Cellular mechanisms of cadmium-induced toxicity: a review

Do freeze-thaw cycles affect the cadmium accumulation, subcellular distribution, and chemical forms in spinach (Spinacia oleracea L.)?

To date, although there are many studies investigating the toxicity of heavy metal to plant, little research exists in the seasonal freeze-thaw (FT) regions where FT cycles often happen during the plant growing process. To reveal the adaptive mechanisms of plants to the combination stresses of cadmium (Cd) and FT, the Cd accumulation, subcellular distribution, chemical forms, and antioxidant enzyme activity (peroxidase (POD)) were investigated in spinach (Spinacia oleracea L.) growing under different soil Cd levels (i.e., 0.10 mg Cd kg-1 soil (low), 1.21 mg Cd kg-1 soil (medium), and 2.57 mg Cd kg-1 soil (high)). Compared to the non-freeze-thaw (NFT) treatments, higher Cd concentrations in the root and lower translocation factors from root to leaf were found for the plants experiencing FT cycles. FT significantly decreased the Cd concentrations in the leaves under the low- and medium-Cd treatments, while similar values were found for the high-Cd treatments. Generally, FT could decrease the concentrations and proportions of Cd stored in the cell wall and soluble fractions and increase them in the organelle fractions for the medium- and high-Cd treatments, while opposite tendency was found for the low-Cd treatments. Moreover, larger Cd amounts in the inorganic and water-soluble forms were found for the low- and medium-Cd treated plants under FT, while lower values were found for the high-Cd treatments. Additionally, POD, which presented higher activities at the low- and medium-Cd treatments and lower activities at the high-Cd treatments under FT, were also significantly influenced by the Cd × FT interaction. This study indicated that FT could significantly change the accumulations of Cd in plant, and it provided a new insight into the Cd accumulation by plants in the seasonal FT region.

Plasma Vitamin B12 and Folate Alter the Association of Blood Lead and Cadmium and Total Urinary Arsenic Levels with Chronic Kidney Disease in a Taiwanese Population

Heavy metals causing chronic nephrotoxicity may play a key role in the pathogenesis of chronic kidney disease (CKD). This study hypothesized that plasma folate and vitamin B₁₂ would modify the association of CKD with total urinary arsenic and blood lead and cadmium levels. We recruited 220 patients with CKD who had an estimated glomerular filtration rate of <60 mL/min/1.73 m² for ≥3 consecutive months and 438 sex- and age-matched controls. We performed inductively coupled plasma mass spectrometry to measure blood cadmium and lead levels. The urinary arsenic level was determined using a high-performance liquid chromatography–hydride generator–atomic absorption spectrometry. Plasma vitamin B₁₂ and folate levels were measured through the SimulTRAC-SNB radioassay. Compared with patients with plasma vitamin B₁₂ ≤ 6.27 pg/mL, the odds ratio (OR) and 95% confidence interval of CKD for patients with plasma vitamin B₁₂ > 9.54 pg/mL was 2.02 (1.15–3.55). However, no association was observed between plasma folate concentration and CKD. A high level of plasma vitamin B₁₂ combined with high levels of blood lead and cadmium level and total urinary arsenic tended to increase the OR of CKD in a dose-response manner, but the interactions were nonsignificant. This is the first study to demonstrate that patients with high plasma vitamin B₁₂ level exhibit increased OR of CKD related to high levels of blood cadmium and lead and total urinary arsenic.

Immunomodulation by heavy metals as a contributing factor to inflammatory diseases and autoimmune reactions: Cadmium as an example

Cadmium (Cd) represents a unique hazard because of the long biological half-life in humans (20-30 years). This metal accumulates in organs causing a continuum of responses, with organ disease/failure as extreme outcome. Some of the cellular and molecular alterations in target tissues can be related to immune-modulating potential of Cd. This metal may cause adverse responses in which components of the immune system function as both mediators and effectors of Cd tissue toxicity, which, in combination with Cd-induced alterations in homeostatic reparative activities may contribute to tissue dysfunction. In this work, current knowledge concerning inflammatory/autoimmune disease manifestations found to be related with cadmium exposure are summarized. Along with epidemiological evidence, animal and in vitro data are presented, with focus on cellular and molecular immune mechanisms potentially relevant for the disease susceptibility, disease promotion, or facilitating development of pre-existing pathologies.

Cadmium hijacks the high zinc response by binding and activating the HIZR-1 nuclear receptor

Cadmium is an environmental pollutant and significant health hazard that is similar to the physiological metal zinc. In Caenorhabditis elegans, high zinc homeostasis is regulated by the high zinc activated nuclear receptor (HIZR-1) transcription factor. To define relationships between the responses to high zinc and cadmium, we analyzed transcription. Many genes were activated by both high zinc and cadmium, and hizr-1 was necessary for activation of a subset of these genes; in addition, many genes activated by cadmium did not require hizr-1, indicating there are at least two mechanisms of cadmium-regulated transcription. Cadmium directly bound HIZR-1, promoted nuclear accumulation of HIZR-1 in intestinal cells, and activated HIZR-1-mediated transcription via the high zinc activation (HZA) enhancer. Thus, cadmium binding promotes HIZR-1 activity, indicating that cadmium acts as a zinc mimetic to hijack the high zinc response. To elucidate the relationships between high zinc and cadmium detoxification, we analyzed genes that function in three pathways: the pcs-1/phytochelatin pathway strongly promoted cadmium resistance but not high zinc resistance, the hizr-1/HZA pathway strongly promoted high zinc resistance but not cadmium resistance, and the mek-1/sek-1/kinase signaling pathway promoted resistance to high zinc and cadmium. These studies identify resistance pathways that are specific for high zinc and cadmium, as well as a shared pathway.

Comparative root transcriptome analysis of two soybean cultivars with different cadmium sensitivities reveals the underlying tolerance mechanisms

Soybean can provide rich protein and fat and has great economic value worldwide. Cadmium (Cd) is a toxic heavy metal to organisms. It can accumulate in plants and be transmitted to the human body via the food chain. Cd is a serious threat to soybean development, particularly root growth. Some soybean cultivars present tolerant symptoms under Cd stress; however, the potential mechanisms are not fully understood. Here, we optimized RNA-seq to identify the differentially expressed genes (DEGs) in Cd-sensitive (KUAI) and Cd-tolerant (KAIYU) soybean roots and compared the DEGs between KAIYU and KUAI. A total of 1506 and 1870 DEGs were identified in the roots of KUAI and KAIYU, respectively. Through Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway, and gene function analyses, we found that genes related to antioxidants and sequestration were responsible for Cd tolerance in KAIYU. In addition, overexpression of Glyma11g02661, which encodes a heavy metal-transporting ATPase, significantly improved Cd tolerance in transgenic hairy roots. These results provide a preliminary understanding of the tolerance mechanisms in response to Cd stress in soybean root development and are of great importance in developing Cd-resistant soybean cultivars by using the identified DEGs through genetic modification.

Bioaccessibility as a determining factor in the bioavailability and toxicokinetics of cadmium compounds

Cadmium toxicity occurs where there is absorption and accumulation of cadmium ions (Cd²⁺) in tissues beyond tolerable levels. Significant differences in the release of Cd²⁺ from cadmium compounds in biological fluids, like gastric fluid, may indicate differences in bioavailability and absorption. This means that direct read-across from high solubility cadmium compounds to lower solubility compounds may not accurately reflect potential hazards. Here, the relative bioaccessibility in gastric fluid of cadmium telluride and cadmium chloride was evaluated using in vitro bioelution tests whilst the toxicokinetic behavior of these two compounds were compared after dietary administration for 90 days in male and female Wistar Han rats following OECD TG 408. Cadmium chloride was highly bioaccessible, whilst cadmium telluride showed low solubility in simulated gastric fluid (90 % and 1.5 % bioaccessibility, respectively). This difference in bioaccessibility was also reflected by a difference in bioavailability as shown by the difference in the liver and kidney concentrations of cadmium after repeat oral exposure. Feeding at doses of 750 and 1500 ppm of cadmium telluride did not result in tissue cadmium levels above the lower limit of quantification (LLOQ). In contrast, feeding with a lower test substance concentration yet higher concentration of bioaccessible cadmium (30 ppm cadmium chloride) resulted in tissue accumulation of cadmium. Only slight, non-adverse changes in hematology and clinical chemistry parameters were seen at these doses, indicating an absence of significant cadmium mediated toxicity towards target organs (kidney and liver), reflected in minimal cadmium accumulation in these organs. This study demonstrates that bioelution tests can help determine the bioaccessibility of cadmium, which can be used to estimate the potential for target tissue toxicity based on known toxicokinetic profiles and threshold levels for cadmium toxicity, while reducing and refining animal testing.

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.

Tissue Bioaccumulation and Toxicopathological Effects of Cadmium and Its Dietary Amelioration in Poultry-a Review

Cadmium (Cd) has been recognized as one of the most toxic heavy metals, which is continuously discharged into environments through anthropogenic (industrial activities, fertilizer production, and waste disposal) and natural sources with anthropogenic sources contributing greater than the natural sources. Therefore, Cd concentration sometimes increases in feeds, fodders, water bodies, and tissues of livestock including poultry in the vicinity of the industrial areas, which causes metabolic, structural, and functional changes of different organs of all animals. In poultry, bioaccumulation of Cd occurs in several organs mainly in the liver, kidney, lung, and reproductive organs due to its continuous exposure. Intake of Cd reduces growth and egg laying performance and feed conversion efficiency in poultry. Chronic exposure of Cd at low doses can also alter the microscopic structures of tissues, particularly in the liver, kidney, brain, pancreas, intestine, and reproductive organs due to increased content of Cd in these tissues. Continuous Cd exposure causes increased oxidative stress at cellular levels due to over-production of reactive oxygen species, exhausting antioxidant defense mechanisms. This leads to disruption of biologically relevant molecules, particularly nucleic acid, protein and lipid, and subsequently apoptosis, cell damage, and necrotic cell death. The histopatholocal changes in the liver, kidneys, and other organs are adversely reflected in hemogram and serum biochemical and enzyme activities. The present review discusses about Cd bioaccumulation and histopathological alterations in different tissues, pathogenesis of Cd toxicity, blood-biochemical changes, and its different ameliorative measures in poultry.

Cadmium significantly changes major morphometrical points and cardiovascular functional parameters during early development of zebrafish

Living organisms are commonly exposed to cadmium and other toxic metals. A vast body of research has shown the significant effects of these toxic metals on developmental processes. In order to study the role of toxic metals on early developmental stages of eukaryotes, we explored the effect of cadmium (Cd²⁺) contaminant on zebrafish. Thus, zebrafish embryos were exposed to 3 mg/L (16.7 μM) Cd²⁺ for 96 h and imaged every 24 h from the exposure onwards. Hatching rates of the eggs were determined at 72 h, followed by analyses at 96 h for: survival rate, morphometrical factors, and functional parameters of the cardiovascular system. Interestingly enough, significant hatching delays along with smaller cephalic region and some morphological abnormalities were observed in the treatment group. Moreover, substantial changes were noticed in the length of notochord and embryo, absorption of yolk sac with shorter extension, area of swimming bladder, as well as pericardium sac after Cd²⁺ treatment. Cadmium also caused significant abnormalities in heart physiology which could be the leading cause of mentioned morphological deformities. Herein, our results shine light on systematic acute embryological effects of cadmium in the early development of zebrafish for the first time.

Emerging role of air pollution in chronic kidney disease

Chronic kidney disease (CKD), a global disease burden related to high rates of incidence and mortality, manifests as progressive and irretrievable nephron loss and decreased kidney regeneration capacity. Emerging studies have suggested that exposure to air pollution is closely relevant to increased risk of CKD, CKD progression and end-stage kidney disease (ESKD). Inhaled airborne particles may cause vascular injury, intraglomerular hypertension, or glomerulosclerosis through non-hemodynamic and hemodynamic factors with multiple complex interactions. The mechanisms linking air pollutants exposure to CKD include elevated blood pressure, worsening oxidative stress and inflammatory response, DNA damage and abnormal metabolic changes to aggravate kidney damage. In the present review, we will discuss the epidemiologic observations linking air pollutants exposure to the incidence and progression of CKD. Then, we elaborate the potential roles of several air pollutants including particulate matter and gaseous co-pollutants, environmental tobacco smoke, and gaseous heavy metals in its pathogenesis. Finally, this review outlines the latent effect of air pollution in ESKD patients undergoing dialysis or renal transplant, kidney cancer and other kidney diseases. The information obtained may be beneficial for further elucidating the pathogenesis of CKD and making proper preventive strategies for this disease.

Resolvin D1 prevents cadmium chloride-induced memory loss and hippocampal damage in rats by activation/upregulation of PTEN-induced suppression of PI3K/Akt/mTOR signaling pathway

This study evaluated the protective effect of resolvin D1 (RVD1) against cadmium chloride (CdCl₂ )-induced hippocampal damage and memory loss in rats and investigated if such protection is mediated by modulating the PTEN/PI3K/Akt/mTOR pathway. Adult male Wistar rats (n = 18/group) were divided as control, control + RVD1, CdCl₂ , CdCl₂  + RVD1 and CdCl₂  + RVD1 + bpV(pic), a PTEN inhibitor. All treatments were conducted for 4 weeks. Resolvin D1 improved the memory function as measured by Morris water maze (MWM), preserved the structure of CA1 area of the hippocampus, and increased hippocampal levels of RVD1 in the CdCl₂ -treated rats. Resolvin D1 also suppressed the generation of reactive oxygen species (ROS), tumour necrosis factor-α and interleukine-6 (IL-6), inhibited nuclear factor κB (NF-κB) p65, stimulated levels of glutathione (GSH), manganese superoxide dismutase (MnSOD), and Bcl2 but reduced the expression of Bax and cleaved caspase 3 in hippocampi of CdCl₂ -treated rats. Concomitantly, it stimulated levels and activity of PTEN and reduced the phosphorylation (activation) of PI3K, Akt and mTOR in hippocampi of CdCl₂ -treated rats. In conclusion, RVD1 attenuates CdCl₂ -induced memory loss and hippocampal damage in rats mainly by activating PTEN-induced suppression of PI3K/Akt/mTOR, an effect that seems secondary to its' anti-oxidant and anti-inflammatory potential.

The effects of cadmium on the development of Drosophila and its transgenerational inheritance effects

A new focus in toxicology research is the impact of parental exposure to environmental toxic substances on the characteristics of offspring. In the present study, newly produced eggs of Drosophila melanogaster were treated with different concentrations of cadmium (0, 1, 2, 4, 8 mg/kg) to study the effects of development. The results showed that cadmium changed the larval body length and weight, prolonged the pupation and eclosion time, and changed the relative expression levels of development-related genes (baz, β-Tub60D, tj). Furthermore, the parental Drosophila (F₀) were treated with cadmium (4.5 mg/kg) from egg stage, and when grows to adults, they mated in standard medium to produce the de-stressed offspring (F₁-F₄) to assess the transgenerational effects of developmental delay. The results showed that the delayed effects of the pupation and eclosion time could be maintained for two generations, and the inhibiting effects of juvenile hormone (JH) and ecdysone (20-hydroxyecdysone, 20E) could be maintained for two or three generations. More importantly, cadmium increased the expression of DNA methylation-related genes (dDnmt2, dMBD2/3) in the ovaries (F₀-F₂) and testicles (F₀ and F₁). In addition, cadmium accumulated in parental Drosophila (F₀) was not transmitted to offspring through reproductive pathway. These results demonstrate that the developmental toxicity caused by cadmium could be transmitted to the de-stressed offspring, and the observed transgenerational inheritance effects may be associated with epigenetic regulation, underscoring the need to consider fitness of future generations in evaluating the toxicity and environmental risks of cadmium.

Cadmium-induced oxidative stress and transcriptome changes in the wolf spider Pirata subpiraticus

Spiders are believed to have enormous potential for indicating heavy metal pollution in ecosystems. The diversity of influencing factors caused significant differences in the toxicities of cadmium (Cd) on spiders. There is limited understanding of the underlying mechanism and response to acute Cd exposure at different concentrations and different poisoning times. We exposed adult female P. subpiraticus to 0.2 mM and 2 mM Cd for 6 and 12 h, respectively, to explore acute Cd toxicities by RNA-seq. We measured the bioaccumulation levels in P. subpiraticus and tested the activities of superoxide dismutase (SOD) and glutathione S-transferase (GST). There were 187, 292, 101 and 155 differentially expressed genes (DEGs) after exposure to 0.2 mM and 2 mM Cd for 6 and 12 h, respectively. The results revealed that Cd accumulated in P. subpiraticus, changed the SOD and GST activities, and caused significant adverse effects at the molecular level on metabolism and immune and oxidative stress, with time- and concentration-dependent differences. Transcriptome analysis showed that acute Cd exposure depressed lipid metabolism and induced protein metabolism, especially serine metabolism. Genes encoding lipoproteins were depressed when exposed to 0.2 mM Cd, while fatty acid-related genes were downregulated under 2 mM Cd stress. In total, 46 cuticle-related genes were upregulated, and 6 cytoskeleton-related genes changed notably in the immune process. Peroxidase-related genes were further upregulated significantly. Meanwhile, the pathways related to metabolism, immunity and oxidative stress were significantly enriched. This report illustrated that acute Cd exposure exerts toxicities on P. subpiraticus and the spiders against acute Cd toxicities by selective differential expression of the genes associated with the physiological process of metabolism and immune and antioxidant stress. This study provides a comprehensive transcriptional basis for understanding the response of the P. sublimations to heavy metals at different concentrations and different treatment times.

Magnesium isoglycyrrhizinate prevents cadmium-induced activation of JNK and apoptotic hepatocyte death by reversing ROS-inactivated PP2A

OBJECTIVES

Cadmium (Cd) induces reactive oxygen species (ROS)-mediated hepatocyte apoptosis and consequential liver disorders. This study aimed to investigate the effect of magnesium isoglycyrrhizinate (MgIG) on Cd-induced hepatotoxicity.

METHODS

L02 and AML-12 cells were used to study MgIG hepatoprotective effects. Cd-evoked apoptosis, ROS and protein phosphatase 2A (PP2A)/c-Jun N-terminal kinase (JNK) cascade disruption were analysed by cell viability assay, 6-diamidino-2-phenylindole (DAPI) and TdT-mediated dUTP Nick-End Labeling (TUNEL) staining, ROS imaging and Western blotting. Pharmacological and genetic approaches were used to explore the mechanisms.

KEY FINDINGS

We show that MgIG attenuated Cd-evoked hepatocyte apoptosis by blocking JNK pathway. Pre-treatment with SP600125 or ectopic expression of dominant-negative c-Jun enhanced MgIG's anti-apoptotic effects. Further investigation found that MgIG rescued Cd-inactivated PP2A. Inhibition of PP2A activity by okadaic acid attenuated the MgIG's inhibition of the Cd-stimulated JNK pathway and apoptosis; in contrast, overexpression of PP2A strengthened the MgIG effects. In addition, MgIG blocked Cd-induced ROS generation. Eliminating ROS by N-acetyl-l-cysteine abrogated Cd-induced PP2A-JNK pathway disruption and concurrently reinforced MgIG-conferred protective effects, which could be further slightly strengthened by PP2A overexpression.

CONCLUSIONS

Our findings indicate that MgIG is a promising hepatoprotective agent for the prevention of Cd-induced hepatic injury by mitigating ROS-inactivated PP2A, thus preventing JNK activation and hepatocyte apoptosis.

Effects of Acute Diquat Poisoning on Liver Mitochondrial Apoptosis and Autophagy in Ducks

Diquat (DQ) is an effective herbicide and is widely used in agriculture. Due to persistent and frequent applications, it can enter into aquatic ecosystem and induce toxic effects to exposed aquatic animals. The residues of DQ via food chain accumulate in different tissues of exposed animals including humans and cause adverse toxic effects. Therefore, it is crucial and important to understand the mechanisms of toxic effects of DQ in exposed animals. We used ducks as test specimens to know the effects of acute DQ poisoning on mechanisms of apoptosis and autophagy in liver tissues. Results on comparison of various indexes of visceral organs including histopathological changes, apoptosis, autophagy-related genes, and protein expression indicated the adverse effects of DQ on the liver. The results of our experimental trial showed that DQ induces non-significant toxic effects on pro-apoptotic factors like BAX, BAK1, TNF-α, caspase series, and p53. The results revealed that anti-apoptotic gene Parkin was significantly upregulated, while an upward trend was also observed for Bcl2, suggesting that involvement of the anti-apoptotic factors in ducklings plays an important role in DQ poisoning. Results showed that DQ significantly increased the protein expression level of the autophagy factor Beclin 1 in the liver. Results on key autophagy factors like LC3A, LC3B, and p62 showed an upward trend at gene level, while the protein expression level of both LC3B and p62 reduced that might be associated with process of translation affected by the pro-apoptotic components such as apoptotic protease that inhibits the occurrence of autophagy while initiating cell apoptosis. The above results indicate that DQ can induce cell autophagy and apoptosis and the exposed organism may resist the toxic effects of DQ by increasing anti-apoptotic factors.

Cadmium chloride induces non-alcoholic fatty liver disease in rats by stimulating miR-34a/SIRT1/FXR/p53 axis

Cadmium (Cd) is associated with non-alcoholic fatty liver disease (NAFLD). The hepatic activation of p53/miR-43a-induced suppression of SIRT1/FXR axis plays a significant role in the development of NAFLD. In this study, we have investigated CdCl₂-induced NAFLD in rats involves activation of miR34a/SIRT1/FXR axis. Adult male rats were divided into 4 groups (n-8/each) as a control, CdCl₂ (10 mg/l), CdCl₂ + miR-34a antagomir (inhibitor), and CdCl₂ + SRT1720 (a SIRT1 activator) for 8 weeks, daily. With no effect on fasting glucose and insulin levels, CdCl₂ significantly reduced rats' final body, fat pads, and liver weights, and food intake. Concomitantly, it increased the circulatory levels of liver markers (ALT, AST, and γ-GTT), increased the serum and hepatic levels of total cholesterol and triglycerides coincided with increased hepatic lipid accumulation. Besides, it increased the mRNA and protein levels of SREBP1, SREBP2, FAS, and HMGCOA reductase but reduced mRNA levels of PPARα, CPT1, and CPT2. Interestingly, CdCl₂ also increased mRNA levels of miR34 without altering mRNA levels of SIRT1 but with a significant reduction in protein levels of SIRT1. These effects were associated with increased total protein levels of p53 and acetylated protein of p53, and FXR. Of note, suppressing miR-34a with a specific anatomic or activating SIRT1 by SRT1720 completely prevented all these effects and reduced hepatic fat accumulations in the livers of rats. In conclusion, CdCl₂ induced NAFLD by increasing the transcription of miR-34a which in turn downregulates SIRT1 at the translational level.

Role of Autophagy in Cadmium-Induced Hepatotoxicity and Liver Diseases

Cadmium (Cd) is a toxic pollutant that is associated with several severe human diseases. Cd can be easily absorbed in significant quantities from air contamination/industrial pollution, cigarette smoke, food, and water and primarily affects the liver, kidney, and lungs. Toxic effects of Cd include hepatotoxicity, nephrotoxicity, pulmonary toxicity, and the development of various human cancers. Cd is also involved in the development and progression of fatty liver diseases and hepatocellular carcinoma. Cd affects liver function via modulation of cell survival/proliferation, differentiation, and apoptosis. Moreover, Cd dysregulates hepatic autophagy, an endogenous catabolic process that detoxifies damaged cell organelles or dysfunctional cytosolic proteins through vacuole-mediated sequestration and lysosomal degradation. In this article, we review recent developments and findings regarding the role of Cd in the modulation of hepatotoxicity, autophagic function, and liver diseases at the molecular level.

Toxicological interaction between tobacco smoke toxicants cadmium and nicotine: An in-vitro investigation

Cigarettes and other tobacco products are used to obtain nicotine that is responsible for their stimulating effects. However, a lot of other organic and inorganic chemicals are also released along with nicotine. Cadmium (Cd) is one of the several heavy metals that are health hazards and is one of the inorganic elements released in tobacco smoke. The in-vitro investigation focused on exploring the effects of nicotine hydrogen tartrate (NHT) and cadmium (Cd) and their toxic interactions in the A549 cell line. In cell viability assay NHT exhibited its IC50 at 11.71 mM concentration, and the IC50 of Cd was found to be 83 µM after a 24 h exposure. Toxic effects of NHT (5 mM and 10 mM), Cd (50 µM and 100 µM), and their combination were also investigated by flowcytometry. The investigation included apoptotic and necrotic events, the effect on different cell cycle phases, and generation of reactive oxygen species by NHT, Cd, and their combination of different concentrations. Data reveal evident toxic effects of NHT, Cd, and NHT + Cd. It also indicates that the toxic interaction of NHT and Cd is not additive and appears to be minimal when compared with NHT or Cd exposures alone.

Association of microRNA expression with changes in immune markers in workers with cadmium exposure

Human exposure to cadmium (Cd) is known to produce severe health effects. Recently, molecular mechanism of Cd toxicity has revealed the role of Cd in causing epigenetic alterations. miRNAs are small, non-coding RNAs which are involved in translational repression of genes. Therefore, the aim of the present study was to evaluate the alterations in expression of miRNAs associated with inflammation, carcinogenesis and, further, study their possible correlation with immune profile, in occupationally Cd exposed workers of Jodhpur. 106 workers from metal handicraft and welding factories were recruited as subjects, while, 80 apparently healthy non-exposed individuals served as control for this study. Blood Cd levels (BCd) were determined by Graphite Furnace Atomic Absorption Spectroscopy (GFAAS). Lymphocyte cell subset were measured by flow cytometry, serum interleukins were assessed by ELISA and miRNA expression was determined by Real Time Polymerase Chain Reaction (RT-PCR). BCd levels were significantly higher in the exposed individuals when compared to the non-exposed, with welders reporting the highest amongst all. Among the lymphocyte subset, exposed group showed significantly higher percentage of Th17 and lower percentage of Treg population. Cytokine profile expressed by exposed workers were predominantly pro-inflammatory in nature. Among, the studied miRNAs, miR-221 was significantly higher in exposed group with a fold change of 3.05. Additionally, miR-221 and miR-155 showed significant positive correlation with Th17 cell %. Regression analysis showed duration of exposure and IL-17 to have significant effect on miR-221 in exposed group. In conclusion, miR-221 was significantly upregulated in exposed and was correlated with immune alteration making it a potential candidate for further exploration of mechanism underlying Cd toxicity.

The adverse impact of cadmium on immune function and lung host defense

Cadmium (Cd) is a transition metal, also referred to as a heavy metal, that is naturally abundant in the earth's crust. It has no known benefit to humans. It is primarily released into our environment through mining and smelting in industrial processes and enters the food chain through uptake by plants from contaminated soil and water. In humans, Cd primarily enters the body through ingestion of foods and cigarette smoke and has an extremely long resident half-life in the body compared to other transition metals. Environmental workplace exposure is also a source through inhalation, although much less common. The principal organs adversely affected by Cd following acute and chronic exposure are the kidneys, bone, vasculature and lung. Cd adversely impacts cell function through changes in gene expression and signal transduction and is recognized as a carcinogen. Despite a substantial body of mechanistic studies in cells and animal models, the overall impact of Cd on innate immune function in humans remains poorly understood. The best evidence is perhaps alteration of reactive oxygen species balance and signaling in cells that regulate innate immunity causing alteration of the inflammatory response that is postulated to contribute to chronic diseases. Epidemiologic studies support this possibility since increased tissue levels in humans are strongly associated with leading chronic diseases including chronic obstructive pulmonary disease (COPD), which will be discussed in depth. Additional studies are required to understand how chronic exposure and accumulation of this leading environmental toxicant in vital organs negatively impact innate immune function and host defense leading to chronic disease in humans.

The endocrine disruptor cadmium: a new player in the pathophysiology of metabolic diseases

Cadmium (Cd), a highly toxic heavy metal, is found in soil, environment and contaminated water and food. Moreover, Cd is used in various industrial activities, such as electroplating, batteries production, fertilizers, while an important non-occupational source is represented by cigarette smoking, as Cd deposits in tobacco leaves. Since many years it is clear a strong correlation between Cd body accumulation and incidence of many diseases. Indeed, acute exposure to Cd can cause inflammation and affect many organs such as kidneys and liver. Furthermore, the attention has focused on its activity as environmental pollutant and endocrine disruptor able to interfere with metabolic and energy balance of living beings. Both in vitro and in vivo experiments have demonstrated that the Cd-exposure is related to metabolic diseases such as obesity, diabetes and osteoporosis even if human studies are still controversial. Recent data show that Cd-exposure is associated with atherosclerosis, hypertension and endothelial damage that are responsible for cardiovascular diseases. Due to the large environmental diffusion of Cd, in this review, we summarize the current knowledge concerning the role of Cd in the incidence of metabolic and cardiovascular diseases.

Acinetobacter tandoii ZM06 Assists Glutamicibacter nicotianae ZM05 in Resisting Cadmium Pressure to Preserve Dipropyl Phthalate Biodegradation

Dipropyl phthalate (DPrP) coexists with cadmium as cocontaminants in environmental media. A coculture system including the DPrP-degrading bacterium Glutamicibacter nicotianae ZM05 and the nondegrading bacterium Acinetobacter tandoii ZM06 was artificially established to degrade DPrP under Cd(II) stress. Strain ZM06 relieved the pressure of cadmium on strain ZM05 and accelerated DPrP degradation in the following three ways: first, strain ZM06 adsorbed Cd(II) on the cell surface (as observed by scanning electron microscopy) to decrease the concentration of Cd(II) in the coculture system; second, the downstream metabolites of ZM05 were utilized by strain ZM06 to reduce metabolite inhibition; and third, strain ZM06 supplied amino acids and fatty acids to strain ZM05 to relieve stress during DPrP degradation, which was demonstrated by comparative transcriptomic analysis. This study provides an elementary understanding of how microbial consortia improve the degradation efficiency of organic pollutants under heavy metals contamination.

Characterization of Brassica rapa metallothionein and phytochelatin synthase genes potentially involved in heavy metal detoxification

Brassica rapa is an important leafy vegetable that can potentially accumulate high concentrations of cadmium (Cd), posing a risk to human health. The aim of the present study was to identify cadmium detoxifying molecular mechanisms in B. rapa using a functional cloning strategy. A cDNA library constructed from roots of B. rapa plants treated with Cd was transformed into the Cd sensitive yeast mutant strain DTY167 that lacks the yeast cadmium factor (YCF1), and resistant yeast clones were selected on Cd containing media. Two hundred genes potentially conferring cadmium resistance were rescued from the surviving yeast clones and sequenced. Sequencing analysis revealed that genes encoding for metallothionein (MT)1, MT2a, MT2b and MT3, and phytochelatin synthase (PCS)1 and PCS2 accounted for 35.5%, 28.5%, 4%, 11.3%, 18.7% and 2%, respectively of the genes identified. MTs and PCSs expressing DTY167 cells showed resistance to Cd as well as to Zn. PCS1 expressing yeast cells were also more resistant to Pb compared to those expressing MTs or PCS2. RT-PCR results showed that Cd treatment strongly induced the expression levels of MTs in the root and shoot. Furthermore, the different MTs and PCSs exhibited tissue specific expression. The results indicate that MTs and PCS genes potentially play a central role in detoxifying Cd and other toxic metals in B. rapa.

Damage to the Testicular Structure of Rats by Acute Oral Exposure of Cadmium

Cadmium (Cd) is one of the most important heavy metal toxicants, used throughout the world at the industrial level. It affects humans through environmental and occupational exposure and animals through the environment. The most severe effects of oral exposure to Cd on the male reproductive system, particularly spermatogenesis, have not been discussed. In this study, we observed the damage to the testes and heritable DNA caused by oral exposure to Cd. Adult male Sprague–Dawley rats were divided into four groups: a control group and three groups treated with 5, 10, and 15 mg Cd/kg/day for 17 days by oral gavage. Our results revealed that Cd significantly decreases weight gain in 10 and 15 mg/kg groups, whereas the 5 mg/kg groups showed no difference in weight gain. The histopathology showed adverse structural effects on the rat testis by significantly reducing the thickness of the tunica albuginea, the diameter of the tubular lumen, and the interstitial space among seminiferous tubules and increasing the height of the epithelium and the diameter of the seminiferous tubules in Cd treated groups. Comet assay in epididymal sperms demonstrated a significant difference in the lengths of the head and comet in all the 3 Cd treated groups, indicating damage in heritable DNA, although variations in daily sperm production were not significant. Only a slight decrease in sperm count was reported in Cd-treated groups as compared to the control group, whereas the tail length, percentage of DNA in head, and tail showed no significant difference in control and all the experimental groups. Overall, our findings indicate that Cd toxicity must be controlled using natural sources, such as herbal medicine or bioremediation, with non-edible plants, because it could considerably affect heritable DNA and induce damage to the reproductive system.

A combined approach to remediate cadmium contaminated sediment using the acidophilic sulfur-oxidizing bacterial SV5 and untreated coffee ground

Cadmium (Cd) contamination in sediment is an emerging concern for the sustainability of aquatic ecosystem due to the toxicity of Cd is correlated to different trophic levels. An effective and inexpensive remediation strategy for Cd-contaminated sediment is desirable. The feasibility of using a newly isolated acidophilic sulfur-oxidizing bacterium and untreated coffee ground to remediate Cd-contaminated sediment was evaluated. The bioleaching approach was firstly conducted with the acidophilic sulfur-oxidizing bacterial SV5, resulting in Cd(II) release from Cd(II)-contaminated sediment. Subsequently, Cd(II) in the acidic leachate was further removed using untreated agricultural wastes. Untreated coffee ground exhibited about 2-fold Cd(II) removal efficiency comparing to that of rice husk and peanut shell. Scanning electron microscope (SEM) and Fourier-transform infrared spectroscopy (FTIR) analysis were conducted to characterize the coffee ground after the adsorption of 0 or 200 mg/L Cd(II). At pH 4, the optimal coffee ground concentration was 30 g/L along with 100 mg/L Cd(II) concentration. Adsorption of Cd(II) by coffee ground was rapid and the adsorption kinetic followed pseudo-second order model. Cd(II) sorption by coffee ground was a favorable process and Langmuir isotherm model well described the experimental data. Taken together, even at pH 4, coffee ground still showed good biosorption capacity for Cd(II) with short equilibrium time. This study suggests that acidophilic sulfur-oxidizing bacterial SV5 and untreated coffee ground could be used as inexpensive and environment-friendly biomaterial and agricultural waste for the remediation of Cd-contaminated sediment.

Comparative study on protective effect of different selenium sources against cadmium-induced nephrotoxicity via regulating the transcriptions of selenoproteome

Cadmium (Cd) is a ubiquitous environmental pollutant, which mainly input to the aquatic environment through discharge of industrial and agricultural waste, can be a threat to human and animal health. Selenium (Se) possesses a beneficial role in protecting animals and ameliorating the toxic effects of Cd. However, the comparative antagonistic effects of different Se sources such as inorganic, organic Se and nano-form Se on Cd toxicity are still under-investigated. Hence, the purpose of this study was to evaluate the comparative of Se sources antagonism on Cd-induced nephrotoxicity via oxidative stress and selenoproteome transcription. In the present study, Cd-diet disturbed in the system balance of 5 trace elements (Zinc (Zn), copper (Cu), Iron (Fe), Se, Cd) and impaired renal function. Se sources, including nano- Se (NS), Se- yeast (SY), sodium selenite (SS) and mixed selenium (MS) significantly recovered the balance of 4 trace elements (Zn, Cu, Cd, Se) and renal impaired indexes (blood urea nitrogen (BUN) and creatinine (CREA)). Histological appearance of Cd-treated kidney indicated renal tubular epithelial vacuoles, particle degeneration and enlarged capsular space. Ultrastructure observation results illustrated that Cd-induced mitochondrial cristae reduction, membrane disappearance, and nuclear deformation. Treatment with Se sources, NS appeared a better impact on improving kidney tissues against the pathological alterations resulting from Cd administration. Meanwhile, NS reflected a significant impact on relieving Cd-induced kidney oxidative damage, and significantly restored the antioxidant defense system of the body. Our findings also showed NS ameliorated the Cd-induced downtrends expression of selenoproteome and selenoprotein synthesis related transcription factors. Overall, NS was the most effective Se source in avoiding of Cd cumulative toxicity, improving antioxidant capacity and regulating of selenoproteome transcriptome and selenoprotein synthesis related transcription factors expression, which contributes to ameliorate Cd-induced nephrotoxicity in chickens. These results demonstrated diet supplement with NS may prove to be an effective approach for alleviating Cd toxicity and minimizing Cd -induced health risk.

Bio-indicators in cadmium toxicity: Role of HSP27 and HSP70

Heat shock proteins (HSPs) are a family of proteins that are expressed by cells in reply to stressors. The changes in concentration of HSPs could be utilized as a bio-indicator of oxidative stress caused by heavy metal. Exposure to the different heavy metals may induce or reduce the expression of different HSPs. The exposure to cadmium ion (Cd²⁺) could increase HSP70 and HSP27 over 2- to 10-fold or even more. The in vitro and in vivo models indicate that the HSP70 family is more sensitive to Cd intoxication than other HSPs. The analyses of other HSPs along with HSP70, especially HSP27, could also be useful to obtain more accurate results. In this regard, this review focuses on examining the literature to bold the futuristic uses of HSPs as bio-indicators in the initial assessment of Cd exposure risks in defined environments.

The Effects of Metal Exposures on Charlson Comorbidity Index Using Zero-Inflated Negative Binomial Regression Model: NHANES 2011-2016

BACKGROUND

With the rising incidence of chronic diseases, and the increase of aging population has led to multimorbidity a serious public health problem. The aim of this study was to explore the association between metal exposures and Charlson comorbidity index (CCI), which will provide valuable information for improving quality of life and reducing mortality.

METHODS

The study sample consists of three continuous cycles (2011-2016) of the National Health and Nutrition Examination Survey (NHANES), and 4901 eligible subjects were included in the study. Zero-inflated negative binomial (ZINB) model was utilized to investigate the effects in metal exposures on CCI, which includes spot urine (arsenic, mercury, and cadmium), whole blood (manganese, selenium, and lead), and serum (copper and zinc).

RESULTS

In count part (CCI ≥ 0), holding other variables constant, the expected change in CCI for a one-unit increase in blood selenium is 0.997 (RR = 0.997, p = 0.017). In logit part (CCI = 0), the log odds of having CCI equals zero would increase by 0.659, 1.073, and 0.963 for every additional urinary cadmium (OR = 0.659, p = 0.007), blood lead (OR = 1.073, p = 0.023), blood manganese (OR = 0.963, p = 0.025), respectively.

CONCLUSIONS

Our findings indicated that cadmium and manganese were likely to increase mortality. Inversely, selenium and lead might be positive on people's health. The findings may be extremely essential for preventing diseases and improving life quality.

Cadmium cytotoxicity and possible mechanisms in human trophoblast HTR-8/SVneo cells

The accumulation of cadmium (Cd) in the human body through food chain can lead to adverse pregnancy outcomes. In this study, Cd cytotoxicity and its mechanisms in HTR-8/SVneo cells were investigated. Cd disrupted the cellular submicrostructure and inhibited the cell viability in a time- and dose-dependent manner. The levels of reactive oxygen species, malondialdehyde content, and the activities of glutathione peroxidase (GSH-Px) and total superoxode dismutase (T-SOD) were concentration-dependently increased by Cd. In addition, Cd dose-dependently inducedcell apoptosis and decreased cell migration and invasion capacities. Finally, Cd significantly upregulated all the genes related to oxidative stress (SOD1, ROS1, and HSPA6), inflammatory response, cell cycle, apoptosis, and migration and invasion. This study will provide insights into the prevention and treatment of pregnancy-related diseases caused by Cd intoxication.

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.

Protective Effect of Resveratrol against Hepatotoxicity of Cadmium in Male Rats: Antioxidant and Histopathological Approaches

Cadmium (Cd) is widely used in some industries and emitted from fossil fuels. It is a heavy metal with a number of side effects, including hepatotoxicity. Resveratrol (Rs) is considered an important polyphenol, which is a secondary plant metabolite and has the ability to scavenge free radicals. The study was designed to evaluate the effects of resveratrol on Cd, which induced hepatotoxicity, by the assessment of some histopathological and biochemical alterations. Forty male albino rats were divided into four groups: the 1st group was the control group, the 2nd group was treated with Cd (5 mg/kg), the 3rd group was given Rs (20 mg/kg), and the 4th group was treated with Cd in combination with Rs intraperitoneally for 30 successive days. The results indicate that Cd increased liver enzymes alanine aminotransferase and aspartate aminotransferase (AST and ALT), alkaline phosphatase ALP and gamma-glutamyl transferase (γ-GT) while reducing the total protein level; Cd increased the malondialdhyde (MDA) level while decreasing the levels of other antioxidant enzymes super oxide dismutase, catalase and glutathione peroxidase (SOD, CAT and GPx). Serious congestion and hemorrhage related to the hepatic tissues were noticed in the Cd group, and Rs plays a major role in alleviating histopathological injuries and hepatic oxidative damage. It is clear that Rs has the ability to minimize the hepatotoxicity induced by Cd in male rats.

Molecular mechanism of heavy metals (Lead, Chromium, Arsenic, Mercury, Nickel and Cadmium) - induced hepatotoxicity - A review

Heavy metals pose a serious threat if they go beyond permissible limits in our bodies. Much heavy metal's viz. Lead, Chromium, Arsenic, Mercury, Nickel, and Cadmium pose a serious threat when they go beyond permissible limits and cause hepatotoxicity. They cause the generation of ROS which in turn causes numerous injuries and undesirable changes in the liver. Epidemiological studies have shown an increase in the levels of such heavy metals in the environment posing a serious threat to human health. Epigenetic alterations have been seen in the event of exposure to such heavy metals. Apoptosis, caspase activation as well as ultrastructural changes in the hepatocytes have also been seen due to heavy metals. Inflammation involving TNF-alpha, pro-inflammatory cytokines, MAPK, ERK pathways have been seen in the event of heavy metal hepatotoxicity. All these have shown that these heavy metals pose a serious threat to human health in particular and the environment as a whole.

Quercetin prevents cadmium chloride-induced hepatic steatosis and fibrosis by downregulating the transcription of miR-21

This study investigated if cadmium chloride (CdCl₂ )-induced hepatic steatosis and fibrosis and the protective effect of quercetin (QUR) are mediated modulating the activity of miR-21, a known hepatic lipogenic and fibrotic miRNA. Male rats (n = 8/group) were divided as control, control + QUR (50 mg/kg; orally), CdCl₂ (10 moml/L; drinking water), CdCl₂  + miR-21 antagomir (inhibitor) (16 mg/kg/first 3 days), and CdCl₂  + QUR (50 mg/kg). Treatments were conducted for 20 weeks, daily. All treatments showed no effect on fasting glucose and insulin levels. Administration of either miR-21 or QUR prevented CdCl₂ -induced hepatic damage, as well as lipid droplets and collagen deposition. They also reduced serum levels of ALT and AST and decreased serum and hepatic levels of total cholesterol, triglycerides, and low-density lipoproteins in CdCl₂ -treated rats. Concomitantly, they reduced hepatic levels of reactive oxygen species, malondialdehyde, interleukin-6, and tumor necrosis factor-α, suppressed the activation of NF-kb P65, and increased hepatic levels of nuclear factor erythroid 2-related factor 2 (Nrf2), glutathione (GSH), and superoxide dismutase (SOD). These effects were associated with reduced expression of SREBP1, TGF-β1, Smad3, and collagen1 A and increased expression of PPARα, CPT1, and smad7. Interestingly, QUR significantly lowered levels of miR-21 and increased the protein levels and activity of Nrf2, as well as levels of GSH and SOD in the livers of both the control and CdCl₂ -treated rats. Of note, levels of Nrf2 were negatively correlated with the transcription of miR-21. In conclusion: QUR prevents CdCl₂ -induced hepatic steatosis and fibrosis mainly through attenuating its ability to upregulate miR-21, at least, by upregulation of Nrf2.

Investigation of Apoptotic and Inflammatory Activity in Liver Tissue of Rats Fed with Clam (Pecten maximus, Linnaeus 1758)

One of the most important threats for living things in aquatic ecosystems is environmental pollution. The changes in water quality caused by environmental pollution also reduce the quality of life for organisms in the environment. Among these, the crustaceans which are most affected by the negative changes of environment, fed by the filtration method, are seen as pollution indicator. The consumption of these creatures reaches all steps of the pyramid, especially humans, through the food chain. People who frequently use seafood in their diets may be affected by these negative changes. Heavy metal contents of the clams obtained from Dardanelles were determined by the ICPOES. Twenty-four female Wistar albino rats were fed for 30 days with the experimental diet using clams (Pecten maximus), which was dried and formed into pellets and added to the food in certain proportions. At the end of the study, the subjects were sacrificed under anesthesia, liver tissues were taken, and histochemical examination was performed. TUNEL method was performed to detect apoptotic activity, and immunohistochemical staining with TNF-α and NF-κB antibodies to determine inflammation. Concluding from the results, it was observed that the degeneration of vital digestive system tissues such as liver was inevitable in living creatures that frequently consume seafood obtained from unhealthy environment in their daily diets. The high analysis values of the heavy metal (P. maximus) in food additive can be considered as a reason for histopathological results.

Toxic Mechanisms of Five Heavy Metals: Mercury, Lead, Chromium, Cadmium, and Arsenic

The industrial activities of the last century have caused massive increases in human exposure to heavy metals. Mercury, lead, chromium, cadmium, and arsenic have been the most common heavy metals that induced human poisonings. Here, we reviewed the mechanistic action of these heavy metals according to the available animal and human studies. Acute or chronic poisonings may occur following exposure through water, air, and food. Bioaccumulation of these heavy metals leads to a diversity of toxic effects on a variety of body tissues and organs. Heavy metals disrupt cellular events including growth, proliferation, differentiation, damage-repairing processes, and apoptosis. Comparison of the mechanisms of action reveals similar pathways for these metals to induce toxicity including ROS generation, weakening of the antioxidant defense, enzyme inactivation, and oxidative stress. On the other hand, some of them have selective binding to specific macromolecules. The interaction of lead with aminolevulinic acid dehydratase and ferrochelatase is within this context. Reactions of other heavy metals with certain proteins were discussed as well. Some toxic metals including chromium, cadmium, and arsenic cause genomic instability. Defects in DNA repair following the induction of oxidative stress and DNA damage by the three metals have been considered as the cause of their carcinogenicity. Even with the current knowledge of hazards of heavy metals, the incidence of poisoning remains considerable and requires preventive and effective treatment. The application of chelation therapy for the management of metal poisoning could be another aspect of heavy metals to be reviewed in the future.

The role of autophagy in metal-induced urogenital carcinogenesis

Environmental and/or occupational exposure to metals such as Arsenic (As), Cadmium (Cd), and Chromium (Cr) have been shown to induce carcinogenesis in various organs, including the urogenital system. However, the mechanisms responsible for metal-induced carcinogenesis remain elusive. We and others have shown that metals are potent inducers of autophagy, which has been suggested to be an adaptive stress response to allow metal-exposed cells to survive in hostile environments. Albeit few, recent experimental studies have shown that As and Cd promote tumorigenesis via autophagy and that inhibition of autophagic signaling suppressed metal-induced carcinogenesis. In light of the newly emerging role of autophagic involvement in metal-induced carcinogenesis, the present review focuses explicitly on the mechanistic role of autophagy and potential signaling pathways involved in As-, Cd-, and Cr-induced urogenital carcinogenesis.

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.

Adverse cardiovascular effects of exposure to cadmium and mercury alone and in combination on the cardiac tissue and aorta of Sprague-Dawley rats

The aim of this study was to identify cardiovascular effects of relevant concentrations of Cd and Hg alone and in combination as a mixture in water. This was achieved by administering to male Sprague-Dawley rats via gavage 0.62 mg/kg Cd or 1.23 mg/kg Hg, or a combination of 0.62 mg/kg Cd and 1.23 mg/kg Hg in the co-exposure group for 28 days. Concentrations were the rat equivalence dosages of 1,000 times the World Health Organization's limits of 0.003 mg/L and 0.006 mg/L for Cd and Hg, respectively, for water. With termination, blood levels of the metals were increased. For all metal exposed groups, histological evaluation and transmission electron microscopy of the myocardium revealed myofibrillar necrosis, increased fibrosis, vacuole formation and mitochondrial damage. Cd caused the most mitochondrial damage while Hg to a greater degree induced fibrosis. In the aorta, both Cd and Hg also increased collagen deposition adversely altering the morphology of the fenestrated elastic fibers in the tunica media. Co-exposure resulted in increased cardiotoxicity with increased mitochondrial damage, fibrosis and distortion of the aortic wall as a result of increased collagen deposition, as well as altered elastin deposition, fragmentation and interlink formation. These are typical features of oxidative damage that correlates with a phenotype of premature ageing of the CVS that potentially can lead to hypertension and premature cardiac failure.

Association between environmental exposure to cadmium and risk of suspected non-alcoholic fatty liver disease

AIM

We evaluated the associations between blood Cadmium (Cd) concentrations and risk of suspected NAFLD using nationally representative data from the Korea National Health and Nutrition Examination Survey (KNHANES) 2008-2013, 2016 and 2017.

METHODS

This cross-sectional study included 12,099 adults for the serum alanine aminotransferase (ALT) and hepatic steatosis index (HSI) analyses and 2,904 adults for the serum gamma-glutamyl transferase (GGT) and fatty liver index (FLI) analyses, without significant alcohol consumption. Blood Cd concentrations were measured by graphite furnace atomic absorption spectrometry. Data were analyzed using survey logistic regression models.

RESULTS

Odds ratios (ORs) of suspected NAFLD increased significantly per unit of natural log-transformed blood Cd concentration (OR [95% (CI)], for ALT, overall: 1.50 [1.34, 1.68], men: 1.64 [1.40, 2.10] and women: 1.29 [1.08, 1.47]; for GGT, overall: 1.77 [1.33, 2.35], men: 2.28 [1.53, 3.41] and women: 1.27 [0.82, 1.97]; for FLI, overall: 1.84 [1.32, 2.57], men: 1.91 [1.24, 2.94] and women: 1.58 [0.87, 2.86]; for HSI, overall: 1.19 [1.07, 1.32], men: 1.17 [1.01, 1.37] and women: 1.14 [0.99, 1.32]). The blood Cd concentrations associated with risk of suspected NAFLD were lower than those previously reported (for ALT, > 0.64 μg/L, for GGT, > 1.41 μg/L, for FLI, > 0.96 μg/L, and for HSI, > 1.41 μg/L).

CONCLUSIONS

This study suggests that the reference level of blood Cd should probably be lower than the previously recommended value to prevent adverse health effects due to Cd exposure.

Cadmium exposure induces TNF-α-mediated necroptosis via FPR2/TGF-β/NF-κB pathway in swine myocardium

Cadmium (Cd) is one common environmental pollutant with systemic toxicity. Lipoxin A4 (LXA4) can regulate transforming growth factor-β (TGF-β) pathway and alleviate tissue injury via binding to formyl peptide receptor 2 (FPR2). The activation of nuclear factor-κB (NF-κB) pathway can promote the occurence of necroptosis. However, whether Cd exposure induces necroptosis in swine myocardium and the role of FPR2/TGF-β/NF-κB pathway in this process are unclear. Hence, we established Cd-exposed swine myocardial injury model by feeding a CdCl₂ added diet (20 mg Cd/kg diet). Hematoxylin-eosin (H&E) staining was used to observe the morphological changes, and inductively coupled plasma mass spectrometry (ICP-MS) was performed to detect the levels of ion elements in myocardium. We further detected LXA4 and its receptor FPR2, TGF-β, Nrf2, NF-κB pathway and necroptosis related-genes expressions by RT-PCR and western blot. The results showed that Cd exposure induced necrotic cell death and ion homeostasis imbalance in swine myocardium. Moreover, Cd exposure increased the LXA4 content, inhibited the FPR2 expression, activated TGF-β pathway and suppressed Nrf2 pathway, activating the NF-κB pathway. In addition, Cd exposure increased the expressions of necroptosis related-genes TNF-α, TNFR1, RIP1, RIP3 and MLKL. It indicated Cd exposure induced necroptosis via FPR2/TGF-β/NF-κB pathway, revealing the potential mechanism of Cd-induced cardiotoxicity in swine myocardium.

NLRP3 inflammasome mediated pyroptosis is involved in cadmium exposure-induced neuroinflammation through the IL-1β/IkB-α-NF-κB-NLRP3 feedback loop in swine

Cadmium (Cd) chloride, as widely distributed toxic environmental pollutants by using in industry, severely imperils animal and human health. Pyroptosis is a Cas1-dependent pro-inflammatory programmed cell death and involves in various types of diseases. Nevertheless, the mechanism of pyroptosis and Cd-induced neurotoxicity remains obscure. To investigate the specific molecular mechanisms of Cd-induced neurotoxicity, 10 weaned piglets were randomly divided into 2 groups treated with 0 and 20 mg/kg CdCl₂ in the diet for 40 days. The levels of pyroptosis, mitochondrial and inflammation-related genes were validated by qRT-PCR and WB in vivo. Our results revealed that Cd caused cerebral histopathology lesions, inducing cerebral pyroptosis and the mass generation of inflammatory cytokines, as indicated by the increased NLRP3 inflammasome activation (NLRP3, Cas1 and ASC) and the upregulation of inflammation factors IL-2, IL-6, IL-7 and inhibition of IL-10. Subsequently, further research indicated that Cd triggered pyroptosis via activating the TRAF6-IkB-α-NF-κB pathway, which interfered with the phosphorylation and ubiquitination of IkB-α. Furthermore, Cd caused mitochondrial dysfunction and fragmentation by inhibiting the AMPK-PGC-1α-NRF1/2 signaling pathway and reduced the expression of mitochondrial-related regulatory factors OPA1, TFAM and mtDNA, resulting in the increase of NLRP3 inflammasome. Besides, we found eight hub genes (IKK, IKB-α, NLRP3, TRAF6, NF-κB, AMPK, TNFα and PGC-1α), mainly related to the interaction between the NF-κB pathway and NLRP3 inflammasome. Overall, these results demonstrated that Cd could promote the IL-1β/IkB-α-NF-κB-NLRP3 inflammasome activation positive feedback loop to result in neuroinflammation in swine, which provided new insights in understanding Cd-induced toxicity.

Recent Advances in Nanotechnology-Based Biosensors Development for Detection of Arsenic, Lead, Mercury, and Cadmium

Heavy metals cause considerable environmental pollution due to their extent and non-degradability in the environment. Analysis and trace levels of arsenic, lead, mercury, and cadmium as the most toxic heavy metals show that they can cause various hazards in humans' health. To achieve rapid, high-sensitivity methods for analyzing ultra-trace amounts of heavy metals in different environmental and biological samples, novel biosensors have been designed with the participation of strategies applied in nanotechnology. This review attempted to investigate the novel, sensitive, efficient, cost-benefit, point of care, and user-friendly biosensors designed to detect these heavy metals based on functional mechanisms. The study's search strategies included examining the primary databases from 2015 onwards and various keywords focusing on heavy metal biosensors' performance and toxicity mechanisms. The use of aptamers and whole cells as two important bio-functional nanomaterials is remarkable in heavy metal diagnostic biosensors' bioreceptor design. The application of hybridized nanomaterials containing a specific physicochemical function in the presence of a suitable transducer can improve the sensing performance to achieve an integrated detection system. Our study showed that in addition to both labeled and label-free detection strategies, a wide range of nanoparticles and nanocomposites were used to modify the biosensor surface platform in the detection of heavy metals. The detection limit and linear dynamic range as an essential characteristic of superior biosensors for the primary toxic metals are studied. Furthermore, the perspectives and challenges facing the design of heavy metal biosensors are outlined. The development of novel biosensors and the application of nanotechnology, especially in real samples, face challenges such as the capability to simultaneously detect multiple heavy metals, the interference process in complex matrices, the efficiency and stability of nanomaterials implemented in various laboratory conditions.

First evidence of the protective role of melatonin in counteracting cadmium toxicity in the rat ovary via the mTOR pathway

Herein, the first evidence of the ability of melatonin (MLT) to counteract cadmium (Cd) toxic effects on the rat ovary is reported. Cd treatment, enhancing oxidative stress, provoked clear morphological, histological and biomolecular alterations, i.e. in the estrous cycle duration, in the ovarian and serum E2 concentration other than in the steroidogenic and folliculogenic genes expression. Results demonstrated that the use of MLT, in combination with Cd, avoided the changes, strongly suggesting that it is an efficient antioxidant for preventing oxidative stress in the rat ovary. Moreover, to explore the underlying mechanism involved, at molecular level, in the effects of Cd-MLT interaction, the study focused on the mTOR and ERK1/2 pathways. Interestingly, data showed that Cd influenced the phosphorylation status of mTOR, of its downstream effectors and of ERK1/2, inducing autophagy and apoptosis, while cotreatment with MLT nullified these changes. This work highlights the beneficial role exerted by MLT in preventing Cd-induced toxicity in the rat ovary, encouraging further studies to confirm its action on human ovarian health with the aim to use this indolamine to ameliorate oocyte quality in women with fertility disorders.

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

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

Long-Term Accumulation of Metals in the Skeleton as Related to Osteoporotic Derangements

The concentrations of metals in the environment are still not within the recommended limits as set by the regulatory authorities in various countries because of human activities. They can enter the food chain and bioaccumulate in soft and hard tissues/organs, often with a long half-life of the metal in the body. Metal exposure has a negative impact on bone health and may result in osteoporosis and increased fracture risk depending on concentration and duration of metal exposure and metal species. Bones are a long-term repository for lead and some other metals, and may approximately contain 90% of the total body burden in birds and mammals. The present review focuses on the most common metals found in contaminated areas (mercury, cadmium, lead, nickel, chromium, iron, and aluminum) and their effects on bone tissue, considering the possibility of the long-term bone accumulation, and also some differences that might exist between different age groups in the whole population.

Effects of myricetin against cadmium-induced neurotoxicity in PC12 cells

Cadmium (Cd) is one of the most prevalent toxic metals widely found in the environment. Cd induces toxicity and apoptosis in various organs and cells. The nervous system is one of the primary organs targeted by Cd. Cd toxicity is correlated with induction of severe oxidative stress. Myricetin, a natural product, has been found to exert protective effects against various disease conditions. The present study aimed to evaluate the potential protective effects of myricetin on Cd-induced neurotoxicity in PC12 cells. The cells were pretreated with myricetin in the absence and presence of Cd. The viability of cells was assessed using the MTT assay. Markers of oxidative stress were investigated by the lipid peroxidation (LPO), glutathione (GSH) content, and total antioxidant capacity (TAC). Moreover, activation of caspase 3 was examined by Western blot analysis. Myricetin could significantly enhance the viability of PC12 cells. Pretreatment of the cells with myricetin, prior to Cd exposure, showed a significant decrease in the levels of LPO whereas GSH and TAC levels were increased. In addition, the activity of caspase-3 was notably prevented by myricetin. These findings revealed that myricetin has protective effects on Cd-induced neurotoxicity in PC12 cells, which can be linked to its antioxidant potential, inhibition of LPO, and prevention of caspase-3 activation.

First baseline for bioenergetic biomarkers in Cnesterodon decemmaculatus as test organism in ecotoxicological studies

Cnesterodon decemmaculatus is a Neotropical teleost fish frequently used in ecotoxicological evaluations, whose biology has been thoroughly studied. Although there is considerable information on its response to different toxicants, no range of reference values has been so far established for the different biological parameters proposed as biomarkers of effect or exposure. Moreover, no study has yet examined the possible influence of the metabolic status of the exposed animals on their response to toxic stress. Therefore, the aim of this work was to provide a first baseline for a set of bioenergetic biomarkers in C. decemmaculatus adults exposed to a control medium under previously standardized conditions, and to assess their possible intrinsic seasonal variability. The responses of the biomarkers obtained from the controls were contrasted with those from the reference toxicant (Cadmio-Cd) and receiving waters (surface waters of the Reconquista River RR, Buenos Aires Province, Argentina). We conducted four 12-day assays (one in each season) of exposure to control media, (reconstituted moderate hard water, MHW) and two assays of exposure to Cd in MHW and surface river water (RR) in both summer and autumn. The variables recorded were: Food intake (In), fecal production (F), specific assimilation (A) and cumulative mortality, oxygen extraction efficiency (OEE), specific metabolic rate (SMR), ammonia excretion (N), ammonia quotient (AQ) and scope for growth (SFG). The seasonal variation shown by some physiological parameters, points to the need for establishing a baseline obtained from standardized media, preferably on a seasonal basis. Moreover, SFG and A appeared as the most sensitive biomarkers, emphasizing the importance to consider the metabolic status of the test organisms for the appropriate interpretation of results from ecotoxicological studies performed under controlled experimental conditions. The obtained results provide useful information on C. decemmaculatus as model species in ecotoxicological bioassays involving biomarkers of early effect.