Daphnetin alleviates experimental autoimmune encephalomyelitis by suppressing Th1 and Th17 cells and upregulating Th2 and regulatory T cells

Multiple sclerosis (MS) is the most typical chronic inflammatory, autoimmune demyelinating disease of the central nervous system (CNS) which leads to physical dysfunction and paralysis in patients. A commonly used animal model for this disease is experimental autoimmune encephalomyelitis (EAE). Daphnetin (7,8-dihydroxycoumarin) has been reported to exert various pharmacological activities, such as being neuroprotective and anti-inflammatory, together with having antioxidant, anticancer, and antiviral properties. Eight-week-old C57BL/6 female mice were segregated into 3 groups, namely 1) a control group receiving PBS, 2) a low-dose treatment group receiving 2 mg/kg of daphnetin, and, 3) a high-dose treatment group receiving 8 mg/kg of daphnetin. EAE was induced with a subcutaneous injection of a combination of myelin oligodendrocyte glycoprotein (MOG) and complete Freund's adjuvant. On the day of induction, and again two days later, mice were injected intraperitoneally with pertussis toxin. Histological studies showed low lymphocyte infiltration and demyelination in the high and low dose treated groups. The ratio of spleen Treg cells and the levels of IL-4, IL-10, TGF-beta, and IL-33 enhanced significantly in the treatment group related to the control group. Furthermore, both IL-27 and IL-35 were also enhanced significantly in the treatment group compared to the control group. Moreover, the levels of IFN-gamma, TNF-alpha, and IL-17 displayed a noticeable reduction in the daphnetin treated group. Daphnetin appears to improve the disease by increasing the expression of anti-inflammatory cytokines and transcription factors (IL-4, IL-10, IL-33, GATA3, TGF-beta, FoxP3), and reducing the production of pro-inflammatory cytokines and transcription factors (IFN-gamma, STAT4, T-bet, IL-17, STAT3, ROR-gamma t, TNF-alpha).