Gestational 1-nitropyrene exposure causes fetal growth restriction through disturbing placental vascularity and proliferation

Adverse neurodevelopment in children associated with prenatal exposure to fine particulate matter (PM2.5) - Possible roles of polycyclic aromatic hydrocarbons (PAHs) and mechanisms involved

Prenatal exposure to ambient fine particles (PM2.5) and polycyclic aromatic hydrocarbons (PAHs) has been associated with adverse birth outcomes including neurodevelopmental effects with cognitive and/or behavioral implications in early childhood. As a background we first briefly summarize human studies on PM2.5 and PAHs associated with adverse birth outcomes and modified neurodevelopment. Next, we add more specific information from animal studies and in vitro studies and elucidate possible biological mechanisms. More specifically we focus on the potential role of PAHs attached to PM2.5 and explore whether effects of these compounds may arise from disturbance of placental function or more directly by interfering with neurodevelopmental processes in the fetal brain. Possible molecular initiating events (MIEs) include interactions with cellular receptors such as the aryl hydrocarbon receptor (AhR), beta-adrenergic receptors (βAR) and transient receptor potential (TRP)-channels resulting in altered gene expression. MIE linked to the binding of PAHs to cytochrome P450 (CYP) enzymes and formation of reactive electrophilic metabolites are likely less important. The experimental animal and in vitro studies support the epidemiological findings and suggest steps involved in mechanistic pathways explaining the associations. An overall evaluation of the doses/concentrations used in experimental studies combined with the mechanistic understanding further supports the hypothesis that prenatal PAHs exposure may cause adverse outcomes (AOs) linked to human neurodevelopment. Several MIEs will likely occur simultaneously in various cells/tissues involving several key events (KEs) which relative importance will depend on dose, time, tissue, genetics, other environmental factors, and neurodevelopmental endpoint in study.

FUNDC1-mediated mitophagy triggered by mitochondrial ROS is partially involved in 1-nitropyrene-evoked placental progesterone synthesis inhibition and intrauterine growth retardation in mice

Intrauterine growth retardation (IUGR) is a major cause of perinatal morbidity and mortality. Previous studies showed that 1-nitropyrene (1-NP), an atmospheric pollutant, induces placental dysfunction and IUGR, but the exact mechanisms remain uncertain. In this research, we aimed to explore the role of mitophagy on 1-NP-evoked placental progesterone (P4) synthesis inhibition and IUGR in a mouse model. As expected, P4 levels were decreased in 1-NP-exposed mouse placentas and maternal sera. Progesterone synthases, CYP11A1 and 3βHSD1, were correspondingly declined in 1-NP-exposed mouse placentas and JEG-3 cells. Mitophagy, as determined by LC3B-II elevation and TOM20 reduction, was evoked in 1-NP-exposed JEG-3 cells. Mdivi-1, a specific mitophagy inhibitor, relieved 1-NP-evoked downregulation of progesterone synthases in JEG-3 cells. Additional experiments showed that ULK1/FUNDC1 signaling was activated in 1-NP-exposed JEG-3 cells. ULK1 inhibitor or FUNDC1-targeted siRNA blocked 1-NP-induced mitophagy and progesterone synthase downregulation in JEG-3 cells. Further analysis found that mitochondrial reactive oxygen species (ROS) were increased and GCN2 was activated in 1-NP-exposed JEG-3 cells. GCN2iB, a selective GCN2 inhibitor, and MitoQ, a mitochondria-targeted antioxidant, attenuated GCN2 activation, FUNDC1-mediated mitophagy, and downregulation of progesterone synthases in JEG-3 cells. In vivo, gestational MitoQ supplement alleviated 1-NP-evoked reduction of placental P4 synthesis and IUGR. These results suggest that FUNDC1-mediated mitophagy triggered by mitochondrial ROS may contribute partially to 1-NP-induced placental P4 synthesis inhibition and IUGR.

Gestational exposure to 1-NP induces ferroptosis in placental trophoblasts via CYP1B1/ERK signaling pathway leading to fetal growth restriction

Fetal growth restriction (FGR) is a prevalent complication in obstetrics, yet its exact aetiology remains unknown. Numerous studies suggest that the degradation of the living environment is a significant risk factor for FGR. 1-Nitropyrene (1-NP) is a widespread environmental pollutant as a representative substance of nitro-polycyclic aromatic hydrocarbons. In this study, we revealed that 1-NP induced FGR in fetal mice by constructing 1-NP exposed pregnant mice models. Intriguingly, we found that placental trophoblasts of 1-NP exposed mice exhibited significant ferroptosis, which was similarly detected in placental trophoblasts from human FGR patients. In this regard, we established a 1-NP exposed cell model in vitro using two human trophoblast cell lines, HTR8/SVneo and JEG-3. We found that 1-NP not only impaired the proliferation, migration, invasion and angiogenesis of trophoblasts, but also induced severe cellular ferroptosis. Meanwhile, the ferroptosis inhibitor ferrostatin-1 (Fer-1) effectively rescued 1-NP-induced trophoblast biological function impairment. Mechanistically, we revealed that 1-NP regulated ferroptosis by activating the ERK signaling pathway. Moreover, we innovatively revealed that CYP1B1 was essential for the activation of ERK signaling pathway induced by 1-NP. Overall, our study innovatively identified ferroptosis as a significant contributor to 1-NP induced trophoblastic functional impairment leading to FGR and clarified the specific mechanism by which 1-NP induced ferroptosis via the CYP1B1/ERK signaling pathway. Our study provided novel insights into the aetiology of FGR and revealed new mechanisms of reproductive toxicity of environmental pollutants.

Evaluating the Effect of Gestational Exposure to Perfluorohexane Sulfonate on Placental Development in Mice Combining Alternative Splicing and Gene Expression Analyses

BACKGROUND

Perfluorohexane sulfonate (PFHxS) is a frequently detected per- and polyfluoroalkyl substance in most populations, including in individuals who are pregnant, a period critical for early life development. Despite epidemiological evidence of exposure, developmental toxicity, particularly at realistic human exposures, remains understudied.

OBJECTIVES

We evaluated the effect of gestational exposure to human-relevant body burden of PFHxS on fetal and placental development and explored mechanisms of action combining alternative splicing (AS) and gene expression (GE) analyses.

METHODS

Pregnant ICR mice were exposed to 0, 0.03, and 0.3 μ g / kg / day  from gestational day 7 to day 17 via oral gavage. Upon euthanasia, PFHxS distribution was measured using liquid chromatography-tandem mass spectrometry. Maternal and fetal phenotypes were recorded, and histopathology was examined for placenta impairment. Multiomics was adopted by combining AS and GE analyses to unveil disruptions in mRNA quality and quantity. The key metabolite transporters were validated by quantitative real-time PCR (qRT-PCR) for quantification and three-dimensional (3D) structural simulation by AlphaFold2. Targeted metabolomics based on liquid chromatography-tandem mass spectrometry was used to detect amino acid and amides levels in the placenta.

RESULTS

Pups developmentally exposed to PFHxS exhibited signs of intrauterine growth restriction (IUGR), characterized by smaller fetal weight and body length (p < 0.01 ) compared to control mice. PFHxS concentration in maternal plasma was 5.01 ± 0.54  ng / mL . PFHxS trans-placenta distribution suggested dose-dependent transfer through placental barrier. Histopathology of placenta of exposed dams showed placental dysplasia, manifested with an attenuated labyrinthine layer area and deescalated blood sinus counts and placental vascular development index marker CD34. Combined GE and AS analyses pinpointed differences in genes associated with key biological processes of placental development, proliferation, metabolism, and transport in placenta of exposed dams compared to that of control dams. Further detection of placental key transporter gene expression, protein structure simulation, and amino acid and amide metabolites levels suggested that PFHxS exposure during pregnancy led to impairment of placental amino acid transportation.

DISCUSSION

The findings from this study suggest that exposure to human-relevant very-low-dose PFHxS during pregnancy in mice caused IUGR, likely via downregulating of placental amino acid transporters, thereby impairing placental amino acid transportation, resulting in impairment of placental development. Our findings confirm epidemiological findings and call for future attention on the health risk of this persistent yet ubiquitous chemical in the early developmental stage and provide a new approach for understanding gene expression from both quantitative and qualitative omics approaches in toxicological studies. https://doi.org/10.1289/EHP13217.

Gestational 1-nitropyrene exposure causes anxiety-like behavior partially by altering hippocampal epigenetic reprogramming of synaptic plasticity in male adult offspring

1-Nitropyrene (1-NP), a typical nitro-polycyclic aromatic hydrocarbon, is a developmental toxicant. This study was to evaluate gestational 1-NP-induced anxiety-like behavior in male adult offspring. Pregnant mice were orally administered to 1-NP daily throughout pregnancy. Anxiety-like behaviors, as determined by Elevated Plus-Maze (EPM) and Open-Field Test (OFT), were showed in male adult offspring whose mothers were exposed to 1-NP. Gestational 1-NP exposure reduced dendritic arborization, dendritic length and dendritic spine density in ventral hippocampus of male adult offspring. Additional experiments showed that gephyrin, an inhibitory synaptic marker, was reduced in fetal forebrain and hippocampus in male adult offspring. Nrg1 and Erbb4, two gephyrin-related genes, were reduced in 1-NP-exposed fetuses. Accordingly, 5hmC contents in two CpG sites (32008909 and 32009239) of Nrg1 gene and three CpG sites (69107743, 69107866 and 69107899) of Erbb4 gene were decreased in 1-NP-exposed fetuses. Mechanistically, ten-eleven translocation (TET) activity and alpha-ketoglutarate (α-KG) content were decreased in 1-NP-exposed fetal forebrain. Supplementation with α-KG alleviated 1-NP-induced downregulation of gephyrin-related genes, prevented hippocampal synaptic damage, and improved anxiety-like behavior in male adult offspring. These results indicate that early-life 1-NP exposure causes anxiety-like behavior in male adulthood partially by altering hippocampal epigenetic reprogramming of synaptic plasticity.

Gestational bisphenol A exposure advances puberty onset in female offspring: Critical time window identification

Increasing evidence shows that the early onset of puberty in female offspring may be caused by maternal prenatal exposure to bisphenol A (BPA) during pregnancy; however, the critical time window of maternal prenatal BPA exposure remains unknown. Here, we identify the critical time window of gestational BPA exposure that induces early onset of puberty in female offspring. Pregnant CD-1 mice were gavaged with BPA (8 mg/kg) daily during the early gestational stage (GD1-GD6), middle gestational stage (GD7-GD12) or late gestational stage (GD13-GD18). We show that maternal BPA exposure during the early and middle gestational stages could advance the vaginal opening time and increase the serum levels of kisspeptin-10 and GnRH in the female offspring at PND 34. Mechanistically, maternal BPA exposure during early and middle gestation could significantly increase CpG island methylation in the Eed gene promoters but reduce the mRNA expression of Eed in the hypothalamus tissues of the female offspring. In conclusion, the critical period of maternal BPA exposure-induced early onset of puberty in female offspring is early and middle gestation; this BPA-induced early onset of puberty might be partly attributed to epigenetic programming of the Eed gene in the hypothalamus. This study provides important insights regarding the relationship and the mechanisms between BPA and offspring pubertal development.

Uterine decidual stromal cell-derived exosomes mediate the indirect effects of 1-nitropyrene on trophoblast biological behaviors

1-nitropyrene (1-NP) is representative nitropolycyclic aromatic hydrocarbon pollutant widely present in exhaust particles of internal combustion engine, which is known for its carcinogenicity and mutagenicity. Previous studies have demonstrated that 1-NP has reproductive toxicity, but the specific mechanism is unknown. In this study, Human decidual stromal cells (HDSCs) were treated by 1-NP, exosomes were extracted from the conditioned medium of HDSCs, which were then used to treat human chorionic trophoblast cells (HTR8/SVneo) for 24 h. The findings showed that human decidual stromal cell-derived exosomes (HDSC-EXOs) can promote the proliferation, migration, invasion and epithelial-mesenchymal transition (EMT; Vimentin and N-cadherin) of HTR8/SVneo by about 64%, 17%, 23%, 81% and 13%. The process of regulating the biological behaviors of embryonic trophoblast cells by maternal decidual stromal cells during pregnancy was simulated. Further investigations showed that HDSC-EXOs treatment activated the Wnt/β-catenin signaling pathway in HTR8/SVneo. Co-treatment by dickkopf-1 (DKK-1) significantly suppressed the activation of Wnt/β-catenin signaling pathway in HTR8/SVneo, and inhibited the proliferation, migration, invasion and EMT (N-cadherin and E-cadherin) of HTR8/SVneo by about 60%, 22%, 42%, 25%, 55% and 21%. These findings indicated that 1-NP exposure could induce the secretion of HDSC-EXOs from HDSCs, which in turn activate the Wnt/β-catenin signaling pathway and enhance the proliferation, migration, invasion and EMT of HTR8/SVneo.

1-Nitropyrene exposure induces mitochondria dysfunction and impairs oocyte maturation in mice

Oocyte quality is essential for a successful pregnancy. 1-Nitropyrene (1-NP) is a widely distributed pollutant in the environment and is well-known for its mutagenicity and carcinogenicity. However, whether 1-NP has toxic effects on mammalian oocyte quality remains unknown. In the present study, we focused on the effect of 1-NP on oocyte maturation using mouse oocytes as an in vitro model. Our study showed that 1-NP exposure disrupted the meiotic spindle assembly and caused chromosome misalignment, further impaired first polar body extrusion, and significantly decreased the fertilization capability in mouse oocytes. Further investigation showed that the mitochondrial membrane potential (MMP) and ATP levels were decreased, and the expression of genes encoding components of the mitochondrial respiratory chain was inhibited in 1-NP exposed oocytes. Meanwhile, 1-NP exposure increased the levels of reactive oxygen species (ROS), inhibited the expression of genes encoding antioxidant enzymes, and increased the frequency of early apoptotic oocytes. Overall, our data suggest that 1-NP exposure disrupts mitochondrial function and intracellular redox balance, ultimately impairing oocyte maturation. These findings reveal the adverse effect of 1-NP exposure on oocyte quality.

1-Nitropyrene disrupts testosterone biogenesis via AKAP1 degradation promoted mitochondrial fission in mouse Leydig cell

Previous study found 1-NP disrupted steroidogenesis in mouse testis, but the underlying mechanism remained elusive. The current work aims to explore the roles of ROS-promoted AKAP1 degradation and excessive mitochondrial fission in 1-NP-induced steroidogenesis disruption in MLTC-1 cells. Transmission electron microscope analysis found 1-NP promoted excessive mitochondrial fission. Further data showed 1-NP disrupted mitochondrial function. pDRP1 (Ser637), a negative regulator of mitochondrial fission, was reduced in 1-NP-treated MLTC-1 cells. Mechanistically, 1-NP caused degradation of AKAP1, an upstream regulator of pDRP1 (Ser637). MG132, a proteasome inhibitor, attenuated 1-NP-induced AKAP1 degradation and downstream pDRP1 (Ser637) reduction, thereby ameliorating 1-NP-downregulated steroidogenesis. Further analysis found that cellular ROS was elevated and NOX4, HO-1 and SOD2 were upregulated in 1-NP-exposed MLTC-1 cells. NAC, a well-known commercial antioxidant, alleviated 1-NP-induced excessive ROS and oxidative stress. 1-NP-induced AKAP1 degradation and subsequent downregulation of pDRP1 (Ser637) were prevented by NAC pretreatment. Moreover, NAC attenuated 1-NP-resulted T synthesis disturbance in MLTC-1 cells. The present study indicates that ROS mediated AKAP1 degradation and subsequent pDRP1 (Ser637) dependent mitochondrial fission is indispensable in 1-NP caused T synthesis disruption. This study provides a new insight into 1-NP-induced endocrine disruption, and offers theoretical basis in public health prevention.

Ambient fine particulate matter exposure disrupts placental autophagy and fetal development in gestational mice

Recent studies have shown that some adverse pregnancy outcomes, especially intrauterine growth restriction (IUGR), are associated with gestational exposure to ambient fine particulate matter (PM_2.5). However, potential mechanism remains to be elucidated. In the present study, pregnant C57BL/6 mice were randomly assigned to be exposed to either filtered air or ambient PM_2.5 in the gestation period via a concentrated whole-body exposure system. We found that gestational PM_2.5 exposure exerted no effect on implantation, preterm delivery, as well as fetal resorption and death. However, in utero fetal exposure to PM_2.5 showed a significant reduction in body weight and crown-rump length on GD13 and GD18. Meanwhile, maternal blood sinusoid in placenta was markedly reduced along with abnormal expression of placental nutrient transporters and growth hormone in dams exposed to PM_2.5. Additional tests showed gestational PM_2.5 exposure decreased autophagy-related protein levels and inhibited autophagy flux mainly on GD15. Correspondingly, AMPK/mTOR signaling pathway, a critical negative regulator of autophagy, was activated in placenta on GD15 by PM_2.5 exposure as well. These findings provide evidences that placental developmental disorder caused by autophagy inhibition might be an important mechanism for the growth restriction caused by PM_2.5 exposure.

Gestational exposure to environmental cadmium induces placental apoptosis and fetal growth restriction via Parkin-modulated MCL-1 degradation

Heavy metal cadmium (Cd), a classical environmental pollutant, causes placental apoptosis and fetal growth restriction (FGR), whereby the mechanism remains unclear. Here, our human case-control study firstly showed that there was a positive association of Parkin mitochondrial translocation, MCL-1 reduction, placental apoptosis, and all-cause FGR. Subsequently, Cd was administered to establish in vitro and in vivo models of placental apoptosis or FGR. Our models demonstrated that Parkin mitochondrial translocation was observed in Cd-administrated placental trophoblasts. Meaningfully, Parkin siRNA (siR) dramatically mitigated Cd-triggered apoptosis in placental trophoblasts. Mdivi-1 (M-1), an inhibitor for Parkin mitochondrial translocation, mitigated Cd-induced apoptosis in placental trophoblasts, which further ameliorated the effect of attenuated placental sizes in Cd-exposed mice. Furthermore, the interaction of MCL-1 with Parkin or Ub in Cd-stimulated cells was stronger than that in controls. MG132, an inhibitor for proteasome, abolished MCL-1 degradation in Cd-stimulated cells. Importantly, Parkin siR and M-1 memorably abolished the ubiquitin-dependent degradation of MCL-1 in placental trophoblasts. Interestingly, mito-TEMPO and melatonin, two mitochondria-targeted antioxidants, obviously rescued Cd-caused mitochondrial membrane potential (MMP) decrease, Parkin mitochondrial translocation, MCL-1 degradation, and apoptosis in placental trophoblasts. In conclusion, cadmium induces placental apoptosis and FGR via mtROS-mediated Parkin-modulated degradation of MCL-1.

miR-6769b-5p targets CCND-1 to regulate proliferation in cadmium-treated placental trophoblasts: Association with the impairment of fetal growth

Environmental cadmium (Cd) is positively associated with placental impairment and fetal growth retardation. Nevertheless, its potential mechanisms remain unclear. microRNAs (miRNAs) are known to influence placental development and fetal growth. This work was aimed to determine which miRNAs are involved in Cd-impaired placental and fetal development based on the mRNA and miRNA expression profiles analysis. As a result, gestational Cd exposure deceased fetal and placental weight, and reduced the protein level of PCNA in human and mouse placentae. Furthermore, the results of mRNA microarray showed that Cd-downregulated mRNAs were predictively correlated with several biological processes, including cell proliferation, differentiation and motility. In addition, the results of miRNA microarray and qPCR assay demonstrated that Cd significantly increased the level of miR-6769b-5p, miR-146b-5p and miR-452-5p. Integrated analysis of Cd-upregulated miRNAs predicted target genes and Cd-downregulated mRNAs found that overlapping mRNAs, such as CCND1, CDK13, RINT1 and CDC26 were also significantly associated with cell proliferation. Further experiments showed that miR-6769b-5p inhibitor, but not miR-146b-5p and miR-452-5p, markedly reversed Cd-downregulated the expression of proliferation-related mRNAs, and thereby restored Cd-decreased the proteins level of CCND1 and PCNA in human placental trophoblasts. Dual luciferase reporter assay further revealed that miR-6769b-5p directly targets CCND1. Finally, the case-control study demonstrated that increased miR-6769b-5p level and impaired cell proliferation were observed in small-for-gestational-age human placentae. In conclusion, miR-6769b-5p targets CCND-1 to regulate proliferation in Cd-treated placental trophoblasts, which is associated with the impairment of fetal growth. Our findings imply that placental miR-6769b-5p may be used as an epigenetic marker for environmental pollutants-caused fetal growth restriction and its late-onset chronic diseases.

1-Nitropyrene exposure impairs embryo implantation through disrupting endometrial receptivity genes expression and producing excessive ROS

Haze problem is an important factor threatening human health. PM2.5 is the main culprit haze. 1-Nitropyrene (1-NP) is the main nitrated polycyclic aromatic hydrocarbon, the toxic component of PM2.5 particles. The effects of 1-NP on various organs and reproductive health have been extensively and deeply studied, but the effects of 1-NP on embryo implantation and endometrial receptivity remain to be determined. The purpose of this study was to investigate the adverse effects of 1-NP on mouse embryo implantation and human endometrial receptivity. In early pregnancy, CD1 mice were given 2 mg/kg 1-NP by oral gavage, which resulted in a decreased embryo implantation number on day 5, inhibited leukemic inhibitory factor (LIF)/STAT3 pathway, decreased expression of estrogen receptor and progesterone receptor, and disrupted regulation of uterine cell proliferation. In addition, in a human in vitro implantation model, 1-NP was found to significantly inhibit the adhesion rate between trophoblast spheroids and endometrial epithelial cells, possibly by inhibiting the expression of receptivity molecules in Ishikawa cells. Promoting reactive oxygen species (ROS) production may be an additional mechanism by which it inhibits trophoblast spheroid adhesion. In this study, we used an in vivo mouse pregnancy model and an in vitro human embryo implantation model to demonstrate that 1-NP can impair endometrial receptivity and compromise embryo implantation.

Reactive oxygen species-evoked endoplasmic reticulum stress mediates 1-nitropyrene-induced epithelial-mesenchymal transition and pulmonary fibrosis

1-Nitropyrene (1-NP) is one component of atmospheric fine particles. Previous report revealed that acute 1-NP exposure induced respiratory inflammation. This study aimed to investigate whether chronic 1-NP exposure induces pulmonary fibrosis. Male C57BL6/J mice were intratracheally instilled to 1-NP (20 μg/mouse/week) for 6 weeks. Diffuse interstitial inflammation, a-smooth muscle actin (a-SMA)-positive cells, a marker of epithelial-mesenchymal transition (EMT), and an extensive collagen deposition, measured by Masson staining, were observed in 1-NP-exposed mouse lungs. Pulmonary function showed that lung dynamic compliance (Cydn-min) was reduced in 1-NP-exposed mice. Conversely, inspiratory resistance (Ri) and expiratory resistance (Re) were elevated in 1-NP-exposed mice. Mechanistically, cell migration and invasion were accelerated in 1-NP-exposed pulmonary epithelial cells. In addition, E-cadherin, an epithelial marker, was downregulated, and vimentin, a-SMA and N-cadherin, three mesenchymal markers, were upregulated in 1-NP-exposed pulmonary epithelial cells. Although TGF-β wasn't altered, phosphorylated Smad2/3 were enhanced in 1-NP-exposed pulmonary epithelial cells. Moreover, reactive oxygen species (ROS) were increased and endoplasmic reticulum (ER) stress was activated in 1-NP-exposed pulmonary epithelial cells. N-Acetylcysteine (NAC), an antioxidant, attenuated 1-NP-evoked excess ROS, ER stress and EMT in pulmonary epithelial cells. Similarly, pretreatment with NAC alleviated 1-NP-caused pulmonary EMT and lung fibrosis in mice. These results demonstrate that ROS-evoked ER stress contributes, at least partially, to 1-NP-induced EMT and pulmonary fibrosis.

Supplementation with high-dose cholecalciferol throughout pregnancy induces fetal growth restriction through inhibiting placental proliferation and trophoblast epithelial-mesenchymal transition

Vitamin D deficiency has been associated with adverse pregnant outcomes. Several studies investigated the effects of maternal vitamin D3 supplementation on fetal development with inconsistent results. The aim of this study was to investigate the effects of maternal supplementation with different doses of vitamin D3 on fetal development. Pregnant mice were administered with different doses of cholecalciferol (0, 2,000, 10,000, 40,000 IU/kg/day) by gavage throughout pregnancy. Fetal weight and crown-rump length were measured. Placental proliferation and mesenchymal characteristics were detected. HTR-8/SVneo cells were incubated in the absence or presence of calcitriol (500 nmol/L) to evaluate the effects of active vitamin D3 on migration and invasion of human trophoblast cells. Although a low dose of cholecalciferol was safe, fetal weight and crown-rump length were decreased in dams treated with high-dose cholecalciferol throughout pregnancy. Placental weight and labyrinth thickness were reduced in mice administered with high-dose cholecalciferol. An obvious calcification was observed in placentae of mice administered with high-dose cholecalciferol. Ki67-positive cells, a marker of placental proliferation, were reduced in mice administered with high-dose cholecalciferol. N-cadherin and vimentin, two mesenchymal markers, were decreased in cholecalciferol-treated mouse placentae and calcitriol-treated human trophoblast cells. MMP-2 and MMP-9, two matrix metalloproteinases, were downregulated in cholecalciferol-treated mouse placentae and calcitriol-treated human trophoblast cells. In addition, trophoblast migration and invasion were suppressed by calcitriol. Supplementation with high-dose cholecalciferol induces fetal growth restriction partially through inhibiting placental proliferation and trophoblast epithelial-mesenchymal transition.

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.

What is necessary for next-generation atmospheric environmental standards? Recent research trends for PM2.5 -bound polycyclic aromatic hydrocarbons and their derivatives

The air pollution associated with PM_2.5 kills 7 million people every year in the world, especially threatening the health of children in developing countries. However, the current air quality standards depend mainly on particle size. PM_2.5 contains many carcinogenic/mutagenic polycyclic aromatic hydrocarbons (PAHs) and their derivatives such as nitropolycyclic aromatic hydrocarbons and oxygenated PAHs. Among them, environmental standards and guidelines have been set for benzo[a]pyrene by few countries and international organizations. Recent research reports showed that these pollutants are linked to diseases other than lungs, and new methods have been developed for determining trace levels of not only PAHs but also their derivatives. It is time to think about the next-generation environmental standards. This article aims to (a) describe recent studies on the health effects of PAHs and their derivatives other than cancer, (b) describe new analytical methods for PAH derivatives, and (c) discuss the targets for the next-generation standards.

Long-term 1-nitropyrene exposure induces endoplasmic reticulum stress and inhibits steroidogenesis in mice testes

1-Nitropyrene (1-NP) is a representative nitro-polycyclic aromatic hydrocarbon from diesel exhaust. Recently, we found that maternal 1-NP exposure caused fetal growth retardation and disturbed cognitive development in adolescent female offspring. To investigate long-term 1-NP exposure on spermatogenesis and steroidogenesis, male mice were exposed to 1-NP (1.0 mg/kg/day) by gavage for 70 days. There was no significant difference on relative testicular weight, number of testicular apoptotic cells and epididymal sperm count between 1-NP-exposed mice and controls. Although long-term 1-NP exposure did not influence number of Leydig cells, steroidogenic genes and enzymes, including STAR, P450scc, P45017α and 17β-HD, were downregulated in 1-NP-expoed mouse testes. Correspondingly, serum and testicular testosterone (T) levels were reduced in 1-NP-exposed mice. Additional experiment showed that testicular GRP78 mRNA and protein were upregulated by 1-NP. Testicular phospho-IRE1α and sliced xbp-1 mRNA, a downstream molecule of IRE1α, were elevated in 1-NP-exposed mice. Testicular phospho-PERK and phospho-eIF2α, a downstream molecule of PERK pathway, were increased in 1-NP-exposed mice. Testicular NOX4, a subunit of NAPDH oxidase, and HO-1, MDA, two oxidative stress markers, were increased in 1-NP-exposed mice. Testicular GSH and GSH/GSSG were decreased in 1-NP-exposed mice. These results suggest that long-term 1-NP exposure induces reactive oxygen species-evoked ER stress and disrupts steroidogenesis in mouse testes.

Reactive oxygen species-mediated cellular genotoxic stress is involved in 1-nitropyrene-induced trophoblast cycle arrest and fetal growth restriction

1-nitropyrene (1-NP) is a key component of diesel exhaust-sourced fine particulate matter (PM2.5). Our recent study demonstrated that gestational 1-NP exposure caused placental proliferation inhibition and fetal intrauterine growth restriction (IUGR). This study aimed to investigate the role of genotoxic stress on 1-NP-induced placental proliferation inhibition and fetal IUGR. Human trophoblasts were exposed to 1-NP (10 μM). Growth index was reduced and PCNA was downregulated in 1-NP-exposed placental trophoblasts. More than 90% of 1-NP-exposed trophoblasts were arrested in either G0/G1 or G2/M phases. CDK1 and cyclin B, two G2/M cycle-related proteins, and CDK2, a G0/G1 cycle-related protein, were reduced in 1-NP-exposed trophoblasts. Phosphorylated Rb, a downstream molecule of CDK2, was inhibited in 1-NP-exposed trophoblasts. Moreover, DNA double-strand break was observed and γ-H2AX, another indicator of DNA double-strand break, was upregulated in 1-NP-exposed trophoblasts. Phosphorylated ATM, a key molecule of genotoxic stress, and its downstream molecule Chk2 were elevated. By contrast, Cdc25A, a downstream target of Chk2, was reduced in 1-NP-exposed trophoblasts. Phenyl-N-t-butylnitrone (PBN), a free radical scavenger, inhibited 1-NP-induced genotoxic stress and trophoblast cycle arrest. Animal experiment showed that N-acetylcysteine (NAC), an antioxidant, rescued 1-NP-induced placental proliferation inhibition and fetal IUGR in mice. These results provide evidence that reactive oxygen species (ROS)-mediated cellular genotoxic stress partially contributes to 1-NP-induced placental proliferation inhibition and fetal IUGR.

Maternal 1-nitropyrene exposure during pregnancy increases susceptibility of allergic asthma in adolescent offspring

1-nitropyrene (1-NP) is widespread in the environment, as a typical nitrated polycyclic aromatic hydrocarbon. The purpose of this research was to explore the effects of gestational 1-NP exposure on susceptibility of allergic asthma in offspring. Maternal mice were exposed to 1-NP (100 μg kg^-1) by gavage throughout the whole pregnancy. Pups were sensitized by injecting with ovalbumin (OVA) on postnatal day (PND)23, 29, and 36, respectively. At 7 days following the last injection, sensitized mice were exposed to aerosol OVA. As expected, there were quite a few inflammatory cells in the lungs of OVA-sensitized pups, accompanied by bronchial wall thickening and hyperemia. Elevated goblet cells and overproduced mucus were observed in the airways of OVA-sensitized pups. Interestingly, gestational 1-NP exposure aggravated infiltration of inflammatory cells, mainly eosinophils, in OVA-sensitized offspring. Although it had little effect on airway smooth muscle layer thickening and basement membrane fibrosis, gestational 1-NP exposure aggravated goblet cell hyperplasia, Muc5ac mRNA upregulation, and mucus secretion in the airways of OVA-sensitized and challenged offspring. Mechanistically, gestational 1-NP exposure aggravated elevation of pulmonary IL-5 in OVA-sensitized pups. These findings suggest that gestational 1-NP exposure increases susceptibility of allergic asthma in offspring.

Acute 1-NP exposure induces inflammatory responses through activating various inflammatory signaling pathways in mouse lungs and human A549 cells

1-Nitropyrene (1-NP), a key component of fine particulate matter (PM2.5), is a representative of nitrated polycyclic aromatic hydrocarbons (NPAHs). The aim of this research is to investigate proinflammatory effects of acute 1-NP exposure in mouse lungs and human A549 cells. All mice except controls were intratracheally instilled with 1-NP (20 μg/mouse). A549 cell, a human lung cancer cell line, was cultured with or without 1-NP (5 μM). Acute 1-NP exposure elevated lung weight and caused infiltration of inflammatory cells, especially neutrophils in mouse lungs. Although it had little effect on serum TNF-α and KC, acute 1-NP exposure elevated the levels of TNF-α and KC in BALF. Correspondingly, acute 1-NP exposure upregulated pulmonary Il-1β, Il-6, Tnf-α and Kc. Mechanistically, acute 1-NP exposure activated nuclear factor kappa B (NF-κB) in mouse lungs and human A549 cells. Additionally, acute 1-NP exposure induced Akt phosphorylation in mouse lungs and human A549 cells. Moreover, acute 1-NP exposure induced phosphorylation of pulmonary JNK and ERK1/2, molecules of the mitogen-activated protein kinase (MAPK) pathway. This study provides evidence that acute 1-NP exposure induces inflammatory responses through activating various inflammatory signaling pathways in mouse lungs and human A549 cells.

Gestational 1-nitropyrene exposure causes gender-specific impairments on postnatal growth and neurobehavioral development in mice

1-Nitropyrene (1-NP), a typical nitrated polycyclic aromatic hydrocarbon, is widely distributed in the environment and is well known for its mutagenic effects. Recently, we found that gestational 1-NP exposure induced fetal growth restriction. In this study, we further evaluated the effect of in utero 1-NP exposure on postnatal growth and neurobehavioral development in the offspring. Pregnant mice were administered with 1-NP (10 μg/kg) by gavage daily in late pregnancy (GD13-GD17). The body weight of each offspring was measured from PND1 to 12 weeks postpartum. Exploration and anxiety related activities were detected by open-field test at 6 weeks postpartum. Learning and memory were assessed by Morris Water Maze at 7 weeks postpartum. And depressive-like behaviors were estimated by sucrose preference test at 10 weeks postpartum. Significant body weight reduction was observed in 1-NP-exposed female offspring at PND1, PND14 and PND21 while the lower body weight was only found at PND1 for 1-NP-exposed male offspring. Exploration and anxiety activities at puberty, and depressive-like behavior in adulthood were not disturbed in offspring prenatally exposed to 1-NP. Interestingly, spatial learning and memory ability at puberty was impaired in females but not in males prenatally exposed to 1-NP. These findings suggest that gestational 1-NP exposure delays postnatal growth and impaired neurobehavioral development in a gender-dependent manner.