Propionate is an inhibitor of the epigenetic regulator HDAC3.40 To test whether FOXK1 was a new substrate of HDAC3 in RA-FLSs, we performed co-immunoprecipitation assay and showed that FOXK1 interacted with HDAC3 (Fig. 5p). Here, FOXK1 is linked to rheumatoid arthritis.