Summary Nucleotide‐binding, oligomerization domain (NOD)‐like receptor family, pyrin domain containing 3 (NLRP3) gene polymorphism was reported to be associated with susceptibility, disease activity or anti‐tumour necrosis factor (TNF) treatment response in rheumatoid arthritis (RA). However, the roles of NLRP3 inflammasome in the development of RA have not yet been elucidated fully. The present study aimed to study the role of NLRP3 inflammasome in RA. NLRP3 inflammasome activation in synovial tissues from RA and osteoarthritis (OA) patients were assessed by Western blot. Active caspase‐1 in synovia was stained by a FAM‐FLICA caspase‐1 probe. Mice with collagen‐induced arthritis (CIA) were treated with MCC950, a selective NLRP3 inhibitor, or vehicle for 2 weeks. The clinical score of arthritis, synovial inflammation and cartilage erosion were assessed. Proinflammatory cytokines were measured by enzyme‐linked immunosorbent assay (ELISA). The results showed that NLRP3 inflammasome was highly activated in both synovia from RA patients and CIA mice. Activation of NLRP3 inflammasome occurred mainly in the infiltrating monocyte/macrophages in synovia, but not in fibroblast‐like synoviocytes. Treatment with MCC950 resulted in significantly less severe joints inflammation and bone destruction. NLRP3 inflammasome activation in the synovia was inhibited significantly by MCC950 with reduced production of interleukin (IL)‐1β. The inhibition of NLRP3 inflammasome activation by MCC950 was confirmed further in a human monocytic cell line, THP‐1. In conclusion, NLRP3 inflammasome is involved in the pathogenesis of RA. Targeting NLRP3 inflammasome with a small molecule inhibitor might be a novel therapeutic strategy for RA.

Follicular T regulatory (Tfr) cells inhibit follicular T helper (Tfh) cells mediated B cell responses. Tfh cells are involved in the pathogenesis of systemic lupus erythematosus (SLE). However, the role of Tfr cells in SLE remains unclear. The frequency of circulating Tfr and Tfh cells were examined in SLE patients and healthy controls. The frequency of circulating Tfr cell decreased and Tfh/Tfr ratio increased in SLE patients. Serum anti-dsDNA antibody level positively correlated with frequency of Tfh cells and Tfh/Tfr ratios but negatively correlated with the frequency of Tfr cells. Moreover, the frequency of Tfr and Tfh/Tfr ratio but not that of Tfh was correlated with diseases activity. In addition, increase in Tfr cell numbers and decrease in the Tfh/Tfr ratios were observed with successful treatments. Thus, Tfr cells should be considered as a biomarker for SLE and their role in the pathogenesis of SLE warrants further investigation.

Objective Development of proteinuria in lupus nephritis (LN) is associated with podocyte dysfunction. The NLRP3 inflammasome has been implicated in the pathogenesis of LN. This study investigates whether NLRP3 inflammasome activation is involved in the development of podocyte injury in LN. Methods A fluorescence-labeled caspase-1 inhibitor probe was used to detect the activation of NLRP3 inflammasomes in podocytes in lupus-prone NZM2328 mice and in renal biopsies from LN patients. MCC950, a selective inhibitor of NLRP3, was used to treat NZM2328 mice. Proteinuria, ultrastructure of podocytes and renal pathology were evaluated. In vitro, sera from diseased NZM2328 mice were used to stimulate a podocyte cell line and cells were subjected to flow cytometry analysis. Results NLRP3 inflammasomes were activated in podocytes of lupus-prone mice and LN patients. Inhibition of NLRP3 with MCC950 ameliorated proteinuria, renal histological lesions and podocyte foot process effacement in lupus-prone mice. In vitro, sera from NZM2328 diseased mice activated NLRP3 inflammasomes in the podocyte cell line through reactive oxygen species (ROS) production. Conclusion NLRP3 inflammasomes were activated in podocytes of both LN patients and in lupus-prone mice. Activation of NLRP3 is involved in the pathogenesis of podocyte injuries and the development of proteinuria in LN.

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