Cadmium inhibits the electron transfer chain and induces reactive oxygen species

Ins and outs of cadmium-induced carcinogenesis: Mechanism and prevention

Cadmium (Cd) is a heavy metal and a highly toxic pollutant that is released into the environment as a byproduct of most modern factories and industries. Cd enters our body in significant quantities from contaminated water, cigarette smoke, or food product to many detrimental health hazards. Based on causal association all the Cd-related or derived compounds have been classified as carcinogens. In this study, we present an overview of the published literature to understand the molecular mechanisms for Cd-induced carcinogenesis and its prevention. In acute Cd poisoning production of reactive oxygen species is a key factor. However, chronic Cd exposure can transform cells to become more resistant to oxidative stress. Also, as an epigenetic mechanism Cd acts indirectly on DNA repair mechanisms via alteration of reactions upstream. Those transformed cells acquire resistance to apoptosis and deregulation of calcium homeostasis. Leading to uncontrolled carcinogenic cell proliferation and inherent DNA lesions. Flavonoids commonly found in plant foods have been shown to have a protective effect against Cd-induced carcinogenicity. A wide variety of tumorigenic mechanisms involved in chronic Cd exposure and the beneficial effects of flavonoids against Cd-induced carcinogenicity necessitate further investigations.

Zinc as a countermeasure for cadmium toxicity

Cadmium (Cd) is an important environmental pollutant and long-term Cd exposure is closely related to autoimmune diseases, cancer, cardiovascular diseases (CVD), and hepatic dysfunction. Zinc (Zn) is an essential metal that plays key roles in protein structure, catalysis, and regulation of their function. Numerous studies have shown that Zn can reduce Cd toxicity; however, the underlying mechanisms have not been extensively explored. Preclinical studies have revealed direct competition for sarcolemmal uptake between these two metals. Multiple sarcolemmal transporters participate in Cd uptake, including Zn transporters, calcium channels, and DMT1 (divalent metal transporter 1). Zn also induces several protective mechanisms, including MT (metallothionein) induction and favorable redox homeostasis. This review summarizes current knowledge related to the role of Zn and metal transporters in reducing Cd toxicity and discusses potential future directions of related research.

Mechanisms of Cd and Cu induced toxicity in human gastric epithelial cells: Oxidative stress, cell cycle arrest and apoptosis

Cadmium (Cd) and copper (Cu) are widely present in foods. However, their adverse effects on human gastric epithelium are not fully understood. Here, human gastric epithelial cells (SGC-7901) were employed to study the toxicity and associated mechanisms of Cd + Cu co-exposure. Their effects on cell viability, morphology, oxidative damage, cell cycle, apoptosis, and the mRNA levels of antioxidases and cell cycle regulatory genes were investigated. Co-exposure to Cd (5 μM)/Cu (10 μM) induced >40% cell viability loss, whereas little effect on cell viability at <10 μM Cd or 40 μM Cu. Compared to individual exposure, co-exposure induced greater oxidative damage by elevating ROS (3.5 folds), malondialdehyde (2.3 folds) and expression of SOD1 and HO-1 besides inhibiting CAT, GPX1 and Nrf2. A marked S cell-cycle arrest was observed in co-exposure, evidenced by more cells staying in the S phase (36%), up-regulation of cyclins-dependent kinase (CDK4) and CDKs inhibitor (p21) and down-regulation of CDK2, CDK6 and p27. Furthermore, higher apoptosis (22%) with floated and round cells occurred in co-exposure group. Our data implicate the cytotoxicity of Cd + Cu co-exposure was higher than individual exposure, and individual assessment would underestimate their potential health risk. Oxidative stress and cell cycle arrest possibly played a role in Cd + Cu induced toxicity and apoptosis in SGC-7901 cells. Our data suggest the importance to reduce Cd in foods to decrease its adverse impacts on human digestive system.

Modulation of mitochondrial site-specific hydrogen peroxide efflux by exogenous stressors

Oxygen (O₂) deprivation and metals are common environmental stressors and their exposure to aquatic organisms can induce oxidative stress by disrupting cellular reactive oxygen species (ROS) homeostasis. Mitochondria are a major source of ROS in the cell wherein a dozen sites located on enzymes of the electron transport system (ETS) and substrate oxidation produce superoxide anion radicals (O₂˙‾) or hydrogen peroxide (H₂O₂). Sites located on ETS enzymes can generate ROS by forward electron transfer (FET) and reverse electron transfer (RET) reactions; however, knowledge of how exogenous stressors modulate site-specific ROS production is limited. We investigated the effects of anoxia-reoxygenation and cadmium (Cd) on H₂O₂ emission in fish liver mitochondria oxidizing glutamate-malate, succinate or palmitoylcarnitine-malate. We find that anoxia-reoxygenation attenuates H₂O₂ emission while the effect of Cd depends on the substrate, with monotonic responses for glutamate-malate and palmitoylcarnitine-malate, and a biphasic response for succinate. Anoxia-reoxygenation exerts a substrate-dependent inhibition of mitochondrial respiration which is more severe with palmitoylcarnitine-malate compared with succinate or glutamate-malate. Additionally, specific mitochondrial ROS-emitting sites were sequestered using blockers of electron transfer and the effects of anoxia-reoxygenation and Cd on H₂O₂ emission were evaluated. Here, we find that site-specific H₂O₂ emission capacities depend on the substrate and the direction of electron flow. Moreover, anoxia-reoxygenation alters site-specific H₂O₂ emission rates during succinate and glutamate-malate oxidation whereas Cd imposes monotonic or biphasic H₂O₂ emission responses depending on the substrate and site. Contrary to our expectation, anoxia-reoxygenation blunts the effect of Cd. These results suggest that the effect of exogenous stressors on mitochondrial oxidant production is governed by their impact on energy conversion reactions and mitochondrial redox poise. Moreover, direct increased ROS production seemingly does not explain the increased adverse effects associated with combined exposure of aquatic organisms to Cd and low dissolved oxygen levels.

Metabolic status of the coral Mussismilia harttii in field conditions and the effects of copper exposure in vitro

It is widely known that metals can alter enzyme functioning, however, little is known about the mechanisms of metal toxicity in energy metabolism enzymes of corals. Thus, the present study had two objectives: firstly, we evaluated the activity of eight metabolic enzymes of the coral Mussismilia harttii to clarify metabolic functioning under field conditions. After that, we investigated the in vitro effect of copper (Cu) exposure in the activity of an enzyme representative of each metabolism stage. We evaluated enzymes involved in glycolysis (hexokinase, HK; phosphofructokinase, PFK; pyruvate kinase, PK and lactate dehydrogenase, LDH), Krebs cycle (citrate synthase, CS and isocitrate dehydrogenase, IDH), electron transport chain (electron transport system activity, ETS) and pentose phosphate pathway (glucose-6-phosphate dehydrogenase, G6PDH). The in vitro tests were performed through contamination of the reaction medium using Cu concentrations of 0, 1.4, 3.7 and 14.2 μg L^-1. The results showed that M. harttii has elevated activity of HK, PK and CS in field conditions compared to the activity of other energy metabolism enzymes evaluated. Moreover, lower activities of LDH and ETS in exposed samples were observed. In conclusion, in field conditions this species has elevated aerobic metabolism and glucose may be an important energetic fuel. Also, exposure to Cu in vitro caused inhibition of LDH and ETS by direct binding.

Interplay between dietary lipids and cadmium exposure in rainbow trout liver: Influence on fatty acid metabolism, metal accumulation and stress response

The present study aimed at investigating interactive effects between dietary lipids and both short- and long-term exposures to a low, environmentally realistic, cadmium (Cd) concentration. Juvenile rainbow trout were fed four isolipidic diets (31.7 g/kg) enriched in either linoleic acid (LA, 18:2n-6), alpha-linolenic acid (ALA, 18:3n-3), eicosapentaenoic acid (EPA, 20:5n-3) or docosahexaenoic acid (DHA, 22:6n-3). From the 4th week of this 10-week experiment, the lipid level of the diet was increased (120.0 g/kg) and half of the fish fed each diet were aqueously exposed to Cd (0.3 μg/L) while the other half were not exposed to Cd (control). Fish were sampled and their liver was harvested for fatty acid profile, hepatic Cd and calcium concentrations, total glutathione level and gene expression assessment, either (i) after 4 weeks of feeding and 24 h of Cd contamination (day 29) (short-term Cd exposure) or (ii) after 10 weeks of feeding and 6 weeks of Cd contamination (day 70) (long-term Cd exposure). We found that both dietary lipids and Cd exposure influenced fatty acid homeostasis and metabolism. The hepatic fatty acid profile mostly reflected that of the diet (e.g. n-3/n-6 ratio) with some differences, including selective retention of specific long chain polyunsaturated fatty acids (LC-PUFAs) like DHA and active biotransformation of dietary LA and ALA into LC-PUFAs. Cd effects on hepatic fatty acid profiles were influenced by the duration of the exposure and the nutritional status of the fish. The effects of diet and Cd exposure on the fatty acid profiles were only sparsely explained by variation of the expression pattern of genes involved in fatty acid metabolism. The biological responses to Cd were also influenced by dietary lipids. Fish fed the ALA-enriched diet seemed to be the least affected by the Cd exposure, as they showed a higher detoxifying ability against Cd with an early upregulation of protective metallothionein a (MTa) and apoptosis regulator BCL2-Like1 (BCLx) genes, an increased long-term phospholipid synthesis and turnover and fatty acid bioconversion efficiency, as well as a lower long-term accumulation of Cd in their liver. In contrast, fish fed the EPA-enriched diet seemed to be the most sensitive to a long-term Cd exposure, with an impaired growth performance and a decreased antioxidant capacity (lower glutathione level). Our results highlight that low, environmentally realistic aqueous concentrations of Cd can affect biological response in fish and that these effects are influenced by the dietary fatty acid composition.

Interaction of Agaric Acid with the Adenine Nucleotide Translocase Induces Mitochondrial Oxidative Stress

Mitochondrial permeability transition is characterized by the opening of a transmembranal pore that switches membrane permeability from specific to nonspecific. This structure allows the free traffic of ions, metabolites, and water across the mitochondrial inner membrane. The opening of the permeability transition pore is triggered by oxidative stress along with calcium overload. In this work, we explored if oxidative stress is a consequence, rather than an effector of the pore opening, by evaluating the interaction of agaric acid with the adenine nucleotide translocase, a structural component of the permeability transition pore. We found that agaric acid induces transition pore opening, increases the generation of oxygen-derived reactive species, augments the oxidation of unsaturated fatty acids in the membrane, and promotes the detachment of cytochrome c from the inner membrane. The effect of agaric acid was inhibited by the antioxidant tamoxifen in association with decreased binding of the thiol reagent eosin-3 maleimide to the adenine nucleotide translocase. We conclude that agaric acid promotes the opening of the pore, increasing ROS production that exerts oxidative modification of critical thiols in the adenine nucleotide translocase.

The Role of Aquaporin Overexpression in the Modulation of Transcription of Heavy Metal Transporters under Cadmium Treatment in Poplar

Populus alba ‘Villafranca’ clone is well-known for its tolerance to cadmium (Cd). To determine the mechanisms of Cd tolerance of this species, wild-type (wt) plants were compared with transgenic plants over-expressing an aquaporin (aqua1, GenBank GQ918138). Plants were maintained in hydroponic conditions with Hoagland’s solution and treated with 10 µM of Cd, renewed every 5 d. The transcription levels of heavy metal transporter genes (PaHMA2, PaNRAMP1.3, PaNRAMP2, PaNRAMP3.1, PaNRAMP3.2, PaABCC9, and PaABCC13) were analyzed at 1, 7, and 60 d of treatment. Cd application did not induce visible toxicity symptoms in wt and aqua1 plants even after 2 months of treatment confirming the high tolerance of this poplar species to Cd. Most of the analyzed genes showed in wt plants a quick response in transcription at 1 d of treatment and an adaptation at 60 d. On the contrary, a lower transcriptional response was observed in aqua1 plants in concomitance with a higher Cd concentration in medial leaves. Moreover, PaHMA2 showed at 1 d an opposite trend within organs since it was up-regulated in root and stem of wt plants and in leaves of aqua1 plants. In summary, aqua1 overexpression in poplar improved Cd translocation suggesting a lower Cd sensitivity of aqua1 plants. This different response might be due to a different transcription of PaNRAMP3 genes that were more transcribed in wt line because of the importance of this gene in Cd compartmentalization.

Bacterial phototoxicity of biomimetic CdTe-GSH quantum dots

AIM

Fluorescent semiconductor nanoparticles or quantum dots (QDs) have excellent properties as photosensitizers in photodynamic therapy. This is mainly a consequence of their nanometric size and the generation of light-activated redox species. In previous works, we have reported the low-cost biomimetic synthesis of glutathione (GSH) capped QDs (CdTe-GSH QDs) with high biocompatibility. However, no studies have been performed to determine their phototoxic effect. The aim of this work was to characterize the light-induced toxicity of green (QDs₅₀₀ ) and red (QDs₆₀₀ ) QDs in Escherichia coli, and to study the molecular mechanism involved.

METHODS AND RESULTS

Photodegradation and reduction power of biomimetic QDs was determined to analyse their potential for radical generation. Escherichia coli cells were exposed to photoactivated QDs and viability was evaluated at different times. High toxicity was determined in E. coli cells exposed to photoactivated QDs, particularly QDs₅₀₀ . The molecular mechanism involved in QDs phototoxicity was studied by determining Cd²⁺ -release and intracellular reactive oxygen species (ROS). Cells exposed to photoactivated QDs₅₀₀ presented high levels of ROS. Cells exposed to photoactivated QDs₅₀₀ presented high levels of ROS. Finally, to understand this phenomenon and the importance of oxidative and cadmium-stress in QDs-mediated phototoxicity, experiments were performed in E. coli mutants in ROS and Cd²⁺ response genes. As expected, E. coli mutants in ROS response genes were more sensitive than the wt strain to photoactivated QDs, with a higher effect in green-QDs₅₀₀ . No increase in phototoxicity was observed in cadmium-related mutants.

CONCLUSION

Obtained results indicate that light exposure increases the toxicity of biomimetic QDs on E. coli cells. The mechanism of bacterial phototoxicity of biomimetic CdTe-GSH QDs is mostly associated with ROS generation.

SIGNIFICANCE AND IMPACT OF THE STUDY

The results presented establish biomimetic CdTe-GSH QDs as a promising cost-effective alternative against microbial infections, particularly QDs₅₀₀ .

Cadmium-Induced Cytotoxicity: Effects on Mitochondrial Electron Transport Chain

Cadmium (Cd) is a well-known heavy metal and environmental toxicant and pollutant worldwide, being largely present in every kind of item such as plastic (toys), battery, paints, ceramics, contaminated water, air, soil, food, fertilizers, and cigarette smoke. Nowadays, it represents an important research area for the scientific community mainly for its effects on public health. Due to a half-life ranging between 15 and 30 years, Cd owns the ability to accumulate in organs and tissues, exerting deleterious effects. Thus, even at low doses, a Cd prolonged exposure may cause a multiorgan toxicity. Mitochondria are key intracellular targets for Cd-induced cytotoxicity, but the underlying mechanisms are not fully elucidated. The present review is aimed to clarify the effects of Cd on mitochondria and, particularly, on the mitochondrial electron transport chain.

Transcriptomic and Proteomic Analysis Reveals Mechanisms of Patulin-Induced Cell Toxicity in Human Embryonic Kidney Cells

Patulin (PAT) is a natural mycotoxin that commonly contaminates fruits and fruit-based products. Previous work indicated that PAT-induced apoptosis in which reactive oxygen species (ROS) are involved in human embryonic kidney (HEK293) cells. To uncover novel aspects of the possible mechanism of PAT nephrotoxicity, the transcriptome and proteome profiles were investigated using the digital gene expression (DGE) and isobaric tags for relative and absolute quantitation (iTRAQ) proteomic approaches. A total of 127 genes and 85 proteins were found to express differentially in response to 5 μM PAT for 10 h in HEK293 cells. The most dramatic changes of expression were noticed with genes or proteins related to apoptosis, oxidative phosphorylation ribosome and cell cycle. Especially, the activation of caspase 3, UQCR11, active transport form and endocytosis appeared to be crucial in PAT kidney cytotoxicity. PAT also seemed to be associated with cancer and neuropathic disease as pathways associated with carcinogenesis, Alzheimer’s disease and Parkinson’s disease were induced. Overall, this study served to uncover overall insights associated with signaling pathway that modulated the PAT toxicity mechanism.

Linking molecular targets of Cd in the bloodstream to organ-based adverse health effects

The chronic exposure of human populations to toxic metals remains a global public health concern. Although chronic Cd exposure is linked to kidney damage, osteoporosis and cancer, the underlying biomolecular mechanisms remain incompletely understood. Since other diseases could also be causally linked to chronic Cd exposure, a systems toxicology-based approach is needed to gain new insight into the underlying exposure-disease relationship. This approach requires one to integrate the cascade of dynamic bioinorganic chemistry events that unfold in the bloodstream after Cd enters with toxicological events that unfold in target organs over time. To this end, we have conducted a systematic literature search to identify all molecular targets of Cd in plasma and in red blood cells (RBCs). Based on this information it is impossible to describe the metabolism of Cd and the toxicological relevance of it binding to molecular targets in/on RBCs is elusive. Perhaps most importantly, the role that peptides, amino acids and inorganic ions, including HCO₃^-, Cl^- and HSeO₃^- play in terms of mediating the translocation of Cd to target organs and its detoxification is poorly understood. Causally linking human exposure to this metal with diseases requires a much better integration of the bioinorganic chemistry of Cd that unfolds in the bloodstream with target organs. This from a public health point of view important goal will require collaborations between scientists from different disciplines to untangle the complex mechanisms which causally link Cd exposure to disease.

Effects of the methanol root extract of Carpolobia lutea on sperm indices, acrosome reaction, and sperm DNA integrity in cadmium-induced reproductive toxicity in male Wistar rats

OBJECTIVE

Oxidative stress is a mechanism of cadmium-induced reproductive dysfunction. Carpolobia lutea is a free radical scavenger. Our study investigated the potential protective effects of Carpolobia lutea root methanol extract against cadmium-induced reproductive toxicity.

METHODS

We obtained the Carpolobia lutea root in Akure, and it was authenticated at the Forestry Research Institute of Nigeria (FRIN) herbarium, Ibadan, Nigeria, with FHI number 109784. We used Soxhlet extraction to obtain its methanol extract. We used thirty male Wistar rats (150-170g) in this study, (n=5 per group), and treated them as follows: Control (1 ml/kg normal saline), Cd (2 mg/kg), Cd+MCL (2 mg/kg+100 mg/kg), Cd+MCL (2 mg/kg+200 mg/kg), MCL (100 mg/kg), MCL (200 mg/kg). We administered Carpolobia lutea orally for 8 weeks. We administered a single dose of 2 mg/kg of cadmium intraperitoneally. We assessed the sperm profile using a computer-aided sperm analyzer. Under microscopy, we determined the sperm acrosome reaction and the DNA damage. We measured the seminal fructose level using spectrophotometry, and the data were analyzed using ANOVA at p<0.05.

RESULTS

Cd+MCL (2mg/kg+200 mg/kg) significantly increased sperm count (339.0±25.0 vs. 29.0±4.5 million/mL), motility (80.0±0.2 vs. 55.0±4.9%), viability (68.7±2.7 vs. 31.3±2.9%) and decreased abnormal sperm (28.3±1.7 vs. 43.3±2.5%), relative to the cadmium group. Cd+MCL (2mg/kg+200 mg/kg) significantly increased acrosome reaction (68.0±7.5 vs. 15.2±2.4%) and seminal fructose level (0.49±0.06 vs. 0.28±0.06 mmol/L) relative to the cadmium group. Cd+MCL (2mg/kg+200 mg/kg) significantly decreased sperm DNA damage (14.1±1.6 vs. 35.9±5.3%) in relation to the cadmium group.

CONCLUSIONS

Carpolobia lutea root extract improves the sperm variables of rats exposed to cadmium.

Hepatotoxicity of Cadmium Telluride Quantum Dots Induced by Mitochondrial Dysfunction

The aim of this study was to investigate the detailed mechanisms of hepatotoxicity induced by cadmium telluride quantum dots (CdTe-QDs) in BALB/c mice after intravenous injection. The study investigated oxidative stress, apoptosis, and effects on mitochondria as potential mechanistic events to elucidate the observed hepatotoxicity. Oxidative stress in the liver, induced by CdTe-QD exposure, was demonstrated by depletion of total glutathione, an increase in superoxide dismutase activity, and changes in the gene expression of several oxidative stress-related biomarkers. Furthermore, CdTe-QD treatment led to apoptosis in the liver via both intrinsic and extrinsic apoptotic pathways. Effects on mitochondria were evidenced by the enlargement and increase in the number of mitochondria in hepatocytes of treated mice. CdTe-QDs also caused changes in the levels and gene expression of electron transport chain enzymes, depletion of ATP, and an increase in the level of the peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), a regulator of mitochondrial biogenesis. The findings from this study suggest that CdTe-QDs-induced hepatotoxicity might have originated from mitochondrial effects which resulted in oxidative stress and apoptosis in the liver cells. This study provides insight into the biological effects of CdT-QDs at the tissue level and the detailed mechanisms of their toxicity in animals. The study also provides important data for bridging the gap between in vitro and in vivo testing and risk assessment of these NPs.

Cadmium-mediated lung injury is exacerbated by the persistence of classically activated macrophages

Heavy metals released into the environment have a significant effect on respiratory health. Lung macrophages are important in mounting an inflammatory response to injury, but they are also involved in repair of injury. Macrophages develop mixed phenotypes in complex pathological conditions and polarize to a predominant phenotype depending on the duration and stage of injury and/or repair. Little is known about the reprogramming required for lung macrophages to switch between these divergent functions; therefore, understanding the mechanism(s) by which macrophages promote metabolic reprogramming to regulate lung injury is essential. Here, we show that lung macrophages polarize to a pro-inflammatory, classically activated phenotype after cadmium-mediated lung injury. Because metabolic adaptation provides energy for the diverse macrophage functions, these classically activated macrophages show metabolic reprogramming to glycolysis. RNA-Seq revealed up-regulation of glycolytic enzymes and transcription factors regulating glycolytic flux in lung macrophages from cadmium-exposed mice. Moreover, cadmium exposure promoted increased macrophage glycolytic function with enhanced extracellular acidification rate, glycolytic metabolites, and lactate excretion. These observations suggest that cadmium mediates the persistence of classically activated lung macrophages to exacerbate lung injury.

The Role of Antioxidants in the Prevention of Cadmium-Induced Endothelial Dysfunction

Background:

Cadmium is a worldwide spread toxicant that accumulates in tissues and affects many organs, mainly through oxidative damage. Oxidative stress is often associated with cardiovascular diseases and, when it affects vessels, it induces endothelial dysfunction, which, in turn, could precipitate atherosclerosis and hypertension. Therefore, it is reasonable to suggest antioxidant supplementation as a therapy against cadmiuminduced endothelial dysfunction.

Objective:

This literature review aims to present the mechanisms involving oxidative stress in which cadmium induces endothelial dysfunction and the benefits of antioxidant supplementation as a therapeutic strategy against its harmful effects.

Methods:

On PubMed Central, articles that contemplated studies on cadmium intoxication and associated oxidative stress with endothelial dysfunction as well as articles that reported the use of antioxidant supplementation in an attempt to prevent or avoid endothelial dysfunction induced by cadmium exposure were selected.

Results:

Most of the studies that associated cadmium intoxication with endothelial dysfunction suggested oxidative stress as the major mechanism for this damage. Furthermore, experimental studies also revealed that the administration of substances with antioxidant properties, such as ascorbic acid and curcumin, has beneficial effects on the prevention of such dysfunction, reducing reactive oxygen species within the vessels, preventing a reduction in the amount of glutathione and the increase in blood pressure observed in animals exposed to cadmium.

Conclusion:

Antioxidant therapy demonstrated to be a potential treatment to reduce cardiovascular injuries provoked by cadmium, but more studies are needed to determine the best antioxidant substance and dose to treat or avoid this complication.

Iron and Cadmium Entry Into Renal Mitochondria: Physiological and Toxicological Implications

Regulation of body fluid homeostasis is a major renal function, occurring largely through epithelial solute transport in various nephron segments driven by Na⁺/K⁺-ATPase activity. Energy demands are greatest in the proximal tubule and thick ascending limb where mitochondrial ATP production occurs through oxidative phosphorylation. Mitochondria contain 20-80% of the cell's iron, copper, and manganese that are imported for their redox properties, primarily for electron transport. Redox reactions, however, also lead to reactive, toxic compounds, hence careful control of redox-active metal import into mitochondria is necessary. Current dogma claims the outer mitochondrial membrane (OMM) is freely permeable to metal ions, while the inner mitochondrial membrane (IMM) is selectively permeable. Yet we recently showed iron and manganese import at the OMM involves divalent metal transporter 1 (DMT1), an H⁺-coupled metal ion transporter. Thus, iron import is not only regulated by IMM mitoferrins, but also depends on the OMM to intermembrane space H⁺ gradient. We discuss how these mitochondrial transport processes contribute to renal injury in systemic (e.g., hemochromatosis) and local (e.g., hemoglobinuria) iron overload. Furthermore, the environmental toxicant cadmium selectively damages kidney mitochondria by "ionic mimicry" utilizing iron and calcium transporters, such as OMM DMT1 or IMM calcium uniporter, and by disrupting the electron transport chain. Consequently, unraveling mitochondrial metal ion transport may help develop new strategies to prevent kidney injury induced by metals.

Rosa persica hydroalcoholic extract improves cadmium-hepatotoxicity by modulating oxidative damage and tumor necrosis factor-alpha status

Rosa persica is a member of the Rosaceae family that has a wide range of pharmacological properties. In this study, the antioxidant and therapeutic potential of this plant was investigated on cadmium (Cd)-induced hepatotoxicity. Rosa persica extract (RPE) was prepared by a maceration method in hydroalcoholic solvent, and its antioxidant properties were determined. Then, 36 mice were divided to six groups and treated for 2 weeks as follows: control, Cd (3 mg/kg), RPE (50 mg/kg), and groups 4-6 received Cd (3 mg/kg) and 12.5, 25, and 50 mg/kg of RPE respectively. The total polyphenol, flavonoids contents, and total antioxidant capacity in RPE were measured 263.4 ± 7.2 mg rutin equivalent/g extract, 72.3 ± 2.3 mg quercetin equivalent/g extract, and 8.46 ± 0.27 μmol ferrous sulfate/g extract, respectively. The in vivo results showed that Cd elicited remarkable hepatic injury that was manifested by the significant increase in serum hepatic enzymes. In addition, Cd significantly increased the levels of lipid peroxidation (LPO) and tumor necrosis factor-alpha (TNF-α) and decreased total thiol molecules (TTM) and total antioxidant capacity (TAC) in hepatic tissue. However, RPE decreased serum hepatic enzyme levels and improved oxidative hepatic damage by lowering the LPO and TNF-α levels and raising TAC and TTM in in Cd-treated groups. Although the RPE increased the metallothionein (MT) protein content, there was no change in MT gene expression. The present study showed that the RPE due to having antioxidant properties might partially prevent hepatic oxidative damage by the improvement of oxidant/antioxidant balance in animals exposed to Cd.

Simultaneous determination of mercury, cadmium and lead in fish sauce using Diffusive Gradients in Thin-films technique

Fish sauce is a popular seasoning liquid originating from southeastern Asian cuisine, consisting of fermented fish, salt and additional ingredients. Fish can contain high amounts of metals, some of which are hazardous for human health. Therefore, authorities responsible for food safety and quality should monitor the levels of these contaminants in fish and fish deviated products. In this work, the passive sampling technique of Diffusive Gradients in Thin-films (DGT) containing Chelex-100 and Purolite S924 resin gels, is used for the determination of dissolved mercury (Hg), cadmium (Cd) and lead (Pb) in fish sauce. The DGT performance test showed linear accumulation of Hg, Cd and Pb on the binding gels versus deployment time. A wide range of pH and salt concentration did not affect the performance of the DGT. The effective diffusion coefficients of Hg, Cd and Pb in diffusive gels were determined by applying a series of deployments in fish sauce solution. Besides the direct sampling with the DGT technique, fish sauce samples were also digested using a microwave oven. Analyses of DGT and microwave oven digested samples were performed with Sector Field Inductively Coupled Plasma Mass Spectrometry (SF-ICP-MS). Both methods were then used for the analysis of fish sauces from local retail stores. Due to the preconcentration ability of DGT, lower detection limits of Hg, Cd and Pb could be achieved compared to the microwave digestion method. The DGT technique offers a more sensitive method for trace element analysis in complex food matrices.

Cadmium Chloride Induces Memory Deficits and Hippocampal Damage by Activating the JNK/p66Shc/NADPH Oxidase Axis

This study investigated whether the mechanism underlying the neurotoxic effects of cadmium chloride (CdCl₂) in rats involves p⁶⁶Shc. This study comprised an initial in vivo experiment followed by an in vitro experiment. For the in vivo experiment, male rats were orally administered saline (vehicle) or CdCl₂ (0.05 mg/kg) for 30 days. Thereafter, spatial and retention memory of rats were tested and their hippocampi were used for biochemical and molecular analyses. For the in vitro experiment, control or p⁶⁶Shc-deficient hippocampal cells were treated with CdCl₂ (25 µM) in the presence or absence of SP600125, a c-Jun N-terminal kinase (JNK) inhibitor. Cadmium chloride impaired the spatial learning and retention memory of rats; depleted levels of glutathione and manganese superoxide dismutase; increased reactive oxygen species (ROS), tumor necrosis factor α, and interleukin 6; and induced nuclear factor kappa B activation. Cadmium chloride also decreased the number of pyramidal cells in the CA1 region and induced severe damage to the mitochondria and endoplasmic reticulum of cells in the hippocampi of rats. Moreover, CdCl₂ increased the total unphosphorylated p66Shc, phosphorylated (Ser³⁶) p⁶⁶Shc, phosphorylated JNK, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, cytochrome c, and cleaved caspase-3. A dose-response increase in cell death, ROS, DNA damage, p⁶⁶Shc, and NADPH oxidase was also observed in cultured hippocampal cells treated with CdCl₂. Of note, all of these biochemical changes were attenuated by silencing p⁶⁶Shc or inhibiting JNK with SP600125. In conclusion, CdCl₂ induces hippocampal ROS generation and apoptosis by promoting the JNK-mediated activation of p⁶⁶Shc.

Genotoxic Effect of Lead and Cadmium on Workers at Wastewater Plant in Iraq

Heavy metal poisoning is a worldwide problem that is caused by different human industrial activities such as battery and painting manufacturing and occupational exposure of those working at petrol stations. Wastewater is known to contain higher amounts of heavy metals such as lead (Pd) and cadmium (Cd) and might be sources of exposure for workers at the wastewater treatment plant. However, to our best knowledge, no studies were done to evaluate the level of cadmium and lead in blood of workers at wastewater treatment plants and evaluate the subsequent effect of lead and cadmium on delta-aminolevulinic acid dehydratase (δ-ALAD), urinary delta-aminolevulinic acid (Uδ-ALA), and 8-hydroxy-2'-deoxyguanosine (8-OHdG) as markers of lead and cadmium toxicity. In this case-control study, 79 workers at the Al-Rustumiya wastewater plant in Baghdad, Iraq, and 40 control subjects were included. The levels of lead and cadmium were measured in blood of the study subjects using the atomic absorption spectroscopy (AAS) method. 8-OHdG was analysed using enzyme-linked immunosorbent assay (ELISA) technique. δ-ALAD and Uδ-ALA were estimated using spectrophotometry-based methods. Our work showed that workers had a significantly higher level of lead and cadmium when compared with the control group (P < 0.05), yet, still within the World Health Organization permissible limit. The level of both metals was positively associated with duration of work at the plant (P < 0.01). The activity of δ-ALAD was inversely associated with the lead level, while both Uδ-ALA and 8-OHdG were positively correlated with the lead level (P < 0.05). These three markers lacked any statistically significant association with the cadmium level (P > 0.05). To sum up, working at the wastewater treatment plant was associated with a higher blood level of lead and cadmium and their possible health hazard. Health and occupational safety authorities are required to set up tighter regulations and protocols to minimize these hazards and ensure a safe working environment.

Cadmium desynchronizes neurotransmitter release in the neuromuscular junction: Key role of ROS

Cd²⁺ is one of the most widespread environmental pollutants and its accumulation in central and peripheral nervous systems leads to neurotoxicity as well as aggravation of common neurodegenerative diseases. Mechanism of the Cd²⁺ toxicity is far from being resolved. Here, using microelectrode recordings of postsynaptic responses and fluorescent redox indicators we studied the effect of Cd²⁺ in the submicromolar range on timing of neurotransmitter release and oxidative status in two functionally different compartments of the same frog motor nerve terminal. Cd²⁺ (0.1-1 μM) acting as typical voltage-gated Ca²⁺channel (VGCC) antagonist decreased neurotransmitter release in both distal and proximal parts of the nerve terminal, but in contrast to the VGCC blockers Cd²⁺(0.1-0.5 μM) desynchronized the release selectively in the distal region. The latter action of Cd²⁺ was completely prevented by inhibitor of NADPH-oxidase and antioxidants, including mitochondrial specific, as well as redox-sensitive TRPV1 channel blocker. Cd²⁺ markedly increased levels of mitochondrial reactive oxygen species (ROS) in both the distal and proximal compartments of the nerve terminal, which was associated with lipid peroxidation mainly in the distal region. Zn²⁺, whose transport systems translocate Cd²⁺, markedly enhanced the effects of Cd²⁺ on both the mitochondrial ROS levels and timing of neurotransmitter release. Furthermore, in the presence of Zn²⁺ ions, Cd²⁺ also desynchronized the neurotransmitter release in the proximal region. Thus, in synapses Cd²⁺ at very low concentrations can increase mitochondrial ROS, lipid peroxidation and disturb the timing of neurotransmitter release via a ROS/TRPV-dependent mechanism. Desynchronization of neurotransmitter release and synaptic oxidative stress could be early events in Cd²⁺ neurotoxicity.

Bacillus siamensis Reduces Cadmium Accumulation and Improves Growth and Antioxidant Defense System in Two Wheat (Triticum aestivum L.) Varieties

Bioavailability of cadmium (Cd) metal in the soils due to the scarcity of good quality water and industrial waste could be the major limiting factor for the growth and yield of crops. Therefore, there is a need for a prompt solution to the Cd toxicity, to fulfill increasing food demand resulting from growing world population. Today, a variable range of plant growth promoting rhizobacteria (PGPR) is being used at a large scale in agriculture, to reduce the risk of abiotic stresses on plants and increase crop productivity. The objective of this study was to evaluate the efficacy of Bacillus siamensis in relieving the Cd induced damage in two wheat varieties (i.e., NARC-2009 and NARC-2011) grown in Cd spiked soil at different concentrations (0, 20, 30, 50 mg/kg). The plants under Cd stress accumulated more Cd in the roots and shoots, resulting in severe oxidative stress, evident by an increase in malondialdehyde (MDA) content. Moreover, a decrease in cell osmotic status, and alteration in antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) were also observed in wheat plants under Cd stress. As a result, the Cd exposed plants showed a reduction in growth, tissue biomass, photosynthetic pigments, membrane stability, total soluble sugars, and amino acids, in comparison to control plants. The extent of damage was observed to be higher with an increase in Cd concentration. However, the inoculation of wheat with B. siamensis improved plant growth, reduced oxidative stress, and enhanced the activities of antioxidant enzymes in both wheat varieties. B. siamensis amendment brought a considerable improvement in every parameter determined with respect to Cd stress. The response of both wheat varieties on exposure to B. siamensis was positively enhanced, whereas NARC-2009 accumulated less Cd compared to NARC-2011, which indicated a higher tolerance to Cd stress mediated by B. siamensis inoculation. Overall, the B. siamensis reduced the Cd toxicity in wheat plants through the augmentation of the antioxidant defense system and sugars production.

Morphine-element interactions - The influence of selected chemical elements on neural pathways associated with addiction

Addiction is a pressing social problem worldwide and opioid dependence can be considered the strongest and most difficult addiction to treat. Mesolimbic and mesocortical dopaminergic pathways play an important role in modulation of cognitive processes and decision making and, therefore, changes in dopamine metabolism are considered the central basis for the development of dependence. Disturbances caused by excesses or deficiency of certain elements have a significant impact on the functioning of the central nervous system (CNS) both in physiological conditions and in pathology and can affect the cerebral reward system and therefore, may modulate processes associated with the development of addiction. In this paper we review the mechanisms of interactions between morphine and zinc, manganese, chromium, cadmium, lead, fluoride, their impact on neural pathways associated with addiction, and on antinociception and morphine tolerance and dependence.

Cadmium mediated phytotoxic impacts in Brassica napus: Managing growth, physiological and oxidative disturbances through combined use of biochar and Enterobacter sp. MN17

Cadmium (Cd) is a toxic heavy metal with unknown biological role. Interactive effect of Enterobacter sp. MN17 and biochar was studied on the growth, physiology and antioxidant defense system of Brassica napus under Cd contaminated soil. A multi-metal tolerant endophytic bacterium, Enterobacter sp. MN17, was able to grow in tryptic soy agar (TSA) medium with up to 160, 200, 300, 700, 160 and 400 μg mL^-1 of Cd, Cu, Cr, Pb, Ni and Zn, respectively. Paper and pulp waste biochar was prepared at 450 °C and applied to pots (7 kg soil) at a rate of 1% (w/w), while Cd was spiked at 80 mg kg^-1 soil. Application of Enterobacter sp. MN17 and biochar, alone or combined, was found effective in the amelioration of Cd stress. Combined application of Enterobacter sp. MN17 and biochar caused the maximum appraisal in shoot and root length (52.5 and 76.5%), fresh and dry weights of shoot (77.1 and 70.7%) and root (81.2 and 57.9%), photosynthetic and transpiration rate (120.2 and 106.6%), stomatal and sub-stomatal conductance (81.3 and 75.5%), chlorophyll content and relative water content (RWC) (78.4 and 102.9%) than control. Their combined use showed a significant decrease in electrolyte leakage (EL), proline, malondialdehyde (MDA), catalase (CAT), glutathione peroxidase (GPX), glutathione S transferase (GST) and superoxide dismutase (SOD) by 39.3, 39.4, 39.5, 37.0, 39.0 42.1 and 30.8%, respectively, relative to control. Likewise, the combined application of bacterial strain MN17 and biochar reduced Cd in soil by 45.6%, thereby decreasing its uptake in root and shoot by 40.1 and 38.2%, respectively in Cd contaminated soil. The application of biochar supported the maximum colonization of strain MN17 in the rhizosphere soil, root and shoot tissues. These results reflected that inoculation with Enterobacter sp. MN17 could be an effective approach to accelerate biochar-mediated remediation of Cd contaminated soil for sustainable production of crops.

Mitigating effect of paxilline against injury produced by Cd2+ in rat pheochromocytoma PC12 and ascites hepatoma AS-30D cells

On two rat cell lines, pheochromocytoma PC12 and ascites hepatoma AS-30D, and on rat liver mitochondria we studied action of paxilline (lipophilic mycotoxin from fungus Penicillium paxilli which is blocker of large-conductance potassium channels) against harmful effects of Cd(II) - one of the most dangerous toxic metals and environmental pollutants. We investigated an influence of paxilline on cell viability and mitochondrial function in the presence and in the absence of Cd2+. As found, paxilline protected partially from the Cd2+-induced cytotoxicity, namely taken in concentration of 1 μM it decreased the Cd2+-induced cell necrosis in average by 10-14 or 13-23% for AS-30D and PC12 cells, respectively. Nevertheless, paxilline did not affect the Cd2+-induced apoptosis of AS-30D cells. The alleviating concentration of paxilline reduced an intracellular production of reactive oxygen species (ROS) in PC12 cells intoxicated by Cd2+ and enhanced the ROS production in control AS-30D cells; however, it weakly affected mitochondrial membrane potential of the cells in the absence and in the presence of Cd2+. The ameliorative concentration of paxilline decreased the maximal respiration rates of control cells of both types after short-term (3-5 h) treatment with it while the rates reached their control levels after long-term (24-48 h) incubation with the drug. Paxilline was not protective against the Cd2+-induced membrane permeability and respiration rate changes in isolated rat liver mitochondria. As result, the mitochondrial electron transport chain was concluded to contribute in the mitigating effect of paxilline against the Cd2+-produced cell injury.

Cadmium-Induced Oxidative Stress: Focus on the Central Nervous System

Cadmium (Cd), a category I human carcinogen, is a well-known widespread environmental pollutant. Chronic Cd exposure affects different organs and tissues, such as the central nervous system (CNS), and its deleterious effects can be linked to indirect reactive oxygen species (ROS) generation. Since Cd is predominantly present in +2 oxidation state, it can interplay with a plethora of channels and transporters in the cell membrane surface in order to enter the cells. Mitochondrial dysfunction, ROS production, glutathione depletion and lipid peroxidation are reviewed in order to better characterize the Cd-elicited molecular pathways. Furthermore, Cd effects on different CNS cell types have been highlighted to better elucidate its role in neurodegenerative disorders. Indeed, Cd can increase blood-brain barrier (BBB) permeability and promotes Cd entry that, in turn, stimulates pericytes in maintaining the BBB open. Once inside the CNS, Cd acts on glial cells (astrocytes, microglia, oligodendrocytes) triggering a pro-inflammatory cascade that accounts for the Cd deleterious effects and neurons inducing the destruction of synaptic branches.

Polydatin attenuates cadmium-induced oxidative stress via stimulating SOD activity and regulating mitochondrial function in Musca domestica larvae

Cadmium (Cd) is a widespread environment contaminant due to the development of electroplating and metallurgical industry. Cd can be enriched by organisms via food chain, causing the enlarged environmental problems and posing threats to the health of humans. Polydatin (PD), a natural stilbenoid compound derived from Polygonum cuspidatum, shows pronouncedly curative effect on oxidative damage. In this work, the protective effects of PD on oxidative damage induced by Cd in Musca domestica (housefly) larvae were evaluated. The larvae were exposed to Cd and/or PD, subsequently, the oxidative stress status, mitochondria activity, oxidative phosphorylation efficiency, and survival rate were assessed. Cd exposure generated significant increases of malondialdehyde (MDA), reactive oxygen species (ROS) and 8-hydroxy-2-deoxyguanosine (8-oxoG) in the housefly larvae, causing mitochondrial dysfunction and survival rate decline. Interestingly, pretreatment with PD exhibited obviously mitochondrial protective effects in the Cd-exposed larvae, as evidenced by reduced MDA, ROS and 8-oxoG levels, and increased activities of superoxide dismutase (SOD), mitochondrial electron transfer chain, and mitochondrial membrane potential, as well as respiratory control ratio. These results suggested that PD could attenuate Cd-induced damage via maintaining redox balance, stimulating SOD activity, and regulating mitochondria activity in housefly larvae. As a natural polyphenolic chemical, PD can act as a potential candidate compounds to relieve Cd injury.

Effects of silver(I) toxicity on microstructure, biochemical activities, and genic material of Lemna minor L. with special reference to application of bioindicator

In this research, several biochemical variations in plant of Lemna minor L. were investigated to reflect Ag⁺ toxicity. Lemna minor L. changed colorless AgNO₃ to colloidal brown at doses equal to and greater than 1 mg L^-1. Optical and fluorescence microscopy revealed the presence of bright spots in roots of tested plant related to Ag/Ag₂O-NPs. Photosynthetic pigment contents of Lemna minor L. declined upon exposure to Ag⁺ with an evidently higher decrease in chlorophyll a than in chlorophyll b. Similarly, Ag⁺ treatment caused an evident reduction in the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT). The reduction in antioxidase activity was significantly higher in POD than in SOD and CAT. Ag⁺ treatment resulted in a significant increment in the level of malondialdehyde (MDA) content as the judging criteria of cellular injury which showed sign of dose-related. The alterations occurred in RAPD profiles of treated samples following Ag⁺ toxicity containing loss of normal bands, appearance of new bands, and variation in band intensities compared with the normal plants. In addition, morphological character and biomass of Lemna minor L. subjected to increasing Ag⁺ concentrations were evaluated to reveal Ag⁺ toxicity. Our study demonstrated that Lemna minor L. have a high sensitivity to indicate fluctuation of water quality. It would be beneficial that modulating the genotype of Lemna minor L. to bear high proportion of contaminates.

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.

Advances in lung cancer biomarkers: The role of (metal-) metabolites and selenoproteins

Lung cancer (LC) is the second most common cause of death in men after prostate cancer, and the third most recurrent type of tumor in women after breast and colon cancers. Unfortunately, when LC symptoms begin to appear, the disease is already in an advanced stage and the survival rate only reaches 2%. Thus, there is an urgent need for early diagnosis of LC using specific biomarkers, as well as effective therapies and strategies against LC. On the other hand, the influence of metals on more than 50% of proteins is responsible for their catalytic properties or structure, and their presence in molecules is determined in many cases by the genome. Research has shown that redox metal dysregulation could be the basis for the onset and progression of LC disease. Moreover, metals can interact between them through antagonistic, synergistic and competitive mechanisms, and for this reason metals ratios and correlations in LC should be explored. One of the most studied antagonists against the toxic action of metals is selenium, which plays key roles in medicine, especially related to selenoproteins. The study of potential biomarkers able to diagnose the disease in early stage is conditioned by the development of new analytical methodologies. In this sense, omic methodologies like metallomics, proteomics and metabolomics can greatly assist in the discovery of biomarkers for LC early diagnosis.

Zinc protects against cadmium-induced toxicity in neonatal murine engineered cardiac tissues via metallothionein-dependent and independent mechanisms

Cadmium (Cd) is a nonessential heavy metal and a prevalent environmental toxin that has been shown to induce significant cardiomyocyte apoptosis in neonatal murine engineered cardiac tissues (ECTs). In contrast, zinc (Zn) is a potent metallothionein (MT) inducer, which plays an important role in protection against Cd toxicity. In this study, we investigated the protective effects of Zn against Cd toxicity in ECTs and explore the underlying mechanisms. ECTs were constructed from neonatal ventricular cells of wild-type (WT) mice and mice with global MT gene deletion (MT-KO). In WT-ECTs, Cd (5-20 μM) caused a dose-dependent toxicity that was detected within 8 h evidenced by suppressed beating, apoptosis, and LDH release; Zn (50-200 μM) dose-dependently induced MT expression in ECTs without causing ECT toxicity; co-treatment of ECT with Zn (50 µM) prevented Cd-induced toxicity. In MT-KO ECTs, Cd toxicity was enhanced; but unexpectedly, cotreatment with Zn provided partial protection against Cd toxicity. Furthermore, Cd, but not Zn, significantly activated Nrf2 and its downstream targets, including HO-1; inhibition of HO-1 by a specific HO-1 inhibitor, ZnPP (10 µM), significantly increased Cd-induced toxicity, but did not inhibit Zn protection against Cd injury, suggesting that Nrf2-mediated HO-1 activation was not required for Zn protective effect. Finally, the ability of Zn to reduce Cd uptake provided an additional MT-independent mechanism for reducing Cd toxicity. Thus, Zn exerts protective effects against Cd toxicity for murine ECTs that are partially MT-mediated. Further studies are required to translate these findings towards clinical trials.

Vacuolar H+ -ATPase is involved in preventing heavy metal-induced oxidative stress in Saccharomyces cerevisiae

In Saccharomyces cerevisiae, vacuolar H⁺ -ATPase (V-ATPase) involved in the regulation of intracellular pH homeostasis has been shown to be important for tolerances to cadmium, cobalt and nickel. However, the molecular mechanism underlying the protective role of V-ATPase against these metals remains unclear. In this study, we show that cadmium, cobalt and nickel disturbed intracellular pH balance by triggering cytosolic acidification and vacuolar alkalinization, likely via their membrane permeabilizing effects. Since V-ATPase plays a crucial role in pumping excessive cytosolic protons into the vacuole, the metal-sensitive phenotypes of the Δvma2 and Δvma3 mutants lacking V-ATPase activity were supposed to result from highly acidified cytosol. However, we found that the metal-sensitive phenotypes of these mutants were caused by increased production of reactive oxygen species, likely as a result of decreased expression and activities of manganese superoxide dismutase and catalase. In addition, the loss of V-ATPase function led to aberrant vacuolar morphology and defective endocytic trafficking. Furthermore, the sensitivities of the Δvma mutants to other chemical compounds (i.e. acetic acid, H₂ O₂ , menadione, tunicamycin and cycloheximide) were a consequence of increased endogenous oxidative stress. These findings, therefore, suggest the important role of V-ATPase in preventing endogenous oxidative stress induced by metals and other chemical compounds.

Cell organelles as targets of mammalian cadmium toxicity

Ever increasing environmental presence of cadmium as a consequence of industrial activities is considered a health hazard and is closely linked to deteriorating global health status. General animal and human cadmium exposure ranges from ingestion of foodstuffs sourced from heavily polluted hotspots and cigarette smoke to widespread contamination of air and water, including cadmium-containing microplastics found in household water. Cadmium is promiscuous in its effects and exerts numerous cellular perturbations based on direct interactions with macromolecules and its capacity to mimic or displace essential physiological ions, such as iron and zinc. Cell organelles use lipid membranes to form complex tightly-regulated, compartmentalized networks with specialized functions, which are fundamental to life. Interorganellar communication is crucial for orchestrating correct cell behavior, such as adaptive stress responses, and can be mediated by the release of signaling molecules, exchange of organelle contents, mechanical force generated through organelle shape changes or direct membrane contact sites. In this review, cadmium effects on organellar structure and function will be critically discussed with particular consideration to disruption of organelle physiology in vertebrates.

The Role of Natural Antioxidants Against Reactive Oxygen Species Produced by Cadmium Toxicity: A Review

Cadmium (Cd) is a significant ecotoxic heavy metal that adversely affects all biological processes of humans, animals and plants. Exposure to acute and chronic Cd damages many organs in humans and animals (e.g. lung, liver, brain, kidney, and testes). In humans, the Cd concentration at birth is zero, but because the biological half-life is long (about 30 years in humans), the concentration increases with age. The industrial developments of the last century have significantly increased the use of this metal. Especially in developing countries, this consumption is higher. Oxidative stress is the imbalance between antioxidants and oxidants. Cd increases reactive oxygen species (ROS) production and causes oxidative stress. Excess cellular levels of ROS cause damage to proteins, nucleic acids, lipids, membranes and organelles. This damage has been associated with various diseases. These include cancer, hypertension, ischemia/perfusion, cardiovascular diseases, chronic obstructive pulmonary disease, diabetes, insulin resistance, acute respiratory distress syndrome, idiopathic pulmonary fibrosis, asthma, skin diseases, chronic kidney disease, eye diseases, neurodegenerative diseases (amyotrophic lateral sclerosis, Parkinson's disease, Alzheimer's disease, and Huntington disease). Natural antioxidants are popular drugs that are used by the majority of people and have few side effects. Natural antioxidants play an important role in reducing free radicals caused by Cd toxicity. Our goal in this review is to establish the relationship between Cd and oxidative stress and to discuss the role of natural antioxidants in reducing Cd toxicity.

Sensitivity to cadmium of the endangered freshwater pearl mussel Margaritifera margaritifera from the Dronne River (France): experimental exposure

Margaritifera margaritifera is a critically endangered species in Europe. Among the causes explaining its decline, metal pollution had never been deeply studied. Thus, an ecotoxicological investigation was developed on this species which comes from the Dronne River (South-West of France). Cadmium (Cd) exposure of mussels at 2 and 5 μg/L for 7 days was conducted to test their vulnerability to this metal, and also the potential endocrine disruption power of Cd. Morphometric analyses, gonad histological observations, metal bioaccumulation, metallothionein (MTs) production, measures of malondialdehyde (MDA), and finally quantitative relative expression analysis of genes involved in various metabolic functions were performed.The main results showed Cd accumulation increasing in a dose-dependent manner, especially in the gills. The same trend was observed for gene expression relative to oxidative stress. Histological analysis of the gonads highlighted a predominance of hermaphrodite individuals, but after 7 days of exposure to Cd, the percentage of female was largely increased compared with controls, from 17 to 33%. These results demonstrate the endocrine disruption effect of Cd on freshwater pearl mussels.The pearl mussel Margaritifera margaritifera is sensitive to cadmium since the metallothioneins are poorly induced, gene expression reveals oxidative stress, and gonads tend to be feminized.

Cadmium-Induced Testicular Toxicity in Mice: Subacute and Subchronic Route-Dependent Effects

This study aimed to compare Cd exposure by intraperitoneal (i.p.) and oral routes, evaluating the testicular subacute and subchronic effects. Adult male mice were separated into three groups subdivided according to the experimental period (7 and 42 days after Cd exposure: subacute and subchronic effects, respectively): one group received water and two groups received CdCl₂ (1.2 mg/kg i.p. and 24 mg/kg oral). The testicular concentration of essential minerals and Cd, activity of antioxidant enzymes and markers of oxidative stress, histology, and testicular histomorphometry were evaluated. The subacute effect of oral Cd showed reduced Fe concentration, while Ca and Cu increased in this route. The subchronic effect promoted decreasing in Mg in i.p. and oral routes, whereas Zn decreased only in the oral, and the Fe concentration did not change. SOD activity decreased in the oral subacute evaluation and in both pathways, i.p. and oral routes, in the subchronic evaluation, while GST activity increased, and MDA concentration decreased. Labeling of apoptotic cells was increased in the subacute and subchronic evaluation. Seminiferous epithelium degeneration, death of germ cells, and Leydig cell damages occurred in i.p. and oral routes. However, these damages were more intense in the oral route, mainly evaluating the subchronic effects. The results confirm that the severity of Cd-induced testicular injury depends on the pathway, as well as the duration of exposure.

Oleic acid protects against cadmium induced cardiac and hepatic tissue injury in male Wistar rats: A mechanistic study

AIMS

The aim of the present study was to evaluate the possible antioxidant role of oleic acid (OA) against Cd-induced injuries in the heart and liver tissues of male Wistar rats.

MAIN METHODS

Rats were treated with either vehicle (control), or OA (10 mg/kg b.w., fed orally), or Cd (0.44 mg/kg b.w., s.c.), or both (OA + Cd) for 15 days. Following completion of the treatment period, biomarkers of organ damage and oxidative stress including ROS, activities of antioxidant enzymes and their level, activities of Krebs cycle enzymes and respiratory chain enzymes were measured. Levels of interleukins (IL-1β, IL-6, IL-10), tumor necrosis factor (TNF-α) and nuclear factor kappa B (NFκB) were estimated to evaluate the state of inflammation. In addition, changes in mitochondrial membrane potential and status of cytochrome c (Cyt c) were also studied.

KEY FINDINGS

Pre-treatment of rats with OA significantly protected against Cd-induced detrimental changes possibly by decreasing endogenous ROS through regulation of antioxidant defense system, inflammatory responses and activities of metabolic enzymes. Moreover, OA was also found to restore mitochondrial membrane potential possibly by regulating Cyt c leakage thereby increasing mitochondrial viability.

SIGNIFICANCE

Our results for the first time demonstrated systematically that OA provided protection against Cd-induced oxidative stress mediated injuries in rat heart and liver tissues through its antioxidant mechanism. The results raise the possibility of using OA singly or in combination with other antioxidants or diet in the treatment of situations arising due to oxidative stress and may have future therapeutic relevance.

Characterization of heavy metal toxicity in some plants and microorganisms-A preliminary approach for environmental bioremediation

In situ bioremediation processes are important for control of pollution and clean-up of contaminated sites. The study and implementation of such processes can be designed through investigations on natural mechanisms of absorption, biotransformation, bioaccumulation and toxicity of pollutants in plants and microorganisms. Here, the phytotoxic effects of Cr(VI) and Cd(II) on seed germination and plant growth of Lepidium sativum have been examined at various concentrations (30-300 mg/L) in single ion solutions. The studies also addressed the ecotoxicity of metal ions on Azotobacter chroococcum and Pichia sp. isolated from soil. Microbial growth was estimated by weighing the dry biomass and determining the enzymatic activities of dehydrogenase and catalase. The results showed that Cr(VI) and Cd(II) can inhibit L. sativum seed germination and root development, depending on the metal ion and its concentration. The phytotoxic effect of heavy metals was also confirmed by the reduced amounts of dried biomass. Toxicity assays demonstrated the adverse effect of Cr(VI) and Cd(II) on growth of Azotobacter sp. and Pichia sp., manifested by a biomass decrease of more than 50 % at heavy metal concentrations of 150-300 mg/L. The results confirmed close links between phytotoxicity of metals and their bioavailability for phytoextraction. Studies on the bioremediation potential of soils contaminated with Cr(VI) and Cd(II) using microbial strains focusing on Azotobacter sp. and Pichia sp. showed that the microbes can only tolerate heavy metal stress at low concentrations. These investigations on plants and microorganisms revealed their ability to withstand metal toxicity and develop tolerance to heavy metals.

Effects of Exogenous Organic Acids on Cd Tolerance Mechanism of Salix variegata Franch. Under Cd Stress

Chelate induction of organic acids has been recognized to enhance metal uptake and translocation in plants, but the underlying mechanism remains unclear. In this study, seedlings of Salix variegata were hydroponically exposed to the combinations of Cd (0 and 50 μM) and three exogenous organic acids (100 μM of citric, tartaric, or malic acid). Plant biomass, antioxidant enzymes, non-protein thiol compounds (NPT) content, and the expression of candidate genes associated with Cd accumulation and tolerance were determined. Results showed that Cd significantly inhibited plant biomass but stimulated the activity of antioxidant enzymes in the roots and leaves, while the lipid peroxidation increased as well. Respective addition of three organic acids greatly enhanced plant resistance to oxidative stress and reduced the lipid peroxidation induced by Cd, with the effect of malic acid showing greatest. The addition of organic acids also significantly increased the content of glutathione in the root, further improving the antioxidant capacity and potential of phytochelatin biosynthesis. Moreover, Cd induced the expression level of candidate genes in roots of S. variegata. The addition of three organic acids not only promoted the expression of candidate genes but also drastically increased Cd accumulation in S. variegata. In summary, application of citric, tartaric, or malic acid alleviated Cd-imposed toxicity through the boost of enzymatic and non-enzymatic antioxidants and candidate gene expression, while their effects on Cd tolerance and accumulation of S. variegata differed.

Photodegradation of porphyrin-bound hIAPP(1–37) fibrils

Amyloid deposits in pancreatic islets of type 2 diabetes mellitus (T2DM) are mainly comprised of human islet amyloid polypeptide (hIAPP), the degradation of hIAPP fibrils by photoactive porphyrin could be a preventive strategy against T2DM.

Effects of quercetin on cadmium-induced toxicity in rat urine using metabonomics techniques

This study aimed to analyse the protective effects of quercetin on the toxicity of cadmium (Cd) using metabonomics techniques. Sixty male Sprague-Dawley rats were randomly divided into six groups (n = 10): control group (C), low-dose quercetin-treated group (Q1; 10 mg/kg bw/day), high-dose quercetin-treated group (Q2; 50 mg/kg bw/day), Cd-treated group (D; 4.89 mg/kg bw/day), low-dose quercetin plus Cd-treated group (DQ1) and high-dose quercetin plus Cd-treated group (DQ2). The rats continuously received quercetin and Cd via gavage and drinking water for 12 weeks, respectively. The rat urine samples were collected for metabonomics analysis. Finally, 10 metabolites were identified via the metabonomics profiles of the rat urine samples. Compared with the control group, the intensities of taurine, phosphocreatine, l-carnitine and uric acid were significantly decreased (p < 0.01) and those of LysoPC (18: 2 (9Z, 12Z)), guanidinosuccinic acid, dopamine, 2,5,7,8-tetramethyl-2(2'-carboxyethyl)-6-hydroxychroman and allantoic acid were significantly increased (p < 0.01) in the Cd-treated group. However, the intensities of the aforementioned metabolites had restorative changes in the high-dose quercetin plus Cd-treated groups unlike those in Cd-treated group (p < 0.01 or p < 0.05). Results indicated that quercetin exerts protective effects on Cd-induced toxicity by regulating energy and lipid metabolism, enhancing the antioxidant defence system and protecting liver and kidney function and so on.

Effects of sublethal Cd, Zn, and mixture exposures on antioxidant defense and oxidative stress parameters in early life stages of the purple sea urchin Strongylocentrotus purpuratus

Oxidative stress parameters were evaluated during the first 72 h of embryonic development of purple sea urchin Strongylocentrotus purpuratus continuously exposed to control conditions, to cadmium alone (Cd, 30 μg/L), to zinc alone (Zn, 9 μg/L) or to a Cd (28 μg/L) plus Zn (9 μg/L) mixture. These sublethal concentrations represent ∼ 10% of the acute EC50. Bioaccumulation, antioxidant capacity against peroxyl radicals (ACAP), total glutathione (GSH) level, glutathione-S-transferase (GST), glucose-6-phosphate dehydrogenase (G6PDH) and superoxide dismutase (SOD) activity, and lipid peroxidation (LPO) were analyzed at 24 h (blastula), 48 h (gastrula), and 72 h (pluteus) stages of development. Zinc (an essential metal) was well-regulated, whereas Cd (non-essential) bioaccumulated and whole-body [Cd] increased from blastula to pluteus stage in sea urchin larvae. In controls, ACAP progressively declined from 24 h to 72 h, while LPO reciprocally increased, but other parameters did not change. Cd alone was more potent than Zn alone as a pro-oxidant, with the major effects being decreases in SOD activity and parallel increases in LPO throughout development; GST activity also increased at 24 h. Zn alone caused only biphasic disturbances of ACAP. In all cases, the simultaneous presence of the other metal prevented the effects, and there was no instance where the oxidative stress response in the presence of the Cd/Zn mixture was greater than in the presence of either Cd or Zn alone. Therefore the sublethal effects of joint exposures were always less than additive or even protective, in agreement with classical toxicity data. Furthermore, our results indicate that SOD and Zn can play important roles in protecting sea urchin embryos against Cd-induced lipid peroxidation.

Effects of Cadmium on ZO-1 Tight Junction Integrity of the Blood Brain Barrier

Cadmium (Cd) is a highly toxic environmental pollutant released from the smelting and refining of metals and cigarette smoking. Oral exposure to cadmium may result in adverse effects on a number of tissues, including the central nervous system (CNS). In fact, its toxicity has been related to neurological disorders, as well as neurodegenerative diseases such as Alzheimer's and Parkinson's diseases. Under normal conditions, Cd barely reaches the brain in adults because of the presence of the blood-brain barrier (BBB); however, it has been demonstrated that Cd-dependent BBB alteration contributes to pathogenesis of neurodegeneration. However, the mechanism underlying Cd-dependent BBB alteration remain obscure. Here, we investigated the signaling pathway of Cd-induced tight junction (TJ), F-actin, and vimentin protein disassembly in a rat brain endothelial cell line (RBE4). RBE4 cells treated with 10 μM cadmium chloride (CdCl2) showed a dose- and time-dependent significant increase in reactive oxygen species (ROS) production. This phenomenon was coincident with the alteration of the TJ zonula occludens-1 (ZO-1), F-actin, and vimentin proteins. The Cd-dependent ROS increase elicited the upregulation of GRP78 expression levels, a chaperone involved in endoplasmic reticulum (ER) stress that induces caspase-3 activation. Further signal profiling by the pannexin-1 (PANX1) specific inhibitor 10Panx revealed a PANX1-independent increase in ATP spillage in Cd-treated endothelial cells. Our results point out that a ROS-dependent ER stress-mediated signaling pathway involving caspase-3 activation and ATP release is behind the BBB morphological alterations induced by Cd.

Allam A, A. El-Serehy H, N. Maodaa S, M. Mahmoud A. Use of Spilopelia senegalensis as a Biomonitor of Heavy Metal Contamination from Mining Activities in Riyadh (Saudi Arabia)

Simple Summary

Bioindicators and biomonitors are living organisms utilized to appraise the health of the environment or natural ecosystem. Mining, which refers to extraction of valuable materials from the earth, represents a source of heavy metals that can impact the environment, biodiversity, and human health. We investigated the value of the laughing dove (Spilopelia senegalensis) as a biomonitor of environmental contamination with heavy metals from mining practices. Our results revealed the accumulation of heavy metals in the liver, kidneys, and lungs of the laughing dove collected from the mining site. The doves exhibited tissue dysfunction and injury, and decreased antioxidants. These results show the value of the laughing dove as a biomonitor of environmental pollution with heavy metals.

Abstract

Environmental pollution with heavy metals (HMs) is of serious ecological and public health concern worldwide. Mining is one of the main sources of HMs and can impact the environment, species diversity, and human health. This study assessed the value of Spilopelia senegalensis as a biomonitor of environmental contamination with metal(loid)s caused by mining activities. S. senegalensis was collected from a gold mining site and a reference site, and metal(loid)s and biochemical parameters were determined. Lead, cadmium, mercury, vanadium, arsenic, copper, zinc, and iron were significantly increased in the liver, kidney, and lung of S. senegalensis from the mining site. Serum transaminases, alkaline phosphatase, creatinine, and urea were significantly elevated in S. senegalensis from the mining site. Lipid peroxidation and nitric oxide were increased, whereas glutathione and antioxidant enzymes were diminished in the liver and kidney of S. senegalensis from the mining site. In addition, multiple histological alterations were observed in the liver, kidney, and lung of S. senegalensis. In conclusion, mining activities provoke the accumulation of metal(loid)s, oxidative stress, and tissue injury in S. senegalensis. Therefore, S. senegalensis is a valuable biomonitor of environmental pollution caused by mining activities and could be utilized in epidemiological avian studies of human health.

Cannabidiol Protects Dopaminergic Neuronal Cells from Cadmium

The protective effect of cannabidiol (CBD), the non-psychoactive component of Cannabis sativa, against neuronal toxicity induced by cadmium chloride (CdCl₂ 10 μM) was investigated in a retinoic acid (RA)-differentiated SH-SY5Y neuroblastoma cell line. CBD (1 μM) was applied 24 h before and removed during cadmium (Cd) treatment. In differentiated neuronal cells, CBD significantly reduced the Cd-dependent decrease of cell viability, and the rapid reactive oxygen species (ROS) increase. CBD significantly prevented the endoplasmic reticulum (ER) stress (GRP78 increase) and the subcellular distribution of the cytochrome C, as well as the overexpression of the pro-apoptotic protein BAX. Immunocytochemical analysis as well as quantitative protein evaluation by western blotting revealed that CBD partially counteracted the depletion of the growth associated protein 43 (GAP43) and of the neuronal specific class III β-tubulin (β3 tubulin) induced by Cd treatment. These data showed that Cd-induced neuronal injury was ameliorated by CBD treatment and it was concluded that CBD may represent a potential option to protect neuronal cells from the detrimental effects of Cd toxicity.