ABSTRACT
Parkinson's disease is characterized by the progressive loss of dopaminergic (DA) neurons in the substantia nigra. The heat-shock protein 70 (Hsp70) reduces protein misfolding and aggregation. It has been shown to protect cells against oxidative stress and apoptotic stimuli in various neurodegenerative disease models. To deliver Hsp70 across cellular membranes and into the brain, we linked it to a cell-penetrating peptide derived from the HIV trans-activator of transcription (Tat) protein. In vitro, Tat-Hsp70 transduced neuroblastoma cells and protected primary mesencephalic DA neurons and their neurites against MPP+-mediated degeneration. In vivo, the systemic application of cell-permeable Hsp70 protected DA neurons of the substantia nigra pars compacta against subacute toxicity of MPTP. Furthermore, Tat-Hsp70 diminished the MPTP induced decrease in DA striatal fiber density. Thus, we demonstrate that systemically applied Tat-Hsp70 effectively prevents neuronal cell death in in vitro and in vivo models of Parkinson's disease. The use of Tat-fusion proteins might therefore be a valuable tool to deliver molecular chaperones like Hsp70 into the brain and may be the starting point for new protective strategies in neurodegenerative diseases.
Subject(s)
Gene Products, tat/genetics , Genetic Therapy/methods , HSP70 Heat-Shock Proteins/metabolism , Oxidative Stress/genetics , Recombinant Fusion Proteins/metabolism , Substantia Nigra/metabolism , Animals , Cell Line, Tumor , Cells, Cultured , Corpus Striatum/metabolism , Corpus Striatum/pathology , Corpus Striatum/physiopathology , Cytoprotection/genetics , Dopamine/metabolism , Gene Products, tat/chemistry , HSP70 Heat-Shock Proteins/genetics , Humans , Male , Mice , Parkinsonian Disorders/genetics , Parkinsonian Disorders/metabolism , Parkinsonian Disorders/therapy , Peptide Fragments/genetics , Rats , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/therapeutic use , Substantia Nigra/cytology , Substantia Nigra/physiopathology , Transduction, Genetic/methods , Treatment Outcome , Wallerian Degeneration/genetics , Wallerian Degeneration/metabolism , Wallerian Degeneration/therapyABSTRACT
Activation of the RET (rearranged during transfection) receptor by glial cell-line-derived neurotrophic factor (GDNF) has been identified as an important differentiation and survival factor for dopaminergic neurons of the midbrain in preclinical experiments. These encouraging results have led to clinical trials of GDNF in patients with Parkinson's disease, which have resulted in conflicting findings. To investigate the potential benefit of Ret-dependent signaling on the challenged dopaminergic system, we tested the effect of tissue-selective ablation of the Ret gene on 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) toxicity in mice, the most widely used animal model for Parkinson's disease. Ablation of Ret did not modify the MPTP-induced loss of dopaminergic neurons in the substantia nigra pars compacta and the dopaminergic innervation of the striatum at 14 days. However, Ret ablation abolished the regeneration of dopaminergic fibers and terminals, as well as the partial recovery of striatal dopamine concentrations, that was observed in control mice between days 14 and 90 after MPTP treatment. We therefore conclude that RET signaling has no influence on the survival of dopaminergic neurons in the MPTP model of Parkinson's disease but rather facilitates the regeneration of dopaminergic axon terminals.
