Assessment of the mode of action for hexavalent chromium-induced lung cancer following inhalation exposures

A whale of a tale: whale cells evade the driving mechanism for hexavalent chromium-induced chromosome instability

Chromosome instability, a hallmark of lung cancer, is a driving mechanism for hexavalent chromium [Cr(VI)] carcinogenesis in humans. Cr(VI) induces structural and numerical chromosome instability in human lung cells by inducing DNA double-strand breaks and inhibiting homologous recombination repair and causing spindle assembly checkpoint (SAC) bypass and centrosome amplification. Great whales are long-lived species with long-term exposures to Cr(VI) and accumulate Cr in their tissue, but exhibit a low incidence of cancer. Data show Cr(VI) induces fewer chromosome aberrations in whale cells after acute Cr(VI) exposure suggesting whale cells can evade Cr(VI)-induced chromosome instability. However, it is unknown if whales can evade Cr(VI)-induced chromosome instability. Thus, we tested the hypothesis that whale cells resist Cr(VI)-induced loss of homologous recombination repair activity and increased SAC bypass and centrosome amplification. We found Cr(VI) induces similar amounts of DNA double-strand breaks after acute (24 h) and prolonged (120 h) exposures in whale lung cells, but does not inhibit homologous recombination repair, SAC bypass, or centrosome amplification, and does not induce chromosome instability. These data indicate whale lung cells resist Cr(VI)-induced chromosome instability, the major driver for Cr(VI) carcinogenesis at a cellular level, consistent with observations that whales are resistant to cancer.

Prolonged Particulate Hexavalent Chromium Exposure Induces DNA Double-Strand Breaks and Inhibits Homologous Recombination Repair in Primary Rodent Lung Cells

Hexavalent chromium [Cr(VI)] is a known lung carcinogen and a driving mechanism in human lung cells for Cr(VI)-induced lung cancer is chromosome instability, caused by prolonged Cr(VI) exposure inducing DNA double-strand breaks, while simultaneously inhibiting the repair of these breaks. In North Atlantic right whales, Cr(VI) induces breaks but does not inhibit repair. It is unclear if this repair inhibition is specific to human lung cells or occurs in other species, as it has only been considered in humans and North Atlantic right whales. We evaluated these outcomes in rodent cells, as rodents are an experimental model for metal-induced lung carcinogenesis. We used a guinea pig lung fibroblast cell line, JH4 Clone 1, and rat lung fibroblasts. Cells were exposed to two different particulate Cr(VI) compounds, ranging from 0 to 0.5 ug/cm2, for 24 or 120 h and assessed for cytotoxicity, DNA double-strand breaks, and DNA double-strand break repair. Both particulate Cr(VI) compounds induced a concentration-dependent increase in cytotoxicity and DNA double-strand breaks after acute and prolonged exposures. Notably, while the repair of Cr(VI)-induced DNA double-strand breaks increased after acute exposure, the repair of these breaks was inhibited after prolonged exposure. These results are consistent with outcomes in human lung cells indicating rodent cells respond like human cells, while whale cells have a markedly different response.

Polymerized PEI-modified lignin polyphenolic materials by acid hydrolysis-phase separation for removal of Cr (VI) from industrial wastewater

Cr (VI) accumulates in an aqueous environment and exhibits huge harm to human health and the ecological system. Developed lignin biomass materials are complicated to prepare and have limited properties, and advances in lignin phenolic modification are lacking. Herein, an aminated poplar lignin-pyrogallol (PLP-PEI) with a simple design and adjustable phenolic hydroxyl content was developed using the acid hydrolysis-phase separation (AH-PS) method, and modified by the atom transfer radical polymerization (ATRP) strategy. Through diverse characterization analysis, the structural changes of PLP-PEI in the step-by-step synthesis process were monitored. An effective biomass capture system (Bio-Cap) was shown via systematically investigating the adsorption behaviors of Cr (VI) on PLP-PEI under various environmental conditions. Benefiting from introducing phenolic hydroxyl and amino groups, PLP-PEI demonstrated efficient adsorption capacity (598.80 mg/g for Cr (VI)). Additionally, the material also exhibited advantages, including monomeric chemisorption properties, strong reduction capability, and stable regeneration properties. Multiple driving forces were involved in the capture and removal process of Cr (VI), including complexation and electrostatic interaction. The low-cost natural biomass resources supported the industrial-scale synthesis and practical application of advanced aminated lignin polyphenol material, which showed outstanding advantages and enormous potential in the field of water environmental restoration.

Hexavalent Chromium Targets Securin to Drive Numerical Chromosome Instability in Human Lung Cells

Hexavalent chromium [Cr(VI)] is a known human lung carcinogen with widespread exposure in environmental and occupational settings. Despite well-known cancer risks, the molecular mechanisms of Cr(VI)-induced carcinogenesis are not well understood, but a major driver of Cr(VI) carcinogenesis is chromosome instability. Previously, we reported Cr(VI) induced numerical chromosome instability, premature centriole disengagement, centrosome amplification, premature centromere division, and spindle assembly checkpoint bypass. A key regulator of these events is securin, which acts by regulating the cleavage ability of separase. Thus, in this study we investigated securin disruption by Cr(VI) exposure. We exposed human lung cells to a particulate Cr(VI) compound, zinc chromate, for acute (24 h) and prolonged (120 h) time points. We found prolonged Cr(VI) exposure caused marked decrease in securin levels and function. After prolonged exposure at the highest concentration, securin protein levels were decreased to 15.3% of control cells, while securin mRNA quantification was 7.9% relative to control cells. Additionally, loss of securin function led to increased separase activity manifested as enhanced cleavage of separase substrates; separase, kendrin, and SCC1. These data show securin is targeted by prolonged Cr(VI) exposure in human lung cells. Thus, a new mechanistic model for Cr(VI)-induced carcinogenesis emerges with centrosome and centromere disruption as key components of numerical chromosome instability, a key driver in Cr(VI) carcinogenesis.

A comprehensive review on environmental pollutants and osteoporosis: Insights into molecular pathways

A significant problem that has an impact on community wellbeing is environmental pollution. Environmental pollution due to air, water, or soil pollutants might pose a severe risk to global health, necessitating intense scientific effort. Osteoporosis is a common chronic condition with substantial clinical implications on mortality, morbidity, and quality of life. It is closely linked to bone fractures. Worldwide, osteoporosis affects around 200 million people, and every year, there are almost 9 million fractures. There is evidence that certain environmental factors may increase the risk of osteoporosis in addition to traditional risk factors. It is crucial to understand the molecular mechanisms at play because there is a connection between osteoporosis and exposure to environmental pollutants such as heavy metals, air pollutants, endocrine disruptors, metal ions and trace elements. Hence, in this scoping review, we explore potential explanations for the link between pollutants and bone deterioration through deep insights into molecular pathways. Understanding and recognizing these pollutants as modifiable risk factors for osteoporosis would possibly help to enhance environmental policy thereby aiding in the improvement of bone health and improving patient quality of life.

Prolonged particulate hexavalent chromium exposure induces RAD51 foci inhibition and cytoplasmic accumulation in immortalized and primary human lung bronchial epithelial cells

Hexavalent chromium [Cr(VI)] is a human lung carcinogen with widespread exposure risks. Cr(VI) causes DNA double strand breaks that if unrepaired, progress into chromosomal instability (CIN), a key driving outcome in Cr(VI)-induced tumors. The ability of Cr(VI) to cause DNA breaks and inhibit repair is poorly understood in human lung epithelial cells, which are extremely relevant since pathology data show Cr(VI)-induced tumors originate from bronchial epithelial cells. In the present study, we considered immortalized and primary human bronchial epithelial cells. Cells were treated with zinc chromate at concentrations ranging 0.05 to 0.4μg/cm2 for acute (24 h) and prolonged (120 h) exposures. DNA double strand breaks (DSBs) were measured by neutral comet assay and the status of homologous recombination repair, the main pathway to fix Cr(VI)-induced DSBs, was measured by RAD51 foci formation with immunofluorescence, RAD51 localization with confocal microscopy and sister chromatid exchanges. We found acute and prolonged Cr(VI) exposure induced DSBs. Acute exposure induced homologous recombination repair, but prolonged exposure inhibited it resulting in chromosome instability in immortalized and primary human bronchial epithelial cells.

Highly compressible and macro-porous hydrogels via the synergy of cryogelation and double-network for efficient removal of Cr(VI)

Mechanically robust and macro-porous hydrogels are urgently required for the dynamic removal of heavy metals in wastewater purification field. Herein, a novel microfibrillated cellulose/polyethyleneimine hydrogel (MFC/PEI-CD) with high compressibility and macro-porous structures was fabricated via the synergy of cryogelation and double-network for Cr(VI) adsorption from wastewater. MFCs were pre-cross-linked by bis(vinyl sulfonyl)methane (BVSM) and then formed double-network hydrogels with PEIs and glutaraldehyde below freezing. The SEM showed that the MFC/PEI-CD possessed interconnected macropores with an average pore diameter of 52 μm. Mechanical tests indicated a high compressive stress of 116.4 kPa at 80 % strain, which was 4 times higher than the corresponding MFC/PEI with a single-network. The Cr(VI) adsorption performance of MFC/PEI-CDs was systematically investigated under different parameters. Kinetic studies indicated that the adsorption process was well described by the pseudo-second-order model. Isothermal adsorption behaviors accorded well with Langmuir model with the maximum adsorption capacity of 545.1 mg/g, which was superior to most adsorption materials. More importantly, the MFC/PEI-CD was applied to dynamically adsorb Cr(VI) with the treatment volume of 2070 mL/g. Therefore, this work demonstrates that the synergy of cryogelation and double-network is a novel method for preparing macro-porous and robust materials with promising heavy metal removal from wastewater.

Hexavalent chromium induces γH2AX and RAD51 involved in DNA damage repair in BEAS-2B cells by modulating LNC-DHFR-4:1

Hexavalent chromium [Cr(VI)] is rarely found in nature. Its occurrence in the environment is mainly due to anthropogenic sources. Our previous studies have shown that Cr(VI) exposure could change the expression profile of long noncoding RNAs (lncRNAs). However, the relationship between lncRNAs and genetic damage induced by Cr(VI) remains unclear. In this study, RT-qPCR was used to verify the expression of genes and lncRNAs involved in DNA damage repair in BEAS-2B cells exposed to different Cr(VI) concentrations. After screening out LNC-DHFR-4:1, overexpression and knockdown models of BEAS-2B cells were used to further identify the relationship between the lncRNA and RAD51. RT-qPCR and indirect immunofluorescence were used to detect expression. Our results revealed that with increasing Cr(VI) concentration, γH2AX expression was increased, while the expression of RAD51 was decreased. Meanwhile, LNC-DHFR-4:1 acted as a competitive endogenous RNA to regulate the expression of γH2AX and RAD51, which further affected DNA damage repair. The overexpression of LNC-DHFR-4:1 induced a twofold decrease in γH2AX and a onefold increase in RAD51, and its knockdown showed the opposite results. These results suggested that LNC-DHFR-4:1 might be a potential biomarker of Cr(VI)-induced DNA damage repair in BEAS-2B cells.

Occupational exposure to nickel and hexavalent chromium and the risk of lung cancer in a pooled analysis of case-control studies (SYNERGY)

There is limited evidence regarding the exposure-effect relationship between lung-cancer risk and hexavalent chromium (Cr(VI)) or nickel. We estimated lung-cancer risks in relation to quantitative indices of occupational exposure to Cr(VI) and nickel and their interaction with smoking habits. We pooled 14 case-control studies from Europe and Canada, including 16 901 lung-cancer cases and 20 965 control subjects. A measurement-based job-exposure-matrix estimated job-year-region specific exposure levels to Cr(VI) and nickel, which were linked to the subjects' occupational histories. Odds ratios (OR) and associated 95% confidence intervals (CI) were calculated by unconditional logistic regression, adjusting for study, age group, smoking habits and exposure to other occupational lung carcinogens. Due to their high correlation, we refrained from mutually adjusting for Cr(VI) and nickel independently. In men, ORs for the highest quartile of cumulative exposure to CR(VI) were 1.32 (95% CI 1.19-1.47) and 1.29 (95% CI 1.15-1.45) in relation to nickel. Analogous results among women were: 1.04 (95% CI 0.48-2.24) and 1.29 (95% CI 0.60-2.86), respectively. In men, excess lung-cancer risks due to occupational Cr(VI) and nickel exposure were also observed in each stratum of never, former and current smokers. Joint effects of Cr(VI) and nickel with smoking were in general greater than additive, but not different from multiplicative. In summary, relatively low cumulative levels of occupational exposure to Cr(VI) and nickel were associated with increased ORs for lung cancer, particularly in men. However, we cannot rule out a combined classical measurement and Berkson-type of error structure, which may cause differential bias of risk estimates.

Effect of Gene 33/Mig6/ERRFI1 on hexavalent chromium-induced transformation of human bronchial epithelial cells depends on the length of exposure

Hexavalent chromium (Cr(VI)) compounds are environmental and occupational lung carcinogens. The present study followed the chronic effect of Cr(VI) on the neoplastic transformation of BEAS-2B lung bronchial epithelial cells with or without deletion of Gene 33 (Mig6, EFFRI1), a multifunctional adaptor protein. We find that Gene 33-deleted cells exhibit increased anchorage-independent growth compared to control cells after transformed by 8-week but not 24-week Cr(VI) exposure. Gene 33-deleted cells show a higher level of cell proliferation and are more resistant to acute Cr(VI) toxicity compared to control cells after transformed by 8-week but not 24-week Cr(VI) exposure, despite that 24-week-transformed cells have increased resistance to acute Cr(VI) toxicity. However, Gene 33-deleted cells show increased migration after transformed by both 8-week and 24-week Cr(VI) exposures. Furthermore, only cells transformed by 24 weeks of Cr(VI) exposure can form subcutaneous tumors in nude mice. Although no significant difference in the size of tumors formed by the two cell types, there is a marked difference in the histological manifestation and more MMP3 expression in tumors from Gene 33-deleted cells. Our results demonstrate progressive neoplastic transformation of BEAS-2B cells and the adaptation of these cells to Gene 33 deletion during chronic exposure to Cr(VI).

Removal of As(V) and Cr(VI) with Low-Cost Novel Virgin and Iron-Impregnated Banana Peduncle-Activated Carbons

This work reports the investigation of activated carbons from virgin banana peduncle (ZR1) and iron-impregnated banana peduncle (ZR2) as adsorbents for the removal of As(V) and Cr(VI) ions from aqueous solutions. Both adsorbents were characterized through the point of zero charge, powder X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray, Brunauer-Emmett-Teller, and Fourier transform infrared spectroscopic techniques. The effects of initial pH, contact time, temperature, and initial concentration on metal ion adsorption were investigated. Adsorbents existed as both crystalline and amorphous species having homogeneous surface cavities and surface area of 749.73 and 369.66 m²/g for ZR1 and ZR2, respectively. The maximum As(V) removal of 79.32 and 69.08% was obtained using ZR1 and ZR2, respectively, whereas the maximum Cr(VI) removal was calculated as 69.73% for ZR1 and 73.78% for ZR2. Kinetic modeling data were found to be best fitted for the pseudo-second-order reaction, and rate constants were calculated. The theoretical adsorption capacities (q _m) of ZR1 and ZR2 were calculated through Langmuir and Freundlich models. The maximum As(V) adsorption capacities calculated for ZR1 and ZR2 were 13.33 and 9.066 mg/g, respectively, whereas the maximum Cr(VI) adsorption capacity for both was 13.26 mg/g at 298-328 K. The reaction was endothermic with decreased randomness at the solid-liquid interface due to positive entropy and enthalpy values. All kinetic and thermodynamic parameters showed the feasibility of the adsorption process, and characterization after adsorption indicated ZR1 and ZR2 novel activated carbons as efficient and cheapest biosorbents for removing As(V) and Cr(VI).

Biosorption and bioreduction of aqueous chromium (VI) by different Spirulina strains

Spirulina has emerged as a promising microorganism for the treatment of industrial heavy metal ions in wastewater due to their simplicity of cultivation and harvesting, rich functional binding groups, and high bioreductive activity during the uptake process. While the capacities of biosorption and bioreduction for heavy metal ions differ significantly among various algal strains. Therefore, the physiological characteristics were investigated to identify the different Spirulina strains, and the chromium (VI) adsorption capacities of the algal strains were also evaluated. In this study, it was found that algal strains YCX2643 and CLQ1848 performed higher removal efficiency (86.5% and 83.7%) than the other four Spirulina strains (59.4%, 56.3%, 65.6%, and 66.5%, respectively). Moreover, the mechanisms of chromium (VI) ions binding and biotransformation in the Spirulina cell were scrutinized by FTIR (Fourier transform infrared) spectroscopy and scanning electron microscopy (SEM), and it indicated that the varieties of cellular components involved in high binding affinity may cause the higher biosorption and bioreduction of aqueous chromium (VI) in algal strains YCX2643 and CLQ1848, which could be used as promising biosorbents in the removing heavy metal pollutants from wastewaters.

Association of environmental exposure to chromium with differential DNA methylation: An epigenome-wide study

Introduction: Previous studies have reported that chromium (Cr)-induced epigenetic alterations and DNA methylation play a vital role in the pathogenesis of diseases induced by chromium exposure. Epigenomic analyses have been limited and mainly focused on occupational chromium exposure; their findings are not generalizable to populations with environmental Cr exposure. Methods: We identified the differential methylation of genes and regions to elucidate the mechanisms of toxicity related to environmental chromium exposure. DNA methylation was measured in blood samples collected from individuals in Cr-contaminated (n = 10) and unexposed areas (n = 10) by using the Illumina Infinium HumanMethylation850K array. To evaluate the relationship between chromium levels in urine and CpG methylation at 850 thousand sites, we investigated differentially methylated positions (DMPs) and differentially methylated regions (DMRs) by using linear models and DMRcate method, respectively. The model was adjusted for biologically relevant variables and estimated cell-type compositions. Results: At the epigenome-wide level, we identified five CpGs [cg20690919 (p _{FDR =}0.006), cg00704664 (p _{FDR =}0.024), cg10809143 (p _{FDR =}0.043), cg27057652 (p _{FDR =}0.047), cg05390480 (p _{FDR =}0.024)] and one DMR (chr17: 19,648,718-19,648,972), annotated to ALDH3A1 genes (p < 0.05) as being significantly associated with log₂ transformed urinary chromium levels. Discussion: Environmental chromium exposure is associated with DNA methylation, and the significant DMPs and DMR being annotated to cause DNA damage and genomic instability were found in this work. Research involving larger samples is required to further explore the epigenetic effect of environmental chromium exposure on health outcomes through DNA methylation.

Quercetin protects mouse oocytes against chromium-induced damage in vitro and in vivo

BACKGROUND

Chromium (Cr) is a naturally-occurring element that is used in various fields of industry. Humans may be exposed to hexavalent chromium [Cr(VI)], which is one of the stable valence states of the chromium through contaminated soil, air, and water. Exposure to Cr(VI) through contaminated drinking water, soil and air causes various cancers and also fertility problems in animals and humans. Quercetin (QCT), a common flavonoid compound, has numerous biological effects as an antioxidant and free radical scavenger, but its function and mechanisms in reproductive processes in various species remain unclear. This study aims to determine the chromium effects on mice oocyte quality and the ameliorative effect of QCT in both in vitro and in vivo experimental models.

METHODS

For the in vitro experiment, oocytes were collected and divided into the control, sham, QCT-treated, Cr(VI) (potassium dichromate), and treatment [Cr(VI)+QCT] groups. Collected oocytes were cultured in maturation medium with or without 10 µM quercetin and 10 µM Cr(VI) for 14 h based on the defined experimental design. For the in vivo experiment, the mice were randomly divided into the control, sham, QCT-treated, Cr(VI), and Cr(VI) + QCT groups. Control and sham mice received regular drinking water and diet. Cr(VI) group received Cr(VI) (50 ppm in drinking water) and Cr(VI) + QCT group received 50 ppm Cr(VI) with QCT (20 mg/kg body wt, through i.p) for a period of 21 days and then oocytes were collected and cultured for 14 h for in vitro maturation. For both experiments, at the end of the culture period, we examined the ameliorative effect of QCT on oocyte maturation, spindle formation, ROS production, mitochondrial function, and apoptosis.

RESULTS

Our in vitro and in vivo results showed that Cr(VI) disrupt the oocyte maturation and spindle formation (P < 0.001). Furthermore, we found that exposure to Cr(VI) significantly increased ROS levels and decreased mitochondrial membrane potential (P < 0.001). In addition, exposure to Cr(VI) induced early apoptosis and downregulated the Bcl-2 mRNA expression and upregulated the Caspase-3 and Bax mRNAs expression (P < 0.01). Finally, quercetin significantly restored the detrimental effects of Cr(VI).

CONCLUSION

The results indicated that quercetin protects the oocytes against Cr(VI) toxicity through the suppression of oxidative stress and apoptosis. The conclusions drawn from our study's findings suggest that quercetin might be useful agent for oocyte maturation in case of possible exposure to toxic substances such as chromium.

The Influence of Graded Amount of Potassium Permanganate on Corrosion of Hot-Dip Galvanized Steel in Simulated Concrete Pore Solutions

This paper evaluates the amount of KMnO₄ in simulated concrete pore solution (pH 12.8) on the corrosion behaviour of hot-dip galvanized steel (HDG). In the range of used MnO₄^- (10^-4, 10^-3, 10^-2 mol·L^-1), corrosion behaviour is examined with regard to hydrogen evolution and composition (protective barrier properties) of forming corrosion products. The corrosion behaviour of HDG samples is evaluated using R_p/E_corr and EIS. The composition of corrosion products is evaluated using SEM, XRD, XPS and AAS. The effective MnO₄^- ion concentration to prevent the corrosion of coating with hydrogen evolution is 10^-3 mol·L^-1; lower concentrations only prolong the time to passivation (corrosion with hydrogen evolution). The highest used MnO₄^- concentration ensures corrosion behaviour without hydrogen evolution but also leads to the formation of less-protective amorphous corrosion products rich in Mn^II/Mn^III phases.

HBM4EU Chromates Study-Genotoxicity and Oxidative Stress Biomarkers in Workers Exposed to Hexavalent Chromium

A study was conducted within the European Human Biomonitoring Initiative (HBM4EU) to characterize occupational exposure to Cr(VI). Herein we present the results of biomarkers of genotoxicity and oxidative stress, including micronucleus analysis in lymphocytes and reticulocytes, the comet assay in whole blood, and malondialdehyde and 8-oxo-2′-deoxyguanosine in urine. Workers from several Cr(VI)-related industrial activities and controls from industrial (within company) and non-industrial (outwith company) environments were included. The significantly increased genotoxicity (p = 0.03 for MN in lymphocytes and reticulocytes; p < 0.001 for comet assay data) and oxidative stress levels (p = 0.007 and p < 0.001 for MDA and 8-OHdG levels in pre-shift urine samples, respectively) that were detected in the exposed workers over the outwith company controls suggest that Cr(VI) exposure might still represent a health risk, particularly, for chrome painters and electrolytic bath platers, despite the low Cr exposure. The within-company controls displayed DNA and chromosomal damage levels that were comparable to those of the exposed group, highlighting the relevance of considering all industry workers as potentially exposed. The use of effect biomarkers proved their capacity to detect the early biological effects from low Cr(VI) exposure, and to contribute to identifying subgroups that are at higher risk. Overall, this study reinforces the need for further re-evaluation of the occupational exposure limit and better application of protection measures. However, it also raised some additional questions and unexplained inconsistencies that need follow-up studies to be clarified.

Curcumin attenuates Cr (VI)-induced cell growth and migration by targeting autophagy-dependent reprogrammed metabolism

Hexavalent chromium [Cr (VI)] is a well-established carcinogen. Cr (VI)-treated cells are phenotypically characterized by aberrant levels of growth and migration. Curcumin, a polyphenolic compound from the plant turmeric, has been found to possess antiproliferation, anti-inflammation, and antioxidant properties. In this study, the effect of curcumin on Cr (VI)-induced cell survival and migration and the underlying mechanism were investigated. Cell viability assay on A549 and human embryonic lung fibroblast cells showed that curcumin at the concentration of 10 µM could significantly attenuate Cr (VI)-induced viability in both cell lines. Following Western blot assay and metabolomics assays, cotreatment with curcumin and Cr (VI) resulted in the suppression of Cr (VI)-induced glycolysis-, autophagy-, and migration-related proteins. Meanwhile, curcumin increased Cr (VI)-reduced oxidative phosphorylation (OXPHOS)-related proteins, COXIV and ND1. Moreover, curcumin suppressed Cr (VI)-induced mitochondrial dysfunction, mitochondrial mass decrease, and mitochondrial membrane potential loss. Treatment with curcumin for 24 h significantly attenuated pcATG4B-induced autophagy and the subsequent expression of glucose transporter 1, hexokinase II, and pyruvate kinase M2. Wound healing and transwell assay demonstrated that curcumin reduced Cr (VI)-induced cell migration. Taken together, these results showed that curcumin was able to attenuate Cr (VI)-induced cell viability and migration by targeting autophagy-dependent reprogrammed metabolism from OXPHOS to glycolysis.

Hexavalent chromium triggers hepatocytes premature senescence via the GATA4/NF-κB signaling pathway mediated by the DNA damage response

Hexavalent chromium [Cr(VI)] is a proven toxin, carcinogen and environmental pollutant. Oral intake of Cr(VI) has been shown to lead to an increasing incidence of primary hepatic carcinoma in the population. Cellular senescence is thought to be a natural barrier to malignant transformation of cells, but senescence-associated secretory phenotype (SASP) is secreted and regulated by senescent cells links cellular senescence to malignant transformation in a dynamic way. In the present research, we demonstrated novel mechanisms of premature hepatocytes senescence induced by Cr(VI). Continuous Cr(VI) stimulation led to DNA damaged in hepatocytes, and DNA damage response (DDR) signals were transmitted by ataxia telangiectasia-mutated gene (ATM)/ataxia telangiectasia and Rad-3-related protein (ATR), resulting in zinc finger transcription factor GATA4 escaping p62-mediated selective autophagy, thereby regulating nuclear factor kappa-B (NF-κB) to induce premature senescence in hepatocytes. In contrast to the classical senescence pathway p53-p21^{WAF1 /CIP1} and Rb/p16^INK4a, GATA4 can directly regulate the secretion of SASP during premature senescence. The results will provide valuable clues for targeted prevention and further individualized treatment of Cr(VI)-associated cancers.

Mechanism of chromium-induced toxicity in lungs, liver, and kidney and their ameliorative agents

Heavy metal Chromium (Cr), can adversely affect humans and their health if accumulated in organs of the body, such as the lungs, liver, and kidneys. Cr (VI) is highly toxic and has a higher solubility in water than Cr (III). One of the most common routes for Cr exposure is through inhalation and is associated with liver, lung, kidney damage, widespread dermatitis, GI tract damage, human lung cancer, cardiomyopathies, and cardiovascular disease. The increase in ROS production has been attributed to most of the damage caused by Cr toxicity. Cr-induced ROS-mediated oxidative stress has been seen to cause a redox imbalance affecting the antioxidant system balance in the body. The Nrf2 pathway dysregulation has been implicated in the same. Deregulation of histone acetylation and methylation has been observed, together with gene methylation in genes such as p16, MGMT, APC, hMLH1, and also miR-143 repression. Several ultra-structural changes have been observed following Cr (VI)-toxicity, including rough ER dilation, alteration in the mitochondrial membrane and nuclear membrane, pycnotic nuclei formation, and cytoplasm vacuolization. A significant change was observed in the metabolism of lipid, glucose, and the metabolism of protein after exposure to Cr. Cr-toxicity also leads to immune system dysregulations with changes seen in the expression of IL-8, IL-4, IgM, lymphocytes, and leukocytes among others. P53, as well as pro-and anti-apoptotic proteins, are involved in apoptosis. These Cr-induced damages can be alleviated via agents that restore antioxidant balance, regulate Nrf-2 levels, or increase anti-apoptotic proteins while decreasing pro-apoptotic proteins.

Removal of hexavalent chromium from water by Z-scheme photocatalysis using TiO2 (rutile) nanorods loaded with Au core-Cu2O shell particles

All-solid-state Z-scheme photocatalysts, containing Cu₂O, TiO₂ (rutile), and Au as the electron mediator, were prepared and applied to the reduction of Cr(VI) in aqueous solutions. The Cu₂O-Au-TiO₂ composites were prepared by loading Au core-Cu₂O shell hemisphere particles on TiO₂ (rutile) nanorods using a two-step photocatalytic deposition process. Under ultraviolet-visible (UV-vis) light illumination, the Cu₂O-Au-TiO₂ composites exhibited higher photocatalytic Cr(VI) reduction activities than those exhibited by single TiO₂ (rutile) and Cu₂O. In this reaction, a precipitate containing Cr, which was considered to be Cr(OH)₃, was deposited site-selectively on the Au core-Cu₂O shell particles of the composites, indicating that the reduction site of the composite was Cu₂O, and the reaction proceeded according to the Z-scheme. The Cu₂O-Au-TiO₂ composites also exhibited photocatalytic activity under visible light illumination. The oxidation state of Cu in the Cu₂O-Au-TiO₂ composite gradually changed from Cu(I) to Cu(II) during the photocatalytic Cr(VI) reduction. However the composite maintained its high photocatalytic performance even after oxidation. The role of Au in the Cu₂O-Au-TiO₂ composite was examined by comparing the properties of the Cu₂O-Au-TiO₂ composite with those of the Cu₂O-TiO₂ composite prepared via direct Cu₂O deposition on TiO₂.

Chromium [Cr(VI)] Exposure Causes Cytotoxicity of Human Bronchial Epithelial Cells (16-HBE) and Proteomic Alterations

Hexavalent chromium [Cr(VI)] is a common industrial pollutant, and exposure may cause toxic effects in multiple organ systems and carcinogenesis, including lung cancer. However, the toxic effect of Cr(VI) on the respiratory system is poorly understood. In the present study, it was demonstrated that Cr(VI) exposure significantly decreased the viability of human bronchial epithelial cells (16-HBE) in a dose-dependent manner. Flow cytometry demonstrated that Cr(VI) enhanced the transition of 16-HBE cells from G₁ to S phase and arrested S-phase progression. Reverse transcription-quantitative polymerase chain reaction analysis revealed a significant alteration in the expression of apoptosis-associated genes in Cr(VI)-treated 16-HBE cells. In addition, using two-dimensional fluorescence differential gel electrophoresis with mass spectrometry, 15 differentially expressed proteins (1 upregulated and 14 downregulated) were identified in 16-HBE cells with Cr(VI) treatment compared with controls. Functional classification revealed that these differentially expressed proteins were involved in apoptosis, cytoskeletal structure, and energy metabolism. In conclusion, these data suggested that Cr(VI) caused toxic effects in bronchial epithelial cells and the mechanisms may involve the abnormal expression of apoptosis-associated proteins, cytoskeletal proteins, and energy metabolism-associated proteins.

Multivariate statistical evaluation of heavy metals in the urine of opium individuals in comparison with healthy people in Western Iran

The current study aimed to evaluate the levels of some toxic and essential elements (Pb, Cd, Cu, Ti, Ni, Cr, Co, Fe, Ca, Hg, Mn, Se, and Zn) in the urine of opium-addicted compared to non-addicted cases. In this study, 126 participants were recruited and their fasting urine samples were collected (63 opium-addicted and 63 non-addicted subjects served as the reference group). ICP-MS was utilized to detect the concentration of trace elements. Results exhibited that the concentration of all elements than Ni, Cu, and Zn was markedly different between the addicted and non-addicted groups. Compared to controls, the Cd, Cr, Co, Hg, Mn, Pb, Se, and Ti levels were higher among opium-addicted cases (p < 0.05) whereas the Fe and Ca concentrations were higher among controls (p < 0.05). Robust regression analysis showed no statistically significant effect of gender on element levels. It revealed that age was associated with the levels of Ni and Cu only and also the route of administration was related to the urinary levels of Co, Cr, Hg, and Mn. In conclusion, results confirmed that it is opium consumption that affects the concentration levels of most elements.

Phototherapeutic anticancer strategies with first-row transition metal complexes: a critical review

Photodynamic therapy (PDT) and photoactivated chemotherapy (PACT) are therapeutic techniques based on a photosensitizer (PS) and light. These techniques allow the spatial and temporal control of the activation of drugs with light. Transition metal complexes are attractive compounds as photoactivatable prodrugs since their excited states can be appropriately designed by subtle modifications of the ligands, the metal centre, or the oxidation state. However, most metal-based PSs contain heavy metals such as Ru, Os, Ir, Pt or Au, which are expensive and non-earth-abundant, contrary to first-row transition metals. In this context, the exploration of the photochemical properties of complexes based on first-row transition metals appears to be extremely promising. This did encourage several groups to develop promising PSs based on these metals. This review presents up-to-date state-of-the-art information on first-row-transition metal complexes, from titanium to zinc in regard to their application as PSs for phototherapeutic applications.

A Statistical Modeling and Optimization for Cr(VI) Adsorption from Aqueous Media via Teff Straw-Based Activated Carbon: Isotherm, Kinetics, and Thermodynamic Studies

Currently, the growth of tannery industries causes a significant volume of waste disposal to the environment due to harmful Cr(VI). Long-time exposure to Cr(VI) imposes serious hazards on all living organisms. Hence, the treatment of tannery waste to remove Cr(VI) is not a choice but mandatory. Therefore, this study focused on the removal of Cr(VI) from the aqueous solutions via a teff (Eragrostis tef) straw based-activated carbon (TSAC) which was derived from locally available agricultural solid waste, teff straw (TS). The prepared TSAC was characterized using BET, FTIR, SEM, and XRD. A central composite approach-based RSM analysis was undertaken for statistical modeling and optimization for maximized Cr(VI) removal with respect to four important factors, namely, initial concentration of Cr(VI), the dosage of TSAC, pH, and adsorption time. Optimized values for maximizing adsorption of Cr(VI) (95% of removal) were acquired to be initial Cr(VI) concentration: 87.57 mg/L, TSAC dosage: 2.742 g/100 mL, pH: 2.2, and contact time:109 min. The results from the design of the experiment were also analyzed for the significance of the interaction between the selected process parameters. In addition, the pseudo-second-order kinetic and Langmuir isotherm models were found suitable for describing the adsorption data. The adsorption capacity of Cr(VI) on TSAC was 19.48 mg/g. The observed thermodynamic characteristics reveal that Cr(VI) adsorption on TASC is endothermic in nature. From the results, TSAC had shown a potential Cr(VI) efficiency on optimized process conditions that can be exploited effectively as adsorbent for removal of Cr(VI)-contaminated wastes.

Current understanding of hexavalent chromium [Cr(VI)] neurotoxicity and new perspectives

Hexavalent chromium [Cr(VI)] is a global environmental pollutant that increases risk for several types of cancers and is increasingly being recognized as a neurotoxicant. Traditionally, the brain has been viewed as a largely post-mitotic organ due to its specialized composition of neurons, and consequently, clastogenic effects were not considered in neurotoxicology. Today, we understand the brain is composed of at least eight distinct cell types - most of which continue mitotic activity throughout lifespan. We have learned these dividing cells play essential roles in brain and body health. This review focuses on Cr(VI), a potent clastogen and known human carcinogen, as a potentially neurotoxic agent targeting mitotic cells of the brain. Despite its well-established role as a human carcinogen, Cr(VI) neurotoxicity studies have failed to find a significant link to brain cancers. In the few studies that did find a link, Cr(VI) was identified as a risk for gliomas. Instead, in the human brain, Cr(VI) appears to have more subtle deleterious effects that can impair childhood learning and attention development, olfactory function, social memory, and may contribute to motor neuron diseases. Studies of Cr(VI) neurotoxicity with animal and cell culture models have demonstrated elevated markers of oxidative damage and redox stress, with widespread neurodegeneration. One study showed mice exposed to Cr(VI)-laden tannery effluent exhibited longer periods of aggressive behavior toward an "intruder" mouse and took longer to recognize mice previously encountered, recapitulating the social memory deficits observed in humans. Here we conducted a critical review of the available literature on Cr(VI) neurotoxicity and synthesize the collective observations to thoroughly evaluate Cr(VI) neurotoxicity - much remains to be understood and recognized.

Proteomic characteristics of PM2.5 -induced differentially expressed proteins in human renal tubular epithelial cells

Human renal epithelial (HK-2) cells were treated with PM_2.5 (50 μg/mL) from Shenzhen and Taiyuan, proteomics and bioinformatics were used to screen the differentially expressed proteins (DEPs). A total of 577 DEPs were screened after HK-2 cells exposed to Shenzhen PM_2.5, of which 426 were up-regulated and 151 were down-regulated. A total of 1250 DEPs were screened in HK-2 cells after exposure to Taiyuan PM_2.5, of which 488 were up-regulated and 185 were down-regulated. The top 10 proteins with the highest number of nodes were screened using the interaction network map of DEPs. HK-2 cells exposed to Shenzhen PM_2.5 contained CYR61, CTGF, and THBS1 proteins, while HK-2 cells exposed to Taiyuan PM_2.5 contained ALB, FN1, and CYR61 proteins. Additionally, PM_2.5 components were detected, PM_2.5 samples from Shenzhen and Taiyuan induced obvious changes in DEPs expression, the difference in DEPs between the two cities was probably associated with the different PM_2.5 components.

A toxicity pathway-based approach for modeling the mode of action framework of lead-induced neurotoxicity

BACKGROUND

The underlying mechanisms of lead (Pb) toxicity are not fully understood, which makes challenges to the traditional risk assessment. There is growing use of the mode of action (MOA) for risk assessment by integration of experimental data and system biology. The current study aims to develop a new pathway-based MOA for assessing Pb-induced neurotoxicity.

METHODS

The available Comparative Toxicogenomic Database (CTD) was used to search genes associated with Pb-induced neurotoxicity followed by developing toxicity pathways using Ingenuity Pathway Analysis (IPA). The spatiotemporal sequence of disturbing toxicity pathways and key events (KEs) were identified by upstream regulator analysis. The MOA framework was constructed by KEs in biological and chronological order.

RESULTS

There were a total of 71 references showing the relationship between lead exposure and neurotoxicity, which contained 2331 genes. IPA analysis showed that the neuroinflammation signaling pathway was the core toxicity pathway in the enriched pathways relevant to Pb-induced neurotoxicity. The upstream regulator analysis demonstrated that the aryl hydrocarbon receptor (AHR) signaling pathway was the upstream regulator of the neuroinflammation signaling pathway (11.76% overlap with upstream regulators, |Z-score|=1.451). Therefore, AHR activation was recognized as the first key event (KE1) in the MOA framework. The following downstream molecular and cellular key events were also identified. The pathway-based MOA framework of Pb-induced neurotoxicity was built starting with AHR activation, followed by an inflammatory response and neuron apoptosis.

CONCLUSION

Our toxicity pathway-based approach not only advances the development of risk assessment for Pb-induced neurotoxicity but also brings new insights into constructing MOA frameworks of risk assessment for new chemicals.

Analysis of serum metabolome of workers occupationally exposed to hexavalent chromium: A preliminary study

Hexavalent chromium (Cr(VI)) compound is considered as a common environmental and occupational pollutant due to widespread application in industry and agriculture. Cr(VI) as a carcinogen poses a serious threat to human health and the underlying mechanisms need further investigation. Previous studies had demonstrated the characteristic expression profiling after Cr(VI) treatment in vitro and in vivo at the levels of gene and protein. The comprehensive metabolic signatures were also conducive to discover potential biomarkers for effects assessment of Cr(VI) toxicity. In the current study, Ultra-performance liquid chromatography coupled with mass spectrometry (UPLC-MS) non-targeted metabolomics was applied to analyze serum metabolic changes in 77 chromate exposure workers and 62 controls. Thirteen metabolites were found significantly decreased and 41 metabolites were increased, which were involved in arginine and proline metabolism, and glycerophospholipid metabolism by bioinformatic analysis. Furthermore, there were significant negative correlations between blood Cr level and Arginine, PC(18:2/24:4) and PC(14:0/16:0), subgroup analyses indicated that these correlations were observed in male-only subgroups, and were not found among chromate workers and controls separately. Diet could be a potential confounder which was not controlled rigorously in this study. These findings provided preliminary clues to investigate the underlying mechanisms of Cr(VI)-induced toxicity and were required to be further verified in future researches.

Investigating the impact of long term exposure to chemical agents on the chromosomal radiosensitivity using human lymphoblastoid GM1899A cells

This study aimed to investigate the impact of chronic low-level exposure to chemical carcinogens with different modes of action on the cellular response to ionising radiation. Human lymphoblastoid GM1899A cells were cultured in the presence of 4-nitroquinoline N-oxide (4NQO), N-nitroso-N-methylurea (MNU) and hydrogen peroxide (H2O2) for up to 6 months at the highest non-(geno)toxic concentration identified in pilot experiments. Acute challenge doses of 1 Gy X-rays were given and chromosome damage (dicentrics, acentric fragments, micronuclei, chromatid gaps/breaks) was scored. Chronic exposure to 20 ng/ml 4NQO, 0.25 μg/ml MNU or 10 μM H2O2 hardly induced dicentrics and did not significantly alter the yield of X-ray-induced dicentrics. Significant levels of acentric fragments were induced by all chemicals, which did not change during long-term exposure. Fragment data in combined treatment samples compared to single treatments were consistent with an additive effect of chemical and radiation exposure. Low level exposure to 4NQO induced micronuclei, the yields of which did not change throughout the 6 month exposure period. As for fragments, micronuclei yields for combined treatments were consistent with an additive effect of chemical and radiation. These results suggest that cellular radiation responses are not affected by long-term low-level chemical exposure.

Inhalation cancer risk assessment for environmental exposure to hexavalent chromium: Comparison of margin-of-exposure and linear extrapolation approaches

Hexavalent chromium [Cr(VI)] exists in the ambient air at low concentrations (average upperbound ~0.1 ng/m³) yet airborne concentrations typically exceed EPA's Regional Screening Level for residential exposure (0.012 ng/m³) and other similar benchmarks, which assume a mutagenic mode of action (MOA) and use low-dose linear risk assessment models. We reviewed Cr(VI) inhalation unit risk estimates developed by researchers and regulatory agencies for environmental and occupational exposures and the underlying epidemiologic data, updated a previously published MOA analysis, and conducted dose-response modeling of rodent carcinogenicity data to evaluate the need for alternative exposure-response data and risk assessment approaches. Current research supports the role of non-mutagenic key events in the MOA, with growing evidence for epigenetic modifiers. Animal data show a weak carcinogenic response, even at cytotoxic exposures, and highlight the uncertainties associated with the current epidemiological data used in risk assessment. Points of departure from occupational and animal studies were used to determine margins of exposure (MOEs). MOEs range from 1.5 E+3 to 3.3 E+6 with a median of 5 E+5, indicating that current environmental exposures to Cr(VI) in ambient air should be considered of low concern. In this comprehensive review, the divergent results from default linear and MOE assessments support the need for more relevant and robust epidemiologic data, additional mechanistic studies, and refined risk assessment strategies.

The crosstalk between mitochondrial dysfunction and endoplasmic reticulum stress promoted ATF4-mediated mitophagy induced by hexavalent chromium

Chromium (Cr) compounds are markedly toxic and carcinogenic. Previously, we found that Cr (VI) induced autophagy in A549 cells. Here, the effect of mitochondrial dysfunction and endoplasmic reticulum (ER) stress on inducing mitophagy was investigated in both A549 and H1299 cells. Exposure to Cr (VI) for 6 h significantly enhanced reactive oxygen species (ROS) production and reduced mitochondrial membrane potential (MMP). Transmission electron microscopy showed that Cr (VI) induced mitochondrial morphological changes, such as, mitochondrial swelling and vacuolization. The elevated expression of GRP78 and p-PERK suggested that Cr (VI) resulted in ER stress. Both mitochondrial dysfunction and ER stress played an important role in Cr (VI)-induced mitophagy, as the mitochondrial function inhibitor, carbonyl cyanide 3-chlorophenylhydrazone (CCCP) induced PINK1 and PARK2 and increased the expression of GRP78 and p-PERK while the levels of Cr (VI)-induced PINK1, PARK2, LC3-II were reduced after ER stress inhibitor, phenylbutyric acid (4PBA) pretreatment. When A549 cells were treated with CCCP and 4-PBA simultaneously, CCCP-induced expressions of PINK1, PARK2 and LC3-II decreased significantly compared with that of only CCCP-treated cells, indicating that there was a crosstalk between mitochondria and ER in inducing mitophagy. Additionally, the crosstalk between mitochondrial dysfunction and ER stress modulated the expression of Cr (VI)-induced ATF4, which resulted in mitophagy. Collectively, our data demonstrated that Cr (VI)-induced mitophagy mediated by ATF4 via the crosstalk between ER stress and mitochondrial dysfunction.

The levels of trace elements in sputum as biomarkers for idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a rare lung disease that quickly leads to death. This paper addressed the issue of whether the levels of trace elements in sputum samples are suitable biomarkers for IPF disease. The sputum Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn concentrations were measured by sector field inductively coupled plasma mass spectrometry in populations sampled in Sardinia Island (Italy) including 31 patients with IPF, 31 patients with other lung-related diseases and 30 age- and gender-matched healthy controls. Risk factors in the disease as gender, age, severity and duration of the disease were assessed. Results showed that IPF patients had significantly increased sputum levels of Cd, Cr, Cu and Pb respect to controls. In males, but not in females, sputum levels of Cd, Cr and Cu were significantly higher in IPF cases respect to controls. In addition, Cr and Pb were increased in male patients with IPF compared to male patients with other lung diseases. Regarding Zn, it was found higher with the more serious stage of disease. Moreover, the ratios Cu/Zn, Fe/Mn and Cu/Mn were significantly increased in IPF patients and in non-IPF patients than in control subjects. These data showed clear increases in the concentration of some trace elements in sputum from patients with IPF and patients with other lung-related diseases that may contribute to the injury. The non-invasiveness of the sputum analysis is beneficial for its use as biomarker of trace element status in diseased patients for both the researcher and the clinic.

Parental Occupation and Risk of Childhood Retinoblastoma in Denmark

OBJECTIVE

Retinoblastoma is the most common primary intraocular tumor affecting children. We examine the role of parental occupational exposures and risk of retinoblastoma among offspring.

METHODS

Our population-based case-control study linked data from four nationwide Danish registries and included all cases of retinoblastoma diagnosed in Danish children (<5 y, n = 144) between 1975 and 2014. We focused on two biologically relevant time periods: 90 days preconception to conception for fathers; conception to birth for mothers. Parents were grouped into major industry headings created from Danish industry codes.

RESULTS

We observed increased risk of all retinoblastoma for children of fathers in the food and drink industry and iron and metal industry. Bilateral disease was associated with paternal work in manufacturing and land transportation.

CONCLUSION

Our results suggest that some occupational exposures may increase the risk of childhood sporadic retinoblastoma.

A Novel Transcriptome Integrated Network Approach Identifies the Key Driver lncRNA Involved in Cell Cycle With Chromium (VI)-Treated BEAS-2B Cells

Hexavalent chromium [Cr(VI)] is a well-known occupational carcinogen, but the mechanisms contributing to DNA damage and cell cycle alternation have not been fully characterized. To study the dose-response effects of Cr(VI) on transcription, we exposed BEAS-2B cells to Cr(VI) at concentrations of 0.2, 0.6, and 1.8 μmol/L for 24 h. Here, we identified 1,484 differentially expressed genes (DEGs) in our transcript profiling data, with the majority of differentially expressed transcripts being downregulated. Our results also showed that these DEGs were enriched in pathways associated with the cell cycle, including DNA replication, chromatin assembly, and DNA repair. Using the differential expressed genes related to cell cycle, a weighted gene co-expression network was constructed and a key mRNA-lncRNA regulation module was identified under a scale-free network with topological properties. Additionally, key driver analysis (KDA) was applied to the mRNA-lncRNA regulation module to identify the driver genes. The KDA revealed that ARD3 (FDR = 1.46 × 10^–22), SND1 (FDR = 5.24 × 10^–8), and lnc-DHX32-2:1 (FDR = 1.43 × 10^–17) were particularly highlighted in the category of G2/M, G1/S, and M phases. Moreover, several genes we identified exhibited great connectivity in our causal gene network with every key driver gene, including CDK14, POLA1, lnc-NCS1-2:1, and lnc-FOXK1-4:1 (all FDR < 0.05 in those phases). Together, these results obtained using mathematical approaches and bioinformatics algorithmics might provide potential new mechanisms involved in the cytotoxicity induced by Cr.

Prolonged exposure to particulate Cr(VI) is cytotoxic and genotoxic to fin whale cells

BACKGROUND

Hexavalent chromium [Cr(VI)] is a human lung carcinogen and global marine pollutant. High Cr concentrations, resembling the ones observed in occupationally exposed workers, have been observed in fin whales (Balaenoptera physalus) in the Gulf of Maine. This outcome suggests Cr might be disrupting the health of fin whale populations. Indeed, Cr in acute (24 h) exposure does cause toxicity in fin whale cells. However, human cell culture data indicate prolonged exposures (120 h) induce a higher amount of toxicity compared to 24 h exposure due to an inhibition of homologous recombination repair. However, whether prolonged exposure causes similar outcomes in fin whale cells is unknown.

OBJECTIVE

Due to the importance of assessing prolonged exposure toxicity, this study focuses on characterizing acute and prolonged exposure of Cr(VI) in male and female fin whale cells.

METHODS

Cytotoxicity was measured by the clonogenic assay, also known as colony forming assay, which measures the ability of cells to proliferate and form colonies after the treatment. DNA double strand breaks were analyzed by neutral comet assay. Clastogenicity was measured using the chromosome aberration assay. Intracellular Cr levels were measured with Graphite Furnace Atomic Absorption Spectrometry (GFAAS) with Syngistix Software.

RESULTS

In this study, we demonstrate that particulate Cr(VI) induces cytotoxicity and genotoxicity in a treatment-dependent manner after 24 h and 120 h exposures. Cytotoxicity levels were generally low with relative survival above 64 %. DNA double strand break data and chromosome aberration data were elevated after a 24 h exposure, but decreased after a 120 h exposure. While cytotoxicity was similar after 24 h and 120 h exposures, less DNA double strand breaks and chromosomal instability occurred with prolonged exposure.

CONCLUSION

Particulate Cr(VI) is cytotoxic and genotoxic to fin whale cells after acute and prolonged exposures. The reduction of genotoxicity we have observed after 120 h exposure may be partly explained by lower intracellular Cr levels after 120 h. However, the decrease in intracellular levels is not reflected by a similar decrease in chromosome aberrations suggesting other mechanisms may be at play. Male fin whale cells appear to be more susceptible to the genotoxic effects of particulate Cr(VI) while female cells are less susceptible possibly due to increased cell death of damaged cells, but more work is needed to clarify if this outcome reflects a sex difference or interindividual variability. Overall, the study shows particulate Cr(VI) does induce toxicity at both acute and prolonged exposures in fin whales cells indicating Cr(VI) exposure is a health risk for this species.

Statistical Assessment of Toxic and Essential Metals in the Serum of Female Patients with Lung Carcinoma from Pakistan

Lung cancer (LC) is the number one cancer killer of women both in the USA and around the world. Besides cigarette smoking, an important feature in the etiology of LC is its strong association with exposure of toxic metals. The primary objective of the present investigation was to assess the concentrations of toxic/essential elements (Ni, Ca, Se, Zn, Co, K, Cr, As, Cu, Na, Fe, Hg, Cd, Mg, Mn, and Pb) in the serum samples of LC female patients with female controls by atomic absorption spectrometry after wet-acid digestion procedure. Carcinoembryonic antigen (CEA) was also measured in the serum of the patients using immunoradiometric method. Comparative appraisal of the data revealed that concentrations of Cr, Mg, Cd, Pb, Hg, As, and Ni were noted to be high significantly in serum of LC female patients, while the average Fe, Co, Mn, Na, K, Zn, Ca, and Se were observed at higher levels in female controls (p < 0.05). The correlation study revealed significantly different mutual associations among the elements in the both donor groups. Markedly, variations in the elemental levels were also noted for different types (non-small cell lung cancer and small cell lung cancer) and stages (I, II, III, & IV) of LC patients. Multivariate analyses showed substantially diverse apportionment of the metals in the female patients and female controls. Hence, present findings suggest that the toxic and essential metals accumulated in the body may pose a high risk for LC progression in Pakistani females.

DNA-protein crosslinks from environmental exposure: Mechanisms of formation and repair

Many environmental carcinogens cause DNA damage, which can result in mutations and other alterations in genomic DNA if not repaired promptly. Because of the bulkiness of the lesions, DNA-protein crosslinks (DPCs) are one of the types of toxic DNA damage with potentially deleterious consequences. Despite the importance of DPCs, how cells remove these complex DNA adducts has been incompletely understood. However, major progress in the DPC repair field over the past 5 years now supports the view that cells are equipped with multiple mechanisms to cope with DPCs. Here, we first provide an overview of environmental substances that induce DPCs, describing the sources of exposure and mechanisms of DPC formation. We then review current models of DPC repair and discuss their significance for environmental carcinogens.

Metal Element Detection and Carcinogenicity Risk Assessment of PM2.5 Samples

The objective of the present study was to conduct metal element analysis and carcinogenicity risk assessment of particulate matter with an aerodynamic diameter <2.5 μm (PM_2.5 ) from Shenzhen and Taiyuan. Samples of PM_2.5 were collected in Shenzhen and Taiyuan during the yeas 2017 and 2018. Ten heavy metal elements were detected by inductively coupled plasma mass spectrometry. Health risk was assessed using the recommended US Environmental Protection Agency model. Metal elements found in PM_2.5 samples from Shenzhen included (in decreasing order of concentration) Al, Pb, Mn, Cr, Cu, V, As, Ni, Cd, and Co. Metal elements found in Taiyuan included (in decreasing order of concentration) Al, Mn, Pb, Cr, Cu, As, Ni, V, Cd, and Co. There were significant differences in Pb, Mn, Al, As, and Ni levels between Shenzhen and Taiyuan (p < 0.05); but the remaining element levels did not show significant differences between the 2 cities. Risk-assessment data showed higher total risk from 5 carcinogenic metal elements in Taiyuan (3.79 × 10^-4 ) compared to Shenzhen (2.44 × 10^-4 ): Cr had the highest carcinogenicity risk (>10^-4 ), followed by As, Ni, and Cd (10^-6  ~ 10^-4 ), and Pb had the lowest risk (<10^-6 ). The results indicated that some of the metal elements in PM_2.5 samples from Shenzhen and Taiyuan pose a carcinogenicity risk; further research and measures for prevention and control should be considered. Environ Toxicol Chem 2020;39:1273-1276. © 2020 SETAC.

Biomonitoring of Trace Elements in Subjects Living Near a Hazardous Waste Incinerator: Concentrations in Autopsy Tissues

The only hazardous waste incinerator (HWI) in Spain started to operate in 1999. Twenty years later, the levels of 11 trace elements (As, Be, Cd, Cr, Hg, Mn, Ni, Pb, Sn, Tl and V) were analyzed in five different autopsy tissues (kidney, liver, brain, bone and lung) from 20 individuals who had been living near the facility. In 2019, As, Be, Tl and V were not detected in any of the analyzed tissues, while Hg could be only quantified in very few samples. The highest levels of Cd and Pb were found in kidney and bone, respectively, while those of Mn were observed in liver and kidney. In turn, the mean concentrations of Cr and Sn were very similar in all tissues. A consistent temporal trend (1998-2019) was only found for Cr and Pb. On the one hand, the mean Cr concentrations in kidney and bone have increased progressively since 1998. In contrast, the mean levels of Pb decreased significantly over time, probably due to ban of Pb as gasoline additive. The data global analysis indicates that the emissions of trace elements by the HWI have not increased the exposure and/or accumulation of these elements in individuals living near the facility.

Taurine attenuates Cr(VI)-induced cellular and DNA damage: an in vitro study using human erythrocytes and lymphocytes

Hexavalent chromium [(Cr(VI)] is widely used in several industries, but human exposure results in multiple organ toxicity. Enhanced generation of free radicals and reactive species is thought to play a key role in Cr(VI)-induced toxicity. We have examined the effect of taurine, a simple sulphur-containing amino acid and an antioxidant, on potassium dichromate [K₂Cr₂O₇, a Cr(VI) compound]-induced cytotoxicity and genotoxicity in human blood cells. Erythrocytes were treated with K₂Cr₂O₇, either alone or after incubation with different concentrations of taurine. Treatment of erythrocytes with K₂Cr₂O₇ alone led to marked increase in generation of reactive oxygen and nitrogen species, lipid and protein oxidation. This was accompanied by decrease in total sulfhydryl and glutathione content and lowered antioxidant power of the cells. This suggests that Cr(VI) induces oxidative stress in the cells. Incubation of erythrocytes with taurine prior to addition of K₂Cr₂O₇, resulted in a concentration-dependent decrease in the generation of reactive oxygen and nitrogen species, mitigation of oxidative stress and amelioration of antioxidant power of these cells. It also restored the activities of several metabolic, antioxidant and membrane-bound enzymes. Cr(VI)-induced damage to erythrocyte membrane and lymphocyte DNA was also significantly attenuated by prior administration of taurine. These results suggest that taurine can function as a chemoprotectant against Cr(VI)-induced oxidative injury and can be potentially used to mitigate the toxic effects of this transition metal ion.

Honeycomb-like magnetic cornstalk for Cr(VI) removal and ammonium release

In this work, cornstalk (CS) was irradiated by high energy electron beam to obtain honeycomb-like porous CS (PCS). The PCS was loaded with ammonium sulfite (AS) and then coated by polyvinyl alcohol (PVA)-Fe₃O₄ to obtain PCS-AS@PVA-Fe₃O₄. The PCS-AS@PVA-Fe₃O₄ could reduce hexavalent chromium (Cr(VI)) to trivalent chromium (Cr(III)) by SO₃^2-, then the Cr(III) combined with PCS-AS@PVA-Fe₃O₄ through hydrogen bonds. The resulting PCS-AS@PVA-Fe₃O₄/Cr with a high magnetism could be conveniently separated from water via a magnet. PCS-AS@PVA-Fe₃O₄/Cr showed a high performance on controlling Cr(VI) migration in soil and uptake by plant. Meanwhile, ammonium could be released from PCS-AS@PVA-Fe₃O₄, favoring plant growth. Therefore, this work not only provides a promising and low-cost approach to remove Cr(VI) and promote plant growth simultaneously, but also provides a new route for CS recycling, which might have a potential application value.

The First-Row Transition Metals in the Periodic Table of Medicine

In this manuscript, we describe medical applications of each first-row transition metal including nutritional, pharmaceutical, and diagnostic applications. The 10 first-row transition metals in particular are found to have many applications since there five essential elements among them. We summarize the aqueous chemistry of each element to illustrate that these fundamental properties are linked to medical applications and will dictate some of nature’s solutions to the needs of cells. The five essential trace elements—iron, copper, zinc, manganese, and cobalt—represent four redox active elements and one redox inactive element. Since electron transfer is a critical process that must happen for life, it is therefore not surprising that four of the essential trace elements are involved in such processes, whereas the one non-redox active element is found to have important roles as a secondary messenger.. Perhaps surprising is the fact that scandium, titanium, vanadium, chromium, and nickel have many applications, covering the entire range of benefits including controlling pathogen growth, pharmaceutical and diagnostic applications, including benefits such as nutritional additives and hardware production of key medical devices. Some patterns emerge in the summary of biological function andmedical roles that can be attributed to small differences in the first-row transition metals.

High variability in toxicity of welding fume nanoparticles from stainless steel in lung cells and reporter cell lines: the role of particle reactivity and solubility

Millions of people in the world perform welding as their primary occupation resulting in exposure to metal-containing nanoparticles in the fumes generated. Even though health effects including airway diseases are well-known, there is currently a lack of studies investigating how different welding set-ups and conditions affect the toxicity of generated nanoparticles of the welding fume. The aim of this study was to investigate the toxicity of nine types of welding fume particles generated via active gas shielded metal arc welding (GMAW) of chromium-containing stainless steel under different conditions and, furthermore, to correlate the toxicity to the particle characteristics. Toxicological endpoints investigated were generation of reactive oxygen species (ROS), cytotoxicity, genotoxicity and activation of ToxTracker reporter cell lines. The results clearly underline that the choice of filler material has a large influence on the toxic potential. Fume particles generated by welding with the tested flux-cored wire (FCW) were found to be more cytotoxic compared to particles generated by welding with solid wire or metal-cored wire (MCW). FCW fume particles were also the most potent in causing ROS and DNA damage and they furthermore activated reporters related to DNA double- strand breaks and p53 signaling. Interestingly, the FCW fume particles were the most soluble in PBS, releasing more chromium in the hexavalent form and manganese compared to the other fumes. These results emphasize the importance of solubility of different metal constituents of the fume particles, rather than the total metal content, for their acute toxic potential.

Mechanisms of Chromium-Induced Toxicity

Chromium is a pervasive environmental contaminant that is of great importance because of its toxicity. Hexavalent chromium is a classified group 1 carcinogen with multiple complex mechanisms by which it triggers cancer development. Increased levels of oxidative stress, chromosome breaks, and DNA-adduct formation are some of the major mechanisms by which C(VI) causes cellular damage. Trivalent chromium is another species of chromium that is described as a non-essential metal, and is used in nutritional supplementation. Evidence on nutritional benefit is conflicting which could suggest that humans absorb enough Cr(III) from diet alone, and that extra supplementation is not necessary. This review highlights the differences between Cr(VI) and Cr(III) from a chemical and toxicological perspective, describes short-comings in nutritional research of Cr(III), and explains the multiple mechanisms by which Cr(VI) is involved in the process of carcinogenesis.

Cancer Risks of Hexavalent Chromium in the Respiratory Tract

Hexavalent chromium (Cr(VI)) compounds are recognized as carcinogens in the respiratory tract, giving rise to cancers of the lung, nose and nasal sinuses, especially in certain occupational environments. Inhalation exposure of Cr(VI)-containing particles, dusts and fumes commonly occurs in chromium-related occupational environments, such as chromium production, plating, welding of chromium-containing metals and alloys, electroplating, chromium-containing pigments and paints. Epidemiological surveys of chromium compounds have shown strong associations between exposure to Cr(VI) and mortality due to lung cancer, as well as positive associations with cancers of the nose and nasal cavity. Nasal symptoms, such as nasal irritation, ulceration and perforation of the nasal septum, nasal turbinate engorgement and hypertrophy, are important signs for the early diagnosis of lung cancer and cancers of the nose and nasal cavity in those with an occupational history of Cr(VI) exposure. Cr(VI) exposure in the workplace remains a serious problem as a cause of lung cancer and cancers of nose and nasal cavity, especially in relatively small enterprises that use chromium compounds. Appropriate protection for workers should be considered in occupations that involve exposure to chromium compounds.