MANGANIC PORPHYRINS POSSESS CATALASE ACTIVITY AND PROTECT ENDOTHELIAL-CELLS AGAINST HYDROGEN PEROXIDE-MEDIATED INJURY

Manganic porphyrins are redox active metal complexes that have been em ployed as superoxide dismutase mimics. We tested whether these metallo porphyrins could also dismute hydrogen peroxide (H2O2) and whether the y could protect endothelial cells against H2O2. Both of the manganic m etalloporphyrins tested were found to catalytically dismute H2O2. Thes e manganic porphyrins also protected endothelial cells in dose-depende nt manners against H2O2-mediated injury with MnTMPyP having an EC50 of 8 mu M and MnTBAP having an EC50 of 15 mu M. The zinc containing anal ogs of these porphyrins were inactive in dismuting H2O, and did not pr otect. These studies further define the antioxidant capacity of metall oporphyrins in converting superoxide to H2O2 and H2O2 to water. These data suggest that manganic porphyrins may be useful therapeutics again st disease states associated with the overproduction of reactive oxyge n species. (C) 1997 Academic Press.