Polymodal Sensory Transduction in Mouse Corneal Epithelial Cells

Area of Science:

• Ophthalmology
• Cell Biology
• Sensory Neuroscience

Background:

• Corneal epithelial cells (CECs) are crucial for maintaining eye health and sensing environmental stressors.
• The precise mechanisms by which CECs detect stimuli like osmotic changes, temperature, and mechanical strain are not fully understood.
• Understanding these sensory pathways is vital for addressing conditions causing discomfort and vision loss.

Purpose of the Study:

• To investigate the signaling mechanisms involved in the transduction of swelling, temperature, strain, and chemical stimuli in mouse CECs.
• To identify the specific ion channels and molecular players responsible for sensory input in the corneal epithelium.
• To elucidate the role of these pathways in potential pain signaling.

Main Methods:

• Utilized intracellular calcium imaging and electrophysiology to monitor cellular responses.
• Employed pharmacology, transcript analysis, and immunohistochemistry to identify key proteins and pathways.
• Assessed adenosine triphosphate (ATP) release using bioluminescence assays.

Main Results:

• TRPV4 was identified as the dominant transient receptor potential vanilloid (TRPV) channel in mouse corneal epithelium.
• TRPV4 activation by specific agonists or stimuli (hypotonic solutions, moderate heat) led to cation influx and elevated intracellular calcium.
• Swelling and heat-evoked signals, but not strain-evoked signals, were sensitive to TRPV4 blockers, indicating TRPV4's role in osmotic and thermal sensing.
• TRPV4 activation and swelling promoted calcium-dependent ATP release, which was inhibited by TRPV4 and hemichannel blockers.

Conclusions:

• Cation influx through TRPV4 channels mediates the transduction of osmotic and thermal stimuli in CECs, but not strain.
• TRPV4 activation facilitates hemichannel-dependent ATP release, suggesting a novel signaling pathway.
• The identified TRPV4-hemichannel-ATP signaling axis may play a significant role in modulating corneal pain responses to various stressors.