Studies On The Molecular Mechanism Of Anti-HBV Effect Of Green Tea Extract Epigallocatechin Gallate

Hepatitis B virus (HBV) is the major cause of hepatitis B and related diseases.Because of some defects of present clinical drugs, it is one of research focus to screennew anti-HBV drugs from nature extract and study its mechanism. Based on existingresearch, green tea extract had strong anti-HBV functions, this paper made furtherstudy on its molecular mechanism.Using HepG2.2.15, a cell line which can stably express HBV, we detected theanti-HBV effect of several components of green tea extract. MTT assay wasconducted to analyze the cytotoxicity effect of different concentration of differentstrutural monomers, epigallocatechin gallate (EGCG), epicatechin gallate (ECG),epigallocatechin (EGC), epicatechin (EC), and catechin (C). The anti-HBV effect ofthe five monomers was also detected respectively in the accepted dose. The results ofenzyme-linked immunosorbent assay (ELISA) showed EGCG, ECG, EGC and ECinhibited the expression of HBV antigen strongly. The inhibition rate of hepatitis Bvirus surface antigen (HBsAg) and hepatitis B e antigen (HBeAg) was up to 99.9%with EGCG post-treatment 9 days. The inhibition rate of HBsAg and HBeAgtreatment with EGC and ECG was about 95%. The inhibition rate of HBeAgtreatment with EC was about 50%. EGCG is the optimal component.For further study on the anti-HBV molecular mechanism of EGCG, weinvestigated the expression of key liver enriched transcription factors by the treatmentof EGCG. These factors including hepatocyte nuclear factor 1 (HNF1), HNF3, HNF4,retinoid X receptor (RXR), peroxisome proliferator-activated receptor (PPAR),farnesoid X receptor (FXR) regulated the transcription and replication of HBV.Semi-quantitative reverse transcription polymerase chain reaction (RT-PCR) was usedto analyze the expression of the key transcription factors. The results indicated thatthe expression of HNF1αand HNF4αdid not changend obviously with the EGCGconcentration increasing. The mRNAs of HNF3βand PPARαwere down-regulated weakly post-treatment with EGCG. However, EGCG obviously down-regulated theexpression of RXRαand FXRαin a dose dependent manner. Using L02 and HepG2cells for comparison, the results showed that different concentration of EGCG had noeffect on the expression of RXRαin the two cells. Without the treatment of EGCG,the expression of RXRαwas no obviously different in the three cell lines, but theexpression of FXRαwas increasing orderly in L02, HepG2 and HepG2.2.15 cells. Itsuggested that HBV up-regulates the expression of FXRα. Therefore, EGCG probablyinhibit the transcription and replication of HBV through down-regulating theexpression of RXRαand FXRα.