Bilirubin and ferritin as protectors against hemin-induced oxidative stress in rat liver

The in vivo effect of hemin on both hepatic oxidative stress and heme oxygenase induction was studied. A marked increase in lipid peroxidation was observed 1 hr after hemin administration. Heme oxygenase-1 activity and expression appeared 6 hr after treatment, reaching a maximum between 12 and 15 hr after hemin administration. Such induction was preceded by a decrease in the soluble and enzymatic defenses, both effects taking place some hours before induction of heme oxygenase. Ferritin content began to increase 6 hr after heme oxygenase induction, and these increases were significantly higher 15 hr after treatment and remained high for at least 24 hr after hemin injection. Co-administration of tin protoporphyrin IX, a potent inhibitor of heme oxygenase, completely prevented the enzyme induction and the increase in ferritin levels, increasing the appearance of oxidative stress parameters. Administration of bilirubin, prevented the heme oxygenase induction as well as the decrease in hepatic GSH and the increase of lipid peroxidation when it was administered 2 hr before hemin treatment. These results indicate that the induction of heme oxygenase by hemin may be a general response to oxidant stress, by increasing bilirubin and ferritin levels and could therefore provide a major cellular defense mechanism against oxidative damage.