Potential antiviral activities of chrysin against hepatitis B virus

BACKGROUND

Interferon and nucleos(t)ide analogues are current therapeutic treatments for chronic Hepatitis B virus (HBV) infection with the limitations of a functional cure. Chrysin (5, 7-dihydroxyflavone) is a natural flavonoid, known for its antiviral and hepatoprotective activities. However, its anti-HBV activity is unexplored.

METHODS

In the present study, the anti-hepatitis B activity of chrysin was investigated using the in vitro experimental cell culture model, HepG2 cells. In silico studies were performed where chrysin and lamivudine (used here as a positive control) were docked with high mobility group box 1 protein (HMGB1). For the in vitro studies, wild type HBV genome construct (pHBV 1.3X) was transiently transfected in HepG2. In culture supernatant samples, HBV surface antigen (HBsAg) and Hepatitis B e antigen (HBeAg) were measured by enzyme-linked immunosorbent assay (ELISA). Secreted HBV DNA and intracellular covalently closed circular DNA (cccDNA) were measured by SYBR green real-time PCR. The 3D crystal structure of HMGB1 (1AAB) protein was developed and docked with the chrysin and lamivudine. In silico drug-likeness, Absorption, Distribution, Metabolism, Excretion and Toxicity (ADMET) properties of finest ligands were performed by using SwissADME and admetSAR web servers.

RESULTS

Data showed that chrysin significantly decreases HBeAg, HBsAg secretion, supernatant HBV DNA and cccDNA, in a dose dependent manner. The docking studies demonstrated HMGB1 as an important target for chrysin as compared to lamivudine. Chrysin revealed high binding affinity and formed a firm kissing complex with HMGB1 (∆G = - 5.7 kcal/mol), as compared to lamivudine (∆G = - 4.3 kcal/mol), which might be responsible for its antiviral activity.

CONCLUSIONS

The outcome of our study establishes chrysin as a new antiviral against HBV infection. However, using chrysin to treat chronic HBV disease needs further endorsement and optimization by in vivo studies in animal models.

Network-based analysis of key regulatory genes implicated in Type 2 Diabetes Mellitus and Recurrent Miscarriages in Turner Syndrome

The information on the genotype-phenotype relationship in Turner Syndrome (TS) is inadequate because very few specific candidate genes are linked to its clinical features. We used the microarray data of TS to identify the key regulatory genes implicated with TS through a network approach. The causative factors of two common co-morbidities, Type 2 Diabetes Mellitus (T2DM) and Recurrent Miscarriages (RM), in the Turner population, are expected to be different from that of the general population. Through microarray analysis, we identified nine signature genes of T2DM and three signature genes of RM in TS. The power-law distribution analysis showed that the TS network carries scale-free hierarchical fractal attributes. Through local-community-paradigm (LCP) estimation we find that a strong LCP is also maintained which means that networks are dynamic and heterogeneous. We identified nine key regulators which serve as the backbone of the TS network. Furthermore, we recognized eight interologs functional in seven different organisms from lower to higher levels. Overall, these results offer few key regulators and essential genes that we envisage have potential as therapeutic targets for the TS in the future and the animal models studied here may prove useful in the validation of such targets.

An in vitro Study on the Role of Hepatitis B Virus X Protein C-Terminal Truncation in Liver Disease Development

Hepatitis B virus X protein C-terminal 127 amino acid truncation is often found expressed in hepatocellular carcinoma (HCC) tissue samples. The present in vitro study tried to determine the role of this truncation mutant in the hepatitis B-related liver diseases such as fibrosis, cirrhosis, HCC, and metastasis. HBx gene and its 127 amino acid truncation mutant were cloned in mammalian expression vectors and transfected in human hepatoma cell line. Changes in cell growth/proliferation, cell cycle phase distribution, expression of cell cycle regulatory genes, mitochondrial depolarization, and intracellular reactive oxygen species (ROS) level were analyzed. Green fluorescent protein (GFP)-tagged version of HBx and the truncation mutant were also created and the effects of truncation on HBx intracellular expression pattern and localization were studied. Effect of time lapse on protein expression pattern was also analyzed. The truncation mutant of HBx is more efficient in inducing cell proliferation, and causes more ROS production and less mitochondrial depolarization as compared with wild type (wt) HBx. In addition, gene expression is altered in favor of carcinogenesis in the presence of the truncation mutant. Furthermore, mitochondrial perinuclear aggregation is achieved earlier in the presence of the truncation mutant. Therefore, HBx C-terminal 127 amino acid truncation might be playing important roles in the development of hepatitis B-related liver diseases by inducing cell proliferation, altering gene expression, altering mitochondrial potential, inducing mitochondrial clustering and oxidative stress, and changing HBx expression pattern.

Impact of length of replication competent genome of hepatitis B virus over the differential antigenic secretion

Hepatitis B virus (HBV) genome consists of circular partially double stranded DNA of 3.2 kb size which gets converted into covalently closed circular DNA (cccDNA) during its life cycle. It then acts as a template for formation of pregenomicRNA (pgRNA) of 3.5 kb. Absence of appropriate animal models prompted a need to establish a better in vitro culture system to uncover the propagation and survival mechanisms of the virus. There is scarcity of data to represent the significance of varying length of replication competent viral genome on the secretion of viral secretory proteins/antigens and in turn on the overall effects on the accomplishment of the viral life cycle. The present study was undertaken to ascertain a suitable replication competent construct in which the viral life cycle of HBV with varying clinical relevance can be studied efficiently. Two constructs (pHBV 1.3 and pHBV 1X) of different sizes were used to transfect hepatoma cells and consequently the secretory antigens were monitored. In vector free approach (pHBV 1X), 3.2 kb viral DNA is directly transfected in the culture system whereas in vector mediated approach more than full length of viral genome is cloned in a vector (pHBV 1.3X) and transfected to obtain a 3.5 kb pgRNA intermediate. HBV secretes two important antigens; HBsAg and HBeAg. HBsAg is a hallmark of infection and is the first to be secreted in the blood stream whereas HBeAg is a secretory protein and remains associated with the viral replication. The construct pHBV 1.3X referring to as more than full length, by virtue of being capable of undergoing transcription without the synthesis of cccDNA intermediate (unlike the clinical situation where an intermediate step of cccDNA synthesis is an essential component to initiate the viral life cycle) appears to be better system for studying viral life cycle in in vitro culture system. The reasons could be assigned to the fact that as low as 100 ng of viral DNA was shown to quantify the replicative phenotypes with this construct. The better efficiency of this construct at prima facie, appears to be mediated through the significantly higher levels of pgRNA transcript during the viral life cycle.