Could an old wives’ tonic prove the cure for asthma?

Asthma is a common inflammatory disease of the airways of the lungs, which varies largely in its severity and duration from person to person.

When exposed to certain asthma triggers (such as cold air, exercise, pollen and viruses), the sensitive airways of asthmatic individuals react. They can become red and inflamed, which causes the muscles to tighten and produce excess mucus. This causes the airways to get constricted and thereby severely reduce breath flow, thus triggering asthma.

Asthma is thought to be caused by a combination of genetic and environmental factors. Environmental factors include exposure to air pollution and allergens.

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A child using an asthma inhaler. 358 million people worldwide are reported to be suffering from asthma in 2015.

Common asthma symptoms include shortness of breath, wheezing, coughing, and a feeling of tightness in the chest. These episodes may occur a few times a day or a few times per week.

On one end, sufferers experience what is euphemistically termed as’ wheezing’, a milder cousin of asthma which can often be relieved by prescription  beta-2 agonists such as salbutamol and corticosteroids taken via inhalation.

On the other extreme, full-blown asthma attacks can be life-threatening as severe shortness of breath restricts oxygen supply to the brain and other vital organs. Treatment in this case invariably involves hospitalization and intravenous administration of corticosteroids, in addition to nebulization until symptoms subside, and the patient is able to breathe well enough on his own.

Currently, there is no cure for asthma, and medical research into asthma has been largely focused on treatment rather than discovering means to cure or prevent it from occurring in the first place. Asthma was always known as a disease that can be largely controlled, but never cured.

New research led by Dr Pawan Sharma from the UTS School of Life Sciences and The Woolcock Institute of Medical Research, Australia seems set to create a precedent  in the hitherto poorly researched field of asthma prevention.

Dr Sharma and a team of American researchers investigated whether the activation of bitter taste receptors could thwart the symptoms of asthma in mice.

They found that bitter substances not only reduced common symptoms of the disease in mice, but also prevented allergic inflammation and structural changes to the airways. This could be a game-changer for the 300 million people worldwide that live with asthma.

The research team induced mice with allergic asthma and tested the effects of chloroquine and quinine on various features of the disease. Chloroquine and quinine are substances that stimulate bitter taste receptors owing to their bitter taste. Both are used as anti-malaria drugs and as ingredients for tonic water, lending the latter its characteristic bitter taste.

Tonic water has been ubiquitous since its creation in British India in the 1800s to combat endemic malaria. (Img)

When inhaled, these two compounds activated the taste-2 receptor protein (TAS2R). In doing so, they also block the allergic reaction in the lungs, thereby preventing asthma from occurring in the first place.

Past research has already shown that TAS2R agonists, compounds that activate the receptors, lead to relaxation in the airway of the lungs. But researchers hadn’t been able to test whether it was able to prevent the airway inflammation associated with asthma.

Excitingly, the spray didn’t just stop airway inflammation in the mice- it was also able to limit other characteristics of asthma, including mucus accumulation and associated structural changes to the airway.

The researchers confirmed these findings on human lung cells, finding that both chloroquine and quinine blocked the immune cells from reaching the airway, thereby limiting inflammation that could lead to an asthma attack.

“We used both in vitro and in vivo approaches using human airway cells and mouse models of asthma to study the effectiveness of novel bitter compounds. We do not have an effective anti-asthma therapy that targets disease progression. Our current research on taste receptors is crucial in identifying new classes of drugs that can be an effective asthma treatment option in future,” Dr Sharma said.

Dr Sharma is now preparing to collaborate with US researchers to synthesize new bitter compounds that may be developed as inhaled therapy for humans.

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