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Cheng-mao Lin, Paul Titchenell, Arivalagan Muthusamy, David Antonetti; VEGF and TNF Interact to Induce Retinal Edema in an Atypical PKC Dependent Manner. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1130.
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© ARVO (1962-2015); The Authors (2016-present)
Changes in permeability of retinal blood vessels contribute to macular edema and the pathophysiology of diabetic retinopathy. Both vascular endothelial growth factor (VEGF) and tumor necrosis factor (TNF) have been implicated in macular edema. We tested the hypothesis that VEGF and TNF interact to induce retinal edema in vivo and require atypical PKC (aPKC) activation.
Male Long-Evans rats weighing 200 to 250 g were used to evaluate retinal vascular permeability and retinal thickening induced by VEGF and TNF treatments. Animals received a single intravitreal injection of vehicle, aPKC inhibitor, VEGF, TNF, combined VEGF and TNF or VEGF/TNF plus aPKC inhibitor to yield final concentration as indicated. Blood-retinal barrier leakage was measured with intravenous FITC-BSA injection. Retinal leakage was calculated from the accumulation of fluorescent albumin in the retina and normalized to the plasma levels. Also, 5 h after intraocular injection of the same factors, eyes were imaged 10 min after FITC-BSA injection for retinal vascular leakage using a Micron III camera. Eyes were then enucleated, fixed and subjected to flat-mount staining for subsequent imaging. Tight junction proteins were examined by immunohistochemistry. Retinal structure and layer thickness, a measure of edema, were assessed with spectral domain optical coherence tomography. Baseline data were obtained before any treatment and used for comparison with the later time points in the longitudinal study.
Partial discontinuity of occludin and ZO-1 immunostaining was observed in the VEGF-treated retinas, whereas loss of ZO-1was observed in the TNF-treated retinas. VEGF/TNF combination treatment dramatically induced tight junction disorganization and interacted to increase retinal thickening. Increased retinal albumin leakage and retinal thickening induced by combined VEGF/TNF treatment were effectively prevented by an aPKC inhibitor in a dose-dependent manner. In the longitudinal study, aPKC inhibition attenuated the initial (24 h) edema response from VEGF/TNF administration by 40%. The group treated with the aPKC inhibitor returned to baseline more rapidly than VEGF/TNF group.
These data demonstrate that VEGF and TNF interact to promote retinal edema in vivo and provide an effective model to test therapeutic intervention to control edema. Co-injection of aPKC inhibitor dramatically reduces induction of edema in vivo.
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