- Scientists suspect that iron accumulation plays a role in
neurodegenerative processes such as Parkinson's disease, but its
distribution in neurons has never been observed because of the lack
of techniques to do so. Until today.
Researchers from CNRS at the University of Bordeaux (France),
University of Sevilla (Spain), INSERM Grenoble Institute of
Neurosciences (France) and ESRF have studied the iron distribution
in an in vitro model of neuronal cells that produce dopamine.
Dopamine is a neurotransmitter, a chemical messenger between nerve
cells in the mammalian brain. Because dopamine can form stable
complexes with iron, Richard Ortega, from the cellular chemical
imaging group in Bordeaux, believed that dopamine may exert a
protective effect by buffering iron in dopaminergic neurons and that
this system might be at fault in Parkinson's disease.

To test this hypothesis, the team used the new nanoprobe imaging
experimental station recently developed at the European Synchrotron
Radiation Facility to study the distribution of elements in cells.
The resolution of 90 nm allowed scientists to visualize the elements
distribution in the neurotransmitter vesicles. The nanoprobe
consists on exciting the sample with a strongly focused X-ray beam
and collecting the characteristic fluorescence signal that is re-
emitted. This allows showing the different trace elements in a
point, and then the sample is scanned point by point to form a
complete multi-element image of the cells.

The team shows that iron is stored within dopamine vesicles inside
the neuronal cells. This is the first evidence of iron-dopamine co-
localization in neuro-vesicles. The results also explain that when
dopamine production is obstructed, the iron in the vesicles
drastically decreases. This new function of dopamine vesicles in
iron storage is of critical importance to understand the molecular
mechanisms involved in Parkinson's disease. In this neurological
disorder, dopamine vesicular storage has been found impaired.
According to these results, this would increase the levels of highly
toxic iron-dopamine complexes in the neurons. The results are
published in PLoS ONE on September 26.

The synchrotron nano-imaging station offers a new tool for
researchers involved not only in the study of neurodegenerative
diseases but also in many other fields where the determination of
metal ions distribution at the subcellular level is important such
as: metal toxicology, chemical carcinogenesis, and cellular
pharmacology of inorganic compounds. This is one of the reasons why
the team decided to submit their results in an open access journal
such as PLoS ONE: " We want the different scientific communities to
know that this machine is available, and the best way is by letting
everyone have access to the results", explains Peter Cloetens, in
charge of the station at ESRF.



September 26, 2007(Science Daily)