Role of purinergic signaling and glia in TMJ nociception

颞下颌关节紊乱病(TMD)包括一系列以关节疼痛为表现的疾病 颞下颌关节(TMJ)和咀嚼肌。TMD是最常见的非牙科疾病 口腔面部疼痛，但其潜在的生理和细胞机制却知之甚少。 值得注意的是，痛性TMD在女性中的患病率高于男性，而且两者之间的相关性很差 明显的受伤迹象和疼痛强度分级。关于促炎因子水平升高的报道 非骨关节炎性TMD患者滑液样本中的分子提示低级别TMJ 炎症是TMD的常见特征，但如果没有直接的滑液，很可能不会被发现。 取样。中心假设是低级别TMJ炎症启动三叉神经节 (TG)神经元，并诱导持续性痛敏，被视为改变的反应特性 延髓(VC/C1-2)神经元和颌肌活动。我们认为，嘌呤能(P2) 受体和神经胶质细胞激活在TMJ启动和维持痛觉过敏中起关键作用 刺激和性依赖的方式。这个项目的长期目标是确定 干扰神经元和神经胶质细胞上的特定P2受体是治疗的靶点 人类TMJ伤害性感受和TMD疼痛的管理。定量感觉测试(QST) 该方案是为了评估对TMJ反应神经元的治疗效果。会聚的线条 使用电生理、行为、分子和解剖学方法的证据表明 三个问题：1)短暂的低级别TMJ炎症是否足以引起持续的变化 TMJ反应性TG和VC/C1-2神经元的特性、颌肌活动和颌骨运动；2) 嘌呤能受体在TMJ启动中的作用是什么；以及3)胶质细胞在TMJ启动中的作用是什么 TMJ伤害性的维持？与以前的研究不同，该模型使用单次暴露于 非组织损伤性炎剂对雄性和大鼠TMJ反应神经元回路的激活作用 雌性大鼠及其配偶这种侮辱对TMJ反应神经元的反应 表型。目的1在TMJ启动条件下建立QST协议，并确定 预激对三叉神经节神经元、VC/C1-2神经元特性、MMemg活动和颌骨的影响 有动静。目的2决定密切相关的P2受体的表达和蛋白水平 TG和VC/C1-2神经元及其受体在神经活动、颌肌活动中的作用 和下巴的运动。目的3与P2受体的表达和蛋白水平密切相关 三叉神经节内卫星胶质细胞和VC/C1-2神经元小胶质细胞的相关性及胶质细胞的作用 TMJ痛觉过敏中的激活。神经元-神经胶质细胞的通讯是持续性的一个重要特征 炎性痛觉过敏在其他模型中存在，但在TMJ伤害性感受中仍不明确。什么时候 再加上神经记录和颌肌反射，P2受体的抑制密切相关 对于神经元或胶质细胞，小胶质细胞抑制炎性小体的形成，并阻断胶质细胞特异性 通过药理和干扰RNA方法产生的分泌产物将增强 了解持续性TMJ痛觉过敏的神经机制。

Temporomandibular joint disorders (TMD) include a family of conditions that present with pain in the temporomandibular joint (TMJ) and muscles of mastication. TMD is the most common non-dental orofacial pain, yet the underlying physiological and cellular mechanisms are poorly understood. Painful TMD is notable for a higher prevalence in women than men, and poor correlation between overt signs of injury and ratings of pain intensity. Reports of elevated levels of pro-inflammatory molecules in synovial fluid samples of non-osteoarthritic TMD patients suggest that low grade TMJ inflammation is a common feature of TMD, but likely goes undetected without direct synovial fluid sampling. The central hypothesis is that low grade TMJ inflammation primes trigeminal ganglion (TG) neurons and induces persistent hyperalgesia seen as altered response properties of spinomedullary (Vc/C1-2) neurons and jaw muscle activity. We propose that purinergic (P2) receptors and glial cell activation play key roles in TMJ priming and maintain hyperalgesia in a stimulus- and sex-dependent manner. The long-term goal of this project is to determine if interference with specific P2 receptors on neurons and glia are therapeutic targets for managing TMJ nociception and TMD pain in humans. A quantitative sensory testing (QST) protocol is developed to assess treatment effects on TMJ-responsive neurons. Converging lines of evidence using electrophysiological, behavioral, molecular, and anatomical approaches address three issues: 1) is transient low grade TMJ inflammation sufficient to cause persistent changes in the properties of TMJ-responsive TG and Vc/C1-2 neurons, jaw muscle activity and jaw movement; 2) what is the role of purinergic receptors in TMJ priming; and 3) what is the role of glial cells in maintenance of TMJ nociception? Unlike previous studies, this model uses a single exposure to a non-tissue damaging inflammatory agent to prime TMJ-responsive neuronal circuits in male and female rats and couples this insult to the responses of TMJ-responsive neurons with identified phenotypes. Aim 1 establishes the QST protocol under TMJ primed conditions and determines the effects of priming on the properties of TG neurons, Vc/C1-2 neurons, on MMemg activity and jaw movement. Aim 2 determines the expression and protein levels of P2 receptors closely associated with TG and Vc/C1-2 neurons and the role of those receptors on neural activity, jaw muscle activity and jaw movement. Aim 3 determines the expression and protein levels of P2 receptors closely associated with satellite glia in TG and microglia at Vc/C1-2 neurons and the role of glial cell activation in TMJ hyperalgesia. Neuron-glia communication is a critical feature of persistent inflammatory hyperalgesia in other models, but remains poorly defined in TMJ nociception. When coupled with neural recording and jaw muscle reflexes, inhibition of P2 receptors closely associated with neurons or glia, inhibition of inflammasome formation by microglia and blockade of glia-specific secretory products by pharmacological and interference RNA approaches will enhance the understanding of neural mechanisms underlying persistent TMJ hyperalgesia.