Researchers at the University of Maryland School of Medicine in Baltimore have discovered that bitter tasting substances can relieve asthma better than drugs currently available.
Stephen B. Liggett said his team found the taste receptors by accident, during an earlier, unrelated study of human lung muscle receptors that regulate airway contraction and relaxation.
In asthma, the smooth muscle airways contract or tighten, impeding the flow of air, causing wheezing and shortness of breath.
The researchers say that in the lung, the taste receptors are not clustered in buds and do not send signals to the brain, yet they respond to substances that have a bitter taste.
When the team exposed bitter-tasting compounds to human and mouse airways they found that they opened the airway more profoundly than any known drug that is used for treatment of asthma or chronic obstructive pulmonary disease (COPD).
Even saccharin, which has a bitter aftertaste, was effective at stimulating these receptors.
"Based on our research, we think that the best drugs would be chemical modifications of bitter compounds, which would be aerosolized and then inhaled into the lungs with an inhaler," Liggett said.
Another paradoxical aspect of their discovery is the unexpected role that the mineral calcium plays when the lung's taste receptors are activated.
"We always assumed that increased calcium in the smooth muscle cell caused it to contract, but we found that bitter compounds increase calcium and cause relaxation of airway muscle in a unique way," said Dr. Deepak A. Deshpande.
"New drugs to treat asthma, emphysema or chronic bronchitis are needed. This could replace or enhance what is now in use, and represents a completely new approach," Liggett said.
The findings are published online in Nature Medicine.