"Tasting" the airway lining fluid.

Area of Science:

• Respiratory system biology
• Cellular biology
• Sensory neuroscience

Background:

• The respiratory tract contains specialized epithelial cells, termed solitary chemosensory cells or brush cells.
• These cells express taste transduction pathway components and possess a distinct apical brush-like tuft.
• A unified terminology and clear classification for these cells are currently lacking.

Purpose of the Study:

• To investigate the distinct characteristics and functions of chemosensory/brush cells across different regions of the respiratory tract.
• To understand the role of these cells in monitoring the chemical environment and initiating defense mechanisms.
• To explore the potential for polymodal chemosensing in respiratory chemosensory cells.

Main Methods:

• Comparative analysis of cellular shape, ultrastructure, and gene expression (taste transduction elements).
• Investigation of innervation and synapse formation.
• Assessment of cellular responses to stimulation and their effects.

Main Results:

• Chemosensory/brush cells in various respiratory locations (nasal mucosa, larynx, airways, alveolar region) represent distinct functional groups.
• These cells collectively monitor mucosal lining fluid, detecting harmful substances like bacteria.
• Evidence suggests respiratory chemosensory cells may act as polymodal chemosensors, responding to multiple stimuli.

Conclusions:

• Respiratory chemosensory/brush cells function as sentinels, initiating defense reflexes and avoidance behaviors.
• These cells play a crucial role in maintaining airway homeostasis and protecting against inhaled threats.
• Further research is needed to differentiate the roles of chemosensory cells and free nerve endings in respiratory chemical sensing.