Prenatal cadmium exposure dysregulates sonic hedgehog and Wnt/beta-catenin signaling in the thymus resulting in altered thymocyte development

Cadmium-induced lung injury disrupts immune cell homeostasis in the secondary lymphoid organs in mice

Cadmium (Cd) is a well-known toxic heavy metal that poses significant health risks, particularly through inhalation, smoking, and the consumption of contaminated food. Exposure to cadmium is linked to the development and exacerbation of chronic lung diseases such as pulmonary fibrosis and chronic obstructive pulmonary disease (COPD). This study investigated the systemic effects of intratracheal cadmium chloride (0.5 mg/kg) instillation in C57BL/6 mice. All parameters, including inflammation assessment, lung function evaluation (using Flexi-vent), and immunophenotyping of T-cells in secondary lymphoid organs (mediastinal lymph nodes and spleen), were analyzed 14 days after cadmium exposure. The results demonstrated that cadmium exposure led to significant immune cell infiltration in bronchoalveolar lavage (BAL) fluid, altered pro-inflammatory cytokine levels, and was associated with impaired lung function, characterized by increased lung resistance and Newtonian resistance. Analysis of T-cell populations revealed no significant changes in total T-cells in mediastinal lymph nodes and spleen, but a decrease in CD4+ T-cells and an increase in CD8+ T-cells were observed. These findings suggest that cadmium disrupts T-cell homeostasis in secondary lymphoid organs. Further research is crucial to elucidate the mechanisms underlying cadmium-induced lung injury and immune dysregulation, essential for developing effective therapeutic interventions against chronic lung diseases caused by cadmium exposure.

Sulforaphane Ameliorate Cadmium-Induced Blood-Thymus Barrier Disruption by Targeting the PI3K/AKT/FOXO1 Axis

Cadmium (Cd) is a transition metal ion that is extremely harmful to human and animal biological systems. Cd is a toxic substance that can accumulate in the food chain and cause various health issues. Sulforaphane (SFN) is a natural bioactive compound with potent antioxidant properties. In our study, 80 1 day-old chicks were fed with Cd (140 mg/kg BW/day) and/or SFN (50 mg/kg BW/day) for 90 days. The blood-thymus barrier (BTB) is a selective barrier separating T-lymphocytes from blood and cortical capillaries in the thymus cortex. Our research revealed that Cd could destroy the BTB by downregulating Wnt/β-catenin signaling and induce immunodeficiency, leading to irreversible injury to the immune system. The study emphasizes the health benefits of SFN in the thymus. SFN could ameliorate Cd-triggered BTB dysfunction and pyroptosis in the thymus tissues. SFN modulated the PI3K/AKT/FOXO1 axis, improving the level of claudin-5 (CLDN5) in the thymus to alleviate BTB breakdown. Our findings indicated the toxic impact of Cd on thymus, and BTB could be the specific target of Cd toxicity. The finding also provides evidence for the role of SFN in maintaining thymic homeostasis for Cd-related health issues.

Vitamin C and/or garlic can antagonize the toxic effects of cadmium on growth performance, hematological, and immunological parameters of growing Japanese quail

This study used 300 1-day-old, sexless, developing chicks of Japanese quail to estimate the ability of vitamin C and/or garlic to antagonize the venomous influence of cadmium (Cd) on the hematological, immunological, and performance characteristics of developing Japanese quail. The quail was separated into 5 similar groups of 60 chicks apiece, and 6 duplicates (10 each) were given to each sub-group. The control group received a basal diet without any supplements. The Cd group was nourished with a basal diet of + 80 mg cadmium chloride (CdCl2)/kg diet. The 3rd group was fed a basal diet + 80 mg CdCl2/kg diet and complemented with a 200 mg Vitamin C (Cd + C)/kg diet. The 4th group was nourished with a basal diet + 80 mg CdCl2/kg diet and complemented by a 500 mg dried garlic powder (Cd + G)/kg diet. The 5th group was fed a basal diet + 80 mg CdCl2/kg diet, complemented by a 200 mg vitamin C/kg diet + 500 mg dried garlic powder (Cd + CG)/kg diet. Results showed that in the 5th group in which cadmium was added together with Vit C + garlic, there was an improvement in both live weight gain (1-42 d) and feed consumption (1-21 and 1-42 d ) compared to the group in which Cd was added alone. The addition of Vit C alone and together with garlic seems to completely improve the cadmium-related increase in alkaline phosphatase (ALP), and Aspartate aminotransferase (AST), and Malondialdehyde (MDA) levels when compared to the control. Compared to cadmium-polluted diets, quail that got cadmium and feed additives significantly reduced cadmium residue. In addition, the cadmium group's serum immunoglobulin M (IgM) level decreased significantly. These data imply that dietary supplementation with (C) or (G) may be beneficial in retrogressing the drop in immunoglobulin G (IgG) and IgM caused by Cd and minimizing Cd's deleterious influence on immunity.

Small fetal thymus and adverse perinatal outcome in maternal vasculitis: A prospective case-control study

BACKGROUND

Ultrasonographic evaluation of fetal thymus size may be used to predict the adverse perinatal outcome in pregnant women with vasculitis.

AIM

To compare fetal thymus size in pregnant women with vasculitis and healthy pregnant women and to evaluate whether fetal thymus size predicts the adverse perinatal outcome.

METHODS

Twenty-two pregnant women with previously diagnosed vasculitis, 18 of them with Behçet's disease, three with Takayasu arteritis, and one with Wegener's granulomatosis, were included in the case group. The control group comprised 66 healthy pregnant women whose gestational ages matched the case group. Thymic thoracic ratio (TTR) was measured to assess fetal thymus size in the view of three vessels and trachea.

RESULTS

In the case group, fetal TTR was significantly lower (0.32 ± 0.03 vs. 0.36 ± 0.02, p = < 0.001). Fetal TTR was significantly lower in those using prednisone than those not (p = .001) in the case group. There was no significant difference in fetal TTR between colchicine used and not used (p = .078) in the case group. Also, for the TTR, a sensitivity of 100% and a specificity of 92% were achieved with a cut-off value of 0.33 for predicting adverse perinatal outcomes.

CONCLUSION

The fetuses of pregnant women with maternal vasculitis had a smaller TTR. The small fetal thymus may alert clinicians to possible adverse perinatal outcomes and, with other supporting risk factors, may help predict adverse perinatal outcomes in pregnant women with vasculitis.

The relationship between cadmium exposure and hepatitis B susceptibility and the establishment of its prediction model

Cadmium, a common metal, is an environmental contaminant that is hepatotoxic and immunotoxic. Cadmium exposure may affect hepatitis B immunity. The purpose of this study was to assess the association between cadmium exposure and hepatitis B serology in the US population and to develop a model to predict susceptibility of hepatitis B. The study included 50,588 individuals in the National Health and Nutrition Examination Survey (NHANES) from 2007 to 2016. Univariate and multivariate logistic regression and dose-response curves were used to evaluate the relationship between cadmium exposure and hepatitis B serology. Through multivariate logistic regression results, a predictive model was established, and relevant indicators were used to verify the clinical value of the model and evaluate prognostic value of serum cadmium concentration in patients with hepatitis B. We selected 5989 (≥ 6 years old) participants. Univariate logistic regression analysis showed that gender (aOR = 0.7192, 95% CI = 0.6492-0.7968), age (aOR = 1.030, 95% CI = 1.026-1.033), race (aOR = 0.8974, 95% CI = 0.8591-0.9374), poverty ratio (aOR = 1.042, 95% CI = 0.9872-1.101), body mass index (BMI) (aOR = 1.052, 95% CI = 1.044-1.061), hypertension (aOR = 2.017, 95% CI = 1.763-2.306), diabetes (aOR = 2.673, 95% CI = 2.119-3.370), vigorous recreational activities (aOR = 0.6369, 95% CI = 0.5725-0.7085), moderate recreational activity (aOR = 0.7681, 95% CI = 0.6935-0.8574) and cadmium (aOR = 1.295, 95% CI = 1.168-1.436) were closely related to hepatitis B virus (HBV) susceptibility. After adjusting for these confounding factors, multivariate logistic regression analysis showed that the odds ratio of HBV susceptibility was positively correlated with the level of cadmium in serum. The effectiveness of the model was then evaluated by establishing a nomogram, and by calibration curves, ROC curves, and clinical decision curves. Our study shows that cadmium exposure is positively associated with HBV susceptibility risk in the US population, and the constructed model has clinical significance.

Asthma susceptibility in prenatal nicotine-exposed mice attributed to β-catenin increase during CD4+ T cell development

Cigarette smoke is a common global environmental pollutant. Asthma, the most frequent allergic airway disease, is related to maternal exposure to cigarette smoke. Our previous studies demonstrated that prenatal exposure to nicotine (PNE), the major active product of smoking, impairs fetal thymopoiesis and CD4⁺ T cell development after birth. This study aimed to investigate whether PNE contributes to asthma susceptibility through CD4⁺ T cell development alterations. First, A PNE model was established by administering 3 mg/kg/day nicotine to maternal mice, and then an ovalbumin-induced asthma model was established in the offspring. Further, β-catenin and downstream pathways were inhibited in vitro to confirm the molecular mechanisms underlying the phenotype observed during the in vivo phase. The results showed that PNE induced Th2 and Th17 biases at developmental checkpoints and aggravated asthma symptoms in the offspring. In fetuses, PNE up-regulated α7 nAChR, activated PI3K-AKT, promoted β-catenin level increase, and established potential Th2- and Th17-biased gene expression patterns during thymopoiesis, which persisted after birth. Similar results were also observed in 1 μM nicotine-treated thymocytes in vitro. Moreover, inhibiting PI3K-AKT by LY294002 abrogated nicotine-mediated β-catenin level increase and thymopoiesis abnormalities, and an α7 nAChR antagonist (α-btx) also reversed nicotine-induced PI3K-AKT activation. Our findings provide strong evidence that PNE is a risk factor for T cell deviation and postnatal asthma, and revealed that nicotine-induced β-catenin level increase induces thymopoiesis abnormalities.

Cadmium impairs zebrafish swim bladder development via ROS mediated inhibition of the Wnt / Hedgehog pathway

The posterior swim bladder is an important organ in teleost fishes, that primarily maintains buoyancy and motility for swimming and survival. In this study, we examined the molecular mechanisms of the toxicity of cadmium (Cd) on the early development of the swim bladder in zebrafish. Embryonic Cd exposure resulted in the non-inflation of the swim bladder when the ambient Cd concentration was greater than or equal to 0.25 mg/L. Cd disturbed surfactant lipid distribution and inhibited the formation of all three tissue layers in the swim bladder. Additionally, excessive Cd down-regulated Wnt (fzd3, nkd1, fzd7 and axin2) and Hedgehog (ihh, shh, ptc1 and ptc2) signaling pathways. Conversely, Wnt signaling activation partially neutralized Cd-induced swim bladder developmental defects. Moreover, ROS scavenger reduced Glutathione (GSH) effectively recovered Cd induced defects in swim bladder and Wnt/Hedgehog signaling. Taken together, our results first revealed that Cd caused swim bladder developmental defects via ROS-mediated inhibition of the Wnt and Hedgehog pathways. These results herein provide important data for future toxicological studies and risk assessments of Cd.

Prenatal Cadmium Exposure Alters Proliferation in Mouse CD4+ T Cells via LncRNA Snhg7

Objective

Prenatal cadmium (Cd) exposure leads to immunotoxic phenotypes in the offspring affecting coding and non-coding genes. Recent studies have shown that long non-coding RNAs (lncRNAs) are integral to T cell regulation. Here, we investigated the role of long non-coding RNA small nucleolar RNA host gene 7 (lncSnhg7) in T cell proliferation.

Methods

RNA sequencing was used to analyze the expression of lncRNAs in splenic CD4+ T cells with and without CD3/CD28 stimulation. Next, T cells isolated from offspring exposed to control or Cd water throughout mating and gestation were analyzed with and without stimulation with anti-CD3/CD28 beads. Quantitative qPCR and western blotting were used to detect RNA and protein levels of specific genes. Overexpression of a miR-34a mimic was achieved using nucleofection. Apoptosis was measured using flow cytometry and luminescence assays. Flow cytometry was also used to measure T cell proliferation in culture. Finally, lncSnhg7 was knocked down in splenic CD4+ T cells with lentivirus to assess its effect on proliferation.

Results

We identified 23 lncRNAs that were differentially expressed in stimulated versus unstimulated T cells, including lncSnhg7. LncSnhg7 and a downstream protein, GALNT7, are upregulated in T cells from offspring exposed to Cd during gestation. Overexpression of miR-34a, a regulator of lncSnhg7 and GALNT7, suppresses GALNT7 protein levels in primary T cells, but not in a mouse T lymphocyte cell line. The T cells isolated from Cd-exposed offspring exhibit increased proliferation after activation in vitro, but Treg suppression and CD4+ T cell apoptosis are not affected by prenatal Cd exposure. Knockdown on lncSnhg7 inhibits proliferation of CD4+ T cells.

Conclusion

Prenatal Cd exposure alters the expression of lncRNAs during T cell activation. The induction of lncSnhg7 is enhanced in splenic T cells from Cd offspring resulting in the upregulation of GALNT7 protein and increased proliferation following activation. miR-34a overexpression decreased GALNT7 expression and knockdown of lncSnhg7 inhibited proliferation suggesting that the lncSnhg7/miR-34a/GALNT7 is an important pathway in primary CD4+ T cells. These data highlight the need to understand the consequences of environmental exposures on lncRNA functions in non-cancerous cells as well as the effects in utero.

Temporal and Geographical Variation of Intestinal Ulcers in Grey Seals (Halichoerus grypus) and Environmental Contaminants in Baltic Biota during Four Decades

Simple Summary

In the 1970s it was discovered that seal populations in the Baltic Sea had decreased severely due to hunting and high levels of contaminants. Lesions were found in several organs and many of the females became sterile. Since then, most of the organ lesions have decreased and so have the levels of some pollutants. However, ulcers in the large intestines of the grey seals increased in the early 1980s and decreased after the mid-1990s. The aims of this study were to: (1) describe the ulcers and investigate if there is a trend over time that coincides with concentrations of some pollutants in Baltic biota; (2) evaluate the significance of different sea areas in the Baltic, grade of parasite intensity, as well as the sex and age of the seals. The results show that seals with ulcers had, in general, higher parasite intensity. Ulcers were more common in older seals and in the Bothnian Sea. The time trend of ulcers coincides with the trend of certain contaminant levels (BDE-47, PFOS and cadmium). The high prevalence of intestinal ulcers and the high intensity of acanthocephalan parasites appear to be unique to the Baltic population of grey seals.

Abstract

The prevalence of intestinal ulcers and parasites was investigated in 2172 grey seals (Halichoerus grypus) collected in the Baltic Sea and 49 grey seals collected outside the Baltic Sea (i.e., the Atlantic). An increase in frequency of ileocaeco-colonic ulcers was observed in the early 1980s, followed by a decrease in the mid-1990s. At the same time, there was an increase followed by a decrease in brominated flame retardants, Perfluorooctanesulfonic acid (PFOS) and cadmium levels in herring (Clupea harengus), the most common prey item in Baltic grey seal diet, as well as in another top predator in the Baltic, the common guillemot (Uria aalge). The frequency of intestinal ulcers was significantly related to the intensity of acanthocephalan parasites, the age of the seal and the region of the Baltic Sea. Perforation of the intestinal wall was the cause of death in 26 of the investigated Baltic grey seals. In contrast, none of the investigated Atlantic grey seals had intestinal ulcers. They showed a thin colonic wall and very few acanthocephalan parasites. The high prevalence of intestinal ulcers and the high parasite intensity appear to be unique to the Baltic population of grey seals.

Environmental Exposure to Heavy Metals Contributes to Diseases Via Deregulated Wnt Signaling Pathways

Wnt signaling plays a critical role during embryogenesis and is responsible for regulating the homeostasis of the adult stem cells and cells fate via a multitude of signaling pathways and associated transcription factors, receptors, effectors, and inhibitors. For this review, published articles were searched from PubMed Central, Embase, Medline, and Google Scholar. The search terms were Wnt, canonical, noncanonical, signaling pathway, β-catenin, environment, and heavy metals. Published articles on Wnt signaling pathways and heavy metals as contributing factors for causing diseases via influencing Wnt signaling pathways were included. Wnt canonical or noncanonical signaling pathways are the key regulators of stem cell homeostasis that control many mechanisms. There is an adequate balance between β-catenin dependent and independent Wnt signaling pathways and remain highly conserved throughout different development stages. Environmental heavy metal exposure may cause either inhibition or overexpression of any component of Wnt signaling pathways such as Wnt protein, transcription factors, receptors, ligands, or transducers to impede normal cellular function via negatively affecting Wnt signaling pathways. Environmental exposure to heavy metals potentially contributes to diseases via deregulated Wnt signaling pathways. 

Prenatal cadmium exposure does not induce greater incidence or earlier onset of autoimmunity in the offspring

We previously demonstrated that exposure of adult mice to environmental levels of cadmium (Cd) alters immune cell development and function with increases in anti-streptococcal antibody levels, as well as decreases in splenic natural regulatory T cells (nTreg) in the adult female offspring. Based on these data, we hypothesized that prenatal Cd exposure could predispose an individual to developing autoimmunity as adults. To test this hypothesis, the effects of prenatal Cd on the development of autoimmune diabetes and arthritis were investigated. Non-obese diabetic (NOD) mice were exposed to Cd in a manner identical to our previous studies, and the onset of diabetes was assessed in the offspring. Our results showed a similar time-to-onset and severity of disease to historical data, and there were no statistical differences between Cd-exposed and control offspring. Numerous other immune parameters were measured and none of these parameters showed biologically-relevant differences between Cd-exposed and control animals. To test whether prenatal Cd-exposure affected development of autoimmune arthritis, we used SKG mice. While the levels of arthritis were similar between Cd-exposed and control offspring of both sexes, the pathology of arthritis determined by micro-computed tomography (μCT) between Cd-exposed and control animals, showed some statistically different values, especially in the female offspring. However, the differences were small and thus, the biological significance of these changes is open to speculation. Overall, based on the results from two autoimmune models, we conclude that prenatal exposure to Cd did not lead to a measurable propensity to develop autoimmune disease later in life.

Immunotoxicology of cadmium: Cells of the immune system as targets and effectors of cadmium toxicity

Cadmium (Cd) has been listed as one of the most toxic substances affecting numerous tissues/organs, including the immune system. Due to variations in studies examining Cd effects on the immune system (exposure regime, experimental systems, immune endpoint measured), data on Cd immunotoxicity in humans and experimental animals are inconsistent. However, it is clear that Cd can affect cells of the immune system and can modulate some immune responses. Due to the complex nature of the immune system and its activities which are determined by multiple interactions, the underlying mechanisms involved in the immunotoxicity of this metal are still vague. Here, the current knowledge regarding the interaction of Cd with cells of the immune system, which may affect immune responses as well as potential mechanisms of consequent biological effects of such activities, is reviewed. Tissue injury caused by Cd-induced effects on innate cell activities depicts components of the immune system as mediators/effectors of Cd tissue toxicity. Cd-induced immune alterations, which may compromise host defense against pathogenic microorganisms and homeostatic reparative activities, stress this metal as an important health hazard.

Morpho-functional alterations in lymphocytes and erythrocytes of Japanese quail due to prolonged in vivo exposure to heavy metal complexes

BACKGROUND

Lead and cadmium are significant environmental pollutants that cause pathophysiological responses in many organs. Heavy metal absorption into many tissues is very fast due to a pronounced affinity for metallothioneins.

METHOD

Japanese quail were exposed to different concentrations of metals (cadmium 0.20 mg/L and lead 0.25 and 0.50 mg/L) for 20 days. Erythrocytes (normal and hemolyzed) and lymphocytes (normal and altered) were monitored in this study. The analysis observed the percentage of normal and altered cells, as well as erythrocyte surface area. Cell counts were analyzed using light microscopy, while surface area and cytological changes in cells and nuclei were analyzed using licensed software.

RESULTS

Different concentrations of metals have caused erythrocyte hemolysis as well as structural and morphological alterations in lymphocytes. Destruction of cell and nucleus membrane, changes in cell size, erythrocyte denucleation and reduced erythrocyte surface area were observed. Cadmium has caused erythrocyte hemolysis (29.30 %) and lymphocyte damage (92.10 %). Higher doses of lead resulted in greater damage to lymphocytes (63 %). Also, treatment with higher dose of lead produced a higher percentage of hemolyzed erythrocytes (19.20 %) in comparison to lower dose (9.90 %).

CONCLUSION

The toxicity of heavy metals leads to reduced maturation of the blast, which causes the appearance of immature cells in peripheral circulation and severe destruction of blood cell membranes. Erythrocyte hemolysis can lead to anemia, while lymphocyte damage can lead to lymphocytopenia.

Inhibition of thymocyte autophagy-associated CD4+T thymopoiesis is involved in asthma susceptibility in mice exposed to caffeine prenatally

Our previous studies demonstrated that prenatal caffeine exposure (PCE) caused thymopoiesis inhibition, immune disorders, and airway remodeling in offspring, which raises the question of whether PCE is a risk factor for postnatal asthma. Meanwhile, the mechanism of PCE-induced thymopoiesis inhibition is not clear yet. Considering caffeine's pro-autophagy effects (lacking evidence in thymus) and the important role of autophagy in maintaining thymopoiesis, this study aimed to investigate whether PCE contributes to asthma susceptibility, and further explore the molecular mechanisms of thymopoiesis inhibition from the perspective of pro-autophagy effects of caffeine both in vivo and in vitro. The PCE mouse model was established by 96 mg/kg/day caffeine administration from gestational day (GD) 9-GD 18, and an asthma model was established on the offspring by ovalbumin sensitization and challenge. The results confirmed our hypothesis that PCE could suppress pulmonary CD4⁺T development and aggravate allergen-induced asthma symptoms in the offspring. In fetuses, PCE significantly suppressed A2AR-PKA signaling, upregulated Beclin1-LC3II autophagy, promoted Bcl10 degradation, reduced A20 expression, and inhibited CD4⁺T thymopoiesis. Similar results were also observed in 4 µM caffeine-treated thymocytes in vitro. Moreover, inhibiting A2AR by antagonist (SCH 58261) performed the same downstream biological effects as caffeine treatment, and autophagy inhibitor (BafilomycinA1) clearly abolished the caffeine-induced Bcl10 degradation and A20 suppression. In conclusion, our findings, for the first time, showed that PCE could attenuate CD4⁺T thymopoiesis and suppress pulmonary CD4⁺T development by directly enhancing autophagy in thymocytes, and provided a firm experimental evidence that PCE is a risk factor for postnatal asthma.

Foetal thymus size in pregnancies after assisted reproductive technologies

PURPOSE

The aim of our study was to compare thymus sizes in foetuses conceived using assisted reproductive technologies (ART) to those conceived naturally (control group).

METHODS

Sonographic foetal thymus size was assessed retrospectively in 162 pregnancies conceived using ART and in 774 pregnancies conceived naturally. The anteroposterior thymic and the intrathoracic mediastinal diameter were measured to calculate the thymic-thoracic ratio (TT-ratio). The ART cases were subdivided into two groups: (1) intracytoplasmic sperm injection (ICSI; n = 109) and (2) in vitro fertilisation (IVF; n = 53).

RESULTS

The TT-ratio was smaller in pregnancies conceived using ART (p < 0.001). In both ART subgroups (ICSI and IVF), the TT-ratio was lower compared to the control group (p < 0.001). However, no difference between the two subgroups could be detected (p = 0.203).

CONCLUSIONS

Our data show reduced thymus size in foetuses conceived using ART compared to controls. These findings indicate that the use of ART may lead to certain deviations in organogenesis.

Maternal Glucocorticoid Elevation and Associated Fetal Thymocyte Apoptosis are Involved in Immune Disorders of Prenatal Caffeine Exposed Offspring Mice

Our previous study showed that prenatal caffeine exposure (PCE) could induce intrauterine growth retardation (IUGR) and glucocorticoid elevation in the fetus. Researchers suggested that IUGR is a risk factor for T helper cell (Th)1/Th2 deviation. However, whether PCE can induce these immune disorders and the underlying mechanisms of that induction remain unknown. This study aimed to observe the effects of PCE on the Th1/Th2 balance in offspring and further explore the developmental origin mechanisms from the perspective of glucocorticoid overexposure-induced thymocyte apoptosis. An IUGR model was established by caffeine administration from gestational day (GD) 9 to GD 18, and the offspring were immunized on postnatal day (PND) 42. The results show that maternal glucocorticoid overexposure increased fetal thymocyte apoptosis by activating both the Fas-mediated and the Bim-regulated apoptotic pathways. After birth, accelerated thymocyte apoptosis and Th1 suppression were also found in the PCE offspring at PND 14 and PND 49. Moreover, the PCE offspring showed immune disorders after immunization, manifesting as increased IgG1/IgG2a ratio and IL-4 production in the serum. In conclusion, PCE could induce fetal overexposure to maternal glucocorticoids and increase thymocyte apoptosis, which could persist into postnatal life and be implicated in Th1 inhibition and further immune disorders.

α7 nAChR mediated Fas demethylation contributes to prenatal nicotine exposure-induced programmed thymocyte apoptosis in mice

This study aimed to investigate the effects of prenatal nicotine exposure (PNE) on thymocyte apoptosis and postnatal immune impairments in vivo and further explore the epigenetic mechanisms of the pro-apoptotic effect of nicotine in vitro. The results showed that PNE caused immune impairments in offspring on postnatal day 49, manifested as increased IL-4 production and an increased IgG1/IgG2a ratio in serum. Enhanced apoptosis of total and CD4+SP thymocytes was observed both in fetus and in offspring. Further, by exposing thymocytes to 0–100 μM of nicotine in vitro for 48 h, we found that nicotine increased α7 nicotinic acetylcholine receptor (nAChR) expression, activated the Fas apoptotic pathway, and promoted thymocyte apoptosis in concentration-dependent manners. In addition, nicotine could induce Tet methylcytosine dioxygenase (TET) 2 expression and Fas promoter demethylation, which can be abolished by TET2 siRNA transfection. Moreover, the α7 nAChR specific antagonist α-bungarotoxin can abrogate nicotine-induced TET2 increase, and the following Fas demethylation and Fas-mediated apoptosis. In conclusion, our findings showed, for the first time, that α7 nAChR activation could induce TET2-mediated Fas demethylation in thymocytes and results in the upregulation of Fas apoptotic pathway, which provide evidence for elucidating the PNE-induced programmed thymocyte apoptosis.

Cadmium-induced toxicity is rescued by curcumin: A review

Cadmium (Cd) is one of the most common environmental and occupational heavy metals with extended distribution. Exposure to Cd may be associated with several deleterious consequences on the liver, bones, kidneys, lungs, testes, brain, immunological, and cardiovascular systems. Overproduction of reactive oxygen species (ROS) as the main mechanism behind its toxicity causes oxidative stress and subsequent damages to lipids, proteins, and DNA. Therefore, antioxidants along with chelating agents have shown promising outcomes against Cd-induced toxicity. Curcumin with various beneficial effects and medical efficacy has been evaluated for its inhibitory activities against biological impairments caused by Cd. Thus, this article is intended to address the effectiveness of curcumin against toxicity following Cd entry. Curcumin can afford to attenuate lipid peroxidation, glutathione depletion, alterations in antioxidant enzyme, and so forth through scavenging and chelating activities or Nrf2/Keap1/ARE pathway induction. © 2017 BioFactors, 43(5):645-661, 2017.

Cord blood T cell subpopulations and associations with maternal cadmium and arsenic exposures

Background

Arsenic and cadmium are environmental pollutants, and although the evidence for adverse immune effects after prenatal arsenic and cadmium exposures is increasing, little is known about the underlying immunological mechanisms.

Methods

We investigated the relationship between prenatal arsenic and cadmium exposures and a variety of T cell subpopulations measured in cord blood for 63 participants in the New Hampshire Birth Cohort Study. Post-partum toenail concentrations of arsenic and cadmium were used as an estimate of maternal exposure during pregnancy. The characteristics of cord blood proportions of T lymphocytes and subpopulations (expression of markers for Th1, Th2, Th17, Th1Th17, induced and natural regulatory T cells and NKTs) are presented.

Results

In regression analyses, maternal arsenic exposure levels were inversely associated with cord blood T helper memory cells (-21%, 95% CI: -36%, -3%) and the association was found to be stronger in females. They were also inversely associated with activated T helper memory cells, particularly in males (-26%, 95% CI: -43%, -3%). Similarly, inverse associations were observed between cadmium exposure levels and activated T helper memory cells (-16%, 95% CI: -30%, -1%) and also for T helper memory cells in females (-20%, 95% CI: -35%, -3%).

Conclusion

The results suggest that prenatal exposures to relatively low levels of arsenic and cadmium may contribute to altered distribution of T cell populations at birth. These changes in theory, could have contributed to the previously reported immunosuppressive effects observed later in infancy/childhood.

Increased Fetal Thymocytes Apoptosis Contributes to Prenatal Nicotine Exposure-induced Th1/Th2 Imbalance in Male Offspring Mice

Nicotine, a definite risk factor during pregnancy, is an immunomodulator. This study was designed to investigate the effects of prenatal nicotine exposure (PNE) on the balance of Th1/Th2 in offspring, and further explore the developmental origin mechanisms from the perspective of fetal thymocytes apoptosis. Pregnant Balb/c mice were administered 1.5 mg/kg nicotine subcutaneously twice per day from gestational day (GD) 9 to GD18. Results showed that PNE could cause a Th2 shift in male offspring, manifested as increased ratio of IgG1/IgG2a, IL-4 production in serum, and IL-4/IFN-γ expression ratio in spleen. Increased apoptosis of total thymocytes and CD4SP and reduced cell proportion of CD4SP were found in PNE male offspring on postnatal day (PND) 14 and PND 49. In the fetuses, decreased body weight and organ index of fetal thymus, histological changes in fetal thymus, reduced CD4SP proportion and increased fetal thymocyte apoptosis were observed in nicotine group. The increased mRNA expression of genes involved in Fas-mediated apoptotic pathway and protein expression of Fas were also detected. In conclusion, PNE could cause a Th2 shift in male offspring mediated by reduced CD4⁺ T cells output, which may result from the increasing apoptosis of total thymocytes and CD4SP.

Cadmium modulates hematopoietic stem and progenitor cells and skews toward myelopoiesis in mice

The heavy metal cadmium (Cd) is known to modulate immunity and cause osteoporosis. However, how Cd influences on hematopoiesis remain largely unknown. Herein, we show that wild-type C57BL/6 (B6) mice exposed to Cd for 3months had expanded bone marrow (BM) populations of long-term hematopoietic stem cells (LT-HSCs), common myeloid progenitors (CMPs) and granulocyte-macrophage progenitors (GMPs), while having reduced populations of multipotent progenitors (MPPs) and common lymphoid progenitors (CLPs). A competitive mixed BM transplantation assay indicates that BM from Cd-treated mice had impaired LT-HSC ability to differentiate into mature cells. In accordance with increased myeloid progenitors and decreased lymphoid progenitors, the BM and spleens of Cd-treated mice had more monocytes and/or neutrophils and fewer B cells and T cells. Cd impaired the ability of the non-hematopoietic system to support LT-HSCs, in that lethally irradiated Cd-treated recipients transplanted with normal BM cells had reduced LT-HSCs after the hematopoietic system was fully reconstituted. This is consistent with reduced osteoblasts, a known critical component for HSC niche, observed in Cd-treated mice. Conversely, lethally irradiated control recipients transplanted with BM cells from Cd-treated mice had normal LT-HSC reconstitution. Furthermore, both control mice and Cd-treated mice that received Alendronate, a clinical drug used for treating osteoporosis, had BM increases of LT-HSCs. Thus, the results suggest Cd increase of LT-HSCs is due to effects on HSCs and not on osteoblasts, although, Cd causes osteoblast reduction and impaired niche function for maintaining HSCs. Furthermore, Cd skews HSCs toward myelopoiesis.

Developmental origins of inflammatory and immune diseases

Epidemiological and experimental animal studies show that suboptimal environments in fetal and neonatal life exert a profound influence on physiological function and risk of diseases in adult life. The concepts of the 'developmental programming' and Developmental Origins of Health and Diseases (DOHaD) have become well accepted and have been applied across almost all fields of medicine. Adverse intrauterine environments may have programming effects on the crucial functions of the immune system during critical periods of fetal development, which can permanently alter the immune function of offspring. Immune dysfunction may in turn lead offspring to be susceptible to inflammatory and immune diseases in adulthood. These facts suggest that inflammatory and immune disorders might have developmental origins. In recent years, inflammatory and immune disorders have become a growing health problem worldwide. However, there is no systematic report in the literature on the developmental origins of inflammatory and immune diseases and the potential mechanisms involved. Here, we review the impacts of adverse intrauterine environments on the immune function in offspring. This review shows the results from human and different animal species and highlights the underlying mechanisms, including damaged development of cells in the thymus, helper T cell 1/helper T cell 2 balance disturbance, abnormal epigenetic modification, effects of maternal glucocorticoid overexposure on fetal lymphocytes and effects of the fetal hypothalamic-pituitary-adrenal axis on the immune system. Although the phenomena have already been clearly implicated in epidemiologic and experimental studies, new studies investigating the mechanisms of these effects may provide new avenues for exploiting these pathways for disease prevention.

Prenatal exposure to arsenic and cadmium impacts infectious disease-related genes within the glucocorticoid receptor signal transduction pathway

There is increasing evidence that environmental agents mediate susceptibility to infectious disease. Studies support the impact of prenatal/early life exposure to the environmental metals inorganic arsenic (iAs) and cadmium (Cd) on increased risk for susceptibility to infection. The specific biological mechanisms that underlie such exposure-mediated effects remain understudied. This research aimed to identify key genes/signal transduction pathways that associate prenatal exposure to these toxic metals with changes in infectious disease susceptibility using a Comparative Genomic Enrichment Method (CGEM). Using CGEM an infectious disease gene (IDG) database was developed comprising 1085 genes with known roles in viral, bacterial, and parasitic disease pathways. Subsequently, datasets collected from human pregnancy cohorts exposed to iAs or Cd were examined in relationship to the IDGs, specifically focusing on data representing epigenetic modifications (5-methyl cytosine), genomic perturbations (mRNA expression), and proteomic shifts (protein expression). A set of 82 infection and exposure-related genes was identified and found to be enriched for their role in the glucocorticoid receptor signal transduction pathway. Given their common identification across numerous human cohorts and their known toxicological role in disease, the identified genes within the glucocorticoid signal transduction pathway may underlie altered infectious disease susceptibility associated with prenatal exposures to the toxic metals iAs and Cd in humans.

Pre-birth world and the development of the immune system: mum's diet affects our adult health: new insight on how the diet during pregnancy permanently influences offspring health and immune fitness

Secondary lymphoid organs form in utero through an inherited and well-established developmental program. However, maternal non-heritable features can have a major impact on the gene expression of the embryo, hence influencing the future health of the offspring. Recently, maternal retinoids were shown to regulate the formation of immune structures, shedding light on the role of maternal nutrition in the genetic signature of emergent immune cells. Here we highlight evidence showing how the maternal diet influences the establishment of the immune system, and we also discuss how unbalanced maternal diets may set the response to infection and vaccination in the progeny.

Developmental toxicity in rare minnow (Gobiocypris rarus) embryos exposed to Cu, Zn and Cd

Using rare minnow (Gobiocypris rarus) embryos as experimental model, the developmental toxicity of Cu, Zn and Cd were investigated following exposure to 0.001-1.000mg/L for 72h, and the toxicity effects were evaluated by larval malformation rate, heart rate, pericardial area, spontaneous movements, tail length, enzyme activities and biomarker genes. Our results revealed that increased malformation rate provide a gradual dose-response relationship, and the most pronounced morphological alteration was heart and body malformations. Values of 72h EC50 with their 95 percent confidence intervals on G. rarus embryos were 0.103 (0.072-0.149)mg/L for Cu, 0.531 (0.330-1.060)mg/L for Zn, 0.219 (0.147-0.351)mg/L for Cd. Enzyme activities can be regard as a type of low-dose stimulation and high-dose inhibition. Stress and metabolism-related genes (hsp70, cyp1a and mt) were significantly up-regulated, development-related genes (wnt8a, vezf1 and mstn) were significantly down-regulated after the treatment by Cu, Zn and Cd. Overall, the present study points out Cu, Zn and Cd are highly toxic to G. rarus embryos. The information presented in this study will be helpful in fully understanding the toxicity induced by Cu, Zn and Cd in fish embryos.

Environmental alterations of epigenetics prior to the birth

The etiology of many brain diseases remains allusive to date after intensive investigation of genomic background and symptomatology from the day of birth. Emerging evidences indicate that a third factor, epigenetics prior to the birth, can exert profound influence on the development and functioning of the brain and over many neurodevelopmental syndromes. This chapter reviews how aversive environmental exposure to parents might predispose or increase vulnerability of offspring to neurodevelopmental deficit through alteration of epigenetics. These epigenetic altering environmental factors will be discussed in the category of addictive agents, nutrition or diet, prescriptive medicine, environmental pollutant, and stress. Epigenetic alterations induced by these aversive environmental factors cover all aspects of epigenetics including DNA methylation, histone modification, noncoding RNA, and chromatin modification. Next, the mechanisms how these environmental inputs influence epigenetics will be discussed. Finally, how environmentally altered epigenetic marks affect neurodevelopment is exemplified by the alcohol-induced fetal alcohol syndrome. It is hoped that a thorough understanding of the nature of prenatal epigenetic inputs will enable researchers with a clear vision to better unravel neurodevelopmental deficit, late-onset neuropsychiatric diseases, or idiosyncratic mental disorders.

Cadmium toxicity and treatment

Cadmium is a heavy metal of considerable toxicity with destructive impact on most organ systems. It is widely distributed in humans, the chief sources of contamination being cigarette smoke, welding, and contaminated food and beverages. Toxic impacts are discussed and appear to be proportional to body burden of cadmium. Detoxification of cadmium with EDTA and other chelators is possible and has been shown to be therapeutically beneficial in humans and animals when done using established protocols.

Regulatory mechanisms of thymus and T cell development

The thymus is a central hematopoietic organ which produces mature T lymphocytes with diverse antigen specificity. During development, the thymus primordium is derived from the third pharyngeal endodermal pouch, and then differentiates into cortical and medullary thymic epithelial cells (TECs). TECs represent the primary functional cell type that forms the unique thymic epithelial microenvironment which is essential for intrathymic T-cell development, including positive selection, negative selection and emigration out of the thymus. Our understanding of thymopoiesis has been greatly advanced by using several important animal models. This review will describe progress on the molecular mechanisms involved in thymus and T cell development with particular focus on the signaling and transcription factors involved in this process in mouse and zebrafish.

Prenatal cadmium exposure produces persistent changes to thymus and spleen cell phenotypic repertoire as well as the acquired immune response

Cadmium (Cd) is a common environmental contaminant. Adult exposure to Cd alters the immune system, however, there are limited studies on the effects of prenatal exposure to Cd. Pregnant C57Bl/6 mice were exposed to an environmentally relevant dose of CdCl(2) (10 ppm) and the effects on the immune system of the offspring were assessed at 20 weeks of age. Prenatal Cd exposure caused an increase in the percent of CD4(-)CD8(-)CD44(+)CD25(-) (DN1) thymocytes in both sexes and a decrease in the percent of CD4(-)CD8(-)CD44(-)CD25(+) (DN3) thymocytes in females. Females had an increase in the percent of splenic CD4(+) T cells, CD8(+) T cells, and CD45R/B220(+) B cells and a decrease in the percent of NK cells and granulocytes (Gr-1(+)). Males had an increase in the percent of splenic CD4(+) T cells and CD45R/B220(+) B cells and a decrease in the percent of CD8(+) T cells, NK cells, and granulocytes. The percentage of neutrophils and myeloid-derived suppressor cells were reduced in both sexes. The percent of splenic nTreg cells was decreased in all Cd-exposed offspring. Cd-exposed offspring were immunized with a streptococcal vaccine and the antibody response was determined. PC-specific serum antibody titers were decreased in Cd exposed female offspring but increased in the males. PspA-specific serum IgG titers were increased in both females and males compared to control animals. Females had a decrease in PspA-specific serum IgM antibody titers. Females and males had a decrease in the number of splenic anti-PspA antibody-secreting cells when standardized to the number of B cells. These findings demonstrate that very low levels of Cd exposure during gestation can result in long term sex-specific alterations on the immune system of the offspring.

A common response to common danger? Comparison of animal and plant signaling pathways involved in cadmium sensing

Exposure to cadmium results in disturbances in cell homeostasis in all living organisms. The first response to stress factors, including cadmium, is activation of signal transduction pathways that mobilize cell defense mechanisms. The aim of this review is a comparison between the signaling network triggered by Cd in plants and animals. Despite differences in the structure and physiology of plant and animal cells, their cadmium signal transduction pathways share many common elements. These elements include signaling molecules such as ROS, Ca(2+) and NO, the involvement of phospholipase C, mitogen-activated protein kinase cascades, and activation of transcription factors. Undoubtedly, both animals and plants also possess specific signaling pathways. In case of animals, Wnt/β-catenin, sonic hedgehog and oestorgen signaling are engaged in the transduction of cadmium signal. Plant specific signal transduction pathways include signaling mediated by plant hormones. The role of ethylene and jasmonic, salicylic and abscisic acid in plant response to cadmium is also discussed.

Prenatal cadmium exposure alters postnatal immune cell development and function

Cadmium (Cd) is generally found in low concentrations in the environment due to its widespread and continual use, however, its concentration in some foods and cigarette smoke is high. Although evidence demonstrates that adult exposure to Cd causes changes in the immune system, there are limited reports of immunomodulatory effects of prenatal exposure to Cd. This study was designed to investigate the effects of prenatal exposure to Cd on the immune system of the offspring. Pregnant C57Bl/6 mice were exposed to an environmentally relevant dose of CdCl(2) (10ppm) and the effects on the immune system of the offspring were assessed at two time points following birth (2 and 7weeks of age). Thymocyte and splenocyte phenotypes were analyzed by flow cytometry. Prenatal Cd exposure did not affect thymocyte populations at 2 and 7weeks of age. In the spleen, the only significant effect on phenotype was a decrease in the number of macrophages in male offspring at both time points. Analysis of cytokine production by stimulated splenocytes demonstrated that prenatal Cd exposure decreased IL-2 and IL-4 production by cells from female offspring at 2weeks of age. At 7weeks of age, splenocyte IL-2 production was decreased in Cd-exposed males while IFN-γ production was decreased from both male and female Cd-exposed offspring. The ability of the Cd-exposed offspring to respond to immunization with a S. pneumoniae vaccine expressing T-dependent and T-independent streptococcal antigens showed marked increases in the levels of both T-dependent and T-independent serum antibody levels compared to control animals. CD4(+)FoxP3(+)CD25(+) (nTreg) cell percentages were increased in the spleen and thymus in all Cd-exposed offspring except in the female spleen where a decrease was seen. CD8(+)CD223(+) T cells were markedly decreased in the spleens in all offspring at 7weeks of age. These findings suggest that even very low levels of Cd exposure during gestation can result in long term detrimental effects on the immune system of the offspring and these effects are to some extent sex-specific.

Ovine fetal thymus response to lipopolysaccharide-induced chorioamnionitis and antenatal corticosteroids

Rationale

Chorioamnionitis is associated with preterm delivery and involution of the fetal thymus. Women at risk of preterm delivery receive antenatal corticosteroids which accelerate fetal lung maturation and improve neonatal outcome. However, the effects of antenatal corticosteroids on the fetal thymus in the settings of chorioamnionitis are largely unknown. We hypothesized that intra-amniotic exposure to lipopolysaccharide (LPS) causes involution of the fetal thymus resulting in persistent effects on thymic structure and cell populations. We also hypothesized that antenatal corticosteroids may modulate the effects of LPS on thymic development.

Methods

Time-mated ewes with singleton fetuses received an intra-amniotic injection of LPS 7 or 14 days before preterm delivery at 120 days gestational age (term = 150 days). LPS and corticosteroid treatment groups received intra-amniotic LPS either preceding or following maternal intra-muscular betamethasone. Gestation matched controls received intra-amniotic and maternal intra-muscular saline. The fetal intra-thoracic thymus was evaluated.

Results

Intra-amniotic LPS decreased the cortico-medullary (C/M) ratio of the thymus and increased Toll-like receptor (TLR) 4 mRNA and CD3 expression indicating involution and activation of the fetal thymus. Increased TLR4 and CD3 expression persisted for 14 days but Foxp3 expression decreased suggesting a change in regulatory T-cells. Sonic hedgehog and bone morphogenetic protein 4 mRNA, which are negative regulators of T-cell development, decreased in response to intra-amniotic LPS. Betamethasone treatment before LPS exposure attenuated some of the LPS-induced thymic responses but increased cleaved caspase-3 expression and decreased the C/M ratio. Betamethasone treatment after LPS exposure did not prevent the LPS-induced thymic changes.

Conclusion

Intra-amniotic exposure to LPS activated the fetal thymus which was accompanied by structural changes. Treatment with antenatal corticosteroids before LPS partially attenuated the LPS-induced effects but increased apoptosis in the fetal thymus. Corticosteroid administration after the inflammatory stimulus did not inhibit the LPS effects on the fetal thymus.

Effects of cadmium on proliferation and self-renewal activity of prostate stem/progenitor cells

Cadmium (Cd) is an occupational and environmental pollutant that induces numerous pathological effects, including injuries to prostate. The aim of the present study was to investigate the effects of Cd on self-renewal and proliferation of prostate stem/progenitor cells (PSPC) and its possible mechanisms. Prostate epithelial cells were prepared from mice to form sphere in Matrigel/PrEGM supplemented with cadmium chloride (CdCl(2)). The data showed that CdCl(2) inhibits sphere-forming ability and proliferation of PSPC in a concentration dependent manner. Primary spheres were then passaged to form daughter spheres and we found that CdCl(2) suppressed PSPC self-renewal activity, which recovered after further passaging. We also detected the protein level of androgen receptor (AR) in the spheres of each passage. The results showed that AR in primary spheres is suppressed by CdCl(2) in a concentration dependent manner. However, no obvious change of AR was found in subsequent passages. The in vivo toxicity of CdCl(2) on PSPC was detected by giving mice drinking water with CdCl(2). Our results demonstrated in vivo inhibition effect of CdCl(2) on self-renewal activity of PSPC. Consistent with in vitro results, self-renewal activity of PSPC was recovered after CdCl(2) withdrawal. In addition, CdCl(2) also in vivo suppressed PSPC proliferation as indicated by Ki67 immunostaining. Our finding suggested that Cd may inhibit proliferation and self-renewal activity of PSPC by suppressing AR, which could be important to further understanding the complex mechanism of Cd toxicity in prostate.

Comparative genomic analyses identify common molecular pathways modulated upon exposure to low doses of arsenic and cadmium

BACKGROUND

Exposure to the toxic metals arsenic and cadmium is associated with detrimental health effects including cancers of various organs. While arsenic and cadmium are well known to cause adverse health effects at high doses, the molecular impact resulting from exposure to environmentally relevant doses of these metals remains largely unexplored.

RESULTS

In this study, we examined the effects of in vitro exposure to either arsenic or cadmium in human TK6 lymphoblastoid cells using genomics and systems level pathway mapping approaches. A total of 167 genes with differential expression were identified following exposure to either metal with surprisingly no overlap between the two. Real-time PCR was used to confirm target gene expression changes. The gene sets were overlaid onto protein-protein interaction maps to identify metal-induced transcriptional networks. Interestingly, both metal-induced networks were significantly enriched for proteins involved in common biological processes such as tumorigenesis, inflammation, and cell signaling. These findings were further supported by gene set enrichment analysis.

CONCLUSIONS

This study is the first to compare the transcriptional responses induced by low dose exposure to cadmium and arsenic in human lymphoblastoid cells. These results highlight that even at low levels of exposure both metals can dramatically influence the expression of important cellular pathways.

Blood cadmium levels in women of childbearing age vary by race/ethnicity

The heavy metal cadmium (Cd) is long-lived in the body and low-level cumulative exposure, even among non-smokers, has been associated with changes in renal function and bone metabolism. Women are more susceptible to the adverse effects of Cd and have higher body burdens. Due to increased dietary absorption of Cd in menstruating women and the long half-life of the metal, reproductive age exposures are likely important contributors to overall body burden and disease risk. We examined blood Cd levels in women of reproductive age in the US and assessed variation by race/ethnicity. Blood Cd concentrations were compared among female NHANES participants aged 20-44, who were neither pregnant nor breastfeeding. Sample size varied primarily based on inclusion/exclusion of smokers (n=1734-3121). Mean Cd concentrations, distributions and odds ratios were calculated using SUDAAN. For logistic regression Cd was modeled as high (the upper 10% of the distribution) vs. the remainder. Overall, Mexican Americans had lower Cd levels than other groups due to a lower smoking prevalence, smoking being an important source of exposure. Among never-smokers, Mexican Americans had 1.77 (95% CI: 1.06-2.96) times the odds of high Cd as compared to non-Hispanic Whites after controlling for age and low iron (ferritin). For non-Hispanic Blacks, the odds were 2.96 (CI: 1.96-4.47) times those of non-Hispanic Whites in adjusted models. Adjustment for relevant reproductive factors or exposure to environmental tobacco smoke had no effect. In this nationally representative sample, non-smoking Mexican American and non-Hispanic Black women were more likely to have high Cd than non-Hispanic White women. Additional research is required to determine the underlying causes of these differences.

Chronic cadmium exposure induces transcriptional activation of the Wnt pathway and upregulation of epithelial-to-mesenchymal transition markers in mouse kidney

The transition metal cadmium (Cd) is an environmental pollutant which damages the kidneys. Chronic Cd exposure may induce renal fibrosis and/or cancer, but the signaling pathways involved are not understood. The Wnt pathway is a key signaling cascade responsible for renal development, fibrosis and cancer. Hence the effect of chronic in vivo Cd exposure (100 mg/l drinking water for 12 weeks) on transcriptional activation of the Wnt pathway and markers of epithelial-to-mesenchymal transition (EMT) was investigated in mouse kidneys. Cd exposure increased kidney Cd content from 0.023+/-0.001 microg/g to 61+/-7 microg/g wet weight (means+/-S.D. of 6-7 animals). This was accompanied by increased expression of Wnt ligands (Wnt3a/6/7a/7b/9a/9b/10a/11), as determined by RT-PCR. The Wnt receptors Frizzled (Fz1/2/4,5,7-10) were also upregulated, as were the co-receptors low-density lipoprotein receptor-related proteins 5/6. Immunoblots with Wnt10a and Fz7 antibodies also revealed increased protein expression induced by Cd exposure. In contrast, Wnt antagonists were largely unaffected. Upregulation of Wnt signaling components induced by Cd was corroborated by increased expression of Wnt target genes, i.e. cell proliferation and survival genes c-Myc, cyclin D1 and the multidrug transporter P-glycoprotein Abcb1b, which promote malignancy. Lastly the EMT markers Twist, fibronectin and collagen I, but not alpha-smooth muscle actin, were also upregulated, suggesting that Cd-induced changes of renal epithelial tissue characteristics towards fibrosis and cancer may be mediated by Wnt signaling.