The Neuruprotective Effects Of Catalpol On Mesencephalic Dopaminergic Neurons

The purpose of this study mainly aims at observation the neuroprotection of catalpol and its action mechanism on inflammation-induced and oxidative stress-induced neurotoxicity in mesencephalic dopaminergic neurons.Bacterial lipopolysaccharide (LPS) and 1-methyl-4-phenylpyridinium (MPP~+), which are inducers of inflammation and oxidative stress, were used as neurotoxin to establish the models in primary mesencephalic dopaminergic neurons cultures. Exposure of dopaminergic neurons to LPS and MPP~+ may cause neurons death. As a result, LPS at concentration of 10μg/ml for 24h and MPP+ at 10μM for 48 h were respectively decided as the proper toxin concentration and time for all subsequent experiments.The neuroprotective effects of catalpol on LPS-induced inflammation in mesencephalic neuron-glia cultures were investigated. Mesencephalic neuron-glia cultures were pretreated with catalpol for 30 min, then stimulated with LPS for additional 24 h. Immunocytochemical analysis for TH-positive neurons demonstrated that catalpol could effectively reduced the degeneration of dopaminergic neurons. Meanwhile, pretreatment with catalpol significantly attenuated the LPS-induced microglial activation, reduced the production of intracellular reactive oxygen species (ROS) and nitric oxide (NO), attenuated iNOS expression. The results indicated that catalpol could effectively attenuated LPS-induced microglial activation, inhibited the production of inflammatory factors and subsequently protected the dopaminergic neurons.The neuroprotective effects of catalpol on MPP~+-induced direat oxidative stress in mesencephalic neuron-enriched cultures were investigated. LDH assay revealed that application of MPP~+ induced the leakage of LDH and catalpol stabilized the cell membrane structure. The apoptosis in MPP~+-induced neurons was associated with the loss of mitochondrial membrane potential and complex I activity, the formation of ROS and MDA, suppression of SOD and GSH-Px. Immunocytochemical analysis for TH-positive neurons demonstrated that catalpol could effectively reduced the degeneration of mesencephalic dopaminergic neurons, and significantly prevented the obove-mentioned mitochondrial dysfunction. These-results suggest that catalpol may have the capacity to counteract the toxicity of MPP~+ by attenuating change of the mitochondrial membrane permeability that is associated with oxidative stress damage.