title: Neutrophil extracellular traps can activate alternative complement pathways.
abstract: The interaction between neutrophils and activation of alternative complement pathway plays a pivotal role in the pathogenesis of anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). ANCAs activate primed neutrophils to release neutrophil extracellular traps (NETs), which have recently gathered increasing attention in the development of AAV. The relationship between NETs and alternative complement pathway has not been elucidated. The current study aimed to investigate the relationship between NETs and alternative complement pathway. Detection of components of alternative complement pathway on NETs in vitro was assessed by immunostain and confocal microscopy. Complement deposition on NETs were detected after incubation with magnesium salt ethyleneglycol tetraacetic acid (Mg-EGTA)-treated human serum. After incubation of serum with supernatants enriched in ANCA-induced NETs, levels of complement components in supernatants were measured by enzyme-linked immunosorbent assay (ELISA). Complement factor B (Bb) and properdin deposited on NETs in vitro. The deposition of C3b and C5b-9 on NETs incubated with heat-inactivated normal human serum (Hi-NHS) or EGTA-treated Hi-NHS (Mg-EGTA-Hi-NHS) were significantly less than that on NETs incubated with NHS or EGTA-treated NHS (Mg-EGTA-NHS). NETs induced by ANCA could activate the alternative complement cascade in the serum. In the presence of EGTA, C3a, C5a and SC5b-9 concentration decreased from 800·42 ± 244·81 ng/ml, 7·68 ± 1·50 ng/ml, 382·15 ± 159·75 ng/ml in the supernatants enriched in ANCA induced NETs to 479·07 ± 156·2 ng/ml, 4·86 ± 1·26 ng/ml, 212·65 ± 44·40 ng/ml in the supernatants of DNase I-degraded NETs (P < 0·001, P = 0·008, P < 0·001, respectively). NETs could activate the alternative complement pathway, and might thus participate in the pathogenesis of AAV.
authors.affiliation: Renal Division, Department of Medicine, Peking University First Hospital, Beijing, China.|Institute of Nephrology, Peking University, Beijing, China.|Key Laboratory of Renal Disease, Ministry of Health of China, Beijing, China.|Key Laboratory of Chronic Kidney Disease Prevention and Treatment (Peking University), Ministry of Education, Beijing, China.|Peking-Tsinghua Center for Life Sciences, Beijing, China.
authors.forename: H
authors.initials: H
authors.lastname: Wang
authors.affiliation: Renal Division, Department of Medicine, Peking University First Hospital, Beijing, China.|Institute of Nephrology, Peking University, Beijing, China.|Key Laboratory of Renal Disease, Ministry of Health of China, Beijing, China.|Key Laboratory of Chronic Kidney Disease Prevention and Treatment (Peking University), Ministry of Education, Beijing, China.|Peking-Tsinghua Center for Life Sciences, Beijing, China.
authors.forename: C
authors.initials: C
authors.lastname: Wang
authors.affiliation: Renal Division, Department of Medicine, Peking University First Hospital, Beijing, China.|Institute of Nephrology, Peking University, Beijing, China.|Key Laboratory of Renal Disease, Ministry of Health of China, Beijing, China.|Key Laboratory of Chronic Kidney Disease Prevention and Treatment (Peking University), Ministry of Education, Beijing, China.|Peking-Tsinghua Center for Life Sciences, Beijing, China.
authors.forename: M-H
authors.initials: MH
authors.lastname: Zhao
authors.affiliation: Renal Division, Department of Medicine, Peking University First Hospital, Beijing, China.|Institute of Nephrology, Peking University, Beijing, China.|Key Laboratory of Renal Disease, Ministry of Health of China, Beijing, China.|Key Laboratory of Chronic Kidney Disease Prevention and Treatment (Peking University), Ministry of Education, Beijing, China.|Peking-Tsinghua Center for Life Sciences, Beijing, China.
authors.forename: M
authors.initials: M
authors.lastname: Chen
mesh_terms: D056648:Anti-Neutrophil Cytoplasmic Antibody-Associated Vasculitis / Q000097:blood / Q000276:immunology* / Q000378:metabolism; D019268:Antibodies, Antineutrophil Cytoplasmic / Q000276:immunology / Q000378:metabolism; D002478:Cells, Cultured; D003167:Complement Activation / Q000187:drug effects / Q000276:immunology; D015926:Complement C3a / Q000276:immunology / Q000378:metabolism; D003179:Complement C3b / Q000276:immunology / Q000378:metabolism; D015936:Complement C5a / Q000276:immunology / Q000378:metabolism; D011415:Complement Factor B / Q000276:immunology / Q000378:metabolism; D015938:Complement Membrane Attack Complex / Q000276:immunology / Q000378:metabolism; D003170:Complement Pathway, Alternative / Q000187:drug effects / Q000276:immunology*; D004533:Egtazic Acid / Q000276:immunology / Q000494:pharmacology; D065206:Extracellular Traps / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism; D006358:Hot Temperature; D006801:Humans; D015151:Immunoblotting; D018613:Microscopy, Confocal; D009504:Neutrophils / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D011414:Properdin / Q000276:immunology / Q000378:metabolism; D044967:Serum / Q000187:drug effects / Q000276:immunology
chemical_list: D019268:Antibodies, Antineutrophil Cytoplasmic; D015938:Complement Membrane Attack Complex; C047610:SC5b-9 protein complex; D011414:Properdin; D004533:Egtazic Acid; D015926:Complement C3a; D003179:Complement C3b; D015936:Complement C5a; D011415:Complement Factor B
keywords: ANCA; alternative complement pathway; complement; neutrophil extracellular traps; vasculitis