Masticatory sensitization of trigeminal ganglion sensory neurons

描述(申请人提供)：慢性治疗-顽固性三叉神经痛是一个主要的医学问题，其中颞下颌关节(TMJ)疼痛是最常见的头面部疼痛形式。开发合理的靶向治疗的障碍之一是现有的TMJD动物模型的缺陷。另一个障碍是对TMJ疼痛和功能障碍背后的分子、细胞和神经回路机制缺乏清晰的了解。我们最近采用咬合力测量方法读出小鼠的TMJ炎性疼痛，并将这种新的方法应用于TRPV4-/-小鼠。TMJ神经支配的三叉神经节(TG)神经元中表达的“渗透性机械”-Trp、TRPV4在TMJ炎症后咬合力降低中起关键作用。此外，TMJ炎症后TG中其他疼痛相关Trp通道(“Pain TRPs”)的表达和细胞外信号调节蛋白激酶(ERK)的激活也受到TRPV4的调控。基于这些机制发现，我们的第一个目标是研究TRPV4是否通过ERK调节TG神经元中其他与疼痛相关的Trp通道。为此，我们提议(1)确定TRPV4依赖的“疼痛TRP”在TMJ-炎症中的TG表达是否为神经元，并与TRPV4表达共存；(2)通过使用TRPV4感觉神经元特异性基因敲除小鼠，测试TRPV4在调节TG神经元“疼痛TRPs”中的作用；(3)通过使用表达神经元特异性阴性丝裂原活化蛋白激酶-激酶(DnMEK)的小鼠，更好地确定ERK在调节TG神经元“疼痛TRPs”中的作用。考虑到TMJD疼痛在临床患者中的慢性，此外，我们建议通过在碳纳米颗粒上注射化学刺激剂来开发更持久的TMJ炎症，从而产生缓释的“制剂”。通过开发一种更持久的致关节炎刺激物，我们的小鼠模型将更准确地反映患者对慢性疼痛的主要主诉。我们将在一个更慢性的模型中验证TRPV4的关键作用。这项研究计划将阐明“疼痛-TRP”通道在TMJ疼痛中的独特作用。其中，TRPV4可能在支配TMJ的TG感觉神经元中发挥重要的伤害性信号调节作用。此外，所提出的研究将促进我们对TMJ疼痛持续性的机制的理解，并导致更合理和有效的治疗。研究议程被嵌入到培训计划中，该计划充分利用了杜克大学和北卡罗来纳大学教堂山分校丰富而多样的机构资源，以便申请者能够在TMJ疼痛研究领域发展独立的职业生涯。

DESCRIPTION (provided by applicant): Chronic therapy-refractory trigeminal pain is a major medical problem, with temporo-mandibular-joint (TMJ) pain the most prevalent form of head-face pain. One of the obstacles to development of rationally targeted therapies lies in the shortcomings of available animal models for TMJD. Another roadblock is the lack of clear understanding of molecular, cellular and neural-circuit mechanisms that underlie TMJ pain and dysfunction. We have recently adapted bite-force measurements as read-out of TMJ inflammatory pain in mice, and applied this novel methodology to Trpv4-/- mice. The "osmo-mechano"-TRP, TRPV4, expressed in TMJ-innervating trigeminal ganglion (TG) neurons, is critical for bite-force reduction after TMJ-inflammation. Also, the expression of other pain-relate TRP channels ("pain TRPs"), and activation of extracellular signal-regulated protein kinase (ERK) in the TG after TMJ inflammation are regulated by TRPV4. Based on these mechanistic findings, our first aim is to investigate whether TRPV4 regulates other pain-related TRP channels through ERK in TG neurons. For this aim, we propose (1) to ascertain whether TRPV4- dependent "pain TRP" expression in the TG in TMJ-inflammation is neuronal, and co-localizes with TRPV4 expression; (2) to test the role of TRPV4 in regulating "pain-TRPs" in TG neurons by using Trpv4 sensory neuron-specific knockout mice; (3) to better define the role of ERK in regulating "pain TRPs" in TG neurons by using mice expressing neuron-specific dominant negative mitogen activated protein kinase-kinase (dnMEK). Considering the chronicity of TMJD pain in clinical patients, in addition, we propose to develop a longer-lasting TMJ inflammation by injecting chemical irritant loaded onto carbon nanoparticles, so that a slow-release" formulation results. By development of a longer-lasting arthritogenic irritant, our mouse model will more accurately reflect patients' cardinal complaints of chronic pain. We will verify th critical role of Trpv4 in a more chronic model. This research plan will elucidate the distinct roleof "pain-TRP" channels in TMJ pain. Amongst those, TRPV4 could possibly function as a significant regulator of pro-nociceptive signaling in TG sensory neurons that innervate the TMJ. Moreover, research as proposed will advance our understanding of the mechanisms of the persistent nature of TMJ pain and lead to more rational and effective treatments. The research agenda is embedded in a training plan that takes full advantage of rich and diverse institutional resources available at Duke University and UNC-Chapel Hill, so that the applicant will be positioned well to develop an independent career in TMJ pain research.