Abstract
ABSTRACT
Heme oxygenase, the rate-limiting enzyme in the degradation of heme to bile-pigments and carbon monoxide, is induced in response to increased oxidative stress and is believed to provide a cytoprotective effect. We investigated the role of heme oxygenase in cultured rabbit corneal epithelial cells (RCE), and its potential to alleviate oxidative stress-induced cell damage. Heme oxygenase in RCE was effectively and potently induced by most metals tested, including tin, silver, and gold, and cytokines such as IL-6, and TGFβ. Stannous chloride and heme-induced heme oxygenase mRNA by 40 and 100 fold within 1-3 hours and increased enzyme activity by 9.2- and 10-fold, respectively, over a 24 hour period. IL-6, TGFβ and H2O2 induced heme oxygenase by 2-3 fold. Zinc protoporphyrins were effective inhibitors of heme oxygenase activity in vitro. However, when incubated with cells for 24 h they induced heme oxygenase mRNA but decreased or had no effect on its activity.
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