Fingolimod, an antagonist of sphingosine 1-phosphate, ameliorates Sjögren's syndrome by reducing the number of STAT3–induced germinal center B cells and increasing the number of Breg cells

Background: Sjögren's syndrome (SS) is an autoimmune disease caused by infiltrating lymphocytes. FTY720 affects the S1P signaling pathway, which plays a role in T and B cell migration from secondary lymphoid tissues to target organs. In this study, we investigate the regulatory mechanism of FTY720 in the context of SS. Method: FTY720 was given orally every day to NOD mice. The salivary flow rate (SFR) and blood glucose level were assayed every 3 weeks. Histopathological features were investigated at the end of the study. In vitro, FTY720 was added to mouse splenocytes, and changes in the lymphocyte subsets were assessed. Results: In vivo, FTY720 increased the SFR and reduced the blood glucose level. The salivary gland histological score and infiltration of the salivary glands by B and T cells were dramatically decreased. Furthermore, STAT expression in the salivary gland was decreased. In vitro, FTY720 inhibited Th17 cells, while increasing regulatory T (Treg) cells, respectively. Also, FTY720 decreased and increased the numbers of germinal center (GC) B cells and regulatory B cells (Breg cells), respectively. FTY720 decreased the IgG level in culture supernatants. Also, STAT3 activation was decreased by FTY720. Conclusion: Our results show the therapeutic potential of FTY720 in the context of SS; FTY720 prevents lymphocyte migration from secondary lymphoid organs to target organs.