Irreversible Caspase-3-Inhibition verringert Apoptose und verbessert das Überleben nach Lebertransplantation an der Ratte

Abstract

Ischemia and reperfusion injury is of critical importance for organ survival and function in liver transplantation. It induces apoptosis which is executed by caspases. Futhermore, apoptosis may be regulated by the rheostat of pro- and anti-apoptotic proteins of the bcl-2 family. Bcl-2 levels can be influenced by caspase 3 inhibition. Aim of this study was to investigate the effect of an irreversible inhibitor of caspase 3 on early graft function, survival and hepatic bcl-2 expression after liver transplantation. Lewis rats underwent syngenic, orthotopic liver transplantation with arterial reconstruction following 16 hours graft storage in UW (4°C). Donor animals and grafts (preservation and flush solution) were treated with the caspase 3 inhibitor Z-DEVD-FMK. Animals treated either with a control protein (Z-FA-FMK) without inhibitory function, with the vehicle (DMSO/PBS) or animals transplanted without specific treatment served as controls. Survival was determined at 7 days after surgery, which was considered definite. As an indicator for early graft function, bile flow was measured during 100 min. following graft reperfusion. Liver tissue specimen were collected after 100 min. and after 7 days. TUNEL staining served for quantification of apoptotic cells. Bcl-2 and bcl-xL protein levels as well as caspase 3 expression were assessed by Western blot technique. Statistics were calculated by ANOVA and Kaplan-Meier/log-rank analysis. TUNEL staining revealed a significant reduction of apoptotic endothelial cells per high power field after caspase 3 inhibition as compared to controls. Survival after caspase inhibition was significantly improved in comparison to all control groups. Interestingly, this was not associated with enhanced bile production in the early postreperfusion phase indicating that early graft function was not altered. Bcl-2 protein levels were increased in the Z-DEVD-FMK group after 7 days. Caspase 3 inhibition therefore seems to be a potent therapeutical access for improvement of survival after ischemia and reperfusion injury in liver grafts. Besides inhibition of caspases this effect might be mediated by higher bcl-2 in the grafts.