title: Arginase 2 deletion reduces neuro-glial injury and improves retinal function in a model of retinopathy of prematurity.
abstract: BACKGROUND
  Retinopathy of prematurity (ROP) is a major cause of vision impairment in low birth weight infants. While previous work has focused on defining the mechanisms of vascular injury leading to retinal neovascularization, recent studies show that neurons are also affected. This study was undertaken to determine the role of the mitochondrial arginine/ornithine regulating enzyme arginase 2 (A2) in retinal neuro-glial cell injury in the mouse model of ROP.
  
  
  RESULTS
  Studies were performed using wild type (WT) and A2 knockout (A2-/-) mice exposed to Oxygen Induced Retinopathy (OIR). Neuronal injury and apoptosis were assessed using immunohistochemistry, TUNEL (terminal deoxynucleotidyl transferase dUTP nick end) labeling and Western blotting. Electroretinography (ERG) was used to assess retinal function. Neuro-glial injury in WT ROP mice was evident by TUNEL labeling, retinal thinning, decreases in number of rod bipolar cells and glial cell activation as compared with room air controls. Significant reduction in numbers of TUNEL positive cells, inhibition of retinal thinning, preservation of the rod bipolar cells and prevention of glial activation were observed in the A2-/- retinas. Retinal function was markedly impaired in the WT OIR mice as shown by decreases in amplitude of the b-wave of the ERG. This defect was significantly reduced in A2-/- mice. Levels of the pro-apoptotic proteins p53, cleaved caspase 9, cytochrome C and the mitochondrial protein Bim were markedly increased in WT OIR retinas compared to controls, whereas the pro-survival Mitochondrial protein BCL-xl was reduced. These alterations were largely blocked in the A2-/- OIR retina.
  
  
  CONCLUSIONS
  Our data implicate A2 in neurodegeneration during ROP. Deletion of A2 significantly improves neuronal survival and function, possibly through the regulation of mitochondrial membrane permeability mediated apoptosis during retinal ischemia. These molecular events are associated with decreased activation of glial cells, suggesting a rescue effect on macroglia as well.
authors.affiliation: Vascular Biology Center, Georgia Health Sciences University, Augusta, Georgia, United States of America.
authors.forename: Subhadra P
authors.initials: SP
authors.lastname: Narayanan
authors.forename: Jutamas
authors.initials: J
authors.lastname: Suwanpradid
authors.forename: Alan
authors.initials: A
authors.lastname: Saul
authors.forename: Zhimin
authors.initials: Z
authors.lastname: Xu
authors.forename: Amber
authors.initials: A
authors.lastname: Still
authors.forename: Robert W
authors.initials: RW
authors.lastname: Caldwell
authors.forename: Ruth B
authors.initials: RB
authors.lastname: Caldwell
mesh_terms: D000818:Animals; D017209:Apoptosis; D001119:Arginase / Q000378:metabolism*; D053453:Caspase 9 / Q000378:metabolism; D019610:Cytoprotection; D004195:Disease Models, Animal; D017353:Gene Deletion; D006801:Humans; D007231:Infant, Newborn; D051379:Mice; D009457:Neuroglia / Q000378:metabolism / Q000473:pathology*; D009474:Neurons / Q000378:metabolism / Q000473:pathology*; D010100:Oxygen; D012160:Retina / Q000201:enzymology* / Q000502:physiology* / Q000503:physiopathology; D051245:Retinal Bipolar Cells / Q000378:metabolism / Q000473:pathology; D012162:Retinal Degeneration / Q000150:complications / Q000473:pathology / Q000503:physiopathology; D012178:Retinopathy of Prematurity / Q000150:complications / Q000473:pathology / Q000503:physiopathology*; D015398:Signal Transduction; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
chemical_list: D016159:Tumor Suppressor Protein p53; D053453:Caspase 9; C481673:Arg2 protein, mouse; D001119:Arginase; D010100:Oxygen