Intermittent Hypoxia-Induced Inflammation Modulates Respiratory Plasticity

描述(申请人提供)：破坏控制呼吸的神经系统的因素降低了对病理的补偿能力，威胁到生命本身。可塑性是神经系统的基本特征，包括控制呼吸的神经系统。指导这一提议的基本假设是，全身炎症损害了呼吸运动的可塑性，破坏了对多种病理的补偿能力，包括慢性肺部疾病、创伤性、缺血性和退行性神经障碍以及阻塞性睡眠呼吸暂停。我们建议研究炎症损害呼吸运动可塑性的机制，即急性间歇性低氧后的膈神经长期易化(PLTF)。我们将比较脂多糖(LPS)引起的炎症和一天严重间歇性低氧(SIH)引起的炎症；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存在的临床疾病，对人类健康具有重大影响。令人兴奋的初步数据表明，内毒素和SiH都通过脊髓炎症来阻断pLTF。由于内毒素和SIH在不同类型的脊髓细胞中诱导不同的基因表达，但对pLTF有相似的影响，我们提出了一个统一的假设，即多个炎性分子聚集在共同的“下游”信号级联上，从而限制呼吸运动的可塑性。我们将使用一种创新的多学科方法来验证我们的假设；实验方法包括：麻醉大鼠的膈神经记录，非麻醉大鼠的隔膜肌电记录，标记的膈运动神经元中蛋白质的免疫组织化学分析，新分离的脊髓星形胶质细胞和小胶质细胞中炎症基因的表达分析，以及用于评估已确定细胞类型的蛋白质的流式细胞术。5个具体的假说将被验证以促进我们的理解：1)全身性内毒素和SIH引起脊髓炎症，从而损害膈和横隔膜LTF；2)内毒素和SIH不同程度地损害到膈运动促进(PMF)的不同通路。我们将确定内毒素和SiH对ERK依赖(例如，pLTF)、Akt依赖和ERK/Akt依赖的PMF的影响；3)LPS和SiH诱导不同的炎症特征。SIH仅影响脊髓小胶质细胞，而内毒素也影响星形胶质细胞；4)尽管有不同的炎症过程，但内毒素和SIH通过共同的“下游”机制损伤pLTF，该机制涉及隔膜运动神经元中p38 MAP激酶的激活；5)脊髓p38活性增加隔膜运动神经元中的蛋白磷酸酶2A活性，从而抑制ERK并抑制pLTF。了解炎症破坏呼吸可塑性的机制是至关重要的，因为炎症可能会在病理状态下降低自然的代偿性可塑性的能力。我们的长期目标是利用和促进呼吸可塑性作为一种治疗策略来治疗毁灭性的呼吸障碍，例如在颈椎损伤或运动神经元疾病期间。 公共卫生相关性：所有挑战产生充足呼吸能力的肺部和中枢神经系统疾病都与炎症有关，包括慢性肺部疾病、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。尽管这些病理对公众健康有深远的影响，但关于炎症对控制呼吸的神经系统的影响几乎一无所知。我们的目标是研究炎症破坏一种被称为长期促进的呼吸运动可塑性模型的机制，因为这一知识可能指导开发治疗呼吸障碍的新治疗策略。

DESCRIPTION (provided by applicant): 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 facilitation (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 (e.g., 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. PUBLIC HEALTH RELEVANCE: All lung and CNS disorders that challenge the ability to generate adequate breathing are associated with inflammation, including chronic lung diseases, traumatic, ischemic and degenerative neural disorders, and obstructive sleep apnea. Although these pathologies have profound consequences for public health, virtually nothing is known concerning the impact of inflammation on the neural system controlling breathing. Our goal is to investigate mechanisms whereby inflammation undermines a well-studied model of respiratory motor plasticity known as long-term facilitation since this knowledge may guide the development of novel therapeutic strategies to treat breathing disorders.