Impact of Cadmium on Intracellular Zinc Levels in HepG2 Cells: Quantitative Evaluations and Molecular Effects

Pollutants to pathogens: The role of heavy metals in modulating TGF-β signaling and lung cancer risk

Lung cancer is a malignant tumor that develops in the lungs due to the uncontrolled growth of aberrant cells. Heavy metals, such as arsenic, cadmium, mercury, and lead, are metallic elements characterized by their high atomic weights and densities. Anthropogenic activities, such as industrial operations and pollution, have the potential to discharge heavy metals into the environment, hence presenting hazards to ecosystems and human well-being. The TGF-β signalling pathways have a crucial function in controlling several cellular processes, with the ability to both prevent and promote tumor growth. TGF-β regulates cellular responses by interacting in both canonical and non-canonical signalling pathways. Research employing both in vitro and in vivo models has shown that heavy metals may trigger TGF-β signalling via complex molecular pathways. Experiments conducted in a controlled laboratory environment show that heavy metals like cadmium and arsenic may directly bind to TGF-β receptors, leading to alterations in their structure that enable the receptor to be phosphorylated. Activation of this route sets in motion subsequent signalling cascades, most notably the canonical Smad pathway. The development of lung cancer has been linked to heavy metals, which are ubiquitous environmental pollutants. To grasp the underlying processes, it is necessary to comprehend their molecular effect on TGF-β pathways. With a particular emphasis on its consequences for lung cancer, this abstract delves into the complex connection between exposure to heavy metals and the stimulation of TGF-β signalling.

Effects of Copper or Zinc Organometallics on Cytotoxicity, DNA Damage and Epigenetic Changes in the HC-04 Human Liver Cell Line

Copper and zinc organometallics have multiple applications and many are considered "data-poor" because the available toxicological information is insufficient for comprehensive health risk assessments. To gain insight into the chemical prioritization and potential structure activity relationship, the current work compares the in vitro toxicity of nine "data-poor" chemicals to five structurally related chemicals and to positive DNA damage inducers (4-nitroquinoline-oxide, aflatoxin-B1). The HC-04 non-cancer human liver cell line was used to investigate the concentration-response effects (24 h and 72 h exposure) on cell proliferation, DNA damage (γH2AX and DNA unwinding assays), and epigenetic effects (global genome changes in DNA methylation and histone modifications using flow cytometry). The 24 h exposure screening data (DNA abundance and damage) suggest a toxicity hierarchy, starting with copper dimethyldithiocarbamate (CDMDC, CAS#137-29-1) > zinc diethyldithiocarbamate (ZDEDC, CAS#14324-55-1) > benzenediazonium, 4-chloro-2-nitro-, and tetrachlorozincate(2-) (2:1) (BDCN4CZ, CAS#14263-89-9); the other chemicals were less toxic and had alternate ranking positions depending on assays. The potency of CDMDC for inducing DNA damage was close to that of the human hepatocarcinogen aflatoxin-B1. Further investigation using sodium-DMDC (SDMDC, CAS#128-04-1), CDMDC and copper demonstrated the role of the interactions between copper and the DMDC organic moiety in generating a high level of CDMDC toxicity. In contrast, additive interactions were not observed with respect to the DNA methylation flow cytometry data in 72 h exposure experiments. They revealed chemical-specific effects, with hypo and hypermethylation induced by copper chloride (CuCl2, CAS#10125-13-0) and zinc-DMDC (ZDMDC, CAS#137-30-4), respectively, but did not show any significant effect of CDMDC or SDMDC. Histone-3 hypoacetylation was a sensitive flow cytometry marker of 24 h exposure to CDMDC. This study can provide insights regarding the prioritization of chemicals for future study, with the aim being to mitigate chemical hazards.

BDNF and KISS-1 Levels in Maternal Serum, Umbilical Cord, and Placenta: The Potential Role of Maternal Levels as Effect Biomarker

Brain-derived neurotrophic factor (BDNF) and kisspeptin-1 (KISS-1) regulate placental development and fetal growth. The predictive value of maternal serum BDNF and KISS-1 concentrations for placental and umbilical cord levels has not yet been explored. The influence of prenatal lead (Pb) and cadmium (Cd) exposure and maternal iron status on BDNF and KISS-1 levels is also unclarified and of concern. In a pilot cross-sectional study with 65 mother-newborn pairs, we analyzed maternal and cord serum levels of pro-BDNF, mature BDNF, and KISS-1, BDNF, and KISS-1 gene expression in placenta, Pb and Cd in maternal and umbilical cord blood (erythrocytes), and placenta. We conducted a series of in vitro experiments using human primary trophoblast cells (hTCs) and BeWo cells to verify main findings of the epidemiological analysis. Strong and consistent correlations were observed between maternal serum levels of pro-BDNF, mature BDNF, and KISS-1 and corresponding levels in umbilical serum and placental tissue. Maternal red blood cell Pb levels were inversely correlated with serum and placental KISS-1 levels. Lower expression and release of KISS-1 was also observed in Pb-exposed BeWo cells. In vitro Pb exposure also reduced cellular BDNF levels. Cd-treated BeWo cells showed increased pro-BDNF levels. Low maternal iron status was positively associated with low BDNF levels. Iron-deficient hTCs and BeWo cells showed a consistent decrease in the release of mature BDNF. The correlations between maternal BDNF and KISS-1 levels, placental gene expression, and umbilical cord serum levels, respectively, indicate the strong potential of maternal serum as predictive matrix for BDNF and KISS-1 levels in placentas and fetal sera. Pb exposure and iron status modulate BDNF and KISS-1 levels, but a clear direction of modulations was not evident. The associations need to be confirmed in a larger sample and validated in terms of placental and neurodevelopmental function.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12403-023-00565-w.

Epigenetic Regulation in Chromium-, Nickel- and Cadmium-Induced Carcinogenesis

Environmental and occupational exposure to heavy metals, such as hexavalent chromium, nickel, and cadmium, are major health concerns worldwide. Some heavy metals are well-documented human carcinogens. Multiple mechanisms, including DNA damage, dysregulated gene expression, and aberrant cancer-related signaling, have been shown to contribute to metal-induced carcinogenesis. However, the molecular mechanisms accounting for heavy metal-induced carcinogenesis and angiogenesis are still not fully understood. In recent years, an increasing number of studies have indicated that in addition to genotoxicity and genetic mutations, epigenetic mechanisms play critical roles in metal-induced cancers. Epigenetics refers to the reversible modification of genomes without changing DNA sequences; epigenetic modifications generally involve DNA methylation, histone modification, chromatin remodeling, and non-coding RNAs. Epigenetic regulation is essential for maintaining normal gene expression patterns; the disruption of epigenetic modifications may lead to altered cellular function and even malignant transformation. Therefore, aberrant epigenetic modifications are widely involved in metal-induced cancer formation, development, and angiogenesis. Notably, the role of epigenetic mechanisms in heavy metal-induced carcinogenesis and angiogenesis remains largely unknown, and further studies are urgently required. In this review, we highlight the current advances in understanding the roles of epigenetic mechanisms in heavy metal-induced carcinogenesis, cancer progression, and angiogenesis.

Is Cadmium Toxicity Tissue-Specific? Toxicogenomics Studies Reveal Common and Specific Pathways in Pulmonary, Hepatic, and Neuronal Cell Models

Several harmful modifications in different tissues-organs, leading to relevant diseases (e.g., liver and lung diseases, neurodegeneration) are reported after exposure to cadmium (Cd), a wide environmental contaminant. This arises the question whether any common molecular signatures and/or Cd-induced modifications might represent the building block in initiating or contributing to address the cells towards different pathological conditions. To unravel possible mechanisms of Cd tissue-specificity, we have analyzed transcriptomics data from cell models representative of three major Cd targets: pulmonary (A549), hepatic (HepG2), and neuronal (SH-SY-5Y) cells. Further, we compared common features to identify any non-specific molecular signatures. The functional analysis of dysregulated genes (gene ontology and KEGG) shows GO terms related to metabolic processes significantly enriched only in HepG2 cells. GO terms in common in the three cell models are related to metal ions stress response and detoxification processes. Results from KEGG analysis show that only one specific pathway is dysregulated in a significant way in all cell models: the mineral absorption pathway. Our data clearly indicate how the molecular mimicry of Cd and its ability to cause a general metal ions dyshomeostasis represent the initial common feature leading to different molecular signatures and alterations, possibly responsible for different pathological conditions.

N-Acetylcysteine Reduces miR-146a and NF-κB p65 Inflammatory Signaling Following Cadmium Hepatotoxicity in Rats

We performed a thorough screening and analysis of the impact of cadmium chloride (CdCl₂) and N-acetylcysteine (NAC) on the miR146a/NF-κB p65 inflammatory pathway and mitochondrial biogenesis dysfunction in male albino rats. A total of 24 male albino rats were divided into three groups: a control group, a CdCl₂-treated group (3 mg/kg, orally), and a CdCl₂ + NAC-treated group (200 mg/kg of NAC, 1 h after CdCl₂ treatment), for 60 consecutive days. Real-time quantitative PCR was used to analyze the expression of miR146a, Irak1, Traf6, Nrf1, Nfe2l2, Pparg, Prkaa, Stat3, Tfam, Tnfa, and Il1b, whereas tumor necrosis factor-α, interleukin-1β, and cyclooxygenase-2 protein levels were assessed using ELISA, and NF-κB p65 was detected using western blotting. A significant restoration of homeostatic inflammatory processes as well as mitochondrial biogenesis was observed after NAC and CdCl₂ treatment. Decreased miR146a and NF-κB p65 were also found after treatment with NAC and CdCl₂ compared with CdCl₂ treatment alone. Collectively, our findings demonstrate that CdCl₂ caused mtDNA release because of Tfam loss, leading to NF-κB p65 activation. Co-treatment with NAC could alleviate Cd-induced genotoxicity in liver tissue. We concluded that adding NAC to CdCl₂ resulted in a decreased signaling of the NF-κB p65 signaling pathway.

Insights into Cadmium-Induced Carcinogenesis through an In Vitro Study Using C3H10T1/2Cl8 Cells: The Multifaceted Role of Mitochondria

In this paper, we report the metabolic characterization of two foci, F1 and F3, obtained at the end of Cell Transformation Assay (CTA), performed by treating C3H10T1/2Cl8 mouse embryo fibroblasts with 1 μM CdCl₂ for 24 h. The elucidation of the cadmium action mechanism can be useful both to improve the in vitro CTA and to yield insights into carcinogenesis. The metabolism of the two foci was investigated through Seahorse and enzyme activity assays; mitochondria were studied in confocal microscopy and reactive oxygen species were detected by flow cytometry. The results showed that F1 focus has higher glycolytic and TCA fluxes compared to F3 focus, and a more negative mitochondrial membrane potential, so that most ATP synthesis is performed through oxidative phosphorylation. Confocal microscopy showed mitochondria crowded in the perinuclear region. On the other hand, F3 focus showed lower metabolic rates, with ATP mainly produced by glycolysis and damaged mitochondria. Overall, our results showed that cadmium treatment induced lasting metabolic alterations in both foci. Triggered by the loss of the Pasteur effect in F1 focus and by mitochondrial impairment in F3 focus, these alterations lead to a loss of coordination among glycolysis, TCA and oxidative phosphorylation, which leads to malignant transformation.

Cadmium-Associated Molecular Signatures in Cancer Cell Models

The exposure of cancer cells to cadmium and its compounds is often associated with the development of more malignant phenotypes, thereby contributing to the acceleration of tumor progression. It is known that cadmium is a transcriptional regulator that induces molecular reprogramming, and therefore the study of differentially expressed genes has enabled the identification and classification of molecular signatures inherent in human neoplastic cells upon cadmium exposure as useful biomarkers that are potentially transferable to clinical research. This review recapitulates selected studies that report the detection of cadmium-associated signatures in breast, gastric, colon, liver, lung, and nasopharyngeal tumor cell models, as specifically demonstrated by individual gene or whole genome expression profiling. Where available, the molecular, biochemical, and/or physiological aspects associated with the targeted gene activation or silencing in the discussed cell models are also outlined.

Superoxide dismutase 1 (SOD1) and cadmium: A three models approach to the comprehension of its neurotoxic effects

Cadmium (Cd) is a widespread toxic environmental contaminant, released by anthropogenic activities. It interferes with essential metal ions homeostasis and affects protein structures and functions by substituting zinc, copper and iron. In this study, the effect of cadmium on SOD1, a CuZn metalloenzyme catalyzing superoxide conversion into hydrogen peroxide, has been investigated in three different biological models. We first evaluated the effects of cadmium combined with copper and/or zinc on the recombinant GST-SOD1, expressed in E. coli BL21. The enzyme activity and expression were investigated in the presence of fixed copper and/or zinc doses with different cadmium concentrations, in the cellular medium. Cadmium caused a dose-dependent reduction in SOD1 activity, while the expression remains constant. Similar results were obtained in the cellular model represented by the human SH-SY5Y neuronal cell line. After cadmium treatment for 24 and 48 h, SOD1 enzymatic activity decreased in a dose- and time-dependent way, while the protein expression remained constant. Finally, a 16 h cadmium treatment caused a 25 % reduction of CuZn-SOD activity without affecting the protein expression in the Caenorhabditis elegans model. Taken together our results show an inhibitory effect of cadmium on SOD1 enzymatic activity, without affecting the protein expression, in all the biological models used, suggesting that cadmium can displace zinc from the enzyme catalytic site.

Metal(loid)s role in the pathogenesis of amyotrophic lateral sclerosis: Environmental, epidemiological, and genetic data

Amyotrophic Lateral Sclerosis (ALS) is a progressive neurodegenerative disorder of the motor system. The etiology is still unknown and the pathogenesis remains unclear. ALS is familial in the 10% of cases with a Mendelian pattern of inheritance. In the remaining sporadic cases, a multifactorial origin is supposed in which several predisposing genes interact with environmental factors. The etiological role of environmental factors, such as pesticides, exposure to electromagnetic fields, and metals has been frequently investigated, with controversial findings. Studies in the past two decades have highlighted possible roles of metals, and ionic homeostasis dysregulation has been proposed as the main trigger to motor-neuron degeneration. This study aims at evaluating the possible role of environmental factors in etiopathogenesis of ALS, with a particular attention on metal contamination, focusing on the industrial Briga area in the province of Novara (Piedmont region, North Italy), characterized by: i) a higher incidence of sporadic ALS (sALS) in comparison with the entire province, and ii) the reported environmental pollution. Environmental data from surface, ground and discharge waters, and from soils were collected and specifically analyzed for metal content. Considering the significance of genetic mechanisms in ALS, a characterization for the main ALS genes has been performed to evaluate the genetic contribution for the sALS patients living in the area of study. The main findings of this study are the demonstration that in the Briga area the most common metal contaminants are Cu, Zn, Cr, Ni (widely used in tip-plating processes), that are above law limits in surface waters, discharge waters, and soil. In addition, other metals and metalloids, such as Cd, Pb, Mn, and As show a severe contamination in the same area. Results of genetic analyses show that sALS patients in the Briga area do not carry recurrent mutations or an excess of mutations in the four main ALS causative genes (SOD1, TARDBP, FUS, C9ORF72) and for ATXN2 CAG repeat locus. This study supports the hypothesis that the higher incidence of sALS in Briga area may be related to environmental metal(loid)s contamination, along with other environmental factors. Further studies, implementing analysis of genetic polymorphisms, as well as investigation with long term follow-up, may yield to key aspects into the etiology of ALS. The interplay between different approaches (environmental, chemical, epidemiological, genetic) of our work provides new insights and methodology to the comprehension of the disease etiology.

LncRNA-ENST00000446135 is a novel biomarker of cadmium toxicity in 16HBE cells, rats, and Cd-exposed workers and regulates DNA damage and repair

Cadmium (Cd) and its compounds are well-known human carcinogens, but the mechanisms underlying the carcinogenesis are not well understood. This study aimed to investigate whether long noncoding RNA (LncRNA)-ENST00000446135 could serve as a novel biomarker of Cd toxicity in cells, animals, and Cd-exposed workers and regulate DNA damage and repair. LncRNA-ENST00000446135 expression increased gradually in cadmium chloride-transformed 16HBE cells. Small interfering RNA-mediated knockdown of LncRNA-ENST00000446135 inhibited the growth of DNA-damaged cells and decreased the expressions of DNA damage-related genes (ATM, ATR, and ATRIP), whereas increased the expressions of DNA repair-related genes (DDB1, DDB2, OGG1, ERCC1, MSH2, XRCC1, and BARD1). Chromatin immunoprecipitation-sequencing showed that MSH2 is a direct transcriptional target of lncRNA-ENST00000446135. Cadmium increased lncRNA-ENST00000446135 expression in the lung of Cd-exposed rats in a dose-dependent manner. A significant positive correlation was observed between blood ENST00000446135 expression and urinary/blood Cd concentrations, and there were significant correlations of LncRNA-ENST00000446135 expression with the DNA damage cell and the expressions of target genes in the lung of Cd-exposed rats and the blood of Cd-exposed workers and significantly correlated with liver and renal function in Cd-exposed workers. These results indicate that the expression of LncRNA-ENST00000446135 is upregulated and may serve as a signature for DNA damage and repair related to the epigenetic mechanisms underlying the cadmium toxicity and become a novel biomarker of cadmium toxicity.

Argon Enclosed Droplet Based 3D Microfluidic Device Online Coupled with Time-Resolved ICPMS for Determination of Cadmium and Zinc in Single Cells Exposed to Cadmium Ion

Time-resolved (TRA)-ICPMS has become a booming subfield of single-cell analysis tools in recent years, while generation of single cells remains the major challenge. Microfluidic devices reveal their great capability and potential in encapsulation of single cells into water droplets. However, current strategies to pinch off droplets require a specific oil phase, which is not compatible to conventional ICPMS and makes the signal of cells in the water phase susceptible. Herein, we built a 3D water-in-gas microfluidic device (3D W/G MFD) with commercially available components, producing single cell droplet enclosed by argon gas. By simply tuning the flow rate of gas and water, the droplets were generated to encapsulate single cells, which significantly reduced the probability of the single signal coming from multiple cells by 1 or 2 orders of magnitude compared to direct injection. The developed oil-free 3D W/G MFD was more friendly to online coupling with TRA-ICPMS than water-in-oil devices. The effect of Cd²⁺ on HepG2 cells was studied by single cell detecting total Zn with 3D W/G MFD-TRA-ICPMS, and the variation of labile Zn was explored by flow cytometry with an N-(6-methoxy-8-quinolyl)-p-toluenesulfonamide probe. To the best of our knowledge, this work pioneered the exploration of variation in cellular metal content and speciation at the single-cell level, compensating for the deficiency of speciation analysis based on TRA-ICPMS and providing new insights into exploring the complexity of biology.

Emerging Roles of MicroRNAs and Long Noncoding RNAs in Cadmium Toxicity

Metal cadmium (Cd) and its compounds are ubiquitous industrial and environmental pollutants and they have been believed to exert severe damage to multiple organs and tissues. MicroRNAs (miRNAs) and long noncoding RNAs (lncRNAs) are the two most common noncoding RNAs and have pivotal roles in various cellular and physiological processes. Since the importance of miRNAs and lncRNAs in Cd toxicity has been widely recognized, we focus our interests on the current researches of miRNAs and lncRNAs as well as their regulation roles in Cd toxicity. In this paper, the keywords "cadmium" in combination with "miRNA" or "LncRNA" or "noncoding RNA" was used to retrieve relevant articles in PubMed, EMbase, CNKI, Wan Fang, and CBM databases. The literatures which contained the above keywords and carried out in animals (in vivo and in vitro) have been collected, collated, analyzed, and summarized. Our summary results showed that hundreds of miRNAs and lncRNAs are involved in the Cd toxicity, which have been demonstrated as multiple organ injury, reproductive toxicity, malignant transformation, and abnormal repair of DNA damage. In this paper, we also discussed the blank in present research field of Cd toxicity as well as suggested some ideas for future study in Cd toxicity.

In vitro and bioinformatics mechanistic-based approach for cadmium carcinogenicity understanding

Cadmium is a toxic metal able to enter the cells through channels and transport pathways dedicated to essential ions, leading, among others, to the dysregulation of divalent ions homeostasis. Despite its recognized human carcinogenicity, the mechanisms are still under investigation. A powerful tool for mechanistic studies of carcinogenesis is the Cell Transformation Assay (CTA). We have isolated and characterized by whole genome microarray and bioinformatics analysis of differentially expressed genes (DEGs) cadmium-transformed cells from different foci (F1, F2, and F3) at the end of CTA (6 weeks). The systematic analysis of up- and down-regulated transcripts and the comparison of DEGs in transformed cells evidence different functional targets and the complex picture of cadmium-induced transformation. Only 34 in common DEGs are found in cells from all foci, and among these, only 4 genes are jointly up-regulated (Ccl2, Ccl5, IL6 and Spp1), all responsible for cytokines/chemokines coding. Most in common DEGs are down-regulated, suggesting that the switching-off of specific functions plays a major role in this process. In addition, the comparison of dysregulated pathways immediately after cadmium treatment with those in transformed cells provides a valuable means to the comprehension of the overall process.

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Cell transformation Assay and toxicogenomics are integrated to study cadmium carcinogenesis mechanisms

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Inflammatory response is the only common feature in Cd-transformed cells from all different foci

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Switching-off of specific functions plays a major role in Cd-induced carcinogenesis

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Comparison of triggering signals and deregulated pathways in transformed cells provides hints on cadmium mechanisms

Choline and Ethanolamine Plasmalogens Prevent Lead-Induced Cytotoxicity and Lipid Oxidation in HepG2 Cells

Plasmalogens derived from dietary phospholipids are considered to be potential protectors against oxidation-related disorders, while lead (Pb) is an environmental contaminant worldwide and is known to induce oxidative stress. However, the protective and antilipid oxidative effects of individual plasmalogen species against Pb damage have received little attention. In this study, six plasmalogen species (with either choline or ethanolamine as the headgroup and p16:0/18:1, p16:0/18:2, or p16:0/20:5 as the side chains) were evaluated in human hepatoma cells. Plasmalogen species showed a remarkable recovery in cell viability as well as elimination of reactive oxygen species and suppressed the accumulation of phosphatidylcholine hydroperoxides (from 63.6 ± 1.8% to 80.3 ± 2.9%) and phosphatidylethanolamine hydroperoxides (from 25.7 ± 9.3% to 76.1 ± 3.7%). Moreover, plasmalogens significantly upregulated the gene expression levels of a series of antioxidant enzymes that are regulated via the Nrf-2-dependent pathway. This study suggested that choline and ethanolamine plasmalogens could prevent Pb-induced cytotoxicity and lipid oxidation in HepG2 cells.

Zn Supplement-Antagonized Cadmium-Induced Cytotoxicity in Macrophages In Vitro: Involvement of Cadmium Bioaccumulation and Metallothioneins Regulation

Cadmium (Cd) is a toxic metal leading to multiple forms of organ damage. Zinc (Zn) was reported as a potential antagonist against Cd toxicity. The present study investigates the antagonistic effect of Zn (20 μM) on Cd (20 or 50 μM) cytotoxicity in macrophages in vitro. The results shows that Cd exposure caused dose-dependent morphologic and ultrastructural alterations in RAW 264.7 macrophages. Zn supplement significantly inhibited Cd cytotoxicity in RAW 264.7 or HD-11 macrophages by mitigating cell apoptosis, excessive ROS output, and mitochondrial membrane depolarization. Notably, Zn supplement for 12 h remarkably prevented intracellular Cd2+ accumulation in 20 μM (95.99 ± 9.93 vs 29.64 ± 5.08 ng/106 cells; P = 0.0008) or 50 μM Cd (179.78 ± 28.66 vs 141.62 ± 22.15 ng/106 cells; P = 0.003) exposed RAW 264.7 cells. Further investigation found that Cd promoted metallothioneins (MTs) and metal regulatory transcription factor 1 (MTF-1) expression in RAW 264.7 macrophages. Twenty μM Zn supplement dramatically enhanced MTs and MTF-1 levels in Cd-exposed RAW 264.7 macrophages. Intracellular Zn2+ chelation or MTF-1 gene silencing inhibited MTs synthesis in Cd-exposed RAW 264.7 macrophages, which was accompanied by the declined expression of MTF-1, indicating that regulation of Zn on MTs was partially achieved by MTF-1 mobilization. In conclusion, this study demonstrates the antagonism of Zn against Cd cytotoxicity in macrophages and reveals its antagonistic mechanism by preventing Cd2+ bioaccumulation and promoting MTs expression.

Specificity of the Metallothionein-1 Response by Cadmium-Exposed Normal Human Urothelial Cells

Occupational and environmental exposure to cadmium is associated with the development of urothelial cancer. The metallothionein (MT) family of genes encodes proteins that sequester metal ions and modulate physiological processes, including zinc homeostasis. Little is known about the selectivity of expression of the different MT isoforms. Here, we examined the effect of cadmium exposure on MT gene and isoform expression by normal human urothelial (NHU) cell cultures. Baseline and cadmium-induced MT gene expression was characterized by next-generation sequencing and RT-PCR; protein expression was assessed by Western blotting using isoform-specific antibodies. Expression of the zinc transporter-1 (SLC30A1) gene was also assessed. NHU cells displayed transcription of MT-2A, but neither MT-3 nor MT-4 genes. Most striking was a highly inducer-specific expression of MT-1 genes, with cadmium inducing transcription of MT-1A, MT-1G, MT-1H, and MT-1M. Whereas MT-1G was also induced by zinc and nickel ions and MT-1H by iron, both MT-1A and MT-1M were highly cadmium-specific, which was confirmed for protein using isoform-specific antibodies. Protein but not transcript endured post-exposure, probably reflecting sequestration. SLC30A1 transcription was also affected by cadmium ion exposure, potentially reflecting perturbation of intracellular zinc homeostasis. We conclude that human urothelium displays a highly inductive profile of MT-1 gene expression, with two isoforms identified as highly specific to cadmium, providing candidate transcript and long-lived protein biomarkers of cadmium exposure.

Suppression of ferroportin expression by cadmium stimulates proliferation, EMT, and migration in triple-negative breast cancer cells

Cadmium (Cd) has been linked to a variety of cancers, including breast cancer; however, the molecular mechanism of its carcinogenic activity is not fully understood. To this end, the present study investigated the roles of ferroportin (FPN), a prognostic marker of breast cancer, in Cd-induced stimulation of cell proliferation and cell migration. Triple-negative MDA-MB-231 cells were treated with 1-3 μM Cd. The cells exhibited significant reduction in FPN expression and concomitant increase in iron concentration. Cells treated with Cd for 8 weeks displayed elevated proliferative and migratory activities which were inversely related with FPN expression. Reduced FPN expression also resulted in EMT as indicated by an increase in the expression of E-cadherin, and a decrease in the expression of N-cadherin, Twist and Slug. Further investigation revealed that Cd suppressed FPN expression at least partially by activating TGF-β, a known regulator of FPN expression. Taken together, these results indicate that Cd-induced stimulation of MDA-MB-231 cell proliferation, EMT, and migration is brought about by suppression of FPN expression and associated disruption of iron homeostasis.

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.

MicroRNAs: Impaired vasculogenesis in metal induced teratogenicity

Certain metals have been known for their toxic effects on embryos and fetal development. The vasculature in early pregnancy is extremely dynamic and plays an important role in organogenesis. Nascent blood vessels in early embryonic life are considered to be a primary and delicate target for many teratogens since the nascent blood islands follow a tightly controlled program to form vascular plexus around and inside the embryo for resourcing optimal ingredients for its development. The state of the distribution of toxic metals, their transport mechanisms and the molecular events by which they notch extra-embryonic and embryonic vasculatures are illustrated. In addition, pharmacological aspects of toxic metal induced teratogenicity have also been portrayed. The work reviewed state of the current knowledge of specific role of microRNAs (miRNAs) that are differentially expressed in response to toxic metals, and how they interfere with the vasculogenesis that manifests into embryonic anomalies.

Oxidative Stress Triggered by Apigenin Induces Apoptosis in a Comprehensive Panel of Human Cervical Cancer-Derived Cell Lines

Recently, the cytotoxic effects of apigenin (4′,5,7-trihydroxyflavone), particularly its marked inhibition of cancer cell viability both in vitro and in vivo, have attracted the attention of the anticancer drug discovery field. Despite this, there are few studies of apigenin in cervical cancer, and these studies have mostly been conducted using HeLa cells. To evaluate the possibility of apigenin as a new therapeutic candidate for cervical cancer, we evaluated its cytotoxic effects in a comprehensive panel of human cervical cancer-derived cell lines including HeLa (human papillomavirus/HPV 18-positive), SiHa (HPV 16-positive), CaSki (HPV 16 and HPV 18-positive), and C33A (HPV-negative) cells in comparison to a nontumorigenic spontaneously immortalized human epithelial cell line (HaCaT). Our results demonstrated that apigenin had a selective cytotoxic effect and could induce apoptosis in all cervical cancer cell lines which were positively marked with Annexin V, but not in HaCaT (control cells). Additionally, apigenin was able to induce mitochondrial redox impairment, once it increased ROS levels and H₂O₂, decreased the Δψm, and increased LPO. Still, apigenin was able to inhibit migration and invasion of cancer cells. Thus, apigenin appears to be a promising new candidate as an anticancer drug for cervical cancer induced by different HPV genotypes.

Cadmium-transformed cells in the in vitro cell transformation assay reveal different proliferative behaviours and activated pathways

The in vitro Cell Transformation Assay (CTA) is a powerful tool for mechanistic studies of carcinogenesis. The endpoint is the classification of transformed colonies (foci) by means of standard morphological features. To increase throughput and reliability of CTAs, one of the suggested follow-up activities is to exploit the comprehension of the mechanisms underlying cell transformation. To this end, we have performed CTAs testing CdCl2, a widespread environmental contaminant classified as a human carcinogen with the underlying mechanisms of action not completely understood. We have isolated and re-seeded the cells at the end (6weeks) of in vitro CTAs to further identify the biochemical pathways underlying the transformed phenotype of foci. Morphological evaluations and proliferative assays confirmed the loss of contact-inhibition and the higher proliferative rate of transformed clones. The biochemical analysis of EGFR pathway revealed that, despite the same initial carcinogenic stimulus (1μM CdCl2 for 24h), transformed clones are characterized by the activation of two different molecular pathways: proliferation (Erk activation) or survival (Akt activation). Our preliminary results on molecular characterization of cell clones from different foci could be exploited for CTAs improvement, supporting the comprehension of the in vivo process and complementing the morphological evaluation of foci.

Developing a Gene Biomarker at the Tipping Point of Adaptive and Adverse Responses in Human Bronchial Epithelial Cells

Determining mechanism-based biomarkers that distinguish adaptive and adverse cellular processes is critical to understanding the health effects of environmental exposures. Shifting from in vivo, low-throughput toxicity studies to high-throughput screening (HTS) paradigms and risk assessment based on in vitro and in silico testing requires utilizing toxicity pathway information to distinguish adverse outcomes from recoverable adaptive events. Little work has focused on oxidative stresses in human airway for the purposes of predicting adverse responses. We hypothesize that early gene expression-mediated molecular changes could be used to delineate adaptive and adverse responses to environmentally-based perturbations. Here, we examined cellular responses of the tracheobronchial airway to zinc (Zn) exposure, a model oxidant. Airway derived BEAS-2B cells exposed to 2–10 μM Zn²⁺ elicited concentration- and time-dependent cytotoxicity. Normal, adaptive, and cytotoxic Zn²⁺ exposure conditions were determined with traditional apical endpoints, and differences in global gene expression around the tipping point of the responses were used to delineate underlying molecular mechanisms. Bioinformatic analyses of differentially expressed genes indicate early enrichment of stress signaling pathways, including those mediated by the transcription factors p53 and NRF2. After 4 h, 154 genes were differentially expressed (p < 0.01) between the adaptive and cytotoxic Zn²⁺ concentrations. Nearly 40% of the biomarker genes were related to the p53 signaling pathway with 30 genes identified as likely direct targets using a database of p53 ChIP-seq studies. Despite similar p53 activation profiles, these data revealed widespread dampening of p53 and NRF2-related genes as early as 4 h after exposure at higher, unrecoverable Zn²⁺ exposures. Thus, in our model early increased activation of stress response pathways indicated a recoverable adaptive event. Overall, this study highlights the importance of characterizing molecular mechanisms around the tipping point of adverse responses to better inform HTS paradigms.