Metallothionein-I- and -II-deficient mice display increased susceptibility to cadmium-induced fetal growth restriction

Plants buffer some of the effects of a pair of cadmium-exposed zebrafish on the un-exposed majority

Certain individuals have a disproportionate effect on group responses. Characteristics may include susceptibility to pollutants, such as cadmium (Cd), a potent trace metal. Here, we show how a pair of Cd-exposed individuals can impact the behavior of unexposed groups. We used behavioral assessments to characterize the extent of the effects of the Cd-exposed individuals on group boldness, cohesion, foraging, activity, and responses to plants. We found that groups with a pair of Cd-exposed fish remained closer to novel stimuli and plants than did groups with untreated (control) fish. The presence of plants reduced Cd-induced differences in shoal cohesion and delays feeding in male shoals. Shoals with Cd- and water-treated fish were equally active. The results suggest that fish acutely exposed to environmentally relevant Cd concentrations can have profound effects on the un-exposed majority. However, the presence of plants may mitigate the effects of contaminants on some aspects of social behavior.

A Pair of Cadmium-exposed Zebrafish Affect Boldness and Landmark use in the Un-exposed Majority

Some individuals have a disproportionate effect on group responses. These individuals may possess distinct attributes that differentiate them from others. These characteristics may include susceptibility to contaminant exposure such as cadmium, a potent trace metal present in water and food. Here, we tested whether a pair of cadmium-exposed individuals could exert an impact on the behavior of the unexposed majority. We used behavioral assessments to characterize the extent of the effects of the cadmium-exposed pair on group boldness, cohesion, activity and responses to landmarks. We found that groups with a pair of cadmium-exposed fish approached and remained closer to novel stimuli and landmarks than did groups with pairs of fish treated with uncontaminated water (control). Shoals with cadmium and water treated fish exhibited similar levels of cohesion and activity. The results suggest that fish acutely exposed to environmentally-relevant cadmium concentrations can have profound effects on the un-exposed majority.

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.

In ovo exposure to cadmium causes right ventricle hyperplasia due to cell proliferation of cardiomyocytes

Cadmium (Cd) is an environmental and occupational pollutant inhaled through smoking or ingested through contaminated food. Yet, little is known about its teratogenicity. In this study, the effects of Cd on embryonic heart development were investigated by exposing Cd to chicken embryos in ovo. Fertilized eggs were treated with Cd at Hamburger-Hamilton Stage (HH)16 and collected at HH35 for histological evaluation of the heart. Cd treatment of 100μM at HH16 increased embryo mortality at HH35. Specific structural heart defects were not observed in any Cd treatment group, but the relative myocardial tissue area of the right ventricle was increased with Cd exposure. When the HH31 hearts were stained with p-H3S10, the right ventricle had an increased number of cells undergoing proliferation, which was associated with upregulation of Cdk1, Cdk6, CycA, CycD, and CycE detected by qPCR. These findings suggest that Cd exposure from HH16 upregulates proliferation genes and drives overgrowth of the right ventricle. These results grant further attention to Cd teratogenicity on embryonic heart development. Such morphological changes in the heart can potentially affect cardiac function and increase the risk for future cardiovascular diseases, such as heart failure.

Increased expression of apoptotic markers in human full-term placenta after exposure to elevated environmental cadmium levels during pregnancy

Cadmium (Cd), a toxic heavy metal, produces various forms of environmental contaminations and health problems in human. In this study, we aimed to examine the localization of several apoptotic markers in human placentas from pregnant women who were environmentally exposed to Cd. Twelve pregnant women participated in this analysis and they were divided into 2 groups according to their living areas: high-Cd (H-Cd) and low-Cd (L-Cd) groups. After delivery, the placentas were immediately harvested, and the placental width, length, and weight were measured. The placental Cd concentration was determined by using ICP-MS. The expression of three apoptotic markers, cleaved caspase-3, cleaved lamin A/C, and TUNEL, was examined in immunohistochemistry. In results, the placental Cd concentration in the H-Cd group was higher than that in the L-Cd group. In contrast, a significant decrease in the BW (birth weight):PW (placenta weight) ratio representing the placental nutrient transport function was found in the H-Cd group, and an inverse correlation between placental Cd concentration and BW:PW ratio was demonstrated. Additionally, significant elevations in the expression of cleaved caspase-3, cleaved lamin A/C proteins, and TUNEL were shown in the H-Cd placenta. Moreover, positive correlations were found between the placental Cd concentration and the expression of cleaved caspase-3 and TUNEL. Collectively, our findings suggest that the exposure of pregnant women to environmental Cd might induce Cd to be transferred to the body and then accumulated in the placenta, resulting in disturbance of the placental function and eventual apoptosis.

Zinc as a countermeasure for cadmium toxicity

Cadmium (Cd) is an important environmental pollutant and long-term Cd exposure is closely related to autoimmune diseases, cancer, cardiovascular diseases (CVD), and hepatic dysfunction. Zinc (Zn) is an essential metal that plays key roles in protein structure, catalysis, and regulation of their function. Numerous studies have shown that Zn can reduce Cd toxicity; however, the underlying mechanisms have not been extensively explored. Preclinical studies have revealed direct competition for sarcolemmal uptake between these two metals. Multiple sarcolemmal transporters participate in Cd uptake, including Zn transporters, calcium channels, and DMT1 (divalent metal transporter 1). Zn also induces several protective mechanisms, including MT (metallothionein) induction and favorable redox homeostasis. This review summarizes current knowledge related to the role of Zn and metal transporters in reducing Cd toxicity and discusses potential future directions of related research.

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.

Bisphenol A stimulates steroidogenic acute regulatory protein expression via an unknown mechanism in adrenal cortical cells

Bisphenol A (BPA) is one of the most widespread endocrine disrupting chemicals in the environment. Exposure to BPA is known to be associated with disruption of steroidogenesis in reproductive tissues, but little is known about its effects on the adrenal gland. We previously showed that prenatal BPA exposure resulted in elevated plasma corticosterone levels concomitant with increased adrenal levels of steroidogenic acute regulatory protein (StAR), the rate-limiting step in steroidogenesis, in adult female mouse offspring. However, the molecular mechanisms underlying the BPA-induced StAR protein expression in the adrenal gland remain unknown. Therefore, the current study was designed to address this important question using the human cortical cell line, H295A cells, as an in vitro model system. We found that: (1) BPA increased StAR protein levels in a dose-dependent manner; (2) both estrogen receptor alpha (ERα)- and ERβ-specific agonists mimicked while the ER antagonist ICI abrogated the stimulatory effects of BPA on StAR protein levels; and (3) BPA did not alter StAR messenger RNA, 37kDa preprotein or protein half-life. Taken together, these findings demonstrate that BPA increases StAR protein levels through an unknown mechanism independent of StAR gene transcription, translation, and protein half-life. Furthermore, such effects are likely mediated by ERα and/or ERβ.

Disruption of the zinc metabolism in rat fœtal brain after prenatal exposure to cadmium

This study was carried out to investigate the effects of maternal Cd and/or Zn exposure on some parameters of Zn metabolism in fetal brain of Wistar rats. Thus, female controls and other exposed by the oral route during the gestation period to Cd (50 mg CdCl2/L) and/or Zn (ZnCl2 60 mg/L) were used. The male fetuses at age 20 days of gestation (GD20) were sacrificed and their brains were taken for histological, chemical and molecular analysis. Zn depletion was observed in the brains of fetuses issued from mothers exposed to Cd. Histological analysis showed that Cd exposure induces pyknosis in cortical region and CA1 region of the hippocampus compared to controls. Under Cd exposure, we noted an overexpression of the genes coding for membrane transporter involved in the intracellular incorporation of Zn (ZIP6) associated with inhibition of that encoding the transporters involved in the output of the Zn into the extracellular medium (ZnT1 and ZnT3). A decrease in the expression of the gene encoding the neuro-trophic factor (BDNF) associated with overexpression of the encoding the metal regulatory transcription factor 1 (MTF1), factor involved in the homeostasis of Zn, was also noted in Cd group. Interestingly, Zn supply provided a total or partial restauration of the changes induced by the Cd exposure. The depletion of brain Zn contents as well as the modification of the profile of expression of genes encoding membrane Zn transporters, suggest that the toxicity of Cd observed in fetal brain level are mediated, in part, by impairment of Zn metabolism.

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

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

N-acetylcysteine alleviates cadmium-induced placental endoplasmic reticulum stress and fetal growth restriction in mice

Cadmium (Cd) is a developmental toxicant that induces fetal growth restriction (FGR). Placental endoplasmic reticulum (ER) stress is associated with FGR. This study investigated the effects of N-acetylcysteine (NAC) on Cd-induced placental ER stress and FGR. Pregnant mice were intraperitoneally injected with CdCl₂ daily from gestational day (GD)13 to GD17. As expected, Cd reduced fetal weight and crown-rump length. Cd decreased the internal space of blood vessels in the placental labyrinth layer and inhibited placental cell proliferation. Several genes of growth factors, such as Vegf-a, placental growth factor, Igf1 and Igf1r, and several genes of nutrient transport pumps, such as Glut1, Fatp1 and Snat2, were down-regulated in placenta of Cd-treated mice. Moreover, Cd evoked placental ER stress. Of interest, NAC alleviated Cd-induced FGR. Additional experiment showed that NAC inhibited Cd-induced impairment of placental development and placental ER stress. Therefore, NAC may be exploited for prevention of Cd-induced placental insufficiency and FGR.

Association of maternal serum cadmium level during pregnancy with risk of preterm birth in a Chinese population

Cadmium (Cd) was a developmental toxicant that induces fetal malformation and growth restriction in mice. However, epidemiological studies about the association of maternal serum Cd level with risk of preterm birth were limited. This study was to investigate whether maternal serum Cd level during pregnancy is associated with risk of preterm birth in a Chinese population. Total 3254 eligible mother-and-singleton-offspring pairs were recruited. Maternal serum Cd level was measured by GFAAS. Based on tertiles, maternal serum Cd concentration was classified as low (LCd, <0.65 μg/L), medium (MCd, 0.65-0.94 μg/L) and high (HCd, ≥0.95 μg/L). Odds ratio (OR) for preterm birth was estimated using multiple logistic regression models. Results showed the rate of preterm birth among LCd, M-Cd and HCd was 3.5%, 3.8%, and 9.4%, respectively. Subjects with HCd had a significantly higher risk for preterm birth (OR: 2.86; 95%CI: 1.95, 4.19; P < 0.001) than did those with LCd. Adjusted OR for preterm birth was 3.02 (95%CI: 2.02, 4.50; P < 0.001) among subjects with HCd compared to subjects with LCd. Taken together, the above results suggest that maternal serum Cd level during pregnancy is positively associated with risk of preterm birth.

Prenatal exposure to bisphenol A disrupts adrenal steroidogenesis in adult mouse offspring

The present study sought to determine if prenatal exposure to bisphenol A (BPA) alters adrenal steroidogenesis in adult offspring. Pregnant mice were exposed to BPA (25mg BPA/kg food pellet) via diet from day 7 to the end of pregnancy. At eight weeks of age, offsprings were sacrificed, blood samples and adrenal glands were collected for hormone assays and western blot analysis, respectively. We found that: (1) BPA increased adrenal gland weight in both males and females; (2) although BPA elevated plasma corticosterone levels in both sexes, it stimulated the expression of StAR and cyp11A1, the two rate-limiting factors in the steroidogenic pathway, only in female adrenal glands; and interestingly (3) BPA did not alter plasma ACTH levels or adrenal expression of the key steroidogenic transcription factor SF-1 in either sex. Taken together, the present study provides novel insights into the long-term consequences of developmental BPA exposure on adrenal steroidogenesis.

Maternal serum cadmium level during pregnancy and its association with small for gestational age infants: a population-based birth cohort study

The association between maternal cadmium (Cd) exposure during pregnancy and the increased risk of fetal growth restriction (FGR) remains controversial. The present study evaluated the association between maternal serum Cd level and risk of small for gestational age (SGA) infants in a Chinese population. The present study analyzed a subsample of the C-ABCS cohort that recruited 3254 eligible mother-and-singleton-offspring pairs. Maternal serum Cd level during pregnancy was measured by graphite furnace atomic absorption spectrometry. The rate and odds ratio (OR) for SGA infant were calculated. The rate for SGA infant was 10.6% among subjects with H-Cd (≥1.06 μg/L), significantly higher than 7.5% among subjects with L-Cd (<1.06 μg/L). OR was 1.45 (95% CI: 1.11, 1.90; P = 0.007) among subjects with H-Cd. Adjusted OR for SGA infants was 1.43 (95% CI: 1.09, 1.88; P = 0.007) among subjects with H-Cd. Taken together, we observe the fact that maternal Cd exposure at middle gestational stage, elevates the risk of SGA in contrast to early gestational stage. The present results might be interesting and worth more discussing, and guarantee to further studies.

Cadmium exposure during lactation causes learning and memory-impairment in F1 generation mice: amelioration by quercetin

Cadmium (Cd) is a known pollutant present in the environment at low levels and is reported to affect reproduction in many ways. The present study was undertaken to explore the effect of Cd in F1 generation mice on cognitive parameters, and to further investigate whether quercetin could modulate these effects. In this study, female lactating mice were exposed to cadmium for seven days just after delivery. The new born pups in their adulthood were tested for learning and memory parameters by passive avoidance task and Morris water maze (MWM) test. It was observed that pups exposed to Cd showed significant impairment of memory in step down latency test, which was reversed by quercetin (100 mg/kg). In MWM test for spatial memory, animals exposed to Cd exhibited increased escape latency, which was reversed by quercetin (50 mg/kg) significantly. Quercetin alone (50 and 100 mg/kg) also demonstrated improved spatial memory, and showed improved retention memory in the passive avoidance paradigm at dose 50 mg/kg. On testing oxidative stress parameters, we observed significantly increased malondialdehyde (MDA) levels in brain tissue of Cd-treated mice. Moreover, co-treatment with quercetin (50 mg/kg) and Cd significantly reduced these MDA levels. The other doses (25 and 100 mg/kg) also showed reduction in MDA levels as compared to the group exposed to Cd alone, though the difference was not statistically significant. Hence, this study highlights the possibility of cognitive impairment in adulthood if there is Cd exposure during lactation and oxidative stress could possibly attribute to this effect.

Prenatal Exposure to Bisphenol A Disrupts Mouse Fetal Liver Maturation in a Sex-Specific Manner

Bisphenol A (BPA) is one of the most prevalent endocrine disrupting chemicals in the environment. Developmental exposure to BPA is known to be associated with liver dysfunction and diseases, such as hepatic steatosis, liver tumors, metabolic syndrome, and altered hepatic gene expression, and DNA methylation profiles. However, the effects of BPA on rodent liver development are unknown. The present study was undertaken to address this important question using the mouse as an experimental model. Pregnant mice were exposed to BPA via diet from embryonic day 7.5 (E7.5) to E18.5. At E18.5, fetal livers were collected, and analyzed for changes in the expression of key hepatocyte maturation markers. We found the following significant alterations in BPA-exposed female but not male fetal livers: (a) levels of the mature hepatocyte markers, albumin and glycogen synthase proteins, were decreased (-65% and -40%, respectively); (b) levels of the immature hepatocyte marker, α-fetoprotein, were increased (+43%); (c) the level of C/EBP-α protein, the master transcription factor essential for hepatocyte maturation, was down-regulated (-50%); and (d) the level of PCNA protein (marker of proliferation) was elevated (+40%), while that of caspase-3 protein and activity (markers of apoptosis) was reduced (-40% and -55%, respectively), suggestive of a perturbed balance between cell proliferation and apoptosis in BPA-exposed female fetuses. Taken together, these findings demonstrate that prenatal exposure to BPA disrupts the mouse fetal liver maturation in a sex-specific manner, and suggest a fetal origin for BPA-induced hepatic dysfunction and diseases.