Preconditioning, organ preservation, and postconditioning to prevent ischemia-reperfusion injury to the liver

Mouse hepatocytes and LSEC proteome reveal novel mechanisms of ischemia/reperfusion damage and protection by A2aR stimulation

BACKGROUND & AIMS

Ischemia-reperfusion (IR) of liver results in hepatocytes (HP) and sinusoidal endothelial cells (LSEC) irreversible damage. Ischemic preconditioning protects IR damage upon adenosine A2a receptor (A2aR) stimulation. Understanding the phenotypic changes that underlie hepatocellular damage and protection is critical to optimize strategies against IR.

METHODS

The proteome of HP and LSEC, isolated from sham or IR exposed mice, receiving or not the A2aR agonist CGS21680 (0.5mg/kg b.w.), was analyzed by 2-D DIGE/MALDI-TOF.

RESULTS

We identified 64 proteins involved in cytoprotection, regeneration, energy metabolism and response to oxidative stress; among them, 34 were associated with IR injury and A2aR protection. The main pathways, downregulated by IR and upregulated by CGS21680 in HP and LSEC, were related to carbohydrate, protein and lipid supply and metabolism. In LSEC, IR reduced stress response enzymes that were instead upregulated by CGS21680 treatment. Functional validation experiments confirmed the metabolic involvement and showed that inhibition of pyruvate kinase, 3-chetoacylCoA thiolase, and arginase reduced the protection by CGS21680 of in vitro hypoxia-reoxygenation injury, whereas their metabolic products induced liver cell protection. Moreover, LSEC, but not HP, were sensitive to H2O2-induced oxidative damage and CGS21680 protected against this effect.

CONCLUSIONS

IR and A2aR stimulation produces pathological and protected liver cell phenotypes, respectively characterized by down- and upregulation of proteins involved in the response to O2 and nutrients deprivation during ischemia, oxidative stress, and reactivation of aerobic energy synthesis at reperfusion. This provides novel insights into IR hepatocellular damage and protection, and suggests additional therapeutic options.

Liver protection strategies in liver transplantation

BACKGROUND

Liver transplantation is the therapy of choice for patients with end-stage liver diseases. However, the gap between the low availability of organs and high demand is continuously increasing. Innovative strategies for organ protection are necessary to expand donor pool and to achieve better outcomes for liver transplantation. The present review analyzed and compared various strategies of liver protection.

DATA SOURCES

Databases such as PubMed, Embase and Ovid were searched for the literature related to donor liver protection strategies using following key words: "ischemia reperfusion injury", "graft preservation", "liver transplantation", "machine perfusion" and "conditioning". Of the 146 studies identified, only those with cutting edge strategies were analyzed.

RESULTS

A variety of therapeutic approaches were proposed to alleviate graft ischemia/reperfusion injury, which included static cold storage, machine perfusion (hypothermic, normothermic and subnormothermic), manual conditioning (pre, post and remote), and pharmacological conditioning. Evidences from animal experiments and clinical trials suggested that all these strategies could potentially protect liver graft; however, their clinical applications are limited partially due to their own disadvantages.

CONCLUSIONS

There are a plenty of methods suggested to decrease the degree of donor liver transplantation-related injury. However, none of these approaches is perfect in clinical practice. More translational researches (molecular and clinical studies) are needed to improve the techniques in liver graft protection.

End of life care in the operating room for non-heart-beating donors: organization at the University Hospital of Liège

Non-heart-beating (NHB) organ donation has become an alternative source to increase organ supply for transplantation. A NHB donation program was implemented in our institution in 2002. As in many institutions the end of life care of the NHB donor (NHBD) is terminated in the operating room (OR) to reduce warm ischemia time. Herein we have described the organization of end of life care for these patients in our institution, including the problems addressed, the solution proposed, and the remaining issues. Emphasis is given to our protocol elaborated with the different contributors of the chain of the NHB donation program. This protocol specifies the information mandatory in the medical records, the end of life care procedure, the determination of death, and the issue of organ preservation measures before NHBD death. The persisting malaise associated with NHB donation reported by OR nurses is finally documented using an anonymous questionnaire.

Intestinal translocation of clinical isolates of vancomycin-resistant Enterococcus faecalis and ESBL-producing Escherichia coli in a rat model of bacterial colonization and liver ischemia/reperfusion injury

The objectives of this study were to develop a rat model of gastrointestinal colonization with vancomycin-resistant Enterococcus faecalis (VRE) and extended-spectrum beta-lactamase (ESBL)-producing E. coli and to evaluate intestinal translocation to blood and tissues after total and partial hepatic ischemia. Methods - We developed a model of rat colonization with VRE and ESBL-E coli. Then we studied four groups of colonized rats: Group I (with hepatic pedicle occlusion causing complete liver ischemia and intestinal stasis); Group II (with partial liver ischemia without intestinal stasis); Group III (surgical manipulation without hepatic ischemia or intestinal stasis); Group IV (anesthetized without surgical manipulation). After sacrifice, portal and systemic blood, large intestine, small intestine, spleen, liver, lungs, and cervical and mesenteric lymph nodes were cultured. Endotoxin concentrations in portal and systemic blood were determined. Results - The best inocula were: VRE: 2.4×10(10) cfu and ESBL-E. coli: 1.12×10(10) cfu. The best results occurred 24 hours after inoculation and antibiotic doses of 750 µg/mL of water for vancomycin and 2.1 mg/mL for ceftriaxone. There was a significantly higher proportion of positive cultures for ESBL-E. coli in the lungs in Groups I, II and III when compared with Group IV (67%; 60%; 75% and 13%, respectively; p:0.04). VRE growth was more frequent in mesenteric lymph nodes for Groups I (67%) and III (38%) than for Groups II (13%) and IV (none) (p:0.002). LPS was significantly higher in systemic blood of Group I (9.761 ± 13.804 EU/mL-p:0.01). No differences for endotoxin occurred in portal blood. Conclusion -We developed a model of rats colonized with resistant bacteria useful to study intestinal translocation. Translocation occurred in surgical procedures with and without hepatic ischemia-reperfusion and probably occurred via the bloodstream. Translocation was probably lymphatic in the ischemia-reperfusion groups. Systemic blood endotoxin levels were higher in the group with complete hepatic ischemia.

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.

Perfusion defatting at subnormothermic temperatures in steatotic rat livers

Hepatic steatosis is a major risk factor in liver transplantation. Use of machine perfusion to reduce steatosis has been reported previously at normothermic (37°C) temperatures, with minimal media as well as specialized defatting cocktails. In this work, we tested if subnormothermic (room temperature) machine perfusion, a more practical version of machine perfusion approach that does not require temperature control or oxygen carriers, could also be used to reduce fat content in steatotic livers. Steatotic livers recovered from obese Zucker rats were perfused for 6 hours. A significant increase of very low density lipoprotein (VLDL) and triglyceride (TG) content in perfusate, with or without a defatting cocktail, was observed although the changes in histology were minimal and changes in intracellular TG content were not statistically significant. The oxygen uptake rate, VLDL secretion, TG secretion, and venous resistance were similar in both groups. This study confirms lipid export during subnormothermic machine perfusion; however, the duration of perfusion necessary appears much higher than required in normothermic perfusion.

Tadalafil enhances the neuroprotective effects of ischemic postconditioning in mice, probably in a nitric oxide associated manner

This study investigates the modulatory effect of tadalafil, a selective phosphodiesterase (PDE-5) inhibitor, on the neuroprotective effects of ischemic postconditioning (iPoCo) in mice. Bilateral carotid artery occlusion (BCAO) for 12 min followed by reperfusion for 24 h was employed to produce ischemia and reperfusion induced cerebral injury. Cerebral infarct size was measured using TTC staining. Memory was assessed using the Morris water maze test. Degree of motor incoordination was evaluated using inclined beam-walking, rota-rod, and lateral push tests. Brain nitrite/nitrate, acetylcholinesterase activity, TBARS, and glutathione levels were also estimated. BCAO followed by reperfusion produced a significant increase in cerebral infarct size, brain nitrite/nitrate and TBARS levels, and acetylcholinesterase activity along with a reduction in glutathione. Marked impairment of memory and motor coordination was also noted. iPoCo consisting of 3 episodes of 10 s carotid artery occlusion and reperfusion instituted immediately after BCAO significantly decreased infarct size, memory impairment, motor incoordination, and altered biochemistry. Pretreatment with tadalafil mimicked the neuroprotective effects of iPoCo. The tadalafil-induced neuroprotective effects were significantly attenuated by l-NAME, a nonselective NOS inhibitor. We concluded that tadalafil mimics the neuroprotective effects of iPoCo, probably through a nitric oxide dependent pathway, and PDE-5 could be a target of interest with respect to the neuroprotective mechanism of iPoCo.

Mechanisms of liver involvement in systemic disease

The liver may be injured during the course of many systemic diseases. The mechanisms of injury can be broadly divided into four pathways: vascular, toxic, immune, and hormonal. Vascular obstruction may be an early event but is also the late common pathway from all mechanisms. Despite the large number of possible initiating factors, the end results are few, including death of hepatocytes or cholangiocytes, leading to the stereotyped syndromes of acute liver failure, non-cirrhotic portal hypertension, or cirrhosis. This small number of outcomes is a reflection of the few anatomic patterns that can be generated by microvascular obstruction. Vascular obstruction may occur by thrombosis, inflammation, or congestive injury. The innate immunity pathway is activated by endotoxin and other agents, leading to inflammatory infiltration, release of cytokines and reactive oxygen species, and necrosis. The adaptive immune pathway involves the generation of antibodies and antigen-specific cell-mediated attack on hepatic cells. Hormonal effects are principally involved when overnutrition leads to hyperinsulinemia followed by hepatocellular necrosis.

Protection against renal ischemia-reperfusion injury by ischemic postconditioning

Ischemia-reperfusion injury (IRI) is inevitable during transplantation. Attempts to reduce IRI have mainly focused on ways to improve hypothermic organ preservation and reduce the nephrotoxic effects of calcineurin inhibitors. Recently, it has been shown that short, repeated sequences of intermittent ischemia and reperfusion after a prolonged ischemic episode, so-called ischemic postconditioning (IPoC), reduce myocardial infarct size by approximately 40% in animal models and in humans. The principle of IPoC could be applied to every organ after ischemic injury, including kidney transplants. In fact, IPoC has demonstrated its clinical potential by reducing IRI in different organs in several animal models. In this review, we provide an overview of animal experiments on renal IRI and IPoC, demonstrating benefits with respect to organ damage and kidney function. We propose potential mechanisms by which IPoC protects against IRI. However, thus far, no human trials investigating IPoC in transplantation have been performed. Such clinical studies are needed to establish whether a simple procedure such as IPoC can improve the outcomes of human organ transplantation.

Current knowledge on oxidative stress in hepatic ischemia/reperfusion

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

Pretreatment of liver grafts in vivo by γ-aminobutyric acid receptor regulation reduces cold ischemia/warm reperfusion injury in rat

BACKGROUND

Gamma-aminobutyric acid (GABA) is found throughout the body. The regulation of GABA receptor (GABAR) reduces oxidative stress (OS). Ischemia/reperfusion injury after orthotopic liver transplantation (OLT) causes OS-induced graft damage. The effects of GABAR regulation in donors in vivo were investigated.

MATERIAL AND METHODS

Donor rats received saline, a GABAR agonist or GABAR antagonist 4 h before surgery. Recipient rats were divided into four groups according to the donor treatments: laparotomy, OLT with saline, OLT with GABAR agonist and OLT with GABAR antagonist. Histopathological, biochemical and immunohistological examinations were performed at 6, 12 and 24 h after OLT. Protein assays were performed at 6 h after OLT. The 4-hydroxynonenal (4-HNE), ataxia-telangiectasia mutated kinase (ATM), phosphorylated histone H2AX (gammaH2AX), phosphatidylinositol-3 kinase (PI3K), Akt and superoxide dismutase (SOD) were assessed by western blot analysis.

RESULTS

In the univariate analysis, histopathological and biochemical profiles verified that the GABAR agonist reduced graft damage. Immunohistology revealed that the GABAR agonist prevented the induction of apoptosis. Measurement of 4-4-HNE levels confirmed OS-induced damage after OLT, and the GABAR agonist improved this damage. In the gammaH2AX, PI3K, Akt and antioxidant enzymes (SODs), ATM and H2AX were greatly increased after OLT, and were reduced by the GABAR agonist. In the multivariate analyses between multiple groups, histopathological assessment, aspartate aminotransferase level, immunohistological examinations for apoptotic induction and gammaH2AX showed statistical differences.

CONCLUSIONS

A specific agonist demonstrated regulation of GABAR in vivo in the liver. This activation in vivo reduced OS after OLT via the ATM/H2AX pathway.

Colorectal liver metastases: hepatic pedicle clamping during hepatectomy reduces the incidence of tumor recurrence in selected patients. Case-matched analysis

BACKGROUND

Hepatic pedicle clamping (HPC) during Liver Resection (LR) is a vascular procedure designed to prevent bleeding from the liver during hepatectomy. Outgrowth of pre-existing colorectal micrometastases may occur 5-6 times faster in occluded liver lobes than in non-occluded lobes. We conducted a case-matched analysis at our Institution to assess the effects of HPC on overall and recurrence-free survival in highly selected patients, who underwent LR due to Colorectal liver metastases (CLM).

MATERIALS AND METHODS

From January 2002 to December 2010, 120 patients operated for CLM were included into this case-matched study. Patients were allocated to two groups: Group-A patients who underwent HPC during LR; Group-B patients who underwent LR without HPC.

RESULTS

HPC during liver resection was associated with better overall patient 5-year survival (47.2% in Group-A and 32.1% in Group-B) (P-value = 0.06), and significantly better 5-year recurrence-free survival (49.9% in Group-A vs 18.3% in Group-B) (P-value = 0.010) The Cox regression model identified the following risk factors for worse prognosis in terms of shorter recurrence-free survival and higher incidence of tumor recurrence: no HPC (Group-B) (P-value = 0.032) and positive lymph nodes at the time of LR (P-value = 0.018).

CONCLUSION

Lack of HPC in selected patients who underwent LR for CLM results to be a strong independent risk factor for higher patient exposure to tumor recurrence. We suggest that hepatic hilum clamping should be seriously taken into consideration in this patient setting.

MINI-ABSTRACT

A case-matched study was performed in 120 patients undergoing liver resection due to colorectal liver metastases, comparing patients who received intermittent hepatic pedicle clamping (HPC) with those who did not. The 5-year overall survival rate was similar, but the 5-year recurrence-free rate was significantly higher with no HPC (p = 0.012).

Extracorporeal membrane oxygenation for resuscitation of deceased cardiac donor livers for hepatocyte isolation

BACKGROUND

Deceased cardiac donors (DCDs) have become a useful source of organs for liver transplantation; nevertheless, there are concerns about the longevity of these grafts. The aim of this study was to evaluate the use of extracorporeal membrane oxygenation (ECMO) to resuscitate DCD porcine livers as a preclinical model using hepatocyte isolation and viability as a marker to assess whole-graft preservation.

MATERIALS AND METHODS

We randomized Landrace pigs into three groups after cardiac death and 30 min of warm ischemia: group 1, peritoneal cooling with intravascular cooling for 2 h; group 2, ECMO for 2 h; and group 3, control (conventional intravascular cooling and retrieval). We then reperfused group 1 and 2 livers for 2 h on an ex vivo reperfusion circuit and isolated hepatocytes.

RESULTS

After reperfusion, hepatocyte viability was significantly improved in the ECMO group compared to the cooling groups, as measured by trypan blue, methylthiazolyldiphenyl-tetrazolium bromide, and seeding efficiency. Glycogen and reduced glutathione content were significantly used in the ECMO group both before and after reperfusion compared with group 2. The adenosine diphosphate:adenosine triphosphate ratio showed an improved trend (lower) in the ECMO group compared with the cooling group but did not reach statistical significance either before or after reperfusion.

CONCLUSIONS

This preclinical study suggests that ECMO is a viable technique for liver preservation that gives an improved yield of hepatocytes when isolated from a DCD liver, suggesting improved liver preservation.

Ischaemia-reperfusion injury in liver transplantation--from bench to bedside

Ischaemia-reperfusion injury (IRI) in the liver, a major complication of haemorrhagic shock, resection and transplantation, is a dynamic process that involves the two interrelated phases of local ischaemic insult and inflammation-mediated reperfusion injury. This Review highlights the latest mechanistic insights into innate-adaptive immune crosstalk and cell activation cascades that lead to inflammation-mediated injury in livers stressed by ischaemia-reperfusion, discusses progress in large animal experiments and examines efforts to minimize liver IRI in patients who have received a liver transplant. The interlinked signalling pathways in multiple hepatic cell types, the IRI kinetics and positive versus negative regulatory loops at the innate-adaptive immune interface are discussed. The current gaps in our knowledge and the pathophysiology aspects of IRI in which basic and translational research is still required are stressed. An improved appreciation of cellular immune events that trigger and sustain local inflammatory responses, which are ultimately responsible for organ injury, is fundamental to developing innovative strategies for treating patients who have received a liver transplant and developed ischaemia-reperfusion inflammation and organ dysfunction.

Effect of ischemia post-conditioning on skeletal muscle oxidative injury, mTOR, Bax, Bcl-2 proteins expression, and HIF-1α/β-actin mRNA, IL-6/β-actin mRNA and caveolin-3/β-actin mRNA expression in ischemia-reperfusion rabbits

This study is designed to investigate the effect of ischemia post-conditioning on IR-induced skeletal muscle injury in limbs of experimental rabbits. Rabbits are randomized to one of the following three groups: sham control, ischemic reperfusion, ischemic postconditioning. The lipid peroxidation level, antioxidant enzymes activities, skeletal muscle mammalian target of rapamycin (mTOR), Bax, Bcl-2 proteins expression and Bcl-2/Bax, and HIF-1α/β-actin mRNA, interleukin-6 (IL-6)/β-actin mRNA and caveolin-3/β-actin mRNA expression were tested in the current study. The results suggested that ischemic postconditioning might decrease lipid peroxidation level, lactic dehydrogenase (LDH), creatine kinase (CK) activities, Bcl-2 proteins expression and Bcl-2/Bax, HIF-1α/β-actin mRNA expression and increase skeletal muscle antioxidant enzymes activities, Bax protein expression and IL-6/β-actin mRNA and caveolin-3/β-actin mRNA expression. These indicated that protective effect of ischemic postconditioning against IR-induced skeletal muscle injury involve into a complex molecular mechanism. Our research results may offer a theoretical guidance for therapy of related clinical diseases.

Protective effect of grape seed proanthocyanidins against liver ischemic reperfusion injury: particularly in diet-induced obese mice

Background: Hepatic ischemia and reperfusion injury (IRI) is a major complication in liver surgery, and hepatic steatosis is a primary factor aggravating cellular injury during IRI. Both pro-inflammatory cytokines and reactive oxygen species (ROS) are key mediators of hepatic IRI. Ischemic preconditioning (IpreC), remote ischemia preconditioning (RIPC) and ischemic postconditioning (IpostC) have offered protections on hepatic IRI, but all these methods have their own shortcomings. Grape seed proanthocyanidins (GSP) has a broad spectrum of pharmacological properties against oxidative stress. Thus, GSP has potential protective effects against hepatic IRI.

Methods: C57BL/6 mice suffering 30mins hepatic ischemia process were sacrificed after 1h reperfusion to build murine warm hepatic IRI model. The mice were injected GSP intraperitoneally 10, 20, 40mg/kg/day for 3 weeks as pharmacological preconditioning. Obese mice fed with high-fat diet for 24 weeks before used. Three pathways related to IRI, including ROS elimination, pro-inflammatory cytokines release and hypoxia responses were examined.

Results: Our data show that GSP could significantly reduce hepatic IRI by protecting hepatocyte function and increasing the activity of ROS scavengers, as well as decreasing cytokines levels. At the same time, GSP also enhance the hypoxia tolerance response. Combined GSP and postconditioning can provided synergistic protection. In the obese mice suffering hepatic IRI group, GSP was more effective than postconditioning on protecting liver against IRI, and the combined strategy was obviously superior to the solo treatment.

Conclusion: GSP could protect liver against IRI: particularly in high-fat diet induced obese mice. GSP used as pharmacological preconditioning and combined with other protocols have huge potential to be used in clinical.

Ischemic pre- and postconditioning has pronounced effects on gene expression profiles in the rat liver after ischemia/reperfusion

Ischemic pre (IPC)- and postconditioning (IPO) protect the liver against ischemia/reperfusion injuries (IRI). Conditioning involves several different trigger factors, mediators, and effectors, many of which are affected during the early phase of reperfusion, ultimately resulting in decreased liver injuries. The aim of the present study was to investigate the genomic response induced by IPC and IPO in ischemia/reperfusion-damaged rat liver biopsies. Forty-eight male Wistar rats were divided into five groups: sham (n = 8), IRI (n = 10), IPC (n = 10), IPO (n = 10), and IPC + IPO (n = 10). The rat livers were subjected to 30 min of ischemia. Liver biopsies and blood samples were taken after 30 min of reperfusion. The biopsies were analyzed using cDNA microarrays with validation by quantitative RT-PCR. The significance analysis of microarray was used to identify genes with changed expression levels. A comparison analysis of the intervention groups showed a highly increased number of genes, with significantly different expression in the conditioned groups compared with the IRI group. A total of 172 genes were identified as the most highly affected, and these genes showed similar patterns with regard to the up- and downregulated expression levels within the conditioned groups. Pathway analysis of the 172 genes identified four networks that were involved in increased gene expression, cellular growth, and proliferation. In conclusion, the present study demonstrated that IPC, IPO, and IPC + IPO had pronounced effects on the expression levels of a large number of genes during early reperfusion. IPC, IPO, and IPC + IPO seem to mediate their protective effects by regulating the same genes and genetic networks. These identified networks are known to be involved in maintaining cellular homeostasis.

Current strategies to minimize hepatic ischemia-reperfusion injury by targeting reactive oxygen species

Ischemia-reperfusion is a major component of injury in vascular occlusion both during liver surgery and during liver transplantation. The pathophysiology of hepatic ischemia-reperfusion includes a number of mechanisms including oxidant stress that contribute to various degrees to the overall organ damage. A large volume of recent research has focused on the use of antioxidants to ameliorate this injury, although results in experimental models have not translated well to the clinic. This review focuses on critical sources and mediators of oxidative stress during hepatic ischemia-reperfusion, the status of current antioxidant interventions, and emerging mechanisms of protection by preconditioning. While recent advances in regulation of antioxidant systems by Nrf2 provide interesting new potential therapeutic targets, an increased focus must be placed on more in-depth mechanistic investigations in hepatic ischemia-reperfusion injury and translational research in order to refine current strategies in disease management.

Atorvastatin protects obese mice against hepatic ischemia-reperfusion injury by Toll-like receptor-4 suppression and endothelial nitric oxide synthase activation

BACKGROUND AND AIM

Steatosis accentuates the severity of hepatic ischemia-reperfusion injury (IRI). 3-Hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors ("statins") protect the heart and brain against post-ischemic injury, without necessarily lowering serum cholesterol. We tested whether 10-day or 1-day atorvastatin administration protects livers with fatty change or non-alcoholic steatohepatitis (NASH) against IRI.

METHODS

Mice with dietary or genetic simple steatosis (SS) or NASH were subjected to 60 min of partial hepatic ischemia/24-h reperfusion, with/without atorvastatin administered with food (5 mg/kg body weight) for 10 days, or injected intravenously (5 mg/kg) 24 h before ischemia. Liver injury, Toll-like receptor-4 (TLR4), cytokines/chemokines, endothelial nitric oxide synthase (eNOS), activation and thromboxane B2 production were determined.

RESULTS

Atorvastatin conferred 70-90% hepatic protection against IRI in obese animals with SS or NASH, in which IRI was accentuated twofold to fivefold. IRI markedly upregulated TLR4 and activated nuclear factor-κB (NF-κB); atorvastatin abrogated these effects, as well as activating eNOS. Atorvastatin dampened the post-ischemic induction of thromboxane B2, macrophage inflammatory protein-1a, monocyte chemotactic protein-1, tumor necrosis factor-α, interleukin (IL)-12 p40, γ-interferon, IL-6, and adhesion molecules (vascular cell adhesion molecule-1, E-selectin, vascular endothelial-cadherin), and reduced macrophage and neutrophil recruitment. There was no reduction in serum cholesterol that could explain these effects, and hepatic cholesterol was normal in these mice. A single 24-h injection of atorvastatin conferred equivalent hepatoprotection.

CONCLUSION

Statins exert major hepatoprotection against IRI in lean, fatty, and NASH livers that is not due to cholesterol removal. Rather, statins downregulate TLR4 to prevent NF-κB activation, with resultant suppression of adhesion molecules, chemokines/cytokines, and thromboxane B2 production. Short-term statin treatment is an effective, readily-available preventive agent against hepatic IRI, irrespective of obesity and fatty liver disease.

Metabolic basis for thyroid hormone liver preconditioning: upregulation of AMP-activated protein kinase signaling

The liver is a major organ responsible for most functions of cellular metabolism and a mediator between dietary and endogenous sources of energy for extrahepatic tissues. In this context, adenosine-monophosphate- (AMP-) activated protein kinase (AMPK) constitutes an intrahepatic energy sensor regulating physiological energy dynamics by limiting anabolism and stimulating catabolism, thus increasing ATP availability. This is achieved by mechanisms involving direct allosteric activation and reversible phosphorylation of AMPK, in response to signals such as energy status, serum insulin/glucagon ratio, nutritional stresses, pharmacological and natural compounds, and oxidative stress status. Reactive oxygen species (ROS) lead to cellular AMPK activation and downstream signaling under several experimental conditions. Thyroid hormone (L-3,3′,5-triiodothyronine, T₃) administration, a condition that enhances liver ROS generation, triggers the redox upregulation of cytoprotective proteins affording preconditioning against ischemia-reperfusion (IR) liver injury. Data discussed in this work suggest that T₃-induced liver activation of AMPK may be of importance in the promotion of metabolic processes favouring energy supply for the induction and operation of preconditioning mechanisms. These include antioxidant, antiapoptotic, and anti-inflammatory mechanisms, repair or resynthesis of altered biomolecules, induction of the homeostatic acute-phase response, and stimulation of liver cell proliferation, which are required to cope with the damaging processes set in by IR.

Ischemic preconditioning of rat livers from non-heart-beating donors decreases parenchymal cell killing and increases graft survival after transplantation

A critical shortage of donors exists for liver transplantation, which non-heart-beating cadaver donors could help ease. This study evaluated ischemic preconditioning to improve graft viability after non-heart-beating liver donation in rats. Ischemic preconditioning was performed by clamping the portal vein and hepatic artery for 10 min followed by unclamping for 5 min. Subsequently, the aorta was cross-clamped for up to 120 min. After 2 h of storage, livers were either transplanted or perfused with warm buffer containing trypan blue. Aortic clamping for 60 and 120 min prior to liver harvest markedly decreased 30-day graft survival from 100% without aortic clamping to 50% and 0%, respectively, which ischemic preconditioning restored to 100 and 50%. After 60 min of aortic clamping, loss of viability of parenchymal and nonparenchymal cells was 22.6 and 5.6%, respectively, which preconditioning decreased to 3.0 and 1.5%. Cold storage after aortic clamping further increased parenchymal and non-parenchymal cell killing to 40.4 and 10.1%, respectively, which ischemic preconditioning decreased to 12.4 and 1.8%. In conclusion, ischemic preconditioning markedly decreased cell killing after subsequent sustained warm ischemia. Most importantly, ischemic preconditioning restored 100% graft survival of livers harvested from non-heart-beating donors after 60 min of aortic clamping.

Combined preconditioning and postconditioning provides synergistic protection against liver ischemic reperfusion injury

Hepatic Ischemia and Reperfusion Injury (IRI) is a major cause of liver damage during liver surgery and transplantation. Ischemic preconditioning and postconditioning are strategies that can reduce IRI. In this study, different combined types of pre- and postconditioning procedures were tested in a murine warm hepatic IRI model to evaluate their protective effects. Proanthocyanidins derived from grape seed was used before ischemia process as pharmacological preconditioning to combine with technical preconditioning and postconditioning. Three pathways related to IRI, including reactive oxygen species (ROS) generation, pro-inflammatory cytokines release and hypoxia responses were examined in hepatic IRI model. Individual and combined pre- and postconditioning protocols significantly reduce liver injury by decreasing the liver ROS and cytokine levels, as well as enhancing the hypoxia tolerance response. Our data also suggested that in addition to individual preconditioning or postconditioning, the combination of these two treatments could reduce liver ischemia/reperfusion injury more effectively by increasing the activity of ROS scavengers and antioxidants. The utilization of grape seed proanthocyanidins (GSP) could improve the oxidation resistance in combined pre- and postconditioning groups. The combined protocol also further increased the liver HIF-1 alpha protein level, but had no effect on pro-inflammatory cytokines release compared to solo treatment.

[Retrospective comparative study between sevoflurane and propofol in maintaining anaesthesia during liver transplant: Effects on kidney and liver function]

OBJECTIVE

To compare the post-operative effects of sevoflurane versus propofol on liver and kidney function while maintaining anaesthesia in the orthotopic liver transplant (OLT), as well as to analyse the short-term survival as regards these functions.

PATIENTS AND METHODS

A retrospective analysis was conducted on patients subjected to an OLT between January 2002 and December 2009. Patients on pre-transplant haemodialysis, re-transplants, and hepatorenal transplants were excluded. The incidence of acute renal failure, initial dysfunction of the graft, reperfusion syndrome, rejection, and the transaminase peak depending value depending on the hypnotic used, were recorded.

RESULTS

About one-third (31.2%) of the patients developed acute renal failure and 11.9% an initial dysfunction, with no differences between the groups. There was a tendency for a lower incidence of initial dysfunction of the graft in the sevoflurane group (8.6% compared to 12.8%), a lower transaminase peak (greater than 2000 U/L, 12.1% versus 15.9%), and a lower incidence of reperfusion syndrome (10.3% compared to 21.6%).

CONCLUSIONS

Despite the fact that the renal metabolism sevoflurane is elevated, we did not find any higher incidence of acute renal failure. Sevoflurane in the liver transplant anaesthesia is as least equally as safe propofol as regards renal function and liver function. New prospective studies are needed to clarify the possible effects of the hypnotic in liver transplant.

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.

Recent advances in liver preconditioning: Thyroid hormone, n-3 long-chain polyunsaturated fatty acids and iron

Liver preconditioning (PC), defined as an enhanced tolerance to injuring stimuli induced by previous specific maneuvers triggering beneficial functional and molecular changes, is of crucial importance in human liver transplantation and major hepatic resection. For these reasons, numerous PC strategies have been evaluated in experimental models of ischemia-reperfusion liver injury, which have not been transferred to clinical application due to side effects, toxicity and difficulties in implementation, with the exception of the controversial ischemic PC. In recent years, our group has undertaken the assessment of alternate experimental liver PC protocols that might have application in the clinical setting. These include thyroid hormone (T(3)), n-3 long-chain polyunsaturated fatty acids (n-3 LCPUFA), or iron, which suppressed liver damage due to the 1 h ischemia-20 h reperfusion protocol. T(3), n-3 LCPUFA and iron are hormetic agents that trigger biologically beneficial effects in the low-dose range, whose multifactorial mechanisms of action are discussed in the work.

Preconditioning donor liver with Nodosin perfusion lessens rat ischemia reperfusion injury via heme oxygenase-1 upregulation

BACKGROUND AND AIM

Ischemia reperfusion injury (IRI) remains a major cause of graft injury, dysfunction and even failure post-transplantation. Heme oxygenase 1 (HO-1) has been found to be an attractive target for anti-inflammatory therapies and a potential candidate responsible for cell injury. The objective of this study was to investigate whether preconditioning the donor liver with Nodosin perfusion upregulates HO-1 and then lessens IRI in rat models.

METHODS

Wistar rats were divided into four groups: experimental group, control group, positive control group and negative control group in which the donor liver was preconditioned with Nodosin, lactated ringer's solution, cobalt protoporphyrin and zinc protoporphyrin perfusion, respectively. We measured HO-1 expression and enzyme activity in rat livers of each group ex vivo at 0, 1 and 2 h after perfusion. At 1 h after perfusion, donor livers of Wistar rats were transplanted into Sprague-Dawley rats orthotopically. Serum transaminase levels, degree of cell apoptosis and Suzuki's score were used to assess ischemia/reperfusion injury in recipients at 24 h after transplantation.

RESULTS

Ex vivo, donor liver preconditioning with Nodosin perfusion induced HO-1 expression and enzyme activity significantly, compared with the control group (P < 0.05). In vivo, serum transaminase levels, cell apoptosis degree and Suzuki's score of representative recipients in the Nodosin group were lower than that in the control group (P < 0.05). Preconditioning with Nodosin perfusion induced HO-1 protein mainly in Kupffer cells.

CONCLUSIONS

This study suggests that preconditioning with Nodosin perfusion provides a potential protective effect through inducing HO-1 expression to attenuate ischemia/reperfusion injury in liver transplantation.

N-3 PUFA supplementation triggers PPAR-α activation and PPAR-α/NF-κB interaction: anti-inflammatory implications in liver ischemia-reperfusion injury

Dietary supplementation with the n-3 polyunsaturated fatty acids (n-3 PUFA) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) to rats preconditions the liver against ischemia-reperfusion (IR) injury, with reduction of the enhanced nuclear factor-κB (NF-κB) functionality occurring in the early phase of IR injury, and recovery of IR-induced pro-inflammatory cytokine response. The aim of the present study was to test the hypothesis that liver preconditioning by n-3 PUFA is exerted through peroxisone proliferator-activated receptor α (PPAR-α) activation and interference with NF-κB activation. For this purpose we evaluated the formation of PPAR-α/NF-κBp65 complexes in relation to changes in PPAR-α activation, IκB-α phosphorylation and serum levels and expression of interleukin (IL)-1β and tumor necrosis factor (TNF)-α in a model of hepatic IR-injury (1 h of ischemia and 20 h of reperfusion) or sham laparotomy (controls) in male Sprague Dawley rats. Animals were previously supplemented for 7 days with encapsulated fish oil (General Nutrition Corp., Pittsburg, PA) or isovolumetric amounts of saline (controls). Normalization of IR-altered parameters of liver injury (serum transaminases and liver morphology) was achieved by dietary n-3 PUFA supplementation. EPA and DHA suppression of the early IR-induced NF-κB activation was paralleled by generation of PPAR-α/NF-κBp65 complexes, in concomitance with normalization of the IR-induced IκB-α phosphorylation. PPAR-α activation by n-3 PUFA was evidenced by enhancement in the expression of the PPAR-α-regulated Acyl-CoA oxidase (Acox) and Carnitine-Palmitoyl-CoA transferase I (CPT-I) genes. Consistent with these findings, normalization of IR-induced expression and serum levels of NF-κB-controlled cytokines IL-lβ and TNF-α was observed at 20 h of reperfusion. Taken together, these findings point to an antagonistic effect of PPAR-α on NF-κB-controlled transcription of pro-inflammatory mediators. This effect is associated with the formation of PPAR-α/NF-κBp65 complexes and enhanced cytosolic IκB-α stability, as major preconditioning mechanisms induced by n-3 PUFA supplementation against IR liver injury.

Excorporeal normothermic machine perfusion resuscitates pig DCD livers with extended warm ischemia

BACKGROUND

The shortage in donor livers has led to increased use of allografts derived from donation after cardiac death (DCD). The compromised viability in these livers leads to inferior post-transplantation allograft function and survival compared with donation after brain death (DBD) donor grafts. In this study, we reconditioned DCD livers using an optimized normothermic machine perfusion system.

METHODS

Livers from 12 Yorkshire pigs (20-30 kg) were subjected to either 0 min (WI-0 group, n = 6) or 60 min (WI-60 group, n = 6) of warm ischemia and 2 h of cold storage in UW solution, followed by 4 h of oxygenated sanguineous normothermic machine perfusion. Liver viability and metabolic function were analyzed hourly.

RESULTS

Warm ischemic livers showed elevated transaminase levels and reduced ATP concentration. After the start of machine perfusion, transaminase levels stabilized and there was recovery of tissue ATP, coinciding with an increase in bile production. These parameters reached comparable levels to the control group after 1 h of machine perfusion. Histology and gross morphology confirmed recovery of the ischemic allografts.

CONCLUSION

Our data demonstrate that metabolic and functional parameters of livers with extended warm ischemic time (60 min) can be significantly improved using normothermic machine perfusion. We hereby compound the existing body of evidence that machine perfusion is a viable solution for reconditioning marginal organs.

Hepatic steatosis prevents heme oxygenase-1 induction by isoflurane in the rat liver

AIM: To characterize the inductive effects of isoflurane (ISO) on hepatic heme oxygenase-1 (HO-1) in an animal model of hepatic steatosis.

METHODS: Lean (LEAN) and obese (FAT) Zucker rats were randomized into 4 groups: 1: LEAN + pentobarbital sodium (PEN); 2: LEAN + ISO; 3: FAT + PEN; 4: FAT + ISO. The animals were mechanically ventilated for 6 h. In vitro analyses of liver tissue included determination of HO-1 mRNA and protein expression as well as measurement of HO enzyme activity and immunohistochemical analyses.

RESULTS: Compared to PEN treatment, ISO administration profoundly induced hepatic HO-1 mRNA and protein expression and significantly increased HO enzyme activity in lean Zucker rats. In contrast, no difference in HO-1 gene expression was observed after ISO or PEN anesthesia in obese Zucker rats.

CONCLUSION: The present study demonstrates that ISO is an inducer of hepatic HO-1 gene expression in non-steatotic organs but failed to upregulate HO-1 in steatotic livers.

Thyroid hormone administration induces rat liver Nrf2 activation: suppression by N-acetylcysteine pretreatment

BACKGROUND

Oxidative stress associated with 3,3',5-triiodo-l-thyronine (T(3))-induced calorigenesis upregulates the hepatic expression of mediators of cytoprotective mechanisms. The aim of this study was to evaluate the hypothesis that in vivo T(3) administration triggers a redox-mediated translocation of the cytoprotective nuclear transcription factor erythroid 2-related factor 2 (Nrf2) from the cytosol to the nucleus in rat liver. Such translocation of transcription factors is considered to be an activating step.

MATERIALS AND METHODS

The effect of T(3) administration in the presence and absence of N-acetylcysteine (NAC) on cytosol-to-nuclear translocation of Nrf2 was evaluated, with inhibition of this process by NAC taken as evidence that the process was redox mediated. Male Sprague-Dawley rats weighing 180-200 g were given a single intraperitoneal dose of 0.1 mg T(3)/kg. Another group of rats were given the same dose of T(3) and were also pretreated with NAC (0.5 g/kg) at 0.5 hour before T(3) administration. Two other groups of rats received vehicle treatment and NAC, respectively. Following these treatments, rectal temperature of the animals, liver O(2) consumption, serum and hepatic levels of 8-isoprostanes, and liver protein levels of Nrf2, Akt, p38, and thioredoxin (Western blot) were determined at different times up to 48 hours.

RESULTS

T(3) administration induced a significant increase in the hepatic nuclear levels of Nrf2 at 1 and 2 hours after treatment and a concomitant decrease in cytosolic Nrf2. It also increased hepatic thioredoxin, a protein whose gene transcription is induced by nuclear Nrf2. Levels of nuclear Nrf2 were at a plateau from 4 to 6 hours after T(3). Rectal temperature of the animals rose from 36.6°C to 37.5°C as did liver O(2) consumption. Serum and liver 8-isoprostanes levels increased (p < 0.05) from 38.4 ± 4.0 pg/mL (n = 4) to 69.2 ± 2.0 pg/mL (n = 3) and from 0.75 ± 0.09 ng/g liver (n = 3) to 1.53 ± 0.10 ng/g liver (n = 5), respectively. In the group of rats pretreated with NAC, the increase in cytosol-to-nuclear translocation of Nrf2 was only 28% that induced by T(3). In addition, T(3) induced liver Akt and p38 activation during the period of 1-4 hours after T(3) administration. p38 activation at 2 hours after T(3) administration was abolished in NAC-pretreated animals.

CONCLUSIONS

In vivo T(3) administration leads to a rapid and transient cytosol-to-nuclear translocation of liver Nrf2. This appears to be promoted by a redox-dependent mechanism as it is blocked by NAC. It may also be contributed by concomitant p38 activation, which in turn promoted Nrf2 phosphorylation. Nrf2 cytosol-to-nuclear translocation may represent a novel cytoprotective mechanism of T(3) to limit free radical or electrophile toxicity, as this would likely entail promoting thioredoxin production.

Continuous monitoring of glucose levels in the hepatic vein and systemic circulation during the Pringle maneuver in beagles

Intraoperative continuous glucose monitoring revealed that liver ischemia/reperfusion causes a rapid and profound transition in glucose concentration. We hypothesized that the washout of the glucose stored in the liver leads to a rapid transition in blood glucose concentration. Six female beagles were studied. A portosystemic shunt was established, and the glucose levels in the jugular, hepatic, and portal veins were continuously monitored. All beagles were stabilized for 30 min, and, subsequently, the hepatic artery and portal vein were clamped (the Pringle maneuver). After 30 min of warm hepatic ischemia, the clamp was removed in order to initiate hepatic reperfusion. The endpoint of the experiment was 60 min after the onset of reperfusion. The glucose levels in the abovementioned veins were recorded continuously. The glucose level in the hepatic vein increased 10 min after the start of the Pringle maneuver and was significantly higher than that in the jugular vein and portal vein just before unclamping. The glucose level in the hepatic vein peaked at 2 min after unclamping and that in the portal and jugular veins started to increase after reperfusion. The glucose level in the hepatic vein was significantly higher than that in the jugular and portal veins between 9 min after clamping and 8 min after reperfusion. In conclusion, our study among beagles showed that glucose release from the hepatic vein and sinusoid leads to a rapid elevation in systemic blood glucose levels after liver ischemia/reperfusion. This knowledge might help in the development of new strategies for blood glucose management during hepatectomy.

HMGB1 translocation and expression is caused by warm ischemia reperfusion injury, but not by partial hepatectomy in rats

Mechanical injury or ischemia/reperfusion (I/R) injury induces high mobility of group box 1 (HMGB1) translocation and release. However, the surgical procedure itself can initiate pathophysiologic processes causing damage to the respective organ. A liver resection, as an example, leads to portal hyperperfusion injury of the remnant liver. Therefore, we aimed to elucidate the impact of different hepatic surgical injury models on cellular localization and expression of HMGB1. Focal warm I/R injury was induced by clamping the vascular blood supply to the median and left lateral liver lobes for 90 min followed by 0.5 h, 6 h and 24 h reperfusion, as reported previously. Liver injury by PH was induced by subjecting rats to 30%, 70% or 90% partial hepatectomy (PH) followed by a 24 h observation period. Additional 12 rats were subjected to 90% PH and sacrificed at 1 h and 6 h to investigate the expression and release pattern of HMGB1. Elevation of serum liver enzymes indicating hepatic injury peaked at 6 h and recovered thereafter in models, warm I/R injury and PH. Liver injury was confirmed by liver histology. HMGB1 was translocated from the nucleus to the cytoplasm in livers subjected to warm I/R; but not in livers subjected to PH. Both protein and mRNA expression of HMGB1 were significantly up-regulated in livers subjected to warm I/R. In contrast, neither 30% PH, 70% PH nor 90% PH caused an elevation of hepatic HMGB1 mRNA and protein expression. High serum levels of HMGB1 (30 ng/ml) were measured at 0.5 h reperfusion period after warm I/R, much lower levels thereafter (<5 ng/ml). Similar low serum levels were measured at all time points after 90% PH. Subsequently expression levels of TNF-a should be changed to tumor necrosis factor-alpha (TNF-α) reached a peak (26-fold elevation) at 6 h and decreased down to 5-fold at 24 h after warm I/R. TNF-α expression levels after PH never exceeded a 5-fold elevation. In conclusion, HMGB1 translocation and expression depends on the type of liver injury as it is induced by ischemia, but not by liver resection/hyperperfusion. These results suggest that HMGB1 may be used as molecular marker to visualize ischemic damage. Mechanic injury in hepatic surgery is associated with focal warm ischemia, and thereby HMGB1 translocation reflects surgical quality in experimental PH. Expression of hepatic TNF-α follows the kinetic pattern of HMGB1, pointing to a muss less pronounced inflammatory response after successful PH compared to warm I/R injury.

Pharmacological postconditioning protects against hepatic ischemia/reperfusion injury

Postconditioning is a procedure based on the induction of intracellular protective reactions immediately after the onset of reperfusion. Because of the growing need to prevent ischemia/reperfusion (I/R) injury during liver surgery and transplantation, we investigated the possibility of pharmacologically inducing hepatic postconditioning. The effects of the adenosine A2A receptor agonist 2p-(2-carboxyethyl)-phenyl-amino-5'-N-ethylcarboxyamido-adenosine (CGS21680; 5 μmol/L) and the phosphatase and tensin homologue deleted from chromosome 10 (PTEN) inhibitor dipotassium bisperoxo-(5-hydroxypyridine-2-carboxyl)-oxovanadate [bpV(HOpic); 250 nmol/L] were investigated in primary rat hepatocytes during reoxygenation after 24 hours of cold storage and in an in vivo model of rat liver warm I/R. The addition of CGS21680 at reoxygenation significantly reduced hepatocyte death through the activation of the phosphoinositide 3-kinase (PI3K)-protein kinase B (PKB)/Akt signal pathway and through the reduction of the intracellular level of PTEN. PTEN lowering was associated with the increased generation of reactive oxygen species after A2A receptor-mediated stimulation of β-nicotinamide adenine dinucleotide phosphate oxidase (NOX). The inhibition of PI3K or NOX with wortmannin or diphenyleneiodonium chloride, respectively, and the addition of the antioxidant N,N'-diphenyl-p-phenylenediamine reversed the effects of CGS21680. The PTEN inhibitor bpV(HOpic) mimicked the protection provided by CGS21680 against reoxygenation damage. An in vivo rat treatment with CGS21680 or bpV(HOpic) during reperfusion after 1 hour of partial hepatic ischemia also promoted PKB/Akt activation and ameliorated alanine aminotransferase release and histological lesions induced by 2 hours of reperfusion. We conclude that adenosine A2A receptor agonists and PTEN inhibitors are possibly useful agents for the pharmacological induction of postconditioning in the liver.

Does arterialisation time influence biliary tract complications after orthotopic liver transplantation?

BACKGROUND

In the cardiac death donor era, many reports deal with biliary tract complications and concerns about ischemic reperfusion injury owing to the exclusive arterial vascularization of the biliary tree, the warm ischemia time has been implicated as responsible for biliary lesions during organ procurement. We defined the arterialization time as the second warm ischemia time. Our purpose was to study the correlation between the arterialization time during liver implantation and the appearance of biliary lesions.

METHODS

We retrospectively collected data from the last 5-years of orthotopic liver transplantation: namely, indications, cold perfusion fluid, cold ischemia time, operative procedure times, and acute rejection events. We excluded split-liver transplantations, retransplantations, pediatric patients, transplantations for cholestatic disease, cases where hepatic artery thrombosis happened before biliary complications, or patients with posttransplant cytomegalovirus infection. We defined 2 groups: A) without biliary complications; and B) with biliary complications. We compared the mean arterialization time using Student t test to define whether the warm ischemic time during implantation was responsible for biliary tract complications. A P value of <.05 was considered to be significant.

RESULTS

Between 2004 and the end of 2008, we grafted 402 patients among whom 243 met the inclusion criteria: 198 in group A and 45 in group B. Only the cold ischemia time was significantly different between the 2 groups (P = .039).

CONCLUSION

After the anhepatic time, the surgeon may take time for the arterial anastomosis without fearing increased biliary damage.

Protection against in vivo liver ischemia-reperfusion injury by n-3 long-chain polyunsaturated fatty acids in the rat

N-3 polyunsaturated fatty acids (n-3 PUFA) affect inflammatory processes. This study evaluated the effects of dietary supplementation with fish oil on hepatic ischemia-reperfusion (IR) injury in the rat. Parameters of liver injury (serum transaminases and histology) and oxidative stress (serum 8-isoprostanes and hepatic GSH and GSSG), were correlated with NF-kappaB DNA binding and FA composition and inflammatory cytokine release. N-3 PUFA supplementation significantly increased liver n-3 PUFA content and decreased n-6/n-3 PUFA ratios. IR significantly modified liver histology and enhanced serum transaminases, 8-isoprotanes and inflammatory cytokines, with net reduction in liver GSH levels and net increment in those of GSSG. Early increase (3 h) and late reduction (20 h) in NF-kappaB activity was induced. All IR-induced changes were normalized by n-3 PUFA supplementation. In conclusion, prevention of liver IR-injury was achieved by n-3 PUFA supplementation, with suppression of oxidative stress and recovery of pro-inflammatory cytokine homeostasis and NF-kappaB functionality lost during IR.

Molecular mechanisms of liver preconditioning

Ischemia/reperfusion (I/R) injury still represents an important cause of morbidity following hepatic surgery and limits the use of marginal livers in hepatic transplantation. Transient blood flow interruption followed by reperfusion protects tissues against damage induced by subsequent I/R. This process known as ischemic preconditioning (IP) depends upon intrinsic cytoprotective systems whose activation can inhibit the progression of irreversible tissue damage. Compared to other organs, liver IP has additional features as it reduces inflammation and promotes hepatic regeneration. Our present understanding of the molecular mechanisms involved in liver IP is still largely incomplete. Experimental studies have shown that the protective effects of liver IP are triggered by the release of adenosine and nitric oxide and the subsequent activation of signal networks involving protein kinases such as phosphatidylinositol 3-kinase, protein kinase C δ/ε and p38 MAP kinase, and transcription factors such as signal transducer and activator of transcription 3, nuclear factor-κB and hypoxia-inducible factor 1. This article offers an overview of the molecular events underlying the preconditioning effects in the liver and points to the possibility of developing pharmacological approaches aimed at activating the intrinsic protective systems in patients undergoing liver surgery.

Postconditioning: From the Bench to Bedside

Infarct size is determined not only by the severity of ischemia but also by pathological processes initiated at reperfusion. Accumulating experimental evidence indicates that lethal reperfusion injury might account for up to half of the final size of the myocardial infarct. Ischemic postconditioning (brief repeated periods of ischemia-reperfusion applied at the onset of coronary reflow) has been recently described as a powerful cardioprotection mechanism that prevents lethal reperfusion injury. This is the first method proven to reduce the final infarct size by about 50% in several in vivo models and to be confirmed in recent preliminary human studies. The molecular pathways are incompletely mapped but they probably converge to a mitochondrial key target: the mitochondrial permeability transition pore (PTP) which opening during early reperfusion is an event that promotes myocardial cell death. In different animal models and experimental settings, pharmacological PTP inhibition at the onset of reperfusion reproduces all the cardioprotective effects of ischemic postconditioning. In a recent proof-of-concept trial, the administration (just before percutaneous coronary intervention) of cyclosporine A, a potent PTP inhibitor, was associated with smaller infarct size. This review will focus on the physiological preclinical data on both ischemic and pharmacological postconditioning that are relevant to their translation to clinical therapeutics.