Inducible nitric oxide synthase and vascular endothelial growth factor are colocalized in the retinas of human subjects with diabetes.
OBJECTIVE
Nitric oxide (NO) mediates vascular endothelial growth factor (VEGF)-induced angiogenesis and vascular hyperpermeability. This study was undertaken to study the cellular distribution of inducible nitric oxide synthase (iNOS) and VEGF in the retinas from human subjects with diabetes mellitus. In addition, glial reactivity and peroxynitrite generation were detected by immunolocalization of glial fibrillary acidic protein (GFAP) and nitrotyrosine, respectively.


METHODS
Eight post-mortem eyes from four consecutive subjects with diabetes mellitus and eight eyes from four subjects without diabetes and without known ocular disease were prospectively collected and examined. We used immunohistochemical techniques and antibodies directed against iNOS, VEGF, GFAP, and nitrotyrosine.


RESULTS
In retinas from all subjects without diabetes, weak GFAP immunoreactivity was confined to nerve fibre and ganglion cell layers. There was no immunoreactivity for iNOS, nitrotyrosine, and VEGF. All diabetic retinas showed GFAP induction in Müller cells and GFAP upregulation in nerve fibre and ganglion cell layers. All diabetic retinas showed cytoplasmic immunoreactivity for iNOS, and VEGF in ganglion cells, cells in the inner nuclear layer, and glial cells. In serial sections, ganglion cells and cells in the inner nuclear layer expressing VEGF were localized in the same area of iNOS-expressing ganglion cells and cells in the inner nuclear layer. Six retinas from three subjects with diabetes showed immunoreactivity for nitrotyrosine in vascular endothelial cells in inner retinal layer.


CONCLUSIONS
iNOS and VEGF are colocalized in diabetic retinas. Increased GFAP immunoreactivity is a pathological event in the retina during diabetes.
Abu El-Asrar
A M
AM
Department of Ophthalmology, College of Medicine, King Saud University, Riyadh, Saudi Arabia. abuasrar@KSU.edu.sa
Meersschaert
A
A
Dralands
L
L
Missotten
L
L
Geboes
K
K
D000328:Adult; D000368:Aged; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism*; D005260:Female; D005904:Glial Fibrillary Acidic Protein / Q000032:analysis; D006801:Humans; D008297:Male; D008875:Middle Aged; D019001:Nitric Oxide Synthase / Q000032:analysis*; D052247:Nitric Oxide Synthase Type II; D011446:Prospective Studies; D012160:Retina / Q000737:chemistry*; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000032:analysis; D042442:Vascular Endothelial Growth Factors / Q000032:analysis*
D005904:Glial Fibrillary Acidic Protein; D042442:Vascular Endothelial Growth Factors; C002744:3-nitrotyrosine; D014443:Tyrosine; C496319:NOS2 protein, human; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II