Vitamin B12 inhibits peptidyl arginine deiminases and ameliorates rheumatoid arthritis in CAIA mice

Rheumatoid arthritis is an autoimmune disease whose early onset corelates with dysregulated citrullination, a process catalyzed by peptidylarginine deiminase isoform 4 (PADI-4). Here, we report that PADI-4 is a novel target of vitamin B12, a water-soluble vitamin that serves as a cofactor in DNA synthesis and the metabolism of fatty and amino acids. Vitamin B12 preferentially inhibited PADI-4 over PADI-2 with comparable inhibitory activity to the reference compound Cl-amidine in enzymatic inhibition assays, and reduced total cellular citrullination levels including that of histone H3 citrullination mediated by PADI-4. We also demonstrated that hydroxocobalamin, a manufactured form of vitamin B12, significantly ameliorated the severity of collagen type II antibody induced arthritis (CAIA) in mice and diminished gene expression of the rheumatoid inflammatory factors and cytokines IL17α, TNFα, IL-6, COX-II and ANNX A2, as well PADI-4. Therefore, the use of vitamin B12 to treat rheumatoid arthritis merits further study.