Intracellular ATP Decrease Mediates NLRP3 Inflammasome Activation upon Nigericin and Crystal Stimulation

Activation of the nucleotide-binding oligomerization domain-like receptor family, pyrin domain-containing 3 (NLRP3) inflammasome initiates an inflammatory response, which is associated with host defense against pathogens and the progression of chronic inflammatory diseases such as gout and atherosclerosis. The NLRP3 inflammasome mediates caspase-1 activation and subsequent IL-1 beta processing in response to various stimuli, including extracellular ATP, although the roles of intracellular ATP (iATP) in NLRP3 activation remain unclear. In this study, we found that in activated macrophages artificial reduction of iATP by 2-deoxyglucose, a glycolysis inhibitor, caused mitochondrial membrane depolarization, leading to IL-1 beta secretion via NLRP3 and caspase-1 activation. Additionally, the NLRP3 activators nigericin and monosodium urate crystals lowered iATP through K+- and Ca2+-mediated mitochondrial dysfunction, suggesting a feedback loop between iATP loss and lowering of mitochondrial membrane potential. These results demonstrate the fundamental roles of iATP in the maintenance of mitochondrial function and regulation of IL-1 beta secretion, and they suggest that maintenance of the intracellular ATP pools could be a strategy for countering NLRP3-mediated inflammation.