Ischaemia reperfusion injury in liver transplantation: Cellular and molecular mechanisms

Hyperspectral Imaging for Viability Assessment of Human Liver Allografts During Normothermic Machine Perfusion

Normothermic machine perfusion (NMP) is nowadays frequently utilized in liver transplantation. Despite commonly accepted viability assessment criteria, such as perfusate lactate and perfusate pH, there is a lack of predictive organ evaluation strategies to ensure graft viability. Hyperspectral imaging (HSI)-as an optical imaging modality increasingly applied in the biomedical field-might provide additional useful data regarding allograft viability and performance of liver grafts during NMP.

METHODS

Twenty-five deceased donor liver allografts were included in the study. During NMP, graft viability was assessed conventionally and by means of HSI. Images of liver parenchyma were acquired at 1, 2, and 4 h of NMP, and subsequently analyzed using a specialized HSI acquisition software to compute oxygen saturation, tissue hemoglobin index, near-infrared perfusion index, and tissue water index. To analyze the association between HSI parameters and perfusate lactate as well as perfusate pH, we performed simple linear regression analysis.

RESULTS

Perfusate lactate at 1, 2, and 4 h NMP was 1.5 [0.3-8.1], 0.9 [0.3-2.8], and 0.9 [0.1-2.2] mmol/L. Perfusate pH at 1, 2, and 4 h NMP was 7.329 [7.013-7.510], 7.318 [7.081-7.472], and 7.265 [6.967-7.462], respectively. Oxygen saturation predicted perfusate lactate at 1 and 2 h NMP (R² = 0.1577, P = 0.0493; R² = 0.1831, P = 0.0329; respectively). Tissue hemoglobin index predicted perfusate lactate at 1, 2, and 4 h NMP (R² = 0.1916, P = 0.0286; R² = 0.2900, P = 0.0055; R² = 0.2453, P = 0.0139; respectively).

CONCLUSIONS

HSI may serve as a noninvasive tool for viability assessment during NMP. Further evaluation and validation of HSI parameters are warranted in larger sample sizes.

Innate Immune Cells during Machine Perfusion of Liver Grafts-The Janus Face of Hepatic Macrophages

Machine perfusion is an emerging technology in the field of liver transplantation. While machine perfusion has now been implemented in clinical routine throughout transplant centers around the world, a debate has arisen regarding its concurrent effect on the complex hepatic immune system during perfusion. Currently, our understanding of the perfusion-elicited processes involving innate immune cells remains incomplete. Hepatic macrophages (Kupffer cells) represent a special subset of hepatic immune cells with a dual pro-inflammatory, as well as a pro-resolving and anti-inflammatory, role in the sequence of ischemia-reperfusion injury. The purpose of this review is to provide an overview of the current data regarding the immunomodulatory role of machine perfusion and to emphasize the importance of macrophages for hepatic ischemia-reperfusion injury.

Connexins in endothelial cells as a therapeutic target for solid organ transplantation

Connexins are a class of membrane proteins widely distributed throughout the body and have various functions based on their location and levels of expression. More specifically, connexin proteins expressed in endothelial cells (ECs) have unique roles in maintaining EC barrier integrity and function-a highly regulated process that is critical for pro-inflammatory and pro-coagulant reactions. In this minireview, we discuss the regulatory influence connexin proteins have in maintaining EC barrier integrity and their role in ischemia-reperfusion injury as it relates to organ transplantation. It is evident that certain isoforms of the connexin protein family are uniquely positioned to have far-reaching effects on preserving organ function; however, there is still much to be learned of their roles in transplant immunology and the application of this knowledge to the development of targeted therapeutics.

Interleukin-18 and High-Mobility-Group-Protein B1 are Early and Sensitive Indicators for Cell Damage During Normothermic Machine Perfusion after Prolonged Cold Ischemic Storage of Porcine Liver Grafts

In the era of organ machine perfusion, experimental models to optimize reconditioning of (marginal) liver grafts are needed. Although the relevance of cytokine signatures in liver transplantation has been analyzed previously, the significance of molecular monitoring during normothermic machine perfusion (NMP) remains elusive. Therefore, we developed a porcine model of cold ischemic liver graft injury after prolonged static cold storage (SCS) and subsequent NMP: Livers obtained from ten minipigs underwent NMP for 6 h directly after procurement (control group) or after 20 h of SCS. Grafts after prolonged SCS showed significantly elevated AST, ALT, GLDH and GGT perfusate concentrations, and reduced lactate clearance. Bile analyses revealed reduced bile production, reduced bicarbonate and elevated glucose concentrations after prolonged SCS. Cytokine analyses of graft perfusate simultaneously demonstrated an increase of pro-inflammatory cytokines such as Interleukin-1α, Interleukin-2, and particularly Interleukin-18. The latter was the only significantly elevated cytokine compared to controls, peaking as early as 2 h after reperfusion (11,012 ng/ml vs. 1,493 ng/ml; p = 0.029). Also, concentrations of High-Mobility-Group-Protein B1 were significantly elevated after 2 h of reperfusion (706.00 ng/ml vs. 148.20 ng/ml; p < 0.001) and showed positive correlations with AST (r² = 0.846) and GLDH (r² = 0.918) levels. Molecular analyses during reconditioning of liver grafts provide insights into the degree of inflammation and cell damage and could thereby facilitate future interventions during NMP reducing acute and chronic graft injury.

Biomolecular Pathways of Cryoinjuries in Low-Temperature Storage for Mammalian Specimens

Low-temperature preservation could effectively extend in vitro storage of biological materials due to delayed or suspended cellular metabolism and decaying as illustrated by the Arrhenius model. It is widely used as an enabling technology for a variety of biomedical applications such as cell therapeutics, assisted reproductive technologies, organ transplantation, and mRNA medicine. Although the technology to minimize cryoinjuries of mammalian specimens during preservation has been advanced substantially over past decades, mammalian specimens still suffer cryoinjuries under low-temperature conditions. Particularly, the molecular mechanisms underlying cryoinjuries are still evasive, hindering further improvement and development of preservation technologies. In this paper, we systematically recapitulate the molecular cascades of cellular injuries induced by cryopreservation, including apoptosis, necroptosis, ischemia-reperfusion injury (IRI). Therefore, this study not only summarizes the impact of low-temperature preservations on preserved cells and organs on the molecular level, but also provides a molecular basis to reduce cryoinjuries for future exploration of biopreservation methods, materials, and devices.

Coagulopathy and hemostasis management in patients undergoing liver transplantation: Defining a dynamic spectrum across phases of care

Patients with acute and chronic liver disease present with a wide range of disease states and severity that may require liver transplantation (LT). Physiologic alterations occur that are dynamic throughout all phases of perioperative care, creating complex management scenarios that necessitate multidisciplinary clinical care. Specifically, alterations in hemostasis in liver disease can be pronounced and evolve with disease progression over time. Recent studies and society guidance address this emerging paradigm and offer recommendations to assist with hemostatic management in patients with liver disease. However, patients undergoing LT are unique and diverse, often with unstable disease that requires specialized approaches. Our aim is to provide a focused review of hemostatic management of the LT patient, distinguish unique aspects of the three main phases of care (before LT, perioperative, and after LT), and identify knowledge gaps and critical areas of future research.

Postreperfusion Syndrome in Liver Transplant: A Risk Factor for Acute Kidney Failure: A Retrospective Analysis

The maximum expression of hemodynamic instability during liver transplant is the so-called postreperfusion syndrome (PRS) that increases both overall mortality and postoperative complications. It was first defined by Aggarwal et al in 1987, but the results are still conflicting when establishing the relationship between PRS and acute kidney failure (AKF). We conducted a retrospective observational study of transplant recipients with deceased-donor liver grafts between January 2002 and December 2018. We analyzed the incidence of PRS and its potential negative impact over kidney function. A total of 551 transplants were analyzed. PRS was recorded in 130 patients (23.6%). The incidence of AKF was 61.5%. A total of 111 patients required kidney replacement therapy (32.7%). Regarding the severity of AKF, 128 patients were classified as acute kidney injury (AKI) 1 (23.2%), 76 as AKI 2 (13.8%), and 135 as AKI 3 (24.5%). In the group with PRS, 75.4% (n = 98) developed AKF vs 57.2% (n = 241) in the group without PRS. In the multivariate analysis we found a relationship between PRS and AKF with an odds ratio of 2.18 (95% CI, 1.30-3.64; P = .003), once adjusted by the length of the anhepatic phase, donor age, Model for End-Stage Liver Disease score, history of ascites, and need for early surgical reintervention. The incidence of AKF decreased (44.5%) ever since the implementation of delayed calcineurin inhibitors therapy and piggyback surgical technique, but a clear influence of the occurrence of PRS on the development of AKF is still observed, with an OR of 3.78 (95% CI, 1.92-7.43; P < .001), once adjusted by albumin and hemoglobin levels, Model for End-Stage Liver Disease score, and Child classification.

Imaging of hypochlorous acid in mitochondria using an asymmetric near-infrared fluorescent probe with large Stokes shift

Small-molecule near-infrared (NIR) imaging facilitates deep tissue penetration, low autofluorescence, non-invasive visualization, and a relatively simple operation. As such it has emerged as a popular technique for tracking biological species and events. However, the small Stokes shift of most NIR dyes often results in a low signal-to-noise ratio and self-quenching due to crosstalk between the excitation and emission spectra. With this research, we developed a NIR-based fluorescent probe WD-HOCl for hypochlorous acid (HOCl) detection using the NIR dye TJ730 as the fluorophore, which exhibits a large Stokes shift of 156 nm, with no crosstalk between the excitation and emission spectra. It contains acyl hydrazide as the responsive group and a pyridinium cation as the mitochondria-targeting group. The fluorescence intensity of WD-HOCl was enhanced by 30.1-fold after reacting with HOCl. Imaging studies performed using BV-2 cells indicated that WD-HOCl could be used for endogenous HOCl detection and imaging in living cells exposed to glucose and oxygen deprivation/reperfusion. Finally, we demonstrated that inhibiting the expression of NOX2 reduced the HOCl levels and the severity of oxidative stress during stroke in a mouse model.

The Role of Sex in Acute and Chronic Liver Damage

Acute and chronic hepatic damages are caused by xenobiotics or different diseases affecting the liver, characterized by different etiologies and pathological features. It has been demonstrated extensively that liver damage progresses differently in men and women, and some chronic liver diseases show a more favorable prognosis in women than in men. This review aims to update the most recent advances in the comprehension of the molecular basis of the sex difference observed in both acute and chronic liver damage. With this purpose, we report experimental studies on animal models and clinical observations investigating both acute liver failure, e.g., drug-induced liver injury (DILI), and chronic liver diseases, e.g., viral hepatitis, alcoholic liver disease (ALD), non-alcoholic fatty liver disease (NAFLD), autoimmune liver diseases, and hepatocellular carcinoma (HCC).

Preservation solutions for static cold storage in donation after circulatory death and donation after brain death liver transplantation in the United States

Static cold preservation remains the cornerstone for storing donor livers following procurement; however, the choice between University of Wisconsin solution (UW) and histidine-tryptophan-ketoglutarate solution (HTK) remains controversial. Recent International Liver Transplantation Society (ILTS) guidelines have recommended avoiding HTK for donation after circulatory death (DCD) grafts based on older reports. We studied the latest US adult graft outcomes in three recent eras (2006-2010, 2011-2015, 2016-2020) comparing HTK and UW among 5956 DCD LTs: 3873 (65.0%) used UW and 1944 (32.7%) used HTK. In a total of 82,679 donation after brain death (DBD) liver transplantations (LTs), 63,511 (76.8%) used UW and 15,855 (19.2%) used HTK. The HTK group had higher 1-year and 5-year graft survival rates of 89.7% and 74.3%, respectively, compared with 85.9% and 70.8% in the UW group in the 2016-2020 era (p = 0.005). This difference remained when adjusted for important potential confounders (hazard ratio, 0.78; 95% confidence interval: 0.60, 0.99). There were no differences between groups among DCD LTs in the earlier eras or among DBD LTs in all eras (all p values > 0.05). The latest US data suggest that HTK is at least noninferior to UW for preserving DCD livers. These data support HTK use in DCD LT and contradict ILTS guidance.

Blood loss during liver transplantation is a predictor of postoperative thrombosis

Liver transplantation (LT) is an effective way to cure end-stage liver diseases (ESLDs), which have generally been regarded as examples of acquired bleeding disorders. However, postoperative thrombosis after LT is recognised and remains a life-threatening complication. This study aimed to show that blood loss during LT is a predictor of postoperative thrombosis and to establish a predictive model. We analysed the medical records of all patients who underwent LT at the First Affiliated Hospital of Xi'an Jiaotong University from January 2017 to April 2019 to identify the risk factors for post-transplant thrombosis. The predictive nomogram was established based on independent predictors identified by logistic regression analysis. Blood loss during LT of ≥31.25 mL/kg can predict postoperative thrombosis, and the nomogram achieved an accurate prediction.

Procalcitonin in early allograft dysfunction after orthotopic liver transplantation: a retrospective single centre study

Background

Ischemia–reperfusion injury (IRI) is the pathophysiological hallmark of hepatic dysfunction after orthotopic liver transplantation (OLT). Related to IRI, early allograft dysfunction (EAD) after OLT affects short- and long-term outcome. During inflammatory states, the liver seems to be the main source of procalcitonin (PCT), which has been shown to increase independently of bacterial infection. This study investigates the association of PCT, IRI and EAD as well as the predictive value of PCT during the first postoperative week in terms of short- and long-term outcome after OLT.

Methods

Patients ≥ 18 years undergoing OLT between January 2016 and April 2020 at the University Hospital of Zurich were eligible for this retrospective study. Patients with incomplete PCT data on postoperative days (POD) 1 + 2 or combined liver-kidney transplantation were excluded. The PCT course during the first postoperative week, its association with EAD, defined by the criteria of Olthoff, and IRI, defined as aminotransferase level > 2000 IU/L within 2 PODs, were analysed. Finally, 90-day as well as 12-month graft and patient survival were assessed.

Results

Of 234 patients undergoing OLT, 110 patients were included. Overall, EAD and IRI patients had significantly higher median PCT values on POD 2 [31.3 (9.7–53.8) mcg/l vs. 11.1 (5.3–25.0) mcg/l; p < 0.001 and 27.7 (9.7–51.9) mcg/l vs. 11.5 (5.5–25.2) mcg/l; p < 0.001] and impaired 90-day graft survival (79.2% vs. 95.2%; p = 0.01 and 80.4% vs. 93.8%; p = 0.033). IRI patients with PCT < 15 mcg/l on POD 2 had reduced 90-day graft and patient survival (57.9% vs. 93.8%; p = 0.001 and 68.4% vs. 93.8%; p = 0.008) as well as impaired 12-month graft and patient survival (57.9% vs. 96.3%; p = 0.001 and 68.4% vs. 96.3%; p = 0.008), while the outcome of IRI patients with PCT > 15 mcg/l on POD 2 was comparable to that of patients without IRI/EAD.

Conclusion

Generally, PCT is increased in the early postoperative phase after OLT. Patients with EAD and IRI have a significantly increased PCT maximum on POD 2, and impaired 90-day graft survival. PCT measurement may have potential as an additional outcome predictor in the early phase after OLT, as in our subanalysis of IRI patients, PCT values < 15 mcg/l were associated with impaired outcome.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12876-022-02486-5.

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.

SIRT5 alleviates hepatic ischemia and reperfusion injury by diminishing oxidative stress and inflammation via elevating SOD1 and IDH2 expression

Hepatic ischemia/reperfusion (I/R) injury, a common and unavoidable pathophysiological process during liver transplantation or resection operation, may impede postoperative liver function recovery, and its mechanism and targeted therapy remain largely unknown. SIRT5 is a well-known deacetylase and participates in the regulation of many physiological and pathological processes, including I/R. The role of SIRT5 in I/R is controversial or tissue-specific, restricting I/R progression in the heart while deteriorating injury in the kidney and brain, while its effect on hepatic I/R remains unclear. In this study, we investigated the function of SIRT5 in hepatic I/R using AAV8 and lentivirus to overexpress SIRT5 in vivo and in vitro. The data showed that SIRT5 overexpression alleviated liver I/R injury in mice and hypoxia/reoxygenation treated AML-12 cells. Moreover, gain- and loss-of-function of SIRT5, SOD1 and IDH2 experiments in AML-12 were performed. Our results demonstrated that SOD1 and IDH2 knockdown abolished the effect of SIRT5 on restraining oxidative stress and inflammation. Therefore, our work revealed that SIRT5 may alleviates hepatic I/R injury by diminishing oxidative stress and inflammation via up-regulating the SOD1 and IDH2 expression, which enriches the theory and therapeutic strategies of hepatic I/R injury.

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.

COVID-19 Pandemic: Insights into Interactions between SARS-CoV-2 Infection and MAFLD

COVID-19, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has become an ongoing global health pandemic. Since 2019, the pandemic continues to cast a long shadow on all aspects of our lives, bringing huge health and economic burdens to all societies. With our in-depth understanding of COVID-19, from the initial respiratory tract to the later gastrointestinal tract and cardiovascular systems, the multiorgan involvement of this infectious disease has been discovered. Metabolic dysfunction-associated fatty liver disease (MAFLD), formerly named nonalcoholic fatty liver disease (NAFLD), is a major health issue closely related to metabolic dysfunctions, affecting a quarter of the world's adult population. The association of COVID-19 with MAFLD has received increasing attention, as MAFLD is a potential risk factor for SARS-CoV-2 infection and severe COVID-19 symptoms. In this review, we provide an update on the interactions between COVID-19 and MAFLD and its underlying mechanisms.

Cordycepin Protects against Hepatic Ischemia/Reperfusion Injury via Inhibiting MAPK/NF-κB Pathway

Hepatic ischemia/reperfusion injury (HIRI) is a common complication of liver surgery requiring hepatic disconnection, such as hepatectomy and liver transplantation. The aim of this study was to investigate the effects of cordycepin on HIRI and to elucidate the underlying mechanisms. Balb/c mice were randomly divided into six groups: a normal control group, sham group, H-cordycepin group, HIRI group, L-cordycepin (25 mg/kg) + HIRI group, and H-cordycepin (50 mg/kg) + HIRI group. Mice were subjected to I/R, and cordycepin was intragastrically administered for seven consecutive days before surgery. Orbital blood and liver specimens were collected at 6 and 24 h after HIRI. Serum levels of ALT and AST were decreased in the cordycepin pretreatment groups. Notably, cordycepin attenuated the inflammatory response and the production of proapoptosis proteins, while increasing expression of antiapoptosis proteins and decreasing expression of autophagy-linked proteins. Furthermore, cordycepin inhibited activation of the MAPK/NF-κB signaling pathway. Collectively, these results indicate that cordycepin pretreatment ameliorated hepatocyte injury caused by HIRI. As compared with the HIRI group, cordycepin pretreatment mitigated the inflammatory response and inhibited apoptosis and autophagy via regulation of the MAPK/NF-κB signaling pathway.

Targeting the Hepatic Microenvironment to Improve Ischemia/Reperfusion Injury: New Insights into the Immune and Metabolic Compartments

Hepatic ischemia/reperfusion injury (IRI) is mainly characterized by high activation of immune inflammatory responses and metabolic responses. Understanding the molecular and metabolic mechanisms underlying development of hepatic IRI is critical for developing effective therapies for hepatic IRI. Recent advances in research have improved our understanding of the pathogenesis of IRI. During IRI, hepatocyte injury and inflammatory responses are mediated by crosstalk between the immune cells and metabolic components. This crosstalk can be targeted to treat or reverse hepatic IRI. Thus, a deep understanding of hepatic microenvironment, especially the immune and metabolic responses, can reveal new therapeutic opportunities for hepatic IRI. In this review, we describe important cells in the liver microenvironment (especially non-parenchymal cells) that regulate immune inflammatory responses. The role of metabolic components in the diagnosis and prevention of hepatic IRI are discussed. Furthermore, recent updated therapeutic strategies based on the hepatic microenvironment, including immune cells and metabolic components, are highlighted.

The Role of Neutrophils as a Driver in Hepatic Ischemia-Reperfusion Injury and Cancer Growth

The innate immune system plays an essential role in the response to sterile inflammation and its association with liver ischemia and reperfusion injury (IRI). Liver IRI often manifests during times of surgical stress such as cancer surgery or liver transplantation. Following the initiation of liver IRI, stressed hepatocytes release damage-associated molecular patterns (DAMPs) which promote the infiltration of innate immune cells which then initiate an inflammatory cascade and cytokine storm. Upon reperfusion, neutrophils are among the first cells that infiltrate the liver. Within the liver, neutrophils play an important role in fueling tissue damage and tumor progression by promoting the metastatic cascade through the formation of Neutrophil Extracellular Traps (NETs). NETs are composed of web-like DNA structures containing proteins that are released in response to inflammatory stimuli in the environment. Additionally, NETs can aid in mediating liver IRI, promoting tumor progression, and most recently, in mediating early graft rejection in liver transplantation. In this review we aim to summarize the current knowledge of innate immune cells, with a focus on neutrophils, and their role in mediating IRI in mouse and human diseases, including cancer and transplantation. Moreover, we will investigate the interaction of Neutrophils with varying subtypes of other cells. Furthermore, we will discuss the role and different treatment modalities in targeting Neutrophils and NETs to prevent IRI.

The Importance of CXCL1 in the Physiological State and in Noncancer Diseases of the Oral Cavity and Abdominal Organs

CXCL1 is a CXC chemokine, CXCR2 ligand and chemotactic factor for neutrophils. In this paper, we present a review of the role of the chemokine CXCL1 in physiology and in selected major non-cancer diseases of the oral cavity and abdominal organs (gingiva, salivary glands, stomach, liver, pancreas, intestines, and kidneys). We focus on the importance of CXCL1 on implantation and placentation as well as on human pluripotent stem cells. We also show the significance of CXCL1 in selected diseases of the abdominal organs, including the gastrointestinal tract and oral cavity (periodontal diseases, periodontitis, Sjögren syndrome, Helicobacter pylori infection, diabetes, liver cirrhosis, alcoholic liver disease (ALD), non-alcoholic fatty liver disease (NAFLD), HBV and HCV infection, liver ischemia and reperfusion injury, inflammatory bowel disease (Crohn’s disease and ulcerative colitis), obesity and overweight, kidney transplantation and ischemic-reperfusion injury, endometriosis and adenomyosis).

Identification of Key Biomarkers and Immune Infiltration in Liver Tissue after Bariatric Surgery

Background

Few drugs are clearly available for nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH); nevertheless, mounting studies have provided sufficient evidence that bariatric surgery is efficient for multiple metabolic diseases, including NAFLD and NASH, while the molecular mechanisms are still poorly understood.

Methods

The mRNA expression profiling of GSE48452 and GSE83452 were retrieved and obtained from the Gene Expression Omnibus (GEO) database. The limma package was employed for identifying differentially expressed genes (DEGs), followed by clusterProfiler for performing Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses, and GSEA software for performing GSEA analyses. The PPI network analyses were constructed using Metascape online analyses. WGCNA was also utilized to identify and verify the hub genes. CIBERSORT tools contributed to the analysis of immune cell infiltration of liver diseases.

Results

We identify coexpressed differential genes including 10 upregulated and 55 downregulated genes in liver tissue after bariatric surgery. GO and KEGG enrichment analyses indicated that DEGs were remarkably involved in the immune response. GSEA demonstrated that DEGs were markedly enriched in the immune response before surgery, while most were enriched in metabolism after surgery. Seven genes were screened through the MCC algorithm and KME values, including SRGN, CD53, EVI2B, MPEG1, NCKAP1L, LCP1, and TYROBP. The mRNA levels of these genes were verified in the Attie Lab Diabetes Database, and only LCP1 was found to have significant differences and correlation with certain immune cells.

Conclusion

Our knowledge of the mechanisms by which bariatric surgery benefits the liver and the discovery of LCP1 is expected to serve as potential biomarkers or therapeutic targets for NAFLD and NASH.

Liver Ischemia and Reperfusion Induce Periportal Expression of Necroptosis Executor pMLKL Which Is Associated With Early Allograft Dysfunction After Transplantation

Background

Early allograft dysfunction (EAD) following liver transplantation (LT) remains a major threat to the survival of liver grafts and recipients. In animal models, it is shown that hepatic ischemia-reperfusion injury (IRI) triggers phosphorylation of Mixed Lineage Kinase domain-like protein (pMLKL) inducing necroptotic cell death. However, the clinical implication of pMLKL-mediated cell death in human hepatic IRI remains largely unexplored. In this study, we aimed to investigate the expression of pMLKL in human liver grafts and its association with EAD after LT.

Methods

The expression of pMLKL was determined by immunohistochemistry in liver biopsies obtained from both human and rat LT. Human liver biopsies were obtained at the end of preservation (T0) and ~1 hour after reperfusion (T1). The positivity of pMLKL was quantified electronically and compared in rat and human livers and post-LT outcomes. Multiplex immunofluorescence staining was performed to characterize the pMLKL-expressing cells.

Results

In the rat LT model, significant pMLKL expression was observed in livers after IRI as compared to livers of sham-operation animals. Similarly, the pMLKL score was highest after IRI in human liver grafts (in T1 biopsies). Both in rats and humans, the pMLKL expression is mostly observed in the portal triads. In grafts who developed EAD after LT (n=24), the pMLKL score at T1 was significantly higher as compared to non-EAD grafts (n=40). ROC curve revealed a high predictive value of pMLKL score at T1 (AUC 0.70) and the ratio of pMLKL score at T1 and T0 (pMLKL-index, AUC 0.82) for EAD. Liver grafts with a high pMLKL index (>1.64) had significantly higher levels of serum ALT, AST, and LDH 24 hours after LT compared to grafts with a low pMLKL index. Multivariate logistical regression analysis identified the pMLKL-index (Odds ratio=1.3, 95% CI 1.1-1.7) as a predictor of EAD development. Immunohistochemistry on serial sections and multiplex staining identified the periportal pMLKL-positive cells as portal fibroblasts, fibrocytes, and a minority of cholangiocytes.

Conclusion

Periportal pMLKL expression increased significantly after IRI in both rat and human LT. The histological score of pMLKL is predictive of post-transplant EAD and is associated with early liver injury after LT. Periportal non-parenchymal cells (i.e. fibroblasts) appear most susceptible to pMLKL-mediated cell death during hepatic IRI.

Transcriptional changes in orthotopic liver transplantation and ischemia/reperfusion injury

Background There are few effective targeting strategies to reduce liver ischemia-reperfusion injury (IRI), which is one of the reasons for the poor prognosis of liver transplant recipients. Methods A systematic approach combining gene expression with protein interaction (PPI) network was used to screen the characteristic genes and related biological functions of post-transplant. Differentially expressed genes (DEGs) between IRI+ and IRI- were identified. Logistic regression model and receiver operating characteristic (ROC) curve were used to identify potential target genes of IRI. The expression of key genes was verified by qRT-PCR and Western-blot experiments. Finally, the ssGSEA was used to identify the immune cell infiltration in patients with IRI. Results The 283 common DEGs in GSE87487 and GSE151648 were mainly related to apoptosis and IL-17 signaling pathway. Through PPI network and logistic regression analysis, we identified that IL6, CCL2 and CXCL8 may be involved in the ischemia/reperfusion (IR) process. In addition, 32 genes were showed associated with IRI through inflammatory and metabolic pathways. Among the key genes identified, the differential expression of AGBL4, CILP2 and IL4I1 was verified by molecular experiments. Th17 cells of differentially infiltrated immune cells were positively correlated with CILP2 and IL4I1. The difference of Th17 cells between IRI+ and IRI- was verified by flow cytometry. Conclusion The study showed that AGBL4, CILP2 and IL4I1 were associated with IRI. Th17 cells may be associated with the regulation of IRI by key genes. These genes and related pathways may be targets for improving IRI.

Protective effect of platinum nano-antioxidant and nitric oxide against hepatic ischemia-reperfusion injury

Therapeutic interventions of hepatic ischemia-reperfusion injury to attenuate liver dysfunction or multiple organ failure following liver surgery and transplantation remain limited. Here we present an innovative strategy by integrating a platinum nanoantioxidant and inducible nitric oxide synthase into the zeolitic imidazolate framework-8 based hybrid nanoreactor for effective prevention of ischemia-reperfusion injury. We show that platinum nanoantioxidant can scavenge excessive reactive oxygen species at the injury site and meanwhile generate oxygen for subsequent synthesis of nitric oxide under the catalysis of nitric oxide synthase. We find that such cascade reaction successfully achieves dual protection for the liver through reactive oxygen species clearance and nitric oxide regulation, enabling reduction of oxidative stress, inhibition of macrophage activation and neutrophil recruitment, and ensuring suppression of proinflammatory cytokines. The current work establishes a proof of concept of multifunctional nanotherapeutics against ischemia-reperfusion injury, which may provide a promising intervention solution in clinical use.

Friend or Foe: The Relativity of (Anti)oxidative Agents and Pathways

An element, iron, a process, the generation of reactive oxygen species (ROS), and a molecule, ascorbate, were chosen in our study to show their dual functions and their role in cell fate decision. Iron is a critical component of numerous proteins involved in metabolism and detoxification. On the other hand, excessive amounts of free iron in the presence of oxygen can promote the production of potentially toxic ROS. They can result in persistent oxidative stress, which in turn can lead to damage and cell death. At the same time, ROS—at strictly regulated levels—are essential to maintaining the redox homeostasis, and they are engaged in many cellular signaling pathways, so their total elimination is not expedient. Ascorbate establishes a special link between ROS generation/elimination and cell death. At low concentrations, it behaves as an excellent antioxidant and has an important role in ROS elimination. However, at high concentrations, in the presence of transition metals such as iron, it drives the generation of ROS. In the term of the dual function of these molecules and oxidative stress, ascorbate/ROS-driven cell deaths are not necessarily harmful processes—they can be live-savers too.

Propionic Acid, Induced in Gut by an Inulin Diet, Suppresses Inflammation and Ameliorates Liver Ischemia and Reperfusion Injury in Mice

Liver ischemia and reperfusion injury (IRI) is one of the obstacles in liver surgery such as liver resection and transplantation. In this study, we investigated the preventive effect on mouse liver IRI by feeding mice with inulin, which is a heterogeneous blend of indigestible fructose polymer. Mice were fed either a control ordinary diet (CD) or an inulin diet (ID) containing 5% inulin in the CD, for 14 days before the ischemia and reperfusion (IR) maneuver. IR induced-liver damages were significantly ameliorated in the ID group, compared with those in the CD group. Feeding mice with an ID, but not a CD, elevated levels of Bacteroidetes among gut microbiota, and especially increased Bacteroides acidifaciens in mouse feces, which resulted in significant elevation of short-chain fatty acids (SCFAs) in the portal vein of mice. Among SCFAs, propionic acid (PA) was most significantly increased. The microbial gene functions related to PA biosynthesis were much higher in the fecal microbiome of the ID group compared to the CD. However, the action of PA on liver IRI has not been yet clarified. Direct intraperitoneal administration of PA alone prior to the ischemia strongly suppressed liver cell damages as well as inflammatory responses caused by liver IR. Furthermore, PA suppressed the secretion of inflammatory cytokines from peritoneal macrophages stimulated in vitro through TLR-4 with high-mobility group box 1 protein (HMGB-1), known to be released from apoptotic liver cells during the IR insult. The present study shows that PA may play a key role in the inulin-induced amelioration of mouse liver IRI.

An antioxidant nanodrug protects against hepatic ischemia-reperfusion injury by attenuating oxidative stress and inflammation

Liver transplantation is currently recognized as the only effective therapeutic option for end-stage liver disease. Hepatic ischemia-reperfusion injury (IRI) remains a major cause of graft damage or dysfunction, and is mediated by the abundant production of reactive oxygen species (ROS) and a complex cascade of inflammation during the reperfusion period. However, no universal antioxidant has been applied in clinical practice due to its low bioavailability and non-specific targeting. Herein, cerium oxide and manganese oxide nanocomposites (CM NCs), with the advantages of high biocompatibility, passive liver-targeting and short-term metabolic excretion, were synthesized as a nanodrug for hepatic IRI therapy. The CM NCs exhibited excellent superoxide dismutase (SOD) and catalase (CAT) mimetic activity to scavenge ROS and generate oxygen (O₂). Therefore, CM NCs could alleviate oxidative stress, subsequently suppress the activation of Kupffer cells (KCs) and neutrophils, and reduce the secretion of inflammatory factors due to the synergistic effect of ROS scavenging and O₂ production. By exploring the underlying mechanisms of the CM NCs in the treatment of hepatic IRI, we suggest that the CM NCs with ROS scavenging and inflammation regulation capacity show clinical potential for hepatic IRI management and provide new perspectives in the treatment of other oxidative-stress-related diseases.

Anisakidae parasitism activated immune response and induced liver fibrosis in wild anadromous Coilia nasus

Anisakidae nematode larvae is one of the most common parasites in wild anadromous Coilia nasus. This study aims to explore the mechanism of the C. nasus immune response to the parasitism of Anisakid nematode larvae. Results found that Anisakid nematode larvae parasitism caused liver injury as evidenced by histomorphology results as well as high levels of aminotransferase and aspertate aminotransferase. Furthermore, Anisakid nematode larvae parasitism induced an immune response in the host, which was characterized by the elevated populations of macrophages and neutrophils in the liver and head-kidney in the Anisakidae-infected group compared to the noninfected group. The expression of immunoglobulin IgM and IgD in the liver and head-kidney was also increased in the Anisakidae-infected group. The Anisakidae-infected group showed higher activity of antioxidant enzymes catalase and superoxide dismutase, which indicates severe oxidative stress, and increased production of pro-inflammatory cytokines, TNF-α, IL-6 as well as MCP-1 in the liver compared with the noninfected group. As a result of inflammation, livers of hosts in the Anisakidae-infected group showed fibrosis, and elevated expression of associated proteins including α-smooth muscle actin, fibronectin, collagen type I and type III compared with the noninfected group. We demonstrated that Anisakid nematode larvae parasitism results in injury and fibrosis in the liver, and triggers immune cell infiltration and inflammation in the liver and head-kidney of C. nasus. Altogether, the results provide a foundation for building an interaction between parasite and host, and will contribute to C. nasus population and fishery resource protection.

Necroptosis in Solid Organ Transplantation: A Literature Overview

Ischemia-reperfusion injury (IRI) is encountered in various stages during solid organ transplantation (SOT). IRI is known to be a multifactorial inflammatory condition involving hypoxia, metabolic stress, leukocyte extravasation, cellular death (including apoptosis, necrosis and necroptosis) and an activation of immune response. Although the cycle of sterile inflammation during IRI is consistent among different organs, the underlying mechanisms are poorly understood. Receptor-interacting protein kinase 3 (RIPK3) and mixed-lineage kinase domain-like pseudokinase (MLKL) are thought to be crucial in the implementation of necroptosis. Moreover, apart from “silent” apoptotic death, necrosis also causes sterile inflammation—necroinflammation, which is triggered by various damage-associated molecular patterns (DAMPs). Those DAMPs activate the innate immune system, causing local and systemic inflammatory responses, which can result in graft failure. In this overview we summarize knowledge on mechanisms of sterile inflammation processes during SOT with special focus on necroptosis and IRI and discuss protective strategies.

Hepatoprotective effects of sevoflurane against hepatic ischemia-reperfusion injury by regulating microRNA-124-3p-mediated TRAF3/CREB axis

The purpose of the present study is to define the role of sevoflurane (SEV) in hepatic ischemia-reperfusion (I/R) injury as well as its underlying mechanism. Initially, hepatic I/R animal models and I/R hepatocyte models were established in C57BL/6 mice and normal mouse hepatocytes (BNL CL.2) after SEV preconditioning, respectively, followed by detection of microRNA-124-3p (miR-124-3p), TRAF3, and CREB expression by RT-qPCR and Western blot analysis. In addition, miR-124-3p, TRAF3 and CREB expression in hepatocytes was altered to identify their roles in modulating the levels of glutathione transferase (GST), aspartate aminotransferase (AST) and alanine aminotransferase (ALT), and inflammation-related factors and hepatocyte apoptosis by ELISA and flow cytometry respectively. The effects of SEV on the miR-124-3p/TRAF3/CREB axis were also verified in vitro and in vivo. IP assay was performed to verify the effect of TRAF3 on CREB ubiquitination in BNL CL.2 cells, and the cycloheximide (CHX) intervention experiment to detect the stability of CREB protein. SEV augmented the miR-124-3p expression in I/R animal and cell models. Moreover, SEV was observed to suppress I/R-induced liver damage, GST, ALT, and AST levels, hepatocyte apoptosis and inflammation. Overexpression of miR-124-3p resulted in alleviation of hepatic I/R injury, which was countered by TRAF3 overexpression. miR-124-3p targeted TRAF3, while TRAF3 promoted CREB ubiquitination and reduced protein stability of CREB. SEV could impede I/R-induced liver damage, GST, ALT, and AST levels, hepatocyte apoptosis and inflammation via mediation of the miR-124-3p/TRAF3/CREB axis in vitro and in vivo. Collectively, SEV may upregulate miR-124-3p to inhibit TRAF3 expression, thereby reducing the ubiquitination and degradation of CREB, alleviating hepatic I/R injury.

Hepatic Ischemia-reperfusion Injury in Mice was Alleviated by Rac1 Inhibition - More Than Just ROS-inhibition

BACKGROUND AND AIMS

Reducing reactive oxygen species (ROS) production has proven an effective way for alleviating oxidative stress during ischemia-reperfusion injury (IRI). Moreover, inhibition of Rac1 could reduce ROS production and prevent oxidative stress injury. Previous studies have suggested a positive interactivation feedback loop between Rac1 and hypoxia-inducible factor (HIF)-1α, the latter being up-regulated early during ischemia. The positive inter-activation between Rac1 and HIF-1α would aggravate ROS production, thereby promoting IRI. This study was designed to verify the effects of Rac1 inhibition on hepatic IRI both at animal and cellular levels and to explore the interaction between Rac1 and HIF-1α during hepatic IRI.

METHODS

C57B/6 mice and AML-12 cells were used for the construction of hepatic IRI animal and cell models. Rac1 inhibition was achieved by NSC23766 (a specific Rac1 inhibitor). Lentiviral vectors were used for Rac1 knockdown. At designated time points, serum and liver tissues were collected from the mice and treated cells were collected for further analysis.

RESULTS

NSC23766 treatment significantly alleviated the hepatic IRI in mice, manifesting as lower vacuolation score and less apoptosis cells, lower ROS and serum/liver alanine aminotransferase/aspartate aminotransferase levels, and fewer activated inflammatory cells. IRI of AML-12 was also alleviated by 50 µM NSC23766 or Rac1-knockdown, manifesting as reduced cell apoptosis, less extensive interruption of mitochondrial membrane potential, down-regulation of apoptosis, and effects on DNA damage-related proteins. Interestingly, Rac1 knockdown also down-regulated the expression level of HIF-1α.

CONCLUSIONS

Our study supports a protective effect of Rac1 inhibition on hepatic IRI. Aside from the classic topics of reducing ROS production and oxidative stress, our study showed an interaction between Rac1 and HIF-1α signaling during hepatic IRI.

Hypothermic oxygenated perfusion ameliorates ischemia-reperfusion injury of fatty liver in mice via Brg1/Nrf2/HO-1 axis

BACKGROUND

After cold storage (CS) and subsequent transplantation, fatty liver is more inclined to develop liver dysfunction and serious postoperative complications in contrast to healthy liver. Hypothermic oxygenated perfusion (HOPE) is a safe and efficacious system, which can repair fatty liver and reduce ischemia-reperfusion injury. The aim of this research is to investigate the function of Brg1/Nrf2/HO-1 signaling pathway in the protective effect of HOPE on ischemia-reperfusion injury of fatty liver.

METHODS

The mouse fatty liver model was successfully established and verified by hematoxylin-eosin (HE) staining and oil red O staining. The animals were divided into Control group, CS group and HOPE group. The levels of liver enzyme and lactate in the perfusate were used to measure liver function and cellular metabolism. HE staining and TUNEL staining were utilized to assess the tissue structure and apoptosis, respectively. The levels of superoxide dismutase, malondialdehyde and reactive oxygen species in liver tissue were measured to quantitatively analyze the degree of oxidative stress, and the expressions of protein Brg1, Nrf2 and HO-1 were detected by means of the western blot. Double-labeling immunofluorescence was to explore the colocalization of Brg1 and Nrf2.

RESULTS

The injury of the liver in the CS group was more serious than that in the control group. However, HOPE could significantly reduce the injury, which was manifested by the improvement of liver function and cellular metabolism, and the lower degrees of apoptosis, necrosis and oxidative stress. Furthermore, the expressions of Brg1, Nrf2 and HO-1 in the HOPE group were significantly increased than those in the CS group.

CONCLUSIONS

One-hour HOPE treatment before reperfusion can obviously improve the injury of fatty liver in mice. The underlying mechanism may be that the interaction of Brg1 and Nrf2 can selectively activate the transcription of HO-1.

Current aspects of renal dysfunction after liver transplantation

The development of chronic kidney disease (CKD) after liver transplantation (LT) exerts a severe effect on the survival of patients. The widespread adoption of the model for end-stage liver disease score strongly impacted CKD incidence after the procedure, as several patients are transplanted with previously deteriorated renal function. Due to its multifactorial nature, encompassing pre-transplantation conditions, perioperative events, and nephrotoxic immunosuppressor therapies, the accurate identification of patients under risk of renal disease, and the implementation of preventive approaches, are extremely important. Methods for the evaluation of renal function in this setting range from formulas that estimate the glomerular filtration rate, to non-invasive markers, although no option has yet proved efficient in early detection of kidney injury. Considering the nephrotoxicity of calcineurin inhibitors (CNI) as a factor of utmost importance after LT, early nephroprotective strategies are highly recommended. They are based mainly on delaying the application of CNI during the immediate postoperative-period, reducing their dosage, and associating them with other less nephrotoxic drugs, such as mycophenolate mofetil and everolimus. This review provides a critical assessment of the causes of renal dysfunction after LT, the methods of its evaluation, and the interventions aimed at preserving renal function early and belatedly after LT.

Intravenous immunoglobulin is effective in alleviating hepatic ischemia-reperfusion injury: a rat model study

BACKGROUND

Hepatic ischemia-reperfusion injury (I/R) is an important factor affecting the prognosis of patients undergoing liver surgery. This study aimed to explore the value of intravenous immunoglobulin (IVIG) in hepatic I/R and its mechanism in a rat model.

MATERIALS AND METHODS

Forty eight adult male Sprague-Dawley (SD) rats were divided into six groups randomly: (1-2) treated with normal saline (NS) without ischemia or reperfusion; (3-4) treated with NS + 30 min ischemia; (5-6) treated with IVIG + 30 min ischemia. Rats of group 1/3/5 were euthanized at 12 h after operation (sham + NS + 12 h, I/R + NS + 12 h, I/R + IVIG + 12 h group) while group 2/4/6 were euthanized at 24 h (sham + NS + 24 h, I/R + NS + 24 h, I/R + IVIG + 24 h group). Interleukin 10 (IL-10), interleukin 6 (IL-6), tumor necrosis factor-alpha (TNF-alpha) were quantified as well as serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT). Hepatic pathological changes were observed while nuclear factor kappa B p65 (NF-κB p65), Inhibitory Subunit of NF Kappa B Alpha (IKB-alpha) and cleaved caspase-3 were detected.

CONCLUSION

ALT, AST, IL-6, TNF-alpha, NF-κB p65 and cleaved caspase-3 were increased by I/R whereas IL-10 and IKB-alpha were decreased. However, IVIG pretreatment reduced ALT, AST, IL-6, TNF-alpha, NF-κB p65 and cleaved caspase-3, but increased IL-10 and IKB-alpha. IVIG treatment attenuates the infiltration of inflammatory cell and cell apoptosis which were observed in I/R groups. IVIG may alleviate hepatic I/R in rats by inhibiting the classical NF-κB signaling pathway, reducing IL-6, TNF-alpha, promoting IL-10, and inhibiting cell apoptosis.

Enzyme Therapeutic for Ischemia and Reperfusion Injury in Organ Transplantation

Ischemia-reperfusion injury (IRI) remains as a critical challenge for organ transplantation. Herein, an enzyme therapeutic based on superoxide dismutase and catalase for effective mitigation of IRI and pathogen-induced liver injury is reported, providing a therapeutic for organ transplantation and other diseases.

The role and function of CD4+ T cells in hepatic ischemia-reperfusion injury

INTRODUCTION

Hepatic ischemia-reperfusion injury (IRI) is a severe complication frequently encountered in liver surgery, seriously affecting the therapeutic effects, tissue function. Various immune cells are involved in hepatic IRI, including macrophages, NKT cells, DCs, CD4 + T cells, and CD8 + T cells, among which CD4 + T cells play a critical role in this process. This article aims to summarize the functions and changes in various CD4 + T cell type counts and related cytokine levels in hepatic IRI and to review the possible mechanisms of mutual conversion between T cell types.

AREAS COVERED

We have covered the functions and changes that occur in Th1, Th17, and Treg cells in liver IRI, as well as the pathways and factors associated with them. We also discuss the prospects of clinical application and future directions for therapeutic advances.

EXPERT OPINION

This section explores the current clinical trials involving CD4 + T cells, especially Tregs, explains the limitations of their application, and summarizes the future development trends of cell engineering and their combination with the CAT technology. We also provide new ideas and therapeutic targets for alleviating liver IRI or other liver inflammatory diseases.

Combination of Early Allograft Dysfunction and Protein Expression Patterns Predicts Outcome of Liver Transplantation From Donation After Cardiac Death

Early allograft dysfunction (EAD) after liver transplantation (LT) accompanies poor prognosis. This study aims to explore the relationship between pretransplant intrahepatic proteins and the incidence of EAD, and the value of combined EAD and protein profiles for predicting recipient and graft survival prognosis. Liver biopsy specimens of 105 pretransplant grafts used for LT were collected and used for immunohistochemistry analysis of 5 proteins. And matched clinical data of donor, recipient, transplantation, and prognosis were analyzed. The incidence of EAD was 41.9% (44/105) in this cohort. Macrovesicular steatosis (P = 0.016), donor body mass index (P = 0.013), recipients' pretransplant serum creatinine (P = 0.036), and intrahepatic expression of heme oxygenase 1 (HO1) (P = 0.015) and tumor necrosis factor α (TNF-α) (P = 0.039) were independent predictors of EAD. Inferior graft and recipient prognosis were observed in patients who experienced EAD (P = 0.028 and 0.031) or received grafts with higher expression of sirtuin 1 (P = 0.005 and 0.013). The graft and recipient survival were worst in patients with both EAD and high expression of sirtuin 1 (P = 0.001 and 0.004). In conclusion, pretransplant intrahepatic expression of HO1 and TNF-α are associated with the incidence of EAD. The combination of EAD and EAD-unrelated proteins showed superiority in distinguishing recipients with worse prognosis.

Modulation of Prostanoids Profile and Counter-Regulation of SDF-1α/CXCR4 and VIP/VPAC2 Expression by Sitagliptin in Non-Diabetic Rat Model of Hepatic Ischemia-Reperfusion Injury

Molecular mechanisms underlying the beneficial effect of sitagliptin repurposed for hepatic ischemia-reperfusion injury (IRI) are poorly understood. We aimed to evaluate the impact of IRI and sitagliptin on the hepatic profile of eicosanoids (LC-MS/MS) and expression/concentration (RTqPCR/ELISA) of GLP-1/GLP-1R, SDF-1α/CXCR4 and VIP/VPAC1, VPAC2, and PAC1 in 36 rats. Animals were divided into four groups and subjected to ischemia (60 min) and reperfusion (24 h) with or without pretreatment with sitagliptin (5 mg/kg) (IR and SIR) or sham-operated with or without sitagliptin pretreatment (controls and sitagliptin). PGI₂, PGE₂, and 13,14-dihydro-PGE₁ were significantly upregulated in IR but not SIR, while sitagliptin upregulated PGD₂ and 15-deoxy-12,14-PGJ₂. IR and sitagliptin non-significantly upregulated GLP-1 while Glp1r expression was borderline detectable. VIP concentration and Vpac2 expression were downregulated in IR but not SIR, while Vpac1 was significantly downregulated solely in SIR. IRI upregulated both CXCR4 expression and concentration, and sitagliptin pretreatment abrogated receptor overexpression and downregulated Sdf1. In conclusion, hepatic IRI is accompanied by an elevation in proinflammatory prostanoids and overexpression of CXCR4, combined with downregulation of VIP/VPAC2. Beneficial effects of sitagliptin during hepatic IRI might be mediated by drug-induced normalization of proinflammatory prostanoids and upregulation of PGD₂ and by concomitant downregulation of SDF-1α/CXCR4 and reinstating VIP/VCAP2 signaling.

Interleukin-27 in liver xenotransplantation: A rational target to mitigate ischemia reperfusion injury and increase xenograft survival

Transplantation of xenogeneic organs is an attractive solution to the existing organ shortage dilemma, thus, securing a clinically acceptable prolongation of xenograft survival is an important goal. In preclinical transplantation models, recipients of liver, kidney, heart, or lung xenotransplants demonstrate significant graft damages through the release of pro-inflammatory molecules, including the C-reactive protein, cytokines, and histone-DNA complexes that all foster graft rejection. Recent studies have demonstrated that mitigation of ischemia reperfusion injury (IRI) greatly improves xenograft survival. Organ IRI develops primarily on a complex network of cytokines and chemokines responding to molecular cues from the graft milieu. Among these, interleukin 27 (IL-27) plays an immunomodulatory role in IRI onset due to graft environment-dependent pro- and anti- inflammatory activities. This review focuses on the impact of IL-27 on IRI of liver xenotransplants and provides insights on the function of IL-27 that could potentially guide genetic engineering strategies of donor pigs and/or conditioning of organs prior to transplantation.

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.

Veratric acid alleviates liver ischemia/reperfusion injury by activating the Nrf2 signaling pathway

Oxidative stress following liver ischemia/reperfusion (I/R) is an important pathological mechanism responsible for liver injury. Veratric acid (VA) is a phenolic benzoic acid that has been reported to have antioxidant properties. However, whether VA has protective effects against liver I/R injury remains unclear. In the present study, a mouse liver I/R injury model was established. VA was administered intragastrically for one week before liver I/R. Biochemical indicators, histological analysis, cell apoptosis, oxidative stress, and pathway proteins were tested to evaluate the protective effects of VA on liver I/R injury. Furthermore, a mouse AML12 hepatocyte hypoxia/reoxygenation (H/R) model was used to explore the underlying mechanism. VA alleviated liver I/R injury, as manifested by decreased alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels, liver necrotic area, oxidative stress, and hepatocyte apoptosis. VA pretreatment increased the expression of Nrf2 and its downstream antioxidant proteins heme oxygenase-1 (HO-1) and NADPH quinone oxidoreductase 1 (NQO-1). In addition, VA pretreatment increased AML12 cell activity and decreased oxidative stress; it also decreased the apoptosis induced by H/R. Moreover, the protective effect of VA on hepatocytes was related to the activation of the Nrf2 signaling pathway, and to increases in the Nrf2, HO-1, and NQO-1 protein expression. The inhibition of Nrf2 with ML385 offseted VA-mediated protection in AML12 cells. In conclusion, these results suggest that VA protects the liver from oxidative stress and apoptosis induced by liver I/R injury by activating the Nrf2 signaling pathway.

Tender Coconut Water Protects Mice From Ischemia-Reperfusion-Mediated Liver Injury and Secondary Lung Injury

ABSTRACT

Organ injury by oxidative and inflammatory mediators occurs during ischemia-reperfusion (I/R) of the liver. Remote organ injury secondary to liver I/R increases the systemic insult. Tender coconut water (TCW) has been studied in chemical and fructose-induced liver injury but its ability to decrease tissue injury in clinically relevant injury models is unknown. We evaluated the therapeutic potential of TCW in preventing liver I/R injury and associated remote organ injury. Mice were fed sugar water (SUG; control) or TCW for a week and then subjected to 60 min of liver ischemia followed by reperfusion for 6 h. Plasma alanine transaminase levels, tissue damage, and mRNA levels of Nos2, Tnf, and Il6 were significantly lower in mice fed TCW prior to I/R. Plasma cytokines followed liver cytokine patterns. TCW increased mRNA levels of the anti-oxidant genes Hmox1 and Ptgs2 in the liver of mice subjected to I/R. Remote lung injury from liver I/R was also decreased by TCW feeding as evident by less neutrophil infiltration, decreased pro-inflammatory Il6, and increased anti-inflammatory Il10 mRNA levels in the lung. To examine macrophage activation as a potential mechanism, TCW pretreatment decreased the amount of nitrite produced by RAW264.7 macrophages stimulated with LPS. The levels of Nos2, Il1b, Tnf, and Il6 were decreased while Il10 and Hmox1 mRNA levels were significantly up-regulated upon LPS stimulation of TCW pretreated RAW264.7 macrophages. Collectively, our results indicate that TCW decreased hepatic I/R-mediated damage to liver and lung and suggest that decreased macrophage activation contributes to this effect.

Mitochondrial Dysfunction and Oxidative Stress in Liver Transplantation and Underlying Diseases: New Insights and Therapeutics

Mitochondria are essential organelles for cellular energy and metabolism. Like with any organ, the liver highly depends on the function of these cellular powerhouses. Hepatotoxic insults often lead to an impairment of mitochondrial activity and an increase in oxidative stress, thereby compromising the metabolic and synthetic functions. Mitochondria play a critical role in ATP synthesis and the production or scavenging of free radicals. Mitochondria orchestrate many cellular signaling pathways involved in the regulation of cell death, metabolism, cell division, and progenitor cell differentiation. Mitochondrial dysfunction and oxidative stress are closely associated with ischemia-reperfusion injury during organ transplantation and with different liver diseases, including cholestasis, steatosis, viral hepatitis, and drug-induced liver injury. To develop novel mitochondria-targeting therapies or interventions, a better understanding of mitochondrial dysfunction and oxidative stress in hepatic pathogenesis is very much needed. Therapies targeting mitochondria impairment and oxidative imbalance in liver diseases have been extensively studied in preclinical and clinical research. In this review, we provide an overview of how oxidative stress and mitochondrial dysfunction affect liver diseases and liver transplantation. Furthermore, we summarize recent developments of antioxidant and mitochondria-targeted interventions.

Non-invasive quantification of the mitochondrial redox state in livers during machine perfusion

Ischemia reperfusion injury (IRI) is a critical problem in liver transplantation that can lead to life-threatening complications and substantially limit the utilization of livers for transplantation. However, because there are no early diagnostics available, fulminant injury may only become evident post-transplant. Mitochondria play a central role in IRI and are an ideal diagnostic target. During ischemia, changes in the mitochondrial redox state form the first link in the chain of events that lead to IRI. In this study we used resonance Raman spectroscopy to provide a rapid, non-invasive, and label-free diagnostic for quantification of the hepatic mitochondrial redox status. We show this diagnostic can be used to significantly distinguish transplantable versus non-transplantable ischemically injured rat livers during oxygenated machine perfusion and demonstrate spatial differences in the response of mitochondrial redox to ischemia reperfusion. This novel diagnostic may be used in the future to predict the viability of human livers for transplantation and as a tool to better understand the mechanisms of hepatic IRI.

T-Cell Immunoglobulin and Mucin Domain-Containing Protein-4 Is Critical for Kupffer Cell Homeostatic Function in the Activation and Resolution of Liver Ischemia Reperfusion Injury

BACKGROUND AND AIMS

Liver ischemia reperfusion injury (IRI) remains an unresolved clinical problem. This study dissected roles of liver-resident macrophage Kupffer cells (KCs), with a functional focus on efferocytosis receptor T-cell immunoglobulin and mucin domain-containing protein-4 (TIM-4), in both the activation and resolution of IRI in a murine liver partial warm ischemia model.

APPROACH AND RESULTS

Fluorescence-activated cell sorting results showed that TIM-4 was expressed exclusively by KCs, but not infiltrating macrophages (iMФs), in IR livers. Anti-TIM-4 antibody depleted TIM-4⁺ macrophages in vivo, resulting in either alleviation or deterioration of liver IRI, which was determined by the repopulation kinetics of the KC niche with CD11b⁺ macrophages. To determine the KC-specific function of TIM-4, we reconstituted clodronate-liposome-treated mice with exogenous wild-type or TIM-4-deficient KCs at either 0 hour or 24 hours postreperfusion. TIM-4 deficiency in KCs resulted in not only increases in the severity of liver IRI (at 6 hours postreperfusion), but also impairment of the inflammation resolution (at 7 days postreperfusion). In vitro analysis revealed that TIM-4 promoted KC efferocytosis to regulate their Toll-like receptor response by up-regulating IL-10 and down-regulating TNF-α productions.

CONCLUSIONS

TIM-4 is critical for KC homeostatic function in both the activation and resolution of liver IRI by efferocytosis.