Rother Nils, Pieterse Elmar, Lubbers Jelle, Hilbrands Luuk, van der Vlag Johan
Department of Nephrology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, Netherlands.
Front Immunol. 2017 Sep 14;8:1136. doi: 10.3389/fimmu.2017.01136. eCollection 2017.
Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by the presence of autoantibodies against nuclear components. Lupus nephritis (LN) is the major cause of morbidity and mortality in patients with SLE. Central to the pathogenesis of SLE is the accumulation of cellular waste, especially apoptotic microparticles (MPs), which stimulates diverse immune reactions including the formation of neutrophil extracellular traps (NETs). In this study, we investigated the content of MPs from SLE patients with and without (active) LN, their capacity to stimulate NET release, and assessed the molecular mechanisms underlying MP-induced NETosis.
MPs from SLE patients with biopsy-proven active LN, remissive LN, without LN, and healthy controls were characterized by flow cytometry. Isolated neutrophils were exposed to MPs derived from either patient plasma or apoptotic human umbilical vein endothelial cells, and NET release was quantified by immunofluorescence imaging, spectrofluorometry or an in-house developed NET ELISA.
MPs from SLE patients with active LN contain higher levels of acetylated chromatin compared to MPs from those with remissive LN, without LN, or healthy controls. MPs enriched in hyperacetylated chromatin are more potent in inducing NETosis when compared to MPs containing moderate acetylated chromatin. The release of NETs in response to MPs occurs rapidly in a concentration-dependent manner and proceeds independent from the formation of reactive oxygen species (ROS).
Our data suggest that MPs containing acetylated chromatin drive ROS-independent NET release in SLE patients with active LN, which may lead to the glomerular deposition of NETs and subsequent NET-driven LN.
系统性红斑狼疮（SLE）是一种自身免疫性疾病，其特征是存在针对核成分的自身抗体。狼疮性肾炎（LN）是SLE患者发病和死亡的主要原因。SLE发病机制的核心是细胞废物的积累，尤其是凋亡微粒（MPs），它会刺激包括中性粒细胞胞外陷阱（NETs）形成在内的多种免疫反应。在本研究中，我们调查了有或无（活动期）LN的SLE患者MPs的含量、它们刺激NET释放的能力，并评估了MP诱导NETosis的分子机制。
通过流式细胞术对经活检证实为活动期LN、缓解期LN、无LN的SLE患者以及健康对照者的MPs进行表征。将分离的中性粒细胞暴露于来自患者血浆或凋亡人脐静脉内皮细胞的MPs中，并通过免疫荧光成像、荧光分光光度法或自行开发的NET ELISA对NET释放进行定量。
与缓解期LN、无LN的患者或健康对照者的MPs相比，活动期LN的SLE患者的MPs含有更高水平的乙酰化染色质。与含有中度乙酰化染色质的MPs相比，富含高度乙酰化染色质的MPs在诱导NETosis方面更有效。对MPs作出反应时，NETs的释放迅速且呈浓度依赖性，并且独立于活性氧（ROS）的形成而进行。
我们的数据表明，含有乙酰化染色质的MPs在活动期LN的SLE患者中驱动不依赖ROS的NET释放，这可能导致NETs在肾小球沉积并随后引发NET驱动的LN。
