When you think about the sense of taste, you probably think about your mouth and the taste buds on your tongue. These taste buds gather flavors and send signals to the brain to help you tell the difference between foods that are sweet, sour, salty, savory, and bitter. Now researchers at the University of Maryland School of Medicine in Baltimore have discovered a surprising collection of taste receptors inside human lungs that could open up new avenues of research to help prevent or reduce the symptoms of asthma attacks.
Air moves in and out of the lungs through tubes that are known as airways. These airways are made up of smooth muscle tissue that can contract and expand like other muscles in the body. For people with asthma, these smooth muscles in the airway sometimes suddenly contract or tighten which makes the opening in the airway smaller so it is harder for air to move in and out of the lungs. An asthma attack can cause wheezing and shortness of breath, while a severe attack can completely close the airway and prevent breathing.
Medications are available to help relieve the symptoms of an asthma attack by reopening the airways, but researchers are constantly looking for better ways to control asthma symptoms. This was the case with the researchers in Maryland who were conducting an unrelated study of the muscle receptors in the lungs that regulate when the airways constrict and relax. Stephen B. Liggett, M.D., professor of physiology at the University of Maryland School of Medicine and senior author of the study said the team discovered the taste receptors in the lungs by accident. "The detection of functioning taste receptors on smooth muscle of the bronchus in the lungs was so unexpected that we were at first quite skeptical ourselves," Liggett said.
The taste receptors found in the lungs are the same as those found on the tongue that detect bitterness. In the lungs, the taste receptors are not clustered together into taste buds and do not send taste sensations to the brain like their counterparts on the tongue. But they do respond to things that have a bitter taste. Liggett’s team initially believed the bitter receptors in the lungs would act like a warning system against bitter poisons that could be inhaled. When they began testing, they expected the airways to the lungs to close down when they sensed something bitter. The opposite proved to be true.
"It turns out that the bitter compounds worked the opposite way from what we thought," Liggett said. "They all opened the airway more profoundly than any known drug that we have for treatment of asthma or chronic obstructive pulmonary disease (COPD)." The team of researchers tested a variety of known bitter compounds by using them as inhalers for mice with asthma. Liggett anticipates that this discovery will lead to new research into ways to treat asthma using known bitter compounds such as quinine, which is currently used to treat malaria. Even the artificial sweetener saccharin, which has a bitter aftertaste, had the effect of opening airways in the lungs.
Liggett warned that eating bitter foods will not affect an asthma attack. In order to be effective, Liggett’s team believes bitter compounds will need to be turned into a gas or aerosol that can be inhaled into the lungs through an inhaler similar to current asthma treatments. "New drugs to treat asthma, emphysema or chronic bronchitis are needed," he said. "This could replace or enhance what is now in use, and represents a completely new approach."
Source:
Science Daily