Antagonizing reactive oxygen by treatment with a manganese (III) metalloporphyrin-based superoxide dismutase mimetic in cardiac transplants.
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. MnTmPyP inhibited antiapoptotic gene expression (Bcl-2 and Bcl-xL) during early rejection but restored expression at later stages. The increase in activated caspase-3 levels in allografts was inhibited by MnTmPyP.


CONCLUSIONS
The mechanism of the beneficial effect of MnTmPyP on graft function appear related, in part, to scavenging O2*- and by decreasing apoptotic signaling rather than an effect on inflammatory cytokine gene expression.
Department of Surgery, Division of Transplant Surgery, Medical College of Wisconsin, Milwaukee, Wis 53226, USA.
Vani
V
Nilakantan
Xianghua
X
Zhou
Gail
G
Hilton
Yang
Y
Shi
John E
JE
Baker
Ashwani K
AK
Khanna
Galen M
GM
Pieper
D000818:Animals; D017209:Apoptosis / Q000502:physiology; D053148:Caspase 3; D020169:Caspases / Q000032:analysis; D016207:Cytokines / Q000032:analysis; D016027:Heart Transplantation / Q000502:physiology; D049449:Luminescence; D008665:Metalloporphyrins / Q000494:pharmacology*; D023421:Models, Animal; D018384:Oxidative Stress; D051381:Rats; D011917:Rats, Inbred Lew; D011920:Rats, Inbred WF; D017382:Reactive Oxygen Species / Q000037:antagonists & inhibitors*; D020133:Reverse Transcriptase Polymerase Chain Reaction
D016207:Cytokines; D008665:Metalloporphyrins; C502230:Mn(III) 5,10,15,20-tetrakis(N-methylpyridinium-2-yl)porphyrin; D017382:Reactive Oxygen Species; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases