4α‐PDD induces Ca2+ influx in human corneal epithelial cells by activating TRPV4 channels

Abstract

Abstract Purpose: Transient receptor potential (TRP) isoform expression is evident in human corneal epithelial cells (HCEC‐SV40). However, their role in maintaining corneal epithelial homeostasis is not fully understood. We probed for gene and protein expression as well as functional activity of the vanilloid subtype, TRPV4, in immortalized HCEC‐SV40 since they elicit Ca2+ dependent regulatory volume decrease (RVD) responses during exposure to a hypotonic challenge. Methods: RT‐PCR and Western blotting analyses identified TRPV4 gene and protein expression. Functional activity was assessed based on determining whether the TRPV4 selective agonist, 4α‐PDD, induced transients increases in intracellular Ca2+ concentration. Results: Single cell fluorescence imaging results showed that 4α‐PDD (3 μM) increased intracellular Ca2+ concentration. The fura2 fluorescence ratio (f340/f380) was 0.39 ± 0.03578 in the resting state (n = 5). After application of 4α‐PDD it increased to 0.904 ± 0.14363 (n = 5; p = 5.72077×10‐5). This increase was abolished by the TRP channel blocker ruthenium red or by Ca2+‐free Ringer's medium. Conclusions: In conclusion, there is functional TRPV4 expression in HCEC‐SV40. TRPV4 expression may provide an osmosensor role to induce RVD behavior during exposure to a hypotonic challenge since this response is mediated through intracellular Ca2+ transients.Supported in part DFG Pl 150/14‐1 and NIH, EY04795. CR: none