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 2

IL-1β secretion upon H. pylori infection requires LPS-induced transcriptional activation of pro–IL-1β and urease- and TLR2-dependent expression of NLRP3.

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IL-1β secretion upon H. pylori infection requires LPS-induced transcript...
(A) Genome-wide screening for H. pylori tn mutants incapable of IL-1β secretion identifies the indicated mutant categories. R-M, restriction modification. (B) Relative IL-1β secretion of individual tn clones with insertions in ureA, ureB, and HPG27_146. (C–E and I–M) Murine BMDCs, (F and G) splenic CD11c+ DCs, and (H) human blood-derived DCs were infected overnight or for the indicated time points with G27 WT, Δure, or Δ146 strains of H. pylori and analyzed by (C, F, H, K, and M) IL-1β ELISA; (G) IL-18 ELISA; (D, J, and L) CASP1 p10 and p45, pro–IL-1β, and NLRP3 Western blotting; and (E and I) qRT-PCR (normalized to Gapdh and to uninfected controls). BMDCs were prestimulated with E. coli LPS where indicated, and 1 μg/ml recombinant GST-tagged UreA, UreB (native or heat-inactivated [HI] for 10 minutes at 70°C), or GST was added to cocultures as noted. Pooled data from 3 to 4 independent experiments are show in C, E, I, K, and M; a representative of 2 experiments is shown in F–H. *P ≤ 0.05, **P ≤ 0.01, Mann-Whitney U test. Error bars represent mean + SD.