Nasal Solitary Chemoreceptor Cells: Detection of Pathogenic Bacteria

描述（由申请人提供）：鼻呼吸上皮包含数千个特化的化学感受器细胞（孤立的化学感觉细胞），它们与三叉神经形成功能性接触。刺激或通过这些细胞的作用直接激活三叉神经，会引起保护性气道反射，如打喷嚏、咳嗽或呼吸暂停。本实验旨在研究这些孤立的化学感觉细胞在病原菌从良性状态转变为毒性状态时，在检测其分泌的群体感应分子中的作用。我们的初步数据表明，细胞和整个三叉神经系统可以对细菌信号分子作出反应。本课题的实验将研究该反应的化学特异性，测试T2R（苦味）受体分子的转导级联及其可能的作用，最后研究化学感觉细胞的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)在半完整的制备中，将化合物应用于鼻上皮引起的呼吸反射，以及ii)从转基因小鼠上皮中分离的化学感觉细胞的Ca ++成像，其中GFP标记相关细胞群。我们将使用相同的制剂来评估T2R受体和相关plc信号级联的潜在作用。如果T2R/PLC通路是必要的，PLC信号的特异性阻滞剂应该破坏转导并消除Ca ++信号。同样，如果TRPM5和gustducin敲除动物的呼吸抑制对细菌信号的转导至关重要，那么这些元素应该会减轻。最后，我们将评估化学感觉细胞的激活是否继发引起周围上皮的变化-通过释放旁分泌介质（如ATP，乙酰胆碱）或通过激活支配上皮的肽能神经纤维的代理。综上所述，这些实验将确定单个化学感觉细胞用于检测细菌信号分子的机制，以及这些细胞是否有助于引发局部组织和/或对潜在病原体的免疫反应。公共卫生相关性：拟议的研究将调查一种新发现的鼻腔化学感觉系统，该系统检测调节致病菌毒力的分子。这项研究旨在测试这些传感器在抵抗细菌性鼻腔和上呼吸道感染的第一线组织防御中的可能作用。

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.