Calpain inhibition prevents sinusoidal endothelial cell apoptosis in the cold ischemic rat liver

Background. Cold preservation of the liver followed by reperfusion results in sinusoidal endothelial cell (SEC) apoptosis. Calpain-like activity is dr amatically increased during reperfusion and inhibition of calpains results in lower graft injury and longer survival. Recently, calpains have been imp licated in inducing apoptosis. Our aim was to determine the effect of calpa in inhibition on SEC apoptosis. Methods. Livers were stored in the University of Wisconsin solution for 24 hr (survival conditions) and 40 hr (nonsurvival conditions) and ex vivo rep erfused for 1 hr at 37 degrees C. Calpain-like activity was inhibited in so me experiments using an i.p. injection of a selective inhibitor 2 hr before explantation. Apoptosis was quantified using the terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling assay. Cross-inhibition by the inhibitor was determined for caspases 1 and 3. Results. Apoptosis of exclusively the SEC was a key feature of reperfusion injury after both storage periods in University of Wisconsin solution after 1 hr normothermic reperfusion. Inhibition of calpain activity with Cbz-Val -Phe methyl ester resulted in a 50% reduction of apoptotic SEC in the 40-hr preserved liver, and an almost complete abrogation of SEC apoptosis after 24 hr preservation. Only minimal cross-inhibition of caspases was determine d at high concentrations in vitro by the calpain inhibitor. Conclusion. Apoptosis of exclusively SEC is a key feature of reperfusion in jury partially mediated through calpain-dependent processes. Calpain inhibi tion reduces the number of apoptotic SEC. Based on these data and our previ ous work, calpain inhibition may prove to be useful in clinical transplanta tion.