Proteinase 3 and neutrophil elastase enhance inflammation in mice by inactivating antiinflammatory progranulin
Kai Kessenbrock, Leopold Fröhlich, Michael Sixt, Tim Lämmermann, Heiko Pfister, Andrew Bateman, Azzaq Belaaouaj, Johannes Ring, Markus Ollert, Reinhard Fässler, Dieter E. Jenne
Kai Kessenbrock, Leopold Fröhlich, Michael Sixt, Tim Lämmermann, Heiko Pfister, Andrew Bateman, Azzaq Belaaouaj, Johannes Ring, Markus Ollert, Reinhard Fässler, Dieter E. Jenne
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Research Article Inflammation

Proteinase 3 and neutrophil elastase enhance inflammation in mice by inactivating antiinflammatory progranulin

Abstract

Neutrophil granulocytes form the body’s first line of antibacterial defense, but they also contribute to tissue injury and noninfectious, chronic inflammation. Proteinase 3 (PR3) and neutrophil elastase (NE) are 2 abundant neutrophil serine proteases implicated in antimicrobial defense with overlapping and potentially redundant substrate specificity. Here, we unraveled a cooperative role for PR3 and NE in neutrophil activation and noninfectious inflammation in vivo, which we believe to be novel. Mice lacking both PR3 and NE demonstrated strongly diminished immune complex–mediated (IC-mediated) neutrophil infiltration in vivo as well as reduced activation of isolated neutrophils by ICs in vitro. In contrast, in mice lacking just NE, neutrophil recruitment to ICs was only marginally impaired. The defects in mice lacking both PR3 and NE were directly linked to the accumulation of antiinflammatory progranulin (PGRN). Both PR3 and NE cleaved PGRN in vitro and during neutrophil activation and inflammation in vivo. Local administration of recombinant PGRN potently inhibited neutrophilic inflammation in vivo, demonstrating that PGRN represents a crucial inflammation-suppressing mediator. We conclude that PR3 and NE enhance neutrophil-dependent inflammation by eliminating the local antiinflammatory activity of PGRN. Our results support the use of serine protease inhibitors as antiinflammatory agents.

Authors

Kai Kessenbrock, Leopold Fröhlich, Michael Sixt, Tim Lämmermann, Heiko Pfister, Andrew Bateman, Azzaq Belaaouaj, Johannes Ring, Markus Ollert, Reinhard Fässler, Dieter E. Jenne

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Figure 6

PGRN is a potent inhibitor of IC-stimulated inflammation in vivo.

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PGRN is a potent inhibitor of IC-stimulated inflammation in vivo. Recomb...
Recombinant mouse PGRN (2 μg) was intradermally applied with anti-OVA IgG, and the RPA was started in WT and Prtn3–/–Ela2–/– mice (n = 5 per group). (A) After 4 h, the effect of PGRN application was evaluated by histological analyses. Representative images show neutrophil infiltrates at the panniculus carnosus muscle (asterisks). Scale bars: 200 μm. (B and C) Effect of PGRN administration on neutrophil influx. In both WT (B) and Prtn3–/–Ela2–/– (C) mice, neutrophil infiltration was significantly diminished at PGRN-treated sites compared with untreated sites. This effect appeared to be more pronounced in the protease-deficient mice. Data are mean ± SEM infiltrated neutrophils per HPF. *P < 0.05; **P < 0.01. (D) Neutrophils isolated ex vivo from inflamed peritoneum of WT and Prtn3–/–Ela2–/– mice were analyzed by anti-mouse PGRN Western blot of concentrated neutrophil lysates. Intact PGRN was found abundantly in Prtn3–/–Ela2–/– but not WT neutrophils. Loading was controlled using anti-actin Western blot.