Pre-S mutant surface antigens in chronic hepatitis B virus infection induce oxidative stress and DNA damage

Abstract

Ground glass hepatocytes (GGHs) are the historic hallmarks for the hepatocytes in the late and non-replicative stages of hepatitis B virus (HBV) infection. We have identified type I and type II GGHs that contain two mutant types of large HBV surface antigens (HBsAg) with deletions over the pre-S1 and pre-S2 regions, respectively. These pre-S mutant HBVsAg accumulate in endoplasmic reticulum (ER), resulting in strong ER stress. Type II GGHs often appear in hepatic nodules in the late phases of HBV infection and proliferate in clusters, suggesting that these mutant pre-S1/S2 HBsAg may be involved in HBV-related hepatocarcinogenesis, associated with ER stress. In this study, we investigated the potential genomic instability imposed by pre-S mutant HBsAg. Based on the analysis of comet assays, we found that the pre-S1 and pre-S2 mutant HBsAg caused oxidative stress and DNA damage. The DNA repair gene ogg1 was greatly induced by over-expression of pre-S mutant HBsAg. Induction of the DNA repair gene ogg1 was also detected in the pre-S2 HBsAg transgenic mice, as well as the type II GGHs from patients with hepatocellular carcinoma, strongly suggesting that the pre-S mutant HBsAg contributes to the oxidative DNA damage to hepatocytes. In addition, the mutation rates in the X-linked hprt gene were enhanced in mouse hepatoma ML1-4a cells, which constitutively expressed the pre-S1/S2 HBsAg. These results indicate that pre-S1/S2 mutant HBsAg, which make up GGHs, induce oxidative DNA damage and mutations in hepatocytes in the late stages of HBV infection.

Hepatitis B virus-related hepatocellular carcinoma: paradigms for viral-related human carcinogenesis

“…These observations are consistent with the hypothesis concerning the selection of some HBV molecules during long-term persistence and HCC development (Minami et al, 1996). In addition, preS mutant may induce oxidative DNA damage and mutagenesis of the host genome and thus plays an important role in HCC (Hsieh et al, 2004). Furthermore, mutations have been identified on HBV X (HBx) encoding sequences that might reduce viral DNA replication, HBV gene expression or enhance transformation (see next section on HBx).…”

“…In another context, the immune response to HBV-expressing hepatocytes in transgenic mice can also trigger such liver cell regeneration and give rise to HCC (Nakamoto et al, 1998;Chen et al, 2005b;Wang et al, 2005). Furthermore, HBV-positive, transgenic mice exhibit extensive oxidative DNA damage, possibly related to cytokine synthesis (Hagen et al, 1994;Hsieh et al, 2004); this observation may explain their increased sensitivity to chemical carcinogens and is probably relevant in humans exposed to both hepatitis viruses and chemical carcinogens (Bannasch et al, 1989;Sell, 1993). Finally, it is also noteworthy that, besides triggering liver cell proliferation, an accumulation of viral proteins, such as HBsAg in so-called 'ground glass' hepatocytes, may modify detoxification pathways such as those implicating cytochrome P450; this effect may enhance the metabolism of chemical carcinogens.…”

Hepatitis B Virus Genetic Variation and TP53 R249S Mutation in Patients with Hepatocellular Carcinoma in Thailand

“…Regarding pre-S deletion, it has been shown in several reports that such mutant is an important risk factor of HCC (Chen et al, 2006;Choi et al, 2007). In vitro studies have also showed that intracellular accumulation of pre-S mutant proteins can modify HBV protein expression, induce ER stress and increased DNA damage (Hsieh et al, 2004). However, pre-S deletion was not considered to be a significant factor associated with HCC in this study.…”

Endoplasmic Reticulum Stress Stimulates the Expression of Cyclooxygenase-2 through Activation of NF-κB and pp38 Mitogen-activated Protein Kinase

“…shown to induce ER stress (11,12). Therefore, it is important to investigate whether the mutant large surface protein can induce the expression of COX-2.…”