Caspase-1 activation by NLRP3 inflammasome dampens IL-33-dependent house dust mite-induced allergic lung inflammation

The cysteine protease caspase-1(Casp-1)contributes to innate immunity through the assembly of NLRP3,NLRC4,AIM2,and NLRP6 inflammasomes.Here we ask whether caspase-1 activation plays a regulatory role in house dust mite(HDM)-induced experimental allergic airway inflammation.We report enhanced airway inflammation in caspase-1-deficient mice exposed toHDMwith a marked eosinophil recruitment,increased expression of IL-4,IL-5,IL-13,aswell as full-length and bioactive IL-33.Furthermore,mice deficient for NLRP3 failed to control eosinophil influx in the airways and displayed augmented Th2 cytokine and chemokine levels,suggesting that the NLPR3 inflammasome complex controls HDM-induced inflammation.IL-33 neutralization by administration of soluble ST2 receptor inhibited the enhanced allergic inflammation,while administration of recombinant IL-33 during challenge phase enhanced allergic inflammation in caspase-1-deficient mice.Therefore,we show that caspase-1,NLRP3,and ASC,but not NLRC4,contribute to the upregulation of allergic lung inflammation.Moreover,we cannot exclude an effect of caspase-11,because caspase-1-deficient mice are deficient for both caspases.Mechanistically,absence of caspase-1 is associated with increased expression of IL-33,uric acid,and spleen tyrosine kinase(Syk)production.This study highlights acritical role of caspase-1 activation andNLPR3/ASCinflammasomecomplex in the down-modulation of IL-33 in vivo and in vitro,thereby regulating Th2 response in HDM-induced allergic lung inflammation.