Major Burn Injury and its Effects on Acute and Superimposed Surgical Pain

强烈的基线疼痛及其在手术中的进一步加重（例如，皮肤移植手术）是伴随的 烧伤（BI）。阿片类药物是主要BI后疼痛治疗的主要药物，但其镇痛效果较差。 不成熟的3周龄（未受伤）受试者表现出更高的疼痛敏感性，以及与年龄相关的改变。 受伤后的免疫反应未经治疗的BI疼痛有长期并发症。因此，阐明病因 年轻人强烈的背景疼痛和夸大的手术疼痛的因素和分子机制 BI受试者和发现新的非阿片类药物治疗，以减轻夸大的疼痛是赠款的目标。 非烧伤文献支持肠道-微生物组-脑-轴之间的强大通讯，可能由两者介导 循环巨噬细胞和迷走神经传入神经从肠道，以诱导神经病变的变化，通过小胶质细胞 activation. BI引起显著的肠道生态失调，并有小胶质细胞活化和神经炎症的证据。 我们认为，背景BI疼痛和叠加夸大手术疼痛是由于先天免疫记忆 小胶质细胞颈部传出迷走神经刺激（VNS）具有抗炎特性， α 7乙酰胆碱受体（α 7 AChRs）表达于单核细胞和小胶质细胞。拟议的研究利用了 通过使用选择性配体GTS-21或VNS激活内源性途径来减少小胶质细胞活化 单核细胞/小胶质细胞中的α 7 AChR或通过外源性口服疗法改善肠道生态失调，所有这些都将提供 消除夸大的BI疼痛并避免阿片类药物副作用的新型非阿片类药物策略。 具体目标1检验了脊髓小胶质细胞炎性表型有助于降低 未受伤的未成熟大鼠（IR）的痛阈和严重BI后的夸大手术疼痛。这些研究 将显示：（a）与成熟大鼠（MR）相比，初始IR具有较低的疼痛阈值;（B）BI至IR的耐受性，以及 通过过度的脊髓小胶质细胞激活和增加脊髓疼痛信号传导来增强术后疼痛 蛋白质表达将比较雄性和雌性大鼠。 具体目标2检验了BI诱导的肠道健康改变和肠道-脊髓轴信号传导发挥作用的假设 这些研究将显示（a）BI诱导肠道生态失调（改变的肠道植物群， 增加的肠道通透性和细菌及其代谢物的易位），这有助于小胶质细胞 （B）代谢组学将证明炎性表型的免疫细胞代谢功能障碍;（c） 蛛网膜下迷走神经切断术或巨噬细胞耗竭减少炎症、小胶质细胞活化和BI疼痛。 具体目标3检验了以下假设：选择性激动剂配体GTS-21刺激或VNS α 7 AChR， 减少炎症或肠道微生物组操纵以改善肠道健康将防止小胶质细胞活化 减轻BI疼痛。（a）GTS-21后的抗伤害感受和抗炎作用 （B）口服丁酸钠或选择性抗生素治疗促进 肠道微生物组健康，减少肠道通透性，全身炎症，小胶质细胞活化和BI疼痛。

Intense baseline pain and its further exaggeration with procedures (e.g., skin graft surgery) is a concomitant feature of burn Injury (BI). Opioids, the main stay of pain treatment after major BI, have poor analgesic effects. Immature 3-week old (uninjured) subjects exhibit higher pain sensitivity, together with age-associated altered immune responses after injury. Untreated BI pain has long-term complications. Thus, elucidating the etiological factors and molecular mechanisms underlying intense background pain and exaggerated surgical pain in young BI subjects and discover novel non-opioid therapeutics to mitigate exaggerated pain are the goals of the grant. Non-burn literature supports the strong gut-microbiome-brain-axis communication, possibly mediated by both circulating macrophages and vagal afferent nerves from the gut, to induce neuropathic changes via microglia activation. BI causes marked gut dysbiosis with evidence of microglia activation and neuro-inflammation. We posit that background BI pain and superimposed exaggerated surgical pain is due to innate immune memory of microglia. Cervical efferent vagus nerve stimulation (VNS) has anti-inflammatory properties mediated via α7acetylcholine receptors (α7AChRs) expressed in monocytes and microglia. The proposed studies harness endogenous pathways to curtail microglia activation by using a selective ligand, GTS-21, or VNS to activate α7AChRs in monocyte/microglia or improve gut dysbiosis by exogenous oral therapies, all of which will provide novel non-opioid strategies to abrogate the exaggerated BI pain and avoid opioid side effects. Specific Aim 1 tests the hypothesis that spinal microglia inflammatory phenotype contributes to the lowered pain thresholds in uninjured immature rats (IR) and exaggerated procedural pain after major BI. These studies will show: (a) naive IR have a lower pain threshold compared to mature rats (MR); (b) BI to IR prolongs and enhances post-surgical pain by exaggerated spinal microglia activation and increased spinal pain-signaling protein expression. Both male and female rats will be compared. Specific Aim 2 tests the hypothesis that BI-induced altered gut health and gut-spinal cord axis signaling plays a pivotal role in microglia priming in IR. These studies will show (a) BI induces gut dysbiosis (altered gut flora, increased gut permeability and translocation of bacteria and their metabolites), which contributes to microglia activation, (b) metabolomics will demonstrate immune cell metabolic dysfunction of inflammatory phenotype; (c) sub-diaphragmatic vagotomy or macrophage depletion decreases inflammation, microglia activation and BI pain. Specific Aim 3 tests the hypothesis that selective agonist ligand, GTS-21, stimulation or VNS of α7AChRs to decrease inflammation, or gut microbiome manipulation to improve gut health will prevent microglia activation and decrease BI pain. This aim will show: (a) anti-nociceptive and anti-inflammatory effects after GTS-21 stimulation or VNS in BI and incisional pain; (b) oral sodium butyrate or selective antibiotic treatment promotes gut microbiome health, reduces gut permeability, systemic inflammation, microglia activation and BI pain.