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Khalil Miloudi, Przemyslaw Sapieha, Agustin Cerani, Francois Binet, Timothy Kennedy, Gaelle Mawambo; Netrin-1 fragmentation influences vascular permeability in diabetic retinopathy.. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):4290.
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© ARVO (1962-2015); The Authors (2016-present)
Diabetic macular edema is a major early complication of diabetic retinopathy (DR). Although trophic factors such as VEGF are often associated with breakdown of barrier function in DR, we recently identified early inducers of vascular permeability secreted by neuronal cells. Here we describe the role of a cleaved form of the classical neuronal guidance cue netrin-1, the VI-V fragment, as a potent inducer of vascular permeability in DR.
Retinal expression of Netrin-1 and its VI-V fragment were investigated by Western Blot analysis in a Streptozotocin-induced model of type I diabetes (4 and 8 weeks). To verify respective effects on vascular permeability, we administrated recombinant netrin-1 or the VI-V fragment subcutaneously or intravitrealy, injected Evans blue dye 24 hrs later and quantified the induced permeability by Evans blue quantitation. Electrical Cell-Subtrate Impedance System (ECIS) on endothelial cell monolayers was used to verify induction of permeability. Presence of netrin-1 receptors was assed by Laser-Capture Microdissection (LCM) on retinal cross-sections and in culture on Human Retinal Microvascular Cells (HRMECs) by qPCR. Signaling by the VI-V fragment of netrin was mapped-out and receptors involved investigated by siRNA.<br />
Our data demonstrates elevated expression of both netrin-1 and the VI-V fragment in retinas of diabetic mice (4 and 8 weeks). However, only the VI-V fragment increased retinal vascular permeability in vivo. ECIS data suggest that netrin-1 prevents VEGF-induced permeability while the VI-V fragment severely compromises barrier function. These effects are mediated via the Unc5b receptor and downstream signaling events that ultimately lead to VE-cadherin phosphorylation. LCM and qPCR data demonstrate that Unc5b is overexpressed in diabetic retinal vasculature.
These results describe a new mechanism of barrier function breakdown in diabetic retinas. The VI-V fragment of netrin-1 . through Unc5b, provokes loosening of adheren junctions in retinal endothelial cells and provokes retinal edema.<br />
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