Naringenin is an inhibitor of T cell effector functions

Selective inhibition of T cells has been implied to prevent and/or treat autoimmune and inflammatory diseases. Some food compounds that have such immune-modulating functions may serve as nutritional approach to this purpose. In this study, we chose naringenin, a citrus fruits-derived compound with antiinflammatory property, to test this possibility. In this in vitro study, we stimulated mouse T cells with anti-CD3/CD28 (polyclonal TCR activation) or autoantigen MOG_35-55 in the presence of naringenin. We found that naringenin dose-dependently suppressed anti-CD3/CD28 and MOG_35-55-induced T cell proliferation, production of T cell cytokines IFN-γ, IL-17, IL-6 and TNF-α. We further showed that inhibited T cell proliferation was associated with T cell cycle arrest at G0/G1 phase, which was in turn related to delayed degradation of the cyclin-dependent kinase inhibitor p27^kip1 and the down-regulation of retinoblastoma protein phosphorylation in activated T cells. Finally, it was revealed that all these T cell-suppressive effects might be related to naringenin's interference with IL-2/IL-2R-mediated signaling pathway and STAT5 phosphorylation in activated T cells. Our results confirmed T cell-suppressive activity of naringenin previously reported by us and others, but for the first time, it was shown that the working mechanism may involve its ability to modulate cell cycle progression, cell cycle-related proteins and IL-2/IL-2R signaling pathway. Together, these results further support proposed potential of naringenin being a preventive/therapeutic agent in T-cell-mediated autoimmune inflammatory disorders.