2011-08-012024-05-13https://scholars.lib.ntu.edu.tw/handle/123456789/643030摘要：感染性心內膜炎是主要由口腔鏈球菌(S. mutans, S. sanguinis, S. mitis/oralis)及葡萄球菌(S. aureus or S. epidermidis) 在心臟瓣膜上所引起的感染性疾病，通常具有高致死率及高再發率，而感染性心內膜炎的病徵為心臟瓣膜上贅生物的產生，而這種贅生物是由纖維蛋白與血小板的凝塊及在其上形成生物膜的細菌所組成，這樣的構造對於抗生素的治療具有高度的抵抗性，直至目前，臨床上心內膜炎還是予以高劑量且長時間的抗生素治療，但即使治癒，也依然存在著高復發率；除此之外，預防性抗生素的使用對於防止感染性心內膜炎的產生依然是具爭議性的。而我們實驗室長久以來的目的是探討感染性心內膜炎的致病機制及試圖為感染性心內膜炎尋找有效的治療的方法，而在過去四年的基因體計畫中，我們建立了實驗性心內膜炎的大鼠模型，並鑑定了在鏈球菌中與感染性心內膜炎致病有關的毒力因子(結果發表於J. Infect Dis. 2009. 199:1488–1496 及Mol.Microbiol. 2009; 74:888–902)。我們的結果率先提出一個觀念，証明除了細菌本身以外，宿主本身的物質對於感染性心內膜炎的致病機轉中也扮演重要角色；其中，屬於防禦性細胞的嗜中性白血球及血小板可能直接參與了細菌生物膜及贅生物的形成；我們初步的結果發現血小板對於鏈球菌在試管內及小鼠模型中形成生物模是必要的，並推測潤浸致至心臟瓣膜上的嗜中性白血球會釋放出胞外網狀結構(NETs) 去進一步引起血小板凝集及增加纖維蛋白凝塊的形成；根據這些結果，我們認為細菌與血小板的交互作用及潤浸致至心臟瓣膜上的嗜中性白血球，在受損的心臟瓣膜上，生物膜及贅生物的形成扮演關鍵性的角色。在這個計劃中，我們將針對血小板在細菌生物膜的形成及嗜中性白血球胞外網狀結構在促進纖維蛋白凝塊的形成的角色做研究，透過已建立好的實驗性心內膜炎大鼠試驗模型，我們可確定這些關鍵性的宿主因子在感染性心內膜炎致病時，直接參與了細菌與血小板生物膜的起始及其後的贅生物形成。這三年計劃的目標為:1. 評估是否可利用干擾細菌血小板間的交互作用來控制細菌生物膜的形成。2. 研究嗜中性白血球釋放出胞外網狀結構的機制及其在細菌所引起的纖維蛋白凝塊的角色。3. 確定在心內膜炎病人的臨床檢體中嗜中性白血球胞外網狀結構的存在；並評估利用抑制細菌血小板間的交互作用或抑制嗜中性白血球胞外網狀結構的形成，在實驗性心內膜炎大鼠試驗模型所造成的影響。在這個計劃中，我們將利用試管內的生物膜模型及活體內實驗性心內膜炎模型，來研究細菌血小板間的交互作用或嗜中性白血球胞外網狀結構在感染性心內膜炎致病機轉的角色，並收集感染性心內膜炎的病人的檢體來證明嗜中性白血球胞外網狀結構的存在。這個轉譯醫學導向的計畫是首次針對血小板的物質及嗜中性白血球胞外網狀結構是否可用於診斷及治療感染性心內膜炎所做的研究，由這個計畫所得到的結果將可對於感染性心內膜炎的預防及治療，除了抗生素以外，提供另一種選擇。<br> Abstract: Infective endocarditis (IE) is an infectious disease caused primarily by oral Streptococci(S. mutans, S. sanguinis, S. mitis/oralis), or Staphylococci (S. aureus or S. epidermidis) on theheart valves, with high mortality and recurrent rates. Histopathologically, IE is characterizedby the formation of vegetations, fibrin-platelet clots with the embedded bacteria formingbiofilm, which is refractory to routine antibiotic treatment. Until now, clinical management ofIE still demands long-lasting and high dose of antibiotic treatment, but possessing highrecurrent rates. In addition, the protective effect of prophylactic antibiotics treatment toprevent IE is controversial. The long-term goal of our laboratory is to elucidate thepathogenesis of IE and search for the therapeutic molecules for IE. During the past 4 years ofgenomic project, we have established a rat model of experimental endocarditis and identifiedessential virulence factors in Streptococci for inducing IE (J. Infect Dis. 2009. 199:1488–1496;Mol. Microbiol. 2009; 74:888–902). Our pioneering results lead to the notion that host factors,in addition to the bacteria, may play important roles in the pathogenesis of IE. Specifically,platelet and neutrophil, two important innate immune effectors may contribute directly to thebacterial biofilm and vegetation formation. Our preliminary data found that platelet is anessential host factor for Streptococci to form bacterial biofilm in vitro and in vivo. In addition,the extracellular DNA secreted from the infiltrated neutrophils (named neutrophilextracellular traps; NETs) may further induce the platelet aggregation and enhance thefibrin-clot formation. According to these findings, we hypothesized that the interaction of thebacteria with the platelet and the recruited neutrophils play the key roles in the bacterialbiofilm and vegetation formation on the damaged valve. In this project, we will focusspecifically on the role of platelet in the bacterial biofilm formation and the role of NETs inenhancing fibrin-thrombus formation. Through our well-established rat experimentalendocarditis model, we can confirm the key host factors contributing directly to the initiationof the bacteria-platelet biofilm and the subsequent formation of vegetation in IE. The specificaims of this three-year project will be1. Evaluate the effect by interfering with the bacteria-platelet interaction in controllingbiofilm formation in vitro.2. Investigate the mechanisms of neutrophil NETs formation and roles of NETs in thefibrin-platelet clot formation induced by bacteria.3. Confirm the existence of NETs in clinical specimens from IE patients and evaluate theeffects by inhibiting the bacteria-platelet interaction or NETs-formation in ratendocarditis model.In this project, we will adopt both in-vitro biofilm model and in-vivo rat IE model toinvestigate the roles of the bacteria-platelet interaction and NETs in the pathogenesis of IE.The specimens harvested from the IE-patients will also be collected for detecting thepresence of NETs. The diagnostic or therapeutic potential of targeting the plateletcomponents or NETs will be the primary focus and anticipated novel results of thistranslation-orientated proposal. Results obtained from this study could offer alternativeapproach to the clinical prevention and therapy, in addition to antibiotics, for IE.感染性心內膜炎生物膜細菌血小板交互作用嗜中性白血球胞外網狀結構Infective endocarditisbiofilmthe interaction of bacteria and plateletneutrophil extracellular traps (NETs)