Therapeutic Effect of Anti–TNF-α Antibodies in an Experimental Model of Anti-Neutrophil Cytoplasm Antibody–Associated Systemic Vasculitis

Pham

et al. 2012

112

119

The pathogenesis of anti-neutrophil cytoplasmic antibody (ANCA)-associated necrotizing crescentic GN (NCGN) is incompletely understood. Dipeptidyl peptidase I (DPPI) is a cysteine protease required for the activation of neutrophil serine proteases (NSPs) cathepsin G, neutrophil elastase, and proteinase 3, which are enzymes that modulate inflammation. We used a mouse model of anti-myeloperoxidase (MPO) antibodyinduced NCGN to determine whether active NSPs contribute to its pathogenesis. MPO-deficient animals immunized with murine MPO, irradiated, and transplanted with wild-type bone marrow developed NCGN. In contrast, transplantation with bone marrow that lacked DPPI or lacked both neutrophil elastase and proteinase 3 protected mice from NCGN induced by anti-MPO antibody. The kidneys of mice reconstituted with DPPI-deficient bone marrow generated significantly less IL-1b than did those of mice reconstituted with wild-type bone marrow; similarly, in vitro, DPPI-deficient monocytes produced significantly less IL-1b in response to anti-MPO antibody than did wild-type monocytes. This reduction in IL-1b was NSP dependent; exogenous addition of PR3 restored IL-b production in DPPI-deficient monocytes. Last, the IL-1 receptor antagonist anakinra protected animals against anti-MPO antibody-induced NCGN (16.7%66.0% versus 2.4%61.7% crescents), suggesting that IL-1b is a critical inflammatory mediator in this model. These data suggest that the development of anti-MPO antibody-induced NCGN requires NSP-dependent IL-1b generation and that these processes may provide therapeutic targets for ANCAmediated diseases in humans.

Section: Discussionmentioning

confidence: 99%

Neutrophil Serine Proteases Promote IL-1β Generation and Injury in Necrotizing Crescentic Glomerulonephritis

Pham

et al. 2012

112

119

“…[1][2][3][4] Animal models firmly established ANCA pathogenicity for NCGN. [5][6][7][8][9][10] Numerous in vitro experiments suggest that phagocyte NADPH oxidase (Nox) and granule proteins, including neutrophil serine proteases (NSPs), participate in ANCA-mediated endothelial damage. 2,[11][12][13] We used a murine ANCA NCGN model and recently showed that IL-1b provides an important disease mediator and that proteolytically active NSPs are essential for processing pro-IL-1b to IL1b.…”

mentioning

confidence: 99%

Phagocyte NADPH Oxidase Restrains the Inflammasome in ANCA-Induced GN

Luft

Kettritz

2015

ANCA-activated phagocytes cause vasculitis and necrotizing crescentic GN (NCGN). ANCA-induced phagocyte NADPH oxidase (Phox) may contribute by generating tissue-damaging reactive oxygen species. We tested an alternative hypothesis, in which Phox restrains inflammation by downregulating caspase-1, thereby reducing IL-1b generation and limiting NCGN. In an antimyeloperoxidase (anti-MPO) antibody-mediated disease model, mice transplanted with either gp91 phox -deficient or p47 phox -deficient bone marrow showed accelerated disease with increased crescents, necrosis, glomerular monocytes, and renal IL-1b levels compared with mice transplanted with wild-type bone marrow. IL-1b receptor blockade abrogated aggravated NCGN in gp91 phox -deficient mice. In vitro, challenge with anti-MPO antibody strongly enhanced caspase-1 activity and IL-1b generation in gp91 phox -deficient and p47 phox -deficient monocytes compared with wild-type monocytes. This enhanced IL-1b generation was abrogated when caspase-1 was blocked. ANCA-induced superoxide and IL-1b generation were inversely related in human monocytes. Furthermore, transplantation of gp91 phox /caspase-1 double-deficient bone marrow rescued the accelerated NCGN phenotype in gp91 phox bone marrow-deficient mice. These results suggest that Phox-generated reactive oxygen species downregulate caspase-1, thereby keeping the inflammasome in check and limiting ANCA-induced inflammation. IL-1 receptor blockade may provide a promising strategy in NCGN, whereas our data question the benefit of antioxidants.

“…With use of these model systems, TNF␣, complement, chemokines, and integrins were identified as potential targets. [22][23][24][25][26] We optimized an MPO-ANCA mouse model and showed that the complement receptor C5a and the PI3K␥ isoform are novel targets. 27,28 We used this model to assess NCGN with the 26S proteasome inhibitor bortezomib (BTZ), compared with standard steroid/cyclophosphamide (S/CYC) treatment.…”

mentioning

confidence: 99%

Myeloperoxidase-Specific Plasma Cell Depletion by Bortezomib Protects from Anti-Neutrophil Cytoplasmic Autoantibodies–Induced Glomerulonephritis

Bontscho

Manz

et al. 2011

Anti-neutrophil cytoplasmic autoantibodies (ANCA) cause vasculitis and necrotizing crescentic glomerulonephritis (NCGN). Steroids and cytotoxic drugs reduce mortality but can cause significant adverse events. The proteasome inhibitor bortezomib (BTZ) prevents glomerulonephritis in mouse models of lupus but its efficacy in ANCA-associated glomerulonephritis is unknown. We induced anti-MPO IgGmediated NCGN by transplanting wild-type bone marrow (BM) into irradiated MPO-deficient mice immunized with MPO. Four weeks after BM transplantation, we treated mice with steroid/cyclophosphamide (S/CYC) or BTZ. Compared with untreated control mice, both S/CYC and BTZ significantly reduced urine abnormalities, NCGN, and infiltration of neutrophils and macrophages. Response to BTZ depended on timing of administration: BTZ abrogated NCGN if begun 3 weeks, but not 5 weeks, after BM transplantation. BTZ treatment significantly reduced total and MPO-specific plasma cells in both the spleen and bone marrow, resulting in significantly reduced anti-MPO titers. Furthermore, BTZ affected neither B cells nor total CD4 and CD8 T cells, including their naive and effector subsets. In contrast, S/CYC reduced the total number of cells in the spleen, including total and MPO-specific plasma cells and B cells. In contrast to BTZ, S/CYC did not affect total and MPO-specific plasma cells in the bone marrow. Three of 23 BTZ-treated mice died within 36 hours after BTZ administration. In summary, BTZ depletes MPO-specific plasma cells, reduces anti-MPO titers, and prevents NCGN in mice.