Department of Rheumatology, Endocrinology, and Nephrology, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Japan.
Division of Rheumatology and Clinical Immunology, Sapporo Medical University, Sapporo, Japan.
JCI Insight. 2023 Aug 8;8(15):e167486. doi: 10.1172/jci.insight.167486.
Neutrophil extracellular trap (NET) formation contributes to immune defense and is a distinct form of cell death. Excessive NET formation is found in patients with anti-neutrophil cytoplasmic antibody-associated (ANCA-associated) vasculitis (AAV), contributing to disease progression. The clearance of dead cells by macrophages, a process known as efferocytosis, is regulated by the CD47-mediated "don't eat me" signal. Hence, we hypothesized that pathogenic NETs in AAV escape from efferocytosis via the CD47 signaling pathway, resulting in the development of necrotizing vasculitis. Immunostaining for CD47 in human renal tissues revealed high CD47 expression in crescentic glomerular lesions of patients with AAV. In ex vivo studies, ANCA-induced netting neutrophils increased the expression of CD47 with the reduction of efferocytosis. After efferocytosis, macrophages displayed proinflammatory phenotypes. The blockade of CD47 in spontaneous crescentic glomerulonephritis-forming/Kinjoh (SCG/Kj) mice ameliorated renal disease and reduced myeloperoxidase-ANCA (MPO-ANCA) titers with a reduction in NET formation. Thus, CD47 blockade would protect against developing glomerulonephritis in AAV via restored efferocytosis of ANCA-induced NETs.
中性粒细胞胞外诱捕网(NET)的形成有助于免疫防御,是一种独特的细胞死亡形式。抗中性粒细胞胞浆抗体相关性血管炎(AAV)患者中发现过量的 NET 形成,这有助于疾病的进展。巨噬细胞通过吞噬作用清除死亡细胞,这一过程被称为吞噬作用,受 CD47 介导的“不要吃我”信号调控。因此,我们假设 AAV 中的致病 NET 通过 CD47 信号通路逃避吞噬作用,导致坏死性血管炎的发生。在人类肾组织的免疫染色中,我们发现 AAV 患者新月体肾小球病变中 CD47 表达较高。在离体研究中,抗中性粒细胞胞浆抗体诱导的 NET 形成中性粒细胞增加了 CD47 的表达,同时吞噬作用减少。吞噬作用后,巨噬细胞表现出促炎表型。在自发性新月体肾小球肾炎形成/Kinjoh(SCG/Kj)小鼠中阻断 CD47 可改善肾脏疾病,并降低髓过氧化物酶-抗中性粒细胞胞浆抗体(MPO-ANCA)滴度,同时减少 NET 形成。因此,通过恢复 ANCA 诱导的 NET 的吞噬作用,CD47 阻断可防止 AAV 发展为肾小球肾炎。