Regulation of Oral Bacteria by Pattern Recognition Receptors

描述(由申请人提供)：宿主通过特定的模式识别受体(PRRs)识别细菌，包括NOD蛋白和Toll样受体(TLRs)，启动抗菌防御机制并调节宿主-细菌相互作用的动态平衡。免疫识别的缺陷导致宿主对病原菌感染的易感性很高。口腔中含有丰富多样的细菌群落，其中一些细菌被认为是常见疾病的病原体，如龋齿和牙周炎。口腔和牙龈组织中的上皮细胞被认为参与了抵抗细菌攻击的免疫反应，包括抗菌肽的产生。然而，宿主细胞检测口腔细菌并诱导抗菌反应的机制在很大程度上尚不清楚。这项提议的目的是检验NOD蛋白和TLRs感知和调节口腔微生物区系的发育和维持以及对包括牙龈假单胞菌在内的病原菌的免疫反应的假设。初步结果表明，缺乏PRR信号的小鼠口腔微生物区系与野生型小鼠不同，这表明PRR介导了对共生和/或病原菌的选择性清除。我们发现，细菌刺激NOD/TLR的活性在不同细菌种类之间存在很大差异，共生细菌表现出较低的刺激活性。因此，我们假设PRRs，特别是Nod1/NOD2，通过宿主免疫反应影响口腔微生物区系发育和病原菌。此外，我们假设口腔微生物区系通过PRR信号控制宿主对牙龈假单胞菌的易感性。在这项建议中，我们提议进行生化和遗传学研究，以检验我们的假设，并了解PRRs在调节口腔微生物区系发育中的作用。这些研究将为控制宿主对口腔病原体感染的易感性提供新的见解，从而可能导致口腔疾病新疗法的开发。人类口腔具有复杂、多样和动态的微生物区系，其中包含700种可培养和不可培养的细菌种类。口腔细菌通过形成生物膜在牙齿、假体、牙床和舌头的表面定居，生物膜是微生物之间高度相互作用的有组织的微生物群落。已知一些细菌与口腔疾病有关；例如，龋齿中的变形链球菌及其相关物种，以及成人牙周炎中的牙龈卟啉单胞菌。此外，口腔细菌还与包括心内膜炎在内的其他类型的人类疾病有关。口腔细菌也通过与病原菌的相互作用参与口腔疾病的发生。因此，目前治疗牙科疾病的方法不仅是消除特定的病原菌，而且要促进细菌种群的发展，防止病原菌群落的定植。然而，口腔微生物区系在正常状态下的发展和口腔疾病在很大程度上是未知的。此外，还没有关于宿主微生物传感受体控制微生物区系的研究，因此，拟议的研究将为宿主如何控制有益和致病微生物区系的发育和动态平衡提供一个新的概念。这些研究的结果不仅有望为微生物传感受体和共生细菌之间的相互作用提供新的见解，而且还将为宿主受体和微生物群在牙周炎中的作用提供新的见解，这对于开发新的和改进的牙周炎治疗方法至关重要。

DESCRIPTION (provided by applicant): Host recognition of bacteria by specific pattern-recognition receptors (PRRs), including Nod proteins and Toll-like receptors (TLRs), initiates antibacterial defense mechanisms and modulates the homeostasis of host-bacterial interactions. The deficiency of immune recognition results in high susceptibility of the host to infection by pathogenic bacteria. The oral cavity harbors an abundant and diverse community of bacteria, some of which have been implicated as etiological agents of common diseases such as dental caries and periodontitis. Epithelial cells lining the oral cavity and gingival tissue are known to be involved in immune responses against bacterial challenge including the production of antimicrobial peptides. However, the mechanisms by which host cells detect oral bacteria and induce antibacterial responses are largely unknown. The goal of this proposal is to test the hypothesis that Nod proteins and TLRs sense and regulate the development and maintenance of the oral microflora and the immune response to pathogenic bacteria including P. gingivalis. Preliminary results demonstrate that mice lacking PRR signaling contains oral microflora different from that of wild-type mice, suggesting that PRRs mediate selective elimination of commensal and/or pathogenic bacteria. We find that the activity of bacteria to stimulate Nod/TLR is highly diverse among bacterial species with commensal bacteria exhibiting low stimulatory activity. Thus, we hypothesize that PRRs, specifically Nod1/ Nod2, affect microflora development and pathogenic bacteria in oral cavity through host immune responses. Furthermore, we hypothesize that the oral microflora controls the susceptilibity of the host to P. gingivalis via PRR signaling. In this proposal, we propose biochemical and genetic studies to test our hypotheses and to understand the role of PRRs in the regulation of oral microflora development. These studies will provide novel insight into the mechanisms that govern the susceptibility of the host to infection by oral pathogens which may lead to the development of novel therapies for oral diseases.The human oral cavity has a complex, diverse and dynamic microflora harboring >700 cultivable and non-cultivable bacterial species. Oral bacteria colonize the surface of teeth, prostheses, gums and tongue by forming biofilm, an organized community of microbes in which microbial organisms highly interact with each other. Some bacteria are known to be involved in oral diseases; for example, Streptococcus mutans and related species in dental caries and Porphymonas gingivalis in adult periodontitis. In addition, oral bacteria have been also linked to other types of human disease including endocarditis. Oral bacteria are also involved in oral diseases through their interaction with pathogenic bacteria. Therefore, the current approach for dental diseases is not only to eliminate particular pathogenic bacteria, but also to promote bacterial populations that prevent colonization of pathogenic bacterial communities. However, the development of oral microflora in the normal state and oral diseases is largely unknown. Furthermore, studies on the control of microflora by host microbial sensing receptors have not been performed and thus the proposed studies will provide a novel concept about how hosts control the development and homeostasis of both beneficial and pathogenic microflora. The outcome of these studies is expected to provide novel insight not only into the interaction between microbial sensing receptors and commensal bacteria, but also into the role of host receptors and the microflora in periodontitis which is critical for the development of novel and improved therapies for the disease.