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S. Mergler, M. Valtink, D. Lindemann, K. Engelmann, U. Pleyer; Temperature-sensing by the Human Corneal Endothelium Through Activation of TRPV1-3 channels. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1802.
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© ARVO (1962-2015); The Authors (2016-present)
The human corneal endothelium is essential for the physiology and transparency of the cornea. This is sustained by a number of different regulatory mechanisms and response to various stimuli. Temperature changes may have major impact. This study was undertaken to identify such possible stimuli pathways in human corneal endothelial cells (HCEC).
The expression patterns of putative temperature-sensing ion channels were investigated by RT-PCR. Responses of HCEC parental population (HCEC-12) and two subcloned cell lines (HCEC-H9C1, HCEC-B4G12) to drug treatment and heat-stimuli were investigated by measurements of intracellular free Ca2+ ([Ca2+]i) with fura-2 and a novel high throughput patch-clamp system.
RT-PCR analysis of cDNA revealed the expression of TRPV1-3 in all investigated HCEC. Capsaicin (CAP) (10-20 µM) increased non-selective cation channel whole-cell currents, resulting in calcium increases that were fully blocked by the TRPV1 antagonists capsazepine (CPZ) or removal of extracellular calcium. In particular, non-selective cation channel outward currents significantly increased from 50 ± 11 pA/pF to 111.77 ± 2 pA/pF (at 100 mV) (p < 1 %; n = 3-4). Recovery occurred to 83.33 ± 4 pA/pF (n = 3). Similarly, heating from room temperature to > 40 °C increased the same currents, resulting in calcium increases that were significantly reduced by the TRP channel blockers lanthanum chloride (La3+) (100 µM) and ruthenium-red (RuR) (10 µM). Correspondingly, application of the TRPV channel opener 2-ABP led to a reversible increase in [Ca2+]i. The fura-2 fluorescence ratio (f340/f380) was 1,197 ± 0,001 in the resting state (base line) (n = 6). After application of 400 µM 2-APB it increased to 1.364 ± 0.03 (n = 4; p < 0.01) (H9C1). Recovery occurred to 1.249 ± 0.05 (n = 4).
There is functional TRPV1-3 expression in HCEC. These findings may have direct clinical implication (eye banking procedures, keratoplasty).
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