Researchers say they have developed an experimental drug, similar to compounds used to treat diabetes, that slows the progression of Parkinson's disease itself -- as well as its symptoms -- in mice. In experiments performed with cultures of human brain cells and live mouse models, they report the drug blocked the degradation of brain cells that is the hallmark of Parkinson's disease. The drug is expected to move to clinical trials this year.
A report of the study's results was published in Nature Medicine.
According to the investigators, NLY01 works by binding to so-called glucagon-like peptide-1 receptors on the surface of certain cells. Similar drugs are used widely in the treatment of type 2 diabetes to increase insulin levels in the blood. Though past studies in animals suggested the neuroprotective potential of this class of drugs, researchers had not shown directly how it operated in the brain.
To find out, the team tested NLY01 on three major cell types in the human brain: astrocytes, microglia and neurons. They found that microglia, a brain cell type that sends signals throughout the central nervous system in response to infection or injury, had the most sites for NLY01 to bind to--two times higher than the other cell types, and 10 times higher in humans with Parkinson's disease compared to humans without the disease.
The team knew that microglia secreted chemical signals that converted astrocytes--the star shaped cells that help neurons communicate with their neighbors--into aggressive "activated" astrocytes, which eat away at the connections between cells in the brain, causing neurons to die off. They speculated that NLY01 might stop this conversion.
"The activated astrocytes we focused on go into a revolt against the brain," says the senior author, "and this structural breakdown contributes to the dead zones of brain tissue found in those with Parkinson's disease. The ideas was that if we could find a way to calm those astrocytes, we might be able to slow the progression of Parkinson's disease."
In a preliminary experiment in laboratory-grown human brain cells, the team treated human microglia with NLY01 and found that they were able to turn the activating signals off. When healthy astrocytes were combined with the treated microglia, they did not convert into destructive activated astrocytes and remained healthy neuroprotective cells. The team suspected that neurons throughout the body could be protected in the same way.
They explored this hypothesis by testing the drug's effectiveness in mice engineered to have a rodent version of Parkinson's disease.
In one experiment, the team injected the mice with alpha-synuclein, the protein known to be the primary driver of Parkinson's disease, and treated mice with NLY01. Similar but untreated mice injected with alpha-synuclein showed pronounced motor impairment over the course of six months in behavioral tests such as the pole test, which allows researchers to measure motor impairment such as that caused by Parkinson's disease. However, the team found that the mice treated with NLY01 maintained normal physical function and had no loss of dopamine neurons, indicating that the drug protected against the development of Parkinson's disease.
In a second experiment, the team used mice that were genetically engineered to naturally produce more human-type alpha-synuclein typically used to model human Parkinson's disease that runs in families. Under normal conditions, these so-called transgenic mice will succumb to the disease in 387 days. However, the team found that treatment with NLY01 extended the lives of the 20 mice treated with the drug by over 120 days.
Upon further investigation, the team found that the brains of the mice treated with NLY01 showed few signs of the neurodegenerative characteristics of Parkinson's disease.
The senior author cautions that the experimental drug must still be tested for safety as well as effectiveness in people, but based on the safety profile of other similar drugs, they do not anticipate any major roadblocks to its use in humans.
The team have reason to be hopeful that NLY01 could, in a relatively short period of time, make an impact on the lives of those with Parkinson's.
Similar drugs to NLY01 already approved by the Food and Drug Administration for the treatment of type 2 diabetes include exenatide, lixisenatide, liraglutide and dulaglutide, each of which can cost approximately $2,000 for a 90-day supply. NLY01 is a long-acting drug with improved the brain penetration compared to these approved drugs for diabetes.
Experimental drug blocks reactive astrocyte formation in Parkinson's models
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