An investigation into cochlear HPA like signaling

噪声性听力损失（NIHL）是一个普遍的和日益严重的健康问题，但知识的基本细胞 参与NIHL和潜在的内源性保护信号系统的过程仍然不完整。 耳蜗保护的最初且仍占主导地位的模型是基于橄榄耳蜗系统活动，但 其他信号系统，包括下丘脑-垂体-肾上腺（HPA）轴也被认为 保护耳蜗免受听觉损伤。对这两种模式提出了重要的警告 保护耳蜗的方法关注的主要问题是刺激的强度和时间， 激活信号，以及保护作用发生的时间过程。我们最近公布的数据表明， 耳蜗受局部神经内分泌控制。所有主要的信号分子表达沿着经典的 HPA轴也表达并完全包含在耳蜗细胞内。这些数据有力地表明 存在局部活跃的HPA等效耳蜗应力轴。我们的初步数据表明， 耳蜗能够响应促肾上腺皮质激素释放而释放皮质酮和醛固酮 因子（CRF）和促肾上腺皮质激素（ACTH），我们以前已经证明这两种激素是 在耳蜗中表达。我们以前也表明，CRF信号在coch中起着不可或缺的作用， 莱亚。CRFR 1的消融产生25 dB的灵敏度损失，而CRFR 2的消融产生20 dB的增益， 敏感性，而在低至50 dB SPL的暴露后，对ABR阈值偏移的敏感性增加 考虑到与当前耳蜗保护模型有关的关于其激活要求的警告， 高强度的声音，我们的数据表明，耳蜗应力轴可能是活跃的，在较低的强度 声音暴露，我们提出，这种耳蜗HPA等效信号系统代表了一种新的， 参与耳蜗保护的未知元素。为了测试耳蜗是否使用类似HPA的信号， 保护的naling系统，更多的信息是需要关于耳蜗细胞应力的基础知识 轴线例如，该系统是否由声音激活，以及其选择性 激活可以防止NIHL。这些未知因素是深入了解耳蜗的障碍 发信号。我们的假设是耳蜗应力轴作为一个独立的局部（快速反应）神经元， 由声音激活的内分泌控制系统，有助于调节敏感性和压力- 通过局部类固醇激素释放后暴露于破坏性刺激的反应。我们将追踪两个特殊- cific的目的，旨在：1）识别耳蜗中接受CRF信号并有能力产生 类固醇激素，并确定是否释放是声音诱发的;和2）测试选择性激活的能力 耳蜗CRF信号系统在预防NIHL中的作用。该项目的数据对于以下方面很重要： 写一个竞争性的R 01，旨在研究类固醇从特定细胞群释放的作用。

Noise-induced hearing loss (NIHL) is a pervasive and growing health problem, yet knowledge of basic cellular processes involved in both NIHL and potential endogenous protective signaling systems remain incomplete. The initial, and still predominant, model of cochlear protection is based on olivocochlear system activity, but other signaling systems, including the hypothalamic-pituitary-adrenal (HPA) axis also have been suggested to protect the cochlea against acoustic injury. Significant, caveats have been raised concerning these two models of cochlear protection, however. The main issues of concern are the intensity and time of stimuli required to activate signaling, and the time course for protective effects to occur. Our recently published data indicate that the cochlea is under local neuroendocrine control. All major signaling molecules expressed along the classic HPA axis are also expressed and completely contained within cells in the cochlea. This data strongly suggests the existence of a locally active HPA-equivalent cochlear stress axis. Our preliminary data demonstrate that the cochlea is capable of releasing both corticosterone and aldosterone in response to corticotropin releasing factor (CRF) and adrenocorticotropin hormone (ACTH), both of which we have previously demonstrated to be expressed in the cochlea. We have also previously shown that CRF signaling plays an integral role in the coch- lea. Ablation of CRFR1 produces a 25dB loss of sensitivity, while ablation of CRFR2 generates a 20dB gain of sensitivity, while increasing susceptibility to ABR threshold shifts following exposures as low as 50dB SPL Given the caveats related to current models of cochlear protection with respect to their requirement for activa- tion by high intensity sounds, and our data suggesting the cochlear stress axis may be active at lower intensity sound exposures, we propose that this cochlear HPA-equivalent signaling system represents a novel, previ- ously unrecognized element involved in cochlear protection. To test whether the cochlea uses an HPA-like sig- naling system for protection, more information is required concerning the basics of the cochlear cellular stress axis. For example, it remains unproven whether the system is activated by sound, and whether its selective activation can protect against NIHL. These unknowns are impediments to a deeper understanding of cochlea signaling. Our hypothesis is that the cochlear stress axis acts as an independent local (fast responding) neuro- endocrine control system activated by sound that contributes to the modulation of sensitivity and stress- responses via local steroid hormone release following exposure to damaging stimuli. We will pursue two spe- cific aims, designed to: 1) identify cells in the cochlea that receive CRF signaling and are competent to produce steroid hormones and to identify whether release is sound evoked; and 2) test the ability of selective activation of the cochlear CRF signaling system in protecting against NIHL. Data from this project will be important for writing a competitive R01 designed to examine the role of steroid release from specific cell populations.