Leptin Transport Across the BBB: The Role of ObR (+) Astrocytes

描述(申请人提供)：在“瘦素跨血脑屏障转运”的第三个资助周期中，我们将重点研究瘦素受体(OBR)阳性的星形胶质细胞在跨越血脑屏障(BBB)后将瘦素从血液中转送到中枢神经系统中的作用。我们假设星形胶质细胞不仅作为血脑屏障的重要组成部分调节瘦素的运输，而且通过使神经元中的瘦素更快地开始和终止来调节神经元的瘦素信号。对小鼠原代星形胶质细胞的细胞研究将确定反应性星形胶质细胞增生症对瘦素受体亚型(OBR)表达和瘦素更新的影响。小鼠研究将测试星形细胞活动和星形细胞OBR在瘦素分布、细胞信号和肥胖发展的中枢神经系统动力学中的作用。在目标1中，我们将检验这一假设，即反应性星形胶质细胞通过加速瘦素在细胞内的降解来促进瘦素在大脑中的周转。在目标2中，我们将检验这样的假设，即培养中的反应性星形胶质细胞和成年肥胖症小鼠的反应性星形胶质细胞显示出由于不同调控而导致的OBR亚型失衡。目标3将侧重于饮食诱导肥胖或Avy突变的成年小鼠的调节变化，这两者都表现出星形细胞OBR的区域性特异性增加。通过使用胶质代谢抑制剂和新产生的星形胶质细胞特异性OBR基因敲除小鼠，我们将证明这些OBR()星形胶质细胞在神经元瘦素信号的调节中发挥重要作用。这一结果将为OBR()星形胶质细胞将血脑屏障转运与中枢神经系统对瘦素的反应联系起来的功能提供第一个证据。了解肥胖者星形胶质细胞增多症和星形胶质细胞OBR上调的后果，可以靶向星形胶质细胞来对抗肥胖者的神经内分泌失调。

DESCRIPTION (provided by applicant): In the third grant cycle of "leptin transport across the BBB", we will focus on the role of leptin receptor (ObR)-positive astrocytes in relaying leptin from blood to the CNS after crossing the blood-brain barrier (BBB). We hypothesize that astrocytes not only regulate leptin transport as vital components of the BBB, but also modulate neuronal leptin signaling by enabling a more rapid onset and faster termination of leptin action in neurons. The cellular studies with primary astrocytes from mice will determine the effects of reactive astrogliosis on subtypes of leptin receptor (ObR) expression and leptin turnover. The mouse studies will test the role of astrocytic activity and astrocytic ObR on CNS kinetics of leptin distribution, cellular signaling, and development of obesity. In Aim 1, we will test the hypothesis that reactive astrocytes facilitate the turnover of leptin in the brain by accelerating intracellular degradation of leptin. In Aim 2, we will test the hypothesis that reactive astrocytes both in culture and in mice with adult-onset obesity show an imbalance of ObR subtypes resulting from differential regulation. Aim 3 will focus on regulatory changes in adult mice with diet-induced obesity or the Avy mutation, both of which exhibit regional specific increases of astrocytic ObR. By use of glial metabolic inhibitors and newly generated astrocyte-specific ObR knockout mice, we will show that these ObR(+) astrocytes play an essential role in the regulation of neuronal leptin signaling. The results will provide the first evidence of the functions of ObR(+) astrocytes in linking BBB transport to the CNS response to leptin. An understanding of the consequence of astrogliosis and upregulation of astrocytic ObR in obesity should enable the targeting of astrocytes to counteract the neuroendocrine dysregulation in obese subjects.