Regulation of Inflammatory Responses in the Cochlea

描述（由申请人提供）：炎症是宿主对外来挑战或组织损伤的有益反应，最终导致组织结构和功能的恢复。白细胞迁移到损伤或感染部位是炎症反应的决定性步骤。然而，在哺乳动物耳蜗中，必须防止白细胞迁移到听觉器官中，因为它可能通过破坏Corti腔缘器官（解剖学上定义为网状层）的紧密连接屏障而消除耳蜗内电位，导致感觉运动外毛细胞凋亡和不可逆的深度耳聋。因此，除了极端的、不可逆的耳蜗损伤外，在Corti器官中从未发现过白细胞。耳蜗用于防止白细胞迁移的机制仍然未知。目前保护Corti器官免受炎症损伤的金标准临床策略是局部递送糖皮质激素。然而，糖皮质激素赋予这种保护的机制也是未知的。这项提议的目标是填补我们知识中的这些空白，这是我们寻求了解哺乳动物耳蜗炎症反应调节的关键一步。我们的初步研究为以下假设提供了有力的支持：1）膜联蛋白A1（Annexin A1，ANXA 1）是先天性和适应性免疫系统的重要调节因子，在阻止白细胞迁移到OC和促进炎症反应的消退阶段中起重要作用; 2）糖皮质激素通过肌球蛋白IIC驱动的机制刺激豚鼠Hensen细胞释放ANXA 1;和3）Hensen细胞将ANXA 1储存在填充其细胞质的显著脂滴内。因此，我们建议使用豚鼠作为体内模型，使用听觉细胞系作为体外模型，并结合非重叠技术和方法学方法，通过解决以下具体目标来测试这些假设：1）证明由Hensen细胞释放的ANXA 1阻止白细胞迁移，2）阐明参与ANXA 1的细胞内转运和释放的机制，和3）鉴定和表征参与Hensen细胞脂滴储存和释放ANXA 1的机制。 公共卫生相关性：由病毒、噪音或耳毒性物质引发的耳蜗炎症反应可导致轻度至重度听力损失。目前保护听觉器官免受炎性损伤的金标准临床策略是局部递送糖皮质激素。然而，糖皮质激素赋予这种保护的机制仍然未知。我们相信，通过实现本提案的目标，我们将能够提供有关耳蜗炎症和抗炎反应相关机制的重要见解，并确定预防和治疗突发性感音神经性听力损失的新分子靶点。

DESCRIPTION (provided by applicant): Inflammation is a beneficial host response to foreign challenges or tissue injury that leads ultimately to the restoration of tissue structure and function. Leukocyte migration to sites of injury or infection is a defining step of inflammatory responses. In the mammalian cochlea, however, leukocyte migration into the auditory organ must be prevented as it may abolish the endocochlear potential by disrupting the tight-junction barrier at the organ of Corti luminal border (anatomically defined as the reticular lamina), leading to apoptosis of sensorimotor outer hair cells and irreversible, profound deafness. Thus, leukocytes are never found in the organ of Corti except in cases of extreme, irreversible cochlear damage. The mechanism used by the cochlea to prevent leukocyte migration is still unknown. The current gold standard clinical strategy to protect the organ of Corti against inflammatory damage is the local delivery of glucocorticoids. However, the mechanism by which glucocorticoids confer this protection is also unknown. The goal of this proposal is to fill these gaps in our knowledge, a crucial step in our quest to understand the regulation of inflammatory responses in the mammalian cochlea. Our preliminary studies provide strong support to the following hypotheses: 1) Annexin A1 (ANXA1), a pivotal regulator of many aspects of the innate and adaptive immune systems, have a major role in preventing leukocyte migration into the OC and facilitating the resolution phase of the inflammatory response; 2) glucocorticoids stimulate guinea pig Hensen cells to release ANXA1 via a myosin IIC-driven mechanism; and 3) Hensen cells store ANXA1 inside the prominent lipid droplets filling their cytoplasm. Thus, we propose to use the guinea pig as an in vivo model, an auditory cell line as an in vitro model, and a combination of non-overlapping techniques and methodological approaches to test these hypotheses by addressing the following Specific Aims: 1) Demonstrate that ANXA1 released by Hensen cells prevents leukocyte migration, 2) Elucidate the mechanism/s involved in the intracellular transport and release of ANXA1, and 3) Identify and characterize the mechanism/s involved in the storage and release of ANXA1 by Hensen cell lipid droplets. PUBLIC HEALTH RELEVANCE: Inflammatory responses in the cochlea, triggered by virus, noise, or ototoxic agents, can result in mild to profound hearing loss. The current gold standard clinical strategy to protect the auditory organ against inflammatory damage is the local delivery of glucocorticoids. However, the mechanism by which glucocorticoids confer this protection is still unknown. We are confident that by accomplishing the aims of the present proposal we will be able to provide critical insights about the mechanisms associated with inflammatory and anti-inflammatory responses in the cochlea, as well as identify new molecular targets for prevention and treatment of sudden sensorineural hearing loss.