CNS Pathways Integrating Respiratory and Metabolic Control

描述(申请人提供)：维持动脉血气和酸碱平衡需要新陈代谢的变化与肺泡通气量的比例变化相匹配。瘦素是一种细胞因子激素，在能量平衡中起着核心作用，在小鼠和人类中，瘦素被认为是将换气与代谢的一个方面相匹配的重要贡献者。这在临床上是相关的，例如，肥胖人群中的一部分对瘦素有抵抗力，并伴有动脉血二氧化碳分压的增加和动脉血氧分压的降低(肥胖症低通气症，OHS)。一般认为，瘦素通过中枢神经系统机制刺激呼吸。然而，中枢神经系统内的多个核团含有瘦素受体表达的神经元(称为LepRb神经元)，几乎没有证据表明哪些神经元参与了呼吸刺激。在前期研究和文献的基础上，我们假设多个特定的脑干和下丘脑LepRb神经元参与了呼吸刺激。此外，肽递质/调节剂与这些细胞群中的许多细胞群有关，对这些通路中活性的药理学操作可能为未来开发临床相关的这些通路中活性的药理操作提供基础。将解决三个具体目标。在目标1中，我们将利用Cre-loxP技术和光遗传激活或沉默转基因小鼠中特定的LepRb神经元群。对特定LepRb神经元群的选择性激活所产生的呼吸刺激将暗示其在呼吸中的作用。神经元活性标记物c-fos的免疫组织化学将被用来识别可能作为中继核参与特定途径的细胞群。 LepRb神经元群至中枢呼吸回路。这种潜在的作用将通过全身注射瘦素来刺激呼吸来测试，同时确定双侧靶核的失活是否会减少呼吸刺激。在目标2中，我们将结合标准的逆行追踪和一种新的跨突触病毒追踪方法，该方法只跨越一个突触来确定瘦素激活的单突触和多突触刺激呼吸的通路。这些途径中包含的多肽递质将通过免疫组织化学进行鉴定。在目标3中，体外研究将确定瘦素途径中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。这两项联合研究将系统地识别中枢神经系统LepRb神经元组，这些神经元组刺激呼吸，对全身注射瘦素做出反应。此外，调节这种影响的少突触通路将被揭示，身份也将被揭示。 它们的多肽传递体。此外，还将定义促进呼吸刺激的相关细胞/分子机制。这一发现可能为OHS患者未来药物治疗的发展奠定基础。

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.