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HBxAg promotes HBV replication and EGFR activation in human placental trophoblasts.

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.

SUBMITTER: Lin Y

PROVIDER: S-EPMC8422389 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:The coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has had a massive impact on human lives worldwide. While the airborne SARS-CoV-2 primarily affects the lungs, viremia is not uncommon. As placental trophoblasts are directly bathed in maternal blood, they are vulnerable to SARS-CoV-2. Intriguingly, the human fetus is largely spared from SARS-CoV-2 infection. We tested whether the human placenta expresses the main SARS-CoV-2 entry factors angiotensin-converting enzyme 2 (ACE2), transmembrane protease serine 2 (TMPRSS2), and furin and showed that ACE2 and TMPRSS2 are expressed in the trophoblast rather than in other placental villous cells. While furin is expressed in the main placental villous cell types, we surveyed, trophoblasts exhibit the highest expression. In line with the expression of these entry factors, we demonstrated that a SARS-CoV-2 pseudovirus could enter primary human trophoblasts. Mechanisms underlying placental defense against SARS-CoV-2 infection likely involve postentry processing, which may be germane for mitigating interventions against SARS-CoV-2.IMPORTANCE Pregnant women worldwide have been affected by COVID-19. As the virus is commonly spread to various organs via the bloodstream and because human placental trophoblasts are directly bathed in maternal blood, feto-placental infection by SARS-CoV-2 seems likely. However, despite the heightened risk to pregnant women, thus far the transmission risk of COVID-19 to the feto-placental unit seems extremely low. This has been recently attributed to a negligible expression of SARS-CoV-2 entry factors in the human placenta. We therefore sought to explore the expression of the entry factors ACE2 and TMPRSS2 in the different cell types of human placental villi. Using a combination of transcriptome sequencing (RNA-seq), real-time quantitative PCR (RT-qPCR), in situ hybridization, and immunofluorescence, we found that trophoblasts, but not the other main villous cell types, express ACE2 and TMPRSS2, with a broad expression of furin. Correspondingly, we also showed that primary human trophoblasts are permissive to entry of SARS-CoV-2 pseudovirus particles.

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HBxAg promotes HBV replication and EGFR activation in human placental trophoblasts.

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