Changes in superoxide dismutase 3 (SOD3) expression in periodontal tissue during orthodontic tooth movement of rat molars and the effect of SOD3 on in vitro hypoxia-exposed rat periodontal ligament cells

Hypoxia during orthodontic tooth movement (OTM) induces reactive oxygen species (ROS) production in periodontal tissues. Superoxide dismutase 3 (SOD3) is an anti-inflammatory enzyme that protects cells from ROS. This study investigated the expression and function of SOD3 during rat OTM and in hypoxia-exposed rat periodontal ligament (PDL) cells.OTM of right maxillary first molars were performed in 8-week-old male Sprague-Dawley rats using closed-coil spring for 1 and 14 days (n = 6 per group). SOD3 and hypoxia-inducible factor 1-alpha (HIF-1α) protein expression was evaluated by immunohistochemistry. The effects of SOD3 on cell viability and proliferation, ROS production, and mRNA expression of Hif1-α, receptor activator of nuclear factor kappa-Β ligand (Rankl), and osteoprotegerin (Opg) in PDL cells and osteoclast differentiation were investigated under normal and hypoxic conditions.SOD3 expression in PDL tissues significantly decreased on the compression side on day 1 and on both sides on day 14 of OTM. HIF-1α levels significantly increased on the compression side on day 14. Cell viability, cell proliferation, and Opg mRNA expression decreased, whereas ROS production and Hif1-α and Rankl mRNA expression increased in the PDL cells upon SOD3 silencing. Hypoxia reduced Sod3 and Opg mRNA expression and increased ROS, Rankl mRNA expression, and osteoclast formation; SOD3 treatment attenuated these effects.SOD3 plays a role in periodontal tissue remodelling during OTM and in hypoxia-exposed PDL cells through ROS, HIF-1α, and RANKL/OPG pathways. Moreover, SOD3 treatment could attenuate the negative effects of hypoxia on the PDL cells.