A drug that is used to treat high blood pressure may be able to slow or even halt the progress of Parkinson’s disease, experiments suggest.

A team from Northwestern University in Chicago has found that isradipine, a calcium-blocker that is marketed in Britain by Novartis as Prescal for the control of high blood pressure, can correct the underlying problem in Parkinson’s: the failure of brain cells to make dopamine.

The disease mainly affects people aged 60 and over, and occurs when dopamine neurons in the brain start to die. The dopamine released by the cells is a chemical messenger that affects the control of movement. When dopamine is lacking, movement becomes more difficult and uncoordinated. Sufferers experience muscle rigidity and tremors and lose the ability to walk or talk.

In Nature online, a team led by James Surmeier reported that mice with a disease related to Parkinson’s were rejuvenated by doses of isradipine. Tests showed that the mice, which had been genetically engineered to have a Parkinson’s-like disease, resisted becoming ill and their dopamine-producing cells began to function as if they were younger. If the same was found to be true in human patients it could be a big advance in managing the disease.

Professor Surmeier said: “Our hope is that this drug will protect dopamine neurons, so that if you began taking it early enough you won’t get Parkinson’s disease, even if you were at risk. It would be like taking a baby aspirin every day to protect your heart.”

Using the drug, or similar calcium blockers, could extend the effectiveness of traditional dopamine-boosting medication – possibly doubling or tripling the length of time that it worked, said Professor Surmeier, who has been researching Parkinson’s disease for 20 years. This in itself would be a huge advance, he said.

The team found that the dopamine cells had two distinct ways of operating. When cells were young they used sodium ions to produce electrical signals. When they were older, they switched to using calcium ions. Potentially, calcium ions can cause a lot of trouble inside cells, and they need to be pumped out efficiently. This uses a lot of energy and puts the cells under stress – one reason, Professor Surmeier surmises, why they tend to die.

When isradipine was used to block the “gateways” through which calcium ions entered the cells, the neurons reverted to their youthful behaviour. After a short “silent” interval they went back to using sodium.

The scientists intend to launch a clinical patient trial. If the treatment works, some patients may already have benefited if they developed high blood pressure and were treated with calcium-channel blockers.

Although some epidemiological studies have shown that people who take blood-pressure drugs have a lower risk of Parkinson’s, a study published in the journal Parkinsonism and Related Disorders in April found no clear benefit from calcium-channel blockers.

A team from the University of Washington in Seattle compared a group of Parkinson’s sufferers with a matched group of healthy people and found no persuasive evidence of a protective effect. But this study involved all calcium-channel blockers. A study that focused on isradipine alone may have reached a different conclusion.

Kieran Breen, director of research and development at the Parkinson’s Disease Society, said that more work had to be done. “The results that have been reported are from a very early stage preclinical trial using a model of Parkinson’s. Further trials are needed to establish whether similar results are seen in people with the condition,” he said.

“It is too early to state with confidence that this drug will be appropriate for the treatment for Parkinson’s disease.”

Case history

- Muhammad Ali, the boxer, had Parkinson’s disease diagnosed in 1983, two years after his retirement from the boxing ring. He was aged 41. Doctors suspected that the blows to the head he took in the latter part of his career contributed to his development of the disease

- Michael J. Fox, the actor, had Parkinson’s diagnosed in 1991, aged 30. He kept it secret until 1998, then became an advocate for embryonic stem cell research

- In 2005 Fox made a number of commercials for Democrat candidates for the US Senate, advocating federal funding for stem-cell research

- Rush Limbaugh, the radio host, claimed that he was “either off his medication or acting”. Experts said that the actor was exhibiting classic symptoms of severe Parkinson’s

- About 10,000 cases of Parkinson’s are diagnosed in Britain every year, and at any time 120,000 are living with the disease

- Existing treatments can reduce the symptoms of Parkinson’s, but they become less effective over time and nothing that is available can stop the disease progressing

Source: Times database

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