Experimental lupus is aggravated in mouse strains with impaired induction of neutrophil extracellular traps
Deborah Kienhöfer, Jonas Hahn, Julia Stoof, Janka Zsófia Csepregi, Christiane Reinwald, Vilma Urbonaviciute, Caroline Johnsson, Christian Maueröder, Malgorzata J. Podolska, Mona H. Biermann, Moritz Leppkes, Thomas Harrer, Malin Hultqvist, Peter Olofsson, Luis E. Munoz, Attila Mocsai, Martin Herrmann, Georg Schett, Rikard Holmdahl, Markus H. Hoffmann
Deborah Kienhöfer, Jonas Hahn, Julia Stoof, Janka Zsófia Csepregi, Christiane Reinwald, Vilma Urbonaviciute, Caroline Johnsson, Christian Maueröder, Malgorzata J. Podolska, Mona H. Biermann, Moritz Leppkes, Thomas Harrer, Malin Hultqvist, Peter Olofsson, Luis E. Munoz, Attila Mocsai, Martin Herrmann, Georg Schett, Rikard Holmdahl, Markus H. Hoffmann
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Research Article Inflammation

Experimental lupus is aggravated in mouse strains with impaired induction of neutrophil extracellular traps

Abstract

Many effector mechanisms of neutrophils have been implicated in the pathogenesis of systemic lupus erythematosus (SLE). Neutrophil extracellular traps (NETs) have been assigned a particularly detrimental role. Here we investigated the functional impact of neutrophils and NETs on a mouse model of lupus triggered by intraperitoneal injection of the cell death–inducing alkane pristane. Pristane-induced lupus (PIL) was aggravated in 2 mouse strains with impaired induction of NET formation, i.e., NOX2-deficient (Ncf1-mutated) and peptidyl arginine deiminase 4–deficient (PAD4-deficient) mice, as seen from elevated levels of antinuclear autoantibodies (ANAs) and exacerbated glomerulonephritis. We observed a dramatically reduced ability to form pristane-induced NETs in vivo in both Ncf1-mutated and PAD4-deficient mice, accompanied by higher levels of inflammatory mediators in the peritoneum. Similarly, neutropenic Mcl-1ΔMyelo mice exhibited higher levels of ANAs, which indicates a regulatory function in lupus of NETs and neutrophils. Blood neutrophils from Ncf1-mutated and human individuals with SLE exhibited exuberant spontaneous NET formation. Treatment with specific chemical NOX2 activators induced NET formation and ameliorated PIL. Our findings suggest that aberrant NET is one of the factors promoting experimental lupus-like autoimmunity by uncontrolled release of inflammatory mediators.

Authors

Deborah Kienhöfer, Jonas Hahn, Julia Stoof, Janka Zsófia Csepregi, Christiane Reinwald, Vilma Urbonaviciute, Caroline Johnsson, Christian Maueröder, Malgorzata J. Podolska, Mona H. Biermann, Moritz Leppkes, Thomas Harrer, Malin Hultqvist, Peter Olofsson, Luis E. Munoz, Attila Mocsai, Martin Herrmann, Georg Schett, Rikard Holmdahl, Markus H. Hoffmann

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Figure 6

ROS production and neutrophil extracellular trap (NET) formation in human individuals with SLE.

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ROS production and neutrophil extracellular trap (NET) formation in huma...
(A) ROS production in neutrophils from systemic lupus erythematosus (SLE) patients and normal healthy donors (NHDs). The capacities of CD14–CD16+ polymorphonuclear leukocytes (PMNs) from NHDs (n = 13), SLE patients (n = 34), and patients with chronic granulomatous disease (CGD, n = 2), to produce ROS spontaneously or upon activation with PMA were investigated using flow cytometry. Scatter plots show individual values, means, and SEM of dihydrorhodamine 123 (DHR-123) mean fluorescence intensity (MFI). n.s., not significant, as determined by Kruskal-Wallis test using Dunn’s multiple comparison test. (B) Quantitative analysis of NETing cells in whole blood drawn from individuals with SLE and NHDs. Scatter plots show individual values, means, and SEM of percentages of propidium iodide– and neutrophil elastase–positive (PI+NE+) events with a 5-fold greater mean nuclear size; n = 24 (NHDs) or n = 27 (SLE). ***P < 0.001, n.s., not significant, as determined by Kruskal-Wallis test using Dunn’s test for multiple comparison. (C) Correlation analysis between ROS production and spontaneous and PMA-induced NET formation in PMNs from SLE patients and NHDs. Spearman coefficients (ρ) and P values (determined by 2-tailed Student’s t test) are depicted within the graphs.