MST1 and rheumatoid arthritis: We then measured the mRNA expression of Sirt3 and Sirt6, the other members of the Sirtuin family, and observed that Sirt3 and Sirt6 levels were downregulated in the H2O2-treated RA-FLSs as well as H2O2-treated Mst1 knockdown RA-FLSs compared to the untreated controls (Figure 3D, 3E).