COVALENT CROSS-LINKING OF THE HEME PROSTHETIC GROUP TO MYOGLOBIN BY H2O2 - TOXICOLOGICAL IMPLICATIONS

It is known that treatment of myoglobin with H2O2 leads to covalent al teration of the heme prosthetic group with concomitant formation of a protein bound heme adduct and transforms myoglobin from an Oxygen stor age protein to an oxidase. In the current study it was shown, with the use of C-14-labeled heme reconstituted into apomyoglobin, that up to 88% of the oxidatively altered heme can be accounted for by the protei n bound product. Furthermore, a partially purified preparation of the protein hound heme adduct was introduced into human fibroblasts using the method of osmotic lysis of pinosomes and found to cause cell death (40%) within 1 h, as evidenced by trypan blue exclusion. Native myogl obin introduced into cells in the same manner or extracellular treatme nt by the protein bound heme adduct had no effect on cell viability. T he extent of cell death could be decreased (50%) by N-acetyl-L-cystein e, indicating a potential role for reactive oxygen intermediates in th is Process These results show that the covalently altered myoglobin ca n elicit cellular damage and suggests that similar processes may occur in vivo in pathologic conditions such as that involving cardiac ische mia and reperfusion injury, where covalently altered myoglobin may for m.