Activation of nuclear factor kappaB in hepatitis C virus infection: implications for pathogenesis and hepatocarcinogenesis

Coleus vettiveroides ethanolic root extract protects against thioacetamide-induced acute liver injury in rats

Acute liver injury is caused by various factors, including oxidative stress and inflammation. Coleus vettiveroides, an ayurvedic medicinal plant, is known to possess antioxidant, antibacterial, and antidiabetic properties. In this current study, we investigated the protective effect of C. vettiveroides ethanolic root extract (CVERE) against thioacetamide (TAA)-induced acute liver injury in rats. A single dose of TAA (300 mg/kg, b.w., i.p.) was administered to induce acute liver injury. The treatment groups of rats were concurrently treated with CVERE (125 and 250 mg/kg, b.w., p.o.) and silymarin (100 mg/kg, b.w., p.o.), respectively. After 24 h of the experimental period, TAA-induced liver injury was confirmed by increased activity of serum transaminases and malondialdehyde levels in liver tissue, decreased levels of antioxidants, upregulated expression of the inflammatory marker gene, and altered liver morphology. Whereas CVERE simultaneous treatment inhibited hepatic injury and prevented the elevation of serum aspartate and alanine transaminases, alkaline phosphatase, and lactate dehydrogenase activities. CVERE attenuated TAA-induced oxidative stress by suppressing lipid peroxidation and restoring antioxidants such as superoxide dismutase, catalase, and reduced glutathione. Further, CVERE treatment was found to inhibit nuclear factor κB-mediated inflammatory signaling, as indicated by downregulated pro-inflammatory cytokines including tumor necrosis factor-α and interleukin-1β. Our findings suggest that CVERE prevents TAA-induced acute liver injury by targeting oxidative stress and inflammation.

Ibrutinib Induces a Dramatic Improvement for Idiopathic Refractory Ascites Following Allogeneic Hematopoietic Cell Transplantation

We herein report a case of idiopathic refractory ascites following allogeneic hematopoietic cell transplantation that was successfully treated with ibrutinib. A 39-year-old man presented with massive transudative ascites. Despite a high portal venous pressure, the liver histology showed traces of alloreactivity inconsistent with veno-occlusive disease/sinusoidal obstructive syndrome. Ibrutinib was administered for ascites possibly secondary to portal hypertension associated with the alloreactivity. The ascites dramatically improved, and the portal venous pressure was reduced. This case may help clarify the mechanism through which refractory ascites develops after allogeneic hematopoietic cell transplantation and establish appropriate treatment protocols.

Interaction of SERINC5 and IFITM1/2/3 regulates the autophagy-apoptosis-immune network under CSFV infection

The host restriction factor serine incorporator 5 (SERINC5) plays a key role in inhibiting viral activity and has been shown to inhibit classical swine fever virus (CSFV) infection. However, the action of SERINC5 in the interaction between host cells and CSFV remains poorly understood. This study found that SERINC5 represses CSFV-induced autophagy through MAPK1/3-mTOR and AKT-mTOR signalling pathways. Further research showed that SERINC5 promotes apoptosis by repressing autophagy. Likewise, it was demonstrated that SERINC5 interacting proteins IFITM1/2/3 inhibit CSFV replication and regulate autophagy in a lysosomal-associated membrane protein LAMP1-dependent manner. In addition, IFITM1/2/3 interference promotes the NF-κB signalling pathway for potential immunoregulation by inhibiting autophagy. Finally, the functional silencing of IFITM1/2/3 genes was demonstrated to enhance the inhibitory effect of SERINC5 on autophagy. Taken together, These data uncover a novel mechanism through SERINC5 and its interacting proteins IFITM1/2/3, which mediates CSFV replication, and provides new avenues for controlling CSFV.

On the Core Prescriptions and Their Mechanisms of Traditional Chinese Medicine in Hepatitis B, Liver Cirrhosis, and Liver Cancer Treatment

Background

As a frequent cause of death in cancer patients, liver cancer usually occurs in hepatitis B and cirrhosis. In China, Chinese people have been using traditional Chinese medicine (TCM) in treating various chronic liver diseases, which could effectively improve the symptoms and slow down the progression of liver diseases. However, due to the complexity rules of TCM prescription, their action mechanisms are still not clearly understood, which may affect the popularization of effective prescriptions. This study aims to identify the core TCM herbs in the treatment of hepatitis B, liver cirrhosis, and liver cancer so as to clarify the mechanism of action of the core herb networks.

Methods

There were 1,673 prescriptions for chronic liver diseases collected in this study, of which 854 were hepatic B prescriptions, 530 were for liver cirrhosis, and 289 were for liver cancer. The basic characteristics of herbal medicine were firstly explained via descriptive analysis, then the core prescriptions of herbal medicine were analyzed through association rule, and finally, the mechanism of core prescriptions was explored with the help of systematic network pharmacology and by applying such databases as TCMIP, HERB, OMIM, GeneCards, KEGG, and software like RStudio and Cytoscape.

Results

The rule of the core prescriptions in these cases was characterized by the application of herbs with both cold and warm properties, in which bitter herbs with cold property took priority. Tonifying deficiency, clearing heat, and activating blood circulations to remove stasis were common treatment principles for the three liver diseases. Turmeric Root Tuber (YuJin), White Peony Root (BaiShao), Bupleurum (ChaiHu), Salvia miltiorrhiza (DanShen), and Astragali Radix (HuangQi) were prescribed the most in hepatitis B treatment to invigorate the spleen and soothe the liver. Astragali Radix (HuangQi), Tuckahoe (FuLing), Atractylodis Macrocephalae Rhizoma (BaiZhu), Fructus Polygoni Orientalis (ShuiHongHuaZi), and Curcumae Rhizome (EZhu) were most frequently applied in liver cirrhosis treatment to replenish qi and activate blood. Oldenlandia (BaiHuaSheSheCao), Bearded Scutellaria (BanZhiLian), Curcumae Rhizome (EZhu), and Cardamom (DouKou) were most frequently prescribed to eliminate cancer toxin, invigorate the spleen, and activate blood. These core herbs mainly act through signal transduction and immune system pathways, in which the PI3K-Akt pathway plays a key role. The core prescription for liver cirrhosis regulated more endocrine system pathways than the hepatitis B prescription, and liver cancer prescription regulated more nervous system-related pathways.

Conclusion

Three core prescriptions for hepatitis B, liver cirrhosis, and liver cancer treatment were identified, which acted mainly through signal transduction and immune system pathways to regulate immunity and cell growth and participate in inflammation inhibition, in which liver cancer prescription regulated more pathways, especially more nervous system-related pathways than the other two.

Heparanase-1 is upregulated by hepatitis C virus and favors its replication

BACKGROUND & AIMS

Over time, chronic HCV infection can lead to hepatocellular carcinoma (HCC), a process that involves changes to the liver extracellular matrix (ECM). However, the exact mechanisms by which HCV induces HCC remain unclear. Therefore, we sought to investigate the impact of HCV on the liver ECM, with a focus on heparanase-1 (HPSE).

METHODS

HPSE expression was assessed by quantitative reverse-transcription PCR, immunoblotting and immunofluorescence in liver biopsies infected or not with HCV, and in 10-day-infected hepatoma Huh7.5 cells. Cell lines deficient for or overexpressing HPSE were established to study its role during infection.

RESULTS

HCV propagation led to significant HPSE induction, in vivo and in vitro. HPSE enhanced infection when exogenously expressed or supplemented as a recombinant protein. Conversely, when HPSE expression was downregulated or its activity blocked, HCV infection dropped, suggesting a role of HPSE in the HCV life cycle. We further studied the underlying mechanisms of such observations and found that HPSE favored HCV release by enhancing CD63 synthesis and exosome secretion, but not by stimulating HCV entry or genome replication. We also showed that virus-induced oxidative stress was involved in HPSE induction, most likely through NF-κB activation.

CONCLUSIONS

We report for the first time that HCV infection is favored by HPSE, and upregulates HPSE expression and secretion, which may result in pathogenic alterations of the ECM.

LAY SUMMARY

Chronic hepatitis C virus (HCV) infection can lead to hepatocellular carcinoma development in a process that involves derangement of the extracellular matrix (ECM). Herein, we show that heparanase-1, a protein involved in ECM degradation and remodeling, favors HCV infection and is upregulated by HCV infection; this upregulation may result in pathogenic alterations of the ECM.

Serum MicroRNA Transcriptomics and Acute Rejection or Recurrent Hepatitis C Virus in Human Liver Allograft Recipients: A Pilot Study

BACKGROUND

Acute rejection (AR) and recurrent hepatitis C virus (R-HCV) are significant complications in liver allograft recipients. Noninvasive diagnosis of intragraft pathologies may improve their management.

METHODS

We performed small RNA sequencing and microRNA (miRNA) microarray profiling of RNA from sera matched to liver allograft biopsies from patients with nonimmune, nonviral (NINV) native liver disease. Absolute levels of informative miRNAs in 91 sera matched to 91 liver allograft biopsies were quantified using customized real-time quantitative PCR (RT-qPCR) assays: 30 biopsy-matched sera from 26 unique NINV patients and 61 biopsy-matched sera from 41 unique R-HCV patients. The association between biopsy diagnosis and miRNA abundance was analyzed by logistic regression and calculating the area under the receiver operating characteristic curve.

RESULTS

Nine miRNAs-miR-22, miR-34a, miR-122, miR-148a, miR-192, miR-193b, miR-194, miR-210, and miR-885-5p-were identified by both sRNA-seq and TLDA to be associated with NINV-AR. Logistic regression analysis of absolute levels of miRNAs and goodness-of-fit of predictors identified a linear combination of miR-34a + miR-210 (P < 0.0001) as the best statistical model and miR-122 + miR-210 (P < 0.0001) as the best model that included miR-122. A different linear combination of miR-34a + miR-210 (P < 0.0001) was the best model for discriminating NINV-AR from R-HCV with intragraft inflammation, and miR-34a + miR-122 (P < 0.0001) was the best model for discriminating NINV-AR from R-HCV with intragraft fibrosis.

CONCLUSIONS

Circulating levels of miRNAs, quantified using customized RT-qPCR assays, may offer a rapid and noninvasive means of diagnosing AR in human liver allografts and for discriminating AR from intragraft inflammation or fibrosis due to R-HCV.

Effects of alcohol consumption on viral hepatitis B and C

The liver is the main target organ for hepatitis viruses and the vital organ for alcohol metabolism. These two factors of viral hepatitis and alcohol abuse in combination can exert dual harmful actions, leading to enhanced damage to the liver. Epidemiological studies have revealed a higher prevalence of hepatitis C virus (HCV) infection among alcoholics than the general population. The interaction of alcohol with viral hepatitis [e.g., hepatitis B virus (HBV), HCV] and the underlying mechanisms are not fully understood. The effects of alcohol on viral hepatitis include promoted viral replication, weakened immune response, and increased oxidative stress. Clinically, alcohol abuse is correlated with an increased risk of developing end-stage liver cirrhosis and hepatocellular carcinoma in patients with chronic hepatitis B and C, suggesting that the combination of alcohol and HBV/HCV lead to more severe liver damage. The influence of mild to moderate alcohol drinking on the HBV-induced liver fibrosis, cirrhosis, and hepatocellular carcinoma among patients infected with HBV remains unclear. Unlike HBV infected patients, no safe level of alcohol intake has been established for patients with HCV. Even light to moderate alcohol use can exert a synergistic effect with viral hepatitis, leading to the rapid progression of liver disease. Furthermore, interferon-based therapy is less effective in alcohol drinkers than in control patients, even after abstinence from alcohol for a period of time. Therefore, abstaining from alcohol is highly recommended to protect the liver, especially in individuals with HBV/HCV infection, to improve the clinical efficacy of antiviral treatment and prevent the rapid progression of chronic viral hepatitis.

The Crosstalk Between Regulatory Non-Coding RNAs and Nuclear Factor Kappa B in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is a highly lethal type of malignancies that possesses great loss of life safety to human beings worldwide. However, few effective means of curing HCC exist and its specific molecular basis is still far from being fully elucidated. Activation of nuclear factor kappa B (NF-κB), which is often observed in HCC, is considered to play a significant part in hepatocarcinogenesis and development. The emergence of regulatory non-coding RNAs (ncRNAs), particularly microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), is a defining advance in cancer biology, and related research in this branch has yielded many diagnostic and therapeutic opportunities. Recent studies have suggested that regulatory ncRNAs act as inhibitors or activators in the initiation and progression of HCC by targeting components of NF-κB signaling or regulating NF-κB activity. In this review, we attach importance to the role and function of regulatory ncRNAs in NF-κB signaling of HCC and NF-κB-associated chemoresistance in HCC, then propose future research directions and challenges of regulatory ncRNAs mediated-regulation of NF-κB pathway in HCC.

Deubiquitination and Activation of the NLRP3 Inflammasome by UCHL5 in HCV-Infected Cells

Chronic hepatitis C virus (HCV) infection induces liver inflammation that can lead to fibrosis, cirrhosis, and hepatocellular carcinoma (HCC). Inflammation is the outcome of the action of proinflammatory cytokines and chemokines, including interleukin-1 beta (IL-1β) and tumor necrosis factor alpha. Mature IL-1β production and secretion are facilitated by active inflammasome complexes, including the NACHT-LRR pyrin domain-containing protein 3 (NLRP3) inflammasome. Our study shows that the NLRP3 inflammasome is activated in HCV-infected hepatocytes and that the activation is regulated by posttranslational modifications. NLRP3 is modified by lysine-63 ubiquitin chains in hepatocytes and is deubiquitinated during HCV infection. Inhibition of deubiquitinases (DUBs) with chemical inhibitors or blocking UCHL5 DUB expression with small interfering RNA (siRNA) abrogated NLRP3 inflammasome assembly and activation. Inhibition of inflammasome deubiquitination was correlated with a reduction in IL-1β maturation, decrease in HCV protein expression, and reduction in release of HCV from the cells. Together, this study suggests that HCV-induced activation of the NLRP3 inflammasome through posttranslational modification is crucial for the HCV life cycle and pathogenesis. IMPORTANCE HCV infection induces inflammation leading to fibrosis, cirrhosis, and cancer. The current study identifies the mechanisms leading to the activation of the NLRP3 inflammasome in hepatocytes, which is an important site of viral replication. Deubiquitination of NLRP3 by UCHL5 is required for inflammasome activation. Inhibition of deubiquitination blocks NLRP3 inflammasome activation and IL-1β maturation and also decreases HCV replication, suggesting the importance of the NLRP3 inflammasome in inflammation as well as other signaling pathways.

Astrocyte elevated gene-1 (AEG-1): A key driver of hepatocellular carcinoma (HCC)

An array of human cancers, including hepatocellular carcinoma (HCC), overexpress the oncogene Astrocyte elevated gene-1 (AEG-1). It is now firmly established that AEG-1 is a key driver of carcinogenesis, and enhanced expression of AEG-1 is a marker of poor prognosis in cancer patients. In-depth studies have revealed that AEG-1 positively regulates different hallmarks of HCC progression including growth and proliferation, angiogenesis, invasion, migration, metastasis and resistance to therapeutic intervention. By interacting with a plethora of proteins as well as mRNAs, AEG-1 regulates gene expression at transcriptional, post-transcriptional, and translational levels, and modulates numerous pro-tumorigenic and tumor-suppressive signal transduction pathways. Even though extensive research over the last two decades using various in vitro and in vivo models has established the pivotal role of AEG-1 in HCC, effective targeting of AEG-1 as a therapeutic intervention for HCC is yet to be achieved in the clinic. Targeted delivery of AEG-1 small interfering ribonucleic acid (siRNA) has demonstrated desired therapeutic effects in mouse models of HCC. Peptidomimetic inhibitors based on protein-protein interaction studies has also been developed recently. Continuous unraveling of novel mechanisms in the regulation of HCC by AEG-1 will generate valuable knowledge facilitating development of specific AEG-1 inhibitory strategies. The present review describes the current status of AEG-1 in HCC gleaned from patient-focused and bench-top studies as well as transgenic and knockout mouse models. We also address the challenges that need to be overcome and discuss future perspectives on this exciting molecule to transform it from bench to bedside.

Pathways involved in viral oncogenesis: New perspectives from virus-host protein interactomics

Oncogenic viruses are among the apparent causes of cancer-associated mortality. It was estimated that 12% to 15% of human malignancies are linked to oncoviruses. Although modernist strategies and traditional genetic studies have defined host-pathogen interactions of the oncoviruses, their host functions which are critical for the establishment of infection still remain mysterious. However, over the last few years, it has become clear that infections hijack and modify cellular pathways for their benefit. In this context, we constructed the virus-host protein interaction networks of seven oncoviruses (EBV, HBV, HCV, HTLV-1, HHV8, HPV16, and HPV18), and revealed cellular pathways hijacking as a result of oncogenic virus infection. Several signaling pathways/processes such as TGF-β signaling, cell cycle, retinoblastoma tumor suppressor protein, and androgen receptor signaling were mutually targeted by viruses to induce oncogenesis. Besides, cellular pathways specific to a certain virus were detected. By this study, we believe that we improve the understanding of the molecular pathogenesis of viral oncogenesis and provide information in setting new targets for treatment, prognosis, and diagnosis.

Porcine RACK1 negatively regulates the infection of classical swine fever virus and the NF-κB activation in PK-15 cells

Classical swine fever (CSF) is one of the main viral diseases of swine worldwide. The causative pathogen is CSF virus (CSFV), a small enveloped RNA virus of the genus Pestivirus. Activation of NF-κB is a hallmark of most viral infections and the viral pathogens frequently kidnap NF-κB pathway for their own advantages, however, it is unclear or even controversial about whether CSFV infection can activate NF-κB signal pathway. RACK1 was shown as an interacting host protein with CSFV NS5A protein, but no studies so far have clearly defined the role of RACK1 during CSFV infection and NF-κB activation. In this study, to properly address these open questions, using RT-qPCR, western blot, indirect fluorescence staining, siRNA knockdown and protein overexpression techniques, we demonstrated that CSFV infection reduced the RACK1 expression at both mRNA and protein levels in PK-15 cells. Downregulation of cellular RACK1 enhanced CSFV infection and subsequent NF-κB activation, while RACK1 overexpression inhibited CSFV infection and the NF-κB activation. In conclusion, RACK1 is a negative cellular regulator for CSFV infection and NF-κB activation in PK-15 cells. Our work addressed a novel aspect concerning the regulation of innate antiviral immune response during CSFV infection. This study may provide some insights into the molecular mechanisms of CSFV infection in swine. However, the elaborate mechanism by which CSFV regulates NF-κB activation and how RACK1 plays its roles in CSFV infection and NF-κB induction require further in-depth studies.

Complexity on modulation of NF-κB pathways by hepatitis B and C: A double-edged sword in hepatocarcinogenesis

Nuclear factor-κB (NF-κB), a family of master regulated dimeric transcription factors, signaling transduction pathways are active players in the cell signaling that control vital cellular processes, including cell growth, proliferation, differentiation, apoptosis, morphogenesis, angiogenesis, and immune responses. Nevertheless, aberrant regulation of the NF-κB signaling pathways has been associated with a significant number of human cancers. In fact, NF-κB acts as a double-edged sword in the vital cellular processes and carcinogenesis. This review provides an overview on the modulation of the NF-κB signaling pathways by proteins of hepatitis B and C viruses. One of the major NF-κB events that are modulated by these viruses is the induction of hepatocellular carcinoma. Given the central function of NF-κB in carcinogenesis, it has turned out to be a considerable therapeutic target for cancer therapy.

Immunopathogenesis of Liver Injury During Hepatitis C Virus Infection

The present report describes current concepts about the mechanism of liver cell injury caused by host immune response against hepatitis C virus (HCV) infection in human beings. This report is based on the observations from experimental studies and follow-up actions on human liver diseases. The results from different investigations suggest that liver injury depends on the presentation of viral antigen and the level of host immune response raised against HCV-related peptides. Both innate and adaptive immunity are triggered to counter the viral onset. During development of host immunity, the cell-mediated immune response involving CD4⁺ Th1 cells and CD8⁺ cytotoxic T-lymphocyte (CTL) cells were found to play a major role in causing liver damage. The hepatic Innate lymphoid cells (ILCs) subsets are involved in the immune regulation of different liver diseases: viral hepatitis, mechanical liver injury, and fibrosis. Humoral immunity and natural killer (NK) cell action also contributed in liver cell injury by antibody-dependent cellular cytotoxicity (ADCC). In fact, immunopathogenesis of HCV infection is a complex phenomenon where regulation of immune response at several steps decides the possibility of viral elimination or persistence. Regulation of immune response was noted starting from viral-host interaction to immune reaction cascade engaged in cell damage. The activation or suppression of interferon-stimulated genes, NK cell action, CTL inducement by regulatory T cells (Treg), B cell proliferation, and so on was demonstrated during HCV infection. Involvement of HLA in antigen presentation, as well as types of viral genotypes, also influenced host immune response against HCV peptides. The combined effect of all these effector mechanisms ultimately decides the progression of viral onset to acute or chronic infection. In conclusion, immunopathogenesis of liver injury after HCV infection may be ascribed mainly to host immune response. Second, it is cell-mediated immunity that plays a predominant role in liver cell damage.

The Immunogenicity in Mice of HCV Core Delivered as DNA Is Modulated by Its Capacity to Induce Oxidative Stress and Oxidative Stress Response

HCV core is an attractive HCV vaccine target, however, clinical or preclinical trials of core-based vaccines showed little success. We aimed to delineate what restricts its immunogenicity and improve immunogenic performance in mice. We designed plasmids encoding full-length HCV 1b core and its variants truncated after amino acids (aa) 60, 98, 152, 173, or up to aa 36 using virus-derived or synthetic polynucleotides (core191/60/98/152/173/36_191v or core152s DNA, respectively). We assessed their level of expression, route of degradation, ability to trigger the production of reactive oxygen species/ROS, and to activate the components of the Nrf2/ARE antioxidant defense pathway heme oxygenase 1/HO-1 and NAD(P)H: quinone oxidoreductase/Nqo-1. All core variants with the intact N-terminus induced production of ROS, and up-regulated expression of HO-1 and Nqo-1. The capacity of core variants to induce ROS and up-regulate HO-1 and Nqo-1 expression predetermined their immunogenicity in DNA-immunized BALB/c and C57BL/6 mice. The most immunogenic was core 152s, expressed at a modest level and inducing moderate oxidative stress and oxidative stress response. Thus, immunogenicity of HCV core is shaped by its ability to induce ROS and oxidative stress response. These considerations are important in understanding the mechanisms of viral suppression of cellular immune response and in HCV vaccine design.

The Diagnostic Impact of C4d, CD68, and NF-κB Expression in the Differentiation Between Recurrent Hepatitis C and Acute Cellular Rejection After Liver Transplantation

Liver transplantation is the selected treatment for patients with advanced liver disease and cirrhosis, mostly as a complication of hepatitis C virus (HCV). Recurrent HCV and acute cellular rejection (ACR) of the graft are the most common causes of graft failure. The distinction between the 2 conditions is essential because they are managed differently. In some cases, the clinical and histopathologic features may overlap between recurrent hepatitis C and ACR, making differentiation difficult. The aim of this study was to investigate the role of C4d, CD68, and nuclear factor kappa-B (NF-κB) in the differentiation between ACR and recurrent HCV in the post-liver-transplant biopsy using immunohistochemistry. C4d expression in endothelial cells of portal or central veins (P=0.001) and the number of macrophages highlighted by CD68 (P=0.02) were in favor of ACR, whereas NF-κB expression by hepatocytes was in favor of recurrent hepatitis C. Vascular injury demonstrated by endothelial expression of C4d and prominent macrophage infiltration identified by CD68 expression were the distinguishing criteria for ACR and representing humoral and cellular-mediated immunity as evoking factors for graft injury. The upregulation of NF-κB in the hepatocytes of recurrent hepatitis C could be an immune response to infection or it may be induced by HCV itself.

PKCζ phosphorylates TRAF2 to protect against intestinal ischemia-reperfusion-induced injury

Intestinal ischemia-reperfusion (I/R) is a common clinical problem that occurs during various clinical pathological processes. Excessive apoptosis has an indispensable role in intestinal I/R injury. Tumor necrosis factor receptor-associated factor 2 (TRAF2) and PKCζ have an essential role in apoptosis. Here, we aimed to investigate the effects of PKCζ and TRAF2 and to explore the correlation between PKCζ and TRAF2 in intestinal I/R injury. Mice were subjected to intestinal I/R injury in vivo. In vitro experiments were conducted by treating Caco-2 cells with hypoxia/reoxygenation (H/R) stimulation to simulate intestinal I/R. Intestinal tissue samples and Caco-2 cells were examined using various approaches. Intestinal I/R induced the membrane translocation and phosphorylation of PKCζ. Pretreatment with the PKCζ activator phosphatidylcholine remarkably attenuated gut injury by suppressing apoptosis. H/R induced PKCζ to combine with TRAF2, which was phosphorylated by PKCζ at Ser⁵⁵, but not at Ser¹¹, under intestinal I/R or H/R conditions. In addition, TRAF2 Ser⁵⁵ phosphorylation increased cell survival by inhibiting cell apoptosis in the H/R model. Mechanistically, TRAF2 Ser⁵⁵ phosphorylation promoted NF-κB activation but suppressed c-Jun activation in Caco-2 cells under H/R conditions. The results of this study demonstrate that the PKCζ/TRAF2 pathway represents a novel protective mechanism against intestinal I/R injury. Therefore, the PKCζ/TRAF2 pathway is a novel target for potential treatments of intestinal I/R injury-related diseases.

Protein kinase D2 contributes to TNF-α-induced epithelial mesenchymal transition and invasion via the PI3K/GSK-3β/β-catenin pathway in hepatocellular carcinoma

Although protein kinase D (PKD) has been shown to contribute to invasion and metastasis in several types of cancer, the role of PKD in the epithelial mesenchymal transition (EMT) of hepatocellular carcinoma (HCC) has remained unclear. We found that PKD2 is up-regulated in HCC and is correlated with the metastasis of HCC. PKD2 positively regulated TNF-α-induced EMT and metastasis of HCC. Mechanistic studies revealed TNF-α-induced PKD2 activation is mediated by the formation of a TNFR1/TRAF2 complex. PKD2 bound directly to the p110α and p85 subunits of PI3K and promoted the PI3K/Akt/GSK-3β signaling cascade to stimulate EMT. In conclusion, our results have uncovered a novel role for the regulation of EMT and suggest inhibition of PKD2 as a potential therapeutic strategy for HCC.

Celecoxib attenuates depressive-like behavior associated with immunological liver injury in C57BL/6 mice through TNF-α and NF-κb dependent mechanisms

AIM

Depression associating patients with chronic liver diseases is a major treatment goal. This study aimed to evaluate the potential hepatoprotective and antidepressant effects of celecoxib in a model of experimental autoimmune hepatitis (EAH) and depressive-like behavior in C57BL/6 mice.

MAIN METHODS

EAH was induced by immunization with S-100 liver antigen emulsified in complete Freund's adjuvant (CFA). Mice were randomly allocated to 5 groups; control phosphate buffered saline group; control CFA group; EAH group, and 2 groups of EAH plus celecoxib (7.5 or 15mg/kg/d respectively). Mice were assessed behaviorally by novelty-suppressed test, tail suspension test, locomotor assessment and forced swimming tests. Serum liver enzymes and hepatic hydroxyproline content were biochemically analyzed. Histopathological analysis for liver and brain sections and immunohistochemical studies for hepatic and hippocampal tumor necrosis factor (TNF-α), nuclear factor Kappa-B (NF-κB) and caspase-3 were performed.

KEY FINDINGS

EAH group exhibited significant depressive-like changes, increase in liver enzymes and hepatic hydroxyproline content. Signs of autoimmune hepatitis and structural changes in hippocampus were confirmed by histopathological studies. Immunohistochemical examination revealed overexpression of hepatic and hippocampal TNF-α, NF-κB and caspase-3 positive cells. Celecoxib (7.5mg/kg/d) significantly ameliorated hepatic biochemical changes, hepatic and hippocampal histopathological and immunohistochemical changes induced in EAH group. Celecoxib (15mg/kg/d) significantly ameliorated the behavioral changes, histopathological and immunohistochemical changes in hippocampus, with non-significant change in hepatic biochemical profile, histopathological and immunohistochemical changes induced in EAH group.

SIGNIFICANCE

The celecoxib (7.5mg/kg/d) through its anti-inflammatory effect may represent a new therapeutic approach to treat autoimmune hepatitis associated with depressive symptoms.

Plasma nuclear factor kappa B and serum peroxiredoxin 3 in early diagnosis of hepatocellular carcinoma

BACKGROUND

Early diagnosis of hepatocellular carcinoma (HCC) is the most important step in successful treatment. However, it is usually rare due to the lack of a highly sensitive specific biomarker so that the HCC is usually fatal within few months after diagnosis. The aim of this work was to study the role of plasma nuclear factor kappa B (NF-?B) and serum peroxiredoxin 3 (PRDX3) as diagnostic biomarkers for early detection of HCC in a high-risk population.

MATERIALS AND METHODS

Plasma nuclear factor kappa B level (NF-?B) and serum peroxiredoxin 3 (PRDX3) levels were measured using enzyme linked immunosorbent assay (ELISA), in addition to alpha-fetoprotein (AFP) in 72 cirrhotic patients, 64 patients with HCC and 29 healthy controls.

RESULTS

NF-?B and PRDX3 were significantly elevated in the HCC group in relation to the others. Higher area under curve (AUC) of 0.854 (for PRDX3) and 0.825 (for NF-?B) with sensitivity of 86.3% and 84.4% and specificity of 75.8% and 75.4% respectively, were found compared to AUC of alpha-fetoprotein (AFP) (0.65) with sensitivity of 72.4% and specificity of 64.3%.

CONCLUSIONS

NF-?B and PRDX3 may serve as early and sensitive biomarkers for early detection of HCC facilitating improved management. The role of nuclear factor kappa B (NF-?B) as a target for treatment of liver fibrosis and HCC must be widely evaluated.

The roles of endoplasmic reticulum overload response induced by HCV and NS4B protein in human hepatocyte viability and virus replication

Hepatitis C virus (HCV) replication is associated with endoplasmic reticulum (ER) and its infection triggers ER stress. In response to ER stress, ER overload response (EOR) can be activated, which involves the release of Ca²⁺ from ER, production of reactive oxygen species (ROS) and activation of nuclear factor κB (NF-κB). We have previously reported that HCV NS4B expression activates NF-κB via EOR-Ca²⁺-ROS pathway. Here, we showed that NS4B expression and HCV infection activated cancer-related NF-κB signaling pathway and induced the expression of cancer-related NF-κB target genes via EOR-Ca²⁺-ROS pathway. Moreover, we found that HCV-activated EOR-Ca²⁺-ROS pathway had profound effects on host cell viability and HCV replication. HCV infection induced human hepatocyte death by EOR-Ca²⁺-ROS pathway, whereas activation of EOR-Ca²⁺-ROS-NF-κB pathway increased the cell viability. Meanwhile, EOR-Ca²⁺-ROS-NF-κB pathway inhibited acute HCV replication, which could alleviate the detrimental effect of HCV on cell viability and enhance chronic HCV infection. Together, our findings provide new insights into the functions of EOR-Ca²⁺-ROS-NF-κB pathway in natural HCV replication and pathogenesis.

Genetic deletion of AEG-1 prevents hepatocarcinogenesis

Activation of the oncogene AEG-1 (MTDH, LYRIC) has been implicated recently in the development of hepatocellular carcinoma (HCC). In mice, HCC can be initiated by exposure to the carcinogen DEN, which has been shown to rely upon activation of NF-κB in liver macrophages. Because AEG-1 is an essential component of NF-κB activation, we interrogated the susceptibility of mice lacking the AEG-1 gene to DEN-induced hepatocarcinogenesis. AEG-1-deficient mice displayed resistance to DEN-induced HCC and lung metastasis. No difference was observed in the response to growth factor signaling or activation of AKT, ERK, and β-catenin, compared with wild-type control animals. However, AEG-1-deficient hepatocytes and macrophages exhibited a relative defect in NF-κB activation. Mechanistic investigations showed that IL6 production and STAT3 activation, two key mediators of HCC development, were also deficient along with other biologic and epigenetics findings in the tumor microenvironment, confirming that AEG-1 supports an NF-κB-mediated inflammatory state that drives HCC development. Overall, our findings offer in vivo proofs that AEG-1 is essential for NF-κB activation and hepatocarcinogenesis, and they reveal new roles for AEG-1 in shaping the tumor microenvironment for HCC development.

Open reading frame 3 of genotype 1 hepatitis E virus inhibits nuclear factor-κappa B signaling induced by tumor necrosis factor-α in human A549 lung epithelial cells

Hepatitis E virus (HEV) is one of the primary causative agents of acute hepatitis, and represents a major cause of severe public health problems in developing countries. The pathogenesis of HEV is not well characterized, however, primarily due to the lack of well-defined cell and animal models. Here, we investigated the effects of genotype 1 HEV open reading frame 3 (ORF3) on TNF-α-induced nucleus factor-κappa B (NF-κB) signaling. Human lung epithelial cells (A549) were transiently transfected with ORF3 containing plasmids. These cells were then stimulated with TNF-α and the nucleus translocation of the p65 NF-κB subunit was assessed using western blot and laser confocal microscopy. DNA-binding activity of p65 was also examined using electrophoretic mobility shift assay (EMSA), and the suppression of NF-κB target genes were detected using real-time RT-PCR and ELISA. These results enabled us to identify the decreased phosphorylation levels of IKBα. We focused on the gene of negative regulation of NF-κB, represented by TNF-α-induced protein 3 (TNFAIP3, also known as A20). Reducing the levels of A20 with siRNAs significantly enhances luciferase activation of NF-κB. Furthermore, HEV ORF3 regulated A20 primarily via activating transcription factor 6 (ATF6), involved in unfolded protein response (UPR), resulting in the degradation or inactivation of the receptor interacting protein 1 (RIP1), a major upstream activator of IKB kinase compounds (IKKs). Consequently, the phosphorylation of IKBα and the nucleus translocation of p65 are blocked, which contributes to diminished NF-κB DNA-binding activation and NF-κB-dependent gene expression. The findings suggest that genotype 1 HEV, through ORF3, may transiently activate NF-κB through UPR in early stage, and subsequently inhibit TNF-α-induced NF-κB signaling in late phase so as to create a favorable virus replication environment.

Hepatic metallothionein expression in chronic hepatitis C virus infection is IFNL3 genotype-dependent

The IFNL3 genotype predicts the clearance of hepatitis C virus (HCV), spontaneously and with interferon (IFN)-based therapy. The responder genotype is associated with lower expression of interferon stimulated genes (ISGs) in liver biopsies from chronic hepatitis C patients. However, ISGs represent many interacting molecular pathways, and we hypothesised that the IFNL3 genotype may produce a characteristic pattern of ISG expression explaining the effect of genotype on viral clearance. For the first time, we identified an association between a cluster of ISGs, the metallothioneins (MTs) and IFNL3 genotype. Importantly, MTs were significantly upregulated (in contrast to most other ISGs) in HCV-infected liver biopsies of rs8099917 responders. An association between lower fibrosis scores and higher MT levels was demonstrated underlying clinical relevance of this association. As expected, overall ISGs were significantly downregulated in biopsies from subjects with the IFNL3 rs8099917 responder genotype (P=2.38 × 10(-7)). Peripheral blood analysis revealed paradoxical and not previously described findings with upregulation of ISGs seen in the responder genotype (P=1.00 × 10(-4)). The higher MT expression in responders may contribute to their improved viral clearance and MT-inducing agents may be useful adjuncts to therapy for HCV. Upregulation of immune cell ISGs in responders may also contribute to the IFNL3 genotype effect.

Oxidative stress and hepatitis C virus

The disproportionate imbalance between the systemic manifestation of reactive oxygen species and body’s ability to detoxify the reactive intermediates is referred to as oxidative stress. Several biological processes as well as infectious agents, physiological or environmental stress, and perturbed antioxidant response can promote oxidative stress. Oxidative stress usually happens when cells are exposed to more electrically charged reactive oxygen species (ROS) such as H2O2 or O2-. The cells’ ability to handle such pro-oxidant species is impeded by viral infections particularly within liver that plays an important role in metabolism and detoxification of harmful substances. During liver diseases (such as hepatocellular or cholestatic problems), the produced ROS are involved in transcriptional activation of a large number of cytokines and growth factors, and continued production of ROS and Reactive Nitrogen Species (RNS) feed into the vicious cycle. Many human viruses like HCV are evolved to manipulate this delicate pro- and antioxidant balance; thus generating the sustainable oxidative stress that not only causes hepatic damage but also stimulates the processes to reduce treatment of damage. In this review article, the oxidant and antioxidant pathways that are perturbed by HCV genes are discussed. In the first line of risk, the pathways of lipid metabolism present a clear danger in accumulation of viral induced ROS. Viral infection leads to decrease in cellular concentrations of glutathione (GSH) resulting in oxidation of important components of cells such as proteins, DNA and lipids as well as double strand breakage of DNA. These disorders have the tendency to lead the cells toward cirrhosis and hepatocellular carcinoma in adults due to constant insult. We have highlighted the importance of such pathways and revealed differences in the extent of oxidative stress caused by HCV infection.

Xanthohumol, a main prenylated chalcone from hops, reduces liver damage and modulates oxidative reaction and apoptosis in hepatitis C virus infected Tupaia belangeri

Hepatitis C virus (HCV) infection in Tupaia belangeri (Tupaia) represents an important model of HCV infection. Xanthohumol (XN), a major prenylated chalcone from hops, has various biological activities including hepatopreventive and anti-viral activities. In this study, Tupaias infected with HCV RNA positive serum were used to evaluate the effects of XN on liver damage, oxidative reaction, apoptosis and viral protein expression in liver tissues. The Tupaias inoculated with HCV positive serum had elevated serum aminotransferase levels and inflammation, especially hepatic steatosis, and HCV core protein expression in liver tissue. In the animals inoculated with HCV positive serum, XN significantly decreased aminotransferase levels, histological activity index, hepatic steatosis score and transforming growth factor β1 expression in liver tissue compared with the animals without XN intervention. XN reduced HCV core protein expression in liver tissue compared with those without XN intervention but the difference was not significant. XN significantly decreased malondialdehyde, potentiated superoxide dismutase and glutathione peroxidase, reduced Bax expression, promoted Bcl-xL and inhibited caspase 3 activity in liver tissues compared with the animals without XN intervention. These results indicate that XN may effectively improve hepatic inflammation, steatosis and fibrosis induced by HCV in Tupaias primarily through inhibition of oxidative reaction and regulation of apoptosis and possible suppression of hepatic stellate cell activation. The anti-HCV potential of XN needs further investigation.

RNA virus capsid proteins: more than just a shell

Capsid proteins are obligatory components of infectious virions. Their primary structural function is to protect viral genomes during entry and exit from host cells. Evidence suggests that these proteins can also modulate the activity and specificity of viral replication complexes. More recently, it has become apparent that they play critical roles at the virus–host interface. Here, we discuss how capsid proteins of RNA viruses interact with key host cell proteins and pathways to modulate cell physiology in order to benefit virus replication. Capsid–host cell interactions may also have implications for viral disease. Understanding how capsids regulate virus–host interactions may lead to the development of novel antiviral therapies based on targeting the activities of cellular proteins.

Bicluster and pathway enrichment analysis of HCV-induced cirrhosis and hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is the sixth most common cancer worldwide and the most common form of liver cancer. However, while it is associated frequently with hepatitis C virus (HCV) there is only an elementary understanding of its molecular pathogenesis.

METHODS

To gain insight into the molecular mechanisms of HCV-induced hepatocarcinogenesis, we performed microarray analysis on 75 surgical liver samples from 48 HCV-infected patients.

RESULTS

There were 395 differentially expressed genes between cirrhotic samples and HCC samples. Of these, 125 genes were up-regulated and 270 genes were down-regulated. We performed pathway enrichment analysis and screened as described previously.

CONCLUSIONS

The differentially expressed genes might be involved in hepatocarcinogenesis through upregulating the pathways of ECM-receptor interaction, focal adhesion, cell adhesion molecules and other cancer-related pathways, and downregulating the pathways of "complement and coagulation cascades". We hope our results could aid in seeking of therapeutic targets for HCV-induced hepatocellular carcinoma.

Hepatitis C virus and hepatocellular carcinoma

Hepatitis C virus (HCV), a hepatotropic virus, is a single stranded-positive RNA virus of ~9,600 nt. length belonging to the Flaviviridae family. HCV infection causes acute hepatitis, chronic hepatitis, cirrhosis and hepatocellular carcinoma (HCC). It has been reported that HCV-coding proteins interact with host-cell factors that are involved in cell cycle regulation, transcriptional regulation, cell proliferation and apoptosis. Severe inflammation and advanced liver fibrosis in the liver background are also associated with the incidence of HCV-related HCC. In this review, we discuss the mechanism of hepatocarcinogenesis in HCV-related liver diseases.

Hepatitis B and C virus infections as possible risk factor for pancreatic adenocarcinoma

Pancreatic adenocarcinoma (PAC) is a very aggressive and lethal cancer, with a very poor prognosis, because of absence of early symptoms, advanced stage at presentation, early metastatic dissemination and lack of both specific tests to detect its growth in the initial phases and effective systemic therapies. To date, the causes of PAC still remain largely unknown, but multiple lines of evidence from epidemiological and laboratory researches suggest that about 15-20% of all cancers are linked in some way to chronic infection, in particular it has been shown that several viruses have a role in human carcinogenesis. The purpose of this report is to discuss the hypothesis that two well-known oncogenic viruses, Human B hepatitis (HBV) and Human C hepatitis (HCV) are a possible risk factor for this cancer. Therefore, with the aim to examine the potential link between these viruses and PAC, we performed a selection of observational studies evaluating this association and we hypothesized that some pathogenetic mechanisms involved in liver carcinogenesis might be in common with pancreatic cancer development in patients with serum markers of present or past HBV and HCV infections. To date the available observational studies performed are few, heterogeneous in design as well as in end-points and with not univocal results, nevertheless they might represent the starting-point for future larger and better designed clinical trials to define this hypothesized relationship. Should these further studies confirm an association between HBV/HCV infection and PAC, screening programs might be justified in patients with active or previous hepatitis B and C viral infection.

Hepatitis C virus infection enhances TNFα-induced cell death via suppression of NF-κB

Hepatitis C virus (HCV) infection results in liver injury and long-term complications, such as liver cirrhosis and hepatocellular carcinoma. Liver injury in HCV infection is believed to be caused by host immune responses, not by viral cytopathic effects. Tumor necrosis factor-alpha (TNF-α) plays a pivotal role in the inflammatory processes of hepatitis C. TNF-α induces cell death that can be ameliorated by nuclear factor kappaB (NF-κB) activation. We investigated the regulation of TNF-α signal transduction in HCV-infected cells and identified HCV proteins responsible for sensitization to TNF-α-induced cell death. We studied the effect of HCV infection on TNF-α signal transduction using an in vitro HCV infection model (JFH-1, genotype 2a) with Huh-7 and Huh-7.5 cells. We found that TNF-α-induced cell death significantly increased in HCV-infected cells. HCV infection diminished TNF-α-induced phosphorylation of IκB kinase (IKK) and inhibitor of NF-κB (IκB), which are upstream regulators of NF-κB activation. HCV infection also inhibited nuclear translocation of NF-κB and expression of NF-κB-dependent anti-apoptotic proteins, such as B-cell lymphoma--extra large (Bcl-xL), X-linked inhibitor of apoptosis protein (XIAP), and the long form of cellular-FLICE inhibitory protein (c-FLIP). Decreased levels of Bcl-xL, XIAP, and c-FLIP messenger RNA and protein were also observed in livers with chronic hepatitis C. Transfection with plasmids encoding each HCV protein revealed that core, nonstructural protein (NS)4B, and NS5B attenuated TNF-α-induced NF-κB activation and enhanced TNF-α-induced cell death.

CONCLUSION

HCV infection enhances TNF-α-induced cell death by suppressing NF-κB activation through the action of core, NS4B, and NS5B. This mechanism may contribute to immune-mediated liver injury in HCV infection.

Curcumin inhibits HCV replication by induction of heme oxygenase-1 and suppression of AKT

Although hepatitis C virus (HCV) affects approximately 130–170 million people worldwide, no vaccines are available. HCV is an important cause of chronic hepatitis, cirrhosis and hepatocellular carcinoma, leading to the need for liver transplantation. In this study, curcumin, a constituent used in traditional Chinese medicine, has been evaluated for its anti-HCV activity and mechanism, using a human hepatoma cell line containing the HCV genotype 1b subgenomic replicon. Below the concentration of 20% cytotoxicity, curcumin dose-dependently inhibited HCV replication by luciferase reporter gene assay, HCV RNA detection and HCV protein analysis. Under the same conditions, curcumin also dose-dependently induced heme oxygenase-1 with the highest induction at 24 h. Hemin, a heme oxygenase-1 inducer, also inhibited HCV protein expression in a dose-dependent manner. The knockdown of heme oxygenase-1 partially reversed the curcumin-inhibited HCV protein expression. In addition to the heme oxygenase-1 induction, signaling molecule activities of AKT, extracellular signal-regulated kinases (ERK) and nuclear factor-κB (NF-κB) were inhibited by curcumin. Using specific inhibitors of PI3K-AKT, MEK-ERK and NF-κB, the results suggested that only PI3K-AKT inhibition is positively involved in curcumin-inhibited HCV replication. Inhibition of ERK and NF-κB was likely to promote HCV protein expression. In summary, curcumin inhibited HCV replication by heme oxygenase-1 induction and AKT pathway inhibition. Although curcumin also inhibits ERK and NF-κB activities, it slightly increased the HCV protein expression. This result may provide information when curcumin is used as an adjuvant in anti-HCV therapy.

Glances in Immunology of HIV and HCV Infection

Since the identification of HIV and HCV much progress has been made in the understanding of their life cycle and interaction with the host immune system. Despite these viruses markedly differ in their virological properties and in their pathogenesis, they share many common features in their immune escape and survival strategy. Both viruses have developed sophisticated ways to subvert and antagonize host innate and adaptive immune responses. In the last years, much effort has been done in the study of the AIDS pathogenesis and in the development of efficient treatment strategies, and a fatal infection has been transformed in a potentially chronic pathology. Much of this knowledge is now being transferred in the HCV research field, especially in the development of new drugs, although a big difference still remains between the outcome of the two infections, being HCV eradicable after treatment, whereas HIV eradication remains at present unachievable due to the establishment of reservoirs. In this review, we present current knowledge on innate and adaptive immune recognition and activation during HIV and HCV mono-infections and evasion strategies. We also discuss the genetic associations between components of the immune system, the course of infection, and the outcome of the therapies.

Inflammation-mediated genomic instability: roles of activation-induced cytidine deaminase in carcinogenesis

Chronic inflammation is a strong risk factor for the development of cancer. Many previous studies have demonstrated that a transcriptional factor, nuclear factor (NF)-κB, plays an important role in the association between inflammation and cancer development, particularly tumor promotion and tumor progression. Although it is well recognized that cancer develops via stepwise accumulation of genetic aberrations, the mechanisms underlying the generation of these genetic alterations in normal epithelial cells under inflammatory conditions are not known. We recently demonstrated that pathogenic bacterial or viral factors and the subsequent inflammatory reactions lead to the aberrant expression of a DNA mutator enzyme, activation-induced cytidine deaminase (AID), in various epithelial cells via NF-κB activation, which causes the accumulation of genetic alterations in tumor-related genes. AID activation is widely observed in gastrointestinal tissues with cancer-associated inflammation, such as chronic viral hepatitis, Helicobacter pylori-related gastritis, Barrett's esophagus and inflammatory bowel disease. Furthermore, a deficiency of endogenous AID expression reduces both accumulation of somatic mutations in tumor-related genes and tumor incidence in a mouse model of inflammation-associated cancer development. These findings strongly suggest that AID plays an integral role in inflammation-associated carcinogenesis and is therefore a potential target molecule for the prevention and treatment of cancers.

Targeted therapy for hepatocellular carcinoma: novel agents on the horizon

Hepatocellular carcinoma (HCC) is the most common liver cancer, accounting for 90% of primary liver cancers. In the last decade it has become one of the most frequently occurring tumors worldwide and is also considered to be the most lethal of the cancer systems, accounting for approximately one third of all malignancies. Although the clinical diagnosis and management of early-stage HCC has improved significantly, HCC prognosis is still extremely poor. Furthermore, advanced HCC is a highly aggressive tumor with a poor or no response to common therapies. Therefore, new effective and well-tolerated therapy strategies are urgently needed. Targeted therapies have entered the field of anti-neoplastic treatment and are being used on their own or in combination with conventional chemotherapy drugs. Molecular-targeted therapy holds great promise in the treatment of HCC. A new therapeutic opportunity for advanced HCC is the use of sorafenib (Nexavar). On the basis of the recent large randomized phase III study, the Sorafenib HCC Assessment Randomized Protocol (SHARP), sorafenib has been approved by the FDA for the treatment of advanced HCC. Sorafenib showed to be able to significantly increase survival in patients with advanced HCC, establishing a new standard of care. Despite this promising breakthrough, patients with HCC still have a dismal prognosis, as it is currently the major cause of death in cirrhotic patients. Nevertheless, the successful results of the SHARP trial underscore the need for a comprehensive understanding of the molecular pathogenesis of this devastating disease. In this review we summarize the most important studies on the signaling pathways implicated in the pathogenesis of HCC, as well as the newest emerging drugs and their potential use in HCC management.

The macrophage response towards LPS and its control through the p38(MAPK)-STAT3 axis

In macrophages detection of gram-negative bacteria particularly involves binding of the outer-wall component lipopolysaccharide (LPS) to its cognate receptor complex, comprising Toll like receptor 4 (TLR4), CD14 and MD2. LPS-induced formation of the LPS receptor complex elicits a signaling network, including intra-cellular signal-transduction directly activated by the TLR4 receptor complex as well as successional induction of indirect autocrine and paracrine signaling events. All these different pathways are integrated into the macrophage response towards an inflammatory stimulus by a highly complex cross-talk of the pathways engaged. This also includes a tight control by several intra- and inter-cellular feedback loops warranting an inflammatory response sufficient to battle invading pathogens and to avoid non-essential tissue damage caused by an overwhelming inflammatory response. Several evidences indicate that the reciprocal cross-talk between the p38(MAPK)-pathway and signal transducer and activator of transcription (STAT)3-mediated signal-transduction forms a critical axis successively activated by LPS. The balanced activation of this axis is essential for both induction and propagation of the inflammatory macrophage response as well as for the control of the resolution phase, which is largely driven by IL-10 and sustained STAT3 activation. In this context regulation of suppressor of cytokine signaling (SOCS)3 expression and the recently described divergent regulatory roles of the two p38(MAPK)-activated protein kinases MK2 and MK3 for the regulation of LPS-induced NF-κB- and IRF3-mediated signal-transduction and gene expression, which includes the regulation of IFNβ, IL-10 and DUSP1, appears to play an important role.

NF-κB in the liver--linking injury, fibrosis and hepatocellular carcinoma

Hepatic cirrhosis and hepatocellular carcinoma (HCC) are the most common causes of death in patients with chronic liver disease. Chronic liver injury of virtually any etiology triggers inflammatory and wound-healing responses that in the long run promote the development of hepatic fibrosis and HCC. Here, we review the role of the transcription factor nuclear factor-κB (NF-κB), a master regulator of inflammation and cell death, in the development of hepatocellular injury, liver fibrosis and HCC, with a particular focus on the role of NF-κB in different cellular compartments of the liver. We propose that NF-κB acts as a central link between hepatic injury, fibrosis and HCC, and that it may represent a target for the prevention or treatment of liver fibrosis and HCC. However, NF-κB acts as a two-edged sword and inhibition of NF-κB may not only exert beneficial effects but also negatively impact hepatocyte viability, especially when NF-κB inhibition is pronounced. Finding appropriate targets or identifying drugs that either exert only a moderate effect on NF-κB activity or that can be specifically delivered to nonparenchymal cells will be essential to avoid the increase in liver injury associated with complete NF-κB blockade in hepatocytes.

Hepatitis C virus core protein induces malignant transformation of biliary epithelial cells by activating nuclear factor-kappaB pathway

In an earlier study, we found that hepatitis C virus core protein, HCV-C, participated in the malignant transformation of HCV-C transfected normal human biliary epithelial (hBE) cells by activating telomerase. Here we further investigated the signaling of the malignant transformation.

METHODS

Reverse transcription-polymerase chain reaction (RT-PCR), western blotting and immunoprecipitation were used to analyze the expression of HCV-C, human telomerase reverse transcriptase (hTERT), nuclear factor-kappaB (NF-kappaB) and NF-kappaB inhibitor alpha (IkappaBalpha) genes and the phosphorylation level of IkappaBalpha protein. Electrophoretic mobility shift assays (EMSA) and NF-kappaB-linked luciferase reporter assays were carried out to measure NF-kappaB activity.

RESULTS

The expression of HCV-C and hTERT was detected only in HCV-C-transfected hBE (hBE-HCV-C) cells but not in vector-transfected or parental hBE cells. More NF-kappaB protein accumulated in nuclear extracts of hBE-HCV-C cells rather than in those of control cells, though total NF-kappaB protein level showed no difference among these cells. DNA binding activity of NF-kappaB and the NF-kappaB-linked luciferase activity were much higher in HCV-C-transfected hBE cells than those in vector- or non-transfected hBE cells. In addition, the IkappaBalpha phosphorylation level, but not the IkappaBalpha mRNA or protein levels, was increased after HCV-C transfection.

CONCLUSIONS

Hepatitis C virus core protein activates NF-kappaB pathway in hBE cells by increasing the phosphorylation of IkappaBalpha. The pathway may be responsible for HCV-C-induced malignant transformation of hBE cells.

NFkappaB, cytokines, TLR 3 and 7 expression in human end-stage HCV and alcoholic liver disease

BACKGROUND/AIMS

Conflicting observations exist concerning the role of nuclear factor kappa B (NFjB) in alcoholic liver disease (ALD) in animal models. To date no studies have examined this aspect in human liver tissue. We here assessed cytokines and toll-like receptors (TLRs) expressions in conjunction with NFkappaB activation in non-active end-stage human ALD compared with normal livers and hepatitis C virus (HCV) related end-stage disease.

METHODS

mRNA and protein expression were examined by quantitative PCR and Western blotting, DNA-binding by electrophoretic mobility shift assays and NFkappaB sub-cellular localization by immunofluorescent staining of livers.

RESULTS

NFkappaB mRNA and protein expression as well as strong DNA-binding were preserved in ALD but significantly down-regulated in HCV compared with normal livers. P50 immunofluorescence was found in hepatocytes and bile ducts in ALD and normal livers, whereas a shift was observed in p65 staining from non-parenchymal cells in normal livers to hepatocytes in ALD. NFkappaB responsive genes mRNA levels IkBalpha and interleukin 6 were significantly higher in ALD compared with HCV. Tumour necrosis factor alpha (TNFalpha), TLRs 3 and 7 mRNA were up-regulated in ALD and HCV compared with normal liver with TNFalpha and TLR7 being the highest in HCV. Strong induction of interferon beta was found in HCV but not in ALD or normal liver tissue.

CONCLUSIONS

Persistent NFkappaB activation together with high pro-inflammatory cytokine expression and upregulation of TLR3 and TLR7 is associated with end-stage ALD in humans and could contribute to disease progression even in absence of alcohol intake.

Role of nuclear factor kappaB in liver health and disease

NF-kappaB (nuclear factor kappaB) is a heterodimeric transcription factor that is constitutively expressed in all cell types and has a central role as a transcriptional regulator in response to cellular stress. In the present review, we discuss the role of NF-kappaB signalling in the maintenance of liver homoeostasis as well as in the pathogenesis of a wide variety of conditions affecting the liver, including viral hepatitis, steatohepatitis, cirrhosis and hepatocellular carcinoma. Much of the current knowledge of NF-kappaB signalling in the liver relates to the canonical pathway, the IKK [IkappaB (inhibitor of kappaB) kinase] complex and the RelA subunit. We explore the weaknesses of the experimental approaches to date and suggest that further work is needed to investigate in detail the discreet functions of each of the Rel subunits in liver physiology and disease.

NF-κB in liver cancer: the plot thickens

The role of the NF-κB signaling pathway in liver cancer is complex. While some evidence suggests that in the liver, like in many other organ systems, NF-κB is oncogenic, there is strong evidence showing that in certain liver cancer models NF-κB suppresses tumorigenesis. These contrasting findings cannot be dismissed on technicalities and are likely due to the complex nature of the NF-κB response. Similar contrasting findings regarding NF-κB activity are revealed in skin cancer models. Thus, it is possible that the contradictory role of NF-κB in tumorigenesis is a general phenomenon and not an oddity related solely to the liver. Further studies are indicated to decipher the underlying molecular mechanisms. Revealing these mechanisms may facilitate the identification of patient subgroups and specific situations in which NF-κB inhibition will be a preferred therapeutic option. Moreover, it is possible that specific interventions could boost the tumor suppressor functions of NF-κB in tumors that harbor mutations that render this pathway constitutively active.

HCV-related hepatocellular carcinoma: From chronic inflammation to cancer

Hepatitis C virus (HCV) infection is a worldwide health problem because of its incidence and pathogenicity. It might evolve into chronic disease, cirrhosis, and/or hepatocellular carcinoma (HCC) and the outcome is mainly determined by the host immune response. For viral clearance, combined innate and adaptive immune responses are required; resolution requires a vigorous, durable, polyclonal CD4(+) and CD8(+) T-cell response, with an increase in virus-specific CD8(+) T cells or cytotoxic T lymphocytes. Failure of efficient immune response can lead to chronic inflammation, tissue remodeling through cell growth, apoptosis and/or necrosis and induction of oxidative stress. Development of fibrosis and/or cirrhosis plus a microenvironment conducive to genomic instability mutations will promote neoplastic transformation. System governance derives from cellular (regulatory cells) and humoral (cytokines and chemokines) immune networks. Therefore, HCC pathogenesis may be a model to study the disease progression from chronic inflammation to cancer allowing design of new strategies targeting the immune response, thereby modifying disease outcome.

Copper activation of NF-kappaB signaling in HepG2 cells

Copper is a persistent environmental contaminant, and exposure to elevated levels of this transition metal can result in a variety of pathologies. Copper affects the transcription of multiple defense and repair genes to protect against metal-induced pathologies. HepG2 cells were treated with copper under multiple conditions and microarray analyses were previously performed to better understand the mechanisms by which copper affects the transcription of stress-responsive genes. Analysis of the microarray data indicated that copper modulates multiple signal transduction pathways, including those mediated by NF-kappaB. Luciferase assays, quantitative reverse transcription real-time PCR, and chemical inhibition in HepG2 cells validated the microarray results and confirmed that NF-kappaB was activated by stress-inducible concentrations of copper. In addition, two novel NF-kappaB-regulated genes, SRXN1 (sulfiredoxin 1 homolog) and ZFAND2A (zinc-finger, AN1-type domain 2A), were identified. Our results indicate that the activation of NF-kappaB may be important for survival under elevated concentrations of copper.

"Hypothesis of seven balances": molecular mechanisms behind alcoholic liver diseases and association with PPARalpha

OBJECTIVES

The purpose of this review to collate current leading scientific advances of molecular mechanisms in alcoholic liver diseases and to propose a working "hypothesis of seven balances" in relation to peroxisome proliferator activated receptor alpha (PPARalpha), which has important roles in fatty acid oxidation, oxidative stress, inflammatory responses, and possibly liver fibrosis.

METHODS

We conducted an extensive literature review of over a hundred publications and collated the findings with evidence generated in our laboratory.

RESULTS

Our research points to a working hypothesis of seven balances for alcoholic liver diseases consisting of: 1) ethanol oxidation balance in hepatocytes; 2) PPAR alpha activities in liver; 3) fatty acid metabolism balance in hepatic mitochondria; 4) gastrointestinal response to ethanol, acetaldehyde and lipopolysaccharide (LPS); 5) Kupffer cells response to LPS, oxidative stress and inflammatory cytokines; 6) adiponectin levels in plasma interchangeably regulated by tumor necrosis factor-alpha (TNF-alpha); and 7) stellate cells response to all of the above promoting hepatic fibrosis. Cellular mechanisms behind alcoholic liver diseases reveal close temporal associations of PPARalpha, adiponectin, TNF-alpha, cellular inflammation, proliferation, and potentially fibrosis as illustrated in "the hypothesis of seven balances."

CONCLUSIONS

The regulation and adjustment of PPARalpha activation underlying the balance of molecular cascades might resolve the progression of alcoholic liver diseases by reducing oxidative stress and inflammatory effects induced by nuclear factor-kappaB as well as the associated adiponectin pathway. Further elucidation of these pathways would reveal exciting new prospects for treating alcoholic liver diseases and other related liver disorders.

Elevated hepatic iron: a confounding factor in chronic hepatitis C

Historically, iron overload in the liver has been associated with the genetic disorders hereditary hemochromatosis and thalassemia and with unusual dietary habits. More recently, elevated hepatic iron levels also have been observed in chronic hepatitis C virus (HCV) infection. Iron overload in the liver causes many changes including induction of oxidative stress, damage to lysosomes and mitochondria, altered oxidant defense systems and stimulation of hepatocyte proliferation. Chronic HCV infection causes numerous pathogenic changes in the liver including induction of endoplasmic reticulum stress, the unfolded protein response, oxidative stress, mitochondrial dysfunction and altered growth control. Understanding the molecular and cellular changes that could occur in a liver which has elevated hepatic iron levels and in which HCV replication and gene expression are ongoing has clinical relevance and represents an area of research in need of further investigation.

Hepatitis C virus F protein inhibits cell apoptosis by activation of intracellular NF-kappaB pathway

AIM

To observe the influence of HCV F protein on apoptosis of HepG2 cells, and explore the association between F protein and NF-kappaB signal pathway.

METHODS

HCV 1b F gene containing HepG2-F cells and HCV 1b C gene containing HepG2-C cells were treated with 100 IU/mL TNF-alpha, and analyzed by flow cytometry, Western blotting, and dual luciferase reporter assay. Empty plasmid pcDNA3.1(+) containing HepG2-3.1 cells were used as control.

RESULTS

(i) With the treatment of TNF-alpha for 18 h, the apoptosis rates (AR) of HepG2-F and HepG2-3.1 cells were 0.41% (+/- 0.11%) and 37.43% (+/- 2.03%) respectively, while that of HepG2-C was 4.07% (+/- 0.18%). At 36 h after TNF-alpha treatment, the AR of HepG2-F and HepG2-3.1 cells were 10.03% (+/- 0.41%) and 44.63% (+/- 3.37%), and that of HepG2-C was 14.95% (+/- 0.85%). (ii) After the treatment of TNF-alpha for 0.5-18 h, the p65 contents in the whole cells of HepG2-F and HepG2-3.1 showed no significant difference (P = 0.34, t = 1.08), while the p65 contents in the nucleus of HepG2-F and HepG2-3.1 cells were 3.8-1.9 times and 1.8-1.0 times higher than that in the non-treated cells (P = 0.013, t = 4.25). (iii) The relative luciferase unit (RLU) of the HepG2 cells, co-transfected with pcDNA3.1-F and pNF-kappaB-luc, and then treated with TNF-alpha (100 IU/mL) for 18 h, showed a pcDNA3.1-F dose-dependent increase.

CONCLUSION

HCV F protein can over-activate NF-kappaB signal pathway, which makes HepG2-F cells able to resist TNF-alpha induced apoptosis.