Oxidative stress induces heme oxygenase-1 immunoreactivity in Müller cells of mouse retina in organ culture.

PURPOSE Heme oxygenase (HO)-1 immunoreactivity (IR) was examined in normal untreated retina and in retinal explants after in vitro treatment with stress agents. METHODS Enucleated eyes from young adult C3H mice were immediately fixed and cryosectioned and the retina sections processed for immunocytochemistry with antibodies against HO-1 and glial fibrillary acidic protein (GFAP). From other eyes retinas were isolated and maintained in organ culture, either untreated for 4 days maximum or for 21 hours during which the explants were treated the first 3 hours with selected doses of sodium arsenate or hydrogen peroxide. Thereafter, the explants were processed identically with the normal tissue. RESULTS In the normal retina, HO-1 and GFAP IR was very low. The culturing itself resulted in an increase in both HO-1 and GFAP immunolabeling in Müller cells of explanted retinas. Both sodium arsenate and hydrogen peroxide further induced strong HO-1 IR in Müller cells but not in other retinal cells. In contrast to HO-1, GFAP staining in Müller cells was not altered as a result of treatment, either by sodium arsenate or hydrogen peroxide at any concentration used. CONCLUSIONS The results show for the first time that HO-1 can be induced in the retina in vitro by conditions of oxidative stress and that enzyme expression is confined exclusively to Müller cells.