Neural Plasticity During Acclimatization to Hypoxia

描述(申请人提供)：本项目的目标是确定慢性持续性低氧(CSH)期间呼吸性化学反射的中枢神经系统成分可塑性的细胞信号。这项研究的意义在于它解决了肺部医学中一个基本但尚未回答的问题：在肺部疾病引起的慢性低氧血症中，增加呼吸动力和增强动脉O2和CO2反射控制的神经机制是什么？更具体地说，我们将检验这一假设，即其他人描述的解释长期促进(LTF)和间歇性低氧(IH)的一些相同的分子信号和细胞机制也有助于CSH期间呼吸性化学反射的可塑性。近些年来，LTF的机制研究取得了很大的进展，这使得我们能够在CSH中有效地测试和评估该模型。比较和对比CSH和IH的可塑性，使我们能够系统地评估慢性低氧血症最重要原因的潜在治疗靶点，即导致CSH的COPD和导致IH的睡眠呼吸障碍。首先，我们将确定麻醉大鼠膈神经转运蛋白的谷氨酸能神经传递增强的分子信号发生在清醒小鼠IH后的呼吸性长时转运蛋白。然后，我们将测量CSH后小鼠的这些分子信号，并利用药理学和条件性基因缺失来测试它们在CSH呼吸习服中的生理学意义。由腺相关病毒表达的药物或Cre重组酶将被显微注射到脊髓内，或在野生型或转基因小鼠的脑干中立体定向注射，以操纵不同呼吸神经元种群的可塑性假定信号。实验目的是比较和对比IH和CSH的塑性。例如，我们假设TrkB的磷酸化在IH和CSH中都是可塑性的信号，而BDNF只在IH中是一个信号。我们还假设，随着IH和CSH的增加，活性氧物种(ROS)的增加是可塑性的重要信号，我们将测量不同缺氧模式下ROS变化的时间进程，并对其进行改变以检验其生理意义。最后，我们将在肺气肿转基因小鼠模型(肺中血管内皮生长因子基因的有条件缺失)中测试CSH导致类似的可塑性分子信号的假设。这是我们朝着解决一个重要问题迈出的第一步，即在适应环境低氧的健康动物中研究的神经可塑性是否发生在患有慢性低氧血症的疾病中，或者如果慢性肺部疾病也涉及异常可塑性。

DESCRIPTION (provided by applicant): The objective of this project is to determine the cellular signals for plasticity in central nervous system components of ventilatory chemoreflexes during Chronic Sustained Hypoxia (CSH). The significance of this research is that it addresses a fundamental but unanswered question in pulmonary medicine: What are the neural mechanisms that increase ventilatory drive and enhance the reflex control of arterial O2 and CO2 during chronic hypoxemia from pulmonary disease? More specifically, we will test the hypothesis that some of the same molecular signals and cellular mechanisms described by others to explain Long Term Facilitation (LTF) with intermittent hypoxia (IH) also contribute to plasticity in ventilatory chemoreflexes during CSH. There has been tremendous progress on mechanisms of LTF recently, which allows us to efficiently test evaluate the model in CSH. Comparing and contrasting plasticity in CSH and IH is significant by allowing us to systematically evaluate potential therapeutic targets for the most important causes of chronic hypoxemia, namely COPD causing CSH and sleep disordered breathing causing IH. First we will establish that the molecular signals for enhanced glutamatergic neurotransmission reported for phrenic LTF in anesthetized rats occur with ventilatory LTF after IH in conscious mice. Then we will measure those molecular signals in mice after CSH and use pharmacology and conditional gene deletion to test their physiological significance for ventilatory acclimatization to CSH. Drugs or Cre-recombinase expressed by adeno-associated virus will be microinjected intrathecally to the spinal cord or stereotaxically in the brainstem of wildtype or transgenic mice to manipulate putative signals for plasticity in different populations of respiratory neurons. Experiments are designed to compare and contrast plasticity with IH vs. CSH. For example, we hypothesize that TrkB phosphorylation is a signal for plasticity in both IH and CSH but BDNF is only a signal in IH. Also, we hypothesize that increases in Reactive Oxygen Species (ROS) with both IH and CSH are an important signal for plasticity and we will measure the time course of ROS changes with different patterns of hypoxia and alter them to test physiological significance. Finally, we will test the hypothesis that CSH causes similar molecular signals for plasticity in a transgenic mouse model of emphysema (conditional deletion of the vascular endothelial growth factor gene in the lung). This is our first step towards addressing the important question of whether the neural plasticity studied in healthy animals acclimatized to environmental hypoxia occurs in diseases with chronic hypoxemia, or if chronic lung disease also involves abnormal plasticity.