Loss of caspase-8 in hepatocytes accelerates the onset of liver regeneration in mice through premature nuclear factor kappa B activation

Exploring caspase functions in mouse models

Caspases are enzymes with protease activity. Despite being known for more than three decades, caspase investigation still yields surprising and fascinating information. Initially associated with cell death and inflammation, their functions have gradually been revealed to extend beyond, targeting pathways such as cell proliferation, migration, and differentiation. These processes are also associated with disease mechanisms, positioning caspases as potential targets for numerous pathologies including inflammatory, neurological, metabolic, or oncological conditions. While in vitro studies play a crucial role in elucidating molecular pathways, they lack the context of the body's complexity. Therefore, laboratory animals are an indispensable part of successfully understanding and applying caspase networks. This paper aims to summarize and discuss recent knowledge, understanding, and challenges in caspase knock-out mice.

Caspase-9 Is a Positive Regulator of Osteoblastic Cell Migration Identified by diaPASEF Proteomics

Caspase-9 is traditionally considered the initiator caspase of the intrinsic apoptotic pathway. In the past decade, however, other functions beyond initiation/execution of cell death have been described including cell type-dependent regulation of proliferation, differentiation/maturation, mitochondrial, and endosomal/lysosomal homeostasis. As previous studies revealed nonapoptotic functions of caspases in osteogenesis and bone homeostasis, this study was performed to identify proteins and pathways deregulated by knockout of caspase-9 in mouse MC3T3-E1 osteoblasts. Data-independent acquisition-parallel accumulation serial fragmentation (diaPASEF) proteomics was used to compare protein profiles of control and caspase-9 knockout cells. A total of 7669 protein groups were quantified, and 283 upregulated/141 downregulated protein groups were associated with the caspase-9 knockout phenotype. The deregulated proteins were mainly enriched for those associated with cell migration and motility and DNA replication/repair. Altered migration was confirmed in MC3T3-E1 cells with the genetic and pharmacological inhibition of caspase-9. ABHD2, an established regulator of cell migration, was identified as a possible substrate of caspase-9. We conclude that caspase-9 acts as a modulator of osteoblastic MC3T3-E1 cell migration and, therefore, may be involved in bone remodeling and fracture repair.

Apoptotic cell death in disease-Current understanding of the NCCD 2023

Apoptosis is a form of regulated cell death (RCD) that involves proteases of the caspase family. Pharmacological and genetic strategies that experimentally inhibit or delay apoptosis in mammalian systems have elucidated the key contribution of this process not only to (post-)embryonic development and adult tissue homeostasis, but also to the etiology of multiple human disorders. Consistent with this notion, while defects in the molecular machinery for apoptotic cell death impair organismal development and promote oncogenesis, the unwarranted activation of apoptosis promotes cell loss and tissue damage in the context of various neurological, cardiovascular, renal, hepatic, infectious, neoplastic and inflammatory conditions. Here, the Nomenclature Committee on Cell Death (NCCD) gathered to critically summarize an abundant pre-clinical literature mechanistically linking the core apoptotic apparatus to organismal homeostasis in the context of disease.

The Role of Caspase Family in Acute Brain Injury: The Potential Therapeutic Targets in the Future

The caspase family is commonly involved in the pathophysiology of acute brain injury (ABI) through complex apoptotic, pyroptotic, and inflammatory pathways. Current translational strategies for caspase modulation in ABI primarily focus on caspase inhibitors. Because there are no caspase-inhibiting drugs approved for clinical use on the market, the development of caspase inhibitors remains an attractive challenge for researchers and clinicians. Therefore, we conducted the present review with the aim of providing a comprehensive introduction of caspases in ABI. In this review, we summarized the available evidence and potential mechanisms regarding the biological function of caspases. We also reviewed the therapeutic effects of caspase inhibitors on ABI and its subsequent complications. However, various important issues remain unclear, prompting further verification of the efficacy and safety regarding clinical application of caspase inhibitors. We believe that our work will be helpful to further understand the critical role of the caspase family and will provide novel therapeutic potential for ABI treatment.

System biology-based investigation of Silymarin to trace hepatoprotective effect

Silymarin is used as a hepatoprotective agent since ancient times which could be via its potent anti-oxidant effect. However, the mode of silymarin for the hepatoprotective effect has not been established with the targets involved in hepatic cirrhosis. The present study investigated the multiple interactions of the flavonolignans from Silybum marianum with targets involved in hepatic cirrhosis using a series of system biology approaches. Chemo-informative tools and databases i.e. DIGEP-Pred and DisGeNET were used to predict the targets of flavonolignans and proteins involved in liver cirrhosis respectively. Further, STRING was used to enrich the protein-protein interaction for the flavonolignans-modulated targets. Similarly, molecular docking was performed using AutoDock Vina. Additionally, molecular dynamics simulation and MM-PBSA calculations were carried out for the lead-hit complexes by GROMACS. Thirteen flavonolignans were identified from S. marianum, in which silymonin exhibited the highest drug-likeness score i.e. 1.09. Similarly, CTNNB1 was found to be regulated by the 12 different flavonolignans and was majorly expressed within the compound(s)-protein(s)-pathway(s) network. Further, silymonin had the highest binding affinity; binding energy -9.2 kcal/mol with the CTNNB1 and formed very stable hydrogen bond interactions with Arg332, Ser336, Lys371, and Arg475 throughout 100 ns molecular dynamic production run. The binding free energy of CTNNB1-silymonin complex was found to be -15.83 ± 2.71 kcal/mol. The hepatoprotective property of S. marianum may be due to the presence of silymonin and silychristin; this could majorly modulate CTNNB1, HMOX1, and CASP8 in combination with other flavonolignans. Our findings further suggest designing the in-vitro and in-vivo studies to validate the interaction of flavonolignans with identified targets to strengthen present findings of S. marianum as a hepatoprotective..

COMMD10 inhibits tumor progression and induces apoptosis by blocking NF-κB signal and values up BCLC staging in predicting overall survival in hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is the third leading cause of cancer mortality worldwide. Currently, there is limited knowledge of dysregulation of cellular proliferation and apoptosis that contribute to the malignant phenotype in HCC. Copper metabolism gene MURR1 domain 10 (COMMD10) is initially identified as a suppressor gene in the pathogenesis of HCC in our observations. Here we aimed to explore its function and prognostic value in the progression of HCC.

METHODS

Functional experiments were performed to explore the role of COMMD10 in HCC. The molecular mechanisms of COMMD10 were determined by luciferase assay, immunofluorescence, and immunoprecipitation. The nomogram was based on a retrospective and multicenter study of 516 patients who were pathologically diagnosed with HCC from three Chinese hospitals. The predictive accuracy and discriminative ability of the nomogram were determined by a C-index and calibration curve and were compared with COMMD10 and the Barcelona Clinic Liver Cancer (BCLC) staging system. The primary endpoint was overall survival (OS).

RESULTS

COMMD10 expression was significantly lower in HCC than that in normal liver tissues. In vitro and in vivo experiments revealed that COMMD10 suppressed cell proliferation and induced apoptosis in HCC. Mechanistically, COMMD10 inhibits TNFα mediated ubiquitination of IκBα and p65 nuclear translocation through the combination of COMMD10-N terminal to the Rel homology domain of p65, which inhibited NF-κB activity and increased expression of cleaved caspase9/3 in HCC. Clinically, COMMD10 stratifies early-stage HCC patients into two risk groups with significantly different OS. Additionally, the nomogram based on COMMD10 and BCLC stage yielded more accuracy than BCLC stage alone for predicting OS of HCC patients in three cohorts.

CONCLUSIONS

COMMD10 suppresses proliferation and promotes apoptosis by inhibiting NF-κB signaling and values up BCLC staging in predicting OS, which provides evidence for the identification of potential therapeutic targets and the accurate prediction of prognosis for patients with HCC.

Expression of the Metalloproteinase ADAM8 Is Upregulated in Liver Inflammation Models and Enhances Cytokine Release In Vitro

Acute and chronic liver inflammation is driven by cytokine and chemokine release from various cell types in the liver. Here, we report that the induction of inflammatory mediators is associated with a yet undescribed upregulation of the metalloproteinase ADAM8 in different murine hepatitis models. We further show the importance of ADAM8 expression for the production of inflammatory mediators in cultured liver cells. As a model of acute inflammation, we investigated liver tissue from lipopolysaccharide- (LPS-) treated mice in which ADAM8 expression was markedly upregulated compared to control mice. In vitro, stimulation with LPS enhanced ADAM8 expression in murine and human endothelial and hepatoma cell lines as well as in primary murine hepatocytes. The enhanced ADAM8 expression was associated with an upregulation of TNF-α and IL-6 expression and release. Inhibition studies indicate that the cytokine response of hepatoma cells to LPS depends on the activity of ADAM8 and that signalling by TNF-α can contribute to these ADAM8-dependent effects. The role of ADAM8 was further confirmed with primary hepatocytes from ADAM8 knockout mice in which TNF-α and IL-6 induction and release were considerably attenuated. As a model of chronic liver injury, we studied liver tissue from mice undergoing high-fat diet-induced steatohepatitis and again observed upregulation of ADAM8 mRNA expression compared to healthy controls. In vitro, ADAM8 expression was upregulated in hepatoma, endothelial, and stellate cell lines by various mediators of steatohepatitis including fatty acid (linoleic-oleic acid), IL-1β, TNF-α, IFN-γ, and TGF-β. Upregulation of ADAM8 was associated with the induction and release of proinflammatory cytokines (TNF-α and IL-6) and chemokines (CX3CL1). Finally, knockdown of ADAM8 expression in all tested cell types attenuated the release of these mediators. Thus, ADAM8 is upregulated in acute and chronic liver inflammation and is able to promote inflammation by enhancing expression and release of inflammatory mediators.

25 years of research put RIPK1 in the clinic

Receptor Interacting Protein Kinase 1 (RIPK1) is a key regulator of inflammation. To warrant cell survival and appropriate immune responses, RIPK1 is post-translationally regulated by ubiquitylations, phosphorylations and caspase-8-mediated cleavage. Dysregulations of these post-translational modifications switch on the pro-death function of RIPK1 and can cause inflammatory diseases in humans. Conversely, activation of RIPK1 cytotoxicity can be advantageous for cancer treatment. Small molecules targeting RIPK1 are under development for the treatment of cancer, inflammatory and neurogenerative disorders. We will discuss the molecular mechanisms controlling the functions of RIPK1, its pathologic role in humans and the therapeutic opportunities in targeting RIPK1, specifically in the context of inflammatory diseases and cancers.

The knowns and unknowns of treatment for alcoholic hepatitis

Alcoholic hepatitis is an acute, inflammatory liver disease associated with high morbidity and mortality both in the short term and long term. Alcoholic hepatitis often arises in patients with a background of chronic liver disease and it is characterised by the rapid onset of jaundice and the development of myriad complications. Medical therapy for severe alcoholic hepatitis relies on corticosteroids, which have modest effectiveness. Abstinence from alcohol is critically important in patients with alcoholic hepatitis, but recidivism is high. Because of the absence of effective medical treatments for alcoholic hepatitis and alcohol dependency, there is a pressing need to develop new and effective therapeutics. Supported by promising preliminary and preclinical studies, many ongoing clinical trials of new therapies for alcoholic hepatitis are currently underway and are discussed further in this Series paper.

Influence of Fat on Differential Receptor Interacting Serine/Threonine Protein Kinase 1 Activity Leading to Apoptotic Cell Death in Murine Liver Ischemia Reperfusion Injury Through Caspase 8

Current understanding is that receptor interacting serine/threonine protein kinase 1 (RIPK1) can lead to two distinct forms of cell death: RIPK3‐mediated necroptosis or caspase 8 (Casp8)‐mediated apoptosis. Here, we report that RIPK1 signaling is indispensable for protection from hepatocellular injury in a steatotic liver undergoing ischemia reperfusion injury (IRI) but not in the lean liver. In lean liver IRI, RIPK1‐mediated cell death is operational, leading to protection in RIP1 kinase‐dead knock‐in (RIPK1^K45A) mice and necrostatin‐1s (Nec1s)‐treated lean wild‐type (WT) mice. However, when fed a high‐fat diet (HFD), RIPK1^K45A‐treated and Nec1s‐treated WT mice undergoing IRI demonstrate exacerbated hepatocellular injury along with decreased RIPK1 ubiquitylation. Furthermore, we demonstrate that HFD‐fed RIPK3^–/–/Casp8^–/– mice show protection from IRI, but HFD‐fed RIPK3^–/–/Casp8^–/+ mice do not. We also show that blockade of RIPK1 leads to increased Casp8 activity and decreases mitochondrial viability. Conclusion: Although more studies are required, we provide important proof of concept for RIPK1 inhibition leading to distinctive outcomes in lean and steatotic liver undergoing IRI. Considering the rising incidence of nonalcoholic fatty liver disease (NAFLD) in the general population, it will be imperative to address this critical difference when treating patients with RIPK1 inhibitors. This study also presents a new target for drug therapy to prevent hepatocellular injury in NAFLD.

Distinct role of nuclear receptor corepressor 1 regulated de novo fatty acids synthesis in liver regeneration and hepatocarcinogenesis in mice

It is urgent that the means to improve liver regeneration (LR) be found, while mitigating the concurrent risk of hepatocarcinogenesis (HCG). Nuclear receptor corepressor 1 (NCoR1) is a co-repressor of nuclear receptors, which regulates the expression level of metabolic genes; however, little is known about its potential contribution for LR and HCG. Here, we found that liver-specific NCoR1 knockout in mice (NCoR1^Δhep ) dramatically enhances LR after partial hepatectomy and, surprisingly, blocks the process of diethylnitrosamine (DEN)-induced HCG. Both RNA-sequencing and metabolic assay results revealed improved expression of Fasn and Acc2 in NCoR1^Δhep mice, suggesting the critical role of de novo fatty acid synthesis (FAS) in LR. Continual enhanced de novo FAS in NCoR1^Δhep mice resulted in overwhelmed adenosine triphosphate ATP and nicotinamide adenine dinucleotide phosphate (NADPH) consumption and increased mitochondrial reactive oxygen species production, which subsequently attenuated HCG through inducing apoptosis of hepatocytes at an early stage after DEN administration.

CONCLUSION

NCoR1 functions as a negative modulator for hepatic de novo FAS and mitochondria energy adaptation, playing distinct roles in regeneration or carcinogenesis. (Hepatology 2018;67:1071-1087).

The in vivo evidence for regulated necrosis

Necrosis is a hallmark of several widespread diseases or their direct complications. In the past decade, we learned that necrosis can be a regulated process that is potentially druggable. RIPK3- and MLKL-mediated necroptosis represents by far the best studied pathway of regulated necrosis. During necroptosis, the release of damage-associated molecular patterns (DAMPs) drives a phenomenon referred to as necroinflammation, a common consequence of necrosis. However, most studies of regulated necrosis investigated cell lines in vitro in a cell autonomous manner, which represents a non-physiological situation. Conclusions based on such work might not necessarily be transferrable to disease states in which synchronized, non-cell autonomous effects occur. Here, we summarize the current knowledge of the pathophysiological relevance of necroptosis in vivo, and in light of this understanding, we reassess the morphological classification of necrosis that is generally used by pathologists. Along these lines, we discuss the paucity of data implicating necroptosis in human disease. Finally, the in vivo relevance of non-necroptotic forms of necrosis, such as ferroptosis, is addressed.

Inhibition of Caspase-8 does not protect from alcohol-induced liver apoptosis but alleviates alcoholic hepatic steatosis in mice

Hepatic apoptosis is involved in the progression of alcoholic liver disease (ALD). Caspase-8, the apical initiator in death receptor-mediated apoptosis, has been implicated in acute liver injury and in non-alcoholic steatohepatitis. However, the relevance of Caspase-8 in the pathogenesis of ALD remains unclear. In the present study, we investigated the impact of Caspase-8 in human and murine alcohol-induced apoptosis and in ALD. We investigated human samples from ALD patients, primary mouse hepatocytes, and hepatocyte-specific Caspase-8 knockout (Casp8^Δhepa) mice in acute and chronic models of ethanol (EtOH) administration. Caspase-8 activation was detected in liver biopsies from ALD patients, as well as in livers of wild-type (WT) mice after chronic ethanol feeding for 8 weeks using the Lieber-DeCarli model. Lack of Caspase-8 expression in Casp8^Δhepa animals failed to prevent alcohol-induced liver damage and apoptosis. Instead, inhibition of Caspase-8 shifted the ethanol-induced death signals towards pronounced activation of the intrinsic, mitochondria-dependent apoptosis pathway in Casp8^Δhepa livers involving enhanced release of cytochrome c, stronger Caspase-9 activation and specific morphological changes of mitochondria. In vitro and in vivo intervention using a pan-caspase inhibitor markedly attenuated alcohol-induced hepatocyte damage in a Caspase-8-independent manner. Surprisingly, EtOH-fed Casp8^Δhepa mice displayed significantly attenuated steatosis and reduced hepatic triglyceride and free fatty acids content. Caspase-8 is dispensable for alcohol-induced apoptosis, but plays an unexpected role for alcohol-dependent fat metabolism. We provide evidence that simultaneous inhibition of extrinsic and intrinsic apoptosis signaling using pan-caspase inhibitors in vivo might be an optimal approach to treat alcohol-induced liver injury.

The Janus Face of Death Receptor Signaling during Tumor Immunoediting

Cancer immune surveillance is essential for the inhibition of carcinogenesis. Malignantly transformed cells can be recognized by both the innate and adaptive immune systems through different mechanisms. Immune effector cells induce extrinsic cell death in the identified tumor cells by expressing death ligand cytokines of the tumor necrosis factor ligand family. However, some tumor cells can escape immune elimination and progress. Acquisition of resistance to the death ligand-induced apoptotic pathway can be obtained through cleavage of effector cell expressed death ligands into a poorly active form, mutations or silencing of the death receptors, or overexpression of decoy receptors and pro-survival proteins. Although the immune system is highly effective in the elimination of malignantly transformed cells, abnormal/dysfunctional death ligand signaling curbs its cytotoxicity. Moreover, DRs can also transmit pro-survival and pro-migratory signals. Consequently, dysfunctional death receptor-mediated apoptosis/necroptosis signaling does not only give a passive resistance against cell death but actively drives tumor cell motility, invasion, and contributes to consequent metastasis. This dual contribution of the death receptor signaling in both the early, elimination phase, and then in the late, escape phase of the tumor immunoediting process is discussed in this review. Death receptor agonists still hold potential for cancer therapy since they can execute the tumor-eliminating immune effector function even in the absence of activation of the immune system against the tumor. The opportunities and challenges of developing death receptor agonists into effective cancer therapeutics are also discussed.

Partial hepatectomy in mice

The surgical procedure of two-thirds partial hepatectomy (PH) in rodents was first described more than 80 years ago by Higgins and Anderson. Nevertheless, this technique is still a state-of-the-art method for the community of liver researchers as it allows the in-depth analysis of signalling pathways involved in liver regeneration and hepatocarcinogenesis. The importance of PH as a key method in experimental hepatology has even increased in the last decade due to the increasing availability of genetically-modified mouse strains. Here, we propose a standard operating procedure (SOP) for the implementation of PH in mice, which is based on our experience of more than 10 years. In particular, the SOP offers all relevant background information on the PH model and provides comprehensive guidelines for planning and performing PH experiments. We provide established recommendations regarding optimal age and gender of animals, use of appropriate anaesthesia and biometric calculation of the experiments. We finally present an easy-to-follow step-by-step description of the complete surgical procedure including required materials, critical steps and postoperative management. This SOP especially takes into account the latest changes in animal welfare rules in the European Union but is still in agreement with current international regulations. In summary, this article provides comprehensive information for the legal application, design and implementation of PH experiments.

Transcriptomic characterization of the dorsal lobes after hepatectomy of the ventral lobe in zebrafish

Background

The liver possesses an ability of compensatory growth after removing three of five lobes in mammals or one of three lobes in zebrafish. The reenter of hepatocytes into the cell cycle is one of the hallmarks for the initiation of liver compensatory growth, but cellular and molecular mechanisms underlying the activation of hepatocytes remain largely unknown.

Results

To better understand the process, transcriptional profiles of the remaining liver dorsal lobes in female zebrafish were generated with RNA-seq. About 44 million raw reads were obtained from three sequencing libraries and 71 % of raw reads were mapped to the reference genome of zebrafish. A total number of 5652 genes were differentially expressed in at least one of two time points during the compensatory growth of liver dorsal lobes and classified into different functional categories. A number of genes encoding angiogenesis-related growth factors/ligands and apoptosis-associated cytokines were strongly expressed at 6-h time point after the removal of the ventral lobe. Gene ontology enrichment analysis of genes up-regulated during early stages of liver compensatory growth revealed that small GTPase-mediated signal transduction, RNA processing and intracellular protein transport were the most highly overrepresented biological processes and SNARE interactions in vesicular transport, proteasome and basal transcription factors were the most highly enriched pathways. Moreover, 477 genes differently expressed during liver compensatory growth of both female zebrafish and mice were involved in the response to stimulus, DNA replication, metabolic processes of fatty acid, lipid and steroid, multicellular organismal homeostasis and extracellular matrix constituent secretion.

Conclusions

Multiple biological processes and signaling pathways are immediately activated in remaining dorsal lobes of female zebrafish right after removal of the ventral lobe and these findings provide crucial clues for further identification of cis-elements and trans-factors that are extensively involved in the initiation of liver compensatory growth.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-2145-5) contains supplementary material, which is available to authorized users.

TNFα in liver fibrosis

Hepatocyte death, inflammation, and liver fibrosis are the hallmarks of chronic liver disease. Tumor necrosis factor-α (TNFα) is an inflammatory cytokine involved in liver inflammation and sustained liver inflammation leads to liver fibrosis. TNFα exerts inflammation, proliferation, and apoptosis. However, the role of TNFα signaling in liver fibrosis is not fully understood. This review highlights the recent findings demonstrating the molecular mechanisms of TNFα and its downstream signaling in liver fibrosis. During the progression of liver fibrosis, hepatic stellate cells play a pivotal role in a dynamic process of production of extracellular matrix proteins and modulation of immune response. Hepatic stellate cells transdifferentiate into activated myofibroblasts in response to damaged hepatocyte-derived mediators and immune cell-derived cytokines/chemokines. Here, we will discuss the role of TNFα in hepatic stellate cell survival and activation and the crosstalk between hepatic stellate cells and hepatocytes or other immune cells, such as macrophages, dendritic cells, and B cells in the development of liver fibrosis.

Alcoholic liver disease: mechanisms of injury and targeted treatment

Alcoholic liver disease (ALD) is a complex process that includes a wide spectrum of hepatic lesions, from steatosis to cirrhosis. Cell injury, inflammation, oxidative stress, regeneration and bacterial translocation are key drivers of alcohol-induced liver injury. Alcoholic hepatitis is the most severe form of all the alcohol-induced liver lesions. Animal models of ALD mainly involve mild liver damage (that is, steatosis and moderate inflammation), whereas severe alcoholic hepatitis in humans occurs in the setting of cirrhosis and is associated with severe liver failure. For this reason, translational studies using humans and human samples are crucial for the development of new therapeutic strategies. Although multiple attempts have been made to improve patient outcome, the treatment of alcoholic hepatitis is still based on abstinence from alcohol and brief exposure to corticosteroids. However, nearly 40% of patients with the most severe forms of alcoholic hepatitis will not benefit from treatment. We suggest that future clinical trials need to focus on end points other than mortality. This Review discusses the main pathways associated with the progression of liver disease, as well as potential therapeutic strategies targeting these pathways.

Haematopoietic cell-derived Jnk1 is crucial for chronic inflammation and carcinogenesis in an experimental model of liver injury

BACKGROUND & AIMS

Chronic liver injury triggers complications such as liver fibrosis and hepatocellular carcinoma (HCC), which are associated with alterations in distinct signalling pathways. Of particular interest is the interaction between mechanisms controlled by IKKγ/NEMO, the regulatory IKK subunit, and Jnk activation for directing cell death and survival. In the present study, we aimed to define the relevance of Jnk in hepatocyte-specific NEMO knockout mice (NEMO(Δhepa)), a genetic model of chronic inflammatory liver injury.

METHODS

We generated Jnk1(-/-)/NEMO(Δhepa) and Jnk2(-/-)/NEMO(Δhepa) mice by crossing NEMO(Δhepa) mice with Jnk1 and Jnk2 global deficient animals, respectively, and examined the progression of chronic liver disease. Moreover, we investigated the expression of Jnk during acute liver injury, evaluated the role of Jnk1 in bone marrow-derived cells, and analysed the expression of NEMO and p-JNK in human diseased-livers.

RESULTS

Deletion of Jnk1 significantly aggravated the progression of liver disease, exacerbating apoptosis, compensatory proliferation and carcinogenesis in NEMO(Δhepa) mice. Conversely, Jnk2(-/-)/NEMO(Δhepa) displayed hepatic inflammation. By using bone marrow transfer, we observed that Jnk1 in haematopoietic cells had an impact on the progression of chronic liver disease in NEMO(Δhepa) livers. These findings are of clinical relevance since NEMO expression was downregulated in hepatocytes of patients with HCC whereas NEMO and p-JNK were expressed in a large amount of infiltrating cells.

CONCLUSIONS

A synergistic function of Jnk1 in haematopoietic cells and hepatocytes might be relevant for the development of chronic liver injury. These results elucidate the complex function of Jnk in chronic inflammatory liver disease.

Old, new and emerging functions of caspases

Caspases are proteases with a well-defined role in apoptosis. However, increasing evidence indicates multiple functions of caspases outside apoptosis. Caspase-1 and caspase-11 have roles in inflammation and mediating inflammatory cell death by pyroptosis. Similarly, caspase-8 has dual role in cell death, mediating both receptor-mediated apoptosis and in its absence, necroptosis. Caspase-8 also functions in maintenance and homeostasis of the adult T-cell population. Caspase-3 has important roles in tissue differentiation, regeneration and neural development in ways that are distinct and do not involve any apoptotic activity. Several other caspases have demonstrated anti-tumor roles. Notable among them are caspase-2, -8 and -14. However, increased caspase-2 and -8 expression in certain types of tumor has also been linked to promoting tumorigenesis. Increased levels of caspase-3 in tumor cells causes apoptosis and secretion of paracrine factors that promotes compensatory proliferation in surrounding normal tissues, tumor cell repopulation and presents a barrier for effective therapeutic strategies. Besides this caspase-2 has emerged as a unique caspase with potential roles in maintaining genomic stability, metabolism, autophagy and aging. The present review focuses on some of these less studied and emerging functions of mammalian caspases.

Hepatic tissue environment in NEMO-deficient mice critically regulates positive selection of donor cells after hepatocyte transplantation

Background

Hepatocyte transplantation (HT) is a promising alternative treatment strategy for end-stage liver diseases compared with orthotopic liver transplantation. A limitation for this approach is the low engraftment of donor cells. The deletion of the I-kappa B kinase-regulatory subunit IKKγ/NEMO in hepatocytes prevents nuclear factor (NF)-kB activation and triggers spontaneous liver apoptosis, chronic hepatitis and the development of liver fibrosis and hepatocellular carcinoma. We hypothesized that NEMO^Δhepa mice may therefore serve as an experimental model to study HT.

Methods

Pre-conditioned NEMO^Δhepa mice were transplanted with donor-hepatocytes from wildtype (WT) and mice deficient for the pro-apoptotic mediator Caspase-8 (Casp8^Δhepa).

Results

Transplantation of isolated WT-hepatocytes into pre-conditioned NEMO^Δhepa mice resulted in a 6-7 fold increase of donor cells 12 weeks after HT, while WT-recipients showed no liver repopulation. The use of apoptosis-resistant Casp8^Δhepa-derived donor cells further enhanced the selection 3-fold after 12-weeks and up to 10-fold increase after 52 weeks compared with WT donors. While analysis of NEMO^Δhepa mice revealed strong liver injury, HT-recipient NEMO^Δhepa mice showed improved liver morphology and decrease in serum transaminases. Concomitant with these findings, the histological examination elicited an improved liver tissue architecture associated with significantly lower levels of apoptosis, decreased proliferation and a lesser amount of liver fibrogenesis. Altogether, our data clearly support the therapeutic benefit of the HT procedure into NEMO^Δhepa mice.

Conclusion

This study demonstrates the feasibility of the NEMO^Δhepa mouse as an in vivo tool to study liver repopulation after HT. The improvement of the characteristic phenotype of chronic liver injury in NEMO^Δhepa mice after HT suggests the therapeutic potential of HT in liver diseases with a chronic inflammatory phenotype and opens a new door for the applicability of this technique to combat liver disease in the human clinic.

MicroRNA-101 suppresses liver fibrosis by targeting the TGFβ signalling pathway

Transforming growth factor-β (TGFβ) is crucial for liver fibrogenesis and the blunting of TGFβ signalling in hepatic stellate cells (HSCs) or hepatocytes can effectively inhibit liver fibrosis. microRNAs (miRNAs) have emerged as key regulators in modulating TGFβ signalling and liver fibrogenesis. However, the regulation of TGFβ receptor I (TβRI) production by miRNA remains poorly understood. Here we demonstrate that the miR-101 family members act as suppressors of TGFβ signalling by targeting TβRI and its transcriptional activator Kruppel-like factor 6 (KLF6) during liver fibrogenesis. Using a mouse model of carbon tetrachloride (CCl4 )-induced liver fibrosis, we conducted a time-course experiment and observed significant down-regulation of miR-101 in the fibrotic liver as well as in the activated HSCs and injured hepatocytes in the process of liver fibrosis. Meanwhile, up-regulation of TβRI/KLF6 was observed in the fibrotic liver. Subsequent investigations validated that TβRI and KLF6 were direct targets of miR-101. Lentivirus-mediated ectopic expression of miR-101 in liver greatly reduced CCl4 -induced liver fibrosis, whereas intravenous administration of antisense miR-101 oligonucleotides aggravated hepatic fibrogenesis. Mechanistic studies revealed that miR-101 inhibited profibrogenic TGFβ signalling by suppressing TβRI expression in both HSCs and hepatocytes. Additionally, miR-101 promoted the reversal of activated HSCs to a quiescent state, as indicated by suppression of proliferation and migration, loss of activation markers and gain of quiescent HSC-specific markers. In hepatocytes, miR-101 attenuated profibrogenic TGFβ signalling and suppressed the consequent up-regulation of profibrogenic cytokines, as well as TGFβ-induced hepatocyte apoptosis and the inhibition of cell proliferation. The pleiotropic roles of miR-101 in hepatic fibrogenesis suggest that it could be a potential therapeutic target for liver fibrosis.