FIGURE 4.

Rhynchophylline provides neuroprotection through the activation of MEF2D. (A) Rhynchophylline reverses the decrease in MEF2D levels caused by MPP⁺ in CGNs. CGNs were pre-treated with rhynchophylline (50 μM) for 2 h, or left untreated, then exposed to 50 μM MPP⁺ for 24 h. The cellular proteins were extracted and subjected to Western blot using MEF2D antibodies (n = 3, ^∗∗p < 0.01, compared to control group. ^##p < 0.01, compared to MPP⁺ group). (B,C) MEF2D gene knockdown renders rhynchophylline largely ineffective in protecting CGNs from MPP⁺-induced neurotoxicity. CGNs were transfected with pGPU6-green fluorescent protein (GFP) plasmid (vector) and pGPU6-GFP plasmid encoding GAPDH (ShNC) or MEF2D ShRNA (ShMEF2D). Forty-eight hour after transfection, cells were subjected to western blot analysis using anti-MEF2D and β-actin antibodies (B) After transfection, CGNs were pre-treated in the presence or absence of 50 μM Rhy for 2 h, then exposed to MPP⁺, and subjected to MTT assay for measuring cell viability (C) (n = 3, ^∗∗p < 0.01, compared to the ShMEF2D group).