Truncated netrin-1 contributes to pathological vascular permeability in diabetic retinopathy
Khalil Miloudi, … , Timothy E. Kennedy, Przemyslaw Sapieha
Khalil Miloudi, … , Timothy E. Kennedy, Przemyslaw Sapieha
Published July 11, 2016
Citation Information: J Clin Invest. 2016;126(8):3006-3022. https://doi.org/10.1172/JCI84767.
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Research Article Angiogenesis

Truncated netrin-1 contributes to pathological vascular permeability in diabetic retinopathy

Abstract

Diabetic retinopathy (DR) is a major complication of diabetes and a leading cause of blindness in the working-age population. Impaired blood-retinal barrier function leads to macular edema that is closely associated with the deterioration of central vision. We previously demonstrated that the neuronal guidance cue netrin-1 activates a program of reparative angiogenesis in microglia within the ischemic retina. Here, we provide evidence in both vitreous humor of diabetic patients and in retina of a murine model of diabetes that netrin-1 is metabolized into a bioactive fragment corresponding to domains VI and V of the full-length molecule. In contrast to the protective effects of full-length netrin-1 on retinal microvasculature, the VI-V fragment promoted vascular permeability through the uncoordinated 5B (UNC5B) receptor. The collagenase matrix metalloprotease 9 (MMP-9), which is increased in patients with diabetic macular edema, was capable of cleaving netrin-1 into the VI-V fragment. Thus, MMP-9 may release netrin-1 fragments from the extracellular matrix and facilitate diffusion. Nonspecific inhibition of collagenases or selective inhibition of MMP-9 decreased pathological vascular permeability in a murine model of diabetic retinal edema. This study reveals that netrin-1 degradation products are capable of modulating vascular permeability, suggesting that these fragments are of potential therapeutic interest for the treatment of DR.

Authors

Khalil Miloudi, François Binet, Ariel Wilson, Agustin Cerani, Malika Oubaha, Catherine Menard, Sullivan Henriques, Gaelle Mawambo, Agnieszka Dejda, Phuong Trang Nguyen, Flavio A. Rezende, Steve Bourgault, Timothy E. Kennedy, Przemyslaw Sapieha

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Figure 3

The VI-V fragment plays a role in early BRB breakdown.

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The VI-V fragment plays a role in early BRB breakdown. (A) Representativ...
(A) Representative images of vascular leakage induced with vehicle (PBS), recombinant VI-V fragment (3 nM), full-length netrin-1 (3 nM), or recombinant VEGF (2 nM) injected into the vitreous. Intravitreal injection resulted in a robust increase of retinal vasopermeability in eyes treated with the VI-V fragment of netrin-1 and with VEGF. n = 3. Scale bars: 30 μm. (B) EB extravasation (vascular leakage) induced by VI-V fragment, full-length netrin-1, and recombinant VEGF, measured by overnight extraction of the dye and spectrophotometric quantification (n = 4–6). (C) Representative images of the vascular leakage induced with vehicle, synthetic VI-V fragment, full-length netrin-1, or recombinant VEGF s.c. injected into adult C57BL/6J mice (n = 5). Original magnification, ×2.5. (D) EB extravasation (vascular leakage) induced by VI-V fragment, full-length netrin-1, and recombinant VEGF was assessed by overnight extraction of the blue dye in formamide and spectrophotometric quantification (n = 5). (E) Representative images of the vascular leakage induced with vehicle (PBS), recombinant VEGF (2 nM), full-length netrin-1 (3 nM), or recombinant VI-V fragment (3 nM) intradermally injected into CD-1 mouse ears (n = 5). Original magnification, ×1.6. (F) Quantification of EB extravasation (vascular leakage) induced by VI-V fragment, full-length netrin-1, and recombinant VEGF (n = 5). Data are expressed as the mean ± SEM. *P < 0.05, **P < 0.01, and ***P < 0.001, by 2-tailed Student’s t test (B and F) and 1-way ANOVA with Tukey’s post-hoc test (D).