Decreased Neutrophil Apoptosis in Quiescent ANCA-Associated Systemic Vasculitis

Abstract

BackgroundANCA-Associated Systemic Vasculitis (AASV) is characterized by leukocytoclasis, accumulation of unscavenged apoptotic and necrotic neutrophils in perivascular tissues. Dysregulation of neutrophil cell death may contribute directly to the pathogenesis of AASV.MethodsNeutrophils from Healthy Blood Donors (HBD), patients with AASV most in complete remission, Polycythemia Vera (PV), Systemic Lupus Erythematosus (SLE), Rheumatoid Arthritis (RA) and renal transplant recipients (TP) were incubated in vitro, and the rate of spontaneous apoptosis was measured by FACS. Plasma levels of cytokines and sFAS were measured with cytometric bead array and ELISA. Expression of pro/anti-apoptotic factors, transcription factors C/EBP-α, C/EBP-β and PU.1 and inhibitors of survival/JAK2-pathway were measured by real-time-PCR.ResultsAASV, PV and RA neutrophils had a significantly lower rate of apoptosis compared to HBD neutrophils (AASV 50±14% vs. HBD 64±11%, p<0.0001). In RA but not in AASV and PV, low apoptosis rate correlated with increased plasma levels of GM-CSF and high mRNA levels of anti-apoptotic factors Bcl-2A1 and Mcl-1. AASV patients had normal levels of G-CSF, GM-CSF and IL-3. Both C/EBP-α, C/EBP-β were significantly higher in neutrophils from AASV patients than HBD. Levels of sFAS were significantly higher in AASV compared to HBD.ConclusionNeutrophil apoptosis rates in vitro are decreased in AASV, RA and PV but mechanisms seem to differ. Increased mRNA levels of granulopoiesis-associated transcription factors and increased levels of sFAS in plasma were observed in AASV. Additional studies are required to define the mechanisms behind the decreased apoptosis rates, and possible connections with accumulation of dying neutrophils in regions of vascular lesions in AASV patients.

Circulating mitochondrial DNA in serum of patients with granulomatosis with polyangiitis

“…However, Abdgawad et al . observed that spontaneous apoptosis of neutrophils is decreased in these diseases . Our results also support decreased neutrophil apoptosis in GPA (Supporting information, Fig.…”

Proteinase 3, the Autoantigen in Granulomatosis with Polyangiitis, Associates with Calreticulin on Apoptotic Neutrophils, Impairs Macrophage Phagocytosis, and Promotes Inflammation

“…Along the same lines, we have recently reported high levels of the cytoplasmic proliferating cell nuclear Ag, thus reflecting a prosurvival state in neutrophils from GPA patients (47). Although in this study no difference was observed in PS externalization in patients with ANCA-associated vasculitis, it has been recently reported that neutrophils from these patients had a delayed apoptosis (48). Regardless of the initiating mechanisms, unscavenged apoptotic neutrophils could release their intracellular content, explaining why patients with ANCA-associated vasculitis develop autoimmunity against neutrophil proteins released in tissues (49).…”

Neutrophil extracellular traps mediate transfer of cytoplasmic neutrophil antigens to myeloid dendritic cells toward ANCA induction and associated autoimmunity

“…In addition, in SVV, the prototypical ANCA-related autoimmune disease, elevated levels of granulopoiesis-related transcription factors (eg, CEBP-␤) and cytokines (eg, G-CSF) have been recently implicated in the decreased rate of PMN apoptosis, which suggests a role for the types of PMN death other than apoptosis in the pathogenesis of ANCA-associated autoimmunity. 39 Would the factors involved in the enhanced granulopoiesis of SVV patients also be responsible for skewing PMN death from apoptosis to NETosis, the arousal of pathogenic ANCA may find an explanation. Here we show that NETosis, is both immunogenic and proinflammatory whereas apoptosis is known to be poorly effective in inducing inflammation.…”