Parkinson's disease comes with slowness, rigidity, tremors, and loss of balance due to an insufficiency of the dopamine that coordinates muscle movement. This disease, of which the rate of diagnosis is rising, occurs when the neurons responsible for producing dopamine malfunction or die. About 500,000 Americans are diagnosed with Parkinson's each year.

Most of the time, Parkinson's disease is a condition of the elderly, diagnosed in people 60 and older. However, about 10% of the time, it's detected in people between 21 and 50. "Young-onset Parkinson's is especially heartbreaking because it strikes people at the prime of life," says Michele Tagliati, an author of a new study from Cedars-Sinai.

The study of brain cells from Parkinson's younger victims has found that the misbehaving neurons are present long before diagnosis typically taking some 20 or 30 years to produce detectable symptoms and may even be present prior to birth. The revelation raises hope for combatting Parkinson's because there's already an approved drug that can mitigate the damage done by the troublemaking neurons before the disease ever appears.

The research is published in the journal Nature Medicine.

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The authors' investigation began with an examination of neurons based on cells from young-onset Parkinson's (YOPD) patients who had no known mutations. From the cells, induced pluripotent stem cells (iPSCs) were generated and differentiated into dishes containing cultures of dopamine neurons. Senior study author Clive Svendsen says, "Our technique gave us a window back in time to see how well the dopamine neurons might have functioned from the very start of a patient's life."

The scientists observed lysosomes within the YOPD neurons malfunctioning. Since lysosomes are counted on as "trash cans" for unnecessary or depleted proteins, the castoff chemicals began to pile up. In particular, substantial accumulations of soluble -synuclein, a protein implicated in different types of Parkinson's, were seen.

Says Svendsen, "What we are seeing using this new model are the very first signs of young-onset Parkinson's,"revealing that, "It appears that dopamine neurons in these individuals may continue to mishandle -synuclein over a period of 20 or 30 years, causing Parkinson's symptoms to emerge."

The researchers also saw unexpectedly high levels of the enzyme protein kinase C in its active form, though what that has to do with Parkinson's, if anything, is unknown.

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The researchers tested a number of drugs on the cultures to see if any might address the observed accumulations of -synuclein. (They performed parallel tests of laboratory mice.) One drug, PEP005, which is already approved by the FDA for treating skin pre-cancers, did effectively reduce the -synuclein buildup, both in the iPSCs and the mice.

Since PEP005 is currently administered in gel form for treating skin, the researchers are now exploring how the drug might be modified so it can be delivered directly to the brain. The team also plans follow-on research to see if their findings apply equally to forms of Parkinson's beyond YOPD.

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