Maternal cadmium exposure reduces placental zinc transport and induces fetal growth restriction in mice

Cadmium Exposure Disrupts Uterine Energy Metabolism and Coagulation Homeostasis During Labor in Institute of Cancer Research Mice: Insights from Transcriptomic Analysis

Background: Cadmium (Cd) is a highly toxic heavy metal. There are very few studies about the effects of Cd on reproductive health and metabolism, and even fewer on metabolic disorders in the uterus of mice in labor. This study is the first to establish a model of Cd exposure in the uterus of laboring mice and investigate the underlying metabolic mechanisms through transcriptomic analysis. Methods: Pregnant mice received intraperitoneal injections of CdCl2 (1.5 mg/kg) on gestational days 12.5, 14.5, and 16.5 were set up as the experimental group (Cd group), and pregnant mice injected with saline were set up as the control group (CT group). A total of 738 differentially expressed genes (DEGs) were screened using DESeq2 software, including 326 upregulated genes and 412 downregulated genes. Results: Through enrichment databases including the KEGG, GO, Reactome, and PANTHER, we identified 76 metabolism-related DEGs and performed protein-protein interaction (PPI) network analysis. The PPI results were visualized using Cytoscape software and further analyzed, with 18 hub genes (maximum clique centrality score > 10) identified through the MCC algorithm of the Cytohubba plugin. The results showed that the highest-scoring hub genes included mt-Co2, mt-Co3, mt-Atp6, mt-Atp8, mt-Nd3, and mt-Nd4l, which are involved in mitochondrial energy metabolism. The remaining lower-scoring hub genes were primarily associated with coagulation processes. Pathway analysis revealed hub genes predominantly involved in oxidative phosphorylation, complement and coagulation cascades, the cGMP-PKG signaling pathway, and thermogenesis. Conclusion: This study successfully established a Cd exposure-induced uterine injury model, providing valuable references for human reproductive health research.

Placental RTN3L-dependent ER-Phagy Contributes to Fetal Testicular Dysplasia Upon Environmental Stress

Prenatal environmental stress damages fetal testicular development, leading to male infertility. However, the precise mechanisms underlying the impact of gestational environmental stress on fetal testicular development require further investigation. This study demonstrates that gestational environmental stressor cadmium exposure caused placental estradiol synthesis inhibition and fetal testicular dysplasia. Gestational estradiol supplementation restores fetal testicular dysplasia caused by environmental stress-induced placental estradiol synthesis inhibition. Analysis of human placentae and cadmium-stimulated human primary placental trophoblasts confirmed that ER-phagy is associated with the inhibition of estradiol synthesis in placentae. Subsequently, the data reveals that environmental stress significantly activates RTN3L-mediated ER-phagy. RTN3L-deficient cells and placental Rtn3l-specific knockout mice confirm that environmental stress-activated RTN3L-mediated ER-phagy inhibited placental estradiol synthesis. Total N6-methyladenosine level increasing in gestational environmental stress-exposed placentae. METTL3-mediated N6-methyladenosine modification suppression obviously restrains environmental stress-activated RTN3L-dependent ER-phagy. In conclusion, gestational environmental stress activates ER-phagy by increasing placental Rtn3l mRNA N6-methyladenosine modification, inhibiting placental estradiol synthesis, and contributing to fetal testicular dysplasia. The study demonstrates the early prevention and treatment of adult male infertility from the perspective of fetal-derived diseases.

Cadmium levels in maternal blood, placenta, and cord blood in relation to preeclampsia and fetal growth: a case-control study in China

This study aims to delineate the levels of Cd exposure in maternal blood, placenta, and cord blood, and to explore the association between Cd levels and the risk of preeclampsia (PE), as well as its potential impact on fetal growth among affected individuals. A case-control study was performed at the First Hospital of Shanxi Medical University, involving 373 pregnant women diagnosed with PE and 485 controls. Cd was measured in maternal blood, placenta, and cord blood using ICP-MS. The association between Cd and birth weight z-score was analyzed by multivariate linear regression. Logistic regression analysis was used to investigate the relationships between Cd and the risk of PE, and Cd and the risk of fetal growth. The concentration of Cd in the placenta was higher than that in maternal blood and cord blood. The highest tertile of placental Cd was identified as a risk factor for PE (OR = 2.704, 95% CI: 1.865, 3.921). Among pregnant women with PE, higher levels of Cd exposure in the placenta were negatively associated with birth weight z-scores (per doubling: β = -0.134, 95% CI: -0.264, -0.004), and the highest tertile of placental Cd was associated with an elevated risk of SGA (OR = 2.103, 95% CI: 1.164, 3.801). Furthermore, an interaction between Cd and PE was identified. In conclusion, Cd can accumulate in the placenta of pregnant women, and high placental Cd exposure not only increases the risk of PE but also exacerbates the risk of SGA outcome in PE pregnant women.

Melatonin alleviates high temperature exposure induced fetal growth restriction via the gut-placenta-fetus axis in pregnant mice

INTRODUCTION

Global warming augments the risk of adverse pregnancy outcomes in vulnerable expectant mothers. Pioneering investigations into heat stress (HS) have predominantly centered on its direct impact on reproductive functions, while the potential roles of gut microbiota, despite its significant influence on distant tissues, remain largely unexplored. Our understanding of deleterious mechanisms of HS and the development of effective intervention strategies to mitigate the detrimental impacts are still limited.

OBJECTIVES

In this study, we aimed to explore the mechanisms by which melatonin targets gut microbes to alleviate HS-induced reproductive impairment.

METHODS

We firstly evaluated the alleviating effects of melatonin supplementation on HS-induced reproductive disorder in pregnant mice. Microbial elimination and fecal microbiota transplantation (FMT) experiments were then conducted to confirm the efficacy of melatonin through regulating gut microbiota. Finally, a lipopolysaccharide (LPS)-challenged experiment was performed to verify the mechanism by which melatonin alleviates HS-induced reproductive impairment.

RESULTS

Melatonin supplementation reinstated gut microbiota in heat stressed pregnant mice, reducing LPS-producing bacteria (Aliivibrio) and increasing beneficial butyrate-producing microflora (Butyricimonas). This restoration corresponded to decreased LPS along the maternal gut-placenta-fetus axis, accompanied by enhanced intestinal and placental barrier integrity, safeguarding fetuses from oxidative stress and inflammation, and ultimately improving fetal weight. Further pseudo-sterile and fecal microbiota transplantation trials confirmed that the protective effect of melatonin on fetal intrauterine growth under HS was partially dependent on gut microbiota. In LPS-challenged pregnant mice, melatonin administration mitigated placental barrier injury and abnormal angiogenesis via the inactivation of the TLR4/MAPK/VEGF signaling pathway, ultimately leading to enhanced nutrient transportation in the placenta and thereby improving the fetal weight.

CONCLUSION

Melatonin alleviates HS-induced low fetal weight during pregnancy via the gut-placenta-fetus axis, the first time highlighting the gut microbiota as a novel intervention target to mitigate the detrimental impact of global temperature rise on vulnerable populations.

Mechanisms of Phytoremediation by Resveratrol against Cadmium Toxicity

Cadmium (Cd) toxicity poses a significant threat to human health and the environment due to its widespread occurrence and persistence. In recent years, considerable attention has been directed towards exploring natural compounds with potential protective effects against Cd-induced toxicity. Among these compounds, resveratrol (RV) has emerged as a promising candidate, demonstrating a range of beneficial effects attributed to its antioxidant and anti-inflammatory properties. This literature review systematically evaluates the protective role of RV against Cd toxicity, considering the various mechanisms of action involved. A comprehensive analysis of both in vitro and in vivo studies is conducted to provide a comprehensive understanding of RV efficacy in mitigating Cd-induced damage. Additionally, this review highlights the importance of phytoremediation strategies in addressing Cd contamination, emphasizing the potential of RV in enhancing the efficiency of such remediation techniques. Through the integration of diverse research findings, this review underscores the therapeutic potential of RV in combating Cd toxicity and underscores the need for further investigation to elucidate its precise mechanisms of action and optimize its application in environmental and clinical settings.

NBR1-dependent autophagy activation protects against environmental cadmium-evoked placental trophoblast senescence

Cadmium (Cd), a well-established developmental toxicant, accumulates in the placentae and disrupts its structure and function. Population study found adverse pregnancy outcomes caused by environmental Cd exposure associated with cell senescence. However, the role of autophagy activation in Cd-induced placental cell senescence and its reciprocal mechanisms are unknown. In this study, we employed animal experiments, cell culture, and case-control study to investigate the above mentioned. We have demonstrated that exposure to Cd during gestation induces placental senescence and activates autophagy. Pharmacological and genetic interventions further exacerbated placental senescence induced by Cd through the suppression of autophagy. Conversely, activation of autophagy ameliorated Cd-induced placental senescence. Knockdown of NBR1 exacerbated senescence in human placental trophoblast cells. Further investigations revealed that NBR1 facilitated the degradation of p21 via LC3B. Our case-control study has demonstrated a positive correlation between placental senescence and autophagy activation in all-cause fetal growth restriction (FGR). These findings offer a novel perspective for mitigating placental aging and placental-origin developmental diseases induced by environmental toxicants.

Genetic and inflammatory factors underlying gestational diabetes mellitus: a review

Gestational diabetes mellitus (GDM) poses a significant global health concern, impacting both maternal and fetal well-being. Early detection and treatment are imperative to mitigate adverse outcomes during pregnancy. This review delves into the pivotal role of insulin function and the influence of genetic variants, including SLC30A8, CDKAL1, TCF7L2, IRS1, and GCK, in GDM development. These genetic variations affect beta-cell function and insulin activity in crucial tissues, such as muscle, disrupting glucose regulation during pregnancy. We propose a hypothesis that this variation may disrupt zinc transport, consequently impairing insulin production and secretion, thereby contributing to GDM onset. Furthermore, we discussed the involvement of inflammatory pathways, such as TNF-alpha and IL-6, in predisposing individuals to GDM. Genetic modulation of these pathways may exacerbate glucose metabolism dysregulation observed in GDM patients. We also discussed how GDM affects cardiovascular disease (CVD) through a direct correlation between pregnancy and cardiometabolic function, increasing atherosclerosis, decreased vascular function, dyslipidemia, and hypertension in women with GDM history. However, further research is imperative to unravel the intricate interplay between inflammatory pathways, genetics, and GDM. This understanding is pivotal for devising targeted gene therapies and pharmacological interventions to rectify genetic variations in SLC30A8, CDKAL1, TCF7L2, IRS1, GCK, and other pertinent genes. Ultimately, this review offers insights into the pathophysiological mechanisms of GDM, providing a foundation for developing strategies to mitigate its impact.

The association of serum toxic metals and essential elements during early pregnancy with body mass index trajectory of infants during the first years: A prospective study

To the best of our knowledge, prior research has yet to delve into the combined and interactive relationships between maternal exposure to essential elements and toxic metals and infancy's continuous growth and trajectories. This study aims to discern infant growth trajectories in the first year of life and to determine the associations of maternal serum levels of essential elements and toxic metals with growth trajectory. Within a Chinese prospective cohort in 2019 - 2021, 407 mother-infant pairs were included, and the serum levels of five essential elements (zinc, calcium, copper, magnesium and iron) and two toxic metals (cadmium and lead) in early pregnancy were assessed. The growth trajectory of infants was followed until age one year. Raw BMI and height values were transformed to age- and sex-specific BMI and height standard deviation (SD) scores. Latent-class group-based trajectory models and piecewise linear mixed regression were estimated to determine infant growth trajectories and growth velocity, respectively. The individual relationship between maternal metallic element levels and infant growth trajectory was examined using multinomial logistic regression models and linear mixed regression, while joint associations and interactive relationships were explored using Bayesian kernel machine regression (BKMR) following confounder adjustments. Four distinct trajectory patterns based on BMI-z score (low-rapid BMI gain group, normal-stable BMI group, very low-rapid BMI gain group and normal-rapid BMI gain group) and length-for-age (high-stable length group, low-stable length group, normal-rapid length gain group, very low-rapid length gain group) were identified during the first year post-birth, respectively. In single-metal and multiple-metal models, infants born to mothers with higher serum Zn and lower serum Cu levels were associated with a normal-rapid BMI gain trajectory during the first year. Serum Cu exhibited a positive correlation with the rate of BMI change solely in infants aged 6-12 months. Further, the BKMR analysis revealed a statistically significant and negative joint effect of the five essential elements on the likelihood of normal-rapid BMI/length gain trajectory when serum levels of these elements fell below the 70th percentile compared to median levels. In addition, high levels of serum copper and calcium interactively affect the rates of BMI change during 6-12 months old (β: -0.21, 95% CI: -0.44, -0.03, P = 0.04, P-interaction=0.04). In conclusion, maternal trace elements at early pregnancy are linked to infant growth patterns and growth velocity in the first year of life.

Fetoplacental Disposition and Toxicity of Cadmium in Mice Lacking the Bcrp Transporter

The environmental toxicant cadmium (Cd) impairs the growth of rodents and humans in utero which in turn heightens susceptibility to diseases later in life. We previously demonstrated that the maternal-facing efflux transporter, breast cancer resistance protein (human BCRP/ABCG2, mouse Bcrp/Abcg2) confers resistance against Cd toxicity in human trophoblasts. In the current study, we sought to determine whether the absence of Bcrp alters the fetoplacental disposition and toxicity of Cd in mice. Pregnant female wild-type (WT) and Bcrp-null mice (n = 9-10/group) were administered a single injection of saline (5 ml/kg) or CdCl2 (5 mg/kg) on gestational day (GD) 9. Following Cd treatment, Bcrp-null offspring were shorter and accumulated more Cd in their placentas on GD 17 compared to WT mice. Because Cd can adversely impact placentation and transplacental nutrient delivery in mice, multiple pathways were assessed using morphometrics and immunohistochemistry including placenta zonation, vasculature development, and nutrient transporter expression. Most notably, the placentas of Bcrp-null mice had reduced immunostaining of the cell adhesion marker, β-catenin, and the trophoblast marker, cytokeratin, as well as decreased expression of divalent metal nutrient transporters (Dmt1, Zip14, and ZnT1) following Cd treatment. In summary, the absence of Bcrp expression increased placental concentrations of Cd which was associated with shorter fetal size that may be related to differential changes in molecular patterns of placental development and nutrition.

Cadmium reduces growth of male fetuses by impairing development of the placental vasculature and reducing expression of nutrient transporters

In utero exposure to the toxic metal cadmium (Cd) alters fetoplacental growth in rodents and has been inversely associated with birth weight and infant size in some birth cohorts. Moreover, studies suggest that Cd may have differential effects on growth and development according to offspring sex. The purpose of the current study was to evaluate changes in male and female fetoplacental development following a single injection of saline (5 ml/kg ip) or cadmium chloride (CdCl2, 2.5, 5 mg/kg, ip) on gestational day (GD) 9. By GD18, no changes in fetal or placental weights were observed after treatment with 2.5 mg/kg CdCl2. By comparison, the weight and length of male fetuses and their placentas were reduced following treatment with 5 mg/kg CdCl2 whereas no change was observed in females. In addition, the area of maternal and fetal blood vessels as well as the expression of the glucose transporters, Glut1 and Glut3, and the endothelial marker, CD34, were reduced in the placentas of CdCl2-treated male offspring compared to females. Interestingly, the placentas of females accumulated 80% more Cd than males after CdCl2 (5 mg/kg) administration. Female placentas also had higher concentrations of zinc and the zinc transporter Znt1 compared to males which may explain the limited changes in fetal growth observed following CdCl2 treatment. Taken together, disruption of vasculature development and reduced expression of glucose transporters in the placenta provide potential mechanisms underlying reduced fetal growth in male offspring despite the greater accumulation of Cd in female placentas.

Zinc alleviates cadmium-induced reproductive toxicity via regulating ion homeostasis, metallothionein expression, and inhibiting mitochondria-mediated apoptosis in the freshwater crab Sinopotamon henanense

Cadmium (Cd) is a carcinogenic environmental pollutant that harms male reproductive systems by lowering sperm quality, impairing spermatogenesis, and causing apoptosis. Although zinc (Zn) has been reported to alleviate Cd toxicity, the underlying mechanisms have not been fully elucidated. The aim of this work was to investigate the mitigating effects of Zn on Cd-induced male reproductive toxicity in the freshwater crab Sinopotamon henanense. Cd exposure not only resulted in its accumulation but also in Zn deficiency, decreased sperm survival rate, poor sperm quality, altered ultrastructure, and increased apoptosis in the testis of the crabs. Morever, Cd exposure increased the expression and distribution of metallothionein (MT) in the testis. However, Zn supplementation effectively mitigated the aforementioned effects of Cd, as demonstrated by preventing Cd accumulation, increasing Zn bioavailability, alleviating apoptosis, increasing mitochondrial membrane potential, decreasing reactive oxygen species (ROS) levels, and restoring MT distribution. Moreover, Zn also significantly reduced the expression of apoptosis-related (p53, Bax, CytC, Apaf-1, Caspase-9, Caspase-3), metal transporter-related ZnT1, metal-responsive transcription factor 1 (MTF1), and the gene and protein expression of MT, while increasing the expression of ZIP1 and Bcl-2 in the testis of Cd-treated crabs. In conclusion, Zn alleviates Cd-induced reproductive toxicity via regulating ion homeostasis, MT expression, and inhibiting mitochondria-mediated apoptosis in the testis of S. henanense. The information obtained in this study may serve as the foundation for further investigation into the development of mitigation strategies for adverse ecological and human health outcomes associated with Cd contamination or poisoning.

Protective role of the placental efflux transporter BCRP/ABCG2 in the relationship between prenatal cadmium exposure, placenta weight, and size at birth

BACKGROUND AND AIM

Placental efflux transporter proteins, such as BCRP, reduce the placental and fetal toxicity of environmental contaminants but have received little attention in perinatal environmental epidemiology. Here, we evaluate the potential protective role of BCRP following prenatal exposure to cadmium, a metal that preferentially accumulates in the placenta and adversely impacts fetal growth. We hypothesized that individuals with a reduced function polymorphism in ABCG2, the gene encoding BCRP, would be most vulnerable to the adverse impacts of prenatal cadmium exposure, notably, smaller placental and fetal size.

METHODS

We measured cadmium in maternal urine samples at each trimester and in term placentas from UPSIDE-ECHO study participants (NY, USA; n = 269). We fit adjusted multivariable linear regression and generalized estimating equation models to examine log-transformed urinary and placental cadmium concentrations in relation to birthweight, birth length, placental weight, and fetoplacental weight ratio (FPR) and stratified models by ABCG2 Q141K (C421A) genotype.

RESULTS

Overall 17% of participants expressed the reduced-function ABCG2 C421A variant (AA or AC). Placental cadmium concentrations were inversely associated with placental weight (β = -19.55; 95%CI: -37.06, -2.04) and trended towards higher FPR (β = 0.25; 95%CI: -0.01, 0.52) with stronger associations in 421A variant infants. Notably, higher placental cadmium concentrations in 421A variant infants were associated with reduced placental weight (β = -49.42; 95%CI: 98.87, 0.03), and higher FPR (β = 0.85, 95%CI: 0.18, 1.52), while higher urinary cadmium concentration was associated with longer birth length (β = 0.98; 95%CI: 0.37, 1.59), lower ponderal index (β = -0.09; 95%CI: 0.15, -0.03), and higher FPR (β = 0.42; 95%CI: 0.14, 0.71).

CONCLUSIONS

Infants with reduced function ABCG2 polymorphisms may be particularly vulnerable to the developmental toxicity of cadmium as well as other xenobiotics that are BCRP substrates. Additional work examining the influence of placental transporters in environmental epidemiology cohorts is warranted.

Toxic effects of maternal cadmium exposure on the metabolism and transport system of amino acids in the maternal livers

Fetal growth restriction (FGR) is one of the most common obstetric diseases, and affects approximately 10 % of all pregnancies worldwide. Maternal cadmium (Cd) exposure is one of the factors that may increase the risk of the development of FGR. However, its underlying mechanisms remain largely unknown. In this study, using Cd-treated mice as an experimental model, we analyzed the levels of some nutrients in the circulation and the fetal livers by biochemical assays; the expression patterns of several key genes involved in the nutrient uptake and transport, and the metabolic changes in the maternal livers were also examined by quantitative real-time PCR and gas chromatography-time of flight-mass spectrometry method. Our results showed that, the Cd treatment specifically reduced the levels of total amino acids in the peripheral circulation and the fetal livers. Concomitantly, Cd upregulated the expressions of three amino acid transport genes (SNAT4, SNAT7 and ASCT1) in the maternal livers. The metabolic profiling of maternal livers also revealed that, several amino acids and their derivatives were also increased in response to the Cd treatment. Further bioinformatics analysis indicated that the experimental treatment activated the metabolic pathways, including the alanine, aspartate and glutamate metabolism, valine, leucine and isoleucine biosynthesis, arginine and proline metabolism. These findings suggest that maternal Cd exposure activate the amino acid metabolism and increase the amino acid uptake in the maternal liver, which reduces the supply of amino acids to the fetus via the circulation. We suspect that this underlies the Cd-evoked FGR.

Pregnancy and lactation mixed exposure to lead, cadmium, and mercury alters maternal-offspring single heavy metal load: A factorial design

Environmental exposure to heavy metal mixture of lead (Pb), cadmium (Cd), and mercury (Hg) would induce hazardous health effects. However, there is a paucity of data on how exposure to heavy metal mixture alters the metabolic dynamics of individual metals. Considering that the dose plays a key role in determining the toxicity of heavy metals, we performed a factorial design with three heavy metals (Pb, Cd, and Hg) at low exposure levels. Female rats were exposed to Pb, Cd, and (or) Hg from successful mating until pup weaning. Their concentrations in maternal blood, breast milk, and postnatal day 0 (PND0) and PND21 offspring blood and whole brain were measured. Using ANOVA analysis, Pearson correlation, and structural equation model, we demonstrated the complex interactions among heavy metals during their absorption, mother-offspring transport, and target organ accumulation. Among all the explored samples, almost all the highest Pb, Cd, and Hg levels were observed in their respective single heavy metal exposure groups. In addition, Hg was found could antagonize the transport of Pb or Cd, when they cross the placental barrier and blood-brain barriers (BBB). However, the effect of Hg no longer presented when they are absorbed through the digestive system. The antagonistic effect of Pb on Cd was observed when they cross the placental barrier. In addition, Cd was also found to compete the transport pathway of Pb when they cross the BBB after birth. Compared to Pb and Hg, we found that the transport efficiency of Cd in the digestive system was lower, whereas the chelation of Cd by the placental barrier was better. This preliminary information may help researchers to explore the mechanism underlying the hazardous effects of heavy metal mixture exposure, or for regulatory agencies to revise guidelines for heavy metal exposure.

Does maternal low-dose cadmium exposure increase the risk of offspring to develop metabolic syndrome and/or type 2 diabetes?

Cadmium is a hazardous metal with multiple organ toxicity that causes great harm to human health. Cadmium enters the human body through occupational exposure, diet, drinking water, breathing, and smoking. Cadmium accumulation in the human body is associated with increased risk of developing obesity, cardiovascular disease, diabetes, and metabolic syndrome (MetS). Cadmium uptake is enhanced during pregnancy and can cross the placenta affecting placental development and function. Subsequently, cadmium can pass to fetus, gathering in multiple organs such as the liver and pancreas. Early-life cadmium exposure can induce hepatic oxidative stress and pancreatic β-cell dysfunction, resulting in insulin resistance and glucose metabolic dyshomeostasis in the offspring. Prenatal exposure to cadmium is also associated with increasing epigenetic effects on the offspring's multi-organ functions. However, whether and how maternal exposure to low-dose cadmium impacts the risks of developing type 2 diabetes (T2D) in the young and/or adult offspring remains unclear. This review collected available data to address the current evidence for the potential role of cadmium exposure, leading to insulin resistance and the development of T2D in offspring. However, this review reveals that underlying mechanisms linking prenatal cadmium exposure during pregnancy with T2D in offspring remain to be adequately investigated.

The inter- and multi- generational epigenetic alterations induced by maternal cadmium exposure

Exposure to cadmium during pregnancy, from environmental or lifestyle factors, has been shown to have detrimental fetal and placental developmental effects, along with negatively impacting maternal health during gestation. Additionally, prenatal cadmium exposure places the offspring at risk for developing diseases in infancy, adolescence, and adulthood. Although given much attention, the underlying mechanisms of cadmium-induced teratogenicity and disease development remain largely unknown. Epigenetic changes in DNA, RNA and protein modifications have been observed during cadmium exposure, which implies a scientific premise as a conceivable mode of cadmium toxicity for developmental origins of health and disease (DOHaD). This review aims to examine the literature and provide a comprehensive overview of epigenetic alterations induced by prenatal cadmium exposure, within the developing fetus and placenta, and the continued effects observed in childhood and across generations.

Toxicity of cadmium salts on indicators of embryogenesis of rats

Cadmium is a toxic heavy metal which is considered a dangerous environmental pollutant and has a detrimental effect on the organs of the reproductive system, the period of implantation and the development of embryos. The experiment presented in this article established the effect of cadmium salts (chloride and citrate) on the general progress of embryogenesis. For this purpose, 60 rats were randomly divided into three groups: control, experimental group with cadmium chloride exposure and experimental group with cadmium citrate exposure. Cadmium chloride solvent, cadmium citrate solvent at a dose of 1.0 mg/kg and distilled intragastric water were injected from the first to the thirteenth (first subgroup) and from the first to the twentieth days of embryogenesis (second subgroup). When cadmium chloride was injected, total embryonic (by 4.24 and 3.67 times), pre-implantation (by 6.50 and 14.03 times) and post-implantation mortality (by 3.07 and 2.49 times) increased with a reduction of the number of surviving fetuses by 24.0% and 25.9% compared with the control group on the 13th and 20th days of embryogenesis respectively. At the same time, during exposure to cadmium citrate, indicators of total embryonic mortality increased by 4.02 and 3.52 times, pre-implantation mortality by 6.04 and 13.03 times, and post-implantation mortality by 3.09 and 2.26 times, and indicators of the number of live fetuses decreased by 18.3% and 22.2% in relation to the control group. When determining the accumulation of cadmium in embryos on the 20th day of gestation, polyelement analysis of biological materials using the atomic emission method with electric arc atomization revealed a 15.83-fold increase in cadmium chloride and 9.00 times in cadmium citrate relative to the control group. Embryolethality rates increased in animals of both experimental groups while the number of live fetuses per female decreased, which indicated an obvious embryotoxic effect of cadmium compounds. It is would be useful to conduct histological studies, which will help detect changes at the tissue level and possibly explain the level of embryonic mortality.

Maternal exposure to cadmium from puberty through lactation induces abnormal reproductive development in female offspring

Four-week-old female ICR mice were exposed to Cd through drinking water from puberty through lactation to investigate the effects of reproductive development in female offspring. Our results showed that maternal Cd exposure from puberty to lactation induced vaginal opening delay, and disturbed estrous cycle in the offspring on postnatal day (PND) 21, without affecting the body weight at vaginal opening. The histopathology results showed the increased primordial follicles and the decreased secondary follicles, and the mRNA level of Amh increased in the offspring's ovaries upon Cd exposure, suggesting the inhibition of ovarian follicular development on PND21. Moreover, the level of serum estradiol reduced and genes associated with steroidogenesis (3β-Hsd, P450scc and P450arom) were downregulated upon Cd exposure on PND 21. Thus, Cd may inhibit the follicular development via disturbing the mRNA level of genes associated with steroidogenesis and then the synthesis of estradiol in prepuberty. Taken together, despite the lack of attention to estrous cycle at termination, maternal Cd exposure from puberty to lactation induced the adverse effects on reproductive development of female offspring, including the delay of vaginal opening, irregular estrous cycle and inhibition of follicular development, via disturbing the mRNA level of genes associated with follicular development and steroidogenesis.

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.

Resveratrol ameliorates toxic effects of cadmium on placental development in mouse placenta and human trophoblast cells

BACKGROUND

Cadmium (Cd) is a common heavy metal pollutant. Prenatal exposure to Cd results in adverse effects on fetal development. Placental apoptosis, inflammation, and epigenetic disruption have been implicated in Cd-induced placental toxicity. Resveratrol (Res) is a naturally occurring polyphenol with anti-apoptotic, anti-inflammatory, and epigenetic regulatory activities. In present study, the effects of Res on placental toxicity induced by Cd were evaluated.

METHODS

Pregnant CD-1 mice were fed with base diet containing 0.2% Res started on gestational day 0 (GD0), and intraperitoneally injected with 4.5 mg/kg CdCl₂ or saline once on GD9. JEG-3 cells were treated with 20 μM Res for 24 hr in the absence or presence of 20 μM CdCl₂ for the second 12 hr. The fetal outcomes, the apoptosis in placenta and JEG-3 cells, the expression of inflammatory cytokines and chemokines including tumor necrosis factor-α (TNF-α), interferon-gamma (IFN-γ), monocyte chemoattractant protein 1 (MCP-1), macrophage inflammatory protein-2 (MIP-2) and chemokine (C-X-C motif) ligand 1 (KC), and expression of endoplasmic reticulum (ER) stress markers were evaluated. The expression and activities of DNA methyltransferase (DNMT), and the activation of Akt signaling pathway were detected.

RESULTS

Cd exposure resulted in decreased fetal weight and crown-rump length while Res ameliorated these outcomes. Res suppressed Cd-induced apoptosis in placenta and JEG-3 cells, and decreased Cd-induced expression of TNF-α, IFN-γ, MCP-1, MIP-2, and KC in placenta. Cd greatly increased ER stress in placenta in mice, which was partially ameliorated by Res treatment. Res decreased Cd-induced upregulation of DNMT activity and suppressed Cd-induced expression of DNMT3B. Res restored estradiol secretion, enhances activity and protein levels of SIRT1 and inhibited Cd-induced activation of Akt signaling pathway.

CONCLUSION

Res ameliorated Cd-induced placental toxicity and regulated DNMT3 expression and PI3K/Akt pathway activation.

Paternal exposure to microcystin-LR induces fetal growth restriction partially through inhibiting cell proliferation and vascular development in placental labyrinth

Microcystin-leucine arginine (MC-LR) has reproductive and developmental toxicities. Previous studies indicated that gestational exposure to MC-LR induced fetal growth restriction in mice. The aim of this study was to further evaluate the effect of paternal MC-LR exposure before mating on fetal development. Male mice were intraperitoneally injected with either normal saline or MC-LR (10 μg/kg) daily for 35 days. Male mouse was then mated with female mice with 1:1 ratio. There was no significant difference on the rates of mating and pregnancy between MC-LR-exposed male mice and controls. Body weight and crown-rump length were reduced in fetuses whose fathers were exposed to MC-LR. Despite no difference on relative thickness of labyrinthine layer, cell proliferation, as measured by Ki67 immunostaining, was reduced in labyrinth layer of MC-LR-exposed mice. Moreover, blood sinusoid area in labyrinth layer was decreased in the fetus whose father was exposed to MC-LR before mating. Correspondingly, cross-sectional area of CD34-positive blood vessel in labyrinth layer was lower in fetuses whose fathers were exposed to MC-LR than in controls. These results provide evidence that paternal MC-LR exposure before mating induces fetal growth restriction partially through inhibiting cell proliferation and vascular development in labyrinth layer.

Umbilical Cord Blood Metal Mixtures and Birth Size in Bangladeshi Children

BACKGROUND

Studies have evaluated environmental exposure to toxic metals such as arsenic (As), cadmium (Cd), manganese (Mn), or lead (Pb) on birth size; however, information on potential effects of exposures to metal mixtures is limited.

OBJECTIVES

We assessed the association between metal mixtures (As, Cd, Mn, Pb) in umbilical cord blood and neonate size in Bangladeshi children.

METHODS

In this birth cohort study, pregnant women who were ≥18 years of age with an ultrasound-confirmed singleton pregnancy of ≤16wk gestation were recruited from two Bangladesh clinics between 2008 and 2011. Neonate size metrics were measured at the time of delivery. Metals in cord blood were measured using inductively coupled plasma mass spectrometry. We employed multivariable linear regression and Bayesian kernel machine regression (BKMR) to estimate associations of individual metals and metal mixtures with birth size parameters.

RESULTS

Data from 1,088 participants was assessed. We found a significant negative association between metal mixture and birth length and head circumference when all metal concentrations were above the 60th and 55th percentiles, respectively, compared with the median. An interquartile range (IQR) increase in log Cd concentration {log[Cd (in micrograms per deciliter)] IQR=2.51} was associated with a 0.13-standard deviation (SD) decrease in mean birth length (95% CI: -0.25, -0.02) and a 0.17-SD decrease in mean head circumference (95% CI: -0.28, -0.05), based on linear regression models adjusted for covariates and the other metals. An IQR increase in log Mn concentration {log[Mn (in micrograms per deciliter)] IQR=0.69} was associated with a 0.07-SD decrease in mean birth weight (95% CI: -0.15, 0.002).

DISCUSSION

Metal mixtures in cord blood were associated with reduced birth size in Bangladeshi children. Results from linear regression models adjusted and the BKMR mixtures analyses suggest adverse effects of Cd and Mn, as individual metal exposures, on birth size outcomes. https://doi.org/10.1289/EHP7502.

Accumulation of different metals in oyster Crassostrea gigas: Significance and specificity of SLC39A (ZIP) and SLC30A (ZnT) gene families and polymorphism variation

The Zrt/Irt-like proteins (ZIP, SLC39A) and zinc transporters (ZnT, SLC30A) are the two major gene families responsible for the import/export of Zn and other metals. In this study, the mRNA expression levels and genetic variations of eight ZnTs and 14 ZIPs were identified in Crassostrea gigas after exposure to Zn, Cd, Cu, Hg, and Pb. Metal exposure induced reactive oxygen species (ROS) and malondialdehyde (MDA) accumulation and antioxidant enzyme expression. The expanded gene numbers of superoxide dismutase (SOD) in the oysters exhibited diverse expression under exposure to the five metals, and the contrasting expressions of both ZnTs and ZIPs under different metal exposures were observed, revealing their ion-specific responses. Zn and Cu have similar transporters and induce high expression levels of ZnT1, 2, 7, and 9 and ZIP1, 3, 6, 9, 10, 11, and 14. Pb induced high expression levels of ZIP7, and 13 and ZnT5, 6, and 7, which are mainly expressed in the endoplasmic reticulum (ER). Cd induced high expression levels of ZnT1, 2, and 7 and ZIP1, 6, 9, 10, 11, and 13. Hg exposure was found to have little effect on the ZIP and ZnT expression levels. Based on 3784 single nucleotide polymorphisms (SNPs) within the ZnTs and ZIPs, genetic association analysis for Zn accumulation was conducted on 427 oyster samples. The 38 SNPs, which were located within 12 genes, were identified to be associated with Zn content (p < 0.01), explaining the phenotypic variation from 1.61% to 3.37%. One nonsynonymous mutation and related haplotypes were identified within ZIP1, explaining 1.69% of the variation in Zn. Its high expression under Zn exposure revealed its important role in Zn transportation. To the best of our knowledge, this study is the first comprehensive investigation of the transportation mechanisms of ZIPs and ZnTs under different metal exposures and the genetic effect of Zn accumulation in oysters, and provides valuable biomarkers and genetic resources to evaluate environmental metal pollution.

Cadmium triggers oxidative stress and mitochondrial injury mediated apoptosis in human extravillous trophoblast HTR-8/SVneo cells

Cadmium (Cd) is a bioaccumulative heavy metal element with potential placental toxicity during pregnancy. Up to now, however, the precise toxic effects of Cd on human placentae, particularly as they pertain to trophoblast cells remain obscure. We therefore sought to investigate the cytotoxic effects of Cd on human extravillous trophoblast HTR-8/SVneo cells and the mechanisms involved in the processes. Results in this present study showed that CdCl2 treatment significantly suppressed cell viability and induced noticeable oxidative stress in HTR-8/SVneo cells. Further studies showed that CdCl2 treatment caused distortion of mitochondrial structure, reduction of mitochondrial membrane potential (Δψm), DNA damage and G0/G1 phase arrest. Under the same condition, CdCl2 treatment increased Bax/Bcl-2 ratios by up-regulating Bax expression and down-regulating Bcl-2 expression, and activated apoptotic executive molecule caspase-3, which irreversibly induced HTR-8/SVneo cell apoptosis. N-acetyl-l-cysteine (NAC), ROS scavenger, significantly attenuated CdCl2-caused mitochondrial injury, DNA damage, G0/G1 phase arrest and apoptosis. In addition, in vivo assay suggested that CdCl2 induced trophoblast cells apoptosis but not other cells in mice placental tissue. Taken together, these data suggest that Cd selectively triggers oxidative stress and mitochondrial injury mediated apoptosis in trophoblast cells, which might contribute to placentae impairment and placental-related disorders after Cd exposure. These findings may provide new insights to understand adverse effects of Cd on placentae during pregnancy.

Developmental toxicity of cadmium in infants and children: a review

Several millions of people are exposed to cadmium worldwide due to natural and anthropogenic activities that led to their widespread distribution in the environment and have shown potential adverse effects on the kidneys, liver, heart and nervous system. Recently human and animal-based studies have been shown that In utero and early life exposure to cadmium can have serious health issues that are related to the risk of developmental disabilities and other outcomes in adulthood. Since, cadmium crosses the placental barrier and reaches easily to the fetus, even moderate or high-level exposure of this metal during pregnancy could be of serious health consequences which might be reflected either in the children’s early or later stages of life. Mortality from various diseases including cancer, cardiovascular, respiratory, kidney and neurological problems, correlation with In utero or early life exposure to cadmium has been found in epidemiological studies. Animal studies with strong evidence of various diseases mostly support for the human studies, as well as suggested a myriad mechanism by which cadmium can interfere with human health and development. More studies are needed to establish the mechanism of cadmium-induced toxicity with environmentally relevant doses in childhood and later life. In this review, we provide a comprehensive examination of the literature addressing potential long- term health issues with In utero and early life exposure to cadmium, as well as correlating with human and animal exposure studies.

Environmental cadmium exposure induces fetal growth restriction via triggering PERK-regulated mitophagy in placental trophoblasts

Cadmium (Cd), an environmental toxicant, is positively associated with fetal growth restriction (FGR). However, the mechanism by which gestational exposure to Cd induces FGR remains unclear. This study designed in vitro and in vivo experiments to explore the role of placental mitophagy in Cd-impaired fetal growth. Based on our case-control study, we also investigated the association of placental mitophagy with reduced progesterone (P4) level and all-cause FGR. We firstly found environmental Cd exposure lowered the P4 content in maternal sera, placentae and amnioticfluids of mice. The level of three mitochondrial P4 synthases, including StAR, CYP11A1 and 3β-HSD, was also reduced in Cd-treated placentae. Furthermore, Cd triggered mitophagy, as determined by the degradation of two mitochondrial proteins HSP60 and COX IV, and the accumulation of co-localizations of TOM20 with LC3B or Parkin in placental trophoblasts. Correspondingly, Cd elevated mitochondrial Parkin level in placental trophoblasts. Mdivi-1, a mitophagy inhibitor, obviously attenuated Cd-induced reduction of placental P4 and FGR in mice. Moreover, mdivi-1 and Parkin siRNA (siR) markedly reversed Cd-caused P4 synthesis inhibition in human placental trophoblasts. Interestedly, the PERK/ATF4 signaling was activated in Cd-stimulated placental trophoblasts. PERK siR inhibited mitochondrial proteins degradation in Cd-stimulated placental trophoblasts. In particularly, mitophagy activation and P4 synthesis suppression occurred in small-for-gestational-age placentae based on our case-control study. Environmental Cd exposure induced FGR via activating PERK-regulated mitophagy and inhibiting P4 synthesis in placentaltrophoblasts. Furthermore, placental mitophagy was related to the reduced progesterone level and all-cause fetal growth restriction based on our case-control study. As above, placental mitophagy maybe the common mechanism of environmental toxicants-impaired fetal growth.

Autophagy in Sertoli cell protects against environmental cadmium-induced germ cell apoptosis in mouse testes

Cadmium (Cd) was an environmental pollutant, which could result in germ cell apoptosis in testes. Sertoli-germ cell communication was vital for germ cell development and maturity. However, little was known about the effect of Sertoli cell autophagy on Cd-induced germ cell apoptosis. Here, we used male Amh-Cre+/Atg5^flox/flox (Atg5^-/-) mice, loss of autophagy-related gene 5 (Atg5) in testicular Sertoli cells, to explore the obscure effects. Atg5^-/- and Wild-type (WT) mice were given with cadmium chloride (CdCl_2, 2.0 mg/kg) for 0-24 h. Our results showed that Cd triggered testicular germ cell apoptosis, as evidenced by the increment of TUNEL-labeled germ cells, cleaved caspase3 and cleaved poly (ADP-ribose) polymerase protein level. Additionally, Cd induced testicular autophagy, as determined by elevating the level of autophagy-related proteins, including Atg5, Atg7, LC3B-II, and the gathering of LC3 puncta. 3-methyladenine, a specific autophagy inhibitor, exacerbated Cd-caused germ cell apoptosis. Inversely, rapamycin, an autophagy inducer, relieved Cd-stimulated germ cell apoptosis. Interestingly, we found that autophagy in Sertoli cells was activated in Cd-treated WT mouse testes as evidenced by the increment of LC3 puncta surrounding SOX9, a specific Sertoli cell marker. More importantly, loss of autophagy in Sertoli cells aggravated Cd-triggered germ cell apoptosis. Taken together, these data indicate that autophagy in Sertoli cells alleviates Cd-triggered germ cell apoptosis in mouse testes.

Melatonin protects against environmental stress-induced fetal growth restriction via suppressing ROS-mediated GCN2/ATF4/BNIP3-dependent mitophagy in placental trophoblasts

Gestational exposure to environmental stress induces fetal growth restriction (FGR), and thereby increasing the risk of infant death and chronic noncommunicable diseases in adults. However, the mechanism by which environmental stress induces FGR remains unclear. Based on case-control study, we found that the reduced level of melatonin (MT), a major secretory product from the pineal gland, was observed in placentae of FGR. This work was to investigate the protective effect of MT on environmental stress-caused FGR and its mechanisms. We used cadmium (Cd) as an environmental stressor to stimulate pregnant mice and thereby establishing a FGR model. The data showed that maternal Cd exposure lowered the P4 concentration in maternal sera, placentae and amniotic fluid, and caused FGR. Correspondingly, the expression of CYP11A1, a critical P4 synthase, was markedly downregulated in Cd-treated placentae. Simultaneously, Cd triggered BNIP3-dependent mitophagy in placental trophoblasts, as determined by the degradation of mitochondrial proteins, including HSP60 and COX IV, and the accumulation of puncta representing co-localization of TOM20 with LC3B or BNIP3 with LC3B. Based on our case-control study, we also found that activated BNIP3-dependent mitophagy and P4 synthesis inhibition occurred in SGA placentae. Most importantly, BNIP3 siRNA reversed Cd-induced P4 synthesis suppression in human placental trophoblasts. It is noteworthy that MT alleviated Cd-caused P4 synthesis suppression and FGR via antagonizing BNIP3-dependent mitophagy in placental trophoblasts. Further results confirmed that MT attenuated Cd-triggered BNIP3-dependent mitophagy via blocking GCN2/ATF4 signaling. Amusingly, Cd triggered oxidative stress and then activating GCN2/ATF4 signaling in placental trophoblasts. As expected, MT obviously suppressed Cd-caused reactive oxygen species (ROS) release. In the present study, we propose a neoteric mechanism by which MT protects against environmental stress-impaired P4 synthesis and fetal growth via suppressing ROS-mediated GCN2/ATF4/BNIP3-dependent mitophagy in placental trophoblasts. As above, MT is a potential therapeutic agent antagonizing environmental stress-induced developmental toxicity.

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Melatonin protects against Cd-induced fetal growth restriction.

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Melatonin attenuates Cd-induced placental P4 synthesis inhibition by mitophagy.

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Melatonin suppresses Cd-triggered placental mitophagy via blocking GCN2/ATF4.

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Melatonin blocks Cd-activated placental GCN2/ATF4 signaling via repressing ROS.

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Activated mitophagy and reduced P4 synthesis occur in SGA placentae.

Environmental exposure to cadmium impairs fetal growth and placental angiogenesis via GCN-2-mediated mitochondrial stress

Cadmium (Cd), a well-known environmental pollutant, can lead to placental insufficiency and fetal growth restriction. However, the underlying mechanism is unknown. The purpose of our study is to explore the effect of Cd on placental angiogenesis and its mechanism using in vitro and in vivo models. Results found that gestational Cd exposure obviously decreased placental weight and impaired placental vascular development in mice. Correspondingly, Cd exposure evidently downregulated the expression of VEGF-A protein (a key indicator of angiogenesis) and progesterone receptor (PR) in placental trophoblasts. Further experiment showed that lentivirus PR overexpression reversed Cd-caused the reduction of VEGF-A level in human placental trophoblasts. In addition, Cd significantly reduced progesterone level, down-regulated the expression of key progesterone synthase (StAR, CYP11A1), and activated mitochondrial stress response and GCN-2/p-eIF2α signaling in placental trophoblasts. Additional experiment showed that GCN-2 siRNA pretreatment markedly alleviated Cd-activated mitochondrial stress response, restored Cd-downregulated the expression of CYP11A1, reversed Cd-reduced the level of progesterone and VEGF-A in human placental trophoblasts. Finally, our case-control study confirmed that impaired placental angiogenesis and reduced progesterone level occurred in all-cause small for gestational age placenta. Taken together, environmental exposure to Cd impairs fetal growth and placental angiogenesis via GCN-2-mediated mitochondrial stress.

An assessment of serum-dependent impacts on intracellular accumulation and genomic response of per- and polyfluoroalkyl substances in a placental trophoblast model

Per- and polyfluoroalkyl substances (PFAS), a class of environmental contaminants, have been detected in human placenta and cord blood. The mechanisms driving PFAS-induced effects on the placenta and adverse pregnancy outcomes are not well understood. This study investigated the impact of perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA), and a replacement PFAS known as hexafluoropropylene oxide dimer acid (HFPO-DA, tradename GenX) on placental trophoblasts in vitro. Several key factors were addressed. First, PFAS levels in cell culture reagents at baseline were quantified. Second, the role of supplemental media serum in intracellular accumulation of PFAS in a human trophoblast (JEG3) cell line was established. Finally, the impact of PFAS on the expression of 96 genes involved in proper placental function in JEG3 cells was evaluated. The results revealed that serum-free media (SFM) contained no detectable PFAS. In contrast, fetal bovine serum-supplemented media (SSM) contained PFNA, PFUdA, PFTrDA, and 6:2 FTS, but these PFAS were not detected internally in cells. Intracellular accumulation following 24 hr treatments was significantly higher when cultured in SFM compared to SSM for PFOS and PFOA, but not HFPO-DA. Treatment with PFAS was associated with gene expression changes (n = 32) in pathways vital to placental function, including viability, syncytialization, inflammation, transport, and invasion/mesenchymal transition. Among the most robust PFAS-associated changes were those observed in the known apoptosis-related genes, BAD and BAX. These results suggest a complex relationship between PFAS, in vitro culture conditions, and altered expression of key genes necessary for proper placentation.

Reduced hepatic metallothionein expression in first trimester fetuses in response to intrauterine smoking exposure: a consequence of low maternal zinc levels?

STUDY QUESTION

Does maternal smoking in early pregnancy affect metallothionein 1 and 2 (MT1 and MT2) mRNA and protein expression in first trimester placenta or embryonic/fetal liver?

SUMMARY ANSWER

In the first trimester, MT protein expression is seen only in liver, where smoking is associated with a significantly reduced expression.

WHAT IS KNOWN ALREADY

Zinc homeostasis is altered by smoking. Smoking induces MT in the blood of smokers properly as a result of the cadmium binding capacities of MT. In term placenta MT is present and smoking induces gene and protein expression (MT2 in particular), but the MT presence and response to smoking have never been examined in first trimester placenta or embryonic/fetal tissues.

STUDY DESIGN, SIZE, DURATION

Cross sectional study where the presence of MT mRNA and protein was examined at the time of the abortion. The material was collected with informed consent after surgical intervention and frozen immediately. For protein expression analysis, liver tissue originating from smoking exposed n = 10 and unexposed n = 12 pregnancies was used. For mRNA expression analyses, placental tissue originating from smokers n = 19 and non-smokers n = 23 and fetal liver tissue from smoking exposed n = 16 and smoking unexposed pregnancies n = 13, respectively, were used.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Tissues were obtained from women who voluntarily and legally chose to terminate their pregnancy between gestational week 6 and 12. Western blot was used to determine the protein expression of MT, and real-time PCR was used to quantify the mRNA expression of MT2A and eight MT1 genes alongside the expression of key placental zinc transporters: zinc transporter protein-1 (ZNT1), Zrt-, Irt-related protein-8 and -14 (ZIP8 and ZIP14).

MAIN RESULTS AND THE ROLE OF CHANCE

A significant reduction in the protein expression of MT1/2 in liver tissue (P = 0.023) was found by western blot using antibodies detecting both MT forms. Overall, a similar tendency was observed on the mRNA level although not statistically significant. Protein expression was not present in placenta, but the mRNA regulation suggested a down regulation of MT as well. A suggested mechanism based on the known role of MT in zinc homeostasis could be that the findings reflect reduced levels of easily accessible zinc in the blood of pregnant smokers and hence a reduced MT response in smoking exposed fetal/embryonic tissues.

LIMITATIONS AND REASONS FOR CAUTION

Smoking was based on self-reports; however, our previous studies have shown high consistency regarding cotinine residues and smoking status. Passive smoking could interfere but was found mainly among smokers. The number of fetuses was limited, and other factors such as medication and alcohol might affect the findings. Information on alcohol was not consistently obtained, and we cannot exclude that it was more readily obtained from non-users. In the study, alcohol consumption was reported by a limited number (less than 1 out of 5) of women but with more smokers consuming alcohol. However, the alcohol consumption reported was typically limited to one or few times low doses. The interaction between alcohol and smoking is discussed in the paper. Notably we would have liked to measure zinc status to test our hypothesis, but maternal blood samples were not available.

WIDER IMPLICATIONS OF THE FINDINGS

Zinc deficiency-in particular severe zinc deficiency-can affect pregnancy outcome and growth. Our findings indicate that zinc homeostasis is also affected in early pregnancy of smokers, and we know from pilot studies that even among women who want to keep their babies, the zinc status is low. Our findings support that zinc supplements should be considered in particular to women who smoke.

STUDY FUNDING/COMPETING INTEREST(S)

We thank the Department of Biomedicine for providing laboratory facilities and laboratory technicians and the Lundbeck Foundation and Læge Sofus Carl Emil Friis og Hustru Olga Doris Friis Legat for financial support. The authors have no competing interests to declare.

TRIAL REGISTRATION NUMBER

N/A.

Cigarette Smoking during Pregnancy: Effects on Antioxidant Enzymes, Metallothionein and Trace Elements in Mother-Newborn Pairs

The effect of maternal smoking as a source of exposure to toxic metals Cd and Pb on superoxide dismutase (SOD) and glutathione peroxidase (GPx) activity, metallothionein (MT), Cd, Pb, Cu, Fe, Mn, Se and Zn concentrations were assessed in maternal and umbilical cord blood and placenta in 74 healthy mother-newborn pairs after term delivery. Sparse discriminant analysis (SDA) was used to identify elements with the strongest impact on the SOD, GPx and MT in the measured compartments, which was then quantified by multiple regression analysis. SOD activity was lower in maternal and cord plasma, and higher in the placenta of smokers compared to non-smokers, whereas GPx activity and MT concentration did not differ between the groups. Although active smoking during pregnancy contributed to higher maternal Cd and Pb concentrations, its contribution to the variability of SOD, GPx or MT after control for other elements identified by SDA was not significant. However, an impaired balance in the antioxidant defence observed in the conditions of relatively low-to-moderate exposure levels to Cd and Pb could contribute to an increased susceptibility of offspring to oxidative stress and risk of disease development later in life. Further study on a larger number of subjects will help to better understand complex interactions between exposure to toxic elements and oxidative stress related to maternal cigarette smoking.

Sp1 participates in the cadmium-induced imbalance of the placental glucocorticoid barrier by suppressing 11β-HSD2 expression

Cadmium (Cd) is widely present in the environment as a heavy metal poison. Prenatal Cd exposure can damage the placental glucocorticoid barrier, leading to foetal growth restriction (FGR), but the molecular mechanism is unknown. We aimed to study the effects of prenatal Cd exposure on 11β-HSD2 and its possible involvement in Cd induced damage in the placental glucocorticoid barrier. Pregnant rats were treated with CdCl2 (1.0 mg/kg/day) by gavage from gestational day (GD) 9-19. Maternal exposure to Cd increased the FGR rate of the offspring, and the levels of corticosterone in the placenta, maternal and foetal serum. Further in vitro experiments with placenta or JEG3 cells indicated that Cd was able to decrease 11β-HSD2 and Sp1 expression in trophoblast cells but did not affect 11β-HSD1. Additionally, decreased p300 and Sp1 enrichment at the 11β-HSD2 promoter region was observed in the cells treated with Cd. Decreasing or increasing Sp1 expression accordingly inhibited or promoted the expression of 11β-HSD2 and further decreased or increased p300 and Sp1 enrichment at the 11β-HSD2 promoter region. In conclusion, Cd inhibits the expression of 11β-HSD2 by affecting the binding of p300 to 11β-HSD2 via a decrease in Sp1 expression, which damages the placental glucocorticoid barrier and exposes the foetus to excessive glucocorticoids, resulting in FGR. These findings reveal a possible underlying molecular mechanism by which Cd exposure leads to FGR.

Maternal cadmium exposure during late pregnancy causes fetal growth restriction via inhibiting placental progesterone synthesis

Cadmium (Cd) is a major environmental pollutant. Maternal Cd exposure throughout pregnancy caused fetal growth restriction (FGR). However, the pivotal time window of Cd-evoked FGR and its mechanism are unknown. Here, we will establish a murine model to explore the effects of maternal Cd exposure at different stages of gestation on fetal growth and placental progesterone biosynthesis. Pregnant mice were randomly divided into four groups. For Cd groups, mice were given with CdCl₂ (150 mg/L) through drinking water at early (GD0-GD6), middle (GD7-GD12) and late (GD13-GD17) gestation, respectively. The controls received reverses osmosis (RO) water. Results showed that maternal cadmium exposure only in late gestation lowered fetal weight and length. Correspondingly, placental Cd level in late gestational Cd exposure is the highest among three different gestational stages. Although gestational Cd exposure had few adverse effects in the weight and diameter of mouse placenta, placental vascular development, as determined by H&E staining and cluster of differentiation-34 (CD-34) immunostaining, was impaired in mice exposed to Cd during late pregnancy. Additionally, late gestational exposure to cadmium markedly reduced progesterone level in maternal serum and placenta. In line, the expression of key progesterone synthetases, including steroidogenic acute regulatory protein (StAR) and 3β-hydroxyl steroid dehydrogenase (3β-HSD), was obviously downregulated in placenta from mice was exposed Cd during late pregnancy. These data suggest that maternal Cd exposure during late pregnancy, but not early and middle pregnancy, induces fetal growth restriction partially via inhibiting placental progesterone synthesis.

Activation of autophagy inhibits cadmium-triggered apoptosis in human placental trophoblasts and mouse placenta

Cadmium (Cd), a ubiquitous environmental pollutant, is known to impair placental development. However, the underlying mechanisms remain unclear. The present study used in vivo and in vitro models to investigate the effects of Cd on apoptosis and autophagy in placental trophoblasts and its mechanism. Pregnant mice were exposed to CdCl₂ (4.5 mg/kg) on gestational day (GD) 9. Human JEG-3 cells were exposed to CdCl₂ (0-40 μM) for different time points. Gestational Cd exposure obviously lowered the weight and diameter of mouse placentas. Number of TUNEL-positive cells was markedly elevated in Cd-administered mouse placentas and JEG-3 cells. Correspondingly, Cd significantly up-regulated cleaved caspase-3 protein level, a key indicator of apoptosis, in murine placentas and JEG-3 cells. Simultaneously, Cd also triggered autophagy, as determined by an elevation of LC3B-II and p62 protein, and accumulation of LC3-positive puncta, in placental trophoblasts. Chloroquine an autophagy inhibitor, obviously aggravated Cd-induced apoptosis in JEG-3 cells. By contrast, rapamycin, a specific autophagy inducer, significantly alleviated Cd-triggered apoptosis in JEG-3 cells. Mechanistically, autophagy inhibited Cd-induced apoptosis mainly via degrading caspase-9. Co-localizations of p62, a classical autophagic receptor, and caspase-9 were observed in Cd-stimulated human JEG-3 cells. Moreover, p62 siRNAs pretreatment markedly blocked the degradation of caspase 9 proteins via Cd-activated autophagy in JEG-3 cells. Collectively, our data suggest that activation of autophagy inhibits Cd-induced apoptosis via p62-mediated caspase-9 degradation in placental trophoblasts. These findings provide a new mechanistic insight into Cd-induced impairments of placental and fetal development.

Maternal Heavy Metal Exposure, Thyroid Hormones, and Birth Outcomes: A Prospective Cohort Study

CONTEXT

Maternal thyroid hormones during pregnancy play a critical role in fetal development. However, whether maternal heavy metal exposure affects their thyroid hormones and the effects on fetal growth are still unclear.

OBJECTIVE

To explore the effect of heavy metal exposure on maternal thyroid hormones and the potential mediation role of thyroid hormones on birth outcomes.

METHODS

Concentrations of heavy metals in urine samples and thyroid hormones in blood samples of 675 pregnant women were measured during early pregnancy in a cohort study conducted in China. Multivariable linear regressions were applied to explore the associations of maternal urinary heavy metal levels with both maternal thyroid hormones and birth outcomes. Mediation analyses were performed to assess the mediation role of thyroid hormones in these associations.

RESULTS

Maternal urinary vanadium (V) exhibited an inverse association with free T3 (FT3) and FT3/free T4 (FT4) ratio levels. Urinary arsenic (As) and lead (Pb) had inverse relationships with FT3. We also observed the positive associations of maternal FT3 and FT3/FT4 ratio with birthweight. The mediation analyses suggested that 5.33% to 30.57% of the associations among V, As, and Pb levels and birth size might be mediated by maternal FT3 or FT3/FT4 ratio.

CONCLUSIONS

We have shown that maternal exposures to V, As, and Pb at early pregnancy were associated with decreased maternal FT3 or FT3/FT4 ratio, which might contribute to reduced birthweight. Mediation analyses indicated that maternal thyroid hormone was a possible mediator of the association between urinary heavy metals and birth size.

Recommended acceptable levels of maternal serum typical toxic metals from the perspective of spontaneous preterm birth in Shanxi Province, China

Preterm birth is an important issue of public reproductive health worldwide. The effects of the toxic metals on the likelihood of spontaneous preterm birth (SPB) are still under discussion. Our study aimed to investigate the association between maternal exposure to the five typical toxic metals or metalloid (i.e. arsenic (As), cadmium (Cd), chromium (Cr), mercury (Hg), and lead (Pb)) and the SPB likelihood. The mothers delivering fetus with SPB (cases) and those with term healthy birth (controls) were chosen from a prospective birth cohort of 3201 women carried out in Shanxi Province, China. A total of 147 SPB cases and 381 controls were included in our nested case-control study. We collected maternal general information by questionnaire and collected their blood sample during recruitment. The serum concentrations of the five toxic metals were measured by inductively coupled-plasma mass spectrometry. We found that the demographic information between the cases and controls were well balanced. The participants in our study had relatively higher serum As concentration. For the other toxic metals (i.e. Cd, Cr, Hg, and Pb), their serum concentrations were overall in the middle range of those from general population. There were no significant associations of the serum concentrations of the five concerned toxic metals with the SPB likelihood. Our study results overall did not support that maternal exposure to As or Cd significantly contribute to the SPB risk in the current exposure level, as well as the other three toxic metals. We further proposed their upper concentration limits in maternal serum from the perspective of SPB likelihood during the early pregnant period, i.e. 18.2 ng/mL of As, 1.05 ng/mL of Cd, 0.96 ng/mL of Cr, 1.07 ng/mL of Hg, and 1.54 ng/mL of Pb.

Cadmium exposure during pregnancy and lactation: materno-fetal and newborn repercussions of Cd(ii), and Cd-metallothionein complexes

Cadmium (Cd) is a non-physiological heavy metal that can be harmful at low concentrations. Increasing anthropogenic activities are incrementing the risk of accumulation of this heavy metal in different organs and tissues of the body. In the case of pregnant women, the threat is more serious due to the implications affecting not only their own health but also fetal development as well. Metallothioneins (MTs), small cysteine-rich proteins, are involved in zinc (Zn) and copper homeostasis in mammals but can, however, also bind with Cd if present. The accumulation of Cd in maternal tissues (e.g. placenta, maternal blood, and mammary glands) induces the synthesis of MTs, preferably MT2, in an attempt to sequester the metal to avoid toxicity. The formed Cd-MT complexes will avoid the Cd transport from the placenta to the fetus and end up accumulating in the maternal kidneys. At the same time, high concentrations of MTs will increase the formation of Zn-MT complexes, therefore decreasing the amount of Zn ions available to be transported to the fetus by means of Zn transporters such as ZnT2, ZIP14 and DMT1. Although MTs cannot transport Cd from the mother to the fetus, the divalent DMT1 transporter is suggested to carry the metal to the fetus. As a consequence, the low levels of Zn(ii) in the fetus, together with the presence of Cd(ii) coming from the mother either via the placenta and cord blood or via breast milk induce changes in the fetal development including fetal growth retardation, and low weight or height of the newborn. Likewise, the concentrations of Cd(ii) in the newborn can cause alterations such as cognitive disabilities. In summary, the presence of Cd(ii) in the maternal tissues will induce MT synthesis in an attempt to detoxify these tissues and reduce the possible toxicity of Cd in fetal and newborn tissues.

Placental metal concentrations in relation to placental growth, efficiency and birth weight

The quality of the intrauterine environment, in which the placenta plays a critical role, affects birth outcomes and lifelong health. The effect of metal contaminants on the growth and functioning of the placenta have not been widely reported but may provide insights into how metal exposures lead to these outcomes. We examined relationships between placental concentrations of cadmium (Cd), arsenic (As), mercury (Hg) and lead (Pb) and measures of placental growth and functioning (placental weight, placental efficiency (the log ratio of placental weight and birth weight), chorionic disc area and disc eccentricity) as part of the New Hampshire Birth Cohort Study (N = 1159). We additionally examined whether these associations were modified by placental concentrations of essential elements zinc (Zn) and selenium (Se). Associations were evaluated using generalized linear models. Multivariable-adjusted differences in placental weight were - 7.81 g (95% CI: -15.42, -2.48) with every ng/g increase in the Cd concentration of placenta (p-Value = 0.0009). Greater decrements in placental weight and efficiency associated with placental Cd were observed for females. For placentae with below median Zn and Se concentrations, decrements in placental weight were - 8.81 g (95% CI: -16.85, -0.76) and - 13.20 g (95% CI: -20.70, -5.70) respectively. The Cd concentration of placenta was also associated with reductions in placental efficiency both overall, and in Zn- and Se-stratified models. No appreciable differences were observed with other elements (As, Hg or Pb) and with other placental measures (chorionic disc area and disc eccentricity). In structural equation models, placental weight was a mediator in the relation between placental Cd concentration and reduced birth weight. Our findings suggest a role of interacting essential and contaminant elements on birth weight that may be mediated by changes in the growth and function of the placenta.

Cadmium: Toxic effects on placental and embryonic development

Cadmium is a non-essential trace metal that has strong teratogenic and mutagenic effects in living organisms. The content is more highly enriched in women than in men and can enter the embryo through the placenta and destroy the placenta's morphological structure, resulting in fetal growth restriction. In this report, we review published data linking pregnancy exposure to cadmium to placenta and fetal growth and development toxicity and summarize the related mechanisms. An understanding of how cadmium exposure contributes to placental and fetal development is necessary for the development of prevention and control strategies for fetal development defects caused by cadmium exposure during pregnancy.

Impact of maternal low-level cadmium exposure on glucose and lipid metabolism of the litter at different ages after weaning

Cadmium (Cd) is a metal which may participate in the development of type II diabetes even if Cd exposure levels are mild. However, experimental studies focusing on daily environmentally relevant doses are scarce, particularly for glucose metabolism of the offspring of chronically exposed mothers. The aim is to measure the impact of maternal low level Cd exposure on glucose and lipid metabolism of offspring. Female rats were exposed to 0, 50 or 500 μg.kg^-1.d^-1 of CdCl₂, 21 days before mating and during 21 days of gestation and 21 days of lactation. Pups exposure was organized in 3 groups (control, Cd1, Cd2) according to renal dams' Cd burden. Parameters of glucose and lipid metabolisms were measured for the pups on post-natal day 21, 26 and 60. Maternal Cd exposure led to significant amounts of Cd in the liver and kidney of pups. At weaning, insulin secretion upon glucose stimulation was unchanged, but the removal of circulating glucose was slower for pups born from the lowest impregnated dams (Cd1). Five days after, glucose tolerance of all groups was identical. Thus, this loss of insulin sensitivity was reversed, in part by increased adiponectin secretion for the Cd1 group. Furthermore, pups from dams accumulating the highest levels of Cd (Cd2) exhibited a compensatory increased insulin pancreatic secretion, together with increased circulating non-esterified fatty acids, indicating the establishment of insulin resistance, 2 months after birth. This study has demonstrated the influence of maternal exposure to low levels of Cd on glucose homeostasis in the offspring that might increase the risk of developing type II diabetes later in life.

Associations between the Level of Trace Elements and Minerals and Folate in Maternal Serum and Amniotic Fluid and Congenital Abnormalities

Congenital birth defects may result in a critical condition affecting the baby, including severe fetal/neonatal handicap and mortality. Several studies have shown that genetic, nutritional, and environmental factors may have an impact on fetal development and neonatal health. The relevance of essential and toxic elements on fetal development has not yet been fully investigated, and the results of recent research indicate that these elements may be crucial in the assessment of the risk of malformations in neonates. We determined the association between essential and toxic elements and the level of folate in maternal serum (MS) and amniotic fluid (AF), along with neonatal abnormalities. A total of 258 pregnant Polish women in the age group of 17⁻42 years participated in this study. AF and MS were collected during vaginal delivery or during cesarean section. An inductively coupled plasma mass spectrometry technique was used to determine the levels of various elements in AF and MS. The results of this exploratory study indicate that the levels of essential and toxic elements are associated with fetal and newborn anatomical abnormalities and growth disorders.

Dietary Cadmium Intake and Sources in the US

Cadmium (Cd) is a toxic heavy metal that can contribute to numerous diseases as well as increased mortality. Diet is the primary source of Cd exposure for most individuals, yet little is known about the foods and food groups that contribute most substantially to dietary Cd intake in the US. Therefore, the objective of this study was to estimate dietary Cd intake and identify major food sources of Cd in the US population and among subgroups of the population. Individuals aged 2 years and older from the National Health and Nutrition Examination Survey (NHANES) 2007⁻2012 were included in this study (n = 12,523). Cd intakes were estimated from two days of 24-h dietary recalls by matching intake data with the Cd database of the Food and Drug Administration (FDA)'s Total Diet Study 2006 through 2013. The average dietary Cd consumption in the population was 4.63 μg/day, or 0.54 μg/kg body weight/week, which is 22% of the tolerable weekly intake (TWI) of 2.5 μg/kg body weight/week. Greater daily Cd intakes were observed in older adults, males, those with higher income, higher education, or higher body mass index. The highest Cd intakes on a body weight basis were observed in children 10 years and younger (38% of TWI), underweight individuals (38% of TWI), and alcohol non-consumers (24% of TWI). The food groups that contributed most to Cd intake were cereals and bread (34%), leafy vegetables (20%), potatoes (11%), legumes and nuts (7%), and stem/root vegetables (6%). The foods that contributed most to total Cd intake were lettuce (14%), spaghetti (8%), bread (7%), and potatoes (6%). Lettuce was the major Cd source for Caucasians and Blacks, whereas tortillas were the top source for Hispanics, and rice was the top contributor among other ethnic subgroups including Asians. This study provides important information on the dietary Cd exposure of Americans, and identifies the groups with the greatest dietary Cd exposure as well as the major sources of dietary Cd among sociodemographic subgroups.

Maternal Cadmium Levels During Pregnancy and the Relationship with Preeclampsia and Fetal Biometric Parameters

Preeclampsia, which is caused by multiple factors, still remains one of the most serious complications of pregnancy. This study was designed to determine cadmium levels in women with preeclampsia compared to those of normotensive women. In this case-control study, maternal blood, umbilical cord blood, and placental cadmium levels were measured by an inductively coupled plasma mass spectrometry system in 51 women presenting consecutively with preeclampsia and 51 normotensive pregnant women. Groups were matched for maternal age, parity, and gestational age. Birth outcomes were recorded, such as gestational age at delivery, birth weight, and Apgar score. Median (interquartile range [IQR]) blood cadmium concentration was 1.21 μg/L (0.76-1.84 μg/L) and 1.09 μg/L (0.72-1.31 μg/L) in women with preeclampsia and normotensive, respectively; values for placental cadmium levels of women with preeclampsia and normotensive were 3.61 μg/kg (2.19-4.37 μg/kg) and 4.28 μg/kg (3.06-5.71 μg/kg), respectively. We observed a statistically significant increase in blood and placental cadmium levels in women with preeclampsia compared to healthy pregnant women. After adjusting for pre-pregnancy body mass index, maternal age, parity, gestational age at sample collection, and maternal calcium and magnesium levels, the odds ratio of having preeclampsia in the high tertile was markedly increased (odds ratio, 7.83 [95% CI, 1.64-37.26]) compared with the low tertile. Interestingly, there was no difference in the cadmium level in umbilical cord blood between the groups. Within the preeclamptic group, higher cadmium status was significantly associated with decreased birth weight. Our study suggested that elevated cadmium level in the maternal circulation could potentially increase the risk of preeclampsia. The results also demonstrate that higher cadmium status may contribute to fetal growth restriction in preeclamptic patients.

Chronic cadmium exposure induced hepatic cellular stress and inflammation in aged female mice

Previous studies have revealed that acute cadmium (Cd) exposure led to inflammation in different organs through an oxidative stress mechanism. However, whether chronic Cd exposure induces inflammation in liver and the mechanistic link between inflammation and cell stress remains unclear. In the present study, we investigated the effects of chronic Cd exposure on hepatic cellular stress and inflammatory responses. Female CD1 mice were administrated with CdCl₂ (10 and 100 mg/L) in drinking water for 57 weeks. Our results showed that the mRNA levels of Inos and the protein content of HO-1, markers of oxidative stress, were markedly increased in Cd-treated mice. In addition, the protein level of GRP78, the chaperone of endoplasmic reticulum (ER) stress, was significantly increased in Cd-treated mice. The expression of the proteins CHOP and peIF2α, two proteins downstream of ER stress, was also upregulated in the Cd-100 mg/L and Cd-10 mg/L group, respectively. Moreover, there were increased inflammatory cells existing in liver after Cd administration. Besides, there was a significant elevation in the mRNA level of Mip-2, Il-10 and Il-12 in the Cd-100 mg/L group. The mRNA level of Tgf-β was also upregulated in Cd-treated mice. Moreover, we also found that the number of Ki67-positive hepatic cells was increased in the Cd-10 mg/L group. Hence, our results indicated that chronic Cd exposure induced oxidative stress, ER stress, inflammatory responses and proliferation in the liver of aged female mice.