Ischemic preconditioning prevents free radical production and mitochondrial depolarization in small-for-size rat liver grafts

Effect of ischemic preconditioning on radiation damage to the submandibular gland in rats

To investigate the effects of radiation on rat submandibular glands and the possible protective effects of ischemic preconditioning, the submandibular glands of Wistar rats were subjected to in situ radiation after ischemic preconditioning. The glands were exposed to X-radiation at a single dose of 20 Gy. Ischemic preconditioning was achieved by three min of ischemia and three min of reperfusion, repeated three times before irradiation. Salivary secretion, histological changes, alterations in tight junctions, and the levels of oxidative stress, pro-inflammatory cytokines, and water secretion proteins mediated by the muscarinic acetylcholine M3 subtype receptor were determined at 1 and 12 weeks post-irradiation. In glands subjected to irradiation only, the secretion, superoxide dismutase activity, tight junction width, acinar cell number, and M3 receptor and aquaporin-5 levels were lower at 1 and 12 weeks than seen in the ischemically preconditioned irradiated glands. In contrast, tumor necrosis factor-α, malondialdehyde, myeloperoxidase activity, and the expression of the tight junction protein claudin-4 were significantly higher in the irradiated only glands. Our study revealed that radiation caused a series of injury-stress responses, especially damage to the water secretion pathway mediated by the M3 receptor that ultimately led to hyposecretion, which might play an important role in the dysfunction of the irradiated only glands. Ischemic preconditioning reduced the radiation-induced injury to submandibular glands and ameliorated salivary hyposecretion.

Effects of non-drug treatment on liver cells apoptosis during hepatic ischemia-reperfusion injury

Hepatic ischemia reperfusion injury (HIRI) is an important cause of liver dysfunction after liver transplantation for the patients suffered from fatty liver, non-alcoholic cirrhosis, or liver cancer. It is closely related to liver cells apoptosis. Therefore, how to maintain the stable state of cell apoptosis is important to protect the liver from HIRI. Drug treatment basically applies some active substances directly or indirectly, reducing HIRI. But their toxic side effects limit the clinical applications. Differently, non-drug treatment means making use of other kinds of measures to reduce the damage, such as non-pharmaceutical preparations, surgical methods, inhalation or perfusion gas, and so on. Non-drug treatments have been shown to balance cell apoptosis and reduce liver damage during HIRI. This review summarized the progresses in the roles of non-drug treatments on liver cells apoptosis during HIRI in recent years, focusing on apoptosis inducing factors, its signal transduction pathway, and downstream molecules, etc., expecting to elucidate non-drug treatments of anti-HIRI more systematically.

Adenosine receptors: regulatory players in the preservation of mitochondrial function induced by ischemic preconditioning of rat liver

Although adenosine A₁ receptors (A1R) have been associated to ischemic preconditioning (IPC), direct evidence for their ability to preserve mitochondrial function upon hepatic preconditioning is still missing and could represent a novel strategy to boost the quality of liver transplants. We tested if the A1R antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) prevented IPC in the liver and if the A1R agonist 2-chloro-N⁶-cyclopentyladenosine (CCPA) might afford a pharmacological preconditioning. Livers underwent a 120 min of 70% warm ischemia and 16 h of reperfusion (I/R), and the IPC group underwent a 5-min ischemic episode followed by a 10-min period of reperfusion before I/R. DPCPX or CCPA was administered intraperitoneally 2 h before IPC or I/R. The control of mitochondrial function emerged as the central element affected by IPC and controlled by endogenous A1R activation. Thus, livers from IPC- or CCPA-treated rats displayed an improved oxidative phosphorylation with higher state 3 respiratory rate, higher respiratory control ratio, increased ATP content, and decreased lag phase. IPC and CCPA also prevented the I/R-induced susceptibility to calcium-induced mitochondrial permeability transition, the rate of reactive oxygen species (ROS) generation, and the decreased mitochondrial content of phospho-Ser⁹ GSK-3β. DPCPX abrogated these effects of IPC. These implicate the control of GSK-3β activity by Akt-mediated Ser⁹-GSK-3β phosphorylation preserving the efficiency of oxidative phosphorylation and ROS-mediated cell death in the ability of A1R activation to mimic IPC in the liver. In conclusion, the parallel between IPC and A1R-mediated preconditioning also paves the way to consider a putative therapeutic use of the later in liver transplants.

Ischemia preconditioning protects rat submandibular glands from ischemia/reperfusion injuries

To investigate the effects of ischemia/reperfusion on rat submandibular glands without denervation and the possible protective effects of ischemia preconditioning on the glands that experienced ischemia/reperfusion, in-situ ischemia/reperfusion and ischemia preconditioning experimental models of submandibular glands of healthy male Wistar rats were conducted. For ischemia/reperfusion groups, the glands were subjected to 90 min of ischemia without denervation, followed by 1, 12, 24, or 72 h of reperfusion. Ischemia preconditioning was achieved by 3 min of ischemia following 3 min of reperfusion, performed three times before ischemia/reperfusion. Salivary secretion, histological changes, alterations of tight junctions, myeloperoxidase activity, cellular apoptosis, and reactive oxygen species levels were detected. In ischemia/reperfusion glands, rising acute-inflammation responses, reduced tight-junction width, and increased myeloperoxidase activity, reactive oxygen species levels, and apoptotic cell numbers were observed, along with secretory dysfunction, especially at 1 and 12 h post-reperfusion, which seemed to gradually return to normal by 72 h post-reperfusion. In contrast, ischemia preconditioning showed the potential to ameliorate the injury-stress responses caused by ischemia/reperfusion. Our study revealed that ischemia/reperfusion could cause a series of injury-stress responses and ultimately lead to hyposecretion, independently of the parasympathetic nerve supply, which might play an important role in the early-phase dysfunction of the transplanted glands. Ischemia preconditioning could protect the involved glands and improve ischemia/reperfusion-induced hyposecretion.

Ameliorating effect of chicory (Chichorium intybus L.) fruit extract against 4-tert-octylphenol induced liver injury and oxidative stress in male rats

The current study was carried out to elucidate the modulating effect of chicory (Cichorium intybus L.) fruit extract (CFR) against 4-tert-OP induced oxidative stress and hepatotoxicity in male rats. Rats were divided into four groups and treated for 8 weeks as follow: group 1: normal control-treated (saline); group 2: chicory fruit extract-treated (100 mg/kg); group 3: 4-tert-OP treated; group 4: 4-tert-OP plus chicory fruit extract. The obtained results revealed that rats which received 4-tert-OP showed a significant increase in liver TBARS and bilirubin, aspartate aminotransferase (AST), alanine transaminase (ALT), alkaline phosphatase (ALP) and gamma-glutamyl transpeptidase (GGTP) activities. While a significant decrease in the levels of GSH, SOD, catalase recorded. On the other hand, CFR extract succeeded to modulate these observed abnormalities resulting from 4-tert-OP as indicated by the reduction of TBARS and the pronounced improvement of the investigated biochemical and antioxidant parameters. Histopathological evidence, together with observed PCNA and DNA fragmentation, supported the detrimental effect of 4-tert-OP and the ameliorating effect of CFR extract on liver toxicity. So, it could be concluded that chicory has a promising role and it worth to be considered as a natural substance for ameliorating the oxidative stress and hepatic injury induced by 4-tert-OP compound.

Hydrogen-rich saline attenuates postoperative liver failure after major hepatectomy in rats

BACKGROUND/AIMS

A major hepatectomy occasionally lead to acute liver failure and death. We demonstrated the anti-oxidative and anti-inflammatory effects and functional mechanisms of hydrogen-rich saline (HS), a novel antioxidant, on an experimental model of rats after a partial hepatectomy (PH).

METHODS

The rats underwent a 90% hepatectomy. HS was given intraperitoneally after the operation and every 8hours after.

RESULTS

HS markedly improved the survival rate of two experimental groups after the massive hepatectomy and inhibited increases in serum levels of TBIL, DBIL, ALT and AST. The histopathological analysis demonstrated that HS attenuated inflammatory changes in the liver. HS administration markedly lowered the massive hepatectomy induced elevation of the serum hyaluronic acid (HA) concentrations. HS inhibited the formation of one of the markers of oxidative damage, malondialdehyde (MDA), and increased the activities of superoxide dismutase (SOD) in liver tissue. In the HS-treated group, increases in inflammatory cytokines, such as TNF-α, IL-6 and HMGB-1, were inhibited in the liver tissue. The NF-κB p65 staining revealed that HS inhibited the activation of the transcription factor nuclear factor kappa B (NF-kB).

CONCLUSIONS

HS attenuates the massive hepatectomy induced liver injury not only by attenuating oxidative damage, but also by reducing the production of inflammatory cytokines, such as TNF-α, IL-6 and HMGB-1, in part through the inhibition of NF-kB activation.

Acute ethanol causes hepatic mitochondrial depolarization in mice: role of ethanol metabolism

Background/Aims

An increase of ethanol metabolism and hepatic mitochondrial respiration occurs in vivo after a single binge of alcohol. Here, our aim was to determine how ethanol intake affects hepatic mitochondrial polarization status in vivo in relation to ethanol metabolism and steatosis.

Methods

Hepatic mitochondrial polarization, permeability transition (MPT), and reduce pyridine nucleotides, and steatosis in mice were monitored by intravital confocal/multiphoton microscopy of the fluorescence of rhodamine 123 (Rh123), calcein, NAD(P)H, and BODIPY493/503, respectively, after gavage with ethanol (1–6 g/kg).

Results

Mitochondria depolarized in an all-or-nothing fashion in individual hepatocytes as early as 1 h after alcohol. Depolarization was dose- and time-dependent, peaked after 6 to 12 h and maximally affected 94% of hepatocytes. This mitochondrial depolarization was not due to onset of the MPT. After 24 h, mitochondria of most hepatocytes recovered normal polarization and were indistinguishable from untreated after 7 days. Cell death monitored by propidium iodide staining, histology and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) was low throughout. After alcohol, mitochondrial NAD(P)H autofluorescence increased and decreased, respectively, in hepatocytes with polarized and depolarized mitochondria. Ethanol also caused steatosis mainly in hepatocytes with depolarized mitochondria. Depolarization was linked to ethanol metabolism, since deficiency of alcohol dehydrogenase and cytochrome-P450 2E1 (CYP2E1), the major ethanol-metabolizing enzymes, decreased mitochondrial depolarization by ∼70% and ∼20%, respectively. Activation of aldehyde dehydrogenase decreased depolarization, whereas inhibition of aldehyde dehydrogenase enhanced depolarization. Activation of aldehyde dehydrogenase also markedly decreased steatosis.

Conclusions

Acute ethanol causes reversible hepatic mitochondrial depolarization in vivo that may contribute to steatosis and increased mitochondrial respiration. Onset of this mitochondrial depolarization is linked, at least in part, to metabolism of ethanol to acetaldehyde.

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.

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.

Ischemic preconditioning enhances hepatocyte proliferation in the early phase after ischemia under hemi-hepatectomy in rats

BACKGROUND

Ischemia/reperfusion (I/R) injury is an important barrier to liver surgery and transplantation because it impairs remnant liver/reduced-size-graft regeneration. Ischemic preconditioning (IPC), as an effective measure to overcome I/R injury, has been shown to enhance the regenerative capacity of hepatocytes. However, investigations have always focused on regeneration in the late phase after reperfusion. This study aimed to investigate whether IPC enhances hepatocyte proliferation in the early phase after reperfusion and possible underlying mechanisms.

METHODS

A total of 90 rats were divided into three groups: hemi-hepatectomy alone (PHx group), 60 minutes of ischemia plus hemi-hepatectomy (I/R group), and a cycle of 10 minutes of alternating I/R prior to 60 minutes of ischemia plus hemi-hepatectomy (IPC group). Each group was divided into five subgroups sacrificed after 0.5, 2, 6, 12 or 24 hours (n=6/subgroup). Subsequently, serum concentrations of alanine aminotransferase (ALT), aspartate aminotransferase (AST), tumor necrosis factor-alpha (TNF-alpha), and interleukin-6 (IL-6) were measured; caspase-3 and proliferating cell nuclear antigen (PCNA) proteins were also determined by Western blotting. Furthermore, PCNA was detected by immunohistochemistry to identify the expression site.

RESULTS

Serum ALT and AST levels after 2-24 hours of reperfusion in the PHx and IPC groups were remarkably decreased compared to the I/R group, and the serum TNF-alpha was relatively lower. A significant increase of serum IL-6 levels was found in the PHx and IPC groups compared with the I/R group at each time point. Furthermore, PCNA expression was remarkably increased in the IPC group after 6-12 hours of reperfusion, and in the earlier 0.5 and 6 hours time points after reperfusion have shown the massive PCNA-positive hepatocytes. At the same time, the expression of liver p-JNK was higher in the IPC group in the early phase after reperfusion than that of the I/R group and its expression was consistent with the PCNA.

CONCLUSION

IPC can initiate hepatocyte proliferation in the early phase after ischemia under hemi-hepatectomy, and may be associated with p-JNK expression and triggered by TNF-alpha/IL-6 signals.

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.

Amphiregulin stimulates liver regeneration after small-for-size mouse liver transplantation

This study investigated whether amphiregulin (AR), a ligand of the epidermal growth factor receptor (EGFR), improves liver regeneration after small-for-size liver transplantation. Livers of male C57BL/6 mice were reduced to ~50% and ~30% of original sizes and transplanted. After transplantation, AR and AR mRNA increased in 50% but not in 30% grafts. 5-Bromodeoxyuridine (BrdU) labeling, proliferating cell nuclear antigen (PCNA) expression and mitotic index increased substantially in 50% but not 30% grafts. Hyperbilirubinemia and hypoalbuminemia occurred and survival decreased after transplantation of 30% but not 50% grafts. AR neutralizing antibody blunted regeneration in 50% grafts whereas AR injection (5 μg/mouse, iv) stimulated liver regeneration, improved liver function and increased survival after transplantation of 30% grafts. Phosphorylation of EGFR and its downstream signaling molecules Akt, mTOR, p70S6K, ERK and JNK increased markedly in 50% but not 30% grafts. AR stimulated EGFR phosphorylation and its downstream signaling pathways. EGFR inhibitor PD153035 suppressed regeneration of 50% grafts and largely abrogated stimulation of regeneration of 30% grafts by AR. AR also increased cyclin D1 and cyclin E expression in 30% grafts. Together, liver regeneration is suppressed in small-for-size grafts, as least in part, due to decreased AR formation. AR supplementation could be a promising therapy to stimulate regeneration of partial liver grafts.

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.

Role of inducible nitric oxide synthase in mitochondrial depolarization and graft injury after transplantation of fatty livers

This study investigated the role of inducible nitric oxide synthase (iNOS) in failure of ethanol-induced fatty liver grafts. Rat livers were explanted 20 h after gavaging with ethanol (5 g/kg) and storing in UW solution for 24h before implantation. Hepatic oil red O staining-positive areas increased from ∼2 to ∼33% after ethanol treatment, indicating steatosis. iNOS expression increased ∼8-fold after transplantation of lean grafts (LG) and 25-fold in fatty grafts (FG). Alanine aminotransferase release, total bilirubin, hepatic necrosis, TUNEL-positive cells, and cleaved caspase-3 were higher in FG than LG. A specific iNOS inhibitor 1400W (5 μM in the cold-storage solution) blunted these alterations by >42% and increased survival of fatty grafts from 25 to 88%. Serum nitrite/nitrate and hepatic nitrotyrosine adducts increased to a greater extent after transplantation of FG than LG, indicating reactive nitrogen species (RNS) overproduction. Phospho-c-Jun and phospho-c-Jun N-terminal kinase-1/2 (JNK1/2) were higher in FG than in LG, indicating more JNK activation in fatty grafts. RNS formation and JNK activation were blunted by 1400W. Mitochondrial polarization and cell death were visualized by intravital multiphoton microscopy of rhodamine 123 and propidium iodide, respectively. After implantation, viable cells with depolarized mitochondria were 3-fold higher in FG than in LG and 1400W decreased mitochondrial depolarization in FG to the levels of LG. Taken together, iNOS is upregulated after transplantation of FG, leading to excessive RNS formation, JNK activation, mitochondrial dysfunction, and severe graft injury. The iNOS inhibitor 1400W could be an effective therapy for primary nonfunction of fatty liver grafts.

Small-for-Size Liver Transplantation Increases Pulmonary Injury in Rats: Prevention by NIM811

Pulmonary complications after liver transplantation (LT) often cause mortality. This study investigated whether small-for-size LT increases acute pulmonary injury and whether NIM811 which improves small-for-size liver graft survival attenuates LT-associated lung injury. Rat livers were reduced to 50% of original size, stored in UW-solution with and without NIM811 (5 μM) for 6 h, and implanted into recipients of the same or about twice the donor weight, resulting in half-size (HSG) and quarter-size grafts (QSG), respectively. Liver injury increased and regeneration was suppressed after QSG transplantation as expected. NIM811 blunted these alterations >75%. Pulmonary histological alterations were minimal at 5–18 h after LT. At 38 h, neutrophils and monocytes/macrophage infiltration, alveolar space exudation, alveolar septal thickening, oxidative/nitrosative protein adduct formation, and alveolar epithelial cell/capillary endothelial apoptosis became overt in the lungs of QSG recipients, but these alterations were mild in full-size and HSG recipients. Liver pretreatment with NIM811 markedly decreased pulmonary injury in QSG recipients. Hepatic TNFα and IL-1β mRNAs and pulmonary ICAM-1 expression were markedly higher after QSG transplantation, which were all decreased by NIM811. Together, dysfunctional small-for-size grafts produce toxic cytokines, leading to lung inflammation and injury. NIM811 decreased toxic cytokine formation, thus attenuating pulmonary injury after small-for-size LT.

Ischemic preconditioning and remote ischemic preconditioning have protective effect against cold ischemia-reperfusion injury of rat small intestine

PURPOSE

To investigate the protective effect of ischemic preconditioning (IPC) and remote ischemic preconditioning (RIPC) against cold ischemia-reperfusion injury (IRI) associated with small bowel transplantation (SBT).

METHODS

Male Lewis rats weighing 200-300 g were used for this study. The rats were assigned to three groups: control, ischemic preconditioning (IPC), or remote ischemic preconditioning (RIPC). Heterotopic SBT was thereafter performed. The recipient rats were killed 3, 6, 12 and 24 h after transplantation. Specimens from the intestine were histologically scored according to a grading system (Park et al.). Serum lactate dehydrogenase (LDH), aspirate aminotransferase (AST), alanine aminotransferase (ALT) were examined and heme oxygenase-1 (HO-1) were analyzed by ELISA where HO-1 served as an indicator of protection against IRI.

RESULTS

The values of tissue injury were significantly lower in the IPC and RIPC groups than in control group at 3 h after SBT. The serum LDH, AST and ALT levels also significantly decreased in the IPC and RIPC groups at 3 h after SBT, but these protective effects against cold IRI diminished by 12 and 24 h after SBT. The serum HO-1 level significantly increased in the IPC and RIPC groups 3 h after SBT.

CONCLUSION

Both IPC and RIPC were found to ameliorate ischemia-reperfusion injury after rat SBT in the early phase. HO-1 may therefore play a protective role against cold IRI.

NIM811 prevents mitochondrial dysfunction, attenuates liver injury, and stimulates liver regeneration after massive hepatectomy

BACKGROUND

Massive hepatectomy (MHX) leads to failure of remnant livers. Excessive metabolic burden in remnant livers may cause mitochondrial dysfunction. This study investigated whether blockade of the mitochondrial permeability transition (MPT) with N-methyl-4-isoleucine cyclosporine (NIM811) improves the outcome of MHX.

METHODS

Mice were gavaged with NIM811 (10 mg/kg before surgery and 5 mg/kg daily afterward) and underwent sham-operation or approximately 90% partial hepatectomy.

RESULTS

Serum alanine aminotransferase, necrosis, and apoptosis increased, respectively, to approximately 1200 U/L, 6.1%, and 7% after MHX. NIM811 decreased peak alanine aminotransferase release, necrosis, and apoptosis by 70%, 100%, and 42%, respectively. 5-Bromo-2'-deoxyuridine incorporation, proliferating cell nuclear antigen expression, and the remnant liver weights were all increased significantly by NIM811 treatment, indicating improved liver regeneration. NIM811 also blunted hyperbilirubinemia by 54%, increased serum albumin by 51%, and improved survival from 6% to 40% after MHX. Hepatic mitochondrial depolarization, cell death, and MPT were detected by intravital confocal/multiphoton microscopy of rhodamine 123, propidium iodide, and calcein. Mitochondrial depolarization occurred in many viable hepatocytes (13 cells/high-power field), and nonviable hepatocytes increased slightly to approximately 1 cell/high-power field at 3 hr after MHX. Entry of calcein into mitochondria after MHX indicated MPT onset. Importantly, NIM811 decreased mitochondria depolarization by more than 60%, blocked MPT onset, and prevented cell death. Decreases of hepatic ATP, mitochondrial cytochrome c release, and caspase-3 activation after MHX were also partially blocked by NIM811.

CONCLUSIONS

NIM811 minimized liver injury and improved liver regeneration after MHX, at least in part, by preventing MPT onset and subsequent compromised energy supply and proapoptotic cytochrome c release.

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.

Inhibition of inducible nitric oxide synthase prevents graft injury after transplantation of livers from rats after cardiac death

This study investigated the roles of inducible nitric oxide synthase (iNOS) in the failure of rat liver grafts from cardiac death donors (GCDD). Livers were explanted after 30-minute aorta clamping and implanted after 4-hour storage in University of Wisconsin solution. The iNOS expression increased slightly in grafts from non-cardiac death donors (GNCDD) but markedly in GCDD. Serum nitrite and nitrate and hepatic 3-nitrotyrosine adducts, indicators of NO and peroxynitrite production, respectively, were substantially higher after transplantation of GCDD than GNCDD. Production of reactive nitrogen species (RNS) was largely blocked by 1400W (N-[1-naphthyl]ethylenediamine dihydrochloride; 5 μM), a specific iNOS inhibitor. Alanine aminotransferase release, bilirubin, necrosis, and apoptosis were 6.4-fold, 6.5-fold, 2.3-fold, and 2.7-fold higher, respectively, after transplantation of GCDD than GNCDD. The inhibitor 1400W effectively blocked these alterations and also increased survival of GCDD to 80% from 33%. Increased RNS production and failure of GCDD were associated with activation of c-Jun-N-terminal kinase (JNK), an effect that was blocked by inhibition of iNOS. Inhibition of JNK also improved the outcome after transplantation of GCDD. Together, the data indicate that iNOS increases substantially in GCDD, leading to RNS overproduction, JNK activation, and more severe graft injury. Inhibitors of iNOS are suggested as effective therapies to improve the outcome after transplantation of GCDD.

Inhibition of inducible nitric oxide synthase prevents mitochondrial damage and improves survival of steatotic partial liver grafts

BACKGROUND

Steatotic liver grafts are excluded for partial liver transplantation because of increased risk of primary nonfunction. Mechanisms underlying the failure of fatty partial liver grafts (FPG) remain unknown. This study investigated whether inducible nitric oxide synthase (iNOS) plays a role in failure of FPG.

METHODS

Fatty livers were induced by feeding rats a high-fat high-fructose diet for 2 weeks. Hepatic triglyceride was approximately 9-fold higher in rats fed the high-fat high-fructose diet than those fed a low-fat low-fructose diet. Lean and fatty liver explants were reduced in size ex vivo to approximately one third, stored in the University of Wisconsin cold storage solution for 2 hr, and implanted.

RESULTS

Posttransplantational hepatic iNOS expression and reactive nitrogen species (RNS) formation (nitrite and nitrate levels and 3-nitrotyrosine adducts) increased more profoundly in FPG than in lean partial grafts (LPG). Serum alanine aminotransferase and bilirubin were 2- and 5.5-fold higher after transplantation of FPG than LPG. 5-Bromo-2'-deoxyuridine incorporation was 25% in LPG but only 5% in FPG, and graft weight increased by 64% in LPG while remaining unchanged in FPG. All rats that received FPG died, whereas all those receiving LPG survived. N-(1-naphtyl)ethylendiamine dihydrochloride (5 microM), a specific iNOS inhibitor, largely blunted the production of RNS, prevented the increase of alanine aminotransferase and bilirubin, restored liver regeneration, and improved survival of FPG. Mitochondrial cytochrome c oxidase-IV, ATP synthase-beta, and NADH dehydrogenase-3 decreased markedly in FPG, and these effects were blocked by N-(1-naphtyl)ethylendiamine dihydrochloride.

CONCLUSION

Thus, hepatic steatosis causes failure of partial liver grafts, most likely by increasing RNS that leads to mitochondrial damage and dysfunction.

Inhibition of transforming growth factor-beta/Smad signaling improves regeneration of small-for-size rat liver grafts

Transforming growth factor-beta (TGF-beta) is a potent inhibitor of cell proliferation. This study investigated whether overexpression of Smad7, which blocks TGF-beta-induced activation of Smad2/3, could prevent the suppression of regeneration of small-for-size liver grafts. Rats were intravenously given adenoviruses (2 x 10(10) pfu/rat) carrying the LacZ gene or the Smad7 gene (Ad-Smad7) 3 days prior to liver harvesting. Half-size livers were implanted into recipients of the same weight or twice the donor weight, and this resulted in half-size or quarter-size liver grafts. Cell proliferation, detected by 5-bromo-2'-deoxyuridine (BrdU) incorporation, increased to 23% in half-size grafts at 38 hours after implantation but was only 4% in quarter-size grafts. Graft weight did not increase after 38 hours in full-size and quarter-size grafts but increased 28% in half-size grafts. Ad-Smad7 restored BrdU labeling to 32%, and the graft weight increased to 43% in quarter-size grafts. Serum total bilirubin increased approximately 30-fold after the implantation of quarter-size grafts. Ad-Smad7 blunted hyperbilirubinemia by 80%. The basal hepatic TGF-beta(1) level was 7 ng/g of liver wet weight, and this increased to 30 ng/g at 1.5 hours after the transplantation of full-size grafts but decreased rapidly afterwards. After the transplantation of quarter-size grafts, however, TGF-beta(1) progressively increased to 159 ng/g in 38 hours. Nuclear phosphorylated Smad2/3 was barely detectable, and p21Cip1 expression was negligible in full-size grafts but increased markedly in quarter-size grafts. Ad-Smad7 blocked Smad2/3 activation and expression of p21Cip1. Together, these data show that TGF-beta is responsible, at least in part, for the defective liver regeneration in small-for-size grafts by activating the Smad signaling pathway.

Mitochondrial glutathione, a key survival antioxidant

Mitochondria are the primary intracellular site of oxygen consumption and the major source of reactive oxygen species (ROS), most of them originating from the mitochondrial respiratory chain. Among the arsenal of antioxidants and detoxifying enzymes existing in mitochondria, mitochondrial glutathione (mGSH) emerges as the main line of defense for the maintenance of the appropriate mitochondrial redox environment to avoid or repair oxidative modifications leading to mitochondrial dysfunction and cell death. mGSH importance is based not only on its abundance, but also on its versatility to counteract hydrogen peroxide, lipid hydroperoxides, or xenobiotics, mainly as a cofactor of enzymes such as glutathione peroxidase or glutathione-S-transferase (GST). Many death-inducing stimuli interact with mitochondria, causing oxidative stress; in addition, numerous pathologies are characterized by a consistent decrease in mGSH levels, which may sensitize to additional insults. From the evaluation of mGSH influence on different pathologic settings such as hypoxia, ischemia/reperfusion injury, aging, liver diseases, and neurologic disorders, it is becoming evident that it has an important role in the pathophysiology and biomedical strategies aimed to boost mGSH levels.

Role of ischemic preconditioning in liver surgery and hepatic transplantation

INTRODUCTION

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

MATERIAL AND METHOD

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

Reactive oxygen species mediate liver injury through parenchymal nuclear factor-kappaB inactivation in prolonged ischemia/reperfusion

Nuclear factor (NF)-kappaB participates in ischemia/reperfusion (I/R) hepatic signaling, stimulating both protective mechanisms and the generation of inflammatory cytokines. After analyzing NF-kappaB activation during increasing times of ischemia in murine I/R, we observed that the nuclear translocation of p65 paralleled Src and IkappaB tyrosine phosphorylation, which peaked after 60 minutes of ischemia. After extended ischemic periods (90 to 120 minutes) however, nuclear p65 levels were inversely correlated with the progressive induction of oxidative stress. Despite this profile of NF-kappaB activation, inflammatory genes, such as tumor necrosis factor (TNF) and interleukin (IL)-1beta, predominantly induced by Kupffer cells, increased throughout time during ischemia (30 to 120 minutes), whereas protective NF-kappaB-dependent genes, such as manganese superoxide dismutase (Mn-SOD), expressed in parenchymal cells, decreased. Consistent with this behavior, gadolinium chloride pretreatment abolished TNF/IL-1beta up-regulation during ischemia without affecting Mn-SOD levels. Interestingly, specific glutathione (GSH) up-regulation in hepatocytes by S-adenosylmethionine increased Mn-SOD expression and protected against I/R-mediated liver injury despite TNF/IL-1beta induction. Similar protection was achieved by administration of the SOD mimetic MnTBAP. In contrast, indiscriminate hepatic GSH depletion by buthionine-sulfoximine before I/R potentiated oxidative stress and decreased both nuclear p65 and Mn-SOD expression levels, increasing TNF/IL-1beta up-regulation and I/R-induced liver damage. Thus, the divergent role of NF-kappaB activation in selective liver cell populations underlies the dichotomy of NF-kappaB in hepatic I/R injury, illustrating the relevance of specifically maintaining NF-kappaB activation in parenchymal cells.