As shown in Figure 3A, expression of AcH3 and AcH4 in RA FLSs was lower than in control FLSs (P < 0.01), and down-regulating SIRT1 in RA FLSs increased AcH3 and AcH4 levels (P < 0.05). Here, SIRT1 is linked to rheumatoid arthritis.