Assosiation of Inflammasome in Periodontal Desease and Atherosclerosis Induced By Porphyromonas Gingivalis Oral Infection

Statement of the problem: Periodontitis has been reported to be associated with atherosclerosis. Porphyromonas gingivalis (P. gingivalis) is detected in atherosclerosis lesion. Atherosclerosis is a disease characterized by inflammation in the arterial wall. Recent studies have suggested that the inflammasome plays a role in the development of  vascular inflammation and atherosclerosis. We examined association of inflammasome in the atherosclerosis induced by P. gingivalis infection using Aporipoprotein E deficient spontaneously hyperlipidemic (Apoe^shl) mice.

Materials and methods: Mice were orally infected with P. gingivalis33277(wild type, WT), KDP136(gingipain-null mutant of ATCC33277), KDP150(an FimA-deficient mutant of ATCC33277) 5 times a week for 3 weeks and sacrificed at 18weeks of age. Bacteria were detected two days after final infection from each organ. Furthermore, alveolar bone loss, lesion area in the proximal aorta, gene expression of NLRP3, proIL-1β, proIL-18, pro-caspase-1 in the gingival tissue and aorta were measured.

Methods of data analysis: For bacterial DNA detection, total DNA was extracted from each organ. The P. gingivalis16S gene was then amplified by PCR. To assess alveolar bone loss skulls were immersed overnight in 3% hydrogen peroxide, and stained with 1% methylene blue. Images from one side with maxillary molar teeth and alveolar bone were captured using a dissection microscope. We examined cryosections of  the aortic arch for atherosclerotic plaque  accumulation by oil red O staining. The lesion area was then quantified under a microscope interfaced with a CCD camera and an image analysis system. For analysis of inflammasome-related gene expression, purified total RNA obtained from each gum and aorta specimen was reverse transcribed with Oligo using SuperScript Ⅱ reverse transcriptase to generate cDNA. Real-time quantative RT-PCR analyses were performed using  the Thermal Cycler Dice real-time PCR system.

Results: P. gingivalis WT-challenge significantly increased alveolar bone loss, lesion area of the aortic sinus that were covered with atherosclerotic plaque, gingival or aortic gene expression of Toll like receptor (TLR2, TLR4,TLR9), Nod-like receptor family, pyrin domain containing 3 (NLRP3), proIL-1β, proIL-18, pro-caspase-1 compared with  KDP136 or KDP150 challenge. P. gingivalis was detected in the aorta, gingival tissue, liver, and spleen of P. gingivalisWT-challenged mice by PCR. The persistence of the WT bacterium in these organs was distinctly different from that of KDP136 or KDP150 challenged mice.

Conclusions: In conclusion, P. gingivalis WT with many virulence factors activates innate immune cells through pattern recognition receptor such as TLR and NLRP3 inflammasome compared with KDP136 or KDP150. Our finding suggest NLRP3 inflammasome followed by IL-1 family response plays a critical role in vascular inflammation and atherosclerosis induced by P. gingivalisWT-challenge.

2 references: Teles R, Wang CY(2011) Mechanisms involved in the association between periodontal diseases and cardiovascular disease. Oral Diseases. 2011; 7(5):450-461.

Nisha Jain Garg(2011) Inflammasomes in cardiovascular diseases. American Journal of Cardiovascular Disease. 2011;1(3):244-254.