Bone mineral health is sensitively related to environmental cadmium exposure- experimental and human data

Cadmium exposure negatively affects the microarchitecture of trabecular bone and decreases the density of a subset of sympathetic nerve fibers innervating the developing rat femur

Cadmium (Cd) is toxic to the skeletal system resulting in bone loss and pain. We aimed at determining the effect of chronic Cd exposure on bone density and microarchitecture along with changes in the density of a subset of sensory and sympathetic nerve fibers innervating the developing rat femur. Newborn male Wistar rats were injected daily for 49 days with CdCl₂ (1 mg/kg i.p.) or saline solution (control group). At the day of sacrifice, levels of Cd in the right femur, liver and kidney were determined by atomic absorption spectrophotometry. Additionally, microCT followed by immunohistochemical analyses were performed in the left femur. Results showed Cd accumulation in trabecular bone neared levels seen in liver and kidney. Cd concentration in cortical bone was significantly lower versus trabecular bone. MicroCT analysis revealed that Cd-exposed rats had a significant decrease in trabecular bone parameters at the distal femoral metaphysis; however, most of the cortical bone parameters were not significantly affected. Cd-exposed rats showed a significant loss of TH⁺ sympathetic nerve fibers, but not of CGRP⁺ sensory nerve fibers, at the level of bone marrow of the femoral diaphysis as compared to control rats. This study shows that Cd negatively affects bone density and microarchitecture of trabecular bone and decreases the density of sympathetic nerve fibers innervating rat femur. Future studies are warranted to determine the toxigenic mechanisms of Cd on sympathetic nerves and how sympathetic denervation influences bone loss in animals exposed to Cd.

Redox and essential metal status in the brain of Wistar rats acutely exposed to a cadmium and lead mixture

Most Pb and Cd neurotoxicity studies investigate exposure to either of the toxic metals alone, while data on co-exposure are scarce. The aim of our study was to fill that gap by investigating acute combined effects of Pb and Cd on redox and essential metal status in the brain of Wistar rats. Animals were randomised in four groups of six to eight rats, which received 15 or 30 mg/kg of Cd, 150 mg/kg of Pb, or 150 mg/kg of Pb + 15 mg/kg of Cd by gavage. The fifth, control, group received distilled water only. Co-treatment with Pb and Cd induced significant increase in malondialdehyde (MDA) and thiobarbituric acid-reactive substances (TBARS) compared to control and groups receiving either metal alone. This is of special importance, as MDA presence in the brain has been implicated in many neurodegenerative disorders. The groups did not significantly differ in Zn, Cu, Mn, and Fe brain levels. Our findings highlight the importance of metal mixture studies. Neurotoxicity assessments of single chemicals do not provide a real insight into exposure to mixtures in real life. Further research should look into interactions between these metals to reveal complex molecular mechanisms of their neurotoxicity.

An assessment of sensitivity biomarkers for urinary cadmium burden

BACKGROUND

Excess cadmium (Cd) intake poses a general risk to health and to the kidneys in particular. Among indices of renal dysfunction under Cd burden measures are the urinary N-acetyl-β-D-glucosidase (UNAG) and urinary β2-microglobulin (Uβ2-MG) enzymes. However, the end-pointed values and the Cd burden threshold remain controversial because the scopes fluctuate widely.

METHODS

To ascertain the clinical benchmark dose of urinary Cd (UCd) burden for renal dysfunction, 1595 residents near a Cd site were surveyed. Urine was sampled and assayed. A benchmark dose low (BMDL) was obtained by fitting UCd levels and index levels.

RESULTS

We found that over 50% of the subjects were suffering from Cd exposure as their UCd levels far exceeded the national standard threshold of 5.000 μg/g creatinine (cr). Further analysis indicated that Uβ2-MG was more sensitive than UNAG for renal dysfunction. The BMDL for UCd was estimated as 3.486 U/g cr (male, where U is unit of enzyme) and 2.998 U/g cr (female) for UNAG. The BMDL for Uβ2-MG, which is released into urine from glomerulus after Cd exposure, was found to be 2.506 μg/g cr (male, where μg is the unit of microglobulin) and 2.236 μg/g cr (female).

CONCLUSIONS

Uβ2-MG is recommended as the sensitivity index for renal dysfunction, with 2.2 μg/g cr as the threshold for clinical diagnosis. Our findings suggest that Uβ2-MG is the better biomarker for exposure to Cd.

Emerging Links between Cadmium Exposure and Insulin Resistance: Human, Animal, and Cell Study Data

Recent research has helped clarify the role of cadmium (Cd) in various pathological states. We have demonstrated Cd involvement in pancreatic cancer, as well as the bioaccumulation of Cd in the pancreas. Bioaccumulation and increased toxicity suggest that Cd may also be involved in other pancreas-mediated diseases, like diabetes. Cd falls into the category of "hyperglycemic" metals, i.e., metals that increase blood glucose levels, which could be due to increased gluconeogenesis, damage to β-cells leading to reduced insulin production, or insulin resistance at target tissue resulting in a lack of glucose uptake. This review addresses the current evidence for the role of Cd, leading to insulin resistance from human, animal, and in vitro studies. Available data have shown that Cd may affect normal insulin function through multiple pathways. There is evidence that Cd exposure results in the perturbation of the enzymes and modulatory proteins involved in insulin signal transduction at the target tissue and mutations of the insulin receptor. Cd, through well-described mechanisms of oxidative stress, inflammation, and mitochondrial damage, may also alter insulin production in β-cells. More work is necessary to elucidate the mechanisms associated with Cd-mediated insulin resistance.

The Effects of Cadmium Toxicity

Cadmium (Cd) is a toxic non-essential transition metal that poses a health risk for both humans and animals. It is naturally occurring in the environment as a pollutant that is derived from agricultural and industrial sources. Exposure to cadmium primarily occurs through the ingestion of contaminated food and water and, to a significant extent, through inhalation and cigarette smoking. Cadmium accumulates in plants and animals with a long half-life of about 25-30 years. Epidemiological data suggest that occupational and environmental cadmium exposure may be related to various types of cancer, including breast, lung, prostate, nasopharynx, pancreas, and kidney cancers. It has been also demonstrated that environmental cadmium may be a risk factor for osteoporosis. The liver and kidneys are extremely sensitive to cadmium's toxic effects. This may be due to the ability of these tissues to synthesize metallothioneins (MT), which are Cd-inducible proteins that protect the cell by tightly binding the toxic cadmium ions. The oxidative stress induced by this xenobiotic may be one of the mechanisms responsible for several liver and kidney diseases. Mitochondria damage is highly plausible given that these organelles play a crucial role in the formation of ROS (reactive oxygen species) and are known to be among the key intracellular targets for cadmium. When mitochondria become dysfunctional after exposure to Cd, they produce less energy (ATP) and more ROS. Recent studies show that cadmium induces various epigenetic changes in mammalian cells, both in vivo and in vitro, causing pathogenic risks and the development of various types of cancers. The epigenetics present themselves as chemical modifications of DNA and histones that alter the chromatin without changing the sequence of the DNA nucleotide. DNA methyltransferase, histone acetyltransferase, histone deacetylase and histone methyltransferase, and micro RNA are involved in the epigenetic changes. Recently, investigations of the capability of sunflower (Helianthus annuus L.), Indian mustard (Brassica juncea), and river red gum (Eucalyptus camaldulensis) to remove cadmium from polluted soil and water have been carried out. Moreover, nanoparticles of TiO2 and Al2O3 have been used to efficiently remove cadmium from wastewater and soil. Finally, microbial fermentation has been studied as a promising method for removing cadmium from food. This review provides an update on the effects of Cd exposure on human health, focusing on the cellular and molecular alterations involved.

Cadmium sulfide-induced toxicity in the cortex and cerebellum: In vitro and in vivo studies

Living organisms have an innate ability to regulate the synthesis of inorganic materials, such as bones and teeth in humans. Cadmium sulfide (CdS) can be utilized as a quantum dot that functions as a unique light-emitting semiconductor nanocrystal. The increased use in CdS has led to an increased inhalation and ingestion rate of CdS by humans which requires a broader appreciation for the acute and chronic toxicity of CdS. We investigated the toxic effects of CdS on cerebellar cell cultures and rat brain. We employed a 'green synthesis' biosynthesis process to obtain biocompatible material that can be used in living organisms, such as Viridibacillus arenosi K64. Nanocrystal formation was initiated by adding CdCl2 (1 mM) to the cell cultures. Our in vitro results established that increased concentrations of CdS (0.1 μg/mL) lead to decreased cell viability as assessed using 3-[4,5-dimethylthiazole-2-yl]-2,5-diphenyltetrazolium bromide (MTT), total antioxidant capacity (TAC), and total oxidant status (TOS). The in vivo studies showed that exposure to CdS (1 mg/kg) glial fibrillary acidic protein (GFAP) and 8-hydroxy-2' -deoxyguanosine (8-OHdG) were increased. Collectively, we describe a model system that addresses the process from the synthesis to the neurotoxicity assessment for CdS both in vitro and in vivo. These data will be beneficial in establishing a more comprehensive pathway for the understanding of quantum dot-induced neurotoxicity.

Identification of metabolite biomarkers in serum of rats exposed to chlorpyrifos and cadmium

Chlorpyrifos (CPF) and cadmium (Cd) are widespread environmental pollutants, which are often present in drinking water and foods. However, the combined effects of CPF and Cd were not entirely clear at present. There was also no biomarker available to diagnose the poisoning of the two chemicals at low dose for long-term exposures. In this study, we investigated the change of serum metabolites of rats with subchronic exposure to CPF, Cd, and CPF plus Cd using gas chromatography-mass spectrometer-based metabolomics approach. We performed a stepwise optimization algorithm based on receiver operating characteristic to identify serum metabolite biomarkers for toxic diagnosis of the chemicals at different doses after 90-day exposure. We found that aminomalonic acid was the biomarker for the toxicity of Cd alone administration, and serine and propanoic acid were unique biomarkers for the toxicities of CPF plus Cd administrations. Our results suggest that subchronic exposure to CPF and Cd alone, or in combination at their low doses, could cause disturbance of energy and amino acid metabolism. Overall, we have shown that analysis of serum metabolomics can make exceptional contributions to the understanding of the toxic effects following long-term low-dose exposure of the organophosphorus pesticide and heavy metal.

Simultaneous adsorption of Cd(II)andAs(III)by a novel biochar-supported nanoscale zero-valent iron in aqueous systems

Biochar-supported nanoscale zero-valent iron (nZVI-BC) is a promising material for Cd(II) and As(III) removal from aqueous systems. In this study, simplified nZVI-BC composites were successfully synthesized and characterized via scanning electron microscopy (SEM), X-ray diffraction spectroscopy (XRD), X-ray photoelectron spectrometry (XPS), and Fourier transform infrared spectroscopy (FTIR) to understand the underlying adsorption mechanism. SEM and FTIR confirmed that nZVI particles were distributed evenly on the biochar surface. XRD and XPS revealed that metal ions were separated from solutions via electrostatic adsorption, complexation, oxidation, precipitation/co-precipitation, and the formation of type B ternary surface complex. Batch experiments showed that nZVI-BC (1:1) had a high removal efficiency in a wide pH range of 5.0-8.0 for Cd(II) and 3.0-8.0 for As(III), the maximum Cd(II) and As(III) adsorption capacities were 33.81 and 148.5 mg/g within 2 and 1 h, respectively. Additionally, synergisticeffects considerably enhanced the adsorption capacity of nZVI-BC(1:1) in mixed adsorption systems, the adsorption capacities of Cd(II) and As(III) reached 179.9 and 158.5 mg/g, respectively. Hence, nZVI-BC(1:1) is an ideal candidate for Cd(II) and As(III) pollution treatment.

The effects of pretreatment with lithium metaborate dihydrate on lipid peroxidation and Ca, Fe, Mg, and K levels in serum of Wistar albino male rats exposed to Cd

Boron and boron compounds have beneficial biological effects. Lithium metaborate dihydrate (LMBDH) is used in many branches of industry. Despite its wide industrial use, there is limited information about its biological effects on antioxidant defense system and trace element homeostasis. Therefore, the aim of this study was to evaluate the in vivo protective effects of LMBDH against CdCl₂-induced oxidative stress and imbalance of some bioelements for the first time. In the study, totally 20 Wistar albino male rats were used. The rats were fed with pellet food and water ad libitum and divided into four groups including five rats in each. Group I was control group (standard pellet food + water + normal saline), Group II was CdCl₂ (4.58 mg/kg/body weight/intraperitoneally/single dose), Group III was LMBDH (15 mg/kg/body weight/day orally, for 5 days), Group IV was CdCl₂ (4.58 mg/kg/body weight/intraperitoneally/single dose in fifth day), and LMBDH (15 mg/kg/body weight/day orally for 5 days). The results showed that CdCl₂ treatment increased blood MDA level and decreased antioxidant enzyme activities and the level of blood GSH compared to control group. Pretreatment with LMBDH significantly decreased MDA levels and increased SOD activity (p < 0.05). In addition, Ca, Fe, and K levels decreased in LMBDH pretreatment group in different statistically levels. However, Mg levels showed an increase in LMBDH pretreatment group. As a result, LMBDH pretreatment decreased MDA status and supported antioxidant system by increasing SOD activity. In addition, it did not exhibit an ameliorative effect on measured bioelement homeostasis.

The influence of smoking habits on cadmium and lead blood levels in the Serbian adult people

According to the World Health Organization, in 2015, the Serbian population ranked among the highest ones in Europe in terms of smoking habit: 44.3% males and 36.2% females aged 18-64 smoked tobacco. In the last 7 years, 25% of total mortality in men and 9% in women from Serbia were associated with smoking. Tobacco smoking is one of the most important sources of exposure to many toxic substances in general population. Our study confirmed higher blood levels of two toxic metals, cadmium and lead, in the blood of smokers (3.5 and 1.5 times higher than in non-smokers, respectively). Furthermore, smoking habits, such as number of smoked cigarettes per day, smoking period and cigarette type, along with age, were shown to influence these metals' blood concentration. Higher blood levels of Cd and Pb were found in smokers consuming more than 10 cigarettes per day for more than 10 years. The present study also highlighted the importance of the controlled tobacco production, since it was shown that consumption of illicit tobacco could manifold the exposure to toxic metals that can subsequently increase the frequency of related diseases as well.

A Review on Coordination Properties of Thiol-Containing Chelating Agents Towards Mercury, Cadmium, and Lead

The present article reviews the clinical use of thiol-based metal chelators in intoxications and overexposure with mercury (Hg), cadmium (Cd), and lead (Pb). Currently, very few commercially available pharmaceuticals can successfully reduce or prevent the toxicity of these metals. The metal chelator meso-2,3-dimercaptosuccinic acid (DMSA) is considerably less toxic than the classical agent British anti-Lewisite (BAL, 2,3-dimercaptopropanol) and is the recommended agent in poisonings with Pb and organic Hg. Its toxicity is also lower than that of DMPS (dimercaptopropane sulfonate), although DMPS is the recommended agent in acute poisonings with Hg salts. It is suggested that intracellular Cd deposits and cerebral deposits of inorganic Hg, to some extent, can be mobilized by a combination of antidotes, but clinical experience with such combinations are lacking. Alpha-lipoic acid (α-LA) has been suggested for toxic metal detoxification but is not considered a drug of choice in clinical practice. The molecular mechanisms and chemical equilibria of complex formation of the chelators with the metal ions Hg2+, Cd2+, and Pb2+ are reviewed since insight into these reactions can provide a basis for further development of therapeutics.