Repetitive ischemia/reperfusion potentiates hepatocellular death by apoptosis

Pretreatment with calcitonin gene-related peptide attenuates hepatic ischemia/reperfusion injury in rats

OBJECTIVE

Oxygen free radicals and apoptosis play important roles in liver ischemia/reperfusion (I/R) injury. We sought to investigate the protective effect of calcitonin gene-related peptide (CGRP) to attenuate liver I/R injury due to oxygen free radicals and apoptosis.

MATERIALS AND METHODS

Harvested rat livers were perfused via the portal vein with 60 mL of 4 degrees C histidine-tryptophan-ketoglutarate (HTK) solution alone in the control group, or with the same solution containing CGRP (3 microg/10 g body weight) in the experimental group. After 24 hours of cold storage, hepatic enzyme leakage, portal venous pressure, oxygen consumption, total adenine nucleotides (TAN), bile production, lipoperoxide (LPO) release, apoptosis, and histochemical changes were evaluated upon 45 minutes of isolated reperfusion.

RESULTS

Compared with control livers, CGRP-treated organs showed significantly decreased alanine aminotransferase (ALT) and glutamate-lactate dehydrogenase (GLDH) leakage and portal venous pressure (2.0 +/- 0.3 vs 4.0 +/- 0.4 mmHg; P < .01), with significantly increased bile production (8.56 +/- 0.76 vs 3.34 +/- 0.68 microL/g/45 min; P < .01), oxygen consumption (5.14 +/- 0.4 vs 2.57 +/- 0.2 microL/g/min; P < .01), and total adenine nucleotides (TAN) (11.1 +/- 0.71 vs 7.02 +/- 0.53 micromol/g; P < .01) upon reperfusion as signs of recovered viability. We observed infrequent positive terminal deoxynucleotidyl transferase-mediated dUTP biotin nick end labeling (TUNEL) staining, especially in sinusoidal lining cells (SLC). The percentage of TUNEL-positive cells in the CGRP group was significantly decreased compared with the control group: (4.1 +/- 0.67 vs 8.0 +/- 1.27; P < .05). Perfusate levels of low molecular weight (LMW) histone-associated DNA fragments (0.36 +/- 0.04 vs 0.53 +/- 0.06 AU; P < .05) were also decreased, coupled with strong 5'-nucleotidase (5'-NT) and LDH activity staining concentrated on the endothelial cells. LPO release in the perfusate was largely decreased: (0.12 +/- 0.02 vs 0.36 +/- 0.04 nmoL/g, P < .01).

CONCLUSION

CGRP ameliorated liver I/R injury due to reactive oxygen species and apoptosis.

Reduced Liver Apoptosis After Venous Systemic Oxygen Persufflation in Non-Heart-Beating Donors

Graft injury caused by warm ischemia in livers from non-heart-beating donors (NHBDs) strongly affects posttransplantation outcome and is associated with liver apoptosis, which is mediated by death receptors, such as Fas, a surface receptor of the tumor necrosis factor (TNF)-alpha family. The aim of this study was to test the ability of venous systemic oxygen persufflation (VSOP) to reduce apoptotic changes and Fas activation in the liver after warm ischemic insult in vivo. Livers of male Wistar rats were harvested 30 min after cardiac arrest from non-heart-beating donors (NHBD) with (NHBD + O2) or without (NHBD) application of gaseous oxygen during the cold storage period via the suprahepatic caval vein. After 24 h of storage in University of Wisconsin solution at 4 degrees C, viability of the livers was assessed upon isolated reperfusion in vitro. Conventional signs of tissue damage like enzyme release and bile production showed a significantly elevated nonspecific cell injury in the NHBD group. TUNEL staining revealed increased DNA fragmentation of sinusoidal endothelial cells in the NHBD group and more apoptotic hepatocytes than in the control group. All these alterations could be almost abrogated by the use of VSOP in the NHBD + O2 group. The immunohistochemical staining of Fas antigen expression showed a significantly elevated Fas receptor expression in the NHBD and NHBD + O2 groups, in accord with an eightfold increase of Fas receptor mRNA detected by real-time reverse-transcription polymerase chain reaction (RT-PCR). These results demonstrate that the postischemic apoptotic rate of sinusoidal endothelial cells in NHBD livers can be reduced by the use of VSOP. A significant improvement in liver integrity and viability was obtained with this technique, without influencing the expression of Fas expression.

Preconditioning with the prostacyclin analog epoprostenol and cobra venom factor prevents reperfusion injury and hyperacute rejection in discordant liver xenotransplantation

Liver xenografts transplanted from guinea pig to rat suffer from inadequate organ reperfusion and initial dysfunction, despite sufficient complement depletion using cobra venom factor (CVF). Reperfusion injury is prevented when complement depleted donors are treated with the prostacyclin analog epoprostenol. Histological analysis suggests that epoprostenol preconditioning prevents post-reperfusion spasms of the intrahepatic branches of the portal vein and strongly reduces appearance of hepatocyte apoptosis shortly after transplantation. Cobra-venom-treated rats show breakdown of glucose metabolism and die in acute hypoglycaemia, whereas the additional application of epoprostenol restores gluconeogenesis. Consequently, recipient survival after epoprostenol and CVF treatment is significantly improved compared with animals receiving CVF only (5.1 +/- 2.6 h vs. 17.9 +/- 5.1 h). These data demonstrate that initial dysfunction of discordant liver grafts in the guinea-pig-to-rat species combination, can be overcome by the application of epoprostenol combined with CVF. Using this pharmacologic regimen, the discordant guinea-pig-to-rat model appears useful to study further questions concerning functional and immunological compatibility of a discordant liver xenograft.