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 August 1, 2016; First 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 1

Elevated levels of truncated netrin-1 in the vitreous humor of patients with DME.

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Elevated levels of truncated netrin-1 in the vitreous humor of patients ...
(A and B) 3D retinal maps and SD-OCT of control eye (left) versus eyes of patients with DME (right). The severity of retinal swelling was particularly evident in the central foveal zones. (C) Netrin-1 Ab targeting a specific peptide sequence in netrin-1 domain V (60). (D) Western blot analysis of equal volumes of vitreous humor revealed the presence of full-length netrin-1 in all samples and of an approximately 55-kDa netrin-1 fragment in a number of patients with DME (n = 4–5). (E) Schematic diagram of a 55-kDa netrin-1 fragment. (F) Quantification of signal density revealed an approximately 8-fold increase in the VI-V fragment in vitreous humor (n = 4–5). (G) Quantification of signal density revealed an approximately 50% decrease in full-length netrin-1 levels (n = 4–5, NS). (H) Correlation curve between the 55-kDa fragment and OCTs, showing that 52% of the OCT variation was associated with the 55-kDa fragment variation. (I) Correlation curve revealed no significant correlation between full-length netrin-1 and OCTs. Data are expressed as the mean ± SEM. *P < 0.05, by 2-tailed Student’s t test. Ctl, control.