TNF-α (25 ng/mL) upregulated the expression of MMP1, MMP2, MMP3, and MMP9 in RA-FLS, and knockdown of nrf2 further enhanced the TNF-α-induced expression of MMP1, MMP3, and MMP9, without affecting the expression of MMP2 (Figures 5(a)–5(d)). This evidence concerns the gene MMP9 and rheumatoid arthritis.