Inhibition of NCOA4/FTH1-mediated ferritinophagy attenuates ferroptosis in PDLCs and alleviates orthodontically induced inflammatory root resorption.

BACKGROUND: Disruption of iron homeostasis is closely associated with ferroptosis and inflammation-related diseases. Nuclear receptor coactivator 4 (NCOA4)-mediated ferritinophagy plays a central role in regulating intracellular iron levels and inducing ferroptosis. However, its involvement in orthodontically induced inflammatory root resorption (OIIRR) remains largely unexplored. METHODS : In vitro, a compressive force (CF) loading model was established using human periodontal ligament cells (hPDLCs). Western blotting and immunofluorescence staining were performed to detect the expression of ferroptosis-related proteins, including NCOA4, FTH1, and GPX4. Intracellular levels of malondialdehyde (MDA), Fe²⁺, and reactive oxygen species (ROS) were measured using a ferroptosis assay kit. JC-1 staining was used to evaluate mitochondrial membrane potential. NCOA4 was silenced via lentiviral transfection, and the small-molecule inhibitor 9a was used to further assess its functional role in ferroptosis. In vivo, an OIIRR mouse model was established. Hematoxylin and eosin (H&E) staining, tartrate-resistant acid phosphatase (TRAP) staining, and micro-computed tomography (micro-CT) were used to assess root resorption. The expression of NCOA4, FTH1, and GPX4 in periodontal tissues was evaluated via immunohistochemistry and immunofluorescence. Ferrostatin-1 (Fer-1), a ferroptosis inhibitor, was administered intraperitoneally to investigate its therapeutic effect on OIIRR. RESULTS: CF and IL-1β stimulation induced ferroptosis in hPDLCs, as indicated by increased intracellular Fe²⁺, ROS, and MDA levels, decreased GPX4 expression, and mitochondrial damage. NCOA4 expression was markedly upregulated in both in vitro and in vivo models, leading to ferritin degradation and iron overload. Fer-1 treatment effectively reduced oxidative stress and iron accumulation in vitro and alleviated OIIRR in vivo. Compound 9a suppressed NCOA4 expression and mitigated ferritinophagy-mediated ferroptosis. CONCLUSIONS: NCOA4/FTH1-mediated ferritinophagy promotes ferroptosis under compressive and inflammatory conditions, contributing to OIIRR pathogenesis. Targeting the NCOA4/FTH1 axis may represent a promising therapeutic strategy for preventing orthodontically induced root resorption.