Past and future approaches to ischemia-reperfusion lesion associated with liver transplantation

Mitigating hepatic ischemia and reperfusion injury with polyethylene glycol-enriched Ringer's lactate fluid: insights from an isolated perfused rat model

BACKGROUND

Cold ischemia-reperfusion (IR) injury is a multifactorial process detrimental to liver graft function during liver transplantation (LT). Although flushing hepatic grafts prior to reperfusion have been well explored, the optimal graft rinse solution to prevent cold IR injury remains largely undefined. The aim of this study was to evaluate whether a new rinse solution combining polyethylene glycol PM 35,000 Da (PEG35) with lactated solution (RLS) could mitigate cold IR injury in Wistar rats.

METHODS

Livers were isolated, preserved for 24 h and flushed immediately before ex vivo reperfusion with either RLS or PEG35-enriched RLS. Liver injury, graft function, energy balance, autophagy, oxidative stress as well as inflammatory response were assessed.

RESULTS

Flushing hepatic grafts with PEG35-enriched RLS resulted in decreased transaminase levels after cold ischemia. The improved graft function was evidenced by increased bile flow, enhanced BSP clearance, and reduced vascular resistance in these flushed grafts. Phospho-AMPK protein expression, as well as LC3B gene and protein expression were significantly increased compared to those unflushed and flushed only with RLS. PEG35-enriched RLS also maintained the oxidative state, as indicated by reduced activities of antioxidant enzymes and decreased MDA concentration. Additionally, this graft rinse solution down-regulated the inflammatory response by inhibiting the expression of genes involved in the HMGB-1/NF-κB/TNF-α signaling pathway.

CONCLUSION

These data strongly suggest that rinsing liver grafts with PEG35-enriched RLS prior to reperfusion represents a simple and cost-effective strategy to enhance liver functional recovery after cold IR injury. This approach could serve as a viable alternative to RLS in clinical applications, highlighting the need for further research to explore its broader implications.

Regulation of Adiponectin and Resistin in Liver Transplantation Protects Grafts from Extended-Criteria Donors

The donor shortage increases liver transplantation (LT) waiting lists, making it crucial to consider extended-criteria donors, such as steatotic donors after brain death (DBDs) or cardiocirculatory death (DCDs). Nevertheless, steatosis, brain death, and cardiocirculatory death are key risk factors for poor LT outcomes. Herein, the role and therapeutic usefulness of several adipocytokines was investigated to protect such grafts from extended-criteria donors. Sprague rats with nutritionally induced steatosis were used in an experimental LT model with grafts from DBDs or DCDs. Adiponectin, resistin, and visfatin were measured and pharmacologically modulated, and effects on liver injury were assessed. Visfatin played no role under conditions of either DBD or DCD LT. Brain death increased adiponectin and reduced resistin. Adiponectin harmed steatotic and nonsteatotic DBD grafts, via a resistin-dependent mechanism; restraining adiponectin increased resistin, reducing damage. Resistin treatment protected both types of DBD grafts, whereas suppressing it increased damage. This adiponectin-resistin pathway was dependent on protein kinase C. In DCD LT, adiponectin and resistin were not modified in nonsteatotic grafts, but reduced in steatotic ones. Adiponectin or resistin treatments protected steatotic grafts: hepatic adiponectin activated AMP-activated protein kinase ; hepatic resistin increased phosphatidylinositol 3-kinase-Akt. Concomitant administration of both adipocytokines increased both signaling pathways, intensifying protection. These data suggest that pharmacologic modulation of adiponectin and resistin as therapies might potentially be translated to clinical studies to improve surgical outcomes for LT from extended-criteria donors.

Machine Perfusion as a Strategy to Decrease Ischemia-Reperfusion Injury and Lower Cancer Recurrence Following Liver Transplantation

Liver transplantation (LT) is a key treatment for primary and secondary liver cancers, reducing tumor burden with concurrent improvement of liver function. While significant improvement in survival is noted with LT, cancer recurrence rates remain high. Mitochondrial dysfunction caused by ischemia-reperfusion injury (IRI) is known to drive tumor recurrence by creating a favorable microenvironment rich in pro-inflammatory and angiogenic factors. Therefore, strategies that decrease reperfusion injury and mitochondrial dysfunction may also decrease cancer recurrence following LT. Machine perfusion techniques are increasingly used in routine clinical practice of LT with improved post-transplant outcomes and increased use of marginal grafts. Normothermic (NMP) and hypothermic oxygenated machine perfusion (HOPE) provide oxygen to ischemic tissues, and impact IRI and potential cancer recurrence through different mechanisms. This article discussed the link between IRI-associated inflammation and tumor recurrence after LT. The current literature was screened for the role of machine perfusion as a strategy to mitigate the risk of cancer recurrence. Upfront NMP ("ischemia free organ transplantation") and end-ischemic HOPE were shown to reduce hepatocellular carcinoma recurrence in retrospective studies. Three prospective randomized controlled trials are ongoing in Europe to provide robust evidence on the impact of HOPE on cancer recurrence in LT.

Oleanolic acid alleviating ischemia-reperfusion injury in rat severe steatotic liver via KEAP1/NRF2/ARE

Severe steatosis in donor livers is contraindicated for transplantation due to the high risk of ischemia-reperfusion injury (IRI). Although Ho-1 gene-modified bone marrow mesenchymal stem cells (HO-1/BMMSCs) can mitigate IRI, the role of gut microbiota and metabolites in this protection remains unclear. This study aimed to explore how gut microbiota and metabolites contribute to HO-1/BMMSCs-mediated protection against IRI in severe steatotic livers. Using rat models and cellular models (IAR20 and THLE-2 cells) of steatotic liver IRI, this study revealed that ischemia-reperfusion led to significant liver and intestinal damage, heightened immune responses, impaired liver function, and altered gut microbiota and metabolite profiles in rats with severe steatosis, which were partially reversed by HO-1/BMMSCs transplantation. Integrated microbiome and metabolome analyses identified gut microbial metabolite oleanolic acid as a potential protective agent against IRI. Experimental validation showed that oleanolic acid administration alone alleviated IRI and inhibited ferroptosis in both rat and cellular models. Network pharmacology and molecular docking implicated KEAP1/NRF2 pathway as a potential target of oleanolic acid. Indeed, OA experimentally upregulated NRF2 activity, which underlies its inhibition of ferroptosis and protection against IRI. The gut microbial metabolite OA protects against IRI in severe steatotic liver by promoting NRF2 expression and activity, thereby inhibiting ferroptosis.

Enhancing Liver Transplant Outcomes through Liver Precooling to Mitigate Inflammatory Response and Protect Mitochondrial Function

Transplanted organs experience several episodes of ischemia and ischemia-reperfusion. The graft injury resulting from ischemia-reperfusion (IRI) remains a significant obstacle to the successful survival of transplanted grafts. Temperature significantly influences cellular metabolic rates because biochemical reactions are highly sensitive to temperature changes. Consequently, lowering the temperature could reduce the degradative reactions triggered by ischemia. In mitigating IRI in liver grafts, the potential protective effect of localized hypothermia on the liver prior to blood flow obstruction has yet to be explored. In this study, we applied local hypothermia to mouse donor livers for a specific duration before stopping blood flow to liver lobes, a procedure called "liver precooling". Mouse donor liver temperature in control groups was controlled at 37 °C. Subsequently, the liver donors were preserved in cold University of Wisconsin solution for various durations followed by orthotopic liver transplantation. Liver graft injury, function and inflammation were assessed at 1 and 2 days post-transplantation. Liver precooling exhibited a significant improvement in graft function, revealing more than a 47% decrease in plasma aspartate transaminase (AST) and alanine aminotransferase (ALT) levels, coupled with a remarkable reduction of approximately 50% in liver graft histological damage compared to the control group. The protective effects of liver precooling were associated with the preservation of mitochondrial function, a substantial reduction in hepatocyte cell death, and a significantly attenuated inflammatory response. Taken together, reducing the cellular metabolism and enzymatic activity to a minimum level before ischemia protects against IRI during transplantation.

Sirtuin 5 Alleviates Liver Ischemia/Reperfusion Injury by Regulating Mitochondrial Succinylation and Oxidative Stress

Aims: Mitochondrial dysfunction is the primary mechanism of liver ischemia/reperfusion (I/R) injury. The lysine desuccinylase sirtuin 5 (SIRT5) is a global regulator of the mitochondrial succinylome and has pivotal roles in mitochondrial metabolism and function; however, its hepatoprotective capacity in liver I/R remains unclear. In this study, we established liver I/R model in SIRT5-silenced and SIRT5-overexpressed mice to examine the role and precise mechanisms of SIRT5 in liver I/R injury. Results: Succinylation was strongly enriched in liver mitochondria during I/R, and inhibiting mitochondrial succinylation significantly attenuated liver I/R injury. Importantly, the levels of the desuccinylase SIRT5 were notably decreased in liver transplant patients, as well as in mice subjected to I/R and in AML12 cells exposed to hypoxia/reoxygenation. Furthermore, SIRT5 significantly ameliorated liver I/R-induced oxidative injury, apoptosis, and inflammation by regulating mitochondrial oxidative stress and function. Intriguingly, the hepatoprotective effect of SIRT5 was mediated by PRDX3. Mechanistically, SIRT5 specifically desuccinylated PRDX3 at the K84 site, which enabled PRDX3 to alleviate mitochondrial oxidative stress during liver I/R. Innovation: This study denoted the new effect and mechanism of SIRT5 in regulating mitochondrial oxidative stress through lysine desuccinylation, thus preventing liver I/R injury. Conclusions: Our findings demonstrate for the first time that SIRT5 is a key mediator of liver I/R that regulates mitochondrial oxidative stress through the desuccinylation of PRDX3, which provides a novel strategy to prevent liver I/R injury. Antioxid. Redox Signal. 40, 616-631.

Effect of PERLA®, a new cold-storage solution, on oxidative stress injury and early graft function in rat kidney transplantation model

BACKGROUND

The composition of organ preservation solutions is crucial for maintaining graft integrity and early graft function after transplantation. The aim of this study is to compare new organ preservation solution PERLA® with the gold standard preservation solution University of Wisconsin (UW) regarding oxidative stress and early graft injury.

METHODS

In order to assess oxidative stress after cold storage, kidney grafts have been preserved for 18 h at 4° C in either UW solution or PERLA® solution and then assessed for oxidative stress injury (protocol 1). To assess kidney injuries and oxidative stress after reperfusion, rat kidneys were harvested, stored in cold UW or in PERLA® solutions for 18 h at 4 °C and then transplanted heterotopically for 6 h (protocol 2). PERLA® is a high Na+/low K+ solution including PEG-35 (1 g/L), trimetazidine (1 µM), carvedilol (10 µM) and tacrolimus (5 µM).

RESULTS

Our results showed that preservation of kidneys in PERLA® solution significantly attenuates oxidative stress parameters after cold storage and reperfusion. We found a significant decrease in oxidative damage indicators (MDA, CD and CP) and a significant increase in antioxidant indicators (GPx, GSH, CAT, SOD and PSH). Moreover, PERLA® solution decreased kidney injury after reperfusion (creatinine, LDH and uric acid).

CONCLUSION

PERLA® solution was more effective than UW storage solution in preserving rat's kidney grafts.

ADAR1 regulates macrophage polarization and is protective against liver ischemia and reperfusion injury

Liver ischemia and reperfusion injury (LIRI) is a major risk for the poor prognosis of patients receiving liver transplantation. The molecular mechanism involved in LIRI is complex and related to various cellular components. We previously reported that adenosine deaminase acting on RNA 1 (ADAR1) alleviated the allogeneic skin graft rejection by regulating macrophage polarization. However, the regulatory effects of ADAR1 on liver macrophages after LIRI remain largely unknown. In this study, we mainly adopted a mouse model of LIRI and cellular experiments with hypoxia and reoxygenation (HR) treatment to explore the regulatory roles of ADAR1 on liver macrophages under LIRI conditions. We found that IRI caused decreased ADAR1 in liver tissues and remarkable changes of liver macrophage polarization and profiles. ADAR1 supplementation alleviated the pathological injury caused by IRI and accelerated the activation of M2 macrophages in the liver of IRI mice. Increased hypoxia duration reduced ADAR1 expression levels in murine RAW264.7 macrophages at the transcriptional level. Further overexpression of ADAR1 significantly increased the expressions of anti-inflammatory cytokines and promoted M2 polarization of macrophages under HR exposure. ADAR1 knockdown exhibited opposite effects on macrophage polarization. Hence, ADAR1 promotes the M2 polarization of liver macrophages that may further alleviate LIRI. The protective effects of ADAR1 against LIRI provide a novel insight into the prevention and treatment of LIRI.

Role of the immune system in liver transplantation and its implications for therapeutic interventions

Liver transplantation (LT) stands as the gold standard for treating end-stage liver disease and hepatocellular carcinoma, yet postoperative complications continue to impact survival rates. The liver's unique immune system, governed by a microenvironment of diverse immune cells, is disrupted during processes like ischemia-reperfusion injury posttransplantation, leading to immune imbalance, inflammation, and subsequent complications. In the posttransplantation period, immune cells within the liver collaboratively foster a tolerant environment, crucial for immune tolerance and liver regeneration. While clinical trials exploring cell therapy for LT complications exist, a comprehensive summary is lacking. This review provides an insight into the intricacies of the liver's immune microenvironment, with a specific focus on macrophages and T cells as primary immune players. Delving into the immunological dynamics at different stages of LT, we explore the disruptions after LT and subsequent immune responses. Focusing on immune cell targeting for treating liver transplant complications, we provide a comprehensive summary of ongoing clinical trials in this domain, especially cell therapies. Furthermore, we offer innovative treatment strategies that leverage the opportunities and prospects identified in the therapeutic landscape. This review seeks to advance our understanding of LT immunology and steer the development of precise therapies for postoperative complications.

Short-Term and Long-Term Effects of Ischemic Conditioning on Liver Transplantation: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

BACKGROUND

Although liver transplantation (LT) is one of the definitive treatments for patients with end-stage liver failure, it inevitably results in ischemic reperfusion injury. It is known that prognosis is improved when temporary ischemic conditioning (IC) is applied to patients with ischemic reperfusion injury. The objective of this meta-analysis was to determine the short-term and long-term effects of IC on the clinical outcomes of LT recipients.

METHODS

Randomized controlled studies on IC in patients with LTs were included. Patients were compared between an IC group and a sham group. Studies were retrieved from PubMed, Embase, and Cochrane Library. The risk of bias was evaluated using RoB 2.0. Mortality, graft function, and major complications were synthesized using RevMan 5.4.1.

RESULTS

Among 316 papers, 17 articles (1196 patients) were included. There was an insignificant increase in short-term mortality (risk ratio [RR]: 3.00, 95% CI: 0.32-28.14, P = .34). However, long-term mortality was lower in the IC group than in the sham group, but not significantly (RR: 0.75; 95% CI: 0.47-1.20, P = .23). Short-term graft function (acute graft rejection and primary graft non-function) was not improved by IC. One-year graft loss tended to show better results in the IC group (RR: 0.53, 95% CI: 0.26-1.07, P = .08).

CONCLUSION

Ischemic conditioning did not have a beneficial effect on LT. Although long-term outcomes appear to be better in the IC group than in the sham group, further randomized controlled trials are needed.

Melatonin Preserves Fluidity in Cell and Mitochondrial Membranes against Hepatic Ischemia-Reperfusion

We evaluated the in vivo effects of melatonin treatment on oxidative damage in the liver in an experimental model of ischemia-reperfusion. A total of 37 male Sprague-Dawley rats were randomly divided into four groups: control, ischemia, ischemia + reperfusion, and ischemia + reperfusion + melatonin. Hepatic ischemia was maintained for 20 min, and the clamp was removed to initiate vascular reperfusion for 30 min. Melatonin (50 mg/kg body weight) was intraperitoneally administered. Fluidity was measured by polarization changes in 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene-p-toluene sulfonate). After 20 min of ischemia, no significant changes were observed in cell and mitochondrial membrane fluidity levels, lipid peroxidation, and protein carbonylation. However, after 30 min of reperfusion, membrane fluidity decreased compared to controls. Increases in lipid and protein oxidation were also seen in hepatic homogenates of animals exposed to reperfusion. Melatonin injected 30 min before ischemia and reperfusion fully prevented membrane rigidity and both lipid and protein oxidation. Livers from ischemia-reperfusion showed histopathological alterations and positive labeling with antibodies to oxidized lipids and proteins. Melatonin reduced the severity of these morphological changes and protected against in vivo ischemia-reperfusion-induced toxicity in the liver. Therefore, melatonin might be a candidate for co-treatment for patients with hepatic vascular occlusion followed by reperfusion.

Impact of Hyperoxia after Graft Reperfusion on Lactate Level and Outcomes in Adults Undergoing Orthotopic Liver Transplantation

BACKGROUND

Hyperoxia is common during liver transplantation (LT), without being supported by any guidelines. Recent studies have shown the potential deleterious effect of hyperoxia in similar models of ischemia-reperfusion. Hyperoxia after graft reperfusion during orthotopic LT could increase lactate levels and worsen patient outcomes.

METHODS

We conducted a retrospective and monocentric pilot study. All adult patients who underwent LT from 26 July 2013 to 26 December 2017 were considered for inclusion. Patients were classified into two groups according to oxygen levels before graft reperfusion: the hyperoxic group (PaO₂ > 200 mmHg) and the nonhyperoxic group (PaO₂ < 200 mmHg). The primary endpoint was arterial lactatemia 15 min after graft revascularization. Secondary endpoints included postoperative clinical outcomes and laboratory data.

RESULTS

A total of 222 liver transplant recipients were included. Arterial lactatemia after graft revascularization was significantly higher in the hyperoxic group (6.03 ± 4 mmol/L) than in the nonhyperoxic group (4.81 ± 2 mmol/L), p < 0.01. The postoperative hepatic cytolysis peak, duration of mechanical ventilation and duration of ileus were significantly increased in the hyperoxic group.

CONCLUSIONS

In the hyperoxic group, the arterial lactatemia, the hepatic cytolysis peak, the mechanical ventilation and the postoperative ileus were higher than in the nonhyperoxic group, suggesting that hyperoxia worsens short-term outcomes and could lead to increase ischemia-reperfusion injury after liver transplantation. A multicenter prospective study should be performed to confirm these results.

Chlorogenic Acid Alleviates Hepatic Ischemia-Reperfusion Injury by Inhibiting Oxidative Stress, Inflammation, and Mitochondria-Mediated Apoptosis In Vivo and In Vitro

Hepatic ischemia-reperfusion injury (HIRI) is the main reason for organ failure following liver surgery; however, its underlying causes are complex, and include oxidative stress, sterile inflammatory, and mitochondrial damage. Unfortunately, treatments for HIRI are based on supportive therapy, and no specific drugs or methods are currently available. Chlorogenic acid (CGA) is a dietary polyphenol with a wide range of pharmacological effects and it has a protective effect on HIRI; however, its specific mechanism remains unclear. In this study, we investigated that CGA pretreatment exerts protective effects against HIRI and the potential underlying mechanisms. We found that CGA pretreatment reduced ALT, AST, MDA, TNF-α, and IL-1β levels following HIRI, improved SOD and GSH levels, and alleviated pathological liver tissue damage, with the highest CGA dose (100 mg/kg.d) exerted the strongest effect. In addition, we showed that CGA pretreatment significantly decreased the levels of reactive oxygen species following HIRI, inhibited HMGB1 release by decreasing IRF-1 expression, inhibited the expression of HMGB1, TLR-4, MyD88, P-IκB-α, NF-κB P65, and P-P65, and promoted IκB-α degradation. Thus, CGA appears to inhibit oxidative stress and inflammatory responses during HIRI. Furthermore, we found that CGA pretreatment reduced hepatocyte apoptosis following HIRI, alleviated mitochondrial damage, promoted BCL-2 expression, inhibited Bax upregulation, and inhibited cytochrome C release to prevent caspase activation, thereby reducing the expression of the caspase-independent pathway components, ENDOG and AIF. Together, our findings suggest that CGA can protect against HIRI by inhibiting oxidative stress, the HMGB1/TLR-4/NF-κB signaling pathway-mediated inflammatory responses, and mitochondria-mediated apoptosis. Thus, CGA appears to be a promising therapeutic approach for treating HIRI.

Mechanism of ASK1 involvement in liver diseases and related potential therapeutic targets: A critical pathway molecule worth investigating

Since the discovery of apoptosis signal-regulated kinase 1 (ASK1), the signal transduction mechanism and pathophysiological process involved in its regulation have been continuously revealed. Many previous studies have identified that ASK1 is involved and plays a critical role in the development of diseases affecting the nervous, cardiac, renal, and other systems. As a mitogen-activated protein kinase (MAPK) kinase kinase, ASK1 mediates apoptosis, necrosis, inflammation, and other pathological processes by activating its downstream c-Jun N-terminal kinase (JNK)/p38 MAPK. Owing to the important role of ASK1, an increasing number of studies in recent years have focused on its status in liver-related diseases. In this paper, we review the mechanisms and targets of ASK1 in liver-related diseases to emphasize its important role in the development of liver disease.

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.

Role of Mesenchymal Stem/Stromal Cells in Modulating Ischemia/Reperfusion Injury: Current State of the Art and Future Perspectives

Ischemia/reperfusion injury (IRI) is a multistep damage that occurs in several tissues when a blood flow interruption is inevitable, such as during organ surgery or transplantation. It is responsible for cell death and tissue dysfunction, thus leading, in the case of transplantation, to organ rejection. IRI takes place during reperfusion, i.e., when blood flow is restored, by activating inflammation and reactive oxygen species (ROS) production, causing mitochondrial damage and apoptosis of parenchymal cells. Unfortunately, none of the therapies currently in use are definitive, prompting the need for new therapeutic approaches. Scientific evidence has proven that mesenchymal stem/stromal cells (MSCs) can reduce inflammation and ROS, prompting this cellular therapy to also be investigated for treatment of IRI. Moreover, it has been shown that MSC therapeutic effects were mediated in part by their secretome, which appears to be involved in immune regulation and tissue repair. For these reasons, mediated MSC paracrine function might be key for injury amelioration upon IRI damage. In this review, we highlight the scientific literature on the potential beneficial use of MSCs and their products for improving IRI outcomes in different tissues/organs, focusing in particular on the paracrine effects mediated by MSCs, and on the molecular mechanisms behind these effects.

Effects of cerium oxide (CeO2) on liver tissue in liver ischemia-reperfusion injury in rats undergoing desflurane anesthesia

INTRODUCTION

During liver surgery and transplantation, periods of partial or total vascular occlusion are inevitable and result in ischemia-reperfusion injury (IRI). Nanomedicine uses the latest technology, which has emerged with interdisciplinary effects, such as biomedical sciences, physics, and engineering, to protect and improve human health. Interdisciplinary research has brought along the introduction of antioxidant nanoparticles as potential therapeutics. The goal of this study was to investigate the effects of cerium oxide (CeO2) administration and desflurane anesthesia on liver tissue in liver IR injury.

MATERIAL AND METHODS

Thirty rats were randomly divided into five groups: control (C), ischemia-reperfusion (IR), IR-desflurane (IRD), cerium oxide-ischemia reperfusion (CeO2-IR), and cerium oxide-ischemia reperfusion-desflurane (CeO2-IRD). In the IR, IRD, and CeO2-IRD groups, hepatic ischemia was induced after the porta hepatis was clamped for 120 min, followed by 120 min of reperfusion. Intraperitoneal 0.5 mg/kg CeO2 was administered to the CeO2 groups 30 min before ischemia. Desflurane (6%) was administered to the IRD and CeO2-IRD groups during IR. All groups were sacrificed under anesthesia. Liver tissue samples were examined under a light microscope by staining with hematoxylin-eosin (H&E). Malondialdehyde (MDA) levels, catalase (CAT), glutathione-s-transferase (GST), and arylesterase (ARE) enzyme activities were measured in the tissue samples.

RESULTS

The IR group had considerably more hydropic degeneration, sinusoidal dilatation, and parenchymal mononuclear cell infiltration than the IRD, CeO2-IR, and CeO2-IRD groups. Catalase and GST enzyme activity were significantly higher in the CeO2-IR group than in the IR group. The MDA levels were found to be significantly lower in the IRD, CeO2-IR, and CeO2-IRD groups than in the IR group.

CONCLUSION

Intraperitoneal CeO2 with desflurane reduced oxidative stress and corrected liver damage.

A Potential Route to Reduce Ischemia/Reperfusion Injury in Organ Preservation

The pathophysiological process of ischemia and reperfusion injury (IRI), an inevitable step in organ transplantation, causes important biochemical and structural changes that can result in serious organ damage. IRI is relevant for early graft dysfunction and graft survival. Today, in a global context of organ shortages, most organs come from extended criteria donors (ECDs), which are more sensitive to IRI. The main objective of organ preservation solutions is to protect against IRI through the application of specific, nonphysiological components, under conditions of no blood or oxygen, and then under conditions of metabolic reduction by hypothermia. The composition of hypothermic solutions includes osmotic and oncotic buffering components, and they are intracellular (rich in potassium) or extracellular (rich in sodium). However, above all, they all contain the same type of components intended to protect against IRI, such as glutathione, adenosine and allopurinol. These components have not changed for more than 30 years, even though our knowledge of IRI, and much of the relevant literature, questions their stability or efficacy. In addition, several pharmacological molecules have been the subjects of preclinical studies to optimize this protection. Among them, trimetazidine, tacrolimus and carvedilol have shown the most benefits. In fact, these drugs are already in clinical use, and it is a question of repositioning them for this novel use, without additional risk. This new strategy of including them would allow us to shift from cold storage solutions to cold preservation solutions including multitarget pharmacological components, offering protection against IRI and thus protecting today's more vulnerable organs.

Paeonol Attenuates Hepatic Ischemia/Reperfusion Injury by Modulating the Nrf2/HO-1 and TLR4/MYD88/NF-κB Signaling Pathways

Hepatic ischemia/reperfusion (HIR) is the most common type of liver injury following several clinical situations. Modulating oxidative stress and inflammation by Nrf2/HO-1 and TLR4/MYD88/NF-κB pathways, respectively, is involved in alleviating HIR injury. Paeonol is a natural phenolic compound that demonstrates significant antioxidant and anti-inflammatory effects. The present study explored the possible protective effect of paeonol against HIR injury and investigated its possible molecular mechanisms in rats. Rats were randomly divided into four groups: sham-operated control, paeonol-treated sham-operated control, HIR untreated, and HIR paeonol-treated groups. The results confirmed that hepatic injury was significantly aggravated biochemically by elevated serum levels of alanine transaminase and aspartate transaminase, as well as by histopathological alterations, while paeonol reduced the increase in transaminases and alleviated pathological changes induced by HIR. Additionally, paeonol inhibited the HIR-induced oxidative stress in hepatic tissues by decreasing the upraised levels of malondialdehyde and nitric oxide and enhancing the suppressed levels of reduced glutathione and superoxide dismutase activity. Furthermore, paeonol activated the protective antioxidative Nrf2/HO-1 pathway. The protective effect of paeonol was associated with inhibiting the expression of the inflammatory key mediators TLR4, MYD88, NF-κB, and TNF-α. Finally, paeonol inhibited the increased mRNA levels of the pro-apoptotic marker Bax and enhanced the reduced mRNA levels of the anti-apoptotic marker Bcl-2. Taken together, our results proved for the first time that paeonol could protect against HIR injury by inhibiting oxidative stress, inflammation, and apoptosis.

Role of hepatic stellate cells in liver ischemia-reperfusion injury

Liver ischemia-reperfusion injury (IRI) is a major complication of liver trauma, resection, and transplantation. IRI may lead to liver dysfunction and failure, but effective approach to address it is still lacking. To better understand the cellular and molecular mechanisms of liver IRI, functional roles of numerous cell types, including hepatocytes, Kupffer cells, neutrophils, and sinusoidal endothelial cells, have been intensively studied. In contrast, hepatic stellate cells (HSCs), which are well recognized by their essential functions in facilitating liver protection and repair, have gained less attention in their role in IRI. This review provides a comprehensive summary of the effects of HSCs on the injury stage of liver IRI and their associated molecular mechanisms. In addition, we discuss the regulation of liver repair and regeneration after IRI by HSCs. Finally, we highlight unanswered questions and future avenues of research regarding contributions of HSCs to IRI in the liver.

Reactive Oxygen Species Induce Fatty Liver and Ischemia-Reperfusion Injury by Promoting Inflammation and Cell Death

Liver transplantation is the ultimate method for treating end-stage liver disease. With the increasing prevalence of obesity, the number of patients with non-alcoholic fatty liver, a common cause of chronic liver disease, is on the rise and may become the main cause of liver transplantation in the future. With the increasing gap between the number of donor livers and patients waiting for liver transplantation and the increasing prevalence of non-alcoholic fatty liver, the proportion of steatosis livers among non-standard donor organs is also increasing. Ischemia-reperfusion injury has historically been the focus of attention in the liver transplantation process, and severe ischemia-reperfusion injury leads to adverse outcomes of liver transplantation. Studies have shown that the production of reactive oxygen species and subsequent oxidative stress play a key role in the pathogenesis of hepatic ischemia and reperfusion injury and non-alcoholic fatty liver. Furthermore, the sensitivity of fatty liver transplantation to ischemia-reperfusion injury has been suggested to be related to the production of reactive oxygen species (ROS) and oxidative stress. In ischemia-reperfusion injury, Kupffer cell and macrophage activation along with mitochondrial damage and the xanthine/xanthine oxidase system promote marked reactive oxygen species production and the inflammatory response and apoptosis, resulting in liver tissue injury. The increased levels of ROS and lipid peroxidation products, vicious circle of ROS and oxidative stress along with mitochondrial dysfunction promoted the progress of non-alcoholic fatty liver. In contrast to the non-fatty liver, a non-alcoholic fatty liver produces more reactive oxygen species and suffers more serious oxidative stress when subjected to ischemia-reperfusion injury. We herein review the effects of reactive oxygen species on ischemia-reperfusion injury and non-alcoholic fatty liver injury as well as highlight several treatment approaches.

The Role of Neuregulin-1 in Steatotic and Non-Steatotic Liver Transplantation from Brain-Dead Donors

BACKGROUND

Brain death (BD) and steatosis are key risk factors to predict adverse post-transplant outcomes. We investigated the role of Neuregulin-1 (NRG1) in rat steatotic and non-steatotic liver transplantation (LT) from brain death donors (DBD).

METHODS

NRG1 pathways were characterized after surgery.

RESULTS

NRG1 and p21-activated kinase 1 (PAK1) levels increased in steatotic and non-steatotic grafts from DBDs. The abolishment of NRG1 effects reduced PAK1. When the effect of either NRG1 nor PAK1 was inhibited, injury and regenerative failure were exacerbated. The benefits of the NRG-1-PAK1 axis in liver grafts from DBDs were associated with increased vascular endothelial growth factor-A (VEGFA) and insulin growth factor-1 (IGF1) levels, respectively. Indeed, VEGFA administration in non-steatotic livers and IGF1 treatment in steatotic grafts prevented damage and regenerative failure resulting from the inhibition of either NRG1 or PAK-1 activity in each type of liver. Exogenous NRG1 induced greater injury than BD induction.

CONCLUSIONS

This study indicates the benefits of endogenous NRG1 in liver grafts from DBDs and underscores the specificity of the NRG1 signaling pathway depending on the type of liver: NRG1-PAK1-VEGFA in non-steatotic livers and NRG1-PAK1-IGF1 in steatotic livers. Exogenous NRG1 is not an appropriate strategy to apply to liver grafts from DBD.

The gut microbial metabolite, 3,4-dihydroxyphenylpropionic acid, alleviates hepatic ischemia/reperfusion injury via mitigation of macrophage pro-inflammatory activity in mice

Hepatic ischemia/reperfusion injury (HIRI) is a serious complication that occurs following shock and/or liver surgery. Gut microbiota and their metabolites are key upstream modulators of development of liver injury. Herein, we investigated the potential contribution of gut microbes to HIRI. Ischemia/reperfusion surgery was performed to establish a murine model of HIRI. 16S rRNA gene sequencing and metabolomics were used for microbial analysis. Transcriptomics and proteomics analysis were employed to study the host cell responses. Our results establish HIRI was significantly increased when surgery occurred in the evening (ZT12, 20:00) when compared with the morning (ZT0, 08:00); however, antibiotic pretreatment reduced this diurnal variation. The abundance of a microbial metabolite 3,4-dihydroxyphenylpropionic acid was significantly higher in ZT0 when compared with ZT12 in the gut and this compound significantly protected mice against HIRI. Furthermore, 3,4-dihydroxyphenylpropionic acid suppressed the macrophage pro-inflammatory response in vivo and in vitro. This metabolite inhibits histone deacetylase activity by reducing its phosphorylation. Histone deacetylase inhibition suppressed macrophage pro-inflammatory activation and diminished the diurnal variation of HIRI. Our findings revealed a novel protective microbial metabolite against HIRI in mice. The potential underlying mechanism was at least in part, via 3,4-dihydroxyphenylpropionic acid-dependent immune regulation and histone deacetylase (HDAC) inhibition in macrophages.

Melatonin attenuates hepatic ischemia-reperfusion injury in rats by inhibiting NF-κB signaling pathway

BACKGROUND

The sterile inflammatory response is one of the key mechanisms leading to hepatic ischemia-reperfusion injury. Melatonin has been shown to prevent organ injuries, but its roles in the inflammatory response after hepatic ischemia-reperfusion injury have not been fully explored, especially in late ischemia-reperfusion injury. The present study aimed to investigate the roles and possible mechanisms of melatonin in the inflammatory response after hepatic ischemia-reperfusion injury.

METHODS

Sixty Sprague-Dawley rats were randomly divided into a sham group, ischemia-reperfusion injury group (I/R group), and melatonin-treated group (M + I/R group). The rats in the I/R group were subjected to 70% hepatic ischemia for 45 min, followed by 5 or 24 h of reperfusion. The rats in the M + I/R group were injected with melatonin (10 mg/kg, intravenous injection) 15 min prior to ischemia and immediately before reperfusion. Serum and samples of ischemic liver lobes were harvested for future analysis, and the 7-day survival rate was assessed after hepatic ischemia-reperfusion surgery.

RESULTS

In comparison with the I/R group, the M + I/R group showed markedly decreased expression levels of inflammatory cytokines (IL-6 and TNF-α) and numbers of apoptotic hepatocytes (P < 0.05). Immunoblotting showed that the expression levels of IL-6, p-NF-κBp65/t-NF-κBp65 and p-IκB-α/t-IκB-α in the M + I/R group were significantly lower than those in the I/R group, and immunofluorescence staining showed that the expression level of p-NF-κBp65 in the M + I/R group was lower than that in the I/R group (P < 0.05). The 7-day survival rates were 20% in the I/R group and 50% in the M + I/R group (P < 0.05).

CONCLUSIONS

Melatonin downregulated the activity of the NF-κB signaling pathway in the early and late stages of hepatic ischemia-reperfusion injury, alleviated the inflammatory response, protected the liver from ischemia-reperfusion injury, and increased the survival rate.

Baicalein pre-treatment alleviates hepatic ischemia/reperfusion injury in mice by regulating the Nrf2/ARE pathway

Hepatic ischemia-reperfusion injury (HIRI) is caused by blood flow recovery following ischemia. Baicalein (BAI), a natural antioxidant used in traditional Chinese medicine, eliminates excessive free radicals and protects the structure of the cell membrane. However, its protective mechanism against HIRI is still unclear. The present study investigated underlying mechanism using a mouse HIRI model. Liver injury was evaluated using serum levels of alanine aminotransferase and aspartate aminotransferase, and hematoxylin-eosin staining was performed to evaluate the pathological changes in liver tissue. Apoptosis of hepatocytes was detected by TUNEL staining. The expression levels of reactive oxygen species (ROS), malondialdehyde (MDA) and superoxide dismutase (SOD) in the liver were detected to evaluate oxidative stress. Western blotting was performed to assess expression levels of nuclear factor E2-related factor 2 (Nrf2)/antioxidant response elements (ARE) pathway proteins in liver tissue. BAI pre-treatment significantly decreased elevation of serum aminotransferase levels induced by IR and alleviated histological damage to the liver. BAI decreased production of ROS and MDA in liver tissue induced by IR and increased the activity of SOD. At the same time, BAI inhibited apoptosis of liver cells induced by oxidative stress. Furthermore, BAI promoted the translocation of Nrf2 into the nucleus and increased the expression of total heme oxygenase-1 and NAD(P)H dehydrogenase quinone-1. The Nrf2 inhibitor ML385 reversed the protective effect of BAI on HIRI. These results indicated that BAI served a protective effect in HIRI by regulating the Nrf2/ARE pathway.

Effect of Edaravone on MicroRNA Expression in Exosomes after Hepatic Ischemia-reperfusion Injury

BACKGROUND AND OBJECTIVE

Hepatic ischemia-reperfusion injury (HIRI) results in serious complications after liver resection and transplantation. Edaravone (ED) has a protective effect on IRI. This study was designed to evaluate whether ED could protect the liver of rats from HIRI injury and explored its exosomal miRNA-related mechanism.

METHODS

The sham group, hepatic ischemia/reperfusion (IR group), and hepatic ischemia/reperfusion + edaravone (ED group) models were established. We determined the protective effect of ED by measuring alanine aminotransferase (ALT), aspartate aminotransferase (AST), malondialdehyde (MDA), superoxide dismutase (SOD); enzyme-linked immunosorbent assay for tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β); hematoxylin-eosin staining and immunohistochemistry for histopathological changes. Exosomal miRNAs were subjected to second-generation sequencing to identify their differential expression. The results were analyzed using bioinformatics methods and validated using real-time quantitative polymerase chain reaction (RT-qPCR).

RESULTS

HIRI rats showed higher levels of ALT, AST, oxidative stress, and inflammatory markers; ED attenuated these effects. The sequencing results showed 6 upregulated and 13 downregulated miRNAs in the IR vs. sham groups, 10 upregulated and 10 downregulated miRNAs in the ED vs. IR groups. PC-3p-190-42101 was screened as an overlapping differentially expressed miRNA, and RT-qPCR validation showed that its expression in HIRI rats was significantly decreased; ED prevented this downregulation. Moreover, the expression of PC-3P-190-42101 was significantly correlated with the level of inflammatory factors.

CONCLUSION

These findings indicate that ED can regulate the level of inflammatory factors by affecting the expression of miRNA PC-3p-190-42101 in plasma exosomes to protect the liver from IRI.

Glutathione S-transferase A2 promotes hepatocellular carcinoma recurrence after liver transplantation through modulating reactive oxygen species metabolism

Hepatocellular carcinoma (HCC) recurrence after liver transplantation remains a significant clinical problem. Ischemia-reperfusion injury (IRI) occurred inevitably at the early phase after liver transplantation (LT) spawns a significant risk of HCC recurrence. However, their linkage and IRI-derived risk factors for HCC recurrence remain exclusive. Understanding the mechanism of post-transplantation hepatic injury could provide new strategies to prevent the later event of HCC recurrence. We demonstrated that glutathione S-transferase A2 (GSTA2) expression was significantly associated with early phase hepatic and systemic injury and ROS level after liver transplantation. Early phase circulating GSTA2 (_EPCGSTA2) protein was a significant predictor of HCC recurrence and survival. Heterogeneous single nucleotide polymorphism at G335C of GSTA2 was significantly associated with poor survival of HCC recipients. Enhancement of GSTA2 could protect HCC cells against H₂O₂-induced cell death by compensating for the elevated ROS stress. We also demonstrated that GSTA2 played crucial roles in regulating the ROS-associated JNK and AKT signaling pathways and ROS metabolism in HCCs in responding to a dynamic ROS environment. Functionally, endogenous or exogenous upregulation of GSTA2 could promote HCC growth and invasion through activating the epithelial–mesenchymal-transition process. Targeted inhibition of GSTA2 could suppress HCC growth and metastasis. In conclusion, GSTA2 could be a novel prognostic and therapeutic target to combat HCC recurrence after liver transplantation.

Role of liver sinusoidal endothelial cells in liver diseases

Liver sinusoidal endothelial cells (LSECs) form the wall of the hepatic sinusoids. Unlike other capillaries, they lack an organized basement membrane and have cytoplasm that is penetrated by open fenestrae, making the hepatic microvascular endothelium discontinuous. LSECs have essential roles in the maintenance of hepatic homeostasis, including regulation of the vascular tone, inflammation and thrombosis, and they are essential for control of the hepatic immune response. On a background of acute or chronic liver injury, LSECs modify their phenotype and negatively affect neighbouring cells and liver disease pathophysiology. This Review describes the main functions and phenotypic dysregulations of LSECs in liver diseases, specifically in the context of acute injury (ischaemia-reperfusion injury, drug-induced liver injury and bacterial and viral infection), chronic liver disease (metabolism-associated liver disease, alcoholic steatohepatitis and chronic hepatotoxic injury) and hepatocellular carcinoma, and provides a comprehensive update of the role of LSECs as therapeutic targets for liver disease. Finally, we discuss the open questions in the field of LSEC pathobiology and future avenues of research.

Aloin protects mice from diet-induced non-alcoholic steatohepatitis via activation of Nrf2/HO-1 signaling

Aloin, a naturally occurring anthraquinone glycoside derived from the Aloe species, has antioxidant and anti-inflammatory activities, but its role in non-alcoholic steatohepatitis (NASH) remains unknown. This study was designed to investigate the anti-inflammatory, antioxidant, and anti-apoptotic effects of aloin and the underlying mechanisms during NASH. Wild-type or nuclear erythroid 2-related factor 2 (Nrf2) knock-out (KO) mice were fed a choline-deficient, l-amino acid-defined, high-fat (CDAAH) diet and treated with aloin (10, 20 or 40 mg per kg bw per day) by gavage for twelve weeks. Liver and blood samples were collected to evaluate liver function, protein abundance, and histopathological status. Supplementing aloin at 20 mg kg^-1 was optimal for mitigating liver damage during NASH, as evidenced by reduced alanine transaminase and aspartate aminotransferase activity in serum. Supplementation with aloin significantly reduced serum concentration or liver protein abundance of malondialdehyde, tumor necrosis factor alpha, Interleukin (IL)-1β and IL-6. Aloin treatment enhanced hepatic superoxide dismutase activity, glutathione and serum IL-10 levels in mice with NASH. Furthermore, supplementation with aloin inhibited hepatocyte apoptosis caused by Bcl-2 up-regulation and cleaved caspase-3 and Bax down-regulation. Mechanistically, by using Nrf2 KO mice, the protective effects of aloin were associated with enhanced antioxidant, anti-inflammatory and anti-apoptotic activity, all of which were mediated by Nrf2/heme oxygenase-1 (HO-1) signaling activation. Data suggested that aloin activates the Nrf2/HO-1 pathway and has protective potential against liver injury during NASH. Therefore, aloin supplementation might contribute to the prevention and treatment of NASH via activation of the Nrf2/HO-1 pathway.

Effects of Gut Metabolites and Microbiota in Healthy and Marginal Livers Submitted to Surgery

Microbiota is defined as the collection of microorganisms within the gastrointestinal ecosystem. These microbes are strongly implicated in the stimulation of immune responses. An unbalanced microbiota, termed dysbiosis, is related to the development of several liver diseases. The bidirectional relationship between the gut, its microbiota and the liver is referred to as the gut-liver axis. The translocation of bacterial products from the intestine to the liver induces inflammation in different cell types such as Kupffer cells, and a fibrotic response in hepatic stellate cells, resulting in deleterious effects on hepatocytes. Moreover, ischemia-reperfusion injury, a consequence of liver surgery, alters the microbiota profile, affecting inflammation, the immune response and even liver regeneration. Microbiota also seems to play an important role in post-operative outcomes (i.e., liver transplantation or liver resection). Nonetheless, studies to determine changes in the gut microbial populations produced during and after surgery, and affecting liver function and regeneration are scarce. In the present review we analyze and discuss the preclinical and clinical studies reported in the literature focused on the evaluation of alterations in microbiota and its products as well as their effects on post-operative outcomes in hepatic surgery.

Impact of Cold Ischemia Time on the Function of Liver Grafts Preserved With Custodiol

OBJECTIVE

This study aimed to evaluate how cold ischemia time (CIT) interferes with liver graft function in the first 7 days after surgery for Custodiol (HTK) preserved organs.

METHODS

This retrospective observational study analyzed the medical records of 38 transplantation patients at Hospital Leforte Liberdade, São Paulo, in 2018. The study population was divided into 2 groups (group A, CIT < 8 hours; group B, CIT > 8 hours). Postoperative parameters-such as international normalized ratio, total bilirubin, aspartate aminotransferase/alanine aminotransferase, alkaline phosphatase, gamma glutamyl transferase (GGT), lactate dehydrogenase, lactate, creatinine, red blood cell transfusion, need for hemodialysis, use of vasoactive drugs, endotracheal intubation time, length of stay in the intensive care unit (ICU), and length of hospital stay-were compared.

RESULTS

Group A (CIT < 8 hours) presented less need for red blood cell transfusions (odds ratio 0.29; confidence interval 0.06-0.98; P = .04), had a shorter hospital stay (P = .024), and had lower levels of total bilirubin (P = .05) and GGT (P = .05) in the first 7 postoperative days. The other variables showed no statistically significant difference.

CONCLUSION

In livers preserved with Custodiol, CIT > 8 hours generated higher levels of total bilirubin and GGT in the postoperative period, in addition to higher hospital costs; greater need for red blood cell transfusions; and longer hospitalization, including longer stays in the ICU.

NLRC3 alleviates hypoxia/reoxygenation induced inflammation in RAW264.7 cells by inhibiting K63-linked ubiquitination of TRAF6

BACKGROUND

NOD-like receptor family CARD domain containing 3 (NLRC3) plays an important role in both innate and adaptive immunity. This study was to explore the function and related mechanisms of NLRC3 in a hypoxia/reoxygenation (H/R)-induced inflammatory response in RAW264.7 cells.

METHODS

Liver ischemia-reperfusion (I/R) model in mice and H/R model in RAW264.7 cells were constructed. Western blotting was used to determine the protein expression level of NLRC3 in liver tissue and NLRC3, TRAF6, p-p65, p65, IκB-α, and the K63-linked ubiquitination level of TRAF6 in cells. The immunofluorescence assay was performed to evaluate the nuclear level of the NF-κB (p65). ELISA was conducted to measure the content of IL-1β in serum and cell supernatant. The interaction between NLRC3 and TRAF6 in cells was analyzed by the Co-IP assay.

RESULTS

The NLRC3 protein level in liver tissue was decreased with the prolongation of reperfusion time (P < 0.05). The expression of NLRC3 and IκB-α protein in RAW264.7 was decreased gradually, while the expression of p-p65 and TRAF6 proteins and K63-linked ubiquitination of TRAF6 were increased gradually with the prolongation of reoxgenation time (P < 0.05). The Co-IP assay revealed that NLRC3 and TRAF6 can bind to each other directly. However, NLRC3 had no effect on the expression of TRAF6 protein. The ubiquitination test results showed that the K63-linked ubiquitination level of TRAF6 in H/R + Lv-NLRC3 group was significantly lower than that in the H/R + negative control (NC) group (P < 0.05). Moreover, the activation of NF-κB in H/R + Lv-NLRC3 group was inhibited compared with that in the H/R + NC group, and the level of the inflammatory factor IL-1β in the cell culture supernatant was also decreased accordingly (P < 0.05).

CONCLUSIONS

NLRC3 might alleviate H/R-induced inflammation in RAW264.7 cells by inhibiting K63-linked ubiquitination of TRAF6.

Extracellular Vesicles Derived from Human Umbilical Cord Mesenchymal Stem Cells Protect Liver Ischemia/Reperfusion Injury by Reducing CD154 Expression on CD4+ T Cells via CCT2

As a cause of postoperative complications and early hepatic failure after liver transplantation, liver ischemia/reperfusion injury (IRI) still has no effective treatment during clinical administration. Although the therapeutic potential of mesenchymal stem cells (MSCs) for liver IRI has been previously shown, the underlying mechanisms are not completely clear. It is accepted that MSC-derived extracellular vesicles (MSC-EVs) are newly uncovered messengers for intercellular communication. Herein, it is reported that umbilical cord-derived MSCs (UC-MSCs) improve liver IRI in mice through their secreted EVs. It is also visualized that UC-MSC-EVs mainly concentrate in liver after 6 h of reperfusion. Furthermore, UC-MSC-EVs are found to significantly modulate the membranous expression of CD154 of intrahepatic CD4+ T cells, which is an initiation of inflammatory response in liver and can aggravate liver IRI. Mechanistically, protein mass spectrum analysis is performed and it is revealed that Chaperonin containing TCP1 subunit 2 (CCT2) enriches in UC-MSC-EVs, which regulates the calcium channels to affect Ca2+ influx and suppress CD154 synthesis in CD4+ T cells. In conclusion, these results highlight the therapeutic potential of UC-MSC-EVs in attenuating liver IRI. This finding suggests that CCT2 from UC-MSC-EVs can modulate CD154 expression of intrahepatic CD4+ T cells during liver IRI through the Ca2+-calcineurin-NFAT1 signaling pathway.

Inositol 1,4,5-trisphosphate receptor type 3 plays a protective role in hepatocytes during hepatic ischemia-reperfusion injury

Hepatic ischemia-reperfusion injury is seen in a variety of clinical conditions, including hepatic thrombosis, systemic hypotension, and liver transplantation. Calcium (Ca²⁺) signaling mediates several pathophysiological processes in the liver, but it is not known whether and how intracellular Ca²⁺ channels are involved in the hepatocellular events secondary to ischemia-reperfusion. Using an animal model of hepatic ischemia-reperfusion injury, we observed a progressive increase in expression of the type 3 isoform of the inositol trisphosphate receptor (ITPR3), an intracellular Ca²⁺ channel that is not normally expressed in healthy hepatocytes. ITPR3 expression was upregulated, at least in part, by a combination of demethylation of the ITPR3 promoter region and the increased transcriptional activity of the nuclear factor of activated T-cells (NFAT). Additionally, expression of pro-inflammatory interleukins and necrotic surface area were less pronounced in livers of control animals compared to liver-specific ITPR3 KO mice subjected to hepatic damage. Corroborating these findings, ITPR3 expression and activation of NFAT were observed in hepatocytes of liver biopsies from patients who underwent liver ischemia caused by thrombosis after organ transplant. Together, these results are consistent with the idea that ITPR3 expression in hepatocytes plays a protective role during hepatic injury induced by ischemia-reperfusion.

Evolution of TLR4 role in mediating the hepatoprotective effects of estradiol after traumatic brain injury in male rats

Several studies have shown that 17β-estradiol (E2) exerted beneficial effects on liver disease, and it has a protective impact on brain damage after traumatic brain injury (TBI). TBI-induced liver injury is associated with the activation of TLR4. However, it remains unknown whether E2 can modulate TBI-induced liver injury through TLR4. The objective of this study was to determine the role of TLR4 in hepatoprotective mechanisms of E2 after TBI. Diffuse TBI induced by the Marmarou model in male rats. TAK-242 as a selective antagonist of TLR4 (3 mg/kg) and E2 (33.3 μg/kg) were injected (i.p) respectively 30 min before and 30 min after TBI. The results showed that E2 and TAK-242 markedly inhibited TBI-induced liver injury, which was characterized by decreased aminotransferase activities, inhibition of the oxidative stress, and reduced levels of pro-inflammatory cytokines tumor necrosis factor-α (TNF-α) and IL-17 in the liver. We also found that TBI induced significant upregulation of TLR4 in the liver, with peak expression occurring 24 h after TBI, and that treatment with E2 significantly inhibited the upregulation of TLR4. Also, both classic [Estrogen receptors alpha (ERα) and beta (ERβ)] and non-classic (G protein-coupled estrogen receptor GPER) E2 receptors are involved in modulating the expression of TLR4. These results suggested that the hepatoprotective effects of estradiol after TBI may be mediated via the downregulation expression of TLR4.

Inhaled Argon Impedes Hepatic Regeneration after Ischemia/Reperfusion Injury in Rats

Organoprotective effects of noble gases are subject of current research. One important field of interest is the effect of noble gases on hepatic regenerative capacity. For the noble gas argon, promising studies demonstrated remarkable experimental effects in neuronal and renal cells. The aim of this study was to investigate the effects of argon on the regenerative capacity of the liver after ischemia/reperfusion injury (IRI). Male, Sprague-Dawley rats underwent hepatic IRI by clamping of the hepatic artery. Expression of hepatoproliferative genes (HGF, IL-1β, IL-6, TNF), cell cycle markers (BrdU, TUNEL, Ki-67), and liver enzymes (ALT, AST, Bilirubin, LDH) were assessed 3, 36, and 96 h after IRI. Expression of IL-1β and IL-6 was significantly higher after argon inhalation after 36 h (IL-1β 5.0 vs. 8.7 fold, p = 0.001; IL-6 9.6 vs. 19.1 fold, p = 0.05). Ki-67 was higher in the control group compared to the argon group after 36 h (214.0 vs. 38.7 positive cells/1000 hepatocytes, p = 0.045). Serum levels of AST and ALT did not differ significantly between groups. Our data indicate that argon inhalation has detrimental effects on liver regeneration after IRI as measured by elevated levels of the proinflammatory cytokines IL-1β and IL-6 after 36 h. In line with these results, Ki-67 is decreased in the argon group, indicating a negative effect on liver regeneration in argon inhalation.

Purine Metabolite Signatures and Type 2 Diabetes: Innocent Bystanders or Actionable Items?

PURPOSE OF REVIEW

This article reviews evidence linking cardiometabolic conditions with changes in purine metabolites, including increased serum uric acid (sUA), and discusses intervention studies that investigated the therapeutic relevance of these associations.

RECENT FINDINGS

Metabolic and epidemiological findings support a correlation between sUA and circulating levels of other purines with insulin resistance (IR) and risk factors for cardiovascular disease (CVD). In addition, increased activity of xanthine oxidoreductase (XOR), the rate-limiting enzyme for UA production, has been detected in tissues targeted by obesity. Yet, inhibition of XOR in pre-clinical and clinical studies generally failed to support a causal role for excess sUA in IR and CVD. The lack of efficacy of XOR inhibitors strongly suggests that UA is a marker of, rather than a direct contributory factor for, cardiometabolic diseases. Validation of the function of other purines will require a paradigm shift, from a "UA-centric" view to a more granular assessment of the entire purine network and its interaction with other pathways.

Protective potential effects of fucoidan in hepatic cold ischemia-rerfusion injury in rats

The necessity to increase the efficiency of organ preservation has pushed physicians to consider the use of pharmacological additives in preservation solutions to minimize ischemia reperfusion injury. Here, we evaluated the effect of fucoidan, sulfated polysaccharide from brown seaweed, as an additive to IGL-1 (Institut Georges Lopez) preservation solution. Livers from Wistar rats were preserved for 24 h at 4 °C in IGL-1 solution, enriched or not with fucoidan (100 mg/L). Thereafter, they were subjected to reperfusion (2 h, at 37 °C) using an isolated perfused rat liver model. The addition of fucoidan to IGL-1 solution reduced hepatic injury (AST, ALT) and improved liver function compared to IGL-1 solution without fucoidan. In addition, we noted a significant increase in the phosphorylation of AMPK, AKT protein kinase and GSK3-β, leading to a reduction in VDAC phosphorylation, as well as a reduction in apoptosis (caspase 3), mitochondrial damage, oxidative stress and endoplasmic reticulum (ER) stress markers. Furthermore, ERK1/2 and P38 MAPKs phosphorylation significantly decreased after supplementation of IGL-1 solution with fucoidan. In conclusion, the supplementation of IGL-1 solution with fucoidan maintained liver graft integrity and function through the prevention of the ER stress, oxidative stress and mitochondrial dysfunction. Fucoidan could be considered as potential natural therapeutic agent to alleviate graft injury.

Six-Transmembrane Epithelial Antigen of the Prostate 3 Deficiency in Hepatocytes Protects the Liver Against Ischemia-Reperfusion Injury by Suppressing Transforming Growth Factor-β-Activated Kinase 1

BACKGROUND AND AIMS

Hepatic ischemia-reperfusion (I/R) injury remains a major challenge affecting the morbidity and mortality of liver transplantation. Effective strategies to improve liver function after hepatic I/R injury are limited. Six-transmembrane epithelial antigen of the prostate 3 (Steap3), a key regulator of iron uptake, was reported to be involved in immunity and apoptotic processes in various cell types. However, the role of Steap3 in hepatic I/R-induced liver damage remains largely unclear.

APPROACH AND RESULTS

In the present study, we found that Steap3 expression was significantly up-regulated in liver tissue from mice subjected to hepatic I/R surgery and primary hepatocytes challenged with hypoxia/reoxygenation insult. Subsequently, global Steap3 knockout (Steap3-KO) mice, hepatocyte-specific Steap3 transgenic (Steap3-HTG) mice, and their corresponding controls were subjected to partial hepatic warm I/R injury. Hepatic histology, the inflammatory response, and apoptosis were monitored to assess liver damage. The molecular mechanisms of Steap3 function were explored in vivo and in vitro. The results demonstrated that, compared with control mice, Steap3-KO mice exhibited alleviated liver damage after hepatic I/R injury, as shown by smaller necrotic areas, lower serum transaminase levels, decreased apoptosis rates, and reduced inflammatory cell infiltration, whereas Steap3-HTG mice had the opposite phenotype. Further molecular experiments showed that Steap3 deficiency could inhibit transforming growth factor-β-activated kinase 1 (TAK1) activation and downstream c-Jun N-terminal kinase (JNK) and p38 signaling during hepatic I/R injury.

CONCLUSIONS

Steap3 is a mediator of hepatic I/R injury that functions by regulating inflammatory responses as well as apoptosis through TAK1-dependent activation of the JNK/p38 pathways. Targeting hepatocytes, Steap3 may be a promising approach to protect the liver against I/R injury.

Aloin Preconditioning Attenuates Hepatic Ischemia/Reperfusion Injury via Inhibiting TLR4/MyD88/NF-κB Signal Pathway In Vivo and In Vitro

Background

Aloin exerts considerable protective effects in various disease models, and its effect on hepatic ischemia-reperfusion (HIR) injury remains unknown. This research is aimed at conducting an in-depth investigation of the antioxidant, anti-inflammatory, and antiapoptosis effects of aloin in HIR injury and explain the underlying molecular mechanisms.

Methods

In vivo, different concentrations of aloin were intraperitoneally injected 1 h before the establishment of the HIR model in male mice. The hepatic function, pathological status, oxidative stress, and inflammatory and apoptosis markers were measured. In vitro, aloin (AL, C₂₁H₂₂O₉) or lipopolysaccharide (LPS) was added to a culture of mouse primary hepatocytes before it underwent hypoxia/reoxygenation (H/R), and the apoptosis in the mouse primary hepatocytes was analyzed.

Results

We found that 20 mg/kg was the optimum concentration of aloin for mitigating I/R-induced liver tissue damage, characterized by decreased serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST). Aloin pretreatment substantially suppressed the generation of hepatic malondialdehyde (MDA), tumor necrosis factor alpha (TNF-α), and IL-6 and enhanced the hepatic superoxide dismutase (SOD) activities as well as glutathione (GSH) and IL-10 levels in the liver tissue of I/R mice; this indicated that aloin ameliorated I/R-induced liver damage by reducing the oxidative stress and inflammatory response. Moreover, aloin inhibited hepatocyte apoptosis and inflammatory response that was caused by the upregulated expression of Bcl-2, the downregulated expression of cleaved caspase3(C-caspase3), Bax, Toll-like receptor 4 (TLR4), FADD, MyD88, TRAF6, phosphorylated IKKα/β (p-IKKα/β), and phosphorylated nuclear factor κB p65 (p-NF-κB p65).

Protective Role of mTOR in Liver Ischemia/Reperfusion Injury: Involvement of Inflammation and Autophagy

Liver ischemia/reperfusion (IR) injury is a common phenomenon after liver resection and transplantation, which often results in liver graft dysfunction such as delayed graft function and primary nonfunction. The mammalian target of rapamycin (mTOR) is an evolutionarily highly conserved serine/threonine protein kinase, which coordinates cell growth and metabolism through sensing environmental inputs under physiological or pathological conditions, involved in the pathophysiological process of IR injury. In this review, we mainly present current evidence of the beneficial role of mTOR in modulating inflammation and autophagy under liver IR to provide some evidence for the potential therapies for liver IR injury.

New Insights into the Liver-Visceral Adipose Axis During Hepatic Resection and Liver Transplantation

In the last decade, adipose tissue has emerged as an endocrine organ with a key role in energy homeostasis. In addition, there is close crosstalk between the adipose tissue and the liver, since pro- and anti-inflammatory substances produced at the visceral adipose tissue level directly target the liver through the portal vein. During surgical procedures, including hepatic resection and liver transplantation, ischemia-reperfusion injury induces damage and regenerative failure. It has been suggested that adipose tissue is associated with both pathological or, on the contrary, with protective effects on damage and regenerative response after liver surgery. The present review aims to summarize the current knowledge on the crosstalk between the adipose tissue and the liver during liver surgery. Therapeutic strategies as well as the clinical and scientific controversies in this field are discussed. The different experimental models, such as lipectomy, to evaluate the role of adipose tissue in both steatotic and nonsteatotic livers undergoing surgery, are described. Such information may be useful for the establishment of protective strategies aimed at regulating the liver-visceral adipose tissue axis and improving the postoperative outcomes in clinical liver surgery.

Protective Role of Hepatocyte Cyclooxygenase-2 Expression Against Liver Ischemia-Reperfusion Injury in Mice

Liver ischemia and reperfusion injury (IRI) remains a serious clinical problem affecting liver transplantation outcomes. IRI causes up to 10% of early organ failure and predisposes to chronic rejection. Cyclooxygenase-2 (COX-2) is involved in different liver diseases, but the significance of COX-2 in IRI is a matter of controversy. This study was designed to elucidate the role of COX-2 induction in hepatocytes against liver IRI. In the present work, hepatocyte-specific COX-2 transgenic mice (hCOX-2-Tg) and their wild-type (Wt) littermates were subjected to IRI. hCOX-2-Tg mice exhibited lower grades of necrosis and inflammation than Wt mice, in part by reduced hepatic recruitment and infiltration of neutrophils, with a concomitant decrease in serum levels of proinflammatory cytokines. Moreover, hCOX-2-Tg mice showed a significant attenuation of the IRI-induced increase in oxidative stress and hepatic apoptosis, an increase in autophagic flux, and a decrease in endoplasmic reticulum stress compared to Wt mice. Interestingly, ischemic preconditioning of Wt mice resembles the beneficial effects observed in hCOX-2-Tg mice against IRI due to a preconditioning-derived increase in endogenous COX-2, which is mainly localized in hepatocytes. Furthermore, measurement of prostaglandin E2 (PGE2 ) levels in plasma from patients who underwent liver transplantation revealed a significantly positive correlation of PGE2 levels and graft function and an inverse correlation with the time of ischemia. Conclusion: These data support the view of a protective effect of hepatic COX-2 induction and the consequent rise of derived prostaglandins against IRI.

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.

Use of Steatotic Grafts in Liver Transplantation: Current Status

In the field of liver transplantation, the demand for adequate allografts greatly exceeds the supply. Therefore, expanding the donor pool to match the growing demand is mandatory. The present review summarizes current knowledge of the pathophysiology of ischemia/reperfusion injury in steatotic grafts, together with recent pharmacological approaches aimed at maximizing the utilization of these livers for transplantation. We also describe the preclinical models currently available to understand the molecular mechanisms controlling graft viability in this specific type of donor, critically discussing the heterogeneity in animal models, surgical methodology, and therapeutic interventions. This lack of common approaches and interventions makes it difficult to establish the pathways involved and the relevance of isolated discoveries, as well as their transferability to clinical practice. Finally, we discuss how new therapeutic strategies developed from experimental studies are promising but that further studies are warranted to translate them to the bedside.

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.

Protective effects of gastrin-releasing peptide receptor antagonist RC-3095 in an animal model of hepatic ischemia/reperfusion injury

AIM

We aimed to evaluate effects of RC-3095 on mice with hepatic ischemia followed by reperfusion (I/R) injury and further explore the possible underlying mechanism.

METHODS

Mice were subjected to partial hepatic ischemia for 60 min followed by different durations of reperfusion. Levels of gastrin-releasing peptide (GRP) and GRP receptor (GRPR) in the blood and liver were detected by enzyme-linked immunosorbent assay (ELISA) or western blotting (WB) after 3, 6, 12, or 24 h of reperfusion. RC-3095 or normal saline (control) was given i.p. at the time of reperfusion. Expressions of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, and IL-10 in blood and liver samples were examined with ELISA. Neutrophil influx into the liver was assessed by flow cytometry and myeloperoxidase assay. Hematoxylin-eosin staining of the liver and terminal deoxynucleotidyl transferase mediated dUTP-biotin nick end labeling assay were used to determine hepatic injury and hepatocellular necrosis. Activation of nuclear factor (NF)-κB and p38/extracellular regulated protein kinase (ERK) mitogen activated protein kinase (MAPK) was investigated with WB.

RESULTS

The expression of GRP was upregulated within 3 h after reperfusion and remained elevated for up to 24 h in the liver, whereas GRPR was also upregulated after 3 or 6 h of reperfusion, but returned to baseline levels within 24 h. RC-3095 significantly reduced the inflammatory hepatic injury, liver neutrophil accumulation, and hepatocellular apoptosis, probably by inhibiting activation of NF-κB or p38/ERK MAPK.

CONCLUSION

These findings supported that GRP-GRPR played an important role in hepatic I/R injury, and RC-3095 ameliorated liver damage by suppressing the inflammatory response and hepatocellular necrosis.

Evaluation of the therapeutic effect of methylene blue on the liver of rats submitted to ischemia and reperfusion

PURPOSE

To analyze the effect of methylene blue (MB) therapy during the liver ischemia-reperfusion injury (I/R) process.

METHODS

Thirty-five male Wistar rats were used, (70%) submitted to partial ischemia (IR) or not (NIR) (30%) were obtained from the same animal. These animals were divided into six groups: 1) Sham (SH), 2) Sham with MB (SH-MB); 3) I/R, submitted to 60 minutes of partial ischemia and 15 minutes of reperfusion; 4) NI/R, without I/R obtained from the same animal of group I/R; 5) I/R-MB submitted to I/R and MB and 6) NI/R-MB, without I/R. Mitochondrial function was evaluated. Osmotic swelling of mitochondria as well as the determination of malondialdehyde (MDA) was evaluated. Serum (ALT/AST) dosages were also performed. MB was used at the concentration of 15mg/kg, 15 minutes before hepatic reperfusion. Statistical analysis was done by the Mann Whitney test at 5%.

RESULTS

State 3 shows inhibition in all ischemic groups. State 4 was increased in all groups, except the I/R-MB and NI/R-MB groups. RCR showed a decrease in all I/R and NI/R groups. Mitochondrial osmotic swelling showed an increase in all I/R NI/R groups in the presence or absence of MB. About MDA, there was a decrease in SH values in the presence of MB and this decrease was maintained in the I/R group. AST levels were increased in all ischemic with or without MB.

CONCLUSIONS

The methylene blue was not able to restore the mitochondrial parameters studied. Also, it was able to decrease lipid peroxidation, preventing the formation of reactive oxygen species.