Rg1 protects the MPP+-treated MES23.5 cells via attenuating DMT1 up-regulation and cellular iron uptake

Ginsenoside-Rg1 is one of the pharmacologically active component isolated from ginseng. Our previous study observed the protective effect of Rg1 on iron accumulation in the substantia nigra (SN) in 1-methyl-4-phenyl-1,2,3,6- tetrahydropyridine (MPTP)-treated Parkinson's disease (PD) mice. However, the mechanisms of this neuroprotective effect of Rg1 are unknown. In this study, we elucidated possible mechanisms for this effect using 1-methyl-4-phenylpyridinium (MPP(+))-treated MES23.5 cells. Previous study showed MPP+ treatment induced up-regulation of divalent metal transporter 1 without iron responsive element (DMT1-IRE) in MES23.5 cells. In the present study, we observed that pretreatment with Rg1 could inhibit MPP+-induced up-regulation of DMT1-IRE in MES23.5 cells. Up-regulation of DMT1-IRE by MPP+ treatment was associated with ROS production and translocation of nuclear factor-kappaB (NF-kappaB) to nuclei, both of which were significantly inhibited by Rg1 pretreatment. The role of ROS and NF-kappaB in the up-regulation of DMT1-IRE was supported by application of an antioxidant NAC and BAY 11-7082, an inhibitor of IkappaBalpha phosphorylation. Furthermore, we also showed Rg1 could decrease DMT1-mediated ferrous iron uptake and iron-induced cell damage by inhibiting the up-regulation of DMT1-IRE. These results indicate that Rg1 protected the MPP+-treated MES23.5 cells via attenuating DMT1-IRE up-regulation likely through inhibition of ROS-NF-kappaB pathway; Attenuation of DMT1-IRE expression decreased the iron influx and iron-induced oxidative stress.