The tongue in your lung that fights asthma

1. Taste receptors for bitter flavours have been discovered in lung tissue. What's more, they respond to bitter substances by dilating the airways of asthmatic mice, paving the way for


2. different approach to asthma treatment.
   "They opened up the bronchi much better than beta-agonists, the standard therapies for asthma," says Stephen Liggett at the University of Maryland School of Medicine in Baltimore, head of the group who made the discovery.
   Liggett's team identified the taste receptors after screening for active genes in the smooth muscle cells that constrict or dilate the airways. They had assumed the receptors would be restricted to the tongue, soft palate, upper oesophagus and epiglottis.
   At first he and his colleagues thought the receptors were there to detect bitter plant toxins and protect the lungs by constricting the airways. But after testing standard bitter compounds on mouse and human smooth muscle tissue, they found the opposite was true. The bitter antimalarial drugs quinine and chloroquine, for example, relaxed the muscle cells. Liggett suggests this reaction might enable bitter toxins to be coughed out easily.
   Tests on dissected mouse airways showed that the bitter compounds were three times as effective at relaxing the tissue as anti-asthma drugs. This was also true when the researchers gave bitter substances and standard asthma drugs to mice with asthma-like symptoms and measured the amount of air able to pass through their airways (Nature Medicine, DOI: 10.1038/nm.2237).
   Liggett has begun screening for bitter substances that could be added to inhalers to improve asthma treatments. But he doubts whether consuming bitter foods or drinks would help people with asthma. "It would need to be taken in an inhaled form," he says.
   "Bronchodilation is consistent with wanting to get rid of toxins from the lungs," says Paul Breslin of the Monell Chemical Senses Center in Philadelphia. "We need to open passageways to cough easily and to allow contaminated mucus being pushed out to flow well," he says.