Gut Mechanisms of Stress-Induced Comorbid Visceral Pain

项目总结/摘要 慢性共病疼痛或重叠疼痛状况（COPC）可能是毁灭性的，从个人和 社会立场。患者-主要是女性-患有两种或多种慢性疼痛疾病。 COPC的病因学知之甚少，但与情绪压力有很强的联系，是一个促成因素。 我们发现，在存在神经性三叉神经痛（CCI）的雌性大鼠中，3天强迫游泳（FS） 压力诱发涉及下背部的持久内脏高敏感性。在患有这种内脏共病的大鼠中， 疼痛时，腰骶（L 6-S1）脊髓中5-HT 3R蛋白表达上调， 背根神经节（DRG）。因此，鞘内阻断5-HT 3R可短暂地减弱涉及 痛觉过敏这些观察结果表明，5-HT 3R介导的致敏性参与了原发性 来自肠道的传入神经在应激诱发的共病内脏痛中的作用。然而，潜在的肠道机制 仍然知之甚少。最近积累的证据支持肠道微生物 在应激性内脏痛发病机制中的失调。但目前还不清楚压力诱导的肠道 生态失调介导内脏疼痛发展的细胞和分子机制。我们 检查FS应激前后患有神经性三叉神经痛的大鼠的粪便微生物群组成。我们 初步数据显示，雌性大鼠的肠道微生物组发生了广泛的组成变化， 痛觉过敏此外，来自CCI+FS供体的粪便微生物群转移（FMT）诱导牵涉痛觉过敏 持续性口面疼痛的CCI受试者。这种治疗对幼稚的接受者影响不大， 强调了CCI诱导的下行多巴胺能易化的重要性。另一方面，FMT从 初次供体可减弱CCI+FS受体的牵涉性痛觉过敏。我们假设CCI+FS诱导肠道 这是一种生态失调，其导致来自肠道的初级传入中5-HT 3R的失调。这种失调 仅在涉及转录后机制的蛋白质水平上是明显的，特别是microRNA。最近 文献支持肠道微生物群在调节宿主microRNA表达中的作用。因此，我们进一步 假设在CCI+FS大鼠中，肠道生态失调导致5-HT 3R靶向microRNA的表达减少， 来自肠道的初级传入神经这导致5-HT 3R蛋白表达增加，而不影响其mRNA 程度.我们将使用多学科的方法来测试我们的假设，如三个目标所述。在目标1中，我们 将研究5-HT 3R在持续性牵涉性腰痛发病机制中的作用。在目标2中，我们将 解决肠道微生物生态失调在发生牵涉性腰痛中的作用。在目标3中，我们 研究肠道微生物群相关的5-HT 3R表达改变的转录后机制。我们的研究 旨在梳理外周肠道机制和分子基础之间可能的因果关系 共病内脏疼痛。这个奖项将帮助申请人建立一个成功的职业生涯，在学习复杂的 慢性疼痛障碍及其更复杂的合并症的机制。

Project Summary/Abstract Chronic comorbid pain or overlapping pain conditions (COPCs) can be devastating from both personal and societal standpoints. Sufferers – predominantly women – present with two or more chronic pain disorders. Etiology of COPCs is poorly understood but there is a strong link to emotional stress as a contributing factor. We showed that in female rats with existing neuropathic trigeminal pain (CCI), 3-day forced swimming (FS) stress induces lasting visceral hypersensitivity referred to the lower back. In rats with such comorbid visceral pain, 5-HT3R protein expression is upregulated in the lumbosacral (L6-S1) spinal cord and corresponding dorsal root ganglia (DRG). Consistently, intrathecal blockade of 5-HT3R transiently attenuates referred hyperalgesia. These observations suggest the involvement of 5-HT3R-mediated sensitization of primary afferents from the gut in stress-induced comorbid visceral pain. However, the underlying gut mechanisms remain poorly understood. Accumulating recent evidence supports the importance of gut microbial dysregulation in the pathogenesis of stress-induced visceral pain. But it is unclear whether stress-induced gut dysbiosis mediates cellular and molecular mechanisms underlying the development of visceral pain. We examined fecal microbiota composition of rats with neuropathic trigeminal pain before and after FS stress. Our preliminary data show extensive compositional changes in the gut microbiome of female rats with referred hyperalgesia. Furthermore, fecal microbiota transfer (FMT) from CCI+FS donors induces referred hyperalgesia in CCI recipients with ongoing orofacial pain. This treatment does not much affect naïve recipients, which underscores the importance of CCI-induced descending serotonergic facilitation. On the other hand, FMT from naïve donors attenuates referred hyperalgesia in CCI+FS recipients. We hypothesize that CCI+FS induces gut dysbiosis that contributes to dysregulation of 5-HT3R in the primary afferents from the gut. This dysregulation is evident only at the protein level implicating a posttranscriptional mechanism, particularly microRNAs. Recent literature supports the role of gut microbiota in regulating host microRNA expression. Therefore, we further hypothesize that in CCI+FS rats, gut dysbiosis leads to reduced expression of 5-HT3R-targeting microRNAs in primary afferents from the gut. This results in increased 5-HT3R protein expression without affecting its mRNA levels. We will use multidisciplinary approaches to test our hypotheses as described in three aims. In aim 1, we will examine the role of 5-HT3R in the pathogenesis of persistent referred low back pain. In aim 2, we will address the role of gut microbial dysbiosis in the development of referred low back pain. In aim 3, we will investigate gut microbiota-associated posttranscriptional mechanisms of altered 5-HT3R expression. Our study is designed to tease out possible causality between peripheral gut mechanisms and molecular underpinnings of comorbid visceral pain. This award will help the applicant build a successful career in studying complex mechanisms of chronic pain disorders and their ever more complex comorbidities.