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 6

Vasoinhibins prevent retinal vasopermeability induced by human diabetic vitreous.

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Vasoinhibins prevent retinal vasopermeability induced by human diabetic ...
(A) Evans blue evaluation of retinal vasopermeability in retinal extracts from rats injected intravitreally with PBS (ctl, n = 5), nondiabetic vitreous (2 μl, n = 5), nondiabetic vitreous plus vasoinhibins (1 μM, n = 5), nondiabetic vitreous depleted of VEGF (anti-VEGF, 2 μl, n = 3), diabetic vitreous (2 μl, n = 6), diabetic vitreous plus vasoinhibins (1 μM, n = 6), or diabetic vitreous depleted of VEGF (anti-VEGF, 2 μl, n = 3). The same VEGF-depleted vitreous was used for the experiments in A and B. l-NAME (1.8 mM) was administered in drinking water for 15 days, and rat retinas that had been intravitreally injected with diabetic vitreous were subsequently analyzed for retinal vasopermeability. Values are mean ± SEM of n independent experiments. *P < 0.05 versus ctl; #P < 0.05 versus diabetic vitreous. (B) Analysis of VEGF concentration (pg/ml) by ELISA in nondiabetic vitreous, nondiabetic vitreous depleted of VEGF (anti-VEGF), diabetic vitreous, and diabetic vitreous depleted of VEGF (anti-VEGF). The VEGF content of the vitreous samples was reduced by immunoprecipitation with anti-VEGF antibody. Values are mean ± SEM of 3 independent vitreous samples. *P < 0.05 versus nondiabetic vitreous; **P < 0.05 versus diabetic vitreous. (C) Evans blue evaluation of retinal vasopermeability in retinal extracts from nondiabetic rats and diabetic rats (induced by streptozotocin), injected with PBS or vasoinhibins (1 μM). Values are mean ± SEM of 6 independent retinal extracts. *P < 0.05 versus PBS-injected nondiabetic rats; **P < 0.05 versus PBS-injected diabetic rats. Vasoinhibin concentrations refer to the final, intravitreal values.