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Genetics and Epidemiology Point to Future Treatment and Cure for Parkinson’s Disease

For release: Monday, February 27, 2006

February 24, 2006 - Recent advances in scientists’ understanding of the genetics and epidemiology of Parkinson’s may point to ways to prevent and, eventually, find a cure for the disease, according to scientists presenting at today’s World Parkinson Congress.

“Parkinson’s disease is a problem now and will be an even bigger problem in the future if we can’t figure out how to intervene,” said Caroline Tanner, M.D., Ph.D., Director of Clinical Research at the Parkinson’s Institute in Sunnyvale, California.

Parkinson’s disease (PD) is the second most common neurodegenerative disorder, affecting more than one million Americans.

Scientists and physicians already know some of the factors—age greater than 50 years, the toxin MPTP, and a number of genes—that make it more likely that someone will develop Parkinson’s disease (PD). They have also found that cigarette smoking, coffee drinking, and use of non-steroidal anti-inflammatory drugs (NSAIDs) are more common in people without PD, and may be somehow protective.

Nicotine and caffeine affect brain receptors that affect the dopamine system, the dysfunction of which underlies PD, and findings about NSAIDs point to the possible role of inflammation in the development of the disease. But the reasons for these links are still unclear.

Studies have found associations between Parkinson’s and broad categories of things, such as pesticides, but they have not tied the disease to specific pesticides, said Dr. Tanner.

Recent research even points to a menu of mid-life factors, including excessive daytime sleepiness, difficulty recognizing odors, constipation, obesity, and prolonged QT intervals on electrocardiograms, that might one day be used to predict development of PD.

While there aren’t yet any good answers about why most people get PD, most researchers believe that a combination of genetic susceptibility and environmental factors “tips the bucket” toward developing PD in some people.

This possible genetic susceptibility to PD is the subject of research by Thomas Gasser, M.D., Director of the Hertie Institute for Clinical Brain Research at the University of Tübingen in Germany. Researchers in his laboratory and others are focusing on a gene called leucine-rich repeat kinase 2, or LRRK2 (pronounced lark 2), discovered in 2004.

LRRK2 codes for a protein called dardarin, which is a kinase—one of a family of proteins that play crucial roles in cell signaling. LRRK2 mutations are “surprisingly common,” said Dr. Gasser.  The mutations appear to cause 10 to 15 percent of familial (inherited) PD and 1 to 2 percent of sporadic cases.

Because the symptoms, course, and cellular pathology of PD linked to LRRK2 mutations are usually the same in familial and sporadic forms of the disease, studying LRRK2 and other genes can help researchers identify the cellular chains of events that lead to the loss of dopamine-producing neurons in PD, and might point to potential treatments.

A greater understanding of the biochemistry of PD is needed to develop effective treatments, said David Eidelberg, M.D., Feinstein Professor of Neurology at the New York University School of Medicine and Vice-Chairman of the Department of Medicine at the North Shore-Long Island Jewish Health System.

This understanding would be enhanced with the discovery of biomarkers—biochemical characteristics that can be used to definitively diagnose PD and to determine whether particular individuals are destined to develop PD, whether treatment is having an effect, and whether the course of the disease is changing.

Today, by the time most people with PD go to the doctor’s office with symptoms, they've lost an average of two-thirds of the dopamine terminals extending between two regions of the brain: the substantia nigra and the striatum.

“It would be nice to have a blood test that, if positive, would detect the development of Parkinson’s,” said Dr. Eidelberg. “What is needed are measures that are quantifiable, precise, and reproducible across populations.”

Dr. Eidelberg and other researchers are using functional brain imaging to quantify abnormalities in brain function that are associated with different features of the disease process. Researchers also are looking at structural, genetic, proteomic, and physiological markers that underlie the features of PD. One day, biomarkers could presage development of the disease, and open a window for potential treatment, perhaps years before symptoms appear.

Howard J. Federoff, M.D., Ph.D, Director of the Center for Aging and Developmental Biology and Senior Associate Dean for Basic Research at the University of Rochester School of Medicine, is studying biological systems in his attempts to find the common pathway by which PD initiates and carries out cell death.

“We want to identify one or more biochemical molecules that contribute to this pathway, both in the central nervous system and peripherally, so that we can then identify targets for therapeutic development,” said Dr. Federoff.

Last Modified January 31, 2007