Catalasic activity in fish liver: improvement of the UV to visible analytic method.

International audienceAntioxidative defenses and more especially catalasic activity (CAT) are studied in a large range of scientific research thematics. In environmental sciences, the problematic of oxidative stress is of great interest as pollutants can induce perturbations of redox homeostasis. Consequently, changes in antioxidative defenses levels in fish tissues and particularly in liver are used as potential biomarkers of pollution. In most studies, the CAT was assayed by following during 5 min the consumption of H2O2 in cytosolic buffered extracts at 240 nm (UV-method). This study proposed a development of this method in the visible, using permanganate and a 525-nm detection, which was more accurate, sensitive, and rapid. Moreover, the hepatic CAT of six different fish species [a cyclidae (Nimbochromis linni), 3 cyprinidae (Brachydanio rerio, Rutilus rutilus, Cyprinus carpio), an anguillidae (Anguilla anguilla), and a percidae (Perca fluviatilus)] was evaluated with the two protocols (UV- and KMnO4-method). The results but also the thermal optimum of the reaction and the interest of CAT as biomarker in ecotoxicology were discussed

Ex vivo immune responses in freshwater fish leucocytes exposed to environmental serotypes of lipopolysaccharides

In aquatic ecosystems, detected endotoxins or lipopolysaccharide (LPS) contamination can be linked to cyanobacteria blooms or enterobacterial contaminations. Water contaminations by endotoxins is of particular interest as these microbiological molecules may be released in freshwater often in combination with other chemicals (pharmaceutics…). Their immunomodulatory properties rise interest towards their pro-inflammatory action on mammalians and aquatic vertebrates. Despite the fact that some E.coli LPS serotypes such as O55:B5 are often used as immunostimulant in experimentations, no data are available concerning some other serotypes as O157:H7 even if they may significantly contaminate freshwater ecosystems, particularly in agricultural field contexts. We aimed to compare here the immunomodulation patterns potentially induced by two E.coli LPS serotypes (O55:B5 and O157:H7) alone or in combination with diclofenac, an anti-inflammatory drugs which chronically contaminate European freshwaters. Using an ex vivo approach, we studied immune parameters (Oxidative activity, Phagocytosis and cytotoxicity) of roach (Rutilus rutilus) leucocytes populations (lymphocytes, monocytes/macrophages and granulocytes) isolated from blood, head-kidney and spleen in response to endotoxins exposure. Leucocytes were exposed from 6 to 12 hours to sub-lethal concentrations of LPS and/or diclofenac (1μg/mL LPS, 0,1μM diclofenac) determined from preliminary results. Like diclofenac, endotoxins induced significant decrease in intracellular ROS production by leucocytes at time 0. After 12 hours of exposure to the E.coli O55:B5 LPS / diclofenac combination, the oxidative activity was stimulated in spleen leucocytes and, simultaneously, they showed a significant decrease in phagocytosis. Moreover, while the E.coli O157:H7 LPS alone showed tendencies to decrease phagocytic activity, the two endotoxin / diclofenac combinations significantly decreased it in head-kidney leucocytes after 6 hours. All these results will be set versus an ongoing in vivo experiment which would allow us to study more inflammation aspects like cytokines and immune-related factors production. Whereas environmental monitoring and studies of endotoxins presently concern only human health like in wastewater units, our results rise the questioning on environmental reality of endotoxins and their potential immunomodulations in fish

Avancées récentes dans le développement du test des comètes chez la moule zébrée (Dreissena polymorpha) et son application en biosurveillance environnementale

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Dreissena polymorpha responses under thermal and hypoxic stress: New insights in the tolerance of this freshwater sentinel species

International audienceDreissena polymorpha is a sentinel freshwater mussel providing key functional ecosystemic services like nutrient recycling and suspended matter filtration. Global warming and especially extreme events imply rapid fluctuations of environmental parameters that sessile organisms could not escape. The increase occurrence of heat waves and the subsequent expansion of hypoxic areas could challenge the survival of mussels. This study provided a deeper knowledge of energy management and cellular function during thermal (+15 ◦C) or hypoxic (30% of dissolved oxygen saturation) stress for 7 days. A potential metabolic rate depression was highlighted in D. polymorpha under hypoxia through a decline in the mitochondrial activity and a constant AMP content over time. A contrasted pattern of response was observed in thermal-stressed mussels between 24 h and 7 days of exposure. A global increase of metabolic activity was noticed in mussels after 24 h while a return to control level was noticed at the end of the experiment. Although D. polymorpha is considered as a temperature tolerant species, a significant increase of ADP:ATP ratio, related to a decrease of mitochondrial activity and density, suggested an overwhelming of organisms. This study pointed to the importance of considering time of exposure to natural factor variations in tolerance window of organisms in a long-term changing environment. The apparent short-term tolerance of D. polymorpha could hide much more deleterious consequences, i.e. mortality, if abiotic stresses persist, as suggested by climate change models

Effects of aluminium and bacterial lipopolysaccharide on oxidative stress and immune parameters in roach, Rutilus rutilus L.

Aluminium is used in diverse anthropogenic processes at the origin of pollution events in aquatic ecosystems. In the Champagne region (France), high concentrations of aluminium (Al) are detected due to vine-growing practices. In fish, little is known about the possible immune-related effects at relevant environmental concentrations. The present study analyzes the simultaneous effects of aluminium and bacterial lipopolysaccharide (LPS), alone and in combination, on toxicological biomarkers in the freshwater fish species Rutilus rutilus. For this purpose, roach treated or not with LPS were exposed to environmental concentrations of aluminium (100 mu g/L) under laboratory-controlled conditions for 2, 7, 14 and 21 days. After each exposure time, we assessed hepatic lipoperoxidation, catalase activity, glutathione reductase activity and total glutathione content. We also analyzed cellular components related to the LPS-induced inflammatory response in possible target tissues, i.e. head kidney and spleen. Our results revealed a significant prooxidant effect in the liver cells and head kidney leukocytes of roach exposed to 100 mu g of Al/L for 2 days. In liver, we observed more lipoperoxidation products and lower endogenous antioxidant activity levels such as glutathione reductase activity and total glutathione content. These prooxidant effects were associated with a higher oxidative burst in head kidney leukocytes, and they were all the more important in fish stimulated by LPS injection. These findings demonstrate that environmental concentrations of Al induce oxidative and immunotoxic effects in fish and are associated to an immunomodulatory process related to the inflammatory response

Recent advances in the development of the comet assay on the hemocytes of zebra mussels and its application in field studies for evaluating environmental genotoxicity

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Recent advances in the development of the comet assay on the hemocytes of zebra mussels and its application in field studies for evaluating environmental genotoxicity

International audienc

Recent advances in the development of the comet assay on the hemocytes of zebra mussels and its application in field studies for evaluating environmental genotoxicity

International audienc