Metal-induced oxidative stress and signal transduction

The applicability of oxidative stress biomarkers in assessing chromium induced toxicity in the fish Labeo rohita

The evaluation of metal's toxicity in freshwater is one of the imperative areas of research and there is an emergent concern on the development of techniques for detecting toxic effects in aquatic animals. Oxidative stress biomarkers are very useful in assessing the health of aquatic life and more in depth studies are necessary to establish an exact cause effect relationship. Therefore, to study the effectiveness of this approach, a laboratory study was conducted in the fish Labeo rohita as a function of hexavalent chromium and the toxicity indices using a battery of oxidative stress biomarkers such as catalase (CAT), superoxide dismutase (SOD), and glutathione reductase (GR) in the liver, muscle, gills, and brain have been studied along with biometric parameters, behavioral changes, and Cr bioaccumulation. A significant increased HSI was observed in contrast to CF which reduced significantly. SOD, CAT, and GR activity increased significantly in all the tissues of treated fishes. The bioaccumulation of Cr was highest in liver followed by gills, muscle, and brain. This study highlights the significance of using a set of integrated biomarker and advocate to include these parameters in National Water Quality Monitoring Program in areas potentially polluted with metals to assess the health of the ecosystem.

Effect of sub-acute exposure to nickel nanoparticles on oxidative stress and histopathological changes in Mozambique tilapia, Oreochromis mossambicus

The aim of the present study was to assess the oxidative stress, antioxidant response and histopathological changes of nickel nanoparticles (Ni NPs) exposure (14 days) in Mozambique tilapia, Oreochromis mossambicus. Ni NPs were synthesized by metal salt reduction method and characterized by X-ray diffraction (XRD) and Transmission electron microscopy (TEM). The XRD peaks at 44°, 51° and 76° were indexed to the (111), (200) and (220) Bragg's reflections of cubic structure of Nickel, respectively. The crystallite sizes were calculated using Scherrer's formula applied to the major intense peaks and found to be the size of 56nm. TEM images showed that the synthesized Ni NPs are spherical in shape. Biochemical analysis indicated that the superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) activity was significantly affected by Ni NPs treated O. mossambicus. Reduced antioxidant enzymes and the contents of antioxidants were lowered in the liver and gills of fishes treated with Ni NPs. After 14 days of exposure, a significant accumulation of Ni in the Ni NPs in experimental group was observed in the gill and skin tissues, with the highest levels found in the liver. Ni NPs exposed fish showed nuclear hypertrophy (NH), nuclear degeneration (ND), necrosis (NC) and irregular-shaped nuclei were observed in liver tissue. The hyperplasia of the gill epithelium (GE), lamellar fusion of secondary lamellae (LF), dilated marginal channel (MC), epithelial lifting (EL) and epithelial rupture were observed in gill tissue. Degeneration in muscle bundles (DM), focal area of necrosis (NC) vacuolar degeneration in muscle bundles (VD), edema between muscle bundles (ED) and splitting of muscle fibers were noticed in skin tissue. Further ecotoxicological evaluation will be made concerning the risk of Ni NPs on aquatic environment.

Hepatic transcriptomic profiling reveals early toxicological mechanisms of uranium in Atlantic salmon (Salmo salar)

BACKGROUND

Uranium (U) is a naturally occurring radionuclide that has been found in the aquatic environment due to anthropogenic activities. Exposure to U may pose risk to aquatic organisms due to its radiological and chemical toxicity. The present study aimed to characterize the chemical toxicity of U in Atlantic salmon (Salmo salar) using depleted uranium (DU) as a test model. The fish were exposed to three environmentally relevant concentrations of DU (0.25, 0.5 and 1.0 mg U/L) for 48 h. Hepatic transcriptional responses were studied using microarrays in combination with quantitative real-time reverse transcription polymerase chain reaction (qPCR). Plasma variables and chromosomal damages were also studied to link transcriptional responses to potential physiological changes at higher levels.

RESULTS

The microarray gene expression analysis identified 847, 891 and 766 differentially expressed genes (DEGs) in the liver of salmon after 48 h exposure to 0.25, 0.5 and 1.0 mg/L DU, respectively. These DEGs were associated with known gene ontology functions such as generation of precursor metabolites and energy, carbohydrate metabolic process and cellular homeostasis. The salmon DEGs were then mapped to mammalian orthologs and subjected to protein-protein network and pathway analysis. The results showed that various toxicity pathways involved in mitochondrial functions, oxidative stress, nuclear receptor signaling, organ damage were commonly affected by all DU concentrations. Eight genes representative of several key pathways were further verified using qPCR No significant formation of micronuclei in the red blood cells or alterations of plasma stress variables were identified.

CONCLUSION

The current study suggested that the mitochondrion may be a key target of U chemical toxicity in salmon. The induction of oxidative stress and uncoupling of oxidative phosphorylation may be two potential modes of action (MoA) of DU. These MoAs may subsequently lead to downstream events such as apoptosis, DNA repair, hypoxia signaling and immune response. The early toxicological mechanisms of U chemical toxicity in salmon has for the first time been systematically profiled. However, no other physiological changes were observed. Future efforts to link transcriptional responses to adverse effects have been outlined as important for understanding of potential risk to aquatic organisms.

Biomedical implications of heavy metals induced imbalances in redox systems

Several workers have extensively worked out the metal induced toxicity and have reported the toxic and carcinogenic effects of metals in human and animals. It is well known that these metals play a crucial role in facilitating normal biological functions of cells as well. One of the major mechanisms associated with heavy metal toxicity has been attributed to generation of reactive oxygen and nitrogen species, which develops imbalance between the prooxidant elements and the antioxidants (reducing elements) in the body. In this process, a shift to the former is termed as oxidative stress. The oxidative stress mediated toxicity of heavy metals involves damage primarily to liver (hepatotoxicity), central nervous system (neurotoxicity), DNA (genotoxicity), and kidney (nephrotoxicity) in animals and humans. Heavy metals are reported to impact signaling cascade and associated factors leading to apoptosis. The present review illustrates an account of the current knowledge about the effects of heavy metals (mainly arsenic, lead, mercury, and cadmium) induced oxidative stress as well as the possible remedies of metal(s) toxicity through natural/synthetic antioxidants, which may render their effects by reducing the concentration of toxic metal(s). This paper primarily concerns the clinicopathological and biomedical implications of heavy metals induced oxidative stress and their toxicity management in mammals.

A comparison of cytotoxicity and oxidative stress from welding fumes generated with a new nickel-, copper-based consumable versus mild and stainless steel-based welding in RAW 264.7 mouse macrophages

Welding processes that generate fumes containing toxic metals, such as hexavalent chromium (Cr(VI)), manganese (Mn), and nickel (Ni), have been implicated in lung injury, inflammation, and lung tumor promotion in animal models. While federal regulations have reduced permissible worker exposure limits to Cr(VI), this is not always practical considering that welders may work in confined spaces and exhaust ventilation may be ineffective. Thus, there has been a recent initiative to minimize the potentially hazardous components in welding materials by developing new consumables containing much less Cr(VI) and Mn. A new nickel (Ni) and copper (Cu)-based material (Ni-Cu WF) is being suggested as a safer alternative to stainless steel consumables; however, its adverse cellular effects have not been studied. This study compared the cytotoxic effects of the newly developed Ni-Cu WF with two well-characterized welding fumes, collected from gas metal arc welding using mild steel (GMA-MS) or stainless steel (GMA-SS) electrodes. RAW 264.7 mouse macrophages were exposed to the three welding fumes at two doses (50 µg/ml and 250 µg/ml) for up to 24 hours. Cell viability, reactive oxygen species (ROS) production, phagocytic function, and cytokine production were examined. The GMA-MS and GMA-SS samples were found to be more reactive in terms of ROS production compared to the Ni-Cu WF. However, the fumes from this new material were more cytotoxic, inducing cell death and mitochondrial dysfunction at a lower dose. Additionally, pre-treatment with Ni-Cu WF particles impaired the ability of cells to phagocytize E. coli, suggesting macrophage dysfunction. Thus, the toxic cellular responses to welding fumes are largely due to the metal composition. The results also suggest that reducing Cr(VI) and Mn in the generated fume by increasing the concentration of other metals (e.g., Ni, Cu) may not necessarily improve welder safety.

Mitogen-activated protein kinase signal transduction and DNA repair network are involved in aluminum-induced DNA damage and adaptive response in root cells of Allium cepa L

In the current study, we studied the role of signal transduction in aluminum (Al(3+))-induced DNA damage and adaptive response in root cells of Allium cepa L. The root cells in planta were treated with Al(3+) (800 μM) for 3 h without or with 2 h pre-treatment of inhibitors of mitogen-activated protein kinase (MAPK), and protein phosphatase. Also, root cells in planta were conditioned with Al(3+) (10 μM) for 2 h and then subjected to genotoxic challenge of ethyl methane sulfonate (EMS; 5 mM) for 3 h without or with the pre-treatment of the aforementioned inhibitors as well as the inhibitors of translation, transcription, DNA replication and repair. At the end of treatments, roots cells were assayed for cell death and/or DNA damage. The results revealed that Al(3+) (800 μM)-induced significant DNA damage and cell death. On the other hand, conditioning with low dose of Al(3+) induced adaptive response conferring protection of root cells from genotoxic stress caused by EMS-challenge. Pre-treatment of roots cells with the chosen inhibitors prior to Al(3+)-conditioning prevented or reduced the adaptive response to EMS genotoxicity. The results of this study suggested the involvement of MAPK and DNA repair network underlying Al-induced DNA damage and adaptive response to genotoxic stress in root cells of A. cepa.

Effects of Hg(II) exposure on MAPK phosphorylation and antioxidant system in D. melanogaster

The heavy metal mercury is a known toxin, but while the mechanisms involved in mercury toxicity have been well demonstrated in vertebrates, little is known about toxicological effects of this metal in invertebrates. Here, we present the results of our study investigating the effects associated with exposure of fruit fly Drosophila melanogaster to inorganic mercury (HgCl2 ). We quantify survival and locomotor performance as well as a variety of biochemical parameters including antioxidant status, MAPK phosphorylation and gene expression following mercury treatment. Our results demonstrate that exposure to Hg(II) through diet induced mortality and affected locomotor performance as evaluated by negative geotaxis, in D. melanogaster. We also saw a significant impact on the antioxidant system including an inhibition of acetylcholinesterase (Ache), glutathione S-transferase (GST) and superoxide dismutase (SOD) activities. We found no significant alteration in the levels of mRNA of antioxidant enzymes or NRF-2 transcriptional factor, but did detect a significant up regulation of the HSP83 gene. Mercury exposure also induced the phosphorylation of JNK and ERK, without altering p38(MAPK) and the concentration of these kinases. In parallel, Hg(II) induced PARP cleavage in a 89 kDa fragment, suggesting the triggering of apoptotic cell death in response to the treatment. Taken together, this data clarifies and extends our understanding of the molecular mechanisms mediating Hg(II) toxicity in an invertebrate model.

A review of metal-catalyzed molecular damage: protection by melatonin

Metal exposure is associated with several toxic effects; herein, we review the toxicity mechanisms of cadmium, mercury, arsenic, lead, aluminum, chromium, iron, copper, nickel, cobalt, vanadium, and molybdenum as these processes relate to free radical generation. Free radicals can be generated in cells due to a wide variety of exogenous and endogenous processes, causing modifications in DNA bases, enhancing lipid peroxidation, and altering calcium and sulfhydryl homeostasis. Melatonin, an ubiquitous and pleiotropic molecule, exerts efficient protection against oxidative stress and ameliorates oxidative/nitrosative damage by a variety of mechanisms. Also, melatonin has a chelating property which may contribute in reducing metal-induced toxicity as we postulate here. The aim of this review was to highlight the protective role of melatonin in counteracting metal-induced free radical generation. Understanding the physicochemical insights of melatonin related to the free radical scavenging activity and the stimulation of antioxidative enzymes is of critical importance for the development of novel therapeutic strategies against the toxic action of these metals.

Efficacy of crude extract of Emblica officinalis (amla) in arsenic-induced oxidative damage and apoptosis in splenocytes of mice

Introduction:

Arsenic, an environmental contaminant naturally occurred in groundwater and has been found to be associated with immune-related health problems in humans.

Objective:

In view of increasing risk of arsenic exposure due to occupational and non-occupational settings, the present study has been focused to investigate the protective efficacy of amla against arsenic-induced spleenomegaly in mice.

Results:

Arsenic exposures (3 mg/kg body weight p.o for 30 days) in mice caused an increase production of ROS (76%), lipid peroxidation (84%) and decrease in the levels of superoxide dismutase (53%) and catalase (54%) in spleen as compared to controls. Arsenic exposure to mice also caused a significant increase in caspases-3 activity (2.8 fold) and decreases cell viability (44%), mitochondrial membrane potential (47%) linked with apoptosis assessed by the cell cycle analysis (subG1-28.72%) and annexin V/PI binding in spleen as compared to controls. Simultaneous treatment of arsenic and amla (500 mg/kg body weight p.o for 30 days) in mice decreased the levels of lipid peroxidation (33%), ROS production (24%), activity of caspase-3 (1.4 fold), apoptosis (subG₁ 12.72%) and increased cell viability (63%), levels superoxide dismutase (80%), catalase (77%) and mitochondrial membrane potential (66%) as compared to mice treated with arsenic alone.

Conclusions:

Results of the present study indicate that the effect of arsenic is mainly due to the depletion of glutathione in liver associated with enhanced oxidative stress that has been found to be protected following simultaneous treatment of arsenic and amla.

Zinc and cadmium hyperaccumulation act as deterrents towards specialist herbivores and impede the performance of a generalist herbivore

Extraordinarily high leaf metal concentrations in metal hyperaccumulator plants may serve as an elemental defence against herbivores. However, mixed results have been reported and studies using comparative approaches are missing. We investigated the deterrent and toxic potential of metals employing the hyperaccumulator Arabidopsis halleri. Effects of zinc (Zn) and cadmium (Cd) on the preferences of three Brassicaceae specialists were tested in paired-choice experiments using differently treated plant material, including transgenic plants. In performance tests, we determined the toxicity and joint effects of both metals incorporated in an artificial diet on the survival of a generalist. Feeding by all specialists was significantly reduced by metal concentrations from above 1000 μg Zn g(-1) DW and 18 μg Cd g(-1) DW. By contrast, metals did not affect oviposition. Generalist survival decreased with increasing concentrations of individual metals, whereby the combination of Zn and Cd had an additive toxic effect even at the lowest applied concentrations of 100 μg Zn g(-1) and 2 μg Cd g(-1) . Metal hyperaccumulation protects plants from herbivory resulting from deterrence and toxicity against a wide range of herbivores. The combination of metals exacerbates toxicity through joint effects and enhances elemental defence. Thus, metal hyperaccumulation is ecologically beneficial for plants.

Inflammation to cancer: The molecular biology in the pancreas (Review)

Inflammatory responses are known to be correlated with cancer initiation and progression, and exploration of the route from inflammation to cancer makes a great contribution in elucidating the mechanisms underlying cancer development. Pancreatic cancer (PC) is a lethal disease with a low radical-resection rate and a poor prognosis. As chronic pancreatitis is considered to be a significant etiological factor for PC development, the current review aims to describe the molecular pathways from inflammation to pancreatic carcinogenesis, in support of the strategies for the prevention, diagnosis and treatment of PC.

Combined use of DGT and transplanted shrimp (Litopenaeus vannamei) to assess the bioavailable metals of complex contamination: implications for implementing bioavailability-based water quality criteria

The diffusive gradients in thin films (DGT) were field deployed alongside the shrimp Litopenaeus vannamei at seven sites with different levels of contamination to assess the potentially bioavailable and toxic fraction of metal contaminants. After 7 days of exposure, several antioxidant biomarkers were quantified in hepatopancreas of exposed shrimps, and tissue levels as well as the total, dissolved, and DGT-labile concentrations of metal contaminants were determined in the pooled site samples. The results showed that the caged shrimps had high tissue contaminant concentrations and significantly inhibited antioxidant responses at the more contaminated sites. DGT-labile metal concentrations provided better spatial resolution of differences in metal contamination when compared with traditional bottle sampling and transplanted shrimp. The total, dissolved, and DGT-labile metal fractions were used to evaluate the potential bioavailability of metal contaminants, comparing with metal accumulation and further linking to antioxidant biomarker responses in tissues of exposed shrimps. Regression analysis showed the significant correlations between DGT-Cu concentrations and tissue-Cu and activities of some biomarker responses in the shrimp hepatopancreas. This indicated that DGT-labile Cu concentrations provided the better prediction of produced biological effects and of the bioavailability than the total or dissolved concentrations. The study supports the use of methods combining transplanted organisms and passive sampling for assessing the chemical and ecotoxicological status of aqueous environments and demonstrates the capability of the DGT technique as a powerful tool for measuring the bioavailability-based water quality in variable coastal environments.

Oxidative stress and mitochondrial dysfunction in aluminium neurotoxicity and its amelioration: a review

Aluminium is light weight and toxic metal present ubiquitously on earth which has gained considerable attention due to its neurotoxic effects. The widespread use of products made from or containing aluminium is ensuring its presence in our body. There is prolonged retention of a fraction of aluminium that enters the brain, suggesting its potential for accumulation with repeated exposures. There is no known biological role for aluminium within the body but adverse physiological effects of this metal have been observed in mammals. The generation of oxidative stress may be attributed to its toxic consequences in animals and humans. The oxidative stress has been implicated in pathogenesis of various neurodegenerative conditions including Alzheimer's disease and Parkinson's disease. Though it remains unclear whether oxidative stress is a major cause or merely a consequence of cellular dysfunction associated with neurodegenerative diseases, an accumulating body of evidence implicates that impaired mitochondrial energy production and increased mitochondrial oxidative damage is associated with the pathogenesis of neurodegenerative disorders. Being involved in the production of reactive oxygen species, aluminium may impair mitochondrial bioenergetics and may lead to the generation of oxidative stress. In this review, we have discussed the oxidative stress and mitochondrial dysfunctions occurring in Al neurotoxicity. In addition, the ameliorative measures undertaken in aluminium induced oxidative stress and mitochondrial dysfunctions have also been highlighted.

Oxidative pathways of chemical toxicity and oxidative stress biomarkers in marine organisms

The antioxidant system of marine organisms consists of low molecular weight scavengers and antioxidant enzymes which interact in a sophisticated network. Environmental pollutants can unbalance this system through closely related mechanisms, indirect relationships and cascade effects acting from pre-transcriptional to catalytic levels. Chemically-mediated pathways have the potential to greatly enhance intracellular formation of reactive oxygen species (ROS); at the same time, excessive levels of oxyradicals down-regulate xenobiotics metabolism, with important environmental implications for organisms exposed to chemical mixtures. Interactions between different classes of chemicals, generation of ROS and onset of oxidative stress conditions are partly modulated by changes in levels and functions of redox-sensitive signaling proteins and transcription factors. The Nrf2-Keap1 pathway still remains largely unexplored in marine organisms, despite the elevated degree of identity and similarity with homolog transcripts and proteins from different species. Recent evidences on transcriptional up-regulation of this system are consistent with the capability to provide a prolonged expression of ARE-regulated cytoprotective genes, and to efficiently switch off this mechanism when oxidative pressure decreases. Although gene expression and catalytic activities of antioxidants are often measured as alternative biomarkers in monitoring biological effects of contaminants, conflicting results between molecular and biochemical responses are quite frequent. The links between effects occurring at various intracellular levels can be masked by non-genomic processes affecting mRNA stability and protein turnover, different timing for transcriptional and translational mechanisms, metabolic capability of tissues, post-transcriptional modifications of proteins, bi-phasic responses of antioxidant enzymes and interactions occurring in chemical mixtures. In this respect, caution should be taken in monitoring studies where mRNA levels of antioxidants could represent a snapshot of cell activity at a given time, not an effective endpoint of environmental pollutants.

Oxidative stress, prooxidants, and antioxidants: the interplay

Oxidative stress is a normal phenomenon in the body. Under normal conditions, the physiologically important intracellular levels of reactive oxygen species (ROS) are maintained at low levels by various enzyme systems participating in the in vivo redox homeostasis. Therefore, oxidative stress can also be viewed as an imbalance between the prooxidants and antioxidants in the body. For the last two decades, oxidative stress has been one of the most burning topics among the biological researchers all over the world. Several reasons can be assigned to justify its importance: knowledge about reactive oxygen and nitrogen species production and metabolism; identification of biomarkers for oxidative damage; evidence relating manifestation of chronic and some acute health problems to oxidative stress; identification of various dietary antioxidants present in plant foods as bioactive molecules; and so on. This review discusses the importance of oxidative stress in the body growth and development as well as proteomic and genomic evidences of its relationship with disease development, incidence of malignancies and autoimmune disorders, increased susceptibility to bacterial, viral, and parasitic diseases, and an interplay with prooxidants and antioxidants for maintaining a sound health, which would be helpful in enhancing the knowledge of any biochemist, pathophysiologist, or medical personnel regarding this important issue.

The impact of early nutrition on the ageing trajectory

Epidemiological studies, including those in identical twins, and in individuals in utero during periods of famine have provided robust evidence of strong correlations between low birth-weight and subsequent risk of disease in later life, including type 2 diabetes (T2D), CVD, and metabolic syndrome. These and studies in animal models have suggested that the early environment, especially early nutrition, plays an important role in mediating these associations. The concept of early life programming is therefore widely accepted; however the molecular mechanisms by which early environmental insults can have long-term effects on a cell and consequently the metabolism of an organism in later life, are relatively unclear. So far, these mechanisms include permanent structural changes to the organ caused by suboptimal levels of an important factor during a critical developmental period, changes in gene expression caused by epigenetic modifications (including DNA methylation, histone modification and microRNA) and permanent changes in cellular ageing. Many of the conditions associated with early-life nutrition are also those which have an age-associated aetiology. Recently, a common molecular mechanism in animal models of developmental programming and epidemiological studies has been development of oxidative stress and macromolecule damage, specifically DNA damage and telomere shortening. These are phenotypes common to accelerated cellular ageing. Thus, this review will encompass epidemiological and animal models of developmental programming with specific emphasis on cellular ageing and how these could lead to potential therapeutic interventions and strategies which could combat the burden of common age-associated disease, such as T2D and CVD.

Protective effect of omega-3 fatty acid against mercury chloride intoxication in mice

The aim of this study was to investigate the protective effect of omega-3 fatty acid in HgCI2 toxicity in mice. Levels of malondialdehyde (MDA), reduced glutathione (GSH), nitric oxide (NO) and total sialic acid (TSA), and histopathological changes in selected organs were evaluated. Twenty-eight mice were equally divided into 4 groups, namely Groups I-IV. Group I animals received intraperitoneal (ip) injection of physiological saline solution; Group II animals received ip injection of 0.4mg/kg/day HgCI2; Group III animals received ip injection of 0.4mg/kg/day HgCI2 in addition to subcutaneous (sc) injection of 0.5g/kg/day omega-3 fatty acid; and Group IV animals received sc injection of 0.5g/kg/day omega-3 fatty acid. All treatments lasted 7 days. The levels of MDA, NO and TSA were significantly higher in Group II and lower in Groups III and IV as compared to the Group I. GSH level was the highest in Group IV. In histopathology, severe degeneration in liver and kidney was observed in Group II animals. These degrading changes were seen to be reduced greatly in Group III animals. The results suggested that omega-3 fatty acid might attenuate HgCI2-induced toxicity by improving antioxidant status and acute phase response in mice.

Impact of long term Fe³⁺ toxicity on expression of glutathione system in rat liver

The free radicals within the body, produced by metabolic activities or derived from environmental sources are relatively related to hepatoxicity. Since heavy metals including iron have the ability to produce free radicals, the liver glutathione system neutralizes them to protect cells against any damage. The objective of this study is to indicate the toxic effects of iron on the glutathione system at the enzymatic and molecular level. Thus, any possible correlation between enzymatic and molecular levels can be determined. According to our results, while mRNA expression of glutathione reductase (Gsr) and glutathione S-transferases (Gsta5) genes were not affected by long-term exposure to various concentrations of iron (Fe(3+)), transcription level of glutathione peroxidase (Gpx2) was influenced in the presence of toxic iron. Whereas the enzyme activites of GSR (GR), GPX and GST were significantly affected in rat liver.

Exposure-dose-response of Tellina deltoidalis to metal contaminated estuarine sediments 2. Lead spiked sediments

Lead accumulation in estuarine sediments, as a result of activities such as mining and ore smelting, and through urban runoff is a continuing problem in the increasingly developed world. Marine organisms accumulate lead, which is known to be highly toxic to biological processes and to degrade organism and ecosystem health. Here the relationship between lead exposure, dose and response was investigated in the sediment dwelling, deposit feeding, marine bivalve Tellina deltoidalis. Bivalves were exposed in the laboratory to individual lead spiked sediments at < 0.01, 100 and 300 μg/g dry mass, for 28 days and accumulated total tissue lead concentrations of 4, 96 and 430 μg/g, respectively. Subcellular fractionation indicated that around 70% of the total accumulated tissue lead was detoxified, three quarters of the detoxified lead fraction was converted into metal rich granules, with the remainder in the metallothionein like protein fraction. The majority of biologically active lead was associated with the mitochondrial fraction with up to a 128 fold increase in lead burden in exposed organisms compared to controls. This indicates lead detoxification was occurring but the organism was unable to prevent lead interacting with sensitive organelles. With increased lead exposure T. deltoidalis showed a suppression in glutathione peroxidase activity, total glutathione concentration and reduced GSH:GSSG ratios, however, these differences were not significant. Lead exposed T. deltoidalis had a significantly reduced total antioxidant capacity which corresponded with increased lipid peroxidation, lysosomal destabilisation and micronuclei frequency. The exposure-dose-response relationships demonstrated for lead exposed T. deltoidalis supports its potential for the development of sublethal endpoints in lead toxicity assessment.

E-waste disposal effects on the aquatic environment: Accra, Ghana

The volume of e-waste is growing around the world, and, increasingly, it is being disposed of by export from developed to developing countries. This is the situation in Ghana, and, in this paper we address the potential consequences of such e-waste disposal. Herein, we describe how e-waste is processed in Ghana, and what the fate is of e-waste-chemical contaminants during recycling and storage. Finally, to the extent it is known, we address the prospective adverse effects of e-waste-related contaminants on health and aquatic life downstream from a large e-waste disposal facility in Accra, Ghana.In developing countries, including Ghana, e-waste is routinely disassembled by unprotected workers that utilize rudimentary methods and tools. Once disassembled,e-waste components are often stored in large piles outdoors. These processing and storage methods expose workers and local residents to several heavy metals and organic chemicals that exist in e-waste components. The amount of e-waste dumped in Ghana is increasing annually by about 20,000 t. The local aquatic environment is at a potential high risk, because the piles of e-waste components stored outside are routinely drenched or flooded by rainfall, producing run-off from storage sites to local waterways. Both water and sediment samples show that e-waste-related contaminant shave entered Ghana's water ways.The extent of pollution produced in key water bodies of Ghana (Odaw River and the Korle Lagoon) underscores the need for aquatic risk assessments of the many contaminants released during e-waste processing. Notwithstanding the fact that pollutants from other sources reach the water bodies, it is clear that these water bodies are also heavily impacted by contaminants that are found in e-waste. Our concern is that such exposures have limited and will continue to limit the diversity of aquatic organisms.There have also been changes in the abundance and biomass of surviving species and changes in food chains. Therefore, the need for actions to be taken to reduce entry of e-waste pollutants into Ghana's aquatic environment is real and is immediate.Heavy metals (e.g., lead, cadmium, copper and zinc) and organic pollutants (e.g.,PCDD/Fs and PBDEs) have been detected in the sediments of local water bodies in quantities that greatly exceed background levels. This fact alone suggests that aquatic organisms that live in the affected water bodies are highly exposed to these toxic, bio-accumulative, and persistent contaminants. These contaminants have been confirmed to result from the primitive methods used to recycle and process e-waste within the local environment.Only limited local data exist on the threats posed by these e-waste-related contaminants on nearby natural resources, especially aquatic organisms. In this review,we have addressed the potential toxicity of selected heavy metals and organic pollutants on aquatic organisms. Since there are no data on concentrations of contaminants in the water column, we have based our predictions of effects on pollutant release rates from sediments. Pollutants that are attached to sediments are routinely released into the water column from diffusion and advection, the rate of which depends on pH and Eh of the sediments. E-waste contaminants have the potential to produce deleterious effects on the behavior, physiology, metabolism, reproduction,development and growth of many aquatic organisms. Because it is confirmed that both heavy metal and organic contaminants are reaching the biota of Ghana's local waterways, we presume that they are producing adverse effects. Because local data on the aquatic toxicity of these contaminants are as yet unavailable, we strongly recommend that future research be undertaken to examine, on a large scale and long-term basis, both contamination levels in biota, and adverse effects on biota of the nearby water bodies.

Cytotoxicity and characterization of particles collected from an indium-tin oxide production facility

Occupational exposure to indium compound particles has recently been associated with lung disease among workers in the indium-tin oxide (ITO) industry. Previous studies suggested that excessive alveolar surfactant and reactive oxygen species (ROS) may play a role in the development of pulmonary lesions following exposure to indium compounds. However, toxicity at the cellular level has not been comprehensively evaluated. Thus, the aim of this study was to assess which, if any, compounds encountered during ITO production are toxic to cultured cells and ultimately contribute to the pathogenesis of indium lung disease. The compounds used in this study were collected from eight different processing stages at an ITO production facility. Enhanced dark field imaging showed 5 of the compounds significantly associated with cells within 1 h, suggesting that cellular reactions to the compound particles may be occurring rapidly. To examine the potential cytotoxic effects of these associations, ROS generation, cell viability, and apoptosis were evaluated following exposures in RAW 264.7 mouse monocyte macrophage and BEAS-2B human bronchial epithelial cell lines. Both exhibited reduced viability with exposures, while apoptosis only occurred in RAW 264.7 cells. Our results suggested that excessive ROS production is likely not the predominant mechanism underlying indium-induced lung disease. However, the effects on cell viability reveal that several of the compounds are cytotoxic, and therefore, exposures need to be carefully monitored in the industrial setting.

An integrated use of multiple biomarkers to investigate the individual and combined effect of copper and cadmium on the marine green mussel (Perna viridis)

The present study documents individual and combined sub-lethal effect of one redox active (copper) and one non-redox active (cadmium) metal on green mussel (Perna viridis). The mussels were exposed to 60 μg L(-1) of Cu and 150 μg L(-1) of Cd (individually and in combination) for 21 days. Histopathological and ultrastructural studies revealed significant metal induced alterations such as vacuolization, fusion of gill lamellae, enhance mucous deposition, hyperplasia and necrosis in gills. Antioxidant enzyme assays revealed significant increase in superoxide dismutase (SOD), glutathione S-transferase (GST) and glutathione peroxidase (GPx) activity. Similarly, single exposure to Cd and Cu caused significant induction in Malate dehydrogenase (MDH) activity. However, combined Cu+Cd exposure modulated suppression in MDH activity. Unlike MDH, Cu and Cd individual exposure resulted in a decrease in esterase (EST) activity, but their combined exposure caused an induction. Non-enzymatic biomarkers such as lipid peroxidation (LPO) and metallothionein (MT) levels showed no significant change in response to Cu exposure, whereas, individual Cd exposure or Cd exposure in combination with Cu caused significant changes in their levels. Comet assay revealed a significant increase in DNA damage upon metal exposure. These results indicate that Cu (redox active) and Cd (non-redox active) can induce measurable physiological, biochemical as well as genotoxic perturbations in mussels even at sub-lethal concentrations. A monitoring programme based on the biomarkers discussed here would be useful to study the effect of metal pollutants reaching the coastal waters.

Contamination assessments of surface water in coastal lagoon (Maluan Bay, China) incorporating biomarker responses and bioaccumulation in hepatopancreas of exposed shrimp (Litopenaeus vannamei)--an integrative approach

Maluan Bay, characterized by various degrees of anthropogenic contamination, is considered as one of the most industrialized and urbanized coastal lagoon in China, where large amounts of metal contaminants in surface water and biota were detected in previous studies. However, no clear discriminating power among sampling sites could be made only through comparisons between contaminant levels and Environmental Quality Standards and especially biological-based monitoring integrating biomarkers and bioaccumulation of exposure are scarce. For this purpose, antioxidants enzymes (superoxide dismutase, catalase, and glutathione peroxidase) and glutathione-S-transferase were assessed using the hepatopancreas of shrimp Litopenaeus vannamei after 7 days laboratory exposure under controlled conditions to characterize the effects of polluted waters to shrimps. The metal concentrations of sampled water and bioaccumulation in hepatopancreatic tissues were also analyzed, and data were linked to biomarkers' responses by multivariate (principal component analysis-factor) analysis. A representation of estimated factor scores was performed to confirm the factor descriptions classifying the pollution status and characterizing the studied sites, which pointed out the impact of multiple sources of contaminants to the water quality and provided further evidences to the existence of clear pollution and toxicological gradients in critical areas. The results of the present investigation underlined that the integrated approach could be a powerful tool for the identification of causal toxic contaminants in complex mixtures and the assessment of human-induced environmental quality of the system in coastal zones.

Iron in intracellular infection: to provide or to deprive?

Due to their chemical versatility, transition metals were incorporated as cofactors for several basic metabolic pathways in living organisms. This same characteristic makes them potentially harmful, since they can be engaged in deleterious reactions like Fenton chemistry. As such, organisms have evolved highly specialized mechanisms to supply their own metal needs while keeping their toxic potential in check. This dual character comes into play in host-pathogen interactions, given that the host can either deprive the pathogen of these key nutrients or exploit them to induce toxicity toward the invading agent. Iron stands as the prototypic example of how a metal can be used to limit the growth of pathogens by nutrient deprivation, a mechanism widely studied in Mycobacterium infections. However, the host can also take advantage of iron-induced toxicity to control pathogen proliferation, as observed in infections caused by Leishmania. Whether we may harness either of the two pathways for therapeutical purposes is still ill-defined. In this review, we discuss how modulation of the host iron availability impacts the course of infections, focusing on those caused by two relevant intracellular pathogens, Mycobacterium and Leishmania.

Consequences of metal exposure on retinoid metabolism in vertebrates: a review

What we generally refer to as 'vitamin A' is a group of naturally-occurring molecules structurally similar to retinol that are capable of exerting biological activity. These retinoids are essential to diverse physiological functions including vision, immune response, bone mineralization, reproduction, cell differentiation, and growth. As well, some retinoids have antioxidant properties. Independent studies published over the last few decades have revealed that many fish and wildlife populations living in highly polluted environments have altered retinoid status possibly associated with retinoid metabolic or homeostatic mechanisms. Substantial evidence links organic contaminant exposure with changes in retinoid status in animal populations, but only a few detailed studies have been published implicating inorganic contaminants such as metals. This mini-review selectively deals with field and laboratory studies reporting associations between environmental contaminants, especially trace metals, and alterations in retinoid status. Both essential and non-essential trace metals have been reported to affect retinoid status. This review focuses on metabolic imbalances of retinoids in relation to metal contamination and illustrates possible modes of action. The role of retinoids as antioxidants and their potential as biomarkers of metal contamination are discussed.

Chemotherapeutic efficacy of an ethanolic Moringa oleifera leaf extract against chromium-induced testicular toxicity in rats

This study was conducted to determine the mechanism underlying the chemotherapeutic efficacy of an ethanolic Moringa oleifera leaf extract (MOLEE) against chromium-induced impairments of rat testes using biochemical methods. Twenty male Wistar rats were divided into four groups of five animals each. Group I (control), group II injected potassium dichromate (8 mg kg(-1) ) i.p., group III gastrogavaged MOLEE (500 mg kg(-1) ) p.o. and group IV received (potassium dichromate plus MOLEE) by the same doses for 60 days. After the blood samples were collected, the animals were sacrificed to determine the testicular antioxidant status and sperm parameters. The chromium-treated group exhibited a significant decrease in testicular antioxidant enzymatic activities, local immunity and sperm parameters as well as an increase in inflammatory markers when compared with the control and MOLEE-treated group. However, concurrent administration of chromium and MOLEE significantly ameliorated the chromium effects on the sperm parameters, local immunity, inflammatory markers and antioxidant enzymatic activities compared with rats exposed to chromium alone. This study concludes that chronic exposure to chromium produces clear testicular toxicity, which can either be prevented or at least decreased by concomitant administration of MOLEE. Interestingly, the metal ion chelation could attribute partly the antioxidant activities of MOLEE.

The protective effect of grape seed procyanidin extract against cadmium-induced renal oxidative damage in mice

As an important environmental pollutant, cadmium (Cd) can lead to serious renal damage. Grape seed procyanidins extract (GSPE), a biological active component of grape seed, has been shown to possess antioxidative effects. Here, we assessed the protective effect of GSPE on Cd-induced renal damage using animal experiment. After 30 days, the oxidative damage of kidney was evaluated through measurement of superoxide dismutase (SOD), glutathione peroxidation (GSH-Px) and malondialdehyde (MDA). Since, oxidative stress could lead to apoptosis, the renal apoptosis was measured using flow cytometer. Moreover, the expression of apoptosis-related protein Bax and Bcl-2 was analyzed by immunohistochemistry and Western blot. The results showed that Cd led to the decrease of SOD and GSH-Px activities, and the increase of MDA level, induced renal apoptosis. However, the coadministration of GSPE attenuated Cd-induced lipid peroxidation, and antagonized renal apoptosis, probably associated with the expression of Bax and Bcl-2. These data suggested that GSPE has protective effect against renal oxidative damage induced by Cd, which provide a potential natural chemopreventive agent against Cd-poisoning.

Submicron and nano formulations of titanium dioxide and zinc oxide stimulate unique cellular toxicological responses in the green microalga Chlamydomonas reinhardtii

The work investigates the eco-cytoxicity of submicron and nano TiO₂ and ZnO, arising from the unique interactions of freshwater microalga Chlamydomonas reinhardtii to soluble and undissolved components of the metal oxides. In a freshwater medium, submicron and nano TiO₂ exist as suspended aggregates with no-observable leaching. Submicron and nano ZnO undergo comparable concentration-dependent fractional leaching, and exist as dissolved zinc and aggregates of undissolved ZnO. Cellular internalisation of solid TiO₂ stimulates cellular ROS generation as an early stress response. The cellular redox imbalance was observed for both submicron and nano TiO₂ exposure, despite exhibiting benign effects on the alga proliferation (8-day EC50>100 mg TiO₂/L). Parallel exposure of C. reinhardtii to submicron and nano ZnO saw cellular uptake of both the leached zinc and solid ZnO and resulting in inhibition of the alga growth (8-day EC50≥0.01 mg ZnO/L). Despite the sensitivity, no zinc-induced cellular ROS generation was detected, even at 100 mg ZnO/L exposure. Taken together, the observations confront the generally accepted paradigm of cellular oxidative stress-mediated cytotoxicity of particles. The knowledge of speciation of particles and the corresponding stimulation of unique cellular responses and cytotoxicity is vital for assessment of the environmental implications of these materials.

Ecological risk assessment of impacted estuarine areas: integrating histological and biochemical endpoints in wild Senegalese sole

The analysis of multiple biomarker responses is nowadays recognized as a valuable tool to circumvent potential confounding factors affecting biomonitoring studies and allows a better understanding of the mechanisms underlying exposure to natural mixtures of toxicants. For the purpose of an environmental risk assessment (ERA) in an impacted estuary in SW Europe (the Sado, Portugal), juvenile Solea senegalensis from commercial fishing areas were surveyed for histopathological liver alterations and biochemical biomarkers. Although the findings revealed moderate differences in the patterns of histopathological traits between urban/industrial- and agricultural-influenced areas within the same estuary, no significant distinction was found between the cumulative alterations in animals from the two sites. The overall level of histopathological injury was low and severe traits like neoplasms or pre-neoplastic foci were absent. While metallothionein induction and lipid peroxidation could relate to histopathological condition indices, the activity of anti-oxidant enzymes appeared to be impaired in animals collected off the estuary's heavy-industry belt (the most contaminated site), which may partially explain some degree of hepatic integrity loss. Overall, the results are consistent with low-moderate contamination of the estuary and indicate that oxidative stress is the most important factor accounting for differences between sites. The study highlights the need of integrating multiple biomarkers when multiple environmental stressors are involved and the advantages of surveying toxicity effects in field-collected, foraging, organisms.

Overexpression of ubiquitin and amino acid permease genes in association with antimony resistance in Leishmania tropica field isolates

The mainstay therapy against leishmaniasis is still pentavalent antimonial drugs; however, the rate of antimony resistance is increasing in endemic regions such as Iran. Understanding the molecular basis of resistance to antimonials could be helpful to improve treatment strategies. This study aimed to recognize genes involved in antimony resistance of Leishmania tropica field isolates. Sensitive and resistant L. tropica parasites were isolated from anthroponotic cutaneous leishmaniasis patients and drug susceptibility of parasites to meglumine antimoniate (Glucantime®) was confirmed using in vitro assay. Then, complementary DNA-amplified fragment length polymorphism (cDNA-AFLP) and real-time reverse transcriptase-PCR (RT-PCR) approaches were utilized on mRNAs from resistant and sensitive L. tropica isolates. We identified 2 known genes, ubiquitin implicated in protein degradation and amino acid permease (AAP3) involved in arginine uptake. Also, we identified 1 gene encoding hypothetical protein. Real-time RT-PCR revealed a significant upregulation of ubiquitin (2.54-fold), and AAP3 (2.86-fold) (P<0.05) in a resistant isolate compared to a sensitive one. Our results suggest that overexpression of ubiquitin and AAP3 could potentially implicated in natural antimony resistance.

Identification of antimony resistance markers in Leishmania tropica field isolates through a cDNA-AFLP approach

Pentavalent antimonial compounds have been the first line therapy for leishmaniasis; unfortunately the rate of treatment failure of anthroponotic cutaneous leishmaniasis (ACL) is increasing due to emerging of drug resistance. Elucidation of the molecular mechanisms operating in antimony resistance is critical for development of new strategies for treatment. Here, we used a cDNA-AFLP approach to identify gene(s) which are differentially expressed in resistant and sensitive Leishmania tropica field isolates. We identified five genes, aquaglyceroporin (AQP1) acts in drug uptake, ATP-binding cassette (ABC) transporter (MRPA) involved in sequestration of drug, phosphoglycerate kinase (PGK) implicated in glycolysis metabolism, mitogen activated protein kinase (MAPK) and protein tyrosine phosphatase (PTP) responsible for phosphorylation pathway. The results were confirmed using real time RT-PCR which revealed an upregulation of MRPA, PTP and PGK genes and downregulation of AQP1 and MAPK genes in resistant isolate. To our knowledge, this is the first report of identification of PTP and PGK genes potentially implicated in resistance to antimonials. Our findings support the idea that distinct biomolecules might be involved in antimony resistance in L. tropica field isolates.

Oxidative stress-induced cyclin D1 depletion and its role in cell cycle processing

BACKGROUND

Cyclin D1 is immediately down-regulated in response to reactive oxygen species (ROS) and implicated in the induction of cell cycle arrest in G2 phase by an unknown mechanism. Either treatment with a protease inhibitor alone or expression of protease-resistant cyclin D1 T286A resulted in only a partial relief from the ROS-induced cell cycle arrest, indicating the presence of an additional control mechanism.

METHODS

Cells were exposed to hydrogen peroxide (H2O2), and analyzed to assess the changes in cyclin D1 level and its effects on cell cycle processing by kinase assay, de novo synthesis, gene silencing, and polysomal analysis, etc.

RESULTS

Exposure of cells to excessive H2O2 induced ubiquitin-dependent proteasomal degradation of cyclin D1, which was subsequently followed by translational repression. This dual control mechanism was found to contribute to the induction of cell cycle arrest in G2 phase under oxidative stress. Silencing of an eIF2α kinase PERK significantly retarded cyclin D1 depletion, and contributed largely to rescuing cells from G2 arrest. Also the cyclin D1 level was found to be correlated with Chk1 activity.

CONCLUSIONS

In addition to an immediate removal of the pre-existing cyclin D1 under oxidative stress, the following translational repression appear to be required for ensuring full depletion of cyclin D1 and cell cycle arrest. Oxidative stress-induced cyclin D1 depletion is linked to the regulation of G2/M transit via the Chk1-Cdc2 DNA damage checkpoint pathway.

GENERAL SIGNIFICANCE

The control of cyclin D1 is a gate keeping program to protect cells from severe oxidative damages.

The response profiles of HSPA12A and TCTP from Mytilus galloprovincialis to pathogen and cadmium challenge

Heat shock 70 kDa protein 12A (HSPA12A) is an atypical member of HSP70 family, and the translationally controlled tumor protein (TCTP) is a novel HSP with chaperone-like activity. They are both involved in protecting organisms against various stressors. In the present study, the cDNAs of HSPA12A and TCTP (called MgHSPA12A and MgTCTP) were identified from Mytilus galloprovincialis by RACE approaches. The full-length cDNA of MgHSPA12A and MgTCTP encoded a peptide of 491 and 171 amino acids, respectively. Real-time PCR was employed to analyze the tissue distribution and temporal expression of these two genes after bacterial challenge and cadmium (Cd) exposure. It was found that the transcripts of MgHSPA12A and MgTCTP were dominantly expressed in gonad and muscle, respectively. The expression level of MgTCTP at 48 h post Vibrio anguillarum challenge was detected to be significantly up-regulated in hepatopancreas (P < 0.05). As concerned to Cd exposure, 2.0-fold increase of MgHSPA12A expression compared to that of the control was observed at 48 h in 5 μg/L Cd(2+)-treated group, while the expression levels of MgTCTP were significantly decreased after exposed to both 5 and 50 μg/L Cd(2+) for 24 h and 96 h. These results suggested the potential involvement of MgHSPA12A and MgTCTP in the mediation of the immune responses and environmental stress in mussels.

Environmental factors and unhealthy lifestyle influence oxidative stress in humans--an overview

Oxygen is the most essential molecule for life; since it is a strong oxidizing agent, it can aggravate the damage within the cell by a series of oxidative events including the generation of free radicals. Antioxidative agents are the only defense mechanism to neutralize these free radicals. Free radicals are not only generated internally in our body system but also trough external sources like environmental pollution, toxic metals, cigarette smoke, pesticides, etc., which add damage to our body system. Inhaling these toxic chemicals in the environment has become unavoidable in modern civilization. Antioxidants of plant origin with free radical scavenging properties could have great importance as therapeutic agents in several diseases caused by environmental pollution. This review summarizes the generation of reactive oxygen species and damage to cells by exposure to external factors, unhealthy lifestyle, and role of herbal plants in scavenging these reactive oxygen species.

Iron overload causes oxidative stress and impaired insulin signaling in AML-12 hepatocytes

BACKGROUND

Iron overload is associated with increased severity of nonalcoholic fatty liver disease (NAFLD) including progression to nonalcoholic steatohepatitis and hepatocellular carcinoma.

AIMS

To identify potential role(s) of iron in NAFLD, we measured its effects on pathways of oxidative stress and insulin signaling in AML-12 mouse hepatocytes.

METHODS

Rapid iron overload was induced with 50 μM ferric ammonium citrate and 8-hydroxyquinoline. Insulin response was measured by Western blot of phospho-protein kinase B. Lipid content was determined by staining with Oil Red O. Reactive oxygen species (ROS) were measured by flow cytometry using 5-(and 6)-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate. Oxidative stress was measured by Western blots for phospho-jnk and phospho-p38.

RESULTS

Iron increased ROS (p < 0.001) and oxidative stress (p < 0.001) and decreased insulin signaling by 33 % (p < 0.001). Treatment with stearic or oleic acids (200 μM) increased cellular lipid content and differentially modulated effects of iron. Stearic acid potentiated iron-induced ROS levels by two-fold (p < 0.05) and further decreased insulin response 59 % (p < 0.05) versus iron alone. In contrast, cells treated with oleic acid were protected against iron-mediated injury; ROS levels were decreased by half (p < 0.01) versus iron alone while insulin response was restored to control (untreated) levels. The anti-oxidant curcumin reduced effects of iron on insulin signaling, ROS, and oxidative stress (p < 0.01). Curcumin was similarly effective in cells treated with both stearic acid and iron.

CONCLUSIONS

An in vitro model of NAFLD progression is described in which iron-induced oxidative stress inhibits insulin signaling. Pathophysiological effects of iron were increased by saturated fat and decreased by curcumin.

Exposure-dose-response of Tellina deltoidalis to metal-contaminated estuarine sediments: 1. Cadmium spiked sediments

Cadmium is a ubiquitous environmental metal contaminant with an affinity for biological membranes; it can enter cells by facilitated transport and it binds therein to various biomolecules and affects membrane system function. The relationship between cadmium exposure, dose and response was investigated in the benthic, deposit feeding, marine bivalve Tellina deltoidalis, using 28 day microcosm spiked cadmium exposures. Tissue cadmium reached steady state with the exposure concentration. Half the accumulated cadmium was detoxified and with increased exposure more was converted into metal rich granules. Most biologically active cadmium was in the mitochondrial fraction, with up to 7320-fold cadmium increases in exposed organisms. Cadmium exposed T. deltoidalis generally had reduced glutathione peroxidase enzyme activity. An increase in total glutathione concentrations, due to a build up of oxidised glutathione, was indicated by the reduced to oxidised glutathione ratio. All cadmium exposed T. deltoidalis had reduced total antioxidant capacity that corresponded with increased lipid peroxidation, lysosomal destabilisation and micronuclei frequency. Clear exposure-dose-response relationships have been demonstrated for T. deltoidalis exposed to cadmium-spiked sediments, supporting this organism's suitability for laboratory or in situ evaluation of sediment cadmium toxicity.

Accumulation and biological effects of metals in wild rats in mining areas of Zambia

The lead-zinc (Pb-Zn) mine in Kabwe City and the copper-cobalt (Cu-Co) mine in the Copperbelt Province are major mining areas in Zambia. To examine the effects of metal pollution on wildlife, wild black rats (Rattus rattus and Rattus tanezumi) were captured in Kabwe and Chingola (in the Copperbelt Province), and in Lusaka (a noncontaminated site). Wild black rats in Kabwe accumulated significantly higher concentrations of Pb and Cd in various organs than rats from Lusaka. In Chingola, significantly higher concentrations of Cu, Co, Pb, and Cd were accumulated in wild black rats than in rats from Lusaka. These results were in accordance with metal accumulation patterns in soil. From toxicological aspects, concentrations of Pb and Cd in rats were generally low. However, metallothionein-1 (MT-1) and metallothionein-2 (MT-2) mRNA expression levels in wild black rats from Kabwe were significantly higher than those in rats from Lusaka. A generalized linear model (GLM) showed that concentrations of Zn and Cu had positive effects on the MT-1 and MT-2 mRNA expression. These results suggest that wild black rats in Zambian mining sites were exposed to metals that accumulated in their organs, causing biological responses such as MT mRNA induction. GLM indicated that heme oxygenase-1 (HO-1) mRNA expression could be a marker for Cr exposure.

Toxicant induced changes on delayed fluorescence decay kinetics of cyanobacteria and green algae: a rapid and sensitive biotest

Algal tests have developed into routine tools for testing toxicity of pollutants in aquatic environments. Meanwhile, in addition to algal growth rates, an increasing number of fluorescence based methods are used for rapid and sensitive toxicity measures. The present study stresses the suitability of delayed fluorescence (DF) as a promising parameter for biotests. DF is based on the recombination fluorescence at the reaction centre of photosystem II, which is emitted only by photosynthetically active cells. We analyzed the effects of three chemicals (3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), 3,5 Dichlorophenol (3,5 DCP) and copper) on the shape of the DF decay kinetics for potential use in phytoplankton toxicity tests. The short incubation tests were done with four phytoplankton species, with special emphasis on the cyanobacterium Microcystis aeruginosa. All species exhibited a high sensitivity to DCMU, but cyanobacteria were more affected by copper and less by 3,5 DCP than the tested green algae. Analyses of changes in the DF decay curve in response to the added chemicals indicated the feasibility of the DF decay approach as a rapid and sensitive testing tool.

Nitric oxide (NO) in alleviation of heavy metal induced phytotoxicity and its role in protein nitration

Nitric oxide (NO) is recognized as a biological messenger in various tissues to regulate diverse range of physiological process including growth, development and response to abiotic and biotic factors. The NO emission from plants is known since the 1970s, and there is copious information on the multiple effects of exogenously applied NO on different physiological and biochemical processes of plants. Heavy metal toxicity is one of the major abiotic stresses leading to hazardous effects in plants and its toxicity is based on chemical and physical property. A common consequence of heavy metal toxicity is the uncontrolled and excessive accumulation of reactive oxygen species (ROS) which leads to peroxidation of lipids, oxidation of protein, inactivation of enzymes, DNA damage and/or interact with other vital constituents of plant cells. Recently, an increasing number of articles have reported the effects of exogenous NO on alleviating heavy metal toxicity in plants but knowledge of physiological mechanisms of NO in alleviating heavy metal toxicity is quite limited, and some results contradict one another. Therefore, to help clarify the roles of NO in heavy metal tolerance, it is important to review and discuss the recent advances on this area of research. NO can provoke both beneficial and harmful effects, which depend on the concentration and location of NO in the plant cells. NO alleviates the harmfulness of the ROS, and reacts with other target molecules, and regulates the expression of stress responsive genes under various stress conditions. This manuscript includes, the latest advances in understanding the effects of endogenous NO on heavy metal toxicity and the mechanisms and role of NO as an antioxidant as well as in protein nitration are highlighted.

Free radicals generated by tantalum implants antagonize the cytotoxic effect of doxorubicin

Little is known about the interaction between antineoplastic drugs and implants in bone cancer patients. We investigated the interaction between commercially available porous tantalum (Ta) implants and the chemotherapeutic drug, Doxorubicin (DOX). DOX solutions were prepared in the presence of Ta implant. The changes in fluorescence intensity of the DOX chromophore were measured by spectrofluorometry and the efficacy of DOX was evaluated by viability of rabbit rectal tumor cells (VX2). After 5 min interaction of the DOX solution (5 μg/ml) with the Ta implant, the fluorescent intensity of the DOX solution was 85% degraded, and only 20% the drug efficacy to kill VX2 cells was retained. However, after adding a reducing agent, Dithiothreitol (DTT, 10 μg/ml), 80% of the original fluorescence and 50% of the drug efficacy were restored while UV irradiation enhanced drug degradation in the presence of Ta implant. The action of DTT and UV irradiation indicated that reactive oxygen species (ROS) were involved in the drug degradation mechanism. We detected that Ta implants in aqueous medium produced hydroxyl radicals. Cells showed higher intracellular ROS activity when culture medium was incubated with the Ta implant prior to cell culture. It is concluded that the porous Ta implant antagonizes the cytotoxicity of DOX via ROS generation of the porous Ta implant.

Seasonal variation of Sarpa salpa fish toxicity, as related to phytoplankton consumption, accumulation of heavy metals, lipids peroxidation level in fish tissues and toxicity upon mice

The aim of this work was to investigate for Sarpa salpa the seasonal trend in the food sources, heavy metals bioaccumulation and the oxidative stress in the organs. In addition, the toxicity was assessed by mouse bioassay of extract of the fish's organs collected in autumn, the peak of occurrence of hallucinatory syndrome. The toxicity was further studied for compounds present in epiphyte collected from the sea at the end of spring and in summer that are digested by the S. salpa in these seasons. We observed a higher lipid peroxydation in different tissues of S. salpa compared to the control fish Diplodus annularis. Furthermore, heavy metals accumulation in organs of these fish showed a significant variation between the two species (P < 0.05). The lethal dose (LD50%) determined for crude ciguatoxin (neurotoxins) extracts of viscera, liver, brain and muscle of S. salpa were as follows: 1.217, 2.195, 14.395, 18.645 g/kg mouse, respectively. We noticed a significant correlation (P < 0.05) between the total amount of toxic dinoflagellates and the level of TBARS in the liver, the brain and the muscle, this for all seasons and all sizes. Moreover, the cytotoxic effect observed for epiphytes extract confirms the transfer of toxins originating from toxic dinoflagellates, which live as epiphytes on P. oceanica leaves, to the fish by grazing. Our work indicates that, toxic phytoplanktons and heavy metals accumulation are responsible for the increase of oxidative stress in the organs of S. salpa. Hence, the edible part of S. salpa, especially the viscera and liver, can cause a threat to human health, and consumption should, for this reason, be dissuaded.

Pretreatment hepatoprotective effect of the marine fungus derived from sponge on hepatic toxicity induced by heavy metals in rats

The aim of this study was to evaluate the pretreatment hepatoprotective effect of the extract of marine-derived fungus Trichurus spiralis Hasselbr (TS) isolated from Hippospongia communis sponge on hepatotoxicity. Twenty-eight male Sprague-Dawley rats were divided into four groups (n = 7). Group I served as −ve control, group II served as the induced group receiving subcutaneously for seven days 0.25 mg heavy metal mixtures, group III received (i.p.) TS extract of dose 40 mg for seven days, and group IV served as the protected group pretreated with TS extract for seven days as a protection dose, and then treated with the heavy metal-mixture. The main pathological changes within the liver after heavy-metal mixtures administrations marked hepatic damage evidenced by foci of lobular necrosis with neutrophilic infiltration, adjacent to dysplastic hepatocytes. ALT and AST measurements show a significant increase in group II by 46.20% and 45.12%, respectively. Total protein, elevated by about 38.9% in induction group compared to the −ve control group, in contrast to albumin, decreased as a consequence of metal administration with significant elevation on bilirubin level. The results prove that TS extract possesses a hepatoprotective property due to its proven antioxidant and free-radical scavenging properties.

Protective effect of naringenin on hepatic and renal dysfunction and oxidative stress in arsenic intoxicated rats

Arsenic has a long history as a potent human poison, chronic exposure over a period of time may result in the manifestation of toxicity in practically all systems of the body. In the present investigation the efficacy of naringenin (NRG), a naturally occurring citrus flavanone against arsenic-induced hepatotoxic and nephrotoxic manifestations have been studied in rats. Arsenic trioxide was administered orally at the dose of 2 mg/kg/day with or without combination of NRG (20 or 50 mg/kg/day) for 28 days. At the end of the experimental period the hepatic and renal dysfunction was evaluated by histological examination, serum biomarkers and markers of oxidative stress; lipid peroxidation (LPO), reduced glutathione (GSH) and antioxidant enzymes. Arsenic intoxication increased serum bilirubin, urea, uric acid and creatinine levels, additionally enhanced the activities of hepatic marker enzymes aspartate transaminase, alanine transaminase and alkaline phosphatase. Also, the hepatic and renal tissues showed a marked elevation in LPO levels with a decrease in GSH content and the activities of antioxidant enzymes such as superoxide dismutase, catalase, glutathione peroxidase and glutathione-S-transferase on arsenic treatment. Simultaneous treatment with NRG restored the activities of serum biomarkers and antioxidant enzymes in the tissues in a dose-dependent manner. Furthermore, the histopathological studies confirmed the protective effect of NRG co-treatment by reducing the pathological changes due to arsenic intoxication in both liver and kidney. Thus, our present study demonstrates that NRG has a potential to protect arsenic-induced oxidative hepatic and renal dysfunction.

Differential gene expression in Iberian green frogs (Pelophylax perezi) inhabiting a deactivated uranium mine

Iberian green frogs (Pelophylax perezi) were found inhabiting a deactivated uranium mine, especially an effluent pond, seriously contaminated with metals and radionuclides. These animals were previously assessed for oxidative stress parameters and did not revealed significant alterations. In order to better understand which mechanisms may be involved in the ability to withstand permanent contamination gene expression analysis was performed in the liver, through suppression subtractive hybridization (SSH). The SSH outcome in the liver revealed the up-regulation of genes coding for the ribosomal protein L7a and for several proteins typical from blood plasma: fibrinogen, hemoglobin and albumin. Besides their normal function, some of these proteins can play an important role as protective agents against oxidative stress. This work provides new insights on possible basal protection mechanisms that may act in organisms exposed chronically to contamination.