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.

Placental BCRP transporter reduces cadmium accumulation and toxicity in immortalized human trophoblasts

Cadmium (Cd) is a ubiquitous environmental metal detectable in most pregnant women. Animal and human studies demonstrate that in utero exposure to Cd reduces birth weight and impairs perinatal growth due to placental toxicity. BCRP is a prominent transporter that can efflux xenobiotics from the placenta. This study sought to investigate Cd transport and toxicity in cultured human BeWo trophoblasts with reduced expression and function of the placental barrier transporter BCRP. Knockdown (KD) of BCRP protein expression and function in BeWo trophoblasts increased the intracellular accumulation of Cd by 100% following treatment with 1 μM CdCl2. No change in the expression of Cd uptake transporters was observed between control and BCRP-KD cells. Reduced BCRP expression impaired viability of BeWo cells exposed to CdCl2 for 48 hr (BCRP-KD IC50: 11 μM, control cells IC50: 18 μM). Moreover, BCRP-KD cells were more sensitive to CdCl2-induced cytotoxicity compared to control BeWo cells. CdCl2 treatment strongly induced the expression of the metal-binding protein metallothionein (MT) in both control and BCRP-KD cells, with significantly greater MT upregulation in Cd-treated BCRP-KD cells. These data suggest that the BCRP transporter reduces Cd accumulation in syncytiotrophoblasts, which may be one mechanism to reduce subsequent toxicity to the placenta and developing fetus.

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.

Development of a human iPSC-derived placental barrier-on-chip model

Although recently developed placenta-on-chip systems opened promising perspectives for placental barrier modeling, they still lack physiologically relevant trophoblasts and are poorly amenable to high-throughput studies. We aimed to implement human-induced pluripotent stem cells (hiPSC)-derived trophoblasts into a multi-well microfluidic device to develop a physiologically relevant and scalable placental barrier model. When cultured in a perfused micro-channel against a collagen-based matrix, hiPSC-derived trophoblasts self-arranged into a 3D structure showing invasive behavior, fusogenic and endocrine activities, structural integrity, and expressing placental transporters. RNA-seq analysis revealed that the microfluidic 3D environment boosted expression of genes related to early placental structural development, mainly involved in mechanosensing and cell surface receptor signaling. These results demonstrated the feasibility of generating a differentiated primitive syncytium from hiPSC in a microfluidic platform. Besides expanding hiPSC-derived trophoblast scope of applications, this study constitutes an important resource to improve placental barrier models and boost research and therapeutics evaluation in pregnancy.

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.

Iron Metabolism and Ferroptosis in Physiological and Pathological Pregnancy

Iron is a vital element in nearly every living organism. During pregnancy, optimal iron concentration is essential for both maternal health and fetal development. As the barrier between the mother and fetus, placenta plays a pivotal role in mediating and regulating iron transport. Imbalances in iron metabolism correlate with severe adverse pregnancy outcomes. Like most other nutrients, iron exhibits a U-shaped risk curve. Apart from iron deficiency, iron overload is also dangerous since labile iron can generate reactive oxygen species, which leads to oxidative stress and activates ferroptosis. In this review, we summarized the molecular mechanism and regulation signals of placental iron trafficking under physiological conditions. In addition, we revealed the role of iron metabolism and ferroptosis in the view of preeclampsia and gestational diabetes mellitus, which may bring new insight to the pathogenesis and treatment of pregnancy-related diseases.

Gestational Cd Exposure in the CD-1 Mouse Sex-Specifically Disrupts Essential Metal Ion Homeostasis

In CD-1 mice, gestational-only exposure to cadmium (Cd) causes female-specific hepatic insulin resistance, metabolic disruption, and obesity. To evaluate whether sex differences in uptake and changes in essential metal concentrations contribute to metabolic outcomes, placental and liver Cd and essential metal concentrations were quantified in male and female offspring perinatally exposed to 500 ppb CdCl2. Exposure resulted in increased maternal liver Cd+2 concentrations (364 µg/kg) similar to concentrations found in non-occupationally exposed human liver. At gestational day (GD) 18, placental Cd and manganese concentrations were significantly increased in exposed males and females, and zinc was significantly decreased in females. Placental efficiency was significantly decreased in GD18-exposed males. Increases in hepatic Cd concentrations and a transient prenatal increase in zinc were observed in exposed female liver. Fetal and adult liver iron concentrations were decreased in both sexes, and decreases in hepatic zinc, iron, and manganese were observed in exposed females. Analysis of GD18 placental and liver metallothionein mRNA expression revealed significant Cd-induced upregulation of placental metallothionein in both sexes, and a significant decrease in fetal hepatic metallothionein in exposed females. In placenta, expression of metal ion transporters responsible for metal ion uptake was increased in exposed females. In liver of exposed adult female offspring, expression of the divalent cation importer (Slc39a14/Zip14) decreased, whereas expression of the primary exporter (Slc30a10/ZnT10) increased. These findings demonstrate that Cd can preferentially cross the female placenta, accumulate in the liver, and cause lifelong dysregulation of metal ion concentrations associated with metabolic disruption.

Human placental cell line HTR-8/SVneo accumulates cadmium by divalent metal transporters DMT1 and ZIP14

Cadmium (Cd) is a global pollutant that accumulates in the placenta and can cause placental dysfunction. Although iron transporters have been suggested to participate in placental Cd uptake, it is still unknown which transporters are actually involved in this process. We specifically aimed to study the role of three iron transporters in the uptake of Cd into the placental cell line HTR-8/SVneo. For this purpose, Divalent Metal Transporter (DMT)1 and ZRT/IRT like protein (ZIP)8 and ZIP14 were downregulated and changes in cellular Cd levels analysed in relation to controls. As clearly shown by the reduction of the Cd content by ∼60% in DMT1- and ZIP14-downregulated cells, the two proteins are essential for Cd accumulation in HTR-8/SVneo cells. Using a validated antibody, we show DMT1 to be localised in situ in trophoblast and stromal cells. We further wanted to investigate how placental cells cope with Cd loading and which metallothionein (MT) isoforms they express. Cd-exposed cells accumulate Cd in a dose-dependent manner and upregulate MT2A accordingly (up to 15-fold induction upon 5 μM CdCl₂ treatment for 72 h). 5 μM Cd exposure for 72 h decreased cell number to 60%, an effect that was aggravated by MT2A depletion (cell number reduced to 30%) indicating additive effects. In conclusion, our data suggest that DMT1 and ZIP14 are required for Cd uptake into human placental cells that upregulate MT2A to store and detoxify the metal. Cd storage in the placenta reduces Cd transport to the fetus, which, however, could impair placental functions and fetal development.

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.

Role of metallothionein-like cadmium-binding protein (MTLCdBP) in the protective mechanism against cadmium toxicity in the testis

The role of metallothionein (MT)-like cadmium (Cd) binding protein (MTLCdBP) in protecting the testes against Cd toxicity was examined. In the acute Cd exposure treatment, cadmium chloride was intraperitoneally injected at 2 mg Cd/kg to Wistar male rats. In the chronic Cd toxicity treatments, 20 mg Cd/kg/d was orally administered for 5 d a week for 5, 10, and 15 wk. MT (-I,-II) and MTLCdBP were measured using ELISA and Cd-Hem methods, respectively. Testicular tissues were immunostained with antibodies of MT-I,-II, MT-III, and MTLCdBP. Expression of HO1, OGG, iNOS, COX2, and p53 was measured by RT-PCR. Cd concentration in the testis increased dose-dependently in response to Cd exposure. MTLCdBP concentration increased markedly with increasing Cd accumulation. Significant increases in expression of iNOS, HO1, COX2, and OGG1 were observed in the acute exposure treatment. In the chronic oral administration group, expression of MT-I, MT-II, MT-III, iNOS, HO1, and COX2 did not change. Positive immunostaining of MTLCdBP was observed in testicular interstitial tissue. In the testis protected from Cd toxicity, MTLCdBP induction increased significantly with increasing Cd accumulation. Our results suggest that MTLCdBP plays an important role in protecting the testis against Cd toxicity.

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.

Exposure of cadmium via smoking and drinking water on zinc levels of biological samples of malnutrition pregnant women: A prospective cohort study

In present study, the interaction of a toxic (cadmium) and essential element (zinc) was determined in scalp hair of pregnant and non-pregnant women resident in a rural area of Thraparkar, Pakistan, where malnutrition is prevalent. In the malnourished group (pregnant and nonpregnant women), deficiency of the essential element (zinc) due to malnutrition and exposure of toxic metal (cadmium) via non-branded cigarette smoking and drinking groundwater were carried out. For comparative purposes, scalp hair samples were also collected from pregnant and non-pregnant women, residing in Hyderabad city, consuming municipal treated drinking water and smoking branded cigarette, termed as the reference group. The domestic treated and ground water, as well as the branded and non-branding cigarettes were analysed for cadmium (Cd). Whereas Zinc (Zn) and Cd were determined in scalp hair samples of malnutrioned and reference women. The groundwater indicated 5 to 12 fold higher levels of Cd than the WHO recommended value in drinking water. Whereas the content of Cd in locally made non-branded cigarettes was found to be two fold higher than branded cigarettes. These data indicate that the malnourished pregnant and non-pregnant smokers women group had three to four times higher levels of Cd in their scalp hair samples than those values obtained for reference non smokers. Whereas, the content of Zn in scalp hair samples of the reference women was ∼20% higher than the malnourished group.

Intrauterine Exposure to Cadmium Reduces HIF-1 DNA-Binding Ability in Rat Fetal Kidneys

During embryonic development, some hypoxia occurs due to incipient vascularization. Under hypoxic conditions, gene expression is mainly controlled by hypoxia-inducible factor 1 (HIF-1). The activity of this transcription factor can be altered by the exposure to a variety of compounds; among them is cadmium (Cd), a nephrotoxic heavy metal capable of crossing the placenta and reaching fetal kidneys. The goal of the study was to determine Cd effects on HIF-1 on embryonic kidneys. Pregnant Wistar rats were exposed to a mist of isotonic saline solution or CdCl₂ (D_Del = 1.48 mg Cd/kg/day), from gestational day (GD) 8 to 20. Embryonic kidneys were obtained on GD 21 for RNA and protein extraction. Results show that Cd exposure had no effect on HIF-1α and prolyl hydroxylase 2 protein levels, but it reduced HIF-1 DNA-binding ability, which was confirmed by a decrease in vascular endothelial growth factor (VEGF) mRNA levels. In contrast, the protein levels of VEGF were not changed, which suggests the activation of additional regulatory mechanisms of VEGF protein expression to ensure proper kidney development. In conclusion, Cd exposure decreases HIF-1-binding activity, posing a risk on renal fetal development.

The Multiple Faces of the Metal Transporter ZIP14 (SLC39A14)

The SLC39A family of metal transporters was identified through homologies with the Zrt- and Irt-like (ZIP) proteins from yeast and plants. Of all the ZIP transporters, ZIP14 is arguably the most robustly characterized in terms of function at the integrative level. Mice with a global knockout of Zip14 are viable, thus providing the opportunity to conduct physiologic experiments. In mice, Zip14 expression is highly tissue specific, with the greatest abundance in the jejunum > liver > heart > kidney > white adipose tissue > skeletal muscle > spleen > pancreas. A unique feature of Zip14 is its upregulation by proinflammatory conditions, particularly increased interleukin 6 (IL-6) and nitric oxide. The transcription factors AP-1, ATF4, and ATF6α are involved in Zip14 regulation. ZIP14 does not appear to be zinc-regulated. The Zip14 knockout phenotype shows multiple sites of ZIP14 function, including the liver, adipose tissue, brain, pancreas, and bone. A prominent feature of the Zip14 ablation is a reduction in intestinal barrier function and onset of metabolic endotoxemia. Many aspects of the phenotype are accentuated with age and accompany increased circulating IL-6. Studies with 65Zn, 59Fe [nontransferrin-bound iron (NTBI)] and 54Mn show that ZIP14 transports these metals. At a steady state, the plasma concentrations of zinc, NTBI, and manganese are such that zinc ions are the major substrate available for ZIP14 at the cell surface. Upregulation of ZIP14 accounts for the hypozincemia and hepatic zinc accumulation associated with acute inflammation and sepsis and is required for liver regeneration and resistance to endoplasmic reticulum (ER) stress. Zip14 ablation in mice produces a defect in manganese excretion that leads to excess manganese accumulation in the brain that produces characteristics of Parkinsonism.

Metallothionein 2A gene polymorphism and trace elements in mother-newborn pairs in the Croatian population

The main source of exposure for all essential and toxic elements in the general population is diet. In smokers, the main route for cadmium (Cd) and lead (Pb) intake is the inhalation of tobacco smoke. Besides gender, age, nutrition, lifestyle, and physiological conditions such as pregnancy, specific genetic characteristics also influence individual element uptake. Metallothionein MT2 is a cysteine-rich low-weight protein found ubiquitously throughout the body. Specific gene polymorphism may influence MT2 expression and subsequent binding, transfer and organ accumulation of metals, though data on these influences are lacking, especially in human mother-newborn pairs. The objective of this study was to determine selected toxic (Cd, Pb, Hg) and essential (Fe, Zn, Cu, Se) elements in maternal blood, placenta, and cord blood (by ICP-MS), and MT2 levels in maternal serum (by ELISA) in relation to maternal MT2A -5A/G (rs28366003) polymorphism (by RFLP-PCR and electrophoresis). Study participants were healthy postpartum women in Croatia (n=268, mean age 29 years) with term vaginal childbirth in a maternity ward assigned into two study groups by self-reporting about their smoking habit (by questionnaire). Smokers vs. non-smokers had increased levels of Cd and Pb in all measured samples, Fe and Cu in cord blood, Zn in placenta, and MT2 in maternal serum. Among subjects with AG/GG genotype, placental Fe was significantly lower only among non-smokers, while MT2 levels in serum were lower, though not significantly, regardless of maternal smoking habit. There was no impact of MT2A -5A/G SNP on any element in maternal or cord blood. In conclusion, the results confirmed maternal smoking-related increases in Cd and Pb levels in the maternal-placental-foetal unit. They also provided additional data on concomitant metal concentrations in representative samples of maternal blood, placenta, and cord blood, as well as increased cord blood Fe and Cu, placental Zn, and maternal serum MT2 in smokers. New evidence is that MT2A -5A/G SNP was associated with decreased placental Fe levels in non-smokers. For a final conclusion on the influence of the MT2A -5A/G polymorphism on toxic and essential element levels in mother-newborn pairs, further research would require a larger number of participants divided across subgroups defined by the main source of particular toxic metal exposure (such as specific food intake, cigarette smoking, air pollution and/or occupational exposure).

Effect of cadmium on uptake of iron, zinc and copper and mRNA expression of metallothioneins in HepG2 cells in vitro

The intake of cadmium contaminated fish was mimicked by incubating human hepatoblastoma cells (Cell line HepG2) with a combination of different levels of cadmium (0-5μM) plus the n-3 fatty acids docosahexaenoic acid and eicosapentaenoic acid, which are typical for fish. Uptake of cadmium, iron, copper and zinc was measured by ICP-MS. In addition mRNA expression of two metallothioneins (mt1 g and mt1 m) was evaluated by real-time PCR. The obtained data shows that the presence of cadmium increases the uptake of iron and zinc into the HepG2 cells while the uptake of copper remains unaffected. The presence of the chosen fatty acids did not affect the uptake of either cadmium or iron, zinc and copper. The presence of already 1μM cadmium increased the mRNA expression of mt1 g and mt1 m significantly, while the fatty acids did not interfere with the effect of cadmium.

Cadmium Handling, Toxicity and Molecular Targets Involved during Pregnancy: Lessons from Experimental Models

Even decades after the discovery of Cadmium (Cd) toxicity, research on this heavy metal is still a hot topic in scientific literature: as we wrote this review, more than 1440 scientific articles had been published and listed by the PubMed.gov website during 2017. Cadmium is one of the most common and harmful heavy metals present in our environment. Since pregnancy is a very particular physiological condition that could impact and modify essential pathways involved in the handling of Cd, the prenatal life is a critical stage for exposure to this non-essential element. To give the reader an overview of the possible mechanisms involved in the multiple organ toxic effects in fetuses after the exposure to Cd during pregnancy, we decided to compile some of the most relevant experimental studies performed in experimental models and to summarize the advances in this field such as the Cd distribution and the factors that could alter it (diet, binding-proteins and membrane transporters), the Cd-induced toxicity in dams (preeclampsia, fertility, kidney injury, alteration in essential element homeostasis and bone mineralization), in placenta and in fetus (teratogenicity, central nervous system, liver and kidney).

Increasing CACNA1C expression in placenta containing high Cd level: an implication of Cd toxicity

Cadmium (Cd) has known to produce many adverse effects on organs including placenta. Many essential transporters are involved in Cd transport pathways such as DMT-1, ZIP as well as L-VDCC. Fourteen pregnant women participated and were divided into two groups: high and low Cd-exposed (H-Cd, L-Cd) groups on the basis of their residential areas, Cd concentrations in the blood (B-Cd), urine (U-Cd), and placenta (P-Cd). The results showed that the B-Cd and U-Cd were significantly increased in H-Cd group (p < 0.05). Interestingly, the P-Cd in H-Cd group was elevated (p < 0.05) and positively related to their B-Cd and U-Cd values (p < 0.05). However, the mean cord blood Cd (C-Cd) concentration in H-Cd group was not significantly increased about 2.5-fold when comparing to L-Cd group. To determine the Cd accumulation in placental tissues, metallothionein-1A (MT-1A) and metallothionein-2A (MT-2A) expressions were used as biomarkers. The results revealed that mean MT-1A and MT-2A mRNAs and MT-1/2 proteins were up-regulated in H-Cd group (p < 0.05). In addition, the Ca channel alpha 1C (CACNA1C) mRNA and protein expressions were noticeably elevated in H-Cd group (p < 0.05). From these findings, we suggested that CACNA1C might be implicated in Cd transport in human placenta.

Maternal cadmium, placental PCDHAC1, and fetal development

Cadmium (Cd) is a ubiquitous environmental contaminant implicated as a developmental toxicant, yet the underlying mechanisms that confer this toxicity are unknown. Mother-infant pairs from a Rhode Island birth cohort were investigated for the potential effects of maternal Cd exposure on fetal growth, and the possible role of the PCDHAC1 gene on this association. Mothers with higher toenail Cd concentrations were at increased odds of giving birth to an infant that was small for gestational age or with a decreased head circumference. These associations were strongest amongst those with low levels of DNA methylation in the promoter region of placental PCDHAC1. Further, we found placental PCDHAC1 expression to be inversely associated with maternal Cd, and PCDHAC1 expression positively associated with fetal growth. Our findings suggest that maternal Cd affects fetal growth even at very low concentrations, and some of these effects may be due to the differential expression of PCDHAC1.

Protective role of zinc against the toxicity induced by exposure to cadmium during gestation and lactation on testis development

To assess the effects of exposure to Cd and Zn on rat testicular development, offspring, from mothers receiving either tap water, Cd, Zn or Cd+Zn during gestation and lactation periods, were observed on gestational day (GD) 20 and on postnatal days (PND) 12, 21 and 35. During gestation, Cd induced maternal hypozincemia and less transfer of Zn to the fetus. During lactation, progressive Cd accumulation and Zn depletion in testis at PND12 and PND21 were noted. An increase of abnormal seminiferous tubules and a decrease in testis weight and plasmatic testosterone concentration were also observed at PND21 and PND35 respectively. Interestingly, Zn supply induced a significant protection against Cd toxicity. These results suggest that the toxic effects of Cd observed during development are mediated by the disruption of Zn metabolism, which is established in mothers during pregnancy causing Zn deficiency in fetuses and continues to become more pronounced during lactation.

Evaluation of kidney injury biomarkers in rat amniotic fluid after gestational exposure to cadmium

Cadmium is a well-characterized nephrotoxic agent that is also capable of accumulating and diffusing across the placenta; however, only a few studies have addressed its effects over fetal kidneys and none of them has used a panel of sensitive and specific biomarkers for the detection of kidney injury. The goal of this study was to determine cadmium renal effects in rat fetuses by the quantification of early kidney injury biomarkers. Pregnant Wistar rats were exposed by inhalation to an isotonic saline solution or to CdCl2 solution (DDel =1.48 mg Cd kg(-1) day(-1) ) during gestational days (GD) 8-20. On GD 21, dams were euthanized and samples obtained. Kidney injury biomarkers were quantified in amniotic fluid samples and fetal kidneys were microscopically evaluated to search for histological alterations. Our results showed that cadmium exposure significantly raised albumin, osteopontin, vascular endothelial growth factor and tissue inhibitor of metalloproteinases-1 levels in amniotic fluid, whereas it decreased creatinine. Clusterin, calbindin and IFN-inducible protein 10 did not show any change. Accordingly, histological findings showed tubular damage and precipitations in the renal pelvis. In conclusion, gestational exposure to cadmium induces structural alterations in fetal renal tissue that can be detected by some kidney injury biomarkers in amniotic fluid samples. Copyright © 2016 John Wiley & Sons, Ltd.

Plant chitinase responses to different metal-type stresses reveal specificity

KEY MESSAGE

Chitinases in Glycine max roots specifically respond to different metal types and reveal a polymorphism that coincides with sensitivity to metal toxicity. Plants evolved various defense mechanisms to cope with metal toxicity. Chitinases (EC 3.2.1.14), belonging to so-called pathogenesis-related proteins, act as possible second line defense compounds in plants exposed to metals. In this work their activity was studied and compared in two selected soybean (Glycine max L.) cultivars, the metal-tolerant cv. Chernyatka and the sensitive cv. Kyivska 98. Roots were exposed to different metal(loid)s such as cadmium, arsenic and aluminum that are expected to cause toxicity in different ways. For comparison, a non-metal, NaCl, was applied as well. The results showed that the sensitivity of roots to different stressors coincides with the responsiveness of chitinases in total protein extracts. Moreover, detailed analyses of acidic and neutral proteins identified one polymorphic chitinase isoform that distinguishes between the two cultivars studied. This isoform was stress responsive and thus could reflect the evolutionary adaptation of soybean to environmental cues. Activities of the individual chitinases were dependent on metal type as well as the cultivar pointing to their more complex role in plant defense during this type of stress.

Comparing gene expression during cadmium uptake and distribution: untreated versus oral Cd-treated wild-type and ZIP14 knockout mice

The nonessential metal cadmium (Cd) is toxic only after entering the cell. Proteins possibly relevant to intracellular Cd accumulation include the divalent metal transporter-1 (DMT1) and all 14 zinc-like iron-like protein (ZIP) importers, 10 zinc transporter (ZnT) exporters, and metallothionein chaperones MT1 and MT2. Comparing oral Cd-treated ZIP14 knockout (KO) with wild-type (WT) mice, we predicted Cd uptake and distribution would be diminished in the KO-because ZIP14 is very highly expressed in GI tract and liver; this was indeed observed for Cd content in liver. However, the reverse was found in kidney and lung from 6 or 12 h through 10 days of Cd exposure; at these times, Cd accumulation was unexpectedly greater in KO than WT mice; mRNA levels of the 27 above-mentioned genes were thus examined in proximal small intestine (PSI) versus kidney to see if these paradoxical effects could be explained by substantial alterations in any of the other 26 genes. PSI genes highly expressed in untreated WT animals included seven ZIP and five ZnT transporters, DMT1, MT1, and MT2; kidney genes included 11 ZIP and 7 ZnT transporters, DMT1, MT1, and MT2. Over 10 days of oral Cd, a bimodal response was seen for Cd content in PSI and for various mRNAs; initially, acute effects caused by the toxic metal; subsequently, the up- or down-regulation of important genes presumably to combat the sustained adversity. These data underscore the complex interplay between the gastrointestinal tract and renal proteins that might be relevant to Cd uptake and distribution in animals exposed to oral Cd.