Department of Biology, Central Michigan University, Mount Pleasant, Michigan, USA.
Department of Microbiology, Immunology and Cancer Biology, University of Virginia, Charlottesville, Virginia, USA.
J Leukoc Biol. 2020 Dec;108(6):1841-1850. doi: 10.1002/JLB.3AB0320-156R. Epub 2020 May 25.
Staphylococcus aureus enhances neutrophil extracellular vesicle (EV) production. To investigate whether S. aureus viability influences EV biogenesis, EVs were isolated from human neutrophils incubated with viable bacteria (bEVs) or heat-killed bacteria (heat-killed EVs). Protein analysis, nanoparticle tracking and transmission electron microscopy showed comparable EV production between subsets, and both viable and nonviable bacteria were also detected in respective EV subsets. As anticipated, S. aureus, as well as bEVs with viable bacteria, were proinflammatory, and killing bacteria with gentamicin reduced cytokine production to baseline levels. Although heat-killed bacteria induced macrophage IL-6 production, heat-killed EVs did not. Additionally, we found that human and bacterial DNA associated with bEVs, but not heat-killed EVs, and that the DNA association could be partially decreased by disrupting electrostatic interactions. We investigated the potential for DNA isolated from EVs (EV-DNA) or EVs to cause inflammation. Although liposomal encapsulation of EV-DNA increased IL-6 production from baseline by 7.5-fold, treatment of bEVs with DNase I had no effect on IL-6 and IL-1β production, suggesting that the DNA did not contribute to the inflammatory response. Filtered EVs, which lacked DNA and associated bacteria, exhibited less proinflammatory activity relative to bEVs, and enhanced macrophage expression of CD86 and HLA-DR. Ultimately, we show that bEVs isolated by differential centrifugation co-purify with bacteria and DNA, and studying their concerted activity and relative contribution to immune response is important to the study of host-pathogen interactions.
金黄色葡萄球菌可增强中性粒细胞细胞外囊泡(EV)的产生。为了研究金黄色葡萄球菌的活力是否影响 EV 的生物发生,我们从与活细菌(bEVs)或热灭活细菌(热灭活 EVs)孵育的人中性粒细胞中分离出 EV。蛋白质分析、纳米颗粒跟踪和透射电子显微镜显示,这两种亚群的 EV 产生相当,并且在各自的 EV 亚群中也检测到活细菌和非活细菌。正如预期的那样,金黄色葡萄球菌以及带有活细菌的 bEVs 都具有促炎作用,用庆大霉素杀死细菌可将细胞因子产生降低至基线水平。尽管热灭活细菌诱导巨噬细胞产生 IL-6,但热灭活 EVs 没有。此外,我们发现与 bEVs 相关但与热灭活 EVs 不相关的人源和细菌 DNA,并且通过破坏静电相互作用可以部分减少 DNA 与 EV 的关联。我们研究了 EV 分离的 DNA(EV-DNA)或 EV 引起炎症的潜力。尽管 EV-DNA 的脂质体包封使 IL-6 的产生从基线增加了 7.5 倍,但用 DNase I 处理 bEVs 对 IL-6 和 IL-1β的产生没有影响,这表明 DNA 不会引起炎症反应。与 bEVs 相比,经滤过的缺乏 DNA 和相关细菌的 EV 显示出较弱的促炎活性,并且增强了巨噬细胞 CD86 和 HLA-DR 的表达。最终,我们表明通过差速离心分离的 bEVs 与细菌和 DNA 共纯化,并且研究它们的协同作用及其对免疫反应的相对贡献对于宿主-病原体相互作用的研究很重要。