Abstract
Purpose: :
The cold receptor TRPM8 is a member of the melastatin-type transient receptor potential ion channel family. Activation by cold or by cooling agents (menthol, icilin) induces a transient rise in intracellular free calcium concentration ([Ca2+]i). Our previous studies demonstrated that Ca2+-permeable heat-sensitive TRP vanilloid channels (TRPV1-4) play a role in temperature-sensing in human corneal endothelial cells (HCEC) (Exp Eye Res 2010, 90, 758-770; 2011, 93, 710-719). Here, we extend our earlier study by probing for functional TRPM8 expression in HCEC.
Methods: :
Intracellular free Ca2+ ([Ca2+]i) was measured in fura2-loaded human corneal endothelial cells (HCEC-12 cell line). TRP channel currents were measured by the planar patch-clamp technique. Nonselective cation currents were analyzed by a color-coded plot method.
Conclusions: :
This study demonstrates for the first time functional expression of TRPM8 in HCEC cells and its complex role in regulating [Ca2+]i as well as cold-sensing. In addition to thermosensitive TRPV1-4, TRPM8 reveals functional activity in Ca2+ regulation and contributes to HCEC homeostasis. Its potential role in the pathophysiology of HCEC such as apoptosis and cell loss has still to be determined.
Keywords: cornea: endothelium • ion channels • calcium