Porous titania beads for remediation of arsenic contamination from acid mine drainage

Hierarchically porous titania beads with and without amine functionalisation have been developed and tested as adsorbents for removal of highly toxic As(V) from environments affected by acid mine drainage (AMD). The unique acid stability of the titania framework enables these adsorbents to function in highly acidified environments and their granular form facilitates practical deployment under continuous flow conditions. Herein, both non-functionalised and amine-functionalised titania beads have been demonstrated to selectively remove As(V) from simulated and real AMD solutions at pH 2.6. Novel selectivity for As(V) over Na(I), Mg(II), Al(III), Si(VI), Ca(II), Co(II), Cu(II), Zn(II), Nd(III) and Ho(III) was achieved, with competing element concentrations similar to or up to an order of magnitude greater than that of As(V). Although Fe(III) and some Fe(II) were also adsorbed by the titania beads, Fe adsorption did not inhibit As(V) adsorption, indicating different adsorption mechanisms for these two elements. The As(V) adsorption capacity of the titania beads decreased from ∼20 mg/g from pure As(V) solution to ∼10 mg/g from real AMD solution, demonstrating the importance of adsorbent testing under applied conditions. Amine functionalisation increased the kinetics of adsorption, but the non-functionalised titania beads showed greater selectivity for As(V) over Fe(II) and Fe(III) and hence were considered preferable for As remediation applications. Nevertheless, the functionalisation ability of the porous titania beads makes them a promising, flexible technology for remediation of a wide range of AMD affected environments.

Integrated probabilistic risk assessment in sites contaminated with arsenic and lead by long-term mining liabilities in San Luis Potosi, Mexico

Mining environmental liabilities (MEL) in San Luis Potosi are the result of more than 450 years of mining activity, which has contaminated the soil mainly with arsenic (As) and lead (Pb) in several areas. Risk assessments are used to estimate the possibility of the occurrence of adverse effects on human health or on ecological receptors; and the most accessible way of performing them is through probabilistic estimates such as the Latin Hypercube Sampling (LHS) model. Therefore, the aim of this study was to carry out an Integrated Probabilistic Environmental Risk Assessment (IPERA) for the estimation of health risks in infants and rodents. The mean concentrations of As and Pb in soil were significantly higher (p<0.05) in all contaminated sites than in their respective reference sites. Villa de la Paz was the site with the highest mean concentration of As (1374 mg/kg), while Charcas was the one with the highest level of Pb (12,929 mg/kg). The Hazard Quotient (HQ) was calculated and Villa de la Paz had the highest values of As in both rodents (11.994) and children (39.32), and Charcas showed the highest values of Pb in both (24.971 and 31.668 for rodents and children respectively). The cumulative hazard Index (HI) reveals there is a very significant health risk due to As and Pb exposure for both rodents and children in contaminated areas of these mining communities.

Ultrathin quasi-hexagonal gold nanostructures for sensing arsenic in tap water

Monodispersed colloidal gold nanoparticles (AuNPs) were synthesized by an easy, cost-effective, and eco-friendly method. The AuNPs were mostly quasi-hexagonal in shape with sizes ranging from 15 to 18 nm. A screen-printed electrode modified with AuNPs (AuNPs/SPE) was used as an electrochemical sensor for the detection of As(iii) in water samples. The mechanistic details for the detection of As(iii) were investigated and an electrochemical reaction mechanism was proposed. Under the optimal experimental conditions, the sensor was highly sensitive to As(iii), with a limit of detection of 0.11 μg L-1 (1.51 nM), which is well below the regulatory limit of 10 μg L-1 established by the United States Environmental Protection Agency and the World Health Organization. The sensor responses were highly stable, reproducible, and linear over the As(iii) concentration range of 0.075 to 30 μg L-1. The presence of co-existing heavy metal cations such as lead, copper, and mercury did not interfere with the sensor response to As(iii). Furthermore, the voltammogram peaks for As(iii), lead, copper, and mercury were sufficiently separate for their potential simultaneous measurement, and at very harsh acidic pH it may be possible to detect As(v). The AuNPs/SPE could detect As(iii) in tap water samples at near-neutral pH, presenting potential possibilities for real-time, practical applications.

Linking Mitochondrial Dysfunction to Organismal and Population Health in the Context of Environmental Pollutants: Progress and Considerations for Mitochondrial Adverse Outcome Pathways

Mitochondria are key targets of many environmental contaminants, because specific chemicals can interact directly with mitochondrial proteins, lipids, and ribonucleic acids. These direct interactions serve as molecular initiating events that impede adenosine triphosphate production and other critical functions that mitochondria serve within the cell (e.g., calcium and metal homeostasis, apoptosis, immune signaling, redox balance). A limited but growing number of adverse outcome pathways (AOPs) have been proposed to associate mitochondrial dysfunction with effects at organismal and population levels. These pathways involve key events such as altered membrane potential, mitochondrial fission/fusion, and mitochondrial DNA damage, among others. The present critical review and analysis reveals current progress on AOPs involving mitochondrial dysfunction, and, using a network-based computational approach, identifies the localization of mitochondrial molecular initiating events and key events within multiple existing AOPs. We also present 2 case studies, the first examining the interaction between mitochondria and immunotoxicity, and the second examining the role of early mitochondrial dysfunction in the context of behavior (i.e., locomotor activity). We discuss limitations in our current understanding of mitochondrial AOPs and highlight opportunities for clarifying their details. Advancing our knowledge of key event relationships within the AOP framework will require high-throughput datasets that permit the development and testing of chemical-agnostic AOPs, as well as high-resolution research that will enhance the mechanistic testing and validation of these key event relationships. Given the wide range of chemicals that affect mitochondria, and the centrality of energy production and signaling to ecologically important outcomes such as pathogen defense, homeostasis, growth, and reproduction, a better understanding of mitochondrial AOPs is expected to play a significant, if not central, role in environmental toxicology. Environ Toxicol Chem 2019;38:1625-1634. © 2019 SETAC.

Profiling microRNA expression in Atlantic killifish (Fundulus heteroclitus) gill and responses to arsenic and hyperosmotic stress

The Atlantic killifish (Fundulus heteroclitus), native to estuarine areas of the Atlantic coast of the United States, has become a valuable ecotoxicological model as a result of its ability to acclimate to rapid environmental changes and adapt to polluted habitats. MicroRNAs (miRNAs) are highly conserved small RNAs that regulate gene expression and play critical roles in stress responses in a variety of organisms. Global miRNA expression in killifish and the potential roles miRNA have in environmental acclimation have yet to be characterized. Accordingly, we profiled miRNA expression in killifish gill for the first time and identified a small group of highly expressed, well-conserved miRNAs as well as 16 novel miRNAs not yet identified in other organisms. Killifish respond to large fluctuations in salinity with rapid changes in gene expression and protein trafficking to maintain osmotic balance, followed by a secondary phase of gene and protein expression changes that enable remodeling of the gills. Arsenic, a major environmental toxicant, was previously shown to inhibit gene expression responses in killifish gill, as well the ability of killifish to acclimate to a rapid increase in salinity. Thus, we examined the individual and combined effects of salinity and arsenic on miRNA expression in killifish gill. Using small RNA sequencing, we identified 270 miRNAs expressed in killifish, and found that miR-135b was differentially expressed in response to arsenic and at 24 h following transfer to salt water. Predicted targets of miR-135b are involved in ion transport, cell motility and migration, GTPase mediated signal transduction and organelle assembly. Consistent with previous studies of these two environmental stressors, we found a significant interaction (i.e., arsenic dependent salinity effect), whereby killifish exposed to arsenic exhibited an opposite response in miR-135b expression at 24 h post hyperosmotic challenge compared to controls. By examining mRNA expression of predicted miRNA targets during salinity acclimation and arsenic exposure, we found that miR-135b targets were significantly more likely to decrease during salinity acclimation than non-targets. Our identification of a significant interaction effect of arsenic and salinity on miR-135b expression supports the hypothesis that arsenic alters upstream regulators of stress response networks, which may adversely affect the killifish response to osmotic stress. The characterization of miRNAs in this ecotoxicological model will be a valuable resource for future studies investigating the role of miRNAs in response to environmental stress.

Inorganic arsenic causes apoptosis cell death and immunotoxicity on European sea bass (Dicentrarchus labrax)

Inorganic arsenic (As) is one of the most toxic pollutants in the water. We have studied their effects on the marine teleost European sea bass (Dicentrarchus labrax) at 2 and 10 days of 5 μM of As₂O₃ (sub-lethal doses) waterborne exposure. Arsenic accumulates in liver and gill tissues. The expression profile of five genes (bax, blc2, casp3, casp8 and casp9) involved in apoptosis cell death confirmed apoptotic effects in liver, slight changes in gill and no effects in skin according with the histopathology findings. Total IgM level and peroxidase activities were increased at 2 and 10 days, respectively. The bactericidal activity was decreased at 2 days after As exposure. A general decrease of cellular immune activities with significant differences in the case of respiratory burst activity was observed after 2 and 10 days of exposure. This work describes for the first time the effects of As exposure on European sea bass.

An ultratrace assay of arsenite based on the synergistic quenching effect of Ru(bpy)32+ and arsenite on the electrochemiluminescence of Au–g-C3N4 nanosheets

An arsenite assay based on the synergistic quenching effect of As(iii) and Ru(bpy)₃²⁺ on the ECL of Au–g-C₃N₄ coupled with the generation of a new ECL signal of Ru(bpy)₃²⁺.

Chronic endosulfan exposure impairs immune response rendering Clarias gariepinus susceptible to microbial infection

Endosulfan, a persistent organochlorine insecticide affects several off-target organisms including fish though the underlying mechanisms remain obscure. In the present study, we monitored the effect of chronic endosulfan exposure on headkidney (HK), an important immune organ in fish and on fish immune system thereof. Clarias gariepinus were exposed to a non-lethal concentration of endosulfan 2.884ppb (1/10th LC₅₀) for 30 d which resulted in suppressed phagocytosis and bactericidal potential of headkidney macrophages (HKM). The same non-lethal concentration of endosulfan also interfered with T-cell proliferation and serum antibody titer in fish. Endosulfan-exposed fish were challenged with non-lethal dose of fish pathogenic bacteria Aeromonas hydrophila and the 'exposure-challenge' study revealed endosulfan-exposed C. gariepinus severely immunocompromised and prone to bacterial infections. Depuration for 30 d suggested that except for phagocytosis and serum agglutination titer other endosulfan-induced immune aberrations could not be restored significantly. Nonetheless, compared to exposed-challenged fish the depurated fish showed significant improvement in viability on challenge with A. hydrophila. Collectively, these findings suggest chronic endosulfan exposure has prolonged effect on fish making them prone to microbial infections.

Low-level arsenic causes chronic inflammation and suppresses expression of phagocytic receptors

The impact of chronic low-level groundwater arsenic (As) exposure [in the range above the WHO-recommended limit of 10 μg/L but ≤50 μg/L (permissible limit of As for many Asian countries)] was investigated for cross talk of inflammatory changes and expression of phagocytic receptors of exposed rural women (N, 45) from districts of 24 Parganas (south) and in matched control groups (N, 43) [As ≤10 μg/L] from the same district. Systemic inflammation was evident from the upregulated levels of pro-inflammatory mediators like tumor necrosis factor-α (TNF-α); interleukins (ILs) like IL-6, IL-8, and IL-12; and C-reactive protein (CRP) in the sera and upregulated expression of protein kinase B phosphorylated at ser473 (pAKTser473)/nuclear factor-κB (NF-κB)/TNF-α axis in the leukocytes of exposed women with respect to control. We found that low-dose As exposure apart from inflicting inflammation altered the expression of phagocytic receptors-Fcγ receptors (FcγRs) and complement receptors (CRs). The leukocytes of the low-As-exposed women exhibited suppression of CD64, CD35, and CD11b and increased expression of CD16 with respect to control. Groundwater As showed a negative correlation with CD64 expression on monocytes [Pearson's r, -0.8205; 95% confidence interval (CI), -0.8789 to -0.7379] and granulocytes [r, -0.7635; 95% CI, -0.8388 to -0.6595] and a positive correlation with CD16 on granulocytes [r, 0.8363; 95% CI, 0.7599 to 0.8899]. A negative correlation of groundwater As was also observed with expression of CD35 on granulocytes [r, -0.8780; 95% CI, -0.9185 to -0.8192] and monocytes [r, -0.7778; 95% CI, -0.8490 to -0.6790] and CD11b on monocytes [r, -0.6035; 95% CI, -0.7218 to -0.4511]. Therefore, it may be indicated that chronic low-level As exposure (11-50 μg/L) not only evoked chronic inflammatory changes but also suppressed the expression of FcγRs and CRs in the exposed women. This, in turn, may lead to susceptibility towards pathogenic infections or in long run may even contribute towards chronic inflammatory diseases including cancer.

Mitochondrial dysfunction, oxidative stress and apoptotic induction in microglial BV-2 cells treated with sodium arsenate

The treatment of microglial BV-2 cells with sodium arsenate (As(V): 0.1-400μmol/L - 48hr) induces a dose-dependent response. The neurotoxic effects of high concentrations of As(V) (100, 200 and 400μmol/L) are characterized by increased levels of mitochondrial complexes I, II, and IV followed by increased superoxide anion generation. Moreover, As(V) triggers an apoptotic mode of cell death, demonstrated by an apoptotic SubG1 peak, associated with an alteration of plasma membrane integrity. There is also a decrease in transmembrane mitochondrial potential and mitochondrial adenosine triphosphate ATP. It is therefore tempting to speculate that As(V) triggers mitochondrial dysfunction, which may lead to defective oxidative phosphorylation subsequently causing mitochondrial oxidative damage, which in turn induces an apoptotic mode of cell death.

Infectious disease models in zebrafish

In recent years, the zebrafish (Danio rerio) has developed as an important alternative to mammalian models for the study of hostpathogen interactions. Because they lack a functional adaptive immune response during the first 4-6weeks of development, zebrafish rely upon innate immune responses to protect against injuries and infections. During this early period of development, it is possible to isolate and study mechanisms of infection and inflammation arising from the innate immune response without the complications presented by the adaptive immune response. Zebrafish possess several inherent characteristics that make them an attractive option to study hostpathogen interactions, including extensive sequence and functional conservation with the human genome, optical clarity in larvae that facilitates the high-resolution visualization of host cell-microbe interactions, a fully sequenced and annotated genome, robust forward and reverse genetic tools and techniques (e.g., CRISPR-Cas9 and TALENs), and amenability to chemical studies and screens. Here, we describe methods for studying hostpathogen interactions both through systemic infections and through localized infections that allow analysis of host cell response, migration patterns, and behavior. Each of the methods described can be modified for use in downstream applications that include ecotoxicant studies and chemical screens.

Could vitamin C and zinc chloride protect the germ cells against sodium arsenite?

Arsenic (As) is commonly associated with natural and human processes such as volcanic emissions, mining and herbicides production, being an important pollutant. Several studies have associated As intake with male fertility reduction, thus the aim of the present study was to evaluate whether vitamin C and/or zinc would counteract As side effects within the testicles. Adult male Wistar rats were divided into six experimental groups: control, sodium arsenite (5 mg/kg/day), vitamin C (100 mg/kg/day), zinc chloride (ZnCl2; 20 mg/kg/day), sodium arsenite + vitamin C and sodium arsenite + ZnCl2. Testicles and epididymis were harvested and either frozen or routinely processed to be embedded in glycol methacrylate resin. As reduced the seminiferous epithelium and tubules diameter due to germ cell loss. In addition, both the round spermatids population and the daily sperm production were reduced. However, ZnCl2 and vitamin C showed to be effective against such side effects, mainly regarding to sperm morphology. Long-term As intake increased the proportions of abnormal sperm, whereas the concomitant intake of As with zinc or vitamin C enhanced the proportions of normal sperm, showing that such compounds could be used to protect this cell type against morphological defects.

Advancing toxicology research using in vivo high throughput toxicology with small fish models

Small freshwater fish models, especially zebrafish, offer advantages over traditional rodent models, including low maintenance and husbandry costs, high fecundity, genetic diversity, physiology similar to that of traditional biomedical models, and reduced animal welfare concerns. The Collaborative Workshop on Aquatic Models and 21st Century Toxicology was held at North Carolina State University on May 5-6, 2014, in Raleigh, North Carolina, USA. Participants discussed the ways in which small fish are being used as models to screen toxicants and understand mechanisms of toxicity. Workshop participants agreed that the lack of standardized protocols is an impediment to broader acceptance of these models, whereas development of standardized protocols, validation, and subsequent regulatory acceptance would facilitate greater usage. Given the advantages and increasing application of small fish models, there was widespread interest in follow-up workshops to review and discuss developments in their use. In this article, we summarize the recommendations formulated by workshop participants to enhance the utility of small fish species in toxicology studies, as well as many of the advances in the field of toxicology that resulted from using small fish species, including advances in developmental toxicology, cardiovascular toxicology, neurotoxicology, and immunotoxicology. We alsoreview many emerging issues that will benefit from using small fish species, especially zebrafish, and new technologies that will enable using these organisms to yield results unprecedented in their information content to better understand how toxicants affect development and health.

Metabolomic Characterizations of Liver Injury Caused by Acute Arsenic Toxicity in Zebrafish

Arsenic is one of the most common metalloid contaminants in groundwater and it has both acute and chronic toxicity affecting multiple organs. Details of the mechanism of arsenic toxicity are still lacking and profile studies at metabolic level are very limited. Using gas chromatography coupled with mass spectroscopy (GC/MS), we first generated metabolomic profiles from the livers of arsenic-treated zebrafish and identified 34 significantly altered metabolite peaks as potential markers, including four prominent ones: cholic acid, glycylglycine, glycine and hypotaurine. Combined results from GC/MS, histological examination and pathway analyses suggested a series of alterations, including apoptosis, glycogenolysis, changes in amino acid metabolism and fatty acid composition, accumulation of bile acids and fats, and disturbance in glycolysis related energy metabolism. The alterations in glycolysis partially resemble Warburg effect commonly observed in many cancer cells. However, cellular damages were not reflected in two conventional liver function tests performed, Bilirubin assay and alanine aminotransferase (ALT) assay, probably because the short arsenate exposure was insufficient to induce detectable damage. This study demonstrated that metabolic changes could reflect mild liver impairments induced by arsenic exposure, which underscored their potential in reporting early liver injury.

Arsenic-induced genotoxicity in Nile tilapia (Orechromis niloticus); the role of Spirulina platensis extract

Arsenic (As) is one of the most relevant environmental global single substance toxicants that have long been regarded as a carcinogenic and genotoxic potential. In this respect, we evaluated the cytogenetic effect of arsenic exposure in Nile tilapia (Oreochromis niloticus), in terms of erythrocyte alteration, apoptosis, and induction of micronuclei. Spirulina platensis (SP) is a filamentous cyanobacterium microalgae with potent dietary phytoantioxidant, anti-inflammatory, and anti-cancerous properties supplementation. The protective role of Spirulina as supplementary feeds was studied in Nile tilapia (O. niloticus) against arsenic-induced cytogenotoxicity. Four groups were assigned as control group (no SP or As), As group (exposed to water-born As in the form of NaAsO2 at 7 ppm), SP1 (SP at 7.5% + As at the same level of exposure), and SP2 (SP at 10% + As at the same level of exposure). As-treated group had a significant increase in all cytogenetic analyses including erythrocyte alteration, apoptosis, and induction of micronuclei after 2 weeks with continuous increase in response after 3 weeks. The combined treatment of Spirulina at two different concentrations of 7.5 and 10% had significantly declined the induction of erythrocyte alteration, apoptosis, and micronuclei formation induced by arsenic intoxication.

Testing multiple hypotheses through IMP weighted FDR based on a genetic functional network with application to a new zebrafish transcriptome study

In genome-wide studies, hundreds of thousands of hypothesis tests are performed simultaneously. Bonferroni correction and False Discovery Rate (FDR) can effectively control type I error but often yield a high false negative rate. We aim to develop a more powerful method to detect differentially expressed genes. We present a Weighted False Discovery Rate (WFDR) method that incorporate biological knowledge from genetic networks. We first identify weights using Integrative Multi-species Prediction (IMP) and then apply the weights in WFDR to identify differentially expressed genes through an IMP-WFDR algorithm. We performed a gene expression experiment to identify zebrafish genes that change expression in the presence of arsenic during a systemic Pseudomonas aeruginosa infection. Zebrafish were exposed to arsenic at 10 parts per billion and/or infected with P. aeruginosa. Appropriate controls were included. We then applied IMP-WFDR during the analysis of differentially expressed genes. We compared the mRNA expression for each group and found over 200 differentially expressed genes and several enriched pathways including defense response pathways, arsenic response pathways, and the Notch signaling pathway.

Sources of variation in innate immunity in great tit nestlings living along a metal pollution gradient: an individual-based approach

Excessive deposition of metals in the environment is a well-known example of pollution worldwide. Chronic exposure of organisms to metals can have a detrimental effect on reproduction, behavior, health and survival, due to the negative effects on components of the immune system. However, little is known about the effects of chronic sublethal metal exposure on immunity, especially for wildlife. In our study, we examined the constitutive innate immunity of great tit (Parus major) nestlings (N=234) living in four populations along a metal pollution gradient. For each nestling, we determined the individual metal concentrations (lead, cadmium, arsenic) present in the red blood cells and measured four different innate immune parameters (agglutination, lysis, haptoglobin concentrations and nitric oxide concentrations) to investigate the relationship between metal exposure and immunological condition. While we found significant differences in endogenous metal concentrations among populations with the highest concentrations closest to the pollution source, we did not observe corresponding patterns in our immune measures. However, when evaluating relationships between metal concentrations and immune parameters at the individual level, we found negative effects of lead and, to a lesser extent, arsenic and cadmium on lysis. In addition, high arsenic concentrations appear to elicit inflammation, as reflected by elevated haptoglobin concentrations. Thus despite the lack of a geographic association between pollution and immunity, this type of association was present at the individual level at a very early life stage. The high variation in metal concentrations and immune measures observed within populations indicates a high level of heterogeneity along an existing pollution gradient. Interestingly, we also found substantial within nest variation, for which the sources remain unclear, and which highlights the need of an individual-based approach.

Depleted uranium disturbs immune parameters in zebrafish, Danio rerio: an ex vivo/in vivo experiment

In this study, we investigated the effects of depleted uranium (DU), the byproduct of nuclear enrichment of uranium, on several parameters related to defence system in the zebrafish, Danio rerio, using flow cytometry. Several immune cellular parameters were followed on kidney leucocytes: cell proportion, cell mortality, phagocytosis activity and associated oxidative burst and lysosomal membrane integrity (LMI). Effects of DU were tested ex vivo after 17 h of contact between DU and freshly isolated leucocytes from 0 to 500 µg DU/L. Moreover, adult zebrafish were exposed in vivo during 3 days at 20 and 250 µg DU/L. Oxidative burst results showed that DU increased reactive oxygen species (ROS) basal level and therefore reduced ROS stimulation index in both ex vivo and in vivo experiments. ROS PMA-stimulated level was also increased at 250 µg DU/L in vivo only. Furthermore, a decrease of LMI was detected after in vivo experiments. Cell mortality was also decreased at 20 µg DU/L in ex vivo experiment. However, phagocytosis activity was not modified in both ex vivo and in vivo experiments. A reduction of immune-related parameters was demonstrated in zebrafish exposed to DU. DU could therefore decrease the ability of fish to stimulate its own immune system which could, in turn, enhance the susceptibility of fish to infection. These results encourage the development and the use of innate immune analysis by flow cytometry in order to understand the effects of DU and more generally radionuclides on fish immune system and response to infectious diseases.

Environmental occurrence of arsenic in Colombia: a review

The international literature on the presence of arsenic (As) in Latin America does not disclose the true magnitude of the presence of As in Colombia. In this paper, we summarize the literature on As occurrence in Colombia. The data reveal that As is present in matrices such as soil, sediments and water and in the food chain. Some of the As concentrations exceed the limits specified by national and international regulations. Arsenic higher concentrations are associated with mining regions (e.g., soils, up to 148 mg/kg; sediments, up to 1400 mg/kg) and agricultural areas (e.g., vegetables, up to 5.40 mg/kg; irrigation water, up to 255 μg/L), and underscore the potential human and environmental risks associated with the presence of As in the country. This review highlights the importance of focusing research on understanding the occurrence, origin and distribution of As in Colombia to better understand its environmental and public health impact.

Immunotoxicological effects of inorganic arsenic on gilthead seabream (Sparus aurata L.)

Arsenic (As) has been associated with multitude of animal and human health problems; however, its impact on host immune system has not been extensively investigated. In fish, there are very few works on the potential risks or problems associated to the presence of arsenic. In the present study we have evaluated the effects of exposure (30 days) to sub-lethal concentrations of arsenic (5 μM As₂O₃) in the teleost fish gilthead seabream (Sparus aurata), with special emphasis in the innate immune response. The arsenic concentration was determined using atomic fluorescence spectrometry (AFS) in liver and muscle of exposed fish showing As accumulation in the liver after 30 days of exposure. The hepatosomatic index was increased at significant extent after 10 days but returned to control values after 30 days of exposure. Histological alterations in the liver were observed including hypertrophy, vacuolization and cell-death processes. Focusing on the immunological response, the humoral immune parameters (seric IgM, complement and peroxidase activities) were no affected to a statistically significant extent. Regarding the cellular innate parameters, head-kidney leucocyte peroxidase, respiratory burst and phagocytic activities were significantly increased after 10 days of exposition compared to the control fish. Overall, As-exposure in the seabream affects the immune system. How this might interfere with fish biology, aquaculture management or human consumers warrants further investigations. This paper describes, for the first time, the immunotoxicological effects of arsenic exposure in the gilthead seabream, which is a species with the largest production in Mediterranean aquaculture.

Environmental hazard of yperite released at sea: sublethal toxic effects on fish

The aim of this study was to evaluate the potential toxicological effects on fish related to the leakage of yperite from rusted bomb shells dumped at sea. Both in vivo and field studies have been performed. As for the in vivo experiment, specimen of European eel were subcutaneously injected with 0.015, 0.15 and 1.5mg/kg of yperite and sacrificed after 24 and 48 h. In the field study, specimen of Conger eel were collected from a dumping site in the Southern Adriatic Sea. The presence/absence of yperite in tissues, genotoxicity, detoxification enzymes, histological alterations and gross abnormalities were investigated. Results of the in vivo experiment showed a significant increase of EROD activity at both 24h and 48 h. UGT activity increased significantly at 48 h post injection. An acute inflammatory response after 24h in skin layers and muscle was observed, associated to cell degeneration and necrosis after 48 h at the highest dose. On field, comet assay revealed genotoxicity in gills of fish from the dumping site. Specimen from the dumping site showed significantly higher EROD activities compared to controls, deep ulcers and papules on skin together with liver and spleen histopathological lesions.

Effects of depleted uranium on oxidative stress, detoxification, and defence parameters of zebrafish Danio rerio

In this study, we investigated the effects of depleted uranium (DU), the by-product of nuclear enrichment of uranium, on several parameters related to oxidative stress, detoxification, and the defence system in the zebrafish Danio rerio. Several parameters were recorded: phenoloxidase-like (PO) activity, reactive oxygen species (ROS) production, and 7-ethoxyresrufin-O-deethylase (EROD) activity. Experiments were performed on adult and larvae D. rerio. Adult fish were exposed for 28 days at 20 μg U/L followed by a 27-day depuration period. Eggs of D. rerio were exposed for 4 days at 0, 20, 100, 250, 500, and 1,000 μg U/L. Results showed that DU increased ROS production both in adult and in larvae even at the low concentrations tested and even during the depuration period for adult D. rerio. DU also modified PO-like activity, both in the D. rerio adult and larvae experiments, but in a more transient manner. EROD activity was not modified by DU, but sex effects were shown. Results are discussed by way of comparison with other known effects of uranium in fish. Overall, these results show that the mechanisms of action of DU in fish tend to be similar to the ones existing for mammals. These results encourage the development and use of innate immune biomarkers to understand the effects of uranium and, more generally, radionuclides on the fish immune system.

Lipoic acid ameliorates arsenic trioxide-induced HO-1 expression and oxidative stress in THP-1 monocytes and macrophages

Inorganic arsenic is a common environmental contaminant; chronic exposure to arsenic can alter the physiology of various key immune cells, particularly macrophages. The aim of this research is to elucidate the key parameters associated with arsenic-induced toxicity and investigate the potential and mechanism of α-lipoic acid (LA), a potent thioreducant, for reducing the toxicity in human promonocytic THP-1 cells. We found that a non-lethal concentration of arsenic trioxide (1 μM) significantly induced the expression of heme oxygenase-1 (HO-1), a response biomarker to arsenic, without stimulating measurable superoxide production. Co-treatment of cells with the HO-1 competitive inhibitor zinc protoporphyrin (Znpp) potentiated arsenic-induced cytotoxicity, indicating that HO-1 confers a cytoprotective effect against arsenic toxicity. In addition, low concentrations of arsenic trioxide (1 and 2.5 μM) markedly inhibited monocyte-to-macrophage differentiation and expression of macrophage markers. Treatment of cells with LA attenuated arsenic trioxide-induced cytotoxicity and HO-1 over-expression and restored the redox state. In addition, LA neutralized arsenic trioxide-inhibition of monocyte maturation into macrophages and reversed the expression and activity of scavenger receptors. In conclusion, the cytotoxicity of arsenic trioxide is associated with an imbalance of the cellular redox state, and LA can protect cells from arsenic-induced malfunctions either through its reducing activity, direct interacting with arsenic or stimulating other unidentified signaling pathways.

Arsenic: toxicity, oxidative stress and human disease

Arsenic (As) is a toxic metalloid element that is present in air, water and soil. Inorganic arsenic tends to be more toxic than organic arsenic. Examples of methylated organic arsenicals include monomethylarsonic acid [MMA(V)] and dimethylarsinic acid [DMA(V)]. Reactive oxygen species (ROS)-mediated oxidative damage is a common denominator in arsenic pathogenesis. In addition, arsenic induces morphological changes in the integrity of mitochondria. Cascade mechanisms of free radical formation derived from the superoxide radical, combined with glutathione-depleting agents, increase the sensitivity of cells to arsenic toxicity. When both humans and animals are exposed to arsenic, they experience an increased formation of ROS/RNS, including peroxyl radicals (ROO•), the superoxide radical, singlet oxygen, hydroxyl radical (OH•) via the Fenton reaction, hydrogen peroxide, the dimethylarsenic radical, the dimethylarsenic peroxyl radical and/or oxidant-induced DNA damage. Arsenic induces the formation of oxidized lipids which in turn generate several bioactive molecules (ROS, peroxides and isoprostanes), of which aldehydes [malondialdehyde (MDA) and 4-hydroxy-nonenal (HNE)] are the major end products. This review discusses aspects of chronic and acute exposures of arsenic in the etiology of cancer, cardiovascular disease (hypertension and atherosclerosis), neurological disorders, gastrointestinal disturbances, liver disease and renal disease, reproductive health effects, dermal changes and other health disorders. The role of antioxidant defence systems against arsenic toxicity is also discussed. Consideration is given to the role of vitamin C (ascorbic acid), vitamin E (α-tocopherol), curcumin, glutathione and antioxidant enzymes such as superoxide dismutase, catalase and glutathione peroxidase in their protective roles against arsenic-induced oxidative stress.

Mortality of centrarchid fishes in the Potomac drainage: survey results and overview of potential contributing factors

Skin lesions and spring mortality events of smallmouth bass Micropterus dolomieu and selected other species were first noted in the South Branch of the Potomac River in 2002. Since that year morbidity and mortality have also been observed in the Shenandoah and Monocacy rivers. Despite much research, no single pathogen, parasite, or chemical cause for the lesions and mortality has been identified. Numerous parasites, most commonly trematode metacercariae and myxozoans; the bacterial pathogens Aeromonas hydrophila, Aeromonas salmonicida, and Flavobacterium columnare; and largemouth bass virus have all been observed. None have been consistently isolated or observed at all sites, however, nor has any consistent microscopic pathology of the lesions been observed. A variety of histological changes associated with exposure to environmental contaminants or stressors, including intersex (testicular oocytes), high numbers of macrophage aggregates, oxidative damage, gill lesions, and epidermal papillomas, were observed. The findings indicate that selected sensitive species may be stressed by multiple factors and constantly close to the threshold between a sustainable (healthy) and nonsustainable (unhealthy) condition. Fish health is often used as an indicator of aquatic ecosystem health, and these findings raise concerns about environmental degradation within the Potomac River drainage. Unfortunately, while much information has been gained from the studies conducted to date, due to the multiple state jurisdictions involved, competing interests, and other issues, there has been no coordinated approach to identifying and mitigating the stressors. This synthesis emphasizes the need for multiyear, interdisciplinary, integrative research to identify the underlying stressors and possible management actions to enhance ecosystem health.

Impacts and pathways of mine contaminants to bull trout (Salvelinus confluentus) in an Idaho watershed

Metals contamination from mining activities is a persistent problem affecting aquatic ecosystems throughout mining districts in the western USA. The Gold Creek drainage in northern Idaho has a history of mining within its headwaters and contains elevated sediment concentrations of As, Cd, Cu, Pb, and Zn. To determine system-wide impacts of increased metals, we measured concentrations of metals in water, sediment, and benthic macroinvertebrate tissues and related them to whole-body fish tissues and histopathological alterations in native salmonids. Water concentrations were higher than those in reference areas, but were below water quality criteria for protection of aquatic biota for most of the study area. Sediment and benthic macroinvertebrate tissue concentrations for all metals were significantly higher at all sites compared with the reference site. Fish tissues were significantly higher for all metals below mine sites compared with the reference site, but only Cd and Pb were higher in fish tissues in the furthest downstream reach in the Gold Creek Delta. Metals concentrations in benthic macroinvertebrate tissues and fish tissues were strongly correlated, suggesting a transfer of metals through a dietary pathway. The concentrations within sediments and biota were similar to those reported in other studies in which adverse effects to salmonids occurred. We observed histopathological changes in livers of bull trout, including inflammation, necrosis, and pleomorphism. Our study is consistent with other work in which sediment-driven exposure can transfer up the food chain and may cause adverse impacts to higher organisms.

Curcumin protects DNA damage in a chronically arsenic-exposed population of West Bengal

Groundwater arsenic contamination has been a health hazard for West Bengal, India. Oxidative stress to DNA is recognized as an underlying mechanism of arsenic carcinogenicity. A phytochemical, curcumin, from turmeric appears to be potent antioxidant and antimutagenic agent. DNA damage prevention with curcumin could be an effective strategy to combat arsenic toxicity. This field trial in Chakdah block of West Bengal evaluated the role of curcumin against the genotoxic effects of arsenic. DNA damage in human lymphocytes was assessed by comet assay and fluorescence-activated DNA unwinding assay. Curcumin was analyzed in blood by high performance liquid chromatography (HPLC). Arsenic induced oxidative stress and elucidation of the antagonistic role of curcumin was done by observation on reactive oxygen species (ROS) generation, lipid peroxidation and protein carbonyl. Antioxidant enzymes like catalase, superoxide dismutase, glutathione reductase, glutathioneS-transferase, glutathione peroxidase and non-enzymatic glutathione were also analyzed. The blood samples of the endemic regions showed severe DNA damage with increased levels of ROS and lipid peroxidation. The antioxidants were found with depleted activity. Three months curcumin intervention reduced the DNA damage, retarded ROS generation and lipid peroxidation and raised the level of antioxidant activity. Thus curcumin may have some protective role against the DNA damage caused by arsenic.

Chronic exposure to arsenic in the drinking water alters the expression of immune response genes in mouse lung

BACKGROUND

Chronic exposure to drinking water arsenic is a significant worldwide environmental health concern. Exposure to As is associated with an increased risk of lung disease, which may make it a unique toxicant, because lung toxicity is usually associated with inhalation rather than ingestion.

OBJECTIVES

The goal of this study was to examine mRNA and protein expression changes in the lungs of mice exposed chronically to environmentally relevant concentrations of As in the food or drinking water, specifically examining the hypothesis that As may preferentially affect gene and protein expression related to immune function as part of its mechanism of toxicant action.

METHODS

C57BL/6J mice fed a casein-based AIN-76A defined diet were exposed to 10 or 100 ppb As in drinking water or food for 5-6 weeks.

RESULTS

Whole genome transcriptome profiling of animal lungs revealed significant alterations in the expression of many genes with functions in cell adhesion and migration, channels, receptors, differentiation and proliferation, and, most strikingly, aspects of the innate immune response. Confirmation of mRNA and protein expression changes in key genes of this response revealed that genes for interleukin 1beta, interleukin 1 receptor, a number of toll-like receptors, and several cytokines and cytokine receptors were significantly altered in the lungs of As-exposed mice.

CONCLUSIONS

These findings indicate that chronic low-dose As exposure at the current U.S. drinking-water standard can elicit effects on the regulation of innate immunity, which may contribute to altered disease risk, particularly in lung.

Chronic exposure to low concentration of arsenic is immunotoxic to fish: role of head kidney macrophages as biomarkers of arsenic toxicity to Clarias batrachus

The present study was aimed at elucidating the effect of chronic low-level arsenic exposure on the head kidney (HK) of Clarias batrachus and at determining the changes in head kidney macrophage (HKM) activity in response to arsenic exposure. Chronic exposure (30 days) to arsenic (As(2)O(3), 0.50 microM) led to significant increase in arsenic content in the HK accompanied by reduction in both HKM number and head kidney somatic index (HKSI). Arsenic induced HK hypertrophy, reduction in melano-macrophage population and increased hemosiderin accumulation. Transmission electron microscopy of 30 days exposed HKM revealed prominent endoplasmic reticulum, chromatin condensation and loss in structural integrity of nuclear membrane. Head kidney macrophages from exposed fish demonstrated significant levels of superoxide anions but on infection with Aeromonas hydrophila were unable to clear the intracellular bacteria and died. Exposure-challenge experiments with A. hydrophila revealed that chronic exposure to micromolar concentration of arsenic interfered with the phagocytic potential of HKM, helped in intracellular survival of the ingested bacteria inside the HKM inducing significant HKM cytotoxicity. The immunosuppressive effect of arsenic was further evident from the ability of A. hydrophila to colonize and disseminate efficiently in exposed fish. Enzyme linked immunosorbent assay indicated that chronic exposure to arsenic suppressed the production of pro-inflammatory 'IL-1beta like' factors from HKM. It is concluded that arsenic even at very low concentration is immunotoxic to fish and the changes observed in HKM may provide a useful early biomarker of low-level xenobiotic exposure.

c-Jun/AP-1 pathway-mediated cyclin D1 expression participates in low dose arsenite-induced transformation in mouse epidermal JB6 Cl41 cells

Arsenic is a well-documented human carcinogen associated with skin carcinogenesis. Our previous work reveals that arsenite exposure is able to induce cell transformation in mouse epidermal cell JB6 Cl41 through the activation of ERK, rather than JNK pathway. Our current studies further evaluate downstream pathway in low dose arsenite-induced cell transformation in JB6 Cl41 cells. Our results showed that treatment of cells with low dose arsenite induced activation of c-Jun/AP-1 pathway, and ectopic expression of dominant negative mutant of c-Jun (TAM67) blocked arsenite-induced transformation. Furthermore, our data indicated that cyclin D1 was an important downstream molecule involved in c-Jun/AP-1-mediated cell transformation upon low dose arsenite exposure, because inhibition of cyclin D1 expression by its specific siRNA in the JB6 Cl41 cells resulted in impairment of anchorage-independent growth of cells induced by low dose arsenite. Collectively, our results demonstrate that c-Jun/AP-1-mediated cyclin D1 expression is at least one of the key events implicated in cell transformation upon low dose arsenite exposure.