d-amphetamine In order to better manage HBV infection and
In order to better manage HBV infection and related liver diseases, it is critical to develop new antiviral strategies to increase the rate of functional or complete cure of HBV infection (HBsAg loss and cccDNA elimination), achieving more than viral suppression (Zeisel et al., 2015). As a result, many novel antiviral treatment strategies targeting several key steps of the HBV life d-amphetamine have been proposed, such as viral entry, cccDNA, viral transcripts, HBx, and virus packaging (Durantel and Zoulim, 2016, Clark and Hu, 2015, Gish et al., 2015b). However, these strategies need to be evaluated by translational studies. Baicalin (BA) is a natural flavonoid present in several medicinal plants including Scutellaria baicalensis Georgi. BA can suppress HBV replication in vitro HBV model and has a significant inhibitory effect on HBsAg secretion (Cheng et al., 2006, Romero et al., 2005). These results prompted us to explore the actions and mechanisms of BA for potential HBV therapy. In this study, we investigated the impact of BA on HBsAg, HBeAg, HBV-DNA, and RNAs, and its role in mediating HBV inhibition. We also discussed the mechanisms by which BA down regulated the transcription and expression of hepatocyte nuclear factors (HNFs).
Discussion Approved anti-HBV drugs such as NAs can significantly suppress the replication of HBV DNA and reduce the occurrence of cirrhosis and HCC (Sundaram and Kowdley, 2015), but their clinical outcomes can be compromised by the increasing drug resistance. There is increasing evidence indicating that HCC is highly associated with the secretion of HBV viral proteins (Li et al., 2016a, Pollicino et al., 2014). Thus, some novel treatment strategies have been proposed aimed at sustained clearance of HBV DNA and viral proteins. In this study, we demonstrated that BA monotherapy efficiently inhibited HBV-DNA replication and HBsAg/HBeAg secretion. Compared with ETV monotherapy, co-treatment of BA with ETV could more effectively control HBV-DNA and viral protein secretion in hepG2.2.15 cell lines and DHBV-infected duckling models. Surprisingly, BA could significantly enhance the ETV's efficacy in the NA-resistant HBVrtM204V/rtLl80M cell lines, indicating that BA had an advantage in overcoming the HBV virus drug-resistance mutation. Which one is the target of BA, viral DNA or RNA? HBV RNAs include precore RNA (3.5kb), S RNAs (2.4/2.1kb), and X RNA (0.7kb). HBV RNA was an effective marker for monitoring anti-HBV therapy (Huang et al., 2015, van Bommel et al., 2015), and it was also associated with the persistence of chronic HBV infection and rebound (Wang et al., 2016). Knock-down of HBV pgRNA significantly suppressed the production and replication of HBV antigens (Li et al., 2016b). In this study, we found that BA dose-dependently reduced the amount of HBV RNAs (3.5, 2.4 and 2.1kb fragments of HBV RNAs), which was consistent with the reduction of HBV-DNA and viral proteins. In DHBV-infected duckling models, co-treatment of BA with ETV had a more powerful antiviral effect and alleviated virus relapse. After nucleos(t)ide analogue discontinuation, relapse was common in patients with chronic hepatitis B (Chi et al., 2015, Jeng et al., 2013). These results also suggested that BA might inhibit HBV DNA replication and viral protein secretion through suppressing HBV RNAs, not targeting HBV polymerase. BA also significantly down-regulated the transcription and expression levels of HNF1 and HNF4. HNFs are believed to be essential for HBV replication. HNF4 binds to HNF4BE(s) in the HBV core promoter and subsequently enhances the transcription of HBV pgRNA. pgRNA acts as the mRNA for HBc synthesis, and decreasing HNF4 expression could dramatically reduce HBV replication and viral protein secretion (Hong et al., 2012, He et al., 2016). HNF1 loss had a repressive effect on HBV replication (Dai et al., 2014, Palumbo et al., 2015). Thus, the anti-HBV effect of BA may be achieved through down-regulating HNF1 and HNF4 to reduce HBV RNAs. However, it remains unclear how BA regulates HNF1/4, and the relationship between BA and HNFs will be investigated in our future experiments.