Age-dependent PPARα activation induces hepatic sulfatide accumulation in transgenic mice carrying the hepatitis C virus core gene

Sulfatides, a type of glycosphingolipid, are associated with carcinogenesis. Peroxisome proliferator-activated receptor α (PPARα) is involved in the regulation of sulfatide metabolism as well as in cancer development. We previously reported that transgenic (Tg) mice expressing hepatitis C virus core protein (HCVcp) exhibited age-dependent PPARα activation and carcinogenesis in liver. However, the metabolism of sulfatides in hepatocellular carcinoma is unknown. To examine the relationship between sulfatide metabolism, carcinogenesis, HCVcp, and PPARα, age-dependent changes of these factors were examined in HCVcpTg, PPARα inhibitor-treated HCVcpTg, and non-Tg mice. The sulfatide content in liver, the hepatic expression of two key enzymes catalyzing the initial and last reactions in sulfatide synthesis, the hepatic expression of known sulfatide-transferring protein, oxidative stress, and hepatic PPARα expression and its activation were age-dependently increased in HCVcpTg mice. The increased synthesis and accumulation of sulfatides and PPARα activation were significantly enhanced in liver cancer lesions. These changes were attenuated by PPARα inhibitor treatment and not observed in non-Tg mice. These results suggest that HCVcp-induced age-dependent PPARα activation increases synthesis of sulfatides and the resulting sulfatide accumulation affects HCV-related liver cancer. The monitoring of hepatic sulfatide content and the modulation of sulfatide generation by intervention using a PPARα inhibitor might be useful for the prediction and prevention of HCV-related hepatocarcinogenesis, respectively.     

MiR‐19a Affects Hepatocyte Autophagy via Regulating lncRNA NBR2 and AMPK/PPARα in D‐GalN/Lipopolysaccharide‐Stimulated Hepatocytes

This study aims to evaluate the potential involvement and regulatory mechanism of miR‐19a in hepatocytes autophagy of acute liver failure (ALF). The in vitro hepatocytes injury model of primary hepatocyte and hepatocytes line HL‐7702 was established by D‐galactosamine (D‐GalN) and lipopolysaccharide (LPS) co‐treatment. Relative expression level of miR‐19a and NBR2 was determined by qRT‐PCR. Protein expression of AMPK/PPARα and autophagy‐related gene was determined by Western blot. In hepatic tissue of 20 ALF patients and D‐GalN/LPS‐stimulated hepatocytes, miR‐19a was upregulated and NBR2 was downregulated. D‐GalN/LPS stimulation caused the inactivation of AMPK/PPARα signaling and the decrease of autophagy‐related LC3‐II/LC3‐I ratio and beclin‐1 expression in hepatocytes. The expression of both AMPK/PPARα and NBR2 were negatively controlled by miR‐19a overexpression or knockdown. Moreover, both NBR2 and PPARα were targeted regulated by miR‐19a according to luciferase reporter assay. In D‐GalN/LPS‐stimulated hepatocytes, AMPK activation promoted PPARα expression. AMPK inactivation inhibited the pro‐autophagy effect of miR‐19a and caused the decrease of LC3‐II/LC3‐I ratio and beclin‐1 expression. PPARα activation abrogated the anti‐autophagy effect of miR‐19a mimic and caused the increase of LC3‐II/LC3‐I ratio and beclin‐1 expression. NBR2 knockdown reversed the anti‐autophagy impact of miR‐19a inhibitor and caused the decrease of LC3‐II/LC3‐I ratio and beclin‐1 expression. In summary, our data suggested that miR‐19a negatively controlled the autophagy of hepatocytes attenuated in D‐GalN/LPS‐stimulated hepatocytes via regulating NBR2 and AMPK/PPARα signaling. J. Cell. Biochem. 119: 358–365, 2018. © 2017 Wiley Periodicals, Inc.     

Hepatitis C virus core inhibits the Fas-mediated p38 mitogen activated kinase signaling pathway in hepatocytes

The p38 mitogen activated kinase (MAPK) signaling pathway plays an essential role in regulating many cellular processes, including inflammation, cell differentiation, and cell death. Here, we report that the hepatitis C virus (HCV) core inhibits the Fas-mediated p38 signaling pathway. The Fas-mediated p38 activation is suppressed in core-expressing HepG2 cell lines, as well as in the hepatocytes of transgenic mice. In addition, core protein blocked the Fas-mediated activation of apoptosis signal-regulating kinase 1 (ASK1), a major upstream MAPKKK of p38. Treatment of a specific p38 inhibitor (SB203580) or overexpression of a kinase-defective mutant, ASK1 (K709R), promoted Fas-mediated cell death in HepG2 cells. This suggests that the p38 and ASK1 activation is required for cell survival against Fas-mediated cell death. In addition, we observed that the HCV core protein enhances Fas-mediated liver injury and lethality in transgenic mice. Collectively, our findings suggest that the HCV core inhibits the Fas-mediated p38 signaling pathway, which results in accelerated Fas-mediated cell death.     

Hepatitis C virus infection activates the immunologic (type II) isoform of nitric oxide synthase and thereby enhances DNA damage and mutations of cellular genes

Hepatitis C virus (HCV) infection causes hepatitis, hepatocellular carcinoma, and B-cell lymphomas in a significant number of patients. Previously we have shown that HCV infection causes double-stranded DNA breaks and enhances the mutation frequency of cellular genes, including proto-oncogenes and immunoglobulin genes. To determine the mechanisms, we studied in vitro HCV infection of cell culture. Here we report that HCV infection activated the immunologic (type II) isoform of nitric oxide (NO) synthase (NOS), i.e., inducible NOS (iNOS), thereby inducing NO, which in turn induced DNA breaks and enhanced the mutation frequencies of cellular genes. Treatment of HCV-infected cells with NOS inhibitors or small interfering RNA specific for iNOS abolished most of these effects. Expression of the core protein or nonstructural protein 3 (NS3), but not the other viral proteins, in B cells or hepatocytes induced iNOS and DNA breaks, which could be blocked by NOS inhibitors. The core protein also enhanced the mutation frequency of cellular genes in hepatocytes derived from HCV core transgenic mice compared with that in control mice. The iNOS promoter was activated more than fivefold in HCV-infected cells, as revealed by a luciferase reporter assay driven by the iNOS promoter. Similarly, the core and NS3 proteins also induced the same effects. Therefore, we conclude that HCV infection can stimulate the production of NO through activation of the gene for iNOS by the viral core and NS3 proteins. NO causes DNA breaks and enhances DNA mutation. This sequence of events provides a mechanism for HCV pathogenesis and oncogenesis.     

Fas ligand is responsible for CXCR3 chemokine induction in CD4+ T cell-dependent liver damage

Immune-mediated hepatic damage has been demonstrated in the pathogenesis of hepatitis C virus (HCV) and other hepatotrophic infections. Fas/Fas ligand (FasL) interaction plays a critical role in immune-mediated hepatic damage. To understand the molecular mechanism(s) of FasL-mediated liver inflammation, we examined the effect of CD4(+) T cells expressing high levels of FasL on the initiation of hepatic damage through analysis of chemokine and chemokine receptor expression in HCV core x TCR (DO11.10) double-transgenic mice. In vivo antigenic stimulation triggers a marked influx of core-expressing Ag-specific CD4(+) T cells into the liver of the immunized core(+) TCR mice but not their core(-) TCR littermates. Strikingly, the inflammatory process in the liver of core(+) TCR mice was accompanied by a dramatic increase in IFN-inducible protein 10 and monokine induced by IFN-gamma production. The intrahepatic lymphocytes were primarily CXCR3-positive and anti-CXCR3 Ab treatment abrogates migration of CXCR3(+) lymphocytes into the liver and hepatic damage. Importantly, the blockade of Fas/FasL interaction reduces the expression of IFN-inducible protein 10 and monokine induced by IFN-gamma and cellular infiltration into the liver. These findings suggest that activated CD4(+) T cells with elevated FasL expression are involved in promoting liver inflammation and hepatic damage through the induction of chemokines.     

Mechanisms of adiponectin‐mediated COX‐2 induction and protection against iron injury in mouse hepatocytes

Adiponectin (APN)‐mediated cyclooxygenase (COX)‐2 induction is known to have various protective effects on cardiovascular diseases. However, the molecular mechanisms of APN‐mediated COX‐2 induction and its protection against iron‐mediated injury in hepatocytes are still unclear. Herein, we show that AMP‐mediated peroxisome proliferator‐activated receptor (PPAR)α activation was attributable to COX‐2 induction by APN, which was further confirmed by identifying novel functional PPAR responsive elements (PPREs) in the mouse COX‐2 promoter region. Prostaglandin (PG)I2 and PGE2, metabolites of COX‐2, time‐dependently increased in hepatocytes treated with APN. Interestingly, beraprost and misoprostol, respective agonists for PGI2 and PGE2, mimicked the protective effects of APN in iron‐mediated inflammation in hepatocytes. The iron dextran‐activated nuclear factor (NF)‐κB pathway was correlated with the increased production of inflammatory cytokines including tumor necrosis factor‐α, intercellular adhesion molecule‐1, and monocyte chemotactic protein‐1. This was eliminated by administration of APN, whereas blockage of PPARα activation, an upstream regulator of COX‐2 induction by APN, and COX‐2 activation reversed the anti‐inflammatory effect of APN, suggesting the crucial role of COX‐2 in this event. Herein, we demonstrate that APN‐mediated COX‐2 induction through a PPARα‐dependent mechanism, and COX‐2 exerted an anti‐inflammatory effect of APN in hepatocytes subjected to iron challenge. J. Cell. Physiol. 224: 837–847, 2010. © 2010 Wiley‐Liss, Inc.     

Farnesol, an isoprenoid, improves metabolic abnormalities in mice via both PPARα-dependent and -independent pathways

Peroxisome proliferator-activated receptors (PPARs) control energy homeostasis. In this study, we showed that farnesol, a naturally occurring ligand of PPARs, could ameliorate metabolic diseases. Obese KK-Ay mice fed a high-fat diet (HFD) containing 0.5% farnesol showed significantly decreased serum glucose level, glucosuria incidence, and hepatic triglyceride contents. Farnesol-containing HFD upregulated the mRNA expressions of PPARα target genes involved in fatty acid oxidation in the liver. On the other hand, farnesol was not effective in upregulating the mRNA expressions of PPARγ target genes in white adipose tissues. Experiments using PPARα-deficient [(-/-)] mice revealed that the upregulation of fatty acid oxidation-related genes required PPARα function, but the suppression of hepatic triglyceride accumulation was partially PPARα-dependent. In hepatocytes isolated from the wild-type and PPARα (-/-) mice, farnesol suppressed triglyceride synthesis. In luciferase assay, farnesol activated both PPARα and the farnesoid X receptor (FXR) at similar concentrations. Moreover, farnesol increased the mRNA expression level of a small heterodimer partner known as one of the FXR target genes and decreased those of sterol regulatory element-binding protein-1c and fatty acid synthase in both the wild-type and PPARα (-/-) hepatocytes. These findings suggest that farnesol could improve metabolic abnormalities in mice via both PPARα-dependent and -independent pathways and that the activation of FXR by farnesol might contribute partially to the PPARα-independent hepatic triglyceride content-lowering effect. To our knowledge, this is the first study on the effect of the dual activators of PPARα and FXR on obesity-induced metabolic disorders.     

Induction of hepatic injury by hepatitis C virus-specific CD8+ murine cytotoxic T lymphocytes in transgenic mice expressing the viral structural genes

In the present study, we generated killer cells specific for hepatitis C virus (HCV) structural protein by re-stimulation of immune spleen cells from H-2(d) haplotype transgenic (Tg) mice, expressing the core, E1, E2, and NS2 genes of HCV regulated by the Cre/loxP switching system. The generated killer cells were conventional CD8(+)L(d) class-I MHC molecule-restricted cytotoxic T lymphocytes (CTLs) and specific for the HCV E1 structural protein. Because the CTLs could also kill hepatocytes from the Tg mice expressing HCV structural proteins in vitro, we attempted to transfer those CTLs intravenously into interferon regulatory factor-1 (IRF-1) negative, CD8-deficient Tg mice representing the HCV structural genes on hepatocytes to examine whether the inoculated CD8(+) CTLs can eliminate hepatocytes expressing the HCV genes in vivo. We observed an elevation of serum ALT level as well as damage of the liver tissue histologically. To our knowledge, this is the first demonstration to show that HCV-specific CD8(+) CTLs specifically attack hepatocytes expressing the HCV structural proteins both in vitro and in vivo.     

The liver-enriched transcription factor CREBH is nutritionally regulated and activated by fatty acids and PPARα

To elucidate the physiological role of CREBH, the hepatic mRNA and protein levels of CREBH were estimated in various feeding states of wild and obesity mice. In the fast state, the expression of CREBH mRNA and nuclear protein were high and profoundly suppressed by refeeding in the wild-type mice. In ob/ob mice, the refeeding suppression was impaired. The diet studies suggested that CREBH expression was activated by fatty acids. CREBH mRNA levels in the mouse primary hepatocytes were elevated by addition of the palmitate, oleate and eicosapenonate. It was also induced by PPARα agonist and repressed by PPARα antagonist. Luciferase reporter gene assays indicated that the CREBH promoter activity was induced by fatty acids and co-expression of PPARα. Deletion studies identified the PPRE for PPARα activation. Electrophoretic mobility shift assay and chromatin immunoprecipitation (ChIP) assay confirmed that PPARα directly binds to the PPRE. Activation of CREBH at fasting through fatty acids and PPARα suggest that CREBH is involved in nutritional regulation.     

Inhibition of the actions of peroxisome proliferator-activated receptor alpha on obesity by estrogen

Objective: To determine whether the major ovarian factor estrogen modulates peroxisome proliferator‐activated receptor (PPAR) α actions on obesity and to investigate the mechanism by which estrogen regulates PPARα actions. Research Methods and Procedures: Female ovariectomized mice were randomly divided into four groups (n = 8/group). After they were treated with combinations of high fat, fenofibrate (FF), or 17β‐estradiol (E) for 13 weeks, variables and determinants of obesity and lipid metabolism were measured using in vivo and in vitro approaches. Results: When female ovariectomized mice were given a high‐fat diet with either FF or E, body weight gain and white adipose tissue mass were significantly reduced and serum lipid profiles were improved compared with control mice fed a high‐fat diet alone. When mice were concomitantly treated with FF and E, however, E reversed the effects of FF on body weight gain, serum lipid profiles, and hepatic PPARα target gene expression. Consistent with the in vivo data, E not only decreased basal levels of PPARα reporter gene activation but also significantly decreased Wy14,643‐induced luciferase reporter activity. In addition, inhibition of PPARα functions by E did not seem to occur by interfering with the DNA binding of PPARα. Discussion: Our results demonstrate that in vivo and in vitro treatment of estrogen inhibited the actions of FF‐activated PPARα on obesity and lipid metabolism through changes in the expression of PPARα target genes, providing evidence that FF does not regulate obesity in female mice with functioning ovaries.     

Peroxisome proliferator-activated receptor {alpha} is responsible for the up-regulation of hepatic glucose-6-phosphatase gene expression in fasting and db/db Mice

Glucose-6-phosphatase (G6Pase) is a key enzyme that is responsible for the production of glucose in the liver during fasting or in type 2 diabetes mellitus (T2DM). During fasting or in T2DM, peroxisome proliferator-activated receptor α (PPARα) is activated, which may contribute to increased hepatic glucose output. However, the mechanism by which PPARα up-regulates hepatic G6Pase gene expression in these states is not well understood. We evaluated the mechanism by which PPARα up-regulates hepatic G6Pase gene expression in fasting and T2DM states. In PPARα-null mice, both hepatic G6Pase and phosphoenolpyruvate carboxykinase levels were not increased in the fasting state. Moreover, treatment of primary cultured hepatocytes with Wy14,643 or fenofibrate increased the G6Pase mRNA level. In addition, we have localized and characterized a PPAR-responsive element in the promoter region of the G6Pase gene. Chromatin immunoprecipitation (ChIP) assay revealed that PPARα binding to the putative PPAR-responsive element of the G6Pase promoter was increased in fasted wild-type mice and db/db mice. These results indicate that PPARα is responsible for glucose production through the up-regulation of hepatic G6Pase gene expression during fasting or T2DM animal models.     

Innate detection of hepatitis B and C virus and viral inhibition of the response

Viral hepatitis caused by hepatitis B virus (HBV) and hepatitis C virus (HCV) infections poses a significant burden to the public health system. Although HBV and HCV differ in structure and life cycles, they share unique characteristics, such as tropism to infect hepatocytes and association with hepatic and extrahepatic disorders that are of innate immunity nature. In response to HBV and HCV infection, the liver innate immune cells eradicate pathogens by recognizing specific molecules expressed by pathogens via distinct cellular pattern recognition receptors whose triggering activates intracellular signalling pathways inducing cytokines, interferons and anti‐viral response genes that collectively function to clear infections. However, HBV and HCV evolve strategies to inactivate innate signalling factors and as such establish persistent infections without being recognized by the innate immunity. We review recent insights into how HBV and HCV are sensed and how they evade innate immunity to establish chronicity. Understanding the mechanisms of viral hepatitis is mandatory to develop effective and safe therapies for eradication of viral hepatitis.     

抑制核转录因子PPARα的反义寡核苷酸的抗乙型肝炎病毒活性研究

目的:研究靶向过氧化物酶体增殖活化受体α(PPARα)的寡核苷酸是否具有抑制乙型肝炎病毒(HBV)复制的活性作用。方法:反义寡核苷酸作用于能稳定表达HBV丹氏颗粒的HepG2.2.15细胞,ELISA检测细胞上清中HBV表面抗原(HBsAg)及e抗原(HBeAg)的分泌;实时荧光定量PCR考察反义寡核苷酸对HBV DNA复制水平的影响;通过反转录PCR和Western印迹考察反义寡核苷酸作用于细胞后靶基因及靶蛋白的差异表达情况。结果:抑制PPARα表达的反义序列PPARα-2可剂量依赖且特异性地抑制肝癌细胞中HBsAg和HBeAg的表达,且显著降低细胞中PPARαmRNA水平和蛋白水平。结论:通过筛选初步确定了基于PPARα设计的反义寡核苷酸有较好的抗HBV活性,同时也验证确定了PPARα可能成为抗HBV药物的新型作用靶点。     

Hepatitis C Virus Core and Envelope Proteins Do Not Suppress the Host's Ability To Clear a Hepatic Viral Infection

Several hepatitis C virus (HCV) proteins have been shown in vitro to interact with host cellular components that are involved in immune regulation. However, there is a paucity of data supporting the relevance of these observations to the in vivo situation. To test the hypothesis that such an interaction suppresses immune responses, we studied a line of transgenic C57BL/6 mice that express the HCV core and envelope proteins in the liver. The potential effects of these proteins on the hepatic immune response were evaluated by challenging these mice with a hepatotropic adenovirus. Both transgenic and nontransgenic mice developed similar courses of infection and cleared the virus from the liver by 28 days postinfection. Both groups of mice mounted similar immunoglobulin G (IgG), IgG2a, interleukin-2, and tumor necrosis factor alpha responses against the virus. Additionally, BALB/c mice were able to clear infection with recombinant adenovirus that does or does not express the HCV core and envelope 1 proteins in the same manner. These data suggest that HCV core and envelope proteins do not inhibit the hepatic antiviral mechanisms in these murine experimental systems and thus favor a model in which HCV circumvents host responses through a mechanism that does not involve general suppression of intrahepatic immune responses.     

Genetic Immunization of Wild-Type and Hepatitis C Virus Transgenic Mice Reveals a Hierarchy of Cellular Immune Response and Tolerance Induction against Hepatitis C Virus Structural Proteins

To study the effect of genetic immunization on transgenic expression of hepatitis C virus (HCV) proteins, we evaluated the immunological response of HCV transgenic mice to HCV expression plasmids. FVB/n transgenic mice expressing HCV structural proteins (core, E1, and E2) and wild-type (WT) FVB/n mice were immunized intramuscularly with plasmids expressing core (pHCVcore) or core/E1/E2 (pHCVSt). After immunization, HCV-specific humoral and cellular immune response was studied. Both WT and transgenic mice immunized with either HCV construct produced antibodies and exhibited T-cell proliferative responses against core or envelope. In WT mice immunized with pHCVSt, cytotoxic T-lymphocyte (CTL) activities were detected against E2 but not against core or E1, whereas strong CTL activities against core could be detected in WT mice immunized with pHCVcore. In pHCVSt-immunized, transgenic mice, CTL activities against the core or envelope were completely absent, but core-specific CTL activities could be detected in pHCVcore-immunized transgenic mice. A similar pattern of immune responses was also observed in other mouse strains, including a transgenic line expressing human HLA-A2.1 molecules (AAD mice). Despite the presence of a peripheral cellular immunity against HCV, no liver pathology or lymphocytic infiltrate was observed in these transgenic mice. Our study suggests a hierarchy of CTL response against the HCV structural proteins (E2 > core > E1) in vivo when the proteins are expressed as a polyprotein. The HCV transgenic mice can be induced by DNA immunization to generate anti-HCV antibodies and anticore CTLs. However, they are tolerant at the CTL level against the E2 protein despite DNA immunization.     

Reduced kidney lipoprotein lipase and renal tubule triglyceride accumulation in cisplatin-mediated acute kidney injury

Peroxisome proliferator-activated receptor-α (PPARα) activation attenuates cisplatin (CP)-mediated acute kidney injury by increasing fatty acid oxidation, but mechanisms leading to reduced renal triglyceride (TG) accumulation could also contribute. Here, we investigated the effects of PPARα and CP on expression and enzyme activity of kidney lipoprotein lipase (LPL) as well as on expression of angiopoietin protein-like 4 (Angptl4), glycosylphosphatidylinositol-anchored-HDL-binding protein (GPIHBP1), and lipase maturation factor 1 (Lmf1), which are recognized as important proteins that modulate LPL activity. CP caused a 40% reduction in epididymal white adipose tissue (WAT) mass, with a reduction of LPL expression and activity. CP also reduced kidney LPL expression and activity. Angptl4 mRNA levels were increased by ninefold in liver and kidney tissue and by twofold in adipose tissue of CP-treated mice. Western blots of two-dimensional gel electrophoresis identified increased expression of a neutral pI Angptl4 protein in kidney tissue of CP-treated mice. Immunolocalization studies showed reduced staining of LPL and increased staining of Angptl4 primarily in proximal tubules of CP-treated mice. CP also increased TG accumulation in kidney tissue, which was ameliorated by PPARα ligand. In summary, a PPARα ligand ameliorates CP-mediated nephrotoxicity by increasing LPL activity via increased expression of GPHBP1 and Lmf1 and by reducing expression of Angptl4 protein in the proximal tubule.     

Catalposide is a natural agonistic ligand of peroxisome proliferator-activated receptor-α

Peroxisome proliferator-activated receptor-alpha (PPARα) is a nuclear receptor that regulates the expression of genes related to cellular lipid uptake and oxidation. Thus, PPARα agonists may be important in the treatment of hypertriglyceridemia and hepatic steatosis. In this study, we demonstrated that catalposide is a novel natural PPARα agonist, identified from reporter gene assay-based activity screening with approximately 900 natural plant and seaweed extracts. Results of time-resolved fluorescence resonance energy transfer analyses suggested that the compound interacted directly with the ligand-binding domain of PPARα. Cultured hepatocytes stimulated with catalposide exhibited significantly reduced cellular triglyceride concentrations, by 21%, while cellular uptake of fatty acids was increased, by 70% (P<0.05). Quantitative PCR analysis revealed that the increase in cellular fatty acid uptake was due to upregulation of fatty acid transporter protein-4 (+19% vs. the control) in cells stimulated with catalposide. Additionally, expression of genes related to fatty acid oxidation and high-density lipoprotein metabolism were upregulated, while that of genes related to fatty acid synthesis were suppressed. In conclusion, catalposide is hypolipidemic by activation of PPARα via a ligand-mediated mechanism that modulates the expression of in lipid metabolism genes in hepatocytes.     

Hepatitis C virus core protein suppresses NF-kappaB activation and cyclooxygenase-2 expression by direct interaction with IkappaB kinase beta

In addition to hepatocytes, hepatitis C virus (HCV) infects immune cells, including macrophages. However, little is known concerning the impact of HCV infection on cellular functions of these immune effector cells. Lipopolysaccharide (LPS) activates IkappaB kinase (IKK) signalsome and NF-kappaB, which leads to the expression of cyclooxygenase-2 (COX-2), which catalyzes production of prostaglandins, potent effectors on inflammation and possibly hepatitis. Here, we examined whether expression of HCV core interferes with IKK signalsome activity and COX-2 expression in activated macrophages. In reporter assays, HCV core inhibited NF-kappaB activation in RAW 264.7 and MH-S murine macrophage cell lines treated with bacterial LPS. HCV core inhibited IKK signalsome and IKKbeta kinase activities induced by tumor necrosis factor alpha in HeLa cells and coexpressed IKKgamma in 293 cells, respectively. HCV core was coprecipitated with IKappaKappabeta and prevented nuclear translocation of IKKbeta. NF-kappaB activation by either LPS or overexpression of IKKbeta was sufficient to induce robust expression of COX-2, which was markedly suppressed by ectopic expression of HCV core. Together, these data indicate that HCV core suppresses IKK signalsome activity, which blunts COX-2 expression in macrophages. Additional studies are necessary to determine whether interrupted COX-2 expression by HCV core contributes to HCV pathogenesis.