JPET #83493 1 Protective Mechanisms of a Metalloporphyrinic Peroxynitrite Decomposition Catalyst, WW85, in Rat Cardiac Transplants

NO derived from iNOS has been implicated in cardiac rejection. However, little is known about the role of the reactive nitrogen species, peroxynitrite. We examined the protective actions of a peroxynitrite decomposition catalyst WW85 in an experimental model of acute cardiac rejection. Heterotopic, abdominal transplantation of rat donor hearts was performed. Groups included: isografts, allografts or allografts treated with either WW85, cyclosporine or cyclosporine + WW85. We determined graft survival, histological rejection and graft function (by in situ sonomicrometry). Intragraft biochemical analysis of cytokines, pro-apoptotic and anti-apoptotic gene expression using RT-PCR were determined. Treatment with WW85 or cyclosporine alone prolonged graft survival, improved graft function and decreased histological rejection. Graft survival was further significantly (P<0.001) enhanced by combination treatment. A decrease was also shown in nitrotyrosine, PARP activation and lipid peroxide formation by WW85 that was potentiated when given in combination with cyclosporine. Benefits could not be ascribed to changes in intragraft myeloperoxidase activity. Only combination therapy produced significant decreases in inflammatory cytokine gene expression suggesting that WW85 acted primarily downstream of these stimuli. In general, WW85 had no direct action on expression of the pro-apoptotic gene, Fas ligand; however, WW85 given alone or with cyclosporine enhanced expression of anti-apoptotic genes, Bcl-2 and Bcl-xL. Collectively, these findings suggest a protective action of the peroxynitrite decomposition catalyst, WW85, on graft rejection that is independent of any action on leukocyte sequestration and cytokine gene expression. Rather, effects appear to be downstream on decreased protein nitration, decreased lipid peroxidation and decreased PARP activation. This article has not been copyedited and formatted. The final version may differ from this version. JPET Fast Forward. Published on March 22, 2005 as DOI: 10.1124/jpet.105.083493 at A PE T Jornals on July 9, 2017 jpet.asjournals.org D ow nladed from