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

剧烈的基线疼痛及其在手术(例如皮肤移植手术)中的进一步夸大是伴随而来的 烧伤(BI)的特点。阿片类药物是BI后疼痛治疗的主要药物，其止痛效果较差。 未成熟的3周大(未受伤)的受试者表现出更高的疼痛敏感性，以及与年龄相关的改变 损伤后的免疫反应。未经治疗的BI疼痛会产生长期的并发症。因此，阐明病原学 青少年剧烈背景性疼痛和夸大性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以减轻夸大的疼痛是赠款的目标。 非烧伤文献支持强大的肠道-微生物组-脑轴通讯，可能由两者介导 肠道巨噬细胞和迷走神经通过小胶质细胞引起神经病理性改变 激活。BI导致明显的肠道生物失调，有证据表明小胶质细胞激活和神经炎症。 我们假设背景BI疼痛和叠加的夸张手术疼痛是由于先天免疫记忆所致 小胶质细胞。颈部传出迷走神经刺激(VNS)具有抗炎作用。 α7乙酰胆碱受体(α7AChRs)表达于单核细胞和小胶质细胞。拟议中的研究利用 使用选择性配体GTS-21或VNS激活抑制小胶质细胞激活的内源性途径 α7AChRs在单核细胞/小胶质细胞中的表达或通过外源性口服疗法改善肠道菌群失调，所有这些都将提供 新的非阿片类药物策略，以消除夸大的BI疼痛，避免阿片类药物副作用。 特异性目标1检验脊髓小胶质细胞炎性表型与低血压有关的假说 未受损伤的未成熟大鼠(IR)的痛阈值和重大BI后夸大的程序性疼痛。这些研究 将显示：(A)幼稚的IR比成熟的大鼠(MR)有更低的痛阈值；(B)BI到IR延长和 通过夸大脊髓小胶质细胞的激活和增加脊髓疼痛信号来增强术后疼痛 蛋白质表达。雄鼠和雌鼠都将被比较。 《特定目标2》验证了BI诱导的肠道健康改变和肠道-脊髓轴信号转导起作用的假设 小胶质细胞启动在IR中的关键作用。这些研究将表明：(A)BI导致肠道菌群失调(肠道菌群改变， 增加肠道通透性和细菌及其代谢物的移位)，这有助于小胶质细胞 激活，(B)代谢组学将显示炎症表型的免疫细胞代谢功能障碍；(C) 隔膜下迷走神经切断术或巨噬细胞减少术可减少炎症、小胶质细胞活化和BI疼痛。 特异靶3验证了选择性激动剂配体、GTS-21、刺激或α7AChRs的VNS对 减少炎症，或通过肠道微生物组操作来改善肠道健康，将防止小胶质细胞激活 并减轻BI疼痛。这一目标将显示：(A)GTS-21后的抗伤害性和抗炎作用 BI和切口痛的刺激或VNS；(B)口服丁酸钠或选择性抗生素治疗促进 肠道微生物群健康，减少肠道通透性，全身炎症，小胶质细胞激活和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.