Evaluation Of The Effect And The Potential Mechanisms Of Silibinin On MPTP-induced Apoptosis In Mice

Background:Parkinson’s disease (PD) is the second most common progressive neurogenerative disease in the world. The degeneration of the nigro-striatal pathway has been linked with the apoptosis involved with mitochondria. Reduction of the detrimental apoptotic markers in the lesioned nigro-striatal pathway is one of the therapeutic strategies for the cure of PD. Silibinin, the most important compound in silymarin, has been reported cytoprotective effects as a potent antioxidant. However, the correlation between the effect of silibinin to dopaminergic neurons apoptosis is still unknown. Our aim was to investigate the effect and potential mechanism of silibinin on dopaminergic neurons in MPTP-induced mice. Methods:After administration, four behavioral tests were used to evaluate animals’behavioral changes as follow:beam walking test, inclined plane test, open field test and sucrose preference test. We also detected the ATP content in substantia nigra and striatum. In addition, we tested the effects of silibinin on Bax, Bcl-2, Cyt c and caspase3protein and mRNA levels by Western blot and RT-PCR. Results:Behavioral tests showed that MPTP could decrease score and the latency to fall down significantly (p<0.01versus vehicle group). Prophylactic treatment with Silibinin at200mg/kg increased the score and latency markedly (p<0.01). In the open field test, MPTP induced a robust decrease (p<0.01) in the horizontal movements and vertical movements and a significant decrease (p<0.05) in sucrose preference. Silibinin was able to produce increases in horizontal movements (p<0.05at100mg/kg and p<0.01at200mg/kg), vertical movements (p<0.01at200mg/kg) and sucrose preference (p<0.01at both doses). MPTP decreased ATP levels in both of the substantia nigra and striatum (P<0.01) significantly.200mg/kg of the silibinin could markedly increased ATP level in the substantia nigra (p<0.05). In the substantia nigra, the Bcl-2protein was significantly decreased in the MPTP group compared to the vehicle group (P<0.05). However, Bcl-2protein level was significantly increased when mice treated with high dose of Silibinin (P<0.05). The pro-apoptotic protein Bax was not influenced by the MPTP in either substantia nigra or striatum. The protien levels of caspase-3and Cyt c were significantly increased in substantia nigra and striatum (P<0.05) by MPTP. Pre-teatment of Silibinin could effiectivly decrease Cyt c protein levels in both brain areas (P<0.05). The caspase3level is also decreased in substantia nigra(P<0.05). The mRNA level of Bcl-2in PD mouse’s substantia nigra decreased markedly (P<0.01), and the mRNA expressions of Cyt c and caspase-3increased significantly (P<0.05). In the striatum, Cyt c and caspase-3was significantly increased in PD mouse in comparison with the control group (P<0.05). Silibinin can ameliorate the anti-apoptotic genes at mRNA level in substantia nigra (P<0.01) and decrease pro-apoptotic genes in substantia nigra and striatum significantly. The mRNA expressions of Bcl-2did not change markerly in the striatum (P>0.05). Conclusions:The prophylactic treatment of Silibinin has a protective effect on Parkinson’s disease model mice. The possible molecular mechanism may be related to regulate neuron apoptosis through mitochondrial pathway.