title: The dipeptide Arg-Gln inhibits retinal neovascularization in the mouse model of oxygen-induced retinopathy.
abstract: OBJECTIVE
  Premature infants undergoing intensive care are highly vulnerable to amino acid deprivation. Supplementation of glutamine or arginine has resulted in beneficial effects in human neonates. This study was conducted to examine the effect of the dipeptide arginyl-glutamine (Arg-Gln) on vascular endothelial cell growth factor (VEGF) levels in primary human retinal pigment epithelial (hRPE) cell cultures and on inhibition of neovascularization in the oxygen-induced retinopathy (OIR) model.
  
  
  METHODS
  The effects of Arg-Gln on VEGF levels were measured in supernates from hRPE cells by using ELISAs. For in vivo studies, mouse pups received twice-daily intraperitoneal injections of Arg-Gln, a control dipeptide (Ala-Gly) or were not injected. Retinal flatmounts from one cohort were prepared and retinal vessel morphology examined. The contralateral eyes were embedded, sectioned, and stained to count preretinal neovascular nuclei. RNA was isolated from retinas of selected animals and was used to quantify VEGF mRNA by real-time RT-PCR.
  
  
  RESULTS
  Treatment of hRPE cells with Arg-Gln decreased VEGF levels in a dose-dependent manner. In the OIR model, Arg-Gln at 5 g/kg per day reduced preretinal neovascularization by 82%+/-7% (P<0.005), when compared with the control dipeptide Ala-Gly, and reduced VEGF mRNA by 64%+/-9% (P<0.001).
  
  
  CONCLUSIONS
  Arg-Gln dramatically inhibited retinal neovascularization in the OIR model. This effect was associated with a reduction in retinal VEGF mRNA levels. Similarly the dipeptide reduced VEGF expression in hRPE cells, a cell type likely to respond to retinal hypoxia by expressing VEGF. Arg-Gln appears to be safe and, with future studies in human infants, may prove beneficial in the prevention of ROP.
authors.affiliation: Departments of Pharmacology and Therapeutics, University of Florida, Gainesville 32610-0267, USA.
authors.forename: Josef
authors.initials: J
authors.lastname: Neu
authors.forename: Aqeela
authors.initials: A
authors.lastname: Afzal
authors.forename: Hao
authors.initials: H
authors.lastname: Pan
authors.forename: Esteban
authors.initials: E
authors.lastname: Gallego
authors.forename: Nan
authors.initials: N
authors.lastname: Li
authors.forename: Sergio
authors.initials: S
authors.lastname: Li Calzi
authors.forename: Sergio
authors.initials: S
authors.lastname: Caballero
authors.forename: Polyxenie E
authors.initials: PE
authors.lastname: Spoerri
authors.forename: Lynn C
authors.initials: LC
authors.lastname: Shaw
authors.forename: Maria B
authors.initials: MB
authors.lastname: Grant
mesh_terms: D020533:Angiogenesis Inhibitors / Q000494:pharmacology; D000818:Animals; D002478:Cells, Cultured; D004151:Dipeptides / Q000494:pharmacology*; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D007274:Injections, Intraperitoneal; D051379:Mice; D008810:Mice, Inbred C57BL; D010100:Oxygen / Q000633:toxicity*; D010857:Pigment Epithelium of Eye / Q000187:drug effects / Q000378:metabolism; D011247:Pregnancy; D012333:RNA, Messenger / Q000378:metabolism; D015861:Retinal Neovascularization / Q000139:chemically induced / Q000235:genetics / Q000517:prevention & control*; D012178:Retinopathy of Prematurity / Q000139:chemically induced / Q000235:genetics / Q000517:prevention & control*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics*
chemical_list: D020533:Angiogenesis Inhibitors; D004151:Dipeptides; D012333:RNA, Messenger; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; C467480:vascular endothelial growth factor A, mouse; D010100:Oxygen; C024362:arginine glutamate