Extracellular Hepatitis C Virus Core Protein Activates STAT3 in Human Monocytes/Macrophages/Dendritic Cells via an IL-6 Autocrine Pathway

Beirne Carter Center for Immunology Research, University of Virginia, Charlottesville, Virginia 22908, USA.
Journal of Biological Chemistry (Impact Factor: 4.57). 03/2011; 286(12):10847-55. DOI: 10.1074/jbc.M110.217653
Source: PubMed


Hepatitis C virus (HCV) infection is highly efficient in the establishment of persistent infection, which leads to the development of chronic liver disease and hepatocellular carcinoma. Impaired T cell responses with reduced IFN-γ production have been reported to be associated with persistent HCV infection. Extracellular HCV core is a viral factor known to cause HCV-induced T cell impairment via its suppressive effect on the activation and induction of pro-inflammatory responses by antigen-presenting cells (APCs). The activation of STAT proteins has been reported to regulate the inflammatory responses and differentiation of APCs. To further characterize the molecular basis for the regulation of APC function by extracellular HCV core, we examined the ability of extracellular HCV core to activate STAT family members (STAT1, -2, -3, -5, and -6). In this study, we report the activation of STAT3 on human monocytes, macrophages, and dendritic cells following treatment with extracellular HCV core as well as treatment with a gC1qR agonistic monoclonal antibody. Importantly, HCV core-induced STAT3 activation is dependent on the activation of the PI3K/Akt pathway. In addition, the production of multifunctional cytokine IL-6 is essential for HCV core-induced STAT3 activation. These results suggest that HCV core-induced STAT3 activation plays a critical role in the alteration of inflammatory responses by APCs, leading to impaired anti-viral T cell responses during HCV infection.

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    • "Interleukin-6 (IL6) is a multifunctional cytokine involved in oestrogen-regulated liver carcinogenesis [61]. Extracellular HCV core protein was suggested to impair antigen-presenting cells via the IL-6 pathway [62]. "
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    ABSTRACT: Hepatitis C virus (HCV) is one of the major aetiologic agents that causes hepatocellular carcinoma (HCC) by generating an inflammatory, fibrogenic, and carcinogenic tissue microenvironment in the liver. HCV-induced HCC is a rational target for cancer preventive intervention because of the clear-cut high-risk condition, cirrhosis, associated with high cancer incidence (1% to 7% per year). Studies have elucidated direct and indirect carcinogenic effects of HCV, which have in turn led to the identification of candidate HCC chemoprevention targets. Selective molecular targeted agents may enable personalized strategies for HCC chemoprevention. In addition, multiple experimental and epidemiological studies suggest the potential value of generic drugs or dietary supplements targeting inflammation, oxidant stress, or metabolic derangements as possible HCC chemopreventive agents. While the successful use of highly effective direct-acting antiviral agents will make important inroads into reducing long-term HCC risk, there will remain an important role for HCC chemoprevention even after viral cure, given the persistence of HCC risk in persons with advanced HCV fibrosis, as shown in recent studies. The successful development of cancer preventive therapies will be more challenging compared to cancer therapeutics because of the requirement for larger and longer clinical trials and the need for a safer toxicity profile given its use as a preventive agent. Molecular biomarkers to selectively identify high-risk population could help mitigate these challenges. Genome-wide, unbiased molecular characterization, high-throughput drug/gene screening, experimental model-based functional analysis, and systems-level in silico modelling are expected to complement each other to facilitate discovery of new HCC chemoprevention targets and therapies.
    Journal of Hepatology 11/2014; 61(1). DOI:10.1016/j.jhep.2014.07.010 · 11.34 Impact Factor
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    • "These evidences suggested that miR-125b may play a role in drug responsiveness. Gene regulation in PBMC has been associated with the pathogenesis of CHC progression and the immune-mediated response of hepatocyte apoptosis (Koziel, 1997; Nasir et al., 2000; Tacke et al., 2011). Increased expression levels of PBMC–miR-155 has been associated with chronic HCV infection, but not in those responded to antiviral therapy (Bala et al., 2012; Zhang et al., 2012). "
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    ABSTRACT: Backgrounds Chronic hepatitis C virus (HCV) infection has been associated with induction of microRNAs (miRNAs) in peripheral blood mononuclear cells (PBMC). We aimed to evaluate the role of PBMC-miRNAs in the treatment outcome to antiviral therapy for HCV genotype 1 (HCV-1) patients. Methods Treatment-naive chronic HCV-1 patients, including 13 in screening phase and 48 in validation phase, were treated with 48 weeks of peginterferon/ribavirin. The primary end-point was the achievement of a sustained virological response (SVR, HCV RNA undetectable during 24 weeks post-treatment follow-up). Expression profiling of PBMC-miRNAs was performed by quantitative PCR-based array in typical responders and null-responders. Then candidate PBMC-miRNAs were validated by quantitative PCR in an independent validation set. Results PBMC-miR-125b was significantly predictive of an SVR, with expression levels of 5.28-fold lower in sustained responders versus null-responders (p=0.0163). In multivariate analysis, PBMC-miR-125b was significantly associated with the achievement of SVR (per 2-fold decrease, odds ratio/95% confidence interval (OR/CI): 2.07/1.14-6.31) independent of sex, age and interleukin-28B genotype. In patients who did not achieve a rapid virological response (RVR, undetectable HCV RNA at treatment week 4), PBMC-miR-125b was the only predictive factor of an SVR (per 2-fold decrease, OR/CI: 2.07/1.14-6.31). However, the circulating and hepatic miR-125b did not show significant difference between responders and non-responders. Conclusions PBMC-miR-125b expression levels were inversely related to the achievement of an SVR in HCV-1 patients, independent of interleukin-28B genotype, and was the single predictor of SVR in non-RVR patients.
    Antiviral research 05/2014; 105(1). DOI:10.1016/j.antiviral.2014.03.003 · 3.94 Impact Factor
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    • "Cells were plated at 1×106 cells/mL and treated with 10 µg/mL rCore or β-galactosidase (Virogen) [26] for 24 hours, then washed twice in PBS and replated. "
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    ABSTRACT: Plasmacytoid Dendritic Cells (pDCs) represent a key immune cell population in the defense against viruses. pDCs detect viral pathogen associated molecular patterns (PAMPs) through pattern recognition receptors (PRR). PRR/PAMP interactions trigger signaling events that induce interferon (IFN) production to initiate local and systemic responses. pDCs produce Type I and Type III (IFNL) IFNs in response to HCV RNA. Extracellular HCV core protein (Core) is found in the circulation in chronic infection. This study defined how Core modulates PRR signaling in pDCs. Type I and III IFN expression and production following exposure to recombinant Core or β-galactosiade was assessed in human GEN2.2 cells, a pDC cell line. Core suppressed type I and III IFN production in response to TLR agonists and the HCV PAMP agonist of RIG-I. Core suppression of IFN induction was linked with decreased IRF-7 protein levels and increased non-phosphorylated STAT1 protein. Circulating Core protein interferes with PRR signaling by pDCs to suppress IFN production. Strategies to define and target Core effects on pDCs may serve to enhance IFN production and antiviral actions against HCV.
    PLoS ONE 05/2014; 9(5):e95627. DOI:10.1371/journal.pone.0095627 · 3.23 Impact Factor
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