Novel immunomodulatory properties of berbamine through selective down-regulation of STAT4 and action of IFN-γ in experimental autoimmune encephalomyelitis

Berbamine (BM) is an herbal compound derived from Berberis vulgaris L commonly used in traditional Chinese medicine. In this study, we show that BM has potent anti-inflammatory properties through novel regulatory mechanisms, leading to reduced encephalitogenic T cell responses and amelioration of experimental autoimmune encephalomyelitis (EAE). The treatment effect of BM was attributable to its selective inhibitory effect on the production and action of IFN-gamma in CD4(+) T cells, which was mediated through altered STAT4 expression in T cells. BM was found to up-regulate SLIM, a ubiquitin E3 ligase for STAT4, and promote STAT4 degradation, resulting in markedly decreased IFN-gamma production in CD4(+) T cells in EAE mice. Regulation of IFN-gamma by BM had profound anti-inflammatory actions through its effect on both CD4(+) T cells and APCs. BM-treated APCs exhibited reduced stimulatory function as a result of altered expression of PD-L1, CD80, and CD86 in treated mice. The treatment effect of BM in EAE was directly related to its action on IFN-gamma, and was abolished in IFN-gamma knockout mice. The study also confirmed that BM was able to inhibit NFAT translocation through effecting calcium mobilization in lymphocytes. However, this effect was not directly responsible for the treatment efficacy of BM in EAE. The study has important implications in our approaches to evaluating the utility of natural compounds in drug discovery and to probing the role of cytokine network in the development of autoimmune conditions.