Ca2+ channels in retinal pigment epithelial cells regulate vascular endothelial growth factor secretion rates in health and disease.
OBJECTIVE
Choroidal neovascularization (CNV) is the most severe complication in age-related macular degeneration. The major angiogenic factor involved is vascular endothelial growth factor (VEGF) secreted by the retinal pigment epithelium (RPE). Since RPE cells express neuroendocrine L-type Ca2+ channels we investigated their involvement in VEGF secretion in normal RPE cells and RPE cells from patients with CNV.


METHODS
Freshly isolated and cultured RPE cells were studied using the patch-clamp technique and ELISA-based secretion assays.


RESULTS
Both freshly isolated and cultured cells showed whole-cell Ba2+ currents with properties of L-type Ca2+ currents: high activation threshold, sensitivity to dihydropyridines (10 muM nifedipine) and slow inactivation. VEGF-A secretion was elevated by BayK8644 (10 microM) or basic fibroblast growth factor (bFGF, 10 ng/ml), both of which are able to activate L-type channels. Cells from CNV tissue also showed nifedipine-sensitive Ba2+ currents, which displayed a voltage-dependent activation at more negative potentials, faster inactivation and changed regulation by tyrosine kinase pp60(c-src). The CNV RPE cells showed higher VEGF secretion rates which were reduced by nifedipine.


CONCLUSIONS
Thus, L-type Ca2+ channels in normal RPE cells regulate the secretion of VEGF. RPE cells from eyes with CNV maintain a VEGF secretion regulated by nifedipine-sensitve Ca2+ channels which might be of importance for the development of CNV.
Rosenthal
Rita
R
Institut für Klinische Physiologie, Charité-Universitatsmedizin Berlin, Campus Benjamin Franklin, Berlin, Germany.
Heimann
Heinrich
H
Agostini
Hansjürgen
H
Martin
Gottfried
G
Hansen
Lutz Lothar
LL
Strauss
Olaf
O
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000368:Aged; D001464:Barium / Q000378:metabolism; D002120:Calcium Channel Agonists / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism*; D020746:Calcium Channels, L-Type / Q000378:metabolism; D002478:Cells, Cultured; D020256:Choroidal Neovascularization / Q000378:metabolism*; D004553:Electric Conductivity; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology; D006262:Health; D006801:Humans; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology; D008297:Male; D009543:Nifedipine / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D010857:Pigment Epithelium of Eye / Q000378:metabolism*; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000494:pharmacology; D042461:Vascular Endothelial Growth Factor A / Q000037:antagonists & inhibitors / Q000378:metabolism*
D002120:Calcium Channel Agonists; D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D007473:Ion Channels; D042461:Vascular Endothelial Growth Factor A; D016222:Fibroblast Growth Factor 2; D001464:Barium; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D016392:Proto-Oncogene Proteins pp60(c-src); D009543:Nifedipine