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S Gaun, K Ohta, T Kikuchi, T Kurokawa, N Yoshimura; Protective Role of Heme Oxygenase-1 on Retinal Ischemia-Reperfusion Injury in Rats . Invest. Ophthalmol. Vis. Sci. 2002;43(13):662.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To evaluate the expression of heme oxygenase-1 (HO-1), which is a heme-catabolizing enzyme induced by oxidative stress and acts against oxidant-induced tissue injury, on ischemia-reperfusion injury in the rat retina. Methods: Retinal ischemia was induced in male 8weeks SD rats by increasing the intraocular pressure to 110 mmHg for 45 minutes. At 6, 12, 24, and 48 hours after reperfusion, rat eyes were enucleated. Expression of HO-1 and HO-2, a constitutive isoform, in mRNA level in the retina was determined by using RT-PCR and that of protein levels were also studied by using Western blotting analysis. For immunohistochemical double-labeling, sections were incubated with antibodies against HO-1 and S-100. To evaluate possible neuroprotective effects of hemin, an inducer of HO-1, we injected 150 mg/kg of hemin intraperitoneally before the ischemia. The degree of retinal damage was assessed by electroretinogram (ERG) recording on 1, 2 and 4 weeks thereafter, by measuring the retinal thickness on day 28, and by counting the number of TdT-dUTP terminal nick-end labeling (TUNEL)-positive cells in the inner and outer nuclear layer. Results: The levels of HO-1 mRNA increased as early as 6 h after reperfusion, whereas those of HO-2 were expressed constitutively. HO-1 protein was expressed at 12 h and peaked at 24 h. HO-1-like immunoreactivities were detected in cell bodies of the inner nuclear layer, in processes of the inner plexiform layer and in the outer nuclear layer. Those HO-1 positive cells were also stained with S-100, a marker of Müller cells. The amplitudes of the ERG b-wave were increased significantly in rats with hemin-treatment compared with those without it (P < 0.05). On day 28 after reperfusion, the thicknesses of retina were increased in rats with hemin treatment, compared with those without. The number of TUNEL-positive cells on day 1 after reperfusion was decreased significantly in hemin-treated rats (P < 0.05). Conclusion: HO-1 was induced at least in Müller cells after ischemia-reperfusion injury in the rat retina. Up-regulation of HO-1 in the retina by hemin reduced cell death of retina. HO-1 may have neuroprotective effect against ischemia-reperfusion injury.
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