Placental growth factor-1 and epithelial haemato-retinal barrier breakdown: potential implication in the pathogenesis of diabetic retinopathy.
OBJECTIVE
Disruption of the retinal pigment epithelial (RPE) barrier contributes to sub-retinal fluid and retinal oedema as observed in diabetic retinopathy. High placental growth factor (PLGF) vitreous levels have been found in diabetic patients. This work aimed to elucidate the influence of PLGF-1 on a human RPE cell line (ARPE-19) barrier in vitro and on normal rat eyes in vivo.


METHODS
ARPE-19 permeability was measured using transepithelial resistance and inulin flux under stimulation of PLGF-1, vascular endothelial growth factor (VEGF)-E and VEGF 165. Using RT-PCR, we evaluated the effect of hypoxic conditions or insulin on transepithelial resistance and on PLGF-1 and VEGF receptors. The involvement of mitogen-activated protein kinase (MEK, also known as MAPK)/extracellular signal-regulated kinase (ERK, also known as EPHB2) signalling pathways under PLGF-1 stimulation was evaluated by western blot analysis and specific inhibitors. The effect of PLGF-1 on the external haemato-retinal barrier was evaluated after intravitreous injection of PLGF-1 in the rat eye; evaluation was by semi-thin analysis and zonula occludens-1 immunolocalisation on flat-mounted RPE.


RESULTS
In vitro, PLGF-1 induced a reversible decrease of transepithelial resistance and enhanced tritiated inulin flux. These effects were specifically abolished by an antisense oligonucleotide directed at VEGF receptor 1. Exposure of ARPE-19 cells to hypoxic conditions or to insulin induced an upregulation of PLGF-1 expression along with increased transcellular permeability. The PLGF-1-induced RPE cell permeability involved the MEK signalling pathway. Injection of PLGF-1 in the rat eye vitreous induced an opening of the RPE tight junctions with subsequent sub-retinal fluid accumulation, retinal oedema and cytoplasm translocation of junction proteins.


CONCLUSIONS
Our results indicate that PLGF-1 may be a potential regulation target for the control of diabetic retinal and macular oedema.
Miyamoto
N
N
INSERM U598, Physiopathology of Ocular Diseases, Therapeutic Innovations, Biomedical Institute des Cordeliers, 15 rue de l'Ecole de médecine, 75006, Paris, France.
de Kozak
Y
Y
Jeanny
J C
JC
Glotin
A
A
Mascarelli
F
F
Massin
P
P
BenEzra
D
D
Behar-Cohen
F
F
D018929:Cell Culture Techniques; D003930:Diabetic Retinopathy / Q000503:physiopathology*; D004594:Electrophysiology; D004847:Epithelial Cells / Q000502:physiology; D006706:Homeostasis; D006801:Humans; D008269:Macular Edema / Q000503:physiopathology; D010857:Pigment Epithelium of Eye / Q000502:physiology*; D000072483:Placenta Growth Factor; D011257:Pregnancy Proteins / Q000502:physiology*; D012171:Retinal Vessels / Q000502:physiology*; D042461:Vascular Endothelial Growth Factor A / Q000502:physiology
C000608036:PGF protein, human; C000608038:Pgf protein, rat; D011257:Pregnancy Proteins; D042461:Vascular Endothelial Growth Factor A; D000072483:Placenta Growth Factor