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S. Mergler, F. Garreis, M. Valtink, M. Sahlmüller, F. P. Paulsen, U. Pleyer; Transient Receptor Potential Vanilloid Channels (TRPVs) in Human Conjunctival Epithelial Cells (HCjE). Invest. Ophthalmol. Vis. Sci. 2010;51(13):1903.
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The conjunctiva secretes lipids and mucous that lubricates the eye. It also contributes to immune surveillance and helps to prevent the entrance of microbes. This is sustained by a number of different regulatory mechanisms and responses to various stimuli such as temperature changes. Temperature-sensitive TRP channels like TRPVs may contribute. There are no reports about a possible TRPV channel activity in HCjE cells. This study was undertaken to examine HCjE cells for TRPV channel activity.
Normal human conjunctiva and permanent HCjE cells (IOBA-NHC) were used. Gene expression of putative TRPVs was investigated by RT-PCR. Responses from IOBA-NHC by drugs and heat-stimuli were investigated by measuring intracellular free Ca2+ ([Ca2+]i) with fura-2. TRP channel currents were detected with a novel high throughput patch-clamp system. Human corneal epithelial cells were used as positive controls.
RT-PCR analysis of cDNA from cultivated HCjE cells revealed expression of the capsaicin receptor TRPV1 and the heat receptor TRPV2 as well as the osmosensor TRPV4. In addition, TRPV1, -2 and -4 could also be detected in human conjunctiva from body donors. Notably, Ca2+ transients in HCjE cells were elicited by rises in ambient temperature from 25 ºC to over 45 ºC. The TRPV channel blocker ruthenium-red (RuR; 10 µM) and another blocker, lanthanum chloride (La3+; 100 µM) suppressed these temperature-induced Ca2+ increases. Moreover, increasing the temperature over 45 ºC induced reversible rises in non-selective cation currents.
Functional expression of TRPV1, -2 and -4 could be registered in cultivated HCjE cells and conjunctiva as a novel finding. These findings may have direct physiological (heat, biomechanics, osmolarity) and clinical implication, e.g. infection, dry eye syndrome, pterygium, and others.
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