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R. Rajendram, E. Gonzalez, N.A. Rao; Neuroglobin Expression Is Increased in the Retina of Human Eyes With Chronic Glaucoma . Invest. Ophthalmol. Vis. Sci. 2005;46(13):1313.
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Purpose:Neuroglobin is a newly discovered, neuron specific, heme protein. The function of this protein is uncertain at present. A recent study in the brain has shown that neuroglobin (Ngb) expression is specifically up–regulated by hypoxia and ischemia, and that it functions as a neuroprotectant under these conditions. Ngb is thought to be an efficient scavenger of reactive oxidizing species, minimizing cytoxicity when peroxynitrite or hydrogen peroxide are present. Ngb is found at a concentration that is 100 times higher in the retina (3% of all retinal protein) than in the brain. Using immunohistochemistry, we examined the pattern of Ngb expression in normal human retina, and searched for any changes when compared with its expression in the retina from glaucomatous eyes, where hypoxia and increased oxidative stress are believed to be key pathological factors. Methods: Sections of human retina were obtained from the files of the A. Ray Irvine Jr, Pathology laboratory of the Doheny Eye Institute at the University of Southern California. Paraffin sections were taken from three eyes with chronic glaucoma (adult and child) and sections from three eyes without glaucoma served as controls. The diagnoses were made on the basis of histological evidence from H&E sections and supported by the clinical case histories. Immunofluorescent sections were viewed and analyzed by confocal microscopy. Results:Markedly increased staining for Ngb protein was present in the inner and outer plexiform layers, with a less intense increase in the inner nuclear layer when the retina from eyes with chronic glaucoma was compared to that from control eyes without glaucoma. Expression of Ngb was not seen in the ganglion cell layers of the glaucoma or control retina. Ngb was present in the photoreceptor inner segments in both groups. Conclusions: In chronic glaucoma, the presence of increased neuroglobin protein in the plexiform layers which are rich in mitochondria, as well as the inner nuclear layer, are consistent with its putative function as a neuroprotectant under conditions of increased oxidative stress. The absence of neuroglobin in the ganglion cell layer may contribute to the relative inability of these cells to survive the hypoxia and increased oxidative stress, which are thought to be major factors in the pathogenesis of chronic glaucoma.
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