eMedicineLive

Scientists have discovered a new class of drugs – the “bitter taste receptor agonists” which have been found to be effective in asthma and COPD. These drugs can ease the constriction of the smooth muscles of the airways, thereby relaxing them and allowing easier passage of air into the lungs.

Scientists had been working for more than five years to find a set of drugs which could activate bitter taste receptors present on the smooth muscles of the airways, which in turn relax these muscles. Researchers from Baltimore, led by Kathryn Robinett, MD, pulmonary and critical care fellow at the University Of Maryland School Of Medicine, have been able to identify certain bitter tasting compounds, which produce considerable relaxation of these muscles in the airways of both mice as well as humans. The findings of the study will be presented at the ATS 2011 International Conference in Denver.

After identifying the bitter compounds, which the scientists thought could relax the airway muscles, the compounds were administered to mice to study their effect. To their surprise, the researchers discovered that these compounds were as effective as beta- agonists and in many cases, even more so, in relaxing the smooth muscles. Even more important is the fact that the mechanism of action of these bitter compounds is entirely different from that of the beta agonists. Therefore, these two classes of drugs can work in tandem, in severe cases of asthma and COPD to achieve the desired results.

Obstructive lung diseases, which include asthma and COPD, affect more than 300 million people worldwide and are a major cause of morbidity and mortality.  Taking measures like environment control, and medicines like beta agonists and inhaled corticosteroids, have not been able to control these diseases. The “bitter taste receptor agonists” could be the next most important set of drugs to take on the challenge thrown by asthma and COPD.

Despite their effectiveness in relaxing the airway smooth muscles, these bitter compounds activate only 2 of the 6 main bitter taste receptors. Hence, they may not taste very bitter on the tongue. There are many such compounds in the plant world which may either themselves act as bitter taste receptor agonists or provide the basis for artificial synthesis of such compounds.

The next important steps to be taken include the identification of more such compounds, and to carry out toxicological studies on some of the selected compounds, so as to produce drugs which are not very unpalatable and yet, effective in relaxing the smooth muscles of the airways, thereby providing relief from asthma and COPD.

References:

• "Bitter Taste Receptor Signaling On Airway Smooth Muscle: A Highly Efficacious Pathway for Treating Obstructive Airway Disease" (Session A30, Sunday, May 15, 8:15-10:45 a.m., Room 501-502 (Street Level), Colorado Convention Center; Abstract 16969)
• http://www.eurekalert.org/pub_releases/2011-05/ats-rmc051111.php