title: Thermosensitive transient receptor potential channels in human corneal epithelial cells.
abstract: Thermosensitive 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 µM 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 µM), a non-selective TRPV channel blocker. These changes were also elicited by rises in ambient temperature from 25 to over 40 °C. RuR (5 µM) and a selective TRPV1 channel blocker capsazepine CPZ (10 µM) or another related blocker, lanthanum chloride (La(3+)) (100 µM) 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 °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.
authors.affiliation: Department of Ophthalmology, Campus Virchow-Clinic, Charité - Universitätsmedizin Berlin, Berlin, Germany. stefan.mergler@charite.de
authors.forename: Stefan
authors.initials: S
authors.lastname: Mergler
authors.forename: Fabian
authors.initials: F
authors.lastname: Garreis
authors.forename: Monika
authors.initials: M
authors.lastname: Sahlmüller
authors.forename: Peter S
authors.initials: PS
authors.lastname: Reinach
authors.forename: Friedrich
authors.initials: F
authors.lastname: Paulsen
authors.forename: Uwe
authors.initials: U
authors.lastname: Pleyer
mesh_terms: D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D002461:Cell Line, Transformed; D048430:Cell Shape; D048429:Cell Size; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism*; D019573:Epithelium, Corneal / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D007038:Hypotonic Solutions; D015640:Ion Channel Gating / Q000187:drug effects; D008564:Membrane Potentials; D049990:Membrane Transport Modulators / Q000494:pharmacology; D008856:Microscopy, Fluorescence; D009997:Osmotic Pressure; D018408:Patch-Clamp Techniques; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050916:TRPV Cation Channels / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D013697:Thermosensing; D013997:Time Factors
chemical_list: D007038:Hypotonic Solutions; D049990:Membrane Transport Modulators; D012333:RNA, Messenger; D050916:TRPV Cation Channels; C494482:TRPV1 protein, human; C400769:TRPV2 protein, human; C416986:TRPV4 protein, human; D002118:Calcium