Calciprotein Particles Induce IL-1β/α-Mediated Inflammation through NLRP3 Inflammasome-Dependent and -Independent Mechanisms.

Calciprotein particles (CPPs) are nanoparticles composed of calcium phosphate crystals and fetuin-A and have been implicated in diseases associated with inflammation. In the current study, we investigated the molecular mechanisms underlying CPP-induced inflammation in mice. CPPs predominantly upregulated IL-1β and IL-1α and provided priming and activation signals for the NLRP3 inflammasome in murine macrophages. Pharmacological and genetic inhibition of the NLRP3 inflammasome revealed that CPPs induced the release of IL-1β and IL-1α via NLRP3 inflammasome-dependent and -independent mechanisms, respectively. CPPs also induced necrotic cell death, but gasdermin D was dispensable for CPP-induced IL-1β release and necrotic cell death. Although phagocytosis of CPPs was required for CPP-induced IL-1β/α release and necrotic cell death, lysosomal dysfunction and K+ efflux were mainly involved in CPP-induced NLRP3 inflammasome activation and subsequent IL-1β release but not in CPP-induced IL-1α release and necrotic cell death. In vivo experiments showed that CPP administration evoked acute inflammatory responses characterized by neutrophil accumulation via both IL-1β and IL-1α. In particular, CPP-induced neutrophil inflammation was mediated predominantly through an IL-1α-induced CXCL1/CXCR2 signaling pathway. These results provide new insights into the mechanism underlying CPP-induced inflammation and suggest that targeting both IL-1β and IL-1α is necessary to regulate the CPP-induced inflammatory response and to treat CPP-associated inflammatory disorders.