Vasoinhibins prevent retinal vasopermeability associated with diabetic retinopathy in rats via protein phosphatase 2A–dependent eNOS inactivation
Celina García, … , Gonzalo Martínez de la Escalera, Carmen Clapp
Celina García, … , Gonzalo Martínez de la Escalera, Carmen Clapp
Published May 22, 2008
Citation Information: J Clin Invest. 2008;118(6):2291-2300. https://doi.org/10.1172/JCI34508.
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Research Article Ophthalmology

Vasoinhibins prevent retinal vasopermeability associated with diabetic retinopathy in rats via protein phosphatase 2A–dependent eNOS inactivation

Abstract

Increased retinal vasopermeability contributes to diabetic retinopathy, the leading cause of blindness in working-age adults. Despite clinical progress, effective therapy remains a major need. Vasoinhibins, a family of peptides derived from the protein hormone prolactin (and inclusive of the 16-kDa fragment of prolactin), antagonize the proangiogenic effects of VEGF, a primary mediator of retinal vasopermeability. Here, we demonstrate what we believe to be a novel function of vasoinhibins as inhibitors of the increased retinal vasopermeability associated with diabetic retinopathy. Vasoinhibins inhibited VEGF-induced vasopermeability in bovine aortic and rat retinal capillary endothelial cells in vitro. In vivo, vasoinhibins blocked retinal vasopermeability in diabetic rats and in response to intravitreous injection of VEGF or of vitreous from patients with diabetic retinopathy. Inhibition by vasoinhibins was similar to that achieved following immunodepletion of VEGF from human diabetic retinopathy vitreous or blockage of NO synthesis, suggesting that vasoinhibins inhibit VEGF-induced NOS activation. We further showed that vasoinhibins activate protein phosphatase 2A (PP2A), leading to eNOS dephosphorylation at Ser1179 and, thereby, eNOS inactivation. Moreover, intravitreous injection of okadaic acid, a PP2A inhibitor, blocked the vasoinhibin effect on endothelial cell permeability and retinal vasopermeability. These results suggest that vasoinhibins have the potential to be developed as new therapeutic agents to control the excessive retinal vasopermeability observed in diabetic retinopathy and other vasoproliferative retinopathies.

Authors

Celina García, Jorge Aranda, Edith Arnold, Stéphanie Thébault, Yazmín Macotela, Fernando López-Casillas, Valentín Mendoza, Hugo Quiroz-Mercado, Hebert Luis Hernández-Montiel, Sue-Hwa Lin, Gonzalo Martínez de la Escalera, Carmen Clapp

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Figure 4

Vasoinhibins prevent VEGF-induced retinal hemorrhages and vasodilation in vivo.

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Vasoinhibins prevent VEGF-induced retinal hemorrhages and vasodilation i...
(A) Representative flat mounts after the peroxidase reaction of a portion of the retina obtained from rats 24 hours after an intravitreous injection of PBS (ctl), 260 nM VEGF, or VEGF and 1 μM vasoinhibins. Each retina was digitized with a ×20 objective and tiled to present the entire preparation. Arrows indicate hemorrhage areas. Original magnification, ×6. (B) Magnification of areas indicated by rectangles (×7; ×40 objective) in the flat mounts shown in A to illustrate the vasodilation of the microcirculation. Insets in B were magnified by an additional 2-fold. Arrows indicate the width of blood vessels. Quantification of hemorrhage areas (C) and averaged diameter of blood vessels (D) from retina flat mounts from rats injected intravitreally 24 hours earlier with PBS, 260 nM VEGF, or VEGF and 1 μM Vi. VEGF and vasoinhibin concentrations refer to the final, intravitreal levels. Values are mean ± SEM of 6 independent samples. *P < 0.05 versus control; **P < 0.05 versus VEGF.