Mechanism of Autophagy Regulation in MPTP-Induced PD Mice via the mTOR Signaling Pathway by Echinacoside

Zhen-Nian Zhang,1,* Zhen Hui,1,* Chang Chen,1 Yan Liang,1 Li-Li Tang,1 Su-Lei Wang,1 Cheng-Cheng Xu,1 Hui Yang,1 Yang Zhao,1 Jing-Si Zhang2 1Department of Neurology, Nanjing Hospital of Chinese Medicine Affiliated to Nanjing University of Chinese Medicine, Nanjing, 210022, People’s Republic of China; 2Department of Neurology, Shuguang Hospital Affiliated to Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, People’s Republic of China*These authors contributed equally to this workCorrespondence: Jing-Si ZhangDepartment of Neurology, Shuguang Hospital Affiliated to Shanghai University of Traditional Chinese Medicine, No. 528 of Zhangheng Road, Pudong New Area, Shanghai, 201203, People’s Republic of ChinaTel/Fax +86 13127823579Email zhangzn88_dr@163.comObjective: The present study aimed to investigate the effect of echinacoside on autophagy-related indicators through the mTOR signaling pathway, especially the effect on the clearance of autophagy substrate P62 and α-synuclein, the core pathological products of Parkinson’s disease (PD), to provide new strategies for the treatment of PD.Methods: A mouse model of subacute PD was established by the intraperitoneal injection of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). First, the neurobehavioral symptoms in mice of each group were evaluated, and the monoamine neurotransmitters in the striatum in each group were measured with a high-performance liquid phase. Immunofluorescence double staining was adopted to observe the expression of tyrosine hydroxylase (TH), α-synuclein, and LC3. The transmission electron microscope was used to observe the changes of ultrastructure in substantia nigra and the formation of autophagosomes. Then, the expressions of TH, α-synuclein, Beclin 1, LC3, P62, mTOR, and the up-stream protein AKT were detected by Western blot.Results: When compared with the model group, the neurobehavioral function significantly improved in the echinacoside group (P < 0.01), together with increased expression of TH, DA, and DOPAC in the brain (P < 0.01). In the echinacoside group, while the expressions of Beclin 1 and LC3-II increased (P < 0.01), the expression levels of P62 and α-synuclein decreased significantly (P < 0.01). Echinacoside could up-regulate the expression level of the survival signal p-AKT/AKT and decrease the expression of mTOR.Conclusion: Echinacoside could increase autophagy by inhibiting the expression of mTOR, thereby promoting the clearance of α-synuclein and the degradation of the autophagy substrate P62 and exerting the neuroprotective effect.Keywords: Parkinson’s disease, MPTP, echinacoside, α-synuclein, P62, autophagy, mTOR