Researchers at the University of the Maryland School of Medicine were surprised to find bitter taste receptors like those found on the tongue in the lungs. Unlike those on the tongue, the taste receptors in the lungs aren't clustered in "buds", and don't send signals to the brain. "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," said Dr. Stephen Liggett, director of the university's cardiopulmonary genomics program and a professor of medicine and physiology.
The researchers were surprised again when the receptors responded to bitter tastes in an unexpected way. They had anticipated they would prompt airways to constrict when exposed to a bitter substance in an attempt to protect the body from potentially toxins, but instead the airways dramatically relaxed and expanded. In fact, aerosolized bitter substances such as quinine administered to mice engineered to have a human form of asthma opened up their airways more than the asthma medication albuterol.
The research tem theorize that this response evolved from the body's attempt to fight upper respiratory conditions like pneumonia and bronchitis, which secrete bitter compounds. They believe that the body responds to these bitter compounds by relaxing lung muscles and opening airways, making it easier to cough up and expel mucus and bacteria.
Unfortunately, just eating bitter tasting foods doesn't have the same medicinal effect as using asthma inhalers, but the hope is that the discovery could lead to new and improved treatments for asthma and other obstructive lung diseases. "New drugs to treat asthma, emphysema or chronic bronchitis are needed. This could replace or enhance what is now in use, and represents an entirely new approach," explains Liggett, "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."
Asthma is a common chronic respiratory disease that causes inflammation and constriction of the airways. Asthma symptoms include coughing, wheezing, shortness of breath and a feeling of tightness in the chest. It is estimated that 10 percent of the general population has asthma, including 7 million children, and those numbers are growing. Prescription asthma inhalers are among the top-selling drugs in the world.
Asthma treatment usually involves two classes of asthma medication, quick-relief or "rescue" asthma inhalers used to treat asthma attacks, and long-term control asthma medications used to manage chronic symptoms and limit or prevent attacks. Asthma medications are typically provided in metered-dose asthma inhalers or as dry powder asthma inhalers.