Biochemical and morphological biomarker responses in the gills of a Neotropical fish exposed to a new flavonoid metal-insecticide

The flavonoid metal-insecticide [Mg(hesp)₂(phen)], denominated MgHP, has high potential for controlling agricultural pests. If applied in large scale, it may reach aquatic ecosystems and be harmful to the biota. This study evaluated the effects of MgHP in the gills of the Neotropical fish, Prochilodus lineatus by determining the activity of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione s-transferase (GST), and the levels of glutathione (GSH) and lipid peroxidation (LPO) after 24 and 96 h exposure to 0, 1, 10, 100 and 1000 μg L^-1. The histopathological changes with emphases to mitochondria-rich cells (MRC) were evaluated as well. After 24 h exposure the enzyme activities and the GSH and LPO levels were unchanged however, after 96 h exposure to high MgHP concentration (1000 μg L^-1), the GST activity and GSH levels increased. Oxidative stress measured as LPO levels did not occur after MgHP exposure in both periods. Gill tissue alterations increased after MgHP exposure to 10, 100 and 1000 μg L^-1. Cellular atrophy, pillar cells changes, filament epithelium hyperplasia and hypertrophy, lamellar epithelium hyperplasia were the most frequent histopathology. MRC in the filament epithelium decreased after exposure to 24 h and increased after 96 h indicating possible transitory osmo-ionic disruption. P. lineatus exhibited high tolerance to MgHP. The increased GST activity and GSH levels after 96 h exposure suggested possible MgHP accumulation and concentration- and time-dependent response. Histopathology in the gills of exposed fish occurred at high MgHP concentrations. These results suggested that the MgHP into water, at high concentrations, affect the gills by changing GST activity, GSH levels and histology being useful biomarkers for MgHP water contamination.

Multi-biomarkers approach to access the impact of novel metal-insecticide based on flavonoid hesperidin on fish

Aquatic ecosystem health is the main concern to increasing pesticides application to control agricultural pests as it is the ultimate receptor of such materials. This study evaluated the impact of new metal-insecticide, the [Mg(hesp)₂(phen)], referred as MgHP, on fish using physiological, genetic, biochemical, and morphological biomarkers. The fish, Prochilodus lineatus, was exposed to 0 (control), 1, 10, 100, 1000 μg L^-1 MgHP, for 24 and 96 h. MgHP was not lethal but caused genotoxicity, altered hematological variables and, the activity of antioxidant and biotransformation enzymes and histology of liver, depending on concentration and time exposure. Hematocrit and erythrocyte number (RBC) increased without change hemoglobin content resulting in changes in hematimetric indexes after 24 h; after 96 h, only RBC was changed. Erythrocyte nuclear abnormalities and crenate cells increased after 24 h but, not after 96 h. Erythrocytes and hepatocytes indicated instability in DNA integrity however, the absence of micronuclei suggested DNA damage repairment. After 24 h, the antioxidant defense system and the phase II biotransformation enzyme was responsiveness and catalase activity decreased at high MgHP concentrations; the antioxidant response was triggered after 96 h. Hepatocyte hypertrophy, intracellular cytoplasmic substances, cytoplasm degeneration, melanomacrophage and hyperemia increased in fish exposed from 10 μg L^-1 to higher MgHP concentrations; the organ alteration index increased as MgHP concentration increased showing dose-dependence. Most of hematological and genotoxic effects occurred after 24 h exposure evidencing potential recover capability of organism by activation of the antioxidant defense system and DNA repairment mechanisms. Nevertheless, the histopathological changes in the liver was maintained over time at high MgHP concentrations, a concentration usually no environmental relevant. In conclusion, this data reinforced the importance of continuing research on MgHP effects in other organisms considering the promising use of such compound to control the leaf-cutter ants and other insects.