Metabolic profiling of neonatal anesthesia toxicity

描述（由申请人提供）：新出现的证据导致对常规临床实践中使用的麻醉剂的安全性提出质疑，尤其是在使用 婴儿全身麻醉大量的数据表明，啮齿动物和非人类灵长类动物非常年轻的大脑中，神经元对全身麻醉的反应是死亡的。到目前为止，人类的平行证据仅限于与儿童早期重复麻醉暴露相关的回顾性研究。这些研究记录了生活后期的学习困难以及异常行为和心理社会问题。目前迫切需要确定在非常年轻的人脑中暴露于全身麻醉是否会干扰正常的大脑发育。我们建议实施一种临床相关的非侵入性成像技术-质子磁共振波谱（1HMRS）-能够跟踪年轻大脑中的细胞凋亡，神经变性，炎症和代谢状态，并将这种方法与传统的行为和组织学技术结合使用，以提供麻醉暴露，脑缺陷和长期行为影响之间的直接联系。拟定研究基于我们的新初步发现，即出生后第7天暴露于七氟烷麻醉的极年幼啮齿动物显示：1）通过神经元标记物N-乙酰天冬氨酸（NAA）的变化确定的脑成熟异常，2）炎症变化，包括反应性神经胶质增生和胆碱代谢物水平变化，和3）这些代谢物的变化与细胞凋亡的增加有关。具体来说，我们提出了一个创新的假设，代谢谱的1HMRS可以衡量麻醉诱导的神经毒性在年轻的大脑随着时间的推移。我们进一步试图确定在发育中的啮齿动物大脑中突触形成峰值时反复暴露于吸入性麻醉剂（七氟烷）是否会导致严重的脑代谢缺陷，包括[NAA]浓度随年龄变化所反映的脑成熟障碍和胆碱和/或肌醇变化所反映的长期反应性神经胶质增生。具体目标是：1）评估13例新生儿脑中的代谢谱， 与在相同时间点评价的未暴露的年龄匹配大鼠幼仔相比，单次或重复暴露于七氟烷的20和90日龄大鼠幼仔，以及2）评价在突触形成峰值时单次或重复暴露于七氟烷后，脑代谢缺陷是否损害认知功能并引发神经元丢失和星形胶质细胞和小胶质细胞的长期激活。将在30 - 80天时收集目标1中暴露于单次或重复七氟烷麻醉的新生大鼠的行为数据，以记录新生大鼠七氟烷暴露对复杂脑功能的影响。将在3个月时评价相同大鼠的神经元损失和反应性星形胶质细胞和小胶质细胞增生，并与未暴露大鼠进行比较。据我们所知，拟议的研究构成了首次尝试开发临床相关的诊断测试，以评估麻醉诱导的神经毒性在年轻的大脑。

DESCRIPTION (provided by applicant): Emerging evidence has led to questions about the safety of anesthetic agents used in routine clinical practice, especially with regard to the use of general anesthesia in infancy. A wealth of data shows neuronal demise in response to general anesthesia in the very young brain of rodents and non-human primates. Thus far, parallel evidence in humans has been limited to retrospective studies correlating repetitive anesthesia exposures during early childhood. These studies have documented learning difficulties later in life as well as abnormal behavior and psychosocial issues. There is an urgent need to establish whether or not exposure to general anesthesia in the very young human brain interferes with normal brain development. We propose to implement a clinically relevant, non-invasive imaging technology - proton magnetic resonance spectroscopy (1HMRS) - that has the ability to track apoptosis, neurodegeneration, inflammation and metabolic status in the young brain, and use this approach in combination with traditional behavioral and histological techniques to provide a direct linkage between anesthesia exposure, brain defects and long-term behavioral effects. The proposed studies are based on our novel preliminary findings that very young rodents exposed to sevoflurane anesthesia on post-natal day 7 show 1) abnormalities in brain maturation determined by changes in the neuronal marker N-acetyl-aspartate (NAA), 2) inflammatory changes including reactive gliosis and changes in levels of choline metabolites, and 3) that these metabolite changes tracked non-invasively by 1HMRS are associated with increased apoptosis. Specifically, we propose an innovative hypothesis that metabolic profiling by 1HMRS can gauge anesthesia-induced neurotoxicity in the young brain over time. We further seek to establish whether repeated exposures to inhalational anesthetics (sevoflurane) at the time of peak synaptogenesis in the developing rodent brain result in severe cerebral metabolic defects including impediment of brain maturation reflected by age-dependent changes in the concentration of [NAA] and long-lasting reactive gliosis reflected by changes in choline and/or myo-inositol. The specific aims are: 1) to evaluate metabolic profiles in the neonatal brain in 13, 20 and 90 day old rat pups with single or repetitive exposure to sevoflurane compared to non- exposed age-matched rat pups evaluated at the same time points, and 2) to evaluate whether cerebral metabolic defects impair cognitive functions and trigger neuronal loss and long-lasting activation of astrocytes and microglia after a single or repetitive exposure to sevoflurane at the time of peak synaptogenesis. Behavioral data in the neonatal rats exposed to single or repetitive sevoflurane anesthesia in Aim 1 will be collected at 30 to 80 days, to document the effect of neonatal sevoflurane exposure on complex brain function. The same rats will be evaluated for neuronal loss and reactive astro- and microgliosis at 3 months and compared to non-exposed rats. To our knowledge the proposed studies constitute the first attempt to develop a clinically relevant diagnostic test to assess anesthesia induced neurotoxicity in the young brain.