Interferon regulatory factor 3 deficiency leads to interleukin-17-mediated liver ischemia-reperfusion injury

The Role of Interferon Regulatory Factors in Liver Diseases

The interferon regulatory factors (IRFs) family comprises 11 members that are involved in various biological processes such as antiviral defense, cell proliferation regulation, differentiation, and apoptosis. Recent studies have highlighted the roles of IRF1-9 in a range of liver diseases, including hepatic ischemia-reperfusion injury (IRI), alcohol-induced liver injury, Con A-induced liver injury, nonalcoholic fatty liver disease (NAFLD), cirrhosis, and hepatocellular carcinoma (HCC). IRF1 is involved in the progression of hepatic IRI through signaling pathways such as PIAS1/NFATc1/HDAC1/IRF1/p38 MAPK and IRF1/JNK. The regulation of downstream IL-12, IL-15, p21, p38, HMGB1, JNK, Beclin1, β-catenin, caspase 3, caspase 8, IFN-γ, IFN-β and other genes are involved in the progression of hepatic IRI, and in the development of HCC through the regulation of PD-L1, IL-6, IL-8, CXCL1, CXCL10, and CXCR3. In addition, IRF3-PPP2R1B and IRF4-FSTL1-DIP2A/CD14 pathways are involved in the development of NAFLD. Other members of the IRF family also play moderately important functions in different liver diseases. Therefore, given the significance of IRFs in liver diseases and the lack of a comprehensive compilation of their molecular mechanisms in different liver diseases, this review is dedicated to exploring the molecular mechanisms of IRFs in various liver diseases.

Analysis and experimental validation of IL-17 pathway and key genes as central roles associated with inflammation in hepatic ischemia-reperfusion injury

Hepatic ischemia-reperfusion injury (HIRI) elicits an immune-inflammatory response that may result in hepatocyte necrosis and apoptosis, ultimately culminating in postoperative hepatic dysfunction and hepatic failure. The precise mechanisms governing the pathophysiology of HIRI remain incompletely understood, necessitating further investigation into key molecules and pathways implicated in disease progression to guide drug discovery and potential therapeutic interventions. Gene microarray data was downloaded from the GEO expression profile database. Integrated bioinformatic analyses were performed to identify HIRI signature genes, which were subsequently validated for expression levels and diagnostic efficacy. Finally, the gene expression was verified in an experimental HIRI model and the effect of anti-IL17A antibody intervention in three time points (including pre-ischemic, post-ischemic, and at 1 h of reperfusion) on HIRI and the expression of these genes was investigated. Bioinformatic analyses of the screened characterized genes revealed that inflammation, immune response, and cell death modulation were significantly associated with HIRI pathophysiology. CCL2, BTG2, GADD45A, FOS, CXCL10, TNFRSF12A, and IL-17 pathway were identified as key components involved in the HIRI. Serum and liver IL-17A expression were significantly upregulated during the initial phase of HIRI. Pretreatment with anti-IL-17A antibody effectively alleviated the damage of liver tissue, suppressed inflammatory factors, and serum transaminase levels, and downregulated the mRNA expression of CCL2, GADD45A, FOS, CXCL10, and TNFRSF12A. Injection of anti-IL17A antibody after ischemia and at 1 h of reperfusion failed to demonstrate anti-inflammatory and attenuating HIRI benefits relative to earlier intervention. Our study reveals that the IL-17 pathway and related genes may be involved in the proinflammatory mechanism of HIRI, which may provide a new perspective and theoretical basis for the prevention and treatment of HIRI.

Targeted macrophage phagocytosis by Irg1/itaconate axis improves the prognosis of intracerebral hemorrhagic stroke and peritonitis

BACKGROUND

Macrophages are innate immune cells whose phagocytosis function is critical to the prognosis of stroke and peritonitis. cis-aconitic decarboxylase immune-responsive gene 1 (Irg1) and its metabolic product itaconate inhibit bacterial infection, intracellular viral replication, and inflammation in macrophages. Here we explore whether itaconate regulates phagocytosis.

METHODS

Phagocytosis of macrophages was investigated by time-lapse video recording, flow cytometry, and immunofluorescence staining in macrophage/microglia cultures isolated from mouse tissue. Unbiased RNA-sequencing and ChIP-sequencing assays were used to explore the underlying mechanisms. The effects of Irg1/itaconate axis on the prognosis of intracerebral hemorrhagic stroke (ICH) and peritonitis was observed in transgenic (Irg1flox/flox; Cx3cr1creERT/+, cKO) mice or control mice in vivo.

FINDINGS

In a mouse model of ICH, depletion of Irg1 in macrophage/microglia decreased its phagocytosis of erythrocytes, thereby exacerbating outcomes (n = 10 animals/group, p < 0.05). Administration of sodium itaconate/4-octyl itaconate (4-OI) promoted macrophage phagocytosis (n = 7 animals/group, p < 0.05). In addition, in a mouse model of peritonitis, Irg1 deficiency in macrophages also inhibited phagocytosis of Staphylococcus aureus (n = 5 animals/group, p < 0.05) and aggravated outcomes (n = 9 animals/group, p < 0.05). Mechanistically, 4-OI alkylated cysteine 155 on the Kelch-like ECH-associated protein 1 (Keap1), consequent in nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf2) and transcriptional activation of Cd36 gene. Blocking the function of CD36 completely abolished the phagocytosis-promoting effects of Irg1/itaconate axis in vitro and in vivo.

INTERPRETATION

Our findings provide a potential therapeutic target for phagocytosis-deficiency disorders, supporting further development towards clinical application for the benefit of stroke and peritonitis patients.

FUNDING

The National Natural Science Foundation of China (32070735, 82371321 to Q. Li, 82271240 to F. Yang) and the Beijing Natural Science Foundation Program and Scientific Research Key Program of Beijing Municipal Commission of Education (KZ202010025033 to Q. Li).

Prolonged warm ischemia time increases mitogen-activated protein kinase activity and decreases perfusate cytokine levels in ex vivo rat liver machine perfusion

Introduction

Machine perfusion is increasingly being utilized in liver transplantation in lieu of traditional cold static organ preservation. Nevertheless, better understanding of the molecular mechanisms underlying the ischemia-reperfusion injury (IRI) during ex vivo perfusion is necessary to improve the viability of liver grafts after transplantation using machine perfusion technology. Since key cellular signaling pathways involved in hepatic IRI may allow a chance for designing a promising approach to improve the clinical outcomes from this technology, we determined how warm ischemia time (WIT) during procurement affects the activity of mitogen-activated protein kinase (MAPK) and perfusate concentration of cytokines in an ex vivo rat liver machine perfusion model.

Methods

Male Sprague-Dawley rats underwent in situ hepatic ischemia with varying WIT (0, 10, 20, 30 min, n = 5 each), and subsequently 3 h of cold ischemia time and 2 h of machine perfusion prior to determining the degree of MAPK activation-phosphorylation and cytokine concentration in liver tissue and perfusates, respectively.

Results

Our data revealed a strong correlation between incremental WIT and a series of liver injury markers, and that prolonged WIT increases ERK1/2 and p54 JNK phosphorylation during machine perfusion. Notably, specific cytokine levels (MCP-1, MIP-2, GRO/KC, IL-10, and IL-5) were inversely correlated with the phosphorylation levels of ERK1/2, p38 MAPK, and p46/p54 JNK.

Discussion

These results suggest that MAPK activation, specifically ERK1/2 and p54 JNK phosphorylation, have potential as a biomarker for hepatic IRI pathophysiology during machine perfusion. Elucidation of their functional significance may lead to designing a novel strategy to increase the clinical benefit of machine perfusion.

A new method for the treatment of myocardial ischemia-reperfusion injury based on γδT cell-mediated immune response

Acute myocardial ischemia is a disease with high morbidity and mortality, and re-perfusion is currently the best intervention. However, re-perfusion may lead to further myocardial injury and increase the area of myocardial infarction. The mechanism of myocardial ischemia-re-perfusion injury is complex, but with more in-depth study, it has been proved that the immune system plays an important role in the process of MIRI. Among them, the γδT cell population has received increasing attention as the main early source of IL-17A in many immune response models. Because γδT cells have the characteristics of linking innate immunity and adaptive immunity,they can rapidly produce IL-17A and produce subsequent immune killing of cardiomyocytes. It can be seen that γδT cells play an important role in MIRI. Therefore, here we review the research progress of immune response in myocardial ischemia-re-perfusion injury, the key characteristics of γδT cells and the role of rapidly produced IL-17 in myocardial ischemia-re-perfusion injury, and propose relevant treatment strategies and prospects for myocardial repair, in order to provide new ideas and methods for clinical treatment of myocardial ischemia-re-perfusion injury.

Tourniquet-induced ischemia creates increased risk of organ dysfunction and mortality following delayed limb amputation

Tourniquets are critical for the control of traumatic extremity hemorrhage. In this study, we sought to determine, in a rodent blast-related extremity amputation model, the impact of prolonged tourniquet application and delayed limb amputation on survival, systemic inflammation, and remote end organ injury. Adult male Sprague Dawley rats were subjected to blast overpressure (120±7 kPa) and orthopedic extremity injury consisting femur fracture, one-minute soft tissue crush injury (20 psi), ± 180 min of tourniquet-induced hindlimb ischemia followed by delayed (60 min of reperfusion) hindlimb amputation (dHLA). All animals in the non-tourniquet group survived whereas 7/21 (33%) of the animals in the tourniquet group died within the first 72 h with no deaths observed between 72 and 168 h post-injury. Tourniquet induced ischemia-reperfusion injury (tIRI) likewise resulted in a more robust systemic inflammation (cytokines and chemokines) and concomitant remote pulmonary, renal, and hepatic dysfunction (BUN, CR, ALT. AST, IRI/inflammation-mediated genes). These results indicate prolonged tourniquet application and dHLA increases risk of complications from tIRI, leading to greater risk of local and systemic complications including organ dysfunction or death. We thus need enhanced strategies to mitigate the systemic effects of tIRI, particularly in the military prolonged field care (PFC) setting. Furthermore, future work is needed to extend the window within which tourniquet deflation to assess limb viability remains feasible, as well as new, limb-specific or systemic point of care tests to better assess the risks of tourniquet deflation with limb preservation in order to optimize patient care and save both limb and life.

Liver ischaemia-reperfusion injury: a new understanding of the role of innate immunity

Liver ischaemia-reperfusion injury (LIRI), a local sterile inflammatory response driven by innate immunity, is one of the primary causes of early organ dysfunction and failure after liver transplantation. Cellular damage resulting from LIRI is an important risk factor not only for graft dysfunction but also for acute and even chronic rejection and exacerbates the shortage of donor organs for life-saving liver transplantation. Hepatocytes, liver sinusoidal endothelial cells and Kupffer cells, along with extrahepatic monocyte-derived macrophages, neutrophils and platelets, are all involved in LIRI. However, the mechanisms underlying the responses of these cells in the acute phase of LIRI and how these responses are orchestrated to control and resolve inflammation and achieve homeostatic tissue repair are not well understood. Technological advances allow the tracking of cells to better appreciate the role of hepatic macrophages and platelets (such as their origin and immunomodulatory and tissue-remodelling functions) and hepatic neutrophils (such as their selective recruitment, anti-inflammatory and tissue-repairing functions, and formation of extracellular traps and reverse migration) in LIRI. In this Review, we summarize the role of macrophages, platelets and neutrophils in LIRI, highlight unanswered questions, and discuss prospects for innovative therapeutic regimens against LIRI in transplant recipients.

The transcription factor interferon regulatory factor-1 is an endogenous mediator of myocardial ischemia reperfusion injury

Myocardial ischemia reperfusion (MIR) injury negatively affects the prognosis of acute myocardial infarction (AMI), while effective suppression of MIR injury remains a largely unmet clinical need. Interferon regulatory factors (IRF) are key players in chronic cardiac disorders such as cardiac remodeling. However, their roles in acute MIR injury remain largely unknown. In the current study, microarray data indicated that IRF1 expression was consistently changed in the human ischemic heart and ischemic reperfused mouse heart. Western blot analysis confirmed the expression alterations of IRF1 in ischemic reperfused mouse heart. Cardiac-specific IRF1 knockdown significantly decreased infarct size, improved cardiac function, and suppressed myocardial apoptosis after MIR injury. Conversely, cardiac-specific IRF1 overexpression significantly promoted MIR injury. Further investigation revealed that IRF1 transcriptionally regulated the expression of inducible nitric oxide synthase (iNOS), and augmented oxidative stress. Taken together, we presented the first direct evidence that IRF1 served as a mediator of MIR injury, and IRF1 may represent a potential therapeutic target for alleviating MIR injury.

Hepatic interferon regulatory factor 8 expression mediates liver ischemia/reperfusion injury in mice

Hepatic ischemia/reperfusion (I/R) injury is an inevitable complication of hepatic surgery occasioned by liver transplantation and resection. The progression from liver ischemia to reperfusion injury is accompanied by abnormal metabolism, Kupffer cell activation, neutrophil recruitment and the release of cytokines. Activation of several interferon regulatory factors (IRFs) has been reported to either enhance or restrict I/R progression, but the role of IRF8 in the regulation of I/R injury progression is still unknown. In this study, we explore the IRF8 function in the I/R-mediated liver injury using overexpressed hepatic IRF8 and knockout mice. According to our results, IRF8 knockout mice had significantly lower inflammatory cells infiltration, inflammatory cytokines release and serum aspartate aminotransferase/alanine aminotransferase levels that improved the necrotic injury after I/R, unlike the control mice. Conversely, the overexpression of IRF8 in WT mice markedly aggravated the liver structure damage and its abnormal function. We further showed that IRF8-mediated inflammatory cells infiltration were partly dependent on early autophagy and NF-κΒ signal pathway during I/R. AAV8-IRF8-I/R mice pretreated with autophagy inhibitor hydroxychloroquine and NF-κΒ signal pathway inhibitor secukinumab could drastically reverse the IRF8-mediated increase of neutrophil infiltration and chemokine release at different degrees. This work uncovered a critical role of IRF8 in the modulation of the hepatic microenvironment and as a potential target in the initial treatment of I/R injury.

Metformin regulates the Th17/Treg balance by glycolysis with TIGAR in hepatic ischemia-reperfusion injury

The balance of Th17/Treg plays an important role in hepatic ischemia-reperfusion (I/R) injury. Glycolysis and glutaminolysis for energy metabolism governs the differentiate of CD 4+ T-cells to Th17/Treg. Metformin can regulate glucose metabolism in the liver, but its protective effect on I/R liver injury and its effect on Th17/Treg balancestill unknown. In this study, the I/R liver injury rat model and the primary hepatocyte hypoxia/reoxygenation injury model were established. The biochemical indexes, inflammatory factor indexes, Th17/Treg balance and energy metabolism were evaluated. RNA-seq and gene knockout cells were used to investigated the target protein of metformin. The results showed that metformin could effectively improve liver injury caused by I/R, significantly inhibit the glycolysis, improve the Th17/Treg balance, and inhibit the expression of inflammatory factors. RNA-seq results showed that TIGAR was a possible regulatory site of metformin. However, the protective effect and the regulating effect of Th17/Treg balance by metformin in TIGAR knock-out cells were disappeared. In conclusion, metformin could regulate TIGAR inhibit glycolysis then regulate Th17/Treg balance, inhibit the release of liver inflammatory factors, and finally play a role in inhibiting the occurrence of liver injury caused by ischemia-reperfusion.

IL-27 Protects the Brain from Ischemia-Reperfusion Injury via the gp130/STAT3 Signaling Pathway

The occurrence of ischemia-reperfusion (I/R) injury leads to dysfunction as well as high rates of morbidity and mortality in stroke, and new effective therapeutic strategies for I/R are still needed. We investigated the effect of IL-27 on I/R injury-induced neurological function impairment, cerebral infarction volume and variation in levels of inflammatory factors in mice with middle cerebral artery occlusion (MCAO), as well as concentration of LDH and neuronal apoptosis in a neuron oxygen-glucose deprivation and reperfusion (OGD/R) model mediated by gp130/STAT3 signaling in vitro. Our results indicated that IL-27 could bind to its receptor of gp130 to attenuate the I/R injury-induced impairment function and cerebral infarction volume, and decrease inflammatory cytokines TNF-α, IL-1β and MCP-1 but increase anti-inflammatory factors IL-10 and TGF-β in vivo, while inhibiting LDH leakage and neuronal apoptosis through activation of STAT3 to antagonize I/R induction. Our results suggest that IL-27 may protect the brain from I/R injury through the gp130/STAT3 signaling pathway.

DJ-1 Deficiency in Hepatocytes Improves Liver Ischemia-Reperfusion Injury by Enhancing Mitophagy

BACKGROUND & AIMS

DJ-1 is universally expressed in various tissues and organs and is involved in the physiological processes in various liver diseases. However, the role of DJ-1 in liver ischemia-reperfusion (I/R) injury is largely unknown.

METHODS

In this study, we first examined the DJ-1 expression changes in the liver tissues of mice and clinical donor after hepatic I/R by both quantitative polymerase chain reaction and Western blotting assays. Then we investigated the role of DJ-1 in I/R injury by using a murine liver I/R model.

RESULTS

We demonstrated that DJ-1 down-regulation in both human and mouse liver tissues in response to I/R injury and Dj-1 deficiency in hepatocytes but not in myeloid cells could significantly ameliorate I/R induced liver injury and inflammatory responses. This hepatoprotective effect was dependent on enhanced autophagy in Dj-1 knockout mice, because inhibition of autophagy by 3-methyladenine and chloroquine could reverse the protective effect on hepatic I/R injury in Dj-1 knockout mice.

CONCLUSIONS

Dj-1 deficiency in hepatocytes significantly enhanced mitochondrial accumulation and protein stability of PARKIN, which in turn promotes the onset of mitophagy resulting in elevated clearance of damaged mitochondria during I/R injury.

Myeloid tumor necrosis factor and heme oxygenase-1 regulate the progression of colorectal liver metastases during hepatic ischemia-reperfusion

The liver ischemia-reperfusion (IR) injury that occurs consequently to hepatic resection performed in patients with metastases can lead to tumor relapse for not fully understood reasons. We assessed the effects of liver IR on tumor growth and the innate immune response in a mouse model of colorectal (CR) liver metastasis. Mice subjected to liver ischemia 2 days after intrasplenic injection of CR carcinoma cells displayed a higher metastatic load in the liver, correlating with Kupffer cells (KC) death through the activation of receptor-interating protein 3 kinase (RIPK3) and caspase-1 and a recruitment of monocytes. Interestingly, the immunoregulatory mediators, tumor necrosis factor-α (TNF-α) and heme oxygenase-1 (HO-1) were strongly upregulated in recruited monocytes and were also expressed in the surviving KC following IR. Using TNF^flox/flox LysM^cre/wt mice, we showed that TNF deficiency in macrophages and monocytes favors tumor progression after IR. The antitumor effect of myeloid cell-derived TNF involved direct tumor cell apoptosis and a reduced expression of immunosuppressive molecules such as transforming growth factor-β, interleukin (IL)-10, inducible nitric oxyde synthase (iNOS), IL-33 and HO-1. Conversely, a monocyte/macrophage-specific deficiency in HO-1 (HO-1^flox/flox LysM^cre/wt ) or the blockade of HO-1 function led to the control of tumor progression post-liver IR. Importantly, host cell RIPK3 deficiency maintains the KC number upon IR, inhibits the IR-induced innate cell recruitment, increases the TNF level, decreases the HO-1 level and suppresses the tumor outgrowth. In conclusion, tumor recurrence in host undergoing liver IR is associated with the death of antitumoral KC and the recruitment of monocytes endowed with immunosuppressive properties. In both of which HO-1 inhibition would reinforce their antitumoral activity.

Characteristics of Changes in Inflammatory Cytokines as a Function of Hepatic Ischemia-Reperfusion Injury Stage in Mice

Liver ischemia-reperfusion injury (IRI) can severely compromise the prognosis of patients receiving liver surgery. While inflammation contributes to the damage resulting from IRI, only a limited number of inflammation biomarkers have been identified as being associated with the different stages of hepatic IRI. As an approach to identify some of these inflammatory cytokines and the molecular mechanisms involved within different stages of hepatic IRI, we used an advanced antibody array assay to detect multiple proteins. With this technology, we observed specific differences in the content of inflammatory cytokines between ischemic and sham controls, as well as a function of the different reperfusion stages in a hepatic IRI mouse model. For example, while liver tissue content of IL-12p40/p70 was significantly increased in the ischemic stage, it was significantly decreased in the reperfusion stage as compared with that of the sham group. For other inflammatory cytokines, no changes were obtained between the ischemic and reperfusion stages with levels of IL-17, Eotaxin-2, Eotaxin, and sTNF RII all being consistently increased, while those of TIMP-1, TIMP-2, BLC, and MCSF consistently decreased as compared with that of the sham group at all reperfusion stages examined. Results from protein function annotation Gene Ontology and the KEGG pathway revealed that inflammatory cytokines are enriched in a network associated with activation of inflammatory response signaling pathways such as TLR, TNF, and IL-17 when comparing responses of the IR versus sham groups. The identification of cytokines along with their roles at specific stages of IRI may reveal important new biological markers for the diagnosis and prognosis of hepatic IRI.

γδ T Cells Promote Steatohepatitis by Orchestrating Innate and Adaptive Immune Programming

BACKGROUND AND AIMS

The recruitment and activation of inflammatory cells in the liver delineates the transition from hepatic steatosis to steatohepatitis (SH).

APPROACH AND RESULTS

We found that in SH, γδT cells are recruited to the liver by C-C chemokine receptor (CCR) 2, CCR5, and nucleotide-binding oligomerization domain-containing protein 2 signaling and are skewed toward an interleukin (IL)-17A⁺ phenotype in an inducible costimulator (ICOS)/ICOS ligand-dependent manner. γδT cells exhibit a distinct Vγ4⁺ , PD1⁺ , Ly6C⁺ CD44⁺ phenotype in SH. Moreover, γδT cells up-regulate both CD1d, which is necessary for lipid-based antigens presentation, and the free fatty acid receptor, CD36. γδT cells are stimulated to express IL-17A by palmitic acid and CD1d ligation. Deletion, depletion, and targeted interruption of γδT cell recruitment protects against diet-induced SH and accelerates disease resolution.

CONCLUSIONS

We demonstrate that hepatic γδT cells exacerbate SH, independent of IL-17 expression, by mitigating conventional CD4⁺ T-cell expansion and modulating their inflammatory program by CD1d-dependent vascular endothelial growth factor expression.

Recipient HO-1 inducibility is essential for posttransplant hepatic HO-1 expression and graft protection: From bench-to-bedside

By documenting potent antioxidative and anti-inflammatory functions, preclinical studies encourage heme oxygenase-1 (HO-1)-inducing regimens in clinical orthotopic liver transplantation (OLT). We aimed to determine the importance of recipient-derived HO-1 in murine and human OLTs. Hepatic biopsies from 51 OLT patients were screened for HO-1 expression (Western blots) prior to put-in (basal) and post reperfusion (stressed) and correlated with the hepatocellular function. In parallel, livers from HO-1 proficient mice (WT; C57/BL6), subjected to ex vivo cold storage (18 hour), were transplanted to syngeneic myeloid HO-1 deficient (mHO-1 KO) or FLOX (control) hosts, and sampled postreperfusion (6 hour). In human OLT, posttransplant but not pretransplant HO-1 expression correlated negatively with ALT levels (P = .0178). High posttransplant but not pretransplant HO-1 expression trended with improved OLT survival. Compared with controls, livers transplanted into mHO-1 KO recipient mice had decreased HO-1 levels, exacerbated hepatic damage/frequency of TUNEL+ cells, increased mRNA levels coding for TNFα/CXCL1/CXCL2/CXCL10, higher frequency of Ly6G+/4HN+ neutrophils; and enhanced MPO activity. Peritoneal neutrophils from mHO-1 KO mice exhibited higher CellRox+ ratio and increased TNFα/CXCL1/CXCL2/CXCL10 expression. By demonstrating the importance of posttransplant recipient HO-1 phenotype in hepatic macrophage/neutrophil regulation and function, this translational study identifies recipient HO-1 inducibility as a novel biomarker of ischemic stress resistance in OLT.

The Evolving Role of Neutrophils in Liver Transplant Ischemia-Reperfusion Injury

Purpose of Review

Hepatic ischemia-reperfusion injury (IRI), an inevitable event during liver transplantation, represents a major risk factor for the primary graft dysfunction as well as the development of acute and chronic rejection. Neutrophils, along macrophages, are pivotal in the innate immune-driven liver IRI, whereas the effective neutrophil-targeting therapies remain to be established. In this review, we summarize progress in our appreciation of the neutrophil biology and discuss neutrophil-based therapeutic perspectives.

Recent Findings

New technological advances enable to accurately track neutrophil movements and help to understand molecular mechanisms in neutrophil function, such as selective recruitment to IR-stressed tissue, formation of neutrophil extracellular traps, or reverse migration into circulation. In addition to pro-inflammatory and tissue-destructive functions, immune regulatory and tissue-repairing phenotype associated with distinct neutrophil subsets have been identified.

Summary

Newly recognized and therapeutically attractive neutrophil characteristics warrant comprehensive preclinical and clinical attention to target IRI in transplant recipients.

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

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

SIRT6 protects against hepatic ischemia/reperfusion injury by inhibiting apoptosis and autophagy related cell death

Silent information regulator 6 (SIRT6), a class III histone deacetylase, has been revealed to participate in multiple metabolic processes in the liver, and it plays important roles in protecting against ischemia/reperfusion (I/R) injury in multiple organs. In this study, we explored whether SIRT6 is protective against hepatic I/R injury and elucidated the underlying mechanisms. The expression of SIRT6 was significantly decreased during reperfusion compared with the control group. SIRT6-LKO mice exhibited significantly aggravated oxidative stress, mitochondrial dysfunction, inflammatory responses, mitogen-activated protein kinase (MAPK) signaling activation, and apoptosis and autophagy related hepatocyte death compared with control mice. In vitro studies in SIRT6-KO hepatocytes exhibited similar results. In contrast, SIRT6 upregulation alleviated liver damage during hepatic I/R injury. Our study demonstrated for the first time that SIRT6 upregulation effectively protects against hepatic I/R injury. The underlying mechanisms involve the maintenance of oxidative homeostasis and mitochondrial function, which subsequently inhibit the inflammatory responses and MAPK signaling, and finally attenuate apoptosis and autophagy related hepatocyte death. These results suggest that the activation of SIRT6 exerts multifaceted protective effects during hepatic I/R injury, which can provide a novel therapeutic target for hepatic I/R injury.

Editor's Highlight: Candidate Risk Factors and Mechanisms for Tolvaptan-Induced Liver Injury Are Identified Using a Collaborative Cross Approach

Clinical trials of tolvaptan showed it to be a promising candidate for the treatment of Autosomal Dominant Polycystic Kidney Disease (ADPKD) but also revealed potential for idiosyncratic drug-induced liver injury (DILI) in this patient population. To identify risk factors and mechanisms underlying tolvaptan DILI, 8 mice in each of 45 strains of the genetically diverse Collaborative Cross (CC) mouse population were treated with a single oral dose of either tolvaptan or vehicle. Significant elevations in plasma alanine aminotransferase (ALT) were observed in tolvaptan-treated animals in 3 of the 45 strains. Genetic mapping coupled with transcriptomic analysis in the liver was used to identify several candidate susceptibility genes including epoxide hydrolase 2, interferon regulatory factor 3, and mitochondrial fission factor. Gene pathway analysis revealed that oxidative stress and immune response pathways were activated in response to tolvaptan treatment across all strains, but genes involved in regulation of bile acid homeostasis were most associated with tolvaptan-induced elevations in ALT. Secretory leukocyte peptidase inhibitor (Slpi) mRNA was also induced in the susceptible strains and was associated with increased plasma levels of Slpi protein, suggesting a potential serum marker for DILI susceptibility. In summary, tolvaptan induced signs of oxidative stress, mitochondrial dysfunction, and innate immune response in all strains, but variation in bile acid homeostasis was most associated with susceptibility to the liver response. This CC study has indicated potential mechanisms underlying tolvaptan DILI and biomarkers of susceptibility that may be useful in managing the risk of DILI in ADPKD patients.

Innate Immune Regulations and Liver Ischemia-Reperfusion Injury

Liver ischemia reperfusion activates innate immune system to drive the full development of inflammatory hepatocellular injury. Damage-associated molecular patterns (DAMPs) stimulate myeloid and dendritic cells via pattern recognition receptors (PRRs) to initiate the immune response. Complex intracellular signaling network transduces inflammatory signaling to regulate both innate immune cell activation and parenchymal cell death. Recent studies have revealed that DAMPs may trigger not only proinflammatory but also immune regulatory responses by activating different PRRs or distinctive intracellular signaling pathways or in special cell populations. Additionally, tissue injury milieu activates PRR-independent receptors which also regulate inflammatory disease processes. Thus, the innate immune mechanism of liver ischemia-reperfusion injury involves diverse molecular and cellular interactions, subjected to both endogenous and exogenous regulation in different cells. A better understanding of these complicated regulatory pathways/network is imperative for us in designing safe and effective therapeutic strategy to ameliorate liver ischemia-reperfusion injury in patients.

The impact of sterile inflammation in acute liver injury

BACKGROUND

The liver has a number of functions in innate immunity. These functions predispose the liver to innate immune-mediated liver injury when inflammation goes unchecked. Significant progress has been made in the last 25 years on sterile inflammatory liver injury in a number of models; however, a great deal of controversy and many questions about the nature of sterile inflammation still exist.

AIM

The goal of this article is to review sterile inflammatory liver injury using both a basic approach to what constitutes the inflammatory injury, and through examination of current models of liver injury and inflammation. This information will be tied to human patient conditions when appropriate.

RELEVANCE FOR PATIENTS

Inflammation is one of the most critical factors for managing in-patient liver disease in a number of scenarios. More information is needed for both scientists and clinicians to develop rational treatments.

Sirtuin 2 aggravates postischemic liver injury by deacetylating mitogen-activated protein kinase phosphatase-1

Sirtuin 2 (Sirt2) is known to negatively regulate anoxia-reoxygenation injury in myoblasts. Because protein levels of Sirt2 are increased in ischemia-reperfusion (I/R)-injured liver tissues, we examined whether Sirt2 is protective or detrimental against hepatic I/R injury. We overexpressed Sirt2 in the liver of C57BL/6 mice using a Sirt2 adenovirus. Wild-type and Sirt2 knockout mice were subjected to a partial (70%) hepatic ischemia for 45 minutes, followed by various periods of reperfusion. In another set of experiments, wild-type mice were pretreated intraperitoneally with AGK2, a Sirt2 inhibitor. Isolated hepatocytes and Kupffer cells from wild-type and Sirt2 knockout mice were subjected to hypoxia-reoxygenation injury to determine the in vitro effects of Sirt2. Mice subjected to I/R injury showed typical patterns of hepatocellular damage. Prior injection with Sirt2 adenovirus aggravated liver injury, as demonstrated by increases in serum aminotransferases, prothrombin time, proinflammatory cytokines, hepatocellular necrosis and apoptosis, and neutrophil infiltration relative to control virus-injected mice. Pretreatment with AGK2 resulted in significant improvements in serum aminotransferase levels and histopathologic findings. Similarly, experiments with Sirt2 knockout mice also revealed reduced hepatocellular injury. The molecular mechanism of Sirt2's involvement in this aggravation of hepatic I/R injury includes the deacetylation and inhibition of mitogen-activated protein kinase phosphatase-1 and consequent activation of mitogen-activated protein kinases.

CONCLUSION

Sirt2 is an aggravating factor during hepatic I/R injury. (Hepatology 2017;65:225-236).

Blocking Notch signal in myeloid cells alleviates hepatic ischemia reperfusion injury by repressing the activation of NF-κB through CYLD

Ischemia-reperfusion (I/R) is a major reason of hepatocyte injury during liver surgery and transplantation. Myeloid cells including macrophages and neutrophils play important roles in sustained tissue inflammation and damage, but the mechanisms regulating myeloid cells activity have been elusive. In this study, we investigate the role of Notch signaling in myeloid cells during hepatic I/R injury by using a mouse model of myeloid specific conditional knockout of RBP-J. Myeloid-specific RBP-J deletion alleviated hepatic I/R injury. RBP-J deletion in myeloid cells decreased hepatocytes apoptosis after hepatic I/R injury. Furthermore, myeloid-specific RBP-J deletion led to attenuated inflammation response in liver after I/R injury. Consistently, Notch blockade reduced the production of inflammatory cytokines by macrophages in vitro. We also found that blocking Notch signaling reduced NF-κB activation and increased cylindromatosis (CYLD) expression and knockdown of CYLD rescued reduction of inflammatory cytokines induced by Notch blockade in macrophages during I/R injury in vitro. On the other hand, activation of Notch signaling in macrophages led to increased inflammatory cytokine production and NF-κB activation and decreased CYLD expression in vitro. These data suggest that activation of Notch signaling in myeloid cells aggravates I/R injury, by enhancing the inflammation response by NF-κB through down regulation of CYLD.

Hepatic ischemia reperfusion injury: A systematic review of literature and the role of current drugs and biomarkers

Hepatic ischemia reperfusion injury (IRI) is not only a pathophysiological process involving the liver, but also a complex systemic process affecting multiple tissues and organs. Hepatic IRI can seriously impair liver function, even producing irreversible damage, which causes a cascade of multiple organ dysfunction. Many factors, including anaerobic metabolism, mitochondrial damage, oxidative stress and secretion of ROS, intracellular Ca(2+) overload, cytokines and chemokines produced by KCs and neutrophils, and NO, are involved in the regulation of hepatic IRI processes. Matrix Metalloproteinases (MMPs) can be an important mediator of early leukocyte recruitment and target in acute and chronic liver injury associated to ischemia. MMPs and neutrophil gelatinase-associated lipocalin (NGAL) could be used as markers of I-R injury severity stages. This review explores the relationship between factors and inflammatory pathways that characterize hepatic IRI, MMPs and current pharmacological approaches to this disease.

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.

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.

ADAR1 Prevents Liver Injury from Inflammation and Suppresses Interferon Production in Hepatocytes

Adenosine deaminase acting on RNA 1 (ADAR1) is an essential protein for embryonic liver development. ADAR1 loss is embryonically lethal because of severe liver damage. Although ADAR1 is required in adult livers to prevent liver cell death, as demonstrated by liver-specific conditional knockout (Alb-ADAR1(KO)) mice, the mechanism remains elusive. We systematically analyzed Alb-ADAR1(KO) mice for liver damage. Differentiation genes and inflammatory pathways were examined in hepatic tissues from Alb-ADAR1(KO) and littermate controls. Inducible ADAR1 KO mice were used to validate regulatory effects of ADAR1 on inflammatory cytokines. We found that Alb-ADAR1(KO) mice showed dramatic growth retardation and high mortality because of severe structural and functional damage to the liver, which showed overwhelming inflammation, cell death, fibrosis, fatty change, and compensatory regeneration. Simultaneously, Alb-ADAR1(KO) showed altered expression of key differentiation genes and significantly higher levels of hepatic inflammatory cytokines, especially type I interferons, which was also verified by inducible ADAR1 knockdown in primary hepatocyte cultures. We conclude that ADAR1 is an essential molecule for maintaining adult liver homeostasis and, in turn, morphological and functional integrity. It inhibits the production of type I interferons and other inflammatory cytokines. Our findings may provide novel insight in the pathogenesis of liver diseases caused by excessive inflammatory responses, including autoimmune hepatitis.

Inhibition of IRF3 expression reduces TGF-β1-induced proliferation of hepatic stellate cells

Therapeutic management of liver fibrosis remains an unresolved clinical problem. Activation of hepatic stellate cell (HSC) is a pivotal event in the progression of liver fibrosis. Recent reports have showed that inhibition of activated HSC proliferation contributes to the reversal of liver fibrosis. Interferon regulatory factor 3 (IRF3), one member of the interferon regulatory factor (IRF) family, is recently proven to be a critical modulator in cardiac fibrosis. And accumulating evidence demonstrated that IRF3 plays a crucial role in liver diseases, such as hepatic steatosis, liver inflammation, and alcoholic liver injury. However, the understanding of the function of IRF3 in liver fibrosis remains limited. Our results identified the role of IRF3 in regulating human HSC (LX-2 cell) cell proliferation and apoptosis. The present study indicated that the expression of IRF3 was significantly increased in HSCs in response to TGF-β1 stimulation. Moreover, a stable and unlimited source of human HSC, the LX-2 cell line, transfected with IRF3-siRNA significantly decreases the expression level of type I collagen (Col1a1) and α-smooth muscle actin (α-SMA) in activated LX-2 cells. On the contrary, overexpression of IRF3 gives rise to an upregulation of Col1a1 and α-SMA in LX-2 cells, and further promoted HSC proliferation. Moreover, the inhibition of IRF3 significantly suppressed TGF-β1-induced HSC proliferation and increased its apoptosis. Of note, the present study indicated IRF3 may regulate LX-2 cell proliferation by via AKT signaling pathway. In summary, these observations suggest IRF3 may function as a novel regulator to modulate TGF-β1-induced LX-2 proliferation, at least in part, via AKT signaling pathway.

Serum interleukin 17 as an early prognostic biomarker of severe acute pancreatitis receiving continuous blood purification

BACKGROUND

Severe acute pancreatitis (SAP) is associated with systemic inflammation, immunoparalysis, and sepsis, and may lead to vital organ failure and death. We evaluated the efficacy of serum interleukin 17 (IL-17) concentration for predicting eventual SAP severity and the clinical benefits of removing IL-17 by continuous veno-venous hemofiltration (CVVH).

METHODS

Patients were divided into 2 groups according to severity: Grade 1 (n = 18, SAP without organ dysfunction) and Grade 2 (n = 18, SAP with organ dysfunction). 20 healthy volunteers served as controls. All patients underwent 24-h CVVH and blood samples were taken at 0, 6, 12, and 24 h for measurement of bacterial load and serum IL-17, IL-6, and endotoxin. Clinical condition was graded by the sequential organ failure assessment (SOFA) score.

RESULTS

Baseline IL-17, IL-6, endotoxin, and bacterial load were higher in Grade 2 patients. SOFA scores improved significantly, and serum IL-17, IL-6, endotoxin, and bacterial load decreased significantly in all patients after CVVH. Serum IL-17 was significantly and positively correlated with IL-6, bacterial load, and endotoxin during CVVH treatment. In addition, post-CVVH serum IL-17 was directly correlated with SOFA scores on days 1 and 7, and with duration of hospital stay. Non-survivors showed both higher SOFA scores on day 1 and higher baseline IL-17 than survivors.

CONCLUSIONS

Earlier and higher serum IL-17 elevation predicted prolonged hospitalization, organ failure, and death, possibly by disrupting gut barrier function. CVVH can remove inflammatory cytokines from serum, including IL-17 and IL-6, thereby attenuating the inflammatory response and diminishing associated systemic complications.

Interferon regulatory factor 9 is a key mediator of hepatic ischemia/reperfusion injury

BACKGROUND & AIMS

Hepatic ischemia/reperfusion (I/R) injury is characterized by anoxic cell injury and the generation of inflammatory mediators, leading to hepatic parenchymal cell death. The activation of interferon regulatory factors (IRFs) has been implicated in hepatic I/R injury, but the role of IRF9 in this progression is unclear.

METHODS

We investigated the function and molecular mechanisms of IRF9 in transgene and knockout mice subjected to warm I/R of the liver. Isolated hepatocytes from IRF9 transgene and knockout mice were subjected to hypoxia/reoxygenation (H/R) injury to determine the in vitro effects of IRF9.

RESULTS

The injuries were augmented in IRF9-overexpressing mice that were subjected to warm I/R of the liver. In contrast, a deficiency in IRF9 markedly reduced the necrotic area, serum alanine amino transferase/aspartate amino transferase (ALT/AST), immune cell infiltration, inflammatory cytokine levels, and hepatocyte apoptosis after liver I/R. Sirtuin (SIRT) 1 levels were significantly higher and the acetylation of p53 was decreased in the IRF9 knockout mice. Notably, IRF9 suppressed the activity of the SIRT1 promoter luciferase reporter and deacetylase activity. Liver injuries were significantly more severe in the IRF9/SIRT1 double knockout (DKO) mice in the I/R model, eliminating the protective effects observed in the IRF9 knockout mice.

CONCLUSIONS

IRF9 has a novel function of inducing hepatocyte apoptosis after I/R injury by decreasing SIRT1 expression and increasing acetyl-p53 levels. Targeting IRF9 may be a potential strategy for ameliorating ischemic liver injury after liver surgery.

Tumor necrosis factor-related apoptosis-inducing ligand on NK cells protects from hepatic ischemia-reperfusion injury

BACKGROUND

Ischemia-reperfusion injury (IRI) significantly contributes to graft dysfunction after liver transplantation. Natural killer (NK) cells are crucial innate effector cells in the liver and express tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), a potent inducer of hepatocyte cell death. Here, we investigated if TRAIL expression on NK cells contributes to hepatic IRI.

METHODS

The outcome after partial hepatic IRI was assessed in TRAIL-null mice and contrasted to C57BL/6J wild-type mice and after NK cell adoptive transfer in RAG2/common gamma-null mice that lack T, B, and NK cells. Liver IRI was assessed by histological analysis, alanine aminotransferase, hepatic neutrophil activation by myeloperoxidase activity, and cytokine secretion at specific time points. NK cell cytotoxicity and differentiation were assessed in vivo and in vitro.

RESULTS

Twenty-four hours after reperfusion, TRAIL-null mice exhibited significantly higher serum transaminases, histological signs of necrosis, neutrophil infiltration, and serum levels of interleukin-6 compared to wild-type animals. Adoptive transfer of TRAIL-null NK cells into immunodeficient RAG2/common gamma-null mice was associated with significantly elevated liver damage compared to transfer of wild-type NK cells. In TRAIL-null mice, NK cells exhibit higher cytotoxicity and decreased differentiation compared to wild-type mice. In vitro, cytotoxicity against YAC-1 and secretion of interferon gamma by TRAIL-null NK cells were significantly increased compared to wild-type controls.

CONCLUSIONS

These experiments reveal that expression of TRAIL on NK cells is protective in a murine model of hepatic IRI through modulation of NK cell cytotoxicity and NK cell differentiation.

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.

Sterile inflammation in hepatic ischemia/reperfusion injury: present concepts and potential therapeutics

Ischemia and reperfusion (I/R) injury is an often unavoidable consequence of major liver surgery and is characterized by a sterile inflammatory response that jeopardizes the viability of the organ. The inflammatory response results from acute oxidative and nitrosative stress and consequent hepatocellular death during the early reperfusion phase, which causes the release of endogenous self-antigens known as damage-associated molecular patterns (DAMPs). DAMPs, in turn, are indirectly responsible for a second wave of reactive oxygen and nitrogen species (ROS and RNS) production by driving the chemoattraction of various leukocyte subsets that exacerbate oxidative liver damage during the later stages of reperfusion. In this review, the molecular mechanisms underlying hepatic I/R injury are outlined, with emphasis on the interplay between ROS/RNS, DAMPs, and the cell types that either produce ROS/RNS and DAMPs or respond to them. This theoretical background is subsequently used to explain why current interventions for hepatic I/R injury have not been very successful. Moreover, novel therapeutic modalities are addressed, including MitoSNO and nilotinib, and metalloporphyrins on the basis of the updated paradigm of hepatic I/R injury.