The heavy subunit of ferritin stimulates NLRP3 inflammasomes in hepatic stellate cells through ICAM-1 to drive hepatic inflammation
Manuel A. Fernández‐Rojo, Michael A. Pearen, Anita G. Burgess, Maria P. Ikonomopoulou, D. Hoang-Le, Berit Genz, Silvia L. Saggiomo, Sujeevi Nawaratna, Maura Poli, Regina Reissmann, Geoffrey N. Gobert, Urban Deutsch, Britta Engelhardt, Andrew J. Brooks, Alun Jones, Paolo Arosio, Grant A. Ramm
Abstract
Serum ferritin concentrations increase during hepatic inflammation and correlate with the severity of chronic liver disease. Here, we report a molecular mechanism whereby the heavy subunit of ferritin (FTH) contributes to hepatic inflammation. We found that FTH induced activation of the NLRP3 inflammasome and secretion of the proinflammatory cytokine interleukin-1β (IL-1β) in primary rat hepatic stellate cells (HSCs) through intercellular adhesion molecule–1 (ICAM-1). FTH–ICAM-1 stimulated the expression of Il1b , NLRP3 inflammasome activation, and the processing and secretion of IL-1β in a manner that depended on plasma membrane remodeling, clathrin-mediated endocytosis, and lysosomal destabilization. FTH–ICAM-1 signaling at early endosomes stimulated Il1b expression, implying that this endosomal signaling primed inflammasome activation in HSCs. In contrast, lysosomal destabilization was required for FTH-induced IL-1β secretion, suggesting that lysosomal damage activated inflammasomes. FTH induced IL-1β production in liver slices from wild-type mice but not in those from Icam1 −/− or Nlrp3 −/− mice. Thus, FTH signals through its receptor ICAM-1 on HSCs to activate the NLRP3 inflammasome. We speculate that this pathway contributes to hepatic inflammation, a key process that stimulates hepatic fibrogenesis associated with chronic liver disease.