To determine the role of gasdermin E (GSDME)-mediated pyroptosis in the pathogenesis and progression of rheumatoid arthritis (RA), and to explore the potential of GSDME as a therapeutic target in RA.Methods. The expression and activation of caspase 3 and GSDME in the synovium, macrophages, and monocytes of RA patients were determined by immunohistochemistry, immunofluorescence, and Western blot analysis. The correlation of activated GSDME with RA disease activity was evaluated. The pyroptotic ability of monocytes from RA patients was tested, and the effect of tumor necrosis factor (TNF) on caspase 3/GSDME-mediated pyroptosis of monocytes and macrophages was investigated. In addition, collagen-induced arthritis (CIA) was induced in mice lacking Gsdme, and the incidence and severity of arthritis were assessed.Results. Compared to cells from healthy controls, monocytes and synovial macrophages from RA patients showed increased expression of activated caspase 3, GSDME, and the N-terminal fragment of GSDME (GSDME-N). The expression of GSDME-N in monocytes from RA patients correlated positively with disease activity. Monocytes from RA patients with higher GSDME levels were more susceptible to pyroptosis. Furthermore, TNF induced pyroptosis in monocytes and macrophages by activating the caspase 3/GSDME pathway. The use of a caspase 3 inhibitor and silencing of GSDME significantly blocked TNF-induced pyroptosis. Gsdme deficiency effectively alleviated arthritis in a mouse model of CIA.Conclusion. These results support the notion of a pathogenic role of GSDME in RA and provide an alternative mechanism for RA pathogenesis involving TNF, which activates GSDME-mediated pyroptosis of monocytes and macrophages in RA. In addition, targeting GSDME might be a potential therapeutic approach for RA.
Background: Necroptosis is a form of regulated necrosis that is involved in various autoimmune diseases. Mixed lineage kinase domain-like pseudokinase (MLKL) has been identified as a key executor of necroptosis, however, the significance of MLKL in peripheral blood mononuclear cells (PBMCs) of systemic lupus erythematosus (SLE) has not been investigated. In this study, we aimed to determine the mRNA level of MLKL in PBMCs and examine its relationship with clinical features and serological parameters in SLE. Methods: Real-time transcription-polymerase chain reaction analysis (RT-PCR) was used to determine expression of MLKL mRNA in PBMCs from 59 patients with SLE, 25 patients with rheumatoid arthritis (RA) and 30 age- and sex-matched healthy controls(HC). Spearman's correlation test was performed to assess the correlation of MLKL mRNA with clinical variables. The receiver operating characteristic curve (ROC) was created to evaluate the diagnostic value. Results: Our results showed MLKL mRNA in PBMCs was upregulated in SLE patients compared to that in RA and HC individuals. SLE patients positive for anti-nuclear antibodies had significantly higher MLKL mRNA than antibody-negative patients. In SLE patients, MLKL mRNA was found to be upregulated in patients with lupus nephritis (LN) as compared with patients without LN, and also higher in active patients than in stable patients. MLKL mRNA level was significantly and positively correlated with c-reaction protein (CRP) (r=0.3577, p=0.0237), erythrocyte sedimentation rate (ESR) (r=0.4091, p=0.0043), serum immunoglobulin G (IgG) concentration (r=0.3546, p=0.0289) and the numbers of positive antinuclear antibodies (ANAs) (r=0.3945, p=0.0432). ROC analysis showed that MLKL mRNA in PBMCs had an area under the curve of 0.9277 (95% CI 0.8779 - 0.9775, p<0.001) to discriminate SLE from controls.Conclusions: These results suggest that increased MLKL mRNA level in the PBMCs of SLE patients is correlated with renal involvement and disease activity, identifying a subgroup of patients with SLE or LN who may benefit from early diagnosis and therapies targeting MLKL.
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