Cadmium stress: an oxidative challenge. Biometals. 2010;23:927-940. [PMID: 20361350 DOI: 10.1007/s10534-010-9329-x]

Environmental biomonitoring by snails

Background: Bio-indicator systems are vital in terms of monitoring of pollutants around the world. The impact of environmental change can be monitored by employing the responsive behaviour of snails. Heavy metal and organic pollutants affects snail reproduction, mortality, and normal metabolic activities. Various changes like a discontinuity in food intake, growth rate, twitching, and quenching of tentacles, are the biomarkers of the snails for biomonitoring. Different snails can bio-monitor eco-toxicological urban pollution, oil pollutant, terrestrial pollution, pesticide pollutants, mercury contamination, ammonia, chlorinated paraffin in soil, ethanol in water, ocean acidification pollutions. These animals can also make bio-sense about diverse environment spheres, which include the biosphere, lithosphere, anthroposphere, cryosphere, and hydrosphere.Methods: We examined the scientific literature and related articles listed in Pub-med, Google Scholar reporting on biomonitoring potential and biomarkers expression of various snail species and consequently explore the value of snails in the respective field by discussing various outcomes of a number of studies on the pollution biomonitoring and biosensing capabilities.Results: Several terrestrial, freshwater and sea snail species are characterized by the high sense of biomonitoring and biosensing potential. Various biomarkers such as expression of heat shock proteins and metallothioneins in the body are found to be the essential in-vivo biomarkers for pollution biomonitoring.Conclusion: It is observed that snails offer an environment friendly approach for the environmental bio monitoring by expressing their numerous physiological, biochemical, genetical and histological biomarkers in their body. Thus, it proved to be a critical bio monitoring tool and early warning indicators.

Ascorbic acid mitigates cadmium-induced stress, and contributes to ionome stabilization in fission yeast

Cadmium is a highly toxic environmental pollutant which through enhancement of reactive oxygen species (ROS) production triggers oxidative stress to the cell. Cell growth, a fundamental feature of all living organisms is closely connected to the cell shape and homeostasis. As these processes largely depend on cell fitness status and environmental conditions we have analyzed, the impact of different cadmium concentrations and the effect of ascorbic acid (ascorbate, AsA) supplementation on cell growth parameters, cell morphology, and ionome balance maintenance in Schizosaccharomyces pombe. We show that cadmium causes membrane lipid peroxidation resulting in cell shape alterations leading to growth impairment and through mineral elements disequilibrium affects ionome homeostasis in a dose- and time-dependent manner. AsA recognized as one of the most prominent antioxidants, when overdosed, displays considerable pro-oxidant activity, though precise dosing of its supplementation is desired. We present here that AsA under efficacious concentration largely improves cell condition affected by cadmium. Although, we clearly demonstrate the beneficial feature of AsA, further studies are required to fully understand its protective nature on cell homeostasis maintenance under conditions of the broken environment.

Differential regulation of endoplasmic reticulum stress-induced autophagy and apoptosis in two strains of gibel carp (Carassius gibelio) exposed to acute waterborne cadmium

Previous studies illustrated that gibel carp F strain displays better lipid mobilization and antioxidant ability and compared to the A strain. We therefore hypothesized that the F strain would exhibit superior defense to cadmium exposure. Comparative studies were conducted between A and F strains using plasma stress biomarkers, histological observations, and analysis of hepatic molecular events to examine exposure to waterborne Cd (11.9 mg L^-1) for 48 h and 96 h. Waterborne Cd exposure stimulated stress response and hepatic metallothionein mRNA induction in both gibel carp strains confirming exposure. Antioxidant responses were stimulated to counteract Cd toxicity, suggested by the upregulation of mRNA levels of genes associated with nuclear factor erythroid 2-related factor 2 (nrf2) signaling. Cd exposure induced endoplasmic reticulum (ER) stress, meanwhile, branches of genes in unfolded protein response (UPR) were activated. Slight time-dependent effects were implied by greater ER stress, UPR, and apoptosis signals with the duration of Cd exposure. Genotype-specific effects were identified, revealing that the F strain showed greater stress at 96 h exposure and higher antioxidant response compared to the A strain, as indicated by the mRNA levels of genes in nrf2 signaling. ER stress and UPR were also stronger in the F strain after Cd exposure. In contrast, the A strain showed higher autophagy and apoptosis response compared to the F strain. Collectively, combined autophagy and apoptosis were triggered under ER stress, which might serve as defense strategies in both gibel carp strains. The F strain showed greater antioxidant detoxification response and UPR to mitigate Cd toxicity, whereas excessive ER stress contributed to higher autophagy and apoptosis in the A strain. The present study uncovered the differential regulation and defense strategies in fish strains exposed to metal exposure.

Lipid peroxidation of kidney of the turtle Mauremys reevesii caused by cadmium

This research was designed to investigate lipid peroxidation of the kidney of turtle (Mauremys reevesii) caused by cadmium. Turtles were injected intraperitoneally with cadmium at the concentration of 0 (control), 7.5, 15, and 30 mg/kg, and 5 turtles were taken from each group after exposure for 1 week (1 w), 2 weeks (2 w), and 3 weeks (3 w). Superoxide dismutase (SOD) and catalase (CAT) activities as well as glutathione (GSH) and malonyldialdehyde (MDA) contents in the homogenate of kidney tissue were analyzed. The results demonstrated that a short time of low dose of cadmium could stimulate the increase of SOD activity in the kidney of turtles, but a long time of high dose of cadmium could induce the decrease of SOD activity in the kidney of turtles. Cadmium could decrease CAT activity and GSH content in turtle kidney, but increased MDA content in turtle kidney. There were some other effects on the turtles, such as depression and diarrhea. The experimental results indicate that cadmium causes temporary oxidative stress on the kidney of turtles.

Oxidative stress in liver of turtle Mauremys reevesii caused by cadmium

The research was designed to examine oxidative stress of the liver of turtle Mauremys reevesii caused by cadmium (Cd). Turtles were injected intraperitoneally with cadmium at the concentration of 7.5, 15, and 30 mg/kg, and 5 turtles were taken from each group after exposure for 1 week (1 w), 2 weeks (2 w), and 3 weeks (3 w). The activities of SOD and CAT as well as the contents of GSH and MDA in liver tissues were detected by using a kit. The results showed that the difference between the control group and the Cd-treated group was statistically significant with the increase of Cd concentration and the prolongation of exposure time, which suggested that Cd caused oxidative stress on the liver of turtles.

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

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

Endothelial Dysfunction Induced by Cadmium and Mercury and its Relationship to Hypertension

Hypertension is an important public health concern that affects millions globally, leading to a large number of morbidities and fatalities. The etiology of hypertension is complex and multifactorial, and it involves environmental factors, including heavy metals. Cadmium and mercury are toxic elements commonly found in the environment, contributing to hypertension. We aimed to assess the role of cadmium and mercury-induced endothelial dysfunction in the development of hypertension. A narrative review was carried out through database searches. In this review, we discussed the critical roles of cadmium and mercury in the etiology of hypertension and provided new insights into potential mechanisms of their effect, focusing primarily on endothelial dysfunction. Although the mechanisms by which cadmium and mercury induce hypertension have yet to be completely elucidated, evidence for both implicates impaired nitric oxide signaling in their hypertensive etiology.

Ribosome profiling reveals ribosome stalling on tryptophan codons and ribosome queuing upon oxidative stress in fission yeast

Translational control is essential in response to stress. We investigated the translational programmes launched by the fission yeast Schizosaccharomyces pombe upon five environmental stresses. We also explored the contribution of defence pathways to these programmes: The Integrated Stress Response (ISR), which regulates translation initiation, and the stress-response MAPK pathway. We performed ribosome profiling of cells subjected to each stress, in wild type cells and in cells with the defence pathways inactivated. The transcription factor Fil1, a functional homologue of the yeast Gcn4 and the mammalian Atf4 proteins, was translationally upregulated and required for the response to most stresses. Moreover, many mRNAs encoding proteins required for ribosome biogenesis were translationally downregulated. Thus, several stresses trigger a universal translational response, including reduced ribosome production and a Fil1-mediated transcriptional programme. Surprisingly, ribosomes stalled on tryptophan codons upon oxidative stress, likely due to a decrease in charged tRNA-Tryptophan. Stalling caused ribosome accumulation upstream of tryptophan codons (ribosome queuing/collisions), demonstrating that stalled ribosomes affect translation elongation by other ribosomes. Consistently, tryptophan codon stalling led to reduced translation elongation and contributed to the ISR-mediated inhibition of initiation. We show that different stresses elicit common and specific translational responses, revealing a novel role in Tryptophan-tRNA availability.

Cadmium mediated redox modulation in germline stem cells homeostasis affects reproductive health of Drosophila males

Maintenance of male germline stem cells (GSCs) homeostasis is crucial for successful reproductive life of adults. New insights gained on dysfunction in stem cell maintenance could be the basis of stem cell dependent ailment during adulthood. Cadmium (Cd), a reported male reproductive toxicant, has been explored inadequately for its impact on male GSCs maintenance. The present study, therefore, has been aimed to evaluate the adverse effect of Cd on the homeostasis of GSCs by using Drosophila testis as an in vivo model. Following developmental exposure of environmentally relevant concentrations of Cd (5.0, 10.0 and 20.0 μg/mL) to Drosophila, we showed that a significantly increased level of reactive oxygen species (ROS) at 20.0 μg/mL of Cd resulted in alteration of GSCs number accompanied by inappropriate differentiation leading to reduced sperm number and eventually poor reproductive performance in exposed organism. Rescuing effect was evident by overexpressing sod in the early germ cell stage. The study suggests that an alteration in GSCs homeostasis due to redox imbalance plays a pivotal role in Cd induced failure in male fertility. The study further advocates for the use of Drosophila as an alternative animal model for in vivo evaluation of male GSCs toxicity with minimal ethical concern.

Global characterization of dose-dependent effects of cadmium in clam Ruditapes philippinarum

Cadmium (Cd) is being frequently detected in marine organisms. However, dose-dependent effects of Cd challenged unraveling the toxicological mechanisms of Cd to marine organisms and developing biomarkers. Here, the dose-dependent effects of Cd on clams Ruditapes philippinarum following exposure to 5 doses of Cd (3, 9, 27, 81, 243 μg/L) were investigated using benchmark dose (BMD) method. By model fitting, calculation of BMD values was performed on transcriptomic profiles, metals concentrations, and antioxidant indices. Cd exposure induced not only significant Cd accumulation in clams, but also marked alterations of essential metals such as Ca, Cu, Zn, Mn, and Fe. Gene regulation posed little influence on essential metal homeostasis, indicated by poor enrichment of differentially expressed genes (DEGs) associated with metal binding and metal transport in lower concentrations of Cd-treated groups. BMD analysis on biological processes and pathways showed that peptide cross-linking was the most sensitive biological process to Cd exposure, followed by focal adhesion, ubiquitin mediated proteolysis, and apoptosis. Occurrence of apoptosis was also confirmed by TUENL-positive staining in gills and hepatopancreas of clams treated with Cd. Furthermore, many DEGs, such as transglutaminases (TGs), metallothionein (MT), STEAP2-like and laccase, which presented linear or monotonic curves and relatively low BMD values, were potentially preferable biomarkers in clams to Cd. Overall, BMD analysis on transcriptomic profiles, metals concentrations and biochemical endpoints unraveled the sensitiveness of key events in response to Cd treatments, which provided new insights in exploring the toxicological mechanisms of Cd in clams as well as biomarker selection.

Jasmonates, Ethylene and Brassinosteroids Control Adventitious and Lateral Rooting as Stress Avoidance Responses to Heavy Metals and Metalloids

Developmental and environmental signaling networks often converge during plant growth in response to changing conditions. Stress-induced hormones, such as jasmonates (JAs), can influence growth by crosstalk with other signals like brassinosteroids (BRs) and ethylene (ET). Nevertheless, it is unclear how avoidance of an abiotic stress triggers local changes in development as a response. It is known that stress hormones like JAs/ET and BRs can regulate the division rate of cells from the first asymmetric cell divisions (ACDs) in meristems, suggesting that stem cell activation may take part in developmental changes as a stress-avoidance-induced response. The root system is a prime responder to stress conditions in soil. Together with the primary root and lateral roots (LRs), adventitious roots (ARs) are necessary for survival in numerous plant species. AR and LR formation is affected by soil pollution, causing substantial root architecture changes by either depressing or enhancing rooting as a stress avoidance/survival response. Here, a detailed overview of the crosstalk between JAs, ET, BRs, and the stress mediator nitric oxide (NO) in auxin-induced AR and LR formation, with/without cadmium and arsenic, is presented. Interactions essential in achieving a balance between growth and adaptation to Cd and As soil pollution to ensure survival are reviewed here in the model species Arabidopsis and rice.

Enhancement of cadmium accumulation in sweet sorghum as affected by nitrate

The Cadmium (Cd)-polluted soils are is an increasing concern worldwide. Phytoextraction of Cd pollutants by high biomass plants, such as sweet sorghum, is considered an environmentally-friendly, cost-effective and sustainable strategy for remediating this problem. Nitrogen (N) is a macronutrient essential for plant growth, development and stress resistance. Nevertheless, how nitrate, as an important form of N, affects Cd uptake, translocation and accumulation in sweet sorghum is still unclear. In the present study, a series of nitrate levels (N1, 0.5 mm; N2, 2 mm; N3, 4 mm; N4, 8 mm and N5, 16 mm) with or without added 5 μm CdCl₂ treatment in sweet sorghum was investigated hydroponically. The results indicate that Cd accumulation in the aboveground parts of sweet sorghum was enhanced by optimum nitrate supply, resulting from both increased dry weight and Cd concentration. Although root-to-shoot Cd translocation was not enhanced by increased nitrate, some Cd was transferred from cell walls to vacuoles in leaves. Intriguingly, expression levels of Cd uptake and transport genes, SbNramp1, SbNramp5 and SbHMA3, were not closely related to increased Cd as affected by nitrate supply. The expression of SbNRT1.1B in relation to nitrate transport showed an inverted 'U' shape with increasing nitrate levels under Cd stress, which was in agreement with trends in Cd concentration changes in aboveground tissues. Based on the aforementioned results, nitrate might regulate Cd uptake and accumulation through expression of SbNRT1.1B rather than SbNramp1, SbNramp5 or SbHMA3, the well-documented genes related to Cd uptake and transport in sweet sorghum.

Cadmium exposure, fasting blood glucose changes, and type 2 diabetes mellitus: A longitudinal prospective study in China

BACKGROUND

Cadmium is a recognized human carcinogen, raising global concern for its ubiquitously environmental exposure on public health. Diabetogenic effects of cadmium have been suggested in previous studies, but the longitudinal associations of chronic cadmium exposure with fasting blood glucose changes and type 2 diabetes mellitus have not been fully elucidated.

OBJECTIVE

To investigate the effects of long-term cadmium exposure on the fasting blood glucose changes and type 2 diabetes mellitus risk in a longitudinal prospective study of China.

METHODS

A total of 3521 urban adults were included as baseline study population from the Wuhan-Zhuhai cohort, and followed up three years later. Urinary cadmium concentrations were determined repeatedly during the follow-up of a three-year period. The within-person and between-person variability of urinary cadmium concentrations over three years was estimated using multilevel random-effects mixed models. Multivariate regression models were performed to evaluate the associations of cadmium exposure with fasting blood glucose changes and type 2 diabetes mellitus risk.

RESULTS

The geometric means of creatinine-corrected urinary cadmium concentration at baseline were 1.13 μg/g creatinine, which were close to the levels of follow-up (1.14 μg/g creatinine). The intra-class correlation coefficient of creatinine-corrected urinary cadmium concentrations was 0.71, achieving good reproducibility of cadmium over three years. With adjustment for potential confounders, each one-unit increase in log10-transformed cadmium was associated with a 0.11 (95%CI: 0.03 to 0.19) elevation in fasting blood glucose concentration, and was associated with a 42% (95%CI: 1.16 to 1.73) increase in risk of prevalent type 2 diabetes mellitus. Upward trends of fasting blood glucose changes and type 2 diabetes mellitus incidence were observed with increasing cadmium exposure. Individuals with the highest urinary cadmium exposure had a significant increase in fasting blood glucose change at follow-up [β (95% CI): 0.49 (0.31-0.67)]. Risk of incident type 2 diabetes mellitus were gradually elevated across increasing quartiles of cadmium exposure, though associations did not reach statistical significance (P = 0.15).

CONCLUSIONS

Our findings suggested that relatively high chronic cadmium exposure for general population adults might contribute to elevated changes of fasting blood glucose resulting in the development of type 2 diabetes mellitus.

Relief of Cadmium-Induced Intestinal Motility Disorder in Mice by Lactobacillus plantarum CCFM8610

Cadmium (Cd) is a toxic metal inducing a range of adverse effects on organs including liver and kidneys. However, the underlying molecular mechanisms of Cd-induced intestinal toxicity through dietary intake is poorly studied. This study evaluated the toxic effects of Cd on intestinal physiology and confirmed the effectiveness of the protective mechanism of the probiotic Lactobacillus plantarum CCFM8610 against chronic Cd toxicity. After treatment with Cd, the HT-29 cell line was subjected to iTRAQ analysis, which revealed that changes in the proteomic profiles after Cd exposure were related to pathways involved in the stress response and carbohydrate metabolism. The results of an animal trial also indicated that 10 weeks of Cd exposure decreased the fecal water content and contractile response of colonic muscle strips in mice, and delayed the excretion time of the first black feces. L. plantarum CCFM8610 treatment provided protective effects against these Cd-induced intestinal motility dysfunctions by recovering the levels of neurotransmitters, including substance P, acetyl cholinesterase, vasoactive intestinal peptide, 5-hydroxytryptamine, calcitonin gene-related peptide, and nitric oxide, and suppressing the cellular stress response in mice (e.g., the inhibition of mitogen-activated protein kinase pathways). The administration of this probiotic was also observed to reduce Cd levels in the tissues and blood of the mice. Our results suggest a newly identified protective mechanism of probiotics against Cd toxicity that involves the recovery of intestinal motility and increase in fecal cadmium excretion.

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 .

Alleviation of cadmium-induced phytotoxicity and growth improvement by exogenous melatonin pretreatment in mallow (Malva parviflora) plants

The present work was aimed to study the effect of melatonin pretreatments on growth, oxidative stress modulation, cadmium (Cd) accumulation, and tolerance in mallow (Malva parviflora, Malvaceae) plants under the hydroponic system. Application of substances that can modulate the harmful effects of Cd on plant yield and reduce its accumulation in the edible parts is of particular importance. Therefore, the mallow plants pretreated with 15, 50, and 100 µM of melatonin were exposed to 50 µM Cd. Our results showed that melatonin, especially at 15 and 50 µM, led to positive effects on Cd tolerance, including a significant increase in growth, photosynthetic pigments, and soluble protein content. Exogenous melatonin could improve relative water content (RWC) and stomatal conductance in the plants treated with Cd, probably through an increase in proline. Further, lower concentrations of melatonin led to a decrease in Cd translocation to the shoots. Based on the results, melatonin considerably increased catalase (CAT), superoxide dismutase (SOD), and guaiacol peroxidase (GPX) activities as well as the production of phenols. The increased activity of antioxidant enzymes led to a decrease in electrolyte leakage (EL), lipid peroxidation, and H₂O₂ content in the plants exposed to Cd stress. Under Cd stress, the increased phenols content in melatonin-pretreated plants could be due to the induction of phenylalanine ammonia-lyase (PAL) activity and an increase in shoot soluble carbohydrates. The results showed that the use of melatonin could reduce oxidative stress and improve biomass in the plants exposed to Cd. At least in our experimental conditions, this information appears to be useful for healthy food production.

Antagonistic effect of N-acetyl-L-cysteine against cadmium-induced cytotoxicity and abnormal immune response on chicken peritoneal macrophages

Cadmium is a highly toxic metal threatening human and animal health. N-acetyl-L-cysteine (NAC) was reported to play a positive role in disease treatment and immune regulation. The present study aimed to explore the effect of NAC administration on Cd-induced cytotoxicity and abnormal immune response on chicken peritoneal macrophages. Peritoneal macrophages isolated from Isa Brown male chickens were exposed to CdCl₂ (20 or 50 μM) and/or NAC (500 μM) for different time periods. Results showed that Cd caused dose-dependent damage on chicken peritoneal macrophages characterized by morphologic and ultrastructural alterations, increased cell apoptosis, reactive oxygen species accumulation and mitochondrial injury. Cd exposure inhibited phagocytic activity of chicken peritoneal macrophages, and promoted transcriptional status of pro-inflammatory cytokines (IL-1β, IL-6 and TNF-α) in both unactivated macrophages and cells in response to lipopolysaccharide (LPS) stimuli. Pretreatment with 500 μM NAC did not affect growth of normal chicken peritoneal macrophages, while remarkably inhibiting Cd-caused cell death, oxidative stress, and mitochondrial membrane depolarization. NAC pretreatment significantly prevented intracellular Cd²⁺ accumulation in the Cd-exposed macrophages. Inhibitory effects of NAC on Cd-induced ROS accumulation and mitochondrial injury on chicken macrophages were confirmed in HD-11 macrophage cell line. In addition, NAC pretreatment promoted the phagocytic activity of Cd-exposed chicken peritoneal macrophages, and significantly inhibited expression of pro-inflammatory factors (IL-1β, IL-6 and TNF-α) in both Cd-exposed macrophages and Cd-treated cells in response to LPS stimuli. In conclusion, the present study firstly demonstrated the antagonistic effect of NAC against Cd-caused damage and abnormal immune response on chicken peritoneal macrophages. Protective effect of NAC on chicken macrophages was highly related to its suppression on Cd-induced ROS overproduction, pro-inflammatory reaction and intracellular Cd²⁺ accumulation.

Effect of sodium molybdate on cadmium-related testicular damage in adult male Wistar rats

BACKGROUND

Molybdenum, as a trace element, has various pharmacological effects, including antioxidant, antiviral, anti-allergic, anti-osteoporosis, anti-tumor, anti-inflammatory, anti-diabetic, anti-obesity, and free radical-scavenging activities. This study aimed at investigating the sodium molybdate impacts on cadmium chloride (CdCl₂)-induced testicular toxicity in adult Wistar rats.

METHODS

The impacts of oral administration of sodium molybdate (0.05, 0.1, 0.2, and 0.4 mg/kg) was evaluated in healthy and infertile animals. Animals were randomly assigned to nine groups, including healthy control, sodium molybdate alone, infertile control (3 mg/kg of CdCl₂), and sodium molybdate plus CdCl₂. Following 30 days of administration, animals were sacrificed for biochemical and histopathological assays.

RESULTS

The results indicated that administration of sodium molybdate to infertile rats significantly mitigated the cadmium impacts on sperm appearance, concentration, and motility parameters. Also, sodium molybdate reduced the production of malondialdehyde (MDA) and enhanced antioxidant enzymes activities in the testicular homogenates in rats; these findings were supported by histopathological examinations. Treatment with sodium molybdate significantly increased aquaporin-9 (AQP9) expression in the testicular tissues of infertile rats.

CONCLUSIONS

The current findings suggested that sodium molybdate performs as a strong protective agent from CdCl₂-related testicular toxicity in rats.

Salicylic acid mediated reduction in grain cadmium accumulation and amelioration of toxicity in Oryza sativa L. cv Bandana

Contamination of agricultural fields with Cadmium (Cd) due to several agricultural practices is increasing worldwide. The rice plants can easily take up Cd and accumulate it into different parts, including the grains, posing a threat to human health even at low concentration exposure. Several phytohormones, including Salicylic acid (SA) have been investigated since long for its alleviating properties under various biotic and abiotic stress conditions. In the present study, 100 μM SA application to ameliorate 25 μM Cd stress was studied for 72 h in hydroponics in Oryza sativa cv. Bandana seedlings. Pot experiments were done with same treatment condition and plants were grown till maturity. SA application to Cd exposed rice seedlings alleviated the stress condition, which was established by several physiological, biochemical, histochemical and gene expression analysis. SA treatment to Cd stressed seedlings showed elevated photosynthetic pigment content, on-protein thiol content and relieved the Cd induced growth inhibition considerably. It lowered the accumulation of ROS like, O2^- and H₂O₂ with a regulated antioxidative enzymatic activity. SA application in Cd exposed rice seedlings had upregulated expression of OsHMA3 and OsPCS1 whereasOsNRAMP2 gene was downregulated. Co-application of SA and Cd led to higher yield and improved agronomic traits in comparison to only Cd exposed plants under pot experimentation. Daily intake of Cd and Carcinogenic risk were also reduced by 99.75% and 99.99% respectively in the SA treated Cd stressed plants. SA positively affected the growth and tolerance of rice seedlings to Cd stress. Hence, SA addition to Cd contaminated soil can ensure rice cultivation without posing health risk to consumers.

Association of plasma trace element levels with neovascular age-related macular degeneration

Although the triggers causing angiogenesis in the context of neovascular age-related macular degeneration (nAMD) are not fully understood, oxidative stress is likely involved. Oxidative stress in the eye can occur through exposure of macular tissues to sunlight and local or systemic exposure to oxidative stressors associated with environmental or lifestyle factors. Because trace elements have been implicated as regulators of oxidative stress and cellular antioxidant defense mechanisms, we hypothesized that they may play a role as a risk factor, modifying the progression toward nAMD. Herein, we determined whether levels of human plasma trace elements are different in 236 individuals with nAMD compared to 236 age-matched controls without AMD. Plasma levels of 16 trace elements including arsenic, barium, calcium, cadmium, cobalt, chromium, copper, iron, magnesium, manganese, molybdenum, lead, antimony, selenium, vanadium and zinc were measured using inductively coupled plasma mass spectrometry. Associations of trace elements with demographic, environmental and lifestyle factors and AMD-associated genetic variants were assessed. Elevated levels of barium and cadmium and reduced levels of chromium were observed in nAMD patients compared to controls. Mean plasma concentrations of barium were 1.35 μg/L (standard deviation [SD] 0.71) in nAMD and 1.15 μg/L (SD 0.63) in controls (P = 0.001). Mean levels of chromium were 0.37 μg/L (SD 0.22) in nAMD and 0.46 μg/L (SD 0.34) in controls (P = 0.001). Median levels for cadmium, which were not normally distributed, were 0.016 μg/L (interquartile range [IQR] 0.001-0.026) in nAMD and 0.012 μg/L (IQR 0.001-0.022) in controls (P = 0.002). Comparison of the Spearman's correlation coefficients between nAMD patients and controls identified a difference in correlations for 8 trace elements. Cadmium levels were associated with the smoking status (P < 0.001), while barium levels showed a trend of association with the usage of antihypertensive drugs. None of the AMD-associated genetic variants were associated with any trace element levels. In conclusion, in this case-control study we detected elevated plasma levels of barium and cadmium and reduced plasma levels of chromium in nAMD patients. An imbalance in plasma trace elements, which is most likely driven by environmental and lifestyle factors, might have a role in the pathogenesis of AMD. These trace elements may be incorporated as biomarkers into models for prediction of disease risk and progression. Additionally, population-based preventive strategies to decrease Cd exposure, especially by the cessation of smoking, could potentially reduce the burden of nAMD. Future studies are warranted to investigate whether supplementation of Cr would have a beneficial effect on nAMD.

Foliar application of zinc and selenium alleviates cadmium and lead toxicity of water spinach - Bioavailability/cytotoxicity study with human cell lines

The present study investigated the effects of foliar application of zinc (Zn) and selenium (Se) on bioavailability of Zn and Se and toxicity of cadmium (Cd) and lead (Pb) to different water spinach ecotypes (LA and HA) grown in slightly (XZ) or moderately (LJY) contaminated fields via in vitro digestion combined with Caco-2/HL-7702 cell model. The obtained results revealed that foliar application of Zn and Se promoted yield, increased total, bioaccessible and bioavailable fractions of Zn and Se in plants, indicating that foliar application is a feasible way of biofortification. Although there was no significant effect on liver cell proliferation (MTT), membrane stability (LDH) and hepatocyte enzyme (ALT and AST) activities, the obvious ecotype and soil dependent fluctuations of lipid peroxidation (MDA) and antioxidant enzyme (SOD, POD and CAT) activities in serum highly suggest that the low accumulator and clean field should be used in agricultural production rather than the high accumulator and contaminated farmland. Moreover, foliar application of Zn and Se improved nutritional quality of all water spinach genotypes in both fields, including increased Fe, vitamin C, cellulose and chlorophyll, maintained concentrations of potassium (K), manganese (Mn), copper (Cu), protein, and nitrate. These results demonstrate that this agricultural management practice may prove to be an effective approach for minimizing health risk and alleviating "hidden hunger" in the developing countries.

Cd-tolerant SY-2 strain of Stenotrophomonas maltophilia: a potential PGPR, isolated from the Nanjing mining area in China

Microbial and plant assisted bioremediation is an emerging way for the remediation of soils polluted with heavy metals. To screen the cadmium tolerant bacteria, soil samples were collected from Nanjing mining area, China. The average cadmium content of the mine soil reached 45.71 mg/kg, which was indicating serious pollution and potential ecological risk. From the mine soil, six cadmium tolerant plant growth-promoting rhizobacteria (PGPR) were isolated. The isolated bacterial strain "SY-2" showed maximum cadmium tolerance and it was selected for further experimentation. This strain was identified as Stenotrophomonas maltophilia by 16S rRNA gene sequencing (GenBank accession number MG597057). SY-2 was found to tolerate maximum cadmium at 1.0 mM concentration. This strain also exhibited good adsorption capacity (up to 35.7%) of heavy metal at 0.5 mM concentration. The results of this study exhibited organic phosphorus solubilization (37.08 mg/L) and IAA biosynthesis (15.11 mg/L) ability of isolated S. maltophilia. Scanning electron microscopy (SEM) revealed cell shrinkage and the cell wall of S. maltophilia was very rough. Moreover, the energy dispersive X-ray (EDX) analysis endorsed the adsorption of Cd ions on the surface of biomass. FT-IR study described the presence of functional groups and the nature of chemical bonds, before and after cadmium stress. At 0.25 mM cadmium concentration, S. maltophilia treated seeds of Capsicum annuum L. developed 1.46 times longer roots than untreated seeds. The results of this study helped us to conclude that SY-2 strain of S. maltophilia possesses significant metal tolerance and bioremediation potential against cadmium. In the future, this strain can be used as a microbial remediation agent to detoxify heavy metals in contaminated soils.

ELECTRONIC SUPPLEMENTARY MATERIAL

The online version of this article (10.1007/s13205-020-02524-7s) contains supplementary material, which is available to authorized users.

Investigating the mechanism of vanadium toxicity in freshwater organisms

Vanadium (V) could present a risk for aquatic organisms from the Alberta oil sands region, if present in high concentrations. An industry pilot project has used petroleum coke (PC) as a sorbent to remove organic toxicants from oil sands process-affected water (OSPW), but it also caused V to leach from PC into the OSPW, reaching concentrations of up to 7 mg V/L (a level known to be toxic to aquatic organisms). Vanadium is a transition metal with several oxidation states, which could potentially elicit its toxicity through either ion imbalance or oxidative stress. This study investigated the effect of V on Daphnia magna and Oncorhynchus mykiss. Daphinds and O. mykiss were exposed to concentrations of V up to their respective calculated median lethal concentration (LC₅₀): 3 mg V/L for D. magna and 7 mg V/L for O. mykiss. For both organisms, the influence of V on sodium flux and whole body sodium was evaluated. Its effect on whole body calcium and the oxidative stress responses in O. mykiss at the gill and liver levels was also studied. Results suggested that 3.1 mg V/L for D. magna and 6.8 mg V/L for O. mykiss caused an overall increase in sodium influx in both the daphnids and rainbow trout. However, concentrations of V ranging between 0.2 and 4 mg V/L for D. magna and 1.8 and 6 mg V/L for O. mykiss reduced whole body sodium in both organisms and whole body calcium in O. mykiss. Concentrations above 3.6 mg V/L caused significant lipid peroxidation in the gills and liver of rainbow trout, while 1.9 mg V/L produced a substantial decrease in the fish gill GSH:GSSG ratio, but no change in the ratio between these thiols in the liver. Concentrations of 6.62 mg V/L sharply increased catalase activity in the liver but not in the gills. Neither liver nor gill superoxide dismutase was altered by V. Overall, results suggest that both ion imbalance and oxidative stress are part of the mechanism of toxicity of V in D. magna and O. mykiss and that further research is warranted to fully elucidate the mechanism(s) of V toxicity in aquatic organisms.

Dose-response analysis of potassium bromate-induced toxicity in Allium cepa L. meristematic cells

In this study, the toxic effects of potassium bromate (KBrO₃) were tested on Allium cepa L. meristematic cells. In order to determine the toxic effect and dose relationship, KBrO₃ toxicity was investigated at doses of 25, 50, and 100 mg/L. The toxic effects were evaluated by using cytogenetic, biochemical, anatomical, and physiological parameters, and serious damages were observed depending on the dose. Significant reductions in germination percentage, weight gain, and radicle length were observed in all KBrO₃-treated groups compared with the control. Mitotic activity decreased in meristematic cells after KBrO₃ application. and mitotic index was decreased by 1.8 times in 100 mg/L KBrO₃-treated group compared with the control group. The frequencies of micronucleus and chromosomal abnormalities tested as cytogenetic parameters were significantly higher in the group treated with 100 mg/L KBrO₃ than those in the control group. Fragment and sticky chromosome were the most common types of chromosomal abnormalities. Lipid peroxidation measured in terms of MDA content increased with increasing doses of KBrO₃. The activities of catalase and superoxide dismutase as antioxidant enzymes were importantly changed in KBrO₃-treated groups. Anatomical changes such as cell deformation, substance accumulation, cell wall thickening, and flattened nucleus were determined after KBrO₃ application, and it was observed that these changes reached a maximum level at 100 mg/L dose of KBrO₃. As a result, KBrO₃ treatments were been found to cause physiological, biochemical, cytogenetic, and anatomically toxic effects in meristematic cells of A. cepa, a eukaryotic model organism. The versatile toxicity induced by KBrO₃ increased depending on the dose and reached a maximum level at 100 mg/L.

Cadmium and immunologically-mediated homeostasis of anatomical barrier tissues

Cadmium (Cd) is a toxic heavy metal that when absorbed into the body causes nephrotoxicity and effects in other tissues.Anatomical barrier tissues are tissues that prevent the entry of pathogens and include skin, mucus membranes and the immune system. The adverse effects of Cd-induced immune cell's activity are the most extensively studied in the kidneys and the liver. There are though fewer data relating the effect of this metal on the other tissues, particularly in those in which cells of the immune system form local circuits of tissue defense, maintaining immune-mediated homeostasis. In this work, data on the direct and indirect effects of Cd on anatomical barrier tissue of inner and outer body surfaces (the lungs, gut, reproductive organs, and skin) were summarized.

Inter-species bystander effect: Eisenia fetida and Enchytraeus albidus exposed to uranium and cadmium

The bystander effect is commonly defined as the observation of effects in nonirradiated cells and tissues when the later are in contact with irradiated cells/ tissues. More recently the occurrence of bystander effect between organisms of the same species has been also demonstrated. Nevertheless, there is limited knowledge about this effect between soil dwelling organisms from different taxonomic groups, as well as in response to stressors other than ionizing radiation. Moreover, data reporting this phenomenon for soil invertebrates are scarce. The results herein presented contribute for the understanding of the impacts of cadmium and uranium in the DNA integrity of two terrestrial oligochaetes species (Eisenia fetida and Enchytraeus albidus). The evaluation was based on the quantification of the effects in the DNA integrity of the coelomocytes using the alkaline comet assay technique. This work reports the existence of bystander signaling from terrestrial earthworms to enchytraeids and from enchytraeids to earthworms when the organisms were exposed to Cd. These results reinforce that the bystander effect seems to be related with the genotoxic activity of stressors, and not exclusive of radiotoxic contaminants. Further, the bystander effect occurs between different species and under real environmental conditions, even in complex matrices, as the soil.

Identification of mesenchymal stromal cell survival responses to antimicrobial silver ion concentrations released from orthopaedic implants

Antimicrobial silver (Ag⁺) coatings on orthopaedic implants may reduce infection rates, but should not be to the detriment of regenerative cell populations, primarily mesenchymal stem/stromal cells (MSCs). We determined intramedullary silver release profiles in vivo, which were used to test relevant Ag⁺ concentrations on MSC function in vitro. We measured a rapid elution of Ag⁺ from intramedullary pins in a rat femoral implantation model, delivering a maximum potential concentration of 7.8 µM, which was below toxic levels determined for MSCs in vitro (EC₅₀, 33 µM). Additionally, we present in vitro data of the reduced colonisation of implants by Staphylococcus aureus. MSCs exposed to Ag⁺ prior to/during osteogenic differentiation were not statistically affected. Notably, at clonal density, the colony-forming capacity of MSCs was significantly reduced in the presence of 10 µM Ag⁺, suggesting that a subpopulation of clonal MSCs was sensitive to Ag⁺ exposure. At a molecular level, surviving colony-forming MSCs treated with Ag⁺ demonstrated a significant upregulation of components of the peroxiredoxin/thioredoxin pathway and processes involved in glutathione metabolism compared to untreated controls. Inhibition of glutathione synthesis using l-buthionine sulfoxamine eliminated MSC clonogenicity in the presence of Ag⁺, which was rescued by exogenous glutathione.

Exposure to waterborne cadmium induce oxidative stress, autophagy and mitochondrial dysfunction in the liver of Procypris merus

The present study was performed to determine the effect of waterborne cadmium (Cd) exposure on oxidative stress, autophagy and mitochondrial dysfunction, and to explore the mechanism of Cd-induced liver damage in freshwater teleost Procypris merus. To this end, P. merus were exposed to waterborne 0, 0.25 and 0.5 mg/L Cd for 30 days (equal to 0, 2.22 and 4.45 μmol Cd/l). The waterborne Cd exposure significantly increased hepatic Cd accumulation and impaired histological structure of the liver of P. merus. both low and high-dose waterborne Cd exposure induced oxidative stress in the liver of P. merus, through increases Malondialdehyde (MDA) and reactive oxide species (ROS) accumulation in the liver. The Cd-induced oxidative stress in liver may result from reduction of enzyme activities (superoxide dismutases (SOD), catalases (CAT), GSH-S-transferases (GST)) and transcriptional expression of antioxidant related genes (gpx1, gpx2, cata, gsta1, sod1). Furthermore, the present study showed that waterborne Cd exposure decreased the transcriptional factor (nrf2) expression, which might lead to the down-regulation of antioxidant gene expression. Transmission electron microscopy (TEM) observations demonstrated that waterborne Cd exposure induced autophagy in the liver of P. merus. Gene expression analysis showed that waterborne Cd exposure also induced mRNA expression of a set of genes (beclin1, ulk1, atg5, lc3a, atg4b, atg9a, and p62) involved in the autophagy process, indicating that the influence of Cd on autophagy involved transcription regulation of autophagy gene expression. Waterborne Cd exposure induced a sharp decrease in ATP content in the liver of P. merus. In addition, the expression of mitochondrial function genes (sdha, cox4i1, cox1, atp5f1, and mt-cyb) are significantly decreased in the liver of P. merus in Cd treated groups, manifesting the suppression of Cd on mitochondrial energy metabolism. Taken together, our experiments demonstrate that waterborne Cd exposure induced oxidative stress, autophagy and mitochondrial dysfunction in the liver of P. merus. These results may contribute to the understanding of mechanisms that hepatotoxicity of Cd in teleost.

Effects of ethylene biosynthesis and signaling on oxidative stress and antioxidant defense system in Nelumbo nucifera G. under cadmium exposure

Water contamination with cadmium (Cd) is a global environmental problem and its remediation becomes urgent. Phytoremediation using ornamental plants has attracted much attention for its advantages of cost-effectiveness and beautification of the environment. Nelumbo nucifera G. is a popular ornamental aquatic macrophyte with fast growth, large biomass, and high capacities for Cd accumulation and removal. However, information about Cd resistance and defense responses in N. nucifera is rather scarce, which restricts its large-scale utilization for phytoremediation. The phytohormone ethylene plays an important role in plant resistance to Cd stress, but the underlying mechanism remains unclear. In this study, we investigated morphophysiological responses of N. nucifera seedlings to Cd stress, and focused on the effects of ethylene on oxidative damage, Cd accumulation, and antioxidant defense system at the metabolic and transcript levels in leaves under Cd stress. Our results showed that Cd exposure led to leaf chlorosis and necrosis, coupled with an increase in contents of hydrogen peroxide, electrolyte leakage, and malondialdehyde, and decrease in chlorophyll content. Exogenous ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) application intensified Cd-induced stress responses and Cd accumulation, and increased ethylene production by inducing ACC synthase (ACS) gene NnACS. Such enhanced ethylene emission inhibited catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) activities, and modulated ascorbate (AsA) and glutathione (GSH) accumulation through transcriptional regulation of their respective metabolic genes. After ethylene action inhibitor silver thiosulfate (STS) supplementation, Cd-induced oxidative damage was abolished, and Cd content declined but still at a relatively high level. Blocking of ethylene perception by STS inhibited ethylene biosynthesis; enhanced CAT, APX, and GR activities and their transcript levels; increased AsA accumulation via inducing its biosynthetic genes; but reduced GSH content and NnGSH2 expression level. These results suggest that ethylene biosynthesis and signaling play an important role in N. nucifera response to Cd stress, and maintaining appropriate ethylene level and low ethylene sensitivity could improve its Cd tolerance via efficient antioxidant defenses.

Cadmium inhibits cell cycle progression and specifically accumulates in the maize leaf meristem

It is well known that cadmium (Cd) pollution inhibits plant growth, but how this metal impacts leaf growth processes at the cellular and molecular level is still largely unknown. In the current study, we show that Cd specifically accumulates in the meristematic tissue of the growing maize leaf, while Cd concentration in the elongation zone rapidly declines as the deposition rates diminish and cell volumes increase due to cell expansion. A kinematic analysis shows that, at the cellular level, a lower number of meristematic cells together with a significantly longer cell cycle duration explain the inhibition of leaf growth by Cd. Flow cytometry analysis suggests an inhibition of the G1/S transition, resulting in a lower proportion of cells in the S phase and reduced endoreduplication in expanding cells under Cd stress. Lower cell cycle activity is also reflected by lower expression levels of key cell cycle genes (putative wee1, cyclin-B2-4, and minichromosome maintenance4). Cell elongation rates are also inhibited by Cd, which is possibly linked to the inhibited endoreduplication. Taken together, our results complement studies on Cd-induced growth inhibition in roots and link inhibited cell cycle progression to Cd deposition in the leaf meristem.

Dose dependent differential effects of toxic metal cadmium in tomato roots: Role of endogenous hydrogen sulfide

In this study, hydroponic experiments were conducted to elucidate mechanism(s) that are associated with differential effects of low (5 μM) and high (25 μM) dose of cadmium (Cd) stress in tomato. Furthermore, emphasis has also been focused on any involvement of endogenous hydrogen sulfide (H₂S) in differential behaviour of low and high doses of Cd stress. At low dose of Cd, root growth i.e. root fresh weight, length and fitness did not significantly alter when compared to the control seedlings. Though at low dose of Cd, cellular accumulation of Cd was slightly increased but this was accompanied by higher endogenous H₂S and phytochelatins, _L-cysteine desulfhydrase (DES) activity, activities of glutathione biosynthetic and AsA-GSH cycle enzymes, and maintained redox status of ascorbate and glutathione. However, addition of hypotaurine (HT, a scavenger of H₂S) resulted in greater toxicity, even at low dose of Cd, and these responses resembled with higher dose of Cd stress such as greater decline in root growth, endogenous H₂S and phytochelatins, activities of DES, glutathione biosynthesis and AsA-GSH cycle enzymes, disturbed redox status of ascorbate and glutathione which collectively led to higher oxidative stress in tomato roots. Moreover, addition of HT with higher dose of Cd also further enhanced its toxicity. Collectively, the results showed that differential behaviour of low and high dose of Cd stress is mediated by differential regulation of biochemical attributes in which endogenous H₂S has a crucial role.

Cadmium induces apoptosis via generating reactive oxygen species to activate mitochondrial p53 pathway in primary rat osteoblasts

Cadmium (Cd), a heavy metal produced by various industries, contaminates the environment and seriously damages the skeletal system of humans and animals. Recent studies have reported that Cd can affect the viability of cells, including osteoblasts, both in vivo and in vitro. However, the mechanism of Cd-induced apoptosis remains unclear. In the present study, primary rat osteoblasts were used to investigate the Cd-induced apoptotic mechanism. We found that treatment with 2 and 5 μM Cd for 12 h decreased osteoblast viability and increased apoptosis. Furthermore, Cd increased the generation of reactive oxygen species (ROS), and, thus, DNA damage measured via p-H2AX. The level of the nuclear transcription factor p53 was significantly increased, which upregulated the expression of PUMA, Noxa, Bax, and mitochondrial cytochrome c, downregulated the expression of Bcl-2, and increased the level of cleaved caspase-3. However, pretreatment with the ROS scavenger N-acetyl-l-cysteine (NAC) or the p53 transcription specific inhibitor PFT-α suppressed Cd-induced apoptosis. Our results indicate that Cd can induce apoptosis in osteoblasts by increasing the generation of ROS and activating the mitochondrial p53 signaling pathway, and this mechanism requires the transcriptional activation of p53.

Hydrogen sulfide decreases Cd translocation from root to shoot through increasing Cd accumulation in cell wall and decreasing Cd2+ influx in Isatis indigotica

Hydrogen sulfide (H₂S), a small gaseous signalling molecule, plays a pivotal role in the plant response to heavy metal stress. Here, we revealed a novel mechanism of Isatis indigotica resistance to cadmium (Cd) stress, in which H₂S promotes Cd accumulation in the root and decreases the long-distance transport of Cd from the root to shoot. Cd significantly inhibited Isatis indigotica growth and induced the endogenous H₂S level. Application of NaHS (a H₂S donor) alleviated the effects of Cd. NaHS restriction of the translocation factor of Cd, elevated the Cd content in roots and depressed the Cd content in shoots. Cd stress decreased the cellulose and pectin contents in the cell wall, but NaHS restored the effect of Cd on the cell wall components. The Cd²⁺ fluxes were detected by noninvasive microtest technology (NMT). The data showed that NaHS pretreatment decreased the Cd²⁺ influx and proportion of the Cd content in organelles. We analyzed the effect of NaHS on the metallothionein and phytochelatin (PC) contents in roots and found that the PC and metallothionein1A (MT1A) contents were induced by NaHS. Additionally, the chemical forms of Cd²⁺ were changed by NaHS. Thus, H₂S alters the content of cell wall component, improves Cd accumulation in the cell wall, depresses Cd²⁺ transmembrane movement, induces the synthesis of metallothioneins and decreases the toxicity of intracellular Cd. Our finding has great value to reduce the loss of Isatis indigotica resulted by heavy metals stress.

The Role of Probiotics in the Amelioration of Cadmium Toxicity

Cadmium is extremely toxic heavy metal, and there is no specific, safe, and efficacious therapeutic management of cadmium toxicity. Scientific literature reveals several probiotic microorganisms which alleviate experimentally induced cadmium toxicity in animals. The present review attempts to collate the experimental studies on probiotics and probiotic-derived natural products with cadmium toxicity ameliorative effects. Literature survey revealed that seven (7) types of probiotic microorganisms exhibited significant protection from cadmium toxicity in experimental pre-clinical studies. Clinical study with significant outcome was not found in literature. From the outcomes of the pre-clinical studies, it appears that probiotics have the prospect for alleviation and treatment of cadmium toxicity.

Biomonitoring of Mercury, Cadmium and Selenium in Fish and the Population of Puerto Nariño, at the Southern Corner of the Colombian Amazon

Heavy metals threaten communities near biodiversity hotspots, as their protein sources come from the environment. This study assessed Hg, Cd, and Se concentrations in fish, as well as the magnitude of exposure and hematological conditions of adult citizens from Puerto Nariño (Colombian Amazon). Among fish samples, greater Hg concentrations were found in higher trophic level species, including Rhaphiodon vulpinus (880 ± 130 ng/g) and Pseudoplatystoma tigrinum (920 ± 87 ng/g). These species presented the highest hazard quotients and lowest Se:Hg molar ratios among those studied, showing their consumption represents a health risk to consumers. Moreover, some samples of Mylossoma duriventre and Prochilodus magdalenae had Cd levels greater than the regulated limit (100 ng/g). The average total Hg (T-Hg) concentrations in human hair and blood were 5.31 µg/g and 13.7 µg/L, respectively. All hair samples exceeded the 1.0 μg/g threshold set by the USEPA, whereas 93% of the volunteers had T-Hg blood levels greater than 5 μg/L, suggesting elevated exposure. The mean Cd level was 3.1 µg/L, with 21% of samples surpassing 5 µg/L, value at which mitigating actions should be taken. Eighty-four percent of participants presented Se deficiencies (<100 μg/L). There was a significant association between fish consumption and T-Hg in hair (ρ = 0.323; p = 0.032) and blood (ρ = 0.381; p = 0.011). In this last matrix, Se correlated with Cd content, whereas lymphocytes were inversely linked to Hg concentrations. The results of this study show that there is  extensive exposure to Hg in fish, the consumption of which may promote detrimental impacts on hematology parameters within the community.

Antioxidant activity as a response to cadmium pollution in three durum wheat genotypes differing in salt-tolerance

Durum wheat is commonly used in various food industry industries and cultivated worldwide. A serious problem with the species cultivation is its capability to accumulate cadmium (Cd) in the grains. The aim of this study is to investigate whether antioxidant activity may be used as a marker of Cd tolerance in durum wheat. The experiment involved three durum wheat genotypes/lines differing in salt tolerance. The plant response to Cd was appraised based on the activity of ascorbate–glutathione (AsA–GSH) cycle enzymes, ascorbate-to-dehydroascorbate ratio, reduced-to-oxidized glutathione ratio (GSH:GSSG), as well as Cd content in the seeds. The highest activity of dehydroascorbate reductase, monodehydroascorbate reductase, and glutathione reductase was noted in control plants of salt-sensitive cultivar “Tamaroi.” In the presence of Cd, activity of these enzymes was considerably reduced. “Tamaroi” plants demonstrated also the highest Cd content in the grain. In conclusion, we identified the cultivar “Tamaroi” as most susceptible to cadmium, and the level of durum wheat sensitivity to the element can be evaluated based on a significant decrease in the activity of AsA–GSH cycle enzymes and GSH:GSSG ratio.

Enhancing the Rice Seedlings Growth Promotion Abilities of Azoarcus sp. CIB by Heterologous Expression of ACC Deaminase to Improve Performance of Plants Exposed to Cadmium Stress

Environmental pollutants can generate stress in plants causing increased ethylene production that leads to the inhibition of plant growth. Ethylene production by the stressed plant may be lowered by Plant Growth-Promoting Bacteria (PGPB) that metabolizes the immediate precursor of ethylene 1-aminocyclopropane-1-carboxylate (ACC). Thus, engineering PGPB with ACC deaminase activity can be a promising alternative to mitigate the harmful effects of pollutants and thus enhance plant production. Here we show that the aromatics-degrading and metal-resistant Azoarcus sp. CIB behaves as a PGP-bacterium when colonizing rice as an endophyte, showing a 30% increment in plant weight compared to non-inoculated plants. The cloning and expression of an acdS gene led to a recombinant strain, Azoarcus sp. CIB (pSEVA237acdS), possessing significant ACC deaminase activity (6716 nmol mg-1 h-1), constituting the first PGPB of the Rhodocyclaceae family equipped with this PGP trait. The recombinant CIB strain acquired the ability to protect inoculated rice plants from the stress induced by cadmium (Cd) exposure and to increase the Cd concentration in rice seedlings. The observed decrease of the levels of reactive oxygen species levels in rice roots confirms such a protective effect. The broad-host-range pSEVA237acdS plasmid paves the way to engineer PGPB with ACC deaminase activity to improve the growth of plants that might face stress conditions.

Mangiferin offers protection against deleterious effects of pharmaceuticals, heavy metals, and environmental chemicals

Mangiferin (MGF) is a polyphenolic C-glucosyl-xanthone extracted from the mango tree (Mangifera indica). MGF has shown diverse effects such as antioxidant, antiapoptotic, radical scavenging, and chelating properties. MGF also has been shown to modulate inflammatory pathways. In this review, we examined and evaluated the literature dealing with the protective effects of MGF against various chemical toxicities. Our literature review indicated that the MGF-induced protective effects against the toxic effects of pharmaceuticals, heavy metals and environmental chemicals were mainly mediated via suppression of lipid peroxidation, oxidative stress (along with enhancement of the antioxidant enzyme), inflammatory factors (TNF-α, IL-6, IL-10, and IL-12), and activation of PI3K/Akt and the MAPK survival signaling pathway.

Suitability of a Cellulose-Based Nanomaterial for the Remediation of Heavy Metal Contaminated Freshwaters: A Case-Study Showing the Recovery of Cadmium Induced DNA Integrity Loss, Cell Proliferation Increase, Nuclear Morphology and Chromosomal Alterations on Dreissena polymorpha

The contamination of freshwaters by heavy metals represents a great problem, posing a threat for human and environmental health. Cadmium is classified as carcinogen to humans and its mechanism of carcinogenicity includes genotoxic events. In this study a recently developed eco-friendly cellulose-based nanosponge (CNS) was investigated as a candidate in freshwater nano-remediation process. For this purpose, CdCl₂ (0.05 mg L⁻¹) contaminated artificial freshwater (AFW) was treated with CNS (1.25 g L⁻¹ for 2 h), and cellular responses were analyzed before and after CNS treatment in Dreissena polymorpha hemocytes. A control group (AFW) and a negative control group (CNS in AFW) were also tested. DNA primary damage was evaluated by Comet assay while chromosomal damage and cell proliferation were assessed by Cytome assay. AFW exposed to CNS did not cause any genotoxic effect in zebra mussel hemocytes. Moreover, DNA damage and cell proliferation induced by Cd(II) turned down to control level after 2 days when CNS were used. A reduction of Cd(II)-induced micronuclei and nuclear abnormalities was also observed. CNS was thus found to be a safe and effective candidate in cadmium remediation process being efficient in metal sequestering, restoring cellular damage exerted by Cd(II) exposure, without altering cellular physiological activity.

Response of Corchorus olitorius Leafy Vegetable to Cadmium in the Soil

Corchorus olitorius, a leafy vegetable with high nutrient content, is normally collected from the wild, in areas that are prone to cadmium (Cd) toxicity. However, studies on how Cd accumulation affects vegetative and reproductive traits of leafy vegetables in South Africa are limited. Therefore, this study tested the effect of Cd accumulation on C. olitorius morphological traits. Plants were grown under various Cd concentrations and studied for variation in vegetative and reproductive traits as well as accumulation in roots and shoots. Plants exposed to 5 mg/kg Cd had longer roots with higher moisture content, heavier fresh and dried stems, as well as dried leaves, which indicated a hormetic effect in C. olitorius after exposure to low Cd concentration in the soil. Again, plants treated with 5–10 mg/kg Cd, accumulated toxic (>10 mg/kg dry weight) Cd within shoots and roots, with minor morphological alterations. Plants could survive, with some morphological defects, Cd toxicity up to 20 mg/kg in soil. Only plants exposed to 5 mg/kg could reproduce. Cd accumulation increased with an increase in the soil, with higher accumulation in shoots. The translocation factor was high (>1) in all Cd concentrations. In conclusion, C. olitorius can accumulate toxic Cd, and yet grow and reproduce either normally or better than the control. The proposed dose of Cd that induces hormesis in C. olitorius is 5 mg/kg in the soil. Therefore, C. olitorius is suitable for phytoremediation of Cd contaminated soils, but unsafe for consumption when it grows in such areas.

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.

Glutathione: A key player in metal chelation, nutrient homeostasis, cell cycle regulation and the DNA damage response in cadmium-exposed Arabidopsis thaliana

Glutathione (GSH) is an important player in plant responses to cadmium (Cd) through its dual function as an antioxidant and precursor for metal-chelating phytochelatins (PCs). In addition, it was shown to be involved in cell cycle regulation in Arabidopsis thaliana roots, but its involvement in this process in leaves is largely unknown and has never been evaluated in Cd-exposed plants. This study aimed to elucidate the role of GSH in leaf growth and development, metal chelation, nutrient homeostasis and cell cycle regulation in A. thaliana plants upon prolonged Cd exposure. Responses were compared between wild-type (WT) plants and three GSH-deficient mutants. Our results indicate that PC production remains important in plants exposed to Cd for an extended duration. Furthermore, an important role for GSH in regulating nutrient homeostasis in Cd-exposed plants was revealed. Cell cycle analysis demonstrated that negative effects of Cd exposure on cell division and endoreplication were more pronounced in leaves of the GSH-deficient cadmium-sensitive 2-1 (cad2-1) mutant in comparison to the WT, indicating the involvement of GSH in cell cycle regulation. Finally, a crucial role for GSH in transcriptional activation of the Cd-induced DNA damage response (DDR) was revealed, as the Cd-induced upregulation of DDR-related genes was either less pronounced or completely abolished in leaves of the GSH-deficient mutants.

The endophytic bacterium relieved healthy risk of pakchoi intercropped with hyperaccumulator in the cadmium polluted greenhouse vegetable field

Planting leafy vegetables, especially pakchoi, in cadmium (Cd) polluted farmland is easy to lead to excessive Cd content in edible parts, which results in high risk of food chain. In this study, a field experiment was carried out to study the effects of intercropping of pakchoi with Cd hyperaccumulator Sedum alfredii Hance, and the roles of endophytic bacterium SaMR12 was also investigated. When intercropping with Sedum, the growth of pakchoi was not affected but their Cd concentration and accumulation were significantly increased, while which were obviously decreased by SaMR12 inoculation. After intercropping, the biomass of Sedum was significantly reduced, but their Cd concentration increased. SaMR12 inoculation significantly increased Cd accumulation of Sedum, and which increased to 3 times in Sedum monoculture. Those results showed that although intercropping with hyperaccumulator could lead to higher risk of pakchoi in Cd polluted field, intercropping with SaMR12 inoculated Sedum can decrease Cd concentration of pakchoi and promote Cd absorption of Sedum, which indicated that this endophyte can be made into a microbial inoculum as a soil additive for the safe production of vegetables and the soil Cd pollution remediation.

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.

Identifying the Pressure Points of Acute Cadmium Stress Prior to Acclimation in Arabidopsis thaliana

The toxic metal cadmium (Cd) is a major soil pollutant. Knowledge on the acute Cd-induced stress response is required to better understand the triggers and sequence of events that precede plant acclimation. Therefore, we aimed to identify the pressure points of Cd stress using a short-term exposure set-up ranging from 0 h to 24 h. Acute responses related to glutathione (GSH), hydrogen peroxide (H₂O₂), 1-aminocyclopropane-1-carboxylic acid (ACC), ethylene and the oxidative challenge were studied at metabolite and/or transcript level in roots and leaves of Arabidopsis thaliana either exposed or not to 5 µM Cd. Cadmium rapidly induced root GSH depletion, which might serve as an alert response and modulator of H₂O₂ signalling. Concomitantly, a stimulation of root ACC levels was observed. Leaf responses were delayed and did not involve GSH depletion. After 24 h, a defined oxidative challenge became apparent, which was most pronounced in the leaves and concerted with a strong induction of leaf ACC synthesis. We suggest that root GSH depletion is required for a proper alert response rather than being a merely adverse effect. Furthermore, we propose that roots serve as command centre via a.o. root-derived ACC/ethylene to engage the leaves in a proper stress response.

The genotoxic effects of mixture of aluminum, arsenic, cadmium, cobalt, and chromium on the gill tissue of adult zebrafish (Danio rerio, Hamilton 1822)

The aim of this study is to investigate the genotoxic effects of mixtures of five metals on zebrafish at two different concentrations; at the permissible maximum contamination levels in drinking water and irrigation waters. The drinking water limits are as follows: 300 µg/L for Aluminum (Al⁺³), 10 µg/L for Arsenic (As⁺³), 5 µg/L for Cadmium (Cd⁺²), 10 µg/L for Cobalt (Co⁺²), and 50 µg/L for Chromium (Cr⁺²). The irrigation water limits: 5000 µg/L for Al⁺³, 100 µg/L for As⁺³, 10 µg/L for Cd⁺², 50 µg/L for Co⁺², and 100 µg/L for Cr⁺². The zebrafish underwent chronic exposure for periods of 5, 10, and 20 days. The gene expressions for mitochondrial superoxide dismutase (SOD2), stress-specific receptor protein NCCRP1, the heat shock proteins: Hsp9, Hsp14, Hsp60, Hsp70, DNA repair (XRCC1 and EXO1), and apoptosis (BOK and BAX) were evaluated. It was found that exposure to the low- and high-concentrations of the heavy metal mixtures caused cell stress, an increased expression of the antioxidant genes, and repair proteins. As the duration of exposure was increased, the cells progressed through the apoptotic pathway. This was more evident in the high-concentration exposure groups. The results demonstrated the necessity for a reevaluation of the maximum values of heavy metal and toxic element concentrations as prescribed by the Local Standing Rules of Water Pollution Control Regulation, as well as a reevaluation of the limitations of heavy metal mixture interactions with respect to ecological balance and environmental health.HighlightsThe purpose of this study was to investigate the genotoxic effects of a mixture of Aluminum, Arsenic, Cadmium, Cobalt, Chromium on zebrafish, within drinking water, and irrigation water limits determining the concentration.The zebrafish were exposed to two different concentrations of each metal mixture for 5-, 10-, and 20-day periods. Following exposure, gene expressions of the zebrafish's gill tissues were examined.As a result of the exposure to the metal mixtures, the following occurred: cell stress, increased antioxidant gene activity, and attempts to protect cell viability. However, the cells progressed through the apoptotic pathway after prolonged exposure.The results demonstrated the necessity for a reevaluation of the maximum limits of metal and toxic element concentrations as stated in the Standing Rules of Water Pollution Control Regulation.