Parkinson disease: etiology, pathogenesis and future of gene therapy.

Parkinson disease (PD) is a progressive neurological disorder with a prevalence of 1-2% in people over the age of 50. It has a world-wide distribution and has no gender preference. The neurological hallmark of PD is the presence of Lewy bodies and is characterized by the degeneration of nigrostriatal dopaminergic neurons. The causes of PD are unknown but considerable evidence suggests a multifactorial etiology involving genetic and environmental factors. A molecular genetic approach identified three genes and at least two additional loci in rare familial forms of PD. Two of these genes are involved in the ubiquitin mediated pathway of protein degradation and the third one is a highly expressed protein in the synaptic terminal and is called alpha-synuclein. In animal models, it has been shown that use of the household pesticide which is known to contain rotenone, causes PD. Thus, a combined action of genetic and environmental factors is responsible for the pathogenesis of PD. Although use of levodopa or dopamine agonists can substantially reduce clinical symptoms, and transplantation of fetal nerve tissue still remains as an alternative therapy (although it has been recently shown to be having no overall benefit), directed delivery of glial cell derived neurotrophic factor (known to have trophic effects on dopaminergic neurons) may also be a beneficial therapeutic option for PD patients.