Cytoprotective and anti-apoptotic action of HSP70 stress protein in Oreochromis niloticus exposed to residual dilutions of insecticides with fipronil and ethiprole.

The objective of this research was to investigate the potential damage caused by the residual concentrations of the insecticides Regent® WS 800 and Curbix® SC 200, containing fipronil and ethiprole, respectively as active ingredients, on the liver of Oreochromis niloticus. The analyses of HSP70 shock protein labelling and cell death process by TUNEL method were performed in order to measure the effects of the exposure of cell repair system of fish to both insecticides. Statistical analyses showed no significant molecular damage to the hepatic tissue of animals. Nevertheless, variations in HSP70 and DNA fragmentation levels, endpoint of cell repair system response and cellular death, respectively, were observed in several groups. These results indicate that the cell repair machinery was efficient when in contact with residual concentrations of insecticides. However, the DNA fragmentation detected by the TUNEL method suggests that even in face of the cytoprotective action of the HSP70 protein, there are damages that become irreparable. To finish, it is worth mentioning that given the results obtained from residual concentrations, use in the field should be with caution.

Histopatology and HSP70 analysis of the midgut of Rhinocricus padbergi (Diplopoda) in the evaluation of the toxicity of two new metallic-insecticides.

Millipedes are organisms of the edaphic fauna and have been used as bioindicators for the evaluation of pollutants in the environment, as they are in constant contact with the soil. This study used the millipede Rhinocricus padbergi as surrogate to evaluate the toxicity of two metallic-insecticides that has been developed for leaf-cutting ants management. Millipedes were exposed in terrariums containing different concentrations of the metallic-insecticides and, after periods of 21 and 90 days, three individuals from each terrarium were dissected in order to remove the midgut, the organ where absorption of nutrients and, consequently, toxic substances occurs. The toxic action of the metallic-insecticides was analyzed through qualitative and semi-quantitative analysis of morphophysiological alterations and by quantitative analysis of the HSP70 stress protein. The results showed that the metallic-insecticides may increase HSP70 labeling, although not at all concentrations and periods of exposure. Histopathological alterations were not significant at any concentration, indicating that the cytoprotective action of HSP70 is able to prevent severe damage to the midgut. It is therefore suggested that the metallic-insecticides are not toxic to the species studied here as no toxicity was observed under the conditions tested. In addition, stress protein localization in midgut helps understand how morphophysiological processes can potentially be affected by pesticide exposure.

Toxicity evaluation of vinasse and biosolid samples in diplopod midgut: heat shock protein in situ localization.

Large amounts of residues generated by agricultural, urban and industrial activities are dumped daily on the soil. This practice deserves special attention because it causes serious environmental problems. This study evaluated the toxic potential of the sugarcane vinasse, a by-product of the sugar-alcohol industry, and the biosolid, a residue produced by wastewater treatment plants, both widely used as fertilizers. The evaluation was performed through bioassays using a typical soil bioindicator, the diplopod Rhinocricus padbergi. The specimens were exposed to soils containing these residues in concentrations that are compatible with the Brazilian regulation for agricultural use. Semi-quantitative immunolabelling analyses of the stress protein HSP70 were performed on the midgut of the studied diplopods. There was a significant increase in the immunolabelling of HSP70 proteins as a response to xenobiotics from both residues, particularly in regions where the function of the cells is the detoxification of the organ (e.g. the hepatic cell layer and specific regions of the epithelium). Higher immunolabelling was observed in the specimens exposed to vinasse in comparison with the biosolid exposure. This demonstrates that the substances in the tested residues had proteotoxic action in the exposed animals and induced a cytoprotective response, which led to higher stress protein immunolabelling. Therefore, caution is needed for the use of such residues in agriculture.

Liver alterations in Oreochromis niloticus (Pisces) induced by insecticide imidacloprid: Histopathology and heat shock protein in situ localization.

Liver is very sensitive to environmental contaminants such as pesticides, it being the first target of toxicity of a substance. The objective of this study was to investigate the possible effects of the insecticide imidacloprid (IMI) on the liver of Oreochromis niloticus according concentrations used for growing sugarcane. A semi-quantitative analysis of histopathological alterations of IMI on liver was performed by light microscopy and cellular labeling of heat shock proteins (HSP70) by immunohistochemistry. The most common changes in liver at all concentrations of IMI were hydropic degeneration, pyknotic nuclei, and loss of cell limits. Steatosis and increased levels of HSP70 were detected in hepatocytes with the highest concentration of IMI. In conclusion, the tested concentrations of IMI induced histopathological changes in the liver of O. niloticus and active defence mechanisms to maintain the morphophysiological integrity of the liver. This insecticide has a toxicity potential for these fish, which is a non-target organism of its action.