Anti-dsDNA antibodies bind to TLR4 and activate NLRP3 inflammasome in lupus monocytes/macrophages

Background: NLRP3 inflammasome has been implicated in the pathogenesis of systemic lupus erythematosus (SLE). The activation of NLRP3 inflammasome results in the production of IL-1 beta and the subsequent inflammation. Anti-dsDNA antibodies (anti-dsDNA Abs) play critical roles in the development and progression of SLE. However, the mechanism of NLRP3 inflammasome activation in SLE is still not known. This study investigated the activation of NLRP3 inflammasome stimulated by anti-dsDNA Abs in monocytes/macrophages from SLE patients. Methods: Monocytes/macrophages from SLE patients or healthy controls were stimulated with anti-dsDNA Ab-positive serum or purified anti-dsDNA Abs. Activation of inflammasome was measured by flow cytometry or Western blot. Anti-dsDNA Abs isolated from active SLE patients were injected into female (NZB x NZW) F1 mice and the activation of NLRP3 inflammasome and the frequencies of Th17 and Treg were examined. Results: The activity of caspase-1 was significantly increased in active SLE patients and was correlated with serum levels of anti-dsDNA Abs and disease activities. The concentrations of IL-1 beta and IL-17A were also significantly higher in SLE patients compared to healthy controls. Anti-dsDNA Ab-positive serum rather than healthy serum or RF (rheumatoid factor)-positive serum stimulated the activation of caspase-1 in monocytes. Anti-dsDNA Abs bound to TLR4 on macrophages and induced the production of ROS. Mitochondria-targeting antioxidant Mito-TEMPO, I kappa B kinase inhibitor peptide or TLR4 siRNA inhibited the activation of NLRP3 inflammasome and the secretion of IL-1 beta induced by antidsDNA Abs. Injection of anti-dsDNA Abs into (NZB x NZW) F1 mice resulted in increased caspase-1 activation and production of IL-1 beta and IL-17A. The Th17/Treg cell ratio also significantly increased following anti-dsDNA Ab injection. Conclusions: Anti-dsDNA Abs activated NLRP3 inflammasome in monocytes/macrophages from SLE patients by binding to TLR4 and inducing the production of mitochondrial ROS.