Helicobacter urease–induced activation of the TLR2/NLRP3/IL-18 axis protects against asthma
Katrin N. Koch, … , Christian Taube, Anne Müller
Katrin N. Koch, … , Christian Taube, Anne Müller
Published July 27, 2015
Citation Information: J Clin Invest. 2015;125(8):3297-3302. https://doi.org/10.1172/JCI79337.
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Brief Report Pulmonology

Helicobacter urease–induced activation of the TLR2/NLRP3/IL-18 axis protects against asthma

Abstract

Inflammasome activation and caspase-1–dependent (CASP1-dependent) processing and secretion of IL-1β and IL-18 are critical events at the interface of the bacterial pathogen Helicobacter pylori with its host. Whereas IL-1β promotes Th1 and Th17 responses and gastric immunopathology, IL-18 is required for Treg differentiation, H. pylori persistence, and protection against allergic asthma, which is a hallmark of H. pylori–infected mice and humans. Here, we show that inflammasome activation in DCs requires the cytoplasmic sensor NLRP3 as well as induction of TLR2 signaling by H. pylori. Screening of an H. pylori transposon mutant library revealed that pro–IL-1β expression is induced by LPS from H. pylori, while the urease B subunit (UreB) is required for NLRP3 inflammasome licensing. UreB activates the TLR2-dependent expression of NLRP3, which represents a rate-limiting step in NLRP3 inflammasome assembly. ureB-deficient H. pylori mutants were defective for CASP1 activation in murine bone marrow–derived DCs, splenic DCs, and human blood-derived DCs. Despite colonizing the murine stomach, ureB mutants failed to induce IL-1β and IL-18 secretion and to promote Treg responses. Unlike WT H. pylori, ureB mutants were incapable of conferring protection against allergen-induced asthma in murine models. Together, these results indicate that the TLR2/NLRP3/CASP1/IL-18 axis is critical to H. pylori–specific immune regulation.

Authors

Katrin N. Koch, Mara L. Hartung, Sabine Urban, Andreas Kyburz, Anna S. Bahlmann, Judith Lind, Steffen Backert, Christian Taube, Anne Müller

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Figure 3

H. pylori urease is required for CASP1 activation, persistence, and asthma protection in neonatally infected mice.

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H. pylori urease is required for CASP1 activation, persistence, and ast...
(A–E) Neonatal C57BL/6 mice were infected for 1 month with WT or Δure H. pylori PMSS1 and assessed with respect to (A) gastric colonization, (B) gastric mucosal NLRP3 and CASP1 (asterisk indicates the NLRP3-specific band), (C) Nlrp3 expression, (D) IL-18, and (E) Ifng expression, as analyzed by (B) Western blotting, (D) ELISA, and/or (C and E) qRT-PCR. (F–M) Neonatally infected mice were additionally sensitized and challenged (s.c.) with (F–I) ovalbumin or (J–M) house dust mite (HDM) allergen starting at 4 weeks after infection to induce allergic asthma; αIL-18 mAb was administered weekly starting at the time of infection. Inf, infection. (F and J) Eosinophils in 1 ml of bronchoalveolar lavage fluid (BALF). (G) IL-5 ELISA of ovalbumin-restimulated lung single cell preparations. (H and L) Lung inflammation, as assessed on H&E-stained sections. (I and M) Goblet cell metaplasia, as quantified on PAS-stained sections. BM, basement membrane. (K) House dust mite–specific serum IgE, as determined by ELISA. (N) H. pylori colonization of WT, Tlr2–/–, and Nlrp3–/– mice 1 month after infection. Symbols represent individual animals, and horizontal lines indicate the medians. Pooled data from 2 (A–E and N) and 3 (F–M) independent experiments are shown. *P ≤ 0.05, **P ≤ 0.01, ***P ≤ 0.001, Mann-Whitney U test.