Activation of caspase-1 is mediated by stimulation of interferon genes and NLR family pyrin domain containing 3 in monocytes of active systemic lupus erythematosus

Emerging evidence has shown the importance of inflammasome activation in the progression of autoimmune diseases. In this study, we aimed to identify the main cell types activating inflammasome in autoimmune diseases and to clarify the intracellular pathway of inflammasome activation in systemic lupus erythematosus (SLE). Active caspase-1 in each subset of human peripheral blood cells from healthy controls (n=18), SLE (n=51), and other rheumatic diseases (n=36) were fluorescently probed with FLICA™-caspase-1 followed by flow cytometric analysis. The correlation of caspase-1 activation in monocytes and clinical parameters in SLE patients were evaluated. In-vitro experiments were performed to identify the pathway involved in caspase-1 activation induced by SLE serum in monocytes. Active caspase-1 in monocytes was upregulated in SLE patients. Cluster of differentiation 14 (CD14)-positive and CD16-positive monocytes showed considerable activation of caspase-1 compared with the other subsets of monocytes. Serum titres of anti-double stranded DNA antibodies were positively correlated with active caspase-1 in monocytes, and serum complement component 3 and platelet count were negatively correlated with active caspase-1 in monocytes. The SLE serum-induced activation of caspase-1 and IL-1β secretion were down-regulated by inhibition of NLR family pyrin domain containing 3 (NLRP3), cyclic GMP-AMP synthase (cGAS), or stimulator of interferon genes (STING). These findings suggest that targeting inflammasome by regulating cGAS/STING and NLRP3 are potential therapeutic strategies for SLE.