Porphyromonas gingivalis protease Rgp induces M1-type polarization and pyroptosis in BV-2 cells by inhibiting SIRT1 expression

Abstract

Background Periodontitis and Alzheimer's disease (AD) are age-related diseases that reciprocally act as risk factors. It has been reported that periodontal pathogen Porphyromonas gingivalis and its gingipains contribute to neuroinflammation mediated by microglial cells, playing a crucial role in the onset of AD. However, it remains unclear whether gingipains play a pro-inflammatory role by inducing senescent phenotypic changes in microglial cells. Methods BV-2 cells were cultured and stimulated with gingival protease (Rgp), in combination with or not SRT1720, an inhibitor of SIRT1. SA-βgal staining was used to observe the altered cellular senescent phenotype. Immunoprotein blotting and real-time fluorescence quantitative polymerase chain reaction (RT-qPCR) were used to confirm the results of SIRT1, NLRP3, Caspase-1 and GSDMD expression. ELISA and flow cytometry were used to detect IL-1β and IL-18 levels in supernatants and altered M1 polarization in BV-2 cells. Results Rgp induced BV-2 cells to present a senescent phenotype and downregulated the expression of senescence-related protein SIRT1. BV-2 cells with the senescent phenotype showed a concentration-dependent upregulation of NLRP3 upon Rgp stimulation, accompanied by a significant increase in the M1-type polarization phenotype. Simultaneously, the expression of pyroptosis-related proteins Caspase-1 and GSDMD increased, and flow cytometry analysis indicated an increase in pyroptosis in BV-2 cells. Further restoration verification using the SIRT1 activator SRT1720 showed that, compared to the Rgp stimulation group, the SRT1720 intervention group exhibited increased SIRT1 protein expression in BV-2 cells, decreased NLRP3 expression, and a significant reduction in M1-type polarization. Additionally, the expression of Caspase-1 and GSDMD proteins decreased, the levels of IL-1β and IL-18 in the supernatants decreased, and cell pyroptosis was significantly reduced. Conclusions Porphyromonas gingivalis protease Rgp induced a senescent phenotype in BV-2 cells and promoted M1-type polarization and pyroptosis of cells by inhibiting SIRT1 expression, thereby exacerbating the inflammatory response.