CXC chemokines play a critical role in liver injury, recovery, and regeneration

New therapeutic concepts against ischemia-reperfusion injury in organ transplantation

INTRODUCTION

Ischemia-reperfusion injury (IRI) involves a positive amplification feedback loop that stimulates innate immune-driven tissue damage associated with organ procurement from deceased donors and during transplantation surgery. As our appreciation of its basic immune mechanisms has improved in recent years, translating putative biomarkers into therapeutic interventions in clinical transplantation remains challenging.

AREAS COVERED

This review presents advances in translational/clinical studies targeting immune responses to reactive oxygen species in IRI-stressed solid organ transplants, especially livers. Here we focus on novel concepts to rejuvenate suboptimal donor organs and improve transplant function using pharmacologic and machine perfusion (MP) strategies. Cellular damage induced by cold ischemia/warm reperfusion and the latest mechanistic insights into the microenvironment's role that leads to reperfusion-induced sterile inflammation is critically discussed.

EXPERT OPINION

Efforts to improve clinical outcomes and increase the donor organ pool will depend on improving donor management and our better appreciation of the complex mechanisms encompassing organ IRI that govern the innate-adaptive immune interface triggered in the peritransplant period and subsequent allo-Ag challenge. Computational techniques and deep machine learning incorporating the vast cellular and molecular mechanisms will predict which peri-transplant signals and immune interactions are essential for improving access to the long-term function of life-saving transplants.

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.

Human Dermcidin Protects Mice Against Hepatic Ischemia-Reperfusion-Induced Local and Remote Inflammatory Injury

Background

Hepatic ischemia and reperfusion (I/R) injury is commonly associated with surgical liver resection or transplantation, and represents a major cause of liver damage and graft failure. Currently, there are no effective therapies to prevent hepatic I/R injury other than ischemic preconditioning and some preventative strategies. Previously, we have revealed the anti-inflammatory activity of a sweat gland-derived peptide, dermcidin (DCD), in macrophage/monocyte cultures. Here, we sought to explore its therapeutic potential and protective mechanisms in a murine model of hepatic I/R.

Methods

Male C57BL/6 mice were subjected to hepatic ischemia by clamping the hepatic artery and portal vein for 60 min, which was then removed to initiate reperfusion. At the beginning of reperfusion, 0.2 ml saline control or solution of DCD (0.5 mg/kg BW) or DCD-C34S analog (0.25 or 0.5 mg/kg BW) containing a Cys (C)→Ser (S) substitution at residue 34 was injected via the internal jugular vein. For survival experiments, mice were subjected to additional resection to remove non-ischemic liver lobes, and animal survival was monitored for 10 days. For mechanistic studies, blood and tissue samples were collected at 24 h after the onset of reperfusion, and subjected to measurements of various markers of inflammation and tissue injury by real-time RT-PCR, immunoassays, and histological analysis.

Results

Recombinant DCD or DCD-C34S analog conferred a significant protection against lethal hepatic I/R when given intravenously at the beginning of reperfusion. This protection was associated with a significant reduction in hepatic injury, neutrophilic CXC chemokine (Mip-2) expression, neutrophil infiltration, and associated inflammation. Furthermore, the administration of DCD also resulted in a significant attenuation of remote lung inflammatory injury. Mechanistically, DCD interacted with epidermal growth factor receptor (EGFR), a key regulator of liver inflammation, and significantly inhibited hepatic I/R-induced phosphorylation of EGFR as well as a downstream signaling molecule, protein kinase B (AKT). The suppression of EGFR expression by transducing Egfr-specific shRNA plasmid into macrophages abrogated the DCD-mediated inhibition of nitric oxide (NO) production induced by a damage-associated molecular pattern (DAMP), cold-inducible RNA-binding protein, CIRP.

Conclusions

The present study suggests that human DCD and its analog may be developed as novel therapeutics to attenuate hepatic I/R-induced inflammatory injury possibly by impairing EGFR signaling.

Application of mesenchymal stem cell exosomes and their drug-loading systems in acute liver failure

Stem cell exosomes are nanoscale membrane vesicles released from stem cells of various origins that can regulate signal transduction pathways between liver cells, and their functions in intercellular communication have been recognized. Due to their natural substance transport properties and excellent biocompatibility, exosomes can also be used as drug carriers to release a variety of substances, which has great prospects in the treatment of critical and incurable diseases. Different types of stem cell exosomes have been used to study liver diseases. Due to current difficulties in the treatment of acute liver failure (ALF), this review will outline the potential of stem cell exosomes for ALF treatment. Specifically, we reviewed the pathogenesis of acute liver failure and the latest progress in the use of stem cell exosomes in the treatment of ALF, including the role of exosomes in inhibiting the ALF inflammatory response and regulating signal transduction pathways, the advantages of stem cell exosomes and their use as a drug‐loading system, and their pre‐clinical application in the treatment of ALF. Finally, the clinical research status of stem cell therapy for ALF and the current challenges of exosome clinical transformation are summarized.

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.

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.

Intravital Microscopic Evaluation of the Effects of a CXCR2 Antagonist in a Model of Liver Ischemia Reperfusion Injury in Mice

Background

Ischemia-reperfusion (IR) is a major contributor to graft rejection after liver transplantation. During IR injury, an intense inflammatory process occurs in the liver. Neutrophils are considered central players in the events that lead to liver injury. CXC chemokines mediate hepatic inflammation following reperfusion. However, few studies have demonstrated in real-time the behavior of recruited neutrophils. We used confocal intravital microscopy (IVM) to image neutrophil migration in the liver and to analyze in real-time parameters of neutrophil recruitment in the inflamed tissue in animals treated or not with reparixin, an allosteric antagonist of CXCR1/2 receptors.

Materials and methods

WT and LysM-eGFP mice treated with reparixin or saline were subjected to 60 min of ischemia followed by different times of reperfusion. Mice received Sytox orange intravenously to show necrotic DNA in IVM. The effect of reparixin on parameters of local and systemic reperfusion-induced injury was also investigated.

Results

IR induced liver injury and inflammation, as evidenced by high levels of alanine aminotransferase and myeloperoxidase activity, chemokine and cytokine production, and histological outcome. Treatment with reparixin significantly decreased neutrophil influx. Moreover, reparixin effectively suppressed the increase in serum concentrations of TNF-α, IL-6, and CCL3, and the reperfusion-associated tissue damage. The number of neutrophils in the liver increased between 6 and 24 h of reperfusion, whereas the distance traveled, velocity, neutrophil size and shape, and cluster formation reached a maximum 6 h after reperfusion and then decreased gradually. In vivo imaging revealed that reparixin significantly decreased neutrophil infiltration and movement and displacement of recruited cells. Moreover, neutrophils had a smaller size and less elongated shape in treated mice.

Conclusion

Imaging of the liver by confocal IVM was successfully implemented to describe neutrophil behavior in vivo during liver injury by IR. Treatment with reparixin decreased not only the recruitment of neutrophils in tissues but also their activation state and capacity to migrate within the liver. CXCR1/2 antagonists may be a promising therapy for patients undergoing liver transplantation.

Cholecystokinin protects mouse liver against ischemia and reperfusion injury

BACKGROUND

Cholecystokinin (CCK), as a gastrointestinal hormone, has an important protective role against sepsis or LPS-induced endotoxic shock. We aim to address the role of CCK in hepatic ischemia followed by reperfusion (I/R) injury.

MATERIALS AND METHODS

A murine model of 60min partial hepatic ischemia followed by 6h of reperfusion was used in this study. CCK and CCKAR Levels in blood and liver were detected at 3h, 6h, 12h and 24h after reperfusion. Then the mice were treated with CCK or proglumide, a nonspecific CCK-receptor (CCK-R) antagonist. Mice were randomly divided into four groups as follows: (1) sham group, in which mice underwent sham operation and received saline; (2) I/R group, in which mice were subjected to hepatic I/R and received saline; (3) CCK group, in which mice were subjected to hepatic I/R and treated with CCK (400μg/kg); (4) proglumide group (Pro), in which mice underwent hepatic I/R and treated with proglumide (3mg/kg); CCK and proglumide were administrated via tail vein at the moment of reperfusion. Serum AST (sAST) and serum ALT (sALT) were determined with a biochemical assay and histological analysis were performed with hematoxylin-eosin (H&E). Cytokines (IL-1β, IL-6, IL-10, TNF-α) expressions in blood were determined with enzyme-linked immunosorbent assay (ELISA). The MPO (myeloperoxidase) assay were used to measure neutrophils' infiltration into the liver. The apoptotic index (TUNEL-positive cell number/total liver cell number×100%) was calculated to assess hepatocelluar apoptosis. Finally, activation of NF-κB and phosphor-p38 expression in liver homogenates were analyzed with Western Blot (WB).

RESULTS

Our findings showed that 1) CCK and CCK-AR were upregulated in our experimental model over time; 2) Treatment with CCK decreased sAST/sALT levels, inflammatory hepatic injury, neutrophil influx and hepatocelluar apoptosis, while proglumide aggravated hepatic injury.

CONCLUSION

These findings support our hypothesis and suggest that CCK played a positive role in the ongoing inflammatory process leading to liver I/R injury.

Role of CXC group chemokines in lung cancer development and progression

BACKGROUND

Clinical and translational research on lung cancer patients undergoing surgical treatment can provide valuable scientific data and unique opportunity to study tumor microenvironment. CXC chemokines, which are members of a big family of cytokines, are undoubtedly involved in tumor growth regulation and metastasizing pathways. For better understanding of CXC chemokine involvement in the process of carcinogenesis we have studied the cohort of early stage non-small cell lung cancer patients undergoing surgery with curative intent. Our aim was to assess CXC chemokine ligand (CXCL) levels in patient blood samples representing systemic circulation and tumor microenvironment; assess CXC chemokine receptor (CXCR) expression in tumor tissue; and measure tumor infiltrating immune cell subpopulations.

METHODS

A total of 54 patients with NSCLC had radical lung resection were enrolled in a single center prospective study and were followed-up annually for up to six years. During surgical procedure peripheral and tumor draining blood samples were taken. CXCL1, CXCL4, CXCL5, CXCL6, CXCL7, CXCL8, CXCL9, CXCL10, CXCL11 and CXCL12 levels were determined by ELISA, and chemokine concentration gradient was calculated. Tumor infiltrating immune cells (T helper cells, T cytotoxic cells, macrophages, B cells, plasma cells) and expression of CXCR1, CXCR2, CXCR3 and CXCR4 in tumor tissue were assessed by immunohistochemistry.

RESULTS

Statistically significant decrease in chemokine concentration was found for CXCL4 (P=0.002) and CXCL5 (P=0.011), and statistically significant concentration increase was found for CXCL7 (P=0.001) in total cohort. We have found statistically significant CXC chemokine concentration change for majority of chemokines-CXCL1 (P=0.002), CXCL4 (P=0.001), CXCL5 (P=0.013), CXCL7 (P=0.036), CXCL8 (P=0.026), CXCL9 (P=0.034) and CXCL10 (P=0.032) in a group of patients who had good clinical result after surgery with no evidence of relapse, on the other hand patients with cancer recurrence including local and systemic cancer spread did not show any change of chemokine concentration in blood except for CXCL1 (P=0.041). We have also found that chemokine levels and gradients correlate with CXC receptor expression and number of tumor infiltrating immune cell subpopulations.

CONCLUSIONS

Assessment of tumor microcirculation is useful for evaluation of different types of circulating biomarkers and application of our method can be very wide, integrating thoracic surgeons into translational cancer research.

Chemokine Receptors, CXCR1 and CXCR2, Differentially Regulate Exosome Release in Hepatocytes

Exosomes are small membrane vesicles released by different cell types, including hepatocytes, that play important roles in intercellular communication. We have previously demonstrated that hepatocyte-derived exosomes contain the synthetic machinery to form sphingosine-1-phosphate (S1P) in target hepatocytes resulting in proliferation and liver regeneration after ischemia/reperfusion (I/R) injury. We also demonstrated that the chemokine receptors, CXCR1 and CXCR2, regulate liver recovery and regeneration after I/R injury. In the current study, we sought to determine if the regulatory effects of CXCR1 and CXCR2 on liver recovery and regeneration might occur via altered release of hepatocyte exosomes. We found that hepatocyte release of exosomes was dependent upon CXCR1 and CXCR2. CXCR1-deficient hepatocytes produced fewer exosomes, whereas CXCR2-deficient hepatocytes produced more exosomes compared to their wild-type controls. In CXCR2-deficient hepatocytes, there was increased activity of neutral sphingomyelinase (Nsm) and intracellular ceramide. CXCR1-deficient hepatocytes had no alterations in Nsm activity or ceramide production. Interestingly, exosomes from CXCR1-deficient hepatocytes had no effect on hepatocyte proliferation, due to a lack of neutral ceramidase and sphingosine kinase. The data demonstrate that CXCR1 and CXCR2 regulate hepatocyte exosome release. The mechanism utilized by CXCR1 remains elusive, but CXCR2 appears to modulate Nsm activity and resultant production of ceramide to control exosome release. CXCR1 is required for packaging of enzymes into exosomes that mediate their hepatocyte proliferative effect.

Model-Based Characterization of Inflammatory Gene Expression Patterns of Activated Macrophages

Macrophages are cells with remarkable plasticity. They integrate signals from their microenvironment leading to context-dependent polarization into classically (M1) or alternatively (M2) activated macrophages, representing two extremes of a broad spectrum of divergent phenotypes. Thereby, macrophages deliver protective and pro-regenerative signals towards injured tissue but, depending on the eliciting damage, may also be responsible for the generation and aggravation of tissue injury. Although incompletely understood, there is emerging evidence that macrophage polarization is critical for these antagonistic roles. To identify activation-specific expression patterns of chemokines and cytokines that may confer these distinct effects a systems biology approach was applied. A comprehensive literature-based Boolean model was developed to describe the M1 (LPS-activated) and M2 (IL-4/13-activated) polarization types. The model was validated using high-throughput transcript expression data from murine bone marrow derived macrophages. By dynamic modeling of gene expression, the chronology of pathway activation and autocrine signaling was estimated. Our results provide a deepened understanding of the physiological balance leading to M1/M2 activation, indicating the relevance of co-regulatory signals at the level of Akt1 or Akt2 that may be important for directing macrophage polarization.

Macrophages are essential cells of the immune system and indispensable for a defense against bacterial infection. They reside as resting, immune modulatory cells in several tissues of the human body where they continuously sense inputs from their local environment. They react to stimuli such as toxins, injury or bacterial products in a process termed macrophage activation or polarization. For example, the bacterial component lipopolysaccharide induces so-called classical activation of macrophages into the M1 phenotype that secretes a number of inflammatory cytokines and chemokines leading to killing of bacteria and resolution of inflammation. Another prominent phenotype of macrophages is the M2 polarization state that is associated with wound healing and tissue regeneration. Unbalanced activation of macrophages is implicated in a number of diseases. An improved knowledge and extensive characterization of these macrophages as well as the factors determining their phenotypes will improve the understanding of the role of macrophages in disease progression.

CXCL6 promotes human hepatocyte proliferation through the CXCR1-NFκB pathway and inhibits collagen I secretion by hepatic stellate cells

Hepatocyte proliferation and collagen I (COLI) secretion are important processes during liver regeneration. This study aimed to investigate the role of CXCL6 in hepatocyte proliferation and COLI secretion. Serum CXCL6 levels in patients with chronic hepatitis B (CHB) were examined and the effects of CXCL6 on the proliferation of L02 hepatocytes and the secretion of COLI from LX2 human hepatic stellate cells were evaluated. We found that serum CXCL6 levels increased gradually with disease progression of CHB, and there was positive correlation between serum CXCL6 level and alanine transaminase (ALT) and aspartate transaminase (AST). In vitro, CXCL6 promoted L02 proliferation but this was blocked upon CXCR1 knockdown. The level of phospho-IκBα was upregulated by CXCL6 but downregulated by CXCR1 siRNA in L02 cells. CXCL6 inhibited the secretion of COLI by LX2 cells, dependent on CXCR1 and CXCR2. Taken together, these data suggest that increased expression of CXCL6 during CHB could promote hepatocyte proliferation through the CXCR1-NFκB pathway and inhibit the secretion of COLI by hepatic stellate cells.

Ischemia reperfusion-facilitated sinusoidal endothelial cell injury in liver transplantation and the resulting impact of extravasated platelet aggregation

Background

The exact sequence of events leading to ultimate hepatocellular damage following ischemia/reperfusion (I/R) is incompletely understood. In this article, we review a mechanism of organ dysfunction after hepatic I/R or immunosuppressive treatment, in addition to the potential of liver sinusoidal endothelial cell (LSEC) protection and antiplatelet treatment for the suppression of hepatocellular damage.

Methods

A review of the literature, utilizing PubMed-NCBI, was used to provide information on the components necessary for the development of hepatocellular damage following I/R.

Results

It is well-established that LSECs damage following hepatic I/R or immunosuppressive treatment followed by extravasated platelet aggregation (EPA) is the root cause of organ dysfunction in liver transplantation. We have classified three phases, from LSECs damage to organ dysfunction, utilizing the predicted pathogenic mechanism of sinusoidal obstruction syndrome. The first phase is detachment of LSECs and sinusoidal wall destruction after LSECs injury by hepatic I/R or immunosuppressive treatment. The second phase is EPA, accomplished by sinusoidal wall destruction. The various growth factors, including thromboxane A2, serotonin, transforming growth factor-beta and plasminogen activator inhibitor-1, released by EPA in the Disse’s space of zone three, induce portal hypertension and the progression of hepatic fibrosis. The third phase is organ dysfunction following portal hypertension, hepatic fibrosis, and suppressed liver regeneration through various growth factors secreted by EPA.

Conclusion

We suggest that EPA in the space of Disse, initiated by LSECs damage due to hepatic I/R or immunosuppressive treatment, and activated platelets may primarily contribute to liver damage in liver transplantation. Endothelial protective therapy or antiplatelet treatment may be useful in the treatment of hepatic I/R following EPA.

Chemokine-mediated robust augmentation of liver engraftment: a novel approach

Effective repopulation of the liver is essential for successful clinical hepatocyte transplantation. The objective was to improve repopulation of the liver with human hepatocytes using chemokines. We used flow cytometry and immunohistochemistry assays to identify commonly expressed chemokine receptors on human fetal and adult hepatocytes. The migratory capacity of the cells to various chemokines was tested. For in vivo studies, we used a nude mouse model of partial hepatectomy followed by intraparenchymal injections of chemokine ligands at various concentrations. Human fetal liver cells transformed with human telomerase reverse transcriptase were used for intrasplenic cell transplantation. Repopulation and functionality were assessed 4 weeks after transplantation. The receptor CXCR3 was commonly expressed on both fetal and adult hepatocytes. Both cell types migrated efficiently toward corresponding CXC chemokine ligands 9, 10, and 11. In vivo, animals injected with recombinant chemokines showed the highest cell engraftment compared with controls (p<.05). The engrafted cells expressed several human hepatic markers such as cytokeratin 8 and 18 and albumin as well as transferrin, UGT1A1, hepatocyte nuclear factor (1α, 1β, and 4α), cytochrome CYP3A1, CCAAT/enhancer binding protein (α and β), and human albumin compared with controls. No inflammatory cells were detected in the livers at 4 weeks after transplantation. The improved repopulation of transplanted cells is likely a function of the chemokines to mediate cell homing and retention in the injured liver and might be an attractive strategy to augment repopulation of transplanted hepatocytes in vivo.

Differential gene expression profile of porcine livers subjected to warm ischemia alone

BACKGROUND

Livers exposed to warm ischemia (WI) are increasingly used for transplantation. The molecular mechanisms activated by WI alone (prior to procurement and transplantation) are not understood. To elucidate the pathways involved, we used microarrays to investigate the gene expression in porcine livers exposed to WI.

METHODS

Porcine livers (n = 6 group) were randomly subjected to WI periods of 15, 30 or 45 minutes. mRNA was extracted and gene expression determined by microarray analysis. Using bioinformatics software, we identified differentially expressed genes and related molecular pathways. We used the corresponding human annotation of the porcine microarray for the functional analysis.

RESULTS

Between 0 and 15 minutes of WI, 3530 genes were altered with a 2-log-fold change of <-0.58 or >+0.58 and P < .05. Between 0 and 30 minutes of WI, 4141 genes were differentially expressed; and between 0 and 45 minutes of WI, 2814 genes. At each time point, ∼50% of genes were up-regulated, whereas 50% were down-regulated. After pathway mapping, we found that the same pathways were induced for observed clustering of in the three WI periods: cell death, proliferation, inflammation, and metabolism pathways. Among the top genes that were up-regulated after 15 minutes of WI, the majority started to return to but did not reach baseline expression with increasing WI. A similar pattern was observed for the top suppressed genes.

CONCLUSIONS

WI causes rapid changes in gene expression that affect several molecular pathways. This phenomenon seems to plateau at 15 to 30 minutes of WI. These new insights in the timing and the nature of molecular pathways induced by WI alone may help to design specific interventions to alter these changes and improve the outcome of livers from cardiac death donors.

Mesenchymal stem cell-derived exosomes promote hepatic regeneration in drug-induced liver injury models

Introduction

Mesenchymal stem cell-conditioned medium (MSC-CM) has been shown to have protective effects against various cellular-injury models. This mechanism of protection, however, has yet to be elucidated. Recently, exosomes were identified as the active component in MSC-CM. The aim of this study is to investigate the effect of MSC-derived exosomes in an established carbon tetrachloride (CCl₄)-induced liver injury mouse model. This potential effect is then validated by using in vitro xenobiotic-induced liver-injury assays: (1) acetaminophen (APAP)- and (2) hydrogen peroxide (H₂O₂)-induced liver injury.

Methods

The exosomes were introduced concurrent with CCl₄ into a mouse model through different routes of administration. Biochemical analysis was performed based on the blood and liver tissues. Subsequently the exosomes were treated in APAP and H₂O₂-toxicants with in vitro models. Cell viability was measured, and biomarkers indicative of regenerative and oxidative biochemical responses were determined to probe the mechanism of any hepatoprotective activity observed.

Results

In contrast to mice treated with phosphate-buffered saline, CCl₄ injury in mice was attenuated by concurrent-treatment exosomes, and characterized by an increase in hepatocyte proliferation, as demonstrated with proliferating cell nuclear antigen (PCNA) elevation. Significantly higher cell viability was demonstrated in the exosomes-treated group compared with the non-exosome-treated group in both injury models. The higher survival rate was associated with upregulation of the priming-phase genes during liver regeneration, which subsequently led to higher expression of proliferation proteins (PCNA and cyclin D1) in the exosomes-treated group. Exosomes also inhibited the APAP- and H₂O₂-induced hepatocytes apoptosis through upregulation of Bcl-_xL protein expression. However, exosomes do not mitigate hepatocyte injury via modulation of oxidative stress.

Conclusions

In summary, these results suggest that MSC-derived exosomes can elicit hepatoprotective effects against toxicants-induced injury, mainly through activation of proliferative and regenerative responses.

Chemokines in chronic liver allograft dysfunction pathogenesis and potential therapeutic targets

Despite advances in immunosuppressive drugs, long-term success of liver transplantation is still limited by the development of chronic liver allograft dysfunction. Although the exact pathogenesis of chronic liver allograft dysfunction remains to be established, there is strong evidence that chemokines are involved in organ damage induced by inflammatory and immune responses after liver surgery. Chemokines are a group of low-molecular-weight molecules whose function includes angiogenesis, haematopoiesis, mitogenesis, organ fibrogenesis, tumour growth and metastasis, and participating in the development of the immune system and in inflammatory and immune responses. The purpose of this review is to collect all the research that has been done so far concerning chemokines and the pathogenesis of chronic liver allograft dysfunction and helpfully, to pave the way for designing therapeutic strategies and pharmaceutical agents to ameliorate chronic allograft dysfunction after liver transplantation.

Roles of hepatocyte and myeloid CXC chemokine receptor-2 in liver recovery and regeneration after ischemia/reperfusion in mice

Previous studies have demonstrated the significance of signaling through the CXC chemokine receptor-2 (CXCR2) receptor in the process of recovery and regeneration of functional liver mass after hepatic ischemia/reperfusion (I/R). CXCR2 is constitutively expressed on both neutrophils and hepatocytes; however, the cell-specific roles of this receptor are unknown. In the present study, chimeric mice were created through bone marrow transplantation (BMT) using wild-type and CXCR2-knockout mice, yielding selective expression of CXCR2 on hepatocytes (Hep) and/or myeloid cells (My) in the following combinations: Hep+/My+; Hep-/My+; Hep+/My-; and Hep-/My-. These tools allowed us to assess the contributions of myeloid and hepatocyte CXCR2 in the recovery of the liver after I/R injury. Flow cytometry confirmed the adoption of the donor phenotype in neutrophils. Interestingly, Kupffer cells from all chimeras lacked CXCR2 expression. Recovery/regeneration of hepatic parenchyma was assessed by histologic assessment and measurement of hepatocyte proliferation. CXCR2(Hep+/My+) mice showed the least amount of liver recovery and hepatocyte proliferation, whereas CXCR2(Hep-/My-) mice had the greatest liver recovery and hepatocyte proliferation. CXCR2(Hep+/My-) mice had enhanced liver recovery, with hepatocyte proliferation similar to CXCR2(Hep-/My-) mice. Myeloid expression of CXCR2 directly regulated CXC chemokine expression levels after hepatic I/R, such that mice lacking myeloid CXCR2 had markedly increased chemokine expression, compared with mice expressing CXCR2 on myeloid cells.

CONCLUSION

The data suggest that CXCR2 on myeloid cells is the predominant regulator of liver recovery and regeneration after I/R injury, whereas hepatocyte CXCR2 plays a minor, secondary role. These findings suggest that myeloid cell-directed therapy may significantly affect liver regeneration after liver resection or transplantation.

Preservation of hepatic blood flow by direct peritoneal resuscitation improves survival and prevents hepatic inflammation following hemorrhagic shock

Conventional resuscitation (CR) from hemorrhagic shock (HS) results in gut and liver hypoperfusion, organ and cellular edema, and vital organ injury. Adjunct direct peritoneal resuscitation (DPR) with dialysate prevents gut vasoconstriction, hypoperfusion, and injury. We hypothesized that DPR might also improve hepatocellular edema, inflammation, and injury. Anesthetized male SD rats were assigned to groups (n = 8/group): 1) sham (no HS); 2) HS (40% MAP/60 min) + intravenous fluid conventional resuscitation [CR; shed blood + 2 vol saline (SAL)/30 min]; 3) HS+CR+DPR (30 ml ip 2.5% glucose dialysate); or 4) HS+CR+SAL (30 ml ip saline). Histopathology showed lung and liver injury in HS+CR and HS+CR+SAL up to 24-h postresuscitation (post-RES) that was not in shams and which was prevented by adjunct DPR. Wet-to-dry weight ratios in HS+CR revealed organ edema formation that was prevented by adjunct DPR. HS+CR and HS+CR+SAL had 34% mortality by 24-h post-RES, which was absent with DPR (0%). Liver IFN-γ and IL-6 levels were elevated in CR compared with DPR or shams. TNF-α mRNA was upregulated in CR/sham and DPR/sham. IL-17 was downregulated in DPR/sham. CXCL10 mRNA was upregulated in CR/sham but downregulated in DPR/sham. Despite restored central hemodynamic performance after CR of HS, liver blood flow was compromised up to 24 h post-RES, and the addition of DPR restores and maintains liver perfusion at 24-h post-RES. DPR prevented liver injury, histological damage, and edema formation compared with CR alone. DPR provided a mitigating anti-inflammatory dampening of the systemic inflammatory response. In all, these effects likely account for improved survivorship in the DPR-treated group.

Interleukin-33 is hepatoprotective during liver ischemia/reperfusion in mice

Interleukin (IL)-33 is a recently identified member of the IL-1 family that binds to the receptor, ST2L. In the current study, we sought to determine whether IL-33 is an important regulator in the hepatic response to ischemia/reperfusion (I/R). Male C57BL/6 mice were subjected to 90 minutes of partial hepatic ischemia, followed by up to 8 hours of reperfusion. Some mice received recombinant IL-33 (IL-33) intraperitoneally (IP) before surgery or anti-ST2 antibody IP at the time of reperfusion. Primary hepatocytes and Kupffer cells were isolated and treated with IL-33 to assess the effects of IL-33 on inflammatory cytokine production. Primary hepatocytes were treated with IL-33 to assess the effects of IL-33 on mediators of cell survival in hepatocytes. IL-33 protein expression increased within 4 hours after reperfusion and remained elevated for up to 8 hours. ST2L protein expression was detected in healthy liver and was up-regulated within 1 hour and peaked at 4 hours after I/R. ST2L was primarily expressed by hepatocytes, with little to no expression by Kupffer cells. IL-33 significantly reduced hepatocellular injury and liver neutrophil accumulation at 1 and 8 hours after reperfusion. In addition, IL-33 treatment increased liver activation of nuclear factor kappa light-chain enhancer of activated B cells (NF-κB), p38 mitogen-activated protein kinase (MAPK), cyclin D1, and B-cell lymphoma 2 (Bcl-2), but reduced serum levels of CXC chemokines. In vitro experiments demonstrated that IL-33 significantly reduced hepatocyte cell death as a result of increased NF-κB activation and Bcl-2 expression in hepatocytes.

CONCLUSION

The data suggest that IL-33 is an important endogenous regulator of hepatic I/R injury. It appears that IL-33 has direct protective effects on hepatocytes, associated with the activation of NF-κB, p38 MAPK, cyclin D1, and Bcl-2 that limits liver injury and reduces the stimulus for inflammation.

Regulatory mechanisms of injury and repair after hepatic ischemia/reperfusion

Hepatic ischemia/reperfusion injury is an important complication of liver surgery and transplantation. The mechanisms of this injury as well as the subsequent reparative and regenerative processes have been the subject of thorough study. In this paper, we discuss the complex and coordinated responses leading to parenchymal damage after liver ischemia/reperfusion as well as the manner in which the liver clears damaged cells and regenerates functional mass.

Mechanistic overview of reactive species-induced degradation of the endothelial glycocalyx during hepatic ischemia/reperfusion injury

Endothelial cells are covered by a delicate meshwork of glycoproteins known as the glycocalyx. Under normophysiological conditions the glycocalyx plays an active role in maintaining vascular homeostasis by deterring primary and secondary hemostasis and leukocyte adhesion and by regulating vascular permeability and tone. During (micro)vascular oxidative and nitrosative stress, which prevails in numerous metabolic (diabetes), vascular (atherosclerosis, hypertension), and surgical (ischemia/reperfusion injury, trauma) disease states, the glycocalyx is oxidatively and nitrosatively modified and degraded, which culminates in an exacerbation of the underlying pathology. Consequently, glycocalyx degradation due to oxidative/nitrosative stress has far-reaching clinical implications. In this review the molecular mechanisms of reactive oxygen and nitrogen species-induced destruction of the endothelial glycocalyx are addressed in the context of hepatic ischemia/reperfusion injury as a model disease state. Specifically, the review focuses on (i) the mechanisms of glycocalyx degradation during hepatic ischemia/reperfusion, (ii) the molecular and cellular players involved in the degradation process, and (iii) its implications for hepatic pathophysiology. These topics are projected against a background of liver anatomy, glycocalyx function and structure, and the biology/biochemistry and the sources/targets of reactive oxygen and nitrogen species. The majority of the glycocalyx-related mechanisms elucidated for hepatic ischemia/reperfusion are extrapolatable to the other aforementioned disease states.

Role of galectin-3 in acetaminophen-induced hepatotoxicity and inflammatory mediator production

Galectin-3 (Gal-3) is a β-galactoside-binding lectin implicated in the regulation of macrophage activation and inflammatory mediator production. In the present studies, we analyzed the role of Gal-3 in liver inflammation and injury induced by acetaminophen (APAP). Treatment of wild-type (WT) mice with APAP (300 mg/kg, ip) resulted in centrilobular hepatic necrosis and increases in serum transaminases. This was associated with increased hepatic expression of Gal-3 messenger RNA and protein. Immunohistochemical analysis showed that Gal-3 was predominantly expressed by mononuclear cells infiltrating into necrotic areas. APAP-induced hepatotoxicity was reduced in Gal-3-deficient mice. This was most pronounced at 48-72 h post-APAP and correlated with decreases in APAP-induced expression of 24p3, a marker of inflammation and oxidative stress. These effects were not due to alterations in APAP metabolism or hepatic glutathione levels. The proinflammatory proteins, inducible nitric oxide synthase (iNOS), interleukin (IL)-1β, macrophage inflammatory protein (MIP)-2, matrix metalloproteinase (MMP)-9, and MIP-3α, as well as the Gal-3 receptor (CD98), were upregulated in livers of WT mice after APAP intoxication. Loss of Gal-3 resulted in a significant reduction in expression of iNOS, MMP-9, MIP-3α, and CD98, with no effects on IL-1β. Whereas APAP-induced increases in MIP-2 were augmented at 6 h in Gal-3(-/-) mice when compared with WT mice, at 48 and 72 h, they were suppressed. Tumor necrosis factor receptor-1 (TNFR1) was also upregulated after APAP, a response dependent on Gal-3. Moreover, exaggerated APAP hepatotoxicity in mice lacking TNFR1 was associated with increased Gal-3 expression. These data demonstrate that Gal-3 is important in promoting inflammation and injury in the liver following APAP intoxication.

Receptor activator of nuclear factor-κB ligand (RANKL) protects against hepatic ischemia/reperfusion injury in mice

The transcription factor nuclear factor kappaB (NF-κB) plays diverse roles in the acute injury response to hepatic ischemia/reperfusion (I/R). Activation of NF-κB in Kupffer cells promotes inflammation through cytokine expression, whereas activation in hepatocytes may be cell protective. The interaction of receptor activator of NF-κB (RANK) and its ligand (RANKL) promotes NF-κB activation; however, this ligand-receptor system has not been studied in acute liver injury. In the current study, we sought to determine if RANK and RANKL were important in the hepatic response to I/R. Mice were subjected to partial hepatic ischemia followed by reperfusion. In some experiments, mice received recombinant RANKL or neutralizing antibodies to RANKL 1 hour prior to surgery or at reperfusion to assess the role of RANK/RANKL signaling during I/R injury. RANK was constitutively expressed in the liver and was not altered by I/R. RANK was strongly expressed in hepatocytes and very weakly expressed in Kupffer cells. Serum RANKL concentrations increased after I/R and peaked 4 hours after reperfusion. Serum levels of osteoprotegerin (OPG), a decoy receptor for RANKL, steadily increased over the 8-hour period of reperfusion. Treatment with RANKL, before ischemia or at reperfusion, increased hepatocyte NF-κB activation and significantly reduced liver injury. These beneficial effects occurred without any effect on cytokine expression or liver inflammation. Treatment with anti-RANKL antibodies had no effect on liver I/R injury.

CONCLUSION

During the course of injury, endogenous OPG appears to suppress the effects of RANKL. However, exogenous administration of RANKL, given either prophylactically or postinjury, reduces liver injury in a manner associated with increased hepatocyte NF-κB activation. The data suggest that RANK/RANKL may be a viable therapeutic target in acute liver injury.

Improving the function of liver grafts exposed to warm ischemia by the Leuven drug protocol: exploring the molecular basis by microarray

Livers exposed to warm ischemia (WI) before transplantation are at risk for primary nonfunction (PNF), graft dysfunction, and ischemic biliary strictures, all associated with ischemia/reperfusion injury (IRI). Our multifactorial approach, Leuven drug protocol (LDP), has been shown to reduce these effects and increase recipient survival in WI/IRI-damaged porcine liver transplantation. The aim was the identification of the molecular mechanisms responsible for the hepatoprotective effects of the LDP. Porcine livers were exposed to 45 minutes of WI, cold-stored for 4 hours, transplanted, and either modulated (LDP group; n = 3) or not modulated (control group; n = 4). In the LDP group, the donor livers were flushed with streptokinase and epoprostenol before cold perfusion; the recipients received intravenous glycine, a-1-acid-glycoprotein, FR167653 (a mitogen-activated protein kinase inhibitor), a-tocopherol, glutathione, and apotransferrin. Liver samples were taken before WI and 1 hour after reperfusion. Gene expression was determined with microarrays and molecular pathways and key regulatory genes were identified. The number of genes changed between baseline and 1 hour after reperfusion was 686 in the LDP group and 325 in the control group. The extra genes in the LDP group belonged predominantly to pathways related to cytokine activity, apoptosis, and cell proliferation. We identified 7 genes that were suppressed in the LDP group. These genes could be linked in part to the administered drugs. New potential drug targets were identified on the basis of genes induced in the control group but unaffected in the LDP group and interactions predicted by the literature. In conclusion, the LDP primarily resulted in the suppression of inflammation-regulating genes in IRI. Furthermore, the microarray technique helped us to identify additional gene targets.

CXCR1 deficiency does not alter liver regeneration after partial hepatectomy in mice

Previous studies have shown that CXC chemokines containing Glu-Leu-Arg (ELR) in their amino-terminus stimulate hepatocyte proliferation and liver regeneration after partial hepatectomy. These ELR+CXC chemokines bind to two receptors, CXCR1 and CXCR2. Previous work has shown that CXCR2 is involved in the proliferative effects of CXC chemokines. However, the function of CXCR1 during the regenerative response has not been studied. The aim of the current study was to investigate the role of CXCR1 in liver regeneration after partial hepatectomy. C57BL/6 (wild type) or CXCR1-/- mice were subjected to 70% partial hepatectomy or sham surgery and sacrificed on day 2 and 4 after operation. There were no significant differences in liver-to-body weight ratio or hepatocyte proliferation. The data suggest that CXCR1 does not mediate the proliferative effects of ELR+ CXC chemokines during liver regeneration after partial hepatectomy.

Loss of CFTR affects biliary epithelium innate immunity and causes TLR4-NF-κB-mediated inflammatory response in mice

BACKGROUND & AIMS

Loss of function of the cystic fibrosis transmembrane conductance regulator (CFTR) in the biliary epithelium reduces bile flow and alkalinization in patients with cystic fibrosis (CF). Liver damage is believed to result from ductal cholestasis, but only 30% of patients with CF develop liver defects, indicating that another factor is involved. We studied the effects of CFTR deficiency on Toll-like receptor 4 (TLR4)-mediated responses of the biliary epithelium to endotoxins.

METHODS

Dextran sodium sulfate (DSS) was used to induce colitis in C57BL/6J-Cftrtm1Unc (Cftr-KO) mice and their wild-type littermates. Ductular reaction and portal inflammation were quantified by keratin-19 and CD45 immunolabeling. Cholangiocytes isolated from wild-type and Cftr-KO mice were challenged with lipopolysaccharide (LPS); cytokine secretion was quantified. Activation of nuclear factor κB (NF-κB), phosphorylation of TLR4, and activity of Src were determined. HEK-293 that expressed the secreted alkaline phosphatase reporter and human TLR4 were transfected with CFTR complementary DNAs.

RESULTS

DSS-induced colitis caused biliary damage and portal inflammation only in Cftr-KO mice. Biliary damage and inflammation were not attenuated by restoring biliary secretion with 24-nor-ursodeoxycholic acid but were significantly reduced by oral neomycin and polymyxin B, indicating a pathogenetic role of gut-derived bacterial products. Cftr-KO cholangiocytes incubated with LPS secreted significantly higher levels of cytokines regulated by TLR4 and NF-κB. LPS-mediated activation of NF-κB was blocked by the TLR4 inhibitor TAK-242. TLR4 phosphorylation by Src was significantly increased in Cftr-KO cholangiocytes. Expression of wild-type CFTR in the HEK293 cells stimulated with LPS reduced activation of NF-κB.

CONCLUSIONS

CFTR deficiency alters the innate immunity of the biliary epithelium and reduces its tolerance to endotoxin, resulting in an Src-dependent inflammatory response mediated by TLR4 and NF-κB. These findings might be used to develop therapies for CF-associated cholangiopathy.

CXC chemokine signaling in the liver: impact on repair and regeneration

The process of liver repair and regeneration following hepatic injury is complex and relies on a temporally coordinated integration of several key signaling pathways. Pathways activated by members of the CXC family of chemokines play important roles in the mechanisms of liver repair and regeneration through their effects on hepatocytes. However, little is known about the signaling pathways used by CXC chemokine receptors in hepatocytes. Here we review our current understanding of the pathways involved in both CXC chemokine receptor signaling in other cell types, most notably neutrophils, and similar pathways operant during hepatocyte proliferation/liver regeneration to formulate a basis for the function of CXC chemokine receptor signaling in hepatocytes.

Interferon regulatory factor 1 mediates acetylation and release of high mobility group box 1 from hepatocytes during murine liver ischemia-reperfusion injury

Damage-associated molecular patterns (DAMPs) initiate inflammatory pathways that are common to both sterile and infectious processes. The DAMP, high-mobility group box 1 (HMGB1), and the transcription factor, interferon regulatory factor 1 (IRF-1), have been independently associated as key players in ischemia-reperfusion (I/R) injury. Our study demonstrates that IRF-1 contributes to hepatocellular release of HMGB1 and further that IRF-1 is a necessary component of HMGB1 release in response to hypoxia or after liver I/R. We also link the nuclear upregulation of IRF-1 to the presence of functional Toll-like receptor 4 (TLR4), a pattern recognition receptor also important in sterile and infectious processes. Using IRF-1 chimeric mice, we show that IRF-1 upregulation in hepatic parenchymal cells, and not in the bone marrow-derived immune cells, is responsible for HMGB1 release during ischemic liver injury. Finally, our study also demonstrates a role for IRF-1 in modulating the acetylation status and subsequent release of HMGB1 through histone acetyltransferases. We found that serum HMGB1 is acetylated after liver I/R and that this process was dependent on IRF-1. Additionally, liver I/R induced a direct association of IRF-1 and the nuclear histone acetyltransferase enzyme p300. Together, these findings suggest that I/R-induced release of acetylated HMGB1 is a process that is dependent on TLR4-mediated upregulation of IRF-1.

Marginal copper deficiency increases liver neutrophil accumulation after ischemia/reperfusion in rats

Copper deficiency can cause a host of major cardiovascular complications including an augmented inflammatory response through effects on both neutrophils and the microvascular endothelium. In the present study, we evaluated the effect of marginal copper deficiency on the neutrophilic response to hepatic ischemia/reperfusion injury, a condition that induces an inflammatory response. Male weanling Sprague-Dawley rats were fed purified diets which were either copper-adequate (6.3 mg/kg) or copper-marginal (1.62 mg/kg) for 4 weeks prior to undergoing 90 min of partial hepatic ischemia followed by 8 h of reperfusion. Liver injury was assessed by serum levels of alanine aminotransferase and by liver histology. Liver neutrophil accumulation was determined by tissue myeloperoxidase content. There was no significant difference in liver injury between copper-adequate and copper-marginal rats. However, liver neutrophil accumulation was significantly increased in copper-marginal rats. These findings were confirmed histologically. Liver expression of the adhesion molecule, intercellular adhesion molecule-1 (ICAM-1), was increased in copper-marginal rats compared to copper-adequate rats. The results suggest that neutrophil accumulation is increased through enhanced ICAM-1 expression in liver of copper-marginal rats after ischemia/reperfusion, but that this does not result in increased liver injury.

Clinical significance of serum expression of GROβ in esophageal squamous cell carcinoma

AIM: To determine the association between serum levels of growth-related gene product β (GROβ) and clinical parameters in esophageal squamous cell carcinoma (ESCC).

METHODS: Using enzyme-linked immunosorbent assay, serum GROβ levels were measured in ESCC patients (n = 72) and healthy volunteers (n = 83). The association between serum levels of GROβ and clinical parameters of ESCC was analyzed statistically.

RESULTS: The serum GROβ levels were much higher in ESCC patients than in healthy controls (median: 645 ng/L vs 269 ng/L, P < 0.05). Serum GROβ levels were correlated positively with tumor size, lymph node metastasis, and tumor-node-metastasis (TNM) staging, but not with gender or the histological grade of tumors in ESCC patients. The sensitivity and specificity of the assay for serum GROβ were 73.61% and 56.63%, respectively.

CONCLUSION: GROβ may function as an oncogene product and contribute to tumorigenesis and metastasis of ESCC.

Hepatic ischemia reperfusion injury: Contemporary perspectives on pathogenic mechanisms and basis for hepatoprotection-the good, bad and deadly

Hepatic ischemia reperfusion (IR) injury is an important clinical problem complicating liver surgery and transplantation. The pathogenesis underlying reperfusion injury after warm ischemia is complex, encompassing a multitude of different cell types and signalling mechanisms innate and/or mobilized to the liver. Since the author's 2003 review in the Journal, considerable progress has been achieved in enhancing our understanding of some of the pathogenic pathways and crucial mediators of hepatic inflammation such as the heme oxygenase system, CXC chemokines, Toll-like receptors as well as the mode of parenchymal cell death in IR injury. A better appreciation of these mechanisms will accelerate efforts in designing optimal interventions to prevent hepatic IR injury and improve outcomes after liver transplantation.

Early post-operative measurement of cytokine plasma levels combined with pre-operative bilirubin levels identify high-risk patients after liver resection

Identification of patients at risk of a complicated course after liver resection is crucial for adapting post-operative care. In the present study, we investigated the diagnostic value of the plasma levels of various cytokines obtained immediately after surgery. IL-6, IL-10, IL-8, monokine induced by interferon-γ (MIG), monocyte chemotactic protein-1 (MCP-1) and interferon-inducible protein-10 (IP-10) concentrations were measured in 26 patients after liver resection using a cytometric bead assay and were correlated with liver function, resectate weight, surgery duration, ischemia/reperfusion, hospitalization time and occurrence of complications. Patients with post-surgical complications showed distinctive patterns of IL-6 and IL-8 as early as minutes to hours after surgery. In addition, although pre-operative bilirubin in most patients remained within the normal range, a cut-off of 1 mg/dl separated the patients into groups with different profiles of IL-6, IL-8, and MCP-1 secretion and different likelihoods of experiencing post-operative complications (bilirubin levels ≥1.0 vs. <1.0 mg/dl; IL-6 (4 h): 701 vs. 265; IL-8 (6 h): 262 vs. 97 pg/ml; p<0.05 for both). Extended hospitalization, related to delayed recovery, was correlated with increased IL-8 and MCP-1 immediately after surgery. In conclusion, on the basis of these observations, we suggest that early measurement of post-operative levels of MCP-1, IL-6, and IL-8 can be used to identify individuals at risk of post-operative complications immediately after liver surgery.

Comparative analysis of expression profiles of chemokines, chemokine receptors, and components of signaling pathways mediated by chemokines in eight cell types during rat liver regeneration

It has been documented that chemokines can positively regulate liver regeneration at the tissue level after partial hepatectomy. However, the precise mechanism of the effects of chemokines on regeneration at the cellular level remains poorly defined. In this study, 8 cell types from rat regenerating liver at 8 recovery time points after 2/3 hepatectomy were isolated and purified using Percoll density gradient centrifugation and immunomagnetic bead methods. The expression profiles of each cell type were monitored using a microarray. RT-PCR analysis was performed to validate the reliability of the microarray results. The results showed that, on the whole, the expression profiles of chemokine and receptor genes varied among different cell types; most genes involved in chemokine signaling pathways showed an increase in expression across the 8 liver cell types during liver regeneration. The implication of these genes in regeneration was analyzed by bioinformatics and systems biology methods. According to the microarray results and gene synergy, activation of chemokine signaling pathways at 24 h in biliary epithelial cells and at 2-12 h in dendritic cells may be triggered by CCL2-CCR2 and CCL7-CCR3, respectively; activation of Plc/Pkc and Pi3k/Akt pathways at 2-12 h in sinusoidal endothelial cells might be caused by CCL7-CCR1; and activation of the Src/Ptk, Src/Vav, and Plc/Pkc pathways at the priming stage may be related to the inductive effect of CCL7. These data suggest the potential relevance of the pro-inflammatory chemokines for liver regeneration at the cellular level.

Endogenous leptin fluctuates in hepatic ischemia/reperfusion injury and represents a potential therapeutic target

AIM: To evaluate the role of leptin in the internal disorders during hepatic ischemia/reperfusion injury.

METHODS: A rat model of 70% hepatic ischemia/reperfusion injury was established, with groups of sham-operation (Sham), 60 min ischemia/60 min reperfusion (I60’R60’), I60’R150’, I60’R240’ and I60’R360’. Serum leptin was detected by a self-produced radioimmunoassay; serum glucose, total anti-oxidation capacity, myeloperoxidase, alanine transaminase and diamine oxidase were determined by relevant kits, while histological alterations and protein levels of leptin in the lung, liver and duodenum were examined by hematoxylin-eosin staining and immunohistochemistry. Spearman’s rank correlation between leptin and other variables or grading of tissue impairment were analyzed simultaneously.

RESULTS: Serum leptin in I60’R360’ was significantly higher than in Sham and I60’R240’ groups (both P < 0.05), serum glucose in I60’R360’ was higher than in Sham and I60’R150’ (both P < 0.05), and serum total anti-oxidation capacity in I60’R240’ and I60’R360’ were higher than in Sham (both P < 0.05) and I60’R150’groups (both P < 0.01). Serum myeloperoxidase in groups of I60’R240’ and I60’R360’ were lower than in I60’R150’group (both P < 0.05), serum alanine transaminase in the four reperfusion groups were higher than in the Sham group (all P < 0.05), while serum DAO in I60’R360’ was lower than in I60’R60’ (P < 0.05). Histological impairment in the lung, liver and duodenum at the early phase of this injury was more serious, but the impairment at the later phase was lessened gradually. Protein levels of leptin in the lung in the four reperfusion groups were significantly lower than in the Sham group (all P < 0.01), decreasing in the order of I60’R150’, I60’R60’, I60’R360’ and I60’R240’; the levels in the liver in I60’R60’ and I60’R240’ were higher than in the Sham group (both P < 0.01), while the levels in I60’R240’ and I60’R360’ were lower than in I60’R60’ (both P < 0.01); the levels in duodenum in I60’R240’ and I60’R360’ were higher than in Sham, I60’R60’ and I60’R150’ (all P < 0.01), while the level in I60’R150’ was lower than in I60’R60’ (P < 0.05). There was a significantly positive correlation between serum leptin and alanine transaminase (ρ = 0.344, P = 0.021), a significantly negative correlation between the protein level of leptin in the lung and its damage scores (ρ = -0.313, P = 0.036), and a significantly positive correlation between the protein level of leptin in the liver and its damage scores (ρ = 0.297, P = 0.047).

CONCLUSION: Endogenous leptin fluctuates in hepatic ischemia/reperfusion injury, exerts a potency to rehabilitate the internal disorders and represents a potential target for supportive therapy.

Liver grafts contain a unique subset of natural killer cells that are transferred into the recipient after liver transplantation

In contrast to other solid organ transplantations, liver grafts have tolerogenic properties. Animal models indicate that donor leukocytes transferred into the recipient after liver transplantation (LTX) play a relevant role in this tolerogenic phenomenon. However, the specific donor cell types involved in modulation of the recipient alloresponse are not yet defined. We hypothesized that this unique property of liver grafts may be related to their high content of organ-specific natural killer (NK) and CD56(+) T cells. Here, we show that a high proportion of hepatic NK cells that detach from human liver grafts during pretransplant perfusion belong to the CD56bright subset, and are in an activated state (CD69(+)). Liver NK cells contained perforin and granzymes, exerted stronger cytotoxicity against K562 target cells when compared with blood NK cells, and secreted interferon-gamma, but no interleukin-10 or T helper 2 cytokines, upon stimulation with monokines. Interestingly, whereas the CD56bright subset is classically considered as noncytolytic, liver CD56bright NK cells showed a high content of cytolytic molecules and degranulated in response to K562 cells. After LTX, but not after renal transplantation, significant numbers of donor CD56dim NK and CD56(+) T cells were detected in the recipient circulation for approximately 2 weeks. In conclusion, during clinical LTX, activated and highly cytotoxic NK cells of donor origin are transferred into the recipient, and a subset of them mixes with the recirculating recipient NK cell pool. The unique properties of the transferred hepatic NK cells may enable them to play a role in regulating the immunological response of the recipient against the graft and therefore contribute to liver tolerogenicity.