HBxAg promotes HBV replication and EGFR activation in human placental trophoblasts

Yayun Lin; Yan Liu; Dongping Xu; Fanfan Guo; Wentao Zhang; Yidan Zhang; Guiqin Bai

doi:10.3892/etm.2021.10645

HBxAg promotes HBV replication and EGFR activation in human placental trophoblasts

Exp Ther Med. 2021 Nov;22(5):1211. doi: 10.3892/etm.2021.10645. Epub 2021 Aug 24.

Authors

Yayun Lin¹, Yan Liu², Dongping Xu², Fanfan Guo³, Wentao Zhang³, Yidan Zhang³, Guiqin Bai¹

Affiliations

¹ Department of Gynecology and Obstetrics, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710061, P.R. China.
² Institute of Infectious Diseases, 5th Medical Center of Chinese PLA General Hospital, Beijing 100141, P.R. China.
³ College of Medicine, Xi'an Jiaotong University, Xi'an, Shaanxi 710061, P.R. China.

Abstract

Hepatitis B virus (HBV) infection is a global epidemic. The main transmission route of chronic HBV infection is from mother to child, yet the mechanisms underlying HBV intrauterine infection remain unclear. In the present study, the effect and the mechanism underlying hepatitis B virus X antigen (HBxAg) on HBV replication and EGFR activation in trophoblasts was investigated. Serum samples from pregnant women with HBV infection were used to infect trophoblasts and HBxAg expression was detected using ELISA. HBV plasmids carrying either full length hepatitis B virus X (HBx) or HBx with a deletion mutation (ΔHBx) were transfected into trophoblasts and expression levels of HBV DNA, hepatitis B e-antigen and pregenomic (pg)RNA, and structural maintenance of chromosomes (Smc) 5/6 were assessed. The association between HBx and EGFR promoters was characterized using a luciferase reporter assay and EGFR/PI3K/phosphorylated (p)-AKT expression and apoptosis rate were also monitored. The results of the present study indicated that HBxAg expression increased with the increasing titre of HBV DNA (P<0.05). Compared with the wild-type group, the amount of HBV DNA in the supernatant and cells was significantly reduced (P<0.05) in the ΔHBx group and the intracellular HBeAg and pgRNA levels were also significantly decreased (P<0.05). In addition, Smc5/6 expression was also significantly decreased (P<0.05) when the intracellular HBx protein was expressed compared with mock-transfected cells. Co-transfection of HBx and EGFR promoter plasmids in JEG-3 and HTR-8 cells significantly elevated EGFR promoter driven luciferase expression relative to the control group (P<0.01). In EGFR overexpressing cells, the expression of PI3K/p-AKT was significantly increased, whereas the apoptosis rate was significantly decreased (P<0.05). These results were reversed in the EGFR-knockdown group. In conclusion, the present study demonstrated that HBx promotes HBV replication in trophoblasts via downregulation of Smc5/6, activates the EGFR promoter and inhibits trophoblast apoptosis via the PI3K/p-AKT downstream signalling pathway, thereby increasing the risk of HBV intrauterine infection.

Keywords: EGFR promoter; HBV DNA; HBx; Smc5/6; trophoblasts.

Grants and funding

Funding: The present study was supported by the National Natural Science Foundation of China (grant no. 81370721) and the National Natural Science Foundation of China (grant no. 81771615).