Preconditioning, organ preservation, and postconditioning to prevent ischemia-reperfusion injury to the liver

Interplay Between Inflammatory-immune and Interleukin-17 Signalings Plays a Cardinal Role on Liver Ischemia-reperfusion Injury-Synergic Effect of IL-17Ab, Tacrolimus and ADMSCs on Rescuing the Liver Damage

BACKGROUND

This study tested the hypothesis that inflammatory and interleukin (IL)-17 signalings were essential for acute liver ischemia (1 h)-reperfusion (72 h) injury (IRI) that was effectively ameliorated by adipose-derived mesenchymal stem cells (ADMSCs) and tacrolimus.

METHODS

Adult-male SD rats (n = 50) were equally categorized into groups 1 (sham-operated-control), 2 (IRI), 3 [IRI + IL-17-monoclonic antibody (Ab)], 4 (IRI + tacrolimus), 5 (IRI + ADMSCs) and 6 (IRI + tacrolimus-ADMSCs) and liver was harvested at 72 h.

RESULTS

The main findings included: (1) circulatory levels: inflammatory cells, immune cells, and proinflammatory cytokines as well as liver-damage enzyme at the time point of 72 h were highest in group 2, lowest in group 1 and significantly lower in group 6 than in groups 3 to 5 (all p < 0.0001), but they did not differ among these three latter groups; (2) histopathology: the liver injury score, fibrosis, inflammatory and immune cell infiltration in liver immunity displayed an identical pattern of inflammatory cells among the groups (all p < 0.0001); and (3) protein levels: upstream and downstream inflammatory signalings, oxidative-stress, apoptotic and mitochondrial-damaged biomarkers exhibited an identical pattern of inflammatory cells among the groups (all p < 0.0001).

CONCLUSION

Our results obtained from circulatory, pathology and molecular-cellular levels delineated that acute IRI was an intricate syndrome that elicited complex upstream and downstream inflammatory and immune signalings to damage liver parenchyma that greatly suppressed by combined tacrolimus and ADMSCs therapy.

Insulin-induced gene 2 protects against hepatic ischemia-reperfusion injury via metabolic remodeling

BACKGROUND

Hepatic ischemia-reperfusion (IR) injury is the primary reason for complications following hepatectomy and liver transplantation (LT). Insulin-induced gene 2 (Insig2) is one of several proteins that anchor the reticulum in the cytoplasm and is essential for metabolism and inflammatory responses. However, its function in IR injury remains ambiguous.

METHODS

Insig2 global knock-out (KO) mice and mice with adeno-associated-virus8 (AAV8)-delivered Insig2 hepatocyte-specific overexpression were subjected to a 70% hepatic IR model. Liver injury was assessed by monitoring hepatic histology, inflammatory responses, and apoptosis. Hypoxia/reoxygenation stimulation (H/R) of primary hepatocytes and hypoxia model induced by cobalt chloride (CoCl2) were used for in vitro experiments. Multi-omics analysis of transcriptomics, proteomics, and metabolomics was used to investigate the molecular mechanisms underlying Insig2.

RESULTS

Hepatic Insig2 expression was significantly reduced in clinical samples undergoing LT and the mouse IR model. Our findings showed that Insig2 depletion significantly aggravated IR-induced hepatic inflammation, cell death and injury, whereas Insig2 overexpression caused the opposite phenotypes. The results of in vitro H/R experiments were consistent with those in vivo. Mechanistically, multi-omics analysis revealed that Insig2 is associated with increased antioxidant pentose phosphate pathway (PPP) activity. The inhibition of glucose-6-phosphate-dehydrogenase (G6PD), a rate-limiting enzyme of PPP, rescued the protective effect of Insig2 overexpression, exacerbating liver injury. Finally, our findings indicated that mouse IR injury could be attenuated by developing a nanoparticle delivery system that enables liver-targeted delivery of substrate of PPP (glucose 6-phosphate).

CONCLUSIONS

Insig2 has a protective function in liver IR by upregulating the PPP activity and remodeling glucose metabolism. The supplementary glucose 6-phosphate (G6P) salt may serve as a viable therapeutic target for alleviating hepatic IR.

Blackberry-Loaded AgNPs Attenuate Hepatic Ischemia/Reperfusion Injury via PI3K/Akt/mTOR Pathway

Liver ischemia-reperfusion injury (IRI) is a pathophysiological insult that often occurs during liver surgery. Blackberry leaves are known for their anti-inflammatory and antioxidant activities. Aims: To achieve site-specific delivery of blackberry leaves extract (BBE) loaded AgNPs to the hepatocyte in IRI and to verify possible molecular mechanisms. Methods: IRI was induced in male Wister rats. Liver injury, hepatic histology, oxidative stress markers, hepatic expression of apoptosis-related proteins were evaluated. Non-targeted metabolomics for chemical characterization of blackberry leaves extract was performed. Key findings: Pre-treatment with BBE protected against the deterioration caused by I/R, depicted by a significant improvement of liver functions and structure, as well as reduction of oxidative stress with a concomitant increase in antioxidants. Additionally, BBE promoted phosphorylation of antiapoptotic proteins; PI3K, Akt and mTOR, while apoptotic proteins; Bax, Casp-9 and cleaved Casp-3 expressions were decreased. LC-HRMS-based metabolomics identified a range of metabolites, mainly flavonoids and anthocyanins. Upon comprehensive virtual screening and molecular dynamics simulation, the major annotated anthocyanins, cyanidin and pelargonidin glucosides, were suggested to act as PLA2 inhibitors. Significance: BBE can ameliorate hepatic IRI augmented by BBE-AgNPs nano-formulation via suppressing, oxidative stress and apoptosis as well as stimulation of PI3K/Akt/mTOR signaling pathway.

The application of optical technology in the diagnosis and therapy of oxidative stress-mediated hepatic ischemia-reperfusion injury

Hepatic ischemia-reperfusion injury (HIRI) is defined as liver tissue damage and cell death caused by reperfusion during liver transplantation or hepatectomy. Oxidative stress is one of the important mechanisms of HIRI. Studies have shown that the incidence of HIRI is very high, however, the number of patients who can get timely and efficient treatment is small. The reason is not hard to explain that invasive ways of detection and lack of timely of diagnostic methods. Hence, a new detection method is urgently needed in clinic application. Reactive oxygen species (ROS), which are markers of oxidative stress in the liver, could be detected by optical imaging and offer timely and effective non-invasive diagnosis and monitoring. Optical imaging could become the most potential tool of diagnosis of HIRI in the future. In addition, optical technology can also be used in disease treatment. It found that optical therapy has the function of anti-oxidative stress. Consequently, it has possibility to treat HIRI caused by oxidative stress. In this review, we mainly summarized the application and prospect of optical techniques in oxidative stress-induced by HIRI.

Incidence and risk factors for anastomotic bile leakage in hepatic resection with bilioenteric reconstruction - A international multicenter study

BACKGROUND

Anastomotic leak (AL) after bilioenteric reconstruction (BR) is a feared complication after bile duct resection, especially in combination with liver resection. Literature on surgical outcome is sparse. This study aimed to determine the incidence and risk factors for AL after combined liver and bile duct resection with a focus on operative or endoscopic reinterventions.

METHODS

Data from consecutive patients who underwent liver resection and BR between 2004 and 2018 in 11 academic institutions in Europe were collected from prospectively maintained databases.

RESULTS

Within 921 patients, AL rate was 5.4% with a 30d mortality of 9.6%. Pringle maneuver (p<0.001),postoperative external biliary (p=0.007) and abdominal drainage (p<0.001) were risk factors for clinically relevant AL. Preoperative biliary drainage (p<0.001) was not associated with a higher rate of AL. AL was more frequent in stented patients (76.5%) compared to PTCD (17.6%) or PTCD+stent (5.9%,p=0.017). AL correlated with increased incidence of postoperative liver failure (p=0.036), cholangitis, hemorrhage and sepsis (all p<0.001).

CONCLUSION

This multicenter data provides the largest series to date of LR with BR and could help in the management of these patients which are often challenging and hampering the patients' postoperative course negatively.

Establishment of a Serum-Free Hepatocyte Cryopreservation Process for the Development of an "Off-the-Shelf" Bioartificial Liver System

To use hepatocytes immediately when necessary for hepatocyte transplantation and bioartificial liver (BAL) systems, a serum-free cryopreservation protocol ensuring the high survival of hepatocytes and maintenance of their functions should be developed. We established a serum-free protocol for the cryopreservation of primary hepatocytes, hepatocyte spheroids, and hepatocyte spheroid beads in liquid nitrogen. The serum-free cryopreservation solutions showed a significantly higher performance in maintaining enhanced viability and ammonia removal, urea secretion, and the albumin synthesis of hepatocyte spheroids and spheroid beads. The serum-free thawing medium, containing human serum albumin (HSA) and N-acetylcysteine (NAC), was compared with a fetal bovine serum-containing thawing medium for the development of a serum-free thawing medium. Our results show that hepatocyte spheroids and spheroid beads thawed using a serum-free thawing medium containing HSA and NAC exhibited increased hepatocyte viability, ammonia removal, urea secretion, and albumin synthesis compared to those thawed using the serum-containing medium. Finally, we evaluated the liver functions of the cryopreserved BAL system-applied serum-free cryopreservation process compared to the fresh BAL system. The ammonia removal efficiency of the cryopreserved hepatocyte spheroids BAL was lower than or similar to that of the fresh BAL system. Additionally, the urea concentrations in the media of all three BAL systems were not significantly different during BAL system operation. This cryopreserved spheroid-based BAL system using a serum-free process will be a good candidate for the treatment of patients.

Blood products and liver transplantation: A strategy to balance optimal preparation with effective blood stewardship

BACKGROUND

Unanticipated transfusion requirements during liver transplantation can delay lifesaving intraoperative resuscitation and strain blood bank resources. Risk-stratified preoperative blood preparation can mitigate these deleterious outcomes.

STUDY DESIGN AND METHODS

A two-tiered blood preparation protocol for liver transplantation was retrospectively evaluated. Eleven binary variables served as criteria for high-risk (HR) allocation. Primary outcomes included red blood cell (RBC), plasma (FFP), and platelet (Plt) utilization. Secondary outcomes included product under- and overpreparation. Contingency tables for transfusion requirements above the population means were generated using 15 clinical variables. Modified protocols were developed and retrospectively optimized using the study population.

RESULTS

Of 225 recipients, 102 received HR preoperative orders, which correlated to higher intraoperative transfusion requirements. However, univariate analysis identified only two statistical risk factors per product: Hgb ≤7.8 g/dl (p < .001) and MELD ≥38 (p = .035) for RBCs, Hgb ≤7.8 g/dl (p = .002) and acute alcoholic hepatitis (p = 0.015) for FFP, and Hgb ≤7.8 g/dl (p = .001) and normothermic liver preservation (p = .037) for Plts. Based on these findings, we developed modified protocols for individual products, which were evaluated retrospectively for their effectiveness at reducing under-preparatory events while limiting product overpreparation. Cohort statistics were used to define the preparation strategy for each protocol. Retrospective comparative analysis demonstrated the superiority of the modified protocols by improving the under-preparation rate from 24% to <10% for each product, which required a 1.56-fold and 1.44-fold increase in RBC and FFP overpreparation, respectively. Importantly, there was no difference in Plt overpreparation.

DISCUSSION

We report translatable data-driven blood bank preparation protocols for liver transplantation.

E3 ubiquitin ligase ring finger protein 5 protects against hepatic ischemia reperfusion injury by mediating phosphoglycerate mutase family member 5 ubiquitination

BACKGROUND AND AIMS

Hepatic ischemia-reperfusion (HIR) injury, a common clinical complication of liver transplantation and resection, affects patient prognosis. Ring finger protein 5 (RNF5) is an E3 ubiquitin ligase that plays important roles in endoplasmic reticulum stress, unfolded protein reactions, and inflammatory responses; however, its role in HIR is unclear.

APPROACH AND RESULTS

RNF5 expression was significantly down-regulated during HIR in mice and hepatocytes. Subsequently, RNF5 knockdown and overexpression of cell lines were subjected to hypoxia-reoxygenation challenge. Results showed that RNF5 knockdown significantly increased hepatocyte inflammation and apoptosis, whereas RNF5 overexpression had the opposite effect. Furthermore, hepatocyte-specific RNF5 knockout and transgenic mice were established and subjected to HIR, and RNF5 deficiency markedly aggravated liver damage and cell apoptosis and activated hepatic inflammatory responses, whereas hepatic RNF5 transgenic mice had the opposite effect compared with RNF5 knockout mice. Mechanistically, RNF5 interacted with phosphoglycerate mutase family member 5 (PGAM5) and mediated the degradation of PGAM5 through K48-linked ubiquitination, thereby inhibiting the activation of apoptosis-regulating kinase 1 (ASK1) and its downstream c-Jun N-terminal kinase (JNK)/p38. This eventually suppresses the inflammatory response and cell apoptosis in HIR.

CONCLUSIONS

We revealed that RNF5 protected against HIR through its interaction with PGAM5 to inhibit the activation of ASK1 and the downstream JNK/p38 signaling cascade. Our findings indicate that the RNF5-PGAM5 axis may be a promising therapeutic target for HIR.

The integrated stress response in ischemic diseases

Ischemic disease is among the deadliest and most disabling illnesses. Prominent examples include myocardial infarction and stroke. Most, if not all, underlying pathological changes, including oxidative stress, inflammation, and nutrient deprivation, are potent inducers of the integrated stress response (ISR). Four upstream kinases are involved in ISR signaling that sense a myriad of input stress signals and converge on the phosphorylation of serine 51 of eukaryotic translation initiation factor 2α (eIF2α). As a result, translation initiation is halted, creating a window of opportunity for the cell to repair itself and restore homeostasis. A growing number of studies show strong induction of the ISR in ischemic disease. Genetic and pharmacological evidence suggests that the ISR plays critical roles in disease initiation and progression. Here, we review the basic regulation of the ISR, particularly in response to ischemia, and summarize recent findings relevant to the actions of the ISR in ischemic disease. We then discuss therapeutic opportunities by modulating the ISR to treat ischemic heart disease, brain ischemia, ischemic liver disease, and ischemic kidney disease. Finally, we propose that the ISR represents a promising therapeutic target for alleviating symptoms of ischemic disease and improving clinical outcomes.

The Effect of Antioxidant Added to Preservation Solution on the Protection of Kidneys before Transplantation

Ischemia–reperfusion injury is a key clinical problem of transplantology. Current achievements in optimizing organ rinse solutions and storage techniques have significantly influenced the degree of graft damage and its survival after transplantation. In recent years, intensive research has been carried out to maintain the viability of tissues and organs outside the integral environment of the body. Innovative solutions for improving the biochemical functions of the stored organ have been developed. The article discusses directions for modifying preservation solutions with antioxidants. Clinical and experimental studies aimed at optimizing these fluids, as well as perfusion and organ preservation techniques, are presented.

Regulator of G-protein signaling 14 protects the liver from ischemia-reperfusion injury by suppressing TGF-β-activated kinase 1 activation

BACKGROUND AND AIMS

Hepatic ischemia-reperfusion injury (IRI) is a common complication of hepatectomy and liver transplantation. However, the mechanisms underlying hepatic IRI have not been fully elucidated. Regulator of G-protein signaling 14 (RGS14) is a multifunctional scaffolding protein that integrates the G-protein and mitogen-activated protein kinase (MAPK) signaling pathways. However, the role of RGS14 in hepatic IRI remains unclear.

APPROACH AND RESULTS

We found that RGS14 expression increased in mice subjected to hepatic ischemia-reperfusion (IR) surgery and during hypoxia reoxygenation in hepatocytes. We constructed global RGS14 knockout (RGS14-KO) and hepatocyte-specific RGS14 transgenic (RGS14-TG) mice to establish 70% hepatic IRI models. Histological hematoxylin and eosin staining, levels of alanine aminotransferase and aspartate aminotransferase, expression of inflammatory factors, and apoptosis were used to assess liver damage and function in these models. We found that RGS14 deficiency significantly aggravated IR-induced liver injury and activated hepatic inflammatory responses and apoptosis in vivo and in vitro. Conversely, RGS14 overexpression exerted the opposite effect of the RGS14-deficient models. Phosphorylation of TGF-β-activated kinase 1 (TAK1) and its downstream effectors c-Jun N-terminal kinase (JNK) and p38 increased in the liver tissues of RGS14-KO mice but was repressed in those of RGS14-TG mice. Furthermore, inhibition of TAK1 phosphorylation rescued the effect of RGS14 deficiency on JNK and p38 activation, thus blocking the inflammatory responses and apoptosis.

CONCLUSIONS

RGS14 plays a protective role in hepatic IR by inhibiting activation of the TAK1-JNK/p38 signaling pathway. This may be a potential therapeutic strategy for reducing incidences of hepatic IRI in the future.

A H2O2-activatable nanoprobe for diagnosing interstitial cystitis and liver ischemia-reperfusion injury via multispectral optoacoustic tomography and NIR-II fluorescent imaging

Developing high-quality NIR-II fluorophores (emission in 1000-1700 nm) for in vivo imaging is of great significance. Benzothiadiazole-core fluorophores are an important class of NIR-II dyes, yet ongoing limitations such as aggregation-caused quenching in aqueous milieu and non-activatable response are still major obstacles for their biological applications. Here, we devise an activatable nanoprobe to address these limitations. A molecular probe named BTPE-NO₂ is synthesized by linking a benzothiadiazole core with two tetraphenylene groups serving as hydrophobic molecular rotors, followed by incorporating two nitrophenyloxoacetamide units at both ends of the core as recognition moieties and fluorescence quenchers. An FDA-approved amphiphilic polymer Pluronic F127 is then employed to encapsulate the molecular BTPE-NO₂ to render the nanoprobe BTPE-NO₂@F127. The pathological levels of H₂O₂ in the disease sites cleave the nitrophenyloxoacetamide groups and activate the probe, thereby generating strong fluorescent emission (950~1200 nm) and ultrasound signal for multi-mode imaging of inflammatory diseases. The nanoprobe can therefore function as a robust tool for detecting and imaging the disease sites with NIR-II fluorescent and multispectral optoacoustic tomography (MSOT) imaging. Moreover, the three-dimensional MSOT images can be obtained for visualizing and locating the disease foci.

Ischemia/Reperfusion Injury of Fatty Liver Is Protected by A2AR and Exacerbated by A1R Stimulation through Opposite Effects on ASK1 Activation

Hepatic ischemia/reperfusion injury (IRI) is aggravated by steatosis and is a main risk factor in fatty liver transplantation. Adenosine receptors (ARs) are emerging as therapeutic targets in liver diseases. By using cellular and in vivo systems of hepatic steatosis and IRI, here we evaluated the effects of pharmacological A2AR and A1R activation. The A2AR agonist CGS21680 protected the primary steatotic murine hepatocyte from IR damage and the activation of ASK1 and JNK. Such an effect was attributed to a phosphatidylinositol-3-kinase (PI3K)/Akt-dependent inhibition of ASK1. By contrast, the A1R agonist CCPA enhanced IR damage, intracellular steatosis and oxidative species (OS) production, thereby further increasing the lipid/OS-dependent ASK1-JNK stimulation. The CGS2680 and CCPA effects were nullified by a genetic ASK1 downregulation in steatotic hepatoma C1C7 cells. In steatotic mice livers, CGS21680 protected against hepatic IRI and ASK1/JNK activation whereas CCPA aggravated hepatic steatosis and IRI, and enhanced ASK1 and JNK stimulation. These results evidence a novel mechanism of CGS21680-mediated hepatoprotection, i.e., the PI3K/AKT-dependent inhibition of ASK1, and they show that CGS21680 and CCPA reduces and enhances the IRI of fatty liver, respectively, by preventing or increasing the activation of the cytotoxic ASK1/JNK axis. They also indicate the selective employment of A2AR agonists as an effective therapeutic strategy to prevent IRI in human fatty liver surgery.

DUSP12 acts as a novel endogenous protective signal against hepatic ischemia-reperfusion damage by inhibiting ASK1 pathway

Ischemia–reperfusion injury (IRI) consequent to major liver surgery is a still unmet clinical problem. The activation of endogenous systems of hepatoprotection can prevent the damaging effects of ischemia–reperfusion (IR) as shown by the phenomenon known as ‘ischemic preconditioning’. The identification of endogenous signal mediators of hepatoprotection is of main interest since they could be targeted in future therapeutic interventions. Qiu et al. recently reported in Clin. Sci. (Lond.) (2020) 134(17), 2279–2294, the discovery of a novel protective molecule against hepatic IR damage: dual-specificity phosphatase 12 (DUSP12). IR significantly decreased DUSP12 expression in liver whereas DUSP12 overexpression in hepatocytes protected IRI and DUSP12 deletion in DUSP12 KO mice exacerbated IRI. The protective effects of DUSP12 depended on apoptosis signal-regulating kinase 1 (ASK1) and acted through the inhibition of the ASK1-dependent kinases c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK). These results enlighten DUSP12 as a novel intermediate negative regulator of the pro-inflammatory and pro-apoptotic ASK1/JNK-p38 MAPK pathway activated during hepatic IR and identify DUSP12 as potential therapeutic target for IRI.

Sevoflurane Postconditioning Attenuates Hepatic Ischemia-Reperfusion Injury by Limiting HMGB1/TLR4/NF-κB Pathway via Modulating microRNA-142 in vivo and in vitro

Preconditioning of sevoflurane (Sevo) has been demonstrated to protect the liver from ischemia/reperfusion (I/R) injury. However, it is unknown whether it has hepatoprotective when given at the onset of reperfusion (postconditioning), a protocol with more clinical impact. The present study aimed to explore the hepatoprotective effects of Sevo postconditioning against hepatic IR injury in vivo and in vitro and the possible mechanisms. Using a mouse model of hepatic I/R, Sevo postconditioning significantly improved hepatic injury after reperfusion, as demonstrated by reduced AST, ALT, and LDH serum levels and reduced histologic damage in liver tissues. Furthermore, Sevo postconditioning could suppress the apoptosis, inhibit oxidative stress and inflammatory response in liver tissue of HIRI mice, as well as improve the survival rate of HIRI mice. Through analyzing GSE72314 from the gene expression omnibus (GEO) database, it was demonstrated that microRNA (miR)-142 is downregulated by HIRI, which was reversed by Sevo treatment. Further investigation showed that agomiR-142 injection could enhance the hepatoprotective effects of Sevo postconditioning on I/R injury, while antagomiR-142 reversed these effects in mice. Notably, high mobility group box 1 (HMGB1), an important inflammatory factor, was directly targeted by miR-142 in hepatic cells, and we further found that Sevo could inhibit the expression of HMGB1 through up-regulating miR-142 expression in HIRI mice model. In addition, we found that I/R injury induced the activation of TLR4/NF-κB inflammatory pathway was partially suppressed by Sevo postconditioning, and miR-142 mediated the regulatory role of Sevo postconditioning. In line with the in vivo results, Sevo treatment improved the cell viability, inhibited cell apoptosis, oxidative stress and inflammatory response in vitro HIRI model, while these effects were reversed by antagomiR-142 transfection. Collectively, our findings demonstrated that Sevo postconditioning counteracts the downregulation of miR-142 provoked by I/R, in turn decreased the expression of HMGB1, blocking TLR4/NF-κB pathway activation, thus improving hepatic I/R injury. Our data suggest that Sevo may be a valuable alternative anaesthetic agent in liver transplantation and major liver surgeries.

Melatonin and its protective role in attenuating warm or cold hepatic ischaemia/reperfusion injury

Although the liver is the only organ with regenerative capacity, various injury factors induce irreversible liver dysfunction and end‐stage liver disease. Liver resection and liver transplantation (LT) are effective treatments for individuals with liver failure, liver cirrhosis and liver cancers. The remnant or transplanted liver tissues will undergo hepatic ischaemia/reperfusion (IR), which leads to oxidative stress, inflammation, immune injury and liver damage. Moreover, systemic ischaemia induced by trauma, stroke, myocardial ischaemia, haemorrhagic shock and other injury factors also induces liver ischaemia/reperfusion injury (IRI) in individuals. Hepatic IRI can be divided into warm IRI, which is induced by liver surgery and systemic ischaemia, and cold IRI, which is induced by LT. Multiple studies have shown that melatonin (MT) acts as an endogenous free radical scavenger with antioxidant capacity and is also able to attenuate hepatic IRI via its anti‐inflammatory and antiapoptotic capacities. In this review, we discuss the potential mechanisms and current strategies of MT administration in liver surgery for protecting against warm or cold hepatic IRI. We highlight strategies to improve the efficacy and safety of MT for attenuating hepatic IRI in different conditions. After the potential mechanisms underlying the interactions between MT and other important cellular processes during hepatic IR are clarified, more opportunities will be available to use MT to treat liver diseases in the future.

Beyond Ice and the Cooler: Machine Perfusion Strategies in Liver Transplantation

Machine perfusion (MP) has emerged as a promising preservation technique to reduce the risks associated with transplant of high risk (steatotic, elderly, and donation after circulatory death) hepatic allografts. Multiple strategies for MP are under investigation. MP facilitates assessment of organ viability and enables liver-directed therapy before transplant. Clinical trials suggest MP may improve the use of hepatic allografts, mitigate ischemia-reperfusion injury, and reduce the incidences of early allograft dysfunction, biliary complications, and ischemic cholangiopathy. As MP sees more widespread use outside of trial settings, more investigation will be needed to establish optimal application of this technology.

Propofol Protects Against Hepatic Ischemia Reperfusion Injury via Inhibiting Bnip3-Mediated Oxidative Stress

Propofol (PRO) protects against hepatic ischemia/reperfusion (I/R) injury. Bnip3 is involved in the I/R-induced injury. This study investigated whether the effect of PRO on hepatic hypoxia/reoxygenation (H/R) injury was realized through regulating Bnip3. After establishing a hepatic ischemia reperfusion (I/R ) injury model in mice, the serum levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were determined by an automatic biochemical analyzer. The histopathology and apoptosis of liver tissues were detected by hematoxylin-eosin and TUNEL staining. After the H/R liver cells were cultured and treated with PRO, the viability, apoptosis, reactive oxygen species (ROS) production, and the levels of lactate dehydrogenase (LDH), malondialdehyde (MDA), TNF-α, and IL-6 were detected by MTT, flow cytometry, colorimetry, and ELISA. The expressions of Bnip3 and apoptosis-related factors in I/R mouse liver tissues and H/R cells were determined by immunohistochemical assay, immunofluorescence, Western blot, or RT-qPCR. PRO ameliorated the abnormal histopathology, reduced cell apoptosis and the levels of AST, ALT, Bnip3, Cleaved Caspase-3, and Bax, but upregulated the Bcl-2 level in the liver tissues of I/R mice. In H/R liver cells, PRO promoted the cell viability, downregulated the levels of LDH, MDA, TNF-α, IL-6, and reduced ROS production. Moreover, PRO promoted the downregulated expressions of cytosolic Bnip3, total Bni3p, Cleaved Caspase-3, and Bax and upregulated the Bcl-2 level. siBnip3 reversed the effect of H/R on the liver cells, and its overexpression also reversed the effect of PRO on H/R-induced liver cells. PRO protects against hepatic I/R injury via inhibiting Bnip3.

Evaluation of Liver Quality after Circulatory Death Versus Brain Death: A Comparative Preclinical Pig Model Study

The current organ shortage in hepatic transplantation leads to increased use of marginal livers. New organ sources are needed, and deceased after circulatory death (DCD) donors present an interesting possibility. However, many unknown remains on these donors and their pathophysiology regarding ischemia reperfusion injury (IRI). Our hypothesis was that DCD combined with abdominal normothermic regional recirculation (ANOR) is not inferior to deceased after brain death (DBD) donors. We performed a mechanistic comparison between livers from DBD and DCD donors in a highly reproducible pig model, closely mimicking donor conditions encountered in the clinic. DCD donors were conditioned by ANOR. We determined that from the start of storage, pro-lesion pathways such as oxidative stress and cell death were induced in both donor types, but to a higher extent in DBD organs. Furthermore, pro-survival pathways, such as resistance to hypoxia and regeneration showed activation levels closer to healthy livers in DCD-ANOR rather than in DBD organs. These data highlight critical differences between DBD and DCD-ANOR livers, with an apparent superiority of DCD in terms of quality. This confirms our hypothesis and further confirms previously demonstrated benefits of ANOR. This encourages the expended use of DCD organs, particularly with ANOR preconditioning.

In vivo multiparametric magnetic resonance imaging study for differentiating the severity of hepatic warm ischemia-reperfusion injury in a rabbit model

OBJECTIVES

To assess the value of multiparametric magnetic resonance imaging including intravoxel incoherent motion (IVIM), diffusion tensor imaging (DTI) and blood oxygen level dependent (BOLD) MRI in differentiating the severity of hepatic warm ischemia-reperfusion injury (WIRI) in a rabbit model.

METHODS

Fifty rabbits were randomly divided into a sham-operation group and four test groups (n = 10 for each group) according to different hepatic warm ischemia times. IVIM, DTI and BOLD MRI were performed on a 3 T MR scanner with 11 b values (0 to 800 s/mm²), 2 b values (0 and 500 s/mm²) on 12 diffusion directions, multiple-echo gradient echo (GRE) sequences (TR/TE, 75/2.57-24.25 ms), respectively. IVIM, DTI and BOLD MRI parameters, hepatic biochemical and histopathological parameters were compared. Pearson and Spearman correlation methods were performed to assess the correlation between these MRI parameters and laboratory parameters. Furthermore, receiver operating characteristic (ROC) curves were compiled to determine diagnostic efficacies.

RESULTS

True diffusion (Dslow), pseudodiffusion (Dfast), perfusion fraction (PF), mean diffusivity (MD) significantly decreased, while R2* significantly increased with prolonged warm ischemia times, and significant differences were found in all of biochemical and histopathological parameters (all P < 0.05). Dslow, PF, and R2* correlated significantly with all of biochemical and histopathological parameters (all |r| = 0.381-0.746, all P < 0.05). ROC analysis showed that the area under the ROC curve (AUC) of IVIM across hepatic WIRI groups was the largest among IVIM, DTI and BOLD.

CONCLUSIONS

Multiparametric MRI may be helpful with characterization of early changes and determination of severity of hepatic WIRI in a rabbit model.

Human Mesenchymal Stromal Cell-Derived Extracellular Vesicles Improve Liver Regeneration After Ischemia Reperfusion Injury in Mice

Hepatic ischemia reperfusion injury (IRI) remains a major obstacle in liver resection and transplantation surgery, especially in diseased organs. Human mesenchymal stromal cells (MSCs) are reported to acutely alleviate hepatic IRI in mice by releasing bioactive membrane-enclosed extracellular vesicles (EVs), but the long-term effects of MSC-derived EV on hepatic IRI are unknown. Given the considerable differentiation capacity of fibroblasts (FBs) during wound healing and their morphological similarities with MSC, the present study aimed to investigate the potential of these two cell types and their cell-derived EV in attenuating liver damage after IRI. EVs were isolated and purified from the supernatant of MSC and FB cultures and, subsequently, characterized by electron microscopy, nanoparticle tracking analysis, and western blot. Liver injury and organ regeneration in a murine in vivo model of IRI were assessed by serum transaminase levels, histopathology, and immunohistochemistry. Changes in expression of inflammation-associated genes within liver tissue were evaluated by reverse transcriptase quantitative polymerase chain reaction. MSC, MSC-derived EV, FB, and FB-derived EV were systemically administered before hepatic IRI. We found that MSC and MSC-derived EV decreased serum transaminase levels, reduced hepatic necrosis, increased the amount of Ki67-positive hepatocytes, and repressed the transcription of inflammation-associated genes. Although they had no impact on organ damage, FB and FB-derived EV showed some regenerative potential in the late phase of hepatic IRI. Compared to FB, MSC and their derived EV had a stronger potential to attenuate liver damage and improve organ regeneration after hepatic IRI. These results suggest that the key therapeutic factors are located within EV.

Aging aggravates hepatic ischemia-reperfusion injury in mice by impairing mitophagy with the involvement of the EIF2α-parkin pathway

Hepatic ischemia-reperfusion (I/R) injury fundamentally influences the performance of aged liver grafts. The significance of mitophagy in the age dependence of sensitivity to I/R injury remains poorly understood. Here, we show that aging aggravated hepatic I/R injury with decreased mitophagy in mice. The enhancement of mitophagy resulted in significant protection against hepatic I/R injury. Parkin, an E3 ubiquitin ligase, was found depleted by I/R in aged livers. In oxygen-glucose deprivation reperfusion (OGD-Rep.)-treated L02 cells, parkin silencing impaired mitophagy and aggravated cell damage through a relative large mitochondrial membrane potential transition. The phosphorylation of the endoplasmic reticulum stress response protein EIF2α, which was also reduced in the aged liver, induced parkin expression both in vivo and vitro. Forty-six hepatic biopsy specimens from liver graft were collected 2 hours after complete revascularization, followed by immunohistochemical analyses. Parkin expression was negatively correlated to donor age and the peak level of aspartate aminotransferase within first week after liver transplantation. Our translational study demonstrates that aging aggravated hepatic I/R injury by impairing the age-dependent mitophagy function via an insufficient parkin expression and identifies a new strategy to evaluate the capacity of an aged liver graft in the process of I/R through the parkin expression.

Combined docosahexaenoic acid and thyroid hormone supplementation as a protocol supporting energy supply to precondition and afford protection against metabolic stress situations

Liver preconditioning (PC) refers to the development of an enhanced tolerance to injuring stimuli. For example, the protection from ischemia-reperfusion (IR) in the liver that is obtained by previous maneuvers triggering beneficial molecular and functional changes. Recently, we have assessed the PC effects of thyroid hormone (T_3; single dose of 0.1 mg/kg) and n-3 long-chain polyunsaturated fatty acids (n-3 LCPUFAs; daily doses of 450 mg/kg for 7 days) that abrogate IR injury to the liver. This feature is also achieved by a combined T₃ and the n-3 LCPUFA docosahexaenoic acid (DHA) using a reduced period of supplementation of the FA (daily doses of 300 mg/kg for 3 days) and half of the T₃ dosage (0.05 mg/kg). T₃ -dependent protective mechanisms include (i) the reactive oxygen species (ROS)-dependent activation of transcription factors nuclear factor-κB (NF-κB), AP-1, signal transducer and activator of transcription 3, and nuclear factor erythroid-2-related factor 2 (Nrf2) upregulating the expression of protective proteins. (ii) ROS-induced endoplasmic reticulum stress affording proper protein folding. (iii) The autophagy response to produce FAs for oxidation and ATP supply and amino acids for protein synthesis. (iv) Downregulation of inflammasome nucleotide-bonding oligomerization domain leucine-rich repeat containing family pyrin containing 3 and interleukin-1β expression to prevent inflammation. N-3 LCPUFAs induce antioxidant responses due to Nrf2 upregulation, with inflammation resolution being related to production of oxidation products and NF-κB downregulation. Energy supply to achieve liver PC is met by the combined DHA plus T₃ protocol through upregulation of AMPK coupled to peroxisome proliferator-activated receptor-γ coactivator 1α signaling. In conclusion, DHA plus T₃ coadministration favors hepatic bioenergetics and lipid homeostasis that is of crucial importance in acute and clinical conditions such as IR, which may be extended to long-term or chronic situations including steatosis in obesity and diabetes. © 2019 IUBMB Life, 71(9):1211-1220, 2019.

Sevoflurane has postconditioning as well as preconditioning properties against hepatic warm ischemia-reperfusion injury in rats

PURPOSE

Ischemia-reperfusion (IR) injury is inevitable after liver transplantation and liver resection with inflow occlusion. Sevoflurane has been widely used during hepatobiliary surgery and was reported to exhibit preconditioning (PreC) properties against hepatic IR injury; however, its postconditioning (PostC) properties remain unknown. This study examined whether a clinically applicable dose of sevoflurane has PostC and PreC properties against hepatic IR injury and roles of heme oxygenase-1 (HO-1).

METHODS

Warm ischemia was induced in male Wistar rats, excluding the sham group, for 1 h, followed by 3 h of reperfusion. Group C received propofol from 60 min before ischemia until the end of the experimental procedure. In the SPreC and SPostC groups, propofol was replaced by 2.5% sevoflurane for 30 min from 35 min before ischemia in the SPreC group and for 30 min from 5 min before reperfusion in the SPostC group. The SPreC+Z and SPostC+Z groups received a HO-1 inhibitor, zinc protoporphyrin (Znpp), 60 min before ischemia, and sevoflurane PreC and PostC were induced.

RESULTS

Serum aspartate aminotransferase, alanine aminotransferase, and lactic dehydrogenase levels, and histological damage scores in the SPreC and SPostC groups were significantly lower than those in group C. Inhibiting HO-1 with Znpp partially blocked these protective effects of sevoflurane. Sevoflurane PreC and PostC significantly increased the number of HO-1-positive Kupffer cells in comparison with group C, and Znpp prevented sevoflurane-induced HO-1 expression.

CONCLUSION

PostC and PreC by sevoflurane at a clinically applicable dose have equally protective effects against hepatic IR injury by increasing HO-1 expression.

Pilot, Open, Randomized, Prospective Trial for Normothermic Machine Perfusion Evaluation in Liver Transplantation From Older Donors

Ex situ normothermic machine perfusion (NMP) might minimize ischemia/reperfusion injury (IRI) of liver grafts. In this study, 20 primary liver transplantation recipients of older grafts (≥70 years) were randomized 1:1 to NMP or cold storage (CS) groups. The primary study endpoint was to evaluate graft and patient survival at 6 months posttransplantation. The secondary endpoint was to evaluate liver and bile duct biopsies; IRI by means of peak transaminases within 7 days after surgery; and incidence of biliary complications at month 6. Liver and bile duct biopsies were collected at bench surgery, end of ex situ NMP, and end of transplant surgery. Interleukin (IL) 6, IL10, and tumor necrosis factor α (TNF-α) perfusate concentrations were tested during NMP. All grafts were successfully transplanted. Median (interquartile range) posttransplant aspartate aminotransferase peak was 709 (371-1575) IU/L for NMP and 574 (377-1162) IU/L for CS (P = 0.597). There was 1 hepatic artery thrombosis in the NMP group and 1 death in the CS group. In NMP, we observed high TNF-α perfusate levels, and these were inversely correlated with lactate (P < 0.001). Electron microscopy showed decreased mitochondrial volume density and steatosis and an increased volume density of autophagic vacuoles at the end of transplantation in NMP versus CS patients (P < 0.001). Use of NMP with older liver grafts is associated with histological evidence of reduced IRI, although the clinical benefit remains to be demonstrated.

Ischemic postconditioning decreases iNOS gene expression but ischemic preconditioning ameliorates histological injury in a swine model of extended liver resection

Background

Both pre- and postconditioning have been shown to protect the liver parenchyma from ischemia/reperfusion (I/R) injury during hepatectomy by altering the production of NO. However, to date there is no study to compare their effect on the inducible nitric oxide synthase (iNOS) and endothelial nitric oxide synthase (eNOS) gene expression, who are the main modulators in the pathway of NO during the acute phase of I/R injury.

Methods

We designed a prospective experimental cohort comprising of three groups (sham group-SG, preconditioning-PrG and postconditioning group-PoG) and consisting of 10 animals per group. All animals underwent extended hepatectomy (70%) under prolonged warm ischemia either after preconditioning or followed by postconditioning or without any protective maneuver (SG). Following reperfusion blood samples and liver biopsies were obtained at the start of reperfusion (0 hours), at 6 and 12 hours post reperfusion. iNOS and eNOS gene expression was assessed on liver tissue by polymerase chain reaction (PCR); in addition, the extent of hepatocellular injury was histologically assessed.

Results

At the beginning of reperfusion iNOS expression was significantly reduced in the PoG in comparison to the SG (Kruskal-Wallis test, P=0.012; Mann-Whitney U test, P<0.0005 Bonferroni correction) and continued to remain at low levels until 6 hours post reperfusion (Kruskal-Wallis test, P=0.01; Mann-Whitney U test, P<0.0005-Bonferroni correction) This difference was eliminated by 12 hours. No significant differences were found in the expression of eNOS between groups and within time measurements. Aspartate aminotransferase (AST) and Alkaline phosphatase (ALP) were found increased at the start of reperfusion; their levels continued to increase by 6 hours in all groups, however only in the PoG the increase attended statistical significance at 12 hours after reperfusion. ALT levels presented only minor alterations during the course of reperfusion. The PrG was found to have more intense hepatocellular injury at the start of reperfusion than the PoG however, that appeared to gradually settle by 12 hours in contrast to PoG where the hepatocellular injury continued to deteriorate.

Conclusions

PoG appeared to decrease iNOS overexpression more effectively than PrG in comparison to animals who have undergone no protective maneuver (SG). However, PrG was more effective than PoG in ameliorating the hepatocellular injury observed at 12 hours after the ischemic insult.

Gene Expression Profiling in Ischemic Postconditioning to Alleviate Mouse Liver Ischemia/Reperfusion Injury

Ischemic postconditioning (IPO) attenuates hepatic ischemia/reperfusion (I/R) injury. However, little is known about the underlying biological pathophysiology, which could be, at least in part, informed by exploring the transcriptomic changes using next-generation RNA sequencing (RNA-Seq). In this study, 18 mice (C57BL/6) were involved and randomly assigned to three groups: normal (n=6), I/R (n=6, subjected to 70% hepatic I/R), and IR+IPO (n=6, applying IPO to mice with I/R injury). We randomly selected 3 mice per group and extracted their liver tissues for next-generation RNA-Seq. We performed a bioinformatics analysis for two comparisons: normal vs. I/R and I/R vs. IR+IPO. From the analysis, 2416 differentially expressed genes (DEGs) were identified (p < 0.05 and fold change ≥ 1.5). Gene ontology (GO) analysis revealed that these genes were mainly related to cellular metabolic processes, nucleic acids and protein binding processes. The enriched Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways for the DEGs were the mitogen-activated protein kinase (MAPK), IL-17 signalling pathway, regulating pluripotency of stem cells, and insulin resistance pathway. Validation of 12 selected DEGs by qRT-PCR showed that Cyr61, Atf3, Nr4a1, Gdf15, Osgin1, Egr1, Epha2, Dusp1, Dusp6, Gadd45a and Gadd45b were significantly amplified. Finally, a protein-protein interaction (PPI) network constructed to determine interactions of these 11 DEGs. In summary, by exploring gene expression profiling in regard to hepatic I/R and IPO using next-generation RNA-Seq, we suggested a few progression-related genes and pathways, providing some clues for future experimental research.

Activation of PPARγ by Curcumin protects mice from ischemia/reperfusion injury induced by orthotopic liver transplantation via modulating polarization of Kupffer cells

Curcumin shows protective effects on various diseases due to its anti-inflammatory and anti-oxidative functions; however, its effect on organ transplantation has not been fully elucidated. To understand its role in liver ischemia/reperfusion (I/R) injury, we studied its impact on orthotopic liver transplantation (OLT) and Kupffer cells (KCs) polarization and its underlying mechanisms. We first investigated the reactive oxygen species (ROS) accumulation and cytokines profile of KCs, intracellular ROS and the mRNA level of pro-inflammatory cytokines were downregulated while the mRNA level of anti-inflammatory cytokine was upregulated by the pretreatment of Curcumin; Then the liver injury was detected by histopathological examination and liver function. Pretreatment with Curcumin significantly alleviated liver injury while improving liver function and overall post-transplantation survival compared with the control groups. The Western blotting showed that Curcumin inhibited the function of KCs via down-regulating the nuclear factor κb (NF-κb) signaling pathway by activating peroxisome proliferator-activated receptor γ (PPARγ) and flow cytometry revealed that Curcumin suppressed pro-inflammatory phenotype (M1) of KCs while promoting its anti-inflammatory phenotype (M2) polarization. These results showed that Curcumin may exert positive effects on I/R injury after OLT through activating PPARγ by inhibiting the activation of NF-κb pathway and remodeling the polarization of KCs. This may reveal a potential therapy for I/R injury after liver transplantation.

Isoglycyrrhizinate Magnesium Enhances Hepatoprotective Effect of FK506 on Ischemia-Reperfusion Injury Through HMGB1 Inhibition in a Rat Model of Liver Transplantation

BACKGROUND

Ischemia-reperfusion injury after liver transplantation (LT) impairs graft function and affects prognosis of recipients. Isoglycyrrhizinate magnesium (Iso) is a hepatoprotective drug usually used after liver injury. In this study, we intended to explore whether Iso alone have protective effect after ischemia-reperfusion injury in a rat model of liver transplantation. We also aimed to study whether Iso could enhance the hepatoprotective effect of FK506 (tacrolimus) and underlying mechanism.

METHODS

Rats after LT were treated with different concentration of FK506 with or without, Iso or lower-dose FK506 plus Iso. Alanine transaminase, aspartate transaminase, and albumin level were measured after 48 hours, 72 hours, and 7 days. A cell ischemic/reperfusion model was established to further study the mechanism of hepatoprotective effect of FK506 and Iso.

RESULTS

Iso treatment alone had no effect on liver grafts after LT, but lower-dose FK506 + Iso was better for maintenance of liver function than lower-dose FK506 alone at 48 hours, 72 hours, and 7 days after LT. In terms of mechanism, FK506 induced autophagy which resulted in significantly reduced apoptosis and maintained proliferative potential. However, autophagy induced by FK506 also lead to high-mobility group box (HMGB) 1 release from nuclei, resulting in hepatocyte injury through triggering of p38 phosphorylation and chemokine release. Iso effectively inhibited the release of HMGB1 and downstream inflammatory cytokines.

CONCLUSIONS

Iso could inhibit release of HMGB1 by FK506 and enhance the hepatoprotective effect of FK506 in rat LT. Combining Iso with FK506 would be promising for the patients after LT.

Modulation of Glutathione Hemostasis by Inhibition of 12/15-Lipoxygenase Prevents ROS-Mediated Cell Death after Hepatic Ischemia and Reperfusion

Background

Reactive oxygen species- (ROS-) mediated ischemia-reperfusion injury (IRI) detrimentally impacts liver transplantation and resection. 12/15-Lipoxygenase (12/15-LOX), an antagonistic protein of the glutathione peroxidase 4 (GPX4) signaling cascade, was proven to mediate cell death in postischemic cerebral and myocardial tissue. The aim of this study was to investigate the impact of 12/15-LOX inhibition on hepatic IRI.

Methods

Livers of C57BL/6 mice were exposed to 60 minutes of partial warm ischemia and 90 minutes of reperfusion after previous Baicalein administration, an inhibitor of 12/15-LOX. Tissue samples were analyzed by TUNEL assay, Western blot, and spectral photometry.

Results

TUNEL labeling showed a significant reduction of hepatic cell death following baicalein pretreatment. Western Blot analysis revealed a significant downregulation of Jun-amino-terminal-kinase (JNK), caspase-3, and poly-ADP-ribose-polymerase (PARP), besides considerably lowered p44/42-MAP-kinase (ERK1/2) expression after Baicalein administration. A significant elevation of glutathione oxidation was measured in Baicalein pretreated livers.

Conclusion

Our data show that inhibition of 12/15-lipoxygenase causes significant cell death reduction after hepatic ischemia and reperfusion by enhancing glutathione metabolism. We conclude that GPX4-dependent cell death signaling cascade might play a major role in development of hepatic IRI, in which the investigated proteins JNK, caspase-3, ERK1/2, and PARP might contribute to tissue damage.

Oral administration of cilostazol improves survival rate after rat liver ischemia/reperfusion injury

BACKGROUND

Cilostazol is a type III phosphodiesterase inhibitor used to treat the symptoms of intermittent claudication. Recent studies have shown that cilostazol decreases ischemia/reperfusion (I/R) injury in several organs.

MATERIALS AND METHODS

We evaluated the effects of cilostazol in a rat model of liver I/R injury. Thirty male Wistar rats with liver I/R injury were divided into a cilostazol or saline (control) group (n = 15 each). Each rat was orally administered cilostazol or saline for 3 d before I/R injury. Liver I/R injury was induced via 1 h of warm ischemia of the median and left lateral liver lobes, followed by 3 h of reperfusion. The rats were then euthanized. Serum aspartate aminotransferase, alanine aminotransferase, interleukin (IL)-1β, IL-6, and tumor necrosis factor-α levels were measured. The Mann-Whitney U test was used to compare the differences between the treatment groups. Histologic examination was performed on the liver tissues. We also conducted a survival study to confirm the effect of cilostazol on the mortality rate in rats. For the survival study, a liver I/R injury model with an ischemia time of 1.5 h was used, and the rats were observed for 1 wk.

RESULTS

Serum aspartate aminotransferase, alanine aminotransferase, IL-1β, and IL-6 levels were significantly lower in the cilostazol group than in the saline group. Treatment with cilostazol significantly improved pathological findings associated with liver I/R injury and increased survival rate compared to that in controls.

CONCLUSIONS

Cilostazol reduced mortality and alleviated the effects of liver I/R injury in Wistar rats.

Delivery of Soluble Heme Oxygenase 1 Cell-Penetrating Peptide into Liver Cells in in vitro and ex vivo Models of Cold Ischemia

BACKGROUND/PURPOSE

Liver transplantation is the treatment of choice in patients with end-stage liver disease. During liver transplantation, ischemia-reperfusion injury (IRI) occurs, which is an inevitable consequence of the transplantation process. To reduce the extent of cellular injury, one of the proteins that have been extensively investigated is heme oxygenase 1 (HO-1), which plays an important role in protecting the organs against IRI. The aim of this study was to introduce an active and functional HO-1 protein conjugated to a cell-penetrating peptide (CPP) in vitro and ex vivo into liver cells in hypothermic and anoxic conditions and to assert its cytoprotective effects.

METHODS

We generated an enzymatically active soluble (s)HO-1-CPP recombinant protein. The ability of the sHO-1-CPP protein to penetrate McA-RH7777, Clone 9, and Hep G2 cells, primary hepatocytes, and Kupffer and human umbilical vein endothelial cells in vitro, as well as its ability to penetrate a whole liver ex vivo under hypothermic and anoxic conditions, was assessed. An in vitro hypoxia-reoxygenation (HR) model was used to determine the cytoprotective effect of the sHO-1-CPP protein.

RESULTS

We showed that our recombinant protein sHO-1-CPP can cross cell membranes into rodent and human liver cells in vitro, and the results were further validated ex vivo, where rodent livers were perfused with an organ preservation solution supplemented with sHO-1-CPP under anoxic and hypothermic conditions. Immunohistochemistry revealed an intracellular localization of sHO-1-CPP in zones 1-3 of the perfused livers. The CPP did not exert any significant toxicity on the cells. Treating cells with sHO-1-CPP showed significant cytoprotection in the in vitro HR model.

CONCLUSIONS

Our findings show that the recombinant protein sHO-1-CPP can be successfully delivered to cells of a whole organ in an ex vivo hypothermic and anoxic perfusion model and that it provides cytoprotection to hepatocytes in an in vitro HR model. These results hold great potential for future repair and protection of donor organs. Future experiments are planned to confirm these data in in vivo models of IRI.

Liver regeneration - mechanisms and models to clinical application

Liver regeneration has been studied for many decades and the mechanisms underlying regeneration of the normal liver following resection or moderate damage are well described. A large number of factors extrinsic (such as bile acids and circulating growth factors) and intrinsic to the liver interact to initiate and regulate liver regeneration. Less well understood, and more clinically relevant, are the factors at play when the abnormal liver is required to regenerate. Fatty liver disease, chronic scarring, prior chemotherapy and massive liver injury can all inhibit the normal programme of regeneration and can lead to liver failure. Understanding these mechanisms could enable the rational targeting of specific therapies to either reduce the factors inhibiting regeneration or directly stimulate liver regeneration. Although animal models of liver regeneration have been highly instructive, the clinical relevance of some models could be improved to bridge the gap between our in vivo model systems and the clinical situation. Likewise, modern imaging techniques such as spectroscopy will probably improve our understanding of whole-organ metabolism and how this predicts the liver's regenerative capacity. This Review describes briefly the mechanisms underpinning liver regeneration, the models used to study this process, and discusses areas in which failed or compromised liver regeneration is clinically relevant.

Activation of Autophagy by Everolimus Confers Hepatoprotection Against Ischemia-Reperfusion Injury

As the criteria for liver donation have been extended to include marginal donors, liver grafts are becoming particularly vulnerable to hepatic ischemia-reperfusion injury (IRI). However, no specific measures have been validated to ameliorate hepatic IRI. In this article, we explored whether everolimus has protective effects against hepatic IRI in relation with autophagy. The effects of everolimus were investigated in both in vitro and in vivo hepatic IRI models. Mouse hepatocyte AML12 cells and BALB/c mice were utilized for the establishment of each model. In the IRI-induced AML12 cells, everolimus treatment increased the expressions of autophagic markers (microtubule-associated protein 1 light chain 3 and p62) and decreased pro-apoptotic proteins (cleaved caspase 3 and cleaved poly-ADP ribose polymerase). The blockage of autophagy, using either bafilomycin A1 or si-autophagy-related protein 5, abrogated these anti-apoptosis effects of everolimus. Subsequently, everolimus administration to the hepatic IRI-induced mice provided hepatoprotective effects in terms of (1) decreasing the expressions of pro-apoptotic proteins, (2) inhibiting the release of pro-inflammatory cytokines (IL-6 and tumor necrosis factor-α), (3) reducing elevated liver enzymes (aspartate transaminase, alanine transaminase, and ammonia), and (4) restoring liver histopathology. These findings suggest that everolimus protects the liver against hepatic IRI by way of activating autophagy, and thus could be a potential therapeutic agent for hepatic IRI.

Baicalein pretreatment reduces liver ischemia/reperfusion injury via induction of autophagy in rats

We previously demonstrated that baicalein could protect against liver ischemia/reperfusion (I/R) injury in mice. The exact mechanism of baicalein remains poorly understood. Autophagy plays an important role in protecting against I/R injury. This study was designed to determine whether baicalein could protect against liver I/R injury via induction of autophagy in rats. Baicalein was intraperitoneally injected 1 h before warm ischemia. Pretreatment with baicalein prior to I/R insult significantly blunted I/R-induced elevations of serum aminotransferase levels and significantly improved the histological status of livers. Electron microscopy and expression of the autophagic marker LC3B-II suggested induction of autophagy after baicalein treatment. Moreover, inhibition of the baicalein-induced autophagy using 3-methyladenine (3-MA) worsened liver injury. Furthermore, baicalein treatment increased heme oxygenase (HO)-1 expression, and pharmacological inhibition of HO-1 with tin protoporphyrin IX (SnPP) abolished the baicalein-mediated autophagy and the hepatocellular protection. In primary rat hepatocytes, baicalein-induced autophagy also protected hepatocytes from hypoxia/reoxygenation injury in vitro and the beneficial effect was abrogated by 3-MA or Atg7 siRNA, respectively. Suppression of HO-1 activity by SnPP or HO-1 siRNA prevented the baicalein-mediated autophagy and resulted in increased hepatocellular injury. Collectively, these results suggest that baicalein prevents hepatocellular injury via induction of HO-1-mediated autophagy.

Causal role of oxidative stress in unfolded protein response development in the hyperthyroid state

L-3,3',5-Triiodothyronine (T3)-induced liver oxidative stress underlies significant protein oxidation, which may trigger the unfolded protein response (UPR). Administration of daily doses of 0.1mg T3 for three consecutive days significantly increased the rectal temperature of rats and liver O2 consumption rate, with higher protein carbonyl and 8-isoprostane levels, glutathione depletion, and absence of morphological changes in liver parenchyma. Concomitantly, liver protein kinase RNA-like endoplasmic reticulum (ER) kinase and eukaryotic translation initiator factor 2α were phosphorylated in T3-treated rats compared to controls, with increased protein levels of binding immunoglobulin protein and activating transcription factor 4. In addition, higher mRNA levels of C/EBP homologous protein, growth arrest and DNA damage 34, protein disulfide isomerase, and ER oxidoreductin 1α were observed, changes that were suppressed by N-acetylcysteine (0.5 g/kg) given before each dose of T3. In conclusion, T3-induced liver oxidative stress involving higher protein oxidation status has a causal role in UPR development, a response that is aimed to alleviate ER stress and promote cell survival.

Pharmacological Preconditioning by Adenosine A2a Receptor Stimulation: Features of the Protected Liver Cell Phenotype

Ischemic preconditioning (IP) of the liver by a brief interruption of the blood flow protects the damage induced by a subsequent ischemia/reperfusion (I/R) preventing parenchymal and nonparenchymal liver cell damage. The discovery of IP has shown the existence of intrinsic systems of cytoprotection whose activation can stave off the progression of irreversible tissue damage. Deciphering the molecular mediators that underlie the cytoprotective effects of preconditioning can pave the way to important therapeutic possibilities. Pharmacological activation of critical mediators of IP would be expected to emulate or even to intensify its salubrious effects. In vitro and in vivo studies have demonstrated the role of the adenosine A2a receptor (A2aR) as a trigger of liver IP. This review will provide insight into the phenotypic changes that underline the resistance to death of liver cells preconditioned by pharmacological activation of A2aR and their implications to develop innovative strategies against liver IR damage.

Molecular pathways in protecting the liver from ischaemia/reperfusion injury: a 2015 update

Ischaemia/reperfusion injury is an important cause of liver damage during surgical procedures such as hepatic resection and liver transplantation, and represents the main cause of graft dysfunction post-transplantation. Molecular processes occurring during hepatic ischaemia/reperfusion are diverse, and continuously include new and complex mechanisms. The present review aims to summarize the newest concepts and hypotheses regarding the pathophysiology of liver ischaemia/reperfusion, making clear distinction between situations of cold and warm ischaemia. Moreover, the most updated therapeutic strategies including pharmacological, genetic and surgical interventions, as well as some of the scientific controversies in the field are described.

Machine perfusion in liver transplantation as a tool to prevent non-anastomotic biliary strictures: Rationale, current evidence and future directions

The high incidence of non-anastomotic biliary strictures (NAS) after transplantation of livers from extended criteria donors is currently a major barrier to widespread use of these organs. This review provides an update on the most recent advances in the understanding of the etiology of NAS. These new insights give reason to believe that machine perfusion can reduce the incidence of NAS after transplantation by providing more protective effects on the biliary tree during preservation of the donor liver. An overview is presented regarding the different endpoints that have been used for assessment of biliary injury and function before and after transplantation, emphasizing on methods used during machine perfusion. The wide spectrum of different approaches to machine perfusion is discussed, including the many different combinations of techniques, temperatures and perfusates at varying time points. In addition, the current understanding of the effect of machine perfusion in relation to biliary injury is reviewed. Finally, we explore directions for future research such as the application of (pharmacological) strategies during machine perfusion to further improve preservation. We stress the great potential of machine perfusion to possibly expand the donor pool by reducing the incidence of NAS in extended criteria organs.

Challenges in early clinical drug development for ischemia-reperfusion injury in kidney transplantation

INTRODUCTION

In an effort to expand the donor pool, kidneys from donation after cardiac death (DCD) donors are increasingly utilised in renal transplantation. These kidneys suffer greater ischemia-reperfusion injury (IRI) and have a higher incidence of delayed graft function. In the last 25 years, relatively few pharmacological therapies to reduce IRI have been tested in randomised controlled trials in renal transplantation and currently no pharmacological agents are routinely utilised for this purpose.

AREAS COVERED

The authors look at why promising treatments in pre-clinical studies have not translated to significant clinical benefit in human trials. This may reflect a translational disconnect between the pre-clinical models used and clinical problems that are encountered in the transplant population. They also discuss the issues in conducting clinical trials and its implication on drug development.

EXPERT OPINION

Translating pharmacological strategies for reducing IRI is highly challenging at every stage of development from pre-clinical studies to clinical trials. Scientific knowledge of the complexity of IRI is rapidly evolving and new treatments are expected to emerge. There are ethical barriers that prevent donor treatments, particularly in the DCD setting. However, new clinical techniques such as normothermic regional and ex-vivo perfusion represent exciting opportunities to utilise pharmacological agents earlier in the process of transplantation.

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

CONTEXT

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

OBJECTIVE

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

MATERIALS AND METHODS

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

RESULTS

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

DISCUSSION AND CONCLUSION

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

Analysis of ischemia/reperfusion injury in time-zero biopsies predicts liver allograft outcomes

Ischemia/reperfusion injury (IRI) that develops after liver implantation may prejudice long-term graft survival, but it remains poorly understood. Here we correlate the severity of IRIs that were determined by histological grading of time-zero biopsies sampled after graft revascularization with patient and graft outcomes. Time-zero biopsies of 476 liver transplants performed at our center between 2000 and 2010 were graded as follows: nil (10.5%), mild (58.8%), moderate (26.1%), and severe (4.6%). Severe IRI was associated with donor age, donation after circulatory death, prolonged cold ischemia time, and liver steatosis, but it was also associated with increased rates of primary nonfunction (9.1%) and retransplantation within 90 days (22.7%). Longer term outcomes in the severe IRI group were also poor, with 1-year graft and patient survival rates of only 55% and 68%, respectively (cf. 90% and 93% for the remainder). Severe IRI on the time-zero biopsy was, in a multivariate analysis, an independent determinant of 1-year graft survival and was a better predictor of 1-year graft loss than liver steatosis, early graft dysfunction syndrome, and high first-week alanine aminotransferase with a positive predictive value of 45%. Time-zero biopsies predict adverse clinical outcomes after liver transplantation, and severe IRI upon biopsy signals the likely need for early retransplantation.

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.