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F. Zhang, Z. Pan, J.E. Capo–Aponte, H. Yang, H. Liu, K. Higa, T. Kawakita, M. Srinivas, P. Reinach; Expression and Characterization of the Transient Receptor Potential Vanilloid 1 (TRPV1) in Corneal Epithelial Cells . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2905.
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© ARVO (1962-2015); The Authors (2016-present)
Functional transient receptor potential vanilloid (TRPV) subtype 1 (TRPV1) receptor expression has been recently described in some epithelial tissues. This receptor subtype has been shown to be involved in mediating responses to heat, low pH, or noxious stimuli that include pro–inflammatory substances. The purpose of the present study was to determine if cultured corneal epithelial cells and the intact mouse corneal epithelium express functional TRPV1 receptors.
Western Blot analysis and immunocytochemistry were used to identify the presence of TRPV1 in both SV40 immortalized human (HCEC), rabbit corneal epithelial cells (RCEC). Immunohistology was used to detect TRPV1 in the intact mouse corneal epithelium and in cultured stratified mouse corneal epithelial (MCE) grown on an amniotic membrane. The effects of the TRPV1 agonists, capsaicin (CAP) and resiniferatoxin (RTX) on [Ca2+]i were determined in fura2–AM–loaded HCEC using a single–cell fluorescence video imaging system. Western Blot probed for phosphorylation of CAP–induced p38 MAPK.
TRPV1 is expressed in SV40–immortalized HCEC, primary HCEC, RCEC, and MCE. CAP induced a dose–dependent increase in [Ca2+]i, with a maximal increase occurring at 1 µM. RTX (10 nM), a more potent TRPV1 receptor agonist, induced a [Ca2+]i transient of the same magnitude as that obtained with CAP. The competitive vanilloid receptor antagonist, capsazepine, at a concentration of 10 µM, inhibited the CAP– and RTX–induced [Ca2+]i responses in SV40–HCEC. Activation of p38 MAPK in HCEC by 1 µM CAP was observed after 5 min, persisting for up to 30 min. p38 MAPK was maximally activated by all concentrations of 0.5–100 µM CAP. Subsequently, the maximal increase in phosphorylation waned towards its baseline value after another 30 min.
TRPV1 receptor is not only expressed, but is also functionally active in corneal epithelial cells. These results suggest that TRPV1 receptors could be essential for maintaining tissue homeostasis during exposure to environmental insults.
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