SLPI LIMITS POSTISCHEMIC INFLAMMATION AND PREVENTS SEVERE MYOCYTE NECROSIS IN RESPONSE TO COLD ISCHEMIA AND HEART TRANSPLANTATION

Abstract

P74 Aims: SLPI is a 12 kD protein with an inhibitory effect on protease activity, crucially involved in wound healing and inflammatory cell activation. We previously demonstrated SLPI upregulation in response to cold ischemia and cardiac transplantation, in this study we analysed the effect of SLPI on graft function and morphology. Methods: Hearts from SLPI knockout mice (SLPI−/−) were heterotopically transplanted to SLPI−/− recipients. Grafts underwent 10 hours of cold ischemia prior to transplantation or were transplanted immediately. C57Bl/6 wild type isografts (WT) undergoing the same procedure served as controls. In selected groups, recombinant SLPI (rSLPI) was given at 200μg i.v. after reperfusion. Hearts were removed at 15min, 12h, 24h and 10 days, graft function was assessed using a 4 point scoring system and morphology was investigated by HE histology. SLPI gene expression was analysed using real-time PCR (Taqman technology). SLPI protein expression was studied by immunohistochemistry using a monoclonal antibody (SLPI mAb Novocastra Lab.). Results: At 15min recovery of graft function was normal in WT and SLPI −/− mice transplanted without cold ischemia (4,0±0,0). In contrast, SLPI −/− hearts showed no or marginal recovery of organ function (0,36±0,51). At 24h cardiac function in SLPI −/− (2,8±0,89) was less when compared with WT (3,36±0,55), at 10 days, however, no difference was observed. Histology demonstrated a mild mononuclear cell infiltrate and small focal necrosis in all groups at 24h. At 10 days, postischemic inflammation as well as myocyte necrosis was significantly higher in the SLPI −/− group (2,5±0,5 vs 1,8±0,4 and 1,6±0,5 vs 0,2±0,4). In addition, myocyte vacuolisation as a sign of sublethal ischemic injury was present at high level in SLPI −/− mice undergoing prolonged cold ischemia only. Single administration of rSLPI did not alter graft function or morphology. Upregulation of SLPI gene expression was detected in WT groups at 12 and 24 hours after reperfusion. Gene transcription at 12h was significantly higher after prolonged cold ischemia (7,99 vs 1,57 orders of magnitude). SLPI protein as demonstrated by immunohistology was found 24 hours after reperfusion in WT groups. High levels of SLPI protein were observed 10 days after transplantation, SLPI-positive cells were mainly identified as macrophages. Conclusions: Herein we demonstrate, that SLPI has a substantial effect in prevention of inflammation and myocyte damage in response to ischemia and reperfusion of the heart. In addition, SLPI seems to be crucial for recovery of organ function early after heart transplantation and represents a promising target for modulating the destructive processes of postischemic inflammation while preserving its restorative nature.