Inducible nitric oxide synthase-mediated alteration of mitochondrial OPA1 expression in ocular hypertensive rats

Invest Ophthalmol Vis Sci. 2011 Apr 16;52(5):2468-76. doi: 10.1167/iovs.10-5873.

Abstract

Purpose: 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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Blotting, Western
  • Cell Survival
  • Disease Models, Animal
  • Enzyme Inhibitors / pharmacology
  • GTP Phosphohydrolases / genetics*
  • Gene Expression Regulation, Enzymologic / physiology*
  • Glial Fibrillary Acidic Protein / metabolism
  • Guanidines / pharmacology
  • Injections, Intraperitoneal
  • Intraocular Pressure
  • Mitochondria / enzymology*
  • Neuroglia / cytology
  • Nitric Oxide / metabolism
  • Nitric Oxide Synthase Type II / antagonists & inhibitors
  • Nitric Oxide Synthase Type II / physiology*
  • Ocular Hypertension / genetics*
  • Ocular Hypertension / metabolism
  • Ocular Hypertension / pathology
  • RNA, Messenger / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Retina / enzymology
  • Retinal Ganglion Cells / cytology
  • Reverse Transcriptase Polymerase Chain Reaction

Substances

  • Enzyme Inhibitors
  • Glial Fibrillary Acidic Protein
  • Guanidines
  • RNA, Messenger
  • Nitric Oxide
  • Nitric Oxide Synthase Type II
  • Nos2 protein, rat
  • GTP Phosphohydrolases
  • Opa1 protein, rat
  • pimagedine