The Effect Of Aggregatibacter Actinomycetemcomitans Infection On Inflammatory Immune Response Of Different Tissue And Organs

Objective To investigate the effect of orally or systemically Aggregatibacteractinomycetemcomitans (Aa) infection on the inflammatory response of differenttissue and organs in New Zealand rabbits with normal diet/high-fat diet, and detect thecorrelated molecular mechanism between periodontitis and hyperlipidemia.Methods Experiment Ⅰ: New Zealand rabbits were fed with the high-fat diet for sixweeks to induce hyperlipemia. Some animals received silk ligatures around theirmandibular premolars followed by an application of Aa for eight weeks, to induceperiodontitis.Animals were divided into four groups, A (ND): normal diet, B (HFD):high-fat diet, C (Aa): local Aa infection, D (HFD+Aa): high-fat diet complicatedwith local Aa infection. Lipopolysaccharide (LPS) isolated from Aa was analyzed byLimulus test and infrared spectroscopy. Rabbits received either repeated intravenousinjections of LPS (55ng/kg, three times per week) for eight weeks. Experiment Ⅱ:Animals were divided into six groups, A (ND): normal diet, B (HFD): high-fat diet, C(Aa-LPS): Aa-LPS injection, D (HFD+Aa-LPS): high-fat diet complicated withAa-LPS injection, E (Ec-LPS): Ec-LPS injection, F (HFD+Ec-LPS): high-fat dietcomplicated with Ec-LPS injection. Animals were carried with euthanasia after14weeks. Periodontal disease severity was quantified radiographically, histologically,and by direct visualization of bone loss. Serum lipids were detected with automaticbiochemistry analyzer and cytokine concentrations were determined usingenzyme-linked immunosorbent assay (ELISA) kits for the assay of rabbit tumornecrosis factor (TNF)-α, interleukin (IL)-6, IL-1β, IL-10and so on. The morphology,mRNA of cytokines in the artery, cardiac, lung, liver, and kidney tissue were investigated by Hematein-Eosin and immununochemistory staining, andRealtime-PCR. Experiment Ⅲ: Animals in experiment I were divided into fourgroups, A (ND): normal diet, B (HFD): high-fat diet, C (Aa): Aa injection, D (HFD+Aa): high-fat diet complicated with Aa injection. The rabbits were treatedintravenously with Aa (1.0×108CFU/ml,0.1ml/kg), or phosphate-buffered salinethree times a week for8weeks and killed at14weeks. The plasma levels of cytokineswere measured. Experiment Ⅳ: Rabbits were induced periodontitis and followed byIL-10(0.1μg/kg) injection. After24hours, the plasma levels of cytokines weremeasured.Results Experiment Ⅰ: Accompanying pronounced changes in inflammatorycytokine expression was a significantly increase in bone loss for hyperlipidemiarabbits with oral infection with Aa. Local infection of Aa on rabbits accelerated thepathological progression of different organs. Experiment Ⅱ: In the early stages,animals with hyperlipidemia exposed systemically Aa-LPS injection developed ablunted inflammatory response with reduced expression of cytokines compared withnormal diet rabbits. However, rabbits with hyperlipidemia exhibited higherinflammatory cytokine expression for long-term Aa-LPS injection and the rabbitswith HFD have more significance in chronic inflammatory factors expression indifferent organs than those with ND. Experiment Ⅲ: The areas of the aortic sinus thatwere covered with atherosclerotic plaque were significantly larger in Group Dcompared with rabbits from B or C. Aa challenge increased serum CRP, TNF-α,IL-1β, IL-6, IL-10, INF-γ, and MCP-1. Experiment Ⅳ:0.1μg/kg IL-10couldtentatively reduce the expression of periodontitis-induced systemic inflammatoryfactors.Conclusion Local or systemic infection Aa may lead to the disorder of lipidmetabolism in rabbits, thereby increasing the inflammatory response of differenttissues and organs. The reactions of different organs to Aa infection appearedvariously, infection with Aa might be an additional risk factor for thedevelopment/progression of systemic diseases. HLP becomes associated with a formof immune paralysis and increases susceptibility to other bacterial infections, including an altered pro-and anti-inflammatory network during the acute phase, andmaintaining on a higher expressing level of inflammatory cytokines in the advancedperiod. IL-10could tentatively inhibit the expression of periodontitis-inducedsystemic inflammatory factors.