NRF2 is a mechanosensitive checkpoint for NLRP3 inflammasome activation

Disconnects between in vitro and in vivo results in experimental biology have long been recognized as potential hurdles to understanding health and disease. A prototypical example of such a disconnect is the NLRP3 inflammasome, which mediates inflammation in diverse settings of disease and protective immunity1,2. Activation of the NLRP3 inflammasome in vitro requires two signals: (1) priming by pathogen-associated molecular patterns such as bacterial lipopolysaccharides and (2) activation by molecules that disrupt cellular homeostasis1,3. By contrast, the NLRP3 inflammasome in vivo is activated by lipopolysaccharide alone. The mechanisms that underlie the difference between in vitro and in vivo activation of the NLRP3 inflammasome are undefined. Here we report that extracellular matrix (ECM) stiffness is a determinant of NLRP3 activities and that in vitro systems using physiological ECM stiffness enable one-signal in vivo-like NLRP3 activities to occur in human and mouse phagocytes. Physiological ECM stiffness induced expression of the transcription factor NRF2, which was found to be necessary for one-signal NLRP3 activation. Mechanistically, we identify Panx1 as an NRF2-regulated gene that promotes NLRP3 activity. Macrophages derived from the stiff matrix of the bone—osteoclasts—had reduced NRF2 levels and impaired NLRP3 activity. Moreover, alveolar macrophages from patients with pulmonary fibrosis displayed reduced NRF2 activity. Finally, NRF2 was required for antitumour immunity induced by cancer vaccines consisting of NLRP3 agonistic adjuvants. These findings indicate that NRF2 may be a transcriptional checkpoint that controls NLRP3 inflammasome activity. The stiffness of the extracellular matrix is identified as a pivotal factor that influences activation of the NLRP3 inflammasome in vitro and in vivo.