Co-exposure to nTiO2 impairs arsenic metabolism and affects antioxidant capacity in the marine shrimp Litopenaeus vannamei

Aquatic animals are vulnerable to arsenic (As) toxicity. However, rarely does a contaminant occur alone in the aquatic environment. For this reason, this study was conducted to evaluate whether titanium dioxide nanoparticles (nTiO2) can interfere with the effects induced by As in Litopenaeus vannamei. Arsenic accumulation and metabolic capacity; expression and enzymatic activity of GSTX (glutathione-S-transferase omega isoform); antioxidant responses such as GSH, GR, and GST (reduced glutathione levels, glutathione reductase, and glutathione-S-transferase activity, respectively); and lipid peroxidation in the gills and hepatopancreas of shrimp were evaluated. The results are summarized as follows: (1) higher accumulation of As occurred in both tissues after exposure to As alone; (2) co-exposure to nTiO2 affected the capacity to metabolize As; (3) GSTX gene expression was not modified, but its activity was decreased by co-exposure to both contaminants; (4) As alone increased the GSH levels in the hepatopancreas, and co-exposure to nTiO2 reduced these levels in both tissues; (5) a decrease in the GST activity in the gills occurred with all treatments; (6) in the gills, GR activity was increased by As, and nTiO2 reversed this increase, whereas in the hepatopancreas co-exposure inhibited enzyme activity; (7) only in the hepatopancreas lipid damage was observed when animals were exposed to As or nTiO2 but not in co-exposure. The results showed that the As induces toxic effects in both tissues of shrimp and that co-exposure to nTiO2 can potentiate these effects and decrease the capacity to metabolize As, favoring the accumulation of more toxic compounds.