Modeling temporomandibular joint disorders pain: role of transient receptor potential ion channels

与颞下颌关节紊乱病（TMJD）相关的咀嚼和自发性疼痛是一种 是导致口面部疼痛的主要原因。TMJD疼痛对太多患者来说是一种 使人衰弱的慢性三叉神经疼痛状况，极大地影响了他们的生活。TMJD疼痛无疑是 严重未满足的医疗需求。不幸的是，目前对TMJD疼痛的治疗缺乏有效性， 这主要是由于：1）当前TMJD临床前模型在忠实地模拟患者的主动脉方面的缺点 TMJD的分子、细胞和神经回路机制尚不明确 痛苦我们的建议旨在解决这两个关键问题。与疼痛相关的TRP通道，疼痛-TRP，表达 三叉神经节（TG）感觉神经元，已严重牵连在急性和慢性疼痛 并代表了开发合理指导的抗疼痛策略的可能的真正目标。然而，在这方面， 它们在TMJD的咀嚼和自发性疼痛中的直接机制作用是难以捉摸的， 澄清。在我们以前发表的和初步的研究中，我们开发和验证了咬合力， 用于测量咀嚼和自发性疼痛的条件性位置偏爱测定， 颞下颌关节炎性损伤或咬肌肌腱结扎，这两种方法都会引起长时间的- 持久的疼痛行为。使用咬合力指标，我们发现颞下颌关节炎症引起的咀嚼疼痛是 在Trpv 4基因敲除（KO）小鼠中，残余疼痛显著减弱，但未完全逆转，这表明 可能是由其他的疼痛TRP介导的。我们的基因表达研究表明，TRPV 1和TRPA 1 TMJ炎症反应中TG的表达上调，而且，以Trpv 4依赖的方式。 因此，我们假设TRPV 1和TRPA 1，像TRPV 4一样，导致TMJD疼痛，特别是通过 他们的信号。这一假设将使用我们的两种TMJ损伤模型进行检验。疼痛- 行为读出度量将是咬合力和条件位置偏好。我们将采用以下组合： 药理学和遗传功能丧失的目标基因以及选择性神经元 使用特异性TRP激动剂与带正电荷的利多卡因衍生物（QX 314）组合进行沉默。另外我们 TMEM 100是最近发现的TRPV 1-TRPA 1功能相互作用的衔接子， TMEM 100-抑制肽用于局部注射和感觉神经元-TMEM 100条件性敲除小鼠。我们 三个具体的目的将研究TRPV 1，TRPV 4，TRPA 1和TMEM 100的发病机制的贡献， TMJD病理性疼痛，包括神经源性炎症的评估， 我们已经收集了令人兴奋的试验数据，揭示了其对TMJD疼痛的关键作用。成功解决我们的 雄心勃勃，但可行的目标将提供丰富的新的基本见解，也很容易翻译 新知识这些将使我们能够克服我们的社会面临的严重未满足的医疗需求， “阿片类药物流行病”的年龄，即慢性TMJD疼痛，通过应用合理指导的新策略。

Masticatory and spontaneous pain associated with temporomandibular joint disorders (TMJD) is a prevalent and significant contributor to orofacial pain. TMJD pain presents for too many patients as a debilitating chronic trigeminal pain condition that impacts their lives overwhelmingly. TMJD pain is undoubtedly a serious unmet medical need. Unfortunately, current treatments for TMJD pain are lacking in effectiveness, primarily due to: 1) shortcomings of current TMJD preclinical models to faithfully model patients’ cardinal complaints; 2) the elusiveness of the molecular, cellular and neural-circuit mechanisms that underlie TMJD pain. Our proposal seeks to address both key issues. TRP channels relevant for pain, pain-TRPs, expressed by trigeminal ganglion (TG) sensory neurons, have been critically implicated in both acute and chronic pain and represent possible bona-fide targets for development of rationally-guided anti-pain strategies. However, their direct-mechanistic roles in masticatory and spontaneous pain of TMJD are elusive and in need of clarification. In our previously published and preliminary studies, we developed and validated bite force and conditioned place preference assays for measuring masticatory and spontaneous pain, induced by inflammatory injury to the TMJ or ligation of the tendon of the masseter muscle, both methods evoking long- lasting pain-behavior. Using bite force metrics, we found TMJ inflammation-induced masticatory pain to be significantly attenuated, but not fully reversed in Trpv4 knockout (KO) mice, suggesting that the residual pain might be mediated by other pain-TRPs. Our gene expression studies demonstrated that TRPV1 and TRPA1 were up-regulated in the TG in response to TMJ inflammation, moreover, in a Trpv4-dependent manner. Therefore, we hypothesize that TRPV1 and TRPA1, like TRPV4, contribute to TMJD pain, in particular via the ensemble of their signaling. This hypothesis will be examined using our two models of TMJ injury. Pain- behavior read-out metrics will be bite force and conditioned place preference. We will employ a combination of pharmacologic and genetic loss-of-function approaches for the targeted genes as well as selective neuronal silencing using specific TRP agonists combined with positively charged lidocaine derivative (QX314). Also, we will target TMEM100, a recently discovered adaptor of TRPV1-TRPA1 functional interactions, by using a TMEM100-inhibitory peptide for local injections and sensory neuron-TMEM100 conditional knockout mice. Our three Specific Aims will examine the contribution of TRPV1, TRPV4, TRPA1 and TMEM100 to pathogenesis of TMJD pathologic pain including assessment of neurogenic inflammation, a pathogenic mechanism for which we have collected exciting pilot data revealing its key contribution to TMJD pain. Successfully addressing our ambitious, yet feasible Aims will provide a rich yield of new fundamental insights and also readily translatable new knowledge. These will empower us to overcome a serious unmet medical need that our society faces in the age of the “opioid epidemic”, namely chronic TMJD pain, by applying a rationally-guided new strategy.