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 4

Exacerbated pristane-induced lupus in NET-deficient PAD4–/– mice.

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Exacerbated pristane-induced lupus in NET-deficient PAD4–/– mice. (A) De...
(A) Development of lupus autoantibodies in C57BL/6 WT and PAD4−/− mice. Autoantibodies against double-stranded DNA (dsDNA), Sm/RNP, and histone were analyzed in sera of naive mice and mice 150 days after pristane priming by ELISA. Scatter plots show individual measurements, means, and SEM of 8 to 12 mice per group. ***P < 0.001 as determined by 2-way ANOVA with Bonferroni post-hoc test. (B) Quantification of proteinuria in C57BL/6 WT and PAD4–/– mice 150 days after pristane injection (n = 8). *P < 0.05 as determined by 2-tailed Student’s t test. (C) Survival plot of C57BL/6 WT and PAD4–/– mice after pristane injection (n = 12). (D) Representative fluorescence microscopy images and (E) quantification of peritoneal cells isolated 1 day after injection of pristane from PAD4–/– and WT mice and stained for DNA with propidium iodide (PI, red) and for neutrophil elastase (NE, green). Scale bars: 100 μm. Scatter plot in E shows individual values, mean, and SEM of cells having undergone neutrophil extracellular trap (NET) formation, defined as PI+NE+ events with a 5-fold greater mean nuclear size. **P < 0.01 as determined by 2-tailed Student’s t test. (F) Concentrations of selected cytokines and chemokines in peritoneal lavages from PAD4–/–and WT mice 0 and 1 day after injection of pristane. Scatter plots show individual values, means, and SEM of 3 mice per group.