Cystic fibrosis patients are vulnerable to infection
Widely-used antidepressants could prevent infections which shorten the lives of many cystic fibrosis patients.
The lung disease is caused by a genetic mutation which creates the perfect environment for bacteria to thrive and cause permanent damage.
German and US scientists, writing in the journal Nature Medicine, say experiments on mice have revealed how this happens.
Their work suggests that amitriptyline drugs could help.
Approximately 80,000 people in the US and northern Europe have cystic fibrosis, and despite the best efforts of doctors, many of these have chronic lung infections, which can lower their life expectancy.
The damage caused by infections is often irreversible, and when it reaches a certain point, the only option may be a lung transplant.
The most obvious symptom of the disease is the production of too much thick mucous inside the lung, which scientists had believed helped bacteria such as Pseudomonas aeruginosa to get established out of the reach of the body's immune system.
However, the work by the German and US teams suggests that something different may be happening.
They believe that a direct result of the genetic mutation is to lower the acidity within certain parts of the cell.
This, in turn, interferes with the efficiency of two body chemicals whose job it is to control levels of a fat called ceramide.
When ceramide levels rise, they say, the end product is the death of lung cells, and increased inflammation, both of which make it easier for bacteria to prosper.
They tested their theory in mice bred to mimic the cystic fibrosis gene defect, and found as they aged, ceramide levels rose, leading to cell death, inflammation and infection.
The scientists believe, however, that this chain reaction can be halted.
Amitriptyline drugs, commonly-used tricyclic antidepressants, are known to block the production of ceramide, and when these were given to mice, levels of the fat reverted to normal, and the animals were healthier, with less susceptability to infection.
Even though no experiments have so far been carried out in humans, they say it could be an important new way of tackling the disease.
As an established drug, much is already known about its safety, potentially speeding up clinical trials.
However, the researchers warned that getting the dose right - reducing ceramide levels without blocking it completely - would require care.
A spokesman for the Cystic Fibrosis Trust echoed this, saying much more research would be needed to make sure the balance could be controlled effectively in humans.
"It may be harmful if you have too little Ceramide as having too much."
"Overall, we should be very positive about this research as it helps understand why Pseudomonas aeruginosa may cause infection in cystic fibrosis and is a potential target for further research."