Increased ischemic injury in old mouse liver: an ATP-dependent mechanism

Left lobe living donor liver transplantation in adults: What is the safety limit?

Small-for-size syndrome (SFSS) is the most significant cause of graft loss after living donor liver transplantation (LDLT), especially after left lobe (LL) LDLT in adults. The safety limit of applying LL-LDLT in adults without severe SFSS with a high rate of lethality needs to be determined. A total of 207 LL-LDLTs in adults since September 2005 were evaluated to analyze the risk factors for severe SFSS, defined as a serum total bilirubin concentration of ≥20.0 mg/dL after LDLT. Although there were no significant differences in cumulative graft survival after LDLT between medium grafts (graft volume [GV] to standard liver volume [SLV] ratio ≥ 40.0%), small grafts (35.0% ≤ GV/SLV < 40.0%), and extra small grafts (GV/SLV < 35.0%), patients with severe SFSS showed a significantly lower 5-year graft survival rate than those without (42.9% versus 94.3%, respectively; P < 0.001). Multivariate analysis for severe SFSS after LL-LDLT showed that donor age of ≥48 years (P = 0.01), Model for End-Stage Liver Disease (MELD) score of ≥ 19 (P < 0.01), and end portal venous pressure of ≥19 mm Hg (P = 0.04) were the significant and independent factors for severe SFSS after LL-LDLT. Within such high-risk subgroups of patients with a donor age of ≥48 years or MELD score of ≥ 19 before LDLT, operative blood loss volume of ≥8.0 L was a risk factor for severe SFSS. LL-LDLT in adults could be indicated and provide acceptable outcomes for the combinations of donors aged < 48 years and recipients with a MELD score of <19. Smaller grafts might yield acceptable outcomes in appropriately selected donor-recipient combinations. Liver Transplantation 22 1666-1675 2016 AASLD.

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

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

Challenges and advances in optimizing liver allografts from donation after circulatory death donors

In recent years, there has been a shift in the donor demographics with an increase in donation after circulatory death (DCD). Livers obtained from DCD donors are known to have poorer outcomes when compared to donors after brainstem death and currently only a small proportion of DCD livers are used. This review outlines the recent technological developments in liver DCD donation, including clinical studies using normothermic regional perfusion and extracorporal machine perfusion of livers from DCD donors.

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

BACKGROUND AND AIM

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

METHODS

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

RESULTS

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

CONCLUSION

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

Inhibition of glycogen synthase kinase 3 ameliorates liver ischemia/reperfusion injury via an energy-dependent mitochondrial mechanism

BACKGROUND & AIMS

The mechanisms of glycogen synthase kinase-3 (GSK-3)-mediated cytoprotection during liver ischemia/reperfusion (I/R) remain controversial, particularly in older organs. This study explores the role and potential mechanisms of GSK-3 in young and aging livers.

METHODS

A rodent partial warm I/R model was used to evaluate the therapeutic potential of GSK-3 modulation during hepatic I/R in young and aging Sprague-Dawley rats.

RESULTS

GSK-3 inhibition through IPC or SB216763 (SB21) preconditioning protected young rats from I/R-induced liver injury. This protection was absent in old animals but could be restored by glucose infusion prior to the I/R insult. The protection conferred by GSK-3 inhibition depended on mitochondrial metabolism regulation. Indeed, the inhibition of GSK-3 suppressed mitochondrial permeability transition pore (MPTP) opening, triggering mitohormesis in young animals, whereas insufficient fuel suppressed mitochondrial metabolism and inactivated the GSK-3-related protection in old animals. SB21 and glucose reactivated the mitochondrial F0F1-ATPase and subsequent protective cascades in the senescent liver. These effects were antagonized by an ATPase inhibitor and by an MPTP opener.

CONCLUSIONS

The protection conferred by GSK-3 inhibition during hepatic I/R insult is energy dependent, particularly in senescent livers. These findings demonstrate a key role for GSK-3-related mitochondrial energy homeostasis, which may shed new light on the clinical use of GSK-3 inhibitors to protect liver function in surgical settings, particularly for older patients.

Excitotoxicity and mitochondrial dysfunction underlie age-dependent ischemic white matter injury

The central nervous system white matter is damaged during an ischemic stroke and therapeutic strategies derived from experimental studies focused exclusively on young adults and gray matter have been unsuccessful in the more clinically relevant aging population. The risk for stroke increases with age and the white matter inherently becomes more susceptible to injury as a function of age. Age-related changes in the molecular architecture of white matter determine the principal injury mechanisms and the functional outcome. A prominent increase in the main plasma membrane Na(+)-dependent glutamate transporter, GLT-1/EAAT2, together with increased extracellular glutamate levels may reflect an increased need for glutamate signaling in the aging white matter to maintain its function. Mitochondria exhibit intricate dynamics to efficiently buffer Ca(2+), to produce sufficient ATP, and to effectively scavenge reactive oxygen species (ROS) in response to excitotoxicity to sustain axon function. Aging exacerbates mitochondrial fusion, leading to progressive alterations in mitochondrial dynamics and function, presumably to effectively buffer increased Ca(2+) load and ROS production. Interestingly, these adaptive adjustments become detrimental under ischemic conditions, leading to increased and early glutamate release and a rapid exhaustion of mitochondrial capacity to sustain energy status of axons. Consequently, protective interventions in young white matter become injurious or ineffective to promote recovery in aging white matter after an ischemic episode. An age-specific understanding of the mechanisms of injury processes in white matter is vital in order to design dynamic therapeutic approaches for stroke victims.

The role of hepatic ischemia-reperfusion injury and liver parenchymal quality on cancer recurrence

Hepatic ischemia/reperfusion (I/R) injury is a common clinical challenge. Despite accumulating evidence regarding its mechanisms and potential therapeutic approaches, hepatic I/R is still a leading cause of organ dysfunction, morbidity, and resource utilization, especially in those patients with underlying parenchymal abnormalities. In the oncological setting, there are growing concerns regarding the deleterious impact of I/R injury on the risk of post-surgical tumor recurrence. This review aims at giving the last updates regarding the role of hepatic I/R and liver parenchymal quality injury in the setting of oncological liver surgery, using a "bench-to-bedside" approach. Relevant medical literature was identified by searching PubMed and hand scanning of the reference lists of articles considered for inclusion. Numerous preclinical models have depicted the impact of I/R injury and hepatic parenchymal quality (steatosis, age) on increased cancer growth in the injured liver. Putative pathophysiological mechanisms linking I/R injury and liver cancer recurrence include an increased implantation of circulating cancer cells in the ischemic liver and the upregulation of proliferation and angiogenic factors following the ischemic insult. Although limited, there is growing clinical evidence that I/R injury and liver quality are associated with the risk of post-surgical cancer recurrence. In conclusion, on top of its harmful early impact on organ function, I/R injury is linked to increased tumor growth. Therapeutic strategies tackling I/R injury could not only improve post-surgical organ function, but also allow a reduction in the risk of cancer recurrence.

Liver transplantation with grafts obtained after cardiac death-current advances in mastering the challenge

The scarcity of donor livers has increased the interest in donation after cardiac death (DCD) as an additional pool to expand the availability of organs. However, the initial results of liver transplantation with DCD grafts have been suboptimal due to an increased rate of complications, as well as decreased graft survival. These challenges have led to many developments in DCD donation outcome, as well as basic and translational research. In this article we review the unique characteristics of DCD donors, nuances of DCD organ procurement, the effect of prolonged warm and cold ischemia times, and discuss major studies that compared DCD to donation after brain death liver transplantation, in terms of outcomes and complications. We also review the different methods of donor treatment that has been applied to ameliorate DCD organ outcome, and we discuss the role of machine perfusion techniques in organ reconditioning. We discuss the two major perfusion models, namely, hypothermic machine perfusion and normothermic machine perfusion; we compare both methods, and delineate their major differences.

Fasting protects liver from ischemic injury through Sirt1-mediated downregulation of circulating HMGB1 in mice

BACKGROUND & AIMS

Fasting and calorie restriction are associated with a prolonged life span and an increased resistance to stress. The protective effects of fasting have been exploited for the mitigation of ischemic organ injury, yet the underlying mechanisms remain incompletely understood. Here, we investigated whether fasting protects liver against ischemia reperfusion (IR) through energy-preserving or anti-inflammatory mechanisms.

METHODS

Fasted C57BL6 mice were subjected to partial hepatic IR. Injury was assessed by liver enzymes and histology. Raw264-7 macrophage-like cells were investigated in vitro. Sirt1 and HMGB1 were inhibited using Ex527 and neutralizing antibodies, respectively.

RESULTS

Fasting for one, but not two or three days, protected from hepatic IR injury. None of the investigated energy parameters correlated with the protective effects. Instead, inflammatory responses were dampened in one-day-fasted mice and in starved macrophages. Fasting alone led to a reduction in circulating HMGB1 associated with cytoplasmic HMGB1 translocation, aggregate formation, and autophagy. Inhibition of autophagy re-elevated circulating HMGB1 and abolished protection in fasted mice, as did supplementation with HMGB1. In vitro, Sirt1 inhibition prevented HMGB1 translocation, leading to elevated HMGB1 in the supernatant. In vivo, Sirt1 inhibition abrogated the fasting-induced protection, but had no effect in the presence of neutralizing HMGB1 antibody.

CONCLUSIONS

Fasting for one day protects from hepatic IR injury via Sirt1-dependent downregulation of circulating HMGB1. The reduction in serum HMGB1 appears to be mediated by its engagement in the autophagic response. These findings integrate Sirt1, HMGB1, and autophagy into a common framework that underlies the anti-inflammatory properties of short-term fasting.

Purinergic signalling in the liver in health and disease

Purinergic signalling is involved in both the physiology and pathophysiology of the liver. Hepatocytes, Kupffer cells, vascular endothelial cells and smooth muscle cells, stellate cells and cholangiocytes all express purinoceptor subtypes activated by adenosine, adenosine 5'-triphosphate, adenosine diphosphate, uridine 5'-triphosphate or UDP. Purinoceptors mediate bile secretion, glycogen and lipid metabolism and indirectly release of insulin. Mechanical stress results in release of ATP from hepatocytes and Kupffer cells and ATP is also released as a cotransmitter with noradrenaline from sympathetic nerves supplying the liver. Ecto-nucleotidases play important roles in the signalling process. Changes in purinergic signalling occur in vascular injury, inflammation, insulin resistance, hepatic fibrosis, cirrhosis, diabetes, hepatitis, liver regeneration following injury or transplantation and cancer. Purinergic therapeutic strategies for the treatment of these pathologies are being explored.

Hepatitis C recurrence: the Achilles heel of liver transplantation

Hepatitis C virus (HCV) infection is the most common indication for liver transplantation worldwide; however, recurrence post transplant is almost universal and follows an accelerated course. Around 30% of patients develop aggressive HCV recurrence, leading to rapid fibrosis progression (RFP) and culminating in liver failure and either death or retransplantation. Despite many advances in our knowledge of clinical risks for HCV RFP, we are still unable to accurately predict those most at risk of adverse outcomes, and no clear consensus exists on the best approach to management. This review presents a critical overview of clinical factors shown to influence the course of HCV recurrence post transplant, with particular focus on recent data identifying the important role of metabolic factors, such as insulin resistance, in HCV recurrence. Emerging data for genetic markers of HCV recurrence and their usefulness for predicting adverse outcomes will also be explored.

Purinergic signaling and blood vessels in health and disease

Purinergic signaling plays important roles in control of vascular tone and remodeling. There is dual control of vascular tone by ATP released as a cotransmitter with noradrenaline from perivascular sympathetic nerves to cause vasoconstriction via P2X1 receptors, whereas ATP released from endothelial cells in response to changes in blood flow (producing shear stress) or hypoxia acts on P2X and P2Y receptors on endothelial cells to produce nitric oxide and endothelium-derived hyperpolarizing factor, which dilates vessels. ATP is also released from sensory-motor nerves during antidromic reflex activity to produce relaxation of some blood vessels. In this review, we stress the differences in neural and endothelial factors in purinergic control of different blood vessels. The long-term (trophic) actions of purine and pyrimidine nucleosides and nucleotides in promoting migration and proliferation of both vascular smooth muscle and endothelial cells via P1 and P2Y receptors during angiogenesis and vessel remodeling during restenosis after angioplasty are described. The pathophysiology of blood vessels and therapeutic potential of purinergic agents in diseases, including hypertension, atherosclerosis, ischemia, thrombosis and stroke, diabetes, and migraine, is discussed.

Hydrogen sulfide preconditioning protects rat liver against ischemia/reperfusion injury by activating Akt-GSK-3β signaling and inhibiting mitochondrial permeability transition

Hydrogen sulfide (H2S) is the third most common endogenously produced gaseous signaling molecule, but its impact on hepatic ischemia/reperfusion (I/R) injury, especially on mitochondrial function, remains unclear. In this study, rats were randomized into Sham, I/R, ischemia preconditioning (IPC) or sodium hydrosulfide (NaHS, an H2S donor) preconditioning groups. To establish a model of segmental (70%) warm hepatic ischemia, the hepatic artery, left portal vein and median liver lobes were occluded for 60 min and then unclamped to allow reperfusion. Preconditioning with 12.5, 25 or 50 μmol/kg NaHS prior to the I/R insult significantly increased serum H2S levels, and, similar to IPC, NaHS preconditioning decreased alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels in the plasma and prevented hepatocytes from undergoing I/R-induced necrosis. Moreover, a sub-toxic dose of NaHS (25 μmol/kg) did not disrupt the systemic hemodynamics but dramatically inhibited mitochondrial permeability transition pore (MPTP) opening and thus prevented mitochondrial-related cell death and apoptosis. Mechanistic studies revealed that NaHS preconditioning markedly increased the expression of phosphorylated protein kinase B (p-Akt), phosphorylated glycogen synthase kinase-3 beta (p-GSK-3β) and B-cell lymphoma-2 (Bcl-2) and decreased the release of mitochondrial cytochrome c and cleaved caspase-3/9 levels. Therefore, NaHS administration prior to hepatic I/R ameliorates mitochondrial and hepatocellular damage through the inhibition of MPTP opening and the activation of Akt-GSK-3β signaling. Furthermore, this study provides experimental evidence for the clinical use of H2S to reduce liver damage after perioperative I/R injury.

Perioperative ischaemia-induced liver injury and protection strategies: An expanding horizon for anaesthesiologists

Liver resection is an effective modality of treatment in patients with primary liver tumour, metastases from colorectal cancers and selected benign hepatic diseases. Its aim is to resect the grossly visible tumour with clear margins and to ensure that the remnant liver mass has sufficient function which is adequate for survival. With the advent of better preoperative imaging, surgical techniques and perioperative management, there is an improvement in the outcome with decreased mortality. This decline in postoperative mortality after hepatic resection has encouraged surgeons for more radical liver resections, leaving behind smaller liver remnants in a bid to achieve curative surgeries. But despite advances in diagnostic, imaging and surgical techniques, postoperative liver dysfunction of varied severity including death due to liver failure is still a serious problem in such patients. Different surgical and non-surgical techniques like reducing perioperative blood loss and consequent decreased transfusions, vascular occlusion techniques (intermittent portal triad clamping and ischaemic preconditioning), administration of pharmacological agents (dextrose, intraoperative use of methylprednisolone, trimetazidine, ulinastatin and lignocaine) and inhaled anaesthetic agents (sevoflurane) and opioids (remifentanil) have demonstrated the potential benefit and minimised the adverse effects of surgery. In this article, the authors reviewed the surgical and non-surgical measures that could be adopted to minimise the risk of postoperative liver failure following liver surgeries with special emphasis on ischaemic and pharmacological preconditioning which can be easily adapted clinically.

Functions of autophagy in normal and diseased liver

Autophagy has emerged as a critical lysosomal pathway that maintains cell function and survival through the degradation of cellular components such as organelles and proteins. Investigations specifically employing the liver or hepatocytes as experimental models have contributed significantly to our current knowledge of autophagic regulation and function. The diverse cellular functions of autophagy, along with unique features of the liver and its principal cell type the hepatocyte, suggest that the liver is highly dependent on autophagy for both normal function and to prevent the development of disease states. However, instances have also been identified in which autophagy promotes pathological changes such as the development of hepatic fibrosis. Considerable evidence has accumulated that alterations in autophagy are an underlying mechanism of a number of common hepatic diseases including toxin-, drug- and ischemia/reperfusion-induced liver injury, fatty liver, viral hepatitis and hepatocellular carcinoma. This review summarizes recent advances in understanding the roles that autophagy plays in normal hepatic physiology and pathophysiology with the intent of furthering the development of autophagy-based therapies for human liver diseases.

Flurbiprofen, a cyclooxygenase inhibitor, protects mice from hepatic ischemia/reperfusion injury by inhibiting GSK-3β signaling and mitochondrial permeability transition

Flurbiprofen acts as a nonselective inhibitor for cyclooxygenases (COX-1 and COX-2), but its impact on hepatic ischemia/reperfusion (I/R) injury remains unclear. Mice were randomized into sham, I/R and flurbiprofen (Flurb) groups. The hepatic artery and portal vein to the left and median liver lobes were occluded for 90 min and unclamped for reperfusion to establish a model of segmental (70%) warm hepatic ischemia. Pretreatment of animals with flurbiprofen prior to I/R insult significantly decreased serum alanine aminotransferase (ALT), aspartate aminotransferase (AST) and lactate dehydrogenase (LDH), and prevented hepatocytes from I/R-induced apoptosis/necrosis. Moreover, flurbiprofen dramatically inhibited mitochondrial permeability transition (MPT) pore opening, and thus prevented mitochondrial-related cell death and apoptosis. Mechanistic studies revealed that flurbiprofen markedly inhibited glycogen synthase kinase (GSK)-3β activity and increased phosphorylation of GSK-3β at Ser9, which, consequently, could modulate the adenine nucleotide translocase (ANT)-cyclophilin D (CyP-D) complex and the susceptibility to MPT induction. Therefore, administration of flurbiprofen prior to hepatic I/R ameliorates mitochondrial and hepatocellular damage through inhibition of MPT and inactivation of GSK-3β, and provides experimental evidence for clinical use of flurbiprofen to protect liver function in surgical settings in addition to its conventional use for pain relief.

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.

Age-related differences in hepatic ischemia/reperfusion: gene activation, liver injury, and protective effect of melatonin

BACKGROUND

Ischemia/reperfusion (I/R) causes functional and structural damage to liver cells, this being more pronounced with increasing age of the tissue. Melatonin is a pineal indole that has been shown to play an important role as a free radical scavenger and anti-inflammatory molecule.

MATERIAL AND METHODS

The age-dependent responses to I/R were compared in 2-mo-old and 14-mo-old male Wistar rats. After 35 min of hepatic ischemia followed by 36 h of reperfusion, rats were sacrificed. Sham-operated control rats underwent the same protocol without real vascular occlusion. Animals were intraperitoneally injected with 10 mg/kg melatonin 24 h before the operation, at the time of surgery, and 12 and 24 h after it. The tissues were submitted to histopathologic evaluation. The levels of ALT and AST were analyzed in plasma. The expression of TNF-α, IL-1β, IL-10, MCP-1, IFN-γ, iNOS, eNOS, Bad, Bax, Bcl2, AIF, PCNA, and NFKB1 genes were detected by RT-PCR in hepatic tissue.

RESULTS

I/R was associated with significant increases in the expression of pro-inflammatory and pro-apoptotic genes in liver. Older rats submitted to I/R were found to respond with increased liver damage as compared with young rats, with serum ALT and AST levels significantly higher than in young animals. Mature rats also showed more evident increases in expression of pro-inflammatory cytokines (IL-1β, MCP-1, and IFN-γ) as well as a decrease in the mRNA expression of IL-10 as compared with young animals. Pro-apoptotic genes (Bax, Bad, and AIF) were significantly enhanced in liver after I/R, without differences between young and mature animals. However, the expression of Bcl2 gene did not show any change. Melatonin treatment was able to lower the expression of pro-inflammatory cytokines and pro-apoptotic genes and to improve liver function, as indicated by normalization of plasma AST and ALT levels and by reduction of necrosis and microsteatosis areas.

CONCLUSIONS

Melatonin treatment was able to reduce the I/R-stimulated pro-inflammatory and pro-apoptotic genes in the rat liver. Since older animals showed a more marked increase in inflammation and in liver injury, the treatment was more effective in those subjects.

An in vitro model of warm hypoxia-reoxygenation injury in human liver endothelial cells

BACKGROUND

Ischemia-reperfusion or hypoxia-reoxygenation (H-R) injury adversely affects hepatic function following transplantation and major resection; the death of human sinusoidal endothelial cells (SECs) by apoptosis may play a central role in this process. Caspase-3 is an important intracellular protease in the intrinsic and extrinsic pathways of apoptosis.

MATERIALS AND METHODS

SECs and EAhy926 cells were exposed to warm hypoxia at 37°C, followed by reoxygenation at 37°C. Activity of caspase-3 was quantified using Western blotting and colorimetric kinase assays.

RESULTS

H-R caused a significant increase in caspase-3 activity compared with controls in both cell types.

CONCLUSIONS

Warm H-R injury causes apoptotic cell death of SECs and immortalized cells, but with differing patterns of caspase activity.

Ischemia-Reperfusion Injury and Ischemic-Type Biliary Lesions following Liver Transplantation

Ischemia-reperfusion (I-R) injury after liver transplantation (LT) induces intra- and/or extrahepatic nonanastomotic ischemic-type biliary lesions (ITBLs). Subsequent bile duct stricture is a significant cause of morbidity and even mortality in patients who underwent LT. Although the pathogenesis of ITBLs is multifactorial, there are three main interconnected mechanisms responsible for their formation: cold and warm I-R injury, injury induced by cytotoxic bile salts, and immunological-mediated injury. Cold and warm ischemic insult can induce direct injury to the cholangiocytes and/or damage to the arterioles of the peribiliary vascular plexus, which in turn leads to apoptosis and necrosis of the cholangiocytes. Liver grafts from suboptimal or extended-criteria donors are more susceptible to cold and warm I-R injury and develop more easily ITBLs than normal livers. This paper, focusing on liver I-R injury, reviews the risk factors and mechanisms leading to ITBLs following LT.

Autophagy suppresses age-dependent ischemia and reperfusion injury in livers of mice

BACKGROUND & AIMS

As life expectancy increases, there are greater numbers of patients with liver diseases who require surgery or transplantation. Livers of older patients have significantly less reparative capacity following ischemia and reperfusion (I/R) injury, which occurs during these operations. There are no strategies to reduce the age-dependent I/R injury. We investigated the role of autophagy in the age dependence of sensitivity to I/R injury.

METHODS

Hepatocytes and livers from 3- and 26-month-old mice were subjected to in vitro and in vivo I/R, respectively. We analyzed changes in autophagy-related proteins (Atg). Mitochondrial dysfunction was visualized using confocal and intravital multi-photon microscopy of isolated hepatocytes and livers from anesthetized mice, respectively.

RESULTS

Immunoblot, autophagic flux, genetic, and imaging analyses all associated the increase in sensitivity to I/R injury with age with decreased autophagy and subsequent mitochondrial dysfunction due to calpain-mediated loss of Atg4B. Overexpression of either Atg4B or Beclin-1 recovered Atg4B, increased autophagy, blocked the onset of the mitochondrial permeability transition, and suppressed cell death after I/R in old hepatocytes. Coimmunoprecipitation analysis of hepatocytes and Atg3-knockout cells showed an interaction between Beclin-1 and Atg3, a protein required for autophagosome formation. Intravital multi-photon imaging revealed that overexpression of Beclin-1 or Atg4B attenuated autophagic defects and mitochondrial dysfunction in livers of older mice after I/R.

CONCLUSIONS

Loss of Atg4B in livers of old mice increases their sensitivity to I/R injury. Increasing autophagy might ameliorate liver damage and restore mitochondrial function after I/R.

The effect of methylene blue during orthotopic liver transplantation on post reperfusion syndrome and postoperative graft function

BACKGROUND/PURPOSE

In orthotopic liver transplantation (OLT), a major component of the post-reperfusion syndrome is hypotension, which may lead to additional graft liver ischemia-reperfusion injury. A proposed mechanism of reperfusion hypotension is the massive induction of oxidative stress triggering the release of pro-inflammatory mediators, including nitric oxide (NO). Methylene blue (MB) is an inhibitor of inducible NO synthase and an NO scavenger that has been shown to attenuate reperfusion hypotension. Of note, recent reports have shown that the exogenous administration of NO during OLT significantly improved the recovery of the graft liver. Therefore, we sought to investigate the effects of MB on the functional recovery of the graft liver following OLT.

METHODS

We analyzed retrospective data from 715 patients who underwent OLT between 2003 and 2008. We classified patients into those who received a 1-1.5 mg/kg intravenous bolus of MB immediately prior to reperfusion (MB group) and those who did not (control group). Propensity score matching was used to adjust for differences between patients who received intraoperative MB and those who did not, and these data were used to determine the association between a single MB bolus during OLT and postoperative graft dysfunction.

RESULTS

Our study cohort consisted of 715 OLT patients, of whom 105 received MB and 610 did not. After propensity score matching, demographic and donor data were similar in the two groups, except for the older age of recipients in the MB group (55.5 ± 0.9 vs 53.1 ± 0.8 years, p = 0.026). No differences were seen in mean arterial pressure changes after reperfusion and no differences were found in vasopressor requirements (bolus or infusion) or transfusion requirements. In addition, there was no significant difference in the incidence of primary nonfunction, retransplantation within 60 days, acute rejection, or graft survival between the groups by multivariate analysis or Kaplan-Meier survival analysis.

CONCLUSIONS

In our study, the administration of MB at 1-1.5 mg/kg immediately prior to reperfusion did not prevent post-reperfusion hypotension and did not decrease vasopressor usage or transfusion requirements after reperfusion. Also, MB did not have any impact on postoperative graft function. These findings may argue against the routine use of MB during OLT.

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-like effect of polyunsaturated fatty acid-rich diet on hepatic ischemia/reperfusion injury

AIM

The aim of this study was to investigate a possible preconditioning effect of oral diet enriched with polyunsaturated fatty acids (PUFAs) on liver ischemia/reperfusion (I/R) injuries.

METHODS

Wistar male rats were fed a standard diet or polyunsaturated fatty acid-rich diet (PRD) enriched with (GII) or without (GIII) ω-3 PUFA. Rats were submitted to partial liver ischemia during 1 h and evaluated in pre- and post-I/R conditions. In pre-I/R condition, livers were collected for determination of fatty acid composition, liver mitochondrial function, malondialdehyde (MDA) content, and histological analysis. Four hours after liver reperfusion serum activities of aspartate aminotransferase (AST) and alanine aminotransferase (ALT), serum levels of tumor necrosis factor-alpha, interleukin-6, interleukin-10, and prostaglandin-E2, liver mitochondrial function, MDA content, and histology were evaluated.

RESULTS

In the pre-I/R condition, GII and GIII groups had an increase on PUFA content and exhibited slight increased macrosteatosis and microsteatosis in the liver. After 4 h of reperfusion, PRD-fed rats showed a marked decrease on steatosis, diminished necrosis, an increase in MDA formation, and mitochondrial uncoupling. We also observed a marked decrease in plasma levels of cytokines and ALT and AST activities in post-I/R condition in PRD groups.

CONCLUSION

In this experimental model in the rat, PRD has a preconditioning effect protecting the liver from I/R injury and should be object of future clinical studies.

Ischemia/reperfusion injury in liver resection: a review of preconditioning methods

Ischemic preconditioning is one of the therapeutic interventions aiming at preventing ischemia/reperfusion-related injury. Numerous experimental studies and a few clinical series have shown that during liver resections, ischemic preconditioning is a promising strategy for optimizing the postoperative outcome. Moreover, various types of pharmacological intervention as well as different types of preconditioning, such as remote preconditioning, the use of heat shock, and hyperbaric oxygen, have been developed to attenuate the functional impairment accompanying ischemia/reperfusion injury. This review summarizes the various forms of preconditioning, thus suggesting that close cooperation between surgeons and anesthesiologists paves the way to apply novel strategies to improve the outcome of liver resection.

Serotonin reverts age-related capillarization and failure of regeneration in the liver through a VEGF-dependent pathway

The function of the liver is well-preserved during the aging process, although some evidence suggests that liver regeneration might be impaired with advanced age. We observed a decreased ability of the liver to restore normal volume after partial hepatectomy in elderly mice, and we identified a pathway that rescued regeneration and was triggered by serotonin. 2,5-dimethoxy-4-iodoamphetamine (DOI), a serotonin receptor agonist, reversed the age-related pseudocapillarization of old liver and improved hepatosinusoidal blood flow. After hepatectomy, the open fenestrae were associated with a restored attachment of platelets to endothelium and the initiation of a normal regenerative response, including the up-regulation of essential growth mediators and serotonin receptors. In turn, hepatocyte proliferation recovered along with regain of liver volume and animal survival. DOI operates through the release of VEGF, and its effects could be blocked with anti-VEGF antibodies both in vitro and in vivo. These results suggest that pseudocapillarization in the aged acts as a barrier to liver regeneration. DOI breaks this restraint through an endothelium-dependent mechanism driven by VEGF. This pathway highlights a target for reversing the age-associated decline in the capacity of the liver to regenerate.

Effect of remote ischemic preconditioning on liver ischemia/reperfusion injury using a new mouse model

Ischemic preconditioning of remote organs (RIPC) reduces liver ischemia/reperfusion (IR) injury in the rabbit and rat. Mice are the only species available with a large number of transgenic strains. This study describes development and validation of a mouse model of hindlimb RIPC that attenuates liver IR injury. Mice were allocated to 4 groups: (1) Sham surgery; (2) RIPC: 6 cycles of 4 × 4 minutes ischemia/reperfusion of hindlimb; (3) IR: 40 minutes lobar (70%) hepatic ischemia and 2 hours reperfusion; (4) RIPC+IR: RIPC followed by IR group procedures. Plasma liver aminotransferases and hepatic histopathological and transmission electron microscopy studies were performed at the end of the experiment. Hepatic microcirculatory blood flow was measured throughout the experiment. Postoperative complications and animal survival were evaluated. Hindlimb RIPC using a tourniquet resulted in limb paralysis. Hindlimb RIPC using direct clamping of the femoral vessels showed no side effects. Compared to liver IR alone, RIPC+IR reduced plasma aminotransferases (P < 0.05) and histopathological and ultrastructural features of injury. Hepatic microcirculatory blood flow was preserved in the RIPC+IR compared to IR group (P < 0.05). There was no mortality in any of the groups. By demonstrating a consistent improvement in these features of liver IR injury with antecedent hindlimb RIPC and by minimizing experimental confounding variables, we validated this mouse model. In conclusion, we describe a validated mouse model of hindlimb RIPC that reduces liver IR injury. With the availability of transgenic mice strains, this model should prove useful in unraveling the mechanisms of protection of hindlimb RIPC.

p66(Shc) has a pivotal function in impaired liver regeneration in aged mice by a redox-dependent mechanism

Liver regeneration involves complicated processes and is affected by various patho-physiological conditions. This study was designed to examine the molecular mechanisms underlying the aging-associated impairment of liver regeneration. Male C57BL/6J mice were used as young and aged mice (<10 weeks and >20 months old, respectively). These mice were subjected to 70% partial hepatectomy (PH). Liver regeneration and liver injury/stresses were evaluated chronologically after PH. Post-hepatectomy liver regeneration was markedly impaired in aged mice. Though the extent of hepatocyte proliferation in the regenerating liver was similar in aged and young mice, cell growth was absent in aged mice. Oxidative stress (OS) was observed immediately after hepatectomy, followed by marked apoptosis in aged mice. Signaling molecules regarding cell proliferation (mitogen-activated protein kinase, STAT3, p46/52(Shc)) and anti-oxidation (catalase, superoxide dismutase, Ref-1, glutathione peroxidase) were expressed/activated after hepatectomy in livers of both aged and young mice. Akt was not activated in aged-mouse liver, but its expression was similar to that in young mice. p66(Shc), known as an age-/oxidant-associated protein, was strongly phosphorylated. By knocking down p66(Shc), the impairment of liver regeneration was normalized. OS immediately after hepatectomy induced subsequent liver injury (apoptosis), and deletion of p66(Shc) suppressed both OS and hepatocyte apoptosis in the regenerating liver of aged mice. Though we need additional data in other animal models to fully understand the mechanism, p66(Shc) may have a pivotal function in the impairment of liver regeneration in aged mice by triggering OS and subsequent apoptosis. This data may provide a clue to understanding the mechanism underlying the association between aging and the impairment of liver regeneration.

TNF-α treatment alters Mfn2 expression and mitochondrial morphology and function in hepatic LO2 cells

AIM: To investigate the influence of treatment with tumor necrosis factor-alpha (TNF-α) on the expression of mitofusin 2 (Mfn2) and mitochondrial morphology and function in hepatic LO2 cells.

METHODS: After pEGFP-Mfn2 plasmid was transfected into LO2 cells with Lipofectamine 2000, transfected LO2 cells were incubated with TNF-α for 12 h. The expression of Mfn2 mRNA and protein was detected by reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blot, respectively. MitoTracker Mitochondrion-Selective Probes were used to detect the changes in mitochondrial morphology. ATP synthesis and reactive oxygen species (ROS) production were measured to assess mitochondrial function.

RESULTS: RT-PCR and Western blot analyses showed that Mfn2 was highly expressed in LO2 cells. After treatment of LO2 cells with TNF-α, Mfn2 expression was significantly suppressed (0.279 ± 0.026 vs 0.742 ± 0.018; 0.196 ± 0.024 vs 0.580 ± 0.011, P < 0.05), ATP level decreased (2.00 µmol/g ± 0.15 µmol/g vs 5.81 µmol/g ± 0.31 µmol/g, P < 0.05), ROS production increased (80.68 ± 4.02 vs 65.44 ± 3.47, P < 0.05), and the normal tubular network of mitochondria was fragmented into short rods or spheres when compared to control cells. In contrast, these changes were not significant in Mfn2-transfected LO2 cells.

CONCLUSION: TNF-α treatment may alter mitochondrial morphology and impair mitochondrial function by decreasing the expression of Mfn2 in hepatic LO2 cells.

Impact of cell cycle disruption on impaired hepatic regeneration in aged livers with ischemic insult

BACKGROUND

The number of elderly patients with hepatobiliary malignancies has increased with the steady growth of elderly population. However, the safety of major hepatectomy for elderly patients remains controversial. This study investigated the effect of aging on the hepatic regenerative response after partial resection of livers subjected to ischemic insult.

METHODS

Two-thirds hepatectomy following 1-h hepatic ischemia was performed in young (12-wk-old) and old (18-mo-old) rats under portosystemic shunt establishment by subcutaneous transposition of the spleen.

RESULTS

The survival rate 48 h after hepatectomy of the old rats was significantly lower (20%) than that of the young rats (53%), whereas all animals without hepatic ischemia were alive at 48 h. Hepatic necrosis and hepatocyte apoptosis during the early post-hepatectomy phase were more severe in the aged livers, which also showed delayed Akt activation. Liver mass restoration was significantly retarded in the old rats, despite higher plasma IL-6 levels, rapid and prolonged activation of hepatic STAT3, and increased hepatocyte nuclear cyclin D1 levels. In the young livers, cyclin E, which is essential for G1/S transition, and cyclin A, a marker of S phase, were observed in the nucleus from 24 h, reaching peaks 48 h after hepatectomy. In contrast, the old livers showed greatly delayed and decreased nuclear cyclin E and cyclin A levels.

CONCLUSION

Age-related reductions in the regenerative ability of ischemically damaged livers may be caused by cell cycle disruption at either the late G1 phase or the G1/S transition, despite increased cyclin D1 levels and compensatory IL-6/STAT3 activation.

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.

Three-dimensional reconstruction of living mouse liver tissues using cryotechniques with confocal laser scanning microscopy

Soluble proteins and glycogen particles are well preserved in paraffin-embedded sections prepared by in vivo cryotechnique (IVCT) and cryobiopsy followed by freeze substitution fixation. We performed confocal laser scanning microscopic analyses on the distributions of glycogen with periodic acid-Schiff (PAS) staining and serum proteins with immunostaining for mouse liver tissues. Livers of fully fed mice showed a strong fluorescence signal of PAS staining in all hepatocytes and immunofluorescence of immunoglobulin kappa light chain (Igκ) in blood vessels and bile canaliculi. However, some hepatocytes in mechanically damaged livers were PAS-negative and Igκ-immunopositive, showing extraction of glycogen particles and infiltration of serum proteins in hepatocytes. By three-dimensional (3D) reconstruction of serial optical sections, interconnecting hepatic sinusoids and bile canaliculi were detected with Igκ immunostaining between trabecular hepatocytes that were PAS stained. In PAS-stained samples under fasting conditions, interstitial structures along sinusoids were clarified in vivo by 3D reconstruction because of the lower PAS staining intensity of hepatocytes. In addition, 100-μm-thick eosin-stained slices provided 3D structural images more than 30 μm in thickness away from tissue surfaces, showing blood vessels with flowing erythrocytes and networks of bile ducts and canaliculi. IVCT and cryobiopsy with histochemical analyses enabled us to visualize native hepatocytic glycogen and 3D structures, such as vascular networks, reflecting their living states by confocal laser scanning microscopy.

Histochemical approach of cryobiopsy for glycogen distribution in living mouse livers under fasting and local circulation loss conditions

Soluble proteins and glycogen particles, which are easily lost upon conventional chemical fixation, have been reported to be better preserved in paraffin-embedded sections by 'cryobiopsy' combined with freeze-substitution fixation (FS). In this study, we examined the distribution of glycogen in living mouse livers under physiologic and pathologic conditions with periodic acid-Schiff (PAS) staining by cryobiopsy. The livers of the fully fed mice showed high PAS-staining intensity in the cytoplasm of all hepatocytes. The PAS-staining intensity gradually decreased away from hepatocytes around portal tracts, depending on treatments with different alpha-amylase concentrations. At 6 or 12 h after fasting, PAS-staining intensity markedly decreased in restricted areas of zone I near the portal tracts. The cryobiopsy was repeatedly performed not only on different mice, but also on individuals. Next, glycogen distributions were evaluated by temporarily clipping of liver tissues of anesthetized mice, followed by recovery of blood circulation. In the liver tissues in which blood was recirculated for 1 h after the 30 min anoxia, PAS staining was still observed in zone II and also in restricted areas of zone I far from the portal tracts. In PAS-unstained hepatocytes, the immunoglobulin-kappa light chain was not detected in the cytoplasm, indicating that cell membrane permeability was retained and that glycogen metabolism was related to the functional state of blood circulation. We propose that the level of consumption or production of glycogen particles could vary in zone I, depending on the distance from the portal tracts. Thus, cryobiopsy combined with FS enabled us to examine time-dependent changes in glycogen distribution in the liver tissues of living mice. This combination might be applicable to the clinical evaluation of human liver tissues.

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.

Pharmacological interventions versus no pharmacological intervention for ischaemia reperfusion injury in liver resection surgery performed under vascular control

BACKGROUND

Vascular occlusion to reduce blood loss is used during elective liver resection but results in significant ischaemia reperfusion injury. This, in turn, might lead to significant postoperative liver dysfunction and morbidity. Various pharmacological drugs have been used with an intention to ameliorate the ischaemia reperfusion injury in liver resections.

OBJECTIVES

To assess the benefits and harms of different pharmacological agents versus no pharmacological interventions to decrease ischaemia reperfusion injury during liver resections where vascular occlusion was performed during the surgery.

SEARCH STRATEGY

We searched The Cochrane Hepato-Biliary Group Controlled Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library, MEDLINE, EMBASE, and Science Citation Index Expanded until January 2009.

SELECTION CRITERIA

We included randomised clinical trials, irrespective of language or publication status, comparing any pharmacological agent versus placebo or no pharmacological agent during elective liver resections with vascular occlusion.

DATA COLLECTION AND ANALYSIS

Two authors independently identified trials for inclusion and independently extracted the data. We analysed the data with both the fixed-effect and the random-effects models using RevMan Analysis. We calculated the risk ratio (RR) or mean difference (MD) with 95% confidence intervals (CI) based on intention-to-treat analysis or available case analysis.

MAIN RESULTS

We identified a total of 15 randomised trials evaluating 11 different pharmacological interventions (methylprednisolone, multivitamin antioxidant infusion, vitamin E infusion, amrinone, prostaglandin E1, pentoxifylline, mannitol, trimetazidine, dextrose, allopurinol, and OKY 046 (a thromboxane A2 synthetase inhibitor)). All trials had high risk of bias. There were no significant differences between the groups in mortality, liver failure, or perioperative morbidity. The trimetazidine group had a significantly shorter hospital stay than control (MD -3.00 days; 95% CI -3.57 to -2.43). There were no significant differences in any of the clinically relevant outcomes in the remaining comparisons. Methylprednisolone improved the enzyme markers of liver function and trimetazidine, methylprednisolone, and dextrose reduced the enzyme markers of liver injury compared with controls. However, there is a high risk of type I and type II errors because of the few trials included, the small sample size in each trial, and the risk of bias.

AUTHORS' CONCLUSIONS

Trimetazidine, methylprednisolone, and dextrose may protect against ischaemia reperfusion injury in elective liver resections performed under vascular occlusion, but this is shown in trials with small sample sizes and high risk of bias. The use of these drugs should be restricted to well-designed randomised clinical trials before implementing them in clinical practice.

Recipient age affects long-term outcome and hepatitis C recurrence in old donor livers following transplantation

We studied the role of donor and recipient age in transplantation/ischemia-reperfusion injury (TIRI) and short- and long-term graft and patient survival. Eight hundred twenty-two patients underwent deceased donor liver transplantation, with 197 donors being > or = 60 years old. We evaluated markers of reperfusion injury, graft function, and clinical outcomes as well as short- and long-term graft and patient survival. Increased donor age was associated with more severe TIRI and decreased 3- and 5-year graft survival (73% versus 85% and 72% versus 81%, P < 0.001) and patient survival (77% versus 88% and 77% versus 82%, P < 0.003). Hepatitis C virus (HCV) infection and recipient age were the only independent risk factors for graft and patient survival in patients receiving an older graft. In the HCV(+) cohort (297 patients), patients > or = 50 years old who were transplanted with an older graft versus a younger graft had significantly decreased 3- and 5-year graft survival (68% versus 83% and 64% versus 83%, P < 0.009). In contrast, HCV(+) patients < 50 years old had similar 3- and 5-year graft survival if transplanted with either a young graft or an old graft (81% versus 82% and 81% versus 82%, P = 0.9). In conclusion, recipient age and HCV status affect the graft and patient survival of older livers. Combining older grafts with older recipients should be avoided, particularly in HCV(+) patients, whereas the effects of donor age can be minimized in younger recipients.

Clinical cardioprotection and the value of conditioning responses

Adjunctive cardioprotective strategies for ameliorating the reversible and irreversible injuries with ischemia-reperfusion (I/R) are highly desirable. However, after decades of research, the promise of clinical cardioprotection from I/R injury remains poorly realized. This may arise from the challenges of trialing and effectively translating experimental findings from laboratory models to patients. One can additionally consider whether features of the more heavily focused upon candidates could limit or preclude therapeutic utility and thus whether we might shift attention to alternate strategies. The phenomena of preconditioning and postconditioning have proven fertile in identification of experimental means of cardioprotection and are the most intensely interrogated responses in the field. However, there is evidence these processes, which share common molecular signaling elements and end effectors, may be poor choices for clinical exploitation. This includes evidence of age dependence, limiting efficacy in target aged or senescent hearts; refractoriness to conditioning stimuli in diseased myocardium; interference from a variety of relevant pharmaceuticals; inadvertent induction of these responses by prior ischemia or commonly used drugs, precluding further benefit; and sex dependence of protective signaling. This review focuses on these features, raising questions about current research strategies, and the suitability of these widely studied phenomena as rational candidates for clinical translation.

Effects of bicyclol on liver regeneration after partial hepatectomy in rats

Bicyclol is a synthetic antihepatitis drug with antioxidative property. The present study was performed to investigate the effect of bicyclol on liver regeneration after partial hepatectomy in rats. Bicyclol (300 mg/kg) was given to rats subjected to 70% hepatectomy three times before operation. At 6, 24, and 48 h after resection, samples were collected for the measurement of serum alanine aminotransferase (ALT), total bilirubin (TBil), hepatic glycogen, malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione (GSH). Moreover, liver regeneration rate, proliferating cell nuclear antigen (PCNA) labeling, proliferation index, and histopathological examination were evaluated at 48 h after hepatectomy. As a result, bicyclol significantly increased regeneration rate, mitotic index (MI), PCNA labeling index, and proliferation index in PH rats. Additionally, bicyclol remarkably inhibited the elevation of serum ALT and TBil levels, alleviated the formation of liver MDA, restored impaired antioxidant SOD and GSH, increased hepatic glycogen content, and also attenuated hepatic vacuolar degeneration. These results suggested that bicyclol had a beneficial effect on liver regenerative capacity of the remnant liver tissue after hepatectomy, probably due to its antioxidative property.

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 of the liver: a few perspectives from the bench to bedside translation

Utilization of ischemic preconditioning to ameliorate ischemia/reperfusion injury has been extensively studied in various organs and species for the past two decades. While hepatic ischemic preconditioning in animals has been largely beneficial, translational efforts in the two clinical contexts--liver resection and decreased donor liver transplantation--have yielded mixed results. This review is intended to critically examine the translational data and identify some potential reasons for the disparate clinical results, and highlight some issues for further studies.

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.

Effect of target-directed regulation of uncoupling protein-2 gene expression on ischemia-reperfusion injury of hepatocytes

The effect of target-directed regulation of the uncoupling protein-2 (UCP-2) gene expression on the ischemia-reperfusion injury of hepatocytes under different conditions was investigated. The expression plasmid and RNAi plasmid targeting UCP-2 gene were constructed and transfected into normal hepatocytes and fatty liver cells, respectively. The expression of UCP-2 mRNA was detected by real time PCR. The cells were divided into normal cell group (NCG), group of normal cells transfected with empty vector (EVNCG), group of normal cells transfected with expression plasmid (EPNCG), fatty liver cell group (FCG) and group of fatty liver cells transfected with RNAi plasmid (RPFCG). The ischemia-reperfusion model in vitro was established. One, 6, 12 and 24 h after reperfusion, Annexin V/PI flow cytometry was used to measure cell necrosis rate, apoptosis rate and survival rate. Simultaneously, the intracellular ATP, ROS and MDA levels were determined. The results showed that 1, 6, 12 and 24 h after ischemia-reperfusion, the intracellular ROS, MDA and ATP levels and cell survival rate in EPNCG were significantly lower, and cell necrosis rate significantly higher than in NCG and EVNCG, but there was no significant difference in apoptosis rate among NCG, EVNCG and EPNCG (P>005). Six, 12 and 24 h after reperfusion there was no significant difference in ROS, MDA levels and apoptosis rate between FCG and RPFCG (P>0.05), but the ATP level and survival rate of cells in RPFCG were higher than in FCG (P<0.05). It was concluded that down-regulation of the UCP-2 gene expression in steatotic hepatocytes could alleviate the ischemia-reperfusion injury of liver cells.

Current studies on therapeutic approaches for ischemia/reperfusion injury in steatotic livers

Steatotic livers are particularly vulnerable to ischemia/reperfusion (I/R) injury, resulting in poor outcomes following liver surgery and transplantation. Therapeutic approaches for I/R injury in steatotic livers are currently under intensive investigation. This review summarizes and discusses the approaches developed during the last few years to prevent hepatic I/R injury in steatotic livers. Among the proposed approaches, ischemic preconditioning and intermittent clamping are the two most promising approaches that have been applied in some clinical centers for liver surgery and transplantation, but most of others have not reached clinical application yet.

White matter vulnerability to ischemic injury increases with age because of enhanced excitotoxicity

Stroke incidence increases with age and this has been attributed to vascular factors. We show here that CNS white matter (WM) is intrinsically more vulnerable to ischemic injury in older animals and that the mechanisms of WM injury change as a function of age. The mouse optic nerve was used to study WM function. WM function in older animals (12 months) was not protected from ischemic injury by removal of extracellular Ca2+ or by blockade of reverse Na+/Ca2+ exchange, as is the case with young adults. Ischemic WM injury in older mice is predominately mediated by glutamate release and activation of AMPA/kainate-type glutamate receptors. Glutamate release, attributable to reverse glutamate transport, occurs earlier and is more robust in older mice that show greater expression of the glutamate transporter. The observation that WM vulnerability to ischemic injury is age dependent has possible implications for the pathogenesis of other age-related CNS conditions.

Intermittent ischemia but not ischemic preconditioning is effective in restoring bile flow after ischemia reperfusion injury in the livers of aged rats

BACKGROUND/AIMS

Ischemic preconditioning (IPC) and intermittent ischemia (INT) reduce liver injury following ischemia reperfusion in liver resections. Aged livers are at higher risk for ischemia reperfusion injury, but little is known of the effectiveness of IPC and INT in aged livers. The aim of this study was to investigate the effects of IPC and INT on ischemia reperfusion injury in aged livers.

METHODS

A rat model of segmental hepatic ischemia (45 min) and reperfusion (60 min) was used. Bile flow, as an indicator of early hepatocyte damage and dynamic liver function, plasma concentrations of bilirubin, liver marker enzymes, and liver histology were assessed.

RESULTS

In young rats (8-13 weeks), IPC regimes of 10 min clamping and 10 min reperfusion, and 5 min clamping and 30 min reperfusion, restored bile flow to 23 and 42%, respectively, of the initial value, compared to 14 and 88% for continuous clamping and controls, respectively. An INT regime of three cycles of alternating 15 min perfusion and 15 min clamping gave a substantially greater (70%) restoration of bile flow. In aged rats (20-24 months), the IPC regimes did not give any restoration of bile flow. By contrast, the INT regime restored bile flow to 68%. Plasma bilirubin concentrations were lowest in the INT groups, whereas alanine transaminase concentrations for the IPC and INT groups compared with the continuous clamping groups showed no significant differences.

CONCLUSIONS

In young rats, INT is more effective than IPC in restoring the immediate consequences of IP-induced damage to hepatocytes and liver function after ischemia-reperfusion. In aged rats INT, but not IPC, reverses hepatocyte damage and restores liver function. INT may promote better hepatocyte and liver function than IPC following the surgical resection of aged livers.

The effect of old age on liver oxygenation and the hepatic expression of VEGF and VEGFR2

In old age, the liver contains less ATP and hypoxia-responsive genes are upregulated. Age-related changes in hepatic perfusion and the liver sinusoidal endothelial cell (LSEC) could contribute to this altered hepatic oxygen-dependent metabolism by causing intrahepatocytic hypoxia. Furthermore, age-related changes in the LSEC ('pseudocapillarization') have been partially induced by ATP depletion. To investigate whether there is intracellular hypoxia in the old rat liver, pimonidazole immunohistochemistry in intact livers and ATP levels in isolated LSECs were studied from young and old rats. There were no age-related changes. To determine whether defenestration of the LSEC could impair oxygen diffusion, pimonidazole immunohistochemistry was performed in rats treated with poloxamer 407. Despite defenestration, there was no change in pimonidazole staining. Immunohistochemistry was then performed to determine whether there are age-related changes in VEGF and VEGFR2. VEGF staining was not associated with age. However, there was an increase in perisinusoidal VEGFR2 expression with increasing age. In conclusion, liver hypoxia does not occur in old age and LSEC pseudocapillarization does not constitute an oxygen-diffusion barrier. There are no age-related changes in VEGF expression but an increase in perisinusoidal VEGFR2 expression, which has implications for the effects of aging on the hepatic sinusoid.