Effects of titanium dioxide nanoparticles on sea urchin immune defence.

The presence of Engineered Nanoparticles and their aggregates in many consumer products has attracted a growing scientific concern on the possible effects of these materials on the environment and biota. Here, we took advantage of an amenable laboratory model organism, the sea urchin Paracentrotus lividus(phylum Echinodermata), to elucidate a potential pathway that can be involved in the persistent Titanium dioxide ( TiO 2 ) engineered nanoparticles-immune cell interaction. Sea urchins are phylogenetically related to humans (at least 70% of their proteins are shared with humankind), and have been proven to possess a complex and effective immune defence. In this study, TiO 2 nanoparticles were injected into the sea urchins body cavity to expose immune cells, that were harvested after 24 hours, and analyzed for their morphology, phagocytic ability, activation of proteins triggering immune defence (e.g. HSPs, TLRs, p38 MAPK) and expression of related immune response genes. We found that TiO 2 nanoparticles elicit a receptor-mediated endocytotic mechanism carried out by phagocytes, and affect the p38 MAPK signaling pathway. Our working hypothesis is based on the role of the TiO2 nanoparticles-mediated p38 MAPK inactivation in the renewal and homeostasis of sea urchin immune "stem" cells. In conclusion, we strongly recommend sea urchin immune cells as a new powerful tool for nanosafety investigations.