Scientists have found a protein within the airways which they believe triggers all asthma attacks

Scientists claim to have found the root cause of asthma, a breakthrough which could pave the way for a new treatment within five years.

Most of the millions of asthma sufferers are able to regulate their symptoms with inhalers, but a minority - about 5 per cent of patients - do not respond to any treatment.

Now scientists have found a protein within the airways which they believe triggers all asthma attacks.

Remarkably, a drug already exists which they think could deactivate the protein, raising hopes for a treatment which may be effective for any asthma patient.

The team, led by Cardiff University, has already shown that the drug works in mice and in human tissue samples in the laboratory.

They have now designed the first clinical trials, which could start within two years.

Lead investigator Professor Daniela Riccardi said: ‘Our findings are incredibly exciting.’

The discovery came quite by chance when Professor Riccardi, formerly a bones specialist, switched from the study of osteoporosis to the study of the lungs five years ago.

She realised that a protein that triggers the growth of calcium within bones also plays a role in the airways.

Further tests revealed that asthmatics had far higher levels of the protein - called a calcium sensing receptor or CaSR - than healthy people.

When an asthmatic breathes in triggers such as dust, smoke, or pollen, the CaSR molecules cause the rapid increase of calcium within the cells of the lung tissue.

The added calcium makes the cells contract, making the airways spasm, triggering an asthma attack.

Professor Riccardi said: ‘For the first time we have found a link between airways inflammation, which can be caused by environmental triggers - such as allergens, cigarette smoke and car fumes – and airways twitchiness in allergic asthma.

‘It makes the cells much more sensitive to the asthma triggers - which then make an attack much more likely.’

A drug already exists that can disable the CaSR protein, meaning it could be available to patients as soon as clinical trials are complete.

The medication - called a calcilytic - was developed 15 years ago to knock out the same protein in osteoporosis.

Although the drug was shown to be safe, it was not effective for osteoporosis patients.

But early tests in mice and human tissue showed promising results as an asthma treatment.

The team, which included scientists from King’s College London and the Mayo Clinic in the US, hope to use the drug in a nebuliser, in which it is turned into a mist and breathed straight into the lungs.

When an asthmatic breathes in triggers such as dust, smoke, or pollen, the newly-identified protein causes the rapid increase of calcium within the cells of the lung tissue. This makes the cells contract and the ing the airways spasm, triggering an asthma attack

A few courses of treatment would be enough to stop asthma attacks from recurring, they hope.

The suspect it might also have a role in tackling chronic obstructive pulmonary disease - COPD - and chronic bronchitis, for which there is currently no effective treatment.

Prof Riccardi said: ‘If we can prove that calcilytics are safe when administered directly to the lung in people, then in five years we could be in a position to treat patients and potentially stop asthma from happening in the first place.’

Dr Samantha Walker, director of research at Asthma UK, who helped fund the research, added: ‘This hugely exciting discovery enables us, for the first time, to tackle the underlying causes of asthma symptoms.

‘Five per cent of people with asthma don’t respond to current treatments so research breakthroughs could be life changing for hundreds of thousands of people.

‘If this research proves successful we may be just a few years away from a new treatment for asthma, and we urgently need further investment to take it further through clinical trials.