Disruption of Type-I IFN pathway ameliorates preservation damage in mouse orthotopic liver transplantation via HO-1 dependent mechanism

Nanoparticle-Based Interventions for Liver Transplantation

Liver transplantation is the only treatment for hepatic insufficiency as a result of acute and chronic liver injuries/pathologies that fail to recover. Unfortunately, there remains an enormous and growing gap between organ supply and demand. Although recipients on the liver transplantation waitlist have significantly higher mortality, livers are often not allocated because they are (i) classified as extended criteria or marginal livers and (ii) subjected to longer cold preservation time (>6 h) with a direct correlation of poor outcomes with longer cold ischemia. Downregulating the recipient's innate immune response to successfully tolerate a graft having longer cold ischemia times or ischemia-reperfusion injury through induction of immune tolerance in the graft and the host would significantly improve organ utilization and post-transplant outcomes. Broadly, technologies proposed for development aim to extend the life of the transplanted liver through post-transplant or recipient conditioning. In this review, we focus on the potential benefits of nanotechnology to provide unique pre-transplant grafting and recipient conditioning of extended criteria donor livers using immune tolerance induction and hyperthermic pre-conditioning.

FcᵧRIIb protects from reperfusion injury by controlling antibody and type I IFN-mediated tissue injury and death

Intestinal ischemia and reperfusion (I/R) is accompanied by an exacerbated inflammatory response characterized by deposition of IgG, release of inflammatory mediators, and intense neutrophil influx in the small intestine, resulting in severe tissue injury and death. We hypothesized that FcᵧRIIb activation by deposited IgG could inhibit tissue damage during I/R. Our results showed that I/R induction led to the deposition of IgG in intestinal tissue during the reperfusion phase. Death upon I/R occurred earlier and was more frequent in FcᵧRIIb^-/- than WT mice. The higher lethality rate was associated with greater tissue injury and bacterial translocation to other organs. FcᵧRIIb^-/- mice presented changes in the amount and repertoire of circulating IgG, leading to increased IgG deposition in intestinal tissue upon reperfusion in these mice. Depletion of intestinal microbiota prevented antibody deposition and tissue damage in FcᵧRIIb^-/- mice submitted to I/R. We also observed increased production of ROS on neutrophils harvested from the intestines of FcᵧRIIb^-/- mice submitted to I/R. In contrast, FcᵧRIII^-/- mice presented reduced tissue damage and neutrophil influx after reperfusion injury, a phenotype reversed by FcᵧRIIb blockade. In addition, we observed reduced IFN-β expression in the intestines of FcᵧRIII^-/- mice after I/R, a phenotype that was also reverted by blocking FcᵧRIIb. IFNAR^-/- mice submitted to I/R presented reduced lethality and TNF release. Altogether our results demonstrate that antibody deposition triggers FcᵧRIIb to control IFN-β and IFNAR activation and subsequent TNF release, tailoring tissue damage, and death induced by reperfusion injury.

Ischemia-reperfusion Injury in Allogeneic Liver Transplantation: A Role of CD4 T Cells in Early Allograft Injury

BACKGROUND

A major discrepancy between clinical and most experimental settings of liver ischemia-reperfusion injury (IRI) is the allogenicity.

METHODS

In the current study, we first established a murine model of allogeneic orthotopic liver transplantation with extended cold ischemia time (18 h). Roles of CD4 T cells in the pathogenesis of IRI in liver allografts were determined using a depleting anti-CD4 antibody. The clinical relevance of CD4 as a marker of liver IRI was analyzed retrospectively in 55 liver transplant patients.

RESULTS

CD4 depletion in both donors and recipients resulted in the most effective protection of liver allografts from IRI, as measured by serum transaminase levels and liver histology. CD4 depletion inhibited IR-induced intragraft neutrophil/macrophage infiltration and proinflammatory gene expressions. Quantitative reverse-transcriptase polymerase chain reaction analysis of human liver biopsies (2 h postreperfusion) revealed that posttransplant, rather than pretransplant, CD4 transcript levels correlated positively with proinflammatory gene expression profile. When we divided patients into subgroups according to intragraft CD4 levels, the high CD4 cohort developed a more severe hepatocellular damage than that with low CD4 levels.

CONCLUSIONS

CD4 T cells play a key pathogenic role in IRI of allogeneic liver transplants, and intragraft CD4 levels in the early postreperfusion phase may serve as a potential biomarker and therapeutic target to ameliorate liver IRI and improve orthotopic liver transplantation outcomes.

Dendritic Cell-Mediated Regulation of Liver Ischemia-Reperfusion Injury and Liver Transplant Rejection

Liver allograft recipients are more likely to develop transplantation tolerance than those that receive other types of organ graft. Experimental studies suggest that immune cells and other non-parenchymal cells in the unique liver microenvironment play critical roles in promoting liver tolerogenicity. Of these, liver interstitial dendritic cells (DCs) are heterogeneous, innate immune cells that appear to play pivotal roles in the instigation, integration and regulation of inflammatory responses after liver transplantation. Interstitial liver DCs (recruited in situ or derived from circulating precursors) have been implicated in regulation of both ischemia/reperfusion injury (IRI) and anti-donor immunity. Thus, livers transplanted from mice constitutively lacking DCs into syngeneic, wild-type recipients, display increased tissue injury, indicating a protective role of liver-resident donor DCs against transplant IRI. Also, donor DC depletion before transplant prevents mouse spontaneous liver allograft tolerance across major histocompatibility complex (MHC) barriers. On the other hand, mouse liver graft-infiltrating host DCs that acquire donor MHC antigen via "cross-dressing", regulate anti-donor T cell reactivity in association with exhaustion of graft-infiltrating T cells and promote allograft tolerance. In an early phase clinical trial, infusion of donor-derived regulatory DCs (DCreg) before living donor liver transplantation can induce alterations in host T cell populations that may be conducive to attenuation of anti-donor immune reactivity. We discuss the role of DCs in regulation of warm and liver transplant IRI and the induction of liver allograft tolerance. We also address design of cell therapies using DCreg to reduce the immunosuppressive drug burden and promote clinical liver allograft tolerance.

Heme oxygenase-1: Equally important in allogeneic hematopoietic stem cell transplantation and organ transplantation?

The intracellular enzyme heme oxygenase-1 (HO-1) is responsible for the degradation of cell-free (cf) heme. Cfheme, released upon cell damage and cell death from hemoglobin, mitochondria and myoglobin, functions as a powerful damage-associated molecular pattern (DAMP). Indeed, cfheme plays a role in a myriad of diseases characterized by (systemic) inflammation, and its rapid degradation by HO-1 is pivotal to maintain homeostasis. In the past decade, HO-1 has been extensively studied for its potential protective role in different transplantation settings, including allogeneic hematopoietic stem cell transplantation (HSCT), solid organ transplantation and pancreatic islet transplantation. These studies have shown that HO-1 can be induced by a wide range of molecules, and that induction of HO-1 has the potential to significantly reduce the incidence and severity of transplantation-related complications such as graft-versus-host disease (GvHD) and ischemia/reperfusion injury (IRI). As such, further investigation into the use of HO-1-inducing agents in human transplantation settings to facilitate the potential use of these agents in the clinic is warranted. In this review, we summarize the literature of the past 10 years on the role of HO-1 in allogeneic HSCT, solid organ transplantation (focusing on kidney and liver) and pancreatic islet transplantation. Furthermore, we provide a hypothesis about the way that HO-1 is able to provide protection against acute GvHD after allogeneic HSCT. A total of 48 research articles and 17 review articles were included in this review.

CEACAM1 and molecular signaling pathways to expand the liver transplant donor pool

Organ shortage continues to limit the lives of patients who require liver transplantation. While extending criteria for liver organs provides a needed resource, tissue damage from prolonged ischemic injury can result in early allograft dysfunction and consequent rejection. In this issue of the JCI, Nakamura et al. used a mouse transplantation model with prolonged ex vivo cold storage to explore liver graft protection. The authors found that liver grafts with absent carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) exhibited increased ischemia-reperfusion injury inflammation and decreased function in wild-type recipients. The authors went on to correlate CEACAM1 levels with postreperfusion damage in human liver transplant recipients. Notably, this study identified a potential biomarker for liver transplant donor graft quality.

Understanding, predicting and achieving liver transplant tolerance: from bench to bedside

In the past 40 years, liver transplantation has evolved from a high-risk procedure to one that offers high success rates for reversal of liver dysfunction and excellent patient and graft survival. The liver is the most tolerogenic of transplanted organs; indeed, immunosuppressive therapy can be completely withdrawn without rejection of the graft in carefully selected, stable long-term liver recipients. However, in other recipients, chronic allograft injury, late graft failure and the adverse effects of anti-rejection therapy remain important obstacles to improved success. The liver has a unique composition of parenchymal and immune cells that regulate innate and adaptive immunity and that can promote antigen-specific tolerance. Although the mechanisms underlying liver transplant tolerance are not well understood, important insights have been gained into how the local microenvironment, hepatic immune cells and specific molecular pathways can promote donor-specific tolerance. These insights provide a basis for the identification of potential clinical biomarkers that might correlate with tolerance or rejection and for the development of novel therapeutic targets. Innovative approaches aimed at promoting immunosuppressive drug minimization or withdrawal include the adoptive transfer of donor-derived or recipient-derived regulatory immune cells to promote liver transplant tolerance. In this Review, we summarize and discuss these developments and their implications for liver transplantation.

Preoperative short-term fasting protects liver injury in patients undergoing hepatectomy

Background

Our previous study demonstrated that preoperative short-term fasting attenuates mice hepatic ischemia/reperfusion injury (IRI), which greatly piqued our interest in verifying if fasting produces similar protective effects in patients undergoing hepatectomy.

Methods

Eighty patients with liver tumors were randomized into control (Ctrl, n=40, preoperative fasting for 6 h) or fasting group (Fasting, n=40, preoperative fasting for 24 h). Serum was collected at pre-operation (Pre-Op), post-operation 1 day (POD-1), post-operation 3 days (POD-3), and post-operation 7 days (POD-7). Liver tissue was removed from the resected specimen.

Results

Sixty-three patients were eventually enrolled, with 33 in Ctrl and 30 in Fasting group. Our data showed that 24 h fasting effectively attenuated elevated sALT and sAST levels after operation (P<0.05), but serum total bilirubin was significantly lower at only POD-3 (P<0.05); and serum albumin was not markedly different in either of the groups. Interestingly, 24 h fasting partially attenuates expression of pro-inflammatory cytokine (TNF-α) and improves oxidative stress (MDA and SOD). Our data further showed short-term fasting triggered Nrf2 signaling pathway.

Conclusions

This study demonstrates preoperative short-term fasting effectively improves clinical outcomes and markedly attenuates inflammatory responses and oxidative stress in patients undergoing hepatectomy, and Nrf2 signaling pathway may play a key role in fasting against inflammatory responses and oxidant stress.

Central role of the TIR-domain-containing adaptor-inducing interferon-β (TRIF) adaptor protein in murine sterile liver injury

Multiple pathways drive the sterile injury response in the liver; however, it is unclear how the type of cells injured or the mechanism of injury activates these pathways. Here, we use a model of selective hepatocyte death to investigate sterile liver injury. In this model, the TIR-domain-containing adaptor-inducing interferon-β (TRIF) was a central mediator of the resulting intrahepatic inflammatory response that was independent of both upstream Toll-like receptor (TLR) 4 signaling and downstream type I interferon (IFN) signaling. TRIF was required for induction of interleukin (IL)-10, IL-6, and IL-1β cytokines. Conversely, although induction of C-C motif chemokine ligand (CCL) 2 and C-X-C motif chemokine ligand (CXCL) 1 chemokines and up-regulation of chemokine (Ccl2, Ccl7, Cxcl1, Cxcl2, and Cxcl10) and cell-adhesion (intracellular adhesion molecule 1 and vascular cell adhesion molecule 1) genes involved in myeloid cell recruitment was reduced in a majority of TRIF^-/- mice, a subset of TRIF^-/- mice showed breakthrough inflammation and the ability to induce these genes and proteins, indicating that redundant pathways exist to respond to hepatocyte death. Furthermore, we found that hepatocytes themselves were the main responders to hepatocyte death, increasing transcription of genes involved in myeloid cell recruitment more than either liver sinusoidal endothelial cells or Kupffer cells.

CONCLUSION

Our studies define a TRIF-dependent, TLR4- and type I IFN-independent pathway of sterile liver injury in which hepatocytes are both the targets of damage and the principal responding cell type. (Hepatology 2017;65:1336-1351).

Interferon β (IFN-β) Production during the Double-stranded RNA (dsRNA) Response in Hepatocytes Involves Coordinated and Feedforward Signaling through Toll-like Receptor 3 (TLR3), RNA-dependent Protein Kinase (PKR), Inducible Nitric Oxide Synthase (iNOS), and Src Protein

The sensing of double-stranded RNA (dsRNA) in the liver is important for antiviral defenses but can also contribute to sterile inflammation during liver injury. Hepatocytes are often the target of viral infection and are easily injured by inflammatory insults. Here we sought to establish the pathways involved in the production of type I interferons (IFN-I) in response to extracellular poly(I:C), a dsRNA mimetic, in hepatocytes. This was of interest because hepatocytes are long-lived and, unlike most immune cells that readily die after activation with dsRNA, are not viewed as cells with robust antimicrobial capacity. We found that poly(I:C) leads to rapid up-regulation of inducible nitric oxide synthase (iNOS), double-stranded RNA-dependent protein kinase (PKR), and Src. The production of IFN-β was dependent on iNOS, PKR, and Src and partially dependent on TLR3/Trif. iNOS and Src up-regulation was partially dependent on TLR3/Trif but entirely dependent on PKR. The phosphorylation of TLR3 on tyrosine 759 was shown to increase in parallel to IFN-β production in an iNOS- and Src-dependent manner, and Src was found to directly interact with TLR3 in the endosomal compartment of poly(I:C)-treated cells. Furthermore, we identified a robust NO/cGMP/PKG-dependent feedforward pathway for the amplification of iNOS expression. These data identify iNOS/NO as an integral component of IFN-β production in response to dsRNA in hepatocytes in a pathway that involves the coordinated activities of TLR3/Trif and PKR.

Liver transplantation in the mouse: Insights into liver immunobiology, tissue injury, and allograft tolerance

The surgically demanding mouse orthotopic liver transplant model was first described in 1991. It has proved to be a powerful research tool for the investigation of liver biology, tissue injury, the regulation of alloimmunity and tolerance induction, and the pathogenesis of specific liver diseases. Liver transplantation in mice has unique advantages over transplantation of the liver in larger species, such as the rat or pig, because the mouse genome is well characterized and there is much greater availability of both genetically modified animals and research reagents. Liver transplant experiments using various transgenic or gene knockout mice have provided valuable mechanistic insights into the immunobiology and pathobiology of the liver and the regulation of graft rejection and tolerance over the past 25 years. The molecular pathways identified in the regulation of tissue injury and promotion of liver transplant tolerance provide new potential targets for therapeutic intervention to control adverse inflammatory responses/immune-mediated events in the hepatic environment and systemically. In conclusion, orthotopic liver transplantation in the mouse is a valuable model for gaining improved insights into liver biology, immunopathology, and allograft tolerance that may result in therapeutic innovation in the liver and in the treatment of other diseases.

ADAR1 Suppresses the Activation of Cytosolic RNA-Sensing Signaling Pathways to Protect the Liver from Ischemia/Reperfusion Injury

Excessive inflammation resulting from activation of the innate immune system significantly contributes to ischemia/reperfusion injury (IRI). Inflammatory reactions in both IRI and infections share the same signaling pathways evoked by danger/pathogen associated molecular pattern molecules. The cytosolic retinoid-inducible gene I(RIG-I)-like RNA receptor (RLR) RNA sensing pathway mediates type I IFN production during viral infection and the sensing of viral RNA is regulated by adenosine deaminase acting on RNA 1 (ADAR1). Using a model of liver IRI, we provide evidence that ADAR1 also regulates cytosolic RNA-sensing pathways in the setting of ischemic stress. Suppression of ADAR1 significantly enhanced inflammation and liver damage following IRI, which was accompanied by significant increases in type I IFN through cytosolic RNA-sensing pathways. In addition, knocking ADAR1 down in hepatocytes exaggerates inflammatory signaling to dsRNA or endotoxin and results in over production of type I IFN, which could be abolished by the interruption of RIG-I. Therefore, we identified a novel ADAR1-dependent protective contribution through which hepatocytes guard against aberrant cytosolic RLR-RNA-sensing pathway mediated inflammatory reaction in response to acute liver IR. ADAR1 protects against over activation of viral RNA-sensing pathways in non-infectious tissue stress.

Signal transducer and activator of transcription 4 in liver diseases

STAT4 is a member of the signal transducer and activator of transcription (STAT) family of molecules that localizes to the cytoplasm. STAT4 regulates various genes expression as a transcription factor after it is phosphorylated, dimerizes and translocates to the nucleus. STAT4 activation is detected virtually in the liver of several mouse models of liver injury, as well as the human liver of chronic liver diseases. STAT4 gene polymorphism has been shown to be associated with the antiviral response in chronic hepatitis C and drug-induced liver injury (DILI), primary biliary cirrhosis (PBC), HCV-associated liver fibrosis and in hepatocellular carcinoma (HCC). However, the roles of STAT4 in the pathogeneses of liver diseases are still not understood entirely. This review summarizes the recent advances on the functional roles of STAT4 and its related cytokines in liver diseases, especially in regulating hepatic anti-viral responses, inflammation, proliferation, apoptosis and tumorigenesis. Targeting STAT4 signaling pathway might be a promising strategy in developing therapeutic approaches for treating hepatitis in order to prevent further injury like cirrhosis and liver cancer.

ATF3-mediated NRF2/HO-1 signaling regulates TLR4 innate immune responses in mouse liver ischemia/reperfusion injury

Activating transcription factor 3 (ATF3) is a stress-induced transcription factor that has been shown to repress inflammatory gene expression in multiple cell types and diseases. However, little is known about the roles and mechanisms of ATF3 in liver ischemia/reperfusion injury (IRI). In warm and cold liver IRI models, we showed that ATF3 deficiency significantly increased ischemia/reperfusion (IR)-stressed liver injury, as evidenced by increased serum alanine aminotransferase levels, histological liver damage, and hepatocellular apoptosis. These may correlate with inhibition of the intrahepatic nuclear factor erythroid-derived 2-related factor 2/heme oxygenase-1 (NRF2/HO-1) signaling pathway leading to enhancing Toll-like receptor 4/nuclear factor kappa beta (TLR4/NF-κB) activation, pro-inflammatory programs and macrophage/neutrophil trafficking, while simultaneously repressing anti-apoptotic molecules in ischemic liver. Interestingly, activation of NRF2/HO-1 signaling using an NRF2 activator, oltipraz (M2), during hepatic IRI-rescued ATF3 anti-inflammatory functions in ATF3-deficient mice. For in vitro studies, ATF3 ablation in lipopolysaccharide (LPS)-stimulated bone marrow-derived macrophages (BMMs) depressed levels of NRF2/HO-1 and PI3K/AKT, resulting in enhanced TLR4/NF-κB activation. Pretreatment of LPS-stimulated BMMs with M2 increased NRF2/HO-1 expression, promoted PI3K/AKT, which in turn suppressed TLR4/NF-κB-mediated proinflammatory mediators. Thus, our results first demonstrate ATF3-mediated NRF2/HO-1 signaling in the regulation of TLR4-driven inflammatory responses in IR-stressed livers. Our findings provide a rationale for a novel therapeutic strategy for managing IR-induced liver injury.

Plasmacytoid dendritic cell-derived IFN-α promotes murine liver ischemia/reperfusion injury by induction of hepatocyte IRF-1

Plasmacytoid dendritic cells (pDC) constitute the body's principal source of type I interferon (IFN) and are comparatively abundant in the liver. Among various cytokines implicated in liver ischemia and reperfusion (I/R) injury, type I IFNs have been described recently as playing an essential role in its pathogenesis. Moreover, type I IFNs have been shown to up-regulate hepatocyte expression of IFN regulatory factor 1 (IRF-1), a key transcription factor that regulates apoptosis and induces liver damage after I/R. Our aim was to ascertain the capacity of IFN-α released by liver pDC to induce liver damage through hepatic IRF-1 up-regulation after I/R injury. Our findings show that liver pDC mature and produce IFN-α in response to liver I/R. Liver pDC isolated after I/R induced elevated levels of IRF-1 production by hepatocytes compared with liver pDC isolated from sham-operated mice. Notably, hepatic IRF-1 expression was reduced significantly by neutralizing IFN-α. In vivo, IFN-α neutralization protected the liver from I/R injury by reducing hepatocyte apoptosis. This was associated with impaired expression of IRF-1 and proapoptotic molecules such as Fas ligand, its receptor (Fas) and death receptor 5, which are regulated by IRF-1. Furthermore, pDC-depleted mice failed to up-regulate hepatic IFN-α and displayed less liver injury associated with reduced levels of hepatic interleukin (IL)-6, tumor necrosis factor-α, and hepatocyte apoptosis after I/R compared with controls.

CONCLUSION

these data support the hypothesis that IFN-α derived from liver pDC plays a key role in the pathogenesis of liver I/R injury by enhancing apoptosis as a consequence of induction of hepatocyte IRF-1 expression.

T cells in organ ischemia reperfusion injury

PURPOSE OF REVIEW

Ischemia and reperfusion injuries occur in multiple clinical settings and contribute to organ dysfunction/failures. Despite the innate inflammatory immune nature, T cells that are critically involved in the pathogenesis of ischemia reperfusion injury (IRI), include not only CD4+ T cells, but also CD8+ and γδT cells. This review focuses on questions of how putative Ag-specific T cells are involved, which include whether they function in an Ag-dependent manner; how they function, cytokine-mediated or costimulatory molecule-mediated mechanisms; and whether different T-cell subsets, Th1, Th17, regulatory T cell (Treg), are all involved and play distinctive roles?

RECENT FINDINGS

Specific T-cell populations, such as effector memory CD4 T cells, promote inflammatory immune activation by ischemia reperfusion independent of their adaptive properties, that is Ag-independently. They function by secreting cytokines and expressing costimulatory molecules to either promote or inhibit innate immune activation, or facilitate tissue repair/homeostasis, as exemplified by Th1, Th17 or Th2, Treg cells, respectively.

SUMMARY

T-cell-targeted therapies need to be refined with strategies to maximally eliminate the proinflammatory but spare the anti-inflammatory/immune regulatory properties of T cells, for future clinical application to ameliorate IRI.

Lung endothelial HO-1 targeting in vivo using lentiviral miRNA regulates apoptosis and autophagy during oxidant injury

The lung endothelium is a major target for inflammatory and oxidative stress. Heme oxygenase-1 (HO-1) induction is a crucial defense mechanism during oxidant challenges, such as hyperoxia. The role of lung endothelial HO-1 during hyperoxia in vivo is not well defined. We engineered lentiviral vectors with microRNA (miRNA) sequences controlled by vascular endothelium cadherin (VE-cad) to study the specific role of lung endothelial HO-1. Wild-type (WT) murine lung endothelial cells (MLECs) or WT mice were treated with lentivirus and exposed to hyperoxia (95% oxygen). We detected HO-1 knockdown (∼55%) specifically in the lung endothelium. MLECs and lungs showed approximately a 2-fold increase in apoptosis and ROS generation after HO-1 silencing. We also demonstrate for the first time that silencing endothelial HO-1 has the same effect on lung injury and survival as silencing HO-1 in multiple lung cell types and that HO-1 regulates caspase 3 activation and autophagy in endothelium during hyperoxia. These studies demonstrate the utility of endothelial-targeted gene silencing in vivo using lentiviral miRNA constructs to assess gene function and that endothelial HO-1 is an important determinant of survival during hyperoxia.

Recombinant adiponectin ameliorates liver ischemia reperfusion injury via activating the AMPK/eNOS pathway

BACKGROUND

It is of importance to minimize ischemia reperfusion (I/R) injury during liver operations. Reducing the inflammatory reaction is an effective way to achieve this goal. Notably, adiponectin (APN) was found to have anti-inflammatory activity in heart and renal I/R injury. Herein, we investigated the role of APN in liver I/R injury.

METHODS

WISTAR RATS WERE RANDOMIZED TO FOUR GROUPS: (1) sham group; (2) I/R control group; (3) I/R+APN group; and (4) I/R+APN+AMPK inhibitor group. Liver and blood samples were collected 6h and 24h after reperfusion. Liver function and histopathologic changes were assessed. Macrophage and neutrophil infiltration was detected by immunohistochemistry staining, while pro-inflammatory cytokines and chemokines released in the liver were measured using ELISA and RT-PCR, respectively. Apoptosis was analyzed by TUNEL staining and caspase-3 expression in the liver. Downstream molecules of APN were investigated by Western blotting.

RESULTS

Circulatory APN was down-regulated during liver I/R. When exogenous APN treatment was administered during liver I/R, alanine transaminase (ALT) and aspartate aminotransferase (AST) were decreased, and less hepatocyte necrosis was observed. Less inflammatory cell infiltration and pro-inflammatory cytokines/chemokines release were also observed in the I/R+APN group when compared with the I/R control group. APN treatment also reduced hepatocyte apoptosis, evidenced by reduced TUNEL positive cells and less caspase-3 expression in the reperfused liver. Finally, the AMPK/eNOS pathway was found to be activated by APN, and administration of an AMPK inhibitor reversed the beneficial effects of APN.

CONCLUSION

APN can protect the liver from I/R injury by reducing the inflammatory response and hepatocyte apoptosis, a process that likely involves the AMPK/eNOS pathway. The current study provides a potential pharmacologic target for liver I/R injury.

Nrf2 is crucial to graft survival in a rodent model of heart transplantation

Currently, the sole treatment option for patients with heart failure is transplantation. The battle of prolonging graft survival and modulating innate and adaptive immune responses is still being waged in the clinic and in research labs. The transcription factor Nrf2 controls major cell survival pathways and is central to moderating inflammation and immune responses. In this study the effect of Nrf2 levels in host recipient C57BL/6 mice on Balb/c allogeneic graft survival was examined. Importantly, Nrf2^−/− recipient mice could not support the graft for longer than 7.5 days on average, whereas activation of Nrf2 by sulforaphane in Nrf2^+/+ hosts prolonged graft survival to 13 days. Several immune cells in the spleen of recipient mice were unchanged; however, CD11b⁺ macrophages were significantly increased in Nrf2^−/− mice. In addition, IL-17 mRNA levels were elevated in grafts transplanted into Nrf2^−/− mice. Although Nrf2 appears to play a crucial role in graft survival, the exact mechanism is yet to be fully understood.

Ischaemia-reperfusion injury in liver transplantation--from bench to bedside

Ischaemia-reperfusion injury (IRI) in the liver, a major complication of haemorrhagic shock, resection and transplantation, is a dynamic process that involves the two interrelated phases of local ischaemic insult and inflammation-mediated reperfusion injury. This Review highlights the latest mechanistic insights into innate-adaptive immune crosstalk and cell activation cascades that lead to inflammation-mediated injury in livers stressed by ischaemia-reperfusion, discusses progress in large animal experiments and examines efforts to minimize liver IRI in patients who have received a liver transplant. The interlinked signalling pathways in multiple hepatic cell types, the IRI kinetics and positive versus negative regulatory loops at the innate-adaptive immune interface are discussed. The current gaps in our knowledge and the pathophysiology aspects of IRI in which basic and translational research is still required are stressed. An improved appreciation of cellular immune events that trigger and sustain local inflammatory responses, which are ultimately responsible for organ injury, is fundamental to developing innovative strategies for treating patients who have received a liver transplant and developed ischaemia-reperfusion inflammation and organ dysfunction.

Type-I IFN signaling is required for the induction of antigen-specific CD8(+) T cell responses by adenovirus vector vaccine in the gut-mucosa

Adenovirus vector (Adv) vaccination at a systemic site, such as intramuscular (i.m.) immunization, can induce antigen-specific CD8(+) T cell responses in both systemic and mucosal compartments. It remains unclear, however, how antigen-specific CD8(+) T cell response is induced in the mucosa. In this study, we found that type-I IFN signaling is required for the induction of mRNA expression of retinal dehydrogenase in the draining lymph nodes following the i.m. Adv vaccination. We show that type-I IFN signaling is required for the induction of antigen-specific CD8(+) T cell response in the gut-mucosal compartment following the i.m. Adv vaccination.