Intermittent Hypoxia-Induced Inflammation Modulates Respiratory Plasticity

项目总结/摘要 破坏控制呼吸的神经系统的因素会降低补偿呼吸的能力。 病理学威胁生命本身可塑性是包括神经系统在内的神经系统的基本特征 控制呼吸。指导这一建议的基本假设是，全身炎症 损害呼吸运动可塑性，破坏补偿多种病理的能力， 包括慢性肺病、创伤性、缺血性和退行性神经疾病以及阻塞性睡眠 呼吸暂停我们建议研究炎症损害一个充分研究的模型的机制， 呼吸运动可塑性，急性间歇性缺氧后膈神经长期易化（pLTF）。我们将 将脂多糖（LPS）诱导的炎症与一天严重间歇性 缺氧（sIH）; sIH模拟阻塞性睡眠呼吸暂停的各个方面，阻塞性睡眠呼吸暂停是一种广泛的临床疾病， 对人类健康的影响。令人兴奋的初步数据表明，LPS和sIH均通过脊髓阻断pLTF， 炎症由于LPS和sIH在不同的脊髓细胞类型中引起不同的基因表达， 类似的影响pLTF，我们提出了一个统一的假设，即多种炎症分子 汇聚在一个共同的“下游”信号级联，限制呼吸运动可塑性。 一个创新的，多学科的方法将被用来测试我们的假设;实验方法 包括：麻醉大鼠的膈神经记录，未麻醉大鼠的膈肌EMG记录， 标记膈运动神经元蛋白免疫组化分析，炎性基因分析 在新鲜分离的脊髓星形胶质细胞和小胶质细胞中的表达，以及流式细胞术来评估 识别细胞类型。我们将检验五个具体的假设以加深我们的理解：1）全身性LPS 和sIH引起脊髓炎症，从而损害膈和膈肌LTF; 2）LPS和sIH差异 损害膈运动促进（pMF）不同途径。我们将确定LPS和sIH对ERK的影响- 依赖（例如，pLTF）、Akt依赖性和ERK/Akt依赖性pMF; 3）LPS和sIH引起不同的炎症反应， 数据区. sIH仅影响脊髓小胶质细胞，而LPS也影响星形胶质细胞; 4）尽管不同 炎症谱、LPS和sIH通过涉及p38 MAP的共同“下游”机制损害pLTF 膈运动神经元中的激酶激活;和5）脊髓p38活性增加蛋白磷酸酶2A 膈运动神经元的活动，从而抑制ERK并限制pLTF。理解机制 其中炎症破坏呼吸可塑性是非常重要的，因为炎症可能 在病理状态下降低自然的、补偿性的可塑性的能力。我们的长远目标是 利用和促进呼吸可塑性作为治疗毁灭性呼吸障碍的治疗策略， 例如在颈椎损伤或运动神经元疾病期间。

PROJECT SUMMARY/ABSTRACT Factors that undermine the neural system controlling breathing diminish the capacity to compensate for pathology, threatening life itself. Plasticity is an essential feature of neural systems, including the neural system controlling breathing. The fundamental hypothesis guiding this proposal is that systemic inflammation impairs respiratory motor plasticity, undermining the ability to compensate for multiple pathologies, including chronic lung disease, traumatic, ischemic and degenerative neural disorders, and obstructive sleep apnea. We propose to investigate mechanisms whereby inflammation impairs a well-studied model of respiratory motor plasticity, phrenic long-term facilitiation (pLTF) following acute intermittent hypoxia. We will contrast inflammation induced by lipopolysaccharide (LPS) with that induced by one day of severe intermittent hypoxia (sIH); sIH simulates aspects of obstructive sleep apnea, a widespread clinical disorder with major implications for human health. Exciting preliminary data suggest that both LPS and sIH block pLTF via spinal inflammation. Since LPS and sIH elicit differential gene expression in different spinal cell types, yet have similar effects on pLTF, we propose a unifying hypothesis whereby multiple inflammatory molecules converge on a common "downstream" signaling cascade that constrains respiratory motor plasticity. An innovative, multidisciplinary approach will be used to test our hypotheses; experimental approaches include: phrenic nerve recordings in anesthetized rats, diaphragm EMG recordings in unanesthetized rats, immunohistochemical analysis of proteins in labeled phrenic motor neurons, analysis of inflammatory gene expression in freshly-isolated spinal astrocytes and microglia, and flow cytometry to assess proteins in identified cell types. Five specific hypotheses will be tested to advance our understanding: 1) Systemic LPS and sIH elicit spinal inflammation, thereby impairing phrenic and diaphragm LTF; 2) LPS and sIH differentially impair distinct pathways to phrenic motor facilitation (pMF). We will determine LPS and sIH effects on ERK- dependent (eg. pLTF), Akt-dependent and ERK/Akt-dependent pMF; 3) LPS and sIH elicit distinct inflammatory profiles. sIH affects only spinal microglia, whereas LPS also affects astrocytes; 4) Despite different inflammatory profiles, LPS and sIH impair pLTF by a common "downstream" mechanism involving p38 MAP kinase activation in phrenic motor neurons; and 5) Spinal p38 activity increases protein phosphatase 2A activity in phrenic motor neurons, thereby inhibiting ERK and constraining pLTF. Understanding mechanisms whereby inflammation undermines respiratory plasticity is of fundamental importance since inflammation may diminish the capacity for natural, compensatory plasticity during pathological states. Our long-range goal is to harness and promote respiratory plasticity as a therapeutic strategy to treat devastating breathing disorders, such as during cervical spinal injury or motor neuron disease.