Taste receptors in our lungs sense bitterness and respond with opened airways

A paper in this week's Nature reports on the discovery of taste receptors inside the lungs, on the airway smooth muscles. These are "the same as those on the tongue" and respond to bitter flavors -- not by transmitting the taste of bitterness to the brain, but by opening the airway "more extensively than any known drug that we have for treatment of asthma or chronic obstructive pulmonary disease."

There are thousands of compounds that activate the body's bitter taste receptors but are not toxic in appropriate doses. Many are synthetic agents, developed for different purposes, and others come from natural origins, such as certain vegetables, flowers, berries and trees.

The researchers tested a few standard bitter substances known to activate these receptors. "It turns out that the bitter compounds worked the opposite way from what we thought," says Dr. Liggett. "They all opened the airway more extensively than any known drug that we have for treatment of asthma or chronic obstructive pulmonary disease (COPD)." Dr. Liggett says this observation could have implications for new therapies. "New drugs to treat asthma, emphysema or chronic bronchitis are needed," he says. "This could replace or enhance what is now in use, and represents a completely new approach."

Quinine and chloroquine have been used to treat completely different diseases (such as malaria), but are also very bitter. Both of these compounds opened contracted airways profoundly in laboratory models. Even saccharin, which has a bitter aftertaste, was effective at stimulating these receptors. The researchers also found that administration of an aerosolized form of bitter substances relaxed the airways in a mouse model of asthma, showing that they could potentially be an effective treatment for this disease.

Bitter taste receptors on airway smooth muscle bronchodilate by localized calcium signaling and reverse obstruction (Nature)

WHEN BAD TASTES GOOD: DISCOVERY OF TASTE RECEPTORS IN THE LUNGS COULD HELP PEOPLE WITH ASTHMA BREATHE EASIER (Press release)

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