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Nitric oxide synthase in the human glaucomatous optic nerve head
A H Neufeld1, M R Hernandez, M Gonzalez
1Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St Louis, Mo., USA. neufelda@am.seer.wustl.edu
Archives of Ophthalmology (Chicago, Ill. : 1960)
|April 1, 1997
Summary
Nitric oxide synthase (NOS) isoforms increase in glaucoma optic nerve heads. Increased NOS-1 and NOS-2 may cause neurotoxicity, while NOS-3 might offer neuroprotection via vasodilation.
Area of Science:
- Ophthalmology
- Neuroscience
- Molecular Biology
Background:
- Primary open-angle glaucoma (POAG) is a leading cause of irreversible blindness.
- The role of nitric oxide (NO) in glaucoma pathogenesis is not fully understood.
- Nitric oxide synthase (NOS) enzymes produce NO, and their isoforms (NOS-1, NOS-2, NOS-3) have distinct functions.
Purpose of the Study:
- To investigate the hypothesis that nitric oxide contributes to neurotoxicity in the optic nerve heads of patients with primary open-angle glaucoma.
- To determine the presence and localization of the three NOS isoforms in glaucomatous and normal optic nerve head tissue.
Main Methods:
- Immunohistochemistry was used to study optic nerve head tissue from normal subjects and POAG patients.
- Polyclonal antibodies against NOS-1, NOS-2, and NOS-3 were employed.
- Immunoperoxidase staining localized the NOS isoforms within the tissue.
Main Results:
- NOS-1 was sparsely present in normal optic nerve heads but abundant in astrocytes of glaucomatous optic nerve heads.
- NOS-2 was induced in the lamina cribrosa of glaucomatous eyes, absent in normal tissue.
- NOS-3 was found in vascular endothelia of normal eyes and in astrocytes and vascular endothelia of glaucomatous eyes.
Conclusions:
- All three NOS isoforms are present in increased amounts in the optic nerve head in POAG.
- Elevated NOS-1 and induced NOS-2 suggest excessive, potentially neurodestructive, nitric oxide levels.
- Increased NOS-3 in vascular endothelia may offer neuroprotection through vasodilation and improved blood flow.