Epidemiologic observations show a higher frequency of hepatitis B virus (HBV) serologic markers in chronic alcoholics compared with the general population. This may be the result of an increased susceptibility of alcoholics to infection and/or to an ethanol-mediated stimulation of HBV gene expression and replication. To test the latter hypothesis, HBV transgenic SCID mice, which support consistent levels of virus replication, were fed with a standard Lieber-DiCarli or isocaloric diet for 5 weeks. In ethanol-fed mice, the levels of hepatitis B surface antigen (HBsAg) and viral DNA in serum increased by up to 7-fold compared with mice fed the control diet. Ethanol-treated mice also had elevated HBV-RNA levels, and increased expression of surface, core, and X antigens in the liver, especially in the pericentral regions. None of these changes were observed in transgenic mice fed isocaloric diets. Thus, chronic alcohol consumption alters the patterns of HBV gene expression and replication in the serum and liver of HBV transgenic SCID mice, and may provide a partial explanation for the increased frequency of HBV markers among alcoholics. (HEPATOLOGY 2001; 34: 792-797.)

SUMMARY. The development of fibrosis and cirrhosis during chronic hepatitis B virus (HBV) infection correlates with the persistent expression of HBV x antigen (HBxAg), which acts in part, by stimulating selected signal transduction pathways, including nuclear factor jB (NF-jB). To identify NF-jB responsive genes that are differentially expressed in HBxAgpositive cells, HepG2 cells were stably transfected with HBxAg, and then with pZeoSV2 or pZeoSV2-IjBa. When RNAs from each culture were compared by PCR-select cDNA subtraction, fibronectin (FN) mRNA was shown to be strongly down-regulated by IjBa. Up-regulated expression of FN and co-expression between FN and HBxAg were observed in liver sections from HBV carriers that were stained for HBxAg and analysed for FN mRNA by in situ hybridization (ISH). In liver cell cultures, HBxAg increased the levels of FN mRNA and protein. This was because of the HBxAg-mediated trans-activation of the FN promoter, which was NF-jBdependent. HBxAg also antagonized the repression of the FN promoter by the tumour suppressor, p53. Hence, the FN gene may be a natural target for HBxAg trans-activation, perhaps through activation of NF-jB and inactivation of p53, thereby contributing to the accumulation of FN in the liver over the course of chronic HBV infection.

Hepatitis B virus encoded X antigen (HBxAg) may contribute to the development of hepatocelIular carcin-oma (HCC) by up-or downregulating the expression of cellular genes that promote cell growth and urvival. To test this hypothesis, HBxAg-positive and-negative HepG2 cells were constructed. and the patterns of cellular gene expression compared by polymerase chain reaction select cDNA subtraction. The full-length clone of one of these upregulated genes (URG), URG4, encoded a rotein of about 104kDa. URG4 was strongly expressed jn hepatitis B-infected Iiver and in HCC cells. where it costained with HBxAg, and was weakly ex

Hepatitis B and related viruses that infect mammalian hosts encode the "X" protein that has been shown to contribute importantly to the pathogenesis of chronic liver disease (CLD) and to the evelopment of hepatocellular carcinoma (HCC). In a variety of tissue culture systems, hepatitis B virus (HBV) X antigen, or HBxAg, has been shown to trigger apoptosis, while other evidence suggests that HBxAg inhibits apoptosis and stimulates the cell cycle by constitutively activating a number of signaling pathways that are important for hepatocellular growth and survival. These apparently contrasting properties of HBxAg may be associated with differences in the X protein itself, since carboxy-terminaltruncated forms of HBxAg appear to be associated with HCC lesions. Alternatively, or in addition, these differences may be due to the cell type, state of cell differentiation, and whether expression occurs in resting or dividing cells. Further, the association between HBxAg expression and chromosomal instability, may also contribute to the apparently contrasting fates of HBxAg positive cells. It is proposed that in many of these systems, the different outcomes of HBxAg expression may be due to the nature of the cellular response to HBxAg, and not due to differences in the fundamental properties of HBxAg, the latter of which promote cell survival, cell cycle rogression, and the development of HCC.