Effect of Nrf2 Activators in Hepatitis B Virus-Infected Cells Under Oxidative Stress

The liver is an active metabolic site that generates high levels of reactive oxygen species (ROS). Oxidative stress has been implicated in the chronicity of hepatitis and hepatitis B virus (HBV) infection. This study aimed to determine the involvement of oxidative stress in HBV-infected cells and the efficacy of natural Nrf2 activators. The intracellular HBV pregenomic RNA copy number relative to total RNA was measured by RT-PCR, and various protein expressions associated with oxidative stress were analyzed by a Western blot analysis. The results showed that the Nrf2, HO-1, Akt, and Bcl-xL proteins were decreased by the continuous infection, indicating that HBV-positive cells were exposed to oxidative stress. The present study evaluated the anti-HBV infection effects of the Nrf2 activator fucoxanthin (Fx), a marine carotenoid from edible biological resources, including the comparative natural Nrf2 activator pteryxin (Ptx). These Nrf2 activators suppressed the HBV pregenomic RNA production in the HBV-infected cells, thus increasing the expression of the proteins of Nrf2 and HO-1. In the persistently infected cells transfected with the HBV genome, the Bcl-xL and Keap1 proteins, which contribute to suppressing the HBx protein involved in the HBV replication, were overexpressed. In particular, the activity of these protein expressions was marked at low concentrations of Fx. This suggests that natural Nrf2 activators may play a significant role in the HBV infection and could be a valuable source for further development through the functional utilization of food resources.