The effect of different amendments on Cd availability and bacterial community after three-year consecutive application in Cd-contaminated paddy soils.

In situ immobilization is a widely used measure for passivating Cd-contaminated soils. Amendments need to be continuously applied to achieve stable remediation effects. However, few studies have evaluated the impact of consecutive application of amendments on soil health and the microecological environment. A field experiment was conducted in a Cd-contaminated paddy (available Cd concentration 0.40 mg kg-1) on the Chengdu Plain to investigate the changes in soil Cd availability and response characteristics of soil bacterial communities after consecutive application of rice straw biochar (SW), fly ash (FM) and marble powder (YH) amendments from 2018 to 2020. Compared with control treatment without amendments (CK), soil pH increased by 0.6, 0.5 and 1.5 under SW, FM and YH amendments, respectively, and the soil available Cd concentration decreased by 10.71%, 21.42% and 25.00%, respectively. The Cd concentration in rice grain was less than 0.2 mg kg-1 under YH amendment, which was within the Chinese Contaminant Limit in Food of National Food Safety Standards (GB2762-2022) in the second and third years. The three amendments had different effects on the transformation of Cd fractions in soil, which may be relevant to the specific bacterial communities shaped under different treatments. The proportion of Fe-Mn oxide-bound fraction Cd (OX-Cd) increased by 11% under YH treatment, which may be due to the promotion of Fe(III) and Cd binding by some enriched iron-oxidizing bacteria, such as Lysobacter, uncultured_Pelobacter sp. and Sulfurifusis. Candidatus_Tenderia and Sideroxydans were enriched under SW and FM amendments, respectively, and were likely beneficial for reducing Cd availability in soil through Cd immobilization. These results revealed the significance of the bacterial community in soil Cd immobilization after consecutive application of amendments and highlighted the potential of applying YH amendment to ensure the safe production of rice in Cd-contaminated soil.

Field evaluation of oil crop rotations for cadmium remediation and safe vegetable oil production across five sites with varying contamination levels.

Oil crops have the potential to remediate cadmium (Cd)-contaminated farmland while producing safe vegetable oil. However, it is currently unknown whether different oil crops can remediate varying levels of Cd contamination in farmland. This study assessed agricultural fields in southern China contaminated with Cd levels ranging from 0.42 to 10.3 mg/kg. Three representative oilseed crops winter rape, oil sunflower, and peanut were selected for field experiments under two rotation systems. The effects of different rotation systems on remediating various Cd contamination levels were compared to evaluate the feasibility and potential of a two oil crop rotation system. All three crops showed good tolerance to Cd without signs of biomass deficiency. The biomass produced by the rape-oil sunflower and rape-peanut rotation systems was 33.44-459.00 g/ha and 30.64-281.40 g/ha, respectively. The Cd concentration in the oil products obtained complied with existing national and international standards (0.05 mg/kg). The remediation efficiency of the rape-oil sunflower and rape-peanut rotation systems was 1.98-7.37 % and 1.21-4.94 %, respectively. However, the remediation efficiencies and enrichment capacities of both rotation systems were somewhat inhibited by heavy Cd contamination (10.3 mg/kg). Therefore, the agricultural model of rotating two oilseed crops can be implemented in Cd-contaminated farmland at all levels but is more suitable for light to moderate Cd contamination.

Effects of combined microplastic and cadmium pollution on sorghum growth, Cd accumulation, and rhizosphere microbial functions.

The interaction between microplastics (MPs) and cadmium (Cd) poses a threat to agricultural soil environments, and their effects on plant growth and rhizosphere microbial community functions are not yet clear. In this study, energy sorghum was used as a test plant to investigate the effects of two types of MPs, polystyrene (PS) and polyethylene (PE), at different particle sizes (13 µm, 550 µm) and concentrations (0.1%, 1% w/w), and Cd, as well as their interactions, on the growth of sorghum in a soil-cultivation pot experiment. The results showed that the combined effects of MP and Cd pollution on the dry weight and Cd accumulation rate in sorghum varied depending on the type, concentration, and particle size of the MPs, with an overall trend of increasing stress from combined pollution with increasing Cd content and accumulation. High-throughput sequencing analysis revealed that combined MP and Cd pollution increased bacterial diversity, and the most significant increase was observed in the abundance-based coverage estimator (ACE), Shannon, and Sobs indices in the 13 µm 1% PS+Cd treatment group. Metagenomic analysis based on the Kyoto Encyclopedia of Genes and Genomes (KEGG) metabolic pathways revealed that 19 groups of metabolic pathways, including microbial metabolism and methane metabolism, differed significantly under combined MP and Cd pollution. Hierarchical clustering results indicated that Cd treatment and combined MP and Cd treatment affected the abundances of sorghum rhizosphere soil nitrogen (N) and phosphorus (P) cycling genes and that the type of MP present was an important factor affecting N and P cycling genes. The results of this study provide a basis for exploring the toxic effects of combined MP and Cd pollution and for conducting soil environmental risk assessments.

Tetramethylpyrazine Antagonizes the Subchronic Cadmium Exposure-Induced Oxidative Damage in Mouse Livers via the Nrf2/HO-1 Pathway.

Hepatic oxidative stress is an important mechanism of Cd-induced hepatotoxicity, and it is ameliorated by TMP. However, this underlying mechanism remains to be elucidated. To investigate the mechanism of the protective effect of TMP on liver injuries in mice induced by subchronic cadmium exposure, 60 healthy male ICR mice were randomly divided into five groups of 12 mice each, namely, control (CON), Cd (2 mg/kg of CdCl2), Cd + 100 mg/kg of TMP, Cd + 150 mg/kg of TMP, and Cd + 200 mg/kg of TMP, and were acclimatized and fed for 7 d. The five groups of mice were gavaged for 28 consecutive days with a maximum dose of 0.2 mL/10 g/day. Except for the control group, all groups were given fluoride (35 mg/kg) by an intraperitoneal injection on the last day of the experiment. The results of this study show that compared with the Cd group, TMP attenuated CdCl2-induced pathological changes in the liver and improved the ultrastructure of liver cells, and TMP significantly decreased the MDA level (p < 0.05) and increased the levels of T-AOC, T-SOD, and GSH (p < 0.05). The results of mRNA detection show that TMP significantly increased the levels of Nrf2 in the liver compared with the Cd group as well as the HO-1 and mRNA expression levels in the liver (p < 0.05). In conclusion, TMP could inhibit oxidative stress and attenuate Cd group-induced liver injuries by activating the Nrf2 pathway.

Spatial-temporal distribution and source analysis of atmospheric particulate-bound cadmium from 1998 to 2021 in China.

Cadmium (Cd) is one of the most serious atmospheric heavy metal pollutants in China. PM2.5, PM10, and total suspended particle (TSP) are all important media for population Cd exposure. However, no studies so far have systematically explored the spatial and temporal distribution of atmospheric Cd bound to all these media in China, and the specific industrial sectors that contribute to the airborne Cd level are still unclear at present. In this study, we constructed the spatial and temporal distribution of PM (PM2.5, PM10, and TSP) binding Cd concentrations in China. Quantitative source apportionment of atmospheric Cd was carried out by analyzing the association of 23 industrial or energy-consuming sectors with Cd concentrations. Our results showed PM2.5, PM10, and TSP binding Cd concentrations decreased by 5.8%, 5.9%, and 6.1% per year at the national level, respectively. High PM-Cd concentrations were concentrated and distributed mainly in central and northwestern China. In addition, the medians of atmospheric PM2.5, PM10, and TSP binding Cd concentrations at the national level were 0.0026 µg/m3, 0.0036 µg/m3, and 0.0042 µg/m3, respectively. The main sources of PM-Cd include nonferrous metal smelting (Zn, Pb, Al) (47%), glass production (13%), pesticide production (12%), cement production (10%), and coal consumption (9%). This study analyzes comprehensively the atmospheric PM-bound Cd pollution, identifies the major industrial sectors that affect atmospheric Cd concentrations at the macroscale for the first time, and provides a basis for further reduction in the atmospheric Cd pollution.

How does the biochar-supported sulfidized nanoscale zero-valent iron affect the soil environment and microorganisms while remediating cadmium contaminated paddy soil?

In previous studies, iron-based nanomaterials, especially biochar (BC)-supported sulfidized nanoscale zero-valent iron (S-nZVI/BC), have been widely used for the remediation of soil contaminants. However, its potential risks to the soil ecological environment are still unknown. This study aims to explore the effects of 3% added S-nZVI/BC on soil environment and microorganisms during the remediation of Cd contaminated yellow-brown soil of paddy field. The results showed that after 49 d of incubation, S-nZVI/BC significantly reduced physiologically based extraction test (PBET) extractable Cd concentration (P < 0.05), and increased the immobilization efficiency of Cd by 16.51% and 17.43% compared with S-nZVI and nZVI/BC alone, respectively. Meanwhile, the application of S-nZVI/BC significantly increased soil urease and sucrase activities by 0.153 and 0.446 times, respectively (P < 0.05), improving the soil environmental quality and promoting the soil nitrogen cycle and carbon cycle. The results from the analysis of the 16S rRNA genes indicated that S-nZVI/BC treatment had a minimal effect on the bacterial community and did not appreciably alter the species of the original dominant bacterial phylum. Importantly, compared to other iron-based nanomaterials, incorporating S-nZVI/BC significantly increased the soil organic carbon (OC) content and decreased the excessive release of iron (P < 0.05). This study also found a significant negative correlation between OC content and Fe(II) content (P < 0.05). It might originate from the reducing effect of Fe-reducing bacteria, which consumed OC to promote the reduction of Fe(III). Accompanying this process, the redistribution of Cd and Fe mineral phases in the soil as well as the generation of secondary Fe(II) minerals facilitated Cd immobilization. Overall, S-nZVI/BC could effectively reduce the bioavailability of Cd, increase soil nutrients and enzyme activities, with less toxic impacts on the soil microorganisms.

Effect of potassium intake on cadmium transporters and root cell wall biosynthesis in sweet potato.

Large areas of farmland soil in southern China are deficient in potassium (K) and are contaminated with cadmium (Cd). Previously, we suggested that the K supplementation could reduce Cd accumulation in sweet potatoes (Ipomoea batatas (L.) Lam). In the present study, we investigated the underlying physiological and molecular mechanisms. A hydroponic experiment with different K and Cd treatments was performed to compare the transcriptome profile and the cell wall structure in the roots of sweet potato using RNA sequencing, Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). The results showed that K supply inhibits the expressions of IRT1 and YSL3, which are responsible for root Cd uptake under Cd exposure. Furthermore, the expressions of COPT5 and Nramp3 were downregulated by K, which increased Cd retention in the root vacuoles. The upregulation of POD, CAD, INT1 and SUS by K contributed to lignin and cellulose biosynthesis and thickening of root xylem cell wall, which further reduced Cd translocation to the shoot. In addition, K affected the expressions of LHT, ACS, TPS and TPP associated with the production of ethylene and trehalose, which involved in plant resistance to Cd toxicity. In general, K application could decrease the uptake and translocation of Cd in sweet potatoes by regulating the expression of genes associated with Cd transporters and root cell wall components.

Cadmium tolerance and hyperaccumulation in plants - A proteomic perspective of phytoremediation.

Cadmium (Cd) is a major environmental pollutant and poses a risk of transfer into the food chain through contaminated plants. Mechanisms underlying Cd tolerance and hyperaccumulation in plants are not fully understood. Proteomics-based approaches facilitate an in-depth understanding of plant responses to Cd stress at the systemic level by identifying Cd-inducible differentially abundant proteins (DAPs). In this review, we summarize studies related to proteomic changes associated with Cd-tolerance mechanisms in Cd-tolerant crops and Cd-hyperaccumulating plants, especially the similarities and differences across plant species. The enhanced DAPs identified through proteomic studies can be potential targets for developing Cd-hyperaccumulators to remediate Cd-contaminated environments and Cd-tolerant crops with low Cd content in the edible organs. This is of great significance for ensuring the food security of an exponentially growing global population. Finally, we discuss the methodological drawbacks in current proteomic studies and propose that better protocols and advanced techniques should be utilized to further strengthen the reliability and applicability of future Cd-stress-related studies in plants. This review provides insights into the improvement of phytoremediation efficiency and an in-depth study of the molecular mechanisms of Cd enrichment in plants.

Integrated physiological and omics analyses reveal the mechanism of beneficial fungal Trichoderma sp. alleviating cadmium toxicity in tobacco (Nicotiana tabacum L.).

Cadmium (Cd) is a highly toxic heavy metal and readily accumulates in tobacco, which imperils public health via Cd exposure from smoking. Beneficial microbes have a pivotal role in promoting plant growth, especially under environmental stresses such as heavy metal stresses. In this study, we introduced a novel fungal strain Trichoderma nigricans T32781, and investigated its capacity to alleviate Cd-induced stress in tobacco plants through comprehensive physiological and omics analyses. Our findings revealed that T32781 inoculation in soil leads to a substantial reduction in Cd-induced growth inhibition. This was evidenced by increased plant height, enhanced biomass accumulation, and improved photosynthesis, as indicated by higher values of key photosynthetic parameters, including the maximum quantum yield of photosystem Ⅱ (Fv/Fm), stomatal conductance (Gs), photosynthetic rate (Pn) and transpiration rate (Tr). Furthermore, element analysis demonstrated that T. nigricans T32781 inoculation resulted in a remarkable reduction of Cd uptake by 62.2% and a 37.8% decrease in available soil Cd compared to Cd-stressed plants without inoculation. The protective role of T32781 extended to mitigating Cd-induced oxidative stress by improving antioxidant enzyme activities of superoxide dismutase (SOD), peroxidase (POD), and ascorbate peroxidase (APX). Metabolic profiling of tobacco roots identified 43 key metabolites, with notable contributions from compounds like nicotinic acid, succinic acid, and fumaric acid in reducing Cd toxicity in T32781-inoculated plants. Additionally, rhizosphere microbiome analysis highlighted the promotion of beneficial microbes, including Gemmatimonas and Sphingomonas, by T32781 inoculation, which potentially contributed to the restoration of plant growth under Cd exposure. In summary, our study demonstrated that T. nigricans T32781 effectively alleviated Cd stress in tobacco plants by reducing Cd uptake, alleviating Cd-induced oxidative stress, influencing plant metabolite and modulating the microbial composition in the rhizosphere. These findings offer a novel perspective and a promising candidate strain for enhancing Cd tolerance and prohibiting its accumulation in plants to reduce health risks associated with exposure to Cd-contaminated plants.

Sly-miR398 Participates in Cadmium Stress Acclimation by Regulating Antioxidant System and Cadmium Transport in Tomato (Solanum lycopersicum).

Cadmium (Cd) pollution is one of the major threats in agricultural production, and can cause oxidative damage and growth limitation in plants. MicroRNA398 (miR398) is involved in plant resistance to different stresses, and the post-transcriptional regulation of miR398 on CSDs plays a key role. Here, we report that miR398 was down-regulated in tomato in response to Cd stress. Simultaneously, CSD1 and SOD were up-regulated, with CSD2 unchanged, suggesting CSD1 is involved in miR398-induced regulation under Cd stress. In addition, the role of miR398 in Cd tolerance in tomato was evaluated using a transgenic line overexpressing MIR398 (miR398#OE) in which the down-expression of miR398 was disrupted. The results showed that Cd stress induced more significant growth inhibition, oxidative damage, and antioxidant enzymes disorder in miR398#OE than that in wild type (WT). Moreover, higher Cd concentration in the shoot and xylem sap, and net Cd influx rate, were observed in miR398#OE, which could be due to the increased Cd uptake genes (IRT1, IRT2, and NRAMP2) and decreased Cd compartmentalization gene HMA3. Overall, our results indicate that down-regulated miR398 plays a protective role in tomato against Cd stress by modulating the activity of antioxidant enzymes and Cd uptake and translocation.

Co-application of TiO2 nanoparticles and hyperaccumulator Brassica juncea L. for effective Cd removal from soil: Assessing the feasibility of using nano-phytoremediation.

Nano-phytoremediation is anticipated as a potential technology for the remediation of heavy metals from soil sites. This study evaluated the feasibility of using titanium dioxide nanoparticles (TiO2 NPs) at various concentrations (0, 100, 250, 500 mg/kg) along with a hyperaccumulator, Brassica juncea L., for effective removal of Cadmium (Cd) from the soil. Plants were grown for a whole life cycle in soil containing 10 mg/kg of Cd and spiked TiO2 NPs. We analyzed the plants for Cd tolerance, phytotoxicity, Cd removal, and translocation. Brassica plants displayed high Cd tolerance with a significant increase in plant growth, biomass, and photosynthetic activity in a concentration-dependent manner. Cd removal from the soil at TiO2 NPs concentrations of 0, 100, 250, and 500 mg/kg treatment was 32.46%, 11.62%, 17.55%, and 55.11%, respectively. The translocation factor for Cd was found to be 1.35, 0.96, 3.73, and 1.27 for 0, 100, 250, and 500 mg/kg concentrations. The results of this study indicate that TiO2 NPs applications in the soil can minimize Cd stress in plants and lead to its efficient removal from soil. Thus, the association of nanoparticles with the phytoremediation process can lead to good application prospects for the remediation of contaminated soil.

Soil properties drive the bacterial community to cadmium contamination in the rhizosphere of two contrasting wheat (Triticum aestivum L.) genotypes.

Cadmium (Cd) bioavailability in the rhizosphere makes an important difference in grain Cd accumulation in wheat. Here, pot experiments combined with 16S rRNA gene sequencing were conducted to compare the Cd bioavailability and bacterial community in the rhizosphere of two wheat (Triticum aestivum L.) genotypes, a low-Cd-accumulating genotype in grains (LT) and a high-Cd-accumulating genotype in grains (HT), grown on four different soils with Cd contamination. Results showed that there was non-significant difference in total Cd concentration among four soils. However, except for black soil, DTPA-Cd concentrations in HT rhizospheres were higher than those of LT in fluvisol, paddy soil and purple soil. Results of 16S rRNA gene sequencing showed that soil type (52.7%) was the strongest determinant of root-associated community, while there were still some differences in rhizosphere bacterial community composition between two wheat genotypes. Taxa specifically colonized in HT rhizosphere (Acidobacteria, Gemmatimonadetes, Bacteroidetes and Deltaproteobacteria) could participate in metal activation, whereas LT rhizosphere was highly enriched by plant growth-promoting taxa. In addition, PICRUSt2 analysis also predicted high relative abundances of imputed functional profiles related to membrane transport and amino acid metabolism in HT rhizosphere. These results revealed that the rhizosphere bacterial community may be an important factor regulating Cd uptake and accumulation in wheat and indicated that the high Cd-accumulating cultivar might improve Cd bioavailability in the rhizosphere by recruiting taxa related to Cd activation, thus promoting Cd uptake and accumulation.

Selenium attenuates the cadmium-induced placenta glucocorticoid barrier damage by up-regulating the expression of specificity protein 1.

Cadmium (Cd) is an environmental pollutant and pregnant women are especially susceptible to the effects of exposure to Cd. Our previous study found Cd can be accumulated in the placenta and causes fetal growth restriction (FGR) through damage the placental glucocorticoid barrier. Selenium (Se), as an essential micronutrient, can allivate Cd-induced toxicity. In this study, we aim to explore the protective mechanism of Se against Cd-induced the placental glucocorticoid barrier damage and FGR. Pregnant Sprague Dawley (SD) rats were exposed to CdCl2 (1 mg/kg/day) and Na2 SeO3 (0.1-0.2-0.3 mg/kg/day) by gavage from gestational day (GD) 0 to GD 19. The results showed that reduced fetal weight, increased corticosterone concentrations in the maternal and fetal serum, and impaired placental labyrinth layer blood vessel development, appeared in pregnant rats after Cd exposure and improved after treated with Se. In cell experiments, we confirmed that Se reduces Cd-induced apoptosis. Moreover, Se can abolish Cd-induced 11ß-HSD2 and specificity protein 1 (Sp1) decreasing in vivo and vitro. In human JEG-3 cells, the knockdown of Sp1 expression by small interfering RNA can suppressed the protective effect of Se on Cd-induced 11ß-HSD2 decreasing. In general, our results demonstrated that Se is resistant to Cd-induced FGR through upregulating the placenta barrier via activation of the transcription factor Sp1.

Identification of a plant endophytic growth-promoting bacteria capable of inhibiting cadmium uptake in rice.

AIMS: The study aims to identify a novel plant growth-promoting bacteria (PGPB), which contributes to promoting growth and reducing cadmium (Cd) concentration in rice under Cd-contaminated conditions. METHODS AND RESULTS: Nine bacterial strains were isolated from plants grown in Cd-contaminated soil. These bacteria were tolerant to 1000 µmol/L CdCl2 , capable of producing indole-3-acetic acid, fixing nitrogen and solubilizing phosphate. The result of hydroponic experiment showed that under the control and Cd stress conditions, the dry weight of the Tm02-inoculated rice seedlings increased significantly. Furthermore, under Cd stress, the concentration of Cd in the shoot of the Tm02-inoculated seedlings decreased significantly, while there was no significant difference in Cd concentration between treatment with other eight strains and noninoculated seedlings. The same results were observed in the pot experiment as well, where there was a significantly reduced Cd concentration in rice grains of the Tm02-inoculated rice plants. Tm02 was classified as Pantoea agglomerans through 16S rDNA sequencing. CONCLUSIONS: A novel PGPB strain Tm02 was identified and confirmed that it has the function of promoting rice growth and reducing Cd concentration in rice grain under Cd-contaminated conditions. This strain has the potential to improve rice yield in Cd-contaminated paddy fields. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides a new example of using PGPB to improve the tolerance of rice to Cd pollution.

Increased incidence of spontaneous abortions on exposure to cadmium and lead: a systematic review and meta-analysis.

BACKGROUND: Spontaneous abortions are the most severe complication of early pregnancy and are a major reproductive health problem. Although this could be caused due to various cytogenetic, immunological, or endocrinological reasons, role of environmental toxicants cannot be ruled out. In order to explore the role of cadmium and lead in causing spontaneous abortions, current systematic review and meta-analysis had been carried out. METHODOLOGY: Literature search was performed using appropriate keywords in PubMed, Science Direct, Cochrane Library, and Google Scholar databases up to December 25 2020 according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines (PRISMA). Metananalysis was carried out with the help of RevMan software (version 5.3). RESULTS: Meta-analysis of nine studies on cadmium concentrations in blood of women with at least one spontaneous abortions and controls revealed standardized mean difference (SMD)=3.39, 95% CI (2.17, 4.61), with p < .05. Similarly, meta-analysis of eight studies on lead concentrations revealed standardized mean difference (SMD)=6.24, 95% CI (4.34, 8.14), with p < .05. CONCLUSION: Populations exposed to heavy metals such as cadmium and lead are at higher risk of pregnancy loss. Therefore, couples experiencing repeated pregnancy losses may be screened for heavy metal load.

Up-flow anaerobic column reactor for sulfate-rich cadmium-bearing wastewater purification: system performance, removal mechanism and microbial community structure.

This study constructed an up-flow anaerobic column reactor fed with synthetic sulfate-rich cadmium (Cd(II))-bearing wastewater, for investigating its Cd(II) removal performance and mechanism. Long-term experiment results manifest that introducing Cd(II) into influent led to an enhanced sulfate removal but did not increase the effluent sulfide concentration, implying the CdS formation. When influent Cd(II) concentration was shifted from 50 to 100 mg/L, the median Cd(II) removal rate was increased from 13.6 to 32.2 mg/(L·d). Batch tests indicate that the uptake and sequestration function of anaerobes merely led to a small portion of Cd(II) removal. A majority of aqueous Cd(II) (86.3%) was eliminated by precipitation reactions. The generated precipitates were found to be dominantly presented in carbonate, Fe-Mn oxide, sulfide bound and residue forms, which account for 92.6-93.9% of total Cd content of sludge obtained at diverse operation phases. The crystallographic CdS (i.e., residue fraction) particles have nano-scale sizes, and the relatively high atomic ratio of S to Cd was likely due to the adsorption/deposition of other sulfides. The dominant sulfate-reducing bacteria (SRB) were recognized as Desulfurella, Desulforhabdus and Desulfovibrio, and the primary competitor with them for substrate utilization were identified to be methanogens.

Wnt/ß-Catenin Signaling Pathway Is Strongly Implicated in Cadmium-Induced Developmental Neurotoxicity and Neuroinflammation: Clues from Zebrafish Neurobehavior and In Vivo Neuroimaging.

Cadmium (Cd) is a toxic heavy metal and worldwide environmental pollutant which seriously threatens human health and ecosystems. It is easy to be adsorbed and deposited in organisms, exerting adverse effects on various organs including the brain. In a very recent study, making full use of a zebrafish model in both high-throughput behavioral tracking and live neuroimaging, we explored the potential developmental neurotoxicity of Cd2+ at environmentally relevant levels and identified multiple connections between Cd2+ exposure and neurodevelopmental disorders as well as microglia-mediated neuroinflammation, whereas the underlying neurotoxic mechanisms remained unclear. The canonical Wnt/ß-catenin signaling pathway plays crucial roles in many biological processes including neurodevelopment, cell survival, and cell cycle regulation, as well as microglial activation, thereby potentially presenting one of the key targets of Cd2+ neurotoxicity. Therefore, in this follow-up study, we investigated the implication of the Wnt/ß-catenin signaling pathway in Cd2+-induced developmental disorders and neuroinflammation and revealed that environmental Cd2+ exposure significantly affected the expression of key factors in the zebrafish Wnt/ß-catenin signaling pathway. In addition, pharmacological intervention of this pathway via TWS119, which can increase the protein level of ß-catenin and act as a classical activator of the Wnt signaling pathway, could significantly repress the Cd2+-induced cell cycle arrest and apoptosis, thereby attenuating the inhibitory effects of Cd2+ on the early development, behavior, and activity, as well as neurodevelopment of zebrafish larvae to a certain degree. Furthermore, activation and proliferation of microglia, as well as the altered expression profiles of genes associated with neuroimmune homeostasis triggered by Cd2+ exposure could also be significantly alleviated by the activation of the Wnt/ß-catenin signaling pathway. Thus, this study provided novel insights into the cellular and molecular mechanisms of Cd2+ toxicity on the vertebrate central nervous system (CNS), which might be helpful in developing pharmacotherapies to mitigate the neurological disorders resulting from exposure to Cd2+ and many other environmental heavy metals.

Mechanisms of Cd-Induced Cytotoxicity in Normal Human Skin Keratinocytes: Implication for Human Health.

Cadmium (Cd) is one of the toxic heavy metals found widely in the environment. Skin is an important target organ of Cd exposure. However, the adverse effects of Cd on human skin are still not well known. In this study, normal human skin keratinocytes (HaCaT cells) were studied for changes in cell viability, morphology, DNA damage, cycle, apoptosis, and the expression of endoplasmic reticulum (ER) stress-related genes (XBP-1, BiP, ATF-4, and CHOP) after exposure to Cd for 24 h. We found that Cd decreased cell viability in a concentration-dependent manner, with a median lethal concentration (LC50) of 11 µM. DNA damage induction was evidenced by upregulation of the level of γ-H2AX. Furthermore, Cd induced G0/G1 phase cell cycle arrest and apoptosis in a dose-dependent manner and upregulated the mRNA levels of ER stress biomarker genes (XBP-1, BiP, ATF4, and CHOP). Taken together, our results showed that Cd induced cytotoxicity and DNA damage in HaCaT cells, eventually resulting in cell cycle arrest in the G0/G1 phase and apoptosis. In addition, ER stress may be involved in Cd-induced HaCaT apoptosis. Our data imply the importance of reducing Cd pollution in the environment to reduce its adverse impacts on human skin.

A porous biochar supported nanoscale zero-valent iron material highly efficient for the simultaneous remediation of cadmium and lead contaminated soil.

Risk associated with heavy metals in soil has been received widespread attention. In this study, a porous biochar supported nanoscale zero-valent iron (BC-nZVI) was applied to immobilize cadmium (Cd) and lead (Pb) in clayey soil. Experiment results indicated that the immobilization of Cd or Pb by BC-nZVI process was better than that of BC or nZVI process, and about 80% of heavy metals immobilization was obtained in BC-nZVI process. Addition of BC-nZVI could increase soil pH and organic matter (SOM). Cd or Pb immobilization was inhibited with coexisting organic compound 2,4-dichlorophenol (2,4-DCP), but 2,4-DCP could be removed in a simultaneous manner with Cd or Pb immobilization at low concentration levels. Simultaneous immobilization of Cd and Pb was achieved in BC-nZVI process, and both Cd and Pb availability significantly decreased. Stable Cd species inculding Cd(OH)2, CdCO3 and CdO were formed, whereas stable Pb species such as PbCO3, PbO and Pb(OH)2 were produced with BC-nZVI treatment. Simultaneous immobilization mechanism of Cd and Pb in soil by BC-nZVI was thereby proposed. This study well demonstrates that BC-nZVI has been emerged as a potential technology for the remediation of multiple heavy metals in soil.

A path toward concurrent biofortification and cadmium mitigation in plant-based foods.

Millions of people are anemic due to inadequate consumption of foods rich in iron and zinc. Plant-based foods provide most of our dietary nutrients but may also contain the toxic heavy metal cadmium (Cd). A low level of Cd silently enters the body through the diet. Once ingested, Cd may remain for decades. Hence, prolonged intake of Cd-containing foods endangers human health. Research that leads towards micronutrient enrichment and mitigation of Cd in foods has therefore dual significance for human health. The breeding of Cd-tolerant cultivars may enable them to grow on Cd-polluted soils; however, they may not yield Cd-free foods. Conversely, sequestration of Cd in roots can prevent its accumulation in grains, but this mechanism also retains nutrients, hence counteracting biofortification efforts. A specific restriction of the Cd absorption capacity of crops would prevent Cd entry into the plant system while maintaining micronutrient accumulation and may thus be a solution to the dilemma. After recapitulating existing strategies employed for the development of Cd-tolerant and biofortified cultivars, this Viewpoint elaborates alternative approaches based on directed evolution and genome editing strategies for excluding Cd while enriching micronutrients in plant foods, which will concurrently help to eradicate malnutrition and prevent Cd intoxication.