In vivo immunomodulatory and antioxidant properties of nanoceria (nCeO 2 ) in the marine mussel Mytilus galloprovincialis

Cerium nanoparticles (nCeO 2 ) are increasingly utilized in a wide variety of industrial, environmental and biomedical applications, and are therefore expected to be released in the aquatic environment. Due to its peculiar redox properties, nCeO 2 may present unique hazards to environmental and human health. Previous data showed that in the hemocytes of the marine bivalve Mytilus galloprovincialis, in vitro exposure to a particular type of nCeO 2 (9 nm, characterized by negative ζ-potential, high H 2 O 2 scavenging capacity and Ce 3+ /Ce 4+ surface ratio) reduced basal ROS production, lysosomal membrane stability and phagocytic activity in the presence of hemolymph serum; the effects observed were partly ascribed to the formation of a SOD-protein corona in the hemolymph. In this work, the in vivo effects of this type of nCeO 2 were investigated in mussels exposed to 100 μg/L nCeO 2 for 96 h; several lysosomal, immune, inflammatory and antioxidant biomarkers were measured at cellular (hemocytes) and tissue (gills, digestive gland) level. Molecular responses were evaluated in hemocytes and digestive gland by determining expression of 11 selected genes related to known biological functions. The results show specific immunomodulatory and antioxidant effects of nCeO 2 at different levels of biological organization in the absence of Cerium tissue accumulation. These data further support the redox mechanisms at the basis of the physiological effects of nCeO 2 . Finally, in order to evaluate the possible impact at the whole organism level, the effects of nCeO 2 were evaluated in the 48 h embryotoxicity assay in a wide concentration range. However, nCeO 2 exposure resulted in a small reduction in normal embryo development. Overall, the results demonstrate that in mussels nCeO 2 can selectively modulate different physiological processes at different levels of biological organization.