Akita University, Akita, Japan.
Sagamihara National Hospital, Kanagawa, Japan.
Arthritis Rheumatol. 2021 Sep;73(9):1683-1693. doi: 10.1002/art.41727. Epub 2021 Aug 11.
Eosinophils are tissue-dwelling immune cells. Accumulating evidence indicates that a type of cell death termed ETosis is an important cell fate involved in the pathophysiology of inflammatory diseases. Although the critical role of eosinophils in eosinophilic granulomatosis with polyangiitis (EGPA; formerly Churg-Strauss syndrome) is well established, the presence of eosinophil ETosis (EETosis) is poorly understood. We undertook this study to better understand the characteristics of EETosis.
In vitro studies using blood-derived eosinophils were conducted to characterize EETosis. The occurrence of EETosis in tissues from patients with EGPA was studied by immunostaining and electron microscopy. Serum concentrations of eosinophil-derived proteins in healthy controls, patients with asthma, and EGPA patients with active disease or with disease in remission (n = 15 per group) were examined.
EETosis was reliant on reactive oxygen species and peptidylarginine deiminase type 4-dependent histone citrullination, resulting in the cytolytic release of net-like eosinophil extracellular traps, free galectin-10, and membrane-bound intact granules. The signature of EETosis, including loss of cytoplasmic galectin-10 and deposition of granules, was observed in eosinophils infiltrating various tissues from EGPA patients. Serum eosinophil granule proteins and galectin-10 levels were increased in EGPA and positively correlated with disease activity as assessed by the Birmingham Vasculitis Activity Score (r = 0.8531, P < 0.0001 for galectin-10). When normalized to blood eosinophil counts, this correlation remained for galectin-10 (r = 0.7168, P < 0.0001) but not for granule proteins. Galectin-10 levels in active EGPA positively correlated with serum interleukin-5 levels.
Eosinophils infiltrating diseased tissues in EGPA undergo EETosis. Considering the exclusive expression and large pool of cytoplasmic galectin-10 in eosinophils, elevated serum galectin-10 levels in patients with EGPA might reflect the systemic occurrence of cytolytic EETosis.
嗜酸性粒细胞是组织驻留的免疫细胞。越来越多的证据表明，一种被称为 ETosis 的细胞死亡类型是参与炎症性疾病病理生理学的重要细胞命运。尽管嗜酸性粒细胞在嗜酸性粒细胞性肉芽肿伴多血管炎（EGPA；以前称为 Churg-Strauss 综合征）中的关键作用已得到充分证实，但嗜酸性粒细胞 ETosis（EETosis）的存在仍知之甚少。我们进行这项研究是为了更好地了解 EETosis 的特征。
使用血液来源的嗜酸性粒细胞进行体外研究以表征 EETosis。通过免疫染色和电子显微镜研究 EGPA 患者组织中 EETosis 的发生。检查健康对照者、哮喘患者和 EGPA 患者（每组 15 例，活动期疾病或缓解期疾病）血清中嗜酸性粒细胞衍生蛋白的浓度。
EETosis 依赖于活性氧和肽基精氨酸脱亚氨酶 4 依赖性组蛋白瓜氨酸化，导致细胞溶解性释放网状嗜酸性细胞细胞外陷阱、游离半乳糖凝集素-10 和膜结合完整颗粒。在 EGPA 患者浸润各种组织的嗜酸性粒细胞中观察到 EETosis 的特征，包括细胞质半乳糖凝集素-10 的丢失和颗粒的沉积。EGPA 患者的血清嗜酸性粒细胞颗粒蛋白和半乳糖凝集素-10 水平升高，并与 Birmingham Vasculitis Activity Score（半乳糖凝集素-10 为 r = 0.8531，P < 0.0001；颗粒蛋白为 r = 0.7168，P < 0.0001）评估的疾病活动呈正相关。当与血嗜酸性粒细胞计数归一化时，这种相关性仍然适用于半乳糖凝集素-10（r = 0.7168，P < 0.0001），但不适用于颗粒蛋白。活动期 EGPA 患者的半乳糖凝集素-10 水平与血清白细胞介素-5 水平呈正相关。
EGPA 中浸润病变组织的嗜酸性粒细胞发生 EETosis。考虑到嗜酸性粒细胞中半乳糖凝集素-10 的独特表达和大量细胞质池，EGPA 患者中升高的血清半乳糖凝集素-10 水平可能反映了系统发生的细胞溶解性 EETosis。
