Repression of Death Receptor-Mediated Apoptosis of Hepatocytes by Hepatitis B Virus e Antigen.

Hepatitis B virus (HBV) e antigen (HBeAg) is associated with viral persistence and pathogenesis. Resistance of HBV-infected hepatocytes to apoptosis is seen as one of the primary promotors for HBV chronicity and malignancy. Fas receptor/ligand (Fas/FasL) and the tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) system plays a key role in hepatic death during HBV infection. We found that HBeAg mediates resistance of hepatocytes to FasL or TRAIL-induced apoptosis. Introduction of HBeAg into human hepatocytes rendered resistance to FasL or TRAIL cytotoxicity in a p53-dependent manner. HBeAg further inhibited the expression of p53, total Fas, membrane-bound Fas, TNF receptor superfamily member 10a, and TNF receptor superfamily member 10b at both mRNA and protein levels. In contrast, HBeAg enhanced the expression of soluble forms of Fas through facilitation of Fas alternative mRNA splicing. In a mouse model, expression of HBeAg in mice injected with recombinant adenovirus-associated virus 8 inhibited agonistic anti-Fas antibody-induced hepatic apoptosis. Xenograft tumorigenicity assay also found that HBeAg-induced carcinogenesis was resistant to the proapoptotic effect of TRAIL and chemotherapeutic drugs. These results indicate that HBeAg may prevent hepatocytes from FasL and TRAIL-induced apoptosis by regulating the expression of the proapoptotic and antiapoptotic forms of death receptors, which may contribute to the survival and persistence of infected hepatocytes during HBV infection.

Hepatitis B virus core protein promotes hepatocarcinogenesis by enhancing Src expression and activating the Src/PI3K/Akt pathway.

Hepatitis B virus core protein (HBc) is expressed preferentially in hepatitis B virus (HBV)-associated hepatocellular carcinoma (HCC). HBc can function as an oncogene arising from its gene regulatory properties, but how it contributes functionally to hepatocarcinogenesis remains unclear. In this study, we determined the molecular and functional roles of HBc during HBV-associated hepatocellular tumorigenesis. HBc increased tumor formation of hepatoma cells. Moreover, expression of HBc specifically promoted proliferation of hepatoma cells in vitro. Mechanistic investigations revealed that these effects were caused by activation of the Src/PI3K/Akt pathway through proximal switch from inactive Src to the active form of the kinase by HBc. HBc-mediated sarcoma (Src) kinase activation was associated with down-regulation of C-terminal Src kinase (Csk). In addition, HBc enhances Src expression by activation of alternative Src 1A promoter in an Sp1 transcription factor-dependent manner. Proliferation induced by stable HBc expression was associated with increased G1-S cell cycle progression mediated by Src kinase activation. HBc-induced cellular proliferation and tumor formation were reversed by administration of the Src inhibitor saracatinib. Together, our findings suggest that HBc promotes tumorigenesis of hepatoma cells by enhancing the expression of total Src and the active form of the kinase and subsequently activates Src/PI3K/Akt signaling pathway, revealing novel insights into the underlying mechanisms of HBV-associated hepatocarcinogenesis.-Liu, W., Guo, T.-F., Jing, Z.-T., Yang, Z., Liu, L., Yang, Y.-P., Lin, X., Tong, Q.-Y. Hepatitis B virus core protein promotes hepatocarcinogenesis by enhancing Src expression and activating the Src/PI3K/Akt pathway.

Anti-inflammation Effects of Sinomenine on Macrophages through Suppressing Activated TLR4/NF-κB Signaling Pathway.

Sinomenine (SN) has been used in the clinical treatment of systemic lupus erythematosus and rheumatoid arthritis for many years. Studies showed that SN held protective effects such as anti-inflammation, scavenging free radicals and suppressing immune response in many autoimmune diseases. The purpose of the present study is to explore the mechanism of anti-inflammation of SN on lipopolysaccharide (LPS)-induced macrophages activation and investigate whether the TLR4/NF-κB signaling pathway participated in. Macrophages isolated from mouse peritoneal cavity were stimulated by 1 µg/mL LPS for 24 h. And then the cells were treated with various concentrations of SN, TLR4 inhibitor respectively for additional 48 h. Drug toxicity was detected by MTT assay and Transwell experiment was used to assess chemotaxis. Furthermore, TLR4 and MyD88 mRNA levels were detected by real-time PCR. Western blotting was used to examine TLR4, MyD88 and phosphorylated IκB protein expression in macrophages. Immunofluorescence assay was applied to observe p65 NF-κB protein expression in macrophage nucleus. We extracted macrophages with high purity and activity from the abdominal cavity of mice. SN remarkably inhibited the chemotaxis and secretion function of LPS-stimulated macrophages. It also down-regulated both the protein levels of inflammatory cytokines (TNF-α, IL-1ß and IL-6) and the RNA and protein levels of the key factors (TLR4, MyD88, P-IκB) in TLR4 pathway. The expression of p65 NF-κB protein in nuclei was down-regulated, which was correlated with a similar decrease in P-IκB protein level. In conclusion, SN can inhibit the LPS induced immune responses in macrophages by blocking the activated TLR4/NF-κB signaling pathway. These results may provide a therapeutic approach to regulate inflammatory responses.

Anti-inflammatory effect of fucoxanthin on dextran sulfate sodium-induced colitis in mice.

The anti-inflammatory activities of fucoxanthin, a marine carotenoid derived from the macroalgae and microalgae, have been demonstrated in the previous studies. However, the effect of fucoxanthin on ulcerative colitis (UC), an inflammatory bowel disease, was still unclear. In this study, we evaluated the in vivo anti-inflammatory effect of fucoxanthin on dextran sulfate sodium(DSS)-induced colitis in mice. Fucoxanthin at the doses of 50 and 100 mg/kg/day significantly protected against DSS-induced gradual loss of body weight, exhibited inhibitory effects on the DSS-induced increase of disease activity index and colon shortening. Moreover, fucoxanthin treatment resulted in a marked amelioration of the histological damage in the colon, and reduced the colonic PGE2 levels in colitic mice. In addition, the DSS-induced overexpressions of inflammation-related molecules including COX-2 and NF-κB were significantly decreased in fucoxanthin-treated mice. These finding suggested that the use of fucoxanthin provides a new and attractive alternative to control UC.

Curcumin attenuates chronic ethanol-induced liver injury by inhibition of oxidative stress via mitogen-activated protein kinase/nuclear factor E2-related factor 2 pathway in mice.

OBJECTIVE: This study aimed to investigate the protective effect of curcumin on chronic ethanol-induced liver injury in mice and to explore its underlying mechanisms. MATERIALS AND METHODS: Ethanol-exposed Balb/c mice were simultaneously treated with curcumin for 6 weeks. Liver injury was evaluated by biochemical and histopathological examination. Lipid peroxidation and anti-oxidant activities were measured by spectrophotometric method. Anti-oxidative genes expression such as NAD(P)H quinone oxidoreductase 1 (NQO1), heme oxygenase-1 (HO-1), and superoxide dismutase (SOD) were determined by real-time polymerase chain reaction. The nuclear factor E2-related factor 2 (Nrf2) and the phosphorylation states of specific proteins central to intracellular signaling cascades were measured by western blotting. RESULTS: Curcumin treatment protected liver from chronic ethanol-induced injury through reducing serum alanine aminotransferase and aspartate aminotransferase activities, improving liver histological architecture, and reversing lipid disorders indicated by decrease of triglyceride, total cholesterol and low-density lipoprotein-cholesterol levels and increase of High-density lipoprotein-cholesterol levels. Meanwhile, curcumin administration attenuated oxidative stress via up-regulating SOD and glutathione peroxidase activities, leading to a reduction of lipid hydroperoxide production. In addition, curcumin increased Nrf2 activation and anti-oxidative genes expressions such as NQO1, HO-1, and SOD through inducing extracellular signal-regulated kinase (ERK) and p38 phosphorylation. CONCLUSION: Our data suggested that curcumin protected the liver from chronic-ethanol induced injury through attenuating oxidative stress, at least partially, through ERK/p38/Nrf2-mediated anti-oxidant signaling pathways.