L-Ascorbic Acid Protected Against Extrinsic and Intrinsic Apoptosis Induced by Cobalt Nanoparticles Through ROS Attenuation

Currently, tissue damage induced by cobalt nanoparticles (CoNPs) and cobalt ions (Co2+) are the most serious syndrome in the patients with metal-on-metal hip prostheses. Therefore, an urgent need exists for the identification of the mechanisms and the development of therapeutic strategies to limit it. The purpose of this study was to explore the mechanism of this damage and to demonstrate if l-ascorbic acid (L-AA) could protect against the cell toxicities induced by CoNPs and Co2+ in vitro. With CoNPs and Co2+ treatment, cell viability was significantly decreased; the ROS (reactive oxygen species) level in mitochondria was dramatically increased in CoNPs treated cells, but cobalt ions could barely induce the ROS. Consistently, the level of cell apoptosis was increased with the upregulation of pro-apoptotic factors (caspases 8, 9, and 3, and Bax) and the downregulation of anti-apoptotic factor Bcl-2. Besides that, the levels of cytochrome c and AIF were increased and released from mitochondria into the cytoplasm. After the cells were pretreated with L-AA, the cell viability decreased by CoNPs was reversed and the ROS induced by CoNPs was suppressed. The level of cell apoptosis induced by CoNPs was decreased as well. But it could not reverse the effects induced by Co2+. These studies demonstrated that CoNPs induce extrinsic and intrinsic apoptotic pathways via generation of ROS, and L-AA could prevent the cytotoxicity by reducing the level of ROS. While Co2+ may induce cytotoxicity through other signals, it could not be protected by L-AA treatment.