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 problem in liver transplants. Sinusoidal endothelial cells (SEC) are a target of CI/WR injury, during which they undergo apoptosis. Because caspase proteases have been implicated in apoptosis, our aim was to determine whether liver CI/WR injury induces a caspase-dependent apoptosis of SEC.


METHODS
Rat livers were stored in the University of Wisconsin (UW) solution 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 transplants (OLT) were also performed using livers stored for 30 hr.


RESULTS
Terminal deoxynucleotide transferase-mediated dUTP nick end labeling (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 demonstrated active caspase 3 only in endothelial cells after CI/WR injury. When IDN-1965, a caspase inhibitor, was given i.v. to the donor animal and added to UW solution and the reperfusion media, TUNEL positive endothelial cells were reduced 63+/-11% (P<0.05). Similarly, the duration of survival after OLT was significantly increased in the presence of the inhibitor.


CONCLUSIONS
During liver CI/WR injury: 1) selective apoptosis of endothelial 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 prove useful in clinical transplantation.
Natori
S
S
Division of Gastroenterology and Hepatology, Mayo Clinic Rochester, MN 55905, USA.
Selzner
M
M
Valentino
K L
KL
Fritz
L C
LC
Srinivasan
A
A
Clavien
P A
PA
Gores
G J
GJ
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism / Q000494:pharmacology*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004727:Endothelium / Q000166:cytology*; D004792:Enzyme Precursors / Q000378:metabolism; D007211:Indoles / Q000494:pharmacology; D008099:Liver / Q000166:cytology* / Q000187:drug effects / Q000293:injuries; D016031:Liver Transplantation; D009842:Oligopeptides / Q000494:pharmacology; D009926:Organ Preservation; D051381:Rats; D015427:Reperfusion Injury / Q000201:enzymology / Q000209:etiology
D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D004792:Enzyme Precursors; D007211:Indoles; C118798:N-((1,3-dimethylindole-2-carbonyl)-valinyl)-3-amino-4-oxo-5-fluoropentanoic acid; D009842:Oligopeptides; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases