Writing about their study in the journal Science Express, the researchers at the University of Iowa Roy J. and Lucille A. Carver College of Medicine said that their findings may help explain why injured lungs are susceptible to further damage.
They add that their study shows that receptors for bitter compounds, which are found in taste buds on the tongue, are also found in hair-like protrusions on airway cells.
They further state that, unlike taste cells on the tongue, these airway cells do not need help from the nervous system to translate detection of bitter taste into an action that expels the harmful substance.
The hair-like protrusions, called motile cilia, were already known to beat in a wave-like motion to sweep away mucus, bacteria and other foreign particles from the lungs.
This is the first time that any study has shown that motile cilia on airway cells not only have this "clearing" function, but also use the receptors to play a sensory role.
The study has shown that when the receptors detect bitter compounds, the cilia beat faster, suggesting that the sensing and the motion capabilities of these cellular structures are linked.
"On the tongue, bitter substances trigger taste cells to stimulate neurons, which then evoke a response, the perception of a bitter taste.
In contrast, the airway cells appear to use a different mechanism that does not require nerves. In the airways, bitter substances both activate the receptors and elicit a response, the increased beating of the cilia-designed to eliminate the offending material," said Alok Shah, a UI graduate student and co-first author of the study.
Dr. Yehuda Ben-Shahar, an assistant professor of biology at Washington University who was a postdoctoral fellow at the UI when the study was conducted, said: "These findings suggest that we have evolved sophisticated mechanisms to guard ourselves from harmful environmental stimuli.
Our work also suggests that losing cilia in the lungs, due to smoking or disease, would result in a reduced general ability to detect harmful inhaled chemicals, increasing the likelihood of further damaging an injured lung."
The study was funded by grants from the National Institutes of Health.