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 1

CASP1 activation by H. pylori depends on NLRP3, ASC, and TLR2.

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CASP1 activation by H. pylori depends on NLRP3, ASC, and TLR2. (A–G) BM...
(A–G) BMDCs from mice of the indicated genotypes were infected overnight with H. pylori NSH57, G27, and/or PMSS1. (A, C, and E) Western blot analysis of CASP1 activation (p10) in the cell supernatant compared to full-length CASP1 p45 and GAPDH in the extract. Representative results of 3 independent experiments are shown (n = 3). (B, D, and F) IL-1β ELISA of culture supernatants; cells were prestimulated with E. coli LPS prior to infection. Uninf, uninfected. (G) Il1b transcription, as measured by qRT-PCR (normalized to Gapdh and to uninfected controls). Mean + SD of 3 independent experiments is shown (n = 3). (H and I) CD11c+ splenic DCs were infected overnight with G27. (H) IL-1β and (I) IL-18 secretion was measured by ELISA. Representative data of 3 independent experiments are shown (n = 3). (J and K) Mice were infected for 1 month with PMSS1 prior to the quantification of (J) gastric colonization and (K) Ifng expression. Pooled data from 2 studies are shown (n = 2). Horizontal lines indicate medians. *P ≤ 0.05, **P ≤ 0.01, ***P ≤ 0.001, Mann-Whitney U test. Error bars represent mean + SD.