Masticatory sensitization of trigeminal ganglion sensory neurons

描述（由申请人提供）：慢性治疗难治性三叉神经痛是一个主要的医疗问题，颞下颌关节（TMJ）疼痛是头面部疼痛的最常见形式。TMJD动物模型的缺陷是阻碍合理靶向治疗的障碍之一。另一个障碍是对TMJ疼痛和功能障碍的分子、细胞和神经回路机制缺乏清晰的理解。我们最近调整了咬合力测量作为小鼠TMJ炎性疼痛的读数，并将这种新方法应用于Trpv 4-/-小鼠。在支配TMJ的三叉神经节（TG）神经元中表达的“机械”-TRP，TRPV 4，是TMJ炎症后咬合力降低的关键。此外，TMJ炎症后TG中其他疼痛相关TRP通道（“疼痛TRP”）的表达和细胞外信号调节蛋白激酶（ERK）的激活受TRPV 4调节。基于这些机制的发现，我们的第一个目标是调查TRPV 4是否通过ERK调节其他痛相关的TRP通道在TG神经元。为此，我们提出：（1）确定TMJ炎症中TG中TRPV 4依赖的“疼痛TRP”表达是否是神经元的，并且与TRPV 4表达共定位;（2）通过使用TRPV 4感觉神经元特异性敲除小鼠来测试TRPV 4在调节TG神经元中的“疼痛TRP”中的作用;（3）利用表达神经元特异性显性负性丝裂原活化蛋白激酶-激酶（dnMEK）的小鼠进一步明确ERK在调节TG神经元“痛TRP”中的作用。此外，考虑到临床患者TMJD疼痛的慢性性，我们建议通过注射负载在碳纳米颗粒上的化学刺激物来开发更持久的TMJ炎症，从而产生“缓释”制剂。通过开发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。我们将在更慢性的模型中验证Trpv 4的关键作用。本研究计划将阐明“疼痛-TRP”通道在颞下颌关节疼痛中的独特作用。其中，TRPV 4可能是支配TMJ的TG感觉神经元中促伤害性信号传导的重要调节剂。此外，所提出的研究将促进我们对颞下颌关节疼痛持续性机制的理解，并导致更合理和有效的治疗。研究议程嵌入在培训计划中，充分利用杜克大学和北卡罗来纳大学教堂山分校丰富多样的机构资源，使申请人能够在TMJ疼痛研究中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.