Pediatric Cystic Fibrosis Sputum Can Be Chemically Dynamic, Anoxic, and Extremely Reduced Due to Hydrogen Sulfide Formation.
Pediatric Cystic Fibrosis Sputum Can Be Chemically Dynamic, Anoxic, and Extremely Reduced Due to Hydrogen Sulfide Formation.
复制标题
DOI：
10.1128/mbio.00767-15
复制
发表时间：
2015-07-28
期刊：
影响因子：
6.4
通讯作者：
Newman DK
中科院分区：
文献类型：
--
作者：
Cowley ES;Kopf SH;LaRiviere A;Ziebis W;Newman DK
囊性纤维化(CF)的特征是严重且持续的细菌性肺部感染。虽然已经有几项研究证明了CF肺粘液中的微生物多样性，但我们对限制微生物代谢过程及其分布的无机化学知之甚少。我们假设痰的化学成分在患者内部和患者之间都是不同的。为了验证这一点，我们测量了来自22名儿童CF患者的48份痰样本的氧和硫化物浓度以及pH和氧化还原电位的微观特征。对12例患者的20份标本进行了无机离子测定。在所有情况下，在痰-空气界面下的最初几毫米内，氧气都被耗尽了。除了这种陡峭的氧跃层外，缺氧也是痰环境的主要因素。不同的痰样本表现出广泛的氧化还原条件，要么氧化(16m V至355m V)，要么降低(−300m V至−107m V)。大多数还原样品含有硫化氢，pH值较低(2.9至6.5)。硫化物浓度以0.30微米/分钟的速度增加。只在一个也含有硫化物的样品中检测到一氧化二氮。在单个患者内和患者之间都观察到了微环境的变化。模拟CF粘液塞内的氧气动力学表明，缺氧区随细菌负荷和粘液厚度的变化而变化，可以占据粘液体积的很大一部分。因此，需氧呼吸只是病原菌在CF痰中存活的部分原因，这促使人们进行研究，以确定在包括硫化物环境在内的波动氧化还原状态下的生存机制。微生物感染是慢性阻塞性肺疾病患者发病和死亡的主要原因，然而微生物在慢性阻塞性肺疾病呼吸道中的生长和存活尚不清楚。关于体内环境化学的信息不足是造成这种知识差距的原因之一。我们对与硫化物的存在或不存在相对应的可变氧化还原状态的记录开始填补这一空白，并促使我们理解不同的机会病原体如何适应这些动态环境。鉴于CF痰的化学状态随着时间的推移而变化，在实验室研究CF病原体时，考虑好氧和厌氧的生活方式是很重要的。这项工作不仅提供了影响实验室实验设计的相关约束条件，还表明硫化物可能是临床上评估痰中氧化还原状态的有用指标。
Severe and persistent bacterial lung infections characterize cystic fibrosis (CF). While several studies have documented the microbial diversity within CF lung mucus, we know much less about the inorganic chemistry that constrains microbial metabolic processes and their distribution. We hypothesized that sputum is chemically heterogeneous both within and between patients. To test this, we measured microprofiles of oxygen and sulfide concentrations as well as pH and oxidation-reduction potentials in 48 sputum samples from 22 pediatric patients with CF. Inorganic ions were measured in 20 samples from 12 patients. In all cases, oxygen was depleted within the first few millimeters below the sputum-air interface. Apart from this steep oxycline, anoxia dominated the sputum environment. Different sputum samples exhibited a broad range of redox conditions, with either oxidizing (16 mV to 355 mV) or reducing (−300 to −107 mV) potentials. The majority of reduced samples contained hydrogen sulfide and had a low pH (2.9 to 6.5). Sulfide concentrations increased at a rate of 0.30 µM H2S/min. Nitrous oxide was detected in only one sample that also contained sulfide. Microenvironmental variability was observed both within a single patient over time and between patients. Modeling oxygen dynamics within CF mucus plugs indicates that anoxic zones vary as a function of bacterial load and mucus thickness and can occupy a significant portion of the mucus volume. Thus, aerobic respiration accounts only partially for pathogen survival in CF sputum, motivating research to identify mechanisms of survival under conditions that span fluctuating redox states, including sulfidic environments. Microbial infections are the major cause of morbidity and mortality in people living with CF, and yet microbial growth and survival in CF airways are not well understood. Insufficient information about the chemistry of the in vivo environment contributes to this knowledge gap. Our documentation of variable redox states corresponding to the presence or absence of sulfide begins to fill this void and motivates understanding of how different opportunistic pathogens adapt in these dynamic environments. Given the changing chemical state of CF sputum over time, it is important to consider a spectrum of aerobic and anaerobic lifestyles when studying CF pathogens in the laboratory. This work not only provides relevant constraints that can shape the design of laboratory experiments, it also suggests that sulfide might be a useful proxy for assessing the redox state of sputum in the clinic.