Tmem178 negatively regulates IL-1β production through inhibition of the NLRP3 inflammasome

Abstract

AbstractObjectiveInflammasomes modulate the release of bioactive IL-1β. Excessive IL-1β levels are detected in patients with systemic juvenile idiopathic arthritis (sJIA) and cytokine storm syndrome (CSS) with mutated and unmutated inflammasome components, raising questions on the mechanisms of IL-1β regulation in these disorders.MethodsTo investigate how the NLRP3 inflammasome is modulated in sJIA, we focused on Tmem178, a negative regulator of calcium levels in macrophages, and measured IL-1β and caspase-1 activation in wild-type (WT) andTmem178-/-macrophages following calcium chelators, silencing of Stim1, a component of store-operated calcium entry (SOCE), or by expressing a Tmem178 mutant lacking Stim1 binding site. Mitochondrial function in both genotypes was assessed by measuring oxidative respiration, mitochondrial reactive oxygen species (mtROS), and mitochondrial damage. CSS development was analyzed inPerforin-/-/Tmem178-/-mice infected with LCMV in which inflammasome or IL-1 signaling was pharmacologically inhibited. HumanTMEM178andIL-1Btranscripts were analyzed in a dataset of peripheral blood monocytes from healthy controls and active sJIA patients.ResultsTMEM178levels are reduced in monocytes from sJIA patients while IL-1B show increased levels. Accordingly,Tmem178-/-macrophages produce elevated IL-1β compared to WT cells. The elevated intracellular calcium levels following SOCE activation inTmem178-/-macrophages induce mitochondrial damage, release mtROS, and ultimately, promote NLRP3 inflammasome activation.In vivo, inhibition of inflammasome or IL-1 neutralization prolongsTmem178-/-mouse survival to LCMV-induced CSS.ConclusionDownregulation of Tmem178 levels may represent a new biomarker to identify sJIA/CSS patients that could benefit from receiving drugs targeting inflammasome signaling.