Modulation of immune and antioxidant responses to Escherichia coli by azinphos-methyl in the freshwater mussel Diplodon chilensis.

CASTRO J.M.; BIANCHI, V.A.; VENTURINO, A.; LUQUET C.M

CABA

Congreso; SETAC Latin America 11th Biennial Meeting; 2015

SETAC Latin America

The aim of this work was to characterize the immune response and the oxidative balance in Diplodon chilensis upon exposure to environmentally relevant concentrations of AZM. Mussels were collected from an unpolluted site and acclimated in laboratory for 3 days. Then, six groups were set: G1) Control: fed with the green algae Scenedesmus vacuolatus (SV, 3 days), G2) Solvent control (Acetone < 0.01%, 3 days), G3) Exposed to Escherichia coli (50,000 cell/mL, 3 days), G4) AZM (0.2 mg/L, 3 days), G5) Acetone (3 days) and then E. coli (3 days), G6) AZM (3 days) and then E. coli (3 days). Data were analyzed by one-way ANOVA and post hoc comparisons. Results: Total hemocyte number tends to increase in all treated groups respect to G1. Cell viability showed no variation among treatments. Hyalocytes proportion decreased in treated groups, being significantly lower in G6 than in any other group. Granulocyte proportions showed the opposite trend to hyalocytes, with highest proportion in G6. Phagocytic activity in hyalocytes increased significantly in all treated groups with a peak in G4. Granulocytes phagocytic activity decreased in G2-5 respect to G1, and increased significantly in G6. Acid phosphatase activity increased in G3-6 respect to G1-2. Alkaline phosphatase and β-glucuronidase activity increased in all treated groups respect to G1, in both enzymes G6 had significantly lower effect than G5. ROS production increased in G3, 5, 6 with respect to G1, 4. TOSC tends to increase in most treated groups. Lysosomal membrane stability decreased in all respect to G1, G6 had lower effects G3-5). Bacteriolytic activity increased in G3, 5 and 6, while phenoloxidase activity decreased in G2, 4 and 6 compared with the other groups. Gill GST activity increased in all treatments respect to G1-2. Gill lipid peroxidation decreased in G4-6 respect to the other groups. Gill carboxyl esterase activity was inhibited in G4 and 6, respect to G2. Conclusion: Short-term exposure to AZM stimulates cellular response, enhancing lysosomal membrane stability and TOSC. AZM also alters cellular proportion towards granulocytes and promotes granulocyte phagocytic activity. In contrast, AZM inhibits alkaline phosphatase and β-glucuronidase activities. ROS production and bacteriolytic activity are increased in all treatments with bacteria. Phenoloxidase activity decreases in treatments with pesticide or acetone. In gills, AZM stimulates antioxidant defenses and inhibits carboxyl esterase activity.