Treatment of Sleep Apnea by Targeting Leptin Signaling

阻塞性睡眠呼吸暂停（OSA）是由于上呼吸道肌肉的丧失而引起的反复发作的上呼吸道阻塞 睡眠时的音调。目前尚无治疗OSA的药物。迫切需要一种治疗方法， 上呼吸道功能的神经肌肉缺陷。我们的努力集中在瘦素，一种脂肪细胞产生的 荷尔蒙，抑制食欲，增加新陈代谢率，并上调呼吸控制。我们有 先前报道过肥胖小鼠会发生阻塞性睡眠呼吸暂停综合征，而瘦素可以治疗阻塞性睡眠呼吸暂停综合征。我们的初步结果表明 （1）瘦素受体（LepRb）缺陷型db/db小鼠发生OSA， 下丘脑背内侧区LepRb表达后，侧脑室（ICV）注射瘦素（db/db-LepRb- （2）在饮食诱导的肥胖（DIO）LepRb-Cre小鼠中，在兴奋性神经递质激活后，OSA改善。 设计者受体仅由设计者药物激活（DREADDs）在LepRb+神经元中表达， （3）舌下神经运动神经元不表达LepRb，但表达LepRb+神经元 LepRb ~+突触投射到舌下神经核，光遗传刺激舌下神经核LepRb ~+突触增加 （4）DMH和NTS中的LepRb+神经元是黑素皮质素4受体 （MCR 4）阳性。我们的假设是，瘦素作用于DMH和NTS中的LepRb+神经元，以维持上丘脑的LepRb+神经元， 睡眠期间的气道通畅。具体目标1将检验以下假设： DMH可缓解上气道阻塞和OSA。我们提出（A）选择性刺激LepRb+ DMH 通过db/db-LepRb-DMH小鼠中ICV瘦素和通过DIO LepRb-Cre中兴奋性DREADD的激活， 小鼠将改善上呼吸道开放并治疗OSA;（B）通过Cre敲除DMH神经元中的LepRb+ 在DIO LepRb flox/flox小鼠中重组酶的表达以及在DIO LepRb-Cre小鼠中这些神经元表达的抑制 抑制性DREADDs将降低上气道通畅性并加重OSA;（C）瘦素对OSA的影响， db/db-LepRb-DMH小鼠将通过MC 4 R阻断剂减毒。具体目标2将审查 瘦素在NTS中对OSA的体内作用，并将被设计为SA 1 A-C，除了我们的干预措施 将针对NTS。具体目标3将检查LepRb+神经元之间的突触连接， DMH和NTS都投射到舌下神经运动神经元并与之形成突触。我们建议， DMH和NTS LepRb+神经元连接到舌下神经运动神经元，并且（A）的光遗传学刺激 表达DMH和（B）NTS LepRb通道视紫红质（ChR 2）的神经元和纤维激活舌下神经 运动神经元在SA 1 -2中，我们将采用我们实验室开发的一系列完整的生理测量方法 包括多导睡眠图、动态磁共振成像和肥胖男性的咽部可吸收性测量 和雌性老鼠。在SA 3中，在靶向的LepRb神经元群体中选择性表达光遗传学工具将使LepRb神经元群体中的L 在离体脑切片中与膜片钳电生理学结合使用。我们的建议将确定 leptin依赖性机制，可以靶向治疗OSA。

Obstructive sleep apnea (OSA) is recurrent upper airway obstruction caused by a loss of upper airway muscle tone during sleep. There is no pharmacotherapy for OSA. There is an urgent need for therapeutics that reverse neuromuscular defects in upper airway function. Our efforts have focused on leptin, an adipocyte-produced hormone, which suppresses appetite, increases metabolic rate, and up-regulates control of breathing. We have previously reported that obese mice develop OSA, which was treated by leptin. Our preliminary results show that (1) leptin receptor (LepRb) deficient db/db mice develop OSA, which was abolished by intracerebroventricular (ICV) leptin after expression of LepRb in the dorsomedial hypothalamus (db/db-LepRb- DMH mice); (2) OSA improved in diet induced obese (DIO) LepRb-Cre mice upon activation of excitatory Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) expressed in LepRb+ neurons of the nucleus of the solitary tract (NTS); (3) hypoglossal motoneurons do not express LepRb, but LepRb+ neurons project to the hypoglossal nucleus and photogenetic stimulation of LepRb+ synapses increased hypoglossal motoneuron activity in LepRb-ChR2 mice; (4) LepRb+ neurons in DMH and NTS are melanocortin 4 receptor (MCR4) positive. Our hypothesis is that leptin acts on LepRb+ neurons in DMH and NTS to maintain upper airway patency during sleep. Specific Aim 1 will test the hypothesis that activation of LepRb+ neurons in the DMH alleviates upper airway obstruction and OSA. We propose that (A) selective stimulation of LepRb+ DMH neurons by ICV leptin in db/db-LepRb-DMH mice and by activation of excitatory DREADDs in DIO LepRb-Cre mice will improve upper airway patency and treat OSA; (B) knockout of LepRb+ in DMH neurons by Cre recombinase in DIO LepRb flox/flox mice and inhibition of these neurons in DIO LepRb-Cre mice expressing inhibitory DREADDs will decrease upper airway patency and aggravate OSA; (C) effects of leptin on OSA in db/db-LepRb-DMH mice will be attenuated by MC4R blockers. Specific Aim 2 will examine mechanisms of leptin’s action in the NTS on OSA in vivo and will be designed as SA1 A-C with exception that our interventions will target NTS. Specific Aim 3 will examine synaptic connections between LepRb+ neurons, originating from both the DMH and NTS, that project to and synapse upon hypoglossal motoneurons. We propose that both DMH and NTS LepRb+ neurons connect to hypoglossal motoneurons and that optogenetic stimulation of (A) DMH- and (B) NTS LepRb-channelrhodopsin (ChR2) expressing neurons and fibers activates hypoglossal motoneurons. In SA1-2, we will employ a full arrays of physiological measurements developed in our laboratory including polysomnograms, dynamic MR imaging, and pharyngeal collapsibility measurements in obese male and female mice. In SA3, selective expression of optogenetic tools in targeted LepRb neuronal populations will be employed in combination with patch clamp electrophysiology in brain slices ex vivo. Our proposal will identify leptin-dependent mechanisms which can be targeted for treatment of OSA.