MAPK3 and Parkinson disease: To further clarify whether the effect of Lf on DA neuron degeneration occurs via inhibiting the activation of the JNK and P38 MAPK signaling pathways and upregulating HIF-1α via activating the ERK/CREB signaling pathway, parallel experiments involving pretreatments with hLf and inhibitors for JNK1/2, ERK1/2, P38 and CREB were performed in our PD cell model.