Neutrophil-mediated oxidative stress and albumin structural damage predict COVID-19-associated mortality

This work reports that COVID-19-induced oxidative stress inflicts structural damages to human serum albumin (HSA) and is linked with mortality outcome in critically ill patients. Analyzing blood samples from patients and healthy individuals, the paper provides evidence that neutrophils are major sources of oxidative stress in blood and that hydrogen peroxide is highly accumulated in plasmas of non-survivors. The electron paramagnetic resonance spectra of spin-labeled fatty acids (SLFAs) bound with HSA in whole blood of control, survivor, and non-survivor subjects (n=10–11) were analyzed to probe structural damages to the protein. Non-survivors’ HSA showed dramatically altered biophysical parameters that reflect remarkably fluid protein microenvironments. Following loading/unloading of 16-DSA, the results show that the transport function of HSA may be impaired in severe patients. Stratified at the means, Kaplan–Meier survival analysis indicated that lower values of S/W ratio and accumulated H2O2 in plasma significantly predicted in-hospital mortality.

Methods
All patients were recruited from Kasr Alainy Cairo University Hospital/ICU-facility at the Internal Medicine Quarantine Hospital. Supportive therapy, including supplemental oxygen and symptomatic treatment, was administered as required. Patients with moderate to severe hypoxia (defined as requiring fraction of inspired oxygen [FiO2]≥40%) were transferred to intensive care for further management including invasive mechanical ventilation when necessary. Patients recruited in the current study were divided into two arms based on future mortality outcome: those who survived the past 15 days following blood samples collection (Sev-R) and those who died within 15 days of samples collection (Sev-D). Details of samples collection and handlings are described in details in the published manuscript.

本研究表明，新冠诱导的氧化应激（COVID-19-induced oxidative stress）会对人血清白蛋白（human serum albumin, HSA）造成结构损伤，并与重症患者的死亡率预后相关。通过分析患者与健康个体的血液样本，本研究揭示中性粒细胞（neutrophils）为血液中氧化应激的主要来源，且非幸存者血浆内过氧化氢（hydrogen peroxide）大量蓄积。本研究通过分析对照组、存活组与非存活组受试者（n=10~11）全血中结合于人血清白蛋白的自旋标记脂肪酸（spin-labeled fatty acids, SLFAs）的电子顺磁共振谱（electron paramagnetic resonance spectra），以探究该蛋白质的结构损伤情况。非幸存者的人血清白蛋白的生物物理参数发生显著改变，提示其蛋白质微环境的流动性明显升高。在对16-DSA（16-二氧硬脂酸）进行装载/卸载操作后，结果显示重症患者的人血清白蛋白转运功能可能受损。以均值作为分层依据进行Kaplan-Meier生存分析（Kaplan–Meier survival analysis）后发现，血浆中较低的S/W比值与过氧化氢蓄积水平可显著预测院内死亡风险。

方法
所有受试者均招募自开罗大学卡斯尔阿莱尼医院内科隔离医院重症监护病房。研究根据患者病情给予包括氧疗（supplemental oxygen）与对症治疗（symptomatic treatment）在内的支持性治疗方案。中重度低氧血症患者（定义为需吸入氧分数[FiO2]≥40%）将被转至重症监护病房接受进一步诊疗，必要时实施有创机械通气（invasive mechanical ventilation）。本研究招募的患者将根据后续转归分为两组：血液样本采集后15天内存活者（Sev-R组）与样本采集后15天内死亡者（Sev-D组）。样本采集与处理的详细方法已发表于本研究已刊出的论文中。