SAT0031 VITAMIN B3 (NAM) SUPPRESSES T CELL ACTIVATION IN AND PRODUCTION OF PRO-INFLAMMATORY CYTOKINES IN VITRO IN A DOSE DEPENDENT MANNER INDICATING THERAPEUTIC POTENTIAL FOR THE TREATMENT OF JIA

Background: Impaired immunological tolerance in Juvenile Idiopathic Arthritis (JIA) is the result of a disturbed balance between regulatory T-cells (Tregs) and effector T-cells (Teffs). Restoring this balance by either enhancing the suppressive function of Tregs or inhibiting activity of pro-inflammatory Teffs seems a promising therapeutic strategy. We have previously demonstrated that high concentrations of Vitamin B3 (VitB3), also known as nicotinamide (NAM), lead to an increase in FOXP3 positive cells in vitro, via suppression of the deacetylase SIRT1. Because the transcription factor FOXP3 is essential for Treg function, this approach could promote immunological tolerance. We now aim to translate these laboratory findings into clinical practice and envision a role for VitB3 as a novel therapeutic strategy for patients with JIA. However, while VitB3 has promising effects on Tregs, the effect of VitB3 on Teff cells, the other side of the scale, is still unexplored. Objectives: To investigate the effect of VitB3/SIRT1 inhibition on proliferation, activation, cytokine production and TCR signaling of Teff cells. Methods: T-cells were isolated from the blood of healthy controls and JIA patients, as well as from the synovial fluid from JIA patients. Cells were stimulated with aCD3/aCD28 and cultured in the presence of increasing concentrations of VitB3 (0-9mM) for 1-4 days. Proliferation and expression of activation makers in primary T cells were determined using flow cytometry. Cytokine production was determined by qPCR, Luminex and flow cytometry. ERK phosphorylation was measured by flow cytometry and Western blot. ERK phosphorylation and GFP expression were also determined by flow cytometry using a murine NFAT-GFP reporter celline. Results: In vitro VitB3 treatment of JIA patient CD4+ Teff-cells significantly decreased the production of the pro-inflammatory cytokines IL-2 and IFNy measured both on mRNA and protein level. Correspondingly, surface activation markers were downregulated after VitB3 incubation, and ERK phosphorylation was decreased. Furthermore, proliferation of both CD4+ and CD8+ T-cells was inhibited with VitB3 treatment in a dose dependent manner. Murine reporter cells showed similar results. Experimental outcomes were verified using another SIRT1 inhibitor; EX-527. Conclusion: In addition to the previously demonstrated increase of Treg numbers and functioning, this data demonstrates that VitB3 treatment also inhibits proliferation and activation of Teff cells in vitro. VitB3 treatment could therefore modulate the immunological balance by both increasing tolerance and suppressing immune activation. We envision that VitB3 treatment as an adjuvant therapy has the potential to benefit JIA patients and potentially patients with other autoimmune diseases. To assess the clinical relevance of these findings, we are currently in the preparation of a phase III clinical trial. Disclosure of Interests: None declared