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Researchers at the University of Maryland School of Medicine recently and quite accidentally discovered that there are taste receptors in the lungs. More impressively, the receptors unlock the door to the most potent bronchodilators ever known.

Dr. Stephen Liggett, professor of physiology at Maryland, and those working in his lab were smooth muscle cells in the lung. While they were certainly consider mechanisms of and treatments for asthma, they never intended to find taste receptors. Liggett discovered that the lungs have receptors that identify compounds that would taste bitter on the tongue. However, these taste receptors are not wired to detect taste. When the receptors are activated by a “bitter” molecule, instead of registering taste, they cause the smooth muscle in the lungs to relax. This muscle relaxation dilates the airways and makes it easier for air to move in and out of the lungs.

While discovering tastes receptors in lung tissue is interesting, showing that bitter molecules may be a treatment for asthma is truly remarkable. Currently, doctors prescribe chemicals that stimulate the Beta2 adrenergic receptors (the sympathetic nervous system) or antagonize cholinergic receptors (the parasympathetic nervous system) in order to treat asthma and COPD. Liggett and colleagues tried a few compounds that would taste bitter to the tongue and found them to be very effective in humans and mice with asthma (experimentally-induced asthma in the case of the mice). From Liggett’s work, it appears that inhaled bitter compounds may open airways to a greater degree than either of these treatments. It seems that this receptor system has an even greater effect on smooth muscle than drugs that affect the sympathetic nervous system.

Considering the wide array of known bitter compounds, this work raises the possible of very effective natural treatments for asthma and COPD. While we do not yet know which bitter molecule is most effective at stimulating the lung’s taste receptor, we do know that when they are stimulated, they have profound effects. Future work will no doubt be aimed at finding the most potent, most selective molecules (agonists) for this new receptor and develop it as a new clinical treatment.