Apoptosis of sinusoidal endothelial, cells occurs during liver preservation injury by a caspase-dependent mechanism

Background Cold ischemia/warm reperfusion (CI/WR) liver injury remains a pr oblem in liver transplants. Sinusoidal endothelial cells (SEC) are a target of CI/WR injury, during which they undergo apoptosis. Because caspase prot eases have been implicated in apoptosis, our aim was to determine whether l iver CI/WR injury induces a caspase-dependent apoptosis of SEC. Methods. Rat livers were stored in the University of Wisconsin (UW) solutio n for 24 hr at 4 degrees C and reperfused for 1 hr at 37 degrees C in vitro . Apoptosis was quantitated using the TUNEL assay, and caspase 3 activation determined by immunohistochemical analysis. Rat liver orthotopic liver tra nsplants (OLT) were also performed using livers stored for 30 hr. Results. Terminal deoxynucleotide transferase-mediated dUTP nick end labeli ng (TUNEL) positive hepatocytes were rare and did not increase during CI/WR injury. In contrast, TUNEL positive SEC increased 6-fold after reperfusion of livers stored under cold ischemic conditions, compared with controls or livers stored but not reperfused, Immunohistochemical analysis demonstrate d active caspase 3 only in endothelial cells after CI/WR injury. When IDN-1 965, a caspase inhibitor, was given i.v. to the donor animal and added to U W solution and the reperfusion media, TUNEL positive endothelial cells were reduced 63+/-11% (P<0.05). Similarly, the duration of survival after OLT w as significantly increased in the presence of the inhibitor. Conclusion. During liver CI/WR injury: 1) selective apoptosis of endothelia l cells occurs; 2) caspase 3 is activated only in endothelial cells; and 3) a caspase inhibitor reduces endothelial cell apoptosis and prolongs animal survival after OLT. The pharmacologic use of caspase inhibitors could prov e useful in clinical transplantation.