Dependence of regulatory volume decrease on transient receptor potential vanilloid 4 (TRPV4) expression in human corneal epithelial cells

Zan Pan, Hua Yang, Stefan Mergler, Hongshan Liu, Souvenir D. Tachado, Fan Zhang, Winston W.Y. Kao, Henry Koziel, Uwe Pleyer, Peter S. Reinach

Research output: Contribution to journalArticlepeer-review

78 Scopus citations

Abstract

TRPV4 is a non-selective cation channel with moderate calcium permeability, which is activated by exposure to hypotonicity. Such a stress induces regulatory volume decrease (RVD) behavior in human corneal epithelial cells (HCEC). We hypothesize that TRPV4 channel mediates RVD in HCEC. Immunohistochemistry revealed centrally and superficially concentrated TRPV4 localization in the corneal tissue. Immunocytochemical and fluorescence activated cell sorter (FACS) analyses identified TRPV4 membrane surface and cytosolic expression. RT-PCR and Western blot analyses identified TRPV4 gene and protein expression in HCEC, respectively. In addition, 4α-PDD or a 50% hypotonic medium induced up to threefold transient intracellular Ca2+ ([Ca2+]i) increases. Following TRPV4 siRNA HCEC transfection, its protein expression level declined by 64%, which abrogated these [Ca2+]i transients. Similarly, exposure to either ruthenium red or Ca2+-free Ringer's solution also eliminated this response. In these transfected cells, RVD declined by 51% whereas in the non-transfected counterpart, ruthenium red and Ca2+-free solution inhibited RVD by 54 and 64%, respectively. In contrast, capsazepine, a TRPV1 antagonist, failed to suppress [Ca2+]i transients and RVD. TRPV4 activation contributes to RVD since declines in TRPV4 expression and activity are associated with suppression of this response. In conclusion, there is TRPV4 functional expression in HCEC.

Original languageEnglish (US)
Pages (from-to)374-385
Number of pages12
JournalCell Calcium
Volume44
Issue number4
DOIs
StatePublished - Oct 2008

Keywords

  • Calcium transients
  • Corneal epithelium
  • Regulatory volume decrease
  • Small interfering RNA
  • Transient receptor potential vanilloid 4

ASJC Scopus subject areas

  • Physiology
  • Molecular Biology
  • Cell Biology

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