Taste receptors in the lungs: Interesting or anecdotal?

The receptors responsible for taste perception distinguish the four basic tastes : salty, sweet, bitter and umami. Among them, the bitter taste receptors (TAS2R) are G protein coupled receptors, including 25 subtypes identified in humans to date. Although the existence of endogenous agonists remains uncertain, the TAS2R receptors have the ability to recognize natural or synthetic molecules, as various molecules produced by bacteria, or caffeine, chloroquine, or erythromycin. The expression of these receptors, initially thought to be confined to the oral cavity, has recently been described in extra-oral tissues such as the gastrointestinal tract and the lungs. The effects in the lung tissue are essentially at three levels : TAS2R receptors expressed on the cilia of epithelial cells increase the cilia vibration frequency; the stimulation of TAS2R receptors expressed in bronchial smooth muscle cells leads to bronchial relaxation; while TAS2R receptors expressed on immune cells in the lung tissue, including macrophages, are involved in the modulation of the production of pro-inflammatory cytokines. In conclusion, in view of these complementary mechanisms, TAS2R receptors may become a pharmacological target of interest for the treatment of obstructive lung diseases. (C) 2014 Elsevier Masson SAS. All rights reserved.