Proteinase 3 on apoptotic cells disrupts immune silencing in autoimmune vasculitis

Abstract

Granulomatosis with polyangiitis (GPA) is a systemic necrotizing vasculitis that is associated with granulomatous inflammation and the presence of anti-neutrophil cytoplasmic antibodies (ANCAs) directed against proteinase 3 (PR3). We previously determined that PR3 on the surface of apoptotic neutrophils interferes with induction of antiinflammatory mechanisms following phagocytosis of these cells by macrophages. Here, we demonstrate that enzymatically active membrane-associated PR3 on apoptotic cells triggered secretion of inflammatory cytokines, including granulocyte CSF (G-CSF) and chemokines. This response required the IL-1R1/MyD88 signaling pathway and was dependent on the synthesis of NO, as macrophages from animals lacking these pathways did not exhibit a PR3-associated proinflammatory response. The PR3-induced microenvironment facilitated recruitment of inflammatory cells, such as macrophages, plasmacytoid DCs (pDCs), and neutrophils, which were observed in close proximity within granulomatous lesions in the lungs of GPA patients. In different murine models of apoptotic cell injection, the PR3-induced microenvironment instructed pDC-driven Th9/Th2 cell generation. Concomitant injection of anti-PR3 ANCAs with PR3-expressing apoptotic cells induced a Th17 response, revealing a GPA-specific mechanism of immune polarization. Accordingly, circulating CD4+ T cells from GPA patients had a skewed distribution of Th9/Th2/Th17. These results reveal that PR3 disrupts immune silencing associated with clearance of apoptotic neutrophils and provide insight into how PR3 and PR3-targeting ANCAs promote GPA pathophysiology.

Proteinase 3 Is a Phosphatidylserine-binding Protein That Affects the Production and Function of Microvesicles

“…However, this type of interaction does not appear to play a role in apoptosis-induced membrane expression of PR3, which is independent of CD177 expression (11). Furthermore, we recently demonstrated that membrane expression of PR3 under resting conditions or following TNF␣ stimulation does not correlate with membrane expression after the induction of apoptosis, strongly suggesting that different pools of PR3 are present within neutrophils that can be mobilized to the cell surface (34). Importantly, regardless of the mechanisms responsible for PR3 externalization, the integrity of the hydrophobic patch is required (10).…”

“…These results clearly demonstrate that PR3 expressed at the plasma membrane affects the generation of MVs during both activation and apoptosis and that the hydrophobic patch was essential for this effect. To determine whether the serine protease activity of PR3 was required for the decreased MV production, RBL cells were transfected with an enzymatically inactive form of PR3 (PR3/S203A) containing a serine to alanine mutation at position 203 (34). The serine protease activity of PR3 was essential for the decrease in MV production during both activation with calcium ionophore (Fig.…”

Expanding Neutrophil Horizons: New Concepts in Inflammation

“…However, when PR3 is expressed at the neutrophil membrane in an inflammatory context, it alters the nature of phagocytosis by macrophages, promoting a pro-inflammatory rather than anti-inflammatory response [39]. This mechanism appears to be of relevance in anti-neutrophil cytoplasmic antibody-associated vasculitis, a severe inflammatory disorder characterised by the presence of circulating autoantibodies against neutrophil granule enzymes including PR3 [40]. …”

Recent insights into the implications of metabolism in plasmacytoid dendritic cell innate functions: Potential ways to control these functions

“…This is the case of systemic lupus erythematosus (SLE) 52– 54 , type 1 diabetes 69 , and psoriasis 41, 71 . Furthermore, PDC may participate in inflammatory autoimmune disorders ( i.e ., systemic sclerosis 70 or autoimmune vasculitis 72 ) via the secretion of other pro-inflammatory cytokines than type I IFN 72 or chimiokines 70 . Since PDC infiltrate inflamed tissues, they may release pro-inflammatory factors participating in the amplification of diseases.…”