Hepatitis B Virus Protein X-induced Expression of the CXC Chemokine IP-10 Is Mediated through Activation of NF-κB and Increases Migration of Leukocytes

Jing-Wei Ma,Hui-Fen Zhu,Ping Lei,Xiong-Wen Wu,Guan-Xin Shen,Qin Ning,Biao Zhang,Zhuo-Shun Yang,Shuo Wang,Xin-Xin Yao,Chuan Shi,Zhang Lei,Bo Huang,Li-Fang Sun,Yu Zhou

doi:10.1074/jbc.m109.067629

Abstract

Interferon-gamma inducible protein 10 (IP-10) involves inflammatory cell recruitment and cellular immune damage during virus infection. Although an increase of the peripheral IP-10 level is known in HBV-infected patients, the molecular basis of HBV infection inducing IP-10 expression has remained elusive. In the present study, we demonstrate that hepatitis B virus protein X (HBx) increases IP-10 expression in a dose-dependent manner. Transfection of the HBx-expressing vector into HepG2 cells results in nuclear translocation of NF-kappaB, which directly binds the promoter of IP-10 at positions from -122 to -113, thus facilitating transcription. The addition of the NF-kappaB inhibitor blocks the effect of HBx on IP-10 induction. In parallel, increase of NF-kappaB subunits p65 and p50 in HepG2 cells also augments IP-10 expression. Furthermore, we show that HBx induces activation of NF-kappaB through the TRAF2/TAK1 signaling pathway, leading to up-regulation of IP-10 expression. As a consequence, up-regulation of IP-10 may mediate the migration of peripheral blood leukocytes in a NF-kappaB-dependent manner. In conclusion, we report a novel molecular mechanism of HBV infection inducing IP-10 expression, which involves viral protein HBx affecting NF-kappaB pathway, leading to transactivation of the IP-10 promoter. Our study provides insight into the migration of leukocytes in response to HBV infection, thus causing immune pathological injury of liver.

Highlights

There is no direct cytopathic effect on hepatocytes, HBV infection induces the infiltration of immune cells, leading to formation of necroinflammatory foci, mediating disease processes [1, 2]
To confirm the previous report, we analyzed the expression of inducible protein 10 (IP-10) in HBV-infected liver tissue, and found that the mRNA levels of IP-10 were much higher in HBV-positive liver cancer tissues, compared with HBV-negative liver cancer tissues or normal liver tissues (Fig. 1A)
hepatitis B virus protein X (HBx) Induces IP-10 Gene Expression in HepG2 Cells—To evaluate the effect of HBV on IP-10 expression, HepG2 cells were transfected with the full-length HBV gene for 48 h and protein levels of IP-10 in the supernatants were measured

Summary

Introduction

There is no direct cytopathic effect on hepatocytes, HBV infection induces the infiltration of immune cells, leading to formation of necroinflammatory foci, mediating disease processes [1, 2]. The result showed that transfection of HBx, rather than HBs, or HBc-expressing vector increased IP-10 protein levels (Fig. 2A).

Results

Conclusion