Hepatic free radical production after cold storage: Kupffer cell-dependent and -independent mechanisms in rats

Hepatic ischemia reperfusion injury: A systematic review of literature and the role of current drugs and biomarkers

Hepatic ischemia reperfusion injury (IRI) is not only a pathophysiological process involving the liver, but also a complex systemic process affecting multiple tissues and organs. Hepatic IRI can seriously impair liver function, even producing irreversible damage, which causes a cascade of multiple organ dysfunction. Many factors, including anaerobic metabolism, mitochondrial damage, oxidative stress and secretion of ROS, intracellular Ca(2+) overload, cytokines and chemokines produced by KCs and neutrophils, and NO, are involved in the regulation of hepatic IRI processes. Matrix Metalloproteinases (MMPs) can be an important mediator of early leukocyte recruitment and target in acute and chronic liver injury associated to ischemia. MMPs and neutrophil gelatinase-associated lipocalin (NGAL) could be used as markers of I-R injury severity stages. This review explores the relationship between factors and inflammatory pathways that characterize hepatic IRI, MMPs and current pharmacological approaches to this disease.

Progress in research of liver ischemia-reperfusion injury

Liver resection is widely used in the treatment of benign and malignancy tumors of the liver, intrahepatic bile duct stones, liver trauma and other diseases, and liver transplantation is the only effective way to treat end-stage liver disease. However, ischemia-reperfusion injury is one of the main restricting factors of liver resection and liver transplantation, and effective control of intraoperative ischemia-reperfusion injury will help to reduce the effects of surgery on the liver function. In this paper, we review the recent advances in research of ischemia-reperfusion injury in terms of staging, pathogenesis, adverse effects and preventive measures.

Astaxanthin Pretreatment Attenuates Hepatic Ischemia Reperfusion-Induced Apoptosis and Autophagy via the ROS/MAPK Pathway in Mice

Background: Hepatic ischemia reperfusion (IR) is an important issue in complex liver resection and liver transplantation. The aim of the present study was to determine the protective effect of astaxanthin (ASX), an antioxidant, on hepatic IR injury via the reactive oxygen species/mitogen-activated protein kinase (ROS/MAPK) pathway. Methods: Mice were randomized into a sham, IR, ASX or IR + ASX group. The mice received ASX at different doses (30 mg/kg or 60 mg/kg) for 14 days. Serum and tissue samples at 2 h, 8 h and 24 h after abdominal surgery were collected to assess alanine aminotransferase (ALT), aspartate aminotransferase (AST), inflammation factors, ROS, and key proteins in the MAPK family. Results: ASX reduced the release of ROS and cytokines leading to inhibition of apoptosis and autophagy via down-regulation of the activated phosphorylation of related proteins in the MAPK family, such as P38 MAPK, JNK and ERK in this model of hepatic IR injury. Conclusion: Apoptosis and autophagy caused by hepatic IR injury were inhibited by ASX following a reduction in the release of ROS and inflammatory cytokines, and the relationship between the two may be associated with the inactivation of the MAPK family.

TNF-α suppression by glutathione preconditioning attenuates hepatic ischemia reperfusion injury in young and aged rats

BACKGROUND AND AIM

Hepatic ischemia reperfusion (I/R) stimulates Kupffer cells and initiates injury through tumor necrosis factor-α (TNF-α) upregulation. Aim of this study was to compare the variable effects of reduced glutathione (GSH) pre-treatment on I/R liver injury in young and aged rats.

METHODS

Wistar male rats were sorted into young (groups I-III) and aged (groups IV-VI). All groups except sham (groups I and IV) were subjected to 90-min ischemia and 2-h reperfusion. The treatment groups received 200 mg/kg bwt (groups III and VI) of GSH, 30 min prior to I/R. Variable effects of GSH were studied by transaminase activities, thiobarbituric acid-reactive substances (TBARS), GSH level, GSH/oxidized GSH (GSSG) ratio, TNF-α level, apoptotic markers and confirmed by histopathological observations.

RESULTS

Our findings revealed that I/R inflicted more liver damage in aged rats than young rats. The GSH treatment prior to surgery significantly lowered the serum transaminase activities, hepatic TBARS level and effectively restored the GSH/GSSG ratio in both young and aged rats more remarkably in the mitochondria. Western analysis depicted that the GSH treatment effectively suppressed TNF-α expression and apoptotic markers in both young and aged rats. These findings were further confirmed by terminal deoxynucleotide transferase dUTP nick end labeling assay and histopathological observations of liver sections of young and aged rats.

CONCLUSION

Restoration of GSH/GSSG ratio through GSH pre-conditioning inhibits TNF-α and apoptosis in hepatic I/R injury. Hence, GSH pre-conditioning may be utilized in both young and aged individuals during liver transplantation/surgery for better post-operative outcomes.

Free radical scavengers improve liver function but not morphological changes induced by reperfusion injury

OBJECTIVE

Reperfusion injury (RI) is associated with high generation of reactive oxygen species (ROS), but the extent of involvement of these agents in the injury remains controversial. The present study aimed to examine the effectiveness of ROS scavengers against hepatic reperfusion injury in the rat.

METHODS

The RI was induced in the liver using an isolated slow-flow, reflow perfused rat liver in both anterograde and retrograde perfusion. The effects of gentisic acid, N-acetyl cysteine, and trolox C on the superoxide production, liver function, and morphological changes were examined using different biochemical and histological assays.

RESULTS

The hepatic RI caused a significant (p < 0.05) increase in superoxide production and enzyme releases and a decrease in bile flow in both directions. Histological changes induced by RI include apoptosis, necrosis, pale cytoplasm, cell vacuolation, and attenuation of cell cords. Although the production of superoxide in retrograde direction was significantly less than the anterograde, the extent of the injury in the retrograde was greater than the anterograde direction. Pretreatment of the livers with each of the test compounds significantly reduced the release of lactate dehydrogenase and aspartate aminotransferase and improved bile flow in the liver exposed to hypoxia/reperfusion. However, they failed to protect the liver against the structural alterations induced by RI.

CONCLUSION

ROS scavengers can reduce superoxide-induced damage and improve the liver function, but they are not able to prevent the structural changes. It shows that ROS are not the sole causative mechanism of hepatic RI and other mechanisms and mediators may be involved.

Mechanisms of hepatic ischemia-reperfusion injury and protective effects of nitric oxide

Hepatic ischemia-reperfusion injury (IRI) is a pathophysiological event post liver surgery or transplantation and significantly influences the prognosis of liver function. The mechanisms of IRI remain unclear, and effective methods are lacking for the prevention and therapy of IRI. Several factors/pathways have been implicated in the hepatic IRI process, including anaerobic metabolism, mitochondria, oxidative stress, intracellular calcium overload, liver Kupffer cells and neutrophils, and cytokines and chemokines. The role of nitric oxide (NO) in protecting against liver IRI has recently been reported. NO has been found to attenuate liver IRI through various mechanisms including reducing hepatocellular apoptosis, decreasing oxidative stress and leukocyte adhesion, increasing microcirculatory flow, and enhancing mitochondrial function. The purpose of this review is to provide insights into the mechanisms of liver IRI, indicating the potential protective factors/pathways that may help to improve therapeutic regimens for controlling hepatic IRI during liver surgery, and the potential therapeutic role of NO in liver IRI.

A comparison of hepatic ischemia/hypoxia-reperfusion injury models

INTRODUCTION

A number of hepatic ischemia/hypoxia-reperfusion models have been described. This study characterised the functional and structural changes induced by the most commonly used in vivo and in situ models for hypoxia/ischemia-reperfusion in the rat liver.

METHODS

A range of no-flow, slow-flow and lobar ischemia and reperfusion models were established in the rat liver. Changes following reperfusion were monitored using physiological, biochemical, histological and pharmacological assessments, including bile production, oxygen consumption, lignocaine extraction, enzyme release, and disposition of exogenous markers.

RESULTS

Short periods of hepatic ischemia/hypoxia-reperfusion led to minimal changes in liver function whereas long periods of ischemia-reperfusion led to substantial liver injury. The most severe injury was found with the slow flow, reflow model. The formation of cell vacuoles, blebs and focal hepatitis were the most important liver morphological changes observed as a consequence of ischemia/hypoxia. The major liver histological findings after reperfusion were dispersed apoptosis and local necrosis. Hepatic ischemia/hypoxia-reperfusion was also associated with significant changes in the hepatic extracellular and intracellular spaces.

DISCUSSION

The morphology and function of the liver associated with a range of hepatic ischemia/hypoxia-reperfusion models varies with the duration of the insult and between models. The choice of model is therefore an important consideration in seeking to resolve any particular hypothesis associated with hepatic ischemia/hypoxia-reperfusion.

Improved hypothermic short-term storage of isolated mouse islets by adding serum to preservation solutions

Preserving isolated islets at low temperature appears attractive because it can keep islet quantity comparable to freshly isolated islets. In this study, we evaluated the effect of serum as an additive to preservation solutions on islet quality after short-term hypothermic storage. Isolated mouse islets were preserved at 4°C in University of Wisconsin solution (UW) alone, UW with serum, M-Kyoto solution (MK) alone or MK with serum. We then assessed islet quantity, morphology, viability and function in vitro as well as in vivo. Islet quantity after storage in all four solutions was well maintained for up to 120 h. However, islets functioned for different duration; glucose-stimulated insulin release assay revealed that the duration was 72 h when islets were stored in UW with serum and MK with serum, but only 24 h in UW alone, and the islet function disappeared immediately in MK alone. Viability assay confirmed that more than 70% islet cells survived for up to 48 h when islets are preserved in UW with serum and MK with serum, but the viability decreased rapidly in UW alone and MK alone. In in vivo bioassays using 48-h preserved isogeneic islets, all recipient mice restored normal blood glucose concentrations by transplants preserved in UW with serum or MK with serum, whereas 33.3% recipients and no recipient restored diabetes by transplants preserved in UW alone and in MK alone respectively. Adding serum to both UW and MK improves their capability to store isolated islets by maintaining islet functional viability.

Hepatic differentiation from human embryonic stem cells using stromal cells

OBJECTIVE

The derivation of hepatocytes from human embryonic stem (hES) cells is of value both in the study of early human liver organogenesis and in the creation of an unlimited source of donor cells for hepatocyte transplantation therapy. Here, we report the generation of hepatocyte-like cells derived from hES cells.

METHODS

Hepatic endoderm cells were generated by adding activin A for 5 d- to 1-d-old embryoid bodies formed from hES cells. The hepatic endoderm cells were cocultured with mitomycin treated 3T3-J2 feeder cells.

RESULTS

After co-culture with mitomycin treated 3T3-J2 feeder cells, these hepatic endodermal cells yielded hepatocyte-like cell colonies, which possessed the proliferation potential to be cultured for an extended period of more than 30 d. With extensive expansion, they co-expressed the hepatic marker AFP and albumin, indicating that they were hepatocyte-like cells.

CONCLUSIONS

We report the generation of proliferative hepatocyte-like cells from hES cells. These hES cell derived hepatic cells can effectively be used as in vitro model for studying the mechanisms of hepatic stem/progenitor cell origin, self-renewal and differentiation.

Protective effects of HGF-MSP chimer (metron factor-1) on liver ischemia-reperfusion injury in rat model

OBJECTIVE

It has been reported that metron factor-1 (MF-1), an engineered chimerical factor containing selected functional domains of hepatocyte growth factor and macrophage-stimulating protein (HGF-MSP), could prevent apoptosis and have an anti-inflammatory effect. In this study, we investigate the protective effect of MF-1 on liver ischemia-reperfusion (I/R) injury.

METHODS

Overall 30 Sprague Dawley rats were randomly divided into three groups: the I/R model group (n=12), the MF-1 treatment group (n=12), and the sham-operated group (n=6). Liver I/R injury was induced by clamping the blood supply to the left and median lobes of liver by an atraumatic clamp for 90 min, then removing the clamp and allowing reperfusion. Blood samples were obtained on days 1, 2, 3 and 7 to assess liver biochemistry and the histology of liver tissue. Levels of malondialdehyde (MDA), superoxide dismutase (SOD), nitric oxide (NO), endothelial nitric oxide synthase and inducible nitric oxide synthase were measured. In addition, the anti-oxidative effect of MF-1 on hepatocytes was assessed in vitro.

RESULTS

MF-1 treatment improved the rat survival rate significantly (P < 0.05). Liver biochemistry and histological changes were significantly ameliorated. MDA increased and SOD and NO decreased in the liver tissue. In vitro, MF-1 protected the human hepatic cell line HL-7702 from damage of oxidative stress.

CONCLUSION

MF-1 could protect the liver from I/R injury, which might involve the reduction of oxygen free radicals and the increase of NO synthesis in an injured liver.

Advances in research on the protective mechanisms of ischemic postconditioning against hepatic ischemia-reperfusion injury

Liver transplantation is the only effective treatment for end-stage liver diseases. Ischemia-reperfusion injury remains a major cause of post-transplantation liver dysfunction and even failure. Ischemic postconditioning is defined as rapid intermittent periods of reperfusion and ischemia in the early phase of repefusion after long ischemia of the tissues and organs. Many investigations have demonstrated that ischemic postconditioning has a protective effect against hepatic ichemia-reperfusion injury. Ischemic postconditioning exerts protective effects through many possible mechanisms such as oxygen free radicals, calcium overload, polymorphonuclear neutrophils, cytokines, cell apoptosis and mitochondria.

Ex vivo transfer of nuclear factor-kappaB decoy ameliorates hepatic cold ischemia/reperfusion injury

Cold ischemia/reperfusion injury of the hepatic graft has been attributed to the release of various inflammatory cytokines. Specific inhibition of these cytokines may improve viability of the hepatic graft upon reperfusion. Herein we have assessed the efficacy of cis element decoy against nuclear factor-kappaB binding site delivery to the hepatic tissue in a rodent liver transplantation model. At 8 hours after reperfusion of the liver, significant reduction was noted in the livers treated with decoy in the release of cytosolic enzymes from the hepatocytes and in serum tumor necrosis factor alpha (P < .05). The neutrophilic infiltration into the hepatic grafts was significantly suppressed in the livers treated with decoy oligodeoxynucleotides (ODNs). Decoy ODNs against nuclear factor-kappaB binding site delivery improved the viability of the hepatic graft against cold ischemia/reperfusion injury in the rodent liver transplantation model.

Histological and biochemical alterations in early-stage lobar ischemia-reperfusion in rat liver

AIM: To investigate the structural and biochemical changes in the early stage of reperfusion in the rat livers exposed to lobar ischemia-reperfusion (IR).

METHODS: The median and left lobes of the liver were subjected to 60 min ischemia followed by 5, 10, 30, 45, 60 and 120 min reperfusion. Blood samples were taken at different time intervals to test enzyme activities and biochemical alterations induced by reperfusion. At the end of each reperfusion period, the animals were killed by euthanasia and tissue samples were taken for histological examination and immunohistochemistry.

RESULTS: Cell vacuolation, bleb formation and focal hepatitis were the most important changes occur during ischemia. While some changes including bleb formation were removed during reperfusion, other alterations including portal hepatitis, inflammation and the induction of apoptosis were seen during this stage. The occurrence of apoptosis, as demonstrated by apoptotic cells and bodies, was the most important histological change during reperfusion. The severity of apoptosis was dependent on the time of reperfusion, and by increasing the time of reperfusion, the numbers of apoptotic bodies was significantly enhanced. The amounts of lactate dehydrogenase, alanine aminotransferase, aspartate aminotransferase, creatinine and urea were significantly increased in serum obtained from animals exposed to hepatic IR.

CONCLUSION: Inflammation and subsequent apoptotic cell death were the most important changes in early-stage hepatic reperfusion injury, and the number of apoptotic bodies increased with time of reperfusion.

The marginal liver donor--an update

The number of patients awaiting liver transplantation keeps steadily rising with no corresponding rise in suitable grafts for transplantation. There also is an increasing trend of patients dying or being taken off waiting lists because of deterioration while waiting for a transplant. Over the preceding years the use of marginal grafts in liver transplantation has been driven by the critical shortage of donor organs and by emerging data that their use has resulted in a favourable outcome. This review revisits the factors defining marginality of a graft, and the issues faced by transplant units in making the decision to use such a graft. It also looks at the innovations in transplantation geared towards increasing the donor pool and the resulting issues of matching marginal grafts to suitable recipients.

Rho-kinase as a novel gene therapeutic target in treatment of cold ischemia/reperfusion-induced acute lethal liver injury: effect on hepatocellular NADPH oxidase system

In the transplant surgery, reactive oxygen species (ROS) from the reperfused tissue cause ischemia-reperfusion injury, resulting in the primary graft failure. We have recently reported that Rho-kinase, an effecter of the small GTPase Rho, plays an important role in the ROS production in the hyperacute phase of reperfusion; however, the sources and mechanisms of the ROS production remain to be elucidated. The aim of this study was to investigate the source of ROS production with a special reference to Rho-kinase to develop a new strategy against ischemia-reperfusion injury. In an in vivo rat model of liver transplantation, Kupffer cells in the graft were depleted using liposome-encapsulated dichloromethylene diphosphonate to examine the source of ROS production. The effect of adenoviral-mediated overexpression of a dominant-negative Rho-kinase (AdDNRhoK) in hepatocytes in the graft was also examined. Kupffer cells were not involved in the ROS production, whereas the AdDNRhoK transfection to hepatocytes significantly suppressed the ROS production. Furthermore, the ROS production was dose-dependently inhibited by apocynin, an NADPH oxidase inhibitor. Expression of DNRhoK also suppressed the release of pro-inflammatory cytokines, and ameliorated the lethal liver injury with a significant prolongation of the survival. These results suggest that the Rho-kinase-mediated pathway plays a crucial role in the ROS production through NADPH oxidase in hepatocytes during the hyperacute phase of reperfusion in vivo. Thus, Rho-kinase in hepatocytes may be a new therapeutic target for the prevention of primary graft failure in liver transplantation.

Role of Kupffer cells in the pathogenesis of liver disease

Kupffer cells, the resident liver macrophages have long been considered as mostly scavenger cells responsible for removing particulate material from the portal circulation. However, evidence derived mostly from animal models, indicates that Kupffer cells may be implicated in the pathogenesis of various liver diseases including viral hepatitis, steatohepatitis, alcoholic liver disease, intrahepatic cholestasis, activation or rejection of the liver during liver transplantation and liver fibrosis. There is accumulating evidence, reviewed in this paper, suggesting that Kupffer cells may act both as effector cells in the destruction of hepatocytes by producing harmful soluble mediators as well as antigen presenting cells during viral infections of the liver. Moreover they may represent a significant source of chemoattractant molecules for cytotoxic CD8 and regulatory T cells. Their role in fibrosis is well established as they are one of the main sources of TGFβ1 production, which leads to the transformation of stellate cells into myofibroblasts. Whether all these variable functions in the liver are mediated by different Kupffer cell subpopulations remains to be evaluated. In this review we propose a model that demonstrates the role of Kupffer cells in the pathogenesis of liver disease.

Effect of normothermic perfusion using fructose-1,6-bisphosphate for maintenance of liver function during in situ extended hepatectomy by the total hepatic vascular exclusion technique

BACKGROUND

Recently, hepatic surgery has made remarkable progress, and it is important to use appropriate liver perfusion. We evaluated the effect of normothermic liver perfusion with the addition of fructose-1, 6-bisphosphate (FBP) and oxygenation to maintain liver parenchymal, non-parenchymal, and Kupffer cell function.

MATERIALS AND METHODS

The rats were divided into five groups according to the perfusate and continuous perfusion was performed: Control group = 4 degrees C lactate Ringer with 10% glucose (LRG) solution; normothermic group = 25 degrees C LRG solution; normothermic oxygenated group = 25 degrees C oxygenated LRG solution; normothermic FBP group = 25 degrees C LRG solution with addition of 10 mmol/L FBP; normothermic oxygenated FBP group = 25 degrees C oxygenated LRG solution with addition of 10 mmol/L FBP. Parameters under evaluation were oxygen consumption, liver energy level (adenosine triphosphate, total adenine nucleotide), glutathione, lipid peroxide, hyaluronic acid uptake ratio, apoptosis, and histomorphology. Moreover, we studied the effect of FBP and normothermia on Kupffer cells activation in vitro.

RESULTS

Liver energy level was lower in the normothermic group than the control group. But, it was improved by oxidation or addition of FBP, and it was satisfactorily maintained up to 120 min in the group with normothermic oxygenated FBP. Hyaluronic acid uptake was maintained highly at all times as measured in normothermic oxygenated FBP group. The uptake of lipopolysaccharide was significantly higher as a result of adding FBP, compared with that in the control group and the normothermic group. Moreover, the apoptotic index in the liver was decreased in normothermic FBP group compared to control group.

CONCLUSIONS

The normothermic liver perfusion under additional FBP and oxygenation protects both parenchymal and non-parenchymal cells from reperfusion injury.

Tumor necrosis factor-a antisense transfer remarkably improves hepatic graft viability

BACKGROUND

Cold ischemia/reperfusion injury of the hepatic graft, an unsolved problem in liver transplantations, is attributed to the release of inflammatory cytokines, especially the tumor necrosis factor- (TNF) alpha, from activated Kupffer cells (KC). Therefore, the specific inhibition of TNF-alpha could improve the viability of the hepatic graft upon reperfusion.

METHODS

We assessed the efficacy of TNF-alpha antisense (TNF-AS) oligodeoxynucleotides (ODNs) delivery to KC in a rodent liver transplantation model.

RESULTS

Seventy-one percent of the animals that received 6 hours preserved grafts in baths of lactated Ringer's solution (4 degrees C) and were treated with TNF-AS survived for over 14 days. Eighty percent of the animals treated with vehicle, sense ODNs, or balanced salt saline (BSS) died. Four hours after reperfusion of the liver, a significant reduction was noted in livers treated with TNF-AS in the release of cytosolic enzymes from the hepatocytes and the serum TNF-alpha (P<0.05). The expressions of TNF-alpha on KC and of intercellular adhesion molecule-1 on sinusoidal endothelial cells were completely suppressed in TNF-AS-treated livers.

CONCLUSIONS

TNF-AS delivery improves the viability of the hepatic graft, and this technique may solve hepatic graft nonfunction in a clinical setting.

Hepatocellular ultrastructure after ischemia/reperfusion injury in human orthotopic liver transplantation

The number of patients requiring organ transplants still outpaces the number of available transplantable organs. During the process of orthotopic liver transplantation (OLTx), donor organs undergo significant stress resulting from ischemia and reperfusion. Healthy organs respond to this stressful environment with compensatory mechanisms that ideally allow for complete recovery. However, "marginal" organs do not compensate as well. Hepatic steatosis typically renders an organ nontransplantable; a liver with 30% or more fat has a 25% chance of primary nonfunction (PNF) or graft failure after a technically sound operation. In this study, we report on the significant markers of cellular ultrastructural change in steatotic livers. These include glycogen content, mitochondrial swelling, and hepatocellular blebbing. The data disclosed here argue that further investigation of these factors in marginal organs subjected to I/R may better facilitate our understanding of PNF.

Cold ischemic injury of transplanted kidneys: new insights from experimental studies

Kidney transplantation is the preferred and definitive treatment for end-stage renal disease (ESRD), and kidneys from deceased donors are a major source for it. These kidneys are routinely cold stored to prolong viability, which, however, when prolonged can cause injury, resulting in reduced graft function and survival. Recent experimental studies have identified the release of iron and free radicals, activation of calpain, and formation of F2-isoprostanes as important components of cold ischemic injury, as are the swelling of mitochondria and activation of mitochondrial apoptotic pathways. Moreover, studies have also suggested that fortifying the storage solution with deferoxamine or preconditioning the donor kidneys with hemeoxygenase-1 may prove viable clinical strategies to limit cold ischemic injury. This review will summarize these and other new experimental data that have implications for reducing cold ischemic transplant injury, a step necessary to improve deceased-donor allograft survival.

Intravenous administration of glutathione protects parenchymal and non-parenchymal liver cells against reperfusion injury following rat liver transplantation

AIM: To investigated the effects of intravenous administration of the antioxidant glutathione (GSH) on reperfusion injury following liver transplantation.

METHODS: Livers of male Lewis rats were transplanted after 24 h of hypothermic preservation in University of Wisconsin solution in a syngeneic setting. During a 2-h reperfusion period either saline (controls, n = 8) or GSH (50 or 100 μmol/(h·kg), n = 5 each) was continuously administered via the jugular vein.

RESULTS: Two hours after starting reperfusion plasma ALT increased to 1 457 ± 281 U/L (mean ± SE) in controls but to only 908 ± 187 U/L (P < 0.05) in animals treated with 100 μmol GSH/(h·kg). No protection was conveyed by 50 μmol GSH/(h·kg). Cytoprotection was confirmed by morphological findings on electron microscopy: GSH treatment prevented detachment of sinusoidal endothelial cells (SEC) as well as loss of microvilli and mitochondrial swelling of hepatocytes. Accordingly, postischemic bile flow increased 2-fold. Intravital fluorescence microscopy revealed a nearly complete restoration of sinusoidal blood flow and a significant reduction of leukocyte adherence to sinusoids and postsinusoidal venules. Following infusion of 50 μmol and 100 μmol GSH/(h·kg), plasma GSH increased to 65 ± 7 mol/L and 97 ± 18 mol/L, but to only 20 ± 3 mol/L in untreated recipients. Furthermore, plasma glutathione disulfide (GSSG) increased to 7.5 ± 1.0 mol/L in animals treated with 100 μmol/(h·kg) GSH but did not raise levels of untreated controls (1.8 ± 0.5 mol/L) following infusion of 50 μmol GSH/(h·kg) (2.2 ± 0.2 mol/L).

CONCLUSION: Plasma GSH levels above a critical level may act as a “sink” for ROS produced in the hepatic vasculature during reperfusion of liver grafts. Therefore, GSH can be considered a candidate antioxidant for the prevention of reperfusion injury after liver transplantation, in particular since it has a low toxicity in humans.

Glutathione protects the rat liver against reperfusion injury after prolonged warm ischemia

OBJECTIVE

To evaluate the potential of postischemic intravenous infusion of the endogenous antioxidant glutathione (GSH) to protect the liver from reperfusion injury following prolonged warm ischemia.

BACKGROUND DATA

The release of reactive oxygen species (ROS) by activated Kupffer cells (KC) and leukocytes causes reperfusion injury of the liver after warm ischemia. Therefore, safe and cost-effective antioxidant strategies would appear a promising approach to prevent hepatic reperfusion injury during liver resection, but need to be developed.

METHODS

Livers of male Lewis rats were subjected to 60, 90, or 120 minutes of normothermic ischemia. During a 120 minutes reperfusion period either GSH (50, 100 or 200 micromol/h/kg; n= 6-8) or saline (n= 8) was continuously administered via the jugular vein.

RESULTS

Postischemic GSH treatment significantly prevented necrotic injury to hepatocytes as indicated by a 50-60% reduction of serum ALT and AST. After 1 hour of ischemia and 2 hours of reperfusion apoptotic hepatocytes were rare (0.50 +/- 0.10%; mean +/- SD) and not different in GSH-treated animals (0.65 +/- 0.20%). GSH (200 micromol GSH/h/kg) improved survival following 2 hours of ischemia (6 of 9 versus 3 of 9 rats; P < 0.05). Intravital fluorescence microscopy revealed a nearly complete restoration of sinusoidal blood flow. This was paralleled by a reduction of leukocyte adherence to sinusoids and postsinusoidal venules. Intravenous GSH administration resulted in a 10- to 40-fold increase of plasma GSH levels, whereas intracellular GSH contents were unaffected. Plasma concentrations of oxidized glutathione (GSSG) increased up to 5-fold in GSH-treated animals suggesting counteraction of the vascular oxidant stress produced by activated KC.

CONCLUSIONS

Intravenous GSH administration during reperfusion of ischemic livers prevents reperfusion injury in rats. Because GSH is well tolerable also in man, this novel approach could be introduced to human liver surgery.

Detection of mitochondrial electron chain carrier redox status by transhepatic light intensity during rat liver reperfusion

The aim of the study was to investigate mitochondrial electron transfer during rat liver reperfusion after cold storage and hypothermic machine perfusion. Livers from male Brown Norway rats were preserved (UW) for 10h either by cold storage (CS) or by hypothermic oxygenated perfusion extracorporal (HOPE). Transhepatic photometric analysis allowed determination of the redox status of mitochondrial cytochromes during preservation, rewarming and reperfusion. Mitochondrial electron chain carriers were inhibited at different sites with rotenone and cyanide in some experiments. reversed transcriptional polymerase chain reaction (RT-PCR) was performed after reperfusion concerning transcription of TNFalpha, caspase 9, and c-jun kinase (JNK). Increased superoxide anion formation as well as transcription of TNFalpha, caspase 9, and JNK during reperfusion after cold storage (CS) were related with completely reduced cytochromes before and during reperfusion. In contrast, hypothermic oxygenated livers (HOPE) showed oxygenated cytochromes as well as decreased superoxide anion formation and no detectable transcription of TNFalpha, caspase 9, and JNK. A similar low level of superoxide anion formation was found when electron chain transfer of cold stored livers was inhibited during reperfusion with rotenone but not with cyanide. After hypothermic oxygenation (HOPE) inhibition of mitochondrial electron chain with rotenone showed no change in formation of superoxide anion formation whereas inhibition with cyanide showed increased superoxide anion formation. Thus mitochondrial cytochrome redox status is suggested to be related: (i) with the release of reactive oxygen substances as well as (ii) with the expressions of TNFalpha, caspase 9, and JNK during reperfusion and may thus be usable as predictive marker of liver grafts.

Protective effect of matrine on sinusoidal endothelial cells of rat liver isograft

AIM

To investigate the protection effect of matrine on cold ischemia and reperfusion injury of sinusoidal endothelial cells (SEC) of liver isograft.

METHODS

Two hundred and twenty-four SD rats were randomly divided into four groups: untreated group, low-dose treated group, high-dose treated group and sham operation group. After 5 hours of cold preservation with Ringer's solution, orthotopic liver transplantation was performed. At 1 h, 2 h and 4 h time-points after reperfusion, 6 rats were killed in each group to collect the serum sample and the middle lobe of liver for detection, and the other 8 rats were raised to study the one week survival rate post-transplantation.

RESULTS

All recipients in control group died within 48 hours, mostly between 10 to 20 hours, and matrine treatment increased one week survival rate to 75% in both treated groups. The level of Hylluronic Acid (HA) and glutamate pyruvate transaminase (ALT) decreased significantly with matrine treatment. And the expression of intercellular adhesion molecule-1 (ICAM-1) decreased significantly in both treated groups, and the pathological changes of SEC ameliorated.

CONCLUSION

Matrine can prevent SEC from cold ischemia and reperfusion injury in rat orthotopic liver transplantation.

Induction of cellular resistance against Kupffer cell-derived oxidant stress: a novel concept of hepatoprotection by ischemic preconditioning

Ischemic preconditioning (IP) triggers protection of the liver from prolonged subsequent ischemia. However, the underlying protective mechanisms are largely unknown. We investigated whether and how IP protects the liver against reperfusion injury caused by Kupffer cell (KC)-derived oxidants. IP before 90 minutes of warm ischemia of rat livers in vivo significantly reduced serum alanine aminotransferase (AST) levels and leukocyte adherence to sinusoids and postsinusoidal venules during reperfusion. This protective effect was mimicked by postischemic intravenous infusion of glutathione (GSH), an antioxidative strategy against KC-derived H(2)O(2). Interestingly, no additional protection was achieved by infusion of GSH to preconditioned animals. These findings and several additional experiments strongly suggest IP mediated antioxidative effects: IP prevented oxidant cell injury in isolated perfused rat livers after selective KC activation by zymosan. Moreover, IP prevented cell injury and pertubations of the intracellular GSH/GSSG redox system caused by direct infusion of H(2)O(2) (0.5 mmol/L). IP-mediated resistance against H(2)O(2) could neither be blocked by the adenosine A2a antagonist DMPX nor mimicked by A2a agonist CGS21680. In contrast, H(2)O(2) resistance was abolished by the p38 mitogen-activated protein kinase (p38 MAPK) inhibitor SB203580, but induced when p38 MAPK was directly activated by anisomycin. In conclusion, we propose a novel concept of hepatoprotection by IP: protection of liver cells by enhancing their resistance against KC-derived H(2)O(2). Activation of p38 MAPK and preservation of the intracellular GSH/oxidized glutathione (GSSG) redox system, but not adenosine A2a receptor stimulation, seems to be pivotal for the development of H(2)O(2) resistance in preconditioned livers.

Beta-galactosidase as a marker of ischemic injury and a mechanism for viability assessment in porcine liver transplantation

Glycohydrolases are a group of enzymes contained predominantly within lysosomes, which are released during Kupffer cell activation or death. One of these, beta-galactosidase, has been proposed as a marker of ischemia-reperfusion injury in the liver because Kupffer cell activation represents a primary event in the injurious reperfusion cascade. In this study, we compared B-galactosidase with more traditional indicators of liver injury and function in a porcine model of liver preservation. Porcine livers were allocated into two groups: group C (n = 5), preserved in University of Wisconsin solution by standard cold storage for 24 hours, and group W (n = 5), perfused with oxygenated autologous blood on an extracorporeal circuit for 24 hours. Both groups were subsequently tested on the circuit during a 24-hour reperfusion phase. The perfusate was sampled for levels of beta-galactosidase, as well as traditional markers of liver injury and function. A sharp increase in beta-galactosidase levels was seen on reperfusion of cold preserved livers to a level of 1,900 IU/mL. This contrasted dramatically with normothermically preserved livers, in which the level never exceeded 208 IU/mL (P =.002). beta-Galactosidase levels showed much earlier and greater increases compared with transaminase levels in livers injured by ischemia. A rapid elevation in beta-galactosidase levels corresponded well with poor liver function and more liver injury. Measurement of beta-galactosidase is a simple test that quantifies ischemia-reperfusion injury of preserved livers. It is more sensitive than transaminases, with faster and larger increases in levels after ischemic injury. It can be useful in assessing the viability of a liver during machine preservation.

Sinusoidal endothelial cell injury by superoxide anion and iron in the Propionibacterium acnes-pretreated and lipopolysaccharide-stimulated rat liver

AIMS/BACKGROUND

We attempted to measure the generation of superoxide anion, examine its site of release and determine its pathological role in Propionibacterium acnes-lipopolysaccharide-induced liver injury in the rat.

METHODS

The P. acnes-pretreated (16 mg/kg i.v.) rat liver was perfused with buffer containing lipopolysaccharide (2.5 microg/ml). Chemiluminescence enhanced with Cypridina luciferin analog, MCLA, and reduction of nitro blue tetrazolium were used for detecting superoxide anion. Leakage of enzymes and release of cytokines into the perfusate, and histological specimens were also examined.

RESULTS

Superoxide dismutase-inhibitable chemiluminescence peaked at 30 min of lipopolysaccharide infusion and blue formazan precipitate was histochemically deposited mainly on hepatic macrophages. Purine nucleoside phosphorylase (PNP) activity in the perfusate, as a marker of sinusoidal endothelial cell injury, reached its maximum at 50 min and aspartate aminotransferase (AST) activity, as a marker of hepatocyte injury, reached a plateau at 90 min. Simultaneous treatment with superoxide dismutase and deferoxamine mesylate significantly suppressed the leakage of PNP and AST. Release of tumor necrosis factor-alpha and growth-related oncogene/cytokine-induced neutrophil chemoattractant-1 lagged behind PNP leakage. Light microscopy showed destruction of the sinusoids followed by hepatocyte necrosis. Electron microscopy revealed adherence of hepatic macrophages to sinusoidal endothelial cells.

CONCLUSION

These results indicate that superoxide anion released from hepatic macrophages may induce sinusoidal endothelial cell injury via interaction with iron in the P. acnes-lipopolysaccharide-treated liver.

Microcirculatory failure after rat liver transplantation is related to Kupffer cell-derived oxidant stress but not involved in early graft dysfunction

BACKGROUND

Microcirculatory failure, activation of Kupffer cells (KC), and the formation of reactive oxygen species (ROS) are considered pivotal mechanisms of reperfusion injury after orthotopic liver transplantation. However, the sequence of these events and their impact on early graft function remain controversial. We therefore investigated whether KC induce microcirculatory disturbances through ROS release and whether microcirculatory failure contributes to early graft function after liver transplantation.

METHODS

Donor livers of Lewis rats were pretreated either with saline or with gadolinium chloride (GdCl3), an inhibitor of KC function (n=8 each). Syngeneic OLT was performed after 24 hr of hypothermic preservation in University of Wisconsin solution.

RESULTS

Intravital microscopy revealed significantly higher sinusoidal perfusion rates in GdCl3-treated allografts (92+/-1.1% vs. 75.7+/-0.8%; P<0.001) compared with untreated controls; permanent leukocyte sticking in sinusoids (23.5+/-2.1 vs. 62.6+/-3.3 cells/lobule, P<0.001) and in postsinusoidal venules (153.1+/-10.4 vs. 446.6+/-46.4 cells/mm(2), P<0.001) were markedly attenuated in GdCl3-treated allografts. Improvement of microcirculatory parameters in GdCl3-treated livers was correlated with a significant reduction of plasma glutathione disulfide formation by KC-derived ROS (0.96+/-0.1 microM vs. 1.79+/-0.5 microM; P<0.01). Despite these beneficial effects, GdCl3-pretreatment failed to improve postischemic alanine aminotransferase release and bile flow.

CONCLUSIONS

Microcirculatory failure after liver transplantation is related to KC-derived oxidant stress but not involved in early graft dysfunction.

Apoptosis versus necrosis during cold storage and rewarming of human renal proximal tubular cells

BACKGROUND

A recent clinical study demonstrated that in renal allografts preserved in the cold apoptosis occurred soon after reperfusion. The mode of cell death during cold storage is generally considered necrotic. Whether apoptosis occurs as a part of cold storage is uncertain. The objective was to determine in human renal tubular cells whether apoptosis is specific for rewarming or it also occurs during cold storage and whether it could be modified.

METHODS AND RESULTS

Cold storage (4 degrees C) of primary human renal proximal tubular epithelial (RPTE) in University of Wisconsin (UW) solution up to 48 hr caused a time-dependent increase in cell death measured by lactic dehydrogenase (LDH) release and vital dye exclusion methods. Transmission electron microscopy (TEM) demonstrated that cell death in the cold was necrotic, involving considerable mitochondrial disruption, and was not apoptotic. The TUNEL assay that provides a specific, quantitative measure for apoptosis showed no increase in TUNEL-positivity during flow cytometry of cells stored in cold: 37 degrees C, 0.23+/-0.14%; 24 hr cold, 0.23+/-0.1%; 48 hr cold, 1.79+/-0.58%. Annexin-V staining, a sensitive method for detecting early apoptosis, similarly showed no increase in positively stained cells during cold storage. Addition of antioxidants 2-methyl aminochroman and deferoxamine to UW solution inhibited necrotic cell death and preserved mitochondrial structure. In contrast to cold storage alone, rewarming (37 degrees C for 24 hr) of cold stored cells, however, resulted in significant apoptosis (TUNEL positive: 48 hr cold: 2+/-0.6%, 48 hr cold and 24 hr rewarming: 54+/-17%), which was confirmed by the TEM based on typical apoptotic features. Addition of 2-MAC and DFO significantly inhibited rewarming-induced apoptotic cell death (plus 2-MAC: 3+/-1%, plus DFO: 3+/-2%).

CONCLUSION

Our study in human tubular cells provides evidence that cold storage per se does not result in apoptosis, but is primarily necrotic. However, rewarming is associated with significant apoptosis in the presence of ongoing necrosis, speculatively due to the activation of the apoptotic enzymic process of sublethally injured cells. Inclusion of antioxidants in the storage solution confers protection against both cold storage and rewarming-induced necrosis and apoptosis.

Mechanism and prevention of cold storage-induced human renal tubular cell injury

BACKGROUND

The recent observation that cold storage of kidneys and tubular cells causes marked increase in free radical-catalyzed F2-isoprostanes suggests that radicals might be formed during cold storage. As cold temperature is associated with reduced metabolic and enzymic activity, the notion that cold temperature causes free radical production appeared less tenable. The objective was, therefore, to seek direct evidence for the free radical production during the cold storage of human renal tubular cells, and to define the roles of extrinsic and intrinsic antioxidants in cold-induced cell injury.

METHODS

Human renal tubular cells were cold-stored at 4 degrees C for varying duration in University of Wisconsin solution and subjected to mRNA analysis, biochemical measurements, and cytoprotective studies.

RESULTS

Cold storage caused a time-dependent reduction in glutathione levels, and an increase in the formation superoxide, hydrogen peroxide, and hydroxyl radicals. Cold-induced lactate dehydrogenase (LDH) release, ATP depletion, DNA damage, and membrane degradation were suppressed with the inclusion of antioxidant 2-methyl aminochroman or deferroxamine. The cells that were structurally protected with antioxidants were also intact functionally, as they had significantly improved cell proliferation. To examine the effect of cold on intrinsic antioxidant gene expression, antioxidant mRNA levels were analyzed using reverse transcription-polymerase chain reaction. The gene expression of mitochondrial Mn-superoxide dismutase (SOD), but not of cytosolic Cu,Zn-SOD or of glutathione peroxidase expression increased with cold exposure. The oxidant-sensitive gene heme oxygenase I increased slightly with 48-hr cold storage.

CONCLUSIONS

Cold storage of human tubular cells causes marked increase in free radicals. These are likely of mitochondrial origin as there is a differential inducement of Mn-SOD gene, and are causal to cold-induced cell injury as extrinsic antioxidants abrogated the injury. Our findings support the strategy of adding antioxidants to preservation solutions or the strategy of pre-conditioning the organs to oxidative stress to minimize cold storage-induced organ damage.

A rapid, simple, and cost-effective method for screening liver preservation solutions in the rat

BACKGROUND

Rat liver transplantation models or isolated liver perfusion models are currently used for assessing efficacy of liver preservation methods. We tested the hypothesis that hepatocellular enzymes released into the washout solution after preservation may predict hepatic function during reperfusion and could thus be alternatively used for evaluating efficiency of liver preservation solutions. Furthermore, we applied this approach for assessing the role of Kupffer cells (KC) in preservation-induced liver damage.

METHODS

After preservation in University of Wisconsin (UW) or Euro-Collins (EC) solution, rat livers were washed with Ringer-lactate solution. Correlations between enzymes released into the washout solution and hepatocyte functional parameters determined during reperfusion on using a blood-free perfusion model were investigated.

RESULTS

In UW-preserved livers, acid phosphatase (ACP) activity correlated negatively with bile flow (R = -0.904), taurocholate intrinsic clearance (R = -0.841), and bromosulfophthalein excretion (R = -0.831). Both alanine transaminase and aspartate transaminase activities correlated with the functional parameters investigated. In EC-stored livers, correlation was also found between ACP activity and bile flow (R = -0.666). Livers stored in UW solution exhibited approximately 3 times lower washout activities of enzymes studied than livers stored in EC solution. Mitochondria isolated from UW-stored livers exhibited significantly better function than those isolated from EC-stored livers. Blockade of KC did not influence enzyme release into the washout solution.

CONCLUSIONS

Determination of ACP, alanine transaminase, and aspartate transaminase activities in the washout solution can be used as a rapid, simple, and cost-effective way for screening liver preservation solutions. The results also suggest that KC were not involved in preservation-induced liver damage.

Cold liver ischemia-reperfusion injury critically depends on liver T cells and is improved by donor pretreatment with interleukin 10 in mice

Kupffer cells are thought to mediate most of the deleterious effects of liver ischemia-reperfusion injury. The role of liver T cells and the impact of resident cell deactivation by interleukin 10 (IL-10) have never been addressed. Using a model of ex vivo liver cold ischemia and reperfusion, we assessed liver injury, tumor necrosis factor (TNF) and interferon gamma (IFN-gamma) release from livers of balb/c mice, nude mice, nude mice reconstituted with T cells, and gadolinium balb/c pretreated mice. The anti-inflammatory cytokine IL-10 was then used to define the best strategy of administration potentially able to modulate ischemia-reperfusion injury. For this purpose IL-10 was administered to the donor before liver harvesting, in the preservation medium during cold ischemia or during reperfusion. TNF and IFN-gamma were released time dependently and paralleled liver injury after reperfusion of cold preserved livers. Reperfused livers from nude or gadolinium pretreated mice disclosed a dramatic decrease in TNF and IFN-gamma release. Tissue injury was reduced by 51% in the absence of T cells and by 88% when Kupffer cells were deactivated. This effect was reverted by T-cell transfer to nude mice. Only donor pretreatment with IL-10 or IL-10 infusion during reperfusion led to a significant decrease in liver injury, TNF, and IFN-gamma release (-66% or -41%, -95% or -94%, and -70% or -70%, respectively). In conclusion, liver resident T cells are critically involved in cold ischemia-reperfusion injury and pretreatment of the donor with IL-10 decreases liver injury and the release of T-cell- and macrophage-dependent cytokines.

Hypothermia affects the phagocytic activity of rat peritoneal macrophages

To examine the effect of hypothermia on the phagocytic capacity of rat peritoneal macrophages for latex particles, male Wistar rats were exposed to 4 degrees C for 8 and 72 h. While the shorter exposure to cold did not affect body temperature and macrophage function, animals exposed to 4 degrees C for 72 h showed a mean decrease of their body temperature by 1.5 degrees C. The superoxide anion production was significantly increased whereas the number of phagocytic cells decreased. In addition, the mean number of latex particles engulfed by each individual cell was lower than that of controls. Peripheral blood mononuclear cells (PBMC) of these animals showed lower mitogen response to phytohaemagglutinin (PHA), while that for concanavalin A (Con-A) remained unchanged. Peritoneal macrophages exposed in vitro to 24 degrees C for 60 min showed a decreased phagocytic capacity in comparison with macrophages kept at 37 degrees C, an observation suggesting the development of an indigenous cell defect for phagocytosis at lower temperatures. On the other hand, the effect of additional humoral factor(s) on macrophage activity, such as an increase in serum level of catecholamines and corticosterone, cannot be excluded. The results of the study may contribute to understanding the predisposition to infections during exposure to cold.

Glutathione protects the rat liver against reperfusion injury after hypothermic preservation

BACKGROUND & AIMS

The extracellular generation of reactive oxygen species (ROS) by Kupffer cells contributes to reperfusion injury of the liver allograft. The endogenous antioxidant glutathione (GSH) can detoxify these ROS; however, this effect might be limited by the low extracellular concentration of GSH. We therefore investigated whether an increase of extracellular GSH protects the liver against reperfusion injury after cold preservation.

METHODS

Livers of male Sprague-Dawley rats subjected to 24 hours of cold ischemia in University of Wisconsin solution (4 degrees C) were reperfused for 2 hours in the absence (controls) or presence of 0.5, 1, 2, or 4 mmol/L GSH (n = 4-6 each).

RESULTS

Two hours after starting reperfusion of control livers, the sinusoidal release of lactate dehydrogenase and purine nucleoside phosphorylase increased to 247 +/- 96 and 27 +/- 13 mU. min(-1). g liver(-1), respectively, but only to 76 +/- 43 and 10 +/- 4 mU. min(-1). g liver(-1) in the presence of 4 mmol/L GSH. This cytoprotective effect was confirmed histologically by a marked reduction of trypan blue staining of hepatocytes. Compared with control livers, postischemic bile flow was significantly enhanced by GSH (0.15 +/- 0.02 vs. 0.41 +/- 0.11 microL. min(-1). g liver(-1)), indicating improved liver function. During reperfusion of control livers, intracellular GSH content declined from 4.5 +/- 0.3 to 2.3 +/- 0.1 micromol/g liver, but only to 3.8 +/- 0.4 micromol/g liver in the presence of 4 mmol/L GSH. Reperfusion of untreated livers was accompanied by a prolonged increase of portal pressure to maximally 12.5 +/- 1.9 cm H2O, which was significantly attenuated by 4 mmol/L GSH (7.2 +/- 1.4 cm H2O). Similar cytoprotective and hemodynamic effects were observed with 2 mmol/L GSH, but not with 0.5 and 1 mmol/L GSH.

CONCLUSIONS

Treatment of cold-preserved livers with GSH upon reperfusion prevents damage of hepatocytes, deterioration of the hepatic circulation, and loss of intracellular GSH. In view of these protective effects and its low toxicity in humans, GSH should be considered a candidate drug for prevention of ROS-related reperfusion injury of the liver allograft.

Cold storage induces time-dependent F2-isoprostane formation in renal tubular cells and rat kidneys

BACKGROUND

Previous findings suggest a possible role for free radicals in cold-storage-associated tissue injury. Because free radical-induced lipid peroxidation catalyzes the cyclooxygenase-independent formation of vasoconstrictive F2-isoprostanes, the hypothesis that isoprostanes are produced during cold storage was tested in this study.

METHODS

Total isoprostanes (free and esterified) in renal tubular epithelial (LLC-PK1) cells or whole kidneys, subjected to cold storage, were quantitated employing the gas chromatographic-mass spectroscopic method. LLC-PK1 cells were stored at 4 degrees C in a University of Wisconsin (UW) solution for 0, 24, 48, and 72 hours or 48 hours with desferrioxamine (DFO) or the lazaroid compound 2-methyl aminochroman (2-MAC). In the rat model, kidneys were perfused and stored for 48 hours in the UW solution with or without added DFO or 2-MAC.

RESULTS

Isoprostanes in LLC-PK1 cells increased by fivefold following 24 hours of cold storage (36 +/- 2 pg/well to 185 +/- 6, mean +/- SE, following 24 hours of cold storage, P < 0.0001), and the levels continued to increase significantly at 48 and 72 hours. DFO and 2-MAC caused significant suppression of isoprostane formation. Cold storage of the kidneys in UW solution for 48 hours was accompanied by an eightfold increase in isoprostanes compared with control kidneys not subjected to cold storage (25.0 +/- 3.0 vs. 2.9 +/- 0.1 ng/g, P < 0.0001). The addition of 2-MAC or DFO to the UW solution was associated with a near complete suppression of 48-hour cold-induced isoprostane formation.

CONCLUSION

Our findings provide evidence for the formation of large quantities of antioxidant-suppressible isoprostanes in kidney cells and whole kidney during cold-preservation. Based on this, it is hypothesized that (a) isoprostanes, which are potent renal vasoconstrictors, may contribute to immediate post-transplant vasoconstriction and dysfunction in kidneys subjected to extended cold storage, and that (b) the addition of 2-MAC or DFO to a UW solution in such circumstances may attenuate these alterations partly by suppressing isoprostane formation.

Prevention of Kupffer cell-induced oxidant injury in rat liver by atrial natriuretic peptide

The generation of reactive oxygen species (ROS) by activated Kupffer cells contributes to liver injury following liver preservation, shock, or endotoxemia. Pharmacological interventions to protect liver cells against this inflammatory response of Kupffer cells have not yet been established. Atrial natriuretic peptide (ANP) protects the liver against ischemia-reperfusion injury, suggesting a possible modulation of Kupffer cell-mediated cytotoxicity. Therefore, we investigated the mechanism of cytoprotection by ANP during Kupffer cell activation in perfused rat livers of male Sprague-Dawley rats. Activation of Kupffer cells by zymosan (150 microgram/ml) resulted in considerable cell damage, as assessed by the sinusoidal release of lactate dehydrogenase and purine nucleoside phosphorylase. Cell damage was almost completely prevented by superoxide dismutase (50 U/ml) and catalase (150 U/ml), indicating ROS-related liver injury. ANP (200 nM) reduced Kupffer cell-induced injury via the guanylyl cyclase-coupled A receptor (GCA receptor) and cGMP: mRNA expression of the GCA receptor was found in hepatocytes, endothelial cells, and Kupffer cells, and the cGMP analog 8-bromo-cGMP (8-BrcGMP; 50 microM) was as potent as ANP in protecting from zymosan-induced cell damage. ANP and 8-BrcGMP significantly attenuated the prolonged increase of hepatic vascular resistance when Kupffer cell activation occurred. Furthermore, both compounds reduced oxidative cell damage following infusion of H2O2 (500 microM). In contrast, superoxide anion formation of isolated Kupffer cells was not affected by ANP and only moderately reduced by 8-BrcGMP. In conclusion, ANP protects the liver against Kupffer cell-related oxidant stress. This hormonal protection is mediated via the GCA receptor and cGMP, suggesting that the cGMP receptor plays a critical role in controlling oxidative cell damage. Thus ANP signaling should be considered as a new pharmacological target for protecting liver cells against the inflammatory response of activated Kupffer cells without eliminating the vital host defense function of these cells.

Morphologic alteration of hepatocytes and sinusoidal endothelial cells in rat fatty liver during cold preservation and the protective effect of hepatocyte growth factor

BACKGROUND

Fatty liver grafts are considered to be one of the main factors of primary nonfunctioning graft in transplantation. We investigated here, the hepatic damage during cold preservation in a rat fatty liver model by ultrastructural observation, and examined the effect of human recombinant hepatocyte growth factor (hrHGF) on amelioration of the cold-preserved graft condition.

METHODS

Wistar rats were fed a choline-deficient diet (CDD) for 7 days. Livers were stored in cold University of Wisconsin (UW) solution for 0, 4, and 24 hr. We evaluated the ultrastructural alteration of the hepatocytes, sinusoidal architecture, and endothelial cells (SECs) by scanning and transmission electron microscopy. Ex vivo, we measured alanine aminotransferase (ALT) in first effluent as an index of hepatocyte injury and the hyaluronic uptake rate (HUR) as that of SEC damage. We injected hrHGF into rats fed CDD for 7 days through the portal vein and also added it to the UW solution to determine whether or not the agent ameliorated the hepatic damage in cold-preserved fatty livers.

RESULTS

In rats fed CDD for 7 days, the lesion occupied by fat deposits appeared to enlarge with the duration of cold preservation leading to the disarrangement of sinusoidal architecture. Furthermore, sinusoidal endothelial damage, in which gaps, blebs, microvilli, and sinusoid denudation were detected, appeared to be more severe in these livers than in the corresponding control livers. ALT significantly increased in the 4-hr cold-preserved livers of rats fed CDD for 7 days. HUR decreased with 4-hr cold preservation and/or with CDD feeding. Administration of hrHGF prevented the expansion of fatty droplets and reduced SEC injury as detected by morphological observations. Increase of ALT in first effluent was inhibited to about one fourth the level observed in the 4-hr cold-preserved livers of rats fed CDD. Moreover, HUR significantly increased with the pretreatment of hrHGF.

CONCLUSION

The hepatic injury in both hepatocytes and SECs in cold-preserved fatty liver graft developed more rapidly and severely than in the corresponding controls and demonstrated a protective effect of hrHGF.

The guanylate cyclase-coupled natriuretic peptide receptor: a new target for prevention of cold ischemia-reperfusion damage of the rat liver

The aim of our studies was to investigate hormonal prevention of hepatic preservation damage by the atrial natriuretic peptide (ANP) and the mechanisms involved. Isolated perfusion of rat livers was performed in a nonrecirculating fashion. Twenty minutes of preischemic perfusion was performed with or without different concentrations of ANP, followed by 24-hour storage in cold University of Wisconsin (UW) solution. Two hundred nanomoles of ANP prevented hepatocellular damage during a 2-hour reperfusion period as indicated by a marked attenuation of the sinusoidal efflux of lactate dehydrogenase (LDH) and purine nucleoside phosphorylase (PNP), and by reduced Trypan blue uptake. Furthermore, postischemic bile flow as an indicator of liver function was significantly improved by about 60% with 200 nmol/L ANP. No protection was conveyed by 20 nmol/L ANP nor by pretreatment with 200 nmol/L ANP for only 10 minutes. The effects of ANP seemed to be mediated by the guanylate cyclase-coupled A (GC-A) receptor and cyclic guanosine monophosphate (cGMP): whereas expression of both GC-A and GC-B receptors as well as of the GC-C receptor was found, cGMP did protect from ischemia-reperfusion damage, but selective ligands of the B and C receptor did not. To begin to determine the mechanisms of ANP-mediated protection, different parameters were investigated: ANP had no effect on portal pressure as an indicator of hepatic circulation, nor on intracellular energy depletion determined by adenosine nucleotide concentration. However, the marked augmentation of nuclear factor kappaB (NF-kappaB) binding activity during reperfusion was prevented in ANP-pretreated livers. In conclusion, pretreatment with ANP protects the rat liver from cold ischemia-reperfusion damage. This effect is mediated via the GC-A receptor and cGMP, and may be linked to an influence of ANP on NF-kappaB activation. Thus, ANP signaling via the GC-A receptor should be considered as a new pharmacological target to prevent preservation injury of the liver.

Hemopexin decreases spontaneous chemiluminescence of cold preserved liver after reperfusion

Hemopexin is a plasma protein with exceptionally high affinity for heme. During liver transplantation heme is released via lysis of transfused blood. This heme may catalyze peroxidative reactions that contribute to "reperfusion" injury of the organ. Using a rat liver model of cold storage and reperfusion we tested the potential anti-oxidant effects of hemopexin. After 3 h of cold storage rat liver was reperfused with warm oxygenated buffer. Spontaneous liver chemiluminescence, which is a parameter of oxyradical production, was measured during reperfusion and expressed as an index of free radical production (IFRP). Chemiluminescence reached a maximum within 5 min of reperfusion and decreased to baseline within 30 min. Addition of hemopexin to the perfusate (5 microM) significantly decreased the IFRP. By contrast, the control proteins albumin and gamma-globulin (10 microM) had a smaller non-significant effect. The data suggest that heme could be complexed by hemopexin during reperfusion, thus inhibiting heme mediated cellular injury.

Reperfusion injury after liver preservation for transplantation

Preservation injury remains an obstacle to greater utilization of liver transplantation therapy. Livers can be preserved a maximum of 24 h in University of Wisconsin solution. After longer times, reperfusion precipitates endothelial cell killing and activation of Kupffer cells (liver macrophages). Together, Kupffer cell activation and endothelial cell killing cause microcirculatory disturbances, leukocyte and platelet adhesion, and a systemic inflammatory response after graft implantation. Down-regulation of Kupffer cells with calcium blockers or pentoxifylline improves graft survival, whereas priming with lipopolysaccharide or alcohol worsens survival. Flushing grafts after storage with Carolina rinse solution containing antioxidants, adenosine, calcium blocker, energy substrates, and glycine at pH 6.5 decreases endothelial cell killing, reduces Kupffer cell activation, and improves graft survival. Understanding of the roles of different cells in storage/reperfusion injury forms the basis for strategies to prolong organ storage, improve graft function, and reduce failure of fatty grafts from alcoholic donors.