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RI Chang, D McCanna, CM Kalsow; Distribution of Heme Oxygenase-1 (HO-1) in Rabbit Cornea . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1678.
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Purpose: Heme oxygenase-1 (HO-1) also named heat shock protein 32 (Hsp32) is a molecular chaperone protein that can be induced in response to increased oxidative stress, hypoxia, heme, metals or inflammatory cytokines. Upregulation of HO-1 mRNA and protein have been measured in rabbit corneal epithelia in response to heme, metals, and inflammatory cytokines as well as hypoxia and oxidative stress (Biochem. Pharmacol. 53:1069, 1997). Homogenization of tissue for these quantitative studies precludes any localization of HO-1. The current immunohistochemical study demonstrates the distribution of HO-1 in rabbit cornea. Method: Corneas of 10 New Zealand white rabbits (2.5-3.5kg) were fixed in 95% ethanol and embedded in paraffin. HO-1 was detected using mouse anti-heme-oxygenase-1 monoclonal antibody (MAb HO-1) as the primary antibody. Distribution of immunoreactivity was visualized with a horseradish peroxidase mouse Envision+ System with DAB substrate. Specificity of reactivity was confirmed by comparison of reactivity patterns for other heat shock proteins, Hsp 47 and inducible and constitutive Hsp70. Results: HO-1 immunoreactivity in the corneal epithelium was primarily observed in the cytoplasm of basal epithelial cells. The reactivity throughout the corneal epithelium was not uniform, i.e., some areas had no reactivity while other areas had reactivity throughout the epithelium including wing and superficial cells. MAb HO-1 reacted consistently and uniformly with limbal vascular endothelium. The epithelial and endothelial patterns of reactivity with MAb HO-1 were distinct from those of the other hsp's tested. Conclusion: These experiments qualitatively demonstrate the distribution of HO-1 in normal rabbit cornea. The variability of expression in different areas of the corneal epithelium indicates the responsive nature of HO-1 expression to changes in the oxidative state of the microenvironment. Communication between the different layers of epithelium and the change in molecular machinery as cells mature from the basal layer to the more superficial area could play a role in the rapid response. Since corneal epithelium and limbal vascular endothelium are at the interface of the cornea with the external environment and the internal (vascular) environment of the cornea, HO-1 is a potentially important protective mechanism for this tissue. HO-1 expression may be exploited as an early indicator of corneal oxidative stress and/or as a means to enhance protection from oxidative stress. Support: Rochester Eye and Human Parts Bank and Bausch and Lomb, Inc.
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