Liquiritigenin attenuates inflammatory periapical bone loss by stabilizing TRIM31 and restraining NLRP3 inflammasome and cGAS-STING inflammatory signaling.

Abstract

Apical periodontitis (AP) is characterized by persistent inflammation and progressive periapical bone resorption, processes increasingly associated with NLRP3 inflammasome activation and cGAS-STING-related inflammatory signaling. However, pharmacological approaches targeting these inflammatory pathways and their upstream regulatory mechanisms remain limited. Here, we investigated whether liquiritigenin, a natural flavonoid derived from licorice, attenuates inflammatory injury and periapical bone loss through TRIM31-associated regulation of NLRP3 and modulation of cGAS-STING-related signaling. Structure-based virtual screening identified several natural compounds with predicted TRIM31-binding potential, among which liquiritigenin showed the strongest protective activity against LPS/ATP-induced loss of cell viability. Pronase-protection and cellular thermal shift assays showed that liquiritigenin increased TRIM31 stability, supporting potential intracellular target engagement without establishing direct physical binding. LPS/ATP stimulation reduced TRIM31 abundance and increased NLRP3 expression, IL-1β release, cleaved caspase-1, mature IL-1β, and cleaved GSDMD. Liquiritigenin reversed these changes, whereas TRIM31 knockdown partially weakened its effects. Moreover, liquiritigenin preferentially enhanced K48-linked, but not K63-linked, NLRP3 ubiquitination; graded TRIM31 knockdown progressively reduced this response. CHX-chase and MG132 experiments further supported accelerated, proteasome-associated turnover of NLRP3. Liquiritigenin also reduced cGAMP production, STING phosphorylation, downstream TBK1-IRF3 phosphorylation, and the expression of IFN-β, ISG15, and CXCL10 under LPS/ATP stimulation. In C57BL/6 mice with LPS/ATP-induced periapical inflammatory bone loss, liquiritigenin alleviated periapical bone loss, improved micro-CT parameters, reduced inflammatory infiltration, restored TRIM31 expression, and attenuated NLRP3 accumulation and TBK1-IRF3 signaling without significantly elevating serum ALT or AST levels. Collectively, these findings identify liquiritigenin as a candidate natural compound for limiting inflammatory periapical bone loss. Its protective effects are partly associated with TRIM31-mediated K48-linked ubiquitination and proteasome-associated turnover of NLRP3 and are accompanied by attenuation of cGAS-STING-related signaling.