ABSTRACT
OBJECTIVE To evaluate these activities of Rg1 in the 1-methyl-4-phenyl-1,2,3,6-tetrahy?dropyridine (MPTP)/probenecid (MPTP/p)-induced PD mouse model for the first time and to elucidate the underlying mechanisms. METHODS Male C57BL/6 mice were randomly assigned to six groups. One hour prior to MPTP/p injection, Group Ⅲ-Ⅵ mice received 10 mg·kg-1, 20 mg·kg-1, or 40 mg·kg-1 Rg1 or 3 mg·kg-1 selegiline, respectively, orally from D (-3) to D49. Group Ⅰ-Ⅱ mice received solvent water. Subsequently, GroupⅡ-Ⅵ mice received by injection MPTP-HCl (25 mg·kg- 1 bw dissolved in 0.9% saline, sc) on a 40-d schedule at intervals of 4 d between consecutive doses in combination with an adjuvant drug, probenecid (250 mg·kg- 1 bw in 0.03 mL of DMSO, ip); GroupⅠ mice were injected with saline and probenecid. Behavioral performance was assessed in the open field test, pole test and rotarod test. Neurotransmitters in the striatum were detected using HPLC. Protein levels were measured by Western blot. Pathological characteristics were examined by immunohistochemistry. Ultrastructure changes were observed by electron microscopy. RESULTS Oral treatment with Rg1 significantly attenuated the high MPTP-induced mortality, behavior defects, loss of dopamine neurons and abnormal ultrastructure changes in the SNpc. Other assays indicated that the protective effect of Rg1 may be mediated by its anti-neuroinflammatory properties. Rg1 regulated MPTP-induced reactive astrocytes and microglia and decreased the release of cytokines such as tumor necrosis factor-α (TNF-α) and interleukin-1b (IL-1b) in the SNpc. Rg1 also alleviated the unusual MPTP induced increase in oligomeric, phosphorylated and disease-related a-synuclein in the SNpc. CONCLUSION Rg1 protects dopaminergic neurons, most likely by reducing aberrant a-synuclein-mediated neuroinflammation, and holds promise for Parkinson disease therapeutics.