The many facets of reperfusion injury

α-lipoic acid reduces postreperfusion syndrome in human liver transplantation - a pilot study

A double-blind randomized controlled trial was performed to compare the safety and efficacy of α-lipoic acid (ALA) in liver transplantation (LT). The grafts were randomized to receive ALA or placebo before the cold ischemia time. Furthermore, patients transplanted with the ALA-perfused graft received 600 mg of intravenous ALA, while patients with the nonperfused graft received the placebo just before graft reperfusion. Hepatic biopsy was performed 2 h postreperfusion. Blood samples were collected before, during and 1 and 2 days after reperfusion. Quantitative polymerase chain reaction (qPCR) analysis was performed on biopsies to assess genes involved in the response to hypoxia, apoptosis, cell growth, survival and proliferation, cytokine production and tissue damage protection. Nine of 40 patients developed postreperfusion syndrome (PRS), but seven of them belonged to the control group. There was a decrease in PHD2 and an increase in alpha subunit of hypoxia-inducible factor-1 (HIF-1α) and baculoviral IAP repeat containing 2 (Birc2) transcript levels in the biopsies from the ALA-treated versus the control group of patients. Additionally, plasma levels of alarmins were lower in ALA-treated patients than control patients, which suggests that ALA-treated grafts are less inflammatory than untreated grafts. These results showed that ALA is safe for use in LT, induces gene changes that protect against hypoxia and oxidative stress and reduces the appearance of PRS.

Ischemic preconditioning modulates ROS to confer protection in liver ischemia and reperfusion

Ischemia reperfusion (IR) injury is a significant cause of morbidity and mortality in liver transplantation. When oxygen is reintroduced to the liver graft it initiates a cascade of molecular reactions leading to the release of reactive oxygen species (ROS) and pro-inflammatory cytokines. These soluble mediators propagate a sterile immune response to cause significant tissue damage. Ischemic preconditioning (IPC) is one method that reduces hepatocellular injury by altering the immune response and inhibiting the production of ROS. Studies quantifying the effects of IPC in humans have demonstrated an improved liver enzyme panel in patients receiving grafts pretreated with IPC as compared to patients receiving the standard of care. In our review, we explore current literature in the field in order to describe the mechanism through which IPC regulates the production of ROS and improves IR injury.

Propofol Is Cardioprotective in a Clinically Relevant Model of Normothermic Blood Cardioplegic Arrest and Cardiopulmonary Bypass

The general anesthetic propofol has been shown to be cardioprotective. However, its benefits when used in cardioplegia during cardiac surgery have not been demonstrated. In this study, we investigated the effects of propofol on metabolic stress, cardiac function, and injury in a clinically relevant model of normothermic cardioplegic arrest and cardiopulmonary bypass. Twenty anesthetized pigs, randomized to propofol treatment ( n = 8) and control ( n =12) groups, were surgically prepared for cardiopulmonary bypass (CPB) and cardioplegic arrest. Doses of warm blood cardioplegia were delivered at 15-min intervals during a 60-min aortic cross-clamped period. Propofol was continuously infused for the duration of CPB and was therefore present in blood cardioplegia. Myocardial biopsies were collected before, at the end of cardioplegic arrest, and 20 mins after the release of the aortic cross-clamp. Hemodynamic parameters were monitored and blood samples collected for cardiac troponin I measurements. Propofol infusion during CPB and before ischemia did not alter cardiac function or myocardial metabolism. Propofol treatment attenuated the changes in myocardial tissue levels of adenine nucleotides, lactate, and amino acids during ischemia and reduced cardiac troponin I release on reperfusion. Propofol treatment reduced measurable hemodynamic dysfunction after cardioplegic arrest when compared to untreated controls. In conclusion, propofol protects the heart from ischemia-reperfusion injury in a clinically relevant experimental model. Propofol may therefore be a useful adjunct to cardioplegic solutions as well as being an appropriate anesthetic for cardiac surgery.

Role of glycogen synthase kinase 3β in protective effect of propofol against hepatic ischemia-reperfusion injury

BACKGROUND

It was previously reported that propofol, an intravenously administered hypnotic and anesthetic agent, protects organs from ischemia-reperfusion (I/R) injury. However, the underlying mechanisms are largely unknown. Glycogen synthase kinase 3β (GSK-3β) is known to play an important role in the oxidative stress-induced apoptosis. In this study, we investigated the role of GSK-3β and mitochondrial permeability transition pore (MPTP) in the protective effects of propofol against hepatic I/R injury.

MATERIALS AND METHODS

The left and median hepatic artery and the portal vein branches were blocked by no-damage artery clips to create the model of partial ischemia (70%), and liver lobes were subjected to warm ischemia for 30, 60, 90 min, respectively. Reperfusion of 120 min was then initiated by the removal of clamp. The MPTP opening was assessed by measuring mitochondrial large amplitude swelling and mitochondrial membrane potential.

RESULTS

Pretreatment with propofol in conditions of hepatic I/R inhibits the apoptosis of hepatocytes as evidenced by decreased terminal deoxynucleotidyl transferase dUTP nick end labeling-positive cells. Importantly, propofol suppressed the mitochondrial GSK-3β by promoting or preserving its phosphorylation at Ser9, thus restraining the opening of MPTP and preventing the mitochondrial swell and mitochondrial membrane potential collapse.

CONCLUSIONS

Propofol protects liver from I/R injury by sustaining the mitochondrial function, which is possibly involved with the modulation of MPTP and GSK-3β.

Ocimum gratissimum Aqueous Extract Protects H9c2 Myocardiac Cells from H(2)O(2)-Induced Cell Apoptosis through Akt Signalling

Increased cell death of cardiomyocyte by oxidative stress is known to cause dysfunction of the heart. O. gratissimum is one of the more well-known medicinal plants among the Ocimum species and widely used in treatment of inflammatory diseases. In this study, we hypothesized that aqueous extract of O. gratissimum leaf (OGE) may protect myocardiac cell H9c2 from oxidative injury by hydrogen peroxide (H₂O₂). Our results revealed that OGE pretreatment dose-dependently protects H9c2 cells from cell death when exposed to H₂O₂. Additionally, DNA condensation induced by H₂O₂ was also reduced by OGE pretreatment, suggesting that Ocimum gratissimum extract may attenuate H₂O₂-induced chromosome damage. Further investigation showed that OGE pretreatment inhibited H₂O₂-induced activation of caspase-3 and caspase-9, as well as H₂O₂-induced upregulation of proapoptotic Apaf-1 and the release of cytosolic cytochrome c, but has little effect on the activation of caspase-8. Additionally, OGE pretreatment significantly upregulated Bcl-2 expression and Akt phosphorylation, and slightly affected the phosphorylation of mitogen-activated protein kinases including p38 MAPK and JNK. Taken together, our findings revealed that Ocimum gratissimum extract effectively inhibited the mitochondrial pathway and upregulated Bcl-2 expression, which may be important in protecting H9c2 cells from H₂O₂-induced cell death.

Indirubin-3'-oxime prevents hepatic I/R damage by inhibiting GSK-3beta and mitochondrial permeability transition

Indirubin-3'-oxime is an indirubin analogue that shows favorable inhibitory activity targeting glycogen synthase kinase 3beta (GSK-3beta). In this study, we evaluated if acute treatment with indirubin-3'-oxime (Ind) prevents hepatic ischemia/reperfusion (I/R) damage. Wistar rats were subjected to 150 min of 70% warm ischemia and 16 h of reperfusion. In the treated group 1 microM indirubin-3'-oxime was administered in the hepatic artery 30 min before ischemia. Acute treatment with Ind decreased serum alanine aminotransferase (ALT), aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) levels, comparatively to I/R livers. Bax translocation to the mitochondria and cytochrome c release were higher in I/R livers. Ind treatment significantly attenuated Bax translocation and preserved mitochondrial cytochrome c content. Ind also protected mitochondria from calcium-induced mitochondrial permeability transition (MPT), as well as the decrease in state 3 mitochondrial respiration, the delay in the repolarization after a phosphorylative cycle and the decrease in ATP content caused by I/R. By addressing GSK-3beta activity and phosphorylated GSK-3beta at Ser(9) content in liver homogenates and isolated mitochondria, data suggests that inhibition of GSK-3beta by indirubin-3'-oxime prevents the increase in mitochondrial phosphorylated GSK-3beta at Ser(9) induced by I/R, thus correlating with MPT inhibition and preservation of cytochrome c content. Pre-treatment with indirubin-3'-oxime in conditions of hepatic I/R, protects the liver by maintaining mitochondrial function and hepatic energetic balance.

Biliary complications after liver transplantation from maastricht category-2 non-heart-beating donors

BACKGROUND

There are unresolved issues regarding the security of liver transplantation with non-heart-beating donors (NHBDs). Recently, an increased incidence of biliary complications, mainly intrahepatic ischemic-type biliary strictures, has been described after controlled NHBDs.

METHODS

We studied the incidence and risk factors for biliary complications among uncontrolled NHBDs recipients compared with a large population of HBD recipients.

RESULTS

Overall, 16.8% of patients in the HBD group and 41.7% of patients in the NHBD group suffered any type of biliary complication (P=0.66). However, the incidence of nonanastomotic biliary strictures was significantly greater in the NHBD group (P<0.001). Multivariate analysis showed that independent risk factors for nonanastomotic strictures were hepatic artery thrombosis (relative risk; 98.7) and receiving a liver from a NHBD (relative risk; 47.1).

CONCLUSIONS

If this type of donors is accepted as a source of liver organs, the high incidence of biliary complications should be considered and efforts should be made to decrease ischemic injury.

Induction of ischemic tolerance in rat liver via reduced nicotinamide adenine dinucleotide phosphate oxidase in Kupffer cells

AIM: To elucidate the mechanisms of hepatocyte preconditioning by H₂O₂ to better understand the pathophysiology of ischemic preconditioning.

METHODS: The in vitro effect of H₂O₂ pretreatment was investigated in rat isolated hepatocytes subjected to anoxia/reoxygenation. Cell viability was assessed with propidium iodide fluorometry. In other experiments, rat livers were excised and subjected to warm ischemia/reperfusion in an isolated perfused liver system to determine leakage of liver enzymes. Preconditioning was performed by H₂O₂ perfusion, or by stopping the perfusion for 10 min followed by 10 min of reperfusion. To inhibit Kupffer cell function or reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, gadolinium chloride was injected prior to liver excision, or diphenyleneiodonium, an inhibitor of NADPH oxidase, was added to the perfusate, respectively. Histological detection of oxygen radical formation in Kupffer cells was performed by perfusion with nitro blue tetrazolium.

RESULTS: Anoxia/reoxygenation decreased hepatocyte viability compared to the controls. Pretreatment with H₂O₂ did not improve such hepatocyte injury. In liver perfusion experiments, however, H₂O₂ preconditioning reduced warm ischemia/reperfusion injury, which was reversed by inhibition of Kupffer cell function or NADPH oxidase. Histological examination revealed that H₂O₂ preconditioning induced oxygen radical formation in Kupffer cells. NADPH oxidase inhibition also reversed hepatoprotection by ischemic preconditioning.

CONCLUSION: H₂O₂ preconditioning protects hepato-cytes against warm ischemia/reperfusion injury via NADPH oxidase in Kupffer cells, and not directly. NADPH oxidase also mediates hepatoprotection by ischemic preconditioning.

2-APB protects against liver ischemia-reperfusion injury by reducing cellular and mitochondrial calcium uptake

Ischemia-reperfusion (I/R) injury is a commonly encountered clinical problem in liver surgery and transplantation. The pathogenesis of I/R injury is multifactorial, but mitochondrial Ca(2+) overload plays a central role. We have previously defined a novel pathway for mitochondrial Ca(2+) handling and now further characterize this pathway and investigate a novel Ca(2+)-channel inhibitor, 2-aminoethoxydiphenyl borate (2-APB), for preventing hepatic I/R injury. The effect of 2-APB on cellular and mitochondrial Ca(2+) uptake was evaluated in vitro by using (45)Ca(2+). Subsequently, 2-APB (2 mg/kg) or vehicle was injected into the portal vein of anesthetized rats either before or following 1 h of inflow occlusion to 70% of the liver. After 3 h of reperfusion, liver injury was assessed enzymatically and histologically. Hep G2 cells transfected with green fluorescent protein-tagged cytochrome c were used to evaluate mitochondrial permeability. 2-APB dose-dependently blocked Ca(2+) uptake in isolated liver mitochondria and reduced cellular Ca(2+) accumulation in Hep G2 cells. In vivo I/R increased liver enzymes 10-fold, and 2-APB prevented this when administered pre- or postischemia. 2-APB significantly reduced cellular damage determined by hematoxylin and eosin and terminal deoxynucleotidyl transferase dUTP-mediated nick-end labeling staining of liver tissue. In vitro I/R caused a dissociation between cytochrome c and mitochondria in Hep G2 cells that was prevented by administration of 2-APB. These data further establish the role of cellular Ca(2+) uptake and subsequent mitochondrial Ca(2+) overload in I/R injury and identify 2-APB as a novel pharmacological inhibitor of liver I/R injury even when administered following a prolonged ischemic insult.

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

BACKGROUND

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSION

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

Modulation of mitochondrial calcium management attenuates hepatic warm ischemia-reperfusion injury

Hepatic warm ischemia and reperfusion (IR) injury occurs in many clinical situations and has an important link to subsequent hepatic failure. The pathogenesis of this injury involves numerous pathways, including mitochondrial-associated apoptosis. We studied the effect of mitochondrial calcium uptake inhibition on hepatic IR injury using the specific mitochondrial calcium uptake inhibitor, ruthenium red (RR). Rats were subjected to 1 hour of 70% warm hepatic ischemia following RR pretreatment or vehicle injection. Sham-operated animals served as controls. Analysis was performed at 15 minutes, 1 hour, 3 hours, or 6 hours after reperfusion. Serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) concentrations were determined. Terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL) staining was performed to assess apoptosis, and hepatocellular necrosis was semiquantitated from hematoxylin and eosin-stained tissue sections. RR pretreatment significantly decreased both AST and ALT serum levels after 6 hours of reperfusion (AST: 1,556 +/- 181 U/L vs. 597 +/- 121 U/L, P = 0.005; ALT: 1,118 +/- 187 U/L vs. 294 +/- 39 U/L, P = 0.005). Apoptosis was observed within 15 minutes of reperfusion in vehicle-pretreated animals and peaked after 3 hours of reperfusion (98 +/- 21 cells/high-power field [hpf]). Apoptosis was inhibited at all time points by RR pretreatment. Histologic evidence of necrosis was not observed prior to 3 hours of reperfusion (23% +/- 4%), and maximal necrosis was observed after 6 hours of reperfusion (26% +/- 1% percent area). RR pretreatment significantly decreased the necrotic percent area at both the 3-hour and the 6-hour time points (4.2% +/- 2%; 3.7% +/- 1%, respectively). Hepatic IR injury resulted in both apoptotic and necrotic cell death, which were attenuated by RR pretreatment. In conclusion, these observations implicate mitochondrial calcium uptake in the pathogenesis of hepatic IR injury.

Ischemic preconditioning protects hepatocytes via reactive oxygen species derived from Kupffer cells in rats

BACKGROUND AND AIMS

Hepatic ischemic preconditioning decreases sinusoidal endothelial cell injury and Kupffer cell activation after cold ischemia/reperfusion, leading to improved survival of liver transplant recipients in rats. Ischemic preconditioning also protects livers against warm ischemia/reperfusion injury, in which hepatocyte injury is remarkable. We aimed to determine whether ischemic preconditioning directly protects hepatocytes and to elucidate its mechanisms.

METHODS

Rats were injected with gadolinium chloride to deplete Kupffer cells or with N -acetyl- l -cysteine, superoxide dismutase, or catalase to scavenge reactive oxygen species. Livers were then preconditioned by 10 minutes of ischemia and 10 minutes of reperfusion. Subsequently, livers were subjected to 40 minutes of warm ischemia and 60 minutes of reperfusion in vivo or in a liver perfusion system. In other rats, livers were preconditioned by H(2)O(2) perfusion instead of ischemia. In the other experiments, livers were perfused with nitro blue tetrazolium to detect reactive oxygen species formation.

RESULTS

Ischemic preconditioning decreased injury in hepatocytes, but not in sinusoidal endothelial cells. Kupffer cell depletion itself did not change hepatocyte injury after ischemia/reperfusion, indicating no contribution of Kupffer cells to ischemia/reperfusion injury. However, Kupffer cell depletion reversed hepatoprotection by ischemic preconditioning. Reactive oxygen species formation occurred in Kupffer cells after ischemic preconditioning. Scavenging of reactive oxygen species reversed the effect of ischemic preconditioning, and H(2)O(2) preconditioning mimicked ischemic preconditioning.

CONCLUSIONS

Ischemic preconditioning directly protected hepatocytes after warm ischemia/reperfusion, which is not via suppression of changes in sinusoidal cells as in cold ischemia/reperfusion injury. This hepatocyte protection was mediated by reactive oxygen species produced by Kupffer cells.

As bases experimentais da lesão por isquemia e reperfusão do fígado: revisão

O transplante hepático tornou-se o procedimento de escolha para o tratamento da doença hepática terminal. Não obstante o sucesso da cirurgia, a disfunção pós-operatória do fígado enxertado ainda representa importante causa de morbidade e mortalidade. O restabelecimento do fluxo sangüíneo ao fígado recém transplantado impõe a ele nova agressão, agravando a lesão causada pelo período de isquemia. Este fenômeno pouco compreendido é conhecido como lesão por isquemia e reperfusão e envolve disfunção endotelial, seqüestro de leucócitos e agregação de plaquetas, lesão por radicais livre de oxigênio, e distúrbios da microcirculação hepática. Essa revisão discute os vários aspectos fisiopatológicos que estão envolvidos na lesão por isquemia e reperfusão do fígado.

Hepatic reticuloendothelial system dysfunction after ischemia-reperfusion: role of P-selectin-mediated neutrophil accumulation

The relationship between hepatic ischemia-reperfusion (I-R) and subsequent injury through neutrophil accumulation is well described. Although alterations in reticuloendothelial system (RES) function (specifically Kupffer cell function) after I-R have been delineated, the degree to which discrete components of RES function (phagocytosis and killing) are independently modulated under these conditions has not been quantified. A hepatic segmental I-R model was established in mice, in which blood supply to the left lateral lobe of the liver was occluded for 45 minutes, the liver was reperfused, and the laparotomy incision was closed. Experimental animals were pretreated with either vinblastin (1.5 mg/kg) to induce neutropenia or anti-P-selectin monoclonal antibody (mAb; 50 microg/mice) 4 days and 5 minutes before ischemia, respectively. We previously reported that after intravenous injection of chromium 51 ((51)Cr) and iodine 125 ((125)I) double-labeled Escherichia coli, hepatic (51)Cr levels could be used to reliably quantify hepatic phagocytic clearance (HPC) of bacteria from blood, whereas the subsequent release of (125)I from the liver accurately paralleled hepatic bacterial killing efficiency (HKE). Using this double-label bacteria clearance assay, HPC and HKE were depressed after I-R, in association with hepatic neutrophil accumulation. Segmental I-R resulted in decreased HPC and HKE activity in both ischemic and nonischemic hepatic lobes. Depressions in HPC and HKE were attenuated by either vinblastin-induced neutropenia or blocking neutrophil adhesion to the hepatic endothelium with anti-P-selectin mAb. These findings support the hypothesis that I-R induces hepatic RES dysfunction, at least in part, through P-selectin-mediated neutrophil accumulation.

Regulation of postischemic liver injury following different durations of ischemia

The objective of this study was to define the relationship among Kupffer cells, O(2)(-) production, and TNF-alpha expression in the pathophysiology of postischemic liver injury following short and long periods of ischemia. Using different forms of superoxide dismutase with varying circulating half-lives, a monoclonal antibody directed against mouse TNF-alpha, and NADPH oxidase-deficient mice, we found that 45 or 90 min of partial (70%) liver ischemia and 6 h of reperfusion (I/R) produced time-dependent increases in liver injury and TNF-alpha expression in the absence of neutrophil infiltration. Furthermore, we observed that hepatocellular injury induced by short periods of ischemia were not dependent on formation of TNF-alpha but were dependent on Kupffer cells and NADPH oxidase-independent production of O(2)(-). However, liver injury induced by extended periods of ischemia appeared to require the presence of Kupffer cells, NADPH oxidase-derived O(2)(-), and TNF-alpha expression. We conclude that the sources for O(2)(-) formation and the relative importance of TNF-alpha in the pathophysiology of I/R-induced hepatocellular injury differ depending on the duration of ischemia.

Beneficial effects of pentoxifylline pretreatment in non-heart-beating donors in rats

BACKGROUND

Pentoxifylline (PTX) pretreatment of recipients was shown to protect against liver graft failure from ischemia-reperfusion injury after orthotopic rat liver transplantation. It has also been shown that PTX protects against normothermic ischemia-reperfusion injury to the liver in lobar ischemia model in the rat. Whether PTX can benefit the liver procured from non-heart-beating donors (NHBDs) with up to 9 hr of cold ischemia is unknown.

METHODS

Donor and recipient rats were pretreated with intraperitoneal PTX (50 mg/kg) 1 hr before cardiac arrest and transplantation, respectively. Grafts were transplanted 0, 30, and 60 min after cardiac arrest with additional 1 and 9 hr of cold ischemia in both PTX-pretreated or untreated (control) groups (10 rats per group). PTX (25 mg/kg/day) was continuously given to the surviving rats for 5 days postoperatively. Recipient survival rates, serum enzyme levels, and histopathological examination of postreperfusion liver biopsies were all analyzed.

RESULTS

The survival rates, serum enzyme levels, and postreperfusion histology were significantly improved in groups pretreated with PTX compared to the controls.

CONCLUSION

Donor and recipient PTX pretreatment significantly improves the viability of the liver grafts procured from NHBDs.

Experimental study of the effects of deletion variant of hepatocyte growth factor on hepatic ischaemia-reperfusion injury

BACKGROUND

Hepatic ischaemia-reperfusion (IR) injury is still a serious complication following liver surgery. The effect of the deletion variant of hepatocyte growth factor (dHGF) on hepatic IR injury was examined in rats.

METHODS

Male Wistar rats were divided into two groups after 90 min of partial liver ischaemia: the dHGF group which was given dHGF 0.5 mg/kg intravenously immediately after reperfusion, followed by 0.5 mg/kg every 12 h, and the control group, which received vehicle buffer only. Serum chemistry, histopathological findings and liver weights were compared between the groups.

RESULTS

In the dHGF group, the increase in serum alanine transaminase and hyaluronic acid levels was significantly reduced, and the serum albumin level increased after reperfusion. The extent of hepatic necrosis 24 h after reperfusion was decreased in the dHGF group. Moreover, the proportion of terminal deoxynucleotidyl transferase-mediated 2'-deoxyuridine 5'-triphosphate nick end labelling-positive hepatocytes 6 h after reperfusion was reduced in the dHGF group. The non-ischaemic-, ischaemic- and whole-liver weight : body-weight ratio significantly increased in the dHGF group after reperfusion. The proportion of proliferating cell nuclear antigen-positive hepatocytes in the dHGF group markedly increased after 6 h after reperfusion in the non-ischaemic lobes, while in the ischaemic lobes it increased 24 h after reperfusion.

CONCLUSION

These data suggest that dHGF not only improves recovery from IR injury, but also accelerates recovery from these injuries. dHGF may be an effective pharmacological agent for prevention and treatment of hepatic IR injury.

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.

Prevention of reoxygenation injury by sodium salicylate in isolated-perfused rat liver

Sodium salicylate can be used as a chemical trap for hydroxyl radicals, the most damaging reactive oxygen species. Because reactive oxygen species are involved in the pathogenesis of hepatic hypoxia/reoxygenation injury, the goal of this study was to determine if trapping hydroxyl radicals with salicylate would prevent or at least ameliorate such injury. Isolated rat livers, continuously perfused with Krebs-Henseleit bicarbonate buffer in the presence or absence of salicylate (2 mM), were exposed, after 30 min of recovery, to 60 min of hypoxia, followed by 30 min of reoxygenation. During reoxygenation, control livers experienced a sharp increase in the rate of lactic dehydrogenase release, taken as index of cell injury, protein carbonyl content, and malondialdehyde, taken as index of protein oxidation and lipid peroxidation, respectively. The presence of salicylate in the solution perfusion significantly reduced the rate of lactic dehydrogenase release, protein carbonyl content, and malondialdehyde production during reoxygenation. Hepatic histology documented a significantly reduced cell injury in salicylate-perfused livers compared to control livers. These data suggest that the hydroxyl radical chemical trap sodium salicylate, acting as an antioxidant, may represents an effective agent to reduce liver injury due to hypoxia/reoxygenation in a model of isolated-perfused rat liver.

Role of endothelins and nitric oxide in hepatic reperfusion injury in the rat

We determined the functional role of nitric oxide (NO) and endothelins (ET), two potent vasoactive mediator systems in the liver, for the pathogenesis of sinusoidal perfusion failure and lethal hepatocyte injury after low-flow ischemia/reperfusion in the isolated perfused rat liver. NO synthase blockade with Nomega-nitro-L-arginine methyl ester (L-NAME) (10[-3] mol/L) before reperfusion prevented increased N02-/NO3- the final products of NO oxidation, which could be observed in the vehicle group. Epifluorescence microscopy revealed that the decrease in functional sinusoid density during reperfusion was much more profound compared with vehicle. This was associated with a lower surface PO2, a substantially higher number of nonviable hepatocytes, as assessed by in situ propidium iodide staining, and enhanced enzyme release into the perfusate compared with vehicle. In contrast, reperfusion in the presence of the endothelinA+B receptor antagonist bosentan (2 x 10(-4) mol/L) restored functional sinusoid density and surface PO2 to baseline values, resulted in a small reduction in the number of propidium iodide-positive hepatocytes, and caused similar increases in enzyme release as compared with vehicle. This indicates that hepatic generation of NO attenuates sinusoidal perfusion failure and improves liver tissue oxygenation, thus limiting hepatocyte injury during early reperfusion after hepatic low-flow ischemia. In contrast, endothelins counteract the microcirculatory effects of NO, i.e., mediate the no-reflow in hepatic sinusoids; however, the restoration of functional sinusoid density with bosentan resulted only in a small reduction in tissue damage, suggesting that additional components, which are independent of microcirculatory failure, contribute to hepatic reperfusion injury under these conditions.