CERIUM OXIDE NANOPARTICLES EXERT ANTIOXIDANT ACTIVITY PROTECTING DUGESIA JAPONICA PLANARIANS FROM HYPERGRAVITY-INDUCED OXIDATIVE STRESS

Oxidative stress in living organisms is strictly related to an unbalance in production/removal of in- tracellular reactive oxygen species (ROS). Potentially harmful to many biomolecules, ROS are associated with a variety of pathological conditions, including cancer and neurodegenerative diseases. Living or- ganisms are normally provided with endogenous defences (including superoxide dismutase {SOD- and catalase {CAT- enzymes) against ROS, but when these become insucient a continuous antioxidant sup- ply is required, as traditional antioxidants are chemically unstable and present short half-life in vivo. The use of nanomaterials with redox-reactive properties, such as cerium oxide nanoparticles (nanoceria), is therefore gaining increasing interest: nanoceria indeed show self-regenerating capability as free radical scavengers, and mimick both SOD and CAT activities. Performed in the framework of the 2016 \Spin Your Thesis!" campaign promoted by the European Space Agency, our work aimed at assessing the abil- ity of nanoceria to protect a model organism, the planarian Dugesia japonica, from the oxidative stress induced by exposure to dierent hypergravity levels (10,20g). Direct detection of the intracellular ROS levels was performed by using a ROS-sensitive uorescent dye (DCFH-DA). Fluorescence imaging was performed at low magnication (5X), by keeping constant LED intensity, exposure time and gain for all experimental conditions. Enhanced uorescence emission (average pixel intensity) was observed in planarians after exposure to 10g (10.8+-1.1 au) and 20g (23.66+-5.1 au) compared to 1g controls (7.8+-0.4 au; p<0.05), indicating hypergravity-induced ROS increment. NC- treated planarians that underwent hypergravity (8.0+-0.5 au for 10g+NC; 7.6+-0.5 au for 20g+NC) were characterized by uorescence intensity similar to that of untreated 1g controls (p>0.05). This suggests that nanoceria treatment is able to counteract hypergravity-induced ROS increment, in agreement with preliminary experiments conducted in our laboratories, where planarians were exposed to 22g for 90 min. 1 Paper ID: 41488 oral No signicant dierence was detected between NC-treated and untreated planarians kept at 1g (7.2+-0.2 au), suggesting that NC did not perturb endogenous levels of ROS in planarians. Concluding, our results demonstrate that planarians represent an in vivo model that can be successfully exploited for the investigation of ROS production in altered gravity conditions. An increase in hyper- gravity levels was demonstrated to be related to an increase of ROS amount in living planarians. Due to their biomimetic antioxidant activity, nanoceria were able to eciently counteract hypergravity-mediated ROS increment in planarians. Future works will investigate biochemical pathways of ROS production during hypergravity treatments, and the eect of long-time hypergravity/nanoceria stimulation on ROS production and cell apoptosis.