Abstract：
BACKGROUND: Circulating histones are released by extensive tissue injury or cell death and play important pathogenic roles in critical illnesses. Their interaction with circulating plasma components and the potential roles in the clinical setting are not fully understood.
OBJECTIVE: We aimed to characterize the interaction of histones with fibrinogen and explore its roles in vitro, in vivo, and in patient samples.
METHODS: Histone-fibrinogen binding was assessed by electrophoresis and enzyme-linked immunosorbent assay-based affinity assay. Functional significance was explored using washed platelets and endothelial cells in vitro and histone-infusion mouse models in vivo. To determine clinical translatability, a retrospective single-center cohort study was conducted on patients requiring intensive care admission (n = 199) and validated in a cohort of hospitalized patients with COVID-19 (n = 69).
RESULTS: Fibrinogen binds histones through its D-domain with high affinity (calf thymus histones, KD = 18.0 ± 5.6 nM; histone 3, KD = 2.7 ± 0.8 nM; and histone 4, KD = 2.0 ± 0.7 nM) and significantly reduces histone-induced endothelial damage and platelet aggregation in vitro and in vivo in a histone-infusion mouse model. Physiologic concentrations of fibrinogen can neutralize low levels of circulating histones and increase the cytotoxicity threshold of histones to 50 μg/mL. In a cohort of patients requiring intensive care, a histone:fibrinogen ratio of ≥6 on admission was associated with moderate-severe thrombocytopenia and independently predicted mortality. This finding was validated in a cohort of hospitalized patients with COVID-19.
CONCLUSIONS: Fibrinogen buffers the cytotoxic properties of circulating histones. Detection and monitoring of circulating histones and histone:fibrinogen ratios will help identify critically ill patients at highest risk of adverse outcomes who might benefit from antihistone therapy.
OBJECTIVE: We aimed to characterize the interaction of histones with fibrinogen and explore its roles in vitro, in vivo, and in patient samples.
METHODS: Histone-fibrinogen binding was assessed by electrophoresis and enzyme-linked immunosorbent assay-based affinity assay. Functional significance was explored using washed platelets and endothelial cells in vitro and histone-infusion mouse models in vivo. To determine clinical translatability, a retrospective single-center cohort study was conducted on patients requiring intensive care admission (n = 199) and validated in a cohort of hospitalized patients with COVID-19 (n = 69).
RESULTS: Fibrinogen binds histones through its D-domain with high affinity (calf thymus histones, KD = 18.0 ± 5.6 nM; histone 3, KD = 2.7 ± 0.8 nM; and histone 4, KD = 2.0 ± 0.7 nM) and significantly reduces histone-induced endothelial damage and platelet aggregation in vitro and in vivo in a histone-infusion mouse model. Physiologic concentrations of fibrinogen can neutralize low levels of circulating histones and increase the cytotoxicity threshold of histones to 50 μg/mL. In a cohort of patients requiring intensive care, a histone:fibrinogen ratio of ≥6 on admission was associated with moderate-severe thrombocytopenia and independently predicted mortality. This finding was validated in a cohort of hospitalized patients with COVID-19.
CONCLUSIONS: Fibrinogen buffers the cytotoxic properties of circulating histones. Detection and monitoring of circulating histones and histone:fibrinogen ratios will help identify critically ill patients at highest risk of adverse outcomes who might benefit from antihistone therapy.
摘要：
背景：循环组蛋白通过广泛的组织损伤或细胞死亡释放，并在危重疾病中发挥重要的致病作用。它们与循环血浆成分的相互作用以及在临床环境中的潜在作用尚未完全了解。
目的：表征组蛋白与纤维蛋白原的相互作用，并探讨其在体外的作用，在体内和患者样本中。
方法:通过电泳和基于ELISA的亲和测定评估组蛋白-纤维蛋白原结合。使用体外洗涤的血小板和内皮细胞以及体内组蛋白输注小鼠模型来探索功能意义。为了确定临床可翻译性，我们对需要接受重症监护的患者(n=199)进行了回顾性单中心队列研究,并在COVID-19住院患者队列(n=69)中进行了验证.
结果：纤维蛋白原通过其D结构域以高亲和力结合组蛋白（小牛胸腺组蛋白KD=18.0±5.6nM；组蛋白3KD=2.7nM±0.8nM；组蛋白4KD=2.0±0.7nM），并在组蛋白输注小鼠模型中在体外和体内显着降低组蛋白诱导的内皮损伤和血小板聚集。纤维蛋白原的生理浓度可以中和低水平的循环组蛋白，并将组蛋白的细胞毒性阈值提高到50μg/ml。在一群需要重症监护的患者中，入院时组蛋白:纤维蛋白原比值≥6与中重度血小板减少症和独立预测的死亡率相关.这一发现在一组COVID-19住院患者中得到了验证。
结论:纤维蛋白原缓冲循环组蛋白的细胞毒性特性。循环组蛋白和组蛋白：纤维蛋白原比率的检测和监测将确定可能受益于抗组蛋白治疗的不良结局风险最高的危重患者。
目的：表征组蛋白与纤维蛋白原的相互作用，并探讨其在体外的作用，在体内和患者样本中。
方法:通过电泳和基于ELISA的亲和测定评估组蛋白-纤维蛋白原结合。使用体外洗涤的血小板和内皮细胞以及体内组蛋白输注小鼠模型来探索功能意义。为了确定临床可翻译性，我们对需要接受重症监护的患者(n=199)进行了回顾性单中心队列研究,并在COVID-19住院患者队列(n=69)中进行了验证.
结果：纤维蛋白原通过其D结构域以高亲和力结合组蛋白（小牛胸腺组蛋白KD=18.0±5.6nM；组蛋白3KD=2.7nM±0.8nM；组蛋白4KD=2.0±0.7nM），并在组蛋白输注小鼠模型中在体外和体内显着降低组蛋白诱导的内皮损伤和血小板聚集。纤维蛋白原的生理浓度可以中和低水平的循环组蛋白，并将组蛋白的细胞毒性阈值提高到50μg/ml。在一群需要重症监护的患者中，入院时组蛋白:纤维蛋白原比值≥6与中重度血小板减少症和独立预测的死亡率相关.这一发现在一组COVID-19住院患者中得到了验证。
结论:纤维蛋白原缓冲循环组蛋白的细胞毒性特性。循环组蛋白和组蛋白：纤维蛋白原比率的检测和监测将确定可能受益于抗组蛋白治疗的不良结局风险最高的危重患者。
