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lüll Thermosensitive transient receptor potential channels in human corneal epithelial cells Mergler S; Garreis F; Sahlmuller M; Reinach PS; Paulsen F; Pleyer UJ Cell Physiol 2011[Jul]; 226 (7): 1828-42Thermosensitive transient receptor potential (TRP) proteins such as TRPV1-TRPV4 are all heat-activated non-selective cation channels that are modestly permeable to Ca(2+). TRPV1, TRPV3, and TRPV4 functional expression were previously identified in human corneal epithelial cells (HCEC). However, the membrane currents were not described underlying their activation by either selective agonists or thermal variation. This study characterized the membrane currents and [Ca(2+)](i) transients induced by thermal and agonist TRPV1 and 4 stimulation. TRPV1 and 4 expressions were confirmed by RT-PCR and TRPV2 transcripts were also detected. In fura2-loaded HCEC, a TRPV1-3 selective agonist, 100 microM 2-aminoethoxydiphenyl borate (2-APB), induced intracellular Ca(2+) transients and an increase in non-selective cation outward currents that were suppressed by ruthenium-red (RuR) (10-20 microM), a non-selective TRPV channel blocker. These changes were also elicited by rises in ambient temperature from 25 to over 40 degrees C. RuR (5 microM) and a selective TRPV1 channel blocker capsazepine CPZ (10 microM) or another related blocker, lanthanum chloride (La(3+)) (100 microM) suppressed these temperature-induced Ca(2+) increases. Planar patch-clamp technique was used to characterize the currents underlying Ca(2+) transients. Increasing the temperature to over 40 degrees C induced reversible rises in non-selective cation currents. Moreover, a hypotonic challenge (25%) increased non-selective cation currents confirming TRPV4 activity. We conclude that HCEC possess in addition to thermosensitive TRPV3 activity TRPV1, TRPV2, and TRPV4 activity. Their activation confers temperature sensitivity at the ocular surface, which may protect the cornea against such stress.|*Calcium Signaling/drug effects[MESH]|*Ion Channel Gating/drug effects[MESH]|*Thermosensing[MESH]|Calcium/*metabolism[MESH]|Cell Line, Transformed[MESH]|Cell Shape[MESH]|Cell Size[MESH]|Epithelial Cells/drug effects/*metabolism[MESH]|Epithelium, Corneal/drug effects/*metabolism[MESH]|Humans[MESH]|Hypotonic Solutions[MESH]|Membrane Potentials[MESH]|Membrane Transport Modulators/pharmacology[MESH]|Microscopy, Fluorescence[MESH]|Osmotic Pressure[MESH]|Patch-Clamp Techniques[MESH]|RNA, Messenger/metabolism[MESH]|Reverse Transcriptase Polymerase Chain Reaction[MESH]|TRPV Cation Channels/drug effects/genetics/*metabolism[MESH]|Time Factors[MESH] |