Effect of Sequestosome-1/p62 Expression on Autophagy of Human Periodontal Ligament Fibroblasts Induced by Porphyromonas gingivalis

Abstract

Porphyromonas gingivalis is the main pathogen of periodontitis. The purpose of this study was to analyze the effect of p62 protein on P. gingivalis-induced autophagy in human periodontal ligament fibroblast (HPDLF). HPDLF cells were first infected with P. gingivalis; autophagy and p62 expression levels were observed at different time points (0, 12, 18, and 24 h) to detect the relationship between p62 and autophagy over time. Autophagy and apoptosis of HPDLF cells infected with P. gingivalis were detected using siRNA specific interference with p62 expression. Fluorescence microscopy and electron microscopy showed autophagic vacuoles in HPDLF cells infected with P. gingivalis. Western blotting showed that p62 expression peaked at 12 h and began to decrease at 18 h. The expression of p62 was silenced by siRNA compared with the control group; the ratio of LC3-II/LC3-I decreased significantly, while the expression level of caspase-3 increased significantly. The the CCK-8 cell viability assay showed that the silencing of p62 reduced HPDLF cell viability, and the plate coating method showed that the silencing of p62 reduced the survival rate of P. gingivalis in the HPDLF cells. Therefore, in vitro studies showed that the presence of p62 is beneficial for maintaining the level of autophagy in HPDLF cells induced by P. gingivalis and inhibiting apoptosis. p62 facilitates the removal of P. gingivalis that are invading cells during this process.