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

项目概要/摘要 在发达国家，人们80%的时间是在室内度过的。二氧化碳（CO2）是一种 呼吸，呼气浓度为40，000 ppm，导致室内浓度高于室外。CO2是 被广泛认为无毒。然而，三项人体实验研究使用高度敏感的测试， 认知功能，包括航空公司飞行模拟器，报告浓度相关的递减较高 在2小时暴露于升高但真实世界的CO2浓度（<2，500 ppm）期间的认知功能。 此外，体外和动物研究表明，相同浓度的CO2可增强 中性粒细胞（PMN）活化和伴随的脑血管渗漏。CO2可以与各种活性物质相互作用， 氧和氮物质（RONS），改变它们随后与生物靶标的反应性。我们推测 CO2吸入将RONS重定向到PMN中的一种新的生物分子亚群，这导致 中性粒细胞活化和氧化应激;这会导致脑血管渗漏，从而导致认知功能障碍。 我们假设，人类暴露于环境水平的吸入CO2将导致人类认知能力下降。 作为CO2介导的亚硝化和硝化细胞内生物分子的结果， PMN，导致细胞活化。这种新颖的高风险高回报机制模型集成了 实验，在体外和体内数据与人类研究的认知影响的二氧化碳。为了验证这个假设， 我们将：（1）分析CO2离子对GSTM 1基因型分层志愿者认知功能的影响; (2)确定CO2吸入是否导致PMN中靶蛋白的亚硝化和硝化修饰， 以及这是否与PMN活化和氧化应激有关。双盲、随机顺序、交叉 将进行研究。健康受试者（n=24）将以随机顺序呼吸600 ppm（对照）和2，500 ppm（对照）。 ppm（暴露）二氧化碳2小时。在我们的受控环境设施中。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PMN 在每次暴露后立即和4小时，并测量活化（氧化爆发，NLRP 3 炎性体活化）和线粒体氧化应激。氧化、亚硝化和硝化 PMN中的细胞内蛋白质将被评估为CO2诱导的细胞内改变的潜在介质。 功能;还将评估微粒的释放。认知功能、PMN氧化应激的变化 靶蛋白的亚硝化和硝化修饰将根据GSTM 1状态分层，预测 影响对CO2吸入反应性。积极的结果将提供关于CO2的重要机理数据 以及认知功能受损，这将为考虑室内环境中可接受的二氧化碳水平提供信息。

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.