Endoplasmic reticulum aminopeptidase 2 regulates CD4+ T cells pyroptosis in rheumatoid arthritis

Objective: Rheumatoid arthritis (RA) is a chronic, progressive autoimmune disease with a complex pathogenesis that has not yet been fully elucidated, and T-cell Pyroptosis is an important pathogenetic factor in RA. This study aimed to investigate the role of endoplasmic reticulum Aminopeptidase 2 (ERAP2) in the Pyroptosis of CD4⁺ T cells in RA and the specific molecular mechanism.

Methods: Peripheral venous blood was collected from human subjects, and CD4⁺ T cells were isolated and activated to measure the level of Pyroptosis and ERAP2 expression. Pyroptosis levels were assessed using immunofluorescence, flow cytometry, qRT-PCR, and Western blotting. Changes in Pyroptosis levels were observed upon knockdown or overexpression of ERAP2. To detect activated Caspase-1 in tissues, chimeric mice were engrafted with human synovial tissue and reconstituted with human CD4⁺ T cells. CD4 + T cells were treated with GLI1 antagonists and Smo receptor agonists to detect changes in Pyroptosis levels.

Results: CD4⁺ T cell levels undergoing Pyroptosis were found to be elevated in the blood and synovium of RA patients. The gene and protein expression of ERAP2 were significantly higher in CD4⁺ T cells from RA patients. Deletion of ERAP2 suppressed Pyroptosis of these cells, attenuated the activation of Caspase-1 in tissue T cells, and reduced tissue inflammatory responses. Reciprocally, overexpression of ERAP2 triggered inflammasome assembly, activated Caspase-1, and induced Pyroptosis in CD4⁺ T cells. Mechanistically, ERAP2 inhibits the Hedgehog signaling pathway and upregulates the expression of nucleotide-binding oligomerization segment-like receptor family 3(NLRP3), cleaved Caspase-1, and Gasdermin D to promote Pyroptosis in CD4⁺ T cells.

Conclusions: Taken together, our results identify a novel mechanism by which ERAP2 regulates RA development and document the effect of the ERAP2/Hedgehog signaling axis on Pyroptosis of CD4⁺ T cells from RA patients.

CD4+ T cells; ERAP2; Hedgehog signaling pathway; Pyroptosis; Rheumatoid arthritis.