The fibroblast growth factor receptors, FGFR-1 and FGFR-2, mediate two independent signalling pathways in human retinal pigment epithelial cells

To examine the effects and potential implications for the expression of the two basic fibroblast growth factor (bFGF) receptors, FGFR-1 and FGFR-2, in retinal pigment epithelial (RPE) cells, bFGF-dependent changes in gene expression and RPE cell function were studied. bFGF increased L-type Ca2+ channel activity of RPE cells, which in turn resulted in an increase of vascular endothelial growth factor A (VEGF-A) secretion from RPE cells. Also, both bFGF and direct stimulation of L-type Ca2+ channels by BayK8644 increased the expression of c-fos in RPE cells, to the same extent. bFGF-induced-c-fos expression was reduced by inhibition of FGFR-1, but not by L-type Ca2+ channel inhibition, demonstrating that stimulation of FGFR-1 results in a Ca2+ channel-independent change of gene expression. In contrast, stimulation of FGFR-2 results in a Ca2+ channel-dependent stimulation of VEGF secretion. Furthermore, immunohistological investigation of neovascular tissues obtained from patients with age-related macular degeneration (AMD) revealed FGFR-1 and FGFR-2 expression in the RPE of the diseased tissue. Our findings support the hypothesis that there are two different FGFR-1- and FGFR-2-dependent pathways that modulate the role of bFGF in induction of neovascularisation in AMD.