Cyclosporin A pretreatment in a rat model of warm ischaemia/reperfusion injury

Cyclophilin D as a potential therapeutic target of liver ischemia/reperfusion injury by mediating crosstalk between apoptosis and autophagy

Background

Liver ischemia/reperfusion (I/R) injury is a complex and multifactorial pathophysiological process. It is well recognized that the membrane permeability transition pore (mPTP) opening of mitochondria plays a crucial role in cell death after I/R injury. Cyclophilin D (CypD) is a critical positive regulator of mPTP. However, the effect of CypD on the pathogenesis of liver I/R injury and whether CypD is a potential therapeutic target are still unclear.

Methods

We constructed liver-specific CypD knockout and AAV8-peptidyl prolyl isomerase F (PPIF) overexpression mice. Then, a 70% liver I/R injury model was established in mice, with 90 min of ischemia and 6 h of reperfusion. The liver function was detected by the level of serum glutamic pyruvic transaminase (alanine transaminase) and glutamic oxaloacetic transaminase (aspartate aminotransferase), the liver damage score and degree of necrosis were measured by hematoxylin and eosin (H&E) staining of liver tissues. Reactive oxygen species (ROS) staining, apoptosis, and autophagy-related molecules were used to detect apoptosis and autophagy during liver I/R.

Results

The liver-specific knockout of CypD alleviated necrosis and dysfunction in liver I/R injury, by reducing the excessive production of ROS, and inhibiting cell apoptosis and autophagy. On the contrary, overexpression of CypD exacerbated I/R-induced liver damage.

Conclusion

We found that the downregulation of CypD expression alleviated liver I/R injury by reducing apoptosis and autophagy through caspase-3/Beclin1 crosstalk; in contrast, the upregulation of CypD expression aggravated liver I/R injury. Therefore, interfering with the expression of CypD seems to be a promising treatment for liver I/R injury.

Reperfusion injury as a target for diminishing infarct size

Therapies for preventing reperfusion injury (RI) have been widely studied. However, the attempts to transfer cardioprotective therapies for reducing RI from experiments into clinical practice have been so far unsuccessful. Pathophysiological mechanisms of RI are complicated and compose of many pathways e.g. hypercontracture-mediated sarcolemma rupture, mitochondrial permeability transition pore persistent opening, reactive oxygen species formation, inflammation and no-reflow phenomenon. Based on research, it cannot be determined which mechanism dominates, probably they cooperate with a domination of one or another in different clinical circumstances. Our hypothesis is, that only intervention that at the same time interferes with different (all?) pathways of RI may turn out to be effective in decreasing the final area of infarction.

Quercetin dose affects the fate of hepatic ischemia and reperfusion injury in rats: An experimental research

BACKGROUND

Quercetin found in fruits and vegetables has an antioxidative effect. We aimed to investigate the protective effects of quercetin according to different doses on hepatic and ischemia-reperfusion (I/R) injury.

METHODS

Fifty mature male Sprague-Dawley rats were randomly divided into five groups (n = 10 for each). All the animal groups underwent laparotomy. Group 1 rats served as a sham-operated group. Groups 2-5 underwent 1 h hepatic ischemia and were followed by 2 h reperfusion. Group 3-5 animals received an additional intraperitoneal dose of 25, 50 or 100 mg/kg quercetin respectively before I/R operation. Blood samples were collected for determining serum aspartate transaminase (AST), alanine transaminase (ALT) and malondialdehyde (MDA) levels. Also, liver tissue samples were taken for measuring of liver MDA concentration and for histopathology assessment.

RESULTS

The highest levels of biochemical parameters were observed in group 2. In quercetin-treated groups, serum AST, ALT, MDA levels, and tissue MDA concentration were decreased as inversely with increasing quercetin dose. Microscopic evaluation revealed that most conspicuous histological improvement was observed in 50 mg/kg quercetin co-treated rats. 25 and 100 mg/kg quercetin co-treatment could not protect completely against hepatic I/R injury.

CONCLUSION

Quercetin can be effective in preventing of hepatic I/R injury when the correct dose was used.

Neutralization of CD95 ligand protects the liver against ischemia-reperfusion injury and prevents acute liver failure

Ischemia-reperfusion injury is a common pathological process in liver surgery and transplantation, and has considerable impact on the patient outcome and survival. Death receptors are important mediators of ischemia-reperfusion injury, notably the signaling pathways of the death receptor CD95 (Apo-1/Fas) and its corresponding ligand CD95L. This study investigates, for the first time, whether the inhibition of CD95L protects the liver against ischemia-reperfusion injury. Warm ischemia was induced in the median and left liver lobes of C57BL/6 mice for 45 min. CD95Fc, a specific inhibitor of CD95L, was applied prior to ischemia. Hepatic injury was assessed via consecutive measurements of liver serum enzymes, histopathological assessment of apoptosis and necrosis and caspase assays at 3, 6, 12, 18 and 24 h after reperfusion. Serum levels of liver enzymes, as well as characteristic histopathological changes and caspase assays indicated pronounced features of apoptotic and necrotic liver damage 12 and 24 h after ischemia-reperfusion injury. Animals treated with the CD95L-blocker CD95Fc, exhibited a significant reduction in the level of serum liver enzymes and showed both decreased histopathological signs of parenchymal damage and decreased caspase activation. This study demonstrates that inhibition of CD95L with the CD95L-blocker CD95Fc, is effective in protecting mice from liver failure due to ischemia-reperfusion injury of the liver. CD95Fc could therefore emerge as a new pharmacological therapy for liver resection, transplantation surgery and acute liver failure.

Does necroptosis have a crucial role in hepatic ischemia-reperfusion injury?

Background

Previous studies have demonstrated protective effects of anti-receptor interacting protein kinase 1 (RIP1), a key necroptosis molecule. However, it is uncertain whether necroptosis has a crucial role in hepatic IR injury. Therefore, we evaluated the role of necroptosis in hepatic IR injury.

Method

The IR mice underwent 70% segmental IR injury induced by the clamping of the hepatic artery and portal vein for 1 hr followed by reperfusion for 4 hr. The key necroptosis molecules (RIP1, RIP3, and MLKL) and other key molecules of regulated necrosis (PGAM5 and caspase-1) were evaluated in the warm IR injury model. A RIP1 inhibitor (necrostain-1s) and/or an anti-mitochondrial permeability transition (MPT)-mediated necrosis mediator (cyclosporine A, CyA) were administered before clamping. Necrotic injury was quantified using Suzuki’s scoring system. qRT-PCR and western blot were performed to evaluate RIP1, RIP3, MLKL and PGAM5 expressions.

Results

RIP1, RIP3, MLKL and PGAM5 expression did not change in the hepatic IR injury model. Moreover, Nec1s pretreatment did not improve histology or biochemical markers. The overall Suzuki score (cytoplasmic vacuolization, sinusoidal congestion and hepatocytes necrosis) was increased in the RIP3^(-/-) mice compared to the IR group (3.5 vs. 5, p = 0.026). CyA pretreatment and/or RIP3^(-/-) mice decreased Bax/Bcl2 expression; however, it did lead to an overall change in the levels of AST, ALT and LDH or necrotic injury. The Bax/Bcl2 ratio and the expression of caspase-1 and caspase-3 did not increase in our hepatic IR injury model.

Conclusion

Key necroptosis molecules did not increase in the necrosis-dominant hepatic IR injury model. Anti-necroptosis and/or cyclosporine-A treatment did not have an overall protective effect on necrosis-dominant hepatic IR injury.

Mitochondrial Ca2+ and regulation of the permeability transition pore

The mitochondrial permeability transition pore was originally described in the 1970's as a Ca2+ activated pore and has since been attributed to the pathogenesis of many diseases. Here we evaluate how each of the current models of the pore complex fit to what is known about how Ca2+ regulates the pore, and any insight that provides into the molecular identity of the pore complex. We also discuss the central role of Ca2+ in modulating the pore's open probability by directly regulating processes, such as ATP/ADP balance through the tricarboxylic acid cycle, electron transport chain, and mitochondrial membrane potential. We review how Ca2+ influences second messengers such as reactive oxygen/nitrogen species production and polyphosphate formation. We discuss the evidence for how Ca2+ regulates post-translational modification of cyclophilin D including phosphorylation by glycogen synthase kinase 3 beta, deacetylation by sirtuins, and oxidation/ nitrosylation of key residues. Lastly we introduce a novel view into how Ca2+ activated proteolysis through calpains in the mitochondria may be a driver of sustained pore opening during pathologies such as ischemia reperfusion injury.

Ischemia/Reperfusion

Ischemic disorders, such as myocardial infarction, stroke, and peripheral vascular disease, are the most common causes of debilitating disease and death in westernized cultures. The extent of tissue injury relates directly to the extent of blood flow reduction and to the length of the ischemic period, which influence the levels to which cellular ATP and intracellular pH are reduced. By impairing ATPase-dependent ion transport, ischemia causes intracellular and mitochondrial calcium levels to increase (calcium overload). Cell volume regulatory mechanisms are also disrupted by the lack of ATP, which can induce lysis of organelle and plasma membranes. Reperfusion, although required to salvage oxygen-starved tissues, produces paradoxical tissue responses that fuel the production of reactive oxygen species (oxygen paradox), sequestration of proinflammatory immunocytes in ischemic tissues, endoplasmic reticulum stress, and development of postischemic capillary no-reflow, which amplify tissue injury. These pathologic events culminate in opening of mitochondrial permeability transition pores as a common end-effector of ischemia/reperfusion (I/R)-induced cell lysis and death. Emerging concepts include the influence of the intestinal microbiome, fetal programming, epigenetic changes, and microparticles in the pathogenesis of I/R. The overall goal of this review is to describe these and other mechanisms that contribute to I/R injury. Because so many different deleterious events participate in I/R, it is clear that therapeutic approaches will be effective only when multiple pathologic processes are targeted. In addition, the translational significance of I/R research will be enhanced by much wider use of animal models that incorporate the complicating effects of risk factors for cardiovascular disease. © 2017 American Physiological Society. Compr Physiol 7:113-170, 2017.

The effect of cyclosporine A in hemorrhagic shock model of rats

BACKGROUND

The inhibition of mitochondrial permeability transition pore opening during ischemia-reperfusion can ameliorate injuries. This study aimed to investigate the effects of cyclosporine A (CsA) in rats after hemorrhagic shock.

METHODS

Male Sprague-Dawley rats were subjected to pressure-controlled hemorrhagic shock (mean arterial pressure, 38 ± 1 mm Hg) for 90 minutes. After the hemorrhagic shock period, rats were randomly allocated to one of three groups as follows: a control group, a CsA10 group, or a CsA50 group. CsA for the treatment groups (10 mg/kg for the CsA10 group and 50 mg/kg for the CsA50 group) or normal saline for the control group was administered via tail vein for 10 minutes, and shed blood was transfused for 15 minutes. For the survival study, animals were observed for up to 9 hours, and their survival time was recorded until death. Separate experiments were performed to examine the effect of CsA on inflammatory responses and liver injury. Rats were sacrificed at 210 minutes after the shock period, and blood and liver tissues were harvested.

RESULTS

Survival times were shown to be significantly longer in the CsA-treated groups (i.e., the CsA10 and CsA50 groups) than in the control group. Plasma interleukin-6 and thiobarbituric acid-reactive substances were significantly lower in the CsA50 group than in the control group and phosphorylation of Akt, GSK-3β, and Bad were significantly increased in the CsA-treated groups compared with the control group. Expressions of Bcl-2, cleaved caspase 3, and cytoplasmic cytochrome C were significantly decreased in the CsA-treated groups compared with the control group. Although histologic liver injury was not significantly different among the groups, ultrastructural changes of mitochondria were more prominent in the control group than in the CsA-treated groups.

CONCLUSION

CsA increased survival time, decreased proinflammatory cytokine and lipid peroxidation, and augmented Akt survival pathways in rats subjected to pressure-controlled hemorrhagic shock.

Rodent models of hepatic ischemia-reperfusion injury: time and percentage-related pathophysiological mechanisms

Ischemia and reperfusion (IR) injury remains one of the major problems in liver surgery and transplantation, which determines the viability of the hepatic tissue after resection and of the grafted organ. This review aims to elucidate the mechanisms involved in IR injury of the liver in rodent experimental studies and the preventative methods and pharmacologic agents that have been applied. Many time- and percentage-related liver IR injury rodent models have been used to examine the pathophysiological mechanisms and the parameters implicated with different morbidity, mortality, and pathology findings. The most preferred experimental rodent model of liver IR is the induction of 70% IR for 45 min, which is associated with almost 100% survival. In this model, plasma levels of several parameters such as alanine transaminase, aspartate aminotransferase, gamma-glutamyltransferase, endothelin-1, malonodialdehyde, tumor necrosis factor α, interleukin 1b, inducible nitric oxide synthase, and caspases are increased. The increase of caspases is associated with the initiation of hepatic cellular apoptosis. The main injuries observed 24 h after reperfusion are nuclear pyknosis, cytoplasmic hypereosinophilia, severe necrosis, and loss of intercellular borders. Both ischemic pre- and post-conditioning preventative methods and pharmacologic agents are successfully applied to alleviate the IR injuries. The selection of the time- and percentage-related liver IR injury rodent model and the potential preventative method should be related to the clinical question being answered.

Cell biology of ischemia/reperfusion injury

Disorders characterized by ischemia/reperfusion (I/R), such as myocardial infarction, stroke, and peripheral vascular disease, continue to be among the most frequent causes of debilitating disease and death. Tissue injury and/or death occur as a result of the initial ischemic insult, which is determined primarily by the magnitude and duration of the interruption in the blood supply, and then subsequent damage induced by reperfusion. During prolonged ischemia, ATP levels and intracellular pH decrease as a result of anaerobic metabolism and lactate accumulation. As a consequence, ATPase-dependent ion transport mechanisms become dysfunctional, contributing to increased intracellular and mitochondrial calcium levels (calcium overload), cell swelling and rupture, and cell death by necrotic, necroptotic, apoptotic, and autophagic mechanisms. Although oxygen levels are restored upon reperfusion, a surge in the generation of reactive oxygen species occurs and proinflammatory neutrophils infiltrate ischemic tissues to exacerbate ischemic injury. The pathologic events induced by I/R orchestrate the opening of the mitochondrial permeability transition pore, which appears to represent a common end-effector of the pathologic events initiated by I/R. The aim of this treatise is to provide a comprehensive review of the mechanisms underlying the development of I/R injury, from which it should be apparent that a combination of molecular and cellular approaches targeting multiple pathologic processes to limit the extent of I/R injury must be adopted to enhance resistance to cell death and increase regenerative capacity in order to effect long-lasting repair of ischemic tissues.

Cyclosporin-A does not prevent cold ischemia/reperfusion injury of rat livers

Cyclosporin-A (CsA) has been reported to protect livers from warm ischemia/reperfusion (I/R) injury. To study if CsA has also a protective effect on cold I/R injury, two models were used: the isolated perfused rat liver (IPRL) and the orthotopic rat liver transplantation (ORLT). (1) IPRL: Livers were preserved for 24 h (5°C) in University of Wisconsin (UW) solution alone (group 1), with CsA (400 nM) dissolved in dimethylsulfoxide (50 μM) (group 2), and with dimethylsulfoxide (DMSO) alone (group 3). Livers were reperfused for 60 min (37°C) (n = 8/group). Cell necrosis was evaluated by trypan blue uptake and apoptosis by laddering and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay, and by caspase-3 activation. Marked and similar sinusoidal endothelial cell necrosis was found in the three groups while apoptosis was found similarly deceased in groups 2 and 3 compared with group 1. (2) ORLT: Donors received either CsA (5 mg/kg) or corn oil 24 h before transplantation. Recipients were sacrificed after 240 min; cell necrosis and apoptosis were then evaluated. No difference was found between treated and control groups. The current data strongly suggest that CsA has no protective effect on hepatic cold I/R injury. Hepatocyte apoptosis can be reduced by antioxidants, as occurred with DMSO, but introduction of CsA does not provide additional protective effect.

Molecular Biology of Apoptosis in Ischemia and Reperfusion

This study reviews the current understanding of the mechanisms that mediate the complex processes involved in apoptosis secondary to ischemia and reperfusion (I/R) and is not intended as a complete literature review of apoptosis. Several biochemical reactions trigger a cascade of events, which activate caspases. These caspases exert their effect through downstream proteolysis until the final effector caspases mediate the nuclear features characteristic of apoptosis, DNA fragmentation and condensation. Within the context of ischemia, the hypoxic environment initiates the expression of several genes involved in inflammation, the immune response, and apoptosis. Many of these same genes are activated during reperfusion injury in response to radical oxygen species generation. It is plausible that inhibition of specific apoptotic pathways via inactivation or downregulation of those genes responsible for the initiation of inflammation, immune response, and apoptosis may provide promising molecular targets for ameliorating reperfusion injury in I/R-related processes. Such inhibitory mechanisms are discussed in this review. Important targets in I/R-related pathologies include the brain during stroke, the heart during myocardial infarction, and the organs during harvesting and/or storage for transplantation. In addition, we present data from our ongoing research of specific signal transduction-related elements and their role in ischemia/reperfusion injury. These data address the potential therapeutic application of anti-inflammatory and anti-ischemic compounds in the prevention of I/R damage.

The protective effects of carnosine and melatonin in ischemia-reperfusion injury in the rat liver

The reperfusion following liver ischemia results in hepatocyte damage and apoptosis. The aim of this study was to investigate the effects of two antioxidant agents, carnosine and melatonin, in rat liver ischemia-reperfusion injury. Five study groups were formed; I. sham, II. ischemia-reperfusion, III. ischemia-reperfusion+melatonin, IV. ischemia-reperfusion+carnosine, V. ischemia-reperfusion+melatonin+carnosine. Then 250 mg/kg carnosine and 10 mg/kg melatonin were administered intraperitoneally 30 min before ischemia and immediately after the reperfusion. Sinusoidal dilatation, congestion and neutrophil infiltration were observed in the ischemia-reperfusion group while these symptoms were less pronounced in the treatment groups. Alanine aminotransferase, aspartate aminotransferase and myeloperoxidase levels were increased in the ischemia-reperfusion group while they were lowered in the treatment groups. Glutathione level was low in the ischemia-reperfusion group while it tended to increase in the ischemia-reperfusion+carnosine administered and ischemia-reperfusion+carnosine+melatonin administered groups. There was an increase in the number of apoptotic cells in the ischemia-reperfusion group while this number was lowered in the treatment groups. Carnosine was more effective than melatonin in the reversal of structural and biochemical alterations that resulted from ischemia-reperfusion injury. The administration of melatonin and carnosine together yielded better outcomes compared to the sole administration of each agent.

Necrosis and apoptosis: sequence of liver damage following reperfusion after 60 min ischemia in rats

This study evaluated the time-dependent modes of cell death that occur during the course of reperfusion after 60 min ischemia. The serum ALT level increased immediately after reperfusion, peaked at 6 h and then declined gradually thereafter. This was supported by the H&E staining of the liver tissues taken at 2 h reperfusion, which revealed massive peri-portal necrosis. The succinate driven mitochondrial-swelling rate, release of cytochrome c into the cytoplasm, increase in caspase-3 activity and TUNEL stained tissue were measured to determine the changes in the biochemical markers of apoptosis. The biochemical markers of apoptosis increased by 2 h of reperfusion, peaked at 6 h and remained elevated throughout the 24 h reperfusion period. Cyclosporin A, an inhibitor of the mitochondrial permeability transition (MPT), inhibited MPT opening, the release of cytochrome c and caspase-3 activation. This indicates that necrotic death occurs particularly in the peri-portal region in the initial period of reperfusion, and delayed apoptotic death occurs primarily in the peri-central region in the liver tissues undergoing I/R.

Mitochondrial membrane permeabilization in cell death

Irrespective of the morphological features of end-stage cell death (that may be apoptotic, necrotic, autophagic, or mitotic), mitochondrial membrane permeabilization (MMP) is frequently the decisive event that delimits the frontier between survival and death. Thus mitochondrial membranes constitute the battleground on which opposing signals combat to seal the cell's fate. Local players that determine the propensity to MMP include the pro- and antiapoptotic members of the Bcl-2 family, proteins from the mitochondrialpermeability transition pore complex, as well as a plethora of interacting partners including mitochondrial lipids. Intermediate metabolites, redox processes, sphingolipids, ion gradients, transcription factors, as well as kinases and phosphatases link lethal and vital signals emanating from distinct subcellular compartments to mitochondria. Thus mitochondria integrate a variety of proapoptotic signals. Once MMP has been induced, it causes the release of catabolic hydrolases and activators of such enzymes (including those of caspases) from mitochondria. These catabolic enzymes as well as the cessation of the bioenergetic and redox functions of mitochondria finally lead to cell death, meaning that mitochondria coordinate the late stage of cellular demise. Pathological cell death induced by ischemia/reperfusion, intoxication with xenobiotics, neurodegenerative diseases, or viral infection also relies on MMP as a critical event. The inhibition of MMP constitutes an important strategy for the pharmaceutical prevention of unwarranted cell death. Conversely, induction of MMP in tumor cells constitutes the goal of anticancer chemotherapy.

Alleviation of ischemia-reperfusion injury in rat liver transplantation by induction of small interference RNA targeting Fas

BACKGROUND

Cellular apoptosis plays an important role in ischemia-reperfusion (I/R) injury during organ transplantation. Synthetic small interference RNA (siRNA) targeting apoptotic receptor Fas has proven effective to protect mice against hepatitis and renal I/R injury. The objective of this study is to investigate the silencing impact of Fas siRNA to alleviate I/R injury in rat liver transplantation.

MATERIALS AND METHODS

Rat hepatocytes (BRL cells) were transfected with three pairs of synthesized Fas siRNA; cells untreated and treated with GFP siRNA were taken as blank and siRNA control. The most effective Fas siRNA was chosen for in vivo experiments. Syngeneic orthotopic liver transplantation was performed in Fas siRNA group, siRNA control group, and blank control group of Sprague-Dawley rats. There were 25 pairs of rats in each group. siRNA transfection of donor rats was done with hydrodynamic injection method 48 h before liver procurement. Blood and liver samples were collected for evaluation of serum ALT levels, Fas protein and mRNA expression, and apoptosis by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining, 1, 3, 6, 12, and 24 h after liver transplantation.

RESULTS

Fas siRNA2, which inhibited Fas gene expression much more than other siRNAs, was chosen for in vivo experiment. The serum ALT levels of Fas siRNA group were much less than those of blank and siRNA control groups 1, 3, 6, 12, and 24 h after blood reperfusion, indicating diminishing ischemia-reperfusion injury. Donor livers in Fas siRNA group had substantially less cell apoptosis. The expression of Fas mRNA and protein was reduced dramatically in the Fas siRNA group compared with the other two groups.

CONCLUSION

Fas-mediated apoptosis play an important role in I/R injury of rat liver transplantation. Silencing Fas by hydrodynamic injection of siRNA holds therapeutic promise to limit I/R injury.

Warm ischemia-induced alterations in oxidative and inflammatory proteins in hepatic Kupffer cells in rats

The aim of the study was to investigate the impact of ischemia/reperfusion injury on the proteome of Kupffer cells. Lean Zucker rats (n = 6 each group) were randomized to 75 min of warm ischemia or sham operation. After reperfusion for 8 h, Kupffer cells were isolated by enzymatic perfusion and density gradient centrifugation. Proteins were tryptically digested into peptides and differentially labeled with iTRAQ (isobaric tags for relative and absolute quantitation) reagent. After fractionation by cation exchange chromatography, peptides were identified by mass spectrometry (ESI-LC-MS/MS). Spectra were interrogated against the Swiss-Prot database and quantified using ProteinProspector. The results for heat shock protein 70 and myeloperoxidase were validated by ELISA. Quantitative information for more than 1559 proteins was obtained. In the ischemia group proteins involved in inflammation were significantly up-regulated. The ratio for calgranulin B in the ischemia/sham group was 1.81 +/- 0.97 (p < 0.0001), for complement C3 the ratio was 1.81 +/- 0.49 (p < 0.0001), and for myeloperoxidase the ratio was 1.30 +/- 0.32. Myeloperoxidase was only recently documented in Kupffer cells. The antioxidative proteins Cu,Zn-superoxide dismutase (1.34 +/- 0.19; p < 0.001) and catalase (1.23 +/- 0.43; p < 0.001) were also elevated. In conclusion, ischemia/reperfusion injury induces alterations in the Kupffer cell proteome. Isotope ratio mass spectrometry is a powerful tool to investigate these reactions. The ability to simultaneously monitor several pathways involved in reperfusion stress may result in important mechanistic insight and possibly new treatment options.

Mitochondrial pathway is responsible for aging-related increase of tubular cell apoptosis in renal ischemia/reperfusion injury

Aging-related changes of tubular cell apoptosis and its mechanisms in renal ischemia/reperfusion (I/R) injury are unclear. In the present study, aged (27-month-old) and young (3-month-old) Wistar rats were used to investigate aging-related tubular cell apoptosis in the setting of renal I/R injury. The renal I/R model was induced by clamping bilateral renal arteries for 30 minutes followed by reperfusion for 18 hours. Cyclosporine A (CsA, 2 mg/kg) or mycophenolate mofetil (MMF, 20 mg/kg/d) was used before ischemia. Age-matched sham-operated rats served as controls. We found that tubular cell apoptosis increased more significantly in aged rats than in young rats after renal I/R. More pronounced increases of Bax/Bcl-2 ratio, cytosolic cytochrome c, and caspase-9, which are involved in mitochondria-mediated apoptosis, were found in aged rats than in young rats, and were associated with a more pronounced decrease in superoxide dismutase activity and increase of malondialdehyde content. However, increases of tumor necrosis factor-alpha and caspase-8, two components of death receptor-mediated apoptosis, showed no aging-related differences. Interfering mitochondria and death receptor pathways with CsA and MMF, respectively, reduced the apoptosis in both age groups, whereas CsA was more effective in aged rats. Our results have demonstrated that there was an aging-related increase of tubular cell apoptosis in the renal I/R model, which may be, at least partly, due to an enhanced mitochondrial pathway resulting possibly from increased oxidative stress.

Fas Ligand Expression Following Normothermic Liver Ischemia-Reperfusion

BACKGROUND

The aim of this study was to evaluate the role of the pro-apoptotic molecule Fas Ligand (FasL) in 120 min normothermic ischemia-reperfusion (I-R) induced apoptosis in rat liver treated or not with Z-Asp-cmk caspase inhibitor.

MATERIALS AND METHODS

Rats were divided into two groups: group 1, control, PBS administration; group 2, Z-Asp-cmk treatment. Z-Asp-cmk was injected intravenously, 2 min before induction of 120 min of normothermic liver ischemia. Immunohistochemical detection of apoptotic liver cells was carried out using the TUNEL method. Fas and FasL expression were measured by qualitative reverse transcription polymerase chain reaction (RT-PCR), Northern and western blot, and by immunofluorescence labeling, in ischemic and non-ischemic liver lobes at different times after reperfusion.

RESULTS

FasL mRNA and protein expression were increased in ischemic liver, while Fas receptor mRNA levels remained unchanged. Pre-treatment of rats with Z-Asp-cmk caspase inhibitor reduced liver apoptosis, but did not modify FasL mRNA levels.

CONCLUSIONS

These results suggest that the pro-apoptotic molecule FasL is involved in the induction of liver apoptosis following I-R.

The immunosuppressant drug FK506 prevents Fas-induced apoptosis in human hepatocytes

FK506 is a potent immunosuppressive drug used for the prevention of graft rejection in organ transplantation. Experimental and clinical studies have shown correlations between apoptosis and graft rejection, and apoptosis also plays a role in cell death after ischemia-reperfusion injury in the rat liver. Fas-mediated apoptosis is very likely involved in allograft rejection and experimental evidence has shown a decrease of FasR expression in mouse hepatocytes produced by the drugs. On the basis of these findings we have investigated the protective effect of FK506 in comparison with cyclosporine A (CsA) on Fas-induced apoptosis, by analysing the activation of downstream effector caspases in human hepatocytes. Apoptosis was induced by treatment with agonistic antibodies against FasR, which resulted in a significant activation of caspase-3 after 12 h. Prevention of the downstream activation of the caspase cascade and apoptosis was observed when hepatocytes were pre-treated for 3 h with immunosuppressant drugs. A significant reduction (ca. 30-40%) of caspase-3 activation by 5 microM FK506 and CsA was observed. Along with less activation of caspase-3 a decrease of apoptotic DNA fragmentation was found. In addition, FK506 significantly reduced not only caspase-8 but also caspase-9 activation, to a similar extent as CsA, thus suggesting a protective effect at the mitochondrial level of this drug, as has already been reported for CsA. These effects of FK506 help to explain its strong anti-rejection properties and suggest promising benefits of pharmacological preconditioning on ischemia-reperfusion injury following liver transplantation.

Immunomodulation of hepatic ischemic injury via increased Bcl-X(L) and decreased Bcl-X(S)

BACKGROUND

Although classic ischemia-reperfusion injury is mediated by reactive oxygen intermediaries, increasing evidence implicates a role for immune-mediated apoptosis during ischemic injury in transplantation. Herein, we report the effects of polyclonal rabbit anti-thymocyte globulin (rATG) on mediators of hepatic apoptosis during cold storage.

METHODS

Three-month-old male Lewis rats were placed under halothane anesthesia and the portal vein cannulated. University of Wisconsin (UW) solution (35 ml) with (n = 5) and without (n = 5) 20 mg/kg anti-rat rATG was infused before hepatectomy. The liver was stored in UW solution +/- rATG (143 ng/ml) at 4 degrees C for various times up to 24 h. Specimens were terminal deoxyuridine nick end labeling-stained for apoptosis. Tissue lysates were analyzed by Western blotting and densitometry.

RESULTS

Compared to UW alone, significantly fewer apoptotic cells were present in UW + rATG perfused and stored livers. There were early and sustained significant increases in Bcl-X(L) and decreases in Bcl-X(S) with rATG. There was an initial, but not sustained, significant decrease in Bax with rATG. Moreover, there was a significant one-third decrease in caspase-9 production with rATG at 0, 6, 12, and 18 h.

CONCLUSION

Decreased proapoptotic Bcl-X(S) and increased antiapoptotic Bcl-X(L), as well as decreased downstream proapoptotic caspase-9 expression, during liver ischemia after treatment with rATG, all favor cell survival. Because apoptotic ischemic injury results in allograft dysfunction, preservation strategies that ameliorate such immunological effects may improve organ function.