Matrix metalloproteinase inhibition protects rat livers from prolonged cold ischemia-warm reperfusion injury

Phosphinic Peptides as Tool Compounds for the Study of Pharmacologically Relevant Zn-Metalloproteases

Phosphinic peptides constitute an important class of bioactive compounds that have found a wide range of applications in the field of biology and pharmacology of Zn-metalloproteases, the largest family of proteases in humans. They are designed to mimic the structure of natural substrates during their proteolysis, thus acting as mechanism-based, transition state analogue inhibitors. A combination of electrostatic interactions between the phosphinic acid group and the Zn cation as well as optimal noncovalent enzyme-ligand interactions can result in both high binding affinity for the desired target and selectivity against other proteases. Due to these unique properties, phosphinic peptides have been mainly employed as tool compounds for (a) the purposes of rational drug design by serving as ligands in X-ray crystal structures of target enzymes and allowing the identification of crucial interactions that govern optimal molecular recognition, and (b) the delineation of biological pathways where Zn-metalloproteases are key regulators. For the latter objective, inhibitors of the phosphinopeptidic type have been used either unmodified or after being transformed to probes of various types, thus expanding the arsenal of functional tools available to researchers. The aim of this review is to summarize all recent research achievements in which phosphinic peptides have played a central role as tool compounds in the understanding of the mechanism and biological functions of Zn-metalloproteases in both health and disease.

Hypothermic treatment reduces matrix metalloproteinase-9 expression and damage in the liver following asphyxial cardiac arrest in rats

BACKGROUND

Hypothermic treatment is known to protect organs against cardiac arrest (CA) and improves survival rate. However, few studies have evaluated the effects of hypothermia on CA-induced liver damages. This study was designed to analyzed the possible protective effects of hypothermia on the liver after asphyxial CA (ACA). Rats were randomly subjected to 5 min of ACA followed by return of spontaneous circulation (ROSC). Body temperature was controlled at 37 ± 0.5 °C (normothermia group) or 33 ± 0.5 °C (hypothermia group) for 4 h after ROSC. Liver tissues were extracted and examined at 6 h, 12 h, 1 day, and 2 days after ROSC.

RESULTS

The expression of infiltrated neutrophil marker CD11b and matrix metallopeptidase-9 (MMP9) was investigated via immunohistochemistry. Morphological damage was assessed via hematoxylin and eosin (H & E) staining. Hypothermic treatment improved the survival rate at 6 h, 12 h, 1 day, and 2 days after ACA. Based on immunohistochemical analysis, the expression of CD11b and MMP9 was significantly increased from 6 h after ACA in the normothermia group. However, the expressions of CD11b and MMP9 was significantly decreased in the hypothermia group compared with that of the normothermia group. In addition, in the results of H & E, sinusoidal dilatation and vacuolization were apparent after ACA; however, these ACA-induced structural changes were reduced by the 4 h-long hypothermia.

CONCLUSIONS

In conclusion, hypothermic treatment for 4 h inhibited the increases in CD11b and MMP9 expression and reduced the morphological damages in the liver following ACA in rats. This study suggests that hypothermic treatment after ACA reduces liver damages by regulating the expression of CD11b and MMP9.

Effect of Liposomal Curcumin on Acetaminophen Hepatotoxicity by Down-regulation of Oxidative Stress and Matrix Metalloproteinases

BACKGROUND/AIM

The hepatoprotective role of various molecules in drug-induced hepatotoxicity arouses great interest. We investigated the effect of liposomal curcumin (LCC) on experimental acetaminophen (APAP)-induced hepatotoxicity.

MATERIALS AND METHODS

Rats were randomly allocated into 5 groups, and the effect of two LCC concentrations was studied: group 1 - 1 ml intraperitoneal (i.p.) saline, group 2 - APAP pretreatment, group 3 - APAP+silymarin (extract of the silybum marianum with anti-inflammatory, anti-oxidant, and anti-fibrotic properties), group 4 - APAP+LCC1, group 5 - APAP+LCC2. The biomarkers of oxidative stress (nitric oxide and malondialdehyde) and antioxidant status of plasma (thiols and catalase), TNF-α, MMP-2 and MMP-9 serum levels were evaluated.

RESULTS

An improvement in oxidative stress, antioxidant status, and TNF-α, MMP-2 and MMP-9 levels was obtained in groups pretreated with LCC compared to silymarin treatment, in a dose-dependent manner. Histopathological examination reinforced the results.

CONCLUSION

Liposomal curcumin improves the oxidative stress/antioxidant balance and alleviates inflammation in experimental APAP-induced hepatotoxicity.

Matrix metalloproteinase functions in hepatic injury and fibrosis

Liver fibrosis is the most common final outcome for chronic liver diseases. The complex pathogenesis includes hepatic parenchymal damage as a result of a persistent noxe, activation and recruitment of immune cells, activation of hepatic stellate cells, and the synthesis of fibrotic extracellular matrix (ECM) components leading to scar formation. Clinical studies and animal models demonstrated that fibrosis can be reversible. In this regard matrix metalloproteinases (MMPs) have been focused as therapeutic targets due to their ability to modulate tissue turnover during fibrogenesis as well as regeneration and, of special interest, due to their influence on cellular behavior like proliferation, gene expression, and apoptosis that, in turn, impact fibrosis and regeneration. The current review aims to summarize and update the knowledge about expression pattern and the central roles of MMPs in hepatic fibrosis.

Protective effect of liver fibrosis against acute liver injury

Liver fibrosis is the excessive accumulation of extracellular matrix proteins in liver tissue. Liver fibrosis as the characteristic change of chronic liver injury has the potential to develop into liver cirrhosis, liver failure and hepatic carcinoma, and is considered a devastating pathologic process. However, recent studies demonstrate that liver fibrosis is not only reversible, but also can protect the liver from acute injury. Currently, the mechanisms of hepatoprotective effect of liver fibrosis have become a hot research area, which include promoted regeneration of the remaining normal liver cells and apoptotic resistance. In the present article, we will review the hepatoprotective effect of liver fibrosis and the underlying molecular mechanisms, aiming to provide a theoretical basis for understanding the pathogenesis of acute-on-chronic liver failure and provide new therapeutic targets for this disease.

Hypothermic Machine Perfusion Reduced Inflammatory Reaction by Downregulating the Expression of Matrix Metalloproteinase 9 in a Reperfusion Model of Donation After Cardiac Death

The exact mechanism by which hypothermic machine perfusion (HMP) improves the graft quality in kidney transplantation of donation after cardiac death (DCD) remains unclear. The aim of this study was to investigate the correlation between the expression of matrix metalloproteinase 9 (MMP-9) and inflammatory reaction in kidney ischemia-reperfusion (I/R) injury injury followed by cold storage (CS) or HMP model of DCD. New Zealand white rabbit kidneys were subjected to 35 min of warm ischemia and 1 h reperfusion, then preserved by either 1 h reperfusion (sham-operated group), 4 h CS or 4 h HMP in vivo. Kidneys were reperfused 24 h followed by further analysis. No treatment was given to rabbits in the normal control group. The expression of MMP-9, nuclear factor-κB (NF-κB), and MMP-2 mRNA were detected by real-time PCR (RT-PCR). MMP-9 was located by immunohistochemistry and immunofluorescence methods. Tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), myeloperoxidase (MPO), superoxide dismutase (SOD), and malondialdehyde (MDA) were measured by kits for each groups. Compared with the CS group, the expression of MMP-9 and NF-κB mRNA were downregulated in HMP group (P < 0.05). In contrast, expression of MMP-2 mRNA had no statistical significance between CS group and HMP group (P > 0.05). In normal control and sham-operated groups, a low level of MMP-9 expression was detected in glomeruli. However, positive signals of MMP-9 were mostly located in the tubulointerstitium and the vascular wall of CS and HMP groups. Expression of TNF-α, IL-6, MDA, and activity of MPO decreased while activity of SOD in the HMP group increased in contrast to the CS group (P < 0.05). In conclusion, inflammatory cytokines mediated MMP-9 expression through NF-κB band to MMP-9 promoter region, resulting in renal injury. Therefore, HMP reduced inflammatory reaction by downregulating the expression of MMP-9, which may be the mechanism of kidney protection in I/R injury.

Role of matrix metalloproteinases in cholestasis and hepatic ischemia/reperfusion injury: A review

Matrix metalloproteinases (MMPs) are a family of proteases using zinc-dependent catalysis to break down extracellular matrix (ECM) components, allowing cell movement and tissue reorganization. Like many other proteases, MMPs are produced as zymogens, an inactive form, which are activated after their release from cells. Hepatic ischemia/reperfusion (I/R) is associated with MMP activation and release, with profound effects on tissue integrity: their inappropriate, prolonged or excessive expression has harmful consequences for the liver. Kupffer cells and hepatic stellate cells can secrete MMPs though sinusoidal endothelial cells are a further source of MMPs. After liver transplantation, biliary complications are mainly attributable to cholangiocytes, which, compared with hepatocytes, are particularly susceptible to injury and ultimately a major cause of increased graft dysfunction and patient morbidity. This paper focuses on liver I/R injury and cholestasis and reviews factors and mechanisms involved in MMP activation together with synthetic compounds used in their regulation. In this respect, recent data have demonstrated that the role of MMPs during I/R may go beyond the mere destruction of the ECM and may be much more complex than previously thought. We thus discuss the role of MMPs as an important factor in cholestasis associated with I/R injury.

Hyaluronic Acid (800 kDa) Supplementation of University of Wisconsin Solution Improves Viability of Osteochondral Grafts and Reduces Matrix Metalloproteinase Expression during Cold Preservation

Osteochondral allografting is a promising option for the treatment of large cartilage defects. However, because the cell viability of osteochondral tissues (OCTs) gradually reduces during storage at 4°C, methods for maintaining the cell viability of fresh OCTs are needed to improve transplantation outcomes. Here, we evaluated whether the supplementation of preservation solution with one of three different molecular weight forms of hyaluronic acid (HA) improved the viability of rat OCTs during long-term cold storage. The supplementation of University of Wisconsin (UW) solution with 800 kDa significantly improved the cell viability of OCT after 14 days at 4°C compared to nonsupplemented UW solution. In contrast, UW solution supplemented with either 1900 or 6000 kDa HA did not markedly improve the cell viability of the OCT. Real-time PCR analysis revealed that the levels of matrix metalloproteinases 2, 3, and 9 were significantly decreased in OCT stored in UW solution supplemented with 800 kDa HA. Although further studies in human OCT are warranted, these findings demonstrate that the use of 800 kDa HA in place of serum may be a suitable approach for the long-term preservation of osteochondral allografts designated for the repair of large cartilage defects in the clinical setting.

Polyethylene glycol rinse solution: An effective way to prevent ischemia-reperfusion injury

AIM: To test whether a new rinse solution containing polyethylene glycol 35 (PEG-35) could prevent ischemia-reperfusion injury (IRI) in liver grafts.

METHODS: Sprague-Dawley rat livers were stored in University of Wisconsin preservation solution and then washed with different rinse solutions (Ringer’s lactate solution and a new rinse solution enriched with PEG-35 at either 1 or 5 g/L) before ex vivo perfusion with Krebs-Heinseleit buffer solution. We assessed the following: liver injury (transaminase levels), mitochondrial damage (glutamate dehydrogenase activity), liver function (bile output and vascular resistance), oxidative stress (malondialdehyde), nitric oxide, liver autophagy (Beclin-1 and LCB3) and cytoskeleton integrity (filament and globular actin fraction); as well as levels of metalloproteinases (MMP2 and MMP9), adenosine monophosphate-activated protein kinase (AMPK), heat shock protein 70 (HSP70) and heme oxygenase 1 (HO-1).

RESULTS: When we used the PEG-35 rinse solution, reduced hepatic injury and improved liver function were noted after reperfusion. The PEG-35 rinse solution prevented oxidative stress, mitochondrial damage, and liver autophagy. Further, it increased the expression of cytoprotective heat shock proteins such as HO-1 and HSP70, activated AMPK, and contributed to the restoration of cytoskeleton integrity after IRI.

CONCLUSION: Using the rinse solution containing PEG-35 was effective for decreasing liver graft vulnerability to IRI.

Matrix metalloproteinase-9 as a therapeutic target for the progression of fulminant liver failure with hepatic encephalopathy: A pilot study in mice

AIM

If progressive liver injury and subsequent hepatic encephalopathy can be prohibited in fulminant liver failure (FLF), it would be ideal for intensive care of FLF and provide an expanded opportunity for liver transplantation (LT). We hypothesized that matrix metalloproteinase (MMP)-9 plays an important role in FLF progression, and investigated MMP-9 behaviors in a murine FLF model, especially at the coma stage.

METHODS

The murine FLF model with azoxymethane recapitulates FLF in humans. The detailed coma status was evaluated, on the assumption that LT is indicated at early, but not late, stage 3. To investigate whether MMP-9 deletion or reduction has beneficial effects, an MMP-9 inhibitor (GM6001) and transfection of tissue inhibitor of metalloproteinases (TIMP)-1 cDNA were used. Mice were divided into five groups: control; FLF; FLF with GM6001 pretreatment; FLF with TIMP-1 plasmid transfection 24 h before disease onset; and FLF with TIMP-1 plasmid transfection 48 h before disease onset. Neurological findings, including survival, were followed. Samples were obtained at early and late stage 3. Biochemical examinations and histopathological assessments were performed. The expression and function of MMP-9 and TIMP-1 were evaluated by western blotting and zymography. A brain permeability study was also performed.

RESULTS

MMP-9 was strongly increased in FLF. The MMP-9 inhibitions worked well, and prolonged the survival, interval to stage 3 and duration of early stage 3. MMP-9 inhibition improved the liver and subsequent brain injuries at early stage 3, with no remarkable improvements at late stage 3.

CONCLUSION

MMP-9 has therapeutic potential for FLF progression.

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

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

Rat model of fractionated (2 Gy/day) 60 Gy irradiation of the liver: long-term effects

The liver is considered a radiosensitive organ. However, in rats, high single-dose irradiation (HDI) showed only mild effects. Consequences of fractionated irradiation (FI) in such an animal model have not been studied so far. Rats were exposed to selective liver FI (total dose 60 Gy, 2 Gy/day) or HDI (25 Gy) and were killed three months after the end of irradiation. To study acute effects, HDI-treated rats were additionally killed at several time points between 1 and 48 h. Three months after irradiation, no differences between FI and HDI treatment were found for macroscopically detectable small "scars" on the liver surface and for an increased number of neutrophil granulocytes distributed in the portal fields and through the liver parenchyma. As well, no changes in HE-stained tissues or clear signs of fibrosis were found around the portal vessels. Differences were seen for the number of bile ducts being increased in FI- but not in HDI-treated livers. Serum levels indicative of liver damage were determined for alkaline phosphatase (AP), aspartate aminotransferase (AST), alanine aminotransferase (ALT), gamma-glutamyltransferase (γGT) and lactate dehydrogenase (LDH). A significant increase of AP was detected only after FI while HDI led to the significant increases of AST and LDH serum levels. By performing RT-PCR, we detected up-regulation of matrix metalloproteinases, MMP-2, MMP-9, MMP-14, and of their inhibitors, TIMP-1, TIMP-2 and TIMP-3, shortly after HDI, but not at 3 month after FI or HDI. Overall, we saw punctual differences after FI and HDI, and a diffuse formation of small scars at the liver surface. Lack of "provisional clot"-formation and absence of recruitment of mononuclear phagocytes could be one explanation for scar formation as incomplete repair response to irradiation.

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.

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.

Matrix metalloproteinase-9 in the initial injury after hepatectomy in mice

AIM: To investigate the role of matrix metalloproteinase (MMP)-9 in the pathogenesis of postoperative liver failure (PLF) after extended hepatectomy (EH).

METHODS: An insufficient volume of the remnant liver (RL) results in higher morbidity and mortality, and a murine model with 80%-hepatectomy was used. All investigations were performed 6 h after EH. Mice were first divided into two groups based on the postoperative course (i.e., the PLF caused or did not), and MMP-9 expression was measured by Western blotting. The source of MMP-9 was then determined by immunohistological stainings. Tissue inhibitor of metalloproteinase (TIMP)-1 is the endogenous inhibitor of MMP-9, and MMP-9 behavior was assessed by the experiments in wild-type, MMP-9(-/-) and TIMP-1(-/-) mice by Western blotting and gelatin zymography. The behavior of neutrophils was also assessed by immunohistological stainings. An anti-MMP-9 monoclonal antibody and a broad-spectrum MMP inhibitor were used to examine the role of MMP-9.

RESULTS: Symptomatic mice showed more severe PLF (histopathological assessments: 2.97 ± 0.92 vs 0.11 ± 0.08, P < 0.05) and a higher expression of MMP-9 (71085 ± 18274 vs 192856 ± 22263, P < 0.01). Nonnative leukocytes appeared to be the main source of MMP-9, because MMP-9 expression corresponding with CD11b positive-cell was observed in the findings of immunohistological stainings. In the histopathological findings, the PLF was improved in MMP-9(-/-) mice (1.65% ± 0.23% vs 0.65% ± 0.19%, P < 0.01) and it was worse in TIMP-1(-/-) mice (1.65% ± 0.23% vs 1.78% ± 0.31%, P < 0.01). Moreover, neutrophil migration was disturbed in MMP-9(-/-) mice in the immunohistological stainings. Two methods of MMP-9 inhibition revealed reduced PLF, and neutrophil migration was strongly disturbed in MMP-9-blocked mice in the histopathological assessments (9.6 ± 1.9 vs 4.2 ± 1.2, P < 0.05, and 9.9 ± 1.5 vs 5.7 ± 1.1, P < 0.05).

CONCLUSION: MMP-9 is important for the process of PLF. The initial injury is associated with MMP-9 derived from neutrophils, and MMP-9 blockade reduces PLF. MMP-9 may be a potential target to prevent PLF after EH and to overcome an insufficient RL.

Mesenchymal stem cell-conditioned medium reduces liver injury and enhances regeneration in reduced-size rat liver transplantation

BACKGROUND

Mesenchymal stem cell (MSC) therapy can prevent parenchymal cell loss and promotes tissue repair through the action of trophic, secreted molecules. In this study, we investigated whether MSC-conditioned medium (MSC-CM) could protect hepatocytes and sinusoidal endothelial cells (SECs) and stimulate their regeneration in 50% reduced-size liver transplantation (RSLT).

MATERIALS AND METHODS

Rats were randomly divided into three groups: sham-operated group, MSC-CM group (rats with 50% RSLT receiving MSC-CM infusion), and medium group (rats with 50% RSLT receiving medium therapy). Graft function, proinflammatory cytokines, incidence of apoptosis, proliferation of hepatocytes and SECs, and the expression of vascular endothelial growth factor and matrix metallopeptidase 9 were assessed in this study.

RESULTS

Systemic infusion of MSC-CM prevented the release of liver injury biomarkers and provided a significant survival benefit. Furthermore, MSC-CM therapy resulted in reduction of apoptosis of hepatocytes and SECs. The number of proliferating hepatocytes and SECs increased 1.2- and 1.6-fold, respectively, accompanied by a decrease in the expression levels of several proinflammatory cytokines and a noticeable decrease in infiltration of neutrophils and activation of Kupffer cells. Also, increased expression of vascular endothelial growth factor and matrix metallopeptidase 9 in the grafts was observed after MSC-CM therapy.

CONCLUSIONS

These data suggest that MSC-CM therapy in RSLT provides trophic support to the injured liver by inhibiting SEC and hepatocellular death and stimulating their regeneration.

Desferrioxamine in warm reperfusion media decreases liver injury aggravated by cold storage

AIM: To evaluate whether desferrioxamine decreases ischemia and perfusion injury aggravated by cold storage (CS) in a rat liver perfusion model.

METHODS: Isolated rat livers were kept in CS in University of Wisconsin Solution for 20 h at 4 °C, then exposed to 25 min of warm ischemia (WI) at 37 °C followed by 2 h of warm perfusion (WP) at 37 °C with oxygenated (95% oxygen and 5% carbon dioxide) Krebs-Henseleit buffer. Desferrioxamine (DFO), an iron chelator, was added at different stages of storage, ischemia and perfusion: in CS only, in WI only, in WP only, in WI and perfusion, or in all stages. Effluent samples were collected after CS and after WI. Perfusate samples and bile were collected every 30 min (0, 0.5, 1, 1.5 and 2 h) during liver perfusion. Cellular injury was assessed by the determination of lactate dehydrogenase (LDH) and aspartate aminotransferase (AST) in the effluent and perfusate samples. Total iron was analysed in the perfusate samples. After WP, the liver was collected for the determination of liver swelling (wet to dry ratio) and liver morphological examination (hematoxylin and eosin staining).

RESULTS: Increased CS time caused increased liver dysfunction during WP. After 2 h of WP, liver injury was indicated by increased release of AST (0.5 h CS: 9.4 ± 2.2 U/g liver vs 20 h CS: 45.9 ± 10.8 U/g liver, P < 0.05) and LDH (0.5 h CS: 59 ± 14 U/g liver vs 20 h CS: 297 ± 71 U/g liver, P < 0.05). There was an associated increase in iron release into the perfusate (0.5 h CS: 0.11 ± 0.03 μmoL/g liver vs 20 h CS: 0.58 ± 0.10 μmoL/g liver, P < 0.05) and reduction in bile flow (0.5 h CS: 194 ± 12 μL/g vs 20 h CS: 71 ± 8 μL/g liver, P < 0.05). When DFO was added during WI and WP following 20 h of CS, release of iron into the perfusate was decreased (DFO absent 0.58 ± 0.10 μmoL/g liver vs DFO present 0.31 ± 0.06 μmoL/g liver, P < 0.05), and liver function substantially improved with decreased release of AST (DFO absent 45.9 ± 10.8 U/g liver vs DFO present 8.1 ± 0.9 U/g liver, P < 0.05) and LDH (DFO absent 297 ± 71 U/g liver vs DFO present 56 ± 7 U/g liver, P < 0.05), and increased bile flow (DFO absent 71 ± 8 μL/g liver vs DFO present 237 ± 36 μL/g liver, P < 0.05). DFO was also shown to improve liver morphology after WP. Cellular injury (the release of LDH and AST) was significantly reduced with the addition of DFO in CS medium but to a lesser extent compared to the addition of DFO in WP or WI and perfusion. There was no effect on liver swelling or bile flow when DFO was only added to the CS medium.

CONCLUSION: DFO added during WI and perfusion decreased liver perfusion injury aggravated by extended CS.

Pretreatment of Small-for-Size Grafts In Vivo by γ -Aminobutyric Acid Receptor Regulation against Oxidative Stress-Induced Injury in Rat Split Orthotopic Liver Transplantation

Background. Graft pretreatment to limit postoperative damage has the advantage of overcoming a current issue in liver transplantation (LT). The strategic potential of graft pretreatment in vivo by a specific agonist for γ -aminobutyric acid receptor (GABAR) was investigated in the rat LT model with a small-for-size graft (SFSG). Methods. Recipient rats were divided into three groups according to donor treatments and recipient surgeries: (i) saline and laparotomy, (ii) saline and split orthotopic liver transplantation (SOLT) with 40%-SFSG, and (iii) GABAR agonist and SOLT with 40%-SFSG. Survival was evaluated. Blood and liver samples were collected 6 h after surgery. Immunohistological assessment for apoptotic induction and western blotting for 4-hydroxynonenal, ataxia-telangiectasia mutated kinase (ATM), histone H2AX, phosphatidylinositol-3 kinase (PI3K), Akt, and free radical scavenging enzymes were performed. Results. Pretreatment by GABAR showed improvement in survival, histopathological assessment, and biochemical tests. Apoptotic induction and oxidative stress were observed after SOLT with an SFSG, and this damage was limited by GABAR regulation. GABAR regulation appeared to reduce DNA damage via the ATM/H2AX pathway and to promote cell survival via the PI3K/Akt pathway. Conclusions. Pretreatment in vivo by GABAR regulation improves graft damage after SOLT with an SFSG. This strategy may be advantageous in LT.

Matrix metalloprotease 9 promotes liver recovery from ischemia and reperfusion injury

BACKGROUND

Matrix metalloprotease (MMP) 9 has been always considered as a destructor of extracellular matrix, promoting liver injury and metastasis of carcinoma. In this study, we investigated the role of MMP-9 in liver wound healing from ischemia and reperfusion injury (IRI).

METHODS

MMP9-/- mice were used to establish partial hepatic IRI model. Serum alanine aminotransferase and hepatic cytokines (tumor necrosis factor alpha, interleukin [IL]-1β, IL-10, and transforming growth factor beta [TGF-β]) levels were analyzed after IRI. Hepatic stellate cells were isolated from wild-type mice to determine the effect of MMP-9 on TGF-β activation. In addition, the effect of TGF-β on liver wound healing from IRI was determined.

RESULTS

Liver recovery from IRI was impaired in MMP9-/- mice, which was described as elevated serum alanine aminotransferase, hepatic tumor necrosis factor alpha, and IL-1β levels. Meanwhile, TGF-β-active protein level was decreased in the liver of MMP9-/- mice. In vitro test, the activation of TGF-β was suppressed in the presence of anti-MMP-9 monoclonal antibody. TGF-β treatment promoted liver recovery from IRI in MMP9-/- mice.

CONCLUSIONS

MMP-9 promoted liver recovery from IRI by activating TGF-β. Thus, MMP-9 plays dual roles (bad and good) in liver IRI, depending on the timing.

Liver graft pretreated in vivo or ex vivo by γ-aminobutyric acid receptor regulation

BACKGROUND

γ-Aminobutyric acid exists throughout the body, and the brain γ-aminobutyric acid receptor (GABAR) regulation reduces oxidative stress (OS). Effects of GABAR regulation in the liver are unknown. Ischemia or reperfusion injury after orthotopic liver transplantation (OLT) or shear stress after split OLT (SOLT) with a small-for-size graft causes OS-induced graft damage. Here, the strategic potential of graft pretreatment in vivo and ex vivo by GABAR regulation was investigated.

MATERIALS AND METHODS

Recipient rats were divided into seven groups according to the graft pretreatments and graft types: (1) laparotomy, (2) OLT, (3) GABAR regulation in vivo and OLT, (4) GABAR regulation ex vivo and OLT, (5) SOLT, (6) GABAR regulation in vivo and SOLT, and (7) GABAR regulation ex vivo and SOLT. Survival study, biochemical assays, histopathologic or immunohistologic assessments, and Western blotting were performed at 6 h after OLT or SOLT.

RESULTS

Graft pretreatment in vivo prolonged survival after SOLT. Histopathologic and biochemical profiles verified that graft pretreatment in vivo reduced graft damage after OLT or SOLT. Immunohistologically, graft pretreatment in vivo prevented apoptotic inductions after OLT or SOLT. The 4-hydroxynonenal confirmed the OS after OLT or SOLT, and graft pretreatment in vivo improved the OS. Graft pretreatment in vivo decreased ataxia-telangiectasia-mutated kinase and H2AX after OLT or SOLT. Graft pretreatment in vivo increased phosphatidylinositol 3 kinase and Akt after SOLT. In contrast, GABAR regulation ex vivo did not work.

CONCLUSIONS

Graft pretreatment in vivo, not ex vivo, prevented the ischemia or reperfusion injury-mediated OS after OLT or SOLT via the ataxia-telangiectasia-mutated kinase/H2AX pathway and the shear stress-mediated OS after SOLT with small-for-size graft via the phosphatidylinositol 3 kinase/Akt pathway.

Matrix metalloproteinase-9 contributes to parenchymal hemorrhage and necrosis in the remnant liver after extended hepatectomy in mice

AIM: To investigate the effect of matrix metalloproteinase-9 (MMP-9) on the remnant liver after massive hepatectomy in the mouse.

METHODS: Age-matched, C57BL/6 wild-type (WT), MMP-9(-/-), and tissue inhibitors of metalloproteinases (TIMP)-1(-/-) mice were used. The mice received 80%-partial hepatectomy (PH). Samples were obtained at 6 h after 80%-PH, and we used histology, immunohistochemical staining, western blotting analysis and zymography to investigate the effect of PH on MMP-9. The role of MMP-9 after PH was investigated using a monoclonal antibody and MMP inhibitor.

RESULTS: We examined the remnant liver 6 h after 80%-PH and found that MMP-9 deficiency attenuated the formation of hemorrhage and necrosis. There were significantly fewer and smaller hemorrhagic and necrotic lesions in MMP-9(-/-) remnant livers compared with WT and TIMP-1(-/-) livers (P < 0.01), with no difference between WT and TIMP-1(-/-) mice. Serum alanine aminotransaminase levels were significantly lower in MMP-9(-/-) mice compared with those in TIMP-1(-/-) mice (WT: 476 ± 83 IU/L, MMP-9(-/-): 392 ± 30 IU/L, TIMP-1(-/-): 673 ± 73 IU/L, P < 0.01). Western blotting and gelatin zymography demonstrated a lack of MMP-9 expression and activity in MMP-9(-/-) mice, which was in contrast to WT and TIMP-1(-/-) mice. No change in MMP-2 expression was observed in any of the study groups. Similar to MMP-9(-/-) mice, when WT mice were treated with MMP-9 monoclonal antibody or the synthetic inhibitor GM6001, hemorrhagic and necrotic lesions were significantly smaller and fewer than in control mice (P < 0.05). These results suggest that MMP-9 plays an important role in the development of parenchymal hemorrhage and necrosis in the small remnant liver.

CONCLUSION: Successful MMP-9 inhibition attenuates the formation of hemorrhage and necrosis and might be a potential therapy to ameliorate liver injury after massive hepatectomy.

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.

Liver fibrosis protects mice from acute hepatocellular injury

BACKGROUND & AIMS

Development of fibrosis is part of the pathophysiologic process of chronic liver disease. Although it is considered deleterious, it also represents a form of tissue repair. Deposition of extracellular matrix changes the cellular environment of the liver; we investigated whether it increases resistance to noxious stimuli and the role of changes in intracellular signaling to hepatocytes in mediating this effect.

METHODS

Primary cultures of mouse hepatocytes were exposed to type I collagen (COL1); cell injury was assessed by morphologic and biochemical criteria. The expression of Bcl-2 family members was evaluated by immunoblot analyses. Activation of extracellular signal-regulated kinase (ERK) was assessed using phospho-specific antibodies. Liver fibrosis was induced by repeated administration of thioacetamide or carbon tetrachloride to mice; mice were then exposed to Fas antibodies.

RESULTS

Hepatocytes exposed to COL1 were more resistant to a variety of hepatotoxins, in a dose-dependent manner, and had lower levels of Bad, Bid, and Bax proapoptotic proteins compared with control hepatocytes. Activation of ERK1/2 was stronger and quicker in hepatocytes exposed to COL1. The MEK1/2 inhibitors U0126 and PD98059 reversed the protective effects of COL1 and the decrease in proapoptotic proteins. Hepatocytes isolated from ERK1(-/-) mice were insensitive to the protective effect of COL1. Fibrotic livers from wild-type mice had high levels of phospho-ERK1 and were resistant to Fas-induced cell death. ERK1(-/-) mice lost this effect.

CONCLUSIONS

Production of COL1 during liver fibrosis induces a hepatoprotective response that is mediated by activation of ERK1 signaling.

Matrix metalloproteinases as drug targets in ischemia/reperfusion injury

Deficient blood supply (ischemia) is a common consequence of some surgical procedures and certain pathologies. Once blood circulation is re-established (reperfusion), a complex series of events results in recruitment of inflammatory cells, rearrangement of the extracellular matrix and induction of cell death, which lead to organ dysfunction. Although ischemia/reperfusion (I/R) injury is an important cause of death, there is no effective therapy targeting the molecular mechanism of disease progression. Matrix metalloproteinases (MMPs), which are important regulators of many cellular activities, have a central role in disease progression after I/R injury, as suggested by numerous studies using MMP inhibitors or MMP-deficient mice. Here, we review the involvement of MMP activity in the various processes following I/R injury and the therapeutic potential of MMP inhibition.

Tissue inhibitor of metalloproteinase 1 (TIMP-1) deficiency exacerbates carbon tetrachloride-induced liver injury and fibrosis in mice: involvement of hepatocyte STAT3 in TIMP-1 production

Background

Tissue inhibitor of metalloproteinase 1 (TIMP-1), which is thought to be produced mainly by activated hepatic stellate cells and Kupffer cells in the liver, plays a pivotal role in matrix remodeling during liver injury and repair; while the effect of TIMP-1 on hepatocellular damage remains obscure.

Results

Hepatic expression of TIMP-1 mRNA and protein was up-regulated both in acute and chronic liver injury induced by carbon tetrachloride (CCl₄). Compared with wild-type mice, TIMP-1 knockout mice were more susceptible to CCl₄-induced acute and chronic liver injury, as shown by higher levels of serum alanine aminotransferase (ALT), greater number of apoptotic hepatocytes, and more extended necroinflammatory foci. TIMP-1 knockout mice also displayed greater degree of liver fibrosis after chronic CCl₄ injection when compared with wild-type mice. In vitro treatment with TIMP-1 inhibited cycloheximide-induced cell death of primary mouse hepatocytes. Finally, up-regulation of TIMP-1 in the liver and serum after chronic CCl₄ treatment was markedly diminished in hepatocyte-specific signal transducer and activator of transcription 3 (STAT3) knockout mice. In vitro treatment with interleukin-6 stimulated TIMP-1 production in primary mouse hepatocytes, but to a lesser extent in STAT3-deficient hepatocytes.

Conclusions

TIMP-1 plays an important role in protecting against acute and chronic liver injury and subsequently inhibiting liver fibrosis induced by CCl₄. In addition to activated stellate cells and Kupffer cells, hepatocytes are also responsible for TIMP-1 production during liver injury via a STAT3-dependent manner.

Hepatic ischemia-reperfusion injury and therapeutic strategies to alleviate cellular damage

Warm hepatic ischemia-reperfusion injury is a significant medical problem in many clinical conditions such as liver transplantation, hepatic surgery for tumor excision, trauma and hepatic failure after hemorrhagic shock. Partial or, mostly, total interruption of hepatic blood flow is often necessary when liver surgery is performed. This interruption of blood flow is termed "warm ischemia" and upon revascularization, when molecular oxygen is reintroduced, the organ undergoes a process called "reperfusion injury" that causes deterioration of organ function. Ischemia reperfusion results in cellular damage and tissue injury associated with a complex series of events. Pathophysiological mechanisms leading to tissue injury following ischemia-reperfusion will be discussed and therapies targeted to reduce liver damage will be summarized within this review.

Hypoxia inducible factor-1α accumulation in steatotic liver preservation: Role of nitric oxide

AIM: To examine the relevance of hypoxia inducible factor (HIF-1) and nitric oxide (NO) on the preservation of fatty liver against cold ischemia-reperfusion injury (IRI).

METHODS: We used an isolated perfused rat liver model and we evaluated HIF-1α in steatotic and non-steatotic livers preserved for 24 h at 4°C in University of Wisconsin and IGL-1 solutions, and then subjected to 2 h of normothermic reperfusion. After normoxic reperfusion, liver enzymes, bile production, bromosulfophthalein clearance, as well as HIF-1α and NO [endothelial NO synthase (eNOS) activity and nitrites/nitrates] were also measured. Other factors associated with the higher susceptibility of steatotic livers to IRI, such as mitochondrial damage and vascular resistance were evaluated.

RESULTS: A significant increase in HIF-1α was found in steatotic and non-steatotic livers preserved in IGL-1 after cold storage. Livers preserved in IGL-1 showed a significant attenuation of liver injury and improvement in liver function parameters. These benefits were enhanced by the addition of trimetazidine (an anti-ischemic drug), which induces NO and eNOS activation, to IGL-1 solution. In normoxic reperfusion, the presence of NO favors HIF-1α accumulation, promoting also the activation of other cytoprotective genes, such as heme-oxygenase-1.

CONCLUSION: We found evidence for the role of the HIF-1α/NO system in fatty liver preservation, especially when IGL-1 solution is used.

Comprehensive and innovative techniques for liver transplantation in rats: A surgical guide

AIM: To investigate our learning curves of orthotopic liver transplantation (OLT) in rats and the most important factor for successful surgery.

METHODS: We describe the surgical procedures for our rat OLT model, and determined the operator learning curves. The various factors that contributed to successful surgery were determined. The most important surgical factors were evaluated between successful and unsuccessful surgeries.

RESULTS: Learning curve data indicated that 50 cases were required for operator training to start a study. Operative time, blood loss, warm ischemic time, anhepatic phase, unstable systemic hemodynamic state, and body temperature after surgery significantly affected surgery success by univariate analysis, while the anhepatic phase was the most critical factor for success by multivariate analysis.

CONCLUSION: OLT in rats is the only liver transplantation model that provides clinically relevant and reliable results. Shortened anhepatic phase is key to success in this model.

Biological modulation of liver ischemia-reperfusion injury

PURPOSE OF REVIEW

This review gives a broad overview of the key factors of ischemic injury to the liver and presents the current modifications of preservation solutions and the few strategies of biological modulation in clinical use today.

RECENT FINDINGS

Protective effects in human-liver transplantation were shown by methylprednisolone treatment in decreased donors, and by inhalation of a nontoxic dose of nitric oxide in recipients. In addition, recent results showed rescue of pig livers, donated after cardiac death by application of a cocktail of substances addressing several previously identified mechanisms of ischemia-reperfusion injury.

SUMMARY

The future of a pharmacological approach attenuating or preventing ischemia-reperfusion injury lies in a combination of drugs acting simultaneously on several steps of the injury cascades. Applying these substances during flush, before, and during implantation appears as an attractive strategy to protect extended criteria liver grafts.

Matrix metalloproteinase 2 in reduced-size liver transplantation: beyond the matrix

We studied the contribution of matrix metalloproteinase 2 (MMP2) and matrix metalloproteinase 9 (MMP9) to the beneficial effects of preconditioning (PC) in reduced-size orthotopic liver transplantation (ROLT). We also examined the role of c-Jun N-terminal kinase (JNK) and whether it regulates MMP2 in these conditions. Animals were subjected to ROLT with or without PC and pharmacological modulation, and liver tissue samples were then analyzed. We found that MMP2, but notMMP9, is involved in the beneficial effects of PC in ROLT. MMP2 reduced hepatic injury and enhanced liver regeneration. Moreover, inhibition of MMP2 in PC reduced animal survival after transplantation. JNK inhibition in the PC group decreased hepatic injury and enhanced liver regeneration. Furthermore, JNK upregulated MMP2 in PC. In addition, we showed that Tissue inhibitors of matrix metalloproteinases 2 (TIMP2) was also upregulated in PC and that JNK modulation also altered its levels in ROLT and PC. Our results open up new possibilities for therapeutic treatments to reduce I/R injury and increase liver regeneration after ROLT, which are the main limitations in living-donor transplantation.

Inhibition of matrix metalloproteinase-9 attenuates acute small-for-size liver graft injury in rats

Ischemia/reperfusion (I/R) and portal hypertension have been implicated in small-for-size liver graft dysfunction. Matrix metalloproteinases-2 and -9 (MMP-2/9) are critically proposed to involve in hepatic I/R injury and activated by hemodynamic force. We hypothesized that MMP-2/9 overexpression played a crucial role in acute graft injury following small-for-size liver transplantation (LT). Rats were randomly assigned into four groups: 75% partial hepatectomy (PH); 100% LT; 25% LT and 25% LT treated with CTT peptide (MMP-2/9 inhibitor). ELISA, real-time PCR, gelatin zymography and immunohistochemistry were used to determine the expression pattern of MMP-2/9 in liver tissue. MMP-9 expression was significantly increased 6 h after reperfusion and reached a peak 12 h in the 25% LT group, whereas MMP-2 was expressed in all groups invariably. Compared with the 25% LT group, rats from CTT-treated group exhibited markedly decreased alanine aminotransferase and total bilirubin values, downregulated proinflammatory cytokines, attenuated malondialdehyde (MDA) and myeloperoxidase (MPO) activities, and improved liver histology. Likewise, MMP-9 inhibition significantly reduced number of TUNEL-positive cells and caspase-3 activity, along with decreased protein levels of Fas and Fas-L. Specifically, rat survival was also improved in the CTT-treated group. These results support critical function of MMP-9 involved in acute small-for-size livergraft injury.

An adult tissue-specific stem cell in its niche: a gene profiling analysis of in vivo quiescent and activated muscle satellite cells

The satellite cell of skeletal muscle provides a paradigm for quiescent and activated tissue stem cell states. We have carried out transcriptome analyses on satellite cells purified by flow cytometry from Pax3(GFP/+) mice. We compared samples from adult skeletal muscles where satellite cells are mainly quiescent, with samples from growing muscles or regenerating (mdx) muscles, where they are activated. Analysis of regulation that is shared by both activated states avoids other effects due to immature or pathological conditions. This in vivo profile differs from that of previously analyzed satellite cells activated after cell culture. It reveals how the satellite cell protects itself from damage and maintains quiescence, while being primed for activation on receipt of the appropriate signal. This is illustrated by manipulation of the corepressor Dach1, and by the demonstration that quiescent satellite cells are better protected from oxidative stress than those from mdx or 1-week-old muscles. The quiescent versus in vivo activated comparison also gives new insights into how the satellite cell controls its niche on the muscle fiber through cell adhesion and matrix remodeling. The latter also potentiates growth factor activity through proteoglycan modification. Dismantling the extracellular matrix is important for satellite cell activation when the expression of proteinases is up-regulated, whereas transcripts for their inhibitors are high in quiescent cells. In keeping with this, we demonstrate that metalloproteinase function is required for efficient regeneration in vivo.

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

Ischemia and reperfusion lead to injury of the liver. Ischemia-reperfusion injury is inevitable in liver transplantation and trauma and, to a great extent, in liver resection. This article gives an overview of the mechanisms involved in this type of injury and summarizes protective and treatment strategies in clinical use today. Intervention is possible at different time points: during harvesting, during the period of preservation, and during implantation. Liver preconditioning and postconditioning can be applied in the transplant setting and for liver resection. Graft optimization is merely possible in the period between the harvest and the implantation. Given that there are 3 stages in which a surgeon can intervene against ischemia-reperfusion injury, we have structured the review as follows. The first section reviews the approaches using surgical interventions, such as ischemic preconditioning, as well as pharmacological applications. In the second section, static organ preservation and machine perfusion are addressed. Finally, the possibility of treating the recipient or postconditioning is discussed.

Polyethylene glycol modified-albumin enhances the cold preservation properties of University of Wisconsin solution in rat liver and a hepatocyte cell line

Liver grafts preserved in cold storage undergo changes mainly manifested by morphological modifications of the sinusoidal endothelium that result in poor graft function upon reperfusion. The present studies aimed to determine if the addition of polyethylene glycol-albumin to University of Wisconsin (Peg-AlbUW) solution ameliorates the cold preservation injuries of liver grafts. Rat livers were preserved cold with various preservation solutions and evaluated for weight changes and endothelial morphology. Solutions that preserved graft weight and endothelial morphology were tested in the isolated perfused rat liver model to assess graft function. A rat hepatocyte cell line was evaluated for both viability and glutathione concentrations emulating cold preservation and reperfusion conditions. Liver grafts preserved with Peg-AlbUW maintained their initial weight and showed a conserved endothelial morphology compared with liver grafts preserved in UW for 30 h (P<0.05). Liver grafts preserved with Peg-AlbUW had improved portal blood flow and bile secretion compared with liver grafts preserved in UW for 30 h (P<0.05). In vitro we noted comparable hepatocyte viability when cells were preserved in Peg-AlbUW versus UW under similar preservation conditions (P>0.05); glutathione concentrations (reduced and total) were significantly increased in hepatocytes preserved in 3% Peg-AlbUW compared with other preservation solutions (P<0.05). The addition of Peg-Alb to UW preservation solution ameliorated the cold preservation injuries of rat liver grafts as shown by stable liver graft weight, a better preservation of the endothelial morphology, improved portal vein blood flow, and increased bile secretion. Peg-Alb-UW solution improved the integrity of the glutathione redox buffer system of a hepatocyte cell line after cold storage and reperfusion.

Gene expression profiling of human liver transplants identifies an early transcriptional signature associated with initial poor graft function

Liver ischemia-reperfusion injury occurring in orthotopic liver transplantation (OLT) may be responsible for early graft failure. Molecular mechanisms underlying initial poor graft function (IPGF) have been poorly documented in human. The purpose of this study was to identify the major transcriptional alterations occurring in human livers during OLT. Twenty-one RNA extracts derived from liver transplant biopsies taken after graft reperfusion were compared with 7 RNA derived from normal control livers. Three hundred seventy-one genes were significantly modulated and classified in molecular pathways relevant to liver metabolism, inflammatory response, cell proliferation and liver protection. Grafts were then subdivided into two groups based on their peak levels of serum aspartate amino transferase within 72 h after OLT (group 1, non-IPGF: 14 patients; group 2, IPGF: 7 patients). The two corresponding data sets were compared using a supervised prediction method. A new set of genes able to correctly classify 71% of the patients was defined. These genes were functionally associated with oxidative stress, inflammation and inhibition of cell proliferation. This study provides a comprehensive picture of the transcriptional events associated with human OLT and IPGF. We anticipate that such alterations provide a framework for the elucidation of the molecular mechanisms leading to IPGF.