P. gingivalis cytokine production in heart of mice

Objectives: Infective endocarditis is a rare, serious and potentially fatal complication following dental treatment. Bacteraemia of oral origin is thought to be important in the pathogenesis of infective endocarditis. Black-pigmented gram-negative anaerobic rods have been implicated in a variety of oral and nonoral diseases. Porphyromonas gingivalis (P. gingivalis) has only occasionally been recovered from nonoral infections. However, the role of P. gingivalis in nonoral diseases may be underestimated. In this study, we deterrmined the cytokine expression in heart of mice after infection to investigate a role of P. gingivalis in infective endocarditis.

Methods: C57BL/6 mice were intravenously inoculated with 2.0×109CFU/ml of P. gingivalis (ATCC 33277). Mice were sacrificed at specified times and their hearts, lungs and spleens were collected. The collected organs were divided into two halves and used for the histological evaluation and the cytokine gene expression analysis. Total RNA was extracted using ISOGEN (Nippon gene, Tokyo, Japan) and the expression of cytokine mRNA was determined by RT-PCR and Real Time PCR method. We analyzed the mRNA expression of interleukin (IL) -1b, IL-6, IL-17, IL-18, tumor necrosis factor (TNF) –a and interferon (IFN) -g.

Results: The expression of IL-1b, IL-6, IL-17, IL-18, and IFN-gmRNA were detected in heart of mice before and after infection with P. gingivalis by RT-PCR. Although the expression of IL-17 and IL-18 mRNA were not changed before and after infection, the levels of IL-1b, IL-6, TNF-a and IFN-gmRNA were significantly increased after P. gingivalis infection. These results demonstrated that the inflammatory cytokines were induced in heart after infection with P. gingivalis.

Conclusion: These findings suggest that P. gingivalis may play a role in the pathogenesis of endocarditis.