The taste buds of the tongue contain bundles of specialized cells bearing sensors that detect chemical attributes of food. Known as taste receptors, these sensors were long believed to reside only on the tongue. Marco Tizzano, an associate professor in the Department of Basic & Translational Sciences at Penn Dental Medicine, was among those who discovered them in many other places in and on the body.
He has since documented taste receptors throughout the airways, especially in the nose, but also the trachea and the lungs, as well as the gums and even dental pulp. These sensors, he and others have found, detect bacterial pathogens and allergens, then alert the innate immune system.
Tizzano’s research has shown that bitter-sensing taste receptors in the nose respond to a compound bacteria use to communicate. These sensors then activate the trigeminal nerve, a cranial nerve that provides sensation to the face, leading to a significant inflammatory response.
Bitter taste receptors also show up in the gums. In experiments, Tizzano’s research team demonstrated that in gum tissue these receptors actually offer some natural protection against periodontitis, the most severe form of gum disease. After sensing pathogenic bacteria, they trigger the production of antimicrobial peptides to kill the germs. Without these receptors, mice suffered from more damaging periodontitis, the researchers found.
In another line of study, Tizzano’s lab is looking at odor-detecting receptors found on neurons in dental pulp. When these relatives of the taste sensors detect eugenol, an odor molecule from cloves, they numb the teeth.
As someone who looks for connections between disciplines, Tizzano ultimately seeks to use naturally occurring compounds, such as eugenol, to stimulate these receptors in ways that benefit health. Such applications could include a new form of pain relief for dental procedures or a therapy to stifle the microbial growth triggering the inflammation that drives periodontal disease.
“I think we are still at the tip of the iceberg,” Tizzano says. “There is so much more to discover about these receptors.”
