Acute Cognitive Impairments Following Exposure to Inhaled CO2: Translating Mouse Mechanisms to Humans

项目摘要/摘要 发达国家的人类80%的时间都在室内度过。二氧化碳(CO2)是一种 呼吸作用在40,000 ppm的浓度下失效，导致室内的呼吸水平高于室外。二氧化碳是 被广泛认为是无毒的。然而，三项使用高度敏感的测试的人体实验研究 包括航空公司飞行模拟器在内的认知功能，报告说与浓度相关的下降在较高 2小时内的认知功能。暴露在升高的、但真实世界的二氧化碳浓度(&lt；2500ppm)中。 此外，体外和动物研究表明，相同浓度的二氧化碳会导致 中性粒细胞(PMN)激活和伴发脑血管渗漏。二氧化碳可与多种反应性物质相互作用 氧和氮物种(RON)，改变它们随后与生物靶标的反应性。我们推测 吸入二氧化碳会将RON重定向到PMN中的一个新的生物分子子集，这导致了 中性粒细胞激活和氧化应激；这会导致脑血管泄漏，从而导致认知功能障碍。 我们假设，人类在环境水平上暴露在可吸入的二氧化碳中将导致人类认知 二氧化碳介导的细胞内生物分子的亚硝化和硝化所致的减量 中性粒细胞，导致细胞激活。这一新颖的高风险高回报机制模型集成了 关于二氧化碳认知影响的人体研究的实验、体外和体内数据。为了检验这一假设， 我们将：(1)分析GSTM1基因对志愿者二氧化碳离子认知功能的影响； (2)确定吸入二氧化碳是否导致PMN中目标蛋白的亚硝化和亚硝化修饰， 以及这是否与中性粒细胞激活和氧化应激有关。双盲、随机顺序、交叉 我们会进行研究。健康受试者(n=24)按随机顺序呼吸600ppm(对照组)和2500 ppm Ppm(暴露)二氧化碳2小时。在我们受控的环境设施里。战略管理系统 将进行认知评估测试。将从受试者的外周血中采集中性粒细胞 即刻和4小时。在每次暴露和测量后进行激活(氧化猝发，NLRP3 炎性小体激活)和线粒体氧化应激。氧化、亚硝化和硝化 PMN中的细胞内蛋白将被评估为二氧化碳诱导的细胞内变化的潜在介体 功能；还将评估微粒的释放。认知功能、中性粒细胞氧化应激的变化 目标蛋白的亚硝化和亚硝化修饰将在GSTM1状态上分层，预计 影响对二氧化碳吸入的反应性。积极的结果将提供有关二氧化碳的重要机理数据 以及认知功能受损，这将有助于考虑室内环境中可接受的二氧化碳水平。

Project Summary/Abstract Humans in developed countries spend 80% of their time indoors. Carbon dioxide (CO2) is a product of respiration, expired at a concentration of 40,000 ppm, leading to higher levels indoors than outdoors. CO2 is widely regarded as nontoxic. However, three human experimental studies using highly sensitive tests of cognitive function including an airline flight simulator, reported concentration-related decrements in higher cognitive function during 2 hr. exposures to elevated, but real-world CO2 concentrations (<2,500 ppm). Additionally, in vitro and animal studies demonstrated that CO2 at the same concentrations caused enhanced neutrophil (PMN) activation and accompanying brain vascular leak. CO2 can interact with a variety of reactive oxygen and nitrogen species (RONS), altering their subsequent reactivity with biological targets. We speculate that CO2 inhalation redirects RONS towards a novel subset of biomolecules in PMN and that this leads to PMN activation and oxidative stress; this causes brain vascular leak, and consequently cognitive dysfunction. We hypothesize that exposure of humans to inhaled CO2 at environmental levels will lead to human cognitive decrements as a consequence of CO2-mediated nitrosation and nitration of intracellular biomolecules in PMN, leading to cellular activation. This novel high-risk high-reward mechanistic model integrates experimental, in vitro, and in vivo data with human studies on cognitive effects of CO2. To test this hypothesis, we will: (1) analyze the effects of CO2 ion cognitive function in volunteers stratified on GSTM1 genotype; and (2) determine whether CO2 inhalation results in nitrosative and nitrative modification of target proteins in PMN, and if this is correlated with PMN activation and oxidative stress. A double-blind, randomized order, cross-over study will be performed. Healthy subjects (n=24) will breathe in random order 600 ppm (control), and 2,500 ppm (exposed) CO2 for 2 hrs. in our controlled environmental facility. The Strategic Management Systems cognitive assessment test will be administered. PMNs will be collected from subjects’ peripheral blood immediately and 4 hr. after each exposure and measurements made of activation (oxidative burst, NLRP3 inflammasome activation) and mitochondrial oxidative stress. Oxidation, nitrosation, and nitration of intracellular proteins in PMN will be assessed as potential mediators of CO2 induced alterations in cellular function; release of microparticles will also be assessed. Changes in cognitive function, PMN oxidative stress and nitrosative and nitrative modification of target proteins will be stratified on GSTM1 status, predicted to influence responsiveness to CO2 inhalation. Positive results will provide important mechanistic data on CO2 and impaired cognitive function that will inform consideration of acceptable CO2 levels in indoor environments.