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

IRF8 aggravates nonalcoholic fatty liver disease via BMAL1/PPARγ axis

Non-alcoholic fatty liver disease (NAFLD) is a hepatic metabolic syndrome arising from lipid metabolic imbalance, with its prevalence increasing globally. In this study, we observed a significant up-regulation of interferon regulatory factor 8 (IRF8) in the liver of NAFLD model mice and patients. Overexpression of IRF8 induced lipid accumulation in the mouse primary hepatocytes. Mice with adeno-associated virus-mediated IRF8 overexpression exhibited hepatic steatosis due to up-regulated peroxisome proliferator-activated receptor γ (PPARγ) expression and increased fatty acid uptake and lipogenesis. In vitro, small interfering RNA-mediated IRF8 knockdown attenuated triglyceride accumulation by dampening PPARγ expression through transcriptional inhibition of brain and muscle ARNT-like 1. The PPARγ-specific antagonist GW9662 abolished the effect of IRF8 overexpression. Furthermore, adeno-associated virus-mediated IRF8 knockdown in the mouse liver markedly alleviated hepatic steatosis and obesity-related metabolic syndrome. These findings indicate that IRF8 plays a vital role in modulating hepatic lipid metabolism in a PPARγ-dependent manner and provide a previously unknown insight into NAFLD therapeutic strategies.

Phosphatidylserine-mediated uptake of extracellular vesicles by hepatocytes ameliorates liver ischemia-reperfusion injury

Compelling evidence suggests that mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) promote regeneration in animal models of liver injury by delivering signaling molecules. However, their target cells and uptake mechanism remain elusive. In this study, MSC-EVs were intravenously administered in a mouse model of liver ischemia-reperfusion injury (IRI). Our results revealed that MSC-EVs exhibit enhanced liver targeting in IRI mice, and injured hepatocytes display a greater capacity for MSC-EV uptake. We found that phosphatidylserine (PS) displayed on the exterior of injured hepatocytes promotes MSC-EV internalization, possibly by binding to MFGE8, a protein expressed on the MSC-EV membrane. Furthermore, the therapeutic effect of MSC-EVs on liver IRI is highly dependent on this PS-mediated uptake pathway. Our findings provide evidence that MSC-EVs preferentially target injured hepatocytes, relying on a PS-dependent uptake route to exert hepatoprotective effects, which are critical for the future design of EV-based therapeutic strategies for liver IRI.

FTO Alleviates Hepatic Ischemia-Reperfusion Injury by Regulating Apoptosis and Autophagy

Objective: Despite N6-methyladenosine (m6A) being closely involved in various pathophysiological processes, its potential role in liver injury is largely unknown. We designed the current research to study the potential role of fat mass and obesity-associated protein (FTO), an m6A demethylase, on hepatic ischemia-reperfusion injury (IRI). Methods: Wild-type mice injected with an adeno-associated virus carrying fat mass and obesity-associated protein (AAV-FTO) or adeno-associated virus carrying green fluorescent protein (GFP) (AAV-GFP) were subjected to a hepatic IRI model in vivo. Hematoxylin-eosin staining was performed to observe IRI. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining was used to observe the cell apoptosis. Reverse transcription polymerase chain reaction (RT-PCR) was used to observe the expression of FTO. The protein levels of FTO, apoptosis, or autophagy-associated signaling proteins were detected by western blot. Reactive oxygen species (ROS) levels were determined by flow cytometry, and immunohistochemistry was used to detect the FTO and LC3-II expression. For in vitro experiments, cultured hepatocytes were subjected to hypoxia/reoxygenation (H/R) stimulation. Monodansylcadaverine (MDC) staining was used to visualize autophagic vesicles. Results: In the present study, we showed that FTO was involved in hepatic IRI, apoptosis, and autophagy. Specifically, the expression level of FTO was significantly reduced in the hepatic IRI. Besides, increasing FTO expression (AAV-FTO) ameliorated the hepatic IRI in animal models, accompanied by decreased apoptosis and autophagy. Furthermore, the FTO inhibitor (FB23-2) aggravated autophagy in hepatocytes upon H/R-induced damage. Conclusion: FTO could act as a protective effector during hepatic IRI, associated with decreased apoptosis and autophagy. FTO-mediated m6A demethylation modification may be an important therapeutic target for hepatic IRI.

ALKBH5 Protects Against Hepatic Ischemia-Reperfusion Injury by Regulating YTHDF1-Mediated YAP Expression

Ischemia/reperfusion (I/R) injury with severe cell death is a major complication involved in liver transplantation and resection. The identification of key regulators improving hepatocyte activity may provide potential strategies to clinically resolve I/R-induced injury. N6-methyladenosine (m6A) RNA modification is essential for tissue homeostasis and pathogenesis. However, the potential involvement of m6A in the regulation of hepatocyte activity and liver injury has not been fully explored. In the present study, we found that hepatocyte AlkB homolog H5 (ALKBH5) levels were decreased both in vivo and in vitro I/R models. Hepatocyte-specific ALKBH5 overexpression effectively attenuated I/R-induced liver necrosis and improved cell proliferation in mice. Mechanistically, ALKBH5-mediated m6A demethylation improved the mRNA stability of YTH N6-methyladenosine RNA-binding protein 1 (YTHDF1), thereby increasing its expression, which consequently promoted the translation of Yes-associated protein (YAP). In conclusion, ALKBH5 is a regulator of hepatic I/R injury that improves hepatocyte repair and proliferation by maintaining YTHDF1 stability and YAP content. The ALKBH5-m6A-YTHDF1-YAP axis represents promising therapeutic targets for hepatic I/R injury to improve the prognosis of liver surgery.

The multiple roles of interferon regulatory factor family in health and disease

Interferon Regulatory Factors (IRFs), a family of transcription factors, profoundly influence the immune system, impacting both physiological and pathological processes. This review explores the diverse functions of nine mammalian IRF members, each featuring conserved domains essential for interactions with other transcription factors and cofactors. These interactions allow IRFs to modulate a broad spectrum of physiological processes, encompassing host defense, immune response, and cell development. Conversely, their pivotal role in immune regulation implicates them in the pathophysiology of various diseases, such as infectious diseases, autoimmune disorders, metabolic diseases, and cancers. In this context, IRFs display a dichotomous nature, functioning as both tumor suppressors and promoters, contingent upon the specific disease milieu. Post-translational modifications of IRFs, including phosphorylation and ubiquitination, play a crucial role in modulating their function, stability, and activation. As prospective biomarkers and therapeutic targets, IRFs present promising opportunities for disease intervention. Further research is needed to elucidate the precise mechanisms governing IRF regulation, potentially pioneering innovative therapeutic strategies, particularly in cancer treatment, where the equilibrium of IRF activities is of paramount importance.

Chinese herbal formula in the treatment of metabolic dysfunction-associated steatotic liver disease: current evidence and practice

Metabolic dysfunction-associated steatotic liver disease (MASLD), formerly known as nonalcoholic fatty liver disease, continues to rise with rapid economic development and poses significant challenges to human health. No effective drugs are clinically approved. MASLD is regarded as a multifaceted pathological process encompassing aberrant lipid metabolism, insulin resistance, inflammation, gut microbiota imbalance, apoptosis, fibrosis, and cirrhosis. In recent decades, herbal medicines have gained increasing attention as potential therapeutic agents for the prevention and treatment of MASLD, due to their good tolerance, high efficacy, and low toxicity. In this review, we summarize the pathological mechanisms of MASLD; emphasis is placed on the anti-MASLD mechanisms of Chinese herbal formula (CHF), especially their effects on improving lipid metabolism, inflammation, intestinal flora, and fibrosis. Our goal is to better understand the pharmacological mechanisms of CHF to inform research on the development of new drugs for the treatment of MASLD.

The Role of IRF9 Upregulation in Modulating Sensitivity to Olaparib and Platinum-Based Chemotherapies in Breast Cancer

Poly(ADP-ribose) polymerase (PARP) inhibitors are targeted therapies that accumulate DNA damage by interfering with DNA repair mechanisms and are approved for treating several cancers with BRCA1/2 mutations. In this study, we utilized CRISPR-dCas9 interference screening to identify genes regulating sensitivity to PARP inhibitors in breast cancer cell lines. Our findings indicated that the interferon (IFN) signaling gene IRF9 was critically involved in modulating sensitivity to these inhibitors. We revealed that the loss of IRF9 leads to increased resistance to the PARP inhibitor in MDA-MB-468 cells, and a similar desensitization was observed in another breast cancer cell line, MDA-MB-231. Further analysis indicated that while the basal expression of IRF9 did not correlate with the response to the PARP inhibitor olaparib, its transcriptional induction was significantly associated with increased sensitivity to the DNA-damaging agent cisplatin in the NCI-60 cell line panel. This finding suggests a mechanistic link between IRF9 induction and cellular responses to DNA damage. Additionally, data from the METABRIC patient tissue study revealed a complex network of IFN-responsive gene expressions postchemotherapy, with seven upregulated genes, including IRF9, and three downregulated genes. These findings underscore the intricate role of IFN signaling in the cellular response to chemotherapy. Collectively, our CRISPR screening data and subsequent bioinformatic analyses suggest that IRF9 is a novel biomarker for sensitivity to DNA-damaging agents, such as olaparib and platinum-based chemotherapeutic agents. Our findings for IRF9 not only enhance our understanding of the genetic basis of drug sensitivity, but also elucidate the role of IRF9 as a critical effector within IFN signaling pathways, potentially influencing the association between the host immune system and chemotherapeutic efficacy.

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.

Radiogenomics-Based Risk Prediction of Glioblastoma Multiforme with Clinical Relevance

Glioblastoma multiforme (GBM)is the most common and aggressive primary brain tumor. Although temozolomide (TMZ)-based radiochemotherapy improves overall GBM patients' survival, it also increases the frequency of false positive post-treatment magnetic resonance imaging (MRI) assessments for tumor progression. Pseudo-progression (PsP) is a treatment-related reaction with an increased contrast-enhancing lesion size at the tumor site or resection margins miming tumor recurrence on MRI. The accurate and reliable prognostication of GBM progression is urgently needed in the clinical management of GBM patients. Clinical data analysis indicates that the patients with PsP had superior overall and progression-free survival rates. In this study, we aimed to develop a prognostic model to evaluate the tumor progression potential of GBM patients following standard therapies. We applied a dictionary learning scheme to obtain imaging features of GBM patients with PsP or true tumor progression (TTP) from the Wake dataset. Based on these radiographic features, we conducted a radiogenomics analysis to identify the significantly associated genes. These significantly associated genes were used as features to construct a 2YS (2-year survival rate) logistic regression model. GBM patients were classified into low- and high-survival risk groups based on the individual 2YS scores derived from this model. We tested our model using an independent The Cancer Genome Atlas Program (TCGA) dataset and found that 2YS scores were significantly associated with the patient's overall survival. We used two cohorts of the TCGA data to train and test our model. Our results show that the 2YS scores-based classification results from the training and testing TCGA datasets were significantly associated with the overall survival of patients. We also analyzed the survival prediction ability of other clinical factors (gender, age, KPS (Karnofsky performance status), normal cell ratio) and found that these factors were unrelated or weakly correlated with patients' survival. Overall, our studies have demonstrated the effectiveness and robustness of the 2YS model in predicting the clinical outcomes of GBM patients after standard therapies.

The role of sirtuin1 in liver injury: molecular mechanisms and novel therapeutic target

Liver disease is a common and serious threat to human health. The progression of liver diseases is influenced by many physiologic processes, including oxidative stress, inflammation, bile acid metabolism, and autophagy. Various factors lead to the dysfunction of these processes and basing on the different pathogeny, pathology, clinical manifestation, and pathogenesis, liver diseases are grouped into different categories. Specifically, Sirtuin1 (SIRT1), a member of the sirtuin protein family, has been extensively studied in the context of liver injury in recent years and are confirmed the significant role in liver disease. SIRT1 has been found to play a critical role in regulating key processes in liver injury. Further, SIRT1 seems to cause divers outcomes in different types of liver diseases. Recent studies have showed some therapeutic strategies involving modulating SIRT1, which may bring a novel therapeutic target. To elucidate the mechanisms underlying the role of sirtuin1 in liver injury and its potentiality as a therapeutic target, this review outlines the key signaling pathways associated with sirtuin1 and liver injury, and discusses recent advances in therapeutic strategies targeting sirtuin1 in liver diseases.

Peptidomic Analysis Reveals that Novel Peptide LDP2 Protects Against Hepatic Ischemia/Reperfusion Injury

BACKGROUND AND AIMS

Hepatic ischemia/reperfusion (I/R) injury has become an inevitable issue during liver transplantation, with no effective treatments available. However, peptide drugs provide promising regimens for the treatment of this injury and peptidomics has gradually attracted increasing attention. This study was designed to analyze the spectrum of peptides in injured livers and explore the potential beneficial peptides involved in I/R injury.

METHODS

C57BL/6 mice were used to establish a liver I/R injury animal model. Changes in peptide profiles in I/R-injured livers were analyzed by mass spectrometry, and the functions of the identified peptides were predicted by bioinformatics. AML12 cells were used to simulate hepatic I/R injury in vitro. After treatment with candidate liver-derived peptides (LDPs) 1-10, the cells were collected at various reperfusion times for further study.

RESULTS

Our preliminary study demonstrated that 6 h of reperfusion caused the most liver I/R injury. Peptidomic results suggested that 10 down-regulated peptides were most likely to alleviate I/R injury by supporting mitochondrial function. Most importantly, a novel peptide, LDP2, was identified that alleviated I/R injury of AML12 cells. It increased cell viability and reduced the expression of inflammation- and apoptosis-related proteins. In addition, LDP2 inhibited the expression of proteins related to autophagy.

CONCLUSIONS

Investigation of changes in the profiles of peptides in I/R-injured livers led to identification of a novel peptide, LDP2 with potential function in liver protection by inhibiting inflammation, apoptosis, and autophagy.

Role of Oxidative Stress in Liver Disorders

Oxygen is vital for life as it is required for many different enzymatic reactions involved in intermediate metabolism and xenobiotic biotransformation. Moreover, oxygen consumption in the electron transport chain of mitochondria is used to drive the synthesis of ATP to meet the energetic demands of cells. However, toxic free radicals are generated as byproducts of molecular oxygen consumption. Oxidative stress ensues not only when the production of reactive oxygen species (ROS) exceeds the endogenous antioxidant defense mechanism of cells, but it can also occur as a consequence of an unbalance between antioxidant strategies. Given the important role of hepatocytes in the biotransformation and metabolism of xenobiotics, ROS production represents a critical event in liver physiology, and increasing evidence suggests that oxidative stress contributes to the development of many liver diseases. The present review, which is part of the special issue “Oxidant stress in Liver Diseases”, aims to provide an overview of the sources and targets of ROS in different liver diseases and highlights the pivotal role of oxidative stress in cell death. In addition, current antioxidant therapies as treatment options for such disorders and their limitations for future trial design are discussed.

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

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

E3 ubiquitin ligase ring finger protein 5 protects against hepatic ischemia reperfusion injury by mediating phosphoglycerate mutase family member 5 ubiquitination

BACKGROUND AND AIMS

Hepatic ischemia-reperfusion (HIR) injury, a common clinical complication of liver transplantation and resection, affects patient prognosis. Ring finger protein 5 (RNF5) is an E3 ubiquitin ligase that plays important roles in endoplasmic reticulum stress, unfolded protein reactions, and inflammatory responses; however, its role in HIR is unclear.

APPROACH AND RESULTS

RNF5 expression was significantly down-regulated during HIR in mice and hepatocytes. Subsequently, RNF5 knockdown and overexpression of cell lines were subjected to hypoxia-reoxygenation challenge. Results showed that RNF5 knockdown significantly increased hepatocyte inflammation and apoptosis, whereas RNF5 overexpression had the opposite effect. Furthermore, hepatocyte-specific RNF5 knockout and transgenic mice were established and subjected to HIR, and RNF5 deficiency markedly aggravated liver damage and cell apoptosis and activated hepatic inflammatory responses, whereas hepatic RNF5 transgenic mice had the opposite effect compared with RNF5 knockout mice. Mechanistically, RNF5 interacted with phosphoglycerate mutase family member 5 (PGAM5) and mediated the degradation of PGAM5 through K48-linked ubiquitination, thereby inhibiting the activation of apoptosis-regulating kinase 1 (ASK1) and its downstream c-Jun N-terminal kinase (JNK)/p38. This eventually suppresses the inflammatory response and cell apoptosis in HIR.

CONCLUSIONS

We revealed that RNF5 protected against HIR through its interaction with PGAM5 to inhibit the activation of ASK1 and the downstream JNK/p38 signaling cascade. Our findings indicate that the RNF5-PGAM5 axis may be a promising therapeutic target for HIR.

Regulator of G-protein signaling 14 protects the liver from ischemia-reperfusion injury by suppressing TGF-β-activated kinase 1 activation

BACKGROUND AND AIMS

Hepatic ischemia-reperfusion injury (IRI) is a common complication of hepatectomy and liver transplantation. However, the mechanisms underlying hepatic IRI have not been fully elucidated. Regulator of G-protein signaling 14 (RGS14) is a multifunctional scaffolding protein that integrates the G-protein and mitogen-activated protein kinase (MAPK) signaling pathways. However, the role of RGS14 in hepatic IRI remains unclear.

APPROACH AND RESULTS

We found that RGS14 expression increased in mice subjected to hepatic ischemia-reperfusion (IR) surgery and during hypoxia reoxygenation in hepatocytes. We constructed global RGS14 knockout (RGS14-KO) and hepatocyte-specific RGS14 transgenic (RGS14-TG) mice to establish 70% hepatic IRI models. Histological hematoxylin and eosin staining, levels of alanine aminotransferase and aspartate aminotransferase, expression of inflammatory factors, and apoptosis were used to assess liver damage and function in these models. We found that RGS14 deficiency significantly aggravated IR-induced liver injury and activated hepatic inflammatory responses and apoptosis in vivo and in vitro. Conversely, RGS14 overexpression exerted the opposite effect of the RGS14-deficient models. Phosphorylation of TGF-β-activated kinase 1 (TAK1) and its downstream effectors c-Jun N-terminal kinase (JNK) and p38 increased in the liver tissues of RGS14-KO mice but was repressed in those of RGS14-TG mice. Furthermore, inhibition of TAK1 phosphorylation rescued the effect of RGS14 deficiency on JNK and p38 activation, thus blocking the inflammatory responses and apoptosis.

CONCLUSIONS

RGS14 plays a protective role in hepatic IR by inhibiting activation of the TAK1-JNK/p38 signaling pathway. This may be a potential therapeutic strategy for reducing incidences of hepatic IRI in the future.

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.

TNFAIP3 Interacting Protein 3 Is an Activator of Hippo-YAP Signaling Protecting Against Hepatic Ischemia/Reperfusion Injury

BACKGROUND AND AIMS

Hepatic ischemia/reperfusion (I/R) injury, a common clinical problem that occurs during liver surgical procedures, causes a large proportion of early graft failure and organ rejection cases. The identification of key regulators of hepatic I/R injury may provide potential strategies to clinically improve the prognosis of liver surgery. Here, we aimed to identify the role of tumor necrosis factor alpha-induced protein 3-interacting protein 3 (TNIP3) in hepatic I/R injury and further reveal its immanent mechanisms.

APPROACH AND RESULTS

In the present study, we found that hepatocyte TNIP3 was markedly up-regulated in livers of both persons and mice subjected to I/R surgery. Hepatocyte-specific Tnip3 overexpression effectively attenuated I/R-induced liver necrosis and inflammation, but improved cell proliferation in mice, whereas TNIP3 ablation largely aggravated liver injury. This inhibitory effect of TNIP3 on hepatic I/R injury was found to be dependent on significant activation of the Hippo-YAP signaling pathway. Mechanistically, TNIP3 was found to directly interact with large tumor suppressor 2 (LATS2) and promote neuronal precursor cell-expressed developmentally down-regulated 4-mediated LATS2 ubiquitination, leading to decreased Yes-associated protein (YAP) phosphorylation at serine 112 and the activated transcription of factors downstream of YAP. Notably, adeno-associated virus delivered TNIP3 expression in the liver substantially blocked I/R injury in mice.

CONCLUSIONS

TNIP3 is a regulator of hepatic I/R injury that alleviates cell death and inflammation by assisting ubiquitination and degradation of LATS2 and the resultant YAP activation.TNIP3 represents a promising therapeutic target for hepatic I/R injury to improve the prognosis of liver surgery.

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.

The Role of Mitochondria in Liver Ischemia-Reperfusion Injury: From Aspects of Mitochondrial Oxidative Stress, Mitochondrial Fission, Mitochondrial Membrane Permeable Transport Pore Formation, Mitophagy, and Mitochondria-Related Protective Measures

Ischemia-reperfusion injury (IRI) has indeed been shown as a main complication of hepatectomy, liver transplantation, trauma, and hypovolemic shock. A large number of studies have confirmed that microvascular and parenchymal damage is mainly caused by reactive oxygen species (ROS), which is considered to be a major risk factor for IRI. Under normal conditions, ROS as a kind of by-product of cellular metabolism can be controlled at normal levels. However, when IRI occurs, mitochondrial oxidative phosphorylation is inhibited. In addition, oxidative respiratory chain damage leads to massive consumption of adenosine triphosphate (ATP) and large amounts of ROS. Additionally, mitochondrial dysfunction is involved in various organs and tissues in IRI. On the one hand, excessive free radicals induce mitochondrial damage, for instance, mitochondrial structure, number, function, and energy metabolism. On the other hand, the disorder of mitochondrial fusion and fission results in further reduction of the number of mitochondria so that it is not enough to clear excessive ROS, and mitochondrial structure changes to form mitochondrial membrane permeable transport pores (mPTPs), which leads to cell necrosis and apoptosis, organ failure, and metabolic dysfunction, increasing morbidity and mortality. According to the formation mechanism of IRI, various substances have been discovered or synthesized for specific targets and cell signaling pathways to inhibit or slow the damage of liver IRI to the body. Here, based on the development of this field, this review describes the role of mitochondria in liver IRI, from aspects of mitochondrial oxidative stress, mitochondrial fusion and fission, mPTP formation, and corresponding protective measures. Therefore, it may provide references for future clinical treatment and research.

Listeria monocytogenes infection rewires host metabolism with regulatory input from type I interferons

Listeria monocytogenes (L. monocytogenes) is a food-borne bacterial pathogen. Innate immunity to L. monocytogenes is profoundly affected by type I interferons (IFN-I). Here we investigated host metabolism in L. monocytogenes-infected mice and its potential control by IFN-I. Accordingly, we used animals lacking either the IFN-I receptor (IFNAR) or IRF9, a subunit of ISGF3, the master regulator of IFN-I-induced genes. Transcriptomes and metabolite profiles showed that L. monocytogenes infection induces metabolic rewiring of the liver. This affects various metabolic pathways including fatty acid (FA) metabolism and oxidative phosphorylation and is partially dependent on IFN-I signaling. Livers and macrophages from Ifnar1-/- mice employ increased glutaminolysis in an IRF9-independent manner, possibly to readjust TCA metabolite levels due to reduced FA oxidation. Moreover, FA oxidation inhibition provides protection from L. monocytogenes infection, explaining part of the protection of Irf9-/- and Ifnar1-/- mice. Our findings define a role of IFN-I in metabolic regulation during L. monocytogenes infection. Metabolic differences between Irf9-/- and Ifnar1-/- mice may underlie the different susceptibility of these mice against lethal infection with L. monocytogenes.

Nonalcoholic Fatty Liver Disease: An Emerging Driver of Cardiac Arrhythmia

Cardiac arrhythmias and the resulting sudden cardiac death are significant cardiovascular complications that continue to impose a heavy burden on patients and society. An emerging body of evidence indicates that nonalcoholic fatty liver disease (NAFLD) is closely associated with the risk of cardiac arrhythmias, independent of other conventional cardiometabolic comorbidities. Although most studies focus on the relationship between NAFLD and atrial fibrillation, associations with ventricular arrhythmias and cardiac conduction defects have also been reported. Mechanistic investigations suggest that a number of NAFLD-related pathophysiological alterations may potentially elicit structural, electrical, and autonomic remodeling in the heart, contributing to arrhythmogenic substrates in the heart. NAFLD is now the most common liver and metabolic disease in the world. However, the upsurge in the prevalence of NAFLD as an emerging risk factor for cardiac arrhythmias has received little attention. In this review, we summarize the clinical evidence and putative pathophysiological mechanisms for the emerging roles of NAFLD in cardiac arrhythmias, with the purpose of highlighting the notion that NAFLD may serve as an independent risk factor and a potential driving force in the development and progression of cardiac arrhythmias.

Negative Regulation of SIRT1 by IRF9 Involved in Hyperlipidemia Acute Pancreatitis Associated with Kidney Injury

BACKGROUND

Interferon regulatory factor 9 (IRF9) acts as a negative regulator of sirtuin-1 (SIRT1) to participate in many diseases. However, the role of SIRT1 and IRF9 in hyperlipidemia acute pancreatitis associated with kidney injury is unclear.

AIMS

To explore the function of SIRT1 and IRF9 in hyperlipidemia acute pancreatitis associated with kidney injury and provide theoretical guidance for disease diagnosis and treatment.

METHODS

Model rats were established by intraperitoneal injection of 20% L-arginine. Apoptosis of kidney tissue was determined by TUNEL staining. Expressions of IRF9, SIRT1, p53, and acetylated p53 were detected by qRT-PCR and Western blot. Dual-Luciferase Reporter Assay was carried out to validate the regulation of IRF9 on SIRT1.

RESULTS

Pancreatic and renal injury was more serious, and apoptosis of kidney epithelial cells increased in acute pancreatitis (AP) and hyperlipidemia acute pancreatitis (HLAP) group. IRF9, p53, and acetylated p53 were up-regulated, and SIRT1 was down-regulated in AP and HLAP group (p < 0.05). Down-regulation of SIRT1 was negatively correlated with up-regulation of IRF9 in AP and HLAP group (p < 0.05). Pancreatic and renal injury and kidney epithelial cells apoptosis in HLAP group were more obvious than AP group (p < 0.05). The up-regulation of IRF9 and down-regulation of SIRT1 in HLAP group were more than AP group (p < 0.05). The promoter activity of SIRT1 was repressed by IRF9.

CONCLUSION

In pancreatitis associated with kidney injury, IRF9 was a negative regulator of SIRT1, down-regulated the expression of SIRT1, increased acetylated p53, and promoted renal cell apoptosis. Hyperlipidemia further aggravated pancreatic and renal injury and renal cell apoptosis.

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.

Immunity as Cornerstone of Non-Alcoholic Fatty Liver Disease: The Contribution of Oxidative Stress in the Disease Progression

Non-alcoholic fatty liver disease (NAFLD) is considered the hepatic manifestation of metabolic syndrome and has become the major cause of chronic liver disease, especially in western countries. NAFLD encompasses a wide spectrum of hepatic histological alterations, from simple steatosis to steatohepatitis and cirrhosis with a potential development of hepatocellular carcinoma. Non-alcoholic steatohepatitis (NASH) is characterized by lobular inflammation and fibrosis. Several studies reported that insulin resistance, redox unbalance, inflammation, and lipid metabolism dysregulation are involved in NAFLD progression. However, the mechanisms beyond the evolution of simple steatosis to NASH are not clearly understood yet. Recent findings suggest that different oxidized products, such as lipids, cholesterol, aldehydes and other macromolecules could drive the inflammation onset. On the other hand, new evidence indicates innate and adaptive immunity activation as the driving force in establishing liver inflammation and fibrosis. In this review, we discuss how immunity, triggered by oxidative products and promoting in turn oxidative stress in a vicious cycle, fuels NAFLD progression. Furthermore, we explored the emerging importance of immune cell metabolism in determining inflammation, describing the potential application of trained immune discoveries in the NASH pathological context.

A novel function of IRF9 in acute pancreatitis by modulating cell apoptosis, proliferation, migration, and suppressing SIRT1-p53

Acute pancreatitis (AP) is an inflammatory disease caused by the abnormal activation of pancreatic enzymes in the pancreas, with a considerably high morbidity and mortality. However, the etiological factor and pathogenesis of AP are still unclear. This study was aimed to explore the role and mechanism of interferon regulatory factor 9 (IRF9) in the occurrence of AP and to provide experimental and theoretical foundation for AP diagnosis and treatment. AP model in vitro was established by caerulein-induced group. Small interfering RNA (siRNA) was designed and constructed to silence IRF9 gene. After siRNA transfected and caerulein treated successfully, the expression levels of IRF9, SIRT1, and acetylated p53 (Ac-p53) were determined by qRT-PCR and Western blot. The apoptosis, proliferation, and migration of AR42J cells were checked by flow cytometry, MTT, and transwell assay. Dual-luciferase reporter assay was implemented to validate the regulatory effect of IRF9 on SIRT1. Here, our study showed that the expression of IRF9 and Ac-p53 was increased, SIRT1 was decreased, and cell apoptosis, proliferation, and migration of AR42J cells were increased after caerulein induced. IRF9 gene silencing upregulated SIRT1, downregulated Ac-p53, and inhibited cell apoptosis, proliferation, and migration. Dual-Luciferase reporter assay showed that IRF9 could negatively regulate SIRT1. The potential mechanism was that IRF9 could modulate cell apoptosis, proliferation, migration, and bind the promoter of SIRT1 to repress SIRT1-p53. It hinted that IRF9 showed a novel function in AP by modulating cell apoptosis, proliferation, migration, and suppressing SIRT1-p53. IRF9 might be a good potential treatment target for AP.

Connexin 32 deficiency protects the liver against ischemia/reperfusion injury

Hepatic ischemia/reperfusion (I/R) injury is a common complication in the clinical setting. Our previous study has shown that connexin 32 (Cx32) plays a major role in renal I/R injury; however, the role of Cx32 in hepatic I/R injury remains unknown. Liver tissue and serum samples from patients undergoing orthotopic liver transplantation (OLT) were used to evaluate the function of Cx32 in OLT post-reperfusion injury. Then, partial hepatic ischemia was established in global Cx32 knockout mice and wild-type mice followed by reperfusion. Hepatic injury markers were examined. Cx32 small interfering RNA and the p53 inhibitor, pifithrin-α, tenovin-1 were used to examine the relationship between Cx32 and the p53/puma pathways in the BRL-3A and murine primary hepatocytes hypoxia/reoxygenation (H/R) model. Corresponding to liver damage, Cx32 was significantly induced both during OLT in human patients and partial hepatic I/R in mice. Cx32 KO mice exhibited less liver injury than controls. Cx32 deficiency significantly suppressed the p53/puma pathways and hepatocyte apoptosis. Similar results were observed in the BRL-3A and murine primary hepatocytes H/R model. Propofol protected against OLT post-reperfusion injury and hepatocyte apoptosis by inhibiting Cx32. In conclusion Cx32 is a novel regulator of hepatic I/R injury through the modulation of hepatocyte apoptosis and damage, largely via the p53/puma signaling pathway.

Relevance of SIRT1-NF-κB Axis as Therapeutic Target to Ameliorate Inflammation in Liver Disease

Inflammation is an adaptive response in pursuit of homeostasis reestablishment triggered by harmful conditions or stimuli, such as an infection or tissue damage. Liver diseases cause approximately 2 million deaths per year worldwide and hepatic inflammation is a common factor to all of them, being the main driver of hepatic tissue damage and causing progression from non-alcoholic fatty liver disease (NAFLD) to non-alcoholic steatohepatitis (NASH), cirrhosis and, ultimately, hepatocellular carcinoma (HCC). The metabolic sensor SIRT1, a class III histone deacetylase with strong expression in metabolic tissues such as the liver, and transcription factor NF-κB, a master regulator of inflammatory response, show an antagonistic relationship in controlling inflammation. For this reason, SIRT1 targeting is emerging as a potential strategy to improve different metabolic and/or inflammatory pathologies. In this review, we explore diverse upstream regulators and some natural/synthetic activators of SIRT1 as possible therapeutic treatment for liver diseases.

Role of oxidative stress in the pathogenesis of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) has emerged as the most common chronic liver disease worldwide and is strongly associated with the presence of oxidative stress. Disturbances in lipid metabolism lead to hepatic lipid accumulation, which affects different reactive oxygen species (ROS) generators, including mitochondria, endoplasmic reticulum, and NADPH oxidase. Mitochondrial function adapts to NAFLD mainly through the downregulation of the electron transport chain (ETC) and the preserved or enhanced capacity of mitochondrial fatty acid oxidation, which stimulates ROS overproduction within different ETC components upstream of cytochrome c oxidase. However, non-ETC sources of ROS, in particular, fatty acid β-oxidation, appear to produce more ROS in hepatic metabolic diseases. Endoplasmic reticulum stress and NADPH oxidase alterations are also associated with NAFLD, but the degree of their contribution to oxidative stress in NAFLD remains unclear. Increased ROS generation induces changes in insulin sensitivity and in the expression and activity of key enzymes involved in lipid metabolism. Moreover, the interaction between redox signaling and innate immune signaling forms a complex network that regulates inflammatory responses. Based on the mechanistic view described above, this review summarizes the mechanisms that may account for the excessive production of ROS, the potential mechanistic roles of ROS that drive NAFLD progression, and therapeutic interventions that are related to oxidative stress.

Emerging Molecular Targets for Treatment of Nonalcoholic Fatty Liver Disease

In parallel with the obesity epidemic, nonalcoholic fatty liver disease (NAFLD) has emerged as the most common chronic liver disease worldwide. Disequilibrium of lipid metabolism and the subsequent metabolic-stress-induced inflammation are believed to be central in the pathogenesis of NAFLD. Of note, metabolic inflammation is primarily mediated by innate immune signaling, which is increasingly recognized as a driving force in NAFLD progression. Currently, a series of agents targeting one or more of these pathomechanisms have shown encouraging results in preclinical models and clinical trials. This review summarizes the emerging molecular targets involved in signaling in the lipid metabolism and innate immunity aspects of NAFLD, focusing on their mechanistic roles and translational potentials.

Hepatic Interferon Regulatory Factor 6 Alleviates Liver Steatosis and Metabolic Disorder by Transcriptionally Suppressing Peroxisome Proliferator-Activated Receptor γ in Mice

Nonalcoholic fatty liver disease (NAFLD) has become a worldwide epidemic. A large and growing unmet therapeutic need has inspired numerous studies in the field. Integrating the published genomic data available in the Gene Expression Omnibus (GEO) with NAFLD samples from rodents, we discovered that interferon regulatory factor 6 (IRF6) is significantly downregulated in high-fat diet (HFD)-induced fatty liver. In the current study, we identified IRF6 in hepatocytes as a protective factor in liver steatosis (LS). During HFD challenge, hepatic Irf6 was suppressed by promoter hypermethylation. Severity of HFD-induced LS was exacerbated in hepatocyte-specific Irf6 knockout mice, whereas hepatocyte-specific transgenic mice overexpressing Irf6 (IRF6-HTG) exhibited alleviated steatosis and metabolic disorder in response to HFD feeding. Mechanistic studies in vitro demonstrated that hepatocyte IRF6 directly binds to the promoter of the peroxisome proliferator-activated receptor γ (PPARγ) gene and subsequently halts the transcription of Pparγ and its target genes (e.g., genes that regulate lipogenesis and lipid acid uptake) under physiological conditions. Conclusion: Irf6 is downregulated by promoter hypermethylation upon metabolic stimulus exposure, which fail to inhibit Pparγ and its targets, driving abnormalities of lipid metabolism.

Insights into the Epidemiology, Pathogenesis, and Therapeutics of Nonalcoholic Fatty Liver Diseases

Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease which affects ≈25% of the adult population worldwide, placing a tremendous burden on human health. The disease spectrum ranges from simple steatosis to steatohepatitis, fibrosis, and ultimately, cirrhosis and carcinoma, which are becoming leading reasons for liver transplantation. NAFLD is a complex multifactorial disease involving myriad genetic, metabolic, and environmental factors; it is closely associated with insulin resistance, metabolic syndrome, obesity, diabetes, and many other diseases. Over the past few decades, countless studies focusing on the investigation of noninvasive diagnosis, pathogenesis, and therapeutics have revealed different aspects of the mechanism and progression of NAFLD. However, effective pharmaceuticals are still in development. Here, the current epidemiology, diagnosis, animal models, pathogenesis, and treatment strategies for NAFLD are comprehensively reviewed, emphasizing the outstanding breakthroughs in the above fields and promising medications in and beyond phase II.

Innate Immune Signaling and Its Role in Metabolic and Cardiovascular Diseases

The innate immune system is an evolutionarily conserved system that senses and defends against infection and irritation. Innate immune signaling is a complex cascade that quickly recognizes infectious threats through multiple germline-encoded cell surface or cytoplasmic receptors and transmits signals for the deployment of proper countermeasures through adaptors, kinases, and transcription factors, resulting in the production of cytokines. As the first response of the innate immune system to pathogenic signals, inflammatory responses must be rapid and specific to establish a physical barrier against the spread of infection and must subsequently be terminated once the pathogens have been cleared. Long-lasting and low-grade chronic inflammation is a distinguishing feature of type 2 diabetes and cardiovascular diseases, which are currently major public health problems. Cardiometabolic stress-induced inflammatory responses activate innate immune signaling, which directly contributes to the development of cardiometabolic diseases. Additionally, although the innate immune elements are highly conserved in higher-order jawed vertebrates, lower-grade jawless vertebrates lack several transcription factors and inflammatory cytokine genes downstream of the Toll-like receptors (TLRs) and retinoic acid-inducible gene-I (RIG-I)-like receptors (RLRs) pathways, suggesting that innate immune signaling components may additionally function in an immune-independent way. Notably, recent studies from our group and others have revealed that innate immune signaling can function as a vital regulator of cardiometabolic homeostasis independent of its immune function. Therefore, further investigation of innate immune signaling in cardiometabolic systems may facilitate the discovery of new strategies to manage the initiation and progression of cardiometabolic disorders, leading to better treatments for these diseases. In this review, we summarize the current progress in innate immune signaling studies and the regulatory function of innate immunity in cardiometabolic diseases. Notably, we highlight the immune-independent effects of innate immune signaling components on the development of cardiometabolic disorders.

Creg in Hepatocytes Ameliorates Liver Ischemia/Reperfusion Injury in a TAK1-Dependent Manner in Mice

Hepatic ischemia/reperfusion (I/R) is a major challenge for liver surgery and specific severe conditions of chronic liver disease. Current surgical and pharmacological strategies are limited to improve liver function after hepatic I/R injury. Thus, an in-depth understanding of the liver I/R mechanism is pivotal to develop new therapeutic methods. The cellular repressor of E1A-stimulated genes (Creg), a key regulator of cellular proliferation, exerts protective roles in cardiovascular diseases and participates in lipid accumulation and inflammatory response in the liver. However, the role of Creg in hepatic I/R remains largely unknown. A genetic engineering technique was used to explore the function of Creg in hepatic I/R injury. Hepatocyte-specific Creg knockout (CregΔHep ) and transgenic mice were generated and subjected to hepatic I/R injury, as were the controls. Creg in hepatocytes prevented against liver I/R injury by suppressing cell death and inflammation. In vitro studies were performed using primary hepatocytes isolated from CregΔHep that were challenged by hypoxia/reoxygenation insult. These cells exhibited more cell death and inflammatory cytokines production similar to observations in vivo. Moreover, further molecular experiments showed that Creg suppressed mitogen-activated protein kinase (MAPK) signaling by inhibiting TAK1 (TGF-β-activated kinase 1) phosphorylation. Inhibiting TAK1 by 5Z-7-ox or mutating the TAK1-binding domain of Creg abolished the protective role of Creg indicating that Creg binding to TAK1 was required for prevention against hepatic I/R injury. Conclusion: These data demonstrate that Creg prevents hepatocytes from liver I/R injury. The Creg-TAK1 interaction inhibited the phosphorylation of TAK1 and the activation of MAPK signaling, which protected against cell death and inflammation during hepatic I/R injury.

Preconditioning of umbilical cord-derived mesenchymal stem cells by rapamycin increases cell migration and ameliorates liver ischaemia/reperfusion injury in mice via the CXCR4/CXCL12 axis

Objectives

Transfusion of umbilical cord‐derived mesenchymal stem cells (UC‐MSCs) is a novel strategy for treatment of various liver diseases. However, the therapeutic effect of UC‐MSCs is limited because only a few UC‐MSCs migrate towards the damaged regions. In this study, we observed the effects of autophagy on the migration of UC‐MSCs in vitro and in a model of liver ischaemia/reperfusion (I/R) injury.

Materials and Methods

We investigated the effects of autophagy on the status of the cell, release of anti‐inflammatory factors and migration of UC‐MSCs in vitro. The therapeutic effects and in vivo migration of rapamycin‐preconditioned UC‐MSCs were observed in a C57/B6 mouse model of liver I/R injury.

Results

Induction of autophagy by rapamycin enhanced the ability of UC‐MSCs to migrate and release anti‐inflammatory cytokines as well as increased expression of CXCR4 without affecting cell viability. Inhibition of CXCR4 activation markedly decreased migration of these cells. In a mouse model of liver I/R injury, we found significantly upregulated expression of CXCR12 in the damaged liver. More rapamycin‐preconditioned UC‐MSCs migrated towards the ischaemic regions than 3‐methyladenine‐preconditioned or non‐preconditioned UC‐MSCs, leading to improvement in hepatic performance, pathological changes and levels of inflammatory cytokines. These effects were abolished by AMD3100.

Conclusions

Preconditioning of UC‐MSCs by rapamycin afforded increased protection against liver I/R injury by enhancing immunosuppression and strengthening the homing and migratory capacity of these cells via the CXCR4/CXCL12 axis.

Monocyte Chemoattractant Protein-Induced Protein 1 Targets Hypoxia-Inducible Factor 1α to Protect Against Hepatic Ischemia/Reperfusion Injury

Sterile inflammation is an essential factor causing hepatic ischemia/reperfusion (I/R) injury. As a critical regulator of inflammation, the role of monocyte chemoattractant protein-induced protein 1 (MCPIP1) in hepatic I/R injury remains undetermined. In this study, we discovered that MCPIP1 downregulation was associated with hepatic I/R injury in liver transplant patients and a mouse model. Hepatocyte-specific Mcpip1 gene knockout and transgenic mice demonstrated that MCPIP1 functions to ameliorate liver damage, reduce inflammation, prevent cell death, and promote regeneration. A mechanistic study revealed that MCPIP1 interacted with and maintained hypoxia-inducible factor 1α (HIF-1α) expression by deubiquitinating HIF-1α. Notably, the HIF-1α inhibitor reversed the protective effect of MCPIP1, whereas the HIF-1α activator compensated for the detrimental effect of MCPIP1 deficiency. Thus, we identified the MCPIP1-HIF-1α axis as a critical pathway that may be a good target for intervention in hepatic I/R injury. (Hepatology 2018; 00:000-000).

Caspase recruitment domain 6 protects against hepatic ischemia/reperfusion injury by suppressing ASK1

BACKGROUND & AIMS

The hepatic injury caused by ischemia/reperfusion (I/R) insult is predominantly determined by the complex interplay of sterile inflammation and liver cell death. Caspase recruitment domain family member 6 (CARD6) was initially shown to play important roles in NF-κB activation. In our preliminary studies, CARD6 downregulation was closely related to hepatic I/R injury in liver transplantation patients and mouse models. Thus, we hypothesized that CARD6 protects against hepatic I/R injury and investigated the underlying molecular mechanisms.

METHODS

A partial hepatic I/R operation was performed in hepatocyte-specific Card6 knockout mice (HKO), Card6 transgenic mice with CARD6 overexpression specifically in hepatocytes (HTG), and the corresponding control mice. Hepatic histology, serum aminotransferases, inflammatory cytokines/chemokines, cell death, and inflammatory signaling were examined to assess liver damage. The molecular mechanisms of CARD6 function were explored in vivo and in vitro.

RESULTS

Liver injury was alleviated in Card6-HTG mice compared with control mice as shown by decreased cell death, lower serum aminotransferase levels, and reduced inflammation and infiltration, whereas Card6-HKO mice had the opposite phenotype. Mechanistically, phosphorylation of ASK1 and its downstream effectors JNK and p38 were increased in the livers of Card6-HKO mice but repressed in those of Card6-HTG mice. Furthermore, ASK1 knockdown normalized the effect of CARD6 deficiency on the activation of NF-κB, JNK and p38, while ASK1 overexpression abrogated the suppressive effect of CARD6. CARD6 was also shown to interact with ASK1. Mutant CARD6 that lacked the ability to interact with ASK1 could not inhibit ASK1 and failed to protect against hepatic I/R injury.

CONCLUSIONS

CARD6 is a novel protective factor against hepatic I/R injury that suppresses inflammation and liver cell death by inhibiting the ASK1 signaling pathway.

LAY SUMMARY

The protein CARD6 plays an important role during the process of liver blood flow restriction (ischemia) and restoration (reperfusion). By suppressing the activity of ASK1, CARD6 can protect against hepatocyte injury. Targeting CARD6 is a potential strategy for prevention and treatment of ischemia/reperfusion injury.

Interferon regulatory factors: Where to stand in transplantation

Interferon regulatory factors (IRFs) are implicated in regulating inflammatory responses to pathogens and alloantigens. Since transplantation is usually accompanied by ischemia reperfusion injury (IRI), acute and chronic rejections, as well as immunodeficiency due to immunosuppressive drugs, IRFs seem to play a considerable role in allograft outcome. For instance, IRF-1 has been shown to be involved in pathogenesis of IRI; however, IRF-2 exhibits an opposite function. Some IRF-3 and 5 SNPs are associated with better or worse graft survival rates. Of note, IRF-4 inhibition has resulted in improved transplant outcomes. Herein we review available studies about IRFs influence on various stages of transplantation.

Danger-Associated Molecular Patterns (DAMPs): Molecular Triggers for Sterile Inflammation in the Liver

Inflammatory liver diseases in the absence of pathogens such as intoxication by xenobiotics, cholestatic liver injury, hepatic ischemia-reperfusion injury (I/R), non-alcoholic steatohepatitis (NASH), or alcoholic liver disease (ALD) remain threatening conditions demanding specific therapeutic options. Caused by various different noxae, all these conditions have been recognized to be triggered by danger- or death-associated molecular patterns (DAMPs), discompartmentalized self-structures released by dying cells. These endogenous, ectopic molecules comprise proteins, nucleic acids, adenosine triphosphate (ATP), or mitochondrial compounds, among others. This review resumes the respective modes of their release—passively by necrotic hepatocytes or actively by viable or apoptotic parenchymal cells—and their particular roles in sterile liver pathology. It addresses their sensors and the initial inflammatory responses they provoke. It further addresses a resulting second wave of parenchymal death that might be of different mode, boosting the release of additional, second-line DAMPs. Thus, triggering a more complex and pronounced response. Initial and secondary inflammatory responses comprise the activation of Kupffer cells (KCs), the attraction and activation of monocytes and neutrophil granulocytes, and the induction of type I interferons (IFNs) and their effectors. A thorough understanding of pathophysiology is a prerequisite for identifying rational therapeutic targets.

Innate Immune Signaling in Nonalcoholic Fatty Liver Disease and Cardiovascular Diseases

The physiological significance of innate immune signaling lies primarily in its role in host defense against invading pathogens. It is becoming increasingly clear that innate immune signaling also modulates the development of metabolic diseases, especially nonalcoholic fatty liver disease and cardiovascular diseases, which are characterized by chronic, low-grade inflammation due to a disarrangement of innate immune signaling. Notably, recent studies indicate that in addition to regulating canonical innate immune-mediated inflammatory responses (or immune-dependent signaling-induced responses), molecules of the innate immune system regulate pathophysiological responses in multiple organs during metabolic disturbances (termed immune-independent signaling-induced responses), including the disruption of metabolic homeostasis, tissue repair, and cell survival. In addition, emerging evidence from the study of immunometabolism indicates that the systemic metabolic status may have profound effects on cellular immune function and phenotypes through the alteration of cell-intrinsic metabolism. We summarize how the innate immune system interacts with metabolic disturbances to trigger immune-dependent and immune-independent pathogenesis in the context of nonalcoholic fatty liver disease, as representative of metabolic diseases, and cardiovascular diseases.

Interferon Regulatory Factor 9 Structure and Regulation

Interferon regulatory factor 9 (IRF9) is an integral transcription factor in mediating the type I interferon antiviral response, as part of the interferon-stimulated gene factor 3. However, the role of IRF9 in many important non-communicable diseases has just begun to emerge. The duality of IRF9's role in conferring protection but at the same time exacerbates diseases is certainly puzzling. The regulation of IRF9 during these conditions is not well understood. The high homology of IRF9 DNA-binding domain to other IRFs, as well as the recently resolved IRF9 IRF-associated domain structure can provide the necessary insights for progressive inroads on understanding the regulatory mechanism of IRF9. This review sought to outline the structural basis of IRF9 that guides its regulation and interaction in antiviral immunity and other diseases.

Common variation near IRF6 is associated with IFN-β-induced liver injury in multiple sclerosis

Multiple sclerosis (MS) is a disease of the central nervous system treated with disease-modifying therapies, including the biologic, interferon-β (IFN-β). Up to 60% of IFN-β-exposed MS patients develop abnormal biochemical liver test results^1,2, and 1 in 50 experiences drug-induced liver injury³. Since genomic variation contributes to other forms of drug-induced liver injury^4,5, we aimed to identify biomarkers of IFN-β-induced liver injury using a two-stage genome-wide association study. The rs2205986 variant, previously linked to differential expression of IRF6, surpassed genome-wide significance in the combined two-stage analysis (P = 2.3 × 10^-8, odds ratio = 8.3, 95% confidence interval = 3.6-19.2). Analysis of an independent cohort of IFN-β-treated MS patients identified via electronic medical records showed that rs2205986 was also associated with increased peak levels of aspartate aminotransferase (P = 7.6 × 10^-5) and alkaline phosphatase (P = 4.9 × 10^-4). We show that these findings may be applicable to predicting IFN-β-induced liver injury, offering insight into its safer use.

The IRF9-SIRT1-P53 axis is involved in the growth of human acute myeloid leukemia

Acute myeloid leukemia (AML) is a highly heterogeneous disease, with biologically and prognostically different subtypes. Although a growing number of distinct AML subsets have been increasingly characterized, patient management has remained disappointingly uniform. The molecular mechanism underlying AML needs to be further investigated. Here we identify IRF9 as a negative regulator of human AML. We show that IRF9 mRNA and protein levels are down-regulated in human AML samples compared with samples from healthy donors. IRF9 knockdown promotes proliferation, colony formation and survival of OCI/AML-2 and OCI/AML-3 cells, whereas IRF9 overexpression obtains oppose results. Mechanism analysis shows that IRF9 binds SIRT1 promoter and represses SIRT1 expression in OCI/AML-2 and OCI/AML-3 cells. In AML samples, the expression of SIRT1 is up-regulated and negatively correlated with IRF9 level. IRF9 also increases the acetylation of p53, a deacetylation substrate of SIRT1, and promotes the expression of p53 target genes. Knockdown of p53 blocks the effects of IRF9 on cell survival and growth in vitro. These findings provide evidence that IRF9 serves as an important regulator in human AML by repressing SIRT1-p53 pathway and that IRF9 may be a potential target for AML treatment.

Identification of biomarkers for pseudo and true progression of GBM based on radiogenomics study

The diagnosis for pseudoprogression (PsP) and true tumor progression (TTP) of GBM is a challenging task in clinical practices. The purpose of this study is to identify potential genetic biomarkers associated with PsP and TTP based on the clinical records, longitudinal imaging features, and genomics data. We are the first to introduce the radiogenomics approach to identify candidate genes for PsP and TTP of GBM. Specifically, a novel longitudinal sparse regression model was developed to construct the relationship between gene expression and imaging features. The imaging features were extracted from tumors along the longitudinal MRI and provided diagnostic information of PsP and TTP. The 33 candidate genes were selected based on their association with the imaging features, reflecting their relation with the development of PsP and TTP. We then conducted biological relevance analysis for 33 candidate genes to identify the potential biomarkers, i.e., Interferon regulatory factor (IRF9) and X-ray repair cross-complementing gene (XRCC1), which were involved in the cancer suppression and prevention, respectively. The IRF9 and XRCC1 were further independently validated in the TCGA data. Our results provided the first substantial evidence that IRF9 and XRCC1 can serve as the potential biomarkers for the development of PsP and TTP.

The deubiquitinating enzyme TNFAIP3 mediates inactivation of hepatic ASK1 and ameliorates nonalcoholic steatohepatitis

Activation of apoptosis signal-regulating kinase 1 (ASK1) in hepatocytes is a key process in the progression of nonalcoholic steatohepatitis (NASH) and a promising target for treatment of the condition. However, the mechanism underlying ASK1 activation is still unclear, and thus the endogenous regulators of this kinase remain open to be exploited as potential therapeutic targets. In screening for proteins that interact with ASK1 in the context of NASH, we identified the deubiquitinase tumor necrosis factor alpha-induced protein 3 (TNFAIP3) as a key endogenous suppressor of ASK1 activation, and we found that TNFAIP3 directly interacts with and deubiquitinates ASK1 in hepatocytes. Hepatocyte-specific ablation of Tnfaip3 exacerbated nonalcoholic fatty liver disease- and NASH-related phenotypes in mice, including glucose metabolism disorders, lipid accumulation and enhanced inflammation, in an ASK1-dependent manner. In contrast, transgenic or adeno-associated virus-mediated TNFAIP3 gene delivery in the liver in both mouse and nonhuman primate models of NASH substantially blocked the onset and progression of the disease. These results implicate TNFAIP3 as a functionally important endogenous suppressor of ASK1 hyperactivation in the pathogenesis of NASH and identify it as a potential new molecular target for NASH therapy.

Insights into innate immune signalling in controlling cardiac remodelling

Canonical innate immune signalling involves complex cascades: multiple germline-encoded pattern recognition receptors rapidly recognize pathogen-associated or damage-associated molecular patterns to induce the production of cytokines, which bind to their corresponding receptors to orchestrate subsequent host defense phases. Inflammation is a healthy response to pathogenic signals, which are typically rapid and specific, and they terminate once the threat has passed. However, excessive activation or suppression of innate immune or inflammatory responses can lead to considerable human suffering, such as cardiac remodelling. Interestingly, recent studies have revealed that innate immune molecules in the parenchymal cells of the heart influence cardiac homeostasis not only by directly regulating innate immune responses but also through reprogrammed signalling pathways, which are independent of conventional innate immune signalling. Elucidating 'innate immune signalling reprogramming' events will help us better understand the functions of innate immune molecules and, moreover, the pathogenesis of cardiac diseases.

Dusp14 protects against hepatic ischaemia-reperfusion injury via Tak1 suppression

BACKGROUND & AIMS

Hepatic ischaemia-reperfusion (I/R) injury is characterised by severe inflammation and extensive cell death. Multiple signalling pathways, including NF-κB and mitogen-activated protein kinase (MAPK)/c-Jun NH2-terminal kinase (JNK), have important roles in this process. Identifying the unknown critical regulators of these signalling pathways could provide potential targets for therapeutic application. Dual-specificity phosphatase 14 (DUSP14) acts as a negative regulator of NF-κB signalling. However, its function in hepatic I/R injury is unknown.

METHODS

Hepatocyte-specific Dusp14 knockout (HKO) and transgenic (TG) mice were subjected to hepatic I/R surgery to examine Dusp14 function in vivo. Primary hepatocytes isolated from Dusp14-HKO and Dusp14-TG mice were cultured and subjected to hypoxia/reoxygenation insult in vitro. Inflammatory cytokine production was measured using quantitative reverse transcription PCR and ELISA. Liver damage was analysed using histopathology. Co-immunoprecipitation and pull-down assays followed by Western blot were performed to detect Dusp14 and transforming growth factor (Tgf)-β-activated kinase 1 (Tak1) interactions.

RESULTS

Dusp14 was significantly downregulated in liver tissues from liver transplantation patients and mice subjected to hepatic I/R surgery. Dusp14-HKO and Dusp14-TG mouse models demonstrated that Dusp14 reduced cell death, ameliorated inflammation, and promoted hepatocyte proliferation and/or regeneration. Dusp14 also suppressed NF-κB and MAPK signalling via a physical interaction with Tak1, leading to its subsequent inhibition. Tak1 inhibition by 5Z-7-ox abolished Dusp14 function in vivo, indicating that TAK1 is required for Dusp14 function in hepatic I/R injury. Finally, mutant Dusp14 lost the ability to bind Tak1 and failed to protect against hepatic I/R injury.

CONCLUSIONS

Dusp14 is a protective factor in hepatic I/R injury, and the Dusp14-Tak1-Jnk1/2 regulatory axis is important for the pathogenesis of hepatic I/R injury. Modulation of this axis could be a novel therapeutic strategy to prevent or interfere with this pathological process.

LAY SUMMARY

Reductions in the level of the protein Dusp14 are closely associated with liver damage caused by inadequate blood supply followed by restoration of blood flow to the liver. Dusp14 protects against liver damage by suppressing the activity of Tak1. Targeting Dusp14 could be a strategy for prevention and treatment of this disease.

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.

Reprogramming Interferon Regulatory Factor Signaling in Cardiometabolic Diseases

Interferon regulatory factors (IRFs) are evolutionarily conserved proteins expressed not only in immune cells but also in other tissues and organs outside the immune system. In this review, we discuss mechanisms responsible for IRF-mediated innate immune responses and the function and mechanism of IRFs in cardiometabolic diseases. We focus on the role of IRFs in innate immunity and cardiometabolic homeostasis, and highlight reprogrammed IRF signaling.

Altered miR-370 expression in hepatic ischemia-reperfusion injury correlates with the level of nuclear kappa B (NF-κB) related factors

BACKGROUND & AIMS

MicroRNAs (miRNAs) are a class of small endogenous, non-coding RNAs that regulate gene expression at both the transcription and translation levels. Whether miRNAs have taken part in liver ischemia-reperfusion (IR) injury was rarely reported. The purpose of this article is to investigate the potential role of miR-370 in hepatic IR injury.

METHODS

Male C57BL/6 mice were divided into 5 groups (sham-operated group, I/R group, IPC group, antagomir-370 group and antagomir-NC), and the expression levels of miR-370 were assessed by quantitative real-time PCR. Serum enzyme analysis and histological examination of liver were used as the index of the effect of miR-370 on hepatic IR injury and following treatment of mice with antagomir-370 or antagomir-NC. The classical pathway factors of NF-κB (TAK₁, TAB₁, TAB₂, IkBα, IKKα, IKKβ, p50, p65) were studied by quantitative real-time PCR and Western blot.

RESULTS

The results showed that the IR group's miR-370 expression level was significantly upregulated as compared with the sham-operated group and IPC group. Also inhibition of miR-370 led to the low expression levels of miR-370 and low levels of serum aminotransferase and hepatic histological damage as compared with the IR group. Quantitative real-time PCR showed the levels of TAK1, TAB₁, TAB2, IkBα, IKKα, p65 was elevated when improving the miR-370 levels, at the same time, Western blot showed the levels of TAK₁, TAB₁, TAB₂, IkBα, IKKα, IKKβ, p50, p65 were all elevated.

CONCLUSION

miR-370 acting via NF-κB might play a crucial role in hepatic IR injury, and inhibition of miR-370 could alleviate the injury to the liver. And miR-370 might positively regulated the NF-κB pathway.