Induction of different types of cell death after normothermic liver ischemia-reperfusion. Transplant Proc. 2010;42:3977-3980. [PMID: 21168604 DOI: 10.1016/j.transproceed.2010.09.140]

ER stress preconditioning ameliorates liver damage after hemorrhagic shock and reperfusion

The mismatch of oxygen supply and demand during hemorrhagic shock disturbs endoplasmic reticulum (ER) homeostasis. The resulting accumulation of unfolded proteins in the ER lumen, which is a condition that is defined as ER stress, triggers the unfolded protein response (UPR). Since the UPR influences the extent of organ damage following hemorrhagic shock/reperfusion (HS/R) and mediates the protective effects of stress preconditioning before ischemia-reperfusion injury, the current study investigated the mechanisms of ER stress preconditioning and its impact on post-hemorrhagic liver damage. Male C56BL/6-mice were injected intraperitoneally with the ER stress inductor tunicamycin (TM) or its drug vehicle 48 h prior to being subjected to a 90 min pressure-controlled hemorrhagic shock (30±5 mmHg). A period of 14 h after hemorrhagic shock induction, mice were sacrificed. Hepatocellular damage was quantified by analyzing hepatic transaminases and hematoxylin-eosin stained liver tissue sections. Additionally, the topographic expression patterns of the ER stress marker binding immunoglobulin protein (BiP), UPR signaling pathways, and the autophagy marker Beclin1 were evaluated. TM injection significantly increased BiP expression and modified the topographic expression patterns of the UPR signaling proteins. In addition, immunohistochemical analysis of Beclin1 revealed an increased pericentral staining intensity following TM pretreatment. The histologic analysis of hepatocellular damage demonstrated a significant reduction in cell death areas in HS/R+TM (P=0.024). ER stress preconditioning influences the UPR and alleviates post-hemorrhagic liver damage. The beneficial effects were, at least partially, mediated by the upregulation of BiP and autophagy induction. These results underscore the importance of the UPR in the context of HS/R and may help identify novel therapeutic targets.

Interferon Regulatory Factor-1 (IRF1) activates autophagy to promote liver ischemia/reperfusion injury by inhibiting β-catenin in mice

Autophagy is an important factor in liver ischemia-reperfusion injury. In the current study we investigate the function of interferon regulatory factor-1 (IRF1) in regulating autophagy to promote hepatic ischemia reperfusion injury (IR). The high expression of IRF1 during hepatic IR exhibited increased liver damage and was associated with activation of autophagy shown by Western blot markers, as well as immunofluorescent staining for autophagosomes. These effects were diminished by IRF1 deficiency in IRF1 knock out (KO) mice. Moreover, the autophagy inhibitor 3-MA decreased IR-induced liver necrosis and markedly abrogated the rise in liver injury tests (AST/ALT). β-catenin expression decreased during liver IR and was increased in the IRF1 KO mice. Immunoprecipitation assay showed the binding between IRF1 and β-catenin. Overexpression of IRF1 induced autophagy and also inhibited the expression of β-catenin. β-catenin inhibitor increased autophagy while β-catenin agonist suppressed autophagy in primary mouse hepatocytes. These results indicate that IRF1 induced autophagy aggravates hepatic IR injury in part by inhibiting β-catenin and suggests that targeting IRF1 may be an effective strategy in reducing hepatic IR injury.

Ischaemia reperfusion injury in liver transplantation: Cellular and molecular mechanisms

Liver disease causing end organ failure is a growing cause of mortality. In most cases, the only therapy is liver transplantation. However, liver transplantation is a complex undertaking and its success is dependent on a number of factors. In particular, liver transplantation is subject to the risks of ischaemia-reperfusion injury (IRI). Liver IRI has significant effects on the function of a liver after transplantation. The cellular and molecular mechanisms governing IRI in liver transplantation are numerous. They involve multiple cells types such as liver sinusoidal endothelial cells, hepatocytes, Kupffer cells, neutrophils and platelets acting via an interconnected network of molecular pathways such as activation of toll-like receptor signalling, alterations in micro-RNA expression, production of ROS, regulation of autophagy and activation of hypoxia-inducible factors. Interestingly, the cellular and molecular events in liver IRI can be correlated with clinical risk factors for IRI in liver transplantation such as donor organ steatosis, ischaemic times, donor age, and donor and recipient coagulopathy. Thus, understanding the relationship of the clinical risk factors for liver IRI to the cellular and molecular mechanisms that govern it is critical to higher levels of success after liver transplantation. This in turn will help in the discovery of therapeutics for IRI in liver transplantation - a process that will lead to improved outcomes for patients suffering from end-stage liver disease.

Quercetin Pretreatment Attenuates Hepatic Ischemia Reperfusion-Induced Apoptosis and Autophagy by Inhibiting ERK/NF-κB Pathway

Background

Hepatic ischemia reperfusion (IR) injury is a common phenomenon in transplantation or trauma. The aim of the present study was to determine the protective effect of quercetin (QE) on hepatic IR injury via the ERK/NF-κB pathway.

Methods

Mice were randomized into the sham, IR, QE100 + IR, and QE200 + IR groups. Quercetin was administered intragastrically daily at two doses (100 mg/kg and 200 mg/kg) for 5 days prior to IR injury. The expression levels of liver enzymes, inflammatory cytokines, and other marker proteins were determined at 2, 8, and 24 hours after IR. And they were compared among these groups.

Results

Compared with the IR group, the treatment of QE reduced the release of cytokines, leading to inhibition of apoptosis and autophagy via downregulation of the ERK/NF-κB pathway in this model of hepatic IR injury.

Conclusion

Apoptosis and autophagy caused by hepatic IR injury were inhibited by QE following a reduction in the release of inflammatory cytokines, and the relationship between the two may be associated with inactivation of the ERK/NF-κB pathway.

In vivo imaging of hepatic hemodynamics and light scattering property during ischemia-reperfusion in rats based on spectrocolorimetry

A red-green-blue camera-based imaging method is proposed for estimating spatial maps of concentrations of oxyhemoglobin (CHbO), deoxyhemoglobin (CHbR), total hemoglobin (CHbT), tissue oxygen saturation (StO2), and scattering power (b) in liver tissue. Hemodynamic responses to hepatic ischemia-reperfusion of in vivo rat liver tissues induced by portal triad occlusion were evaluated. Upon portal triad occlusion, this method yielded images of decreased CHbO, CHbT, StO2, and b, and increased CHbR followed by a progressive increase in CHbO and StO2 during reperfusion. Time courses of the changes in CHbO, CHbR, CHbT, and StO2 over different regions of interest (ROIs) revealed that ischemia results in an abrupt significant (P<0.05) reduction in CHbO, CHbT, and StO2 with a simultaneous increase in CHbR compared to the baseline level, indicative of the hemodynamic responses during hepatic ischemia-reperfusion. Upon reperfusion, there was a gradual increase in CHbO and StO2, and decrease in CHbR. The change in average scattering power b implies the presence of morphological alterations in the cellular and subcellular structures induced by ischemia or anoxia. This study shows the potential of monitoring spatiotemporal changes in hemodynamic parameters and morphological changes in studies of hepatic pathophysiology.

Role of autophagy related protein Beclin 1 in model of hepatic ischemia-reperfusion injury

Surgical resection is the optimal treatment for primary liver cancer, but surgery is often faced with recession of the liver function reserve, ischemia-reperfusion injury of the residual liver and other disadvantages. Autophagy is a form of programmed cell death after hepatic ischemia-reperfusion, and its role in ischemia-reperfusion injury is a hotspot of research in recent years. In the experimental research of simulated liver ischemia-reperfusion injury, the variation of autophagy related protein Beclin 1 is often detected, which suggests the change of autophagy activity. Many pretreatment methods have been found to be able to reduce the level of Beclin 1 and relieve the hepatic damage in the model of hepatic ischemia-reperfusion injury. Here we discuss the research progress in understanding the role of Beclin 1 in hepatic ischemia-reperfusion injury.

Autophagy and liver ischemia-reperfusion injury

Liver ischemia-reperfusion (I-R) injury occurs during liver resection, liver transplantation, and hemorrhagic shock. The main mode of liver cell death after warm and/or cold liver I-R is necrosis, but other modes of cell death, as apoptosis and autophagy, are also involved. Autophagy is an intracellular self-digesting pathway responsible for removal of long-lived proteins, damaged organelles, and malformed proteins during biosynthesis by lysosomes. Autophagy is found in normal and diseased liver. Although depending on the type of ischemia, warm and/or cold, the dynamic process of liver I-R results mainly in adenosine triphosphate depletion and in production of reactive oxygen species (ROS), leads to both, a local ischemic insult and an acute inflammatory-mediated reperfusion injury, and results finally in cell death. This process can induce liver dysfunction and can increase patient morbidity and mortality after liver surgery and hemorrhagic shock. Whether autophagy protects from or promotes liver injury following warm and/or cold I-R remains to be elucidated. The present review aims to summarize the current knowledge in liver I-R injury focusing on both the beneficial and the detrimental effects of liver autophagy following warm and/or cold liver I-R.

Ethyl pyruvate ameliorates hepatic ischemia-reperfusion injury by inhibiting intrinsic pathway of apoptosis and autophagy

Background. Hepatic ischemia-reperfusion (I/R) injury is a pivotal clinical problem occurring in many clinical conditions such as transplantation, trauma, and hepatic failure after hemorrhagic shock. Apoptosis and autophagy have been shown to contribute to cell death in hepatic I/R injury. Ethyl pyruvate, a stable and simple lipophilic ester, has been shown to have anti-inflammatory properties. In this study, the purpose is to explore both the effect of ethyl pyruvate on hepatic I/R injury and regulation of intrinsic pathway of apoptosis and autophagy. Methods. Three doses of ethyl pyruvate (20 mg/kg, 40 mg/kg, and 80 mg/kg) were administered 1 h before a model of segmental (70%) hepatic warm ischemia was established in Balb/c mice. All serum and liver tissues were obtained at three different time points (4 h, 8 h, and 16 h). Results. Alanine aminotransferase (ALT), aspartate aminotransferase (AST), and pathological features were significantly ameliorated by ethyl pyruvate (80 mg/kg). The expression of Bcl-2, Bax, Beclin-1, and LC3, which play an important role in the regulation of intrinsic pathway of apoptosis and autophagy, was also obviously decreased by ethyl pyruvate (80 mg/kg). Furthermore, ethyl pyruvate inhibited the HMGB1/TLR4/ NF-κb axis and the release of cytokines (TNF-α and IL-6). Conclusion. Our results showed that ethyl pyruvate might attenuate to hepatic I/R injury by inhibiting intrinsic pathway of apoptosis and autophagy, mediated partly through downregulation of HMGB1/TLR4/ NF-κb axis and the competitive interaction with Beclin-1 of HMGB1.

Remifentanil protects liver against ischemia/reperfusion injury through activation of anti-apoptotic pathways

BACKGROUND

Remifentanil protects against ischemia/reperfusion (I/R)-induced organ injury, although its underlying mechanism remains elusive. This study was designed to examine the protective effect of remifentanil preconditioning, if any, against hepatic I/R injury in rats and the underlying mechanism involved.

MATERIALS AND METHODS

Adult Sprague-Dawley rats were randomly divided into sham operation (S group), ischemia/reperfusion (I/R group), and remifentanil preconditioning (R group) groups. Rats in the I/R group were subjected to a partial (70%) hepatic ischemia for 45 min, followed by 1 h, 3 h, and 6 h of reperfusion. Rats in the R group received venous injection of remifentanil (2 μg/kg/min) from 30 min prior to hepatic ischemia to the end of ischemia. Hepatic morphology and apoptosis were examined. Markers of liver damage, oxidative stress, and inflammation were evaluated. Mitochondrial function was assessed using mitochondrial membrane potential and appearance of mitochondrial swelling.

RESULTS

Compared with the S group, rats in the I/R group displayed a massive degenerative death in liver tissues and significantly enhanced cell apoptosis. Remifentanil preconditioning significantly reduced I/R-induced hepatocyte apoptosis. In addition, remifentanil protected against I/R-induced mitochondrial swelling and loss of membrane potential. Remifentanil preconditioning inhibited I/R-induced increases in tumor necrosis factor α, intercellular adhesion molecule 1, and nuclear factor κB p65 levels in liver tissues. Remifentanil preconditioning also inhibited the loss in superoxide dismutase and rise in malondialdehyde levels in liver tissues going through I/R injury.

CONCLUSIONS

Our data revealed that remifentanil preconditioning may turn on multiple cellular pathways in hepatocytes to protect the liver from I/R injury by alleviating hepatic apoptosis.

The glucagon-like peptide-1 receptor agonist Exendin 4 has a protective role in ischemic injury of lean and steatotic liver by inhibiting cell death and stimulating lipolysis

Nonalcoholic fatty liver disease is an increasingly prevalent spectrum of conditions characterized by excess fat deposition within hepatocytes. Affected hepatocytes are known to be highly susceptible to ischemic insults, responding to injury with increased cell death, and commensurate liver dysfunction. Numerous clinical circumstances lead to hepatic ischemia. Mechanistically, specific means of reducing hepatic vulnerability to ischemia are of increasing clinical importance. In this study, we demonstrate that the glucagon-like peptide-1 receptor agonist Exendin 4 (Ex4) protects hepatocytes from ischemia reperfusion injury by mitigating necrosis and apoptosis. Importantly, this effect is more pronounced in steatotic livers, with significantly reducing cell death and facilitating the initiation of lipolysis. Ex4 treatment leads to increased lipid droplet fission, and phosphorylation of perilipin and hormone sensitive lipase - all hallmarks of lipolysis. Importantly, the protective effects of Ex4 are seen after a short course of perioperative treatment, potentially making this clinically relevant. Thus, we conclude that Ex4 has a role in protecting lean and fatty livers from ischemic injury. The rapidity of the effect and the clinical availability of Ex4 make this an attractive new therapeutic approach for treating fatty livers at the time of an ischemic insult.