Preconditioning protects against systemic disorders associated with hepatic ischemia-reperfusion through blockade of tumor necrosis factor-induced P-selectin up-regulation in the rat

Genomics of liver transplant injury and regeneration

While improved surgical techniques, post-operative care, and immunosuppression regimens have reduced morbidity and mortality associated with orthotopic liver transplantation (OLT), further improvement of outcomes requires personalized treatment and a better understanding of genomic mechanisms involved. Gene expression profiles of ischemia/reperfusion (I/R) injury, regeneration, and rejection, may suggest mechanisms for development of better predictive tools and treatments. The liver is unique in its regenerative potential, recovering lost mass and function after injury from ischemia, resection, and rejection. I/R injury, an inevitable consequence of perfusion cessation, cold storage, and reperfusion, is regulated by the interaction of the immune system, inflammatory cytokines, and reduced microcirculatory blood flow in the liver. Rejection, a common post-operative complication, is mediated by the recipient's immune system through T-cell-dependent responses activating proinflammatory and apoptotic pathways. Characterizing distinctive gene expression signatures for these events can identify therapies to reduce injury, promote regeneration, and improve outcomes. While certain markers of liver injury and regeneration have been observed in animals, many of these are unverified in human studies. Further investigation of these genomic signatures and mechanisms through new technology offers promise, but continues to pose a significant challenge. An overview of the current fund of knowledge in this area is reviewed.

The effects of remote ischemic preconditioning and N-acetylcysteine with remote ischemic preconditioning in rat hepatic ischemia reperfusion injury model

Background. Remote ischemic preconditioning (RIP) and pharmacological preconditioning are the effective methods that can be used to prevent ischemia reperfusion (IR) injury. The aim of this study was to evaluate the effects of RIP and N-Acetylcysteine (NAC) with RIP in the rat hepatic IR injury model. Materials and Methods. 28 rats were divided into 4 groups. Group I (sham): only laparotomy was performed. Group II (IR): following 30 minutes of hepatic pedicle occlusion, 4 hours of reperfusion was performed. Group III (RIP + IR): following 3 cycles of RIP, hepatic IR was performed. Group IV (RIP + NAC + IR): following RIP and intraperitoneal administration of NAC (150 mg/kg), hepatic IR was performed. All the rats were sacrificed after blood samples were taken for the measurements of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels and liver was processed for conventional histopathology. Results. The hepatic histopathological injury scores of RIP + IR and RIP + NAC + IR groups were significantly lower than IR group (P = 0.006, P = 0.003, resp.). There were no significant differences in AST and ALT values between the IR, RIP + IR, and RIP + NAC + IR groups. Conclusions. In the present study, it was demonstrated histopathologically that RIP and RIP + NAC decreased hepatic IR injury significantly.

Hepatic ischemia and reperfusion injury: effects on the liver sinusoidal milieu

Ischemia-reperfusion injury is an important cause of liver damage occurring during surgical procedures including hepatic resection and liver transplantation, and represents the main underlying cause of graft dysfunction post-transplantation. Cellular and biochemical processes occurring during hepatic ischemia-reperfusion are diverse and complex, and include the deregulation of the healthy phenotype of all liver cellular components. Nevertheless, a significant part of these processes are still unknown or unclear. The present review aims at summarizing the current knowledge in liver ischemia-reperfusion, but specifically focusing on liver cell phenotype and paracrine interaction deregulations. Moreover, the most updated therapeutic strategies including pharmacological, genetic and surgical interventions, as well as some of the scientific controversies in the field will be described. Finally, the importance of considering the subclinical situation of liver grafts when translating basic knowledge to the bedside is discussed.

Apolipoprotein a-I is a potential mediator of remote ischemic preconditioning

Background

Remote ischemic preconditioning (RIPC) has emerged as an attractive strategy in clinical settings. Despite convincing evidence of the critical role played by circulating humoral mediators, their actual identities remain unknown. In this study, we aimed to identify RIPC-induced humoral mediators using a proteomic approach.

Methods

and Results Rats were exposed to 10-min limb ischemia followed by 5- (RIPC 5′) or 10-min (RIPC 10′) reperfusion prior to blood sampling. The control group only underwent blood sampling. Plasma samples were analyzed using surface-enhanced laser desorption and ionization - time of flight - mass spectrometry (SELDI-TOF-MS). Three protein peaks were selected for their significant increase in RIPC 10′. They were identified and confirmed as apolipoprotein A-I (ApoA-I). Additional rats were exposed to myocardial ischemia-reperfusion (I/R) and assigned to one of the following groups RIPC+myocardial infarction (MI) (10-min limb ischemia followed by 10-min reperfusion initiated 20 minutes prior to myocardial I/R), ApoA-I+MI (10 mg/kg ApoA-I injection 10 minutes before myocardial I/R), and MI (no further intervention). In comparison with untreated MI rats, RIPC reduced infarct size (52.2±3.7% in RIPC+MI vs. 64.9±2.6% in MI; p<0.05). Similarly, ApoA-I injection decreased infarct size (50.9±3.8%; p<0.05 vs. MI).

Conclusions

RIPC was associated with a plasmatic increase in ApoA-I. Furthermore, ApoA-I injection before myocardial I/R recapitulated the cardioprotection offered by RIPC in rats. This data suggests that ApoA-I may be a protective blood-borne factor involved in the RIPC mechanism.

Protection of organs other than the heart by remote ischemic conditioning

Organ or tissue dysfunction due to acute ischemia-reperfusion injury (IRI) is the leading cause of death and disability worldwide. Acute IRI induces cell injury and death in a wide variety of organs and tissues in a large number of different clinical settings. One novel therapeutic noninvasive intervention, capable of conferring multiorgan protection against acute IRI, is 'remote ischemic conditioning' (RIC). This describes an endogenous protective response to acute IRI, which is triggered by the application of one or more brief cycles of nonlethal ischemia and reperfusion to one particular organ or tissue. Originally discovered as a therapeutic strategy for protecting the myocardium against acute IRI, it has been subsequently demonstrated that RIC may confer protection against acute IRI in a number of different noncardiac organs and tissues including the kidneys, lungs, liver, skin flaps, ovaries, intestine, stomach and pancreas. The discovery that RIC can be induced noninvasively by applying the RIC stimulus to the skeletal tissue of the upper or lower limb has facilitated its application to a number of clinical settings in which organs and tissues are at high risk of acute IRI. In this article, we review the experimental studies that have investigated RIC in organs and tissues other than the heart, and we explore the therapeutic potential of RIC in preventing organ and tissue dysfunction induced by acute IRI.

Effect of remote ischemic preconditioning on serum troponin T level following elective percutaneous coronary intervention

BACKGROUND

Elective percutaneous coronary intervention (PCI) is associated with myocardial necrosis, as evidenced by troponin release, in approximately one-third of cases. This is known to be linked with subsequent cardiovascular events. This study assessed the ability of remote ischemic preconditioning (RIPC) to attenuate cardiac troponin T (cTnT) release after elective PCI.

OBJECTIVE

Evaluation of effect of RIPC on myocardial markers following elective PCI.

METHODS

One hundred and forty nine consecutive patients undergoing elective PCI with undetectable preprocedural cTnT were recruited. Subjects were randomized to receive RIPC (induced by three 5-min inflations of a blood pressure cuff to 200 mm Hg around the upper arm, followed by 5-min intervals of reperfusion) or control (cuff deflated) immediately before arrival in the cardiac catheterization room. The primary outcome was cTnT level at approximately 16 hr after PCI. Secondary outcomes included occurrence of postprocedural myocardial infarction (MI), CKMB levels at 16 hr after PCI and assessment of the inflammatory response as measured by C-reactive protein (CRP) levels.

RESULTS

The mean cTnT at 16 hr after PCI was lower in the RIPC group compared with the control group. (0.020 vs. 0.047 ng/ml; P = 0.047) Occurrence of postprocedural MI, CKMB and CRP levels did not differ in both groups (P = 0.097, 0.537, and 0.481 respectively).

CONCLUSION

The use of RIPC immediately prior to PCI attenuates procedure-related cTnT release and does not affect occurrence of post procedural MI, CKMB, or CRP levels.

The emerging application of remote ischemic conditioning in the clinical arena

Remote ischemic conditioning (RIC) is an intervention, in which intermittent episodes of ischemia and reperfusion in an organ or tissue distant from the target organ requiring protection, provide armour against lethal ischemia-reperfusion injury. Although the exact mechanisms underlying the protection mediated through RIC have not been clearly established, the release of humoral factors and the activation of neural pathways have been implicated. There is now clinical evidence suggesting that this form of protection can be induced by a simple, noninvasive, and cost-effective procedure such as inflation and deflation of a blood pressure cuff and that this intervention provides increased organ protection in a variety of clinical scenarios, for example, in myocardial infarction. Here we provide an overview of the history and evolution of RIC, the potential mechanisms underlying its protective effects, and published randomized clinical trials in cardiovascular procedures.

Regulatory mechanisms of injury and repair after hepatic ischemia/reperfusion

Hepatic ischemia/reperfusion injury is an important complication of liver surgery and transplantation. The mechanisms of this injury as well as the subsequent reparative and regenerative processes have been the subject of thorough study. In this paper, we discuss the complex and coordinated responses leading to parenchymal damage after liver ischemia/reperfusion as well as the manner in which the liver clears damaged cells and regenerates functional mass.

Remote ischemic perconditioning--a simple, low-risk method to decrease ischemic reperfusion injury: models, protocols and mechanistic background. A review

Interruption of blood flow can cause ischemic reperfusion injury, which sometimes has a fatal outcome. Recognition of the phenomenon known as reperfusion injury has led to initial interventional approaches to lessen the degree of damage. A number of efficient pharmacologic agents and surgical techniques (e.g., local ischemic preconditioning and postconditioning) are available. A novel, alternative approach to target organ protection is remote ischemic conditioning triggered by brief repetitive ischemia and reperfusion periods in distant organs. Among the different surgical techniques is so-called remote ischemic perconditioning, a method that applies short periods of ischemic reperfusion to a distant organ delivered during target organ ischemia. Although ischemic reperfusion injury is reduced by this technique, the explanation for this phenomenon is still unclear, and approximately only a dozen reports on the topic have appeared in the literature. In our study, therefore, we investigated the connective mechanisms, signal transduction, and effector mechanisms behind remote perconditioning, with a review on molecular background and favorable effects. In addition, we summarize the various treatment protocols and models to promote future experimental and clinical research.

Ischemia/Reperfusion injury in liver surgery and transplantation: pathophysiology

Liver ischemia/reperfusion (IR) injury is caused by a heavily toothed network of interactions of cells of the immune system, cytokine production, and reduced microcirculatory blood flow in the liver. These complex networks are further elaborated by multiple intracellular pathways activated by cytokines, chemokines, and danger-associated molecular patterns. Furthermore, intracellular ionic disturbances and especially mitochondrial disorders play an important role leading to apoptosis and necrosis of hepatocytes in IR injury. Overall, enhanced production of reactive oxygen species, found very early in IR injury, plays an important role in liver tissue damage at several points within these complex networks. Many contributors to IR injury are only incompletely understood so far. This paper tempts to give an overview of the different mechanisms involved in the formation of IR injury. Only by further elucidation of these complex mechanisms IR injury can be understood and possible therapeutic strategies can be improved or be developed.

The current state of knowledge of hepatic ischemia-reperfusion injury based on its study in experimental models

The present review focuses on the numerous experimental models used to study the complexity of hepatic ischemia/reperfusion (I/R) injury. Although experimental models of hepatic I/R injury represent a compromise between the clinical reality and experimental simplification, the clinical transfer of experimental results is problematic because of anatomical and physiological differences and the inevitable simplification of experimental work. In this review, the strengths and limitations of the various models of hepatic I/R are discussed. Several strategies to protect the liver from I/R injury have been developed in animal models and, some of these, might find their way into clinical practice. We also attempt to highlight the fact that the mechanisms responsible for hepatic I/R injury depend on the experimental model used, and therefore the therapeutic strategies also differ according to the model used. Thus, the choice of model must therefore be adapted to the clinical question being answered.

In vivo tissue engineering chamber supports human induced pluripotent stem cell survival and rapid differentiation

Pluripotent stem cells are a potential source of autologous cells for cell and tissue regenerative therapies. They have the ability to renew indefinitely while retaining the capacity to differentiate into all cell types in the body. With developments in cell therapy and tissue engineering these cells may provide an option for treating tissue loss in organs which do not repair themselves. Limitations to clinical translation of pluripotent stem cells include poor cell survival and low cell engraftment in vivo and the risk of teratoma formation when the cells do survive through implantation. In this study, implantation of human induced-pluripotent stem (hiPS) cells, suspended in Matrigel, into an in vivo vascularized tissue engineering chamber in nude rats resulted in substantial engraftment of the cells into the highly vascularized rat tissues formed within the chamber. Differentiation of cells in the chamber environment was shown by teratoma formation, with all three germ lineages evident within 4 weeks. The rate of teratoma formation was higher with partially differentiated hiPS cells (as embryoid bodies) compared to undifferentiated hiPS cells (100% versus 60%). In conclusion, the in vivo vascularized tissue engineering chamber supports the survival through implantation of human iPS cells and their differentiated progeny, as well as a novel platform for rapid teratoma assay screening for pluripotency.

Remote ischemic conditioning: from bench to bedside

Remote ischemic conditioning (RIC) is a therapeutic strategy for protecting organs or tissue against the detrimental effects of acute ischemia-reperfusion injury (IRI). It describes an endogenous phenomenon in which the application of one or more brief cycles of non-lethal ischemia and reperfusion to an organ or tissue protects a remote organ or tissue from a sustained episode of lethal IRI. Although RIC protection was first demonstrated to protect the heart against acute myocardial infarction, its beneficial effects are also seen in other organs (lung, liver, kidney, intestine, brain) and tissues (skeletal muscle) subjected to acute IRI. The recent discovery that RIC can be induced non-invasively by simply inflating and deflating a standard blood pressure cuff placed on the upper arm or leg, has facilitated its translation into the clinical setting, where it has been reported to be beneficial in a variety of cardiac scenarios. In this review article we provide an overview of RIC, the potential underlying mechanisms, and its potential as a novel therapeutic strategy for protecting the heart and other organs from acute IRI.

Modulation of microcirculatory changes in the late phase of hepatic ischaemia-reperfusion injury by remote ischaemic preconditioning

BACKGROUND

  Remote ischaemic preconditioning (RIPC) is a novel method of protecting the liver from ischaemia-reperfusion (I-R) injury. Protective effects in the early phase (4-6 h) have been demonstrated, but no studies have focused on the late phase (24 h) of hepatic I-R. This study analysed events in the late phase of I-R following RIPC and focused on the microcirculation, inflammatory cascade and the role of cytokine-induced neutrophil chemoattractant-1 (CINC-1).

METHODS

  A standard animal model was used. Remote preconditioning prior to I-R was induced by intermittent limb ischaemia. Ischaemia was induced in the left and median lobes of the liver (70%). The animals were recovered after 45 min of liver ischaemia. At 24 h, the animals were re-evaluated under anaesthesia. Hepatic microcirculation, sinusoidal leukocyte adherence and hepatocellular death were assessed by intravital microscopy, hepatocellular injury by standard biochemistry and serum CINC-1 by enzyme-linked immunosorbent assay (ELISA).

RESULTS

  At 24 h post I-R, RIPC was found to have improved sinusoidal flow by increasing the sinusoidal diameter. There was no effect of preconditioning on the velocity of red blood cells, by contrast with the early phase of hepatic I-R. Remote ischaemic preconditioning significantly reduced hepatocellular injury, neutrophil-induced endothelial injury and serum CINC-1 levels.

CONCLUSIONS

  Remote ischaemic preconditioning is amenable to translation into clinical practice and may improve outcomes in liver resection surgery and transplantation.

The effect of preconditioning on liver regeneration after hepatic resection in cirrhotic rats

Background/Aims

Ischemic preconditioning (IP) decreases severity of liver necrosis and has anti-apoptotic effects in previous studies using liver regeneration in normal rats. This study assessed the effect of IP on liver regeneration after hepatic resection in cirrhotic rats.

Methods

To induce liver cirrhosis, thioacetamide (300 mg/kg) was injected intraperitoneally into Sprague-Dawley rats twice per week for 16 weeks. Animals were divided into four groups: non-clamping (NC), total clamping (TC), IP, and intermittent clamping (IC). Ischemic injury was induced by clamping the left portal pedicle including the portal vein and hepatic artery. Liver enzymes alanine transaminase (ALT) and aspartate aminotransferase (AST) were measured to assess liver damage. Terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL) staining for apoptosis and proliferating cell nuclear antigen (PCNA) staining for cell replication were also performed.

Results

Day-1 ALT and AST were highest in IP, however, levels in NC and IC were comparably low on days 1-7. There was no significant correlation of AST or ALT with experimental groups (P=0.615 and P=0.186). On TUNEL, numbers of apoptotic cells at 100× magnification (cells/field) were 31.8±24.2 in NC, 69.0±72.3 in TC, 80.2±63.1 in IP, and 21.2±20.8 in IC (P<0.05). When regeneration capacity was assessed by PCNA staining, PCNA-positive cells (cells/field) at 400× were 3.4±6.0 in NC, 16.9±69 in TC, 17.0±7.8 in IP and 7.4±7.6 in IC (P<0.05).

Conclusions

Although regeneration capacity in IP is higher than IC, the liver is vulnerable to ischemic damage in cirrhotic rats. Careful consideration is needed in applying IP in the clinical setting.

Preconditioning, postconditioning, and remote conditioning in solid organ transplantation: basic mechanisms and translational applications

Ischemia and reperfusion (I/Rp) injury is inherent to solid organ transplantation and can result in primary nonfunction or delayed function of grafts, which is associated with a significant morbidity and mortality posttransplantation. It is also a major obstacle for the use of marginal grafts to increase the donor pool, as these grafts are prone to a higher degree of I/Rp injury. Pre-, post-, and remote conditioning are protective strategies against I/Rp injury, which can be applied in the transplant setting. These strategies hold the potential to reduce graft injury and to safely expand the donor pool. However, despite convincing experimental data, the protective effects of the "conditioning" protocols remain unclear, and only few have translated to clinical practice. This review summarizes pre-, post-, and remote conditioning strategies in clinical use in solid organ transplantation and discusses an overview of the mechanistic pathways involved in each strategy.

Ischemic preconditioning attenuates lactate release by the liver during hepatectomies under vascular control: a case-control study

BACKGROUND

We have previously demonstrated lactate release by the liver itself in hepatectomies performed under selective hepatic vascular exclusion. We hypothesized that ischemic preconditioning applied in this setting might lead to a reduction of hepatic lactate production.

METHODS

Twenty-one patients underwent hepatectomy under inflow and outflow occlusion combined with ischemic preconditioning (IP group, n = 21). These patients were matched 1:1 with patients subjected to the same technique of hepatectomy under vascular occlusion without ischemic preconditioning (control group, n = 21). The transhepatic lactate gradient (hepatic vein-portal vein) was calculated before liver dissection and 60 min post-reperfusion.

RESULTS

In the control group, the transhepatic lactate gradient before liver resection was negative indicating consumption by the liver. After 60 min post-reperfusion, this gradient became positive, indicating net lactate production by the liver (0.2 ± 0.3 vs. -0.3 ± 0.2 mmol/L, P < 0.001). In the IP group, the liver consumed lactate both before resection and 60 min post-reperfusion (gradients -0.2 ± 1.1 and -0.1 ± 0.6 mmol/L, respectively). The magnitude of lactate release by the liver correlated with systemic hyperlactatemia post-reperfusion and 24 h postoperatively (r(2) = 0.54, P < 0.001 and r(2) = 0.67, P < 0.001, respectively). Significant correlations between the transhepatic lactate gradient post-reperfusion and peak postoperative AST as well as the apoptotic response of the liver remnant were also demonstrated (r(2) = 0.72, P < 0.001 and r(2) = 0.66, P < 0.001, respectively).

CONCLUSION

The microcirculatory derangement and cellular aerobic metabolism breakdown elicited by ischemia-reperfusion insults can be prevented with hepatoprotective measures such as ischemic preconditioning. The transhepatic lactate gradient could act as a monitoring and prognostic tool of the efficacy of ischemic preconditioning.

Activation of peroxisome-proliferator-activated receptors α and γ mediates remote ischemic preconditioning against myocardial infarction in vivo

Remote ischemic preconditioning (remote IPC) elicits a protective cardiac phenotype against myocardial ischemic injury. The remote stimulus has been hypothesized to act on major signaling pathways; however, its molecular targets remain largely undefined. We hypothesized that remote IPC exerts its effects by activating the peroxisome-proliferator-activated receptors (PPARs) α and γ, which have been previously implicated in cardioprotective signaling. Male New Zealand white rabbits (n = 78) were subjected to a 30-min coronary artery occlusion followed by three hours of reperfusion. Three cycles of remote IPC consisting of 10-min renal ischemia/reperfusion were performed. The animals either received the PPARα-antagonist GW6471 or the PPARγ-antagonist GW9662 alone or combined with remote IPC. Infarct size was determined gravimetrically. Tissue levels of 15d-prostaglandin J(2) (15d-PGJ(2)), as well as the PPAR DNA binding were measured using specific assays. Reverse transcriptase polymerase chain reaction was used to analyze changes in endothelial nitric oxide synthase or inducible nitric oxide synthase (iNOS) mRNA expression in relative quantity (RQ). Data are mean ± SD. As a result, remote IPC significantly reduced the myocardial infarct size (42.2 ± 4.9%* versus 61 ± 1.9%), accompanied by an increased PPAR DNA-binding (189.6 ± 19.8RLU* versus 44.4 ± 9RLU), increased iNOS expression (3.5 ± 1RQ* versus 1RQ), as well as 15d-PGJ(2) levels (179.7 ± 7.9 pg/mL* versus 127.9 ± 7.6 pg/mL). The protective response elicited by remote IPC, as well as the accompanying molecular changes were abolished by inhibiting PPARα (56.8 ± 4.7%; 61.1 ± 14.2RLU; and 1.91 ± 0.96RQ, respectively) or PPARγ (57.4 ± 3.3%; 52.7 ± 16.9RLU; and 1.54 ± 0.25RQ, respectively). (*Significantly different from control P < 0.05). In conclusion, the obtained results indicate that both PPARα and PPARγ play an essential role in remote IPC against myocardial infarction, impinging on the transcriptional control of iNOS expression.

Non-invasive limb ischemic pre-conditioning reduces oxidative stress and attenuates myocardium ischemia-reperfusion injury in diabetic rats

This study was to explore whether repeated non-invasive limb ischemic pre-conditioning (NLIP) can confer an equivalent cardioprotection against myocardial ischemia-reperfusion (I/R) injury in acute diabetic rats to the extent of conventional myocardial ischemic pre-conditioning (MIP) and whether or not the delayed protection of NLIP is mediated by reducing myocardial oxidative stress after ischemia-reperfusion. Streptozotocin-induced diabetic rats were randomized to four groups: Sham group, the I/R group, the MIP group and the NLIP group. Compared with the I/R group, both the NLIP and MIP groups showed an amelioration of ventricular arrhythmia, reduced myocardial infarct size, increased activities of total superoxide dismutase (SOD), manganese-SOD and glutathione peroxidase, increased expression of manganese-SOD mRNA and decreased xanthine oxidase activity and malondialdehyde concentration (All p < 0.05 vs I/R group). It is concluded that non-invasive limb ischemic pre-conditioning reduces oxidative stress and attenuates myocardium ischemia-reperfusion injury in diabetic rats.

Hepatic ischaemia-reperfusion injury from bench to bedside

BACKGROUND

Vascular occlusion to prevent haemorrhage during liver resection causes ischaemia-reperfusion (IR) injury. Insights into the mechanisms of IR injury gathered from experimental models have contributed to the development of therapeutic approaches, some of which have already been tested in randomized clinical trials.

METHODS

The review was based on a PubMed search using the terms 'ischemia AND hepatectomy', 'ischemia AND liver', 'hepatectomy AND drug treatment', 'liver AND intermittent clamping' and 'liver AND ischemic preconditioning'; only randomized controlled trials (RCTs) were included.

RESULTS

Twelve RCTs reported on ischaemic preconditioning and intermittent clamping. Both strategies seem to confer protection and allow extension of ischaemia time. Fourteen RCTs evaluating pharmacological interventions, including antioxidants, anti-inflammatory drugs, vasodilators, pharmacological preconditioning and glucose infusion, were identified.

CONCLUSION

Several strategies to prevent hepatic IR have been developed, but few have been incorporated into clinical practice. Although some pharmacological strategies showed promising results with improved clinical outcome there is not sufficient evidence to recommend them.

Liver ischemia/reperfusion injury: processes in inflammatory networks--a review

Liver ischemia/reperfusion (IR) injury is typified by an inflammatory response. Understanding the cellular and molecular events underpinning this inflammation is fundamental to developing therapeutic strategies. Great strides have been made in this respect recently. Liver IR involves a complex web of interactions between the various cellular and humoral contributors to the inflammatory response. Kupffer cells, CD4+ lymphocytes, neutrophils, and hepatocytes are central cellular players. Various cytokines, chemokines, and complement proteins form the communication system between the cellular components. The contribution of the danger-associated molecular patterns and pattern recognition receptors to the pathophysiology of liver IR injury are slowly being elucidated. Our knowledge on the role of mitochondria in generating reactive oxygen and nitrogen species, in contributing to ionic disturbances, and in initiating the mitochondrial permeability transition with subsequent cellular death in liver IR injury is continuously being expanded. Here, we discuss recent findings pertaining to the aforementioned factors of liver IR, and we highlight areas with gaps in our knowledge, necessitating further research.

Water extract of Zizyphus Jujube attenuates ischemia/reperfusion-induced liver injury in rats (PP106)

AIMS

Ischemia and reperfusion (I/R) injuries in the liver remain important clinical problems. Free oxygen radicals and nitrosative stress have been shown to be involved in the pathogenesis I/R-related liver injury. The purpose of this study was to characterize the effects of an extract of Zizyphus Jujube (ZJ), which has strong antioxidant effects, on I/R-induced liver injury.

MATERIALS AND METHODS

Ischemia (I) was induced in rat livers by clamping the common hepatic artery and portal vein for 40 minutes, after which flow was restored, and the liver was reperfused for 90 minutes. Blood samples were collected prior to I and after reperfusion to assay blood levels of alanine transaminase (ALT), lactic dehydrogenase (LDH), oxygen radical (OH), and nitric oxide (NO). In the pharmacologic intervention group a water extract of the fruit of ZJ was administered orally to rats (100 mg/mL for 7 days) that were subsequently exposed to the I/R liver injury.

RESULTS

The data showed that reperfusion (R) of the liver produced increases in blood concentrations of ALT (41.9+/-8.2 vs 338.0+/-89.6; P<.01; N=7) and LDH (317+/-129 vs 4073+/-950; P<.001; N=7). Oxygen radicals (55.1+/-14.3 vs 262.4+/-60.3; P<.001; N=7) and NO (69.3+/-14.9 vs 121.6+/-27.1; P<.01; N=7) also increased significantly in this R group. In the ZJ intervention group the liver injury, oxidative stress, and nitrosative stress were all significantly attenuated.

CONCLUSION

These results suggested that I/R-induced liver injury with white blood cell activation, oxidative stress, and nitrosative stress. Pretreatment with an extract of ZJ, which shows high antioxidant effects, significantly attenuated the I/R-induced liver injury.

Ischemic preconditioning confers antiapoptotic protection during major hepatectomies performed under combined inflow and outflow exclusion of the liver. A randomized clinical trial

BACKGROUND

Extensive experimental studies and a few clinical series have shown that ischemic preconditioning (IPC) attenuates oxidative ischemia/reperfusion (I/R) injuries in liver resections performed under inflow vascular control. Selective hepatic vascular exclusion (SHVE) employed during hepatectomies completely deprives the liver of blood flow, as it entails simultaneous clamping of the portal triad and the main hepatic veins. The aim of the present study was to identify whether IPC can also protect hepatocytes during liver resections performed under SHVE.

METHODS

Patients undergoing major liver resection were randomly assigned to have either only SHVE (control group, n = 43) or SHVE combined with IPC--10 min of ischemia followed by 15 min of reperfusion before SHVE was applied (IPC group, n = 41).

RESULTS

The two groups were comparable with regard to age, liver resection volume, blood loss and transfusions, warm ischemic time, and total operative time. In liver remnant biopsies obtained 60 min post-reperfusion, IPC patients had significantly fewer cells stained positive by TUNEL compared to controls (19% +/- 8% versus 45% +/- 12%; p < 0.05). Also IPC patients had attenuated hepatocyte necrosis, systemic inflammatory response, and oxidative stress as manifested by lower postoperative peak values of aspartate transaminase, interleukin-6, interleukin-8, and malondialdehyde compared to controls. Morbidity was similar for the two groups, as were duration of intensive care unit stay and extent of total hospital stay.

CONCLUSIONS

In major hepatectomies performed under SHVE, ischemic preconditioning appears to attenuate apoptotic response of the liver remnant, possibly through alteration of inflammatory and oxidative pathways.

Effect of ischemic preconditioning on the genomic response to reperfusion injury in deceased donor liver transplantation

Ischemic preconditioning (IP) is an effective method for protecting organs from ischemia/reperfusion (IR) injury; however, the molecular basis of this protective effect is poorly understood. This study assessed the gene expression profile in liver allografts during transplantation and evaluated the impact of IP. Prereperfusion and postreperfusion biopsy specimens from livers subjected to IP (n = 19) or no preconditioning (the IR group; n = 16) were obtained. Total RNA was extracted and hybridized to GeneChip microarrays, and the findings were validated with real-time quantitative reverse-transcription polymerase chain reaction (qRT-PCR). IP livers showed less of an increase in aspartate aminotransferase after transplantation. A microarray analysis of the IR group showed increased expression of 57 genes mainly involved in cell death, inflammation and immune response, stress, and modulation of the cell cycle. The IP group showed attenuation of the expression of these genes after reperfusion. Additionally, IP led to increased expression of 43 genes involved in growth and maintenance, cell-cycle regulation, proliferation, and development. The expression of the 12 most significant genes was validated in all patients with real-time qRT-PCR, and the fold changes of a number of genes correlated with clinical parameters and graft outcomes. IP protection of liver allografts was associated with a reduction in the expression of immune response genes and promotion of those involved in protection and repair.

Role of ischemic preconditioning in liver surgery and hepatic transplantation

INTRODUCTION

The purpose of this review is to summarize intraoperative surgical strategies available to decrease ischemia-reperfusion injury associated with liver resection and liver transplantation.

MATERIAL AND METHOD

We conducted a critical review of the literature evaluating the potential applications of hepatic ischemic preconditioning (IPC) for hepatic resection surgery and liver transplantation. In addition, we provide a basic bench-to-bedside summary of the liver physiology and cell signaling mechanisms that account for the protective effects seen with hepatic IPC.

Exaggerated up-regulation of tumor necrosis factor alpha-dependent apoptosis in the older mouse liver following reperfusion injury: targeting liver protective strategies to patient age

Although it is becoming increasingly common to accept livers from older donors for transplantation, old livers are more damaged by hepatic ischemia and reperfusion injury (HIRI) than young livers. We hypothesized that this age-related susceptibility to HIRI is due to increased hepatocellular apoptosis driven by tumor necrosis factor alpha (TNFalpha). Young (6-week-old) and old (60-week-old) mice underwent 60 minutes of hepatic ischemia and increasing periods of reperfusion. TNFalpha was determined by enzyme-linked immunosorbent assay. Liver injury (enzyme release), apoptosis (terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-digoxigenin nick-end labeling staining, cytochrome C release, and caspase activation), and necrosis (hematoxylin and eosin staining) were assessed. We assessed the impact of apoptosis by blocking TNFalpha production or effect (pentoxifylline and TNFalpha receptor knockout), inhibiting apoptotic pathways (caspase inhibition), or imposing a hepatic protective strategy [glucose infusion with ischemic preconditioning (Glc/PC)]. In comparison with young livers, old livers subjected to HIRI had more pronounced liver aspartate aminotransferase release (6200 versus 3900 U/L, P = 0.02), necrosis (45% versus 25%, P = 0.03), and apoptosis with increased 30-minute TNFalpha release (19.02 versus 10.62 pg/mg, P = 0.03). Eliminating TNFalpha production reversed the effect of age, as did inhibition of apoptotic pathways with caspase inhibition. Glc/PC of old mice attenuated TNFalpha release (9.56 versus 19.02 pg/mg, P = 0.001) and age-related exaggerated HIRI and improved survival (60% versus 0%). In conclusion, the age-related susceptibility to HIRI is driven by an exaggerated induction of TNFalpha-dependent hepatocellular apoptosis. Targeting the apoptotic cascade has implications for the older donor liver population.

Effects of ischemic postconditioning on reperfusion injury in rat liver grafts after orthotopic liver transplantation

AIM

The effects of ischemic postconditioning (IPostC) on ischemia reperfusion (IR) injury of liver grafts was examined in rats after orthotopic liver transplantation (OLT).

METHODS

Male Wistar rats were used as donors and recipients to establish a liver transplantation model. The animals were randomly divided into four groups: sham-operated (SO, n = 6), IR (n = 6), IPostC1 (n = 6) and IPostC2 (n = 6). IPostC was achieved by several intermittent interruptions of blood flow in the early phase of reperfusion. Several parameters of hepatic damage, oxidative stress, neutrophil infiltration and the expression of TNF-alpha and MIP-2 were detected as well as microscopic examination. Nitric oxide release and liver NO synthases (endothelial NO synthase and inducible NO synthase) expression were also measured.

RESULTS

We observed that a significant reduction in alanine aminotransferase, aspartate aminotransferase and lactate dehydrogenase values in two IPostC groups when compared with IR group. The increases in hepatic malondialdehyde, and decreases in superoxide dismutase and reduced glutathione levels after orthotopic liver transplantation were significantly inhibited by IPostC. IR induced increase in hepatic myeloperoxidase content, TNF-alpha and MIP-2 expression were also lowered by IPostC. The increases in NO content and NOS protein expression were much more prominent in IPostC treated groups. Animals treated with IPostC presented minimal hemorrhage and reduced signs of liver injury. There was no significant difference between two IPostC treated groups.

CONCLUSIONS

IPostC provided significant protection against IR injury to liver grafts. The protective effect of IPostC is closely related to the NO production following the increase in endothelial and inducible NO synthases expression and the suppression of tumor necrosis factor-alpha and macrophage inflammatory protein-2 overproduction.

Ischemic preconditioning in hepatic ischemia and reperfusion

PURPOSE OF REVIEW

Ischemic preconditioning that consists of a short period of hepatic inflow occlusion followed by reperfusion has the potential to increase tolerance to a subsequent prolonged ischemic insult. This review outlines current insight into ischemic preconditioning for hepatic ischemia and reperfusion injury in experimental and clinical settings.

RECENT FINDINGS

Experimental evidence suggests that interleukin-6 signaling and increased phosphorylation of STAT3 (signal transducer and activator of transcription-3) are involved in the protective effects of ischemic preconditioning. The benefit of ischemic preconditioning is restricted, however, by old liver and prolonged ischemic time (>60 min). To overcome this, ascorbic acid or glucose administration combined with ischemic preconditioning potentially can maintain the integrity of hepatic mitochondrial function through signal transduction pathways. The influence of ischemic preconditioning on hepatic regeneration varies with partial hepatectomy or small-for-size liver graft models, and remains controversial. Clinically, ischemic preconditioning in deceased donors protects against ischemia and reperfusion injury, as demonstrated by lowered liver enzyme levels, reduced incidence of primary nonfunction, and increased hepatic hypoxia-induced factor-1alpha concentrations.

SUMMARY

Enhanced understanding of the mechanisms of organ tolerance induced by ischemic preconditioning would strengthen the significance of this potential therapeutic strategy in liver transplantation.

Ischaemic and pharmacological preconditionings protect liver via adenosine and redox status following hepatic ischaemia/reperfusion in rats

Although IPC (ischaemic preconditioning) is considered as a protective strategy in HI/R (hepatic ischaemia/reperfusion), the mechanisms for this effect have not been fully elucidated. In the present study we investigate whether PPC (pharmacological preconditioning) by transient activation of A(1)R (adenosine A(1) receptor) protects against long-term HI/R and whether the protective effects of IPC depend on A(1)R activation and whether both preconditionings affect remote organs. Wistar rats underwent IPC and long-term HI/R. Another set of animals were pharmacologically preconditioned with the A(1)R-agonist CCPA [2-chloro-N(6)-cyclopentyladenosine; 0.1 mg/kg of body weight, i.p. (intraperitoneally)] 24 h before HI/R. In other groups, rats received an A(1)R-antagonist, DPCPX (1,3-dipropyl-8-cyclopentylxanthine; 0.1 mg/kg of body weight, i.p.) 24 h before HI/R. Hepatic damage was evaluated by transaminase [AST (aspartate transaminase), ALT (alanine transaminase)] release; inflammation was assessed by hepatic MPO (myeloperoxidase) and serum TNFalpha (tumour necrosis factor alpha) and NO; oxidative stress was estimated by MDA (malondialdehyde) and 4-HDA (4-hydroxyalkenals), SOD (superoxide dismutase) activity, GSH and ADA (adenosine deaminase) as adenosine metabolism. Both preconditionings protected liver and lung against HI/R as indicated by the reduction in transaminases, MPO, MDA+4-HDA, NO, TNFalpha and ADA activity as compared with HI/R (P<0.05). However, pre-treatment with DPCPX abolished the protective effects of IPC and PPC. Preconditionings induced a significant increase in hepatic MnSOD (manganese SOD) activity and NO generation compared with the sham group, and this activity was abolished by DPCPX pre-treatment. A(1)R activation induced hepatic delayed preconditioning and blockade of A(1)R abolished hepatic IPC. IPC, as well as PPC, were able to prevent lung damage. These protective effects are associated with a reduction in oxidative stress, inflammation and endogenous antioxidant preservation.

Remote ischaemic preconditioning: underlying mechanisms and clinical application

Remote ischaemic preconditioning (RIPC) represents a strategy for harnessing the body's endogenous protective capabilities against the injury incurred by ischaemia and reperfusion. It describes the intriguing phenomenon in which transient non-lethal ischaemia and reperfusion of one organ or tissue confers resistance to a subsequent episode of lethal ischaemia reperfusion injury in a remote organ or tissue. In its original conception, it described intramyocardial protection, which could be relayed from the myocardium served by one coronary artery to another. It soon became apparent that myocardial infarct size could be dramatically reduced by applying brief ischaemia and reperfusion to an organ or tissue remote from the heart before the onset of myocardial infarction. The concept of remote organ protection has now been extended beyond that of solely protecting the heart to providing a general form of inter-organ protection against ischaemia-reperfusion injury. This article reviews the history and evolution of the phenomenon that is RIPC, the potential mechanistic pathways underlying its cardioprotective effect, and its emerging application in the clinical setting.

Remote ischemic preconditioning: a novel protective method from ischemia reperfusion injury--a review

BACKGROUND

Restoration of blood supply to an organ after a critical period of ischemia results in parenchymal injury and dysfunction of the organ referred to as reperfusion injury. Ischemia reperfusion injury is often seen in organ transplants, major organ resections and in shock. Ischemic preconditioning (IPC) is an adaptational response of briefly ischemic tissues which serves to protect against subsequent prolonged ischemic insults and reperfusion injury. Ischemic preconditioning can be mechanical or pharmacological. Direct mechanical preconditioning in which the target organ is exposed to brief ischemia prior to prolonged ischemia has the benefit of reducing ischemia-reperfusion injury (IRI) but its main disadvantage is trauma to major vessels and stress to the target organ. Remote (inter organ) preconditioning is a recent observation in which brief ischemia of one organ has been shown to confer protection on distant organs without direct stress to the organ.

AIM

To discuss the evidence for remote IPC (RIPC), underlying mechanisms and possible clinical applications of RIPC. METHODS OF SEARCH: A Pubmed search with the keywords "ischemic preconditioning," "remote preconditioning," "remote ischemic preconditioning," and "ischemia reperfusion" was done. All articles on remote preconditioning up to September 2006 have been reviewed. Relevant reference articles from within these have been selected for further discussion.

RESULTS

Experimental studies have demonstrated that the heart, liver, lung, intestine, brain, kidney and limbs are capable of producing remote preconditioning when subjected to brief IR. Remote intra-organ preconditioning was first described in the heart where brief ischemia in one territory led to protection in other areas. Translation of RIPC to clinical application has been demonstrated by the use of brief forearm ischemia in preconditioning the heart prior to coronary bypass and in reducing endothelial dysfunction of the contra lateral limb. Recently protection of the heart has been demonstrated by remote hind limb preconditioning in children who underwent surgery on cardiopulmonary bypass for congenital heart disease. The RIPC stimulus presumably induces release of biochemical messengers which act either by the bloodstream or by the neurogenic pathway resulting in reduced oxidative stress and preservation of mitochondrial function. Studies have demonstrated endothelial NO, Free radicals, Kinases, Opioids, Catecholamines and K(ATP) channels as the candidate mechanism in remote preconditioning. Experiments have shown suppression of proinflammatory genes, expression of antioxidant genes and modulation of gene expression by RIPC as a novel method of IRI injury prevention.

CONCLUSION

There is strong evidence to support RIPC. The underlying mechanisms and pathways need further clarification. The effective use of RIPC needs to be investigated in clinical settings.

The ischemic preconditioning paradox in deceased donor liver transplantation-evidence from a prospective randomized single blind clinical trial

While animal studies show that ischemic preconditioning (IPC) is beneficial in liver transplantation (LT), evidence from few smaller clinical trials is conflicting. From October 2003 to July 2006, 101 deceased donors (DD) were randomized to 10 min IPC (n = 50) or No IPC (n = 51). Primary objective was efficacy of IPC to decrease reperfusion (RP) injury. Both groups had similar donor risk index (DRI) (1.54 vs. 1.57). Aminotransferases on days 1 and 2 were significantly greater (p < 0.05) in IPC recipients. In multivariate analyses, IPC had an independent effect only on day 2 aspartate transferase. Prothrombin time, bilirubin and histological injury were similar in both groups. IPC had no significant effect on plasma TNF-alpha, IL-6 and IL-10 in the donor and TNF-alpha and IL-6 in the recipient. In contrast, IPC recipients had a significant rise in systemic IL-10 levels after RP (p < 0.05) and had fewer moderate/severe rejections within 30 days (p = 0.09). Hospital stay was similar in both groups. One-year patient and graft survival in IPC versus No IPC were 88% versus 78% (p = 0.1) and 86 versus 76% (p = 0.25), respectively. IPC increases RP injury after DDLT, an 'IPC paradox'. Other potential benefits of IPC are limited. IPC may be more effective in combination with other preconditioning regimens.

Triptolide inhibits NF-kappaB activation and reduces injury of donor lung induced by ischemia/reperfusion

AIM

To investigate the protective effect of triptolide (TRI) on ischemia/reperfusion-induced injury of transplanted rabbit lungs and to investigate the mechanisms underlying the actions of TRI.

METHODS

We established the rabbit lung transplantation model and studied lung injury induced by ischemia/reperfusion and the inhibitory effect of TRI on NF-kappaB. The severity of lung injury was determined by a gradual decline in PvO2, the degree of lung edema, the increase in the myeloperoxidase (MPO) activity, and the ultrastructural changes of transplanted lungs. The activation of NF-kappaB was measured by immunohistochemistry. The increase in intercellular adhesion molecule-1 (ICAM-1), which is the target gene of NF-kappaB, was evaluated by ELISA.

RESULTS

After reperfusion, there was a gradual decline in the PvO2 level in the control group (group I). The level of PvO2 in the group treated with lipopolysaccharide (group II) was significantly decreased, whereas that of the group treated with TRI (group III) was markedly improved (P<0.01). In group III, the activity of MPO was downregulated, and the pulmonary edema did not become severe and the ultrastructure of the donor lung remained normal. The activity of NF-kappaB and the expression of ICAM-1 was significantly increased in the donor lungs. TRI blocked NF-kappaB activation and ICAM-1 expression.

CONCLUSION

The effects of TRI on reducing injury to donor lungs induced by ischemia/reperfusion may possibly be mediated by inhibiting the activity of NF-kappaB and the expression of the NF-kappaB target gene ICAM-1. Thus, TRI could be used in lung transplantations for improving the function of donor lungs.

Remote preconditioning reduces microcirculatory disorders in pancreatic ischemia/reperfusion injury

OBJECTIVES

Remote preconditioning (RPC) can protect from ischemia/reperfusion injury (IRI). We investigated the influence of RPC in pancreatic IRI.

METHODS

Wistar rats were randomized to 2 hours of ischemia and 2 hours of reperfusion of a pancreatic tail segment with or without 15 minutes of infrarenal ischemia 60 minutes before IRI. Microcirculatory measurements before ischemia and 1 and 2 hours after reperfusion included functional capillary density and leukocyte adherence in postcapillary venules, quantified by intravital fluorescence microscopy. Histology and tissue myeloperoxidase activity were further parameters of pancreatic injury.

RESULTS

Remote preconditioning caused an improvement of microcirculation (functional capillary density: 1 hour after reperfusion, 460 +/- 13 vs 350 +/- 9 cm/cm2; 2 hours after reperfusion, 437 +/- 13 vs 295 +/- 13 cm/cm2; P < 0.01) and reduced inflammatory tissue response (leukocyte adherence in postcapillary venules: 2 hours after reperfusion, 155 +/- 55 vs 748 +/- 187 cells/mm2; P < 0.01). Histology was significantly better in preconditioned animals (IR, 8.1+/- 1.3 score points; RPC, 6.2 +/- 1.3 score points; P < 0.05). The difference in myeloperoxidase activity was not significant (ischemia/reperfusion [IR], 105 +/- 72; RPC, 245 +/- 209 mU x min(-1) x mg(ti)(-1); P = 0.13).

CONCLUSIONS

With our dynamic functional microcirculatory measurements, we could demonstrate that RPC is a feasible method to reduce experimental pancreatic IRI. This was seen in an attenuation of nutritive tissue perfusion and a reduction of inflammatory tissue response and a lower histological damage. Because it is easy to perform before organ harvest, RPC could be a step to improve organ procurement in pancreas transplantation. Clinical studies are the next step to evaluate RPC in pancreas transplantation.

Ischemic pre-conditioning in deceased donor liver transplantation: a prospective randomized clinical trial

To assess the immediate and long-term effects of ischemic preconditioning (IPC) in deceased donor. liver transplantation (LT), we designed a prospective, randomized controlled trial involving 60 donors: control group (CTL, n = 30) or study group (IPC, n = 30). IPC was induced by 10-min hiliar clamping immediately before recovery of organs. Clinical data and blood and liver samples were obtained in the donor and in the recipient for measurements. IPC significantly improved biochemical markers of liver cell function such as uric acid, hyaluronic acid and Hypoxia-Induced Factor-1 alpha (HIF-1 alpha) levels. Moreover, the degree of apoptosis was significantly lower in the IPC group. On clinical basis, IPC significantly improved the serum aspartate aminotransferase (AST) levels and reduced the need for reoperation in the postoperative period. Moreover, the incidence of primary nonfunction (PNF) was lower in the IPC group, but did not achieve statistical significance. We conclude that 10-min IPC protects against I/R injury in deceased donor LT.

Protocols and Mechanisms for Remote Ischemic Preconditioning: A Novel Method for Reducing Ischemia Reperfusion Injury

Ischemia reperfusion injury (IRI) results in damage to local and remote organs. Remote ischemic preconditioning (RIPC) is a strategy to protect against IRI by inducing a prior brief period(s) of IRI to an organ remote from that undergoing sustained injury. RIPC has been shown to protect organs against IRI; however, the protocols and mechanisms for RIPC are unclear. For this review, a Medline/Pubmed search (January 1985 to January 2007) was conducted and all relevant articles were included. RIPC protocols are organ and species specific and both humoral and neurogenic pathways are involved in triggering intracellular signal pathways for protection.

Ischemia reperfusion injury, preconditioning and critical illness

The purpose of this review is to describe in more detail ischemia reperfusion injury and preconditioning, and to speculate on the potential role of preconditioning in the care of critically ill patients. Current hemodynamic treatment of hypotension and hypoperfusion in critically ill patients is directed at ensuring essential organ perfusion by maintaining intravascular volume and cardiac output, and ensuring adequate oxygen delivery by maintaining arterial oxygen partial pressure and hemoglobin levels. However, morbidity and mortality remain high and new approaches to critically ill patients are required. Treatments are needed that can protect against organ ischemia during periods of low blood flow. In recent years, there has been a growing appreciation of the importance of ischemia reperfusion injury. Ischemia associated with reperfusion may result in greater injury than ischemia alone. Ischemic preconditioning is used to describe the protective effect of short periods of ischemia to an organ or tissue against longer periods of ischemia. Although first described in the myocardium, there is now evidence that this phenomenon occurs in a wide variety of organs and tissues, including the brain and other nervous tissue such as the retina and spinal cord, liver, stomach, intestines, kidney, and the lungs. Preconditioning therapy may offer a new avenue of treatment in critically ill patients. Both traditional preconditioning methods and pharmacologic agents that mimic or induce such preconditioning may be used in the future. Clinical trials of pharmacologic agents are underway in patients with coronary artery disease. Further trials of such methods and agents are needed in critically ill patients suffering from sepsis or multiorgan system failure.

PANCREATIC INJURY AFTER THORACOABDOMINAL AORTIC OCCLUSION IN A PORCINE MODEL

BACKGROUND

The aim of this study was to investigate pancreatic injury after 45 min of thoracoabdominal aortic occlusion in a porcine model.

METHODS

Twenty-four pigs were used. Six pigs underwent sham operation and 18 intravascular balloon thoracoabdominal aortic occlusions for 45 min. The animals were randomly killed at 12, 48 and 120 h after reperfusion. After killing, all pancreata were examined macroscopically for any signs of acute pancreatitis, whereas gland specimens were harvested for histological study to evaluate pancreatic injury (haematoxylin and eosin staining) and acinar cell apoptosis (Terminal deoxynucleotidyl transferase mediated dUTP Nick-End Labelling staining).

RESULTS

Pancreatic injury severity score was mildly increased in terms of oedematous features at 12 h after reperfusion, but normalized to sham levels by the second day and thereafter. Necrotic injury was not statistically significant at any time point. Acinar cell apoptotic index was mildly increased at 12 and 48 h, but showed a tendency to decrease towards sham levels by the fifth day. One animal developed acute pancreatitis.

CONCLUSION

Acute pancreatitis is unlikely to occur after 45 min of thoracoabdominal aortic occlusion. However, an early, mild oedematous and apoptotic injury that occurs subclinically seems to be a constant event. This injury might have clinical significance when combined with pre-existent pancreatic pathologies.

Effects of ischemic liver preconditioning on hepatic ischemia/reperfusion injury in the rat

To minimize bleeding during major liver resections or liver transplantation, surgical measures have been adopted that induce ischemia-reperfusion injury (I/R) which may significantly contribute to morbidity and mortality of partial liver resections. Several methods have sought to minimize I/R hepatic lesions. The present project assessed the protective role of ischemic preconditioning (IPC) in rat livers. The IPC was accomplished by clamping the hepatic pedicle for 5 minutes, followed by a 5-minute reperfusion (R) period before a 2-hour ischemia. Thereafter, reperfusions of 1, 3, and 24 hours were compared among IPC and control groups without IPC. Liver biopsy and blood samples were measured for mitochondrial respiratory control ratio (RCR), serum aspartate aminotransferase (AST), and alanine aminotransferase (ALT). IPC protected liver mitochondrial function. Serum aminotransferase levels were significantly lower among animals undergoing IPC compared with groups without IPC. Thus, we verified the effects of IPC for hepatocellular protection against I/R lesions.

Improving outcome in patients undergoing liver surgery

Liver surgery is associated with many factors, which may affect outcome. Preoperative assessment of patient's general condition, resectability, and liver reserve are paramount for success. The Child-Pugh score and other scoring systems only partially enables to assess the risk associated with liver surgery. The presence of portal hypertension per se is a major risk factor for hepatectomy. Intraoperatively, any attempts should be made to minimize blood loss. Low central venous pressure and inflow occlusion best prevent bleeding. Ischemic preconditioning and intermittent clamping are routinely applied in many centers to protect against long periods of ischemia, although the mechanisms of protection remain unclear. In this review we describe recent advances in activated pathways associated with protection against ischemia. Postoperatively, the best factor impacting on outcome probably resides in experienced medical care particularly in the intensive care setting. Currently, no drug or gene therapy approaches has reached the clinic. The future relies on new insight into mechanisms of ischemia-reperfusion injury.

Liver and lung late alterations following hepatic reperfusion associated to ischemic preconditioning orN-acetylcysteine

This study aimed the effect of n-acetylcysteine or ischemic preconditioning in hepatic and pulmonary damage after liver ischemia-reperfusion injury. Twenty-four male Wistar-EPM rats were assigned into four groups: (IR) Hepatic ischemia-reperfusion; (IPC) IPC achieved before hepatic ischemia; (NAC) Animals received NAC pretreatment; and Sham operated group. After 24 h of hepatic reperfusion, blood, liver, and pulmonary samples were evaluated. Nonparametric tests were used (P <or= 0.05). Aspartate aminotransferase levels were similar among experimental groups. Lower alanine aminotrasnferase levels were observed in sham group (P = 0.04). IPC and NAC groups prevented from necrosis (P = 0.027), apoptosis (P = 0.003), and microvesicular steatosis (P = 0.0007), but not from neutrophil infiltration in liver tissue. IPC and NAC treatment reduced alveolar septal edema (P = 0.014), but did not prevent from neutrophil infiltration or vascular congestion. In conclusion, IPC and NAC attenuated hepatic and pulmonary damage after hepatic ischemia-reperfusion injury.

[Ischemic preconditioning of the liver: from molecular bases to clinical application]

Ischemia-reperfusion injury is produced when an organ is deprived of blood flow (ischemia), which is then restored (reperfusion). In certain circumstances, this injury leads to irreversible organ damage. Several therapeutic strategies have been used to reduce the severity of this injury. One of these strategies is the application of brief and repetitive episodes of ischemia-reperfusion before prolonged ischemia-reperfusion (ischemic preconditioning). In the present article we review the molecular mechanisms through which ischemic preconditioning confers protection against ischemia-reperfusion injury. The application of ischemic preconditioning during liver surgery is discussed, both in normothermic situations such as liver resection and in situations of low temperature such as liver transplantation.