Hepatitis C Virus Core Protein Inhibits Tumor Necrosis Factor Alpha-Mediated Apoptosis by a Protective Effect Involving Cellular FLICE Inhibitory Protein (original) (raw)
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Virology, 2006
Hepatitis C virus (HCV) Core protein is implicated in the development of hepatocellular carcinoma (HCC). We utilized a HepG2 human hepatocyte cell line with inducible expression of HCV Core protein (HCV-1b) to investigate the early effects of Core protein on hepatocyte gene expression and to identify molecular processes modulated by the Core protein. A significant change was observed in the expression of 407 genes, which included genes regulating apoptosis, immune response, and cell cycle. Some of these genes were previously known to be tumor markers. The decreased expression of chemo-attractants such as TNFSF10, CCL20, and osteopontin was observed, which suggested that HCV Core expression could lead to suppression of inflammatory response as well as trafficking of macrophages and neutrophils to the site of HCV infection. An increased expression of anti-apoptosis factors including PAK2, API5, BH1, Tax1BP1, DAXX, and TNFAIP3/A20 was observed. Some of these genes were also linked to the regulation of NFKB activation and that the alteration of their expression levels, by HCV Core, might lead to the suppression NFKB activation of inflammatory responses. Our data suggested that Core expression may contribute to the viral persistence by protecting infected hepatocytes from cell death by the suppressing apoptosis and inflammatory reaction to HCV viral infection.
Virology, 2005
Hepatitis C virus (HCV) core protein has multifunctional activities. We have previously reported that the core protein of HCV immortalizes primary human hepatocytes, which may relate to multistage hepatocarcinogenic events. These immortalized human hepatocytes (IHH) served as a model to study the mechanism of HCV core protein-mediated cell growth regulation. Inhibition of core protein expression in earlier stages after hepatocyte immortalization leads to the induction of apoptosis. Here, we have observed that introduction of antisense core (AS-Core) sequences for inhibition of core protein expression enhanced the expression of E2F1 and p53 levels in early passage IHH. Inhibition of core protein expression also altered the expression level of Bcl-2 family proteins, displaying an increase of the proapoptotic Bax and a decrease in the level of the anti-apoptotic Bcl-xL proteins. These alterations, however, did not result in the release of cytochrome c from the mitochondria. Apaf-1 is frequently deregulated under various pathologic conditions, and examination of AS-Core-expressing apoptotic cells indicated a significant increase in the level of Apaf-1, which coincided with caspase-9 activation. Knockdown of Apaf-1 or the transcriptional regulatory proteins, E2F1 or p53, by small interfering RNA (siRNA) duplexes inhibited the activation of caspase-9 and enhanced cell viability in AS-Core-expressing cells. These findings may contribute to the understanding of the pathophysiology of HCV core protein-mediated hepatocyte growth regulation and disease progression.
Hepatitis C virus-induced hepatocyte cell death and protection by inhibition of apoptosis
The Journal of general virology, 2014
Chronic hepatitis C virus (HCV) infection results in progressive liver fibrosis leading to cirrhosis and liver cancer. The mechanism for this remains unclear but hepatocyte apoptosis is thought to play a major role. Hepatocyte apoptosis in human liver tissue was determined by immunohistochemistry for cytokeratin 18 (M30 CytoDEATH) and cleaved poly(ADP-ribose) polymerase (PARP). In vitro studies were performed with replication-defective recombinant adenoviruses expressing HCV proteins (rAdHCV) to study the effects of HCV on cell death in Huh7 cells, primary mouse hepatocytes (PMoHs) and primary human hepatocytes (PHHs). Cell viability and apoptosis were studied using crystal violet assays and Western blots probed for cleaved caspase-3 and cleaved PARP, with and without treatment with the pan-caspase inhibitor Q-VD-OPh and necrostatin-1. Liver tissue of HCV-infected patients expressed elevated levels of apoptotic markers compared with HCV-negative patients. rAdHCV infection reduced ce...
Virology, 2003
The hepatitis C virus (HCV) core protein is considered to influence multiple cellular processes. We developed a human hepatoblastoma HepG2-derived inducible cell line, Hep191, which allows tightly regulated expression of the core protein at relatively low but physiological levels under control of the ecdysone-regulated promoter. By transcriptional profiling, we identified differentially expressed genes, some of which are involved in cell growth or apoptosis such as inhibitor of caspase-activated DNase (ICAD), defender against cell death 1, tumor necrosis factor (TNF) receptor 1, and cytochrome c oxidase subunit VIII. Furthermore, we found that core protein expression increases a steady-state level of ICAD protein, possibly through enhancing its promoter activity, and inhibits caspase-3 activity induced by anti-Fas antibody. Since Fas-or TNF-mediated DNA fragmentation is suppressed in the core-induced Hep191 cells, these findings suggest that expression of HCV core at physiological levels confers blocking activity of caspase-activated DNase and consequently inhibiting apoptotic cell death.
Hepatitis C virus NS5A protein protects against TNF-α mediated apoptotic cell death
Virus Research, 2000
Hepatitis C virus (HCV) often causes a prolonged and persistent infection which may lead to hepatocellular carcinoma. We have previously reported that the nonstructural 5A (NS5A) protein of HCV promotes cell growth [Ghosh, A.K., Steele, R., Meyer, K., Ray, R., Ray, R.B., 1999. Hepatitis C virus NS5A protein modulates cell cycle regulatory genes and promotes cell growth. J. Gen. Virol. 80, 1179 -1183. In this study, we investigated the role of HCV NS5A (genotype 1a, strain H) in TNF-a induced apoptotic cell death. HepG2 cells expressing NS5A exhibited an inhibitory role in relation to TNF-a mediated apoptotic cell death. The NS5A protein blocked the activation of caspase-3 and inhibited proteolytic cleavage of the death substrate poly (ADP-ribose) polymerase in TNF-a induced cells. Together, these results suggest that HCV NS5A protein protects against TNF-a mediated apoptotic cell death.
Modulation of Cell Death Pathways by Hepatitis C Virus Proteins in Huh7.5 Hepatoma Cells
International journal of molecular sciences, 2017
The hepatitis C virus (HCV) causes chronic liver disease leading to fibrosis, cirrhosis, and hepatocellular carcinoma. HCV infection triggers various types of cell death which contribute to hepatitis C pathogenesis. However, much is still unknown about the impact of viral proteins on them. Here we present the results of simultaneous immunocytochemical analysis of markers of apoptosis, autophagy, and necrosis in Huh7.5 cells expressing individual HCV proteins or their combinations, or harboring the virus replicon. Stable replication of the full-length HCV genome or transient expression of its core, Е1/Е2, NS3 and NS5B led to the death of 20-47% cells, 72 h posttransfection, whereas the expression of the NS4A/B, NS5A or NS3-NS5B polyprotein did not affect cell viability. HCV proteins caused different impacts on the activation of caspases-3, -8 and -9 and on DNA fragmentation. The structural core and E1/E2 proteins promoted apoptosis, whereas non-structural NS4A/B, NS5A, NS5B suppresse...