ERK1/2-HNF4α axis is involved in epigallocatechin-3-gallate inhibition of HBV replication

Epigallocatechin gallate (EGCG), a major polyphenol in green tea, exhibits diverse biological activities. Previous studies show that EGCG could effectively suppress HBV gene expression and replication, but the role of EGCG in HBV replication and its underlying mechanisms, especially the signaling pathways involved, remain unclear. In this study we investigated the mechanisms underlying EGCG inhibition on HBV replication with a focus on the signaling pathways. We showed that EGCG (12.5-50 μM) dose-dependently inhibited HBV gene expression and replication in HepG2.2.15 cells. Similar results were observed in HBV mice receiving EGCG (25 mg· kg-1· d-1, ip) for 5 days. In HepG2.2.15 cells, we showed that EGCG (12.5-50 μM) significantly activate ERK1/2 MAPK signaling, slightly activate p38 MAPK and JAK2/STAT3 signaling, while had no significant effect on the activation of JNK MAPK, PI3K/AKT/mTOR and NF-κB signaling. By using specific inhibitors of these signaling pathways, we demonstrated that ERK1/2 signaling pathway, but not other signaling pathways, was involved in EGCG-mediated inhibition of HBV transcription and replication. Furthermore, we showed that EGCG treatment dose-dependently decreased the expression of hepatocyte nuclear factor 4α (HNF4α) both at the mRNA and protein levels, which could be reversed by pretreatment with the ERK1/2 inhibitor PD98059 (20 μM). Moreover, we revealed that EGCG treatment dose-dependently inhibited the activity of HBV core promoter and the following HBV replication. In summary, our results demonstrate that EGCG inhibits HBV gene expression and replication, which involves ERK1/2-mediated downregulation of HNF4α.These data reveal a novel mechanism for EGCG to inhibit HBV gene expression and replication.

[Effect and mechanism of danshensu on hepatitis B virus reverse transcriptase and antigen expression]

MTT assay was used in this study to investigate the inhibitory effect of danshensu on the activity of 2.2.15 cells among human hepatoma cell line (HepG2); indirect fluorescence labeling method was used to measure the changes of reactive oxygen levels in the cells; ELISA method was used to determine hepatitis B surface antigen (HBsAg) and hepatitis B e antigen (HBeAg) levels in cellular supernatants; HBV DNA level was measured with fluorogenic quantitative PCR method. The inhibitory effect of danshensu on HBV RT(hepatitis B virus reverse transcriptase) was studied by using enzyme inhibition dynamics, and the effect of danshensu on secondary structure of HBV reverse transcriptase was monitored by using circular dichroism. The results showed that danshensu had a good inhibitory effect on the growth of HepG2.2.15 cells, with a half inhibitory concentration (IC₅₀) of (15.35±2.43) μmol•L⁻¹; danshensu could significantly inhibit HBsAg and HBeAg expressions, and showed an inhibitory effect on HBV DNA replication. In addition, danshensu was an effective inhibitor for HBV reverse transcriptase [IC₅₀ (21.32±2.43) μmol•L⁻¹]. The fluorescence labeling results showed that the reactive oxygen levels in the cells were increased with the increase of danshensu concentration. Circular dichroism analysis showed that danshensu could induce partial change of conformation of HBV reverse transcriptase and gradually increased α-helical content. These results indicated that danshensu could make the structure of the enzyme become closer by binding to HBV reverse transcriptase, which was not conducive to the formation of the active center, so it could finally decrease the activity of HBV reverse transcriptase. Such decrease in enzyme activity would directly affect the HBV DNA replication, and combined with the decrease of the antigen levels, the effect of danshensu on HBV was increased.

Discovery and mechanism of action of Novel Baicalein modified derivatives as potent antihepatitis agent

Anti-hepatitis B virus (HBV) activity was evaluated in HepG2 2.2.15 cells by novel Baicalein derivatives. The result showed that compounds 4k and 4h was found to be effective anti-HBV agent. Further, the effect of compounds 4k and 4h showed dose-dependent inhibition of HBV-DNA as compared to control together with significant inhibition of HbeAG and HbsAG expression in the tested dose. Both compounds showed considerable affinity against the HepG2.2.15 cells. Moreover, the docking study of compound 4k was carried out with HLA molecule showing excellent intermolecular interactions with the receptor via creation of numerous bonds with Ser5, Thr27, Asp29 and Phe8. The compound 4k showed significant effect on the HO-1 expression in HepG2.2.15 cells together with excellent anti-HBV activity in transgenic mouse confirmed by biochemical and histopathological parameters. Compound 4k also showed excellent pharmacokinetic profile in experimental animal and thus, provide a novel class of potent anti-HBV agents.

Anti-HBV Activities of Three Compounds Extracted and Purified from Herpetospermum Seeds

The goal of this research was to evaluate the anti-hepatitis B virus (HBV) activities of three compounds extracted and purified from Herpetospermum seeds (HS) on HepG2.2.15 cells. Herpetin (HPT), herpetone (HPO), and herpetfluorenone (HPF) were isolated from HS and identified using HR-ESI-MS and NMR. Different concentrations of the drugs were added to the HepG2.2.15 cells. Cell toxicity was observed with an MTT assay, cell culture supernatants were collected, and HBsAg and HBeAg were detected by ELISA. The content of HBV DNA was determined via quantitative polymerase chain reaction (PCR) with fluorescent probes. The 50% toxicity concentration (TC₅₀) of HPF was 531.48 μg/mL, suggesting that this species is less toxic than HPT and HPO. HPT and HPF showed more potent antiviral activities than HPO. The 50% inhibition concentration (IC₅₀) values of HPF on HBsAg and HBeAg were 176.99 and 134.53 μg/mL, respectively, and the corresponding therapeutic index (TI) values were 2.66 and 3.49, respectively. HPT and HPF were shown to significantly reduce the level of HBV DNA in the HepG2.2.15 culture medium compared to the negative control. This initial investigation of the anti-HBV constituents of HS yielded three compounds that revealed a synergistic effect of multiple components in the ethnopharmacological use of HS.

[Thymopolypeptides combined with matrine type alkaloids suppress HBV replication]

To investigate the antiviral effect of thymopolypeptides combined with 4 kinds of matrine type alkaloids on HepG2.2.15 cells, oxymatrine, sophocarpidine, sophocarpine, and sophoridine (at concentration of 0.2 mmol•L⁻¹ respectively) were respectively combined with thymopolypeptides (0.025, 0.1 g•L⁻¹), and after 48 h and 72 h treatment on HepG2.2.15 cells, the cells and supernatants were collected. The cells activity in various groups was determined by CCK-8 method to evaluate the toxic effects of the drugs on HepG2.2.15 cells. Enzyme linked immunosorbent assay (ELISA) was used to determine HBeAg and HBsAg levels in cellular supernatants. HBV DNA levels in cellular supernatants andcells were quantified with fluorogenic quantitative PCR method; and the expression level of IFN-α in supernatants was detected with CBA method. The results indicated that single thymopolypeptides at 0.025-0.4 g•L⁻¹ had no toxicity to cells. Thymopolypeptides in this concentration range combined with 0.2 mmol•L⁻¹ matrine type alkaloids also had no toxicity to cells. Anti-HBV activity of drug combination was better than that of alkali or thymopolypeptides alone. Thymopolypeptides at 0.025 g•L⁻¹ had better inhibitory effect than thymopolypeptides at 0.1 g•L⁻¹ on intracellular HBV DNA expression, but the inhibitory effect on supernatant HBeAg level was on the contrary. Anti-HBV activity was similar between alkaloids combined with 0.1 g•L⁻¹ and alkaloids combined with 0.025 g•L⁻¹. There was no statistical difference in anti-HBV effect between various combined groups (P<0.05). In general, 72 h anti-HBV effect was better than 48 h anti-HBV effect (P<0.05). The expression of IFN-α was increased after drug combination, with positive correlation to the changes of other four indicators (P<0.05). In conclusion, oxymatrine, sophocarpidine, sophocarpine and sophoridine combined with thymopolypeptides could inhibit HBsAg and HBeAg secretion in HepG2.2.15 cells and HBV DNA replication, and further promote the antiviral effect by promoting the expression of IFN-α.

Construction of a eukaryotic vector expressing human miR-155 and inhibitory effect of miR-155 on HBeAg in HepG2.2.15 cells

AIM: To construct an eukaryotic vector carrying human microRNA-155 (miR-155) and to analyze the inhibitory effect of miR-155 on HBeAg in HepG2.2.15 cells.

METHODS: The pre-miR-155 was amplified from total DNA of human hepatoma cell line HepG2.2.15 by PCR. The target gene fragment was digested with EcoRⅠ and BamHⅠ, and cloned into the pmR-mCherry plasmid. Restriction digestion and DNA sequencing were performed to evaluate the recombinant vector. miR-155 was transfected into HepG2.2.15 cells by liposome-mediated method. The cells transfected with empty plasmid and untransfected cells were used as controls. The expression of cherry was detected by fluorescence microscopy after 24 h. The intracellular expression of miR-155 was detected by RT-PCR. ELISA was carried out to analyze the levels of HBeAg.

RESULTS: The pmiR-155 eukaryotic expression vector was successfully constructed. Fluorescence microscopy showed that the cherry protein was expressed in the HepG2.2.15 cells. miR-155 level in HepG2.2.15 cells transfected with the recombinant plasmid was significantly higher than those in controls. Compared with cells transfected with empty plasmid and untransfected cells, specific miR-155 could significantly decrease HBeAg gene expression in HepG2.2.15 cells.

CONCLUSION: A recombinant plasmid expressing miR-155 has been successfully constructed, and miR-155 is expressed stably in HepG2.2.15 cells. miR-155 can inhibit the expression of HBeAg in HepG2.2.15 cells.

5'-triphosphate-siRNA activates RIG-I-dependent type I interferon production and enhances inhibition of hepatitis B virus replication in HepG2.2.15 cells

Hepatitis B virus (HBV) infection often results in acute or chronic viral hepatitis and other liver diseases including cirrhosis and hepatocellular carcinoma. Current therapies for HBV usually have severe side effects and can cause development of drug-resistant mutants. An alternative and safe immunotherapeutic approach for HBV infection is urgently needed for effective anti-HBV therapy. In this study, we propose a new strategy for anti-HBV therapy that activates type-I interferon (IFN) antiviral innate immunity through stimulating pattern-recognition receptors with RNA interference (RNAi) using a 5'-end triphosphate-modified small interfering RNA (3p-siRNA). We designed and generated a 3p-siRNA targeting overlapping region of S gene and P gene of the HBV genome at the 5'-end of pregenomic HBV RNA. Our results demonstrated that 3p-siRNA induced a RIG-I-dependent antiviral type-I IFN response when transfected into HepG2.2.15 cells that support HBV replication. The 3p-siRNA significantly inhibited HBsAg and HBeAg secretion from HepG2.2.15 cells in a RIG-I-dependent manner, and the antiviral effect of 3p-siRNA was superior to that of siRNA. Furthermore, 3p-siRNA had more pronounced inhibition effects on the replication of HBV DNA and the transcription of mRNA than that of siRNA. Finally, 3p-siRNA displayed antiviral activity with long-term suppression of HBV replication. In conclusion, our findings suggest that 3p-siRNA could act as a powerful bifunctional antiviral molecule with potential for developing a promising therapeutic against chronic HBV infection.

Effects of SAHA on proliferation and apoptosis of hepatocellular carcinoma cells and hepatitis B virus replication

AIM: To investigate the effects of suberoylanilide hydroxamic acid (SAHA) on proliferation and apoptosis of a human hepatocellular carcinoma cell line (HepG2.2.15) and hepatitis B virus (HBV) replication.

METHODS: HepG2.2.15 cells were treated with different concentrations of SAHA. Cell morphology was examined by confocal laser scanning microscopy, and cell proliferation was determined using a MTT colorimetric assay. Flow cytometry was used to detect apoptosis and determine cell cycle phase, while hepatitis B surface antigen and hepatitis B e antigen content were measured using chemiluminescence. Reverse transcription polymerase chain reaction was performed to measure HBV DNA in cell lysate.

RESULTS: Cell proliferation rates were significantly reduced by the addition of SAHA. The inhibitory effect of SAHA on cell proliferation was both time- and dose-dependent. After 24 h of treatment with SAHA, the early cell apoptotic rate increased from 3.25% to 21.02% (P = 0.041). The proportion of G₀/G₁ phase cells increased from 50.3% to 65.3% (P = 0.039), while that of S phase cells decreased from 34.9% to 20.6% (P = 0.049). After 48 h of treatment, hepatitis B surface antigen and hepatitis B e antigen content increased from 12.33 ± 0.62 to 25.42 ± 2.67 (P = 0.020) and 28.92 ± 1.24 to 50.48 ± 1.85 (P = 0.026), respectively. Furthermore, HBV DNA content increased from 4.54 ± 0.46 to 8.34 ± 0.59 (P = 0.029).

CONCLUSION: SAHA inhibits HepG2.2.15 cell proliferation, promotes apoptosis, and stimulates HBV replication. In combination with anti-HBV drugs, SAHA may potentially be used cautiously for treatment of hepatocellular carcinoma.

Effect of recombinant adenovirus-associated virus-mediated RNA interference on HBV replication and expression

AIM: To observe the effect of recombinant adenovirus-associated virus (rAAV)-mediated RNA interference on HBV replication and expression in HepG2.2.15 cells.

METHODS: The expression box of hu6-shRNA was placed between two ITRs of AAV and then ligated to the basic core promoter (BCP) of HBV and BCP-driven Rep gene of AAV, which resulted in rAAV. The rAAV was transfected into HepG2.2.15 cells (HCC cells in which the HBV gene was inserted). The expression of HBsAg and HBeAg and replication of HBV-DNA in cultured supernatant were determined on days 1, 2, 3 and 10 after transfection, and the AAVS1 region was sequenced on day 3 after transfection.

RESULTS: The target sequence-containing vectors PLRBR322-324, PLRBR522-324, PLRBR322-2424 and PLRBR522-2424 were successfully constructed. All the four vectors had inhibitory effects on the expression of HBsAg and HBeAg and on HBV-DNA replication, with the former two (PLRBR322-324 and PLRBR522-324) having more significant inhibitory effect on HBsAg expression, the latter two on HBeAg expression and the third on HBV-DNA replication. The inhibitory effects on HBsAg and HBeAg expression and HBV-DNA replication were most obvious on day 3 after transfection, and the inhibition rate remained high on day 10. Site-directed integration of the target sequence was located in the AAVS1 region.

CONCLUSION: The rAAV constructed by several elements of AAV and HBV, together with the help of site-directed integration mediated by Rep protein, is a good exploration to solve the problem of short-term effect of RNAi against HBV.

Inhibitory effect of locked nucleic acid antisense oligonucleotides versus lamivudine on HBV replication in HepG2.2.15 cells

AIM: To compare the inhibitory effect of locked nucleic acid antisense oligonucleotides (antisense-LNA) and lamivudine on HBV replication in HepG2.2.15 cells.

METHODS: Antisense-LNA was introduced into HepG2.2.15 cells by cationic liposome-mediated transfection. Supernatants were collected 2, 4, 6, 8, 10 days after medication. The concentrations of HBsAg and HBeAg in cell supernatants were tested by ELISA. HBV DNA levels in cell supernatants were determined by FQ-PCR. Cell toxicity of antisense-LNA and lamivudine was detected by MTT assay.

RESULTS: Lamivudine only inhibited viral DNA synthesis. Antisense-LNA effectively inhibited the expression of HBsAg and HBeAg and the replication of HBV DNA (67.69%, 59.71%, 62.96%, P < 0.05) in a time-dependent manner. Both antisense-LNA and lamivudine showed no obvious cell toxicity.

CONCLUSION: The anti-HBV effect of antisense-LNA is more effective than that of lamivudine in HepG2.2.15 cells.

Comparison of the antiviral effect between matrine and oxymatrine against hepatic B virus in vitro

AIM: To evaluate the effect of matrine and oxymatrine on secreting HBsAg, HBeAg and Pre-S1 in HepG2.2.15 cells.

METHODS: HepG2.2.15 cell lines were cultured in vitro at different concentrations of matrine and oxymatrine. Nine days later, inhibitory effects of the experimental drugs on HepG2.2.15 cell lines were estimated using MTT and serum HBsAg, HBeAg and Pre-S1 were detected using ELISA.

RESULTS: The inhibitory effects of matrine and oxymatrine on HepG2.2.15 cells under the concentration of 0.001 mol/L was lower (<25%). When concentration was between 1000 μmol/L and 0.1 μmol/L, the inhibition ratios for either matrine or oxymatrine were more than 50% for secreting HBsAg, but lower than 50% for HBeAg. At the concentration of 0.001 mol/L, the inhibitory rates of matrine and oxymatrine on Pre-S1 were 53.58%, and 59.33%, respectively.

CONCLUSION: Both Matrine and Oxymatrine have effect of anti-HBV in vitro in some degrees, and no significant difference is noted. Their inhibitory effects on HBsAg and Pre-S1 are superior to Lamivudine.

Combination of small interfering RNAs mediates greater suppression on hepatitis B virus cccDNA in HepG2.2.15 cells

AIM: To observe the inhibition of hepatitis B virus (HBV) replication and expression in HepG2.2.15 cells by combination of small interfering RNAs (siRNAs).

METHODS: Recombinant plasmid psil-HBV was constructed and transfected into HepG2.2.15 cells. At 48 h, 72 h and 96 h after transfection, culture media were collected and cells were harvested for HBV replication assay. HBsAg and HBeAg in the cell culture medium were detected by enzyme-linked immunoadsorbent assay (ELISA). Intracellular viral DNA and covalently closed circular DNA (cccDNA) were quantified by real-time polymerase chain reaction (PCR). HBV viral mRNA was reverse transcribed and quantified by reverse-transcript PCR (RT-PCR).

RESULTS: siRNAs showed marked anti-HBV effects. siRNAs could specifically inhibit the expression of HBsAg and the replication of HBV DNA in a dose-dependent manner. Furthermore, combination of siRNAs, compared with individual use of each siRNA, exerted a stronger inhibition on antigen expression and viral replication. More importantly, combination of siRNAs significantly suppressed HBV cccDNA amplification.

CONCLUSION: Combination of siRNAs mediates a stronger inhibition on viral replication and antigen expression in HepG2.2.15 cells, especially on cccDNA amplification.