Effects of pro-inflammatory cytokines induced by Porphyromonas gingivalis on cell cycle regulation in brain endothelial cells

Objectives

Advanced periodontitis potentially contributes to Alzheimer's disease (AD) development and progression by altering the blood–brain barrier microenvironment in the cerebral microvascular endothelium. This results, in cytotoxicity, cell cycle disruption, and increased pro-inflammatory cytokine expression, allowing pathogens to enter the brain and damage the central nervous system (CNS). This study evaluated the effects of Porphyromonas gingivalis W83 infection on pro-inflammatory response, cell viability, and cell cycle regulation in mouse brain endothelial cells (mBECs).

Methods

mBECs were stimulated with live P. gingivalis at different multiplicity of infection (MOI) values (1:5, 1:10, 1:50, 1:100, 1:200) for 6, 12, 24, and 48 h. Cell viability, cell cycle regulation, and pro-inflammatory cytokine mRNA expression were assessed using the alamarBlue assay, flow cytometry, and reverse transcription quantitative polymerase chain reaction (RT-qPCR), respectively.

Results

P. gingivalis reduced cell viability, induced morphological changes in mBECs by >50 % after 48 h (p < 0.05) and caused concentration-dependent arrest in the S and G0/G1 phases of the cell cycle at MOI = 1:100 and 1:200. The Il6, Il1b, and tumor necrosis factor alpha (Tnf) mRNA expression increased significantly compared to that of the controls (p < 0.05).

Conclusions

P. gingivalis reduced cellular metabolism and induced early cell cycle arrest at the G0/G1 phase in mBECs cells. It also increased the pro-inflammatory response, which could be associated with cell death and possible senescence of brain endothelial cells. These results suggested a possible role for P. gingivalis in the pathogenesis of AD. Further studies are required to elucidate these underlying mechanisms.