Identification of JNK-JUN-NCOA axis as a therapeutic target for macrophage ferroptosis in chronic apical periodontitis

<b>Objectives:</b> This study aimed to investigate the involvement of macrophage ferroptosis in chronic apical periodontitis (CAP) and determine if blocking JNK/JUN/NCOA4 axis could alleviate CAP by regulating macrophage ferroptosis. <b>Materials and Methods:</b> Firstly, the <i>in vitro</i> models of apical periodontitis (AP) and <i>in vivo</i> models of CAP, including clinical specimens and rats' periapical lesions, were utilized to investigate the role of macrophage ferroptosis in CAP by detecting the ferroptosis related factors. The activation of the JNK/JUN/NCOA4 axis was observed in CAP <i>in vivo</i> models. Pearson's correlation and linear tendency tests were employed to analyze the correlation between the JNK/JUN/NCOA4 axis and macrophage ferroptosis during CAP progression. Subsequently, the JNK/JUN/NCOA4 axis was blocked by SP600125, and the alterations in ferroptosis associated variables and inflammation levels in macrophages were evaluated. <b>Results:</b> The <i>in vitro</i> AP model demonstrated that macrophage ferroptosis mainly occurred during the late phase of inflammatory conditions, with the reduction of GPX4, SLC7A11 and the increase of TFR1 in macrophages. Additionally, a higher accumulation of iron was observed in the periapical lesions derived from clinic samples and animal model. Furthermore, we found that differences in macrophage ferroptosis levels within periapical lesions corresponded altered activation of JNK/JUN/NCOA4 axis. Significantly, the inhibition of JNK/JUN/NCOA4 axis reduced the aforementioned changes and inflammation levels induced by <i>E. coli</i> LPS in macrophages. <b>Conclusions:</b> The occurrence of ferroptosis in macrophages contributes to the development of CAP. Targeting the JNK/JUN/NCOA4 axis is an effective therapeutic strategy to rescue the periapical lesions from inflammation due to its anti-macrophage ferroptosis function. Consequently, the current study provides support for further investigation on the JNK/JUN/NCOA4 axis as a targeted signaling pathway for CAP treatment.