Toll-Like Receptor-2 Plays a Fundamental Role in Periodontal Bacteria-Accelerated Abdominal Aortic Aneurysms

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Background: Periodontopathic bacteria are detected at a high rate in specimens obtained from the aortic walls of patients with abdominal aortic aneurysm (AAA) and are involved in AAA development. The purpose of this study was to clarify the role of Toll-like receptors (TLRs), which are key receptors of virulence factors of many periodontal bacteria, on periodontopathic bacteria-accelerated AAA progression. Methods and Results: AAA was produced by peri-aortic application of 0.25mol/L CaCl₂, with NaCl used as a control. The mice were inoculated with live Porphyromonas (P.) gingivalis or vehicle once weekly. At 4 weeks after the application of CaCl₂, the aortic diameter of the P. gingivalis-infected wild-type mice showed a significant increase in comparison with vehicle control mice (P<0.05). The P. gingivalis-infected TLR-2 deficient mice showed no statistical increase in aortic diameter over the same period. The aortic diameter of the P. gingivalis-infected TLR-4 deficient mice statistically increased. Immunohistochemically, the levels of matrix metalloproteinase-2 and -9 in the aneurysmal samples from wild-type mice were higher than in TLR-2 deficient mice. Conclusions: P. gingivalis accelerated the progression of experimental AAA through TLR-2 signaling.