Perspectives on cadmium toxicity research

Understanding heavy metal toxicity: Implications on human health, marine ecosystems and bioremediation strategies

Heavy metals are constituents of the natural environment and are of great importance to both natural and artificial processes. But in recent times the indiscriminate use of heavy metals especially for human purposes has caused an imbalance in natural geochemical cycles. This imbalance has caused contamination of heavy metals into natural resources and such as soil and a marine ecosystem. Long exposure and higher accumulation of given heavy metals are known to impose detrimental and even lethal effects on humans. Conventional remediation techniques of heavy metals provide good results but have negative side effects on surrounding environment. The role played by microbes in bioremediation of heavy metals is well reported in the literature and understanding the role of molecules in the process of metal accumulation its reduction and transformation into less hazardous state, has myriads of biotechnological implications for bioremediation of metal-contaminated sites. The current review presents the implications of heavy metals on human health and marine ecosystems, conventional methods of heavy metal removal and their side effects on the environment. Bioremediation approaches have been discussed as well in this review, proving to be a more sustainable and eco-friendly approach towards remediation of heavy metals.

Adverse effects of cadmium on lymphoid organs, immune cells, and immunological responses

Humans and animals possess robust immune systems to safeguard against foreign pathogens. However, recent reports suggest a greater incidence of immunity breakdown due to exposure to environmental pollutants, with heavy metals emerging as potential candidates in such immuno-toxicological studies. While we have extensive data on the general toxicity resulting from exposure to heavy metals, comprehensive documentation of their role as immune disruptors remains scarce. Cd (Cadmium) exerts immunomodulation by interfering with immune organs and cells, leading to altered structure, physiology, and function, thereby inducing symptoms of immune deregulation, inflammation and/or autoimmunity. This review aims to summarize the link between Cd exposure and immune dysfunction, drawing from case studies on exposed human subjects, as well as research conducted on various model organisms and in-vitro culture systems.

Improving acid mine drainage treatment by combining treatment technologies: A review

The mining and processing of some minerals and coal result in the production of acid mine drainage (AMD) which contains elevated levels of sulfate and metals, which tend to pose serious environmental issues. There are different technologies that have been developed for the treatment of wastewater or AMD. However, there is no "one-size-fits-all" solution, hence a combination of available technologies should be considered to achieve effective treatment. In this review, AMD treatment technologies and the possible alignment in tandem of the different treatment technologies were discussed. The alignment was based on the target species of each technology and AMD composition. The choice of the technologies to combine depends on the quality of AMD and the desired quality of effluent depending on end use (e.g., drinking, industrial, irrigation or release into the environment). AMD treatment technologies targeting metals can be combined with membrane and/or ettringite precipitation technologies that focus on the removal of sulfates. Other technologies can be added to deal with the secondary waste products (e.g., sludge and brines) from the treatment processes. Moreover, some technologies such as ion exchange and adsorption can be added to target specific valuable elements in AMD. Such combinations have the potential to result in effective AMD treatment and minimum waste production, which are not easily achievable with the individual technologies. Overall, this review presents combinations of AMD treatment technologies which can work best together to produce optimal water quality and valuable products in a cost-effective manner.

Transport Behavior of Cd2+ in Highly Weathered Acidic Soils and Shaping in Soil Microbial Community Structure

The mining and smelting site soils in South China present excessive Cd pollution. However, the transport behavior of Cd in the highly weathered acidic soil layer at the lead-zinc smelting site remains unclear. Here, under different conditions of simulated infiltration, the migration behavior of Cd2+ in acid smelting site soils at different depths was examined. The remodeling effect of Cd2+ migration behavior on microbial community structure and the dominant microorganisms in lead-zinc sites soils was analyzed using high-throughput sequencing of 16S rRNA gene amplicons. The results revealed a specific flow rate in the range of 0.3-0.5 mL/min that the convection and dispersion have no obvious effect on Cd2+ migration. The variation of packing porosity could only influence the migration behavior by changing the average pore velocity, but cannot change the adsorption efficiency of soil particles. The Cd has stronger migration capacity under the reactivation of acidic seepage fluid. However, in the alkaline solution, the physical properties of soil, especially pores, intercept the Cd compounds, further affecting their migration capacity. The acid-site soil with high content of SOM, amorphous Fe oxides, crystalline Fe/Mn/Al oxides, goethite, and hematite has stronger ability to adsorb and retain Cd2+. However, higher content of kaolinite in acidic soil will increase the potential migration of Cd2+. Besides, the migration behavior of Cd2+ results in simplified soil microbial communities. Under Cd stress, Cd-tolerant genera (Bacteroides, Sphingomonas, Bradyrhizobium, and Corynebacterium) and bacteria with both acid-Cd tolerance (WCHB 1-84) were distinguished. The Ralstonia showed a high enrichment degree in alkaline Cd2+ infiltration solution (pH 10.0). Compared to the influence of Cd2+ stress, soil pH had a stronger ability to shape the microbial community in the soil during the process of Cd2+ migration.

Long-Term Exposure to Cadmium Causes Hepatic Iron Deficiency through the Suppression of Iron-Transport-Related Gene Expression in the Proximal Duodenum

Cadmium (Cd) is an environmental pollutant that damages various tissues. Cd may cause a depletion of iron stores and subsequently an iron deficiency state in the liver. However, the molecular mechanism of decreased iron accumulation in the liver induced by long-term exposure to Cd is unknown. In this study, we investigated the hepatic accumulation of iron and the proximal duodenal expression of the genes involved in iron transport using mice chronically exposed to Cd. Five-week-old female C57BL/6J mice were fed a diet containing 300 ppm Cd for 12, 15, 19 and 21 months. The iron concentration in the liver was markedly decreased by Cd. Among iron-transport-related genes in the proximal duodenum, the gene expression of HCP1 and Cybrd1 was significantly decreased by Cd. HCP1 is an influx transporter of heme iron. Cybrd1 is a reductase that allows non-heme iron to enter cells. The expression of iron-transport-related genes on the duodenal basolateral membrane side was hardly altered by Cd. These results suggest that long-term exposure to Cd suppresses the expression of HCP1 and Cybrd1 in the proximal duodenum, resulting in reduced iron absorption and iron accumulation in the liver.

Cadmium aggravates the blood-brain barrier disruption via inhibition of the Wnt7A/β-catenin signaling axis

Cadmium (Cd) is a non-biodegradable widespread environmental pollutant, which can cross the blood-brain barrier (BBB) and cause cerebral toxicity. However, the effect of Cd on the BBB is still unclear. In this study, a total of 80 (1-day-old) Hy-Line white variety chicks (20 chickens/group) were selected and randomly divided into four (4) groups: the control group (Con group) (fed with a basic diet, n = 20), the Cd 35 group (basic diet with 35 mg/kg CdCl₂, n = 20), the Cd 70 group (basic diet with 70 mg/kg CdCl₂, n = 20) and the Cd 140 group (basic diet with 140 mg/kg CdCl₂, n = 20), and fed for 90 days. The pathological changes, factors associated with the BBB, oxidation level and the levels of Wingless-type MMTV integration site family, member 7 A (Wnt7A)/Wnt receptor Frizzled 4 (FZD4)/β-catenin signaling axis-related proteins in brain tissue were detected. Cd exposure induced capillary damage and neuronal swelling, degeneration and loss of neurons. Gene Set Enrichment Analysis (GSEA) showed the weakened Wnt/β-catenin signaling axis. The protein expression of the Wnt7A, FZD4, and β-catenin was decreased by Cd expusure. Inflammation generation and BBB dysfunction were induced by Cd, as manifested by impaired tight junctions (TJs) and adherens junctions (AJs) formation. These findings underscore that Cd induced BBB dysfunction via disturbing Wnt7A/FZD4/β-catenin signaling axis.

Cadmium, Lead, Chronic Physiological Stress and Endometrial Cancer: How Environmental Policy Can Alter the Exposure of At-Risk Women in the United States

The health and life outcomes of individuals are intertwined with the context in which they grow and live. The totality of exposures one experiences affects health in the short term and throughout the life course. Environmental exposure to multiple contaminants can increase stress levels in individuals and neighborhoods with psychosocial stressors such as crime, drug and alcohol misuse, and violence also taking a toll on individual and neighborhood wellbeing. In addition, the availability, organization, and quality of local institutions and infrastructure all affect health in the short and long term. The role of these factors in endometrial cancer will be explored in this paper. In addition, policy implications regarding lead, chronic physiological stress, and endometrial cancer will be explored to ascertain the impact of these factors on at-risk women.

The relationship between cadmium and cognition in the elderly: a systematic review

Context: The relationship between cadmium (Cd) and the cognition of the elderly is indistinct.Objective: To summarise the studies on the relationship between the cognition of the elderly and Cd.Methods: Literatures were searched in PubMed, Web of Science, China National Knowledge Infrastructure (CNKI), and Wan fang database on April 25, 2022. The entries in the STROBE statement were used to evaluate the literature quality; all the quantitative studies that met the requirements were systematically summarised.Results: Blood Cd was negatively correlated with the cognitive ability of the elderly, corresponding to different cognitive ability assessment methods, the regression coefficients were: -0.11 (-0.20, -0.03), -0.46 (-0.71, -0.21), -0.54 (-0.90, -0.17), -0.19 (-0.37, -0.01), and -2.29 (-3.41, -1.16). The regression coefficients between urinary Cd level and cognition score were -1.42 (-2.38, -0.46), and 0.76 (-1.28, -0.23). When dietary Cd increased by 1 μg/kg, the composite z-score decreased by 3.64 (p = 0.001). There was no significant correlation between drinking water Cd, fingernail Cd and cognition (p > 0.05).Conclusion: We concluded that blood Cd (including whole blood and plasma), urine Cd and dietary Cd were negatively correlated with the cognition of the elderly, but the relationship between Cd in drinking water and fingernails and cognition was not statistically significant.

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

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

Early Exposure to Environmental Pollutants: Imidacloprid Potentiates Cadmium Toxicity on Zebrafish Retinal Cells Death

In the present study, we analyzed the combination of non-toxic concentrations per se, of Cd and a pesticide the imidacloprid (IMI) (10 and 50 μM for Cd and 195 μM for IMI), to highlight early developmental toxicity and possible damage to retinal cells. Co-exposure to Cd and IMI showed a toxic effect in zebrafish larval development, with lowered degrees of survival and hatching, and in some cases the induction of structural alterations and edema. In addition, co-exposure to 50 and 195 μM, respectively, for Cd and IMI, also showed increased apoptosis in eye cells, accompanied by up regulation of genes associated with antioxidant markers (cat, sod1, nrf2 and ho-1). Thus, the present study aims to highlight how the presence of multiple contaminants, even at low concentrations, can be a risk factor in a model of zebrafish (Danio rerio). The presence of other contaminants, such as IMI, can cause an enhancement of the toxic action of Cd on morphological changes in the early life stage of zebrafish, but more importantly disrupt the normal development of the retina, eventually triggering apoptosis.

Exposure to multiple toxic metals and polycystic ovary syndrome risk: Endocrine disrupting effect from As, Pb and Ba

BACKGROUND

Polycystic ovarian syndrome (PCOS) affects 5 % ~ 20 % of women of reproductive age and is a serious health problem. Whether exposure to lead (Pb), mercury (Hg), arsenic (As), barium (Ba) or (cadmium) Cd is associated with an increased risk of PCOS, particularly their joint effect as well as their association with the clinical phenotype of PCOS is limited and unclear.

OBJECTIVES

We aimed to explore the associations of the blood Pb, Hg, As, Ba and Cd levels and risk of PCOS in Chinese women of reproductive age.

METHODS

A case-control study was used and included 369 women with PCOS and 441 controls. The levels of Pb, Hg, As, Ba and Cd were measured in fasting blood samples collected on the 2nd or 3rd day of menstruation or vaginal bleeding after drug withdrawal; basal sex hormone levels, fasting glucose and fasting insulin were measured simultaneously. Unconditional logistic regression models were used to assess the relationship of the blood Pb, Hg, As, Ba or Cd levels with PCOS risk. Bayesian kernel machine regression (BKMR) was used to assess the joint effect of Pb, Hg, As, Ba and Cd on PCOS risk and estimate which metal or metals contributed most to the association. Multiple linear regression models were used to investigate the relationships between the levels of selected metals and parameters of the clinical PCOS phenotype.

RESULTS

The mean ± SD ages of women in the case and control groups were 28.80 ± 3.39 and 28.97 ± 2.39 years, respectively; their mean ± SD BMIs were 23.86 ± 3.51 kg/m² and 22.08 ± 3.14 kg/m², respectively. The blood levels of three metals (Pb, As and Ba) were statistically associated with PCOS risk based on single-metal models. With each natural logarithm transformed (ln) unit increase in blood concentrations of Pb, higher likelihood of PCOS can be found, the adjusted odd ratio (aOR) and 95 % confidence interval (CI) was 1.83 (1.35-2.48), and these for As and Ba were 2.49 (1.86-3.33) and 1.20 (1.04-1.39), respectively. Compared with women at the first tertile group, higher likelihoods of PCOS among women in the second and third tertiles of the Pb group were observed, aORs and 95 % CIs were 1.81 (1.22-2.68) and 2.08 (1.42-3.04), respectively; and higher likelihoods of PCOS among women in the third tertiles of As and Ba group were also observed, the aORs and 95%CIs were 2.83 (1.93-4.15) and 1.89 (1.32-2.72), respectively. BKMR analysis also showed a statistically significant and positive joint effect of five metals on PCOS risk when the blood levels of five metals were all above the 55th percentile compared with their median levels, and As (100 %) and Pb (67.44 %) were the major contributors to the association. The blood As levels were positively associated with the luteinizing hormone (LH) levels and LH/FSH (follicle-stimulating hormone) ratio values, the blood Ba levels were negatively associated with the FSH levels, and the blood Pb levels were positively associated with the fasting insulin levels and homeostasis model assessment of insulin resistance (HOMA-IR) values.

CONCLUSIONS

Our results suggest a positive association between exposure to multiple toxic metals (Pb, Hg, As, Ba and Cd) and PCOS risk. As and Pb were the major contributors, evaluated either as a single agent or metal mixture; and Pb, As, and Ba were associated with different parameters of the clinical PCOS phenotype. Additional studies are warranted to confirm these associations, particularly regarding the synergistic effect of toxic metals.

[Elucidation and Application of Novel Action of Therapeutic Agents for Diabetic Neuropathy]

Epalrestat is the only aldose reductase inhibitor that is currently available for diabetic peripheral neuropathy. Oxidative stress impairs endothelial cells, thereby leading to numerous pathological conditions. Increasing antioxidative ability is important to prevent cellular toxicity induced by reactive oxygen species. Epalrestat increases antioxidant defense factors such as glutathione and γ-glutamylcysteine ligase in vascular endothelial cells through activation of the transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2). This increases suppression of oxidative stress-induced cellular toxicity. Cadmium is an industrial and environmental pollutant that targets the vascular endothelium. The vascular system is critically affected by cadmium toxicity. Therapeutic treatment against cadmium toxicity is chelation therapy that promotes metal excretion; however, cadmium chelators can cause renal toxicity. Therefore, safe and efficient therapeutic agents are required. Epalrestat suppresses cadmium-induced cytotoxicity in vascular endothelial cells through activation of Nrf2. In addition, epalrestat affects the intracellular levels of cadmium, cadmium transporter Zrt-Irt-like protein 8 (ZIP8), and metallothionein (MT). The upregulation of ZIP8 and MT may be involved in the suppression of cadmium-induced cytotoxicity by epalrestat. Drug repurposing is a new strategy for drug discovery in which the pharmacological action of existing medicines whose safety and pharmacokinetics have already been confirmed clinically and whose use has been approved is examined comprehensively at the molecular level. The results can be applied to the development of existing drugs for use as medicines for the treatment of other diseases. This review provides useful findings for future expansion of indications as research leading to drug repurposing of epalrestat.

Effect of cadmium administration on the antioxidant system and neuronal death in the hippocampus of rats

Cadmium (Cd) is a heavy metal classified as a carcinogen whose exposure could affect the function of the central nervous system. Studies suggest that Cd modifies neuronal morphology in the hippocampus and affects cognitive tasks. The oxidative stress pathway is proposed as a mechanism of toxicity. However, this mechanism is not precise yet. This study aimed to evaluate the effect of Cd administration on oxidative stress markers in the male rat's hippocampus. Male Wistar rats were divided into (1) control (drinking water) and (2) treatment with Cd (32.5 ppm of cadmium chloride (CdCl₂ ) in water). The Cd was administered for 2, 3, and 4 months. The results show that the oral administration of CdCl₂ increased the concentration of Cd in plasma and hippocampus, and this response is time-dependent on its administration. Likewise, it caused an increase in lipid peroxidation and nitrosative stress markers. Moreover, it increased reactive astrogliosis and antioxidant enzyme activity. Consequently, the progression of the oxidative response exacerbated neurodegeneration in hippocampal cells. Our results suggest that Cd exposure induces a severe oxidative response that contributes critically to hippocampal neurodegeneration. It is suggested that exposure to Cd increases the risk of developing neurological diseases, which contributes to a decrease in the quality of life of the human and the environment in which it lives.

Cadmium perturbed metabolomic signature in pancreatic beta cells correlates with disturbed metabolite profile in human urine

Cd exposure has been demonstrated to induce a variety of metabolic disorders accompanied with imbalance of glucose and lipid homeostasis. The metabolic toxicity of Cd exposure at metabolome-wide level remains elusive. In our study, we demonstrated that Cd exposure via drinking water increased blood glucose levels, decreased serum insulin levels, led to glucose intolerance and suppressed insulin expression in the pancreas of C57/6J mice. Cd exposure significantly inhibited cell viability and suppressed insulin secretion in MIN6 cells in vitro. Since pancreatic β-cells are the only source of insulin production in the body and play a pivotal role in modulating glucose and lipid metabolisms, we further delineated the metabolomic signatures of Cd exposure in insulin-secreting MIN6 cells by using non-target metabolomics. PCA and OPLS-DA analysis clearly suggested that Cd exposure led to a marked metabolic alteration in MIN6 cells. 76 perturbed metabolites were identified after Cd exposure. Classification of metabolites suggested that Cd perturbed metabolites belong to nucleosides, nucleotides and analogues, organic acids and derivatives, and lipids and lipid-like molecules. 28 perturbed metabolites existed in mitochondrion, suggesting mitochondrion as the major target organelle in metabolic toxicity of Cd exposure. KEGG pathway analysis revealed that 20 metabolic pathways were disturbed by Cd exposure. Mitochondrial TCA cycle and glycerophospholipid metabolism were remarkably disturbed. The mRNA expressions of genes in mitochondrial TCA cycle and fatty acid oxidation in pancreas and MIN6 cells were significantly dysregulated by Cd exposure. Disturbances in mitochondrial TCA cycle and glycerophospholipid metabolism result in producing perturbed metabolites in pancreatic β-cells. Moreover, 14 perturbed metabolites identified in MIN6 cells co-existed in the urine of Cd exposed workers. 11 biomarkers of diabetes mellitus were also found to be significantly altered in the urine of Cd exposed workers. In conclusion, findings of this study greatly extend our understanding of metabolic toxicity of Cd exposure in pancreatic β-cells at metabolome-wide level and offer some new clues for linking Cd exposure to development of diabetes mellitus. Results of this study also support the notion that Cd induced metabolic toxicity could be monitored by examining perturbed urinary metabolites in humans and highlight the significance of reducing Cd exposure via drinking water at population level.

The role of glutathione-mediated triacylglycerol synthesis in the response to ultra-high cadmium stress in Auxenochlorella protothecoides

Under ultra-high cadmium (Cd) stress, large amounts of glutathione are produced in Auxenochlorella protothecoides UTEX 2341, and the lipid content increases significantly. Glutathione is the best reductant that can effectively remove Cd, but the relationship between lipid accumulation and the cellular response to Cd stress has not been ascertained. Integrating analyses of the transcriptomes and lipidomes, the mechanism of lipid accumulation to Cd tolerance were studied from the perspectives of metabolism, transcriptional regulation and protein glutathionylation. Under Cd stress, basic metabolic pathways, such as purine metabolism, translation and pre-mRNA splicing process, were inhibited, while the lipid accumulation pathway was significantly activated. Further analysis revealed that the transcription factors (TFs) and genes related to lipid accumulation were also activated. Analysis of the TF interaction sites showed that ABI5, MYB_rel and NF-YB could further regulate the expression of diacylglycerol acyltransferase through glutathionylation/deglutathionylation, which led to increase of the triacylglycerol (TAG) content. Lipidomes analysis showed that TAG could help maintain lipid homeostasis by adjusting its saturation/unsaturation levels. This study for the first time indicated that glutathione could activate TAG synthesis in microalga A. protothecoides, leading to TAG accumulation and glutathione accumulation under Cd stress. Therefore, the accumulation of TAG and glutathione can confer resistance to high Cd stress. This study provided insights into a new operation mode of TAG accumulation under heavy metal stress.

Effects of heavy metals on reproduction owing to infertility

The reproductive performance of most of the species is adversely affected by hazardous heavy metals like lead, cadmium, mercury, arsenic, zinc, and copper. Heavy metals are liberated in the environment by natural sources like rock weathering, volcanic eruption, and other human activities like industrial discharge, mineral mining, automobile exhaust, and so forth. Heavy metals alter several reproductive functions in both males and females like a decrease in sperm count, motility, viability, spermatogenesis, hormonal imbalance, follicular atresia, and delay in oocyte maturation, and so forth, and thus, forms an important aspect of reproductive toxicology. The present review compiles toxicity aspects of various heavy metals and their efficacy and mechanism of action in mammals.

Nephrotoxicity Profile of Cadmium Revealed by Proteomics in Mouse Kidney

Cadmium (Cd) is a highly toxic metal and kidney is its main target. However, the molecular effects and associated potential impacts of Cd-accumulated kidney have not been well investigated. In this study, mouse was used as a model to investigate the Cd-induced proteomic profile change in kidney, and a total of 34 differentially expressed proteins were detected by two-dimensional gel electrophoresis (2-DE) and further identified by matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS). Through Gene Ontology analysis and KEGG pathway annotation, it showed that Cd-regulated kidney metabolism and promoted renal damage and cell migration. By validation of Western blotting and RT-qPCR, metastasis-related proteins LIM and SH3 domain protein 1 (LASP1) and phosphoenolpyruvate carboxykinase/cytosolic [GTP] (PEPCK1) were confirmed to be upregulated; Acyl-CoA synthetase medium-chain family member 3 (ACSM3) was downregulated. Furthermore, carcinoma development-related proteins initiation factor 4A (eIF4A) and pyridoxine-5'-phosphate oxidase (PNPO) were upregulated, and pyridoxal kinase (PK) was downregulated. The downregulation of Na(+)/H(+) exchange regulatory cofactor (NHERF3) might promote renal damage which associated with decrease of transferrin (TRF) in kidney. Taken together, our results revealed proteomic profile of Cd-induced nephrotoxicity and provided data for further insights into the mechanisms of Cd toxicity.

CdO/CdCO3 nanocomposite physical properties and cytotoxicity against selected breast cancer cell lines

Cadmium Oxide nanoparticles have the lowest toxicity when compared to nanoparticles of other semiconductors and they are not detrimental to human and mammalian cells, thereby making them candidates for targeting cancer cells. Synadenium cupulare plant extracts were used to synthesize CdO/CdCO3 nanocomposite using cadmium nitrate tetrahydrate 98% as a precursor salt. The resultant nanoparticles were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy, ultraviolet visible spectroscopy, and Fourier transform infrared spectroscopy (FTIR). The nanoparticles were then screened for effect on breast cancer cell lines (MCF-7 and MDA MB-231) and Vero cell line to determine their growth inhibition effect. Cytotoxicity effect was evaluated using 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. XRD showed the peaks of monteponite CdO and otavite CdCO3 nanoparticles. TEM results showed irregular and spherical particles of varying sizes, whilst SEM revealed a non-uniform morphology. FTIR results showed peaks of functional groups which are present in some of the phytochemical compounds found in S. cupulare, and point to the presence of CdO. Annealed CdO/CdCO3 NPs showed selectivity for MCF7 and MDA MB231 in comparison to Vero cell line, thereby supporting the hypothesis that cadmium oxide nanoparticles inhibit growth of cancerous cells more than non-cancerous cells.

Cadmium induces iron deficiency anemia through the suppression of iron transport in the duodenum

Cadmium (Cd) is an environmental contaminant that triggers toxic effects in various tissues such as the kidney, liver, and lung. Cd can also cause abnormal iron metabolism, leading to anemia. Iron homeostasis is regulated by intestinal absorption. However, whether Cd affects the iron absorption pathway is unclear. We aimed to elucidate the relationship between the intestinal iron transporter system and Cd-induced iron deficiency anemia. C57BL/6J female and male mice, 129/Sv female mice, and DBA/2 female mice were given a single oral dose of CdCl₂ by gavage. After 3 or 24 h, Cd decreased serum iron concentrations and inhibited the expression of iron transport-related genes in the duodenum. In particular, Cd decreased the levels of divalent metal transporter 1 and ferroportin 1 in the duodenum. In addition, human colon carcinoma Caco-2 cells were treated with CdCl₂. After 72 h, Cd decreased the expression of iron transport-related factors in Caco-2 cells with a pattern similar to that seen in the murine duodenum. These findings suggest that Cd inhibits iron absorption through direct suppression of iron transport in duodenal enterocytes and contributes to abnormal iron metabolism.

Transcription Factors and Downstream Genes in Cadmium Toxicity

Cadmium (Cd) is a harmful heavy metal widely present in the environment which can cause severe kidney damage. The proximal tubular cells are the main target of renal Cd toxicity. The consequences of Cd cytotoxicity involve apoptosis and necrosis. Recently, we and others have focused on how Cd affects transcription factors and the regulation of their target genes. Those studies showed that transcription factors initiate numerous pathways upon Cd exposure, leading to apoptosis, autophagic cell death, disruption of cell-cell adhesion, and generation of mitochondrial reactive oxygen species. Of particular note, Cd induces endoplasmic reticulum stress, resulting in not only apoptosis but also autophagic dysregulation, which can trigger cell damage. In some cases, however, Cd-regulated transcription factors can induce cell survival signaling. This review centers on our own research to elucidate the transcription factor-downstream gene cascades that are central to Cd-induced renal toxicity.

Adsorption behavior of engineered carbons and carbon nanomaterials for metal endocrine disruptors: Experiments and theoretical calculation

Adsorption behaviors and mechanisms of metal endocrine disruptors (Pb²⁺, Cd²⁺, and Hg²⁺) by pyrogenic carbonaceous materials including engineered carbons (biochar and activated carbon) and carbon nanomaterials (multi-walled carbon nanotubes and graphene oxide) have been investigated by experimental and density functional theory (DFT) studies. The adsorption isotherms of metal endocrine disruptors on carbonaceous materials were better fitted by Langmuir models. The adsorption capacities were in the order as follows: GO > BC600 > BC300 > CNT > AC for Pb²⁺, GO > BC300 > AC > BC600 > CNT for Cd²⁺, and GO > BC300 ≥ AC > CNT > BC600 for Hg²⁺, respectively. The DFT-computed binding energy (kcal/mol) of different oxygen-containing functional groups with metal endocrine disruptors followed the orders: (ⅰ) CMCOCPb (-136.70) > CM-COO^--Pb (-91.58) > CMCOPb (-33.57) > CMOHPb (-4.69), (ⅱ) CM-COO^--Cd (-45.91) > CMCOCCd (-4.49) > CMOHCd (-3.68) > CMCOCd (1.08), (ⅲ) CM-COO^--Hg (-25.51) > CMCOCHg (-3.58) > CMOHHg (-0.63) > CMCOHg (0.23). And COC has the highest binding energy for Pb²⁺, whereas COC has much lower binding energy for Cd²⁺ and Hg²⁺. Comprehensively considering DFT calculations, competitive adsorption results and the cost analysis, this work may provide insights into the design of selective adsorbent for specific contaminant.

Protective effects of polydatin and grape seed extract in rats exposed to cadmium

The current study aimed to investigate the protective role of polydatin (PD) and grape seed extracts (GSEs) against the effects of cadmium chlorine (CD) application in the rats. Forty-nine adult Wistar albino male rats were used in the study. Rats were assigned into control (saline), CD (5 mg/kg CdCI₂), PD (120 mg/kg PD), GSE (120 mg/kg GSE), CD + PD (5 mg/kg CdCI₂ + 120 mg/kg PD), CD + GSE (5 mg/kg CdCI₂ + 120 mg GSE), and CD + PD + GSE (5 mg/kg CdCI₂+120 mg/kg PD +120 mg/kg GSE) treatments (n = 7 per group). The treatments were administered orally for four weeks. CD accumulation was observed in all tissues studied except for the brain tissue. PD and GSE inhibited CD accumulation in erythrocytes and tissues at varying levels. The liver, kidney, brain, and testes showed extensive degenerative histopathological changes in CD group. Liver total oxidant status (TOS) in the CD group increased significantly compared to the control. TOS of kidney, brain, and testis suggested that PD and GSE did not show a strong antioxidant effect in these tissues. Malondialdehyde (MDA) levels in blood and liver raised significantly in CD-treated rats compared to controls. PD, GSE, and their combinations increased antioxidant potential in all tissues and decreased MDA levels in blood plasma and liver. Overall, the protective effects of PD were more effective than GSE. Results suggested that although the initiation of histopathological changes was present in all tissues, the initiating factor was not the oxidative stress in the tissues studied except for the liver and blood.

Metals in Fishes from Yongshu Island, Southern South China Sea: Human Health Risk Assessment

In order to assess the bioaccumulation of metals associated with gender, tissues, and their potential ecological risk, four species of fish were collected from the Yongshu Island in the Southern South China Sea. Metals and stable Pb isotopes in their tissues (muscle, gill, liver, intestine, and ovary) were determined. The concentrations of metals (mg/kg, dry weight) in these species were ND-21.60 (Cd), 1.21-4.87 (Cr), 0.42-22.4 (Cu), 1.01-51.8 (Mn), 0.30-3.28 (Ni), 6.04-1.29 × 103 (Zn), 14.89-1.40 × 103 (Fe), and 0.22-3.36 (Pb). In general, the liver and intestine absorbed more metals than the other tissues. Metals accumulation can be influenced by gender and feeding behavior and in fact, female fish and dietary exposure are more prone to accumulate metals. In addition, Pb isotopic ratios indicated that all species had significant biological fractionation, which may not make them good tracers for source identification. The metal concentrations of most samples were lower than the national standard values of the FAO (USA), which suggested that human consumption of these species may not cause health risks. However, since the surrounding areas are developing rapidly, the potential environmental risk of metals will intensify and should receive more attention.

GPER/ERK&AKT/NF-κB pathway is involved in cadmium-induced proliferation, invasion and migration of GPER-positive thyroid cancer cells

The higher incidence of thyroid cancer in women during reproductive years compared with men and the increased risk associated with the therapeutic use of estrogen have strongly suggested that estrogen may be involved in the occurrence and development of thyroid cancer. Cadmium (Cd) is a potent metalloestrogen that disrupts the endocrine system by mimicking the effects of 17β-estradiol (E2). In the present study, we demonstrate that similar to E2 and G1, a specific agonist for G protein-coupled estrogen receptor (GPER), Cd induces the proliferation, invasion and migration of human WRO and FRO thyroid cancer cells that have endogenous GPER. Moreover, like E2 and G1, Cd leads to a rapid activation of ERK/AKT, and then nuclear translocation of NF-κB, increased expression of cyclin A and D1, and secretion of IL-8, all of which are significantly attenuated by GPER blockage or knock-down in both WRO and FRO cells. Furthermore, the Cd-induced proliferation, invasion and migration are suppressed either by specific inhibitors for GPER, ERK, AKT and NF-κB, or by knock-down of GPER. These results suggest that GPER/ERK&AKT/NF-κB signaling pathway is involved in the Cd-induced proliferation, invasion and migration of GPER-positive thyroid cancer cells.

Anti-Apoptotic and Anti-Oxidant Effects of Caffeic Acid Phenethyl Ester on Cadmium-Induced Testicular Toxicity in Rats

Cadmium (Cd) is a serious environmental and occupational contaminant and may represent a serious health hazard to humans and other animals. Cd is reported to induce the generation of reactive oxygen species, and induces testicular damage in many species of animals. The goal of our study was to examine the anti-apoptotic and anti-oxidant effects of caffeic acid phenethyl ester (CAPE) on Cd-induced oxidative stress, apoptosis, and testicular injury in rats. A total of 40 male Wistar albino rats were divided into four groups: control, CAPE alone, Cd-treated, and Cd-treated with CAPE; each group consisted of 10 animals. To induce toxicity, Cd (1 mg/kg body weight) was dissolved in normal saline and subcutaneously injected into rats for 30 days. The rats in CAPE-treated group were given a daily dose of 10 μmol/kg body weight of CAPE by using intraperitoneal injection. This application was continued daily for a total of 30 days. To date, no examinations of the anti-apoptotic and anti-oxidant properties of CAPE on Cd-induced apoptosis, oxidative damage, and testicular injury in rat testes have been reported. CAPE-treated animals showed an improved histological appearance and serum testosterone levels in Cd-treated group. Our data indicate a significant reduction in the number of apoptotic cells in testis tissues of the Cd-treated group with CAPE treatment. Moreover, CAPE significantly suppressed lipid peroxidation, compensated deficits in the anti-oxidant defenses in testes tissue resulted from Cd administration. These findings suggest that the protective potential of CAPE in Cd toxicity might be due to its anti-oxidant and anti-apoptotic properties, which could be useful for achieving optimum effects in Cd-induced testicular injury.

Epigenetic effects of cadmium in cancer: focus on melanoma

Cadmium is a highly toxic heavy metal, which has a destroying impact on organs. Exposure to cadmium causes severe health problems to human beings due to its ubiquitous environmental presence and features of the pathologies associated with pro-longed exposure. Cadmium is a well-established carcinogen, although the underlying mechanisms have not been fully under-stood yet. Recently, there has been considerable interest in the impact of this environmental pollutant on the epigenome. Be-cause of the role of epigenetic alterations in regulating gene expression, there is a potential for the integration of cadmium-induced epigenetic alterations as critical elements in the cancer risk assessment process. Here, after a brief review of the ma-jor diseases related to cadmium exposure, we focus our interest on the carcinogenic potential of this heavy metal. Among the several proposed pathogenetic mechanisms, particular attention is given to epigenetic alterations, including changes in DNA methylation, histone modifications and non-coding RNA expression. We review evidence for a link between cadmium-induced epigenetic changes and cell transformation, with special emphasis on melanoma. DNA methylation, with reduced expression of key genes that regulate cell proliferation and apoptosis, has emerged as a possible cadmium-induced epigenetic mechanism in melanoma. A wider comprehension of mechanisms related to this common environmental contaminant would allow a better cancer risk evaluation.

Relationship between blood cadmium, lead, and serum thyroid measures in US adults - the National Health and Nutrition Examination Survey (NHANES) 2007-2010

Experimental studies have shown that both cadmium (Cd) and lead have potent endocrine disrupting activity. However, studies on whether these heavy metals disrupt thyroid system in humans, especially in general populations with low levels of exposure, are sparse. The study analyzed 6,231 participants aged 20 and older with measurements from 2007-2010 of the National Health and Nutrition Examination Survey (NHANES) to investigate whether whole blood Cd and lead level are associated with serum thyroid hormones measures. Our study suggests that thyroid function may be disrupted by both Cd and lead exposures in the general population and the specific roles of Cd and lead exposure on thyroid axis may differ by sex. However, the mechanisms by which these heavy metals may disrupt thyroid system function in general population needs to be further investigated.

Monensin ameliorates cadmium-induced hepatic injury in mice, subjected to subacute cadmium intoxication

This study was designed to evaluate the potential application of monensin as an oral drug for the treatment of cadmium-induced hepatic dysfunction. The study was performed using ICR mouse model. Twenty-seven adult ICR male mice were divided into three groups of nine animals each: control (received distilled water and food ad libitum for 28 days); Cd-intoxicated (treated orally with 20 mg/kg b.w. Cd(II) acetate from the 1st to the 14th day of the experimental protocol); and monensin treated group (intoxicated with Cd(II) acetate as described for the Cd-intoxicated group followed by an oral treatment with 16 mg/kg b.w. tetraethylammonium salt of monensic acid for two weeks). The obtained results demonstrated that the treatment of Cd-intoxicated animals with monensin restored the liver weight/body weight index to normal values, decreased the concentration of the toxic metal ion by 50% compared to the Cd-treated controls, and recovered the homeostasis of Cu and Zn. Monensin reduced the activity of aspartate aminotransferase, alanine aminotrasnferase and alkaline phosphatase in the plasma of Cd-treated animals to the normal control levels and ameliorated the Cd-induced inflammation in the liver. Taken together, these data demonstrated that monensin could be an effective chelating agent for the treatment of Cd-induced hepatotoxicity.

[Cadmium induces p53-dependent apoptosis through the inhibition of Ube2d family gene expression]

Cadmium (Cd), a harmful metal, exerts severe toxic effects on various tissues such as those in the kidney, liver, lung, and bone. In particular, renal toxicity with damage to proximal tubule cells is caused by chronic exposure to Cd. However, the molecular mechanism underlying chronic Cd renal toxicity remains to be understood. In this review, we present our recent findings since we examined to search for the target molecules involved in the renal toxicity of Cd using toxicogenomics. In NRK-52E rat renal tubular epithelial cells, we found using DNA microarrays that Cd suppressed the expression of the gene encoding Ube2d4, a member of the Ube2d family. The Ube2d family consists of selective ubiquitin-conjugating enzymes associated with p53 degradation. Moreover, Cd suppressed the expressions of genes encoding all Ube2d family members (Ube2d1/2/3/4) prior to the appearance of cytotoxicity in NRK-52E cells. Cd markedly increased p53 protein level and induced p53 phosphorylation and apoptosis in the cells. In vivo studies showed that chronic Cd exposure also suppressed Ube2d family gene expression and induced p53 accumulation and apoptosis in the renal tubules of the mouse kidney. These findings suggest that Cd causes p53-dependent apoptosis due to the inhibition of p53 degradation through the down-regulation of Ube2d family genes in NRK-52E cells and mouse kidney. Thus, the Ube2d family genes may be one of the key targets of renal toxicity caused by Cd.

Protective effect of soybeans as protein source in the diet against cadmium-aorta redox and morphological alteration

We investigated the effects of cadmium exposition on thoracic aorta redox status and morphology, and the putative protective effect of soybeans in the diet. Male Wistar rats were separated into 6 groups: 3 fed with a diet containing casein and 3 containing soybeans, as protein source. Within each protein group, one was given tap water (control) and the other two tap water containing 15 and 100 ppm of Cd(2+), respectively, for two months. In rats fed with casein diet, 15 ppm of Cd induced an increase of thiobarbituric acid-reactive substances (TBARS), and of the catalase (CAT) and glutathione peroxidase (GPx) activities, which were even higher with 100 ppm of Cd(2+), in aorta. Also, 100 ppm Cd(2+) exposure increased superoxide dismutase (CuZnSOD) activity; CAT, GPX, SOD, Nrf2 and metallothioneine II mRNA expressions and CAT, GPx and NOX-2 protein levels, compared with control. Aorta endothelial and cytoplasmic alterations were observed. However, with the soybeans diet, 15 and 100 ppm of Cd(2+) did not modify TBARS levels; CAT, GPX and Nrf2 mRNA expressions; CAT, GPx and NOX-2 protein; and the aorta morphology, compared with control. The soybean diet attenuates the redox changes and protects against morphological alterations induced, in a dose-dependent way, by Cd in aorta.

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

Maternal cadmium exposure induces fetal growth restriction (FGR), but the underlying mechanisms remain largely unknown. The placenta is the main organ known to protect the fetus from environmental toxins such as cadmium. In this study, we examine the role of the two key placental factors in cadmium-induced FGR. The first is placental enzyme 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2), which is known to protect the fetus from exposure to high cortisol levels and subsequently FGR, and the second the cadmium binding/sequestering proteins metallotheionein (MT)-I and -II. Using the MT-I/II(-/-) mouse model, pregnant mice were administered cadmium, following which pups and placentas were collected and examined. MT-I/II(-/-) pups exposed to cadmium were significantly growth restricted, but neither placental weight nor 11β-HSD2 was altered. Although cadmium administration did not result in any visible structural changes in the placenta, increased apoptosis was detected in MT-I/II(-/-) placentas following cadmium exposure, with a significant increase in levels of both p53 and caspase 3 proteins. Additionally, glucose transporter (GLUT1) was significantly reduced in MT-I/II(-/-) placentas of pups exposed to cadmium, whereas zinc transporter (ZnT-1) remained unaltered. Taken together, these results demonstrate that MT-I/II(-/-) mice are more vulnerable to cadmium-induced FGR. The present data also suggest that increased apoptosis and reduced GLUT1 expression in the placenta contribute to the molecular mechanisms underlying cadmium-induced FGR.

Role of glutathione in detoxification of copper and cadmium by yeast cells having different abilities to express cup1 protein

ABSTRACT Although copper is an essential metal and cadmium is an environmental pollutant, both are toxic when present in excess. Metallothionein and glutathione are two of the key components that participate in detoxification of copper and cadmium. In the present study the role of glutathione in resistance to copper and cadmium was investigated with the yeast Saccharomyces cerevisiae. The yeast cells used in this study have different abilities to produce glutathione and Cup1 protein, the yeast metallothionein homolog encoded by CUP1 gene. It was demonstrated that Cup1 protein plays a dominant role in buffering excess copper, and yeast does not depend on glutathione to reduce copper toxicity whether it possesses single or multiple copies of CUP1. In fact, excess copper can cause glutathione oxidation and depletion and damage the glutathione system. On the other hand, it was indicated that Cup1 protein is an important cadmium-detoxifying component, and the glutathione system can positively respond to cadmium. In yeast containing single or multiple copies of CUP1, glutathione is an indispensable line of defense against cadmium. Yeast having glutathione and no Cup1 protein is not able to grow in medium containing excess copper, but can tolerate higher concentrations of cadmium. In addition, it was found that yeast, independent of glutathione, can efficiently remove excess copper, whereas it cannot promptly eliminate accumulated cadmium regardless of having glutathione or not.

The tetraethylammonium salt of monensic acid-An antidote for subacute cadmium intoxication: a study using an ICR mouse model

In this study, the ability of the chelating agent monensic acid (administered as the tetraethylammonium salt) to reduce the cadmium (Cd) concentration in the kidneys, liver, heart, lungs, spleen and testes of Cd-intoxicated mice was investigated. Chelation therapy with the tetraethylammonium salt of monensic acid led to a significant decrease of the Cd concentration in all of the organs of the Cd-treated mice. This effect varied from 50% in the kidneys to 90% in the hearts of the sacrificed animals (compared to the Cd-treated controls). No redistribution of the toxic metal ions to the brain of the animals as a result of the detoxification with the chelating agent was observed. The detoxification of the animals with the antibiotic salt did not perturb the endogenous levels of copper (Cu) or zinc (Zn). The tetraethylammonium salt of monensic acid significantly ameliorated the Cd-induced total iron (Fe) depletion in the liver and spleen of Cd-treated mice. It also restored to control levels the values of transferrin-bound Fe and the total iron binding capacity (TIBC) of the plasma. These results imply that the tetraethylammonium salt of monensic acid could be an efficient antidote in cases of Cd-intoxication.

Bismuth protects against arsenite-induced inhibition of proteoglycan synthesis in cultured vascular endothelial cells

Chronic ingestion of arsenic is associated with an increased risk of vascular disease such as atherosclerosis. Previously, we showed that arsenite inhibits the synthesis of general proteoglycans (PGs), which are key molecules in the progression of atherosclerosis, in vascular endothelial cells. In the present study, we investigated the effect of several metals on arsenite-induced inhibitory effect in endothelial cells. The results indicate that, after 24-hr incubation, the inhibition of PG synthesis caused by sodium arsenite was protected by bismuth nitrate but not zinc sulfate, manganese chloride, nickel chloride or cobalt chloride. The accumulation of arsenic in the cell layer was significantly decreased by bismuth after 12-hr incubation and that of bismuth was also decreased by arsenite. It was therefore suggested that the protective effect of bismuth against the inhibitory effect of arsenite on PG synthesis in vascular endothelial cells may be due, at least in part, to the decrease in cellular arsenic accumulation.

Cadmium accumulation in tissues of Sarotherodon melanotheron (Rüppel, 1852) from the Aby Lagoon system in Côte d'Ivoire

This study assessed the concentrations of cadmium in the gills, livers and muscles of a commercially important tilapia fish (Sarotherodon melanotheron) from Aby Lagoon in Adiaké, Côte d’Ivoire, between January and December, 2010. The organisms were grouped into two composite samples (juvenile and adult) of five individuals. Levels of cadmium were determined in tissues using Perkin-Elmer (AAnalyst 200) Atomic Absorption Spectrophotometry (AAS) after a digestion method. Fish muscle appeared to have a significantly higher tendency to accumulate cadmium (1.19–5.18 µg/g dw) while gills and livers had minimum concentrations (0.07–1.32 and 0.12–1.25 µg/g dw). This study has revealed that the concentrations of Cd in Sarotherodon melanotheron muscle tissue were above the maximum acceptable concentrations for human consumption, thus precautions need to be taken in order to prevent future contamination.

Anti-apoptotic effects of curcumin on cadmium-induced apoptosis in rat testes

Cadmium (Cd) is one of the environmental pollutants affecting various tissues and organs including testis. The aim of this study was to investigate the anti-apoptotic effects of curcumin (Cur) on Cd-induced apoptosis in rat testes. The rats were randomly allotted into one of three experimental groups: control, Cd treated and Cd treated with Cur; each group contained 10 animals. The control group received 2 ml/day of dimethyl sulfoxide (DMSO). To induce toxicity, Cd (1 mg/kg body weight) was dissolved in normal saline and subcutaneously injected into rats for 4 weeks. The rats in Cur-treated group was given a daily dose of 100 mg/kg of Cur for 4 weeks. To date, no examinations of the anti-apoptotic properties of Cur on Cd-induced apoptosis in rat testes have been reported. The mean seminiferous tubule diameter, mean testicular biopsy score values and serum testosterone levels were significantly decreased in Cd-treated groups were compared to the control group. Furthermore, the Cur-treated animals showed an improved histological appearance and serum testosterone levels in Cd-treated group. Our data indicate a significant reduction in the activity of in situ identification of apoptosis using terminal dUTP nick end-labeling in testis tissues of the Cd-treated group with Cur therapy. The present study showed that Cur treatment protected testes against toxic effects of Cd. We believe that further preclinical research into the utility of Cur may indicate its usefulness as a potential treatment on the spermatogenesis after testicular injury caused by Cd-treated rats.

Role of the morphology and polyphosphate in Trichoderma harzianum related to cadmium removal

This study concerns the metabolism of polyphosphate in Trichoderma harzianum, a biocontrol agent with innate resistance against most chemicals used in agriculture, including metals, when grown in the presence of different concentrations of cadmium. The biomass production was affected by the concentration of metal used. Control cultures were able to accumulate polyphosphate under the conditions used. Moreover, the presence of cadmium induced a reduction in polyphosphate content related to the concentration used. The morphological/ultrastructural aspects were characterized by using optical and scanning electron microscopy, and were affected by the heavy metal presence and concentration. The efficiency of cadmium removal revealed the potential of the microorganism for use in remediation. The data indicate the potential for polyphosphate accumulation by the fungus, as well as its degradation related to tolerance/survival in the presence of cadmium ions.

Cadmium is a catalytic inhibitor of DNA topoisomerase II

Cadmium (Cd(2+)) is a highly toxic and carcinogenic metal that is an environmental and occupational hazard. DNA topoisomerase II is an essential nuclear enzyme and its inhibition can result in the formation of genotoxic and recombinogenic DNA double strand breaks. In this study we showed that cadmium chloride strongly inhibited the DNA decatenation activity of human topoisomerase IIα in the low micromolar concentration range and that its inhibitory effects were reduced by glutathione. Because the activity of topoisomerase II is strongly inhibited by thiol-reactive compounds this result suggested that cadmium may be binding to critical topoisomerase II cysteine thiols. Cadmium, however, did not stabilize DNA-topoisomerase II covalent complexes, as measured by the lack of formation of DNA double strand breaks. Hence, it is not likely to be a topoisomerase II poison. Consistent with the idea that cadmium cytotoxicity may be modulated by glutathione levels, buthionine sulfoximine pretreatment to decrease glutathione levels resulted in a greatly increased cadmium-induced cytotoxicity in K562 cells. The results of this study suggest that cadmium may exert some of its cell growth inhibitory, and possibly its toxicity and carcinogenicity, by inhibiting topoisomerase IIα through reaction with critical cysteine thiols.