Borneol Is a TRPM8 Agonist that Increases Ocular Surface Wetness

Area of Science:

• Pharmacology
• Ophthalmology
• Neuroscience

Background:

• Borneol is a traditional Chinese medicine ingredient used in eye preparations.
• Its precise therapeutic mechanism in ocular treatments remains largely uncharacterized.

Purpose of the Study:

• To identify the pharmacological target of borneol in ophthalmic applications.
• To elucidate the role of borneol in treating eye conditions, particularly dry eye syndrome.

Main Methods:

• Calcium imaging and electrophysiological recordings to assess TRPM8 channel activity.
• In vivo studies in guinea pigs to measure tear production.
• Cell viability assays on human corneal epithelial cells.

Main Results:

• Borneol activated the TRPM8 channel in a temperature- and dose-dependent manner.
• Borneol increased tear production at 25°C but not 35°C, unlike menthol.
• TRPM8 blockers (AMTB, BCTC) inhibited borneol-induced tearing.
• Borneol showed no cytotoxicity to corneal cells.

Conclusions:

• The transient receptor potential melastatin 8 (TRPM8) channel is a pharmacological target of borneol.
• Borneol enhances ocular surface wetness by activating TRPM8, supporting its use in dry eye treatments.