Biomarkers of oxidative stress and cell damage in freshwater bivalves Diplodon parodizi exposed to landfill leachate.

Landfill is a public and environmental health problem; establishing and understanding methodologies to decrease its toxicity are thus necessary. Leachate samples were collected, at a sanitary landfill, immediately after the exit from the landfill, i.e. raw leachate (collection point A), after conventional treatment (point B) and after treatment by wetlands (point C). D. parodizi specimens were exposed to 3%, 10% and control (0%) dilutions of leachate from these collection points for 7 days. Markers of antioxidant defences and cell damage were analysed. At point B, the gills of D. parodizi showed higher glutathione-S-transferase (GST) and glutathione reductase (GR) activity; the latter is a supplier of glutathione reductase (GSH). The low GST activity at point A was associated with the hormesis effect. Higher levels of superoxide dismutase (SOD), ethoxyresorufin-O-deethylase (EROD) and glutathione peroxidase (GPx) occurred at point A. Glucose-6-phosphate dehydrogenase (G6PDH) was inhibited at the points with the highest pollutant load and at the highest leachate dilutions. Higher levels of markers at point A may be related to the high pollutant charge and specific compounds present in the untreated leachate. The multi-xenobiotic resistance mechanism (MXR), metallothionein-like proteins (MT) and lipid peroxidation (LPO) did not vary among treatments. The biomarker responses showed negative effects of the leachate on the freshwater bivalve and simultaneously showed that the wetland treatment employed at the Caximba sanitary landfill is effective.

MXR response in sea anemones: Effect of temperature, salinity and copper.

Multixenobiotic resistance (MXR) phenotype is a cellular defense which can eliminate toxic substances from cells. Several studies describe the MXR activity after pollutant exposure, but little is known about the interference of abiotic factors in this mechanism. The present study aimed to evaluate MXR activity in sea anemones Bunodosoma cangicum after in vivo and in vitro exposures to different temperatures (15, 20 and 25C) and salinities (15, 30 and 45‰) associated or not with copper (0, 7.8 and 15.6 µg/L). Results showed that low temperature inhibited the MXR activity in vivo and in vitro, while salinity did not alter this activity. Copper could change the response, mainly at different temperatures (15 and 25 °C) - 7.8 µg/L Cu activated in vivo and in vitro and 15.6 µg/L Cu in vitro inhibited MXR activity in relation to same copper concentrations at 20 °C. Results for MXR activity found between in vivo and in vitro exposures were similar among temperature treatments and salinities; however, under hyperosmotic shock, in vivo exposure showed that animals has different response than isolated cells. The animals exposed to salinity 45‰ produced a mucus layer as a defense mechanism, because of this protection the response was different between in vivo and in vitro exposures. Concluding, temperature affects MXR activity independently of the presence of copper and each model of exposure contributes with different type of knowledge (cellular mechanism/systemic response).

Characterization of MXR activity in the sea anemone Bunodosoma cangicum exposed to copper.

Transmembrane proteins of the ABC family contribute to a multiple xenobiotic resistance (MXR) phenotype in cells, driving the extrusion of toxic substances. This phenotype promotes a high degree of protection against xenobiotics. The present study provides a better understanding of the MXR activity in the podal disk cells of Bunodosoma cangicum exposed to copper, and further establishes the relationship between protein activity (measured by accumulation of rhodamine-B) and bioaccumulation of copper in these cells. Sea anemone cells were exposed for 24h to copper (0, 7.8 and 15.6µg/L) in presence and absence of MXR blocker (verapamil 50µM). Results indicate that copper exposure increases intracellular metal content when ABC proteins were blocked, causing an increase in cellular death. The present study also verified the relationship between MXR activity, ATP depletion, and general metabolic activity (by MTT). MXR activity decreased in treatment groups exposed to copper concentrations of 15.6µg/L and 10mM energy depleting potassium cyanide. Metabolic activity increased in cells exposed to 7.8µgCu/L, but 15.6µgCu/L was similar to 0 and 7.8µg/L. The presence of copper decreased the ABC proteins expression. The present study improves the knowledge of MXR in anemone cells and shows that this activity is closely associated with copper extrusion. Also, the copper exposure is able to modify the metabolic state and to lead to cytotoxicity when cells cannot defend themselves.