Ganoderic acid A attenuates Porphyromonas gingivalis-induced adhesion molecule expression in gingival fibroblasts and tissues via inhibition of NLRP6 inflammasome activation

Objectives

This study aimed to elucidate the regulatory effects and mechanisms of Ganoderic acid A (GAA) on Porphyromonas gingivalis (P. gingivalis)-induced expression of adhesion molecules in human gingival fibroblasts (hGFs) and periodontal tissues, focusing on NLRP6 inflammasome modulation.

Design

HGFs were stimulated with P. gingivalis strain W83. The expression levels of NLRP6, caspase-1, IL-1β,IL-18 and adhesion molecules ICAM-1 & VCAM-1 were analyzed by RT-PCR, Western blotting and ELISA, with or without GAA pretreatment. To further explore the regulatory role of GAA on the NLRP6 inflammasome, NLRP6 overexpression assays were performed in hGFs, followed by assessment of ICAM-1 and VCAM-1 expressions. Additionally, a ligature-induced periodontitis mice model was established to evaluate the effects of GAA on NLRP6 expression and inflammatory cell infiltration in periodontal tissues.

Results

GAA exhibited no cytotoxicity toward hGFs at low concentrations (within 16 μM). GAA pretreatment significantly inhibited P. gingivalis-induced activation of the NLRP6 inflammasome. Beyond IL-1β and IL-18, it also reduced ICAM-1 and VCAM-1 expression at both mRNA and protein levels. Overexpression of NLRP6 increased the expression of NLRP6 inflammasome components and adhesion molecules, whereas GAA treatment effectively suppressed these elevations. Furthermore, GAA administration markedly downregulated NLRP6 expression and attenuated inflammatory cell infiltration and periodontal inflammation in the mice periodontitis model.

Conclusions

GAA attenuates P. gingivalis-induced expression of adhesion molecules by inhibiting NLRP6 inflammasome activation in gingival fibroblasts and periodontal tissues, thereby alleviating inflammatory cell infiltration. These findings suggest the potential of GAA as a therapeutic agent for the management of periodontal inflammation.