Benzo(a)pyrene inhibits endometrial cell apoptosis in early pregnant mice via the WNT5A pathway

Enhancing endometrial receptivity: the roles of human chorionic gonadotropin in autophagy and apoptosis regulation in endometrial stromal cells

Inadequate endometrial receptivity often results in embryo implantation failure and miscarriage. Human chorionic gonadotropin (hCG) is a key signaling molecule secreted during early embryonic development, which regulates embryonic maternal interface signaling and promotes embryo implantation. This study aimed to examine the impact of hCG on endometrial receptivity and its underlying mechanisms. An exploratory study was designed, and endometrial samples were obtained from women diagnosed with simple tubal infertility or male factor infertile (n = 12) and recurrent implantation failure (RIF, n = 10). Using reverse transcription-quantitative PCR and western blotting, luteinizing hormone (LH)/hCG receptor (LHCGR) levels and autophagy were detected in the endometrial tissues. Subsequently, primary endometrial stromal cells (ESCs) were isolated from these control groups and treated with hCG to examine the presence of LHCGR and markers of endometrial receptivity (HOXA10, ITGB3, FOXO1, LIF, and L-selectin ligand) and autophagy-related factors (Beclin1, LC3, and P62). The findings revealed that the expressions of receptivity factors, LHCGR, and LC3 were reduced in the endometrial tissues of women with RIF compared with the control group, whereas the expression of P62 was elevated. The administration of hCG to ESCs specifically activated LHCGR, stimulating an increase in the endometrial production of HOXA10, ITGB3, FOXO1, LIF and L-selectin ligands. Furthermore, when ESCs were exposed to 0.1 IU/mL hCG for 72 h, the autophagy factors Beclin1 and LC3 increased within the cells and P62 decreased. Moreover, the apoptotic factor Bax increased and Bcl-2 declined. However, when small interfering RNA was used to knock down LHCGR, hCG was less capable of controlling endometrial receptivity and autophagy molecules in ESCs. In addition, hCG stimulation enhanced the phosphorylation of ERK1/2 and mTOR proteins. These results suggest that women with RIF exhibit lower levels of LHCGR and compromised autophagy function in their endometrial tissues. Thus, hCG/LHCGR could potentially improve endometrial receptivity by modulating autophagy and apoptosis.

Chronic exposure to low levels of phenanthrene induces histological damage and carcinogenic risk in the uterus of female mice

Phenanthrene (Phe), a polycyclic aromatic hydrocarbon with low molecular weight, is detected in the environment at high frequency. To study the toxic effects of Phe on the uterine structure and function, female Kunming mice were exposed to Phe (0.05, 0.5, 5 ng/mL) for 270 days by drinking water. Pathological alterations and their action pathways were analyzed using immunohistochemical and biomolecular technology. Phe significantly increased the percentage of blood vessel area, the number of endometrial neutrophils (indicating the occurrence of inflammation), collagen deposition (indicating fibrosis), and the percentage of Ki-67-positive cells (indicating carcinogenesis) in the uterus. Transcriptome sequencing identified differentially expressed genes that were mainly enriched in some signaling pathways, including inflammation and carcinogenesis, suggesting a carcinogenic risk in the Phe-exposed uterus. Elevated serum estrogen levels and decreased progesterone levels exhibited a disturbance of steroid hormone balance, which might be related to uterine damage. Upregulated protein levels of uterine androgen receptor and estrogen receptor α were linked to the pathological effects. Most of the effects exhibited a nonmonotonic dose response, which might be attributed to the corresponding change in the serum levels of Phe. The results suggest that exposure to low levels of Phe could exert adverse effects on the uterus.

Interactions between Benzo(a)pyrene exposure and genetic polymorphisms of AhR signaling pathway on missed abortion

Benzo(a)pyrene (BaP) is an environmental pollutant widely exposed to human beings. While the relationship between BaP and missed abortion is few understood. To explore the association between missed abortion and BaP, genetic polymorphisms of AhR pathway, we recruited 112 cases women with missed abortion and 137 controls women with normal pregnancy from Shanxi, China. The BPDE-DNA adducts level in the case group was higher than that in the control group (P < 0.001). The subjects were categorized according to the tertiles of BPDE-DNA adduct concentrations: T1 ( Collapse

Key Words

• AhR signaling pathway
• BaP
• genetic polymorphisms
• missed abortion

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MESH Headings

• Pregnancy
• Humans
• Female
• DNA Adducts
• Benzo(a)pyrene/toxicity
• 7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide/metabolism
• Abortion, Missed
• Signal Transduction
• Polymorphism, Genetic

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Affiliation(s)

Sha Liu Department of Epidemiology, School of Public Health, Shanxi Medical University, Taiyuan, Shanxi, China
Mei Han Department of Epidemiology, School of Public Health, Shanxi Medical University, Taiyuan, Shanxi, China
Jiayu Zhang Department of Epidemiology, School of Public Health, Shanxi Medical University, Taiyuan, Shanxi, China
Jingru Ji Department of Obstetrics, The First Affiliated Hospital, Shanxi Medical University, Taiyuan, Shanxi, China
Yanfei Wu Department of Obstetrics, The First Affiliated Hospital, Shanxi Medical University, Taiyuan, Shanxi, China Department of Chinese Medicine, The First Affiliated Hospital, Shanxi Medical University, Taiyuan, Shanxi, China
Junni Wei Department of Epidemiology, School of Public Health, Shanxi Medical University, Taiyuan, Shanxi, China

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Exposure to Benzo(a)pyrene promotes proliferation and inhibits differentiation of stromal cells in mice during decidualization

The environmental pollutant Benzo(a)pyrene (BaP) has an adverse effect on the reproductive performance of mammals. We previously showed that BaP treatment during early pregnancy damages endometrial morphology and impairs embryo implantation. Endometrial decidualization at the implantation site (IS) after embryo implantation is crucial for pregnancy maintenance and placental development. The balance between proliferation and differentiation in endometrial stromal cells (ESCs) is a crucial event of decidualization, which is regulated by the cell cycle. Here, we report that abnormal decidualization caused by BaP is associated with cell cycle disturbance of stromal cells. The mice in the treatment group were gavaged with 0.2 mg/kg/day BaP from day 1-8 of pregnancy, while those in control were gavaged with corn oil in parallel. BaP damaged the decidualization of ESCs and reduced the number of polyploid cells. Meanwhile, BaP up-regulated the expression of Ki67 and PCNA, affecting the differentiation of stromal cells. The cell cycle progression analysis during decidualization in vivo and in vitro showed that BaP induced polyploid cells deficiency with enhanced expressions of CyclinA(E)/CDK2, CyclinD/CDK4 and CyclinB/CDK1, which promote the transformation of cells from G₁ to S phase and simultaneously activate the G₂/M phase. The above results indicated that BaP exposure accelerates cell cycle progression, promotes ESC proliferation, inhibits differentiation, and impedes proper decidualization and polyploidy development. Thus, the imbalance of ESC proliferation and differentiation would be an important mechanism for BaP-induced defective decidualization.

Benzo(a)pyrene induces airway epithelial injury through Wnt5a-mediated non-canonical Wnt-YAP/TAZ signaling

Wnt5a is a key mediator of non-canonical Wnt signaling, and an early indicator of epithelial injury and lung dysfunction. Polycyclic aromatic hydrocarbons (PAHs) could induce acute pulmonary pathogenesis, of which the underlying mechanism remains unclear. To elucidate the potential role of Wnt5a-mediated non-canonical Wnt-YAP/TAZ signaling in the lung injury induced by short-term exposure of benzo(a)pyrene (BaP, a representative PAHs), intratracheally instilled mouse model was used and further interfered with its Wnt5a level by small molecule antagonists and agonists. Our data revealed that BaP exposure induced the lung inflammatory response and reduced the expression of Clara cell secretory protein (CC16) in a dose-dependent manner. More importantly, the activation of Wnt5a and downstream YAP/TAZ were accompanied with the enhanced release of epithelial-derived thymic stromal lymphopoietin and interleukin-33, which acted as pro-inflammatory cytokines. Functionally, inhibition of Wnt5a attenuated the BaP-induced inflammation and recuperated CC16 expression, as well as suppressed the epithelial cytokines release. Whereas promoting Wnt5a expression affected the toxic effects of BaP oppositely. Our findings together suggest that Wnt5a is a potential endogenous regulator in lung inflammation and airway epithelial injury, and Wnt5a-YAP/TAZ signaling contributes to lung dysfunction in acute exposure to BaP.

Peri-implantation expression and regulation of ITGB8 in goat uterus

Ruminants have a superficial implantation pattern. The extended conceptus attaches to the receptive endometrium to form the cotyledonary placenta. During the attachment, a large number of events occur at the maternal-fetal interface. However, the related molecular mechanisms have not been fully understood. Integrin beta8 (ITGB8) is a subunit of integrin beta involved in embryo implantation. In this study, we determined peri-implantation expression and regulation of ITGB8 in goat uterus. The mRNA and protein levels of ITGB8 were both high in goat endometrial luminal epithelium (LE) and superficial glandular epithelium (sGE) during the adhesion period (Days 16-19 of pregnancy). Such expression profile was opposite to that of microRNA-187 (miR-187). Then, we validated that miR-187 targeted the 3' untranslated region (UTR) of ITGB8 in primary goat endometrial epithelial cells (EECs). In EECs, inhibition of miR-187 resulted in not only up-regulated ITGB8 level but also reduced cell proliferation and focal adhesion kinase (FAK) activity. Moreover, ITGB8 and miR-187 were regulated by interferon tau (IFNT). Altogether, in goat, the miR-187/ITGB8 axis may be involved in conceptus attachment and is downstream of IFNT. Our results will help us better understand the mechanisms of ruminant implantation and may provide a useful tool to improve the reproduction ratio for ruminants.

Environmental dose of 16 priority-controlled PAHs mixture induce damages of vascular endothelial cells involved in oxidative stress and inflammation

Epidemiological studies have shown that cardiovascular diseases caused by PM_2.5 pollution account for the second death rate in China. Polycyclic aromatic hydrocarbons (PAHs) are one important group of persistent organic pollutants absorbed on PM_2.5. Though individual PAH is related to vascular disease, the relationship between environmental PAHs exposure and vascular damages is still unclear. To explore the effect of PAHs on blood vessel, human umbilical vein endothelial cells (HUVECs) are treated with 16 priority-controlled PAHs at various concentrations to study their cytotoxicity and morphological alteration. Results showed that, after 48 h treatment, PAHs mixture generally attenuated the ability of wound healing, transwell migration and tube formation of HUVECs (p < 0.01) except for 1 × PAHs in transwell migration. Moreover, PAHs increased the levels of ROS and 8-hydroxy-2'-deoxyguanosine (p < 0.05), indicating that it exceeded the scavenging ability of superoxide dismutase activity. However, PAHs mixture did not increase apoptosis rate, which may be attribute to the difference of PAH concentration and composition between this study and previous reports. Downstream signaling cascades significantly and generally upregulated the relative expression of proteins in Nrf2/HO-1 and NF-ƙB/TNF-α pathway with the activation of oxidative stress, including HO-, TNF-α and Nrf2. In summary, this study suggests that environmental mixture of 16 priority-controlled PAHs can induce the damages of vascular endothelial cells involved in cellular oxidative stress and inflammation.

Cellular signaling crosstalk between Wnt signaling and gap junctions inbenzo[a]pyrene toxicity

Gap junctional intercellular communication (GJIC) is considered a key biological mechanism to maintain homeostasis in cell differentiation and growth. In addition, as another major signaling pathway associated with cell proliferation and differentiation, Wnt/β-catenin signaling appears to trigger several cellular responses against injury. The purpose of the present study was to investigate the effects of a known toxic agent, benzo[a]pyrene (BaP), on the regulation and interaction between GJIC and Wnt/β-catenin signaling. BaP treatment resulted in GJIC inhibition and decreases the major GJIC protein connexin 43 (Cx43) in WB-F344 rat liver epithelial cells. We also found BaP-mediated downregulation of Wnt/β-catenin signaling related to the PI3K-Akt pathway. To identify the relationship between GJIC and Wnt/β-catenin signaling, we treated WB-F344 cells with the Wnt agonist CHIR99021 and found that it inhibited GJIC while causing a significant reduction in Cx43 expression at both the mRNA and protein levels, through the repression of promoter activity. This Wnt agonist-mediated GJIC inhibition was confirmed using a small interfering RNA directed against the Wnt antagonist Dact2, indicating that Wnt/β-catenin signaling negatively regulates GJIC. Despite the inverse correlation between Wnt/β-catenin signaling and Cx43 promoter activation as indicated by downregulation of β-catenin nuclear translocation and upregulation of Cx43 promoter activation involving HNF3β, BaP treatment decreased the Cx43 protein expression, which was associated with protein degradation, possibly through protein kinase C activation. In conclusion, our results revealed the mechanism of BaP-induced inhibition of GJIC and Wnt/β-catenin signaling. More importantly, linking Wnt/β-catenin signaling to Cx protein expression will have profound implications in understanding the relationships among different major signaling pathways associated with cell proliferation and differentiation in toxicity.

Effects of Endocrine-Disrupting Chemicals on Endometrial Receptivity and Embryo Implantation: A Systematic Review of 34 Mouse Model Studies

Several available studies have already analyzed the systemic effects of endocrine-disrupting chemicals (EDCs) on fertile woman and neonatal outcomes, but little is still known in humans about the precise mechanisms of interference of these compounds with the endometrial receptivity. There is consistent evidence that continuous and prolonged exposure to EDCs is a risk factor for reduced fertility and fecundity in women. Preliminary studies on mammalian models provide robust evidence about this issue and could help gynecologists worldwide to prevent long term injury caused by EDCs on human fertility. In this systematic review, we aimed to systematically summarize all available data about EDC effects on blastocyst endometrial implantation. We performed a systematic review using PubMed^®/MEDLINE^® to summarize all in vivo studies, carried out on mice models, analyzing the molecular consequences of the prolonged exposure of EDC on the implantation process. 34 studies carried out on mouse models were included. Primary effects of EDC were a reduction of the number of implantation sites and pregnancy rates, particularly after BPA and phthalate exposure. Furthermore, the endometrial expression of estrogen (ER) and progesterone receptors (PR), as well as their activation pathways, is compromised after EDC exposure. Finally, the expression of the primary endometrial markers of receptivity (such as MUC1, HOXA10, Inn and E-cadherin) after EDC contact was analyzed. In conclusion EDC deeply affect blastocyst implantation in mouse model. Several players of the implantation mechanism are strongly influenced by the exposure to different categories of EDC.

Environmental Pollutant Benzo[a]pyrene Upregulated Long Non-coding RNA HZ07 Inhibits Trophoblast Cell Migration by Inactivating PI3K/AKT/MMP2 Signaling Pathway in Recurrent Pregnancy Loss

Benzo(a)pyrene (BaP) is a ubiquitous environmental endocrine-disrupting chemical that is known to have toxic effects on reproduction. However, the underlying mechanisms describing how BaP and its metabolite benzo[a]pyrene-7, 8-diol-9, 10-epoxide (BPDE) induce recurrent pregnancy loss (RPL) are still largely unclear. In this study, we identified a novel long non-coding RNA (lnc-HZ07, NCBI MT936329) that was upregulated in trophoblast cells after exposure to BPDE, and lnc-HZ07 expression was significantly higher in RPL villous tissues than that in control villous tissues. Knockdown of lnc-HZ07 promoted trophoblast cell migration, whereas overexpression of lnc-HZ07 inhibited trophoblast cell migration. Further study showed that lnc-HZ07 inhibited trophoblast migration by downregulating matrix metalloproteinase 2 (MMP2) expression via dephosphorylation of AKT. These results demonstrated a novel regulatory pathway in which BaP downregulated AKT phosphorylation and inhibited MMP2 expression by upregulating lnc-HZ07, suggesting that lnc-HZ07 could be considered as a potential pathological marker of BaP-induced RPL and therapeutic target for this disease.

MiR-543 Inhibits the Migration and Epithelial-To-Mesenchymal Transition of TGF-β-Treated Endometrial Stromal Cells via the MAPK and Wnt/β-Catenin Signaling Pathways

Intrauterine adhesion (IUA) is one of the most prevalent reproductive system diseases in females. MicroRNAs (miRNAs) are reported to be master regulators in a variety of diseases, including IUA, but the role of microRNA-543 (miR-543) in IUA remains to be elucidated. In this study, we observed that miR-543 was downregulated in transforming growth factor-beta (TGF-β)-treated endometrial stromal cells (ESCs). Functionally, we observed that miR-543 suppressed the migration, epithelial-to-mesenchymal transition (EMT), and inhibited expression of extracellular matrix (ECM) proteins in TGF-β-treated ESCs. Mechanistically, MAPK1 is targeted by miR-543 after prediction and screening. A luciferase reporter assay demonstrated that miR-543 complementarily binds with the 3' untranslated region of mitogen-activated protein kinase 1 (MAPK1), and western blot analysis indicated that miR-543 negatively regulates MAPK1 protein levels. In addition, results from rescue assays showed that miR-543 inhibits the migration and EMT of TGF-β-treated ESCs by targeting MAPK1. In addition, we observed that miR-543 inactivates the Wnt/β-catenin signaling pathway through inhibiting the phosphorylation of MAPK1 and β-catenin. Finally, we confirmed that miR-543 represses migration, EMT and inhibits levels of ECM proteins in TGF-β-treated ESCs by targeting the Wnt/β-catenin signaling pathway. Our results demonstrated that miR-543 suppresses migration and EMT of TGF-β-treated ESCs by targeting the MAPK and Wnt/β-catenin pathways.

Upregulated lnc-HZ02 and miR-hz02 inhibited migration and invasion by downregulating the FAK/SRC/PI3K/AKT pathway in BPDE-treated trophoblast cells

BPDE (benzo(a)pyren-7,8-dihydrodiol-9,10-epoxide), a metabolite of environmental carcinogenic BaP, weakens the migration and invasion of human villous trophoblast cells and may further induce miscarriage. However, the underlying mechanisms remain largely unknown. In this study, we identified that in trophoblast Swan 71 and HTR-8/SVneo cells, miR-hz02 upregulates the level of lnc-HZ02, which inhibits the expression of an RNA-binding protein HuR. HuR could interact with FAK mRNA and promote its mRNA stability, thus upregulating the FAK level and the FAK/SRC/PI3K/AKT pathway, and finally maintaining the normal migration and invasion of trophoblast cells. If trophoblast cells are exposed to BPDE, both miR-hz02 and lnc-HZ02 are upregulated, which reduce the level of HuR, weaken the interactions of HuR with FAK mRNA, downregulate FAK level and the FAK/SRC/PI3K/AKT pathway, and finally inhibit cell migration and invasion. This study provides a novel scientific understanding of the dysfunctions of human trophoblast cells.

Risk of breast cancer associated with long-term exposure to benzo[a]pyrene (BaP) air pollution: Evidence from the French E3N cohort study

BACKGROUND

Benzo[a]pyrene (BaP) is an endocrine-disrupting pollutant formed during incomplete combustion of organic materials. It has been recognized as a reproductive and developmental toxicant, however epidemiological evidence of the long-term effect of ambient air BaP on breast cancer (BC) is limited. Thus we evaluated associations between ambient air BaP exposure and risk of BC, overall and according to menopausal status and molecular subtypes (estrogen receptor negative/positive (ER-/ER+) and progesterone receptor negative/positive (PR-/PR+)), stage and grade of differentiation of BC in the French E3N cohort study.

METHODS

Within a nested case-control study of 5222 incident BC cases and 5222 matched controls, annual BaP exposure was estimated using a chemistry-transport model (CHIMERE) and was assigned to the geocoded residential addresses of participants for each year during the 1990-2011 follow-up period. Multivariable conditional logistic regression models were used to estimate odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

Overall, cumulative airborne BaP exposure was significantly associated with the overall risk of BC, for each 1 interquartile range (IQR) increase in the concentration levels of BaP (1.42 ng/m³), the OR = 1.15 (95% CI: 1.04-1.27). However, by menopausal status, the significant positive association remained only in women who underwent menopausal transition (i.e. premenopausal women at inclusion who became postmenopausal at diagnosis), OR per 1 IQR = 1.20 (95% CI: 1.03-1.40). By hormone receptor status, positive associations were observed for ER+, PR + and ER + PR + BC, with ORs = 1.17 (95% CI: 1.04-1.32), 1.16 (95% CI: 1.01-1.33), and 1.17 (95% CI: 1.01-1.36) per 1 IQR, respectively. There was also a borderline positive association between BaP and grade 3 BC (OR per 1 IQR = 1.15 (95% CI: 0.99-1.34).

CONCLUSIONS

We provide evidence of increased risk of BC associated with cumulative BaP exposure, which varied according to menopausal status, hormone receptor status, and grade of differentiation of BC. Our results add further epidemiological evidence to the previous experimental studies suggesting the adverse effects of BaP.

Ectopic pregnancy and epithelial to mesenchymal transition: is there a link?

Ectopic pregnancy (EP) is defined as the implantation of an embryo outside of the uterus and is a leading cause of first trimester maternal mortality and morbidity. This article discusses a possible role for epithelial to mesenchymal transition in the pathogenesis of EP, given the notable similarity of protein expression between the two processes.

Novel lnc-HZ03 and miR-hz03 promote BPDE-induced human trophoblastic cell apoptosis and induce miscarriage by upregulating p53/SAT1 pathway

Normal pregnancy is essential for human reproduction. However, environmental BaP (benzo(a)pyrene) and its metabolite BPDE (benzo(a)pyrene-7,8-dihydrodiol-9,10-epoxide) induce dysfunctions of human trophoblastic cells, which could further result in miscarriage. Yet, the molecular mechanisms remain poorly understood. In this work, a novel lnc-HZ03 and a novel miR-hz03 were identified. Both lnc-HZ03 and miR-hz03 were highly expressed in human recurrent miscarriage villous tissues and in BPDE-exposed trophoblastic cells. Lnc-HZ03 and miR-hz03 upregulated each other, forming a positive feedback loop. MiR-hz03 could also upregulate p53 level by enhancing its mRNA stability. Both lnc-HZ03 and p53 mRNA contained the target site for miR-hz03 and could directly interact with miR-hz03. It was this target site instead of its mutant on lnc-HZ03 that regulated p53 expression. Subsequently, the upregulated p53 facilitated SAT1 transcription and enhanced SAT1-catalyzed spermine metabolism, which further resulted in trophoblastic cell apoptosis and induced miscarriage. All together, the p53/SAT1 pathway upregulated by lnc-HZ03 and miR-hz03 could promote BPDE-induced human trophoblastic cell apoptosis and the occurrence of miscarriage, shedding novel light on the causes of miscarriage. Graphical abstract Lnc-HZ03 and miR-hz03 regulate the occurrence of recurrent miscarriage (RM). In human trophoblastic cells, lnc-HZ03 upregulates miR-hz03 level. MiR-hz03 increases the RNA stability of lnc-HZ03 and p53 mRNA. P53 promotes SAT1 transcription and reduces its cellular spermine content, resulting in cell apoptosis. Under normal conditions, lnc-HZ03/miR-hz03 and p53/SAT1 pathways are downregulated, maintaining normal pregnancy. After exposure to BPDE, lnc-HZ03/miR-hz03 and p53/SAT1 pathways are upregulated and finally induce miscarriage.

Increased apoptosis, reduced Wnt/β-catenin signaling, and altered tail development in zebrafish embryos exposed to a human-relevant chemical mixture

A wide variety of anthropogenic chemicals is detected in humans and wildlife and the health effects of various chemical exposures are not well understood. Early life stages are generally the most susceptible to chemical disruption and developmental exposure can cause disease in adulthood, but the mechanistic understanding of such effects is poor. Within the EU project EDC-MixRisk, a chemical mixture (Mixture G) was identified in the Swedish pregnancy cohort SELMA by the inverse association between levels in women at around gestational week ten with birth weight of their children. This mixture was composed of mono-ethyl phthalate, mono-butyl phthalate, mono-benzyl phthalate, mono-ethylhexyl phthalate, mono-isononyl phthalate, triclosan, perfluorohexane sulfonate, perfluorooctanoic acid, and perfluorooctane sulfonate. In a series of experimental studies, we characterized effects of Mixture G on early development in zebrafish models. Here, we studied apoptosis and Wnt/β-catenin signaling which are two evolutionarily conserved signaling pathways of crucial importance during development. We determined effects on apoptosis by measuring TUNEL staining, caspase-3 activity, and acridine orange staining in wildtype zebrafish embryos, while Wnt/β-catenin signaling was assayed using a transgenic line expressing an EGFP reporter at β-catenin-regulated promoters. We found that Mixture G increased apoptosis, suppressed Wnt/β-catenin signaling in the caudal fin, and altered the shape of the caudal fin at water concentrations only 20-100 times higher than the geometric mean serum concentration in the human cohort. These findings call for awareness that pollutant mixtures like mixture G may interfere with a variety of developmental processes, possibly resulting in adverse health effects.

Environmental Pollutant Benzo[a]pyrene Induces Recurrent Pregnancy Loss through Promoting Apoptosis and Suppressing Migration of Extravillous Trophoblast

Methods

The implantation sites, fetus resorption, and abnormal fetuses were studied in pregnant mice treated with different doses of BaP by oral gavage from day 1 to day 10 of gestation. Additionally, apoptosis and related signaling pathway, and the migration and invasion of trophoblasts, were assessed before and after exposure of BPDE in Swan 71 trophoblast cell. Besides, the migration and invasion, and its related signaling pathway, were assessed in villi obtained from women.

Results

We observed a concentration-dependent incidence of abnormal murine fetuses, beginning with 0.1 mg/kg BaP; with a BaP concentration of 2 mg/kg, no fetuses developed. Correspondingly, a BPDE concentration-dependent apoptosis of human trophoblasts. Beginning with 0.5 μM BPDE exposure, Bax/Caspase-3 were increased and Bcl-2 decreased. Furthermore, BPDE also inhibited, in a dose-dependent manner, the migration of villous explants from elective abortion women, consistent with the reduced migration of villous explants from women with recurrent pregnancy loss (RPL), and reduced the cell immigration in Swan 71 trophoblasts, in a dose-dependent manner measured by transwell assays.

Conclusions

Our study results provide mechanistic insight to the effect of BPDE on trophoblast dysfunction through enhanced cell apoptosis and inhibited migration, providing further experimental evidence to the causative links between BaP exposure and PRL.

Exposure to Benzo[a]pyrene impairs the corpus luteum vascular network in rats during early pregnancy

Benzo [a]pyrene (BaP) is a well-known endocrine disruptor. Exposure to BaP is known to impair embryo implantation. The corpus luteum (CL), the primary source of progesterone during early pregnancy, plays a pivotal role in embryo implantation and pregnancy maintenance. The inappropriate luteal function may result in implantation failure and spontaneous abortions. However, the effect of BaP on CL remains unknown. This study investigated the deleterious effects of BaP on the structure and function of CL during early pregnancy. Pregnant rats were dosed with BaP at 0.2 mg.kg-1. d from day 1 (D1) to day 9 (D9) of gestation. We found that BaP reduced the number of CLs, disturbed the secretion of steroid and impacted the luteal vascular networks. BaP significantly decreased the angiogenesis factor (VEGFR, Ang-1 and Tie2) and increased the anti-angiogenic factor THBS1. Inhibited THBS1 function by LSKL partially rescued the angiogenesis defect caused by BaP. In vitro, BaP metabolite BPDE also interfered the expression levels of angiogenesis-related factors in HUVECs and impaired the angiogenesis, whereas supplemented with rAng-1 can alleviate the anti-angiogenic effect of BPDE. Furthermore, Notch signaling molecules, including Notch1, Dll4, Jag1 and Hey2, which are essential for the establishment and maturation of vascular networks, were affected by BaP exposure. Collectively, BaP broke the molecular regulatory balance between luteal angiogenesis and vascular maturation, impaired the construction of luteal vascular networks, and further affected luteal formation and endocrine function during early pregnancy. Our findings might provide new insight into the relationship between BaP and luteal insufficiency in early pregnancy. These data also give a new line of evidence for curtailing BaP emissions and protecting the women of childbearing age from occupational exposure.

In vitro and in vivo approaches for identifying the role of aryl hydrocarbon receptor in the development of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is a chronic hepatic disease associated with the excessive accumulation of lipids in the liver. Premenopausal women are protected from the liver metabolic complications of obesity compared with body mass index (BMI)-matched men. This protection may be related to estrogen's ability to limit liver fat accumulation. Aryl hydrocarbon receptor (AhR), a novel regulator of NAFLD, may be an important target for regulating estrogen homeostasis. In present study, we used benzo[a]pyrene (BaP), a classic and potent ligand of AhR, to activate AhR pathway causes overexpression of the estrogen-metabolizing enzyme cytochrome P450 1A1 (CYP1A1) and affects the expression of important genes involved in hepatic lipid regulation. BaP induces CYP1A1 expression through AhR signaling and inhibits the protective effect of 17β-estradiol (E2) on hepatic steatosis, characterized by triglyceride accumulation, and markers of liver damage are significantly elevated. The expression of adipogenic genes involved in the hepatic lipid metabolism of sterol regulatory element-binding protein-1c (SREBP-1c) was increased compared with that in the control group. Furthermore, the mRNA and protein levels of peroxisome proliferator-activated receptor alpha (PPARα), which is involved in fatty acid oxidation, were significantly reduced. Taken together, our results revealed that the steatotic effect of AhR is likely due to overexpression of the E2 metabolic enzyme CYP1A1, which affects the estrogen signaling pathway, leading to the suppression of fatty acid oxidation, inhibition of the hepatic export of triglycerides, and an increase in peripheral fat mobilization. The results from this study may help establish AhR as a novel therapeutic and preventive target for fatty liver disease.