Odor Receptors Discovered in Lungs: Nose Isn't the Only Organ That Smells

It turns out that the nose isn't the only thing that can smell. Scientists have discovered that lungs also have odor receptors. The findings could have implications for smokers and reveal a bit more about how the human body senses smell.

The newly discovered cells in the lungs are called pulmonary neuroendocrine cells (PNECs). Unlike the receptors in the nose, which are located in the membranes of nerve cells, these cells are in the membranes of neuroendocrine cells. Instead of sending nerve impulses to the brain that allow it to "perceive" smell, the cells trigger the flask-shaped neuroendocrine cells to dump hormones that make airways constrict.

When someone inhales, volatile chemicals flow over two patches of specialized epithelial tissue high up in the nasal passages. These patches are rich in nerve cells with specialized odorant-binding molecules embedded in their membranes. A similar thing happens within the lungs. Tissues express odor receptors on neuroendocrine cells, flask-shaped cells that dump serotonin and various neuropeptides when they are stimulated. The findings could explain how people with airway disease respond.

"When people with airway disease have pathological responses to odors, they're usually pretty fast and violent," said Yehuda Ben-Shahar, one of the researchers, in a news release. "Patients suddenly shut down and can't breathe, and these cells may explain why."

Because the cells in the airways are secretory, not neuronal, they are broadly tuned. Instead of sending nerve impulses to the brain, they flood local nerves with hormones. Most likely, they're designed to elicit a rapid, physiological response if someone inhales something that is bad for them.

The findings could be important for better understanding the chemical hypersensitivity that characterizes respiratory diseases, such as chronic obstructive pulmonary disease (COPD) and asthma. This could help scientists develop better treatments for these diseases. In fact, the odor receptors on the cells might be a therapeutic target. By blocking them, it might be possible to prevent some attacks, allowing people to cut down on the use of steroids or bronchodilators.

The findings are published in the American Journal of Respiratory Cell and Molecular Biology.