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Invest Ophthalmol Vis Sci. 2010 Nov;51(11):6001-8. doi: 10.1167/iovs.09-4720. Epub 2010 Jun 10.

Heat-sensitive TRPV channels in retinal pigment epithelial cells: regulation of VEGF-A secretion.

Author information

1
Experimentelle Ophthalmologie, Klinik und Poliklinik für Augenheilkunde, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany.

Abstract

PURPOSE:

Choroidal neovascularization in age-related macular degeneration is caused, to a large extent, by increased secretion of vascular endothelial growth factor (VEGF)-A by the retinal pigment epithelium (RPE). The purpose of the study was to identify pathways that lead to increased VEGF secretion by the RPE.

METHODS:

Ca(2+) signaling was studied in ARPE-19 and human RPE cells in primary culture by means of Ca(2+) imaging. Membrane conductance was measured in the whole-cell configuration of the patch-clamp technique. VEGF-A secretion was measured by using ELISA.

RESULTS:

Freshly isolated RPE cells or ARPE-19 cells were shown to express TRPV1, -2, -3, and -4 channels. Increasing the temperature or stimulation by IGF-1 increased the VEGF-A secretion rate in both cell types. These effects were both sensitive to the TRPV channel blocker ruthenium red (20 μM). The heat-inducible Ca(2+) signals were blocked by the TRPV channel blockers La(3+) and ruthenium red by 68% and 52%, respectively. In contrast, high concentrations of 2-APB (3 mM) increased [Ca(2+)](i), whereas the TRPV1 channel opener capsaicin and the TRPV3 channel opener camphor had no effect. Reduction of TRPV2 expression by siRNA attenuated the heat-evoked Ca(2+) response. In addition, a heat-activated inwardly rectifying current was measured that was completely blocked by ruthenium red. IGF-1 also increased whole-cell current with a corresponding increase in [Ca(2+)](i), which was blocked by the PI3-kinase blocker LY294002.

CONCLUSIONS:

The data strongly suggest that TRPV2 channels expressed by the RPE are involved in the Ca(2+) signaling that mediates both heat-dependent and IGF-1 (via PI3-kinase activation)-induced VEGF secretion.

PMID:
20539001
DOI:
10.1167/iovs.09-4720
[Indexed for MEDLINE]

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