Neural Plasticity During Acclimatization to Hypoxia

描述（由申请人提供）：本项目的目的是确定慢性持续缺氧（CSH）期间中枢神经系统通气化学反射成分可塑性的细胞信号。这项研究的意义在于它解决了肺医学中一个基本但尚未解决的问题：在肺部疾病引起的慢性低氧血症中，增加通气驱动和增强动脉O2和CO2反射控制的神经机制是什么？更具体地说，我们将验证其他人描述的一些相同的分子信号和细胞机制来解释间歇性缺氧（IH）的长期促进（LTF）也有助于CSH期间通气化学反射的可塑性。近年来，人们对LTF机制的研究取得了巨大进展，这使我们能够在CSH中有效地测试评估模型。比较和对比CSH和IH的可塑性具有重要意义，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COPD引起CSH和睡眠呼吸障碍引起IH。首先，我们将证实在麻醉大鼠的膈LTF中报道的谷氨酸能神经传递增强的分子信号出现在清醒小鼠IH后的通气LTF中。然后，我们将在小鼠CSH后测量这些分子信号，并通过药理学和条件基因缺失来测试它们对CSH通气适应的生理意义。将腺相关病毒表达的药物或cre -重组酶微注射到野生型或转基因小鼠的脊髓鞘内或脑干立体定向中，以操纵不同种群呼吸神经元可塑性的假定信号。实验旨在比较和对比IH和CSH的可塑性。例如，我们假设TrkB磷酸化是IH和CSH的可塑性信号，但BDNF仅是IH的一个信号。此外，我们假设IH和CSH时活性氧（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变化的时间过程并改变它们以测试生理学意义。最后，我们将在肺气肿转基因小鼠模型（肺血管内皮生长因子基因的条件缺失）中验证CSH引起类似可塑性分子信号的假设。这是我们解决在适应环境缺氧的健康动物中研究的神经可塑性是否发生在慢性低氧血症疾病中，或者慢性肺部疾病是否也涉及异常可塑性这一重要问题的第一步。

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.