Tranilast inhibits protein kinase C-dependent signalling pathway linked to angiogenic activities and gene expression of retinal microcapillary endothelial cells
Abstract
Tranilast, first developed as an anti-allergic drug, has been reported to inhibit vascular endothelial growth factor (VEGF)-induced angiogenesis and vasopermeability. To further clarify the inhibitory mechanism, we investigated the effects of tranilast on VEGF binding and subsequent intracellular signalling pathway linked to angiogenic activities and gene expression of bovine retinal microcapillary endothelial cells.
Tranilast significantly (P<0.01) inhibited VEGF, basic fibroblast growth factor (bFGF), and hypoxia conditioned media-induced BREC proliferation in a dose dependent manner with IC50's of 22, 82 and 10 μM, respectively.
VEGF-induced migration was also inhibited by tranilast in a dose dependent manner, with IC50 of 18 μM, and complete inhibition was observed at 300 μM (P<0.01). Tranilast suppressed VEGF-induced tube formation in a dose dependent manner with maximum (46%) inhibition observed at 300 μM (P<0.05).
Tranilast inhibited phorbol myristate acetate (PMA)-dependent stimulation of [H]-thymidine incorporation and VEGF- and PMA-induced gene expression of integrin αv and c-fos in BREC.
Tranilast suppressed VEGF- and PMA-stimulated PKC activity in BREC.
Tranilast did not affect VEGF binding or VEGF-induced phosphorylation of tyrosine residues of VEGF receptor- and phospholipase Cγ and their associated proteins.
These data suggest that tranilast might prove an effective inhibitor to prevent retinal neovascularization in ischaemic retinal diseases, and that its inhibitory effect might be through suppression of PKC-dependent signal transduction in BREC.
Acknowledgments
We thank Dr Mortimer Poncz for integrin β3 plasmid. This study was supported by a grant-in-aid for scientific research from the Ministry of Education and Ministry of Health and Welfare of Japanese Government.
Abbreviations
bFGF | basic fibroblast growth factor |
BREC | bovine retinal microcapillary endothelial cell |
BSA | bovine serum albumin |
DMEM | Dulbecco's modified Eagle's medium |
GFX | GF109203X |
IL | interleukin |
PDGF | platelet derived growth factor |
PDHS | plasma derived horse serum |
PKC | protein kinase C |
PLCγ | phospholipase Cγ |
PMA | phorbol myristate acetate |
PTCA | percutaneous transluminal coronary angioplasty |
SMC | smooth muscle cell |
TGF | transforming growth factor |
VEGF | vascular endothelial growth factor |