Knockdown of LSD1 ameliorates the severity of rheumatoid arthritis and decreases the function of CD4 T cells in mouse models.

Rheumatoid arthritis (RA) is an immune-mediated disease that causes chronic inflammation of the joints and involves CD4+ T cell activation. In RA, CD4+ T cells are the main drivers of disease initiation and the perpetuation of the damaging inflammatory process. In the present study, we investigated the role of Lysine-specific histone demethylase 1 (LSD1) in RA. The frequency of LSD1-positive CD4+ T cells in the synovial fluid (SF) of active RA patients was higher than that of inactive RA patients. In CD4+ T cells isolated from SF of active RA patients, LSD1 downregulation significantly increased cell proliferation, as shown by MTT assay. LSD1 knockdown also significantly increased the production of IFN-γ and IL-17, and increased that of IL-10, as determined by ELISA and qRT-PCR aasay. In CD4+ T cells isolated from SF of inactive RA patients, LSD1 was overexpressed by LSD1 plasmid transfection. As expected, LSD1 overexpression resulted in an opposite effect on cell proliferation and the production of cytokines, including IFN-γ, IL-17 and IL-10. LSD1 was downregulated in RA mouse by lenti-vector infection. As expected, LSD1 knockdown in vivo significantly alleviated the disease severity and increased the levels of anti-collagen II antibodies. LSD1 downregulation in the early stage was more effective to ameliorate disease severity. Our data suggested the potential therapeutic role of LSD1 in RA patients.