School of Medicine, Institute of Biochemistry, Justus-Liebig-University, Giessen, Germany.
PLoS One. 2012;7(2):e32366. doi: 10.1371/journal.pone.0032366. Epub 2012 Feb 28.
Neutrophils play an important role in innate immunity by defending the host organism against invading microorganisms. Antimicrobial activity of neutrophils is mediated by release of antimicrobial peptides, phagocytosis as well as formation of neutrophil extracellular traps (NET). These structures are composed of DNA, histones and granular proteins such as neutrophil elastase and myeloperoxidase. This study focused on the influence of NET on the host cell functions, particularly on human alveolar epithelial cells as the major cells responsible for gas exchange in the lung. Upon direct interaction with epithelial and endothelial cells, NET induced cytotoxic effects in a dose-dependent manner, and digestion of DNA in NET did not change NET-mediated cytotoxicity. Pre-incubation of NET with antibodies against histones, with polysialic acid or with myeloperoxidase inhibitor but not with elastase inhibitor reduced NET-mediated cytotoxicity, suggesting that histones and myeloperoxidase are responsible for NET-mediated cytotoxicity. Although activated protein C (APC) did decrease the histone-induced cytotoxicity in a purified system, it did not change NET-induced cytotoxicity, indicating that histone-dependent cytotoxicity of NET is protected against APC degradation. Moreover, in LPS-induced acute lung injury mouse model, NET formation was documented in the lung tissue as well as in the bronchoalveolar lavage fluid. These data reveal the important role of protein components in NET, particularly histones, which may lead to host cell cytotoxicity and may be involved in lung tissue destruction.
中性粒细胞通过抵御入侵的微生物来保护宿主生物体，从而在先天免疫中发挥重要作用。中性粒细胞的抗菌活性是通过释放抗菌肽、吞噬作用以及形成中性粒细胞胞外陷阱（NET）来介导的。这些结构由 DNA、组蛋白和颗粒蛋白（如中性粒细胞弹性蛋白酶和髓过氧化物酶）组成。本研究重点关注 NET 对宿主细胞功能的影响，特别是对肺泡上皮细胞的影响，肺泡上皮细胞是肺部气体交换的主要细胞。NET 与上皮细胞和内皮细胞直接相互作用，以剂量依赖的方式诱导细胞毒性作用，并且 NET 中的 DNA 消化不会改变 NET 介导的细胞毒性。NET 与针对组蛋白的抗体、多涎酸或髓过氧化物酶抑制剂预孵育，但与弹性蛋白酶抑制剂不孵育，可降低 NET 介导的细胞毒性，表明组蛋白和髓过氧化物酶是 NET 介导的细胞毒性的原因。虽然活化蛋白 C（APC）在纯化系统中确实降低了组蛋白诱导的细胞毒性，但它没有改变 NET 诱导的细胞毒性，表明 NET 的组蛋白依赖性细胞毒性受到 APC 降解的保护。此外，在 LPS 诱导的急性肺损伤小鼠模型中，在肺组织和支气管肺泡灌洗液中都记录到了 NET 的形成。这些数据揭示了 NET 中蛋白质成分的重要作用，特别是组蛋白，这可能导致宿主细胞毒性，并可能参与肺组织破坏。
