THE NEURAL BASIS OF OCULAR ITCH

描述(申请人提供)：眼部瘙痒是许多眼部疾病的顽固性症状，严重影响生活质量和生产力。眼痒被认为是由三叉神经节中的一组初级感觉神经元介导的。这些神经元通过结膜中的外周轴突检测内源性瘙痒诱导介质(瘙痒原)，并通过中央轴突将信号传递到脑干。然而，这些瘙痒感觉神经元的分子鉴定仍然难以捉摸。此前，我们发现了一种新的瘙痒受体，名为MRGprA3。我们发现，mrgprA3标记了一组高度受限的初级感觉神经元，这些神经元介导了皮肤的急性和慢性瘙痒。有趣的是，我们的最新结果显示，表达MRGPrA3的感觉神经元也投射到结膜，但不投射到所研究的其他粘膜组织。然而，MRGPrA3表达的神经元在眼部瘙痒中的功能仍有待确定。这项提议旨在揭示眼部瘙痒的神经机制。目的1研究结膜中表达mrgprA3的感觉纤维的神经支配模式和生理特性。利用基因标记工具，我们将对在结膜发育和成年期表达MRgprA3的感觉纤维的神经支配进行详细的解剖学分析。此外，我们将测试结膜中表达mrgprA3的感觉纤维是否可以被各种瘙痒原激活。这些研究将提供有关表达mrgprA3的感觉纤维在眼部瘙痒中的潜在作用的重要信息。目的2研究MRGPrA3表达的神经元是否参与急性眼痒的发生。我们将确定消融表达mrgprA3的神经元是否能减轻由各种瘙痒原引起的眼部瘙痒。此外，我们将研究选择性激活结膜中表达mrgprA3的感觉纤维的行为后果。这些功能丧失和功能获得的研究将确定MRgprA3表达的神经元在眼痒中的作用，这将首次在外周水平上解开眼痒的神经机制。在目的3中，我们试图了解在过敏性结膜炎中表达mrgprA3的感觉纤维和肥大细胞之间的相互作用，并确定mrgprA3表达的纤维是否介导了相关的眼部瘙痒。根据我们的初步数据，我们假设肥大细胞在变应原诱导的脱颗粒过程中释放内源性瘙痒原，并刺激表达MRgprA3的感觉纤维诱导瘙痒。使用一种新的成像工具，结合分子和行为分析，我们将研究这一假说。这些研究将揭示眼部瘙痒的神经基础。 发生在常年性和季节性过敏性结膜炎中，并将对 眼痒发病机制的研究和慢性瘙痒的临床治疗。

DESCRIPTION (provided by applicant): Ocular itch is a refractory symptom of many ocular conditions, and severely affect the quality of life and productivity. Ocular itch is thought to be mediated by a group of primary sensory neurons residing in the trigeminal ganglia. These neurons detect endogenous itch-inducing mediators (pruritogens) via their peripheral axons in the conjunctiva, and transmit signals to the brainstem via their central axons. However, the molecular identification of these itch-sensing neurons remains elusive. Previously, we identified a novel itch receptor, called MrgprA3. We found that MrgprA3 marks a highly restricted population of primary sensory neurons that mediates acute and chronic itch in the skin. Interestingly, our latest results revealed that MrgprA3-expressing sensory neurons also project to the conjunctiva but not to other mucosal membrane tissues examined. However, the function of MrgprA3-expressing neurons in ocular itch remains to be determined. This proposal aims to uncover the neural mechanisms of ocular itch. Aim 1 will characterize the innervation pattern and physiological properties of MrgprA3-expressing sensory fibers in the conjunctiva. Using genetic labeling tools, we will perform detailed anatomical analysis of the innervation of MrgprA3-expressing sensory fibers in the conjunctiva during development and in adulthood. In addition, we will test whether MrgprA3-expressing sensory fibers in the conjunctiva can be activated by various pruritogens. These studies will provide important information about the potential role of MrgprA3-expressing sensory fibers in ocular itch. Aim 2 will investigate whether MrgprA3-expressing neurons mediate acute ocular itch. We will determine whether ablation of MrgprA3-expressing neurons alleviates the ocular itch produced by various pruritogen. Furthermore, we will examine the behavioral consequence of selective activation of MrgprA3-expressing sensory fibers in the conjunctiva. These loss-of-function and gain-of-function studies will firmly establish the role of MrgprA3- expressing neurons in ocular itch, which will, for the frst time, unravel the neural mechanism of ocular itch at the peripheral level. In Aim 3, we seek to understand the interaction between MrgprA3-expressing sensory fibers and mast cells in allergic conjunctivitis and determine whether MrgprA3-expressing fibers mediate related ocular itch. Based on our preliminary data, we hypothesize that mast cells release endogenous pruritogens upon allergen-induced degranulation and excite MrgprA3-expressing sensory fibers to induce itch. Using a novel imaging tool combined with molecular and behavioral analysis, we will investigate this hypothesis. These studies will reveal the neural basis underlying ocular itch that occurs in perennial and seasonal allergic conjunctivitis and will have a significant impact on both the study of ocular itch pathogenesis and the clinical treatment of chronic itch.