Curcuma phaeocaulis Inhibits NLRP3 Inflammasome in Macrophages and Ameliorates Nanoparticle-Induced Airway Inflammation in Mice

The activation of NLRP3 results in the assembly of inflammasome that regulates caspase-1 activation and the subsequent secretion of bioactive interleukin (IL)-1β. Excessive activation of the NLRP3 inflammasome is mechanistically linked to diverse pathophysiological conditions, including airway inflammation. Here, we discovered that Curcuma phaeocaulis can suppress caspase-1 activation and processing of pro-IL-1β into mature cytokine in macrophages stimulated with NLRP3 inflammasome activators, such as SiO(2) or TiO(2) nanoparticles. Furthermore, in the bronchoalveolar lavage fluids of animals administered the nanoparticles, the in vitro effects of C. phaeocaulis translated into a decrease in IL-1β levels and cell infiltration. Demethoxycurcumin (DMC) and curcumin were found to be responsible for the inflammasome inhibitory activity of C. phaeocaulis. Interestingly, in contrast to the previously reported higher antioxidant- and NFκB-inhibitory activities of curcumin, DMC exhibited approximately two-fold stronger potency than curcumin against nanoparticle induced activation of NLRP3 inflammasome. In the light of these results, both compounds seem to act independently of their antioxidant- and NFκB-inhibitory properties. Although how C. phaeocaulis inhibits nanoparticle-activated NLRP3 inflammasome remains to be elucidated, our results provide a basis for further research on C. phaeocaulis extract as an anti-inflammatory agent for the treatment of disorders associated with excessive activation of NLRP3 inflammasome.