenic influences of uterine bacteria on endometrial carcinogenesis remain unclear. The aim of this pilot study was to compare the microbiota composition of endometrial lavage samples obtained from women with either endometrial hyperplasia (EH) or endometrial cancer (EC) versus those with benign uterine conditions. We hypothesized that specific microbiota signatures would distinguish between the two groups, possibly leading to the identification of bacterial species associated with endometrial tumorigenesis. A total of 35 endometrial lavage specimens (EH, n = 18; EC, n = 7; metastatic EC, n = 2; benign endometrial lesions, n = 8) were collected from 32 women who had undergone office hysteroscopy. Microbiota composition was determined by sequencing the V3−V4 region of 16S rRNA genes and results were validated by real-time qPCR in 46 patients with EC/EH and 13 control women. Surprisingly, we found that Bacillus pseudofirmus and Stenotrophomonas rhizophila – two plastic-degrading bacterial species – were over-represented in endometrial lavage specimens collected from patients with EC/EH. Using computational analysis, we found that the functional profile of endometrial microbiota in EC/EH was associated with fatty acid and amino acid metabolism. In summary, our hypothesis-generating data indicate that the plastic-degrading bacteria Bacillus pseudofirmus and Stenotrophomonas rhizophila are over-represented within the endometrial lavage microbiota of women with EC/EH living in Taiwan. Whether this may be related to plastic pollution deserves further investigation.

LncRNA TUG1 promotes the migration and invasion in type I endometrial carcinoma cells by regulating E-N cadherin switch

OBJECTIVE

Accumulating evidence has demonstrated that lncRNA Taurine-upregulated gene 1 (TUG1) plays an important role in regulation of cell morphology, migration, proliferation and apoptosis. Our aim was to evaluate the oncogenic role of TUG1 in type I Endometrial Carcinoma (EC) and explore the precise mechanism of TUG1 involved in tumor progression.

MATERIALS AND METHODS

The GSE17025 data set was used to analyze the correlation of TUG1 expression with type I EC patients' prognosis. Furthermore, TUG1 expression profiles were measured by qRT-PCR from carcinoma tissues and adjacent nonneoplastic tissues (NNT) of 105 type I EC patients. The regulation of epithelial-mesenchymal transition (EMT) related molecules, p-AKT and AKT by TUG1 knockdown was investigated using Western blot analysis; meanwhile, the oncogenic roles of TUG1 were evaluated using cell viability and transwell migration/invasion assay in Hec-1-A and Ishikawa cell lines.

RESULTS

Firstly, we observed a significant association between higher TUG1 expression and lower survival rate in type I EC patients using the GSE17025 data set. A significant elevation of TUG1 levels was confirmed in type I EC tissues compared with NNT in the 105 type I EC patients, and high expression of TUG1 was associated with lymph vascular space invasion (LVSI) and lymph node metastasis (LNM). Subsequently, TUG1 knockdown could remarkably inhibit the Hec-1-A and Ishikawa cell invasion and migration in the functional experiment. Furthermore, our results showed that the protein levels of E-cadherin increased and N-cadherin decreased significantly, while β-catenin and Vimentin were not significantly altered upon TUG1 silencing in both Hec-1-A and Ishikawa cells. Finally, we found the p-AKT and AKT protein levels, and the rate of p-AKT/t-AKT has a tendency to be down-regulate in Hec-1-A cells, while the AKT pathway was not change significantly in Ishikawa cells after TUG1 knockdown.

CONCLUSION

Collectively, our data reveal that TUG1 might be regarded as an oncogenic molecule that promotes type I EC cells metastasis leading to tumor progression, at least partially, by regulating E-N cadherin switch and the AKT pathway.

The emerging role of noncoding RNAs in the Hedgehog signaling pathway in cancer

Hedgehog (HH), a conserved signaling pathway, is involved in embryo development, organogenesis, and other biological functions. Dysregulation and abnormal activation of HH are involved in tumorigenesis and tumor progression. With the emergence of interest in noncoding RNAs, studies on their involvement in abnormal regulation of biological processes in tumors have been published one after another. In this review, we focus on the crosstalk between noncoding RNAs and the HH pathway in tumors and elaborate the mechanisms by which long noncoding RNAs and microRNAs regulate or are regulated by HH signaling in cancer. We also discuss the interaction between noncoding RNAs and the HH pathway from the perspective of cancer hallmarks, presenting this complex network as concisely as possible and organizing ideas for cancer diagnosis and treatment.

Genome-wide microRNA profiles identify miR-107 as a top miRNA associating with expression of the CYP3As and other drug metabolizing cytochrome P450 enzymes in the liver

Cytochrome P450 (CYP) drug metabolizing enzymes are responsible for the metabolism of over 70% of currently used medications with the CYP3A family being the most important CYP enzymes in the liver. Large inter-person variability in expression/activity of the CYP3As greatly affects drug exposure and treatment outcomes, yet the cause of such variability remains elusive. Micro-RNAs (miRNAs) are small noncoding RNAs that negatively regulate gene expression and are involved in diverse cellular processes including metabolism of xenobiotics and therapeutic outcomes. Target prediction and in vitro functional assays have linked several miRNAs to the control of CYP3A4 expression. Yet, their co-expression with CYP3As in the liver remain unclear. In this study, we used genome-wide miRNA profiling in liver samples to identify miRNAs associated with the expression of the CYP3As. We identified and validated both miR-107 and miR-1260 as strongly associated with the expression of CYP3A4, CYP3A5, and CYP3A43. Moreover, we found associations between miR-107 and nine transcription factors (TFs) that regulate CYP3A expression, with estrogen receptor alpha (ESR1) having the largest effect size. Including ESR1 and the other TFs in the regression model either diminished or abolished the associations between miR-107 and the CYP3As, indicating that the role of miR-107 in CYP3A expression may be indirect and occur through these key TFs. Indeed, testing the other nine CYPs previously shown to be regulated by ESR1 identified similar miR-107 associations that were dependent on the exclusion of ESR1 and other key TFs in the regression model. In addition, we found significant differences in miRNA expression profiles in liver samples between race and sex. Together, our results identify miR-107 as a potential epigenetic regulator that is strongly associated with the expression of many CYPs, likely via impacting the CYP regulatory network controlled by ESR1 and other key TFs. Therefore, both genetic and epigenetic factors that alter the expression of miR-107 may have a broad influence on drug metabolism.

Endocrine Disruptors and Endometrial Cancer: Molecular Mechanisms of Action and Clinical Implications, a Systematic Review

It has been widely demonstrated that endocrine disruptors play a central role in various physiopathological processes of human health. In the literature, various carcinogenic processes have been associated with endocrine disruptors. A review of the molecular mechanisms underlying the interaction between endocrine disruptors and the endometrial cancer has been poorly developed. A systematic review was performed using PubMed^®/MEDLINE. A total of 25 in vivo and in vitro works were selected. Numerous endocrine disruptors were analyzed. The most relevant results showed how Bisphenol A (BPA) interacts with the carcinogenesis process on several levels. It has been demonstrated how BPA can interact with hormonal receptors and with different transcription proliferative and antiproliferative factors. Furthermore, the effect of Polycyclic aromatic hydrocarbons on Aryl hydrocarbon receptors was investigated, and the role of flame retardants in promoting proliferation and metastasis was confirmed. The results obtained demonstrate how the mechanisms of action of endocrine disruptors are manifold in the pathophysiology of endometrial cancer, acting on different levels of the cancerogenesis process.

MicroRNA Transcriptomics Analysis Identifies Dysregulated Hedgehog Signaling Pathway in a Mouse Model of Acute Intracerebral Hemorrhage Exposed to Hyperglycemia

OBJECTIVE

Hyperglycemia is often observed in the patients after acute stroke. This study aims to elucidate the potential effect and mechanism of hyperglycemia by screening microRNAs expression in intracerebral hemorrhage mice.

METHODS

We employed the collagenase model of intracerebral hemorrhage. Twenty male C57BL/6 mice were used and randomly divided in normo- and hyperglycemic. The hyperglycemia was induced by intraperitoneally injection of 50% of Dextrose (8 mL/kg) 3 hours after intracerebral hemorrhage. The neurologic impairment was investigated by neurologic deficit scale. To study the specific mechanisms of hyperglycemia, microRNAs expression in perihematomal area was investigated by RNA sequencing. MicroRNAs expression in hyperglycemic intracerebral hemorrhage animals were compared normoglycemic mice. Functional annotation analysis was used to indicate potential pathological pathway, underlying observed effects. Finally, polymerase chain reaction validation was administered.

RESULTS

Intraperitoneal injection of dextrose significantly increased blood glucose level. That was associated with aggravation of neurological deficits in hyperglycemic compared to normoglycemic animals. A total of 73 differentially expressed microRNAs were identified via transcriptomics analysis. Bioinformatics analyses showed that these microRNAs were significantly altered in several signaling pathways, of which the hedgehog signaling pathway was regarded as the most potential pathway associated with the effect of hyperglycemia on acute intracerebral hemorrhage. Furthermore, polymerase chain reaction results validated the correlation between microRNAs and hedgehog signaling pathway.

CONCLUSIONS

MicroRNA elevated in hyperglycemia group may be involved in worsening the neurological function via inhibiting the hedgehog signaling, which provides a novel molecular physiological mechanism and lays the foundation for treatment of intracerebral hemorrhage.

miRNA changes in the mouse placenta due to bisphenol A exposure

Aim: To determine small RNA expression changes in mouse placenta induced by bisphenol A (BPA) exposure. Methods: Exposing female mice to BPA two weeks prior to conception through gestational day 12.5; whereupon fetal placentas were collected, frozen in liquid nitrogen and stored at -80°C. Small RNAs were isolated and used for small RNA-sequencing. Results: 43 small RNAs were differentially expressed. Target mRNAs were closely aligned to those expressed by thymus and brain, and pathway enrichment analyses indicated that such target mRNAs regulate neurogenesis and associated neurodevelopment processes. Conclusions: BPA induces several small RNAs in mouse placenta that might provide biomarkers for BPA exposure. Further, the placenta might affect fetal brain development through the secretion of miRNAs.

Oncogenic Role of miRNA in Environmental Exposure to Plasticizers: A Systematic Review

The daily environmental exposure of humans to plasticizers may adversely affect human health, representing a global issue. The altered expression of microRNAs (miRNAs) plays an important pathogenic role in exposure to plasticizers. This systematic review summarizes recent findings showing the modified expression of miRNAs in cancer due to exposure to plasticizers. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) methodology, we performed a systematic review of the literature published in the past 10 years, focusing on the relationship between plasticizer exposure and the expression of miRNAs related to cancer. Starting with 535 records, 17 articles were included. The results support the hypothesis that exposure to plasticizers causes changes in or the deregulation of a number of oncogenic miRNAs and show that the interaction of plasticizers with several redundant miRNAs, such as let-7f, let-7g, miR-125b, miR-134, miR-146a, miR-22, miR-192, miR-222, miR-26a, miR-26b, miR-27b, miR-296, miR-324, miR-335, miR-122, miR-23b, miR-200, miR-29a, and miR-21, might induce deep alterations. These genotoxic and oncogenic responses can eventually lead to abnormal cell signaling pathways and metabolic changes that participate in many overlapping cellular processes, and the evaluation of miRNA-level changes can be a useful target for the toxicological assessment of environmental pollutants, including plastic additives and plasticizers.

Metabolic pathways, alterations in miRNAs expression and effects of genetic polymorphisms of bisphenol a analogues: A systematic review

Bisphenol A (BPA) is one of the most common endocrine disruptors found in the environment and its harmful health effects in humans and wildlife have been extensively reported One of the main aims of this review was to examine the metabolic pathways of BPA and BPA substitutes and the endocrine disrupting properties of their metabolites. According to the available literature, phase I and phase II metabolic reactions play an important role in the detoxification process of bisphenols (BPs), but their metabolism can also lead to the formation of highly reactive metabolites. The second part of this work addresses the associations between exposure to BPA and its analogues with the alterations in miRNAs expression and the effects of single nucleotide polymorphisms (SNPs). Available scientific evidence shows that BPs can dysregulate the expression of several miRNAs, and in turn, these miRNAs could be considered as epigenetic biomarkers to prevent the development of a variety of BP-mediated diseases. Interestingly, genetic polymorphisms are able to modify the relationship of BPA exposure with the risk of adverse health effects, suggesting that interindividual genetic differences modulate the susceptibility to the effects of environmental contaminants.

A comprehensive review on the carcinogenic potential of bisphenol A: clues and evidence

Bisphenol A [BPA; (CH₃)₂C(C₆H₄OH)₂] is a synthetic chemical used as a precursor material for the manufacturing of plastics and resins. It gained attention due to its high chances of human exposure and predisposing individuals at extremely low doses to diseases, including cancer. It enters the human body via oral, inhaled, and dermal routes as leach-out products. BPA may be anticipated as a probable human carcinogen. Studies using in vitro cell lines, rodent models, and epidemiological analysis have convincingly shown the increasing susceptibility to cancer at doses below the oral reference dose set by the Environmental Protection Agency for BPA. Furthermore, BPA exerts its toxicological effects at the genetic and epigenetic levels, influencing various cell signaling pathways. The present review summarizes the available data on BPA and its potential impact on cancer and its clinical outcome.

LINC00461 Promoted Endometrial Carcinoma Growth and Migration by Targeting MicroRNA-219-5p/Cyclooxygenase-2 Signaling Axis

Endometrial carcinoma (EC) ranks as the most common female genital cancer in developed countries. Lately, more and more long noncoding RNAs (lncRNAs) have been identified as vital regulators in numerous physiological and pathological processes, including EC. However, the expression pattern and precise functions of different lncRNAs in EC remain unclear. In this study, we reported LINC00461 was upregulated in EC patient tissues and cell lines. In addition, LINC00461 knockdown could remarkably suppress cell proliferation, cell cycle progression, cell migration, and promote cell apoptosis in EC cells. We discovered LINC00461 could sponge microRNA-219-5p (miR-219-5p) and suppress its expression, thereby upregulating expression level of miR-219-5p’s target, cyclooxygenase-2 (COX-2). In vivo animal models, LINC00461 knockdown inhibited tumor growth by increasing miR-219-5p level and reducing COX-2 expression, thus confirming LINC00461 functions as an oncogene in EC. In this study, a novel regulatory role of LINC00461/miR-219-5p/COX-2 axis was systematically investigated in context of EC, with the aim to provide promising intervention targets for EC therapy from bench to clinic.

Endocrine Disruptors Acting on Estrogen and Androgen Pathways Cause Reproductive Disorders through Multiple Mechanisms: A Review

Increasing contamination of the environment by toxic compounds such as endocrine disrupting chemicals (EDCs) is one of the major causes of reproductive defects in both sexes. Estrogen/androgen pathways are of utmost importance in gonadal development, determination of secondary sex characteristics and gametogenesis. Most of the EDCs mediate their action through respective receptors and/or downstream signaling. The purpose of this review is to highlight the mechanism by which EDCs can trigger antagonistic or agonistic response, acting through estrogen/androgen receptors causing reproductive defects that lead to infertility. In vitro, in vivo and in silico studies focusing on the impact of EDCs on estrogen/androgen pathways and related proteins published in the last decade were considered for the review. PUBMED and PUBCHEM were used for literature search. EDCs can bind to estrogen receptors (ERα and ERβ) and androgen receptors or activate alternative receptors such as G protein-coupled receptors (GPCR), GPR30, estrogen-related receptor (ERRγ) to activate estrogen signaling via downstream kinases. Bisphenol A, dichlorodiphenyltrichloroethane, dichlorodiphenyldichloroethylene, polychlorinated biphenyls and phthalates are major toxicants that interfere with the normal estrogen/androgen pathways leading to infertility in both sexes through many ways, including DNA damage in spermatozoids, altered methylation pattern, histone modifications and miRNA expression.

Disruption of global hypothalamic microRNA (miR) profiles and associated behavioral changes in California mice (Peromyscus californicus) developmentally exposed to endocrine disrupting chemicals

Developmental exposure to endocrine disrupting chemicals (EDCs), e.g., bisphenol A (BPA) or genistein (GEN), causes longstanding epigenome effects. MicroRNAs (miRs) regulate which mRNAs will be translated to proteins and thereby serve as the final checkpoint in epigenetic control. Scant amount is known, however, whether EDCs affect neural miRNA (miR) patterns. We aimed to test the hypothesis that developmental exposure of California mice (Peromyscus californicus) to GEN, BPA, or both chemicals influences hypothalamic miR/small RNA profiles and ascertain the extent such biomolecular alterations correlate with behavioral and metabolic changes. California mice were developmentally exposed to GEN (250 mg/kg feed weight, FW), GEN (250 mg/kg FW)+BPA (5 mg/kg FW), low dose (LD) BPA (5 mg/kg FW), or upper dose (UD) BPA (50 mg/kg FW). Adult offspring were tested in a battery of behavioral and metabolic tests; whereupon, mice were euthanized, brains were collected and frozen, small RNAs were isolated from hypothalamic punches, and subsequently sequenced. California mice exposed to one or both EDCs engaged in one or more repetitive behaviors. GEN, LD BPA, and UD BPA altered aspects of ultrasonic and audible vocalizations. Each EDC exposure led to sex-dependent differences in differentially expressed miR/small RNAs with miR7-2, miR146, and miR148a being increased in all female and male EDC exposed groups. Current findings reveal that developmental exposure to GEN and/or BPA affects hypothalamic miR/small RNA expression patterns, and such changes correlate with EDC-induced behavioral and metabolic alterations. miR146 is likely an important mediator and biomarker of EDC exposure in mammals, including humans.

Transcriptomic pathway and benchmark dose analysis of Bisphenol A, Bisphenol S, Bisphenol F, and 3,3',5,5'-Tetrabromobisphenol A in H9 human embryonic stem cells

Bisphenol A (BPA) is a chemical used in the manufacturing of plastics to which human exposure is ubiquitous. Numerous studies have linked BPA exposure to many adverse health outcomes prompting the replacement of BPA with various analogues including bisphenol-F (BPF) and bisphenol S (BPS). Other bisphenols are used in various consumer applications, such as 3,3',5,5'-Tetrabromobisphenol A (TBBPA), which is used as a flame retardant. Few studies to date have examined the effects of BPA and its analogues in stem cells to explore potential developmental impacts. Here we used transcriptomics to investigate similarities and differences of BPA and three of its analogues in the estrogen receptor negative, human embryonic stem cell line H9 (WA09). H9 cells were exposed to increasing concentrations of the bisphenols and analyzed using RNA-sequencing. Our data indicate that BPA, BPF, and BPS have similar potencies in inducing transcriptional changes and perturb many of the same pathways. TBBPA, the least structurally similar bisphenol of the group, exhibited much lower potency. All bisphenols robustly impacted gene expression in these cells, albeit at concentrations well above those observed in estrogen-positive cells. Overall, we provide a foundational data set against which to explore the transcriptional similarities of other bisphenols in embryonic stem cells, which may be used to assess the suitability of chemical grouping for read-across and for preliminary potency evaluation.

A systematic review of microRNA expression studies with exposure to bisphenol A

Bisphenol A (BPA), as a common industrial component, is generally consumed in the synthesis of polymeric materials. To gain a deeper understanding of the detrimental effects of BPA, BPA-induced microRNA (miRNA) alterations were investigated. A systematic search was performed in the PubMed, SCOPUS and Web of Science databases to evoke relevant published data up to August 10, 2019. We identified altered miRNAs that have been repeated in at least three studies. Moreover, miRNA homology analysis between human and nonhuman species was performed to determine the toxicity signatures of BPA in human exposure. In addition, to reflect the effects of environmental exposure levels of BPA, the study designs were categorized into two groups, including low and high doses according to the previous definitions. In total, 28 studies encountered our criteria and 17 miRNAs were identified that were differentially expressed in at least three independent studies. Upregulating miR-146a and downregulating miR-192, miR-134, miR-27b and miR-324 were found in three studies. MiR-122 and miR-29a were upregulated in four studies after BPA exposure, and miR-21 was upregulated in six studies. The results indicate that BPA at low-level exposures can also alter miRNA expression in response to toxicity. Finally, the miRNA-related pathways showed that BPA seriously can affect human health through various cell signaling pathways, which were predictable and consistent with existing studies. Overall, our findings suggest that further studies should be conducted to examine the role of miRNA level changes in human BPA exposure.

Hedgehog signal disruption, gonadal dysgenesis and reproductive disorders: Is there a link to endocrine disrupting chemicals?

Developmental exposure to chemicals that can disrupt sex hormone signaling may cause a broad spectrum of reproductive disorders. This is because reproductive development is tightly regulated by steroid sex hormones. Consequently, non-animal screening methods currently used to test chemicals for potential endocrine disrupting activities typically include steroidogenesis and nuclear receptor assays. In many cases there is a correlation between in vitro and in vivo data examining endocrine disruption, for example between blocked androgen receptor activity and feminized male genitals. However, there are many examples where there is poor, or no, correlation between in vitro data and in vivo effect outcomes in rodent studies, for various reasons. One possible, and less studied, reason for discordance between in vitro and in vivo data is that the mechanisms causing the in vivo effects are not covered by those typically tested for in vitro. This knowledge gap must be addressed if we are to elaborate robust testing strategies that do not rely on animal experimentation. In this review, we highlight the Hedgehog (HH) signaling pathway as a target for environmental chemicals and its potential implications for reproductive disorders originating from early life exposure. A central proposition is that, by disrupting HH signal transduction during critical stages of mammalian development, the endocrine cells of the testes or ovaries fail to develop normally, which ultimately will lead to disrupted sex hormone synthesis and sexual development in both sexes. If this is the case, then such mechanism must also be included in future test strategies aimed at eliminating chemicals that may cause reproductive disorders in humans.

Endocrine disruption of gene expression and microRNA profiles in hippocampus and hypothalamus of California mice: Association of gene expression changes with behavioural outcomes

The hypothalamus and hippocampus are sensitive to early exposure to endocrine disrupting chemicals (EDCs). Two EDCs that have raised particular concerns are bisphenol A (BPA), a widely prevalent chemical in many common household items, and genistein (GEN), a phyto-oestrogen present in soy and other plants. We hypothesised that early exposure to BPA or GEN may lead to permanent effects on gene expression profiles for both coding RNAs (mRNAs) and microRNAs (miRs), which can affect the translation of mRNAs. Such EDC-induced biomolecular changes may affect behavioural and metabolic patterns. California mice (Peromyscus californicus) male and female offspring were developmentally exposed via the maternal diet to BPA (5 mg kg^-1 feed weight low dose [LD] and 50 mg kg^-1 feed weight upper dose [UD]), GEN (250 mg kg^-1 feed weight) or a phyto-oestrogen-free diet (AIN) control. Behavioural and metabolic tests were performed at 180 days of age. A quantitative polymerase chain reacttion analysis was performed for candidate mRNAs and miRs in the hypothalamus and hippocampus. LD BPA and GEN exposed California mice offspring showed socio-communication impairments. Hypothalamic Avp, Esr1, Kiss1 and Lepr were increased in LD BPA offspring. miR-153 was elevated but miR-181a was reduced in LD BPA offspring. miR-9 and miR-153 were increased in the hippocampi of LD BPA offspring, whereas GEN decreased hippocampal miR-7a and miR-153 expression. Correlation analyses revealed neural expression of miR-153 and miR-181a was associated with socio-communication deficits in LD BPA individuals. The findings reveal a cause for concern such that developmental exposure of BPA or GEN in California mice (and potentially by translation in humans) can lead to long standing neurobehavioural consequences.

Involvement of the Endocrine-Disrupting Chemical Bisphenol A (BPA) in Human Placentation

Background: Endocrine-disrupting chemicals (EDCs) are environmental chemicals/toxicants that humans are exposed to, interfering with the action of multiple hormones. Bisphenol A (BPA) is classified as an EDC with xenoestrogenic activity with potentially adverse effects in reproduction. Currently, a significant knowledge gap remains regarding the complete spectrum of BPA-induced effects on the human placenta. As such, the present study examined the effects of physiologically relevant doses of BPA in vitro. Methods: qRT-PCR, Western blotting, immunofluorescence, ELISA, microarray analyses, and bioinformatics have been employed to study the effects of BPA using nonsyncytialised (non-ST) and syncytialised (ST) BeWo cells. Results: Treatment with 3 nM BPA led to an increase in cell number and altered the phosphorylation status of p38, an effect mediated primarily via the membrane-bound estrogen receptor (GPR30). Nonbiased microarray analysis identified 1195 and 477 genes that were differentially regulated in non-ST BeWo cells, whereas in ST BeWo cells, 309 and 158 genes had altered expression when treated with 3 and 10 nM, respectively. Enriched pathway analyses in non-ST BeWo identified a leptin and insulin overlap (3 nM), methylation pathways (10 nM), and differentiation of white and brown adipocytes (common). In the ST model, most significantly enriched were the nuclear factor erythroid 2-related factor 2 (NRF2) pathway (3 nM) and mir-124 predicted interactions with cell cycle and differentiation (10 nM). Conclusion: Collectively, our data offer a new insight regarding BPA effects at the placental level, and provide a potential link with metabolic changes that can have an impact on the developing fetus.

The Promises and Challenges of Toxico-Epigenomics: Environmental Chemicals and Their Impacts on the Epigenome

BACKGROUND

It has been estimated that a substantial portion of chronic and noncommunicable diseases can be caused or exacerbated by exposure to environmental chemicals. Multiple lines of evidence indicate that early life exposure to environmental chemicals at relatively low concentrations could have lasting effects on individual and population health. Although the potential adverse effects of environmental chemicals are known to the scientific community, regulatory agencies, and the public, little is known about the mechanistic basis by which these chemicals can induce long-term or transgenerational effects. To address this question, epigenetic mechanisms have emerged as the potential link between genetic and environmental factors of health and disease.

OBJECTIVES

We present an overview of epigenetic regulation and a summary of reported evidence of environmental toxicants as epigenetic disruptors. We also discuss the advantages and challenges of using epigenetic biomarkers as an indicator of toxicant exposure, using measures that can be taken to improve risk assessment, and our perspectives on the future role of epigenetics in toxicology.

DISCUSSION

Until recently, efforts to apply epigenomic data in toxicology and risk assessment were restricted by an incomplete understanding of epigenomic variability across tissue types and populations. This is poised to change with the development of new tools and concerted efforts by researchers across disciplines that have led to a better understanding of epigenetic mechanisms and comprehensive maps of epigenomic variation. With the foundations now in place, we foresee that unprecedented advancements will take place in the field in the coming years. https://doi.org/10.1289/EHP6104.

The effects of different bisphenol derivatives on oxidative stress, DNA damage and DNA repair in RWPE-1 cells: A comparative study

Bisphenol A (BPA) is a well-known endocrine disruptor and it is widely used mainly in the plastics industry. Due to recent reports on its possible impact on health (particularly on the male reproductive system), bisphenol F (BPF) and bisphenol S (BPS) are now being used as alternatives. In this study, RWPE-1 cells were used as a model to compare cytotoxicity, oxidative stress-causing potential and genotoxicity of these chemicals. In addition, the effects of the bisphenol derivatives were assessed on DNA repair proteins. RWPE-1 cells were incubated with BPA, BPF, and BPS at concentrations of 0-600 μM for 24 h. The inhibitory concentration 20 (IC₂₀ , concentration that causes 20% of cell viability loss) values for BPA, BPF, and BPS were 45, 65, and 108 μM, respectively. These results indicated that cytotoxicity potentials were ranked as BPA > BPF > BPS. We also found alterations in superoxide dismutase, glutathione peroxidase and glutathione reductase activities, and glutathione and total antioxidant capacity in all bisphenol-exposed groups. In the standard and modified Comet assay, BPS produced significantly higher levels of DNA damage vs the control. DNA repair proteins (OGG1, Ape-1, and MyH) involved in the base excision repair pathway, as well as p53 protein levels were down-regulated in all of the bisphenol-exposed groups. We found that the BPA alternatives were also cytotoxic and genotoxic, and changed the expressions of DNA repair enzymes. Therefore, further studies are needed to assess whether they can be used safely as alternatives to BPA or not.

MicroRNAs: potential targets and agents of endocrine disruption in female reproduction

MicroRNAs are short non-coding RNAs that have been widely recognized as key mediators in the epigenetic control of gene expression and which are present in virtually all cells and tissues studied. These regulatory molecules are generated in multiple steps in a process called microRNA biogenesis. Distinct microRNA expression patterns during the different stages of oocyte and embryo development suggest important regulatory roles for these small RNAs. Moreover, studies antagonizing specific microRNAs and enzymes in microRNA biogenesis pathways have demonstrated that interference with normal miRNA function leads to infertility and is associated with some reproductive abnormalities. Endocrine disrupting chemicals such as Bisphenol A (BPA) are synthetic hormone mimics that have been found to negatively impact reproductive health. In addition to their direct effects on gene expression, these chemicals are widely implicated in the disruption of epigenetic pathways, including the expression and activity of miRNAs, thereby altering gene expression. In this review, the roles of microRNAs during mammalian oocyte and embryo development are outlined and the different mechanisms by which endocrine disruptors such as BPA interfere with these epigenetic regulators to cause reproductive problems is explored.

Urinary concentrations of phenols and phthalate metabolites reflect extracellular vesicle microRNA expression in follicular fluid

BACKGROUND

Phenols and phthalates are potential endocrine disrupting chemicals (EDCs) that are associated with adverse health outcomes. These EDCs dysregulate a number of biomolecules and pathways, including microRNAs. MicroRNAs can be carried in transport systems called extracellular vesicles (EVs) that are present in most biofluids. EVs in the follicular fluid, which fills the ovarian follicle and influences oocyte developmental competency, carry microRNAs (EV-miRNAs) that have been associated with In Vitro Fertilization (IVF) outcomes. However, it remains unclear whether EDCs affect EV-miRNAs in follicular fluid.

OBJECTIVES

This study sought to determine whether urinary concentrations of phenols and phthalates biomarkers are associated with EV-miRNAs expression in follicular fluid collected from women undergoing IVF treatment.

METHODS

This cross-sectional study included 130 women recruited between January 2014 and August 2016 in a tertiary university-affiliated hospital. Participants provided urine samples during ovarian stimulation and on the day of oocyte retrieval. We assessed urinary concentrations of five phenols, eight phthalate metabolites, and one phthalate alternative metabolite. EV-miRNAs were isolated from follicular fluid and their expression profiles were measured using the TaqMan Open Array® Human microRNA panel. We fitted multivariable linear regression models and principal component analysis to examine associations between individual and molar sums of exposure biomarkers and EV-miRNAs.

RESULTS

Of 754 miRNAs tested, we detected 133 EV-miRNAs in the microRNA array which expressed in at least 50% of the follicular fluid samples. After adjusting for multiple testing, we identified eight EV-miRNAs associated with individual phenols and phthalate metabolites, as well as molar ΣDEHP that met a q < 0.10 false-discovery rate (FDR) threshold. Hsa-miR-125b, hsa-miR-106b, hsa-miR-374a, and hsa-miR15b was associated with mono(2-ethylhexyl) phthalate concentrations, hsa-let-7c with concentrations mono-2-ethyl-5-hydroxyhexyl phthalate (MEHHP), mono-2-ethyl-5-oxohexyl phthalate (MEOHP), mono-2-ethyl-5-carboxypentyl phthalate (MECPP), and the sum of metabolites of di(2-ethylhexyl) phthalate, hsa-miR-24 with mono-n-butyl phthalate concentrations, hsa-miR-19a with cyclohexane-1,2-dicarboxylic acid monohydroxy isononyl ester (MHiNCH), and hsa-miR-375 with ethyl paraben concentrations. Using Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses, gene targets and pathways of these EV-miRNAs were predicted in silico and 17 KEGG FDR-significant pathways related to follicular development and oocyte competence were identified.

CONCLUSIONS

Our results show that urinary concentrations of select phenol and phthalate metabolites are correlated with altered EV-miRNAs expression in follicular fluid. These findings may provide insight regarding the molecular mechanisms underlying adverse effects of phenol and phthalate exposure on female fertility.

MicroRNAs and their role in environmental chemical carcinogenesis

MicroRNAs (miRNAs) are a class of small, noncoding RNA species that play crucial roles across many biological processes and in the pathogenesis of major diseases, including cancer. Recent studies suggest that the expression of miRNA is altered by certain environmental chemicals, including metals, organic pollutants, cigarette smoke, pesticides and carcinogenic drugs. In addition, extensive studies have indicated the existence and importance of miRNA in different cancers, suggesting that cancer-related miRNAs could serve as potential markers for chemically induced cancers. The altered expression of miRNA was considered to be a vital pathogenic role in xenobiotic-induced cancer development. However, the significance of miRNA in the etiology of cancer and the exact mechanisms by which environmental factors alter miRNA expression remain relatively unexplored. Hence, understanding the interaction of miRNAs with environmental chemicals will provide important information on mechanisms underlying the pathogenesis of chemically induced cancers, and effectively diagnose and treat human cancers resulting from chronic or acute carcinogen exposure. This study presents the current evidence that the miRNA deregulation induced by various chemical carcinogens, different cancers caused by environmental carcinogens and the potentially related genes in the onset or progression of cancer. For each carcinogen, the specifically expressed miRNA may be considered as the early biomarkers of the cancer process. In this review, we also summarize various target genes of the altered miRNA, oncogenes or anti-oncogenes, and the existing evidence regarding the gene regulation mechanisms of cancer caused by environmentally induced miRNA alteration. The future perspective of miRNA may become attractive targets for the diagnosis and treatment of carcinogen-induced cancer.

Bisphenol A-elicited miR-146a-5p impairs murine testicular steroidogenesis through negative regulation of Mta3 signaling

The epigenetic effects on expression of non-coding RNAs (e.g. microRNAs) of environmental toxin bisphenol A (BPA) have extended our understanding of the etiology of human reproductive disorders including hypospermatogenesis and androgen deficiency. BPA-induced miR-146a-5p is a potent regulator of endocrine and immune homeostasis, but its role in testis remain unexplored. We show here that in murine testis, miR-146a-5p was exclusively expressed in interstitial Leydig cells (LCs). This expression was significantly induced by BPA exposure. Consequently, the elevated miR-146a-5p exacerbated the deleterious effects of BPA on testicular steroidogenesis. Mechanistically, miR-146a-5p repressed the expression of Mta3, a pivotal chromatin remodeling transcription factor recently involved in controlling the steroidogenic activity, via directly targeting its 3'UTR. This repression thereafter rendered LCs more sensitive to BPA-elicited inhibitory effects. Conversely, ectopic expression of hMTA3 successfully rescued miR-146a-5p-elicited inhibitory effects on testicular steroidogenesis in BPA-challenged LCs. Taken together, the available data provide novel evidence that deregulation of testicular miR-146a-5p/Mta3 cascade mediates, at least in part, the steroidogenic dysfunction caused by BPA exposure.

Bisphenol A stimulates adrenal cortical cell proliferation via ERβ-mediated activation of the sonic hedgehog signalling pathway

We previously demonstrated that prenatal exposure to bisphenol A (BPA) resulted in increased adrenal gland weight independent of changes in plasma ACTH levels in adult mouse offspring. This finding suggested that BPA exposure likely had a direct effect on adrenal development. Given that (1) sonic hedgehog (Shh) signaling is essential for adrenal development; (2) deletion of the Shh gene in mice results in adrenal hypoplasia; (3) BPA is known to signal through estrogen receptor β (ERβ); and (4) ERβ is highly expressed in adrenal glands; we hypothesized that BPA stimulates adrenal cell proliferation via ERβ-mediated activation of the Shh pathway. To test this hypothesis, the human adrenal cell line, H295A cells, was used as an in vitro model system. Our main findings were: (1) BPA increased cell number and protein levels of proliferating cell nuclear antigen (PCNA; a universal marker of cell proliferation), cyclin D1 and D2 (key proliferation factors), as well as Shh and its key transcriptional regulator Gli1; (2) cyclopamine, a Shh pathway inhibitor, blocked these stimulatory effects of BPA on cell proliferation; (3) BPA increased the nuclear translocation of ERβ; and (4) the ERβ-specific agonist DPN mimicked while the ERβ-specific antagonist PHTPP abrogated the stimulatory effects of BPA on cell proliferation and Shh signaling. Taken together, these findings demonstrate that BPA stimulates adrenal cell proliferation likely through ERβ-mediated activation of the Shh signaling pathway. Thus, the present study provides novel insights into the molecular mechanisms underlying our previously reported BPA-induced aberrant adrenal phenotype.

Long noncoding RNA HOTAIR mediates the estrogen-induced metastasis of endometrial cancer cells via the miR-646/NPM1 axis

LncRNA homeobox (HOX) transcript antisense intergenic RNA (HOTAIR) has been confirmed to be involved in the tumorigenic progression of endometrial carcinoma (EC). However, the molecular mechanisms of HOTAIR in EC are not fully elucidated. The expression of HOTAIR and miR-646 in human EC tissues was determined by qRT-PCR. The effect of miR-646 on EC cells was assessed by the cell viability, migration, and invasion using CCK-8 assays and transwell assays. RNA-binding protein immunoprecipitation assays and RNA pull-down assays were performed to explore the interaction between HOTAIR and miR-646. The regulation of miR-646 on nucleophosmin 1 (NPM1) was tested using luciferase reporter assays. MiR-646 expression was significantly decreased both in human EC tissues ( n = 23) and cell lines (Ishikawa and HEC-1-A) compared with the control. Moreover, miR-646 expression was negatively related to HOTAIR in human EC tissues ( n = 23). Our results also showed that miR-646 overexpression considerably attenuated the E2-promoted viability, migration, and invasion of Ishikawa and HEC-1-A cells in vitro. In addition, HOTAIR was confirmed to regulate the viability, migration, and invasion of EC cells through negative regulating miR-646. More importantly, we also demonstrated that NPM1 was the target of miR-646, and HOTAIR promoted NPM1 expression through interacting with miR-646 in EC cells. Taken together, our findings presented that HOTAIR could regulate NPM1 via interacting with miR-646, thereby governing the viability, migration, and invasion of EC cells.

miR-149 in Human Cancer: A Systemic Review

MicroRNAs (miRNAs) are small noncoding RNAs that regulate post-transcriptional gene expression via binding to the 3'-untranslated region (3'-UTR) of targeted mRNAs. They are reported to play important roles in tumorigenesis and progression of various cancers. Among them, miR-149 was confirmed to be aberrantly regulated in various tumors. In this review, we provide a complex overview of miR-149, particularly summarize the critical roles of it in cancers and expect to lay the foundation for future works on this important microRNA.

Roles of Arf6 in cancer cell invasion, metastasis and proliferation

ADP-ribosylation factor 6 (Arf6), a member of small GTPases ADP-ribosylation factor (Arf) family, expresses widely in mammalian cells and mainly regulates the functions of membrane traffic and actin remodeling. Current studies indicated that the activation and high expression of Arf6 protein may be significantly correlated with the invasion and metastasis of several tumors, such as breast cancer, pancreatic cancer, lung cancer, etc. Meanwhile, the ability of tumor invasion and metastasis can be suppressed when Arf6 activity is blocked by the inhibitors or small-interfering RNAs of Arf6. To explore the precisely potential mechanisms between Arf6 and the process of tumor invasion, metastasis and proliferation, we concludes the functions and potential signaling pathways of Arf6 in tumor cells and provides an overview about clinical prospects of Arf6 in the screening, diagnosis, treatment and evaluation of prognosis of neoplasms.