BRECKENRIDGE, CO, Jan 26 (Reuters Health) -- Studies in progress and new
drugs in development may revolutionize the treatment of Parkinson's disease,
researchers report.
"There is good reason to be optimistic about making headway in Parkinson's
disease," Dr. Michael Zigmond of the University of Pittsburgh told attendees of
the 33rd annual Winter Conference on Brain Research underway here. "Drug
companies are developing 'neuroprotectors.' Within 5 years we will have drugs
that retard disease progression."
Zigmond chaired a panel that discussed what is known about the causes of
Parkinsons's disease at the cellular level. The panel also included Dr. Robert
Burke and Dr. David Sulzer, both of Columbia University in New York, and Dr.
Suzanne Roffler-Tarlov of Tufts University School of Medicine in Boston.
Parkinson's disease, a neurodegenerative disease that affects 500,000 to
1,000,000 people in the United States, is most common in people over the age of
65. Problems with movement, including tremor, muscle rigidity, and impaired
coordination are features of Parkinson's disease. The cause of the disease is
believed to be related to a loss of brain cells that produce dopamine -- a
neurotransmitter that plays an important role in how the brain controls
movement.
"We know a tremendous amount about this disease," said Burke. "But not
what causes it or how to treat it. The core issue is: What kills these neurons?"
"If you lose 60% of your dopamine neurons, you're fine," Zigmond
commented. "After about 70%, people get tremors. Further loss results in severe
motor disabilities. If you lose all your dopamine neurons, you're akinetic" --
that is, unable to move.
The panel members discussed their work, research into the potential causes
of the disease at the cellular level. Sulzer noted that dopamine, unlike other
neurotransmitters, produces toxic metabolites, and speculated that excess
amounts of dopamine may trigger breakdown of nerve cells.
Roffler-Tarlov noted that her studies in mice suggest that changes in the
natural charge, or resting potential, normally present across the cell membrane
-- the outer covering of cells -- may also play a role in the development of the
disease.
"It may be that many diseases... are downstream of a gene or condition
which doesn't allow cells to maintain normal resting potential, and eventually
results in cell death," she said.
In some cases, Parkinson's disease has a familial component. Two genes
were isolated from three extended families with Parkinson's. One gene, for the
protein synuclein, has two different mutations and another gene, for the protein
'parkin' has one mutation. Zigmond suggests that once the role of these proteins
is discovered, new therapies may be found.
