Ischaemic preconditioning in transplantation and major resection of the liver

Physiological and cellular mechanisms of ischemic preconditioning microRNAs-mediated in underlying of ischemia/reperfusion injury in different organs

Ischemia-reperfusion (I/R) injury, as a pathological phenomenon, takes place when blood supply to an organ is disrupted and then aggravated during restoration of blood flow. Ischemic preconditioning (IPC) is a potent method for attenuating subsequent events of IR damage in numerous organs. IPC protocol is determined by a brief and sequential time periods of I/R before the main ischemia. MicroRNAs are endogenous non-coding RNAs that regulate post-transcriptionally target mRNA translation via degrading it and/or suppressing protein synthesis. This review introduces the physiological and cellular mechanisms of ischemic preconditioning microRNAs-mediated after I/R insult in different organs such as the liver, kidney, heart, brain, and intestine. Data of this review have been collected from the scientific articles published in databases such as Science Direct, Scopus, PubMed, Web of Science, and Scientific Information Database from 2000 to 2023. Based on these literature studies, IPC/IR intervention can affect cellular mechanisms including oxidative stress, apoptosis, angiogenesis, and inflammation through up-regulation or down-regulation of multiple microRNAs and their target genes.

MAPK Signaling Pathways in Hepatic Ischemia/Reperfusion Injury

The mitogen-activated protein kinase signaling pathway can be activated by a variety of growth factors, cytokines, and hormones, and mediates numerous intracellular signals related to cellular activities, including cell proliferation, motility, and differentiation. It has been widely studied in the occurrence and development of inflammation and tumor. Hepatic ischemia-reperfusion injury (HIRI) is a common pathophysiological phenomenon that occurs in surgical procedures such as lobectomy and liver transplantation, which is characterized by severe inflammatory reaction after ischemia and reperfusion. In this review, we mainly discuss the role of p38, ERK1/2, JNK in MAPK family and TAK1 and ASK1 in MAPKKK family in HIRI, and try to find an effective treatment for HIRI.

To Protect Fatty Livers from Ischemia Reperfusion Injury: Role of Ischemic Postconditioning

BACKGROUND

The benefit of ischemic postconditioning (IPostC) might be the throttled inflow following cold ischemia. The current study investigated advantage and mechanisms of IPostC in healthy and fatty rat livers.

METHODS

Male SD rats received a high-fat diet to induce fatty livers. Isolated liver perfusion was performed after 24 h ischemia at 4 °C as well as in vivo experiments after 90 min warm ischemia. The so-called follow-up perfusions served to investigate the hypothesis that medium from IPostC experiments is less harmful. Lactate dehydrogenase (LDH), transaminases, different cytokines, and gene expressions, respectively, were measured.

RESULTS

Fatty livers showed histologically mild inflammation and moderate to severe fat storage. IPostC reduced LDH and TXB₂ in healthy and fatty livers and increased bile flow. LDH, TNF-α, and IL-6 levels in serum decreased after warm ischemia + IPostC. The gene expressions of Tnf, IL-6, Ccl2, and Ripk3 were downregulated in vivo after IPostC.

CONCLUSIONS

IPostC showed protective effects after ischemia in situ and in vivo in healthy and fatty livers. Restricted cyclic inflow was an important mechanism and further suggested involvement of necroptosis. IPostC represents a promising and easy intervention to improve outcomes after transplantation.

microRNAs in liver and kidney ischemia reperfusion injury: insight to improve transplantation outcome

Ischemia reperfusion injury (IRI) is a condition that occurs wherever blood flow and oxygen is reduced or absent, such as trauma, vascular disease, stroke, and solid organ transplantation. This condition can lead to tissue damage, especially during organ transplantation. Under such circumstances, some signaling pathways are activated, leading to up- or down- regulation of several genes such as microRNAs (miRNAs) that might attenuate or ameliorate this status. Therefore, by manipulating miRNAs level, they can be used as a biomarker for early diagnosis of IRI or suggestive to be therapeutic agents in clinical situation in future.

Pringle Maneuver in Extended Liver Resection: A propensity score analysis

Despite the ongoing decades-long controversy, Pringle maneuver (PM) is still frequently used by hepatobiliary surgeons during hepatectomy. The aim of this study was to investigate the effect of PM on intraoperative blood loss, morbidity, and posthepatectomy hemorrhage (PHH). A series of 209 consecutive patients underwent extended hepatectomy (EH) (≥5 segment resection). The association of PM with perioperative outcomes was evaluated using multivariate analysis with a propensity score method to control for confounding. Fifty patients underwent PM with a median duration of 19 minutes. Multivariate analysis revealed that risk of excessive intraoperative bleeding (≥1500 ml; odds ratio [OR] 0.27, 95%-confidence interval [CI] 0.10–0.70, p = 0.007), major morbidity (OR 0.41, 95%-CI 0.18–0.97, p = 0.041), and PHH (OR 0.22, 95%-CI 0.06–0.79, p = 0.021) were significantly lower in PM group after EH. Furthermore, there was no significant difference in 3-year recurrence-free-survival between groups. PM is associated with lower intraoperative bleeding, PHH, and major morbidity risk after EH. Performing PM does not increase posthepatectomy liver failure and does not affect recurrence rate. Therefore, PM seems to be justified in EH.

Mitogen Activated Protein Kinases in Steatotic and Non-Steatotic Livers Submitted to Ischemia-Reperfusion

We analyzed the participation of mitogen-activated protein kinases (MAPKs), namely p38, JNK and ERK 1/2 in steatotic and non-steatotic livers undergoing ischemia-reperfusion (I-R), an unresolved problem in clinical practice. Hepatic steatosis is a major risk factor in liver surgery because these types of liver tolerate poorly to I-R injury. Also, a further increase in the prevalence of steatosis in liver surgery is to be expected. The possible therapies based on MAPK regulation aimed at reducing hepatic I-R injury will be discussed. Moreover, we reviewed the relevance of MAPK in ischemic preconditioning (PC) and evaluated whether MAPK regulators could mimic its benefits. Clinical studies indicated that this surgical strategy could be appropriate for liver surgery in both steatotic and non-steatotic livers undergoing I-R. The data presented herein suggest that further investigations are required to elucidate more extensively the mechanisms by which these kinases work in hepatic I-R. Also, further researchers based in the development of drugs that regulate MAPKs selectively are required before such approaches can be translated into clinical liver surgery.

Indirubin and NAD+ prevent mitochondrial ischaemia/reperfusion damage in fatty livers

BACKGROUND

Fatty livers are considerably more susceptible to acute stressors, such as ischaemia/reperfusion (I/R). As the incidence of I/R is high due to surgical events and some pathologies, there is an urgent need to find strategies against I/R injury (I/RI) in fatty livers. We postulate that an acute pretreatment with indirubin-3'-oxime (Ind) or NAD+ prevents mitochondrial dysfunction associated with warm I/RI in fatty livers.

MATERIALS AND METHODS

Zucker fatty rats were subjected to warm ischaemia and 12 hours of reperfusion. Ind or NAD+ was administered in the hepatic artery 30 minutes before ischaemia. Hepatic mitochondrial isolation was performed, and functional assays as well as molecular analysis were performed.

RESULTS

Pretreatment decreased markers of liver injury while preserving mitochondrial cytochrome c content, which is related to the prevention of calcium-induced mitochondrial permeability transition (mPT), the decline in mitochondrial respiratory state 3 and ATP content. The generation of reactive oxygen species (ROS) was also diminished. Inhibition of GSK-3ß by Ind resulted in the prevention of cyclophilin-D (CypD) phosphorylation, unabling it to bind to the adenine nucleotide translocator (ANT), thus, preventing mPT induction. Furthermore, deacetylation of CypD at Lys residue by sirtuin 3 (SIRT3) caused its dissociation from ANT, contributing to an increase in mPT threshold in NAD+ -pretreated animals.

CONCLUSIONS

Pretreatment with Ind or NAD+ protects fatty livers by maintaining mitochondrial calcium homoeostasis, thus, preserving mitochondrial function and energetic balance. As such, CypD might be a new protective target against I/RI in fatty livers.

miR-494 up-regulates the PI3K/Akt pathway via targetting PTEN and attenuates hepatic ischemia/reperfusion injury in a rat model

A rat HIRI model was constructed and treated with an intraperitoneal injection of agomir-miR-494 or agomir-NC (negative control) for 7 days after the surgery. The pathophysiological changes in sham-operated rats, HIRI, HIRI + agomir-miR-494, and HIRI + agomir-NC were compared. The effect of miR-494 was also assessed in an H₂O₂-induced apoptosis model. Hepatic AML12 cells were transfected with mimics NC or miR-494 mimics, followed by 6-h H₂O₂ treatment. Cell proliferation and apoptosis were detected by CCK8 assay and flow cytometry, respectively. Further, the miR-494 target gene was identified by luciferase reporter assay, and verified both in vitro and in vivo experiments. The activity of AKT pathway was further analyzed in vivo by Western blot. HIRI + agomir-miR-494 rats exhibited significantly higher miR-494 expression, lower serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), and glutamate dehydrogenase (GLDH) level, lower hepatic MDA, TOA, and OSI, alleviated hepatic necrosis, reduced hepatocyte apoptosis, and decreased expression of apoptosis-related proteins, when compared with HIRI + agomir-NC rats (P<0.05 or 0.01). After H₂O₂ treatment, AML-12 cells transfected with miR-494 mimics had significantly higher proliferation and lower apoptosis rate compared with mimics NC group (P<0.01). PTEN was identified as an miR-494 target gene. PTEN expression was significantly down-regulated in AML12 cells transfected with miR-494 mimics, and was up-regulated by treatment of miR-494 inhibitor (P<0.01). Moreover, HIRI + agomir-miR-494 rats exhibited significantly lower PTEN expression, and higher p-AKT, p-mTOR, and p-p70S6K levels compared with HIRI + agomir-NC rats. Therefore, miR-494 protected rats against hepatic ischemia/reperfusion (I/R) injury through down-regulating its downstream target gene PTEN, leading to the activation of PI3K/AKT signaling pathway.

NKT cells are important mediators of hepatic ischemia-reperfusion injury

Introduction

IRI results from the interruption then reinstatement of an organ's blood supply, and this poses a significant problem in liver transplantation and resectional surgery.

In this paper, we explore the role T cells play in the pathogenesis of this injury.

Materials & methods

We used an in vivo murine model of warm partial hepatic IRI, genetically-modified mice, in vivo antibody depletion, adoptive cell transfer and flow cytometry to determine which lymphocyte subsets contribute to pathology. Injury was assessed by measuring serum alanine aminotransfersase (ALT) and by histological examination of liver tissue sections.

Results

The absence of T cells (CD3εKO) is associated with significant protection from injury (p = 0.010). Through a strategy of antibody depletion it appears that NKT cells (p = 0.0025), rather than conventional T (CD4 + or CD8 +) (p = 0.11) cells that are the key mediators of injury.

Discussion

Our results indicate that tissue-resident NKT cells, but not other lymphocyte populations are responsible for the injury in hepatic IRI. Targeting the activation of NKT cells and/or their effector apparatus would be a novel approach in protecting the liver during transplantation and resection surgery; this may allow us to expand our current criteria for surgery.

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Hepatic IRI worsens outcome in liver transplantation.

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T cells are important in hepatic IRI.

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These are tissue-resident rather than recruited T cells.

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NKT, but not conventional T or NK cells, are key mediators of hepatic IRI.

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Targeting NKT activation or their effector apparatus may offer therapeutic potential.

Lidocaine Administration Controls MicroRNAs Alterations Observed After Lung Ischemia-Reperfusion Injury

BACKGROUND

Ischemia-reperfusion injury (IRI) is associated with morbidity and mortality. MicroRNAs (miRNAs) have emerged as regulators of IRI, and they are involved in the pathogenesis of organ rejection. Lidocaine has proven anti-inflammatory activity in several tissues but its modulation of miRNAs has not been investigated. This work aims to investigate the involvement of miRNAs in lung IRI in a lung auto-transplantation model and to investigate the effect of lidocaine.

METHODS

Three groups (sham, control, and Lidocaine), each comprising 6 pigs, underwent a lung autotransplantation. All groups received the same anesthesia. In addition, animals of lidocaine group received a continuous intravenous administration of lidocaine (1.5 mg/kg/h) during surgery. Lung biopsies were taken before pulmonary artery clamp, before reperfusion, 30 minutes postreperfusion (Rp-30), and 60 minutes postreperfusion (Rp-60). Samples were analyzed for different miRNAs (miR-122, miR-145, miR-146a, miR-182, miR-107, miR-192, miR-16, miR-21, miR-126, miR-127, miR142-5p, miR152, miR155, miR-223, and let7) via the use of reverse-transcription quantitative polymerase chain reaction. Results were normalized with miR-103.

RESULTS

The expression of miR-127 and miR-16 did not increase after IRI. Let-7d, miR-21, miR-107, miR-126, miR-145, miR-146a, miR-182, and miR-192 significantly increased at the Rp-60 (control versus sham P < .001). miR-142-5p, miR-152, miR-155, and miR 223 significantly increased at the Rp-30 (control versus sham P < .001) and at the Rp-60 (control versus. sham P < .001). The administration of lidocaine was able to attenuate these alterations in a significant way (control versus Lidocaine P < .001).

CONCLUSIONS

Lung IRI caused dysregulation miRNA. The administration of lidocaine reduced significantly miRNAs alterations.

Effects of remifentanil on hemodynamics, liver function and ICAM-1 expression in liver cancer patients undergoing surgery

The objective of the present study was to investigate the effects of remifentanil on hemodynamics, liver function, and expression of intercellular adhesion molecule-1 (ICAM-1) in patients with liver cancer undergoing surgery. A total of 60 patients who underwent liver cancer resection in The First People's Hospital of Xiangyang, Hubei University of Medicine from January 2014 to January 2016 were selected, including 33 males and 27 females, with an average age of 54.12±4.77 years. Patients were randomly divided into the control group and experimental group (n=30 each). The control group and experimental group were anesthetized with propofol/isoflurane and remifentanil/propofol, respectively. In addition to general parameters, the following parameters were analyzed: mean systolic blood pressure and mean diastolic blood pressure were obtained before treatment, during anesthesia induction and intubation, during blockade of traction reflexes in surgery, and before extubation at the end of surgery. The recovery time from anesthesia withdrawal to spontaneous breathing, time of eye opening, time of extubation, and level of consciousness were recorded. Liver expression of ICAM-1 was measured with SABC staining, and the expression of aspartate aminotransferase (AST), alanine aminotransferase (ALT), and total bilirubin (TBIL) were recorded on the first, third, fifth, and seventh day after surgery. According to hemodynamic parameters, patients in the experimental group experienced a more stable condition than patients in the control group (P<0.05). In addition, the recovery time of the experimental group was shorter than that of the control group (P<0.05). Markers of liver function (AST, ALT and TBIL) of the two groups after surgery were higher than those before surgery, and the increases of the experimental group were significantly lower than those of the control group. ICAM-1 expression in the experimental group was significantly lower than in the control group (P<0.05). In conclusion, anesthesia with remifentanil better maintained the stability of hemodynamics, played a protective role against hepatic ischemia-reperfusion injury, and reduced ICAM-1 expression.

Liver resections can be performed safely without Pringle maneuver: A prospective study

AIM

To evaluate liver resections without Pringle maneuver, i.e., clamping of the portal triad.

METHODS

Between 9/2002 and 7/2013, 175 consecutive liver resections (n = 101 major anatomical and n = 74 large atypical > 5 cm) without Pringle maneuver were performed in 127 patients (143 surgeries). Accompanying, 37 wedge resections (specimens < 5 cm) and 43 radiofrequency ablations were performed. Preoperative volumetric calculation of the liver remnant preceeded all anatomical resections. The liver parenchyma was dissected by water-jet. The median central venous pressure was 4 mmHg (range: 5-14). Data was collected prospectively.

RESULTS

The median age of patients was 60 years (range: 16-85). Preoperative chemotherapy was used in 70 cases (49.0%). Liver cirrhosis was present in 6.3%, and liver steatosis of ≥ 10% in 28.0%. Blood loss was median 400 mL (range 50-5000 mL). Perioperative blood transfusions were given in 22/143 procedures (15%). The median weight of anatomically resected liver specimens was 525 g (range: 51-1850 g). One patient died postoperatively. Biliary leakages (n = 5) were treated conservatively. Temporary liver failure occurred in two patients.

CONCLUSION

Major liver resections without Pringle maneuver are feasible and safe. The avoidance of liver inflow clamping might reduce liver damage and failure, and shorten the hospital stay.

Reperfusion Syndrome: Cellular Mechanisms of Microvascular Dysfunction and Potential Therapeutic Strategies

Reperfusion injury is the paradoxical and complex phenomenon of exacerbation of cellular dysfunction and increase in cell death after the restoration of blood flow to previously ischemic tissues. It involves biochemical and cellular changes causing oxidant production and complement activation, which culminates in an inflammatory response, mediated by neutrophil and platelet cell interactions with the endothelium and among the cells themselves. The mounted inflammatory response has both local and systemic manifestations. Despite improvements in imaging, interventional techniques, and pharmacological agents, morbidity from reperfusion remains high. Extensive research has furthered the understanding of the various pathophysiological mechanisms involved and the development of potential therapeutic strategies. Preconditioning has emerged as a powerful method of ameliorating ischemia reperfusion injury to the myocardium and in transplant surgery. More recently, postconditioning has been shown to provide a therapeutic counter to vasoocclusive emergencies. More research and well-designed trials are needed to bridge the gap between experimental evidence and clinical implementation.

Global MicroRNA Expression Profiling of Mouse Livers following Ischemia-Reperfusion Injury at Different Stages

Hepatic ischemia-reperfusion injury is a dynamic process consisting of two stages: ischemia and reperfusion, and triggers a cascade of physiological and biochemical events. Given the important role of microRNAs in regulating gene expression, we analyzed gene expression changes in mouse livers at sham control, ischemia stage, and reperfusion stage. We generated global expression profiles of microRNA and mRNA genes in mouse livers subjected to ischemia-reperfusion injury at the three stages, respectively. Comparison analysis showed that reperfusion injury had a distinct expression profile whereas the ischemia sample and the sham control were clustered together. Consistently, there are 69 differentially expressed microRNAs between the reperfusion sample and the sham control whereas 28 differentially expressed microRNAs between the ischemia sample and the sham control. We further identified two modes of microRNA expression changes in ischemia-reperfusion injury. Functional analysis of both the differentially expressed microRNAs in the two modes and their target mRNAs revealed that ischemia injury impaired mitochondrial function, nutrient consumption, and metabolism process. In contrast, reperfusion injury led to severe tissue inflammation that is predominantly an innate-immune response in the ischemia-reperfusion process. Our staged analysis of gene expression profiles provides new insights into regulatory mechanisms of microRNAs in mouse hepatic IR injury.

Spironolactone Effect in Hepatic Ischemia/Reperfusion Injury in Wistar Rats

Introduction. Ischemia/reperfusion (IR) injury, often associated with liver surgery, is an unresolved problem in the clinical practice. Spironolactone is an antagonist of aldosterone that has shown benefits over IR injury in several tissues, but its effects in hepatic IR are unknown. Objective. To evaluate the effect of spironolactone on IR-induced damage in liver. Materials and Methods. Total hepatic ischemia was induced in rats for 20 min followed by 60 min of reperfusion. Spironolactone was administered and hepatic injury, cytokine production, and oxidative stress were assessed. Results. After IR, increased transaminases levels and widespread acute inflammatory infiltrate, disorganization of hepatic hemorrhage trabeculae, and presence of apoptotic bodies were observed. Administration of SPI reduced biochemical and histological parameters of liver injury. SPI treatment increased IL-6 levels when compared with IR group but did not modify either IL-1β or TNF-α with respect to IR group. Regarding oxidative stress, increased levels of catalase activity were recorded in IR + SPI group in comparison with group without treatment, whereas MDA levels were similar in IR + SPI and IR groups. Conclusions. Spironolactone reduced the liver damage induced by IR, and this was associated with an increase in IL-6 production and catalase activity.

Hypoxia preconditioning induced HIF-1α promotes glucose metabolism and protects mitochondria in liver I/R injury

BACKGROUND

Ischemia and reperfusion (I/R) injury is one of the main lesions after liver transplantation. This study aims to detect hypoxia-induced HIF-1α protects transplanted liver against I/R injury by promoting glucose metabolism to decrease mitochondrial injury and apoptosis on rat model.

METHODS

The rats were given a treatment of 90 min non-lethal hypoxic preconditioning to induce and increase the HIF-1α expression. The autologous orthotopic liver transplantation model was used to imitate liver I/R injury.

RESULTS

Hypoxic-induced HIF-1α was detected to increase in liver tissue after 90-minute hypoxic environment (HP vs. Ctrl, *P<0.001). After operation, the expression of HIF-1α in liver tissue was also stayed at a high level. At 24h after operation, several genes were promoted, such as the levels of HK-2 (HP vs. AT, 24h, *P=0.004), Lactate dehydrogenase (LDHA) (HP vs. AT, 24h, *P=0.003), pyruvate dehydrogenase kinase (PDK-1) (HP vs. AT, 24h, *P=0.007), even the NF-κB and Erk pathways. From the TUNEL assay, the apoptosis in hypoxic preconditioning liver tissue was decreased compared with non-HP operative group at 12h after operation. The expressions of cleaved-caspase 3 (HP vs. AT, *P=0.0119) and PARP (HP vs. AT, *P=0.0134) in HP group were also significantly lower than AT group.

CONCLUSION

The hypoxia-induced HIF-1α could promote glucose metabolism to protect hepatocellular mitochondria from damage. It could be a useful way to protect liver against I/R injuries and inflammatory injury, and particularly promote the recovery of graft function.

Comparative Effects of Ischemic Preconditioning and Iron Chelation in Hepatectomy

PURPOSE/AIM

Major hepatectomies can result in severe ischemia/reperfusion (I/R) injury of the liver. The aim of this survey is to comparatively evaluate the effects of a surgical and a pharmacological hepatoprotective modality on the liver remnant in a porcine model of hepatectomy.

MATERIAL AND METHODS

Twenty-one Landrace pigs were randomly divided into three groups: a control group (CON) (n = 7), an Ischemic Preconditioning (PRE) group (n = 7) and a Desferoxamine (DFX) treated one (n = 7). Animals were subjected to 120 min of liver ischemia with subsequent 75% hepatectomy followed by 24-hr reperfusion. In all animals, continuous intracranial pressure (ICP) monitoring was employed. Blood samples were collected at t0, t6, t12, and t24 hrs after reperfusion. Liver remnant specimens were excised for histological examination.

RESULTS

In the PRE group, ICP was statistically lower at t6 time point compared to CON group and in comparison with t0. In addition, ICP was significantly lower at all-time points after reperfusion in the DFX group. Finally, with regard to DFX and PRE group correlation, ICP was significantly lower at t0, t12, and t24 time points after reperfusion in the DFX group. In the PRE group, NH3 levels were significantly lower at t12 after reperfusion compared to CON and DFX groups. Histological evaluation elucidated significantly less hepatocellular necrosis, apoptosis, and degeneration in the PRE and DFX groups correlated to CON group.

CONCLUSIONS

Both hepatoprotective modalities including PRE and DFX administration are associated with lower ICP levels and correlated with attenuated liver remnant injury.

A role of microRNA-370 in hepatic ischaemia-reperfusion injury by targeting transforming growth factor-β receptor II

BACKGROUND & AIMS

MicroRNAs (miRNAs) are a group of small non-coding RNAs with modulator activity of gene expression. The role of miRNAs in hepatic ischaemia-reperfusion (IR) injury is currently largely unknown. The aim of this study was to investigate the potential role of miR-370 in hepatic IR injury.

METHODS

The expression levels of hepatic miR-370 in male C57BL/6 mice subjected to hepatic IR injury or ischaemia preconditioning were assessed by quantitative real-time PCR. The effect of miR-370 on hepatic IR injury was investigated by serum enzyme analysis and histological examination of liver following treatment of mice with antagomir-370 or control. The levels of proinflammatory cytokines and apoptosis- and proliferation-related genes were also determined by quantitative real-time PCR. Furthermore, the potential targets of miR-370 in this injury were studied by bioinformatics analysis, luciferase assays, quantitative real-time PCR and Western blot.

RESULTS

The results showed that miR-370 expression was significantly upregulated in the mice subjected to hepatic IR injury as compared with the sham-operated mice. Inhibition of miR-370 led to the downregulation of serum aminotransferase and proinflammatory cytokines, as well as the improvement of hepatic histological damage. Reporter assays confirmed that miR-370 directly targeted the 3' untranslated region of transforming growth factor-β receptor II (TβRII). Inhibition of miR-370 was sufficient to reinstate the expression of TβRII and its downstream target phosphorylated Smad3.

CONCLUSION

Our data suggest that miR-370 acting via TβRII might play a potential role in hepatic IR injury, and inhibition of miR-370 efficiently attenuated the damage to the liver.

Some mechanisms of the protective effect of ischemic preconditioning on rat liver ischemia-reperfusion injury

Ischemia-reperfusion (I/R) injury is a multifactorial process that affects graft function after liver transplantation. An understanding of the mechanisms involved in I/R injury is essential for the design of therapeutic strategies to improve the outcome of liver transplantation. The generation of reactive oxygen species subsequent to reoxygenation inflicts tissue damage and initiates a cascade of deleterious cellular responses, leading to inflammation, cell death, and ultimate organ failure. Increasing experimental evidence has suggested that Kupffer cells and T-cells mediate activation of neutrophil inflammatory responses. Activated neutrophils infiltrate the injured liver in parallel with increased expression of adhesion molecules on endothelial cells. The heme oxygenase system is among the most critical of the cytoprotective mechanisms activated during cellular stress, exerting antioxidant and anti-inflammatory functions, modulating the cell cycle, and maintaining the microcirculation. Finally, the activation of toll-like receptors on Kupffer cells may play a fundamental role in exploring new therapeutic strategies based on the concept that hepatic I/R injury represents a case for host “innate” immunity. In the present study, there was a significant decrease in hepatic activity of glycogen in the I/R group as compared with corresponding values in the control group. On the other hand, there was a significant increase in the hepatic activity of glycogen in the I/R-IP (ischemic preconditioning) group as compared with corresponding values in the I/R group.

MiR-124 protects human hepatic L02 cells from H2O2-induced apoptosis by targeting Rab38 gene

BACKGROUND

Hepatic ischemia reperfusion injury (IRI) is an inevitable clinical problem for liver surgeons. Because microRNAs (miRNAs) participate in various hepatic pathophysiological processes, this study aimed to explore the role and potential mechanism of miR-124 in hepatic IRI.

METHODS

A liver IRI model was established in rats. The differential expression of miRNAs was detected using microarrays, and the expression of miR-124 was measured by qRT-PCR. A hydrogen peroxide (H2O2)-induced oxidative stress apoptosis model was also established. Cell apoptosis was detected by flow cytometry, and viability was detected by CCK8. The expression of Rab38 was detected by Western blotting and qRT-PCR, and a luciferase reporter assay was used to verify the expression of the miR-124 target gene.

RESULTS

The miRNA spectrum changes dramatically after hepatic IRI in rats, and miR-124 is significantly down-regulated after liver IRI. MiR-124 decreases the H2O2-induced apoptosis of human hepatic L02 cells by up-regulating the activation of the AKT pathway. Rab38 is a target gene of miR-124 and is involved in H2O2-induced apoptosis. Interference with the expression of the Rab38 gene can protect hepatic L02 from H2O2-induced apoptosis by increasing the phosphorylation of AKT. These protective effects of miR-124 are attenuated by over-expression of Rab38.

CONCLUSIONS

Many miRNAs are involved in hepatic IRI in rats, and miR-124 is significantly decreased in this model. MiR-124 significantly decreases the H2O2-induced apoptosis of human hepatic L02 cells by targeting the Rab38 gene and activating the AKT pathway.

Systematic review of pathophysiological changes following hepatic resection

OBJECTIVES

Major hepatic resection is now performed frequently and with relative safety, but is accompanied by significant pathophysiological changes. The aim of this review is to describe these changes along with interventions that may help reduce the risk for adverse outcomes after major hepatic resection.

METHODS

The MEDLINE, EMBASE and CENTRAL databases were searched for relevant literature published from January 2000 to December 2011. Broad subject headings were 'hepatectomy/', 'liver function/', 'liver failure/' and 'physiology/'.

RESULTS

Predictable changes in blood biochemistry and coagulation occur following major hepatic resection and alterations from the expected path indicate a complicated course. Susceptibility to sepsis, functional renal impairment, and altered energy metabolism are important sequelae of post-resection liver failure.

CONCLUSIONS

The pathophysiology of post-resection liver failure is difficult to reverse and thus strategies aimed at prevention are key to reducing morbidity and mortality after liver surgery.

Effects of andiroba (Carapa guianensis) oil on hepatic function of rats subjected to liver normothermic ischemia and reperfusion

OBJECTIVE

To evaluate the effects of the Andiroba (carapa guianensis) oil on liver function in rats subjected to normothermic ischemia / reperfusion injury.

METHODS

we divided 12 Wistar rats into two groups: saline (n = 6) and Andiroba (n = 6). The Andiroba group was treated with Andiroba oil (0.63 ml/kg orally) for seven days before surgery. Ischemia was induced by occlusion of the blood supply to the lateral and median lobes of the liver, using vascular clips, in both groups, for 45min, followed by reperfusion for 60 minutes later. We analyzed dosages of AST, ALT, Gamma-GT, and liver biodistribution of 99mTc phytate.

RESULTS

There was no significant difference in the percentage of radioactivity / gram of tissue (%ATI/g) in the right lobe of the saline group (17.53 ± 2.78) compared with the Andiroba group (18.04 ± 3.52) p = 0.461, the same occurring in the%ATI/g of the left lobe of the liver when the two groups were compared (p = 0.083). In the saline group, the%ATI/g was significantly higher in the non-ischemic right hepatic lobe (17.53 ± 2.78) when compared with the left lobe (5.04 ± 0.82) that suffered ischemia / reperfusion (p = 0.002). Significant differences also occurred when comparing the right (18.04 ± 3.52) and left (7.11 ± 1.86) lobes of the animals of the Andiroba group (p = 0.004). There was no significant difference in dosages of AST, ALT and Gamma- GT when comparing the two groups (p > 0.05).

CONCLUSION

Andiroba oil did not contribute to the protection of liver function in a rat model of liver injury induced by normothermic ischemia and reperfusion.

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.

Reestablishment of ischemia-reperfusion liver injury by N-acetylcysteine administration prior to a preconditioning iron protocol

The role of iron (Fe)-induced prooxidant status in Fe preconditioning against ischemia (1 h)-reperfusion (20 h) induced liver injury was assessed using N-acetylcysteine (NAC) (1 g/kg) before Fe (50 mg/kg), given to male Sprague Dawley rats on alternate days during 10 days. IR significantly increased serum aspartate transaminase (AST) and alanine transaminase (ALT) levels, with drastic changes in liver histology, hepatic glutathione depletion, and nuclear factor-κB (NF-κB) p65 diminution (P < 0.05) (ELISA). Fe-induced liver oxidative stress, as evidenced by higher protein carbonyl/glutathione content ratios (P < 0.05) at days 11 and 12 after treatment, was abolished by NAC. Under these conditions, short-term Fe administration exerted significant protection against IR liver injury, as shown by 85% and 60% decreases in IR-induced serum AST and ALT (P < 0.05), respectively, and normalization of hepatic histology, glutathione levels, and NF-κB activation, changes that were suppressed by NAC administration prior to Fe. Results of this study indicate that NAC administration prior to an iron protocol reestablishes IR liver injury, supporting the role of Fe-induced transient oxidative stress in hepatoprotection and its potential clinical application.

Hepatic ischemia and reperfusion injury and trauma: current concepts

Context

Ischemia-reperfusion injury is a fascinating topic which has drawn a lot of interest in the last several years. Hepatic ischemia reperfusion injury may occur in a variety of clinical situations. These include transplantation, liver resection, trauma, and vascular surgery.

Evidence Acquisition

The purpose of this review was to outline the molecular mechanisms underlying hepatic I/R injury and present the latest approaches, both surgical and pharmacological, regarding the prevention of it. A comprehensive electronic literature search in MEDLINE/PubMed was performed to identify relative articles published within the last 2 years.

Results

The basic mechanism of hepatic ischemia – reperfusion injury is one of blood deprivation during ischemia, followed by the return of flow during reperfusion. It involves a complex series of events, such as mitochondrial deenergization, adenosine-5'-triphosphate depletion, alterations of electrolyte homeostasis, as well as Kupffer cell activation, oxidative stress changes and upregulation of proinflammatory cytokine signaling. The great number of variable pathways, with several mediators interacting with each other, leads to a high number of candidates for potential therapeutic intervention. As far as surgical approaches are concerned, the modification of existing clamping techniques and the ischemic preconditioning are the most promising techniques till recently. In the search for novel techniques of protecting against hepatic ischemia reperfusion injury, many different strategies have been used in experimental models. The biggest part of this research lies around antioxidant therapy, but other potential solutions have been explored as well.

Conclusions

The management of hepatic trauma, in spite of the fact that it has become increasingly nonoperative, there still remains the possibility of hepatic resection in the hepatic trauma setting, especially in severe injuries. Hence, clinicians should be familiar with the concept of hepatic ischemia-reperfusion injury and respond appropriately and timely.

Extracorporeal membrane oxygenation for resuscitation of deceased cardiac donor livers for hepatocyte isolation

BACKGROUND

Deceased cardiac donors (DCDs) have become a useful source of organs for liver transplantation; nevertheless, there are concerns about the longevity of these grafts. The aim of this study was to evaluate the use of extracorporeal membrane oxygenation (ECMO) to resuscitate DCD porcine livers as a preclinical model using hepatocyte isolation and viability as a marker to assess whole-graft preservation.

MATERIALS AND METHODS

We randomized Landrace pigs into three groups after cardiac death and 30 min of warm ischemia: group 1, peritoneal cooling with intravascular cooling for 2 h; group 2, ECMO for 2 h; and group 3, control (conventional intravascular cooling and retrieval). We then reperfused group 1 and 2 livers for 2 h on an ex vivo reperfusion circuit and isolated hepatocytes.

RESULTS

After reperfusion, hepatocyte viability was significantly improved in the ECMO group compared to the cooling groups, as measured by trypan blue, methylthiazolyldiphenyl-tetrazolium bromide, and seeding efficiency. Glycogen and reduced glutathione content were significantly used in the ECMO group both before and after reperfusion compared with group 2. The adenosine diphosphate:adenosine triphosphate ratio showed an improved trend (lower) in the ECMO group compared with the cooling group but did not reach statistical significance either before or after reperfusion.

CONCLUSIONS

This preclinical study suggests that ECMO is a viable technique for liver preservation that gives an improved yield of hepatocytes when isolated from a DCD liver, suggesting improved liver preservation.

Immediately transcripted genes in various hepatic ischemia models

PURPOSE

To elucidate the characteristic gene transcription profiles among various hepatic ischemia conditions, immediately transcribed genes and the degree of ischemic injury were compared among total ischemia (TI), intermittent clamping (IC), and ischemic preconditioning (IPC).

METHODS

Sprague-Dawley rats were equally divided into control (C, sham-operated), TI (ischemia for 90 minutes), IC (ischemia for 15 minutes and reperfusion for 5 minutes, repeated six times), and IPC (ischemia for 15 minutes, reperfusion for 5 minutes, and ischemia again for 90 minutes) groups. A cDNA microarray analysis was performed using hepatic tissues obtained by partial hepatectomy after occluding hepatic inflow.

RESULTS

THE CDNA MICROARRAY REVEALED THE FOLLOWING: interleukin (IL)-1β expression was 2-fold greater in the TI group than in the C group. In the IC group, IL-1α/β expression increased by 2.5-fold, and Na+/K+ ATPase β1 expression decreased by 2.4-fold. In the IPC group, interferon regulatory factor-1, osteoprotegerin, and retinoblastoma-1 expression increased by approximately 2-fold compared to that in the C group, but the expression of Na+/K+ ATPase β1 decreased 3-fold.

CONCLUSION

The current findings revealed characteristic gene expression profiles under various ischemic conditions. However, additional studies are needed to clarify the mechanism of protection against IPC.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Recent advances in liver preconditioning: Thyroid hormone, n-3 long-chain polyunsaturated fatty acids and iron

Liver preconditioning (PC), defined as an enhanced tolerance to injuring stimuli induced by previous specific maneuvers triggering beneficial functional and molecular changes, is of crucial importance in human liver transplantation and major hepatic resection. For these reasons, numerous PC strategies have been evaluated in experimental models of ischemia-reperfusion liver injury, which have not been transferred to clinical application due to side effects, toxicity and difficulties in implementation, with the exception of the controversial ischemic PC. In recent years, our group has undertaken the assessment of alternate experimental liver PC protocols that might have application in the clinical setting. These include thyroid hormone (T(3)), n-3 long-chain polyunsaturated fatty acids (n-3 LCPUFA), or iron, which suppressed liver damage due to the 1 h ischemia-20 h reperfusion protocol. T(3), n-3 LCPUFA and iron are hormetic agents that trigger biologically beneficial effects in the low-dose range, whose multifactorial mechanisms of action are discussed in the work.

Protective effects of hypothermic ex vivo perfusion on ischemia/reperfusion injury and transplant outcomes

Hypothermic machine preservation (HMP) has been used in renal transplantation since the late 1960s with recent robust prospective, multicenter data showing lower rates of delayed graft function and improved graft survival. Although now clearly beneficial for renal transplantation, extrarenal machine perfusion has remained predominantly in preclinical investigations. Pancreatic HMP has drawn little clinical interest because HMP has been suggested to cause graft edema and congestion, which is associated with early venous thrombosis and graft failure. Early investigation showed no benefit of HMP in whole-organ pancreas transplant. One report did show that HMP increases islet cell yield after isolation. Preclinical work in liver HMP has been promising. Short- and long-term HMP has been shown to improve graft viability and reduce preservation injury, even in animal models of steatotic and donation after cardiac death. The first clinical study of liver HMP using a centrifugal dual perfusion technique showed excellent results with lower hepatocellular injury markers and no adverse perfusion-related outcomes. In addition, a dramatic attenuation of proinflammatory cytokine expression was observed. Further studies of liver HMP are planned with focus on developing a reproducible and standard protocol that will allow the widespread availability of this technology. Future research and clinical trials of novel organ preservation techniques, solutions, and interventions are likely to bring about developments that will allow further reduction of preservation-related ischemia/reperfusion injury and improved outcomes and allow safer utilization of the precious and limited resource of donor organs.

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.

Effect of a Diet Supplemented with alpha-Tocopherol and beta-Carotene on ATP and Antioxidant Levels after Hepatic Ischemia-Reperfusion

Ischemia-reperfusion injury associated with liver transplantation remains a serious complication in clinical practice. In the present study the effect of intake of α-tocopherol or β-carotene to limit liver injury by oxidative stress in ischemia and reperfusion was explored. Wistar rats were fed with diets enriched with α-tocopherol (20 mg/day) or β-carotene (3 mg/day) for 21 days. After 21 days, their livers were subjected to 15 and 30 min of ischemia and afterwards were reperfused for 60 min. The recovery of levels of ATP during reperfusion was better in the group of rats whose diets were supplemented with α-tocopherol or β-carotene than in the group control. The supplementation of the diet induced changes in the profile of enzymatic antioxidants. The supplementation with α-tocopherol and β-carotene resulted in a decreased of superoxide dismutase during the ischemia and a recovery was observed after reperfusion. Not changes were observed for the enzymes catalase and glutathione peroxidase and glutathione but their values were higher to those of the group control. In conclusion, the supplementation with α-tocopherol and β-carotene improve the antioxidant and energetic state of liver after ischemia and reperfusion injury.

Pharmacological postconditioning protects against hepatic ischemia/reperfusion injury

Postconditioning is a procedure based on the induction of intracellular protective reactions immediately after the onset of reperfusion. Because of the growing need to prevent ischemia/reperfusion (I/R) injury during liver surgery and transplantation, we investigated the possibility of pharmacologically inducing hepatic postconditioning. The effects of the adenosine A2A receptor agonist 2p-(2-carboxyethyl)-phenyl-amino-5'-N-ethylcarboxyamido-adenosine (CGS21680; 5 μmol/L) and the phosphatase and tensin homologue deleted from chromosome 10 (PTEN) inhibitor dipotassium bisperoxo-(5-hydroxypyridine-2-carboxyl)-oxovanadate [bpV(HOpic); 250 nmol/L] were investigated in primary rat hepatocytes during reoxygenation after 24 hours of cold storage and in an in vivo model of rat liver warm I/R. The addition of CGS21680 at reoxygenation significantly reduced hepatocyte death through the activation of the phosphoinositide 3-kinase (PI3K)-protein kinase B (PKB)/Akt signal pathway and through the reduction of the intracellular level of PTEN. PTEN lowering was associated with the increased generation of reactive oxygen species after A2A receptor-mediated stimulation of β-nicotinamide adenine dinucleotide phosphate oxidase (NOX). The inhibition of PI3K or NOX with wortmannin or diphenyleneiodonium chloride, respectively, and the addition of the antioxidant N,N'-diphenyl-p-phenylenediamine reversed the effects of CGS21680. The PTEN inhibitor bpV(HOpic) mimicked the protection provided by CGS21680 against reoxygenation damage. An in vivo rat treatment with CGS21680 or bpV(HOpic) during reperfusion after 1 hour of partial hepatic ischemia also promoted PKB/Akt activation and ameliorated alanine aminotransferase release and histological lesions induced by 2 hours of reperfusion. We conclude that adenosine A2A receptor agonists and PTEN inhibitors are possibly useful agents for the pharmacological induction of postconditioning in the liver.

Current protective strategies in liver surgery

During liver resection surgery for cancer or liver transplantation, the liver is subject to ischaemia (reduction in blood flow) followed by reperfusion (restoration of blood flow), which results in liver injury [ischemia-reperfusion (IR) or IR injury]. Modulation of IR injury can be achieved in various ways. These include hypothermia, ischaemic preconditioning (IPC) (brief cycles of ischaemia followed by reperfusion of the organ before the prolonged period of ischaemia i.e. a conditioning response), ischaemic postconditioning (conditioning after the prolonged period of ischaemia but before the reperfusion), pharmacological agents to decrease IR injury, genetic modulation of IR injury, and machine perfusion (pulsatile perfusion). Hypothermia decreases the metabolic functions and the oxygen consumption of organs. Static cold storage in University of Wisconsin solution reduces IR injury and has prolonged organ storage and improved the function of transplanted grafts. There is currently no evidence for any clinical advantage in the use of alternate solutions for static cold storage. Although experimental data from animal models suggest that IPC, ischaemic postconditioning, various pharmacological agents, gene therapy, and machine perfusion decrease IR injury, none of these interventions can be recommended in clinical practice. This is because of the lack of randomized controlled trials assessing the safety and efficacy of ischaemic postconditioning, gene therapy, and machine perfusion. Randomized controlled trials and systematic reviews of randomized controlled trials assessing the safety and efficacy of IPC and various pharmacological agents have demonstrated biochemical or histological improvements but this has not translated to clinical benefit. Further well designed randomized controlled trials are necessary to assess the various new protective strategies in liver resection.

Up-regulation of heme oxygenase-1 by sevoflurane is not dependent on Kupffer cells and associates with ERK1/2 and AP-1 activation in the rat liver

Sevoflurane is a potent non-toxic inducer of the hepatoprotective enzyme heme oxygenase-1 (HO-1). So far, little is known about the underlying molecular mechanism. Therefore the aim of this study was to characterize the respective signal transduction pathway and in particular to elucidate the role of Kupffer cells in this context. Rats were treated with or without sevoflurane. The effects on hepatic HO-1 gene expression, mitogen-activated protein kinases and transcription factors were studied by Northern and Western blot analyses, immunostaining, electrophoretic mobility shift assays, and enzymatic activity assays. Kupffer cells were depleted by administration of clodronate liposomes in vivo to characterize their role in HO-1 signal transduction. In additional in vitro experiments, HO-1 mRNA expression in primary rat hepatocytes and HepG2 cells was assessed. Sevoflurane up-regulated HO-1 gene expression in pericentral hepatocytes and increased HO enzyme activity in vivo. This was associated with activation of ERK1/2 and activator protein-1. We identified c-jun/AP-1, JunD, c-fos, and Fra-1 as active subunits of the activator protein-1 complex. Administration of clodronate liposomes to rats led to depletion of Kupffer cells without affecting sevoflurane induced HO-1 expression. Moreover, sevoflurane up-regulated HO-1 mRNA in primary rat hepatocytes but not in HepG2 cells. Our results suggest that sevoflurane induced HO-1 gene expression in pericentral hepatocytes does not depend on Kupffer cells and is associated with activation of ERK1/2 and activator protein-1. Since we could recently demonstrate significant hepatoprotective effects of HO-1 induced by isoflurane, the present results may help to establish new concepts in hepatic organ protection.

Negative regulation of diacylglycerol kinase theta mediates adenosine-dependent hepatocyte preconditioning

In liver ischemic preconditioning (IP), stimulation of adenosine A2a receptors (A2aR) prevents ischemia/reperfusion injury by promoting diacylglycerol-mediated activation of protein kinase C (PKC). By concerting diacylglycerol to phosphatidic acid, diacylglycerol kinases (DGKs) act as terminator of diacylglycerol signalling. This study investigates the role of DGK in the development of hepatocyte IP. DGK activity and cell viability were evaluated in isolated rat hepatocytes preconditioned by 10 min hypoxia followed by 10 min re-oxygenation or by the treatment with the A2aR agonist, CGS21680, and subsequently exposed to prolonged hypoxia. We observed that after IP or A2aR activation, a decrease in DGK activity was associated with the onset of hepatocyte tolerance to hypoxia. CGS21680-induced stimulation of A2aR specifically inhibited DGK isoform theta by activating RhoA-GTPase. Consistently, both siRNA-mediated downregulation of DGK theta and hepatocyte pretreatment with the DGK inhibitor R59949 induced cell tolerance to hypoxia. The pharmacological inhibition of DGK was associated with the diacylglycerol-dependent activation of PKC delta and epsilon and of their downstream target p38 MAPK. In conclusion, we unveil a novel signalling pathway contributing to the onset of hepatocyte preconditioning, which through RhoA-GTPase, couples A2aR to the downregulation of DGK. Such an inhibition is essential for the sustained accumulation of diacylglycerol required for triggering PKC-mediated survival signals.

Role of ischemic preconditioning in liver surgery and hepatic transplantation

INTRODUCTION

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

MATERIAL AND METHOD

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

Association of MicroRNA-223 expression with hepatic ischemia/reperfusion injury in mice

MicroRNAs are a group of small non-coding RNAs with modulator activity of gene expression. Recent studies have uncovered a profound role of microRNAs in liver diseases. This study aimed to investigate a potential relationship between microRNA-223 (miR-223) expression and hepatic ischemia/reperfusion injury in mice. Quantitative RT-PCR analysis showed that miR-223 expression levels were greatly up-regulated in the livers after 75 min ischemia followed by 120 min reperfusion when compared to sham controls (2.59 +/- 0.23 vs. 0.83 +/- 0.15; P < 0.01). Correlation analysis also revealed that hepatic miR-223 expression level was significantly positively correlated with serum markers of ischemic injury. By prediction assay of miRNA targets mRNA, acyl-CoA synthetase long-chain family member 3, ephrin A1, and ras homolog gene family member B were predicted to be downstream targets of miR-223. Thus, we conclude that hepatic ischemia/reperfusion injury might be another form of liver disease that is associated with alteration in miR-223 expression.

Proteomic analysis of hepatic ischemia/reperfusion injury and ischemic preconditioning in mice revealed the protective role of ATP5beta

Hepatic ischemia/reperfusion (I/R) injury is an inevitable consequence during liver surgery. Ischemic preconditioning (IPC) has been shown to protect the livers from I/R injury, partially mediated by preservation of hepatic ATP contents. However, the precise molecular mechanisms of these events remain poorly elucidated. In this study, liver proteomes of the mice subjected to I/R injury pretreated with or without IPC were analyzed using 2-DE combined with MALDI-TOF/TOF mass analysis. Twenty proteins showing more than 1.5-fold difference were identified in the livers upon I/R injury. Among these proteins, four proteins were further regulated by IPC when compared with nonpretreated controls. One of these proteins, ATP synthase beta subunit (ATP5beta) catalyzes the rate-limiting step of ATP formation. The expression level of ATP5beta, which was further validated by Western blot analysis, was significantly decreased upon I/R injury while turned over by IPC pretreatment. Change pattern of hepatic ATP corresponded with that of ATP5beta expression, indicating that increasing hepatic ATP5beta expression might be a reason for ATP-preserving effect of IPC. In summary, this study provided new clues for understanding the mechanisms of IPC against I/R injury. The protective role of ATP5beta might give evidences for developing new therapeutic approaches against hepatic I/R injury.

Ischemic preconditioning (IP) of the liver as a safe and protective technique against ischemia/reperfusion injury (IRI)

The aim of the study was to evaluate safety and efficacy of IP in LT, particularly in marginal grafts. From 2007 to 2008, 75 LT donors were randomized to receive IP (IP+) or not (IP-). Considering the graft quality, we divided the main groups in two subgroups (marg+/marg-). IP was performed by 10-min inflow occlusion (Pringle maneuver utilizing a toruniquet). Donor variables considered were gender, age, AST/ALT, ischemia time and steatosis. Recipient variables were gender, age, indication to LT and MELD/CHILD/UNOS score. AST/ALT levels, INR, bilirubin, lactic acid, bile output on postoperative days 1, 3 and 7 were evaluated. Histological analysis was performed evaluating necrosis/steatosis, hepatocyte swelling, PMN infiltration and councilman bodies. Thirty patients received IP+ liver. No differences were seen between groups considering recipient and donor variables. Liver function and AST/ALT levels showed no significant differences between the main two groups. Marginal IP+ showed lower AST levels on day1 compared with untreated marginal livers (936.35 vs. 1268.23; p = 0.026). IP+ livers showed a significant reduction of moderate-severe hepatocyte swelling (33.3% vs. 65.9%; p = 0.043). IP+ patients had a significant reduction of positive early microbiological investigations (36.7% vs. 57.1%; p = 0.042). In our experience IP was safe also in marginal donors, showing a protective role against IRI.

Variable activation of phosphoinositide 3-kinase influences the response of liver grafts to ischemic preconditioning

BACKGROUND/AIMS

The efficacy of ischemic preconditioning (IPC) in preventing reperfusion injury in human liver transplants is still questioned. Phosphoinositide-3-kinase (PI3K) is essential for IPC development in rodent livers. This work investigates whether PI3K-dependent signals might account for the inconsistent responses to IPC of transplanted human livers.

METHODS

Forty livers from deceased donors were randomized to receive or not IPC before recovery. PI3K activation was evaluated in biopsies obtained immediately before IPC and 2 h after reperfusion by measuring the phosphorylation of the PI3K downstream kinase PKB/Akt and the levels of the PI3K antagonist phosphatase tensin-homologue deleted from chromosome 10 (PTEN).

RESULTS

IPC increased PKB/Akt phosphorylation (p = 0.01) and decreased PTEN levels (p = 0.03) in grafts, but did not significantly ameliorate post-transplant reperfusion injury. By calculating T(2h)/T(0) PKB/Akt phosphorylation ratios, 10/19 (53%) of the preconditioned grafts had ratios above the control threshold (IPC-responsive), while the remaining nine grafts showed ratios comparable to controls (IPC-non-responsive). T(2h)/T(0) PTEN ratios were also decreased (p < or = 0.03) only in IPC-responsive grafts. The patients receiving IPC-responsive organs had ameliorated (p < or = 0.05) post-transplant aminotransferase and bilirubin levels, while prothrombin activity was unchanged.

CONCLUSIONS

Impaired PI3K signaling might account for the variability in the responses to IPC of human grafts from deceased donors.

Human adrenomedullin and its binding protein attenuate organ injury and reduce mortality after hepatic ischemia-reperfusion

OBJECTIVE

To determine whether administration of a vasoactive peptide, human adrenomedullin (AM), in combination with its binding protein (ie, AMBP-1), prevents or minimizes hepatic ischemia-reperfusion (I/R) injury.

SUMMARY BACKGROUND DATA

Hepatic I/R injury results from tissue hypoxia and subsequent inflammatory responses. Even though numerous pharmacological modalities and substances have been studied to reduce I/R-induced mortality, none have been entirely successful. We have shown that administration of AM/AMBP-1 produces significant beneficial effects under various pathophysiological conditions. However, it remains unknown if human AM/AMBP-1 has any protective effects on hepatic I/R-induced tissue damage and mortality.

METHODS

Seventy percent hepatic ischemia was induced in male adult rats by placing a microvascular clip across the hilum of the left and median lobes for 90 minutes. After removing the clip, human AM alone, human AMBP-1 alone, human AM in combination with human AMBP-1 or vehicle was administered intravenously over a period of 30 minutes. Blood and tissue samples were collected 4 hours after reperfusion for various measurements. In additional groups of animals, the nonischemic liver lobes were resected at the end of 90-minute ischemia. The animals were monitored for 7 days and survival was recorded.

RESULTS

After hepatic I/R, plasma levels of AM were significantly increased, whereas AMBP-1 levels were markedly decreased. Likewise, gene expression of AM in the liver was increased significantly, whereas AMBP-1 expression was markedly decreased. Administration of AM in combination with AMBP-1 immediately after the onset of reperfusion down-regulated inflammatory cytokines, decreased hepatic neutrophil infiltration, inhibited liver cell apoptosis and necrosis, and reduced liver injury and mortality in a rat model of hepatic I/R. On the other hand, administration of human AM alone or human AMBP-1 alone after hepatic I/R failed to produce significant protection.

CONCLUSIONS

Human AM/AMBP-1 may be a novel treatment to attenuate tissue injury after an episode of hepatic ischemia.

WITHDRAWN: Methods of vascular occlusion for elective liver resections

BACKGROUND

Vascular occlusion is used to reduce blood loss during liver resection surgery. There is considerable controversy regarding whether vascular occlusion should be used or not during elective liver resections. The method of vascular occlusion employed is also controversial. There is also considerable debate on the role of ischaemic preconditioning before vascular occlusion.

OBJECTIVES

To assess the advantages (decreased blood loss and peri-operative morbidity) and disadvantages (liver dysfunction from ischaemia) of vascular occlusion during liver resections. To compare the advantages (in decreasing blood loss or decreasing ischaemia-reperfusion injury) and disadvantages of different types of vascular occlusion versus total, continuous portal triad clamping.

SEARCH STRATEGY

We searched The Cochrane Hepato-Biliary Group Controlled Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library, MEDLINE, EMBASE, and Science Citation Index Expanded until March 2007.

SELECTION CRITERIA

We included randomised clinical trials comparing vascular occlusion versus no vascular occlusion during elective liver resections (irrespective of language or publication status). We also included randomised clinical trials comparing the different methods of vascular occlusion and those investigating the role of ischaemic preconditioning in liver resection.

DATA COLLECTION AND ANALYSIS

We collected the data on the characteristics of the trial, methodological quality of the trials, mortality, morbidity, blood loss, blood transfusion requirements, liver function tests, markers of neutrophil activation, operating time, and hospital stay. We analysed the data with both the fixed-effect and the random-effects models using RevMan Analysis. For each binary outcome we calculated the odds ratio (OR) with 95% confidence intervals (CI) based on intention-to-treat analysis. For continuous outcomes, we calculated the weighted mean difference (WMD) with 95% confidence intervals.

MAIN RESULTS

We identified a total of 16 randomised trials. Five trials including 331 patients compared vascular occlusion (n = 166) versus no vascular occlusion (n = 165). Six trials including 521 patients compared different methods of vascular occlusion. Three trials including 210 patients compared ischaemic preconditioning before continuous portal triad clamping (n = 105) versus no ischaemic preconditioning (n = 105). Two trials including 127 patients compared ischaemic preconditioning before continuous portal triad clamping (n = 63) versus intermittent portal triad clamping (n = 64).The blood loss was significantly lower in vascular occlusion compared with no vascular occlusion. The liver enzymes were significantly elevated in the vascular occlusion group compared with no vascular occlusion. There was no difference in the mortality, liver failure, or other morbidities. Four of the five trials comparing vascular occlusion and no vascular occlusion used intermittent vascular occlusion. Trials comparing complete inflow and outflow occlusion to the liver, ie, hepatic vascular exclusion and portal triad clamping demonstrate significant detrimental haemodynamic changes in hepatic vascular exclusion compared to portal triad clamping. There was no significant difference in the number of units transfused and the number of patients needing transfusion. There was no difference in mortality, liver failure, or morbidity between total and selective methods of portal triad clamping. All four cases of mortality and liver failure in the comparison between the intermittent and continuous portal triad clamping occurred in the continuous portal triad clamping (statistically not significant). Intermittent portal triad clamping does not increase the total blood loss or operating time compared to continuous portal triad clamping.There was no statistically significant difference in the mortality, liver failure, morbidity, blood loss, or haemodynamic changes between ischaemic preconditioning versus no ischaemic preconditioning before continuous portal triad clamping. Liver enzymes used as markers of liver injury were significantly lower in the early post-operative period in the ischaemic preconditioning group. The intensive therapy unit stay and hospital stay were statistically significantly lower in the ischaemic preconditioning group than in the no ischaemic preconditioning group.There was no statistically significant difference in the mortality, liver failure, morbidity, intensive therapy unit stay, or hospital stay between ischaemic preconditioning before continuous portal triad clamping and intermittent portal triad clamping. The blood loss and transfusion requirements were lower in the ischaemic preconditioning group. Aspartate aminotransferase level was lower in the intermittent portal triad clamping group than the ischaemic preconditioning group on the third post-operative day. There was no difference in the peak aspartate aminotransferase levels or in the aspartate aminotransferase levels on first or sixth post-operative days of aspartate aminotransferase .

AUTHORS' CONCLUSIONS

Intermittent vascular occlusion seems safe in liver resection. However, it does not seem to decrease morbidity. Among the different methods of vascular occlusion, intermittent portal triad clamping has most evidence to support the clinical application. Hepatic vascular exclusion cannot be recommended routinely. Ischaemic preconditioning before continuous portal triad clamping may be of clinical benefit in reducing intensive therapy unit and hospital stay.

Vascular occlusion for elective liver resections

BACKGROUND

Vascular occlusion is used to reduce blood loss during liver resection. There is considerable controversy regarding whether vascular occlusion should be used or not during elective liver resections.

OBJECTIVES

To assess the advantages (decreased blood loss and peri-operative morbidity) and disadvantages (ischaemia-reperfusion injury related complications like liver dysfunction) of vascular occlusion during elective liver resections.

SEARCH STRATEGY

We searched The Cochrane Hepato-Biliary Group Controlled Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library, MEDLINE, EMBASE, and Science Citation Index Expanded until August 2008.

SELECTION CRITERIA

We included randomised clinical trials comparing vascular occlusion versus no vascular occlusion during elective liver resections (irrespective of language or publication status).

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trials for inclusion and independently extracted the data. We analysed the data with both the fixed-effect and the random-effects models using RevMan Analysis. We calculated the risk ratio (RR), mean difference (MD), or standardised mean difference (SMD) with 95% confidence intervals (CI) based on intention-to-treat or available case analysis.

MAIN RESULTS

We identified a total of five trials (of high bias-risk) which compared vascular occlusion (n = 166) versus no vascular occlusion (n = 165). Three of the five trials comparing vascular occlusion and no vascular occlusion used intermittent vascular occlusion. There was no difference in mortality, liver failure, or other morbidities. The blood loss was significantly lower in vascular occlusion compared with no vascular occlusion. The liver enzymes were significantly elevated in the vascular occlusion group compared with no vascular occlusion.

AUTHORS' CONCLUSIONS

Intermittent vascular occlusion seems safe in liver resection. However, it does not seem to decrease morbidity. More randomised trials seem to be needed.

Ischaemic pre-conditioning for elective liver resections performed under vascular occlusion

BACKGROUND

Vascular occlusion is used to reduce blood loss during liver resection surgery. The enzyme markers of liver injury are elevated if vascular occlusion is employed during liver resection. It is not clear whether ischaemic preconditioning prior to vascular occlusion has a protective effect during elective liver resections.

OBJECTIVES

To assess the advantages (decreased ischaemia-reperfusion injury) and any potential disadvantages of ischaemic preconditioning prior to vascular occlusion during liver resections.

SEARCH STRATEGY

We searched The Cochrane Hepato-Biliary Group Controlled Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library, MEDLINE, EMBASE, and Science Citation Index Expanded until August 2008.

SELECTION CRITERIA

We included randomised clinical trials comparing ischaemic preconditioning versus no ischaemic preconditioning prior to vascular occlusion (irrespective of the method of vascular occlusion) during elective liver resections (irrespective of language or publication status).

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trials for inclusion and independently extracted the data. We analysed the data with both the fixed-effect and the random-effects models using RevMan Analysis. We calculated the risk ratio, mean difference, or standardised mean difference with 95% confidence intervals based on intention-to-treat or available data analysis.

MAIN RESULTS

We included four trials with 271 patients undergoing open liver resections. The patients were randomised to ischaemic preconditioning (n = 135) and no ischaemic preconditioning (n = 136) prior to continuous vascular occlusion (portal triad clamping in three trials and hepatic vascular exclusion in one trial). All the trials excluded cirrhotic patients. We assessed all the four trials as having high risk of bias. There was no difference in mortality, liver failure, other peri-operative morbidity, hospital stay, intensive therapy unit stay, and operating time between the two groups. The proportion of patients requiring blood transfusion was lower in the ischaemic preconditioning group. There was also a trend towards a lower amount of red cell transfusion favouring ischaemic preconditioning group. There was no difference in the haemodynamic changes, blood loss, bilirubin, or prothrombin activity between the two groups. The enzyme markers of liver injury were lower in the ischaemic preconditioning group on the first post-operative day.

AUTHORS' CONCLUSIONS

Currently, there is no evidence to suggest a protective effect of ischaemic preconditioning in non-cirrhotic patients undergoing liver resection under continuous vascular occlusion. Ischaemic preconditioning reduces the blood transfusion requirements in patients undergoing liver resection.