Nasal Solitary Chemoreceptor Cells: Detection of Pathogenic Bacteria

描述(申请人提供)：鼻呼吸道上皮含有数千个特殊的化学感受器细胞(孤立的化学感受器细胞)，它们与三叉神经形成功能性接触。三叉神经被刺激物直接激活或通过这些细胞的代理激活，都会引起保护性的呼吸道反射，如打喷嚏、咳嗽或呼吸暂停。拟议的实验研究了这些孤立的化学感觉细胞在检测病原菌从良性向毒力状态转变时分泌的群体感应分子的作用。我们的初步数据显示，细胞和三叉神经系统总体上可以对细菌信号分子做出反应。该方案中的实验将检查反应的化学特异性，测试T2R(苦味)受体分子的转导级联和可能的作用，最后检查化学感觉细胞激活对周围上皮和三叉神经纤维的影响。为了评估各种细菌信号分子的有效性，我们将使用两种生物测定系统：i)在半完整制剂中将化合物应用于鼻黏膜上皮所引起的呼吸反射，以及ii)从转基因小鼠的鼻黏膜上分离出的化学感觉细胞的钙成像，其中GFP标记相关的细胞群。我们将使用相同的准备来评估T2R受体和相关的PLC信号级联的潜在作用。如果T2R/PLC途径是必要的，特定的PLC信号阻断剂应该干扰信号转导并消除Ca++信号。同样，如果Trpm5和Gustducin基因敲除动物的呼吸抑制对细菌信号的转导至关重要，那么这些因素都应该得到缓解。最后，我们将评估化学感觉细胞的激活是否继而导致周围上皮细胞的变化--要么是通过释放旁分泌介质(例如，ATP、乙酰胆碱)，要么是通过激活支配上皮的肽能神经纤维。综上所述，这些实验将确定孤立的化学感觉细胞用来检测细菌信号分子的机制，以及这些细胞是否有助于激发局部组织和/或对潜在病原体的免疫反应。与公共卫生相关：拟议的研究将调查一种新发现的鼻部化学传感系统，该系统检测调节病原菌毒力的分子。这项研究旨在测试这些传感器在抵御细菌性鼻腔和上呼吸道感染的组织防御第一线中的可能作用。

Description (provided by applicant): The nasal respiratory epithelium contains thousands of specialized chemoreceptor cells (solitary chemosensory cells) that form functional contacts with the trigeminal nerve. Activation of the trigeminal nerve either directly by irritants or through the agency of these cells evokes protective airway reflexes such as sneezing, coughing or apnea. The proposed experiments investigate the role of these solitary chemosensory cells in the detection of quorum sensing molecules secreted by pathogenic bacteria as they transition from being benign to the virulent state. Our preliminary data show that the cells and the trigeminal system at large can respond to bacterial signaling molecules. The experiments in this proposal will examine the chemical specificity of the response, test the transduction cascade and possible role of T2R (bitter taste) receptor molecules, and finally examine the effects on the surrounding epithelium and the trigeminal sensory nerve fibers of activation of the chemosensory cells. In order to assess the effectiveness of various bacterial signaling molecules, we will use two bioassay systems: i) respiratory reflexes evoked by application of the compound to the nasal epithelium in a semi-intact preparation, and ii) Ca ++ -imaging of chemosensory cells isolated from the epithelium of transgenic mice in which GFP marks the relevant cell population. We will use the same preparations to assess the potential role of T2R receptors and the associated PLC-signal cascade. Specific blockers of PLC- signalling should disrupt transduction and eliminate the Ca ++ signal if the T2R/PLC pathway is necessary. Similarly, respiratory depression should be lessened in both TRPM5 and gustducin-knockout animals if these elements are crucial for the transduction of bacterial signals. Finally, we will assess whether activation of the chemosensory cells secondarily causes changes in the surrounding epithelium - either via release of paracrine mediators (e.g. ATP, acetyl choline) or through the agency of activation of the peptidergic nerve fibers that innervate the epithelium. Taken together, these experiments will determine the mechanisms used by solitary chemosensory cell to detect the bacterial signaling molecules and whether the cells are instrumental in provoking a local tissue and/or immune response to the potential pathogens. PUBLIC HEALTH RELEVANCE: The proposed research will investigate a newly discovered nasal chemosensory system that detects molecules that regulate the virulence of pathogenic bacteria. This research is designed to test the possible role of these sensors in a first line of tissue defense against bacterial nasal and upper respiratory infections.