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

与颞下颌关节紊乱病(TMJD)相关的咀嚼和自发疼痛是一种 是口腔面部疼痛的普遍和重要因素。对于太多患者来说，TMJD疼痛是一种 令人衰弱的慢性三叉神经疼痛状况，对他们的生活产生了压倒性的影响。TMJD的痛苦无疑是 严重的未得到满足的医疗需求。不幸的是，目前治疗TMJD疼痛的方法缺乏有效性， 主要是由于：1)现有的TMJD临床前模型不能忠实地模拟患者的基数 抱怨；2)TMJD背后的分子、细胞和神经回路机制的难以捉摸 疼痛。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，Pain-TRPs，表达 三叉神经节(TG)感觉神经元与急性和慢性疼痛密切相关。 并代表了开发合理指导的止痛策略的可能的真实靶点。然而， 它们在TMJD咀嚼和自发性疼痛中的直接机械作用是难以捉摸的，需要 澄清。在我们之前发表的初步研究中，我们开发并验证了咬合力和 条件性位置偏爱分析用于测量咀嚼痛和自发性疼痛 TMJ炎症性损伤或咬肌肌腱结扎，这两种方法都会引起长时间的 持久的痛苦行为。使用咬合力测量方法，我们发现TMJ炎症引起的咀嚼痛 TRPV4基因敲除(KO)小鼠的疼痛显著减弱，但并未完全逆转，提示残余疼痛 可能是由其他疼痛-TRP介导的。我们的基因表达研究表明，TRPV1和TRPA1 在TMJ炎症反应中，TG中的表达上调，而且是以TRPV4依赖的方式。 因此，我们假设TRPV1和TRPA1与TRPV4一样，与TMJD疼痛有关，特别是通过 它们发出的信号。这一假设将使用我们的两个TMJ损伤模型进行验证。痛苦- 行为读出的量度将是咬合力和条件性位置偏好。我们将采用以下组合 靶基因和选择性神经元的药理学和遗传功能丧失方法 使用特定色氨酸激动剂与带正电的利多卡因衍生物(QX314)联合沉默。另外，我们 将针对TMEM100，一个最近发现的TRPV1-TRPA1功能相互作用的适配器，通过使用 TMEM100-局部注射抑制肽和感觉神经元-TMEM100条件基因敲除小鼠。我们的 三个特定的目标将检查TRPV1，TRPV4，TRPA1和TMEM100在TMEM100的发病机制中的作用 TMJD病理性疼痛包括神经源性炎症的评估，其发病机制 我们收集了令人兴奋的飞行员数据，揭示了它对TMJD疼痛的关键贡献。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的未得到满足的医疗需求 阿片类药物流行的时代，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.