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Most drugs are designed to latch onto one specific protein in one specific tissue. But that protein, or one close by, may perform a function in a different tissue. That’s one reason why drugs have off-target effects. This is usually a problem but researchers are finding some drugs are surprisingly effective against diseases they were never intended to target.

For instance, researchers found that a handful of asthma medications, including one called clenbuterol, seem to lower a person’s risk of getting Parkinson’s disease.

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Parkinson’s disease occurs when a specific group of neurons die. These neurons help control muscle activity and as they die off, people progressively lose control of their voluntary muscles until they suffer from uncontrolled tremors. Like other neurodegenerative diseases, Parkinson’s has been associated with malformed proteins that become tangled and accumulate in the dying cells.

Tracking brain changes in people with Parkinson’s: researchers find that drugs that activate the adrenaline receptor seem to lower a person’s risk of getting Parkinson’s disease.

Researchers have identified that Parkinson’s tangles are made from a protein called α-synuclein. People with extra copies of this gene are more susceptible to developing Parkinson’s later in life. So, researchers decided to look for drugs that may suppress this gene.

A large international team of researchers examined over 1,000 drugs and potential drugs, and identified 35 that may lower the expression of the gene. Three of them reduce the activity of α-synuclein.

Most of the chemicals in the drugs activate adrenaline receptors, which should also reduce α-synuclein levels. Conveniently, these chemicals are already used in asthma medications since adrenaline helps relax the muscles in our airways.

The medications the researchers tracked varied from salbutamol (people who received this medication were two-thirds less likely to be diagnosed with Parkinson’s) to propranolol, which is typically used to calm irregular heartbeats and high blood pressure by blocking activation of adrenaline receptors. People who took this medication were two times more likely to be diagnosed with Parkinson’s.

Not only did researchers study the effect of current medications, but they also looked at what happened to stem cells treated with these drugs. Here’s John Timmer reporting for Ars Technica:

[The] authors obtained cells from an individual that carries an extra copy of the α-synuclein gene, which predisposes them to Parkinson’s. These cells were converted to stem cells, and the stem cells converted to neurons. Treating them with one of the drugs that came through the screen reduced α-synuclein expression, lowered the mortality of the cells, and kept their energy metabolism under better control.

The researchers urge people not to rush and get prescriptions for these drugs. They’re currently not FDA-approved to treat Parkinson’s and the drugs can actually increase cardiovascular disease.