Porphyromonas gingivalis (P. gingivalis) is one of the most responsible periodontopathogenic bacteria in the development of periodontal disease (PD); however, its role in the development of other diseases still needs to be understood, specially its implications in the causation of cardiovascular pathogenesis. The aim of this study is to determine whether there is a direct association between P. gingivalis-induced PD with that of the development of cardiovascular disease, and whether a long-term administration of probiotic(s) could help improve the cardiovascular disease outcome. To test this hypothesis, we employed four different experimental groups of mice, designated as: Group I: Wild-type (WT) mice (C57BL/6J); Group II: Lactobacillus rhamnosus GG (LGG) (WT mice treated with a probiotic; LGG), Group III: PD (WT mice treated with P. gingivalis), and Group IV: PD + LGG (WT mice treated with P. gingivalis and LGG). PD was created by injecting 2 µL (i.e., 20 µg) of P. gingivalis lipopolysaccharide (LPS) intragingivally between the 1st and 2nd mandibular molars, two times a week for a total period of 6 weeks. The PD (LGG) intervention was done orally employing 2.5 × 105 CFU/day for a continuous period of 12 weeks. Immediately before the mice were sacrificed, echocardiography of the heart was performed, and after sacrifice, we collected serum samples, hearts, and the periodontal tissue. Histological assessment, cytokine analysis, and zymography of the cardiac tissue were performed. Results revealed inflammation of the heart muscle in the PD group that was marked by infiltration of neutrophils and monocytes, followed by fibrosis. Cytokine analysis of the mice sera revealed significantly elevated levels of tumor necrosis factor-α, IL-1β, IL-6, and IL-17A in the PD group along with LPS-binding protein, and CD14. Most importantly, we observed elevated levels of P. gingivalis mRNAs in the heart tissues of PD mice. Zymographic analysis demonstrated matrix remodeling as revealed by increasing content of MMP-9 in the heart tissues of PD mice. Interestingly, LGG treatment was able to mitigate most of the pathological effects. The findings suggest that P. gingivalis could lead to cardiovascular system disorder and that probiotic intervention could alleviate, and most likely prevent bacteremia and its harmful effect(s) on the cardiovascular function.
Keywords: Lactobacillus rhamnosus; MMP; bacteremia; echocardiography; periodontal disease.