metalloporphyrin-based superoxide dismutase mimetic in cardiac transplants Antagonizing reactive oxygen by treatment with a manganese (III)

Objective: Oxidative stress might be an important factor contributing to injury during alloimmune activation. Herein, we evaluated the efficacy of a superoxide dismutase mimetic, manganese (III) tetrakis (1-methyl-4-pyridyl) porphyrin pentachloride (MnTmPyP), on cytokine gene expression and apoptotic signaling in a rat model of cardiac transplantation. Methods: Lewis - Lewis (isografts) or Wistar-Furth-Lewis (allografts) heterotopic rat transplants without and with treatment with MnTmPyP were used. Reactive oxygen formation was determined on the basis of dihydroethidine fluorescence and lucigenin-enhanced chemiluminescence. In situ graft function was determined by means of sonomicrometry. Inflammatory cytokine, proapoptotic, and antiapoptotic gene expression at either postoperative day 4 ( early rejection) or postoperative day 6 ( late rejection) was determined by means of reverse transcriptase polymerase chain reaction. Results: An increased production of reactive oxygen in allografts was inhibited to isograft control levels by MnTmPyP. MnTmPyP restored either the percentage of fractional shortening, the distended diastolic and systolic myocardial segment lengths, or both in allografts. Of the increases in cytokine and proapoptotic gene expression in allografts, only interleukin 6 was decreased by MnTmPyP. Conclusions: The mechanism of the beneficial effect of MnTmPyP on graft function appear related, in part, to scavenging O-2.(-) and by decreasing apoptotic signaling rather than an effect on inflammatory cytokine gene expression.