Genetic and epigenetic mechanisms in metal carcinogenesis and cocarcinogenesis: nickel, arsenic, and chromium

The effect of fluoride gel on tensile properties, surface morphology and chemical composition of two types of orthodontic wires (an in-vitro study)

OBJECTIVE:

Stainless steel and nickel-titanium wires are commonly used in fixed orthodontic appliances. Orthodontists often prescribe fluoride gel to avoid demineralization of teeth. This study investigated the effect of acidulated phosphate fluoride gel on the tensile properties, surface morphology and surface chemical composition of stainless steel and nickel-titanium wires.

METHODS:

Forty samples of stainless steel and nickel-titanium wires were examined, twenty for each type. Each wire type was divided into four subgroups. The first subgroup was not immersed in fluoride gel and considered as control, while the other three subgroups were immersed in 10 mL of fluoride gel for different periods of time. Then, the wires were removed from the gel, rinsed in a distilled water and left to dry. The ultimate tensile force of each wire was measured using a tensile testing machine. Scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDX) were used to examine the control and 24 h immersed subgroups.

RESULTS:

One-way analysis of variance ANOVA showed that there were no significant differences in the ultimate tensile forces between control and fluoride-treated subgroups (P = 0.172 for SS wires and P = 0.672 for NiTi wires). However, changes in the surface morphology and elemental composition of wires were shown by the SEM and EDX.

CONCLUSIONS:

Although immersion of stainless steel and nickel-titanium wires in the fluoride gel did not affect their tensile properties, however, surface deterioration was evident. So, further investigations are recommended to study the effect of these changes on the oral health of patients.

Occupational exposure to hexavalent chromium. Part II. Hazard assessment of carcinogenic effects

Hexavalent chromium (Cr(VI)) compounds have been studied extensively and several agencies have described their toxicological profile. In the past, personnel of the Dutch Ministry of Defence may have been exposed to Cr(VI) during maintenance activities on NATO equipment. To investigate if this exposure may have caused irreversible adverse health effects, the Dutch National Institute for Public Health and the Environment (RIVM) summarized all available knowledge from previous evaluations. This information was complemented with a scoping review to retrieve new scientific literature. All scientific evidence was evaluated in workshops with external experts to come to an overview of irreversible adverse health effects that could be caused by occupational exposure to Cr(VI) compounds. This review provides the hazard assessment for occupational exposure to Cr(VI) and carcinogenic effects by integrating and weighting evidence provided by international agencies complemented with newly published studies. It was concluded that occupational exposure to Cr(VI) can cause lung cancer, nose and nasal sinus cancer in humans. Cr(VI) is suspected to cause stomach cancer and laryngeal cancer in humans. It is currently insufficiently clear if Cr(VI) can cause cancer of the small intestine, oral cavity, pancreas, prostate or bladder in humans.

Toxicity assessment of metallic nickel nanoparticles in various biological models: An interplay of reactive oxygen species, oxidative stress, and apoptosis

Nickel nanoparticles (Ni-NPs) are widely used for multiple purposes in industries. Ni-NPs exposure is detrimental to ecosystems owing to widespread use, and so their toxicity is important to consider for real-world applications. This review mainly focuses on the notable pathophysiological activities of Ni-NPs in various research models. Ni-NPs are stated to be more toxic than bulk forms because of their larger surface area to volume ratio and are reported to provoke toxicity through reactive oxygen species generation, which leads to the upregulation of nuclear factor-κB and promotes further signaling cascades. Ni-NPs may contribute to provoking oxidative stress and apoptosis. Hypoxia-inducible factor 1α and mitogen-activated protein kinases pathways are involved in Ni-NPs associated toxicity. Ni-NPs trigger the transcription factors p-p38, p-JNK, p-ERK1/2, interleukin (IL)-3, TNF-α, IL-13, Fas, Cyt c, Bax, Bid protein, caspase-3, caspase-8, and caspase-9. Moreover, Ni-NPs have an occupational vulnerability and were reported to induce lung-related disorders owing to inhalation. Ni-NPs may cause serious effects on reproduction as Ni-NPs induced deleterious effects on reproductive cells (sperm and eggs) in animal models and provoked hormonal alteration. However, recent studies have provided limited knowledge regarding the important checkpoints of signaling pathways and less focused on the toxic limitation of Ni-NPs in humans, which therefore needs to be further investigated.

Research progress on the association between environmental pollutants and the resistance mechanism of PARP inhibitors in ovarian cancer

The occurrence and progression of ovarian cancer are closely related to genetics and environmental pollutants. Poly(ADP-ribose) polymerase (PARP) inhibitors have been a major breakthrough in the history of ovarian cancer treatment. PARP is an enzyme responsible for post-translational modification of proteins and repair of single-stranded DNA damage. PARP inhibitors can selectively inhibit PARP function, resulting in a synthetic lethal effect on tumor cells defective in homologous recombination repair. However, with large-scale application, drug resistance also inevitably appears. For PARP inhibitors, the diversity and complexity of drug resistance mechanisms have always been difficult problems in clinical treatment. Herein, we mainly summarized the research progress of DNA damage repair and drug resistance mechanisms related to PARP inhibitors and the impact of environmental pollutants on DNA damage repair to aid the development prospects and highlight urgent problems to be solved.

New advances in the method validation, extraction methods and measurement uncertainty for the determination of water-soluble hexavalent chromium in hydraulic cement

The quantification of Cr (VI) in the cement matrix is highly important, given the possibility of suffering illnesses including dermatitis, induced nasal carcinoma, and DNA damage produced by inhalation of and/or direct contact with this substance by construction workers. This study presents an analytical validation of the determination of water-soluble Cr (VI) using Ultraviolet-Visible Spectroscopy (UV-Vis) with 1.5-diphenylcarbazide. To do so, different performance characteristics were determined: working interval, analytical sensitivity, linearity, limits of detection (LOD) and quantification (LOQ), as well as measurement uncertainty, in order to provide better metrological information about the performance of this method. The study also focused on evaluating the impact of use of different types of standard sands (ASTM C-778 and CEN) for preparing mortar cement and extracting water soluble Cr (VI) present in the cement. For this purpose, two cements with different concentrations (2.01 ± 0.21 and 0.75 ± 0.09 mg-kg^-1) of Cr (IV) were created to evaluate extraction using three types of treatments: oxidized with potassium peroxidisulfite, non-oxidized, and an alternative method using cement paste. It was observed that mortar cement using ASTM C-778 sand tends to underestimate Cr (IV) content when concentrations are below 0.8 mg kg^-1, while at higher concentrations of ~2.0 mg kg^-1 it does not generate different results compared to those obtained using mortar cement made with CEN-standard sand. An alternative method called "paste extraction" also showed statistically comparable results with respect to standard mortar for both concentration levels evaluated. Finally, samples of cement marketed in Costa Rica were analyzed using different types of water soluble Cr (IV) extraction methods. The results show concentrations between 0.70 ± 0.13 mg kg^-1 and 1.30 ± 0.13 mg kg^-1, demonstrating that they comply with the limits established by international standards and national regulations in Costa Rica.

Health risk assessment of trace metals in selected food crops at Abuakwa South Municipal, Ghana

Trace metals contamination has recently been a major issue due to its damaging effects on public health and environmental receptors. This study focussed on the health risk assessment of trace metals (As, Pb, Cr, and Ni) associated with the direct intake of some selected food crops (namely cocoyam and plantain) at Abuakwa South Municipal, Ghana. The food crops and soil samples were selected randomly from three reclaimed mined sites and one non-mining site in the study area. Results from the trace metal concentration analyses in the soil samples showed that As, Cr, and Ni were above the control. The daily intake of metals (DIM), target hazard quotient (THQ), and carcinogenic risk (CR) assessments of health risks accompanied by the continuous ingestion of the selected food crops polluted through these trace metals were evaluated. 0.23 mg/kg and 0.05 mg/kg, 0.11 mg/kg and 0.02 mg/kg, 0.78 mg/kg and 0.65 mg/kg, and 0.23 mg/kg and 0.09 mg/kg were recorded for As, Cr, Ni, and Pb in that order in the cocoyam and plantain, respectively. The As and Pb concentrations in the food crops were above the WHO recommended limits. This implies that individuals within the vicinity are exposed to high levels of As and Pb through food intake which could result in varying health implications. The DIM and THQ for the studied trace metals were below their permissible limits suggesting that there is a tolerable non-carcinogenic adverse health risk level for adults and children within the studied area. In addition, the lifetime probability of contracting cancer by ingesting Ni, Pb, and Cr in plantain grown in the study area is high. It is recommended that regular monitoring of these trace metals in food crops be carried out in preventing their excessive accumulation.

Environmentally induced ribosomal DNA (rDNA) instability in human cells and populations exposed to hexavalent chromium [Cr (VI)]

Hexavalent Chromium [Cr (VI)] is an established toxicant, carcinogen, and a significant source of public health concern. The multicopy ribosomal DNA (rDNA) array is mechanistically linked to aging and cancer, is the most evolutionarily conserved segment of the human genome, and gives origin to nucleolus, a nuclear organelle where ribosomes are assembled. Here we show that exposure to Cr (VI) induces instability in the rDNA, triggering cycles of rapid, specific, and transient amplification and contraction of the array in human cells. The dynamic of environmentally responsive rDNA copy number (CN) amplification and contraction occurs at doses to which millions of individuals are regularly exposed. Finally, analyses of human populations occupationally exposed to Cr (VI) indicate that environmental exposure history and drinking habits but not age shape extensive naturally occurring rDNA copy number variation. Our observations identify a novel pathway of response to hexavalent chromium exposure and raise the prospect that a suite of environmental determinants of rDNA copy number remain to be discovered.

Cr(V)-Cr(III) in-situ transition promotes ROS generation to achieve efficient cancer therapy

The development of metal-based anticancer drugs is of considerable interest and significance in inorganic medicine. In contrast to noble metal-based small molecules, the anticancer property of earth abundant metal-based small molecules is much less explored which are usually essential trace element for the human body. Among earth abundant metals, chromium (Cr) in the +3 valent is an essential trace element for the human body to low down the blood lipids and maintain the blood sugar; on the other hand, Cr(VI) are known to be highly toxic due to their oxidation power. To design stable high-valent Cr small molecules to construct Cr(high-valent)-Cr(III) in-situ transition system to achieve low-toxic and highly efficient anti-cancer therapy is a very desirable approach. Herein we report the Cr(V)-Cr(III) in-situ transition system promotes ROS generation to achieve efficient cancer therapy in vivo and in vitro. To the best of our knowledge, these Cr-based small molecules are the first stable Cr(V) compounds with potent anticancer efficacy, especially towards malignant cancers.

An Ion Chromatography Method for Simultaneous Quantification of Chromate, Arsenate, Selenate, Perchlorate, and Other Inorganic Anions in Environmental Media

Chromium (Cr) (VI) is a toxic, mutagenic, and carcinogenic water pollutant. The standard ion chromatography (IC) method for quantification of Cr (VI) in water samples is Environmental Protection Agency Method 218.7, which requires postcolumn derivatization with 1,5-diphenylcarbazide and UV-Vis spectroscopy detection. Method 218.7 is Cr (VI) specific; thus, it does not allow detection of co-occurring natural and anthropogenic anions in environmental media. In this study, we developed an isocratic IC method with suppressed conductivity detection, a Metrohm Metrosep A Supp 7 column, and sodium carbonate/acetonitrile as mobile phase for simultaneous quantification of Cr (VI),C l O 4 - , As (V) as arsenate, Se (VI) as selenate, and the common anions F-, Cl-,N O 2 - ,N O 3 - , andS O 4 2 - . The determination coefficient for every analyte was >0.99 and the method showed good accuracy in quantification. Cr (VI), As (V), Se (VI), andC l O 4 - limit of detection and limit of quantification were 0.1-0.6 μg/L and 0.5-2.1 μg/L, respectively. Recovery of Cr (VI) in various aqueous samples (tap water, surface water, groundwater, and wastewater) was between 97.2% and 102.8%. Overall, most analytes showed acceptable recovery (80-120%) in the environmental samples tested. The IC method was applied to track Cr (VI) and other anion concentrations in laboratory batch microcosms experiments with soil, surface water, and anaerobic medium. The IC method developed in this study should prove useful to environmental practitioners, academic and research organizations, and industries for monitoring low concentrations of multiple anions in environmental media, helping to decrease the sample requirement, time, and cost of analysis.

Biotechnology-based microbial degradation of plastic additives

Plastic additives are agents responsible to the flame resistance, durability, microbial resistance, and flexibility of plastic products. High demand for production and use of plastic additives is associated with environmental accumulation and various health hazards. One of the suitable methods of depleting plastic additive in the environment is bioremediation as it offers cost-efficiency, convenience, and sustainability. Microbial activity is one of the effective ways of detoxifying various compounds as microorganisms can adapt in an environment with high prevalence of pollutants. The present review discusses the use and abundance of these plastic additives, their health-related risks, the microorganisms capable of degrading them, the proposed mechanism of biodegradation, and current innovations capable of improving the efficiency of bioremediation.

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.

The exposure of gadolinium at environmental relevant levels induced genotoxic effects in Arabidopsis thaliana (L.)

Rare Earth Elements (REEs) are increasingly being used in agriculture and are also used to produce high end technological devices, thereby increasing their anthropogenic presence in the environment. However, the ecotoxicological mechanism of REEs on organisms is not fully understood. In this study, the effects of gadolinium (Gd) addition on Arabidopsis thaliana (L.) were investigated at both physiological and molecular levels. Four treatments (0, 10, 50 and 200 μmol·L^-1 Gd) were used in the exposure tests. Biomass, root length and chlorophyll content in shoots/roots were measured to investigate the plant's physiological response to Gd stress. Random amplified polymorphic (RAPD)-Polymerase Chain Reaction (PCR) and methylation sensitive arbitrarily primed (MSAP)-PCR were used to investigate changes in genetic variation and DNA methylation of A. thaliana when exposed to Gd. At the physiological level, it was found that low concentration of Gd (10 μmol·L^-1) could significantly increase the plant biomass and root length, while the growth of A. thaliana was significantly inhibited when exposed to 200 μmol·L^-1 of Gd, yet the total soluble protein content in aerial plant parts increased significantly by 24.2% when compared to the control group. Among the 12 primers considered in the RAPD assessment, at the molecular level, only four primers revealed different patterns in their genomic DNA. Compared to the control group, the treatment with 50 μmol·L^-1 of Gd was associated with lower polymorphism, while the treatment with 200 μmol·L^-1 of Gd was associated with higher polymorphism. The polymorphism frequencies for the 50 μmol·L^-1 of Gd and the 200 μmol·L^-1 of Gd were 4.67% and 20.33%, respectively. The MSAP analysis revealed that the demethylation (D) type of Arabidopsis genomic DNA increased significantly under 10 and 50 μmol·L^-1 of Gd, while the methylation (M) type was also significantly increased under 200 μmol·L^-1 of Gd. Generally, the total methylation polymorphism (D+M) increased with an increase of Gd concentration. It was found that high concentrations of Gd appeared to cause DNA damage, but low concentrations of Gd (as low as 10 μmol·L^-1) were associated with DNA methylation change. Further, it was verified by Real time Reverse Transcription PCR (RT-PCR) on the bands detected by the MSAP analysis, that the genes relative to processes including cell cycle, oxidative stress and apoptosis, appeared to be regulated by methylation under Gd stress. These findings reveal new insight regarding ecotoxicity mechanisms of REEs on plants.

Mediated relationships between multiple metals exposure and fasting blood glucose by reproductive hormones in Chinese men

Previous studies have reported metals exposure contribute to the change of fasting blood glucose (FBG) level. However, the roles of reproductive hormones in their associations have not been fully elucidated. The aim of the study is to investigate the associations of multiple serum metals with reproductive hormones, and to further explore potential roles of reproductive hormones in relationships between metals exposure and FBG level. A total of 1911 Chinese Han men were analyzed by a cross-sectional study. We measured serum levels of 22 metals by inductively coupled plasma mass spectrometer (ICP-MS). FBG, total testosterone (TT), estradiol (E2), follicle stimulating hormone (FSH), and sex hormone-binding globulin (SHBG) levels were determined. Least absolute shrinkage and selection operator (LASSO) regression models were conducted to select important metals, and restricted cubic spline models were then used to estimate dose-response relationships between selected metals and reproductive hormones. We also conducted mediation analyses to evaluate whether reproductive hormones played mediating roles in the associations between metals and FBG. We found significant inverse dose-dependent trends of copper, tin and zinc with E2; zinc with SHBG; copper and nickel with TT, while significant positive dose-dependent trend of iron with E2, respectively. Moreover, approximately inverted U-shaped associations existed between lead and SHBG, iron and TT. In addition, E2, SHBG and TT were negatively associated with FBG level. In mediation analyses, the association of copper with FBG was mediated by E2 and TT, with a mediation ratio of 10.4% and 22.1%, respectively. Furthermore, E2 and SHBG mediated the relationship of zinc with FBG, with a mediation ratio of 7.8% and 14.5%, respectively. E2 mediated 11.5% of positive relationship between tin with FBG. Our study suggested that the associations of metals exposure with FBG may be mediated by reproductive hormones.

Cr(VI)-induced DNA damage is lessened by the modulation of hsp70 via increased GSH de novo synthesis in Drosophila melanogaster

Hexavalent chromium [Cr(VI)] is a genotoxic chemical, and in the chemical-exposed organism, oxidative stress is one of the leading causative mechanisms of genotoxicity. Heat shock protein-70 (Hsp70) is reported to be modulated in environmental chemical exposed organisms. Inadequate information on the protective role of Hsp70 in chemical-induced DNA lesions prompted us to investigate this possibility in a well-studied genetically tractable in vivo model Drosophila melanogaster. In the midgut cells of Cr(VI)-exposed hsp70-knockout (KO), -knockdown (KD), and -overexpression Drosophila strains, no significant change in double-strand breaks generation was observed in comparison to similarly exposed w ¹¹¹⁸ and the respective genetic control strain after 48 h. Therefore, the role of hsp70 was investigated on oxidative DNA damage induction in the exposed organisms after 24 h. Oxidized DNA lesions (particularly oxidized purine-based lesions), 8-oxo-dG level, and oxidative stress endpoints were found to be significantly elevated in hsp70-KO and -KD strains in comparison to similarly exposed w ¹¹¹⁸ and respective genetic control strain. On the contrary, in ubiquitous hsp70-overexpression strain exposed to Cr(VI), these endpoints were significantly lowered concurrently with increased GSH level through elevated gclc, and gclm expression, Gclc level, and GCL activity. The study suggests that as a consequence of hsp70 overexpression, the augmented GSH level in cells vis-a-vis GSH de novo synthesis can counteract Cr(VI)-induced oxidized DNA lesions.

Molecular mechanism of heavy metals (Lead, Chromium, Arsenic, Mercury, Nickel and Cadmium) - induced hepatotoxicity - A review

Heavy metals pose a serious threat if they go beyond permissible limits in our bodies. Much heavy metal's viz. Lead, Chromium, Arsenic, Mercury, Nickel, and Cadmium pose a serious threat when they go beyond permissible limits and cause hepatotoxicity. They cause the generation of ROS which in turn causes numerous injuries and undesirable changes in the liver. Epidemiological studies have shown an increase in the levels of such heavy metals in the environment posing a serious threat to human health. Epigenetic alterations have been seen in the event of exposure to such heavy metals. Apoptosis, caspase activation as well as ultrastructural changes in the hepatocytes have also been seen due to heavy metals. Inflammation involving TNF-alpha, pro-inflammatory cytokines, MAPK, ERK pathways have been seen in the event of heavy metal hepatotoxicity. All these have shown that these heavy metals pose a serious threat to human health in particular and the environment as a whole.

Chromium contamination and effect on environmental health and its remediation: A sustainable approaches

Chromium (Cr) is a trace element critical to human health and well-being. In the last few decades, its contamination, especially hexavalent chromium [Cr(VI)] form in both terrestrial and aquatic ecosystems, has amplified as a result of various anthropogenic activities. Chromium pollution is a significant environmental threat, severely impacting our environment and natural resources, especially water and soil. Excessive exposure could lead to higher levels of accumulation in human and animal tissues, leading to toxic and detrimental health effects. Several studies have shown that chromium is a toxic element that negatively affects plant metabolic activities, hampering crop growth and yield and reducing vegetable and grain quality. Thus, it must be monitored in water, soil, and crop production system. Various useful and practical remediation technologies have been emerging in regulating chromium in water, soil, and other resources. A sustainable remediation approach must be adopted to balance the environment and nature.

Low-grade adenosquamous carcinoma of the breast: a review with focus on imaging and management

Low-grade adenosquamous carcinoma is a less frequent variant of metaplastic breast carcinoma, incidentally detected during screening and has an age distribution similar to other breast carcinomas. It shares characteristics with both benign and malignant carcinomas: its mammographic and sonographic features are therefore nonspecific. Breast conserving surgery with adjuvant radiation therapy is currently the preferred therapeutic approach. The aim of this review is to describe the imaging and clinical features of low-grade adenosquamous carcinoma for appropriate identification and diagnosis. The associated pitfalls, histopathologic and epidemiologic factors, natural course, and management of low-grade adenosquamous carcinoma are also discussed.

Toxic Mechanisms of Five Heavy Metals: Mercury, Lead, Chromium, Cadmium, and Arsenic

The industrial activities of the last century have caused massive increases in human exposure to heavy metals. Mercury, lead, chromium, cadmium, and arsenic have been the most common heavy metals that induced human poisonings. Here, we reviewed the mechanistic action of these heavy metals according to the available animal and human studies. Acute or chronic poisonings may occur following exposure through water, air, and food. Bioaccumulation of these heavy metals leads to a diversity of toxic effects on a variety of body tissues and organs. Heavy metals disrupt cellular events including growth, proliferation, differentiation, damage-repairing processes, and apoptosis. Comparison of the mechanisms of action reveals similar pathways for these metals to induce toxicity including ROS generation, weakening of the antioxidant defense, enzyme inactivation, and oxidative stress. On the other hand, some of them have selective binding to specific macromolecules. The interaction of lead with aminolevulinic acid dehydratase and ferrochelatase is within this context. Reactions of other heavy metals with certain proteins were discussed as well. Some toxic metals including chromium, cadmium, and arsenic cause genomic instability. Defects in DNA repair following the induction of oxidative stress and DNA damage by the three metals have been considered as the cause of their carcinogenicity. Even with the current knowledge of hazards of heavy metals, the incidence of poisoning remains considerable and requires preventive and effective treatment. The application of chelation therapy for the management of metal poisoning could be another aspect of heavy metals to be reviewed in the future.

Exposure to intranasal chromium triggers dose and time-dependent behavioral and neurotoxicological defects in rats

The extensive recorded environmental and occupational dispersal of hexavalent chromium (CrVI) dust contributes to an increased interest in its toxicological consequences. A previous study of our team described a brain injury induced by acute intranasal instillation of Cr(VI) in rats, which was characterized by oxidative stress and inflammation. This proposed a high risk of brain damage among Cr(VI) exposed individuals either environmentally or occupationally especially through the nasal cavity. Accordingly, the main aim of this study was to evaluate the effects of subacute/subsubacute/subchronic exposure to intranasal potassium dichromate (inPDC) solution in three dose levels (0.125, 0.25, or 0.5 mg/kg/day for five successive days/week) for 3 different intervals/dose: two weeks, one month, and two months, on the brain of rats. The rats were sacrificed 24 h following the last inPDC dose. The locomotor activity, motor coordination, and object recognition behavior of the rats have been measured. Evaluation of oxidative stress; evidenced by lipid peroxidation and reduced glutathione, and inflammatory markers; evidenced by interleukin 1-beta in the brain tissues, as well as the brain PI3K and PKB contents were performed. Furthermore, the brain anti-glial fibrillary acidic protein (GFAP); marker of neurotoxicity was assessed immunohistochemically. Brain histopathological alterations were also studied. The findings of the current study revealed a dose- and time-dependent inPDC-induced brain toxicity in rats, as displayed by the biochemical, immunohistochemical and histopathological evaluation. Behaviorally, the major toxic effects of inPDC were observed on the locomotor and cognition functions, however, minor effects were observed on the motor coordination. The results suggest that short-term exposure to intranasal Cr(VI), in theses doses, does not trigger a major brain injury in rats; however, observation of more toxic alterations in a time-dependent manner is a threat of more sever toxicity upon longer exposure.

Smartphone-enabled field monitoring tool for rapid hexavalent chromium detection in water

Chromium contamination of soil and water is a serious environmental and public health concern as the hexavalent form of chromium [Cr(VI)] is readily soluble in water and is a confirmed carcinogen. There is an imminent need for a robust, low-cost, and simple analytical technique to facilitate in situ monitoring of Cr(VI) in water. Current quantitative methods of Cr(VI) detection are largely laboratory-based, time-consuming, expensive, and require training for implementation. In this contribution, a portable, easy-to-use, and compact measuring tool is presented that provides Cr(VI) concentration within 10 min of water sampling over a linear range of 0-3 mg L^-1. This tool utilizes a relatively inexpensive camera-enabled smartphone with a custom-made test chamber attachment to seamlessly perform Cr(VI) measurements on water samples in the field. For analysis, an android-based software application was developed that directs the user to perform a simple series of steps following the diphenylcarbazide-based colorimetric method prescribed by the American Public Health Association. The tool was validated against a standard UV-visible spectrophotometer for a variety of synthetic and naturally contaminated water samples, with correlation factors greater than 0.993 (p < .001). The colorimetric method was also validated against a non-colorimetric Cr(VI) detection technique-ion chromatography-inductively coupled plasma mass spectrometry. Furthermore, Cr(VI) detection limits for the smartphone-enabled colorimetric method were found to be within 1.3-11.6 μg L^-1, which were significantly better than reported for commercially available field test kits, and even surpassed the limits exhibited by a typical spectrophotometer (25-50 μg L^-1). Finally, real-time mapping of source waters at a contaminated site was demonstrated by remote logging of Cr(VI) water quality data and corresponding GPS coordinates into a cloud server. This study highlights the potential role of smartphone-based monitoring tool in providing information to the affected community and enabling safe access to drinking water. An accurate, robust, simple-to-use, and economic method to measure hexavalent chromium in water within 10 min of sampling at site.

Lung Cancer Occurrence-Correlation with Serum Chromium Levels and Genotypes

Lung cancer is the leading cause of cancer-related death worldwide. Exposure to environmental and occupational carcinogens is an important cause of lung cancer. One of these substances is chromium, which is found ubiquitously across the planet. The International Agency for Research on Cancer has classified chromium(VI) as a human carcinogen. The aim of this study was to assess whether serum chromium levels, as well as DNA variants in selected genes involved in carcinogenesis, xenobiotic-metabolism, and oxidative stress could be helpful in the detection of lung cancer. We conducted a study using 218 lung cancer patients and 218 matched healthy controls. We measured serum chromium levels and genotyped ten genetic variants in ERCC2, XRCC1, MT1B, GSTP1, ABCB1, NQ01, CRTC3, GPX1, SOD2 and CAT. The odds ratios of being diagnosed with lung cancer were calculated using conditional logistic regression with respect to serum chromium level and genotypes. The odds ratio for the occurrence of lung cancer increased with increasing serum chromium levels. The difference between the quartiles with the lowest vs. highest chromium level was more than fourfold in the entire group (OR 4.52, CI 2.17-9.42, p < 0.01). This correlation was significantly increased by more than twice when specific genotypes were taken into consideration (ERCC-rs12181 TT, OR 12.34, CI 1.17-130.01, p = 0.04; CRTC3-rs12915189 non GG, OR 9.73, CI 1.58-60.10, p = 0.01; GSTP1-rs1695 non AA, OR 9.47, CI 2.06-43.49, p = < 0.01; CAT-rs1001179 non CC, OR 9.18, CI 1.64-51.24, p = 0.01). Total serum chromium levels > 0.1 μg/L were correlated with 73% (52/71) of lung cancers diagnosed with stage I disease. Our findings support the role of chromium and the influence of key proteins on lung cancer burden in the general population.

Prenatal exposure to hexavalent chromium disrupts testicular steroidogenic pathway in peripubertal F1 rats

We have reported sub-fertility in F1 progeny rats with gestational exposure to hexavalent chromium [Cr(VI)], which had disrupted Sertoli cell (SC) structure and function, and decreased testosterone (T). However, the underlying mechanism for reduced T remains to be understood. We tested the hypothesis "transient prenatal exposure to Cr(VI) affects testicular steroidogenesis by altering hormone receptors and steroidogenic enzyme proteins in Leydig cells (LCs)." Pregnant Wistar rats were given drinking water containing 50, 100, and 200 mg/L potassium dichromate during gestational days 9-14, encompassing fetal differentiation window of the testis from the bipotential gonad. F1 male rats were euthanized on postnatal day 60 (peripubertal rats with adult-type LCs alone). Results showed that prenatal exposure to Cr(VI): (i) increased accumulation of Cr(III) in the testis of F1 rats; (ii) increased serum levels of luteinizing and follicle stimulating hormones (LH and FSH), and 17β estradiol, and decreased prolactin and T; (iii) decreased steroidogenic acute regulatory protein, cytochrome P450 11A1, cytochrome P450 17A1, 3β- and 17β-hydroxysteroid dehydrogenases, cytochrome P450 aromatase and 5α reductase proteins, (iv) decreased specific activities of 3β and 17β hydroxysteroid dehydrogenases; (v) decreased receptors of LH, androgen and estrogen in LCs; (vi) decreased 5α reductase and receptor proteins of FSH, androgen, and estrogen in SCs. The current study concludes that prenatal exposure to Cr(VI) disrupts testicular steroidogenesis in F1 progeny by repressing hormone receptors and key proteins of the steroidogenic pathway in LCs and SCs.

Toxicant effects on mammalian oocyte mitochondria†

Oocyte mitochondria are unique organelles that establish a founder population in primordial germ cells (PGCs). As the oocyte matures in the postnatal mammalian ovary during folliculogenesis it increases exponentially in volume, and the oocyte mitochondria population proliferates to about 100 000 mitochondria per healthy, mature murine oocyte. The health of the mature oocyte and subsequent embryo is highly dependent on the oocyte mitochondria. Mitochondria are especially sensitive to toxic insults, as they are a major source of reactive oxygen species (ROS), they contain their own DNA (mtDNA) that is unprotected by histone proteins, they contain the electron transport chain that uses electron donors, including oxygen, to generate ATP, and they are important sensors for overall cellular stress. Here we review the effects that toxic insults including chemotherapeutics, toxic metals, plasticizers, pesticides, polycyclic aromatic hydrocarbons (PAHs), and ionizing radiation can have on oocyte mitochondria. This is very clearly a burgeoning field, as our understanding of oocyte mitochondria and metabolism is still relatively new, and we contend much more research is needed to understand the detrimental impacts of exposure to toxicants on oocyte mitochondria. Developing this field further can benefit our understanding of assisted reproductive technologies and the developmental origins of health and disease (DOHaD).

Cellulose and Vanadium Plasmonic Sensor to Measure Ni2+ Ions

A novel vanadium–cellulose composite thin film-based on angular interrogation surface plasmon resonance (SPR) sensor for ppb-level detection of Ni(II) ion was developed. Experimental results show that the sensor has a linear response to the Ni(II) ion concentrations in the range of 2–50 ppb with a determination coefficient (R2) of 0.9910. This SPR sensor can attain a maximum sensitivity (0.068° ppb−1), binding affinity constant (1.819 × 106 M−1), detection accuracy (0.3034 degree−1), and signal-to-noise-ratio (0.0276) for Ni(II) ion detection. The optical properties of thin-film targeting Ni(II) ions in different concentrations were obtained by fitting the SPR reflectance curves using the WinSpall program. All in all, the proposed Au/MPA/V–CNCs–CTA thin-film-based surface plasmon resonance sensor exhibits better sensing performance than the previous film-based sensor and demonstrates a wide and promising technology candidate for environmental monitoring applications in the future.

Toxicity assessment of industrial engineered and airborne process-generated nanoparticles in a 3D human airway epithelial in vitro model

The advanced ceramic technology has been pointed out as a potentially relevant case of occupational exposure to nanoparticles (NP). Not only when nanoscale powders are being used for production, but also in the high-temperature processing of ceramic materials there is also a high potential for NP release into the workplace environment. In vitro toxicity of engineered NP (ENP) [antimony tin oxide (Sb₂O₃•SnO₂; ATO); zirconium oxide (ZrO₂)], as well as process-generated NP (PGNP), and fine particles (PGFP), was assessed in MucilAir™ cultures at air-liquid interface (ALI). Cultures were exposed during three consecutive days to varying doses of the aerosolized NP. General cytotoxicity [lactate dehydrogenase (LDH) release, WST-1 metabolization], (oxidative) DNA damage, and the levels of pro-inflammatory mediators (IL-8 and MCP-1) were assessed. Data revealed that ENP (5.56 µg ATO/cm² and 10.98 µg ZrO₂/cm²) only caused mild cytotoxicity at early timepoints (24 h), whereas cells seemed to recover quickly since no significant changes in cytotoxicity were observed at late timepoints (72 h). No meaningful effects of the ENP were observed regarding DNA damage and cytokine levels. PGFP affected cell viability at dose levels as low as ∼9 µg/cm², which was not seen for PGNP. However, exposure to PGNP (∼4.5 µg/cm²) caused an increase in oxidative DNA damage. These results indicated that PGFP and PGNP exhibit higher toxicity potential than ENP in mass per area unit. However, the presence of a mucociliary apparatus, as it occurs in vivo as a defense mechanism, seems to considerably attenuate the observed toxic effects. Our findings highlight the potential hazard associated with exposure to incidental NP in industrial settings.

Efficient removal of chromate ions from aqueous solution using a highly cost-effective ferric coordinated [3-(2-aminoethylamino)propyl]trimethoxysilane-MCM-41 adsorbent

The present investigation involves synthesis and characterization of MCM-41-AEAPTMS-Fe(iii)Cl using coordinated Fe(iii) on MCM-41-AEAPTMS for efficient removal of hazardous Cr(vi) ions from aqueous solution. The adsorbent MCM-41-AEAPTMS-Fe(iii)Cl was characterized using small-angle X-ray diffraction (SAX), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Fourier-transform infrared (FT-IR) and Brunauer-Emmett-Teller (BET) surface analyzer techniques. The BET surface area was found to be 87.598 m2 g-1. The MCM-41-AEAPTMS-Fe(iii)Cl effectively adsorbs Cr(vi) with an adsorption capacity acquiring the maximum value of 84.9 mg g-1 at pH 3 at 298 K. The data followed pseudo-second-order kinetics and obeyed the Langmuir isotherm model. The thermodynamic data proved the exothermic and spontaneous nature of Cr(vi) ion adsorption on MCM-41-AEAPTMS-Fe(iii). Further, the higher value of ΔH° (-64.339 kJ mol-1) indicated that the adsorption was chemisorption in nature.

Nano-remediation of toxic heavy metal contamination: Hexavalent chromium [Cr(VI)]

The inexorable industrialization and modern agricultural practices to meet the needs of the increasing population have polluted the environment with toxic heavy metals such as Cr(VI), Cu²⁺, Cd²⁺, Pb^2+, and Zn²⁺. Among the hazardous heavy metal(loid)s contamination in agricultural soil, water, and air, hexavalent chromium [Cr(VI)] is the most virulent carcinogen. The metallurgic industries, tanneries, paint manufacturing, petroleum refineries are among various such human activities that discharge Cr(VI) into the environment. Various methods have been employed to reduce the concentration of Cr(VI) contamination with nano and bioremediation being the recent advancement to achieve recovery at low cost and higher efficiency. Bioremediation is the process of using biological sources such as plant extracts, microorganisms, and algae to reduce the heavy metals while the nano-remediation uses nanoparticles to adsorb heavy metals. In this review, we discuss the various activities that liberate Cr(VI). We then discuss the various conventional, nano-remediation, and bioremediation methods to keep Cr(VI) concentration in check and further discuss their efficiencies. We also discuss the mechanism of nano-remediation techniques for better insight into the process.

Electrochemical reduction of Cr(VI) in water: lessons learned from fundamental studies and applications

Converting toxic Cr(vi) to benign Cr(iii) would offer a solution to decontaminate drinking water. Electrochemical methods are ideally suited to carry out this reduction without added external reductants. Achieving this transformation at low overpotentials requires mediating the transfer of protons and electrons to Cr(vi). In this review thermodynamic parameters will be discussed to understand Cr(vi) speciation in water and identify reduction pathways. The electrochemical reduction of Cr(vi) at bare electrodes is reviewed and mechanistic considerations are discussed. Works on modified electrodes are compared to identify key parameters influencing the reduction. An overview of current applications to Cr(vi) reduction is briefly discussed to link fundamental studies to applications.

The Double Face of Metals: The Intriguing Case of Chromium

Chromium (Cr) is a common element in the Earth’s crust. It may exist in different oxidation states, Cr(0), Cr(III) and Cr(VI), with Cr(III) and Cr(VI) being relatively stable and largely predominant. Chromium’s peculiarity is that its behavior relies on its valence state. Cr(III) is a trace element in humans and plays a major role in glucose and fat metabolism. The beneficial effects of Cr(III) in obesity and types 2 diabetes are known. It has been long considered an essential element, but now it has been reclassified as a nutritional supplement. On the other hand, Cr(VI) is a human carcinogen and exposure to it occurs both in occupational and environmental contexts. It induces also epigenetic effects on DNA, histone tails and microRNA; its toxicity seems to be related to its higher mobility in soil and swifter penetration through cell membranes than Cr(III). The microorganisms Acinetobacter sp. Cr1 and Pseudomonas sp. Cr13 have been suggested as a promising agent for bioremediation of Cr(VI). This review intends to underline the important role of Cr(III) for human health and the dangerousness of Cr(VI) as a toxic element. The dual and opposing roles of this metal make it particularly interesting. An overview of the recent literature is reported in support.

Investigation of materials for reactive permeable barrier in removing cadmium and chromium(VI) from aquifer near a solid domestic waste landfill

The sorption characteristics of raw and biofilm-coated materials: vermiculite, lightweight expanded clay aggregate (LECA), perlite, zeolite, and shungite toward Cd and Cr(VI) ions were investigated to evaluate the possibility of their use as filtration barrier in the aquifer near a solid domestic waste landfill. The effectiveness of Cr(VI) removal by the raw materials changed in the following order: shungite > zeolite > perlite > vermiculite > LECA and for Cd: zeolite > shungite > vermiculite > perlite > LECA. After biofilm formation on the surface of the materials, the sorption capacity increased in some (perlite, LECA), while in others (zeolite) it was reduced. Four kinetic models were used to describe the experimental data. Mechanisms of metal removal were proposed: for Cr(VI), a characteristic combination of sorption processes was suggested, while the removal of Cd ions could occur by ion exchange and by complexation on the surface of the sorbent. Cr(VI) reduction by living bacterial cells forming a biofilm on the sorbent surface was assessed.

Epigenetic influence of environmentally neurotoxic metals

Continuous globalization and industrialization have ensured metals are an increasing aspect of daily life. Their usefulness in manufacturing has made them vital to national commerce, security and global economy. However, excess exposure to metals, particularly as a result of environmental contamination or occupational exposures, has been detrimental to overall health. Excess exposure to several metals is considered environmental risk in the aetiology of several neurological and neurodegenerative diseases. Metal-induced neurotoxicity has been a major health concern globally with intensive research to unravel the mechanisms associated with it. Recently, greater focus has been directed at epigenetics to better characterize the underlying mechanisms of metal-induced neurotoxicity. Epigenetic changes are those modifications on the DNA that can turn genes on or off without altering the DNA sequence. This review discusses how epigenetic changes such as DNA methylation, post translational histone modification and noncoding RNA-mediated gene silencing mediate the neurotoxic effects of several metals, focusing on manganese, arsenic, nickel, cadmium, lead, and mercury.

A critical review on recent developments in MOF adsorbents for the elimination of toxic heavy metals from aqueous solutions

Effective and substantial remediation of contaminants especially heavy metals from water is still a big challenge in terms of both environmental and biological perspectives because of their adverse effects on the human health. Many techniques including adsorption, ion exchange, co-precipitation, chemical reduction, ultrafiltration, etc. are reported for eliminating heavy metal ions from the water. However, adsorption has preferred because of its simple and easy handlings. Several types of adsorbents are observed and documented well for the purpose. Recently, highly porous metal-organic frameworks (MOFs) were developed by incorporating metals and organic ligands together and claimed as potent adsorbents for the remediation of highly toxic heavy metals from the aqueous solutions due to their unique features like greater surface area, high chemical stability, green and reuse material, etc. In this review, the authors discussed systematically some recent developments about secure MOFs to eliminate the toxic metals such as arsenic (both arsenite and arsenate), chromium(VI), cadmium (Cd), mercury (Hg) and lead (Pb). MOFs are observed as the most efficient adsorbents with greater selectivity as well as high adsorption capacity for metallic contamination. Graphical abstract.

An adverse outcome pathway for small intestinal tumors in mice involving chronic cytotoxicity and regenerative hyperplasia: a case study with hexavalent chromium, captan, and folpet

Small intestinal (SI) tumors are relatively uncommon outcomes in rodent cancer bioassays, and limited information regarding chemical-induced SI tumorigenesis has been reported in the published literature. Herein, we propose a cytotoxicity-mediated adverse outcome pathway (AOP) for SI tumors by leveraging extensive target species- and site-specific molecular, cellular, and histological mode of action (MOA) research for three reference chemicals, the fungicides captan and folpet and the transition metal hexavalent chromium (Cr(VI)). The gut barrier functions through highly efficient homeostatic regulation of SI epithelial cell sloughing, regenerative proliferation, and repair, which involves the replacement of up to 10¹¹ cells per day. This dynamic turnover in the SI provides a unique local environment for a cytotoxicity mediated AOP/MOA. Upon entering the duodenum, cytotoxicity to the villous epithelium is the molecular initiating event, as indicated by crypt elongation, villous atrophy/blunting, and other morphologic changes. Over time, the regenerative capacity of the gut epithelium to compensate declines as epithelial loss accelerates, especially at higher exposures. The first key event (KE), sustained regenerative crypt proliferation/hyperplasia, requires sufficient durations, likely exceeding 6 or 12 months, due to extensive repair capacity, to create more opportunities for the second KE, spontaneous mutation/transformation, ultimately leading to proximal SI tumors. Per OECD guidance, biological plausibility, essentiality, and empirical support were assessed using modified Bradford Hill considerations. The weight-of-evidence also included a lack of induced mutations in the duodenum after up to 90 days of Cr(VI) or captan exposure. The extensive evidence for this AOP, along with the knowledge that human exposures are orders of magnitude below those associated with KEs in this AOP, supports its use for regulatory applications, including hazard identification and risk assessment.

Elevated non-essential metals and the disordered metabolism of essential metals are associated to abnormal pregnancy with spontaneous abortion

Spontaneous abortion is a considerable threat to the physiology and mental health of the mother. The etiology of spontaneous abortion is multifactorial with complicated mechanisms, of which overexposure to non-essential metals (especially heavy metals) has been proposed to be associated with adverse birth outcomes. However, significant knowledge gaps remain to be filled in, such as the deleterious profile of non-essential metals and their interplay with essential metals in abnormal pregnancy. Under this setting, we aimed to address these challenges by conducting a cross-sectional study on 56 patients with spontaneous abortion in the 1^st trimester, by comparing to 55 healthy pregnant women in 1^st the trimester and 41 non-pregnant healthy women. Overexposure to a few non-essential metals, such as arsenic (As), antimony (Sb) and bismuth (Bi), was found in patients with spontaneous abortion, and likewise, some essential elements, such as magnesium (Mg), copper (Cu), vanadium (V), strontium (Sr) and tin (Sn), were also found to be elevated under spontaneous abortion. Further evidence of abnormal pregnancy was induced by a reduced level of internal hormones necessary for normal gestation, such as estradiol (E2) and progesterone (PRGE) in women with spontaneous abortion. Lactate dehydrogenase (LDH) and thyroid-stimulating hormone (TSH) levels were slightly increased in patients with spontaneous abortion. Comprehensive correlation analyses were carried out to identify the crucial factors that result in abortion. Our data stratified the important variables in decreasing order: PRGE, As, Mg, Sb, Sr, Sn, Bi and pregnant times in the progress of spontaneous abortion. Moreover, labyrinthine associations were uncovered between PRGE, non-essential metals and essential elements in causing spontaneous abortion. Therefore, our combined data unveiled the likely synergistic implications of elevated non-essential metals and the disordered metabolism of essential metals in abnormal pregnancy.

Metal-organic frameworks based adsorbents: A review from removal perspective of various environmental contaminants from wastewater

Rapidly increasing water contamination has turned into a major threat globally. The pollutants such as organic and inorganic compounds, heavy metals, and biological organisms are among the major contributor to water pollution. Therefore, the removal of these contaminants has attracted the researchers a lot. Various methodologies are being carried out for the purpose. Among them, the metal-organic frameworks (MOFs) with several active sites and tailorable porous architectures as adsorbents or photocatalytic removal agents is a fast-growing class of coordination chemistry to remove these agents from water. To date, numerous approaches dealing with water treatment including conservative and advanced technologies have been presented. This article thoroughly reviews the application of MOFs toward how to remove the toxic agents from water. The leading objective is to present up-to-date information and references regarding MOFs based materials toward wastewater treatment applications.

Comprehensive review of the basic chemical behaviours, sources, processes, and endpoints of trace element contamination in paddy soil-rice systems in rice-growing countries

Rice is the leading staple food for more than half of the world's population, and approximately 160 million hectares of agricultural area worldwide are under rice cultivation. Therefore, it is essential to fulfil the global demand for rice while maintaining food safety. Rice acts as a sink for potentially toxic metals such as arsenic (As), selenium (Se), cadmium (Cd), lead (Pb), zinc (Zn), manganese (Mn), nickel (Ni), and chromium (Cr) in paddy soil-rice systems due to the natural and anthropogenic sources of these metals that have developed in the last few decades. This review summarizes the sources and basic chemical behaviours of these trace elements in the soil system and their contamination status, uptake, translocation, and accumulation mechanisms in paddy soil-rice systems in major rice-growing countries. Several human health threats are significantly associated with these toxic and potentially toxic metals not only due to their presence in the environment (i.e., the soil, water, and air) but also due to the uptake and translocation of these metals via different transporters. Elevated concentrations of these metals are toxic to plants, animals, and even humans that consume them regularly, and the uniform deposition of metals causes a severe risk of bioaccumulation. Furthermore, the contamination of rice in the global rice trade makes this a critical problem of worldwide concern. Therefore, the global consumption of contaminated rice causes severe human health effects that require rapid action. Finally, this review also summarizes the available management/remediation measures and future research directions for addressing this critical issue.

Novel Biochemical Properties and Physiological Role of the Flavin Mononucleotide Oxidoreductase YhdA from Bacillus subtilis

Cr(VI) is mutagenic and teratogenic and considered an environmental pollutant of increasing concern. The use of microbial enzymes that convert this ion into its less toxic reduced insoluble form, Cr(III), represents a valuable bioremediation strategy. In this study, we examined the Bacillus subtilis YhdA enzyme, which belongs to the family of NADPH-dependent flavin mononucleotide oxide reductases and possesses azo-reductase activity as a factor that upon overexpression confers protection on B. subtilis from the cytotoxic effects promoted by Cr(VI) and counteracts the mutagenic effects of the reactive oxygen species (ROS)-promoted lesion 8-OxoG. Further, our in vitro assays unveiled catalytic and biochemical properties of biotechnological relevance in YhdA; a pure recombinant His10-YhdA protein efficiently catalyzed the reduction of Cr(VI) employing NADPH as a cofactor. The activity of the pure oxidoreductase YhdA was optimal at 30°C and at pH 7.5 and displayed Km and Vmax values of 7.26 mM and 26.8 μmol·min-1·mg-1 for Cr(VI), respectively. Therefore, YhdA can be used for efficient bioremediation of Cr(VI) and counteracts the cytotoxic and genotoxic effects of oxygen radicals induced by intracellular factors and those generated during reduction of hexavalent chromium.IMPORTANCE Here, we report that the bacterial flavin mononucleotide/NADPH-dependent oxidoreductase YhdA, widely distributed among Gram-positive bacilli, conferred protection to cells from the cytotoxic effects of Cr(VI) and prevented the hypermutagenesis exhibited by a MutT/MutM/MutY-deficient strain. Additionally, a purified recombinant His10-YhdA protein displayed a strong NADPH-dependent chromate reductase activity. Therefore, we postulate that in bacterial cells, YhdA counteracts the cytotoxic and genotoxic effects of intracellular and extracellular inducers of oxygen radicals, including those caused by hexavalent chromium.

Nanoscale battery cathode materials induce DNA damage in bacteria

The increasing use of nanoscale lithium nickel manganese cobalt oxide (Li x Ni y Mn z Co1-y-z O2, NMC) as a cathode material in lithium-ion batteries poses risk to the environment. Learning toxicity mechanisms on molecular levels is critical to promote proactive risk assessment of these complex nanomaterials and inform their sustainable development. We focused on DNA damage as a toxicity mechanism and profiled in depth chemical and biological changes linked to DNA damage in two environmentally relevant bacteria upon nano-NMC exposure. DNA damage occurred in both bacteria, characterized by double-strand breakage and increased levels of many putative chemical modifications on bacterial DNA bases related to direct oxidative stress and lipid peroxidation, measured by cutting-edge DNA adductomic techniques. Chemical probes indicated elevated intracellular reactive oxygen species and transition metal ions, in agreement with DNA adductomics and gene expression analysis. By integrating multi-dimensional datasets from chemical and biological measurements, we present rich mechanistic insights on nano-NMC-induced DNA damage in bacteria, providing targets for biomarkers in the risk assessment of reactive materials that may be extrapolated to other nano-bio interactions.

Genotoxic properties of materials used for endoprostheses: Experimental and human data

Approximately 2 million endoprostheses are implanted annually and metal ions as well as particles are released into the body from the materials which are used. This review describes the results of studies concerning genotoxic damage caused by artificial joints. DNA damage leads to various adverse long-term health effects in humans including cancer. Experiments with mammalian cells showed that metal ions and particles from orthopedic materials cause DNA damage. Induction of chromosomal aberrations (CA) was found in several in vitro experiments and in studies with rodents with metals from orthopedic materials. Human studies focused mainly on induction of CA (7 studies). Only few investigations (4) concerned sister chromatid exchanges, oxidative DNA damage (2) and micronucleus formation (1). CA are a reliable biomarker for increased cancer risks in humans) and were increased in all studies in patients with artificial joints. No firm conclusion can be drawn at present if the effects in humans are due to oxidative stress and if dissolved metal ions or release particles play a role. Our findings indicate that patients with artificial joints may have increased cancer risks due to damage of the genetic material. Future studies should be performed to identify safe materials and to study the molecular mechanisms in detail.

Prenatal exposure to excess chromium attenuates transcription factors regulating expression of androgen and follicle stimulating hormone receptors in Sertoli cells of prepuberal rats

We have reported that gestational exposure to hexavalent chromium (CrVI) represses androgen receptor (Ar) and follicle stimulating hormone receptor (Fshr) in Sertoli cells (SCs) of adult rats, while the mechanism underlying remains obscure. We tested the hypothesis "transient gestational exposure to CrVI during the critical embryonic windows of testicular differentiation and growth may have adverse impact on transcription factors controlling the expression of Ar and Fshr in SCs of the F₁ progeny". CrVI (K₂Cr₂O₇) was given through drinking water (50 ppm, 100 ppm and 200 ppm), to pregnant rats from gestational day 9-14 (testicular differentiation) and 15 to 21 (prenatal differentiation and proliferation of SC); male progenies were sacrificed on postnatal day 30 (Completion of postnatal SC maturation). A significant increase in free radicals and decrease in enzymatic and non-enzymatic antioxidants were observed in SCs of experimental rats. Real time PCR and western blot data showed decreased expression of Ar, Fshr, Inhibin B, Transferrin, Androgen binding protein, Claudin 11 and Occludin in SCs of experimental rats; concentrations of lactate, pyruvate and retinoic acid also decreased. Serum FSH, luteinizing hormone and estradiol increased, whereas testosterone and prolactin decreased in experimental rats. Western blot detection revealed decreased levels of transcription factors regulating Fshr viz., USF-1, USF-2, SF-1, c-fos, c-jun and GATA 1, and those of Ar viz., Sp-1, ARA54, SRC-1 and CBP in experimental rats, whereas the levels of cyclinD1 and p53, repressors of Ar increased. ChIP assay detected decreased USF-1 and USF-2 binding to Fshr promoter, and binding of Sp-1 to Ar promoter. We conclude that gestational exposure to CrVI affects SC structure and function in F₁ progeny by inducing oxidative stress and diminishing the expression of Ar and Fshr through attenuation of their specific transcriptional regulators and their interaction with the respective promoter.

Metals and Mechanisms of Carcinogenesis

Metal exposure is pervasive and not limited to sporadic poisoning events or toxic waste sites. Hundreds of millions of people around the globe are affected by chronic metal exposure, which is associated with serious health concerns, including cancer, as demonstrated in a variety of studies at the molecular, systemic, and epidemiologic levels. Metal-induced toxicity and carcinogenicity are sophisticated and complex in nature. This review provides a broad context and holistic view of currently available studies on the mechanisms of metal-induced carcinogenesis. Specifically, we focus on the five most prevalent carcinogenic metals, arsenic, nickel, cadmium, chromium, and beryllium, and their potential to drive carcinogenesis in humans. A comprehensive understanding of the mechanisms behind the development of metal-induced cancer can provide valuable insights for therapeutic intervention involving molecular targets in metal-induced carcinogenesis.

The guanidine thiocyanate-high EDTA method for total microbial RNA extraction from severely heavy metal-contaminated soils

Molecular analyses relying on RNA, as a direct way to unravel active microbes and their functional genes, have received increasing attention from environmental researchers recently. However, extracting sufficient and high‐quality total microbial RNA from seriously heavy metal‐contaminated soils is still a challenge. In this study, the guanidine thiocyanate‐high EDTA (GTHE) method was established and optimized for recovering high quantity and quality of RNA from long‐term heavy metal‐contaminated soils. Due to the low microbial biomass in the soils, we combined multiple strong denaturants and intense mechanical lysis to break cells for increasing RNA yields. To minimize RNAase and heavy metals interference on RNA integrity, the concentrations of guanidine thiocyanate and EDTA were increased from 0.5 to 0.625 ml g⁻¹ soil and 10 to 100 mM, respectively. This optimized GTHE method was applied to seven severely contaminated soils, and the RNA recovery efficiencies were 2.80 ~ 59.41 μg g⁻¹ soil. The total microbial RNA of non‐Cr(VI) (NT) and Cr(VI)‐treated (CT) samples was utilized for molecular analyses. The result of qRT‐PCR demonstrated that the expressions of two tested genes, chrA and yieF, were respectively upregulated 4.12‐ and 62.43‐fold after Cr(VI) treatment. The total microbial RNA extracted from NT and CT samples, respectively, reached to 26.70 μg and 30.75 μg, which were much higher than the required amount (5 μg) for metatranscriptomic library construction. Besides, ratios of mRNA read were more than 86%, which indicated the high‐quality libraries constructed for metatranscriptomic analysis. In summary, the GTHE method is useful to study microbes of contaminated habitats.

Picomolar-level detection of mercury within non-biological/biological aqueous media using ultra-sensitive polyaniline-Fe3O4-silver diethyldithiocarbamate nanostructure

Mercury as the 3rd most toxic, non-biodegradable, and carcinogenic pollutant can adversely affect the ecosystem and health of living species through its bioaccumulation within the nature that can affect the top consumer in the food chain; therefore, it is vital to sense/remove Hg²⁺ within/from aqueous media using practical approaches. To address this matter, we modified the glassy carbon electrode (GCE) with ultra-sensitive, interconnected, sulfurized, and porous nanostructure consisted of polyaniline-Fe₃O₄-silver diethyldithiocarbamate (PANi-F-S) to enhance the sensitivity, selectivity, and limit of detection (LOD) of the sensor. Obtained results showed that at optimum conditions (i.e., pH value of 7, deposition potential of - 0.8 V, and accumulation time of 120 s), for Hg²⁺ concentration ranging from 0.4 to 60 nM, the modified electrode showing linear relative coefficient of 0.9983, LOD of 0.051 nM, LOQ of 0.14 nM, and sensitivity of 1618.86 μA μM^-1 cm^-2 highlights superior sensitivity of the developed platform until picomolar level. Additionally, the modified electrode showed ideal repeatability, stability, reproducibility, and selectivity (by considering Zn²⁺, Cd²⁺ Pb²⁺, Cu²⁺, Ni²⁺, and Co²⁺ as metal interferences) and recovered more than 99% of the Hg²⁺ ions within non-biological (mineral, tap, and industrial waters) and biological (blood plasma sample) fluids. Graphical abstract.

Chromium and human low-density lipoprotein oxidation

Chromium is a catalytic metal able to foster oxidant damage, albeit its capacity to induce human LDL oxidation is to date unkown. Thus, we have investigated whether trivalent and hexavalent chromium, namely Cr(III) and Cr(VI), can induce human LDL oxidation. Cr(III) as CrCl₃ is incapable of inducing LDL oxidation at pH 7.4 or 4.5. However, Cr(III), specifically at physiological pH of 7.4 and in the presence of phosphates, causes an absorbance increase at 234 resembling a spectrophotometric kinetics of LDL oxidation with a lag- and propagation-like phase. In this regard, it is conceivable that peculiar Cr(III) forms such as Cr(III) hydroxide and, especially, Cr(III) polynuclear hydroxocomplexes formed at pH 7.4 interact with phosphates generating species with an intrinsic absorbance at 234 nm, which increases over time resembling a spectrophotometric kinetics of LDL oxidation. Cr(VI), as K₂Cr₂O₇, can instead induce substantial human LDL oxidation at acidic pH such as 4.5, which is typical of the intracellular lysosomal compartment. LDL oxidation is related to binding of Cr(VI) to LDL particles with quenching of the LDL tryptophan fluorescence, and it is inhibited by the metal chelators EDTA and deferoxamine, as well as by the chain-breaking antioxidants butylated hydroxytoluene and probucol. Moreover, Cr(VI)-induced LDL oxidation is inhibited by mannitol conceivably by binding Cr(V) formed from LDL-dependent Cr(VI) reduction and not by scavenging hydroxyl radicals (OH); indeed, the OH scavengers sodium formate and ethanol are ineffective against Cr(VI)-induced LDL oxidation. Notably, heightened LDL lipid hydroperoxide levels and decreased LDL tryptophan fluorescence occur in Cr plating workers, indicating Cr-induced human LDL oxidation in vivo. The biochemical, pathophysiological and clinical implications of these novel findings on chromium and human LDL oxidation are discussed.

Shewanella oneidensis MR-1 impregnated Ca-alginate capsule for efficient Cr(VI) reduction and Cr(III) adsorption

Shewanella oneidensis MR-1 (MR-1)-impregnated alginate capsules with 3D porous structure were prepared through cation crossing-linking and was used for the Cr(VI) reduction and removal. After being encapsulated by alginate, the endurance of the MR-1 was largely enhanced under conditions of high Cr(VI) concentrations (up to 4 mM) and low pH (pH 5). The Cr(VI) reduction over the MR-1-impregnated alginate capsules could be fitted by pseudo first-order kinetic model. With the Cr(VI) initial concentration increasing from 1 to 4 mM, the first-order rate constant for the encapsulated MR-1 (k_capsules) and free cells (k_cells) fell by 26.3% and 82.4%, respectively. At pH 5, the k_capsules value was 0.19 h^{- 1}, which was about 3.7 times higher than k_cells. Moreover, the encapsulated MR-1 held 90.5% of the Cr(VI) reduction ability after 15 days of resting time, while the free MR-1 held 19.7%. After bioreduction, 73.6% of total chromium was adsorbed on the MR-1 impregnated Ca-alginate capsules. XPS results showed 85% of the adsorbed chromium was Cr(III). The mechanism for chromium removal over the MR-1-impregnated Ca-alginate capsules was proposed with the following steps: (1) Cr(VI) was bioreduced via the encapsulated MR-1; (2) the reduced soluble Cr(III) was adsorbed by alginate selectively. In the study, the Ca-alginate shell of the cabbage-like MR-1 impregnated capsules could be a shelter for encapsulated MR-1 to endure unfavorable conditions (e.g., low pH and high concentration of Cr(VI)) and immobilize the soluble chromium. Considering the obtained capsules derived from biomolecules were environment-friendly, the MR-1-impregnated Ca-alginate capsules were potential for the application in the remediation of environmental pollution. Graphical abstract.

Synthesis of char-based adsorbents from cotton textile waste assisted by iron salts at low pyrolysis temperature for Cr(VI) removal

Char-based adsorbents (char-FeCl₃, char-FeCl₂, and char-FeCit) derived from cotton textile waste (CTW) were synthesized by one-step low-temperature pyrolysis approach with different iron salts. The properties of the samples were conducted by BET, SEM, EDS, XRD, XPS, TEM, and FTIR. The results suggested that the surface areas of char-FeCl₃ and char-FeCl₂ were higher than those of char-FeCit. The presence of Fe₂O₃ as well as pyrolysis gas (HCl (g) and H₂O (g)) could catalyze the formation of porosity. Meanwhile, FeCl₃ showed the strongest catalysis effect to decompose cellulose to produce char. The pyrolysis process analysis was investigated by means of thermogravimetry-DSC. FeCl₃ and FeCl₂ could accelerate the breakage of cellulose structure whereas FeC₆H₅O₇ was not beneficial to form char at low temperature as the incomplete decomposition of citrate. The adsorption property of Cr(VI) for the chars was evaluated. Adsorption processes were fitted well with the Freundlich model, and char-FeCl₃ presented the best adsorptive capacity (70.39 mg/g). Thus, this low-temperature pyrolysis method was economical and technologically simplified as well as efficient adsorption capacity of Cr(VI) removal. Graphical abstract.

Do Battlefield Injury-acquired Indwelling Metal Fragments Induce Metal Immunogenicity?

BACKGROUND

A battlefield-related injury results in increased local and systemic innate immune inflammatory responses, resulting in wound-specific complications and an increased incidence of osteoarthritis. However, little is known about whether severe injuries affect long-term systemic homeostasis, for example, immune function. Moreover, it also remains unknown whether battlefield-acquired metal fragments retained over the long term result in residual systemic effects such as altered immune reactivity to metals.

QUESTIONS/PURPOSES

Does a retained metal fragment from a battlefield injury contribute to increased (1) adaptive metal-specific immune responses, (2) systemically elevated metal ion serum levels, and (3) serum immunoglobulin levels compared with combat injuries that did not result in a retained metal fragment?

METHODS

In this pilot study, we analyzed metal-immunogenicity in injured military personnel and noninjured control participants using lymphocyte transformation testing (LTT, lymphocyte proliferation responses to cobalt, chromium and nickel challenge at 0.001, 0.01 and 0.1-mM concentrations in triplicate for each participant), serum metal ion analysis (ICP-mass spectroscopy), and serum immunoglobulin analysis (IgE, IgG, IgA, and IgM ). Military personnel with a battlefield-sustained injury self-recruited without any exclusion for sex, age, degree of injury. Those with battlefield injury resulting in retained metal fragments (INJ-FRAG, n = 20 male, mean time since injury ± SD was 12 ± 10 years) were compared with those with a battlefield injury but without retained metal fragments (INJ-NO-FRAG, n = 12 male, mean time since injury ± SD was 13 ± 12 years). A control group comprised of male noninjured participants was used to compare measured immunogenicity metrics (n = 11, males were selected to match battlefield injury group demographics).

RESULTS

Military participants with sustained metal fragments had increased levels of metal-induced lymphocyte responses. The lymphocyte stimulation index among military participants with metal fragments was higher than in those with nonretained metal fragments (stimulation index = 4.2 ± 6.0 versus stimulation index = 2.1 ± 1.2 (mean difference 2.1 ± 1.4 [95% confidence interval 5.1 to 0.8]; p = 0.07) and an average stimulation index = 2 ± 1 in noninjured controls. Four of 20 participants injured with retained fragments had a lymphocyte proliferation index greater than 2 to cobalt compared with 0 in the group without a retained metal fragment or 0 in the control participants. However, with the numbers available, military personnel with retained metal fragments did not have higher serum metal ion levels than military participants without retained metal fragment-related injuries or control participants. Military personnel with retained metal fragments had lower serum immunoglobulin levels (IgG, IgA, and IgM) than military personnel without retained metal fragments and noninjured controls, except for IgE. Individuals who were metal-reactive positive (that is, a stimulation index > 2) with retained metal fragments had higher median IgE serum levels than participants who metal-reactive with nonmetal injuries (1198 ± 383 IU/mL versus 171 ± 67 IU/mL, mean difference 1027 ± 477 IU/mL [95% CI 2029 to 25]; p = 0.02).

CONCLUSIONS

We found that males with retained metal fragments after a battlefield-related injury had altered adaptive immune responses compared with battlefield-injured military personnel without indwelling metal fragments. Military participants with a retained metal fragment had an increased proportion of group members and increased average lymphocyte reactivity to common implant metals such as nickel and cobalt. Further studies are needed to determine a causal association between exposure to amounts of retained metal fragments, type of injury, personnel demographics and general immune function/reactivity that may affect personal health or future metal implant performance.

LEVEL OF EVIDENCE

Level IV, therapeutic study.