Decreased survival in rat liver transplantation with extended cold preservation: role of portal vein clamping time

Carbon monoxide as an emerging pharmacological tool to improve lung and liver transplantation protocols

Carbon monoxide (CO) has long been considered purely as a toxic gas. It binds to hemoglobin at high concentrations and displaces oxygen from its binding site, resulting in carboxyhemoglobin formation, which reduces oxygen-carrying capacity of blood and culminates in tissue hypoxia and its associated complications. Recently, however, CO is quickly moving past its historic notorious tag as a poisonous gas to a physiological signaling molecule with therapeutic potentials in several clinical situations including transplant-induced injury. This review discusses current knowledge of CO gas and CO-releasing molecules (CO-RMs) in preclinical models of lung and liver transplantation, and underlying molecular mechanisms of cyto- and organ protection during organ procurement, preservation, implantation and post-transplant periods. In addition, a discussion of the future of CO in clinical organ transplantation is provided.

Interferon regulatory factor-1 activates autophagy to aggravate hepatic ischemia-reperfusion injury via the P38/P62 pathway in mice

Increasing evidence has linked autophagy to a detrimental role in hepatic ischemia- reperfusion (IR) injury (IRI). Here we focus on the role of interferon regulatory factor-1 (IRF-1) in regulating autophagy to aggravate hepatic IRI. We found that IRF-1 was up-regulated during hepatic IRI and was associated with an activation of the autophagic signaling. This increased IRF-1 expression, which was allied with high autophagic activity, amplified liver damage to IR, an effect which was abrogated by IRF-1 depletion. Moreover, IRF-1 contributed to P38 induced autophagic and apoptotic cell death, that can play a key role in liver dysfunction. The levels of P62 mRNA and protein were increased when P38 was activated and decreased when P38 was inhibited by SB203580. We conclude that IRF-1 functioned as a trigger to activate autophagy via P38 activation and that P62 was required for this P38-mediated autophagy. IRF-1 appears to exert a pivotal role in hepatic IRI, by predisposing hepatocytes to activate an autophagic pathway. Such an effect promotes autophagic cell death through the P38/P62 pathway. The identification of this novel pathway, that links expression levels of IRF-1 with autophagy, may provide new insights for the generation of novel protective therapies directed against hepatic IRI.

Intereukin-10 and Kupffer cells protect steatotic mice livers from ischemia-reperfusion injury

Steatotic livers are more sensitive to ischemia/reperfusion (I/R) and are thus routinely rejected for transplantation because of their increased rate of primary nonfunction (PNF). Lean livers have less I/R-induced damage and inflammation due to Kupffer cells (KC), which are protective after total, warm, hepatic I/R with associated bowel congestion. This protection has been linked to KC-dependent expression of the potent anti-inflammatory cytokine interleukin-10 (IL-10). We hypothesized that pretreatment with exogenous IL-10 would protect the steatotic livers of genetically obese (ob/ob) mice from inflammation and injury induced by I/R. Lean and ob/ob mice were pretreated with either IL-10 or liposomally-encapsulated bisphosphonate clodronate (shown to deplete KC) prior to total, warm, hepatic I/R. IL-10 pretreatment increased survival of ob/ob animals at 24 hrs post-I/R from 30% to 100%, and significantly decreased serum ALT levels. At six hrs post-I/R, IL-10 pretreatment increased IL-10 mRNA expression, but suppressed up-regulation of the pro-inflammatory cytokine IL-1β mRNA. However, ALT levels were elevated at six hrs post-I/R in KC-depleted animals. These data reveal that pretreatment with IL-10 protects steatotic livers undergoing I/R, and that phagocytically active KC retain a hepatoprotective role in the steatotic environment.

Differential bradykinin B1 and B2 receptor regulation in cell death induced by hepatic ischaemia/reperfusion injury

In the present study, we have demonstrated that the kinin B1 receptor may participate in apoptotic cell death signalling, whereas the B2 receptor may be involved in necrotic cell death during IRI.

Orthotopic liver transplantation in rats

Clinical progress in the field of liver transplantation has been largely supported by animal models(1,2). Since the publication of the first orthotopic rat liver transplantation in 1979 by Kamada et al.(3), this model has remained the gold standard despite various proposed alternative techniques(4). Nevertheless, its broader use is limited by its steep learning curve(5). In this video paper, we show a simple and easy-to-establish revision of Kamada's two-cuff technique. The suprahepatic vena cava anastomosis is performed manually with a running suture, and the vena porta and infrahepatic vena cava anastomoses are performed utilizing a quick-linker cuff system(6). Manufacturing the quick-linker kit is shown in a separate video paper.

Cyclosporin-A does not prevent cold ischemia/reperfusion injury of rat livers

Cyclosporin-A (CsA) has been reported to protect livers from warm ischemia/reperfusion (I/R) injury. To study if CsA has also a protective effect on cold I/R injury, two models were used: the isolated perfused rat liver (IPRL) and the orthotopic rat liver transplantation (ORLT). (1) IPRL: Livers were preserved for 24 h (5°C) in University of Wisconsin (UW) solution alone (group 1), with CsA (400 nM) dissolved in dimethylsulfoxide (50 μM) (group 2), and with dimethylsulfoxide (DMSO) alone (group 3). Livers were reperfused for 60 min (37°C) (n = 8/group). Cell necrosis was evaluated by trypan blue uptake and apoptosis by laddering and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay, and by caspase-3 activation. Marked and similar sinusoidal endothelial cell necrosis was found in the three groups while apoptosis was found similarly deceased in groups 2 and 3 compared with group 1. (2) ORLT: Donors received either CsA (5 mg/kg) or corn oil 24 h before transplantation. Recipients were sacrificed after 240 min; cell necrosis and apoptosis were then evaluated. No difference was found between treated and control groups. The current data strongly suggest that CsA has no protective effect on hepatic cold I/R injury. Hepatocyte apoptosis can be reduced by antioxidants, as occurred with DMSO, but introduction of CsA does not provide additional protective effect.

Protective effects of a carbon monoxide-releasing molecule (CORM-3) during hepatic cold preservation

There is increasing evidence that carbon monoxide (CO), a signaling molecule generated during the degradation of heme by heme oxygenase-1 (HO-1) in biological systems, has a variety of cytoprotective actions, including anti-hypoxic effects at low temperatures. However, during liver cold preservation, a direct effect needs to be established. Here, we designed a study to analyze the role of CO, delivered via a carbon monoxide-releasing molecule (CO-RM) in the maintenance of liver function, and integrity in rats during cold ischemia/reperfusion (CI/R) injury. We used an isolated normothermic perfused liver system (INPL) following a clinically relevant model of ex vivo 48 h cold ischemia stored in a modified University of Wisconsin (UW) solution, to determine the specific effects of CO in a rat model. CO was generated from 50 microM tricarbonylchloro ruthenium-glycinato (CORM-3), a water-soluble transition metal carbonyl that exerts pharmacological activities via the liberation of controlled amounts of CO in biological systems. The physiological effects of CORM-3 were confirmed by the parallel use of a specific inactive compound (iCORM-3), which does not liberate CO in the cellular environment. CORM-3 addition was found to prevent the injury caused by cold storage by improving significantly the perfusion flow during reperfusion (by almost 90%), and by decreasing the intrahepatic resistance (by 88%) when compared with livers cold preserved in UW alone. Also, CORM-3 supplementation preserved good metabolic capacity as indicated by hepatic oxygen consumption, glycogen content, and release of lactate dehydrogenase. Liver histology was also partially preserved by CORM-3 treatment.

CONCLUSIONS

These findings suggest that CO-RM could be utilized as adjuvant therapeutics in UW solutions to limit the injury sustained by donor livers during cold storage prior to transplantation, as has been similarly proposed for the heart, and kidney.

Evaluation of the mortality rate caused by different periods of selective portal vein occlusion in rats

Mortality from acute selective portal vein occlusion (SPVO) is a matter of concern for surgeons during the management of traumatic portal vein injury. However, mortality rates related to different periods of SPVO remains undetermined.

PURPOSE

To determine the mortality rates resulting from different periods of acute SPVO in rats.

METHODS

Wistar male rats were randomized into 8 experimental, and 8 control groups. Experimental animals underwent SPVO during 15 to 75 minutes, and control groups underwent sham procedures. All surviving animals were followed up to 14 days for assessment of mortality rate.

RESULTS

Death rates varied from 0% in the 15 min SPVO group, to 100% with 65 and 75 minutes of SPVO. A strongly positive correlation was observed between mortality rates and SPVO periods (p<0.001) with either linear or quadratic regression analysis tests. All deaths in the 20 min and 25 min SPVO groups occurred after 75 min from the moment of clamping (or after 60 min from unclamping); death from 30 or more min SPVO occurred predominantly within 75 min from clamping moment (or within 60 min from unclamping). (Exact Fisher test, p=0.009).

CONCLUSIONS

The mortality from SPVO in rats increases with longer duration of SPVO; with deaths occurring later for short periods (<or= 25 min) of SPVO and earlier for longer periods (>or= 30 min) of SPVO.

New evidence for the role of TNF-alpha in liver ischaemic/reperfusion injury

BACKGROUND

Tumour necrosis factor-alpha (TNF-alpha) plays a key role in causing ischaemia/reperfusion (I/R) injury. I/R also causes activation of xanthine oxidase and dehydrogenase (XDH + XO) system that, via generated free radicals, causes organ damage. We investigated the effect of ischaemia, reperfusion and non-ischaemic prolonged perfusion (NIP) on TNF-alpha and XDH + XO production in an isolated perfused rat liver model.

MATERIALS AND METHODS

Rat livers underwent 150 min NIP (control group) or two hours of ischaemia followed by reperfusion (I/R group). TNF-alpha (TNF-alpha mRNA and protein level), XDH + XO production and bile secretion were determined in tissue and effluent at baseline, at 120 min of ischaemia, after 30 min of reperfusion (I/R group) and after 120 and 150 min of prolonged perfusion (control).

RESULTS

Unexpectedly, neither ischaemia nor reperfusion had any effect on TNF-alpha production. TNF-alpha in effluent was 11 +/- 4.8 pg mL(-1) at baseline, 7 +/- 3.2 pg mL(-1) at the end of ischaemia, and 13 +/- 5.3 pg mL(-1) after 30 min of reperfusion. NIP, however, caused a significant increase of TNF-alpha synthesis and release. TNF-alpha effluent level after 120 and 150 min of perfusion was 392 +/- 78.7 pg mL(-1) and 408 +/- 64.3 pg mL(-1), respectively. TNF-alpha mRNA in tissue was also significantly elevated compared to baseline levels (1.31 +/- 0.2 P < 0.001 and 1.38 P < 0.002, respectively). Decrease of liver function (expressed by bile secretion) during I/R and NIP was accompanied by significant XDH + XO elevation.

CONCLUSION

This is the first evidence that NIP, and not I/R, is the decisive trigger for TNF-alpha production. This study leads to a better understanding of pathogenesis of liver I/R and perfusion damage.

Effect of cold ischemia-warm reperfusion on the cirrhotic rat liver

Cirrhosis is known to induce capillarization of the sinusoidal endothelial cells (SECs) and collagenization of the space of Disse, resulting in a reduced access of plasma and plasma-dissolved substances to hepatocytes due to their limited diffusion in the extravascular space. The aim of the present study was to use a well known effect of cold ischemia-warm reperfusion (CI-WR) on liver SECs, that is, their retraction and detachment, progressing to a denudation of the SEC lining. The disappearance of the capillarized SEC lining would improve the access of plasma and plasma-dissolved substances to the hepatocytes and consequently might improve the metabolic function of cirrhotic livers. This study was performed using the isolated perfused rat liver model subjected to 24-hour CI followed by a 60-minute WR in thioacetamide-induced cirrhosis. Liver microcirculation was evaluated using the multiple indicator dilution curve (MIDC) technique. Hepatocyte, SEC, and Kupffer cell functions were evaluated using specific elimination processes. As occurs in normal livers, CI-WR induced extensive SEC necrosis with a marked reduction of the hyaluronic acid elimination. By contrast, the hepatic microcirculation was not modified: vascular, extravascular, and the cellular spaces were similar before and following CI-WR. In addition, the hepatic metabolic functions, as evaluated by propranolol and taurocholate hepatic uptake, were neither improved nor decreased, as were Kupffer cell functions. The present data strongly suggest that capillarization of SECs plays a lesser role than collagenization of the space of Disse in the reduced exchange between sinusoids and hepatocytes in thioacetamide-induced cirrhotic rat livers, which appear to be quite resistant to CI-WR.

Matrix metalloproteinase inhibition protects rat livers from prolonged cold ischemia-warm reperfusion injury

Matrix metalloproteinases (MMPs) have been implicated in the hepatic injury induced after cold ischemia-warm reperfusion (CI-WR), by altering the extracellular matrix (ECM), but their precise role remains unknown. The hepatic MMP expression was evaluated after 2 conditions of CI (4 degrees C for 24 and 42 hours: viable and nonviable livers) followed by different periods of WR, using isolated perfused rat livers. CI-WR induced moderate changes in hepatic MMP transcript levels not influenced by CI duration, whereas gelatinase activities accumulated in liver effluents. Therefore, the protective effect of a new phosphinic MMP inhibitor, RXP409, was tested after prolonged CI. RXP409 (10 microM) was added to the University of Wisconsin solution, and livers were preserved for 42 hours (4 degrees C), then reperfused for 1 hour in Krebs solution (37 degrees C), containing 20% erythrocytes. Liver viability parameters were recorded, and the extent of cell necrosis was evaluated on liver biopsies, using trypan blue nuclear uptake. Treatment with RXP409 significantly improved liver function (transaminase release and bile secretion) and liver injury. In particular, the MMP inhibitor significantly modified the extent of cell death from large clusters of necrotic hepatocytes as found in control livers (2%-60% of liver biopsies; mean, 26% +/- 9%) to isolated necrotic hepatocytes as found in treated livers (0.2%-12%; mean, 3% +/- 2%) (P < 0.05).

CONCLUSION

These data demonstrate that MMPs, by altering the ECM, play a major role in liver CI-WR injury leading to extensive hepatocyte necrosis and that their inhibition might prove to be a new strategy in improving preservation solutions.

Effects of methylprednisolone and its liver-targeted dextran prodrug on ischemia-reperfusion injury in a rat liver transplantation model

PURPOSE

To evaluate the effectiveness of a liver-targeted dextran prodrug (DMP) of methylprednisolone (MP) in cold preservation-warm reperfusion injury associated with liver transplantation.

METHODS

The effects of donor pretreatment with single 5 mg/kg doses of MP or DMP on ischemia-reperfusion damage to the liver were studied after 8 or 24 h of cold preservation in both isolated perfused rat liver (IPRL) and syngeneic orthotopic rat liver transplantation (OLT) models.

RESULTS

In IPRL studies, donor pretreatment with DMP, and to a lesser degree MP, significantly improved the uptake of hyaluronic acid (HA), a marker of endothelial cell function, following 8 h of cold preservation. However, neither pretreatment was protective after 24 h of preservation. In the OLT model using 24-h-preserved livers, the seven-day survival of untreated grafts was 50%. DMP pretreatment of donors significantly improved graft survival to 100%, whereas MP pretreatment was ineffective. Additionally, only DMP significantly increased the blood glucose concentrations and decreased the plasma concentrations of tumor necrosis factor-alpha after OLT. Other measured markers of liver injury were not affected by either pretreatment.

CONCLUSIONS

Selective delivery of methylprednisolone to the liver as a donor pretreatment strategy improves 24-h preserved graft survival in the OLT model.

Role of reactive metabolites of oxygen and nitrogen in partial liver transplantation: lessons learned from reduced-size liver ischaemia and reperfusion injury

1. Hepatic resection with concomitant periods of ischaemia and reperfusion (I/R) is required to perform reduced-size liver (RSL) transplantation procedures, such as living donor or split liver transplantation. Although a great deal of progress has been made using these types of surgical procedures, a significant number of patients develop tissue injury from these procedures, ultimately resulting in graft failure. 2. Because of this, there is a real need to understand the different mechanisms responsible for the tissue injury induced by I/R of RSL transplantation (RSL + I/R), with the ultimate goal to develop new and improved therapeutic agents that may limit the tissue damage incurred during RSL transplantation. 3. The present paper reviews the recent studies that have been performed examining the role of reactive metabolites of oxygen and nitrogen in a mouse model of RSL + I/R. In addition, we present data demonstrating how the pathophysiological mechanisms identified in this model compare with those observed in a model of RSL transplantation in rats.

The effect of intraportal prostaglandin E1 on adhesion molecule expression, inflammatory modulator function, and histology in canine hepatic ischemia/reperfusion injury

BACKGROUND

Prostaglandin E1 (PGE1) is known to protect the liver from I/R, however, the mechanism of cytoprotection is not well understood. This study investigates the effect of intraportal infusion of PGE1 in a warm liver ischemia/reperfusion (I/R) model on cytokines, adhesion molecules and liver structure.

MATERIALS AND METHODS

Twenty dogs underwent laparotomy under general anesthesia. PGE1 (0.02 microg\kg\min) was perfused through the portal vein in the PGE1 group (n = 10), or a similar volume of Ringer's solution in the control group (n = 10) for 15 min. Liver ischemia was induced by hepatic artery and portal vein occlusion and PGE1 was infused via the portal vein for 60 min. The occlusion was released and PGE1 infusion recommenced for 30 min. Blood and liver biopsies were sampled at baseline, 60 min ischemia, and 30 min reperfusion and assessed for transaminases, cytokines, adhesion molecules, and electron microscopy.

RESULTS

PGE1 infusion significantly reduced transaminases TNF-alpha, sICAM-1, sP-selectin, and sE-selectin on ischemia and reperfusion. PGE1 reduced hepatocytic degeneration, portal and central ICAM-1 expression, central and sinusoidal VCAM-1 expression, portal and central P-selectin expression, and portal and sinusoidal E-selectin expression on reperfusion.

CONCLUSION

Intraportal PGE1 infusion reduced I/R injury and was associated with down-regulation of ICAM-1, VCAM-1, P-selectin, and E-selectin on reperfusion.

Divergent roles of superoxide and nitric oxide in reduced-size liver ischemia and reperfusion injury: Implications for partial liver transplantation

Hepatic resection with concomitant periods of ischemia and reperfusion (I/R) are required to perform partial liver transplantation procedures such as split liver or living donor transplantation. Although great progress has been made using these types of surgeries, there remains substantial risk to both donors and recipients, with a significant number of patients developing liver injury and failure during the course these operations. Therefore, there is need to investigate the different mechanisms responsible for the tissue injury induced by ischemia and reperfusion of a reduced-size liver (RSL+I/R) with the ultimate objective of developing new therapeutic agents that may limit hepatocellular damage induced during partial liver transplantation. This review summarizes recent studies that have been performed in a mouse model of RSL+I/R. In addition, we present data demonstrating how the pathophysiological mechanisms identified in this model compare to those observed in a rat model of RSL transplantation.

Effects of L-arginine on serum nitric oxide, nitric oxide synthase and mucosal Na+-K+-ATPase and nitric oxide synthase activity in segmental small-bowel autotransplantation model

AIM: To explore a simple method to create intestinal autotransplantation in rats and growing pigs and to investigate the effect of L-arginine supplementation on serum nitric oxide (NO), nitric oxide synthase (NOS) and intestinal mucosal NOS and Na⁺-K⁺-ATPase activity during cold ischemia-reperfusion (IR) in growing pigs.

METHODS: In adult Wistar rat models of small bowel autotransplantation, a fine tube was inserted into mesenteric artery via the abdominal aorta. The superior mesenteric artery and vein were occluded. Isolated terminal ileum segment was irrigated with Ringer’s solution at 4 °C and preserved in the same solution at 0-4 °C for 60 min. Then, the tube was removed and reperfusion was established. In growing pig models, a terminal ileum segment, 50 cm in length, was isolated and its mesenteric artery was irrigated via a needle with lactated Ringer’s solution at 4 °C. The method and period of cold preservation and reperfusion were described above. Ten white outbred pigs were randomly divided into control group and experimental group. L-arginine (150 mg/kg) was continuously infused for 15 min before reperfusion and for 30 min after reperfusion in the experimental group. One, 24, 48, and 72 h after reperfusion, peripheral vein blood was respectively collected for NO and NOS determination. At the same time point, intestinal mucosae were also obtained for NOS and Na⁺-K⁺-ATPase activity measurement.

RESULTS: In adult rat models, 16 of 20 rats sustained the procedure, three died of hemorrhage shock and one of deep anesthesia. In growing pig models, the viability of small bowel graft remained for 72 h after cold IR in eight of 10 pigs. In experimental group, serum NO level at 1 and 24 h after reperfusion increased significantly when compared with control group at the same time point (152.2±61.4 μmol/L vs 60.8±31.6 μmol/L, t = 2.802, P = 0.02<0.05; 82.2±24.0 μmol/L vs 54.0±24.3 μmol/L, t = 2.490, P = 0.04<0.05). Serum NO level increased significantly at 1 h post-reperfusion when compared with the same group before cold IR, 24 and 48 h post-reperfusion (152.2±61.4 μmol/L vs 75.6±16.2 μmol/L, t = 2.820, P = 0.02<0.05, 82.2 ±24.0 μmol/L, t = 2.760, P = 0.03<0.05, 74.2±21.9 μmol/L, t = 2.822, P = 0.02<0.05). Serum NOS activity at each time point had no significant difference between two groups. In experimental group, intestinal mucosal NOS activity at 1 h post-reperfusion reduced significantly when compared with pre-cold IR (0.79±0.04 U/mg vs 0.46±0.12 U/mg, t = 3.460, P = 0.009<0.01). Mucosal NOS activity at 24, 48, and 72 h post-reperfusion also reduced significantly when compared with pre-cold IR (0.79±0.04 U/mg vs 0.57±0.14 U/mg, t = 2.380, P = 0.04<0.05, 0.61±0.11 U/mg, t = 2.309, P = 0.04<0.05, 0.63±0.12U/mg, t = 2.307, P = 0.04<0.05). In control group, mucosal NOS activity at 1 and 24 h post-reperfusion was significantly lower than that in pre-cold IR (0.72±0.12 U/mg vs 0.60±0.07 U/mg, t = 2.320, P = 0.04<0.05, 0.58±0.18 U/mg, t = 2.310, P = 0.04<0.05). When compared to the normal value, Na⁺-K⁺-ATPase activity increased significantly at 48 and 72 h post-reperfusion in experimental group (2.48±0.59 μmol/mg vs 3.89±1.43 μmol/mg, t = 3.202, P = 0.04<0.05, 3.96±0.86 μmol/mg, t = 3.401, P = 0.009<0.01) and control group (2.48±0.59 μmol/mg vs 3.58±0.76 μmol/mg, t = 2.489, P = 0.04<0.05, 3.67±0.81 μmol/mg, t = 2.542, P = 0.03<0.05).

CONCLUSION: This novel technique for intestinal autotransplantation provides a potentially consistent and practical model for experimental studies of graft cold preservation. L-arginine supplementation during cold IR may act as a useful adjunct to preserve the grafted intestine.

Initial blood washout during organ procurement determines liver injury and function after preservation and reperfusion

Organ procurement is the first step toward effective liver preservation and comprises a thorough washout of blood components from the microvasculature. To study the efficacy of optimal blood washout of the liver, three groups were compared including low-pressure perfusion with UW-CSS (12 mmHg, group A), which is the routine method in clinical practice, high-pressure perfusion with UW-CSS (100 mmHg, group B) and low-pressure perfusion with modified UW solution (12 mmHg, group C). After procurement all livers were preserved in original UW-CSS for 0, 24 or 48 h, followed by reperfusion in oxygenated Williams Medium E for 24 h at 37 degrees C. Histology results of livers procured in group A, showed good hepatocyte viability but also remaining erythrocytes. However, injury parameters were high and ATP concentrations were low. No functional differences were found. Group B, high pressure, and group C, modified UW-CSS, both showed better results. High-pressure washout is preferable since the warm ischemia time during procurement is short. We propose to use high-pressure UW-CSS perfusion for the initial blood washout of the donor liver instead of the usually used low-pressure washout.

Rat liver transplantation without preservation of “phrenic ring” using double cuff method

AIM: To develop a double cuff method for rat liver transplantation without preservation of “phrenic ring” to shorten the portal vein clamping time.

METHODS: “Phrenic ring” was completely excluded from the donor liver, and end to end anastomosis of suprahepatic inferior vena cava was performed.

RESULTS: The portal vein clumping time was shortened to 10.6 min, the successful rate was 83.1%.

CONCLUSION: This method can simplify the operation and shorten the portal vein clumping time.

Sinusoidal endothelial cell and hepatocyte death following cold ischemia-warm reperfusion of the rat liver

Cold ischemia-warm reperfusion (CI-WR) injury of the liver is characterized by marked alterations of sinusoidal endothelial cells (SECs), whereas hepatocytes appear to be relatively unscathed. However, the time course and mechanism of cell death remain controversial: early versus late phenomenon, necrosis versus apoptosis? We describe the occurrence and nature of cell death after different periods of CI with University of Wisconsin (UW) solution and after different periods of WR in the isolated perfused rat liver model. After 24- and 42-hour CI (viable and nonviable livers, respectively), similar patterns of liver cell death were seen: SEC necrosis appeared early after WR (10 minutes) and remained stable for up to 120 minutes. After 30 minutes of WR, apoptosis increased progressively with WR length. Based on morphological criteria, apoptotic cells were mainly hepatocytes within liver plates or extruded in the sinusoidal lumen. In addition, only after 42-hour CI were large clusters of necrotic hepatocytes found in areas of congested sinusoids. In these same livers, the hepatic microcirculation, evaluated by means of the multiple-indicator dilution technique, revealed extracellular matrix disappearance with no-flow areas. In conclusion, different time courses and mechanisms of cell death occur in rat livers after CI-WR, with early SEC necrosis followed by delayed hepatocyte apoptosis. These processes do not appear to be of major importance in the mechanism of graft failure because they are similar under both nonlethal and lethal conditions; this is not the case for the loss of the extracellular matrix found only under lethal conditions and associated with hepatocyte necrosis.

Protective effect of nitric oxide induced by ischemic preconditioning on reperfusion injury of rat liver graft

AIM: Ischemic preconditioning (IP) is a brief ischemic episode, which confers a state of protection against the subsequent long-term ischemia-reperfusion injuries. However, little is known regarding the use of IP before the sustained cold storage and liver transplantation. The present study was designed to evaluate the protective effect of IP on the long-term preservation of liver graft and the prolonged anhepatic-phase injury.

METHODS: Male Sprague-Dawley rats were used as donors and recipients of orthotopic liver transplantation. All livers underwent 10 min of ischemia followed by 10 min of reperfusion before harvest. Rat liver transplantation was performed with the portal vein clamped for 25 min. Tolerance of transplanted liver to the reperfusion injury and liver damage were investigated. The changes in adenosine concentration in hepatic tissue and those of nitric oxide (NO) and tumor necrosis factor (TNF) in serum were also assessed.

RESULTS: Recipients with IP significantly improved their one-week survival rate and liver function, they had increased levels of circulating NO and hepatic adenosine, and a reduced level of serum TNF, as compared to controls. Histological changes indicating hepatic injuries appeared improved in the IP group compared with those in control group. The protective effect of IP was also obtained by administration of adenosine, while blockage of the NO pathway using Nω-nitro-L-arginine methyl ester abolished the protective effect of IP.

CONCLUSION: IP appears to have a protective effect on the long-term preservation of liver graft and the prolonged anhepatic-phase injuries. NO may be involved in this process.

Hepatic ischemia-reperfusion syndrome after partial liver resection (LR): hepatic venous oxygen saturation, enzyme pattern, reduced and oxidized glutathione, procalcitonin and interleukin-6

The hepatic ischemia-reperfusion syndrome was investigated in 28 patients undergoing elective partial liver resection with intraoperative occlusion of hepatic inflow (Pringle maneuver) using the technique of liver vein catheterization. Hepatic venous oxygen saturation (ShvO2) was monitored continuously up to 24 hours after surgery. Aspartate aminotransferase, glutamate dehydrogenase, gamma-glutamyl transpeptidase, pseudocholinesterase, alpha-glutathione S-transferase, reduced and oxidized glutathione, procalcitonine, and interleukin-6 were serially measured both before and after Pringle maneuver during the resection and postoperatively in arterial and/or hepatic venous blood. ShvO2 measurement demonstrated that peri- and postoperative management was suitable to maintain an optimal hepatic oxygen supply. As expected, we were able to demonstrate a typical enzyme pattern of postischemic liver injury. There was a distinct decrease of reduced glutathione levels both in arterial and hepatic venous plasma after LR accompanied by a strong increase in oxidized glutathione concentration during the phase of reperfusion. We observed increases in procalcitonin and interleukin-6 levels both in arterial and hepatic venous blood after declamping. Our data support the view that liver resection in man under conditions of inflow occlusion resulted in ischemic lesion of the liver (loss of glutathione synthesizing capacity with disturbance of protection against oxidative stress) and an additional impairment during reperfusion (liberation of reactive oxygen species, local and systemic inflammation reaction with cytokine production). Additionally, we found some evidence for the assumption that the liver has an export function for reduced glutathione into plasma in man.

Biliary inorganic phosphate as a tool for assessing cold preservation-reperfusion injury: a study in the isolated perfused rat liver model

Ischemia-reperfusion injury is a major cause of early graft dysfunction after liver transplantation. The bile flow has been suggested as an index of ischemic damage, and severely impaired bile flow seems to be predictive of poor survival in experimental studies. Looking for injury markers, biliary inorganic phosphate has the potential of being a useful endogenous marker of diminished hepatobiliary function because this anion is excreted in the bile by a paracellular pathway and it can detect changes in permeability. The goal of this study was to evaluate the effects of cold preservation-reperfusion of the liver on bile flow and bile inorganic phosphate and their relationship with storage-related graft failure. The isolated and perfused rat liver was used to evaluate the injury for ischemia-reperfusion. The intrahepatic resistance, lactate dehydrogenase release, and potassium and biliary inorganic phosphate concentration were used to estimate viability and function of freshly isolated or cold-preserved livers. The intrahepatic resistance and the bile flow were consistent and significantly decreased throughout the perfusion time in relation to the increment in storage. Inorganic phosphate is more concentrated in bile from preserved livers, showing an alteration in paracellular pathway, confirmed by the biliary excretion of horseradish peroxidase. After preservation, concentration and excretion of the paracellular marker were increased during the first peak. The second peak appears earlier in preserved livers (10 minutes) with a different shape but without changes in concentration. In conclusion, inorganic phosphate in bile shows changes in paracellular permeability as occurs in livers after 48 hours of cold preservation.

Fate of hepatocyte and sinusoidal lining cell function and kinetics after extended cold preservation and transplantation of the rat liver

We investigated the chronological profile of graft damage and recovery after liver cold ischemia-reperfusion (I/R) injury, with particular attention to the role of apoptosis on hepatocyte and sinusoidal endothelial cell (SEC) damage. Male Lewis rats underwent rearterialized orthotopic liver transplantation using grafts subjected to a short (University of Wisconsin [UW] solution for 1 hour [UW1h]) and prolonged period (UW16h) of cold preservation. Experiments were performed immediately after preservation and 4 hours, 24 hours, 3 days, and 7 days after reperfusion. At each time, graft function, incidence of apoptotic cells, expression of the epitope recognized by a monoclonal antibody specific to rat SECs (SE-1), and incidence of proliferating cells were estimated. In the UW16h group, the proportion of apoptotic SECs was markedly elevated at 4 hours. The incidence of hepatocyte apoptosis was very low, although massive hepatocyte necrosis was evident at 24 hours. The incidence of proliferating hepatocytes and SECs peaked at 3 days, then returned to normal by 7 days. SE-1 expression was reduced immediately after preservation, followed by a marked reduction at 4 and 24 hours after reperfusion, and expression returned to normal by 7 days. Although SEC apoptosis was induced in the early phase of cold I/R injury, hepatocyte damage developed without the occurrence of apoptosis. Regeneration of both hepatocytes and SECs after cold I/R injury peaked at 3 days and was complete by 7 days, whereas functional recovery of these cell populations was complete 3 days after reperfusion.

Donor brain death reduces survival after transplantation in rat livers preserved for 20 hr

BACKGROUND

Eighty percent of donor organs come from donors who have suffered brain trauma (brain-dead donors). This unphysiological state alters the hemodynamic and hormonal status of the organ donor. This can cause organ injury, which has been suggested to alter the immunological or inflammatory status of the organ after transplantation, and may lead to increased sensitivity of the organ to preservation/transplantation injury. In this study we asked the question: does brain death cause injury to the liver that decreases successful liver preservation?

METHODS

The rat liver transplant model was used to compare survival in rats receiving a liver from a brain-dead donor versus a non-brain-dead donor. Brain death was induced by inflation of a cranially placed balloon catheter. The rats were maintained normotensive with fluid infusion for 6 hr. The livers were flushed with University of Wisconsin (UW) solution and immediately transplanted or cold stored for 20 hr before transplantation.

RESULTS

Recipient survival with immediately transplanted livers or those stored for 20 hr was 100% with livers from non-brain-dead donors. However, survival decreased when livers were procured from brain-dead donors. Survival was 75% (6/8) when storage time was 0 hr and 20% (2/10) when the liver was cold stored for 20 hr before transplantation.

CONCLUSION

This study shows that brain death induces alterations in the donor liver that make it more sensitive to preservation/reperfusion injury than livers from donors without brain death. The mechanism of injury to the liver caused by brain death is not known. Because most livers used clinically for transplantation come from brain-dead donors, it is possible that poor function of these livers is due to the intrinsic condition of the donor organ, more than the quality of the preservation. Methods to treat the brain-dead donor to improve the quality of the liver may be needed to allow better preservation of the organ and to give better outcome after liver transplantation.

Rapid changes in alcoholic hepatitis histology under steroids: correlation with soluble intercellular adhesion molecule-1 in hepatic venous blood

BACKGROUND/AIMS

In alcoholic hepatitis (AH), enhanced expression of intercellular adhesion molecule-1 (ICAM-1) correlates to neutrophil infiltration and histology. In severe AH under steroids, the evolution of the hepatocyte membranous ICAM-1 expression and its soluble form (sICAM-1) is not known.

METHODS

Twenty-six consecutive patients with biopsy-proven severe AH had liver tissue studies for hepatocyte membranous ICAM-1 expression by immunostaining. Lobular neutrophils (mean per high power field) were counted after chloracetate esterase staining. Histological damage was assessed semiquantitatively. Circulating levels of sICAM-1 and TNFalpha in peripheral and hepatic vein were measured using immunoassays. After 8 days on steroids, 19 patients had repeat biopsy.

RESULTS

At baseline, hepatocyte membranous ICAM-1 correlated both to histology (r=0.55, P<0.01) and to lobular neutrophils (r=0.56, P<0.01). On steroids, sICAM-1 in hepatic vein and TNFalpha in both vascular beds decreased. Hepatocyte membranous ICAM-1 and hepatocellular damage decreased, but lobular neutrophils increased. Changes in sICAM-1 in hepatic vein correlated to histological changes (r=0.68, P<0.01).

CONCLUSIONS

In severe AH under steroids, the short term histological improvement was associated with a decrease in circulating TNFalpha, a decrease in ICAM-1 expression, and correlated to hepatic vein sICAM-1 changes.

Procalcitonin following elective partial liver resection--origin from the liver?

BACKGROUND

The origin of the inflammatory peptide procalcitonin (PCT) is still unknown. In the present study PCT concentrations in arterial and hepatic-venous blood were examined in patients undergoing elective partial liver resection (LR) using a fiberoptic pulmonary arterial catheter placed in a liver vein to obtain further information on the origin of PCT.

METHODS

In 28 patients (21 male/7 female; average age of 58.8+/-8.8 years) undergoing LR, arterial and hepatic venous PCT concentrations were measured during 24 h perioperatively. The parallel blood withdrawals occurred immediately before the Pringle maneuver (Hx), 2 min, 1, 2, 6, 12, and 24 h after Hx. Over the whole period, the oxygen saturation in hepatic venous blood (ShvO2) was monitored. PCT concentrations were assayed by immunoluminometry.

RESULTS

We observed a significant increase in PCT concentration already 6 h after Hx compared to the values before Hx. Twenty-four hours after Hx we found the highest plasma concentrations. It was conspicuous that hepatic venous PCT concentrations were always higher than the arterial ones (significantly from the 6th hour after Hx). There was no correlation between the courses of ShvO2 and PCT rise. A significant correlation was verified between Hx duration and PCT concentration measured 24 h after Hx both in the hepatic venous and arterial blood.

CONCLUSIONS

The results of our investigation can be interpreted as evidence that liver (or the hepatosplanchnicus?) is a source of PCT. The mechanism of PCT induction cannot be clarified by our study: whether the induction of PCT was caused by an endotoxin translocation during the impeded splanchnic outflow or by the direct surgery-induced lesion (hypoxia) of the liver remains unclear. However, the latter appears more probable because of the observed correlation between Hx duration and PCT concentration rise.

Role of hepatocytes and bile duct cells in preservation-reperfusion injury of liver grafts

In liver transplantation, it is currently hypothesized that nonparenchymal cell damage and/or activation is the major cause of preservation-related graft injury. Because parenchymal cells (hepatocytes) appear morphologically well preserved even after extended cold preservation, their injury after warm reperfusion is ascribed to the consequences of nonparenchymal cell damage and/or activation. However, accumulating evidence over the past decade indicated that the current hypothesis cannot fully explain preservation-related liver graft injury. We review data obtained in animal and human liver transplantation and isolated perfused animal livers, as well as isolated cell models to highlight growing evidence of the importance of hepatocyte disturbances in the pathogenesis of normal and fatty graft injury. Particular attention is given to preservation time-dependent decreases in high-energy adenine nucleotide levels in liver cells, a circumstance that (1) sensitizes hepatocytes to various stimuli and insults, (2) correlates well with graft function after liver transplantation, and (3) may also underlie the preservation time-dependent increase in endothelial cell damage. We also review damage to bile duct cells, which is increasingly being recognized as important in the long-lasting phase of reperfusion injury. The role of hydrophobic bile salts in that context is particularly assessed. Finally, a number of avenues aimed at preserving hepatocyte and bile duct cell integrity are discussed in the context of liver transplantation therapy as a complement to reducing nonparenchymal cell damage and/or activation.

Ischemic preconditioning of rat livers against cold storage-reperfusion injury: role of nonparenchymal cells and the phenomenon of heterologous preconditioning

Brief periods of ischemia followed by reperfusion render tissues resistant against subsequent prolonged ischemia, a phenomenon called ischemic preconditioning. The effect of ischemic preconditioning on liver transplantation was investigated in relation to sinusoidal endothelial cell injury and Kupffer-cell activation, which are prominent features of storage and reperfusion injury leading to liver graft failure. Rat livers were preconditioned by 5 or 10 minutes of ischemia and 5 minutes of reperfusion and stored in University of Wisconsin (UW) solution for 30 hours. Livers were then reperfused for 15 minutes with physiological buffer containing trypan blue. Under these conditions, injury occurs predominantly to sinusoidal endothelial cells, reflected by trypan blue staining of nonparenchymal cells in histological sections. Ischemic preconditioning decreased nonparenchymal cell killing by more than 50%. When half the liver was preconditioned, sinusoidal endothelial cells were also protected in the contralateral half. Other stored livers were reperfused with nitroblue tetrazolium, which is converted to insoluble formazan by superoxide radicals. Ischemic preconditioning decreased the intensity of formazan deposition over Kupffer cells. Finally, stored livers were transplanted into nontreated rats. Ischemic preconditioning improved recipient long-term survival after 30 hours of cold ischemic storage in UW solution from 30% to 80% and decreased serum tumor necrosis factor-alpha levels in posthepatic blood 4 hours postoperatively from 98 to 54 pg/mL. In conclusion, ischemic preconditioning protects sinusoidal endothelial cells and suppresses Kupffer-cell activation after storage and reperfusion. As a result, graft survival improves after liver transplantation. Moreover, ischemia to half the liver confers protection to the other half. Such heterologous preconditioning provides a new means to protect liver tissue against ischemia-reperfusion injury without imposing ischemia on the target tissue.

Role of Kupffer cells in the survival after rat liver transplantation with long portal vein clamping times

Applying the orthotopic rat liver transplantation (ORLT) model, postoperative survival has been shown to be mainly dependent on the portal vein clamping time (PVCT). It was hypothesized that prolonged intestinal congestion was responsible for the activation of Kupffer cells (KC) with overproduction of TNF, secondary to splanchnic endotoxin accumulation and release on reperfusion. The role of KCs was directly investigated in the context of long PVCTs by eliminating them (using liposome-encapsulated dichloromethylene diphosphonate), by preventing their activation (using a calcium channel blocker, nisoldipine) and by inhibiting TNF production (using thalidomide). Livers from different groups of rats were transplanted following 24-h cold preservation in the UW solution with long PVCTs (from 18-21 min). KCs depletion, preservation with nisoldipine and pretreatment with thalidomide significantly improved survival in conditions using long PVCTs. KC depletion and nisoldipine preservation had no effect on liver enzymes or pathological findings while lung injury was significantly improved. The present data confirm that, in the context of ORLT with long PVCTs, KCs are directly responsible for the systemic endotoxin-like shock syndrome and their effect is mediated through overproduction of TNF.

Marked difference in tumor necrosis factor-alpha expression in warm ischemia- and cold ischemia-reperfusion of the rat liver

Although tumor necrosis factor-alpha has been implicated in liver injury after both warm ischemia- and cold ischemia-reperfusion, it is unclear whether reactivity of the liver to these stimuli is similar with regard to cytokine expression. Here we compare the effects of warm and cold ischemia on tumor necrosis factor-alpha expression and test the hypothesis that cold ischemia preceding warm ischemia causes overexpression of this cytokine. Rat livers were flushed out with University of Wisconsin solution and subjected to varying periods of warm ischemia, cold ischemia, or cold ischemia plus warm ischemia followed by reperfusion using a blood-free perfusion model. Tumor necrosis factor-alpha and interleukin-10 release into the perfusate and bile were measured by ELISA, and expression of these cytokines and that of c-fos, c-jun, and c-myc were studied by reverse-transcriptase polymerase chain reaction. We found high levels of tumor necrosis factor-alpha in the perfusates of livers subjected to warm ischemia-reperfusion, whereas minimal or no tumor necrosis factor-alpha was detected in livers subjected to cold ischemia-reperfusion or to cold ischemia plus warm ischemia-reperfusion. Reverse-transcriptase polymerase chain reaction confirmed the above findings and showed that immediate early genes were expressed in reperfused groups of livers. Measurements of cytokine release into bile showed that neither tumor necrosis factor-alpha nor interleukin-10 were upregulated by cold ischemia-reperfusion. The results suggest that (1) warm ischemia- and cold ischemia-reperfusion of rat liver lead to very different outcomes with regard to tumor necrosis factor-alpha expression and (2) cold ischemia preceding warm ischemia prevents upregulation of tumor necrosis factor-alpha.

Cold-preservation-induced sensitivity of rat hepatocyte function to rewarming injury and its prevention by short-term reperfusion

With increasing time of cold preservation, levels of high-energy nucleotides in the liver are reducing. The authors hypothesized that cold preservation sensitizes hepatocyte function to ischemic injury occurring during graft rewarming and that the injury can be prevented by short-term reperfusion. Rat livers were cold-preserved in University of Wisconsin solution for 0 to 18 hours and ischemically rewarmed for 0 to 45 minutes to simulate the implantation stage of transplantation. Hepatobiliary function was assessed using a blood-free perfusion model. In comparison with controls, neither 18-hour preservation nor 45-minute ischemic rewarming significantly influenced hepatocyte function. Compared with livers subjected to 45-minute ischemic rewarming, livers subjected to 9-hour preservation and 45-minute rewarming, and livers subjected to 18-hour preservation and 45-minute rewarming exhibited, respectively: 3.8 and 24 times reduced bile production, 4.3- and 116-fold decreased taurocholate excretion, and 3.1 and 42 times depressed bromosulfophthalein excretion. Thirty-minute oxygenated warm reperfusion after 9- and 18-hour preservation nearly completely blunted sensitization of hepatocyte function to rewarming ischemia. The authors found that short-term oxygenated reperfusion restored adenine nucleotides in liver tissue to the values found before organ preservation and that reperfusion with energy substrate containing solutions increased tissue adenosine triphosphate concentration to a higher level than that found before preservation. In conclusion, sensitization of hepatocyte function to rewarming ischemia increases disproportionally with storage time, suggesting that this phenomenon may play a role in graft dysfunctions with increasing liver preservation time. Short-term oxygenated reperfusion of the liver may protect hepatocyte functions against warm ischemic insult, even after extended preservation.

TT virus infection during chronic hepatitis C

OBJECTIVE

The pathogenic role of TT virus (TTV) is not well known, especially during chronic hepatitis C virus (HCV) infection. We retrospectively investigated the presence of TTV DNA in the plasma of patients with chronic HCV infection and compared the characteristics of TTV-DNA-positive and -negative groups.

METHODS

Between November 1996 and November 1998, 234 patients were included. Inclusion criteria were persistently elevated serum alanine aminotransferase (ALT) levels, anti-HCV and HCV-RNA positivity, and seronegativity for hepatitis B virus and human immunodeficiency virus markers. TTV DNA was amplified in nested polymerase chain reaction with TTV-specific primers, and products were analyzed by agarose-gel electrophoresis. Data were analyzed using the chi2, Fisher's exact test, or Mann-Whitney test, as appropriate.

RESULTS

TTV DNA was detected in 19 (8.1%; 95% confidence interval: 4.6-11.6%) patients. TTV-DNA-positive and TTV-DNA-negative patients did not differ statistically for age, gender ratio, source of HCV infection, HCV disease duration, biological parameters, histological grade, HCV-RNA load, or HCV genotype. Although nonsignificant (p = 0.21), there was a trend for a higher prevalence of TTV DNA in patients with an unknown cause of HCV infection (4/22, 18.2%) than in intravenous drug users (4/84; 4.8%), in those exposed to potential risk factors (4/49; 8.2%), or in those having received blood transfusion (7/79; 8.9%).

CONCLUSIONS

Because the rates of HCV replication and the severity of liver lesions in TTV-DNA-negative and -positive patients were similar, the hepatic pathogenicity of TTV in chronic hepatitis C patients is questionable.

The portosystemic shunt protects liver against ischemic reperfusion injury

BACKGROUND

The goal of this study was to characterize the importance of splanchnic viscera in liver ischemic reperfusion injury and to enhance the tolerance of liver to warm ischemia injury with portosystemic shunt.

METHODS

The hepatic blood flow of male Sprague Dawley rats was subjected to 45, 60, 120, and 150 min liver warm ischemia with or without portosystemic shunt (splenic-caval shunt). The production of tumor necrosis factor a (TNFa), nuclear factor-kappaB activation, inducible NO synthase (iNOS) expression, and apoptosis were examined.

RESULTS

A total of 67% of rats with 45 min liver warm ischemia (n=6) and 100% of rats with 60 min liver warm ischemia (n=6) died within 1 day. However, all rats with 120 min (n=8) liver warm ischemia in splenic-caval shunt group survived for over 1 day, 6/8 for over 3 days, and 5/8 for over 5 days without significant histological changes of the liver. Serum tumor necrosis factor levels in liver warm ischemic rats were increased, This increase was significantly reversed after portosystemic shunt. After challenge with lipopolysaccharide (1 mg/kg, p.v.), naive rats survived for over 5 days (n=4) with the peak value of rat tumor necrosis factor (240 pg/ml) at 90 min. In contrast, all rats died within one day (n=5) with the peak value of rat tumor necrosis factor a (465 pg/ml) at 45 min after administration of lipopolysaccharide in the rats with liver warm ischemia plus splenic-caval shunt. iNOS expression and nuclear factor-kappaB activation were very strongly increased in the hepatocytes after liver warm ischemia with portosystemic shunt, compared with liver ischemia without portosytemic shunt.

CONCLUSIONS

We conclude that the splanchnic viscera can contribute to liver ischemic reperfusion injury. Portosystemic shunt enhances the tolerance of liver to warm ischemia through the protective role of iNOS and nuclear factor-kappaB (NF-kappaB).