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Activation of chemokine and inflammatory cytokine response in hepatitis C virus-infected hepatocytes depends on Toll-like receptor 3 sensing of hepatitis C virus double-stranded RNA intermediates.

ABSTRACT: Chemokines and inflammatory cytokines are key regulators of immunity and inflammation during viral infections. Hepatitis C virus (HCV) is a hepatotropic RNA virus frequently associated with chronic liver inflammation and hepatocellular carcinoma. Intrahepatic levels of chemokines and cytokines are elevated in chronic HCV infections, but the underlying mechanisms remain unclear. We found that Toll-like receptor-3 (TLR3) senses HCV infection in cultured hepatoma cells, leading to nuclear factor kappa B (NF-?B) activation and the production of numerous chemokines and inflammatory cytokines, such as regulated on activation normal T cell expressed and secreted (RANTES), macrophage inflammatory protein (MIP)-1?, MIP-1?, IP-10, and interleukin-6. The chemokine/cytokine induction occurred late in HCV infection and was abrogated when HCV was ultraviolet-inactivated before infection, indicating a dependence on the cellular recognition of HCV replication products. Gel-shift and chromatin immunoprecipitation assays revealed that NF-?B plays a pivotal role in HCV-induced chemokine/cytokine transcription. Mutations specifically disrupting the double-stranded RNA (dsRNA)-binding activity of TLR3 ablated the chemokine/cytokine response to HCV infection, indicating that HCV dsRNA was the pathogen-associated molecular pattern triggering TLR3 signaling. In vitro synthesized HCV dsRNAs, with a minimal length of ?80-100 base pairs, activated TLR3-dependent chemokine expression, regardless of the genome position from which they derived. In contrast, HCV single-stranded RNAs, including those derived from the structured 3'nontranslated region highly potent for RIG-I activation, failed to do so. Moreover, robust production of chemokines and inflammatory cytokines was also observed in primary human hepatocytes after stimulation with extracellular poly-I:C, a TLR3 ligand.Our data suggest that TLR3-mediated chemokine and inflammatory cytokine responses may play an important role in host immune responses to HCV and the pathogenesis of HCV-associated liver diseases.

SUBMITTER: Li K

PROVIDER: S-EPMC3272326 | biostudies-literature | 2012 Mar

REPOSITORIES: biostudies-literature

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Activation of chemokine and inflammatory cytokine response in hepatitis C virus-infected hepatocytes depends on Toll-like receptor 3 sensing of hepatitis C virus double-stranded RNA intermediates.

Li Kui K Li Nan L NL Wei Dahai D Pfeffer Susan R SR Fan Meiyun M Pfeffer Lawrence M LM

Hepatology (Baltimore, Md.) 20120130 3

<h4>Unlabelled</h4>Chemokines and inflammatory cytokines are key regulators of immunity and inflammation during viral infections. Hepatitis C virus (HCV) is a hepatotropic RNA virus frequently associated with chronic liver inflammation and hepatocellular carcinoma. Intrahepatic levels of chemokines and cytokines are elevated in chronic HCV infections, but the underlying mechanisms remain unclear. We found that Toll-like receptor-3 (TLR3) senses HCV infection in cultured hepatoma cells, leading t ...[more]

PMID: 22030901

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Project description:Toll-like receptor-3 (TLR3) senses double-stranded RNA intermediates produced during hepatitis C virus (HCV) replication, leading to activation of interferon regulatory factor-3 (IRF3) and NF-κB and subsequent antiviral and proinflammatory responses. Yet, how this TLR3-dependent pathway operates in hepatocytes is unclear. Upon fractionating cultured hepatocytes into various cellular organelles, we observed that TLR3 predominantly resides in endolysosomes of hepatocytes. To determine the critical regulators of TLR3 signaling in response to HCV infection in human hepatocytes, we isolated endolysosome fractions from mock-infected and HCV-infected hepatoma Huh7.5 cells that had been reconstituted for TLR3 expression, separated these fractions on two-dimensional gels, and identified up-regulated/down-regulated proteins by mass spectrometry. Approximately a dozen of cellular proteins were found to be differentially expressed in endolysosome fractions following HCV infection. Of these, expression of several molecular chaperone proteins was elevated. Knockdown of one of these chaperones, glucose-regulated protein 78 kDa (GRP78), compromised TLR3-dependent induction of interferon-stimulated genes and chemokines following HCV infection or poly(I:C) stimulation in cultured hepatocytes. Consistent with this finding, GRP78 depletion impaired TLR3-mediated establishment of an antiviral state. Mechanistically, although TLR3 trafficking to endolysosomes was not affected, phosphorylated IRF3 diminished faster following GRP78 knockdown. Remarkably, GRP78 transcript was significantly up-regulated in liver biopsies of chronic hepatitis C patients as compared with normal liver tissues. Moreover, the GRP78 expression level correlated with that of RANTES (regulated upon activation, normal T-cell expressed and secreted) and CXCL10, two inflammatory chemokines most frequently elevated in HCV-infected liver. Altogether, our data suggest that GRP78 contributes to TLR3-mediated, IRF3-dependent innate immune response to HCV in hepatocytes.

Dataset Information

Activation of chemokine and inflammatory cytokine response in hepatitis C virus-infected hepatocytes depends on Toll-like receptor 3 sensing of hepatitis C virus double-stranded RNA intermediates.

Publications

Activation of chemokine and inflammatory cytokine response in hepatitis C virus-infected hepatocytes depends on Toll-like receptor 3 sensing of hepatitis C virus double-stranded RNA intermediates.

Similar Datasets

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