Liver ischemic preconditioning: a new strategy for the prevention of ischemia-reperfusion injury

Ethyl Pyruvate; from Liver Preservation Solutions University of Wisconsin (UW) Increases the Effectiveness of the Solution

BACKGROUND

The most important factor affecting the success rate of liver transplants is the preservation of the normal histologic and biochemical properties of the cells in the tissue taken. The study aimed to identify the possible increase in efficacy of ethyl pyruvate, which has a hepatoprotective effect, on the University of Wisconsin (UW) solution.

METHODS

Rats were randomly selected and divided into 4 groups. After a laparotomy, the small intestines were removed from the abdomen and the portal pedicle was identified. Arterial and venous circulation of the liver was interrupted. After the portal vein was cannulated (and the distal of the portal pedicle was ligated, the liver was perfused with a solution. Perfusion solution was selected as Ringer Lactate in Group 1. In group 2, UW solution was chosen as the perfusion solution. In Group 3, the perfusion solution was chosen as the UW solution, but ethyl pyruvate at a dose of 40 mg/kg was administered intraperitoneally to the experimental animals 30 minutes before hepatectomy. In Group 4, as a perfusion solution, a UW solution with 40 mg/kg dose of ethyl pyruvate added to it was used.

RESULTS

With TUNEL and Caspase-3 staining, a significant decrease was found in the apoptosis rates of Groups 2, 3, and 4 at the 12th hour post hepatectomy when compared with Group 1. When the morphometric liver sinusoid/parenchyma ratios and vena centralis diameters of the groups were examined, it was found that all preservation solutions containing the UW solution were more protective than the RL solution.

CONCLUSIONS

Ethyl pyruvate is regarded as a promising agent that can increase the effect of the UW solution on organ preservation solutions. Because this study is the first in literature to apply ethyl pyruvate in preservation solutions, additional studies with larger series and different doses are needed.

Lithium Microdialysis and Its Use for Monitoring of Stomach and Colon Submucosal Blood Perfusion – A Pilot Study Using Ischemic Preconditioning in Rats

During shock, exposure of gut to ischemia determines patient’s survival. Ischemic preconditioning (ISP) elevates nitric oxide and blood perfusion, whereby it protects organs against subsequent severe ischemia/reperfusion. Using appropriate flow marker, microdialysis may serve to monitor interstitial microcirculation. Hence, our aim was to test the reliability of lithium as a flow marker (lithium microdialysis, LM) on an ISP model. Rats were divided into three groups. Two (ischemic and preconditioned) groups underwent 30 min celiac artery occlusion (CAO) with 2.5 h reperfusion. 25 min before CAO, the latter experienced 5 min ischemia. Sham–operated animals served as controls. LM in stomach and colon submucosa, serum nitric oxide, hepatic and pancreatic enzymes were measured. In stomach, LM indicated a decrease in blood perfusion evoked by CAO (p<0.01) in both experimental groups. During reperfusion, the ischemic animals showed a restoration of microcirculation, unlike the preconditioned ones, whose blood perfusion failed to regenerate (p<0.001). For any group, LM showed no microcirculation modification in colon. Serum analytes remained unchanged. We conclude that LM appears to be a potentially suitable indicator of gastrointestinal interstitial microcirculation. However, we failed to demonstrate any beneficial effect of ISP on pancreas, systemic nitric oxide and local/remote microcirculation within studied organs.

Preconditioning boosts regenerative programmes in the adult zebrafish heart

During preconditioning, exposure to a non-lethal harmful stimulus triggers a body-wide increase of survival and pro-regenerative programmes that enable the organism to better withstand the deleterious effects of subsequent injuries. This phenomenon has first been described in the mammalian heart, where it leads to a reduction of infarct size and limits the dysfunction of the injured organ. Despite its important clinical outcome, the actual mechanisms underlying preconditioning-induced cardioprotection remain unclear. Here, we describe two independent models of cardiac preconditioning in the adult zebrafish. As noxious stimuli, we used either a thoracotomy procedure or an induction of sterile inflammation by intraperitoneal injection of immunogenic particles. Similar to mammalian preconditioning, the zebrafish heart displayed increased expression of cardioprotective genes in response to these stimuli. As zebrafish cardiomyocytes have an endogenous proliferative capacity, preconditioning further elevated the re-entry into the cell cycle in the intact heart. This enhanced cycling activity led to a long-term modification of the myocardium architecture. Importantly, the protected phenotype brought beneficial effects for heart regeneration within one week after cryoinjury, such as a more effective cell-cycle reentry, enhanced reactivation of embryonic gene expression at the injury border, and improved cell survival shortly after injury. This study reveals that exposure to antecedent stimuli induces adaptive responses that render the fish more efficient in the activation of the regenerative programmes following heart damage. Our results open a new field of research by providing the adult zebrafish as a model system to study remote cardiac preconditioning.

Involvement of glycogen synthase kinase-3β in liver ischemic conditioning induced cardioprotection against myocardial ischemia and reperfusion injury in rats

Remote ischemic conditioning has been convincingly shown to render the myocardium resistant to a subsequent more severe sustained episode of ischemia. Compared with other organs, little is known regarding the effect of transient liver ischemic conditioning. We proposed the existence of cardioprotection induced by remote liver conditioning. Male Sprague-Dawley rats were divided into sham-operated control (no further hepatic intervention) and remote liver ischemic conditioning groups. For liver ischemic conditioning, three cycles of 5 min of liver ischemia-reperfusion stimuli were conducted before-(liver preconditioning), post-myocardial ischemia (liver postconditioning), or in combination of both (liver preconditioning + liver postconditioning). Rats were exposed to 45 min of left anterior descending coronary artery occlusion, followed by 3 h of reperfusion thereafter. ECG and hemodynamics were measured throughout the experiment. The coronary artery was reoccluded at the end of reperfusion for infarct size determination. Blood samples were taken for serum lactate dehydrogenase and creatine kinase-MB test. Heart tissues were taken for apoptosis measurements and Western blotting. Our data demonstrate that liver ischemic preconditioning, postconditioning, or a combination of both, offered strong cardioprotection, as evidenced by reduction in infarct size and cardiac tissue damage, recovery of cardiac function, and inhibition of apoptosis after ischemia-reperfusion. Moreover, liver ischemic conditioning increased cardiac (not hepatic) glycogen synthase kinase-3β (GSK-3β) phosphorylation. Accordingly, inhibition of GSK-3β mimicked the cardioprotective action of liver conditioning. These results demonstrate that remote liver ischemic conditioning protected the heart against ischemia and reperfusion injury via GSK-3β-dependent cell-survival signaling pathway.NEW & NOTEWORTHY Remote ischemic conditioning protects hearts against ischemia and reperfusion (I/R) injury. However, it is unclear whether ischemic conditioning of visceral organs such as the liver, the largest metabolic organ in the body, can produce cardioprotection. This is the first study to show the cardioprotective effect of remote liver ischemic conditioning in a rat model of myocardial I/R injury. We also, for the first time, demonstrated these protective properties are associated with glycogen synthase kinase-3β-dependent cell-survival signaling pathway.

Remote Liver Ischemic Preconditioning Protects against Sudden Cardiac Death via an ERK/GSK-3β-Dependent Mechanism

BACKGROUND

Preconditioning stimuli conducted in remote organs can protect the heart against subsequent ischemic injury, but effects on arrhythmogenesis and sudden cardiac death (SCD) are unclear. Here, we investigated the effect of remote liver ischemia preconditioning (RLIPC) on ischemia/reperfusion (I/R)-induced cardiac arrhythmia and sudden cardiac death (SCD) in vivo, and determined the potential role of ERK/GSK-3βsignaling.

METHODS/RESULTS

Male Sprague Dawley rats were randomized to sham-operated, control, or RLIPC groups. RLIPC was induced by alternating four 5-minute cycles of liver ischemia with 5-minute intermittent reperfusions. To investigate I/R-induced arrhythmogenesis, hearts in each group were subsequently subjected to 5-minute left main coronary artery ligation followed by 20-minute reperfusion. RLIPC reduced post-I/R ventricular arrhythmias, and decreased the incidence of SCD >threefold. RLIPC increased phosphorylation of cardiac ERK1/2, and GSK-3β Ser9 but not Tyr216 post-I/R injury. Inhibition of either GSK-3β (with SB216763) or ERK1/2 (with U0126) abolished RLIPC-induced antiarrhythmic activity and GSK-3β Ser9 and ERK1/2 phosphorylation, leaving GSK-3β Tyr216 phosphorylation unchanged.

CONCLUSIONS

RLIPC exerts a powerful antiarrhythmic effect and reduces predisposition to post-IR SCD. The underlying mechanism of RLIPC cardioprotection against I/R-induced early arrhythmogenesis may involve ERK1/2/GSK-3β Ser9-dependent pathways.

Protective Effects of Adenosine Receptor Agonist in a Cirrhotic Liver Resection Model

OBJECTIVES

To investigate the role of CGS21680, a selective adenosine A2A receptor agonist, on a bile-duct-ligated cirrhotic liver resection model in rats.

METHODS

Male Wistar rats were allotted into 3 groups (n = 7 per time-point): the control group, the bile duct ligation + CGS21680 group (BDL + CGS), and the bile duct ligation group (BDL). Biliary cirrhosis had been previously induced by ligature of the common bile duct in the BDL + CGS and BDL groups. After 2 weeks, the animals underwent partial hepatectomy (50%). The BDL + CGS group received a single dose of CGS21680 15 minutes prior to hepatectomy. Blood samples were collected and analyzed.

RESULTS

Aspartate transaminase levels were found to be lower in the control vs BDL groups (1, 3, and 24 h) (P < 0.01) and the BDL + CGS (1 and 3 hours) (P < 0.01) and BDL + CGS vs BDL (24 hours) (P < 0.05) groups. Hepatic flow was measured and BDL showed significantly lower values at the 3, 24, and 168 h time-points compared to the control (P < 0.01) and BDL + CGS groups (P < 0.05 at 3 and 168 hours; P < 0.01 at 24 h). O2C velocity was reduced in the BDL compared to the control group (P < 0.001 at 3 hours; P < 0.01 at 24 and 168 hours) and the BDL + CGS group (P < 0.01 at 24 hours). Interleukin-6 levels were abrogated in the BDL + CGS (P < 0.05) and control (P < 0.01) groups versus BDL. Histone-bound low-molecular-weight DNA fragments in the BDL + CGS (P < 0.01) and control (P < 0.05) groups were low compared to the BDL group.

CONCLUSIONS

Administration of CGS21680, an adenosine receptor agonist, after the resection of bile-duct-ligated cirrhotic livers led to improved liver function, regeneration, and microcirculation.

Protective effects of Hammada scoparia flavonoid-enriched fraction on liver injury induced by warm ischemia/reperfusion

CONTEXT

Hepatic ischemia/reperfusion injury (IRI) is a major cause of liver damage during liver surgery and transplantation. Plants have historically been used in treating liver damage, and Hammada scoparia (Pomel) (Chenopodiaceae) has been reported to possess a broad spectrum of pharmacological and therapeutic activities.

OBJECTIVE

In this study, a flavonoid-enriched fraction was used before the warm ischemia (WI) process as pharmacological preconditioning and in combination with technical postconditioning to evaluate their protective effects.

MATERIALS AND METHODS

The rats were divided into five groups: a sham group; a control group (Control-IR) that was submitted to 60 min WI; a Pharmacological Preconditioning group (PreC-IR) that received flavonoid-enriched fraction (200 mg/kg body weight); a Postconditioning group (PostC) and a PreC + PostC group.

RESULTS

The use of the flavonoid-enriched fraction was noted to significantly (p < 0.05) reduce liver injury, as evidenced by the decrease in liver transaminase activities (AST and ALT) and lactic dehydrogenase (LDH), alkaline phosphatase (ALP), and lipid peroxidation (TBARS), levels as well as the enhancement of antioxidant enzymes (catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx)) responses. The results also indicated that, compared with the separate application of pharmacological preconditioning and postconditioning, the combination of both treatments was more effective in reducing tissue oxidative stress levels through modulating SOD, GSH-PX, and CAT activities. Furthermore, the combined protocol further decreased the liver morphological score compared with solo treatment.

DISCUSSION AND CONCLUSION

Overall, the results indicate that the H. scoparia flavonoid-enriched fraction could be a promising candidate for future application as a pharmacological preconditioning agent against hepatic IRI.

Sevoflurane prevents liver inflammatory response induced by lung ischemia-reperfusion

BACKGROUND

Transplants cause ischemia-reperfusion (IR) injury that can affect distant organs. Liver is particularly sensitive to IR injury. The present randomized experimental study was designed to investigate a possible protective effect of sevoflurane against liver inflammatory response to lung IR in a lung upper lobe left autotransplant model.

METHODS

Two groups (sevoflurane and control) of eight swines each were submitted to upper lobe left lung autotransplant. Hypnotic maintenance was performed with sevoflurane 3% or propofol 8 to 10 mg/kg per hr until pneumonectomy was done; then propofol was used for all animals. Blood and liver samples were taken in four different moments: prepneumonectomy, prereperfusion, 10 min postreperfusion and 30 min postreperfusion to measure levels of interleukin (IL)-1β, IL-10, tumor necrosis factor (TNF)-α, monocyte chemotactic protein (MCP)-1, nuclear factor (NF)-κB, C-reactive protein, ferritin and caspase 3. Non-parametric test was used to find statistical meaning.

RESULTS

Lung IR markedly increased the expression of TNF-α, IL-1β, MCP-1, NF-κB and caspase activity in control livers compared with basal levels, whereas liver IL-10 expression decreased 10 and 30 min post-reperfusion. Sevoflurane significantly decreased TNF-α, IL-1β, MCP-1, NF-κB liver expression and caspase 3 activity. Sevoflurane also reverted the lung IR-induced decrease in IL-10 expression.

CONCLUSIONS

The present results indicate that lung IR caused hepatic injury. Sevoflurane attenuated liver injury in a model of upper lobe left lung autotransplant in pigs.

Use of lung allografts from brain-dead donors after cardiopulmonary arrest and resuscitation

RATIONALE

Patients who progress to brain death after resuscitation from cardiac arrest have been hypothesized to represent an underused source of potential organ donors; however, there is a paucity of data regarding the viability of lung allografts after a period of cardiac arrest in the donor.

OBJECTIVES

To analyze postoperative complications and survival after lung transplant from brain-dead donors resuscitated after cardiac arrest.

METHODS

The United Network for Organ Sharing database records donors with cardiac arrest occurring after brain death. Adult recipients of lung allografts from these arrest/resuscitation donors between 2005 and 2011 were compared with nonarrest donors. Propensity score matching was used to reduce the effect of confounding. Postoperative complications and overall survival were assessed using McNemar's test for correlated binary proportions and Kaplan-Meier methods.

MEASUREMENTS AND MAIN RESULTS

A total of 479 lung transplant recipients from arrest/resuscitation donors were 1:1 propensity matched from a cohort of 9,076 control subjects. Baseline characteristics in the 1:1-matched cohort were balanced. There was no significant difference in perioperative mortality, airway dehiscence, dialysis requirement, postoperative length of stay (P ≥ 0.38 for all), or overall survival (P = 0.52). A subanalysis of the donor arrest group demonstrated similar survival when stratified by resuscitation time quartile (P = 0.38).

CONCLUSIONS

There is no evidence of inferior outcomes after lung transplant from brain-dead donors who have had a period of cardiac arrest provided that good lung function is preserved and the donor is otherwise deemed acceptable for transplantation. Potential expansion of the donor pool to include cardiac arrest as the cause of brain death requires further study.

Ischemic preconditioning promotes intrinsic vascularization and enhances survival of implanted cells in an in vivo tissue engineering model

Ischemic preconditioning (IPC) is a potent and effective means of protecting cells against ischemic injury. The protection has been demonstrated to involve release of paracrine factors that promote cell survival and angiogenesis, factors important for successful tissue engineering. The aim of the present study was to determine whether IPC of a vascular bed in vivo is an effective strategy to prepare it for tissue engineering with implanted cells. To test this hypothesis, an in vivo vascularized tissue engineering approach was employed, whereby polyacrylic chambers were placed around the femoral vessels of adult Sprague-Dawley rats. IPC was induced by 3 cycles of 5 min femoral artery occlusion interspersed with 5-min periods of reperfusion. Rats subjected to IPC generated bigger tissue constructs at 7 and 28 days postimplantation of empty chambers (∼50% increase in weight and volume, p<0.05). Morphometric counting of Masson trichrome stained tissue sections revealed significantly greater tissue construct volumes in ischemic preconditioned vascular beds at 7 and 28 days, increasing both fibrin matrix and vascularized tissue. Furthermore, morphometry of lectin-labeled blood vessels indicated an increase in vascular volume in IPC tissue constructs (∼100% increase vs. control, p<0.05). To investigate the cytoprotective effect of IPC, we implanted DiI-labeled neonatal rat cardiomyocytes in the chambers for 3 days, and IPC significantly reduced apoptosis of implanted cells as determined by the TUNEL assay and cleaved caspase-3 immunostaining. Furthermore, IPC significantly increased the cardiac muscle volume and vascular volume at 28 days after implantation of cardiomyocytes. In conclusion, in vivo IPC promotes survival of implanted cardiomyocytes and is associated with enhanced angiogenesis. IPC may represent a new approach to optimize tissue engineering with implanted cells.

All-trans retinoic acid preconditioning protects against liver ischemia/reperfusion injury by inhibiting the nuclear factor kappa B signaling pathway

BACKGROUND

Inflammatory response plays a pathogenic role in liver ischemia/reperfusion (I/R) injury. All-trans retinoic acid (ATRA) is an active metabolite of vitamin A with anti-inflammatory effects. However, there are few reports on the anti-inflammatory effects of ATRA on liver I/R injury. The purpose of this study was to investigate the effects of ATRA on liver I/R injury and related mechanisms.

METHODS

A total of 54 male Sprague-Dawley rats were randomly divided into three groups (18 rats each), namely, sham, I/R, and I/R+ATRA groups. ATRA was intraperitoneally administered at a dose of 15mg/kg/d 14d before ischemia surgery. The segmental (70%) hepatic ischemia model was used by clamping the portal vein, hepatic artery, and bile duct of the left and median for 1h. The rats were sacrificed 3, 6, and 24h after reperfusion, and blood and liver tissue samples were obtained. Liver injury was evaluated by biochemical and histopathologic examinations. Myeloperoxidase activity was spectrophotometrically measured. The expression of pro-inflammatory cytokines, such as tumor necrosis factor-α and interleukin-6 was measured by enzyme-linked immunosorbent assay and real-time polymerase chain reaction. Liver nuclear factor kappa B (NF-κB) was detected by immunohistochemistry. The expression of NF-κB p65 and inhibitor NF-κB-α (IκBα) was determined by Western blot analysis.

RESULTS

The serum alanine aminotransferase level, Suzuki scores of hepatic histology, and hepatic myeloperoxidase activity, as indices of hepatic injury, were increased after reperfusion. The increase was attenuated by preadministration with ATRA. Compared with the I/R group, ATRA treatment increased IκBα expression and suppressed NF-κB p65 expression. Subsequently, the levels of tumor necrosis factor-α and interleukin-6 after liver I/R were effectively downregulated.

CONCLUSIONS

ATRA administration can significantly attenuate I/R injury in rat liver. The protective mechanism is related to its anti-inflammatory function of inhibiting NF-κB activation.

Calcium-sensing receptors induce apoptosis during simulated ischaemia-reperfusion in Buffalo rat liver cells

1. Calcium-sensing receptors (CaSR) exist in a variety of tissues. In 2010, we first identified its functional expression in Buffalo rat liver (BRL) cells and demonstrated that the activation of CaSR was involved in an increased intracellular calcium through the Gq subunit-phospholipase C-inositol triphosphate pathway. However, its role and related mechanism in hepatic ischaemia/reperfusion (I/R) injury is still unclear. 2. Therefore, in the present study, BRL cells were incubated in ischaemia-mimetic solution for 4 h, then reincubated in the normal culture medium for 10 h to establish a simulated I/R model. We assayed the apoptotic ratio of BRL cells by flow cytometry and Hoechst 33342 staining; analyzed the expression of CaSR, cytochrome c (Cyt-c), caspase-3, Bcl-2, Bax, extracellular signal-regulated protein kinase (ERK), and p38 by Western blotting; and measured the concentration of intracellular calcium by laser-scanning confocal microscopy. 3. The results showed that simulated I/R increased the expression of CaSR and induced apoptosis in BRL cells. GdCl(3), a specific activator of CaSR, further increased CaSR expression, intracellular calcium, and apoptosis in BRL cells during I/R. The activation of CaSR downregulated Bcl-2 expression, upregulated Cyt-c, caspase-3, and Bax expressions, and promoted p38 and ERK-1/2 phosphorylation. 4. In conclusion, increased CaSR expression plays a vital role in apoptosis induced by I/R injury, in which its mechanism is related with calcium overload and the activation of the mitochondrial and mitogen-activated protein kinase apoptotic pathways. The regulation of CaSR activity might serve as a novel pharmacological target to prevent and treat liver disease.

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

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

Randomized clinical trial of ischaemic preconditioning in major liver resection with intermittent Pringle manoeuvre

BACKGROUND

Vascular inflow occlusion is effective in avoiding excessive blood loss during hepatic parenchymal transection but may cause ischaemic damage to the remnant liver. Intermittent portal triad clamping (IPTC) is superior to continuous hepatic pedicle clamping as it avoids severe ischaemia-reperfusion (IR) injury in the liver remnant. Ischaemic preconditioning (IPC) before continuous Pringle manoeuvre may protect against IR during major liver resection.

METHODS

This RCT assessed the impact of IPC in major liver resection with intermittent vascular inflow occlusion. Patients undergoing major liver resection with intermittent vascular inflow occlusion were randomized, during surgery, to receive IPC (10 min inflow occlusion followed by 10 min reperfusion) or no IPC (control group). Data analysis was on an intention-to-treat basis. The primary endpoint was serum alanine aminotransferase (ALT) level on the day after surgery.

RESULTS

Eighty four patients were enrolled and randomized to IPC (n = 41) and no IPC (n = 43). The groups were comparable in terms of demographic data, preoperative American Society of Anesthesiologists grade and extent of liver resection. Intraoperative morbidity and postoperative outcomes were also similar. ALT levels on the day after operation were not decreased by IPC (mean(s.d.) 537·6(358·5) versus 525·0(400·6) units/ml in IPC and control group respectively; P = 0·881). Liver biochemistry tests in the week after operation showed the same pattern in both groups.

CONCLUSION

IPC did not reduce liver damage in patients undergoing major liver resection with IPTC.

REGISTRATION NUMBER

NCT00908245 (http://www.clinicaltrials.gov).

Cardioprotective effects of nitrite during exercise

Exercise training has been shown to reduce many risk factors related to cardiovascular disease, including high blood pressure, high cholesterol, obesity, and insulin resistance. More importantly, exercise training has been consistently shown to confer sustainable protection against myocardial infarction in animal models and has been associated with improved survival following a heart attack in humans. It is still unclear how exercise training is able to protect the heart, but some studies have suggested that it increases a number of classical signalling molecules. For instance, exercise can increase components of the endogenous antioxidant defences (i.e. superoxide dismutase and catalase), increase the expression of heat shock proteins, activate ATP-sensitive potassium (K(ATP)) channels, and increase the expression and activity of endothelial nitric oxide (NO) synthase resulting in an increase in NO levels. This review article will provide a brief summary of the role that these signalling molecules play in mediating the cardioprotective effects of exercise. In particular, it will highlight the role that NO plays and introduce the idea that the stable NO metabolite, nitrite, may play a major role in mediating these cardioprotective effects.

Essential role of the redox-sensitive kinase p66shc in determining energetic and oxidative status and cell fate in neuronal preconditioning

Ischemic preconditioning is a phenomenon in which low-level stressful stimuli upregulate endogenous defensive programs, resulting in subsequent resistance to otherwise lethal injuries. We previously observed that signal transduction systems typically associated with neurodegeneration such as caspase activation are requisite events for the expression of tolerance and induction of HSP70. In this work, we sought to determine the extent and duration of oxidative and energetic dysfunction as well as the role of effector kinases on metabolic function in preconditioned cells. Using an in vitro neuronal culture model, we observed a robust increase in Raf and p66(Shc) activation within 1 h of preconditioning. Total ATP content decreased by 25% 3 h after preconditioning but returned to baseline by 24 h. Use of a free radical spin trap or p66(shc) inhibitor increased ATP content whereas a Raf inhibitor had no effect. Phosphorylated p66(shc) rapidly relocalized to the mitochondria and in the absence of activated p66(shc), autophagic processing increased. The constitutively expressed chaperone HSC70 relocalized to autophagosomes. Preconditioned cells experience significant total oxidative stress measured by F(2)-isoprostanes and neuronal stress evaluated by F(4)-neuroprostane measurement. Neuroprostane levels were enhanced in the presence of Shc inhibitors. Finally, we found that inhibiting either p66(shc) or Raf blocked neuroprotection afforded by preconditioning as well as upregulation of HSP70, suggesting both kinases are critical for preconditioning but function in fundamentally different ways. This is the first work to demonstrate the essential role of p66(shc) in mediating requisite mitochondrial and energetic compensation after preconditioning and suggests a mechanism by which protein and organelle damage mediated by ROS can increase HSP70.

Involvement of mitochondrial ATP-sensitive potassium channels in etomidate preconditioning-induced protection in human myeloid HL-60 cells

Exposure of HL-60 cells, a human myeloid cell line, to 500μM etomidate for 24h reduced cell viability and increased nitric oxide production and mitochondrial permeability transition pore (mPTP) opening. Preconditioning (1h) with 1μM etomidate 4h before exposure to the 500μM dose of etomidate attenuated those detrimental effects. The mitochondrial ATP-sensitive potassium channel (mitoK(ATP) channel) inhibitor 5-hydroxydecanoic acid reduced the etomidate preconditioning effects. The mitoK(ATP) channel opener diazoxide attenuated the mPTP opening caused by the large dose of etomidate. Our results suggest that etomidate can induce a preconditioning effect that may involve mitoK(ATP) channel activation.

Autofluorescence properties of rat liver under hypermetabolic conditions

Autofluorescence response to oxygen supply modulation has been investigated in livers of rats under the hypermetabolic state associated to a pathological condition-hyperthyroidism-that is known to enhance hepatocyte metabolic activities involving both NAD, i.e. oxidative pathways engaged in ATP synthesis, and NADP, i.e. reductive bio-synthesis and antioxidant functions. Experiments have been performed on rats in normal condition or submitted to long-term thyroxine (T(4)) administration. Histological inspection did not show any appreciable morphological alteration in liver parenchyma; biochemical analysis indicated an increase in both NADP(+) and NADPH contents. Autofluorescence properties have been monitored in vivo, via a fiber optic probe, on exposed livers both during induction of global ischemia and after restoration of blood circulation. Alteration of oxygen supply modulated liver autofluorescence properties, mainly as to NAD(P)H contribution, in dependence of changes in pyridine coenzymes redox state. With respect to euthyroid, hyperthyroid rat livers exhibited higher autofluorescence signals in all phases of the experiment, and a faster signal decay time upon reoxygenation. The results have been interpreted on the basis of a larger content of NADPH-the coenzyme not directly oxidized in respiratory processes and likely providing an almost constant autofluorescence background contribution-and of uncoupling effects facilitating the respiratory NADH oxidation, associated with the hyperthyroid condition. The results obtained in the liver hypermetabolic model provide interesting perspectives for a further improvement of the diagnostic implications of autofluorescence.

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

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

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

Although livers exhibit only minimal morphologic changes with age, how older livers tolerate pathologic conditions such as normothermic ischemia is unknown. Young 6-week-old mice and old 60-week-old mice underwent 60 minutes of hepatic ischemia and various periods of reperfusion. Markers of hepatocyte injury, hepatic energy content, and mitochondrial function were determined. Ischemic preconditioning and glucose injection were evaluated as protective strategies against reperfusion injury in old mice. Reperfusion injury was far worse in old mice compared with mice in the young control group. Ischemic preconditioning was highly protective against reperfusion injury in young but not in old mice. Older livers had dramatically reduced adenosine triphosphate (ATP) levels and glycogen contents. The low intrahepatic energy level in old mice was associated with a reduced mitochondrial ATP production. Preoperative injection of glucose restored the intrahepatic ATP content and protected against reperfusion injury. Furthermore, glucose injection restored the protective effect of ischemic preconditioning, resulting in additive protection when both strategies were combined. Aging of the liver is associated with mitochondrial dysfunction and decreased intrahepatic energy content, resulting in poorer tolerance against ischemic injury. Improving intrahepatic ATP levels in old livers by glucose injection protects the old liver against ischemic injury and restores the protective effects of ischemic preconditioning.

Effect of remote preconditioning on mild or severe ischemia-reperfusion injury to rat liver

In this study we examined the effect of remote ischemic preconditioning (RIPC) on liver ischemia-reperfusion (IR) injury. Anesthetized Wistar rats (200 to 250 g body weight, n = 32) had the right femoral artery (FA) dissected. Protocol I. The hepatic artery (HA) was clamped for 60 minutes; peripheral liver blood flow (PLBF) and alanine aminotransferase (ALT) were measured prior to clamping as well as 60 minutes after reperfusion. The cohorts were group 1 (no RIPC; n = 10) and group 2 (RIPC; n = 10) 35 minutes after surgery, the FA was clamped for 10 minutes. After 15 minutes, the HA was clamped as in group 1. In protocol II, a rubber band was applied around the entire vascular supply to about 70% of the liver, yielding group 3 (no RIPC; n = 6) that 60 minutes after surgery, had vascular occlusion performed for 30 minutes and group 4 (RIPC; n = 6) with the FA clamped as above, in a procedure otherwise identical to that of group 3.

RESULTS

In protocol I, there was no significant difference in PLBF between the two groups after reperfusion, but the increased ALT levels in the RIPC group were reduced (.70 +/- .05 vs. 1.0 +/- .15 microkat/L, P = .049). In protocol II, we observed no significant differences in ALT levels or PLBF between the two groups. Thus, a beneficial effect of RIPC was demonstrated in protocol I with relative hypoxemia to the liver. However, the effect could not be demonstrated in protocol II, which induced a more severe IR injury.

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

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

Ex Vivo Evaluation of Human Lungs for Transplant Suitability

BACKGROUND

If lungs could be retrieved from non-heart-beating donors, the critical shortage of lungs for transplant could be alleviated. An obstacle to this approach is the inability to predict these lungs' suitability for transplant. We used human lungs deemed unsuitable for transplant to develop a method to perfuse and ventilate human lungs ex vivo to assess gas exchange and vascular resistance, and to perform bronchoscopic inspection and radiographic evaluation.

METHODS

Lungs were retrieved from six brain-dead organ donors after cold Perfadex (Vitrolife, Kungsbacka, Sweden) flush, stored cold for 6 to 13 hours (mean, 8.7 hours) then perfused and rewarmed in a modified cardiopulmonary bypass circuit. Circuit perfusate was buffered colloid-crystalloid containing type-specific leukocyte-filtered blood (hematocrit of 10%-12%), circulated through a membrane oxygenator ventilated with CO2 and nitrogen to deoxygenate it. Lungs were ventilated with fraction of inspired oxygen (Fio2) 0.5 when 32 degrees C was reached. Gas exchange and vascular resistance was assessed at 5 L/minute flow at 37 degrees C, Fio2 0.5 and 1.0. Bronchoscopy, plain radiographs, and spiral computed tomographic (CT) scans were performed. Lung biopsies were obtained pre- and post-reperfusion.

RESULTS

Ex vivo perfusion did not cause increased wet to dry ratio, or major abnormalities by microscopy but was associated with elevated tissue levels of conjugated dienes. The alveolar-arterial difference in partial pressure of oxygen (Pao2)/Fio2 ratio in the ex vivo circuit was generally higher than in the six donors. Ex vivo radiographs and CT scans were abnormal in all lungs, confirming unsuitability of these lungs for transplant.

CONCLUSIONS

Ex vivo evaluation of human lungs is feasible and may be useful to evaluate transplant suitability of lungs retrieved after circulatory arrest from non-heart-beating donors.

Increased antioxidant capacity of serum did not prevent lipid peroxidation in the intermittent ischemia-reperfusion of rat small intestine

Changes in small molecular antioxidants were followed up in a model of small intestinal ischemia in Wistar rats to evaluate their possible role in ischemic preconditioning. The superior mesenteric artery was occluded either for 60 minutes only or for 60 minutes preceded by one to three 15-minute periods of ischemia with 5-minute reperfusion periods interposed. Total antioxidant capacity (TRAP) in serum, serum antioxidants (uric acid, ascorbic acid, bilirubin), and the thiobarbituric acid reactive substances in both serum and mucosa were measured. An increase in TRAP observed after 60 minutes of ischemia was prevented in preconditioned animals. Ascorbic and uric acid concentrations increased generally in comparison to intact controls, but this increase was not sufficient to prevent lipid peroxidation in serum and intestinal mucosa. In short, the small molecular antioxidants measured did not contribute to the phenomenon of ischemic preconditioning.

Protective role of supplement with foreign Bifidobacterium and Lactobacillus in experimental hepatic ischemia-reperfusion injury

BACKGROUND AND AIM

Intestinal microflora play a crucial role in some severe liver diseases. The purpose of this study was to evaluate the effects of a Lactobacillus strain and a Bifidobacterium strain on ischemia-reperfusion (I/R) liver injury.

METHODS

Rats were divided into six groups. Each group received either Bifidobacterium Catenulatum ZYB0401; Lactobacillus Fermentum ZYL0401; a mixture of these two bacterial strains; gentamicin; or saline by daily gavage for 7 days. On the sixth day, all rats, except those in the control group, were subjected to 20 min of liver ischemia. After 22 h of hepatic reperfusion, liver enzymes and histology, malondialdehyde (MDA), superoxide dismutase (SOD), endotoxemia, serum tumor necrosis factor-alpha (TNF-alpha), intestinal bacteria, intestinal mucosal ultrastructure, and bacterial translocation were studied.

RESULTS

All administered bacteria increased intestinal Bifidobacterium and Lactobacillus, decreased endotoxemia (P < 0.01), alanine aminotransferase (ALT) (P < 0.01), and markedly ameliorated liver histology and intestinal mucosal ultrastructure. Only rats treated with Bifidobacterium Catenulatum ZYB0401 and Lactobacillus Fermentum ZYL0401 showed reduced incidence of bacterial translocation to the kidney (P < 0.05), associated with decreased serum TNF-alpha and liver MDA (P < 0.05) and increased liver SOD (P < 0.05) compared to the I/R group. Gentamicin decreased almost all kinds of intestinal bacteria (P < 0.01) and decreased ALT (P < 0.01) and serum TNF-alpha, but failed to reduce both endotoxemia and the incidence of bacterial translocation and had no effects on liver MDA and SOD.

CONCLUSION

Bifidobacterium Catenulatum ZYB0401 in combination with Lactobacillus Fermentum ZYL0401 could be useful in restoring intestinal microflora and in preventing liver injury in hepatic I/R of rats.

Elevated semicarbazide-sensitive amine oxidase (SSAO) activity in lung with ischemia-reperfusion injury: protective effect of ischemic preconditioning plus SSAO inhibition

Ischemic preconditioning (IP) has been shown to protect the lung against ischemia-reperfusion (I/R) injury. Although the production of reactive oxygen species (ROS) has been postulated to play a crucial role in I/R injury, the sources of these radicals in I/R and the mechanisms of protection in IP remain unknown. Since it was postulated that deamination of endogenous and exogenous amines by semicarbazide-sensitive amine oxidase (SSAO) in tissue damage leads to the overproduction of hydrogen peroxide (H2O2), we investigated the possible contribution of tissue SSAO to excess ROS generation and lipid peroxidation during I/R and IP of the lung. Male Wistar rats were randomized into 6 groups: control lungs were subjected to 30 min of perfusion in absence and presence of SSAO inhibitor, whereas the lungs of the I/R group were subjected to 2 h of cold ischemia following the 30 min of perfusion in absence and presence of SSAO inhibitor. IP was performed by two cycles of 5 min ischemia followed by 5 min of reperfusion prior to 2 h of hypothermic ischemia in absence and presence of SSAO inhibitor. Lipid peroxidation, reduced (GSH) and oxidized (GSSG) glutathione levels, antioxidant enzyme activities, SSAO activity, and H2O2 release were determined in tissue samples of the study groups. Lipid peroxidation, glutathione disulfide (GSSG) content, SSAO activity and H2O2 release were increased in the I/R group, whereas GSH content, GSH/GSSG ratio and antioxidant enzyme activities were decreased. SSAO activity, H2O2 release, GSSG content and lipid peroxidation were markedly decreased in the IP group, whereas GSH content, GSH/GSSG ratio and antioxidant enzyme activities were significantly increased. SSAO activity was found to be positively correlated with H2O2 production in all study groups. Increased lipid peroxidation, SSAO activity, GSSG and H2O2 contents as well as decreased GSH and antioxidant enzyme levels in I/R returned to their basal levels when IP and SSAO inhibition were applied together. The present study suggests that application of IP and SSAO inhibition together may be more effective than IP alone against I/R injury in the lung.

Effect of ischemic preconditioning on reactive oxygen species-mediated ischemia–reperfusion injury in the isolated perfused rat lung

OBJECTIVE

To investigate the protective effect of ischemic preconditioning (IP) in the early phase of reperfusion injury.

DESIGN AND METHODS

Control rat lungs were subjected to 3 h of perfusion, whereas the lungs of the ischemia-then-reperfusion (I/R) group were subjected to 2 h of cold ischemia following 30 min of perfusion. IP was performed by two cycles of 5-min ischemia followed by 5 min of reperfusion prior to 2-h cold ischemia. Lipid peroxidation and antioxidant status were determined in tissue samples.

RESULTS

Lipid peroxidation and reduced/oxidized glutathione (GSH/GSSG) ratio were increased; antioxidant enzyme activities were decreased in the I/R group whereas lipid peroxidation and GSH/GSSG ratio were decreased; antioxidant enzyme activities were increased in the IP group.

CONCLUSION

IP appeared to have a protective effect against reactive oxygen species-mediated I/R injury in isolated rat lung.

Modulation of liver oxidant-antioxidant system by ischemic preconditioning during ischemia/reperfusion injury in rats

AIM: To investigate effects of ischemic pre-conditioning on the liver endogenous oxidant-antioxidant system during ischemia/reperfusion injury.

METHODS: Twenty-four male Sprague-Dawley rats were randomly divided into sham-operated (Sham), ischemia/reperfusion (I/R), ischemic pre-conditioning plus ischemia/reperfusion (IPC) groups. Serum ALT, AST and hyaluronic acid levels were assayed and pathologic alterations observed. Liver malondialdehyde (MDA) contents, endogenous antioxidant enzymes, superoxidase dismutase (SOD), catalase (CAT), gultathionine peroxidase (GSH-Px) activities, neutrophils accumulation marker, myeloperoxidase (MPO) activities were measured respectively.

RESULTS: Compared with I/R group, sinusoidal endothelial cells as well as hepatocytes damages, as assessed biochemically and histochemically, were improved significantly in IPC group; neutrophils infiltration was also markedly reduced. In IPC group, liver peroxidation, as measured by MDA contents, was significantly decreased when compared with I/R group; endogenous antioxidant enzymes, SOD, CAT and GSH-Px activities were markedly higher than that in I/R group.

CONCLUSION: Ischemic pre-conditioning exerts protective effects on both hepatic sinusoidal endothelial cells and hepatocytes during liver I/R injury. Its mechanisms may involve dimunition of neutrophils infiltration and modulation of the imbalance of endogenous oxidant-antioxidant system in the organism.