Oxidative stress induces heme oxygenase-1 immunoreactivity in Muller cellsof 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 str ess agents. METHODS. Enucleated eyes from young adult C3H mice were immediately fixed a nd cryosectioned and the retina sections processed for immunocytochemistry with antibodies against HO-1 and glial fibrillary acidic protein (GFAP). Fr om other eyes retinas were isolated and maintained in organ culture, either untreated for 4 days maximum or for 21 hours during which the explants wer e treated the first 3 hours with selected doses of sodium arsenate or hydro gen 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-I and GFAP immunolabeling in Mul ler cells of explanted retinas. Both sodium arsenate and hydrogen peroxide further induced strong HO-1 IR in Muller cells but not in other retinal cel ls. In contrast to HO-1, GFAP staining in Muller cells was not altered as a result of treatment, either by sodium arsenate or hydrogen peroxide at any concentration used. CONCLUSION. 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 expr ession is confined exclusively to Muller cells.