CNS Pathways Integrating Respiratory and Metabolic Control

描述（由申请人提供）：动脉血气和酸碱平衡的维持需要代谢的变化与肺泡通气的比例变化相匹配。瘦素是一种细胞因子激素，在能量平衡中具有核心作用，并被认为是小鼠和人类中通气与代谢方面匹配的重要贡献者。这在临床上是相关的，因为例如，一部分肥胖人群对瘦素和低血糖具有抗性，同时伴有动脉PCO 2增加和动脉PO 2减少（肥胖低通气综合征，OHS）。一般认为，瘦素通过中枢神经系统机制刺激呼吸。然而，CNS内的多个核含有表达瘦素受体的神经元（称为LepRb神经元），并且几乎没有证据表明哪些组参与呼吸刺激。基于初步的研究和文献，我们假设，多个特定群体的脑干和下丘脑LepRb神经元有助于呼吸刺激。此外，肽递质/调节剂已与许多这些细胞群和药理学操纵这些途径中的活性可以提供基础，为未来的发展，临床相关的药理学操纵这些途径中的活性。将有三个具体目标。在目的1中，我们将利用Cre-loxP技术和转基因小鼠中特定LepRb神经元群的光遗传学激活或沉默。响应于特定LepRb神经元组的选择性激活的呼吸刺激将表明在呼吸中的作用。神经元活性标记物c-Fos的免疫组织化学将用于鉴定可能作为中继核参与特异性神经元凋亡途径的细胞群。 LepRb神经元群参与中枢神经系统呼吸回路。这种潜在的作用将通过使用全身瘦素给药刺激呼吸，同时确定靶核的双侧失活是否减少呼吸刺激来测试。在目标2中，我们将结合联合收割机标准的逆行追踪与一种新的跨突触病毒追踪方法，该方法仅穿过1个突触，以指定瘦素激活的刺激呼吸的单突触和多突触通路。这些通路中所含的肽递质将通过化学方法进行鉴定。在目标3中，体外研究将确定瘦素通路内的肽递质对脑干呼吸神经元的影响，并确定其影响的细胞/分子机制。联合研究将系统地确定中枢神经系统LepRb神经元群刺激呼吸响应全身瘦素管理。此外，介导这种影响的少突触通路将被揭示， 它们的肽递质。此外，将定义有助于刺激呼吸的相关细胞/分子机制。这些发现可以为OHS患者的药物治疗的未来发展奠定基础。

DESCRIPTION (provided by applicant): Maintenance of arterial blood gas and acid-base homeostasis requires that a change in metabolism be matched by a proportional change in alveolar ventilation. Leptin, a cytokine hormone, has a central role in energy balance and has been implicated as an important contributor to the matching of ventilation to an aspect of metabolism in both mice and humans. This is clinically relevant as, for example, a subset of obese humans is resistant to leptin and hypoventilate with both an increase in arterial PCO2 and decrease in arterial PO2 (obesity hypoventilation syndrome, OHS). It is generally believed that leptin stimulates breathing through a CNS mechanism. However, multiple nuclei within the CNS contain leptin receptor expressing neurons (termed LepRb neurons) and there is almost no evidence as to which groups are involved in the stimulation of breathing. Based on preliminary studies and the literature we hypothesize that multiple specific groups of brainstem and hypothalamic LepRb neurons contribute to the respiratory stimulation. Additionally, peptide transmitters/modulators have been associated with many of these cell groups and pharmacologic manipulation of activity in these pathways could provide the basis for future development of clinically relevant pharmacological manipulation of activity in these pathways. Three Specific Aims will be addressed. In Aim 1, we will take advantage of Cre-loxP technology and optogenetic activation or silencing of specific LepRb neuronal groups in transgenic mice. Stimulation of breathing in response to selected activation of a specific LepRb neuronal group will suggest a role in breathing. Immunohistochemistry for the neuronal activity marker, c-Fos, will be used to identify cell groups that may participate as relay nuclei in pathways from specific LepRb neuronal groups to the CNS respiratory circuits. This potential role will be tested by using systemic leptin administration to stimulate breathing while determining whether bilateral inactivation of the target nucleus reduces the respiratory stimulation. In Aim 2, we will combine standard retrograde tracing with a novel transynaptic viral tracing method that crosses only 1 synapse to specify leptin-activated mono- and poly-synaptic pathways stimulating breathing. The peptide transmitters contained within these pathways will be identified immunohistochemically. In Aim 3, in vitro studies will define the impact of peptide transmitters within the leptin pathways on brainstem respiratory neurons and identify the cellular/molecular mechanisms underlying their influence. The combined studies will systematically identify CNS LepRb neuronal groups that stimulate breathing in response to systemic leptin administration. Additionally, paucisynaptic pathways mediating this influence will be revealed as will the identity of their peptide transmitters. Moreover, associated cellular/molecular mechanisms contributing to a stimulation of breathing will be defined. The findings could form the basis for the future development of pharmacotherapies for OHS patients.