Conditioning of liver grafts by donor bolus pretreatment with epoprostenol

GPR120 on Kupffer cells mediates hepatoprotective effects of ω3-fatty acids

BACKGROUND & AIMS

Many of the beneficial effects of ω3-fatty acids (ω3FAs) are being attributed to their anti-inflammatory properties. In animal models, ω3FAs also protect from hepatic ischemia reperfusion injury (IRI), a significant cause of complications following liver surgery. Omegaven®, a clinical ω3FA-formulation, might counteract the exaggerated inflammatory response underlying IRI, but the according mechanisms are unresearched. Recently, GPR120 has been identified as a first receptor for ω3FAs, mediating their anti-inflammatory effects. Here, we sought to investigate whether Omegaven® protects from hepatic IRI through GPR120.

METHODS

Using a mouse model of liver IRI, we compared the effects of a GPR120 agonist with those of Omegaven®.

RESULTS

GPR120 in liver was located to Kupffer cells (KCs). Agonist and Omegaven® provided similar protection from IRI, which was abolished by clodronate-depletion of KCs or by pretreatment with an αGpr120-siRNA. In vitro and in vivo, both agents dampened the NFκB/JNK-mediated inflammatory response. Dampening was associated with an M1>M2 macrophage polarization shift as assessed by marker expression. In αGpr120-siRNA-pretreated mice with or without ischemia, Omegaven® was no more able to promote M2 marker expression, indicating its anti-inflammatory properties are dependent on GPR120 in liver.

CONCLUSIONS

These findings establish KC-GPR120 as a key mediator of Omegaven® effects and suggest GPR120 as a therapeutic target to mitigate inflammatory stress in liver.

[Technique of liver procurement in postmortem donation]

BACKGROUND

The procurement of the liver is a standardized surgical procedure in the hands of qualified transplantation and organ procurement surgeons which is defined in the German guidelines.

METHODS

Literature review and discussion of critical aspects concerning the procurement of liver allografts. The procurement of livers should be performed by qualified transplantation and organ procurement surgeons (certification). The technique is standardized in German guidelines. A thoracotomy can help to optimize exposition which is essential to avoid technical complications and injuries to the graft especially in a training situation. Dissection in the cold is recommended. Knowledge of the anatomic variations of the hepatic artery is essential in procuring liver allografts. Documentation of errors and anatomic variations, packing of organs and a standardized closure of the thorax and abdomen are obligations of the responsible leading organ procurement surgeon.

Heat preconditioning ameliorates hepatocyte viability after cold preservation and rewarming, and modulates its immunoactivity

BACKGROUND

Heat preconditioning significantly preserved liver graft function after cold preservation in animal experimental model. The elevation of heat shock protein 70 (HSP70) was claimed to play a critical role in protecting grafts against cold preservation-induced hepatocyte apoptosis. However, little is known about whether HSP70 also plays an immunomodulatory role in cold preserved cells. This study aimed at investigating the relationship between HSP70 protein and the immunoactivity in response to lipopolysaccharide (LPS) stimulation.

METHODS AND RESULTS

A normal rat hepatocyte cell line was preserved with University of Wisconsin (UW) solution, Ringer's lactate solution (RL), and phosphate-buffered saline (PBS) at 4 degrees C. No significant morphological alteration was noted in UW-preserved cells after 24 h through phase-contrast microscopic observation and fluorescent viability stain. Western blotting showed a two-fold increase in the ratio of HSP70/Bax proteins in cells after 24 h of UW preservation. Heat preconditioning significantly enhanced the recovery of lactate dehydrogenase (LDH) activity in both RL- and UW-preserved cells that were stored for a period of 12 h or less. Moreover, heat preconditioning promoted HSP70 and NF-kappaB p50 nuclear translocation and suppressed the LPS-induced nuclear p50 accumulation in cells before UW preservation. Immunofluorescent stain revealed that the LPS-induced p50 protein redistribution to nuclear membrane might contribute to NF-kappaB activation, while heat preconditioning and UW cold preservation completely abrogated the p50 intranuclear redistribution. Thus NF-kappaB p50 might be responsible for the endotoxin tolerance induction.

CONCLUSIONS

These findings strongly suggest that heat preconditioning not only preserves hepatocyte viability after cold preservation and rewarming, but also ameliorates its immunoactivity.

Conditioning of liver grafts with prostaglandins improves bile acid transport

INTRODUCTION

Conditioning of liver grafts by bolus pretreatment with prostaglandins has been previously demonstrated to improve hepatic bile flow. However, the underlying mechanisms have not been investigated. To elucidate whether improved bile flow after prolonged ischemia is due to maintained bile acid secretion or due to increased paracellular permeability, we performed a study using increasing doses of the marker acid taurocholate in the isolated perfused rat liver system.

METHODS

Livers were harvested from adult Lewis rats and stored for 24 hours in UW solution. Pretreatment of livers was performed 1 minute before preservation. One group received prostaglandin I2, the second group received prostaglandin E1, and the control group was treated with saline. After 24 hours of cold storage the grafts were investigated in the isolated perfused rat liver system by perfusion with an oxygenated Krebs-Ringer-Henseleit buffer. Increasing doses of the radiolabeled marker bile acid taurocholate were infused to investigate bile acid transport.

RESULTS

Bile flow and bile acid output were increased by pretreatment of the livers with prostaglandin I2 and prostaglandin E1, as compared to the control group. More specifically, the maximum transport rate was tripled by prostaglandin I2 and by prostaglandin E1 preconditioning of liver grafts, in comparison to the control group (P < .01 vs prostaglanin I2 and E1).

CONCLUSION

The results clearly demonstrate that increased bile flow after conditioning of liver grafts with prostaglandins is not due to increased paracellular permeability but is based on markedly improved bile acid output.

The protective effect of erythropoietin on ischaemia/reperfusion injury of liver

BACKGROUND

Besides its haematopoietic effect, erythropoietin (EPO) has multiple protective effects, i.e. antiapoptotic, antioxidant and angiogenic properties. The neuroprotective effects of EPO against ischaemia have all been demonstrated in cell culture and animal models. The aim of the study was to evaluate the effect of erythropoietin on ischaemia-reperfusion injury (I/R injury) of the liver.

METHODS

Forty-eight adult male Sprague-Dawley rats weighing 250-300 g were divided into three groups: group I, hepatic ischaemia-reperfusion (Hepatic I/R); group II, hepatic ischaemia-reperfusion + EPO (Hepatic I/R+ EPO); group III, sham. Hepatic ischaemia was created by placing a microvascular clamp on the hepatic pedicle for 45 minutes. EPO was given to group II at a dose of 1000 U/kg 120 minutes before the onset of the ischaemia. Blood samples and liver tissues were obtained after 45 minutes of reperfusion from half of the rats in each group. The remaining rats were killed after a 24-hour observation period and blood and tissue samples were obtained. Blood alanine aminotransferase, tumour necrosis factor-alpha (TNF-alpha), interleukin-2 (IL-2) and liver tissue malondialdehyde (MDA) levels were determined. Liver tissue histopathology was also evaluated by light microscopy.

RESULTS

In rats with hepatic ischaemia, serum levels of ALT, TNF-alpha, IL-2 and liver tissue levels of MDA were reduced by the administration of erythropoietin and the histopathological score was also less severe.

CONCLUSION

This study demonstrates that pre-ischaemic administration of EPO has protective effects on hepatic I/R injury.

Protective effect of heat preconditioning of rat liver graft resulting in improved transplant survival

BACKGROUND

The protective effect of heat preconditioning of the liver against ischemia-reperfusion injury has been reported mostly in models of transient ischemia in relation to heat shock protein 70 (HSP70). We estimated the effect of heat preconditioning of liver grafts on the transplant survival rate and on apoptosis of sinusoidal endothelial cells (SEC) as well as hepatocytes in a rat model of liver transplantation.

METHODS

Donor rats of the heat shock (HS) group were subjected to heat preconditioning 48 hr before graft harvest, and HSP70 levels were estimated by. Western blot analysis and immunohistochemistry. The liver isografts from the HS group and control (C) group were preserved in Euro-Collins solution for 6 or 8 hr and transplanted orthotopically. Serum hyaluronic acid and alanine aminotransferase were measured, and apoptosis of the SEC and hepatocytes was analyzed by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling staining and electron microscopy.

RESULTS

HSP70 expression was detected not only in hepatocytes but also in SEC. In the 8-hr preservation model, the 1-week survival rate was 60% in the HS group and 0% in the C group. Serum hyaluronic acid and alanine aminotransferase levels in the HS group were significantly lower than those in the C group at 3 hr after reperfusion, and the number of terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling-positive SEC in the C group (35.2%) was markedly increased compared with the HS group (10.1%). Electron microscopic examination confirmed the features of apoptosis of SEC.

CONCLUSIONS

Heat preconditioning of the graft improved the survival rate of the liver transplants. Induction of HSP70 in SEC as well as in hepatocytes might attenuate preservation-reperfusion injury by inhibiting apoptosis of SEC.

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.

Preconditioning of donor livers with prostaglandin I2 before retrieval decreases hepatocellular ischemia-reperfusion injury

BACKGROUND

Prostaglandins have been shown to protect against a variety of liver insults, including ischemia-reperfusion injury. Decreased graft injury and improved survival have been demonstrated in animal studies of liver transplantation after donor pretreatment with prostaglandin before organ retrieval. This potential clinical application has not been examined in human subjects.

PATIENTS AND METHODS

One hundred and six liver donors were randomly assigned to receive either prostaglandin I2 (epoprostenol, 500 microg intravenous bolus) immediately before cold perfusion or no drug as control. Donor and recipient characteristics were recorded, and liver function tests were monitored after transplant to assess the effect of epoprostenol on graft injury.

RESULTS

Donor pretreatment with epoprostenol significantly improved the rapidity and homogeneity of graft reperfusion. Epoprostenol pretreatment also significantly reduced peak values of transaminases after transplantation: serum glutamic-pyruvic transaminase, control (851+/-121 international units [IU]/L) and epoprostenol (463+/-78 IU/L); serum glutamic-oxalaacetic transaminase, control (870+/-127 IU/L) and epoprostenol (463+/-78 IU/L); serum glutamate dehydrogenase, control (458+/-95 IU/L) and epoprostenol (170+/-30 IU/L); P<0.01 for all, by t test. Serum levels of bilirubin and alkaline phospatase were not significantly altered by donor pretreatment with epoprostenol.

CONCLUSIONS

Reduction of ischemia-reperfusion injury by administration of epoprostenol before graft retrieval may have important applications in liver transplantation. Further studies are required to establish the mechanism of this effect and to define its precise role in clinical practice.