Abstract
P 063
Temperature sensing by the human corneal and conjunctival epithelium through activation of transient receptor potential (TRP) channels
Fabian Garreis1, Monika Valtink2, Friedrich Paulsen1, Uwe Pleyer3, Stefan Mergler3
1Institut für Anatomie&Zellbiologie, Martin Luther-Universität, Halle/Saale, 2Institut für Anatomie, Medizinische Fakultät TU Dresden, Dresden, 3Institut für Ophthalomologie, Campus Virchow-Klinikum, Charité - Universitätsmedizin Berlin, Berlin
Objective
The members of transient receptor potential vanilloid (TRPV) subfamily are non-selective cation ion channels and are important membrane sensors, responding to thermal, chemical, osmotic or mechanical stress. The corneal and conjunctival epithelium contributes to immune surveillance and help to prevent the entrance of microbes into the eye. This is sustained by a number of different regulatory mechanisms and responses to various stimuli. Temperature changes may have a major impact on the physiology of the ocular surface epithelium.This study was undertaken to identify such possible stimuli pathways in corneal (HCE) and conjunctival epithelial (HCjE) cells as well as human conjunctival tissue.
Methods
Gene expression of putative temperature-sensing ion channels (TRPVs) in these cells was investigated by RT-PCR. Responses from these cells to drugs and heat-stimuli were investigated by measurements of intracellular free Ca2+ ([Ca2+]i) with fura-2 and a novel high throughput patch-clamp system.
Results
RT-PCR analysis of RNA isolates from HCjE cells revealed the expression of TRPV-1 and -2. In addition, TRPV-2 transcript could also be detected in human conjunctiva. Furthermore, temperature rises from room temperature to >45 °C clearly induced an increase in fluorescence ratio (f340/f380) corresponding to a transient increase of [Ca2+]i in HCjE cells. This Ca2+ transient was significantly reduced in the presence of the TRP channel blocker lanthanum chloride (La3+) (100 µM). Moreover, similar results were obtained with the TRPV channel blocker ruthenium-red (RuR) (10 µM). Finally, TRP-like non-selective cation channel outward currents could be detected in HCjE.
Conclusions
In conclusion, TRPV channels are functionally expressed in HCjE cells and also in human conjunctiva. These findings may have direct clinical implication, i.e. in multifactorial dry eye disease.
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