Abstract
Parkinson's disease (PD) is one of the most epidemic neurodegenerative diseases and is characterized by movement disorders arising from loss of midbrain dopaminergic (DA) neurons. Recently, the relationship between PD and autophagy has received considerable attention, but information about the mechanisms involved is lacking. Here, we report that autophagy-related gene 5 (ATG5) is potentially important in protecting dopaminergic neurons in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD model in zebrafish. Using analyses of zebrafish swimming behavior, in situ hybridization, immunofluorescence, and expressions of genes and proteins related to PD and autophagy, we found that the ATG5 expression level was decreased and autophagy flux was blocked in this model. The ATG5 down-regulation led to the upgrade of PD-associated proteins, such as β-synuclein, Parkin, and PINK1, aggravation of MPTP-induced PD-mimicking pathological locomotor behavior, DA neuron loss labeled by tyrosine hydroxylase (TH) or dopamine transporter (DAT), and blocked autophagy flux in the zebrafish model. ATG5 overexpression alleviated or reversed these PD pathological features, rescued DA neuron cells as indicated by elevated TH/DAT levels, and restored autophagy flux. The role of ATG5 in protecting DA neurons was confirmed by expression of the human atg5 gene in the zebrafish model. Our findings reveal that ATG5 has a role in neuroprotection, and up-regulation of ATG5 may serve as a goal in the development of drugs for PD prevention and management.
Highlights
Parkinson’s disease (PD)2 is one of the most prevalent motorrelated neurodegenerative diseases, which is diagnosed clini
A locomotion assay showed that swimming behavior of the larvae was disturbed after exposure to MPTP, in which zebrafish swimming velocity and distance were significantly suppressed, and their activity duration was moderately reduced by MPTP treatment (Fig. 1A)
Expression of the dopaminergic neuron marker gene th was down-regulated at both transcription and translation levels (Fig. 1B), which suggests that MPTP resulted in a decrease in dopaminergic neuron number
Summary
A PD-like model was established by exposing zebrafish larvae to MPTP. A locomotion assay showed that swimming behavior of the larvae was disturbed after exposure to MPTP, in which zebrafish swimming velocity and distance were significantly suppressed, and their activity duration was moderately reduced by MPTP treatment (Fig. 1A). The PD-related proteins -syn, PINK1, and Parkin were detected and up-regulated by MPTP in a dose-dependent manner, but their mRNA levels were not changed (Fig. 1, C–E) These results indicate that MPTP-induced PD-like symptoms of motor dysfunction, loss of dopaminergic neurons, and abnormal increase of the PD proteins were similar to those in the mouse MPTP-PD model [46]. Further experiments showed that when zebrafish larvae were injected with ATG5 mRNA, the level of TH protein was similar to the WT group, and -syn, Parkin, and PINK1 proteins were moderately suppressed or had no obvious change compared with the WT group and lacZ group. The results showed that the number of DA neurons was increased or recovered in the larval ventral diencephalon as indicated by the th signal in the MPTP plus hATG5 mRNA groups compared with MPTP groups without ATG5 mRNA and lacZ plus MPTP groups (Fig. 8, B and C). Both ATG5 proteins antagonized MPTP-induced dopaminergic neuronal toxicity in zebrafish
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
