A new study has shown that combining two toxic substances commonly found in the environment damaged neurons associated with Parkinson's disease (PD) in mice. This raises the issue of whether Parkinson's may, in part, be caused by exposure to environmental toxins.
According to scientists at the Buck Institute for Age Research, their study also showed that treating the mice with an antioxidant weakened the impact of the environmental exposures. The toxins involved include excess iron intake at an early age and exposure to the herbicide paraquat.
The study points to a role for environmental factors in the development of PD, an incurable neurodegenerative disorder that causes shaking, slowness of movement and rigidity.
Only five percent of the 160,000 cases of PD diagnosed in the U.S. each year are considered strictly genetic; most of those afflicted have been subject to a combination of environmental exposures and genetic susceptibility.
"Research keeps pointing to Parkinson's disease as being a very complex disorder," said Buck Institute faculty member Julie K. Andersen, lead author of the study. "This research looked at environmental risk factors in the context of aging which is essential, given the fact that aging is the single major risk factor for PD in humans."
"The fact that the antioxidant treatment prevented much of the nerve damage in the mice points to the need for an early diagnostic test for Parkinson's disease," said Andersen. "Currently, by the time humans are diagnosed with the disease they have already lost 60% of the neurons implicated in PD; treatment with an antioxidant would likely be maximally effective if taken before symptoms appear in order to halt disease progression."
The study was published in the June 27, 2007 issue of The Journal of Neuroscience.