The neuroprotective effect of the
glial cell line-derived neurotrophic factor has been extensively studied in various toxic models of
Parkinson's disease. However, it remains unclear whether this neurotrophic factor can protect against the toxicity induced by the aggregation-prone protein α-
synuclein. Targeted overexpression of human wild-type α-
synuclein in the nigrostriatal system, using adeno-associated viral vectors, causes a progressive degeneration of the nigral
dopamine neurons and the development of axonal pathology in the striatum. In the present study, we investigated, using different paradigms of delivery, whether
glial cell line-derived neurotrophic factor can protect against the neurodegenerative changes and the cellular stress induced by α-
synuclein. We found that viral vector-mediated delivery of
glial cell line-derived neurotrophic factor into substantia nigra and/or striatum, administered 2-3 weeks before α-
synuclein, was inefficient in preventing the wild-type α-
synuclein-induced loss of
dopamine neurons and terminals. In addition,
glial cell line-derived neurotrophic factor overexpression did not ameliorate the behavioural deficit in this rat model of
Parkinson's disease. Quantification of striatal α-
synuclein-positive aggregates revealed that
glial cell line-derived neurotrophic factor had no effect on α-
synuclein aggregation. These data provide the evidence for the lack of neuroprotective effect of
glial cell line-derived neurotrophic factor against the toxicity of human wild-type α-
synuclein in an in vivo model of
Parkinson's disease. The difference in neuroprotective efficacy of
glial cell line-derived neurotrophic factor seen in our model and the commonly used neurotoxin models of
Parkinson's disease, raises important issues pertinent to the interpretation of the results obtained in preclinical models of
Parkinson's disease, and their relevance for the therapeutic use
glial cell line-derived neurotrophic factor in patients with
Parkinson's disease.