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News in Brief
Proteins May Travel from Cell to Cell, Spreading Parkinson’s in the Brain
A new study suggests that a damaged protein can spread from sick cells to healthy ones in the brain, providing a possible explanation for how Parkinson’s disease (PD) progresses. The study appears in the January 19 online edition of the Journal of Clinical Investigation.
In people with Parkinson’s, neurons — the nerve cells in the brain that help control the body’s movements — develop clusters of a protein called alpha-synuclein. When these proteins clump together, they are known as Lewy bodies, and these have been linked to the cell death that triggers PD.
In earlier research, two separate teams — one led by Patrik Brundin, Ph.D., M.D., at Lund University in Sweden and the other led by Jeffrey Kordower, Ph.D., at the Parkinson’s Disease Foundation (PDF) Center for Parkinson’s Research at Rush University in Chicago — studied the brains of people with PD who had received transplants of healthy young neurons as a therapy. Both teams found that the newly transplanted neurons also developed Lewy bodies, suggesting that they “contracted” PD from the brain in which they were transplanted.
In the new study, Dr. Brundin and his colleagues tested the idea that alpha-synuclein can travel from one cell to another. First, the team studied the process in cell culture. They moved on to experiments with mice with PD symptoms, that showed excess alpha-synuclein in their brains. The researchers transplanted healthy neurons into the brains of these mice and observed their effects.
- Alpha-synuclein did indeed move from one neuron to another in both cell culture and in living animals
- There is a specific mechanism by which this travel takes place
- When alpha-synuclein enters a healthy neuron, it can initiate or “seed” the formation of Lewy body clumps.
What Does it Mean?
This study aimed to assess the “contagious protein” hypothesis of Parkinson’s, which theorizes that neurons may “infect” other neurons with damaged alpha-synuclein, a protein that seems to be important in determining how PD develops. In 1997, Stanley Pruziner, M.D., received the Nobel Prize for his surprising discovery that some damaged proteins, rather than live organisms such as viruses, can be infectious. Damaged or mis-folded proteins have since been implicated in such conditions as mad cow disease. The new study demonstrates that alpha-synuclein is able to enter and affect healthy neurons. It also suggests that the protein may initiate the formation of new Lewy body clumps which are the hallmark of Parkinson’s. Much about the nature of the alpha-synuclein “seeding” process remains unclear. Additional research is required to assess whether alpha-synuclein “infectivity” is a cause of PD disease progression, or is simply a minor aspect of the disease itself. Lastly, these results — if they are confirmed by future studies — suggest that the toxic form of alpha-synuclein should be seen as a target of new therapies.
New Tool is Approved to Help with Diagnosis of Parkinson’s
The US Food and Drug Administration (FDA), on January 17, approved the use of DaTscan, a novel imaging technique that can be used to help diagnose Parkinson’s disease (PD) in its early stages. The technique, which combines the injection of an iodine-based radioactive chemical with an imaging process (known as “SPECT”) that detects and measures the presence of dopamine, has been used successfully in Europe for more than a decade.
What is DaTscan and what does it mean for you? To find out, PDF News & Review recently posed some of your questions to our Director of Research Programs, James Beck, Ph.D.
Q: What is DaTscan?
Dr. Beck: DaTscan is an imaging technology that uses small amounts of a radioactive drug to help determine how much dopamine is available in a person’s brain. A machine similar to but smaller than an MRI machine, called a “single photon emission computed tomography machine,” or SPECT scanner, measures the amount and location of the drug in the brain.
Q: Can DaTscan diagnose Parkinson’s?
Dr. Beck: DaTscans cannot diagnose Parkinson’s disease. These scans are used to help a doctor confirm a diagnosis. In Europe more than 300,000 people have undergone the procedure. A DaTscan can be used to help rule out other diseases that may have clinical symptoms similar to those seen in Parkinson’s — such as essential tremor — that do not show the deficiency in dopamine that marks Parkinson’s disease. However, it will not differentiate PD from those diseases that — like Parkinson’s — are marked by a dopamine deficiency, such as multiple system atrophy (MSA) or progressive supranuclear palsy (PSP).
Q: What is the role of the DaTscan for people living with Parkinson’s?
Dr. Beck: Currently, there is no objective test for Parkinson's disease. While the specificity and sensitivity of DaTscans are not 100 percent, the test can help doctors to confirm or refute the diagnosis they have made based on a clinical examination. DaTscans will therefore be helpful in people whose symptoms present an inconclusive or confusing diagnosis.
Q: Are there any risks associated with DaTscan?
Dr. Beck: Among some individuals, there have been reports of headache, nausea, vertigo, dry mouth, and mild to moderate dizziness. There have also been cases of hypersensitivity reaction and pain at the site of the injection. No other major side-effects have been reported.
Q: I have Parkinson’s. Should I get a DaTscan?
Dr. Beck: Likely, no — especially if you are someone who has been diagnosed with Parkinson’s for several years and who responds well to standard Parkinson’s medications. A DaTscan is most useful for people whose diagnosis is clinically uncertain or who have failed to respond well to common Parkinson’s medication therapy. If a person is unable to see a Parkinson’s specialist or his or her clinical signs are not clearly those of PD, this is when a DaTscan may be deemed helpful.
Q: How can I get a DaTscan?
Dr. Beck: PDF recommends that you speak with your doctor to see if a DaTscan is right for you. If you are interested in learning more, we suggest you visit http://us.datscan.com/.
Q: Is the DaTscan test covered by insurance, Medicare and Medicaid?
Dr. Beck: DaTscan will be covered by Medicare and Medicaid. Insurers are likely to cover DaTscan but will policies vary, so contact your insurer for more information.
What Does it Mean?
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