Inflammasome dependent IL-1β secretion requires Dnase1L3 activity

Abstract

Abstract Inflammation is driven by inflammatory cell death and the secretion of pro-inflammatory cytokines like IL-1β and alarmins like High Mobility Group Box Protein 1 (HMGB1) by the inflammasome. The inflammasome is a cytosolic multiprotein complex that typically contains a Nod-like receptor (NLR), like NLRP3 or NLRC4, and the adaptor ASC which links to caspase-1 for activation. How signals from the cytoplasmic NLR induce nuclear ASC and HMGB1 translocation into the cytosol for inflammasome function remains elusive. Here we hypothesize that Dnase1L3 (DNase γ), a Ca2+/Mg2+-dependent endonuclease, facilitates inflammasome-mediated release of cytokines and alarmins. When we treated murine macrophages with the Dnase1L3 inhibitors Fmoc-D-cyclohexylalanine (FCA) or pontacyl violet 6R (PV), HMGB1 and IL-1β release were inhibited following NLRP3 or NLRC4 stimulation. FCA and PV did not directly inhibit Casp1. We confirmed the specificity of the inhibitors using RNAi silencing of Dnase1L3 in THP-1 cell lines. Interestingly, pyroptosis was only slightly blocked by Dnase1L3 inhibition. Mechanistically, we found that ASC nuclear translocation and speck formation was impaired following FCA treatment, as was Casp1 cleavage. These data suggest that Dnase1L3 inhibition prevents Asc release from the nucleus. This demonstrates that pyroptosis and cytokine release can be mechanistically separated. Taken all together, these data show that Dnase1L3 is necessary for inflammasome-mediated release of cytokines and alarmins.