THE NEURAL BASIS OF OCULAR ITCH

描述（由申请人提供）：眼痒是许多眼部疾病的难治性症状，严重影响生活质量和生产力。眼痒被认为是由位于三叉神经节中的一组初级感觉神经元介导的。这些神经元通过其在结膜中的外周轴突检测内源性瘙痒诱导介质（致痒原），并通过其中央轴突将信号传递到脑干。然而，这些痒感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，称为MrgprA3。我们发现，MrgprA3标志着一个高度限制的初级感觉神经元，介导急性和慢性瘙痒的皮肤。有趣的是，我们最新的结果显示，MrgprA3表达的感觉神经元也投射到结膜，但不投射到其他检查的粘膜组织。然而，MrgprA3表达神经元在眼痒中的功能仍有待确定。本研究旨在揭示眼痒的神经机制。目的1将表征结膜中表达MrgprA3的感觉纤维的神经支配模式和生理特性。使用遗传标记工具，我们将进行详细的解剖学分析的神经支配的MrgprA3表达的感觉纤维在结膜发育过程中和成年期。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促炎原激活。这些研究将提供重要的信息MrgprA3表达的感觉纤维在眼痒的潜在作用。目的2研究表达MrgprA3的神经元是否介导急性眼痒。我们将确定MrgprA3表达神经元的消融是否能减轻各种过敏原引起的眼痒。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牢固地确立MrgprA3表达神经元在眼痒中的作用，这将首次在外周水平上阐明眼痒的神经机制。在目的3中，我们试图了解过敏性结膜炎中MrgprA3表达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相关的眼痒。基于我们的初步数据，我们假设肥大细胞释放内源性致敏原过敏原诱导的脱粒和刺激MrgprA3表达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，我们将调查这一假设。这些研究将揭示眼痒的神经基础 发生在常年性和季节性过敏性结膜炎，并将有显着影响， 无论是对眼痒发病机制的研究，还是对慢性眼痒的临床治疗。

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.