Protective effects of cerium oxide nanoparticles on MC3T3-E1 osteoblastic cells exposed to X-ray irradiation

Abstract

Background/Aims: Exposure to ionizing radiation can result in bone damage, including decreased osteocyte number and suppressed osteoblastic activity. However, molecular mechanisms remain to be elucidated, and effective prevention strategies are still limited. This study was to investigate whether cerium oxide nanoparticles (CeO 2 NP) can protect MC3T3-E1 osteoblast-like cells from damaging effects of X-ray irradiation, and to study the underpinning mechanism(s). Methods: MC3T3-E1, a osteoblast-like cell line, was exposed to X-ray irradiation and treated with different concentration of CeO 2 nanoparticles. The micronucleus frequency was counted under a fluorescence microscope. Cell viability was evaluated using MTT assay. The effects of irradiation and CeO 2 nanoparticles on alkaline phosphatase activity and MC3T3-E1 mineralization were further assayed. Results: We found that the ratio of micronuclei to binuclei was dose-dependently increased with X-ray irradiation (from 2 to 6 Gy), but diminished with the increased concentration of CeO 2 NP treatment (from 50 to 100 nM). Exposure to X-rays (6 Gy) decreased cell viability, differentiation and the mineralization, but CeO 2 NP treatment (100 nM) attenuated the deteriorative effects of irradiation. Both intracellular reactive oxygen species (ROS) production and extracellular H 2 O 2 concentration were increased after X-ray irradiation, but reduced following CeO 2 NP treatment. Similar to irradiation, exposure to H 2 O 2 (10 μM) elevated the frequency of micronuclei and diminished cell viability and mineralization, while these changes were ameliorated following CeO 2 NP treatment. Conclusions: Taken together, our findings suggest that CeO 2 nanoparticles exhibit astonishing protective effects on irradiation-induced osteoradionecrosis in MC3T3-E1 cells, and the protective effects appear to be mediated, at least partially, by reducing oxidative stress.