Expression and activity of AIM2-inflammasome in rheumatoid arthritis patients

AIM2 inflammasome activation leads to the release of IL-β, which plays an important role in rheumatoid arthritis pathogenesis. In this work, we evaluated AIM2 expression and activity in RA patients and healthy controls.

AIM2 and RANKL expression were evaluated by flow cytometry. Inflammasome activity was determined in monocyte cultures stimulated with synthetic DNA by measuring IL-1β levels in supernatants using an ELISA assay. The caspase-1 expression in monocytes was measured by western blot, the POP3 expression was analysed by qPCR, and serum levels of IFN-γ were evaluated using ELISA assay.

We observed a diminution of CD14+AIM2+ cells in RA patients, associated with disease activity and evolution. Likewise, the levels of IL-1β were increased in monocyte cultures un-stimulated and stimulated with LPS from RA patients with DAS28 ≥ 4. The Caspase-1 activity and RANKL + monocytes in RA patients were slightly increased. Finally, augmented POP3 expression and diminished IFN-γ serum levels were detected in RA patients.

Our results showed that the monocytes from RA patients were prone to release IL-1β in the absence of the AIM2 inflammasome signal. The down-regulation of AIM2 to a systemic level in RA patients might be a consequence of augmented POP3 expression and might imply the survival of pro-inflammatory cells contributing to the inflammation process.