The Role Of HBx Up-regulating MPGES-1Expression Via EGR1in Hepatocyte Inflammatory Reaction

AIM：HBV X protein (HBx) has various important functions, including regulation ofsignal transduction, cell cycle, cell growth, apoptosis, invasion and metastasis. Studiesshowed that the synthesis of prostaglandin E2(PGE2) is increased in many tumorcells,which promotes the proliferation and migration of tumor cells, and inhibits theapoptosis of tumor cells and the immune function of host. In recent years, the researchon COX-2pathway and the use of COX-2specific inhibitor have been paid moreattention. However, the selective inhibition of COX-2changes the ratio of otherproducts in the PGE2synthesis pathway, such as PGI2and TxA2. As such, more TxA2is produced, thereby resulting in the occurrence of cardiovascular disease. Newresearch shows that DMC can reduce mPGES-1promoter activity and inhibit theexpression of mPGES-1, especially, DMC does not influence the activity of COX-2even at high concentration, which indicated that DMC is better than the COX-2inhibitor. The study of mPGES-1has become a hot issue in recent years, so mPGES-1inhibitor is expected to develop a new pharmaceutical treatment of inflammation andcancer.METHODS: RT-qPCR and Western blot were used to detect the RNA and proteinexpression in HL7702cells and HL7702-HBx cells. Full-length mPGES-1promoter(nucleotides628to+1) and a series of truncated promoter regions were cloned.Site-directed mutagenesis mPGES-1promoter regions were cloned. Theelectrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitationassay (ChIP) were revealed that HBx can increase EGR1binding to the promotertranscription site. The overexpression and knockdown of EGR1were affected thetranscription and protein level of mPGES-1in HL7702-HBx cells. Enzyme linkedimmunosorbent assay (ELISA) showed that HBx and EGR1upregulated the PGE2secretion in HL7702cells.RESULTS: The RNA and protein expression of mPGES-1in HL7702-HBx cells were higher than HL7702cells (P<0.05). HBx enhanced the mPGES-1promoteractivity in HL7702cells, and nucleotides177to+1in the promoter region exhibitedfull maximum mPGES-1promoter activity (P<0.05). EGR1mutation significantlyreduced the mPGES-1promoter activity in HL7702cells treated with HBx (P<0.05).The overexpression of EGR1enhanced the transcription and protein level ofmPGES-1in HL7702-HBx cells (P<0.05), whereas the knockdown of EGR1showedthe opposite effects (P<0.05). Both the overexpression and knockdown of EGR1didnot affect COX-2transcription and protein (P>0.05). HBx and EGR1upregulated thePGE2secretion in HL7702cells (P<0.05).COCLUSIONS:1) HBx can upregulate mPGES-1transcription and protein viaEGR1.2) The overexpression of EGR1enhances the transcription and protein level ofmPGES-1in HL7702-HBx cells, whereas the knockdown of EGR1shows theopposite effects. Both the overexpression and knockdown of EGR1do not affectCOX-2transcription and protein.3) Both HBx and EGR1upregulate the PGE2secretion in HL7702cells.