Neuroprotective effects of gypenosides in experimental autoimmune optic neuritis

To determine whether gypenosides have protective effects in experimental autoimmune optic neuritis (EAON).

Mice were randomly divided into seven groups: control group, model group, three different density gypenosides monotherapy, methylprednisolone monotherapy, combination of gypenosides and methylprednisolone group. The control group was subcutaneously injected with oil emulsion adjuvant and all other groups were subcutaneously immunized with an emulsified mixture of myelin oligodendrocyte glycoprotein (MOG) 35-55 peptide to induce EAON. Mice in the gypenosides groups were administered injections daily with three concentrations (15 mg/kg, 30 mg/kg, 45 mg/kg) of gypenosides respectively. Mice in the methylprednisolone group and the combination treatment group were injected daily with methylprednisolone (20 mg/kg) or methylprednisolone (20 mg/kg) + gypenosides (30 mg/kg), respectively. After MOG immunization, visual evoked potential (VEP), optical coherence tomography (OCT), and histopathologic examination were performed at 14, 20, 30, and 40d post-inoculation (p.i.). All results were expressed as mean±SEM. The data were evaluated by one-way ANOVA followed by Tukey or Games-Howell test.

Compared with the control group, p2 latency was prolonged in the model group (P=0.041). Combination treatment can alleviated the change in VEP at 20d p.i. (P=0.012). Average peripapillary retinal nerve fiber layer (RNFL) thickness was reduced in the model group (P=0.000, 30d; P=0.000, 40d) and gypenosides treatment remarkably diminished the degree of RNFL degeneration at 30d and 40d p.i (P=0.000, 30d; P=0.000, 40d). The pathomorphological results showed a decrease in demye-lination (P=0.020) and inflammatory reactions in the combination group compared with the model group (20d p.i.). Gypenosides treatment also alleviated the degree of axonal loss (40d p.i.) (P=0.003).

Treatment with gypenosides exerts protective effects on retinal nerve fibers and axons in EAON. When combined with gypenosides, methylprednisolone reduces demyelination in the acute stage of EAON.