Autophagy Modulates the Expression of Interferon Regulatory Factor 8 in Apical Periodontitis

Objectives: This study aims to investigate how autophagy regulates interferon regulatory factor 8 (IRF8) and other inflammation-related genes in apical periodontitis. Materials and Methods: Autophagy was induced and inhibited in human leukemia monocytic cell line THP-1 and macrophages via the treatment of various concentrations of rapamycin and 3-Methyladenine (3-MA), respectively. The cytotoxicity and proliferation of the cells under these treatments were assessed using the cell counting kit 8 (CCK8) assay, and optimum concentrations of rapamycin and 3-MA were determined. Changes in the expression of IRF8 and other key markers of autophagy were measured at the transcription and protein levels via quantitative real-time polymerase chain reaction and Western Blot. Total RNAs from those cells were also subject to RNA sequencing, bioinformatics, and statistical analyses. The differentially expressed genes, especially in IRF8 and inflammation-related pathways, were analyzed. Results: IRF8 was significantly downregulated at both transcription and protein levels upon inhibition of autophagy (P< 0.05, one-way ANOVA). In addition, pro-inflammatory factors involved in apical periodontitis, such as TNF-α and IL1-β, were significantly upregulated upon inhibition of autophagy. Moreover, RNA sequencing revealed many differentially expressed genes, including IRF8 and its related inflammatory pathways. Conclusions: Autophagy regulates the expressions of IRF8 and related genes, which may play a pivotal role in modulating apical periodontitis. Clinical Relevance: Dissecting the interrelationship between autophagy and IRF8 is essential to understanding the disease pathogenesis in apical periodontitis and may lead to the development of adjunct therapies in endodontics.