Asthma is characterised by reversible narrowing of airways in the lungs, which makes breathing difficult. An estimated 300 million people suffer from this condition worldwide. There is, to date, no cure for asthma, although the condition can be well managed with proper treatment.
According to Professor Bradding of the Department of Infection, Immunity and Inflammation at the University of Leicester (UK) asthma treatment can be broadly classified into preventer and reliever treatments. Preventers control swelling and inflammation of lung airways. Their protective effect is not immediate, but develops gradually with time. It is therefore, essential to take preventer medication regularly. Relievers on the other hand have an immediate effect. They help ‘relieve’ asthma symptoms by relaxing airways, making breathing easier. But, despite their usefulness in rapidly relieving asthma, relievers may cause asthma to worsen when used too frequently. Moreover, they are not always as effective as predicted.
Professor Bradding’s team investigated mechanisms behind this by studying interactions between reliever medicines and the immune system.
The immune system uses antibodies (a type of protein found in blood and other body fluids) to identify foreign bacteria and viruses and neutralise their effects. Asthma is commonly associated with allergies, which are caused by IgE antibodies which react with allergens such as house dust mite and grass. IgE binds to mast cells in lungs of asthma sufferers. This, in turn, causes mast cells to release chemicals such as histamine, which cause narrowing of lung airways and thus, lead to an asthma attack.
Mast cells need a chemical known as stem cell factor to survive and function and this chemical is present in asthmatic lungs. Professor Bradding’s research shows that when lung mast cells are exposed to reliever drugs, in the presence of both IgE and stem cell factor, relievers lose their ability to prevent chemical release from mast cells. Interestingly, under these circumstances, relievers may actually cause mast cells to release more chemicals, causing asthma to worsen.This research might explain why reliever drugs are not always as effective as predicted and why they might worsen and destabilise asthma.
These findings are very relevant for individuals with poorly controlled asthma and for those who rely too heavily on relievers, whilst not using their preventer medication regularly.
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First Publshed in Jnuary 2010
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