Changes in oxidative metabolism in selected tissues of the crab (Scylla serrata) in response to cadmium toxicity

Urea cycle promotion via ammonia-upregulated CPS1 is involved in arsenite-induced pulmonary fibrosis through enhancing collagen synthesis

Arsenic exposure is connected with lung toxicity and is related to lung fibrotic changes. Idiopathic pulmonary fibrosis (IPF) is characterized by extracellular matrix (ECM) deposition. Various genetic mechanisms and environmental factors induce or exacerbate pulmonary fibrosis. Collagen synthesis induced by sodium arsenite (NaAsO2) is closely associated with IPF. Fibroblasts tend to fine-tune their metabolic networks to support their synthetic requirements in response to environmental stimuli. Alterations in metabolism have an influential role in the pathogenesis of IPF. However, it is unclear how arsenic affects the metabolism in IPF. The urea cycle (UC) is needed for collagen formation, which provides adequate levels of proline (Pro) for biosynthesis of collagen. Carbamoyl phosphate synthetase 1 (CPS1) converts the ammonia to carbamoyl phosphate, which controls the first reaction of the UC. We show that, in arsenite-exposed mice, high amounts of ammonia in the lung microenvironment promotes the expression levels of CPS1 and the Pro metabolism. Reduction of ammonia and CPS1 ablation inhibit collagen synthesis and ameliorate IPF phenotypes induced by arsenite. This work takes advantage of multi-omics data to enhance understanding of the underlying pathogenic mechanisms, the key molecules and the complicated cellular responses to this pollutant, which provide a target for the prevention of pulmonary fibrosis caused by arsenic.

Effects of dispersant-treated oil upon behavioural and metabolic parameters of the anti-predator response in juvenile European sea bass (Dicentrarchus labrax)

Acute exposure to oil and oil dispersants can cause a wide range of physiological dysfunctions in marine fish species and evidences for consequences on behaviour are also increasing. In response to the presence of predators or to food availability, the modulation of locomotor activity and schools' behaviour enable fish to maximize their survival rates. However, the degree to which this regulatory process is affected by exposure to oil and/or dispersants is yet unknown. Here we investigated the effect of a 62-h experimental exposure to dispersant-treated oil on the behavioural (shoal cohesion, spontaneous activity) and metabolic (oxygen consumption) responses to simulated predation in juvenile European sea bass, Dicentrarchus labrax L. Our results suggest that exposure to petroleum hydrocarbons may affect negatively individual fitness through impaired ability to respond to predation. Shoal cohesion was not affected, but fish swimming activity was higher than control individuals under predation pressure and the amplitude of their metabolic response was significantly reduced. Fish recovered from alteration of their metabolic response 7 days post-exposure. Additionally, a strong habituation component was observed in C fish and the absence of such pattern in E fish suggest altered capacity to habituate over time to the surrounding environment and possible impairments of the related cognitive performances. Altogether, our data show that juvenile sea bass exposed to oil exhibit transient physiological dysfunctions and impairments of complex behaviours that may have major population-level consequences.

In vivo appraisal of oxidative stress response, cell ultrastructural aberration and accumulation in Juvenile Scylla serrata exposed to uranium

In vivo studies were performed to evaluate the organ specific tissue accumulation and cellular toxicity of uranium to mud crab Scylla serrata. The specimens were acclimated in natural seawater and the exposure to 50-250 μg/L uranium was investigated up to 60 days. The present study examined the effects of concentration and duration of uranium exposure in the tissue of S. serrata at cellular and subcellular level using scanning electron microscopy and bright field transmission electron microscopy in addition to histological analysis. The results indicated that accumulation of U in S. serrata was organ specific and followed the order gills > hepatopancreas > muscle. The response of key antioxidant enzyme activities such as SOD, GPx and CAT in different organs of crabs indicated oxidative stress due to U in the ambient medium and tissue. At 50 and 100 μg/L of U exposure, individuals were able to acclimate the oxidative stress and withstand the uranium exposure. This acclimation could not be sustained at higher concentrations (250 μg/L), affecting the production of CAT in the tissues. Cellular and subcellular changes were observed in the hemocytes with reduction in their number in consonance with the antioxidant enzymes. Histological aberrations like lamellar disruption of gill, necrosis of hepatopancreas, disruption and rupture of muscle bundles were observed at different concentrations and were severe at higher concentration (250 μg/L). Necrosis was observed in the electron micrographs of tissues shortly after 15 days of exposure. SEM micrograph clearly shows disrupted lamellae, folding of marginal canal and reduction of inter lamellar spaces in the gills of crab exposed to high concentration of uranium. Mitochondrial anomalies are reported for the first time in the present study in addition to the subcellular changes and vacuoles on exposure uranium in the cells of gill and hepatopancreas.

Chronic exposure to low-dose cadmium facilitated nonalcoholic steatohepatitis in mice by suppressing fatty acid desaturation

Exposure to cadmium (Cd), a toxic metal, is epidemiologically linked to nonalcoholic steatohepatitis (NASH) in humans. However, the role of Cd in NASH remains to be fully elucidated. This study employed a novel murine NASH model to investigate the effects of chronic low-dose Cd on hepatic pathology and its underlying mechanisms. NASH is characterized by lipid accumulation, extensive cell death, and persistent inflammation in the liver. We found that treatment with Cd in drinking water (10 mg/L) for 6 or 12 weeks significantly boosted hepatic fat deposition, increased hepatocyte destruction, and amplified inflammatory responses in mice, confirming that low-dose Cd can facilitate NASH development in vivo. Mechanistically, chronic Cd exposure reshaped the hepatic transcriptional landscape, with PPAR-mediated fatty acid metabolic pathways being the most significantly altered. In particular, Cd repressed fatty acid desaturation, leading to the accumulation of saturated fatty acids whose lipotoxicity exacerbated cell death and, consequently, inflammatory activation. In summary, we validated the causal effects of chronic low-dose Cd on NASH in vivo and identified the fatty acid desaturation program as a novel target for Cd to instigate hepatopathological alterations.

Implications of long-term exposure of a Lymantria dispar L. population to pollution for the response of larval midgut proteases and acid phosphatases to chronic cadmium treatment

Cadmium (Cd) presence in terrestrial ecosystems is a serious threat that requires continuous development of biomonitoring tools. Ideally, a suitable biomarker of exposure should respond to the toxicant consistently in different populations regardless of previous exposure to pollution. Here we considered the activities and isoform patterns of certain proteases and acid phosphatases (ACP) in the midgut of Lymantria dispar larvae as well as the integrated biomarker response (IBR) for application in Cd biomonitoring. We compared the responses of caterpillars originating from unpolluted and polluted localities after they had been chronically subjected to dietary Cd (50 and 100 μg Cd/g dry food). The population inhabiting the unpolluted forest was far more sensitive to Cd exposure as the activities of total proteases, trypsin (TRY) and leucine aminopeptidase (LAP) were mostly reduced while the activities of total and non-lysosomal ACP were increased. Non-lysosomal ACP activity was elevated in larvae from the contaminated site in response to the higher Cd concentration. Exposure to the metal resulted in numerous alterations in the pattern of enzyme isoforms, but the responses of the two populations were similar except that larvae from the polluted locality were more tolerant to the lower Cd concentration. Non-lysosomal ACP activity and the appearance of ACP isoforms 4 and 5 together with the IBR index are the most promising indicators of Cd presence, potentially applicable even in populations with a history of exposure to pollution. TRY and total ACP activities could be used to monitor populations at uncontaminated localities.

Dark septate endophyte Falciphora oryzae-assisted alleviation of cadmium in rice

Dark septate endophytes (DSEs) are the typical representatives of root endophytic fungi in heavy metal (HM)-contaminated environments. However, little is known about their roles in the HMs tolerance of hosts and the underlying mechanism. Here, we investigated the biological roles and molecular mechanisms of a DSE strain Falciphora oryzae in alleviating cadmium (Cd) toxicities in rice. It was found that F. oryzae possessed a capacity of accumulating Cd in its vacuoles and chlamydospores. During symbiosis, F. oryzae conferred improved Cd tolerance to rice, decreasing Cd accumulation in roots and translocation to shoots. F. oryzae alleviated Cd toxicity to rice by sequestering Cd in its vacuoles. Further application of F. oryzae as fertilizer in the field could reduce Cd content in rice grains. We identified a SNARE Syntaxin 1 gene through proteomics, which participated in Cd tolerance of F. oryzae by regulating chlamydospore formation and vacuole enlargement. This study provided novel insights into how the DSEs and their host plants combat Cd stress.

Effects of combined treatment of cadmium and oxytetracycline on the terrestrial isopod Porcellio leavis

The influence of pharmaceutical residues and heavy metals on living organisms has received global attention. The present study assessed the interactive effect of antibiotic residues and heavy metals in soil, as contaminated food with cadmium (Cd) and oxytetracycline (OTC) on the isopod Porcellio leavis. It was fed on fresh plant leaves contaminated with different concentrations of cadmium, Cd+OTC1000 ppm, Cd+OTC2000 ppm and Cd+OTC3000 ppm for 4 weeks. The changes in the feeding patterns, protein, lipid peroxidation (LPO), catalase activity (CAT), and total free amino acids (TFAA) were recorded. There were significant differences in the obtained results where Cd reduced the egestion ratio (ER) however, OTC enhanced this ratio. Biochemical analysis illustrated that combination between OTC and Cd inhibits the toxic effects of Cd at low concentration (1000 ppm), while at high concentration (3000 ppm) raise the toxicity. Detailed studies are required for further understanding of the interaction between OTC and heavy metals, and also its impact on soil animals and for improving soil risk evaluation.

Neurodevelopmental exposome: The effect of in utero co-exposure to heavy metals and phthalates on child neurodevelopment

In this study, the exposome paradigm has been applied on a mother-child cohort adopting an optimised untargeted metabolomics approach for human urine followed by advanced bioinformatics analysis. Exposome-wide association algorithms were used to draw links between in utero co-exposure to metals and phthalates, metabolic pathways deregulation, and clinically observed phenotypes of neurodevelopmental disorders such as problems in linguistic, motor development and cognitive capacity. Children (n = 148) were tested at the first and second year of their life using the Bayley Scales of Infant and Toddler Development, Third Edition (Bayley-III). Their mothers had been exposed to metals and phthalates during the pregnancy, according to human biomonitoring results from previously performed studies. Untargeted metabolomics analysis of biobanked urine samples from the mothers was performed using a combination of the high throughput analytical methods liquid chromatography-high resolution mass spectrometry (LC-HRMS) and nuclear magnetic resonance (NMR). Most perturbed metabolic pathways from co-exposure heavy metals and phthalates were pathways related to the tricarboxylic acid cycle (TCA cycle) and oxidative phosphorylation, indicating the possibility of disruption of mitochondrial respiration. Overproduction of reactive oxygen species (ROS); the presence of glutathione peroxidase 3 (GPx3) during pregnancy and presence of glutathione peroxidase 1 (GPx1) in the umbilical cord were linked to verbal development problems. Another finding of the study is that in real life, adverse outcomes occur as a combination of environmental and social factors, all of them acting synergistically towards the deployment of an observed phenotype. Finally, the two-steps association process (exposure to pathways and pathways to adverse outcomes) was able to (a) provide associations that are not evident by directly associating exposure to outcomes and (b) provides additional insides on the mechanisms of environmental disease.

Temperature elevation stage-specifically increases metal toxicity through bioconcentration and impairment of antioxidant defense systems in juvenile and adult marine mysids

Metals are of serious concern due to their toxicity, persistency, and accumulation potential in aquatic animals. However, limited information is available on the combined effects of metal with temperature elevation, which is one of the future climate changes suggested for the oceans. In this study, the effect of temperature elevation was investigated by analyzing toxicity, bioconcentration, and antioxidant response in juvenile and adult marine mysids upon exposure to 20 °C and 25 °C for 48 h and 96 h. Based on LC₅₀ values, toxicity of metals was highly reliant on temperature, exposure period, and age. Elevation in temperature significantly increased the whole metal toxicity in juveniles. Bioconcentration was elevated by increasing exposure period and metal concentration. Significant elevation of malondialdehyde (MDA) and depletion of glutathione (GSH) was measured in juveniles, while significant elevation of both MDA and GSH was detected in adults. Subsequently, enzymatic activities of antioxidant enzymes in catalase (CAT) and superoxide dismutase (SOD) increased significantly in adults at 48 h and 96 h, whereas most activities were significantly lowered in juveniles at 96 h. These results suggest that the early life stage of marine mysids is more sensitive to the combined effect of metal and temperature than adult stage due to an impairment in the induction of the antioxidant defense system.

Impact of climate change on the American lobster (Homarus americanus): Physiological responses to combined exposure of elevated temperature and pCO2

The physiological consequences of exposing marine organisms to predicted future ocean scenarios, i.e. simultaneous increase in temperature and pCO₂, have only recently begun to be investigated. Adult American lobster (Homarus americanus) were exposed to either current (16 °C, 47 Pa pCO₂, pH 8.10) or predicted year 2300 (20 °C, 948 Pa pCO₂, pH 7.10) ocean parameters for 14-16 days prior to assessing physiological changes in their hemolymph parameters as well as whole animal ammonia excretion and resting metabolic rate. Acclimation of lobster simultaneously to elevated pCO₂ and temperature induced a prolonged respiratory acidosis that was only partially compensated for via accumulation of extracellular HCO₃^- and ammonia. Furthermore, acclimated animals possessed significantly higher ammonia excretion and oxygen consumption rates suggesting that future ocean scenarios may increase basal energetic demands on H. americanus. Enzyme activity related to protein metabolism (glutamine dehydrogenase, alanine aminotransferase, and aspartate aminotransferase) in hepatopancreas and muscle tissue were unaltered in future ocean scenario exposed animals; however, muscular citrate synthase activity was reduced suggesting that, while protein catabolism may be unchanged, the net energetic output of muscle may be compromised in future scenarios. Overall, H. americanus acclimated to ocean conditions predicted for the year 2300 appear to be incapable of fully compensating against climate change-related acid-base challenges and experience an increase in metabolic waste excretion and oxygen consumption. Combining our study with past literature on H. americanus suggests that the whole lifecycle from larvae to adult stages is at risk of severe growth, survival and reproductive consequences due to climate change.

Identification of immune-related genes in gills of Chinese mitten crabs (Eriocheir sinensis) during adaptation to air exposure stress

The Chinese mitten crab, Eriocheir sinensis, is the most important crab in China. Air exposure is regarded as one of the crucial restriction factors in the crab cultivation and transportation process. Numerous studies have shown that air exposure stress can cause many negative effects on aquatic farming animals. However, the molecular mechanisms of drying on Chinese mitten crabs are still poorly studied. In this study, gill reference transcriptome was assembled and differentially expressed gene (DGE) analysis was conducted between air exposure 16 h and normal dissolved oxygen of Chinese mitten crab. A total of 76075 transcripts were generated and 50800 unigenes with a mean length of 1090 bp and N50 length of 1584 bp were observed. Transcriptomic comparison revealed 352 DEGs between air exposure 16 h group and control group, including 122 up-regulated genes and 230 down-regulated genes. Gene ontology (GO) analysis revealed that these DEGs involved in 16 biological process subcategories, 8 cellular component subcategories and 6 molecular function subcategories. Further Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis annotated 352 DEGs to 85 pathways, and some pathways were regarded as related with immune system and diseases, such as phagosome, systemic lupus erythematosus, and alcoholism. Eight genes involved in multiple KEGG signaling pathways were validated by qRT-PCR. This study demonstrates the first gill transcriptomic analysis challenged with air exposure stress in Chinese mitten crab and provides valuable gene resources for understanding the crab gill immunity, which can provides insight into the immune response of crab against air exposure stress.

Effects of perfluorooctane sulfonate on the immune responses and expression of immune-related genes in Chinese mitten-handed crab Eriocheir sinensis

Perfluorooctane sulfonate (PFOS) has been widely studied due to its global distribution, slow degradation, high bioaccumulation and toxicological effects on vertebrates. However, the potential toxicity of PFOS to crustaceans is little known. The present study investigated the effects of PFOS on the immune responses and expression of immune-related genes in the Chinese mitten-handed crab Eriocheir sinensis. Crabs were exposed to 0, 0.01, 0.1, 1.0 and 10mg/L of PFOS, and sampled on 1, 4, 7, 14 and 21days respectively. The total hemocyte count and lysozyme activity in PFOS-treated crab were significantly lower than in the control. The exposure to 10mg/L of PFOS led to a marked inhibition in phenoloxidase and superoxide dismutase activities. At other PFOS levels, phenoloxidase and superoxide dismutase showed an initial increase and a subsequent decrease over time. The alkaline and acid phosphatase activities were stimulated in 10mg/L PFOS until 21days. The mRNA expression of immune related genes including hepatopancreas-specific C-type lectin and prophenoloxidase activating factors were up-regulated after the exposure to the concentrations of 1 and 10mg/L of PFOS, while the expression of lysozyme gene was up-regulated only in the crab exposed to 0.1mg/L PFOS. The results demonstrate that the high dose of PFOS leads to immune toxicity and the hepatopancreas is a major target organ for PFOS accumulation and immunotoxicity. Hemocyte counts, phenoloxidase and acid phosphatase are useful biomarkers for the risk assessment of PFOS toxicity to crustaceans.

Metabolic signatures associated with environmental pollution by metals in Doñana National Park using P. clarkii as bioindicator

Bioindicators can reflect the effects of pollutants on their metabolism, being widely used to assess environmental stress. In this sense, the crab Procambarus clarkii has been previously proposed to monitor the contamination in Doñana National Park (southwest Spain) using conventional biomarkers. In this work, a metabolomic approach based on direct infusion mass spectrometry, which allows an easy and quick study of a large number of metabolites in a single run, was used for pollution assessment of this area, considering the biological response of this organism to contamination. In addition, metal accumulation in crab tissues was determined. Thus, the integrated analysis of metabolomic and metallomic data enabled the study of metabolic response of the organism against pollution. Several metabolites were discovered as potential biomarkers of pollution, such as decreased levels of carnosine, alanine, niacinamide, acetoacetate, pantothenic acid, ascorbate, glucose-6-phosphate, arginine, glucose, lactate, phospholipids, and tryglicerides, as well as elevated levels of acetyl carnitine, phosphocholine, choline, and uric acid. In this way, metal-induced toxicity could be related to metabolic impairments, principally oxidative stress, metabolic dysfunction, and dyslipidemia.

Bioaccumulation and toxicodynamics of cadmium to freshwater planarian and the protective effect of N-acetylcysteine

Although toxic responses of freshwater planarians after exposure to environmental toxicants can be observed through external toxicological end points, physiological responses inside the bodies of treated planarians have rarely been investigated. The present study was designed, using cadmium (Cd) as a reference toxicant, to determine its bioaccumulation and toxicodynamics in the freshwater planarian, Dugesia japonica, after acute toxicity was obtained. Accumulated Cd concentrations, metallothionein levels, and the oxidative status in planarians were determined after exposure to Cd. Furthermore, we hypothesized that the acute death of Cd-treated planarians was associated with increased oxidative stress. After Cd-treated planarians were coexposed to antioxidant, N-acetylcysteine (NAC), we found that NAC protected planarians from Cd lethality by maintaining the oxidative status and decreasing the bioaccumulation of Cd. The results of the present study support planarians being used as a practical model for toxicological studies of environmental contaminants in the future.

Immune responses and ultrastructural changes of hemocytes in freshwater crab Sinopotamon henanense exposed to elevated cadmium

Cadmium (Cd) is one of the most toxic heavy metals that can impact immunological parameters in aquatic animals. To investigate the immunotoxicity and ultrastructural changes of hemocytes, specimens of Sinopotamon henanense were exposed to different concentrations of cadmium and the differences in immunologic parameters between Cd exposure groups and control groups were investigated. Total hemocyte count (THC) in Cd-exposure groups were decreased significantly when compared with the control groups, especially in the groups treated with higher Cd concentrations and longer exposure time, while no significant differences were observed in the proportions of the three types of hemocytes. Phenoloxidase (PO) activities were significantly higher in Cd-exposure groups than the control groups. Superoxide dismutase (SOD) activities gradually increased in 7.25 and 14.5 mg L⁻¹ Cd groups, but in other higher Cd groups, they showed first increase and following decrease with the exposure time prolonged. Acid phosphatase (ACP) activities were induced at 48 h, and then decreased, while alkaline phosphatase (AKP) activities increased gradually until 96 h. Electron microscopic results showed that nucleus, mitochondria and rough endoplasm recutulum (rER) of three types of hemocytes were sensitive to acute Cd toxicity. In Cd-exposed groups, chromatin condensation, nucleus deformation and nucleus envelope rupture were noted. Additionally, mitochondrial dilation and rER degranulation were observed in Cd-treated crabs. These results suggested that immune response and organelles of hemocyte of S. henanense were impacted by Cd exposure, and the changes of these immunologic parameters reflect changes in crab immune response capability consequent to Cd exposure.

Proteomics in aquatic amphipods: can it be used to determine mechanisms of toxicity and interspecies responses after exposure to atrazine?

Proteomics has gained popularity in the field of ecotoxicology as a holistic tool for unraveling novel mechanisms of toxicity and elucidating subtle effects of contaminant exposure. The holoarctic amphipod Diporeia spp. is declining at precipitous rates in the Great Lakes, and we are evaluating the use of the well-studied amphipod model Hyalella azteca as a surrogate for Diporeia spp. This article presents proteomics data from both amphipod species exposed to atrazine (ATZ) and one of its metabolites, desethylatrazine (DEA; 3 and 30 µg/L for 21 and 42 d). We used a proteomics approach to determine whether these two species of amphipods responded similarly to the same chemicals and to understand better the mechanisms of toxicity of ATZ and DEA in aquatic invertebrates. We observed disruption in energy production and mitochondrial function as well as hormesis in exposed organisms. In addition, we identified a two proteins (GAPDH and HSP 90 kDa) that have been linked to hormonal disruptions, suggesting potential endocrine disruption. Finally, we found that H. azteca and Diporeia spp. responded with similar proteomic profiles after ATZ and DEA exposure, suggesting that H. azteca may be used as a surrogate model organism for Diporeia spp.

Cadmium and mercury-induced hyperglycemia in the fresh water crab, Oziotelphusa senex senex: involvement of neuroendocrine system

The effect of exposure to sublethal concentrations of cadmium chloride and mercuric chloride on hemolymph glucose levels of the freshwater crab, Oziotelphusa senex senex, was studied. Intact crabs exposed to cadmium or mercury exhibited a significant hyperglycemia compared to controls, but no significant differences in hemolymph glucose level were detected among the eyestalkless crabs after exposure to metals, suggesting that the effect of metals could be on the sinus gland in the eyestalks, increasing secretion of the hyperglycemic hormone. To test this hypothesis, eyestalks were collected from control and metal exposed crabs, and tested for hyperglycemic effect and also for the hyperglycemic hormone levels. The levels of hyperglycemic hormone and the hyperglycemic effect were significantly low in the eyestalks collected from metal exposed crabs when compared with eyestalks from control crabs. These results strongly suggest that metals act, at least in part, by triggering the secretion of hyperglycemic hormone from the eyestalk.

Rapid sublethal toxicity assessment using bioluminescent Caenorhabditis elegans, a novel whole-animal metabolic biosensor

Sublethal metabolic effects are informative toxicological end points. We used a rapid quantitative metabolic end point, bioluminescence of firefly luciferase expressing Caenorhabditis elegans, to assess effects of sublethal chronic exposure (19 h) to the oxidative stress agent and environmental pollutant cadmium (provided as chloride salt). Bioluminescence declined in a concentration-dependent manner in the concentration range tested (0-30 microM Cd), with comparable sensitivity to reproduction and developmental assay end points (after 67 and 72 h, respectively). Cd concentrations that resulted in 20% reduction in bioluminescence (EC(20)) were 11.8-13.0 microM, whereas the reproduction EC(20) (67 h exposure) was 10.2 microM. At low concentrations of Cd (< or = 15 microM), the decline in bioluminescence reflected a drop in ATP levels. At Cd concentrations of 15-30 microM, decreased bioluminescence was attributable both to effects of Cd on ATP levels and decreased production of luciferase proteins, concomitant with a decline in protein levels. We show that whole-animal bioluminescence is a valid toxicological end point and a rapid and sensitive predictor of effects of Cd exposure on development and reproduction. This provides a platform for high-throughput sublethal screening and will potentially contribute to reduction of testing in higher animals.

Levels of transaminases, alkaline phosphatase, and protein in tissues of Clarias gariepienus fingerlings exposed to sublethal concentrations of cadmium chloride

The freshwater fish, Clarias gariepienus fingerlings, were exposed to sublethal concentrations (1.7 and 3.4 mg/L) of cadmium chloride for 12 days. Aspartate aminotransferase (AAT), alanine aminotransferase (ALT), alkaline phosphatase (ALP), and total protein levels were assayed in the gill, brain, and muscle of the fish at regular intervals of 6 and 12 days. The activities of AAT, ALT, and ALP of the treated fishes increased significantly in all the tissues compared with the control fish. Protein level in all the tissues showed a significant decrease in comparison to unexposed controls throughout the experimental periods. These results revealed that cadmium chloride effects the intermediary metabolism of C. gariepienus fingerlings and that the assayed enzymes can work as good biomarkers of contamination.

Metabolomics reveals unique and shared metabolic changes in response to heat shock, freezing and desiccation in the Antarctic midge, Belgica antarctica

The midge, Belgica antarctica Jacobs, is subjected to numerous environmental stressors during its 2-year life cycle on the Antarctic Peninsula, and in response it has evolved a suite of behavioral, physiological, and life-cycle modifications to counter these stressors, but thus far only a limited number of biochemical adaptations have been identified. In this study, we use a metabolomics approach to obtain a broad overview of changes in energy metabolism, amino acids, and polyols in response to three of the midge's major stresses: heat, freezing, and desiccation. Using GC-MS analysis, a total of 75 compounds were identified. Desiccation (50% water loss) elicited the greatest physiological response (as determined by principal components analysis) when compared to untreated controls, with many elevated metabolites from pathways of central carbohydrate metabolism and a decrease in free amino acids. When larvae were frozen (6h at -10 degrees C), alanine and aspartate increased as well as urea. Freezing also increased three polyols (glycerol, mannitol, erythritol), while desiccation increased only two polyols (glycerol, erythritol). Heating the midges for 1h at 30 degrees C elevated alpha-ketoglutarate and putrescine while suppressing glycerol, glucose, and serine levels. Freezing and desiccation elicited elevation of four shared metabolites, whereas no shared metabolites were elevated by heat. All three treatments resulted in a reduction in serine, potentially identifying this amino acid as a marker for stress in this species. A number of metabolic changes, especially those in the sugar and polyol pools, are adaptations that have potential to enhance survival during both cold and desiccation.

Effect of retinoic acid on hemolymph glucose regulation in the fresh water edible crab Oziotelphusa senex senex

9-cis-Retinoic acid (9CRA) and all-trans-retinoic acid (ATRA) are known to be involved in the regulation of glucose homeostasis in vertebrates by inducing insulin release and expression of glucose reporter proteins. In view of the fact that 9CRA and ATRA are endogenous in crustaceans and a retinoic acid X-receptor exists in crabs, we investigated whether 9CRA and ATRA also plays a role in glucose homeostasis in freshwater crab, Oziotelphusa senex senex. Injection of 9CRA into intact crabs significantly increased the hemolymph glucose level in a dose-dependent manner. Such 9CRA-induced hyperglycemia was apparently mediated by the CHH since injection of 9CRA into eyestalk-ablated crabs did not result in hyperglycemia. In support of this, administration of 9CRA in to crabs resulted in reduced hyperglycemic activity of eyestalks and elevated titers of CHH in hemolymph. ATRA injection did not cause any changes in hemolymph glucose and CHH levels. The results provide the first evidence that 9-cis-retinoic acid, but not all-trans-retinoic acid, is involved in the regulation of glucose homeostasis and apparently mediated by the eyestalk hormone CHH.

Differential protein expression profiles in anterior gills of Eriocheir sinensis during acclimation to cadmium

Using a proteomic approach, we characterized different protein expression profiles in anterior gills of the Chinese mitten crab, Eriocheir sinensis, after cadmium (Cd) exposure. Two experimental conditions were tested: (i) an acute exposure (i.e. 500 microg Cd l(-1) for 3 days) for which physiological, biochemical and ultrastructural damage have been observed previously; (ii) a chronic exposure (i.e. 50 microg Cd l(-1) for 30 days) resulting in physiological acclimation, i.e. increased resistance to a subsequent acute exposure. Two-dimensional gel electrophoresis (2-DE) revealed six protein spots differentially expressed after acute, and 31 after chronic Cd exposure. From these spots, 15 protein species were identified using MS/MS micro-sequencing and MS BLAST database searches. Alpha tubulin, glutathione S-transferase and crustacean calcium-binding protein 23 were down-regulated after an acute exposure, whereas another glutathione S-transferase isoform was up-regulated. Furthermore, analyses revealed the over-expression of protein disulfide isomerase, thioredoxin peroxidase, glutathione S-transferase, a proteasome subunit and cathepsin D after chronic exposure. Under the same condition, ATP synthase beta, alpha tubulin, arginine kinase, glyceraldehyde-3-phosphate dehydrogenase and malate dehydrogenase were down-regulated. These results demonstrate that acute and chronic exposure to waterborne Cd induced different responses at the protein expression level. Protein identification supports the idea that Cd mainly exerts its toxicity through oxidative stress induction and sulfhydryl-group binding. As a result, analyses showed the up-regulation of several antioxidant enzymes and chaperonins during acclimation process. The gill proteolytic capacity seems also to be increased. On the other hand, the clearly decreased abundance of several enzymes involved in energy transfer suggests that chronic metal exposure induced an important metabolic reshuffling.

Variation of crustacean hyperglycemic hormone (cHH) level in the eyestalk and haemolymph of the shrimp Palaemon elegans following stress

This study investigates (by means of bioassays and ELISA using an antibody against recombinant cHH) the variation of cHH levels in the eyestalks and haemolymph of Palaemon elegans (Decapoda, Caridea) following exposure to various stresses (heavy metals and lipopolysaccharide), and correlates them with the variation in amount and time course of blood glucose. The dose-relationship between exposure to copper and quick release of cHH from the eyestalk into haemolymph was confirmed by variation of blood glucose with a dose-related hyperglycaemia, that peaked 2 h after immersion in contaminated seawater. Animals exposed to a sublethal concentration of mercury showed the same dose relation between toxicant, release of cHH from the eyestalk, increment of circulating hormone level and subsequent hyperglycaemia as observed for copper contamination. It is of note that although the highest lethal mercury concentration induced the release of cHH from the eyestalk into the haemolymph, it was not followed by a significant variation of blood glucose. Step doses of a bacterial contaminant [such as lipopolysaccharide (LPS) from E. coli injected into shrimps] confirmed the dose-relationship and convergent chain of events that bring about hyperglycaemia. These are the first data that relate the release of cHH from the eyestalk, the circulating hormone level and the consequent glycaemic response to stress. Moreover, they confirm the dose-related pathway that leads to variation of blood glucose as a quantitative biomarker of environmental quality, even at sublethal toxicant concentrations.

Effect of gestational and lactational exposure to lead and/or cadmium on reproductive performance and hepatic oestradiol metabolising enzymes

Adult female rats were treated subcutaneously (0.05 mg/kg body wt./day) with lead acetate and cadmium acetate separately and in combination during the gestational and lactational periods with a pre-exposure before mating. No change in the reproductive cyclicity was observed in any of the treated groups. The number of pregnancies was similar in all groups and no effect was observed on reproductive performance. The litter size, placental weights, pup weights, pup liver weights, maternal weights or maternal liver weights did not differ significantly. The activities of hepatic steroid metabolising enzyme 17-beta-hydroxy steroid oxidoreductase and of UDP glucoronyl transferase were decreased and the hepatic cytochrome P450 (CYP450) content was reduced by the metal exposure. Hepatic DNA and glycogen content were decreased in the cadmium and the combined treated groups in both lactating mother and pups at post-natal day 21 (PND 21). Lead and cadmium accumulated in the liver of the metal treated pregnant and lactating rats. The accumulation of the metals was also observed in foetal and pups (PND 21). Hepatic zinc content was increased in the cadmium and the combined treated pregnant and lactating mothers whereas foetal and neonatal livers showed a decrease in the zinc as compared to control. The results of the study indicate that despite the ability of lead and cadmium to alter various biochemical parameters the effect in the liver is not intensified at combined exposure to both lead and cadmium. The observed biochemical alterations in the liver of rats co-exposed to lead and cadmium may result from an independent effect of lead and/or cadmium and also from their interaction. However, these results suggest that when lead and cadmium are administered together in similar concentrations, the major effects are mediated by cadmium.

Diel variation in ammonia excretion, glutamine levels, and hydration status in two species of terrestrial isopods

Terrestrial isopods (suborder Oniscidea) excrete most nitrogen diurnally as volatile ammonia, and ammonia-loaded animals accumulate nonessential amino acids, which may constitute the major nocturnal nitrogen pool. This study explored the relationship between ammonia excretion, glutamine storage/mobilization, and water balance, in two sympatric species Ligidium lapetum (section Diplocheta), a hygric species; and Armadillidium vulgare (Section Crinocheta), a xeric species capable of water-vapor absorption (WVA). Ammonia excretion (12-h), tissue glutamine levels, and water contents were measured following field collection of animals at dusk and dawn. In both species, diurnal ammonia excretion exceeded nocturnal excretion four- to fivefold while glutamine levels increased four- to sevenfold during the night. Most glutamine was accumulated in the somatic tissues ("body wall"). While data support the role of glutamine in nocturnal nitrogen storage, potential nitrogen mobilization from glutamine breakdown (162 micromol g(-1) in A. vulgare) exceeds measured ammonia excretion (2.5 micromol g(-1)) over 60-fold. This may serve to generate the high hemolymph ammonia concentrations (and high P(NH3)) seen during volatilization. The energetic cost of ammonia volatilization is discussed in the light of these findings. Mean water contents were similar at dusk and dawn in both species, indicating that diel cycles of water depletion and replenishment were not occurring.

Effects of long-term exposure to Cu2+ and Cd2+ on the pentose phosphate pathway dehydrogenase activities in the ovary of adult Bufo arenarum: possible role as biomarker for Cu2+ toxicity

The effects of copper and cadmium on metabolism through the pentose phosphate pathway were evaluated in Bufo arenarum toad ovary. The effects of the two metals on dehydrogenases from this pathway were evaluated by three experiments: (1) in samples obtained from control females with addition of the metals to the reaction mixture (in vitro), (2) in samples obtained from control females and after long-term exposure of females to 4 and 100 microg/L of Cu or Cd in the incubation media (in vitro after exposure to the metals in vivo), and (3) 14CO2 production through the pentose phosphate pathway was evaluated after [U-14C]glucose microinjection on ovulated oocytes (in vivo after microinjection of the metals). Results from (1) evidenced inhibition of both enzyme activities but only above 1.5 mM Cu and Cd added to the reaction mixture. In (2) both glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase activities decreased in samples from the ovaries of females exposed in vivo to Cu, in a concentration-dependent manner (up to 90% in females exposed to 100 microg/L Cu: 2.12 +/- 1.57 NADPH micromol/min microg protein x 10(-5) vs 19.97 +/- 8.54 in control females). Cd treatment of the toads only rendered an inhibitory effect on 6-phosphogluconate dehydrogenase activity after exposure to 4 microg/L of the bivalent cation. (3) In vivo 14CO2 evolution significantly decreased in oocytes coinjected with 6.3 x 10(-3) mM Cu (calculated intracellular final concentration of the metal injected) and radioactive glucose. Cu and Cd concentration in samples from exposed females were always under detection limit by particle-induced X-ray emission. The results presented here are in agreement with a role for both glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase activities determination as biomarkers of effect and exposure for Cu but not for Cd toxicity.

Certain metals trigger fibrillation of methionine-oxidized alpha-synuclein

The aggregation and fibrillation of alpha-synuclein has been implicated as a key step in the etiology of Parkinson's disease and several other neurodegenerative disorders. In addition, oxidative stress and certain environmental factors, including metals, are believed to play an important role in Parkinson's disease. Previously, we have shown that methionine-oxidized human alpha-synuclein does not fibrillate and also inhibits fibrillation of unmodified alpha-synuclein (Uversky, V. N., Yamin, G., Souillac, P. O., Goers, J., Glaser, C. B., and Fink, A. L. (2002) FEBS Lett. 517, 239-244). Using dynamic light scattering, we show that the inhibition results from stabilization of the monomeric form of Met-oxidized alpha-synuclein. We have now examined the effect of several metals on the structural properties of methionine-oxidized human alpha-synuclein and its propensity to fibrillate. The presence of metals induced partial folding of both oxidized and non-oxidized alpha-synucleins, which are intrinsically unstructured under conditions of neutral pH. Although the fibrillation of alpha-synuclein was completely inhibited by methionine oxidation, the presence of certain metals (Ti3+, Zn2+, Al3+, and Pb2+) overcame this inhibition. These findings indicate that a combination of oxidative stress and environmental metal pollution could play an important role in triggering the fibrillation of alpha-synuclein and thus possibly Parkinson's disease.

Stress responses and changes in protein metabolism in carp Cyprinus carpio during cadmium exposure

Stress responses and changes in protein metabolism were studied in common carp Cyprinus carpio exposed to 0, 0.8, 4, and 20 microM cadmium (Cd) over a 29-day period. Blood and other tissue samples were taken after 4 and 29 days of exposure. The highest Cd concentration proved to be lethal to the fish, resulting in 100% mortality after 21 days of exposure. Cd accumulated in the tissues in the following order: kidney>liver>gills. Blood hematocrit, blood hemoglobin, plasma glucose, plasma lactate, and tissue total protein contents were not significantly altered. The concentrations of Cd and zinc (Zn) binding metallothioneins ((Cd, Zn)-MTs) were in the following order=liver>kidney>gills. An increase in (Cd, Zn)-MTs was observed at all exposure concentrations at days 4 and 29 in kidney and at Day 29 in gills. No significant changes in (Cd, Zn)-MT contents were found in liver. The concentrations of free amino acids and the activities of proteases were increased at Day 4 in gills, liver, and kidney of carp exposed to 4 and 20 microM Cd, and in gills and kidney at Day 29 in carp exposed to 4 microM Cd. The observed increases in the activities of aspartate aminotransferase and alanine aminotransferase suggest that the observed proteolysis is intended to increase the role of proteins in the energy production during Cd stress. However, this increased activity of both aminotransferases was not found in gills during exposure to the lethal Cd concentration, indicating that Cd may also cause an inhibitory effect on the activity of these enzymes above a certain level.

Influence of paraquat, glyphosate, and cadmium on the activity of some serum enzymes and protein electrophoretic behavior (in vitro)

In vitro study for the determination of the toxicity of some pesticides (glyphospate and paraquat) and cadmium chloride (CdCl2) on the activities of serum acetylcholinesterase (AChE), lactate dehydrogenase (LDH), aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (AlP), and acid phosphatase (AcP) is described. Changes in electrophoretic patterns of serum proteins were also tested. Results revealed that glyphosate was effective on all enzymes except AcP. Its IC50 values (the concentration of compound that inhibits 50% of the enzyme activity in 1 h at 37 degrees C) were 714.3, 750, 54.2, 270.8, and 71.4 mM for AChE, LDH, AST, ALT, and AlP, respectively. The inhibitory effect of paraquat varied markedly among all enzymes. The IC50 values of paraquat were 321.4 and 750 mM for AST and ALT, respectively. It had mild effect on AChE and LDH; and no effect on the activities of AlP and AcP. The effect of CdCl2 was pronounced with AChE, ALT, AlP, and AcP, and no effect on LDH and AST was found. The corresponding IC50 values were 77.7, 22.2, 33.3, and 83.3 mM for AChE, ALT, AlP, and AcP, respectively. Polyacrylamide gel electrophoretic patterns of serum proteins showed marked differences with glyphosate and CdCl2 but not with paraquat. The results suggest that the in vitro enzyme-activity test seems to have a potential for the assessment of pesticide and heavy metal toxicity.

Effect of cadmium and zinc salts on energy metabolism and survival of Unio tumidus Philipsson

Energy metabolism of aquatic invertebrates is one of the most important targets of environmental pollutants, in particular, heavy metals. In this study, we determined changes in survival, oxygen uptake and hepato-pancreas glycogen level of the bivalve mollusk Unio tumidus Philipsson following chronic exposure of Cd and Zn salts (chlorides and sulfates). The concentrations of Cd salts were equal to 0.001, 0.01 and 0.1 mg/l and concentrations of Zn salts were equal to 0.01, 0.1, 1.0 mg/l (maximal contamination level for Cd is 0.005 mg/l and for Zn is 0.01 mg/l). Survival was registered daily whereas oxygen consumption and glycogen level were determined on days 3, 7 and 14. Changes in survival of U. tumidus along the course of Cd and Zn salt concentrations was not monotonic; the sulfates were more inhibitory than the chlorides. No correlation was found between changes in survival and changes in the oxygen uptake and the glycogen level. By analysis of data in the literature, it was possible to construct a general scheme of adaptation of aquatic invertebrates' energy metabolism to heavy metals impact: (1) "exhaustive" or "economical" activation of aerobic metabolism (with or without depletion of energy resources); (2) change to "exhaustive" anaerobic mechanism (with depletion of glycogen); (3) change to "economical" anaerobic metabolism (involving mechanisms of glycogen expenditure economy); (4) late-term activation of aerobic metabolism due to need for binding and excretion of accumulated metals. Different severity of the pollutants' impact may lead to prevalence of different stages of this scheme. Our results revealed most of these stages in U. tumidus: "economical" activation of aerobic metabolism, change to "exhaustive" and "economical" anaerobic metabolism, and late-term activation of aerobic metabolism. It can be suggested that Cd is more toxic due to late-term decrease in oxygen consumption whereas Zn resulted only in transient early-term decrease. On the other hand, mechanisms of glycogen economy during anaerobic metabolism were involved in the effect of Cd and not involved in the effect of Zn. Concerning the effect of anions, chlorides promoted transient activation of aerobic metabolism, while sulfates promoted the passage to anaerobic metabolism. Thus, the effect of sulfates seems to be more inhibitory than the effect of chlorides.