NETs activate AIM2 to mediate synovial fibroblast pyroptosis and promote acute gouty arthritis development

Acute gouty arthritis is a metabolic disease characterized by hyperuricemia, with acute attacks involving neutrophil-released NETs activating immune responses through their major component, DNA, as danger-associated molecular patterns (DAMPs).

To investigate whether DNA from NETs activates the AIM2 inflammasome in synovial fibroblasts during acute gouty arthritis attacks, inducing pyroptosis and exacerbating inflammation.

The AIM2 gene knockdown mouse model of acute gouty arthritis was constructed, the joint pathological changes were observed by H&E staining, the synovium fibroblasts and neutrophils were sorted by flow cytometry, and the expressions of AIM2, Caspase-1 and GSDMD related proteins were detected by Western blot. The levels of TNF-α, IL-6, IL-1β and IL-18 in serum and cell supernatant were detected by ELISA. Neutrophils were induced to release NETs by urate, and NETs markers (dsDNA, MPO-DNA, NE-DNA) were detected by immunofluorescence (Cit-H3, PAD4) and ELISA. NETs media were co-cultured with synovial fibroblasts, cell activity and migration were evaluated by CCK8 and scrape assay, markers of synovitis (Thy1, VCAM-1, PDPN) were detected by immunofluorescence, and pyroptosis was evaluated by TUNEL and LDH release. By silencing or overexpression of AIM2 gene, Western blot and ELISA, the role of AIM2 in NETs induced pyrodeath and inflammatory response was investigated.

AIM2 gene knockdown significantly alleviated the symptoms of MSU-induced acute gouty arthritis in mice, reducing joint swelling and pathological damage. Expression levels of inflammatory factors (TNF-α, IL-6, IL-1β, IL-18) and cleaved Caspase-1/Caspase-1, GSDMD-NT/GSDMD) were decreased. It was found that neutrophils released NETs in response to sodium urate stimulation, manifested by significant upregulation of Cit-H3 and PAD4, as well as increased dsDNA, MPO-DNA, and NE-DNA complexes. NETs can induce inflammatory response in synovial fibroblasts, which is manifested as decreased cell activity and migration ability, increased release of inflammatory factors, and significantly increased markers of synovitis (Thy1, VCAM-1, PDPN). In addition, NETs induce scorch death of synovium fibroblasts by activating AIM2 inflammatories, which aggravates the inflammatory response, and AIM2 gene knockdown can effectively inhibit the scorch death and inflammatory response induced by NETs, indicating that NETs play a key role in the occurrence and development of gout arthritis through AIM2-mediated scorch death of synovium fibroblasts.

NETs-activated AIM2-mediated synovial fibroblast pyroptosis plays a crucial role in acute gouty arthritis, providing a new therapeutic target.