HBxAg suppresses apoptosis of human placental trophoblastic cell lines via activation of the PI3K/Akt pathway

The aim of this study is to investigate the effect of hepatitis B virus X (HBx) protein on the apoptosis of placental trophoblastic cells and its potential mechanism. A pcDNA3.1 expression vector of HBx gene was built and transfected into JEG-3 and HTR-8 human placental trophoblastic cell lines, respectively. After transfection for 48 h, RT-PCR and immunofluorescence analyses showed that HBx mRNA and protein expression was detected in JEG-3 and HTR-8 cells. Flow cytometry revealed that early apoptosis of JEG-3 and HTR-8 cells was reduced by pcDNA-HBx transfection. Immunofluorescence and Western blotting showed that PI3K and p-Akt were significantly upregulated in HTR-8 cells. HBx ectopic expression did not change the viability of JEG-3 and HTR-8 cells when the PI3K/Akt pathway was blocked by its specific inhibitor LY294002. Moreover, the pcDNA-PI3K expression vector and pcDNA-HBx were transfected individually or co-transfected into the cells. The results showed that pcDNA-PI3K/pcDNA-HBx co-transfection promoted the expression of PI3K protein compared with the pcDNA-PI3K transfection group but did not increase the expression of HBx protein compared with pcDNA-HBx transfection group. In conclusion, HBx gene can be transferred into JEG-3 and HTR-8 human placental trophoblastic cell lines and cause inhibition of cell apoptosis. Its effect of apoptosis inhibition is related to the activation of the PI3K/Akt signaling pathway.