IL-1β and TNFα enhance the CXC chemokine expression of Hepatitis C Virus infected cells

Background & aims The Hepatitis C Virus (HCV) has developed several strategies to persist in infected cells without being cleared by the immune system. HCV intervenes in various cellular processes, e.g. via cleavage of host proteins. Transgenic mice expressing the viral protease NS3/4A are protected against LPS challenge due to elevated TNFα levels. Both TNFα and IL-1β are known to be upregulated in sera of HCV-infected patients. Recently, we were able to show that HCV further upregulates EGF-induced CXC chemokine expression. The present study aims to analyse the influence of the cytokines TNFα and IL-1β on the CXC chemokine expression pattern of HCV infected cells.

Methods Cells harbouring the subgenomic replicon of HCV or HCV infected cells were stimulated with either IL-1β or TNFα or left untreated. Specific siRNAs or inhibitors were used and mRNA of CXCR2 ligands determined via qPCR. Activation of p65 and MEK1 was determined by Immunoblot. Binding of the NFκB subunit p65 to the CXCL8 promoter region was determined by chromatin immunoprecipitation (ChIP).

Results TNFα and IL-1β-induced expression of the transcripts encoding CXCR2 ligands is in part substantially enhanced by HCV. Knock down of the p65 subunit of the NFkB complex results in a significant decrease of basal as well as inducible CXCL8 mRNA expression. Consistently HCV significantly enhances p65 DNA binding to the CXCL8 promoter in response to stimulation with IL-1β as well as the IL-1β-induced phosphorylation of p65 at the serine residue 536. Interestingly, inhibition of EGFR likewise resulted in a downregulation of in particular the enhancing effect of HCV on IL-1β-inducible CXCL8 mRNA expression.

Conclusion The study demonstrates that TNFα- and IL-1β-induced upregulation of CXCR2 ligand mRNA expression is further enhanced by HCV. Strikingly, the data suggest trans-activation of the EGFR by IL-1β in HCV infected cells. Furthermore, the NFκB subunit p65 seems to be crucial for HCV-dependent further upregulation of TNFα- and IL-1β-induced enhancement of CXCR2 ligand mRNA expression. HCV further upregulates the IL-1β-induced induction of NFκB p65 phosphorylation at Ser536, indicating enhanced transcriptional activity of p65 due to increased translocation of NFκB p65 into the nucleus. In summary, the present study demonstrates that HCV significantly enhances IL-1β-induced CXCL8 mRNA in its host cell involving enhancement of NFκB DNA binding and activation of EGFR.

Publication History

Article published online:
04 January 2021