Objective To determine the distribution of 2 intracellular oxygen-carrying molecules, neuroglobin (NGB) and cytoglobin (CYGB), in specific retinal cell types of human retinas.

Methods Specific antibodies against NGB and CYGB were used in immunohistochemical studies to examine their distribution patterns in human retinal sections. Double-labeling studies were performed with the anti-NGB and anti-CYGB antibodies along with antibodies against neuronal (microtubule-associated protein 2, class III β-tubulin [TUJ1], protein kinase C alpha, calretinin) and glial (vimentin, glial fibrillary acid protein) markers. Confocal microscopy was used to examine the retinal sections.

Results Immunohistochemical analysis of human retinal tissue showed NGB and CYGB immunoreactivity in the ganglion cell layer, inner nuclear layer, inner and outer plexiform layers, and retinal pigment epithelium. Neuroglobin immunoreactivity was also present in the outer nuclear layer and photoreceptor inner segments. Neuroglobin and CYGB were coexpressed in the neurons in the ganglion cell layer and inner nuclear layer but not within glial cells.

Conclusion Neuroglobin and CYGB are colocalized within human retinal neurons and retinal pigment epithelium but not within glial cells.

Clinical Relevance Our results suggest that NGB and CYGB may serve a neuroprotective role as scavengers of reactive oxygen species and therefore should be considered when developing therapeutic strategies for treatment of hypoxia-related ocular diseases.