Astrocyte elevated gene-1 promotes inflammation and invasion of fibroblast-like synoviocytes in rheumatoid arthritis

Astrocyte elevated gene-1 (AEG-1) was initially induced by HIV-1 infection and involved in tumor progression, migration and invasion as a nuclear factor-κB (NF-κB)-dependent gene. The present study we intended to investigate the protein expression of AEG-1 significantly associated with rheumatoid arthritis. Western blot analysis and immunohistochemistry demonstrated that AEG-1 was upregulated in synovial tissue of RA patients compared with the controls. Double immunofluorescent staining suggested that AEG-1 was expressed in fibroblast-like synoviocytes (FLS) of RA patients. Furthermore, the expression of AEG-1 in FLS was increased in time-dependent manner by TNF-α stimulation. Upon TNF-α-treated FLS, AEG-1 transferred from the cytoplasm to nucleus where it interacted with the p65 subunit of NF-κB, as examined by immunoprecipitation and immunofluorescent staining assay. Moreover, the inhibition of AEG-1 by RNA interference significantly suppressed TNF-α-induced IL-6 and MMP-3 expression, leading to attenuation of FLS migration and invasion and markedly decreased the phosphorylation of P65 and IκBα, as well as AKT in FLS. Collectively, Our findings provided evidence that AEG-1 contributed to the production of inflammatory cytokines, migration and invasion of RA FLS, and underscored the importance of AEG-1 in the inflammation process of RA.