Evidence that free radicals are involved in graft failure following orthotopic liver transplantation in the rat--an electron paramagnetic resonance spin trapping study

Para-Substituted α-Phenyl-N-tert-butyl Nitrones: Spin-Trapping, Redox and Neuroprotective Properties

In this work, a series of para-substituted α-phenyl-N-tert-butyl nitrones (PBN) were studied. Their radical-trapping properties were evaluated by electron paramagnetic resonance, with 4-CF₃-PBN being the fastest derivative to trap the hydroxymethyl radical (^•CH₂OH). The redox properties of the nitrones were further investigated by cyclic voltammetry, and 4-CF₃-PBN was the easiest to reduce and the hardest to oxidize. This is due to the presence of the electron-withdrawing CF₃ group. Very good correlations between the Hammett constants (σ_p) of the substituents and both spin-trapping rates and redox potentials were observed. These correlations were further supported by computationally determined ionization potentials and atom charge densities. Finally, the neuroprotective effect of these derivatives was studied using two different in vitro models of cell death on primary cortical neurons injured by glutamate exposure or on glial cells exposed to ^t BuOOH. Trends between the protection afforded by the nitrones and their lipophilicity were observed. 4-CF₃-PBN was the most potent agent against ^t BuOOH-induced oxidative stress on glial cells, while 4-Me₂N-PBN showed potency in both models.

Substituted α-Phenyl and α-Naphthlyl-N-tert-butyl Nitrones: Synthesis, Spin-Trapping, and Neuroprotection Evaluation

New derivatives of α-phenyl-N-tert-butyl nitrone (PBN) bearing a hydroxyl, an acetate, or an acetamide substituent on the N-tert-butyl moiety and para-substituted phenyl or naphthlyl moieties were synthesized. Their ability to trap hydroxymethyl radical was evaluated by electron paramagnetic resonance spectroscopy. The presence of two electron-withdrawing substituents on both sides of the nitronyl function improves the spin-trapping properties, with 4-HOOC-PBN-CH₂OAc and 4-HOOC-PBN-CH₂NHAc being ∼4× more reactive than PBN. The electrochemical properties of the derivatives were further investigated by cyclic voltammetry and showed that the redox potentials of the nitrones are largely influenced by the nature of the substituents both on the aromatic ring and on the N-tert-butyl function. The acetamide derivatives PBN-CH₂NHAc, 4-AcNHCH₂-PBN-CH₂NHAc, and 4-MeO-PBN-CH₂NHAc were the easiest to oxidize. A computational approach was used to rationalize the effect of functionalization on the free energies of nitrone reactivity with hydroxymethyl radical as well as on the electron affinity and ionization potential. Finally, the neuroprotection of the derivatives was evaluated in an in vitro model of cellular injury on cortical neurons. Five derivatives showed good protection at very low concentrations (0.1-10 μM), with PBN-CH₂NHAc and 4-HOOC-PBN being the two most promising agents.

Protection of rat liver against hepatic ischemia-reperfusion injury by a novel selenocysteine-containing 7-mer peptide

Hepatic ischemia-reperfusion (I-R) injury causes acute organ damage or dysfunction, and remains a problem for liver transplantation. In the I-R phase, the generation of reactive oxygen species aggravates the injury. In the current study, a novel selenocysteine-containing 7‑mer peptide (H-Arg-Sec-Gly-Arg-Asn-Ala-Gln-OH) was constructed to imitate the active site of an antioxidant enzyme, glutathione peroxidase (GPX). The 7‑mer peptide which has a lower molecular weight, and improved water‑solubility, higher stability and improved cell membrane permeability compared with other GPX mimics. Its GPX activity reached 13 U/µmol, which was 13 times that of ebselen (a representative GPX mimic). The effect of this GPX mimic on I‑R injury of the liver was assessed in rats. The 7‑mer peptide significantly inhibited the increase in serum hepatic amino‑transferases, tissue malondialdehyde, nitric oxide contents, myeloperoxidase activity and decrease of GPX activity compared with I‑R tissue. Following treatment with the 7‑mer peptide, the expression of B‑cell CLL/lymphoma‑2 (Bcl‑2) was significantly upregulated at the mRNA and protein level compared with the I‑R group, as determined by reverse transcription‑polymerase chain reaction and immunohistochemistry, respectively. By contrast, Bcl‑2 associated X protein (Bax) was downregulated by the 7‑mer peptide compared the I‑R group. Histological and ultrastructural changes of the rat liver tissue were also compared among the experimental groups. The results of the current study suggest that the 7‑mer peptide protected the liver against hepatic I‑R injury via suppression of oxygen‑derived free radicals and regulation of Bcl‑2 and Bax expression, which are involved in the apoptosis of liver cells. The findings of the present study will further the investigation of the 7-mer peptide as an effective therapeutic agent in hepatic I-R injury.

CD47 blockade reduces ischemia/reperfusion injury and improves survival in a rat liver transplantation model

Orthotopic liver transplantation (OLT) remains the standard treatment option for nonresponsive liver failure. Because ischemia/reperfusion injury (IRI) is an important impediment to the success of OLT, new therapeutic strategies are needed to reduce IRI. We investigated whether blocking the CD47/thrombospondin-1 inhibitory action on nitric oxide signaling with a monoclonal antibody specific to CD47 (CD47mAb400) would reduce IRI in liver grafts. Syngeneic OLT was performed with Lewis rats. Control immunoglobulin G or CD47mAb400 was administered to the donor organ at procurement or to both the organ and the recipient at the time of transplant. Serum transaminases, histological changes of the liver, and animal survival were assessed. Oxidative stress, inflammatory responses, and hepatocellular damage were also quantified. A significant survival benefit was not achieved when CD47mAb400 was administered to the donor alone. However, CD47mAb400 administration to both the donor and the recipient increased animal survival afterward. The CD47mAb400-treated group showed lower serum transaminases, bilirubin, oxidative stress, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling staining, caspase-3 activity, and proinflammatory cytokine expression of tumor necrosis factor α, interleukin-1β, and interleukin-6. Thus, CD47 blockade with CD47mAb400 administered both to the donor and the recipient reduced liver graft IRI in a rat liver transplantation model. This may translate to decreased liver dysfunction and increased survival of liver transplant recipients.

Temporal changes in hepatic antioxidant enzyme activities after ischemia and reperfusion in a rat liver ischemia model

This study investigated the hypothesis that administration of tilapia fish oil diet would attenuate warm liver ischemia/reperfusion injury (IRI) and whether fish oil modulates prooxidant/antioxidant status. Male Wistar rats were subjected to 30 min of approximately 70% hepatic ischemia followed by 1, 12, and 24 h reperfusion. Rats were randomly divided into three groups: sham-operated group (SO), control–warm hepatic ischemia (WI) group, and Oil–WI group given tilapia oil for 3 weeks followed by liver IRI. Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels were measured in the plasma. Levels of thiobarbituric acid reactive substances (TBARS) and antioxidant enzymes as superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) activities were measured in liver fractions.

In the sham group, there was no enzymatic or histological change. I/R caused significant increase in serum AST, ALT, and tissue TBARS levels. As compared to the control group, animals treated with tilapia oil experienced a significant decrease ( p < 0.05) in AST and ALT levels in reperfusion periods. Tissue TBARS levels in Oil–WI group were significantly ( p < 0.05) reduced as compared to control group at 60 min after reperfusion. After ischemia, 1, 12, and 24 h of reperfusion, CAT, SOD, and GPx values were the lowest in the Oil–WI group and highest in the control group and were statistically significant ( p < 0.05). Histological analysis also revealed that fish oil provided some protection compared with the control group.

Tilapia oil exerts a protective effect during the early phase of reperfusion, and it modulates prooxidant/antioxidant status of rat liver subjected to warm IRI.

Current knowledge on oxidative stress in hepatic ischemia/reperfusion

Ischemia/reperfusion (I/R) injury associated with hepatic resections and liver transplantation remains a serious complication in clinical practice, despite several attempts to solve the problem. The redox balance, which is pivotal for normal function and integrity of tissues, is dysregulated during I/R, leading to an accumulation of reactive oxygen species (ROS). Formation of ROS and oxidant stress are the disease mechanisms most commonly invoked in hepatic I/R injury. The present review examines published results regarding possible sources of ROS and their effects in the context of I/R injury. We also review the effect of oxidative stress on marginal livers, which are more vulnerable to I/R-induced oxidative stress. Strategies to improve the viability of marginal livers could reduce the risk of dysfunction after surgery and increase the number of organs suitable for transplantation. The review also considers the therapeutic strategies developed in recent years to reduce the oxidative stress induced by hepatic I/R, and we seek to explain why some of them have not been applied clinically. New antioxidant strategies that have yielded promising results for hepatic I/R injury are discussed.

Hyperacute rejection in the xenogenic transplanted rat liver is triggered by the complement system only in the presence of leukocytes and free radical species

BACKGROUND

Reactive oxygen species (ROS) and nitric oxide species (NOS) are pivotal after ischemia-reperfusion. However, the role of different cells on the formation of free radical species after xenotransplantation remains elusive. We hypothesized that ROS and NOS formed during hyperacute rejection are dependent on leukocytes, erythrocytes, activated thrombocytes, and Kupffer cells (KCs). To address this issue, we developed a model of xenoperfused rat liver and assessed the relationship between free radical production and graft dysfunction.

METHODS

Livers from Sprague-Dawley rats were isolated, flushed with cold Ringer solution, and perfused at physically flow rates for 120 min after 1 h of ischemia. The control group was perfused with rat whole blood (n = 9). In the study groups, the livers were perfused with human whole blood, human plasma with erythrocytes, and plasma with erythrocytes and isolated thrombocytes (n = 9/group). In an additional group, gadolinium chloride (GdCl3), a selective Kupffer cell (KC) toxic agent, was applied. Liver damage, hyperacute rejection, and the depletion of KCs were monitored histologically. Liver damage and function were determined by means of liver enzymes, portal pressure, and bile production. Malondialdehyde (MDA), nitric oxide formation, and peroxynitrite concentration, as well as total glutathione (tGSH) level, were measured as indicators for free radical formation and anti-oxidative status.

RESULTS

Significant differences in the MDA, NO, peroxynitrite levels, and GSH levels after reperfusion with various cell populations were observed. Markedly high ROS/RNS production was evident in the KCs and the xenogeneic whole-blood group. The oxidative stress was mainly caused by leukocytes and to lower extent by KCs, but only in combination with leukocytes. Neither erythrocytes, thrombocytes, nor hepatocytes had an effect on the release of ROS and RNS, as we could not observe significant differences in the MDA, peroxynitrite, and NO levels in these groups compared with control. Tissue injury and hyperacute rejection were more evident in the KC and whole-blood livers. No sign of damage was observed for the control, erythrocyte, and thrombocyte group. Removal of leukocytes from the perfusate by filtration had a major protective effect on the liver function and the grade of hyperacute rejection, whereas KC depletion reduced the ROS production, but did not have an impact on the hyperacute rejection and liver damage. In all xenogeneic perfused groups, the activation of the complement was histologically observed by positive C3c and C9b. Neither KC depletion nor the removal of leukocytes or thrombocytes from the perfusate had an effect on the activation of the complement system. Damage of the rat liver by the complement system was only observed in association with leukocytes.

CONCLUSION

Our data revealed that various cell populations contribute to the formation of free radicals in our model. The production of free radicals was mainly linked to leukocytes and to a minor extent to KCs, but only in combination with leukocytes. Free radicals critically contribute to injury, rejection, and dysfunction of the xenotransplanted liver. Furthermore, hyperacute rejection in the xenogeneic perfused liver is triggered by the complement system only in the presence of leukocytes and free radical formation.

Role of EC-SOD overexpression in preserving pulmonary angiogenesis inhibited by oxidative stress

Angiogenesis is one of the most important processes for normal lung development. Oxidative stress can impair the pulmonary angiogenesis, leading to chronic lung disease or Bronchopulmonary dysplasia (BPD).

Impact of age on liver regeneration response to injury after partial hepatectomy in a rat model

BACKGROUND

Liver resection is a feasible treatment for multiple liver diseases. There is no evidence about the impact of age on liver regeneration.

OBJECTIVE

To assess the effect of age on liver regeneration in an experimental in vivo animal model of 70%-partial hepatectomy.

METHODS

Forty young (Y) and old (O) Wistar male rats (n = 80) were distributed into four groups [controls (C), sham operated (SO), hepatectomy 6 h (H6), and 48 h (H48)]. Different morphometric and biochemical factors, oxidative and nitrosative stress, lipid peroxidation, cytokines kinetics, and histopathologic tissular parameters were determined.

RESULTS

Early postoperative mortality was higher in aged rats (P = 0.049). Morphometric determinations, liver regeneration index, and total volume weight were favorable to young rats. Serum transaminase levels were higher in aged rats. Parameters of necrosis (measured by histopathologic injury [HI: 0-I-II-III]), regeneration (measured by bromodeoxyuridine-BrdU incorporation) and apoptosis (determined by the TDT-mediated dUTP nick end labeling-TUNEL) were well-synchronized in young rats. Parameters of oxidative stress such as reduced (GSH), oxidized (GSSG) glutathione and lipid peroxidation (measured by hepatic malondialdehyde -MDA-) were lower in young animals throughout the studied period. Nitrosative stress measured by nitric oxide (NO) end-products was higher in late stages in resected old rats. Pro-inflammatory cytokines (TNF- α) reached higher and earlier levels in aged rats while pro-regenerative cytokines (IL-6) were significantly higher in early stages for young rats and in late stages for aged rats. The levels of TGF-β were higher in young rats.

CONCLUSION

Liver regeneration is delayed and reduced in aged animals submitted to liver resection.

Role of transcription factors in small intestinal ischemia-reperfusion injury and tolerance induced by ischemic preconditioning

BACKGROUND

Small intestinal ischemia-reperfusion (I/R) injury, a clinically important condition, induces severe organ damage. Ischemic preconditioning (IPC) produces tolerance to long-term I/R by inducing a short-term I/R. Herein, we have examined the reduction in the extent of injury by IPC.

METHODS

Small intestinal I/R injury was induced in rats by clamping the superior mesenteric artery (SMA) for 30 minutes followed by reperfusion for various 30 minutes. The IPC + I/R group underwent a short-term I/R (IPC) prior to long-term I/R. Nuclear factor-κB (NF-κB) activity was analyzed by an electrophoretic mobility shift assay and cytokine mRNA levels, by reverse transcription-polymerase chain reaction. Apoptosis-related genes were analyzed by Western blotting and immunohistochemistry, and apoptotic cells, by TUNEL staining.

RESULTS

The animals were subjected to 30 minutes of ischemia followed by 30 minutes of reperfusion. NF-κB activity increased in the I/R group and decreased in the IPC + I/R group. The IPC + I/R group showed decreased cytokine in mRNA levels. Expression of the proapoptotic gene caspase-3 was increased in the I/R and decreased in the IPC + I/R group. Expression of the antiapoptotic gene Bcl-xL was increased in the IPC + I/R group. The number of apoptotic cells was increased in the I/R and decreased in the IPC + I/R group.

CONCLUSION

Small intestinal I/R injury was reduced by IPC produced by clamping the SMA; thus, IPC may have potential clinical applications in the future.

Effects of tetrandrine on ischemia/reperfusion injury in mouse liver

OBJECTIVE

Hepatic ischemia/reperfusion injury (IRI) may cause acute inflammatory damage, producing significant organ dysfunction, an important problem for liver transplantation. Previous studies have demonstrated that Tetrandrine (Tet), a component of traditional Chinese herbal medicine, shows protective effects to scavenge active oxygen radicals and inhibit lipid peroxidation. In this study, we examined whether Tet has a protective effect on mouse hepatic IRI.

MATERIALS AND METHODS

Male C57BL/6 mice were divided into sham, ischemic, and Tet-treated groups; 90 minutes of warm ischemia was performed on the left liver lobe. Tet (20 mg/kg) was injected intraperitoneally at 1 hour before ischemia with a second intravenous dose was injected just before reperfusion. Blood and liver samples were collected at 6 hours after reperfusion. We analyzed the hepatocellular injury, oxidative stress, neutrophil recruitment, and tumor necrosis factor-alpha (TNF-alpha) generation associated with hepatic IRI.

RESULTS

Undergoing 90 minutes of ischemia and 6 hours reperfusion caused dramatic injuries in mouse livers. Administration of Tet (20 mg/kg) reduced serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and lactate dehydrogenase (LDH); decreased liver edema, TNF-alpha, myeloperoxidase (MPO) and malondialdehyde (MDA) contents; and ameliorated the down-regulation of superoxide dismutase (SOD) activity.

CONCLUSION

Tet showed protective effects on mouse hepatic IRI.

C-Jun N-terminal kinase 2 promotes graft injury via the mitochondrial permeability transition after mouse liver transplantation

The c-Jun N-terminal kinase (JNK) pathway enhances graft injury after liver transplantation (LT). We hypothesized that the JNK2 isoform promotes graft injury via the mitochondrial permeability transition (MPT). Livers of C57BL/6J (wild-type, WT) and JNK2 knockout (KO) mice were transplanted into WT recipients after 30 h of cold storage in UW solution. Injury after implantation was assessed by serum ALT, histological necrosis, TUNEL, Caspase 3 activity, 30-day survival, and cytochrome c and 4-hydroxynonenal immunostaining. Multiphoton microscopy after LT monitored mitochondrial membrane potential in vivo. After LT, ALT increased three times more in WT compared to KO (p < 0.05). Necrosis and TUNEL were more than two times greater in WT than KO (p < 0.05). Immunostaining showed a >80% decrease of mitochondrial cytochrome c release in KO compared to WT (p < 0.01). Lipid peroxidation was similarly decreased. Every KO graft but one survived longer than all WT grafts (p < 0.05, Kaplan-Meier). After LT, depolarization of mitochondria occurred in 73% of WT hepatocytes, which decreased to 28% in KO (p < 0.05). In conclusion, donor JNK2 promotes injury after mouse LT via the MPT. MPT inhibition using specific JNK2 inhibitors may be useful in protecting grafts against adverse outcomes from ischemia/reperfusion injury.

Effects of mannitol in the prevention of lipid peroxidation during liver resection with hepatic vascular exclusion

STUDY OBJECTIVE

To examine the efficacy of mannitol in the prevention of lipid peroxidation during major liver resections performed during hepatic inflow occlusion.

DESIGN

Prospective, randomized, open-label study.

SETTING

Aretaieion Hospital, a university-affiliated hospital.

PATIENTS

30 ASA physical status II and III patients, less than 75 years of age, scheduled for elective liver resection.

INTERVENTIONS

All patients received combined general and epidural anesthesia. Laparotomy was performed through a bilateral subcostal incision, and hepatectomy was performed by inflow vascular exclusion (Pringle's maneuver). Before this maneuver, and if the patients were hemodynamically stable, they were randomized to receive either mannitol 20% 1.5 mL kg(-1) (group M) or normal saline 1.5 mL kg(-1) (group S) intravenously for 30 minutes.

MEASUREMENTS

Venous blood malondialdehyde (MDA) concentration, as an index of lipid peroxidation, was measured spectrophotometrically at selected time points.

MAIN RESULTS

Patients in both groups presented with raised MDA values (P < 0.05) for the period starting before the release of vascular occlusion until 6 days postoperatively. In patients receiving mannitol, lower MDA values were observed (P < 0.05) compared with group S at the end of operation.

CONCLUSION

Mannitol has an antioxidant activity, but we were unable to confirm a positive impact on the postoperative clinical course.

Minimizing oxidative stress by gene delivery of superoxide dismutase accelerates regeneration after transplantation of reduced-size livers in the rat

Transplantation of reduced-size livers may lead to a hypermetabolic state and increased production of oxygen radicals. Since oxygen radicals may cause liver injury and impair liver regeneration, we tested the hypothesis that overexpression of superoxide dismutase (SOD) in reduced-size livers (RSL) would accelerate regeneration and reduce injury in a rat model of transplantation of RSL. Donor rats were infected with adenoviruses either expressing SOD1 (Ad.SOD1) or beta-galactosidase (Ad.lacZ). Livers were harvested 72 hours later, reduced to 45% of weight, and transplanted. After transplantation, hepatic SOD activity, graft survival, histopathology, AST/ALT release, and bilirubin were examined. Regeneration was evaluated by BrdU-staining, graft weight, and expression of cyclin D1 and p21. In Ad.SOD1-treated livergrafts, SOD activity increased three-fold compared to controls. Survival was dramatically increased in recipients of Ad.SOD1-RSL (100% vs. 20% in Ad.lacZ-RSL), and peak levels of AST/ALT and bilirubin levels were reduced by 75% and 87.5%, respectively (P < 0.001). In histological sections, hepatocyte necrosis decreased from 24% after Ad.lacZ-treatment to 6% after Ad.SOD1-treatment (P <0.001). Regeneration was also accelerated after Ad.SOD1-treatment as demonstrated by an increase of BrdU-stained cells 24 hours after reperfusion and increased liver weight after 1 week. In conclusion, overexpression of SOD1 in RSL prevents primary non-function of reduced-size liver grafts and accelerates liver regeneration.

Role of nitric oxide in resveratrol-induced renal protective effects of ischemic preconditioning

BACKGROUND

Resveratrol, a natural antioxidant and polyphenol found in red wine and grapes, has been found to pharmacologically precondition the heart through upregulation of nitric oxide (NO). This study was designed to explore the involvement of NO in the renoprotective effect of resveratrol in renal ischemic preconditioning in rat kidney.

METHODS

Ischemic preconditioning was induced by three cycles 2-minutes of ischemia followed by 5 minutes of reperfusion before 45 minutes of prolonged ischemia. Resveratrol was given 1 hour before the surgical procedures.

RESULTS

Ischemic preconditioning and resveratrol treatment significantly improved the renal dysfunction, decrease in total NO levels, and oxidative stress induced by 45 minutes of ischemia followed by 24 hours of reperfusion. Histopatholgic examination of the kidneys of ischemic/reperfusion rats revealed severe renal damage, which was attenuated in both preconditioned and resveratrol-treated animals. Preconditioning and resveratrol administration led to a marked increase in NO levels in kidney. Renoprotective effects of resveratrol were abolished when animals were pretreated with NG-nitro-L-arginine methyl ester, a nonspecific NO synthase inhibitor.

CONCLUSIONS

These findings demonstrate an important contributory role of NO in the protection afforded by resveratrol in renal ischemic preconditioning.

CLINICAL RELEVANCE

It is now well established that brief periods of ischemia followed by reperfusion render a variety of tissues tolerant to subsequent ischemia/reperfusion-induced injury. This phenomenon, referred to as ischemic preconditioning, was first demonstrated in the dog myocardium. The potential for clinical application of such a powerful protective phenomenon has generated enormous interest in identifying the underlying intracellular signaling pathways, with the ultimate aim of pharmacologically exploiting these mechanisms to develop therapeutic strategies that can enhance tolerance to ischemia/reperfusion injury in patients. This study explored the possible involvement of nitric oxide in renal ischemic preconditioning.

Free radical-dependent dysfunction of small-for-size rat liver grafts: prevention by plant polyphenols

BACKGROUND & AIMS

The mechanisms by which small-for-size liver grafts decrease survival remain unclear. This study investigated the role of free radicals in injury to small-for-size grafts.

METHODS

Rat liver explants were reduced in size ex vivo and transplanted into recipients of the same or greater body weight, resulting in a graft weight and standard liver weight of approximately 50% and 25%, respectively. A polyphenol extract from Camellia sinenesis (20 microg/mL) or an equivalent concentration of epicatechin was added to the storage solution and the lactated Ringer poststorage rinse solution.

RESULTS

Serum alanine aminotransferase release increased from approximately 60 U/L before implantation to 750, 1410, and 2520 U/L after full-size, half-size, and quarter-size transplantation, respectively. Total bilirubin increased slightly after transplantation of full-size and half-size grafts but increased 104-fold in quarter-size grafts. In quarter-size grafts, histological changes included necrosis, leukocyte infiltration, and eosinophilic inclusion body formation. Polyphenol treatment ameliorated these effects by > or =67%. Survival was 30% after transplantation of small-for-size grafts. After polyphenol treatment, survival increased to 70%. Free radicals in bile assessed by spin trapping and 4-hydroxynonenal adducts measured by immunohistochemistry were also greater in reduced-size grafts, an effect ameliorated by polyphenols. Epicatechin, a major polyphenol from Camellia sinenesis, also improved graft function and decreased enzyme release, histopathologic changes, and free radical formation.

CONCLUSIONS

Increased formation of free radicals occurs after transplantation of reduced-size livers, which contributes to graft dysfunction and failure. Plant polyphenols decrease liver graft injury and increase survival of small-for-size liver grafts, most likely by scavenging free radicals.

The reduced tolerance of rat fatty liver to ischemia reperfusion is associated with mitochondrial oxidative injury

BACKGROUND

Oxidative stress contributes to the pathogenesis of hepatic ischemia-reperfusion injury. This study aimed to determine whether fatty degeneration affects the oxidative damage during warm ischemia reperfusion and whether mitochondria, the major intracellular site of energy synthesis, represent a preferential target of this injury.

MATERIALS AND METHODS

Fed rats with control or fatty liver induced by choline deficiency underwent 60' lobar ischemia and reperfusion. Oxidative damage was assessed by measuring in whole liver tissue and in isolated mitochondria the thiobarbituric acid-reactive substances (TBARs), protein carbonyls (PC), and total and oxidized glutathione (GSH and GSSG) concentrations. The mitochondrial F0-F1-ATPase content and the oxidative phosphorylation activity were also determined. Rat survival and ALT release were assessed as parameters of liver injury.

RESULTS

In the whole liver tissue, with the exception of TBARs, no differences were observed for GSH, GSSG, and PC between the two groups throughout all of the experiment. In contrast, in isolated mitochondria, fatty infiltration was associated with a mild oxidative imbalance already under basal conditions. The preischemic differences in the mitochondrial TBARs, PC, and GSSG levels were significantly amplified by reperfusion in the presence of steatosis. The enhanced oxidative damage was associated to a reduced F0-F1-ATPase content and oxidative phosphorylation activity in fatty liver mitochondria. Finally, serum ALT levels were significantly greater and survival significantly lower in rats with steatotic liver.

CONCLUSIONS

Fatty infiltration exacerbates mitochondrial oxidative injury during warm ischemia reperfusion. The increased oxidative stress can alter mitochondrial functions, including key processes for ATP synthesis, thus, contributing to the reduced tolerance to reperfusion injury.

Treatment with α-Phenyl-N-tert-butylnitrone, a Free Radical-Trapping Agent, Abrogates Inflammatory Cytokine Gene Expression during Alloimmune Activation in Rat Cardiac Allografts

Spin-trapping nitrones such as alpha-phenyl-N-tert-butylnitrone (PBN) have traditionally been used to trap and stabilize free radicals for detection by electron paramagnetic resonance (EPR) spectroscopy. Unlike classical antioxidants, these agents have never been evaluated therapeutically in allograft transplantation. In the present study, we examined potential mechanisms of action of treatment with PBN in a rat model of acute cardiac allograft transplantation. Graft rejection was determined by histological examination and graft function determined by in situ sonomicrometry. DNA binding for nuclear factor (NF)-kappaB and activator protein (AP-1) were determined by gel shift assays. Western blot and reverse transcriptase-polymerase chain reaction (RT-PCR) analysis was performed for inducible nitric-oxide synthase (iNOS) and inflammatory cytokines. Histological rejection scores were elevated in untreated allografts and decreased by treatment with PBN. In situ sonomicrometry revealed decreased heart rate and distended end diastolic and end systolic segment lengths with rejection. Although PBN did not alter heart rate, it did normalize the distention of both diastolic and systolic cardiac dimension. EPR spectroscopy revealed nitrosylation of myocardial heme protein in untreated allografts that was decreased by treatment with PBN. PBN also decreased iNOS protein and iNOS mRNA. RT-PCR analysis revealed enhanced cytokine gene expression for interferon-gamma, interleukin-6, and interleukin-10 in untreated allografts. Expression for these genes was potently inhibited or abolished in recipients treated with PBN. PBN treatment also decreased DNA binding of transcription factors, NF-kappaB and AP-1. Thus, PBN retains significant anti-inflammatory properties through its action to down-regulate cytokine gene expression that contribute to protection against acute alloimmune activation in cardiac allografts.

Role of free radicals in failure of fatty liver grafts caused by ethanol

Alcohol is associated with accidental deaths and suicides leading to organ donation, and hepatic steatosis is an important risk factor for initial poor function and failure of human liver grafts. Mechanisms of fatty graft failure are not fully understood, but increased oxidative stress may be a major factor. To characterize the role of free radical stress and the efficacy of antioxidant treatments in fatty liver graft injury, donors for orthotopic rat liver transplantation were treated chronically (3 or more weeks) and acutely (single dose) with ethanol. After transplantation, necrosis and alanine aminotransferase release were threefold to fourfold higher in recipients of fatty grafts from donors treated with ethanol either acutely or chronically compared with findings for recipients of grafts from untreated donors. Moreover, graft survival decreased from nearly 100% to less than 20%. Free radical adducts, as measured by electron spin resonance spectroscopy, were detected in the blood and bile of rats receiving fatty grafts caused by ethanol. Markers of lipid peroxidation also increased after transplantation. Destruction of Kupffer cells with gadolinium chloride decreased free radical production and improved graft survival. Leukocyte adhesion increased beginning early after implantation, and adherent white blood cells obtained from transplanted fatty livers produced the same free radical species as were detected in blood. Therefore, Kupffer cells and adherent white blood cells are important sources of free radicals. Free radicals not only damage fatty grafts directly but also lead to enhanced inflammation and disturbed microcirculation. Delivery of superoxide dismutase-1 and superoxide dismutase-2 genes, free radical-scavenging polyphenols, and antioxidant-containing Carolina Rinse solution reduced injury and improved survival of fatty grafts caused by ethanol. Taken together, these findings indicate that free radicals increase in fatty grafts after transplantation and play an important role in injury of fatty grafts obtained from ethanol-exposed donors. Treatment of fatty donor livers with antioxidants and free radical scavengers may thus be an effective clinical therapy to prevent failure of fatty grafts.

Polyphenols from Camellia sinenesis prevent primary graft failure after transplantation of ethanol-induced fatty livers from rats

Fatty liver caused by ethanol decreases survival after liver transplantation in rats. This study investigated if antioxidant polyphenols from Camellia sinenesis (green tea) prevent failure of fatty grafts from ethanol-treated rats. Donor rats were given ethanol intragastrically (6 g/kg). After 20 h, livers were explanted and stored in University of Wisconsin solution for 24 h. Prior to implantation, the explanted grafts were rinsed with lactated Ringer's solution containing 0 to 60 microg/ml polyphenols. Alanine aminotransferase (ALT) release after liver transplantation was 4.5-fold higher in recipients receiving ethanol-induced fatty grafts than in those receiving normal grafts. Liver grafts from ethanol-treated donors also developed severe focal necrosis. Graft survival was 11% in the ethanol group versus 88% for normal grafts. Polyphenol treatment at 60 microg/ml blunted ALT release by 66%, decreased necrotic areas by 84%, and increased survival to 75%. Ethanol increased alpha-(4-pyridyl-1-oxide)-N-tert.-butylnitrone free radical adducts in bile by 2.5-fold, as measured by electron spin resonance spectroscopy, and caused accumulation of 4-hydroxynonenal in liver sections, effects blunted by polyphenols. Epicatechin gallate, a major polyphenol from C. sinenesis, also decreased enzyme release, minimized pathological changes, and decreased free radical adduct formation. In conclusion, polyphenols scavenged free radicals in ethanol-induced fatty livers and decreased injury after liver transplantation.

The protective mechanism of Yisheng Injection against hepatic ischemia reperfusion injury in mice

AIM: Hepatic ischemia/reperfusion injury may cause acute inflammatory, significant organ damage or dysfunction, and remains an important problem for liver transplantation. Our previous in vivo and in vitro studies demonstrated that Yisheng injection (YS), a traditional Chinese medicine, had protective effect on ischemia/reperfusion injury. In this study, we examined whether YS had protective effect for hepatic ischemia/reperfusion injury and explored its protective mechanism.

METHODS: Hepatic warm ischemia/reperfusion was induced in mice. YS at different doses (5, 10, 20 mg/kg) was injected intraperitoneally 24 h and 1 h before ischemia and a third dose was injected intravenously just before reperfusion. The hepatocellular injury, oxidative stress, neutrophil recruitment, proinflammatory mediators and adhesion molecules associated with hepatic ischemia/ reperfusion injury were assayed by enzyme-linked immunosorbent assay (ELISA), immunohistochemical assay and reverse transcription polymerase chain reaction (RT-PCR).

RESULTS: Undergoing 90 min of ischemia and 6 h of reperfusion caused dramatical injuries in mouse livers. Administration of YS at doses of 5, 10 and 20 mg/kg effectively reduced serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and lactate dehydrogenase (LDH), from 3 670 ± 463 U/L, 2 362 ± 323 U/L and 12 752 ± 1 455 U/L in I/R group to 1 172 ± 257 U/L, 845 ± 193 U/L and 2 866 ± 427 U/L in YS (20 mg/kg) treated group, respectively (P < 0.01). The liver myeloperoxidase (MPO) and malondialdehyde (MDA) contents were decreased from 1.1 ± 0.2 (U/mg protein) and 9.1 ± 0.7 (nmol/mg protein) in I/R group to 0.4 ± 0.1 (U/mg protein) and 5.5 ± 0.9 (nmol/mg protein) in YS (20 mg/kg) treated group, respectively (P < 0.01). Moreover, the serum levels of tumor necrosis factor-alpha (TNF-α) were reduced from 55 ± 9.9 (pg/mL) in I/R group to 16 ± 4.2 (pg/mL) (P < 0.01). Furthermore, the over-expressions of TNF-α and intercellular adhesion molecule-1 (ICAM-1) were suppressed by YS treatment in a dose-dependent manner.

CONCLUSION: YS attenuates hepatic warm ischemia/reperfusion injury by reducing oxidative stress and suppressing the over-expression of proinflammatory mediators and adhesion molecules.

Ischaemia–reperfusion is an event triggered by immune complexes and complement

Background

Reperfusion injury is a common clinical problem that lacks effective therapy. Two decades of research implicating oxygen free radicals and neutrophils has not led to a single successful clinical trial.

Methods

The aim was to review new clinical and preclinical data pertaining to the alleviation of reperfusion injury. A review of the literature was undertaken by searching the MEDLINE database for the period 1966–2003 without language restrictions.

Results and conclusion

Evidence now points to complement and immune complexes as critical players in mediating reperfusion injury. Ischaemia is postulated to induce a phenotypical cellular change through the surface expression of a neoantigen. Preformed circulating natural IgM antibodies are then trapped and complement is activated. Final events leading to reperfusion injury include formation of the membrane attack complex and mast cell degranulation.

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.

Effects of three superoxide dismutase genes delivered with an adenovirus on graft function after transplantation of fatty livers in the rat

BACKGROUND

Oxygen-derived free radicals play a central role in ischemia/reperfusion injury after organ transplantation and are degraded by endogenous radical scavengers such as superoxide dismutase (SOD). Overexpression of SOD by delivery of the cytosolic SOD gene with an adenovirus (Ad.SOD1) decreases organ injury and increases survival in a rat model of liver transplantation. However, it is unclear which of the three isoforms of SOD provides the most protective effect. The purpose of this study was to identify the isoform with the highest effectiveness against ischemia/reperfusion injury after transplantation of fatty livers, which are particularly susceptible.

METHODS

Donor rats were given ethanol by gavage before harvest to induce steatotic livers. Some of the donors were infected with adenoviruses expressing either the gene lacZ encoding bacterial beta-galactosidase (Ad.lacZ), Ad.SOD1, Ad.SOD2 (mitochondrial isoform), or Ad.SOD3 (extracellular isoform). After transplantation, SOD activity in liver, survival, histopathology, transaminases, and activation of nuclear factor (NF)-kappaB, IkappaB kinase, Jun-N-terminal kinase (JNK), and tumor necrosis factor (TNF)-alpha were evaluated.

RESULTS

Ad.SOD1 treatment increased survival, blunted transaminase release, and reduced necrosis, whereas Ad.SOD3 had no protective effect. Ad.SOD2 was not as protective as Ad.SOD1. Ad.SOD1 reduced the activation of NF-kappaB, blunted JNK activity, and reduced TNF-alpha activity. Ad.SOD2 treatment resulted in lower kinase, TNF-alpha, and NF-kappaB activities but was not as effective as Ad.SOD1. IkappaB kinase activity was not affected.

CONCLUSION

This study demonstrates that cytosolic SOD represents the most effective isoform of SOD to protect transplanted livers from failure; this may be related to lowered NF-kappaB and JNK activities because of reduced oxygen-derived radical production.

Liver transplantation from controlled non-heart-beating donors: an increased incidence of biliary complications

BACKGROUND

Hepatic allografts from non-heart-beating donors (NHBD) have been cited as a means to expand the supply of donor livers. Concern exists that donor warm ischemic time in addition to subsequent cold ischemia-reperfusion injury may result in damage to sensitive cell populations within the liver. Because the biliary epithelium is sensitive to ischemia-reperfusion injury, the authors surmised that an increased incidence of biliary complications might occur among recipients of an NHBD allograft.

METHODS

This study was a retrospective evaluation of NHBD recipients compared to a group of heart-beating donor (HBD) recipients from a single institution.

RESULTS

Fifteen patients received a hepatic allograft from a controlled NHBD donor. NHBD and HBD (n=221) graft survival did not differ at 1 (71.8% vs. 85.4%, P=0.23) or 3 years (71.8% vs. 73.9%, P=0.68). Patient survival at 1 (79% vs. 90.9%, P=0.16) and 3 years (79.0% vs. 77.7%, P=0.8) was also similar. Major biliary complications occurred in five (33.3%) NHBD recipients; 66.6% of the NHBD biliary complications consisted of intrahepatic strictures versus 19.2% among HBD recipients (P<0.01). Major biliary complications in the NHBD recipients resulted in multiple interventional procedures, retransplantation, and death.

CONCLUSIONS

Donor warm ischemic time may predispose hepatic allografts to an increased incidence of ischemic type strictures. Although graft and patient survival was similar to a cohort of HBD recipients, caution is urged with the use of these organs.

Oxygen consumption and electron spin resonance studies of free radical production by alveolar cells exposed to anoxia: inhibiting effects of the antibiotic ceftazidime

By EPR spectroscopy, we investigated free radical production by cultured human alveolar cells subjected to anoxia/re-oxygenation (A/R), and tested the effects of ceftazidime, an antibiotic previously demonstrated to possess antioxidant properties. Two A/R models were performed on type II pneumocytes (A549 cell line), either on cells attached to culture dishes (monolayer A/R model; 3.5 h of anoxia, 30 min of re-oxygenation) or after cell detachment (suspension A/R model; 1 h of anoxia, 10 min of re-oxygenation). Ceftazidime and selective inhibitors (SOD, Tiron, L-NMMA) were added before anoxia. Free radical production was assessed by the EPR spin trapping technique. Oxygen consumption was monitored, in parallel with EPR studies, in the suspension A/R model. The production of free radical species was demonstrated by the generation of PBN-radical adducts: (a(N) = 15.2 G) in the monolayer A/R model and a six-line EPR spectrum (a(N) = 15.7 G and a(H) = 2.7 G) in the suspension A/R model. A kinetic study performed by oximetry, in parallel with EPR spectroscopy, demonstrated marked alterations of the cell respiratory function and that the free radical production started during anoxia and increased during re-oxygenation. In the suspension A/R model, the amplitude of EPR spectra were decreased upon the addition of 200 U/ml SOD (37% inhibition), 0.1 mM Tiron (67% inhibition) and 1 mM L-NMMA (43% inhibition). Addition of 1 mM ceftazidime decreased the amplitude of EPR spectra (37% inhibition) in both A/R models. Complementary in vitro EPR studies demonstrated that CAZ scavenged the hydroxyl radical (produced by the Fenton reaction). The protective effect of ceftazidime in the cell model could thus be linked to its ability to scavenge superoxide anions, nitrogen-derived species and hydroxyl radicals.

Evaluation of warm ischemia-reperfusion injury using heat shock protein in the rat liver

We focused on heat shock protein 70 (HSP70) as a marker of viability in hepatic warm ischemia-reperfusion. Segmental hepatic warm ischemia was produced in rats for 15, 30, 60, 90, 120, or 180 min. Liver sections were evaluated at 30, 60, and 120 min of reperfusion. Expression of HSP70 and messenger RNA (mRNA), apoptosis, and apoptosis-associated genes such as Bcl-2 and Bax were studied. Expression of HSP70 and mRNA was augmented as warm ischemia was prolonged, but was markedly suppressed in livers with more than 120 min of ischemia. The highest accumulation of HSP70 was observed in the nucleus. In livers subjected to longer duration of warm ischemia, necrosis and apoptosis were evident and Bcl-2 mRNA expression and Bcl-2/Bax protein ratio were markedly diminished. Apoptosis may be related to the process of cellular injury induced by warm ischemia-reperfusion. Expression of HSP70 and the Bcl-2 family can be effective markers of viability in hepatic warm ischemia-reperfusion.

Preconditioning protects liver and lung damage in rat liver transplantation: role of xanthine/xanthine oxidase

This study was designed to evaluate whether ischemic preconditioning could confer protection against liver and lung damage associated with liver transplantation. The effect of preconditioning on the xanthine/xanthine oxidase (XOD) system in liver grafts subjected to 8 and 16 hours of cold ischemia was also evaluated. Increased xanthine levels and marked conversion of xanthine dehydrogenase (XDH) to XOD were observed after hepatic cold ischemia. Xanthine/XOD could play a role in the liver and lung damage associated with liver transplantation. This assumption is based on the observation that inhibition of XOD reduced postischemic reactive oxygen species (ROS) generation and hepatic injury as well as ensuing lung inflammatory damage, including neutrophil accumulation, oxidative stress, and edema formation. Ischemic preconditioning reduced xanthine accumulation and conversion of XDH to XOD in liver grafts during cold ischemia. This could diminish liver and lung damage following liver transplantation. In the liver, preconditioning prevented postischemic ROS generation and hepatic injury as well as the injurious effects in the lung following liver transplantation. Administration of xanthine and XOD to preconditioned rats led to hepatic ROS and transaminase levels similar to those found after reperfusion and abolished the protective effect of preconditioning on the lung inflammatory damage. In conclusion, ischemic preconditioning reduces both liver and lung damage following liver transplantation. This endogenous protective mechanism is capable of blocking xanthine/XOD generation in liver grafts during cold ischemia.

Ischemic preconditioning: a defense mechanism against the reactive oxygen species generated after hepatic ischemia reperfusion

BACKGROUND

Preconditioning protects against both liver and lung damage after hepatic ischemia-reperfusion (I/R). Xanthine and xanthine oxidase (XOD) may contribute to the development of hepatic I/R.

OBJECTIVE

To evaluate whether preconditioning could modulate the injurious effects of xanthine/XOD on the liver and lung after hepatic I/R.

METHODS

Hepatic I/R or preconditioning previous to I/R was induced in rats. Xanthine and xanthine dehydrogenase/xanthine oxidase (XDH/XOD) in liver and plasma were measured. Hepatic injury and inflammatory response in the lung was evaluated.

RESULTS

Preconditioning reduced xanthine accumulation and conversion of XDH to XOD in liver during sustained ischemia. This could reduce the generation of reactive oxygen species (ROS) from XOD, and therefore, attenuate hepatic I/R injury. Inhibition of XOD prevented postischemic ROS generation and hepatic injury. Administration of xanthine and XOD to preconditioned rats led to hepatic MDA and transaminase levels similar to those found after hepatic I/R. Preconditioning, resulting in low circulating levels of xanthine and XOD activity, reduced neutrophil accumulation, oxidative stress, and microvascular disorders seen in lung after hepatic I/R. Inhibition of XOD attenuated the inflammatory damage in lung after hepatic I/R. Administration of xanthine and XOD abolished the benefits of preconditioning on lung damage.

CONCLUSIONS

Preconditioning, by blocking the xanthine/XOD pathway for ROS generation, would confer protection against the liver and lung injuries induced by hepatic I/R.

Evidence of oxidative imbalance in long-term liver transplant patients

BACKGROUND

Oxidative stress in patients undergoing liver transplantation results both from the pre-existing cirrhosis and ischaemia-reperfusion injury related to surgery. Previous studies have provided information limited to the immediate post-operative period. It remains to be established whether this oxidative imbalance is reversed in a longer time.

AIM, METHODS AND PATIENTS

This study aimed to compare plasma concentrations of thiobarbituric acid-reactant substances and alpha-tocopherol in 20 cirrhotic patients before liver transplantation and 22 patients in whom transplant had been carried out at least 6 months previously. Thirty healthy age and sex-matched volunteers served as controls (cross-sectional study). Five patients were evaluated before and after liver transplantation (longitudinal study).

RESULTS AND CONCLUSIONS

Pre-transplant patients showed greater thiobarbituric acid-reactant substances and lower alpha-tocopherol levels than controls. Transplanted patients presented lower thiobarbituric acid-reactant substances and greater alpha-tocopherol levels than cirrhotic patients without reaching, however, the levels observed in controls. No correlations were found between oxidative parameters and liver tests. Hypertransaminasaemia, liver disease recurrence, and rejection episodes did not significantly influence the oxidative parameters. In the longitudinal study, transplantation induced a significant decrease in plasma thiobarbituric acid-reactant substances and a rise in alpha-tocopherol. Although a long-term improvement in the oxidative injury observed in cirrhotic patients occurs after liver transplantation, mild oxidative stress persists even in successfully transplanted patients.

Thiram inhibits angiogenesis and slows the development of experimental tumours in mice

Thiram-tetramethylthiuram disulphide--a chelator of heavy metals, inhibited DNA synthesis and induced apoptosis in cultured bovine capillary endothelial cells. Bovine capillary endothelial cells were 10-60-fold more sensitive to thiram than other cell types. These effects were prevented by addition of antioxidants, indicating involvement of reactive oxygen species. Exogenously added Cu2+ impeded specifically and almost completely the inhibitory effect of thiram for bovine capillary endothelial cells. Moreover, thiram had markedly inhibited human recombinant Cu/Zn superoxide dismutase enzymatic activity (85%) in vitro. Moreover, PC12-SOD cells with elevated Cu/Zn superoxide dismutase were less sensitive to thiram treatment than control cells. These data indicate that the effects of thiram are mediated by inhibition of Cu/Zn superoxide dismutase activity. Oral administration of thiram (13-30 microg mouse(-1)), inhibited angiogenesis in CD1 nude mice. Tumour development is known to largely depend on angiogenesis. We found that oral administration of thiram (30 microg) to mice caused significant inhibition of C6 glioma tumour development (60%) and marked reduction (by 3-5-fold) in metastatic growth of Lewis lung carcinoma. The data establish thiram as a potential inhibitor of angiogenesis and raise the possibility for its use as therapy in pathologies in which neovascularisation is involved, including neoplasia.

Cu/Zn superoxide dismutase plays a role in angiogenesis

Endothelial cells produce oxygen radicals spontaneously and this process is augmented by hypoxia/reoxygenation. Cu/Zn superoxide dismutase (SOD-1) is an important enzyme in cellular oxygen metabolism. To determine whether alterations in SOD-1 activity affect angiogenesis we used transgenic SOD-1 (Tg-SOD) mice with elevated level of SOD-1. Angiogenesis induced subcutaneously by bFGF in Tg-SOD mice was 3-fold higher than in control non-transgenic (ntg) mice. Oral administration of disulfiram (DSF), an inhibitor of SOD-1, inhibited angiogenesis in Tg-SOD mice as well as in CD1 nude mice. Effects of DSF on cultured cells were also tested. Application of DSF to cultured bovine capillary endothelial (BCE) cells caused inhibition of DNA synthesis and induction of apoptosis. These effects were prevented by addition of antioxidants, further indicating involvement of reactive oxygen species. DSF also reduced the level of glutathione and the production of H(2)O(2) in BCE cells. Moreover, PC12-SOD cells with elevated SOD-1 were less sensitive to DSF treatment then control cells. These data indicate that the effects of DSF are mediated by inhibition of SOD-1 activity. Tumor development is known to largely depend on angiogenesis. We found that oral administration of DSF to mice caused significant inhibition of C6 glioma tumor development and marked reduction (by 10-19-fold) in metastatic growth of Lewis lung carcinoma. The data suggest a role for SOD-1 in angiogenesis, establish DSF as a potential inhibitor of angiogenesis and raise the possibility that attenuating SOD-1 activity may be important in treatment of angiogenesis-dependent pathologies.

Effect of ischemia-reperfusion injury on the microcirculation of the steatotic liver of the Zucker rat

BACKGROUND

Much discussion has been focused on the use of steatotic livers for transplantation due to the prevalence of steatosis in the potential donor liver pool (1). The aim of this study was to investigate the possibility that the microcirculation of steatotic liver is more sensitive to the ischemia-reperfusion (IR) injury than normal liver.

METHODS

The left liver lobe of obese (n=9) and lean Zucker rats (n=9) were subjected to 40 min of warm ischemia followed by 60 min of reperfusion. Fluorescent probes rhodamine 123 (Rh123), bisbenzimide (Bis), and rhodamine 6G (Rh6G) were administered for the identification by intravital fluorescence microscopy (IVFM) of mitochondrial membrane potential, hepatocyte nuclei and leukocytes, respectively before hepatic ischemia and at 15, 30, 45, and 60 min after reperfusion. Blood samples were obtained before and after 60 min of reperfusion. Liver tissue was taken at the end of experiment for histological analysis.

RESULTS

The liver of the obese rats showed prominent macro- and microvesicular fatty changes (MAFC and MIFC) and hepatocyte swelling. Under IVFM, the obese animals had significantly wider hepatic cords (23.1+/-0.8 microm) than the lean ones (15.9+/-0.5 microm) (P<0.01), whereas no significant difference in sinusoidal diameters was noted. The number of functional sinusoids significantly decreased after 30 min of reperfusion in both groups but no significant change was noted in the nucleus count throughout the experiment. Rh123 fluorescence intensity dropped significantly in the obese group after 60 min of reperfusion but not in the lean rats. Leukocyte adherence showed a significant rise after reperfusion in both groups. Plasma AST and ALT levels were 40- and 24-fold higher respectively for the obese animals after IR compared with their preischemic values, whereas the corresponding increase were 4.2- and 3.4-fold for the lean animals, respectively.

CONCLUSIONS

Our results indicate that the liver of the obese Zucker rat is steatotic and presents with an abnormal microcirculation manifested by a reduced sinusoidal density. IR led to significantly greater hepatic injury in the steatotic than in the normal liver. This injury was accompanied by a significant reduction in the functional sinusoidal density and mitochondrial membrane potential as assessed by Rh123-associated fluorescence in the steatotic liver. In conclusion, the increased sensitivity of the steatotic liver to IR injury would appear to involve both alterations in blood flow in the microcirculation and to cellular changes.

SPC-100270, a protein kinase C inhibitor, reduced hypoxic injury due to reperfusion following orthotopic liver transplantation in the rat

Recently, we reported that SPC-100270, a sphingosine derivative and inhibitor of protein kinase C (50-90 microM) in mixed micelle assays, reduced reperfusion injury resulting from hypoxia in a low-flow, reflow model of liver perfusion. Here we report that SPC-100270 has similar beneficial effects following liver transplantation in vivo. Rat liver transplantation was performed using nonarterial and rearterial techniques. Livers from syngenic rats were harvested surgically, prepared with vascular cuffs and a splint, and stored for 24 or 48 h in University of Wisconsin (UW) cold storage solution. Just prior to completion of vascular reconstruction, the organ was rinsed with 3 or 10 ml of Ringer's solution, vehicle, or a solution containing SPC-100270 (up to 500 microM). Following implantation surgery, low doses of SPC-100270 were ineffective at reducing both parenchymal and nonparenchymal cell death, yet significant (P < 0.05) reductions were observed with 500 microM. Further, nonparechnymal cell viability was improved nearly four fold by the drug. SPC-100270 (500 microM) tended to increase survival following 48 h cold storage in UW solution, but the improvement was not statistically significant. SPC-100270 also did not diminish carbon-centered free radical formation in transplanted livers from alcohol-treated rats. Collectively, these data support the hypothesis that pretreatment of donor livers with an inhibitor of protein kinase C is effective in vivo at reducing reperfusion injury, particularly to nonparenchymal cells, following orthotopic liver transplantation in the rat.

Efficacy of prostacyclin analogue (OP-2507) in viable hepatic grafts from pigs with non-beating hearts

We investigated whether the stable prostacyclin analogue (OP-2507; OP) would ameliorate warm ischemia-related injury of the liver graft under conditions of a nonbeating heart. Thirty-six mongrel pigs were arranged into 3 groups of 6 pairs. Group 1 pigs underwent orthotopic liver transplantation from heart-beating donors (HBD). In group 2, animals received liver grafts from nonheart-beating donors (NHBD), defined as 30 min of cardiac arrest. Group 3 pigs received grafts from NHBD, but the donor had been pretreated with OP by intraportal infusion (2 microg/kg x min for 30 min immediately before the induction of cardiac arrest). The grafts were preserved at 4 degrees C in Euro-Collins solution in which OP was dissolved at 200 microg/l. Five-day survival rates after transplantation improved significantly in OP-treated animals (3/6, for group 3), compared with 0/6 for group 2 (P < 0.05, generalized Wilcoxon test). Five of 6 animals survived more than 5 days in the HBD group (group 1). Although the serum transaminase activities and bile production did not differ in the early phase of recirculation among the groups, there was a significant improvement in the hepatic microcirculatory environment in the surviving groups (groups 1 and 3). Analysis of arterial prostanoid levels showed a substantial suppression of PGE2 release by OP treatment following reperfusion. Our data indicate that a stable prostacyclin analogue can be clinically useful for expanding the donor pool by improving the quality of the liver graft.

Antioxidant treatment inhibits activation of myocardial nuclear factor kappa B and inhibits nitrosylation of myocardial heme protein in cardiac transplant rejection

Nitric oxide production via inducible nitric oxide synthase (iNOS) is believed to play a role in cardiac allograft rejection. Previously, we showed that antioxidants can significantly prolong cardiac graft survival, but the nature of this protection is unknown. In the present study, we examined the protective effect of another antioxidant, dimethylthiourea (DMTU), in a model of cardiac allograft rejection. Specifically, we hypothesized that DMTU would prolong graft survival and decrease activation of nuclear factor-kappa B (NF-kappa B), an important redox-sensitive transcription factor necessary for iNOS gene expression. NF-kappa B was activated by twofold as early as postoperative day 2 in allografts. NF-kappa B activation in allografts progressed to a peak of ninefold by postoperative day and remained increased until postoperative day 6. No activation of NF-kappa B was observed in isografts for comparable time periods. Treatment with DMTU resulted in a significant prolongation of graft survival. This beneficial effect was associated with diminished activation of myocardial NF-kappa B. Treatment with DMTU also resulted in decreased formation of iron-nitrosylprotein complexes as evidenced by electron paramagnetic resonance spectroscopy. These studies provide evidence that reactive oxygen plays a significant role in signal transduction for activation via the transcription factor, NF-kappa B, thereby modulating distal actions and consequences of iNOS-derived nitric oxide.

Gene delivery of Cu/Zn-superoxide dismutase improves graft function after transplantation of fatty livers in the rat

Oxygen-derived free radicals play a central role in reperfusion injury after organ transplantation, and fatty livers are particularly susceptible. Endogenous radical scavengers such as superoxide dismutase (SOD) degrade these radicals; however, SOD is destroyed rapidly when given exogenously. Therefore, an adenoviral vector encoding the Cu/Zn-SOD gene (Ad.SOD1) was used here to test the hypothesis that organ injury would be reduced and survival increased in a rat model of transplantation of fatty livers. Donors received chow diet (untreated), high-fat diet, or ethanol-containing high-fat diet. Some of the ethanol-fed donors were infected either with the gene lacZ encoding bacterial beta-galactosidase (Ad.lacZ), or Ad.SOD1. After liver transplantation, SOD activity and protein expression in liver, survival, histopathology, release of transaminases, free radical adducts in bile, and activation of NF-kappaB, IkappaB kinase (IKK), Jun-N-terminal kinase (JNK), and TNFalpha were evaluated. Ad.SOD1 treatment increased survival dramatically, blunted transaminase release, and reduced necrosis and apoptosis significantly. Free radical adducts were increased two-fold in the ethanol group compared with untreated controls. Ad. SOD1 blunted this increase and reduced the activation of NF-kappaB. However, release of TNFalpha was not affected. Ad.SOD1 also blunted JNK activity after transplantation. This study shows that gene therapy with Ad.SOD1 protects marginal livers from failure after transplantation because of decreased oxygen radical production. Genetic modification of fatty livers using viral vectors represents a new approach to protect marginal grafts against primary nonfunction.

Delivery of Cu/Zn-superoxide dismutase genes with a viral vector minimizes liver injury and improves survival after liver transplantation in the rat

BACKGROUND

Oxygen-derived free radicals play a central role in pathomechanisms of reperfusion injury after organ transplantation. Endogenous radical scavenger systems such as superoxide dismutase (SOD) degrade toxic radicals; however, SOD is degraded rapidly when given exogenously. Therefore, the hypothesis that treatment of the donor liver with an adenoviral vector encoding the Cu/Zn-SOD gene (Ad-SOD1) would lead to permanent gene expression and therefore protect the organ against injury and increase survival in a rat model of liver transplantation was tested.

METHODS

Some donors were infected with Ad-SOD1, whereas untreated grafts and livers infected with the indicator gene lacZ encoding bacterial beta-galactosidase (Ad-lacZ) served as controls. After orthotopic liver transplantation, survival, serum transaminases, and histopathology were evaluated.

RESULTS

Approximately 80% of hepatocytes expressed beta-galactosidase 72 hr after injection of Ad-lacZ. Moreover, SOD1 gene expression and activity were increased 3- and 10-fold in the Ad-SOD1 group, respectively. After transplantation, 20-25% of rats treated with Ad-lacZ survived. In contrast, all SOD1-treated animals survived. Transaminases measured 8 hr after transplantation in Ad-SOD1 rats were only 40% of those in controls, which increased 40-fold above normal values. Approximately 20% of hepatocytes in untreated and Ad-lacZ-infected organs were necrotic 8 hr after reperfusion, whereas necrosis was nearly undetectable in grafts from rats treated with Ad-SOD1.

CONCLUSIONS

This study provides clear evidence for the first time that gene therapy with Ad-SOD1 increases survival and decreases hepatic injury after liver transplantation. Genetic modification of the liver represents a future approach to protect organs against injury where oxygen-derived free radicals are involved.

Activation of immediate early gene, c-fos, and c-jun in the rat small intestine after ischemia/reperfusion

BACKGROUND

Activated immediate early genes (IEGs) play key roles in mediating cellular response after ischemia/reperfusion (I/R) injuries in some organs such as liver, heart and kidney. However, there is no report investigating an association between the activation of IEGs and cellular regeneration or programmed cell death after I/R in small intestine.

METHODS

We examined a sequential expression of c-fos and c-jun after I/R in rat small intestine using reverse transcription-polymerase chain reaction and Northern blot analysis, and compared the patterns with coexistent two parameters: (1) regeneration determined by immunohistochemical detection of proliferating cell nuclear antigen, (2) programmed cell death determined with the terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end-labeling (TUNEL) method and DNA fragmentation.

RESULTS

The expression of c-fos and c-jun mRNA increased markedly 15 min after reperfusion and was, respectively, 6.3 and 4.4 times higher than in controls. Proliferating cell nuclear antigen expression was significantly elevated between 5 min and 4 hr, peaking at 30 min after reperfusion. Apoptosis showed a peak 60 min after reperfusion. Apoptosis after I/R was detected in the nuclei of absorptive epithelial cells by the TUNEL method, and these apoptotic signals were consistent with the expression of c-Fos and c-Jun proteins using an immunohistochemical method.

CONCLUSIONS

These results suggest that overexpression of c-fos and c-jun after I/R in the small intestine correlates with programmed cell death and subsequent cellular regeneration.

Functional interactions between oxidative stress, membrane Na(+) permeability, and cell volume in rat hepatoma cells

BACKGROUND & AIMS

Oxidative stress leads to a rapid initial loss of liver cell volume, but the adaptive mechanisms that serve to restore volume have not been defined. This study aimed to evaluate the functional interactions between oxidative stress, cell volume recovery, and membrane ion permeability.

METHODS

In HTC rat hepatoma cells, oxidative stress was produced by exposure to H(2)O(2) or D-alanine plus D-amino acid oxidase (40 U/mL).

RESULTS

Oxidative stress resulted in a rapid decrease in relative cell volume to 0.85 +/- 0.06. This was followed by an approximately 100-fold increase in membrane cation permeability and partial volume recovery to 0.97 +/- 0.05 of original values. The volume-sensitive conductance was permeable to Na(+) approximately K(+) >> Tris(+), and whole-cell current density at -80 mV increased from -1.2 pA/pF at 10(-5) mol/L H(2)O(2) to -95.1 pA/pF at 10(-2) mol/L H(2)O(2). The effects of H(2)O(2) were completely inhibited by dialysis of the cell interior with reduced glutathione, and were markedly enhanced by inhibition of glutathione synthase.

CONCLUSIONS

These findings support the presence of dynamic functional interactions between cell volume, oxidative stress, and membrane Na(+) permeability. Stress-induced Na(+) influx may represent a beneficial adaptive response that partially restores cell volume over short periods, but sustained cation influx could contribute to the increase in intracellular [Na(+)] and [Ca(2+)] associated with cell injury and necrosis.

Neutrophil elastase and oxygen radicals enhance monocyte chemoattractant protein- expression after ischemia/reperfusion in rat liver

BACKGROUND

The monocyte chemoattractant protein-1 (MCP-1) is produced during reperfusion injury and induces tissue factor that is the initiator of the clotting cascade. Neutrophil elastase is a crucial mediator of inflammatory tissue damage. Activation of the coagulation system stimulates cytokine production by activated leukocytes. We investigated the effects of neutrophil elastase and oxygen radicals generated by hypoxia associated with microthrombus formation on MCP-1 expression after ischemia/reperfusion in rat liver.

METHODS

In vitro MCP-1 production by macrophages after stimulation with human neutrophil elastase (HNE) or oxygen radicals generated by hypoxanthine and xanthine oxidase was examined. Liver ischemia was induced in rats by occluding the portal vein for 30 min. An inhibitor of human neutrophil elastase (ONO-5046*Na, 10 mg/kg) and antithrombin III (AT-III, 250 U/kg) were injected i.v. 5 min before vascular clamping. Serum concentrations of MCP-1 were measured by enzyme-linked immunosorbent assay.

RESULTS

Human neutrophil elastase or oxygen radicals significantly enhanced in vitro MCP-1 production by macrophage. Serum MCP-1 concentrations reached a peak at 6 hr after reperfusion and then gradually decreased. However, pretreatment of animals with AT-III or ONO-5046*Na alone resulted in significantly smaller increases in serum concentrations of MCP-1 after reperfusion. Pretreatment with both ONO-5046*Na and AT-III produced additive effects. The combined treatment with ONO-5046*Na and AT-III significantly reduced MCP-1 mRNA in liver after ischemia/reperfusion.

CONCLUSIONS

MCP-1 production by macrophages is stimulated by neutrophil elastase and oxygen radicals generated by hypoxia, probably due to microthrombus formation after ischemia/reperfusion of the rat liver.

N-acetylcysteine in pig liver transplantation from non-heart-beating donors

Lipid peroxidation due to oxygen free radicals (OFR) seems to play a major role in loss of liver graft viability after warm ischemia, preservation, and transplantation. N-acetylcysteine (NAC) is an antioxidant that has a direct effect on OFR, and is also a glutathione precursor, another antioxidant. This study was designed to evaluate the efficacy of NAC in preventing ischemia-reperfusion damage of liver grafts harvested from non-heart-beating donors. Liver transplantation was performed on pigs divided into five groups: group 1 (control group; n=5) received livers from heart-beating donors; livers were subjected to 30 min of warm ischemia in groups 2 (n=3, no NAC) and group 3 (n=3; NAC treatment); warm ischemia time lasted 60 min in groups 4 (n=4; no NAC) and 5 (n=5; NAC treatment). Studied parameters included graft survival for more than 3 days, aspartate aminotransferase plasma levels, liver histology, and hepatic total glutathione concentrations. Graft survival was 100% in groups 1, 2, and 3, 0% in group 4, and 20% in group 5. NAC treatment did not influence initial mean aspartate aminotransferase release which was greater in warm ischemic livers than in controls. NAC treatment had no effect on liver hepatic total glutathione after reperfusion of animals receiving warm ischemic grants. Finally, no effect on liver histology was observed with NAC treatment. Our study suggests that in liver transplantation from non-heart-beating donors, NAC has no effect in both graft viability and lipid peroxidation. The role of OFR in primary dysfunction of transplanted warm ischemic livers remains controversial.

Intraportal perfusion of prostaglandin E1 attenuates hepatic postischaemic microcirculatory impairments in rats

BACKGROUND

The efficacy of intraportal perfusion with prostaglandin E1(PGE1) in decreasing postischaemic hepatic microcirculatory damage was studied in rats.

METHODS

An extrahepatic portosystemic shunt was created by attaching the spleen to a subcutaneous site on the left lateral wall of the abdomen in male Wistar rats weighing between 200 and 350 g. Four weeks later, when the shunt was mature, the portal vein and hepatic artery were occluded for 60 min. The animals were divided into the following three groups according to the type of intraportal perfusion during the ischaemic phase: group 1 consisted of untreated animals; group 2, animals perfused with lactated Ringer's solution; and group 3, animals perfused with PGE1 (0.1 microg/kg per min). The hepatic microcirculation was observed under an inverted intravital microscope after the injection of fluorescent dyes to label leucocytes and damaged cells 30 and 60 min after reperfusion. The liver was removed 60 min after reperfusion and stained immunohistochemically using 1A29, an anti-rat intercellular adhesion molecule-1 (ICAM-1) antibody.

RESULTS

The leucocyte velocity during reperfusion was lowest in group 1 and highest in group 3. Of the three groups, group 3 showed the least leucocyte adhesion to the sinusoidal walls and terminal venules, the lowest damaged cell count and the lowest ICAM-1 expression on the sinusoidal walls.

CONCLUSION

The results of this study suggest that hepatic perfusion with PGE1 markedly alleviates microcirculatory damage associated with ischaemia and reperfusion through the inhibition of leucocyte-endothelium interactions.

Activation of nuclear factor-kappaB during orthotopic liver transplantation in rats is protective and does not require Kupffer cells

Reperfusion after liver transplantation results in the induction of tumor necrosis factor-alpha (TNFalpha) as well as activation of the stress-associated signaling proteins, c-Jun N-terminal kinase (JNK), activating protein-1 (AP-1), and nuclear factor-kappaB (NF-kappaB). To test the hypothesis that Kupffer cells are involved in the activation of signal transduction cascades during rat liver transplantation, Kupffer cells were depleted from donor liver using gadolinium chloride (GdCl3), and then the activation of JNK, AP-1, and NF-kappaB were assessed after transplantation. The results showed that GdCl3 treatment did not inhibit the activation of these stress signals, although transplanted livers were depleted of Kupffer cells and partially protected from reperfusion injury. Interleukin-6 (IL-6) and IL-10 messenger RNAs (mRNAs) were induced by transplantation, and the induction was suppressed by Kupffer cell depletion. The induction of TNFalpha mRNA and serum protein during liver transplantation was unaffected by GdCl3. These results show that Kupffer cells are not a major source of TNFalpha production after liver transplantation and that stress-signaling protein activation occurs independently of Kupffer cells. Transplantation strongly activates the transcription factor NF-kappaB, which blocks TNFalpha-mediated apoptosis in hepatocytes in vitro. To assess the role of NF-kappaB activation during liver transplantation, the IkappaBalpha superrepressor was expressed in donor livers using adenoviral-mediated gene transfer. Inhibition of NF-kappaB resulted in increased serum alanine aminotransferase levels after 3 hours of transplantation. In addition, the blockade of NF-kappaB resulted in increased histological tissue injury and increased hepatic terminal deoxyribonucleotide transferase-mediated deoxyuridine triphosphate nick end labeling (TUNEL) staining, indicating apoptosis. These results show that NF-kappaB activation has a protective role in the transplanted liver.

Correlation between von Willebrand factor levels and early graft function in clinical liver transplantation

Cold preservation/reperfusion leads to sinusoidal endothelial cell (SEC) activation and damage in nearly every liver transplantation; the extent of these changes influences early graft function. Upon reperfusion, activated SEC show increased expression of adhesion molecules, including von Willebrand factor (vWF) which is released into the circulation. This study was designed to evaluate the levels of vWF measured in the caval effluent and correlate these findings with known markers of SEC damage and early graft function. Data were obtained from 35 patients undergoing orthotopic liver transplantation (LTx). Two samples were taken from each patient for measurement of vWF: a) from the portal vein immediately prior to reperfusion; and b) from the first 50 ml of the caval effluent. Commercial assays were used to measure vWF, as well as hyaluronic acid (HA), thrombomodulin (TM), IL-1 beta, IL-6, IL-8 and TNF-alpha. Patients were divided into two groups based on early graft function. Poor early graft function (PEGF) was defined as a peak aspartate transaminase (AST) or alanine transaminase (ALT) level > 2500 U/L during the first three postoperative days (POD) and a prothrombin time (PT) > 16 s on POD 2 (n = 8). The remaining 27 patients had good early graft function (GEGF). In patients with GEGF, vWF levels dropped significantly between the two time points. This change was not observed in those with PEGF. A positive linear correlation was observed in the PEGF group between vWF and HA and IL-6. The different pattern of change in vWF between the two groups, as well as the positive correlation between HA, IL-6 and vWF in PEGF, suggest that vWF may be a useful marker of early graft function.

Effects of exogenous superoxide anion and nitric oxide on the scavenging function and electron microscopic appearance of the sinusoidal endothelium in the isolated, perfused rat liver

BACKGROUND/AIMS

Functional and morphological alterations of the hepatic sinusoidal endothelial cell occur in several models of experimental liver injury and in clinical settings. The causes of these alterations are multiple. The aim of this study was to test the hypothesis that the early functional impairment and morphological alterations of the sinusoidal endothelial cell and hepatic sinusoid associated with liver injury are mediated by free radical species, such as superoxide anion and nitric oxide.

METHODS

Isolated rat livers were perfused by recirculation with hemoglobin-free, Krebs-Henseleit bicarbonate buffer and presented with a source of superoxide anion (xanthine oxidase+hypoxanthine) or nitric oxide (S-nitroso-N-acetyl penicillamine). Hyaluronan uptake (an index of sinusoidal endothelial cell scavenging function), thiobarbituric acid-reactive substances content of the tissue (a marker of lipid peroxidation), reduced and oxidized glutathione (a marker of the thiol system oxidation/reduction state), lactate dehydrogenase and alanine aminotransferase activities (markers of cytolysis), as well as scanning and transmission electron microscopic appearance of the sinusoid were evaluated.

RESULTS

At the high concentrations used, both free radical generating systems suppressed hyaluronan uptake, increased malondialdehyde content of the tissue, enhanced the release of both liver enzymes, decreased the total glutathione content of the liver, and altered the ratio of reduced/oxidized glutathione. Both free radical species induced dose-dependent morphological alterations of the sinusoid, consisting of the appearance of large gaps replacing the sieve-plated fenestration.

CONCLUSIONS

The free radical species-induced functional impairment and morphological alterations of the liver sinusoid, presented in this study, closely resemble the early in vivo changes associated with liver injury under a variety of conditions, such as preservation and reperfusion, or administration of hepatotoxicants such as D-galactosamine, Gram-negative bacterial lipopolysaccharides, acetaminophen, alcohol and others. Therefore, we suggest that early liver sinusoid injury, observed under these conditions, can be attributed to the action of free radicals, such as superoxide anion and nitric oxide.