The results showed reduced expression of GPX4 in both the gingiva and alveolar bone by immunofluorescence staining (Figs. 2G–I, S1G–I), consistent with a lower gingival Gpx4 level and higher Acsl4 and Ptgs2 levels by RT‒qPCR in the periodontitis group (Fig. S1M). The gene discussed is PTGS2; the disease is periodontitis.