Hemoglobin Toxicity in Experimental Bacterial Peritonitis Is Due to Production of Reactive Oxygen Species

Hemoglobin (Hb) is a toxic molecule responsible for the extreme lethality associated with experimental Escherichia coli peritonitis, but the mechanism has yet to be elucidated. Hb, but not globin, showed toxic effects in a live E. coli model but not in a model using killed E. coli. Methemoglobin, hematin, and the well-known Fenton reagents iron and iron-EDTA demonstrated the same lethal effect in E. coli peritonitis as Hb, while the addition of the Fenton inhibitors desferrioxamine (DF) and diethylenetriamine pentaacetate removed most of the cytotoxic activity of iron. Administration of a combined dose of superoxide dismutase and catalase minimized the action of Hb and iron-EDTA, suggesting that both O2˙ 2 and H2O2 are involved in the toxic action of Hb in this rat model. The combination of the antioxidative enzymes and DF further suppressed iron-mediated lethality. An electron spin resonance technique with the spin-trapping reagent 5,5-dimethyl-1-pyroline-N-oxide (DMPO) showed O2˙ 2 generation in the peritoneal fluid of rats injected with E. coli alone or E. coli plus iron