Netrin-1 simultaneously suppresses corneal inflammation and neovascularization.
OBJECTIVE
To investigate the effect of netrin-1 on alkali burn-induced corneal inflammation and neovascularization.


METHODS
The expression of netrin-1 and its receptors UNC5A, UNC5B, UNC5C, UNC5D, adenosine 2b receptor (A2BAR), deleted in colorectal cancer (DCC), and neogenin in normal and alkali-burned rat cornea were determined by RT-PCR and/or Western blot analysis, or immunostaining. Topical netrin-1 protein was applied to treat rat corneal alkali-burn injury for 14 consecutive days, started right after the injury or 10 days postinjury. Corneal inflammation and neovascularization were observed under slit lamp microscope. The apoptosis of corneal cells was determined by terminal deoxynucleotidyl transferase-mediated nick end labeling assay. Corneal inflammatory cell infiltration was evaluated by immunostaining of anti-PMN and anti-ED1 antibodies. The expression of epidermal growth factor (EGF), vascular epidermal growth factor (VEGF), and pigment epithelium-derived factor (PEDF) in rat cornea was determined by Western blot analysis.


RESULTS
Netrin-1 and its receptor UNC5B were expressed in normal rat corneal epithelium and stromal cells, and their expression decreased after corneal alkali burn. Exogenous netrin-1 administered on rat ocular surfaces resolved alkali burn-induced corneal inflammation, and also suppressed corneal neovascularization. Furthermore, netrin-1 could reverse neovascularization in alkali-burned cornea. The authors found that netrin-1 executed the functions through various mechanisms, including upregulating EGF expression, accelerating epithelial wound healing, inhibiting neutrophil and macrophage infiltration, reducing corneal cell apoptosis, and restoring the equilibrium of VEGF and PEDF in the wounded cornea.


CONCLUSIONS
Netrin-1 could dampen inflammation, inhibit, and reverse neovascularization in alkali-burned cornea.
Eye Institute of Xiamen University, Xiamen, Fujian, China.
Yun
Y
Han
Yi
Y
Shao
Zhirong
Z
Lin
Yang-Luowa
YL
Qu
He
H
Wang
Yueping
Y
Zhou
Wensheng
W
Chen
Yongxiong
Y
Chen
Wei-Li
WL
Chen
Fung-Rong
FR
Hu
Wei
W
Li
Zuguo
Z
Liu
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D016510:Corneal Neovascularization / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D004195:Disease Models, Animal; D029721:Drosophila Proteins; D005786:Gene Expression Regulation; D007634:Keratitis / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D008297:Male; D009414:Nerve Growth Factors / Q000008:administration & dosage* / Q000096:biosynthesis / Q000235:genetics; D000075388:Netrin-1; D009883:Ophthalmic Solutions / Q000008:administration & dosage; D012313:RNA / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D060888:Real-Time Polymerase Chain Reaction; D025521:Tumor Suppressor Proteins / Q000008:administration & dosage* / Q000096:biosynthesis / Q000235:genetics
D029721:Drosophila Proteins; D009414:Nerve Growth Factors; C000617354:Ntn1 protein, rat; D009883:Ophthalmic Solutions; D025521:Tumor Suppressor Proteins; D000075388:Netrin-1; D012313:RNA