title: Inducible nitric oxide synthase-mediated alteration of mitochondrial OPA1 expression in ocular hypertensive rats.
abstract: OBJECTIVE
  To investigate how OPA1 expression and distribution are altered by increased nitric oxide (NO) and whether aminoguanidine, a relative selective NO synthase (NOS)-2 inhibitor, can restore OPA1 expression and subsequently increase retinal ganglion cell (RGC) survival in ocular hypertensive rats.
  
  
  METHODS
  Elevated intraocular pressure was induced unilaterally by translimbal laser photocoagulation of the trabecular meshwork in Sprague-Dawley rats. Aminoguanidine (100 mg/kg) was administered by intraperitoneal injection for 3 consecutive days in rats after laser treatment. Preservation of fluorochrome-labeled RGCs was assessed 2 weeks later. GFAP, NOS-2, or OPA1 protein expression and distribution were assessed by Western blot analysis and immunohistochemistry. OPA1 mRNA was measured by qPCR.
  
  
  RESULTS
  OPA1 mRNA and protein expression were significantly increased in the vehicle-treated hypertensive rat retina. Aminoguanidine treatment significantly reduced expression of the 90- and 65-kDa OPA1 isoforms but did not significantly change the 80-kDa OPA1 isoform in hypertensive retina. In addition, the increases in NOS-2 and GFAP protein expression were blocked by aminoguanidine treatment in the hypertensive retina. NOS-2 immunoreactivity was induced in cells of the ganglion cell layer in the vehicle-treated hypertensive retina. Aminoguanidine treatment significantly increased RGC survival at 2 weeks after IOP elevation.
  
  
  CONCLUSIONS
  Although NOS-2/NO induction may contribute to hypertensive retinal cell death, an increase in mitochondrial OPA1 may provide an important cellular defense mechanism against pressure-mediated retinal damage. These findings suggest that mitochondrial preservation after inhibition of NOS-2 may be useful for protecting RGCs against glaucomatous damage.
authors.affiliation: The Sophie and Arthur Brody Optic Nerve Laboratory, Hamilton Glaucoma Center, University of California San Diego, La Jolla, California, USA.
authors.forename: Yi
authors.initials: Y
authors.lastname: Dai
authors.forename: Robert N
authors.initials: RN
authors.lastname: Weinreb
authors.forename: Keun-Young
authors.initials: KY
authors.lastname: Kim
authors.forename: Duy
authors.initials: D
authors.lastname: Nguyen
authors.forename: Sangwoo
authors.initials: S
authors.lastname: Park
authors.forename: Xinghuai
authors.initials: X
authors.lastname: Sun
authors.forename: James D
authors.initials: JD
authors.lastname: Lindsey
authors.forename: Mark H
authors.initials: MH
authors.lastname: Ellisman
authors.forename: Won-Kyu
authors.initials: WK
authors.lastname: Ju
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002470:Cell Survival; D004195:Disease Models, Animal; D004791:Enzyme Inhibitors / Q000494:pharmacology; D020558:GTP Phosphohydrolases / Q000235:genetics*; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D006146:Guanidines / Q000494:pharmacology; D007274:Injections, Intraperitoneal; D007429:Intraocular Pressure; D008928:Mitochondria / Q000201:enzymology*; D009457:Neuroglia / Q000166:cytology; D009569:Nitric Oxide / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000037:antagonists & inhibitors / Q000502:physiology*; D009798:Ocular Hypertension / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012160:Retina / Q000201:enzymology; D012165:Retinal Ganglion Cells / Q000166:cytology; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D004791:Enzyme Inhibitors; D005904:Glial Fibrillary Acidic Protein; D006146:Guanidines; D012333:RNA, Messenger; D009569:Nitric Oxide; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat; D020558:GTP Phosphohydrolases; C498811:Opa1 protein, rat; C004479:pimagedine