The fact that HCV replication in FL subclones was both harder to inhibit as well as reverse, suggests that there are significant effects of the structural proteins that influence these processes

The fact that HCV replication in FL subclones was both harder to inhibit as well as reverse, suggests that there are significant effects of the structural proteins that influence these processes. levels at baseline and increased resistance to oxidant-induced cytotoxicity. HO-1 induction with hemin also markedly decreased HCV replication in both parental FL and NS replicon cell lines. On the other hand, knock-down of HO-1 mRNA by siRNA in parental FL or NS replicons did not significantly affect HCV replication suggesting that less than basal levels of HO-1 had minimal affect on HCV replication. == Conclusion == Overexpression MK-0557 or induction of HO-1 results in decreased HCV replication as well as protection from oxidative damage. These findings suggest a potential role for HO-1 in antiviral therapy and therapeutic protection against hepatocellular injury in HCV contamination. Keywords:Anti-oxidative enzymes, oxidative stress, viral replication, replicons, Huh7 cells == Introduction == Chronic HCV contamination is usually a worldwide health problem which can lead to chronic hepatitis, cirrhosis, and end stage liver MK-0557 disease (1). The virus has a plus-stranded RNA genome with a single long open-reading frame made up of 5 and 3 flanking non-translated nucleotide regions that are important for translation and replication. Although wild type virus grows poorly in cell culture (2) the development of subgenomic and full length HCV replicons that stably replicate HCV RNA in permissive human hepatoma cells has provided the opportunity for detailed investigation of HCV cellular activities (3;4). Standard treatment of patients with chronic HCV includes alpha-interferon and Ribavirin for 24-48 weeks, depending on HCV genotype. Nearly half of all patients treated fail to achieve sustained viral eradication or they relapse after therapy (5). Consequently, new interest has focused on development of additional treatment options (6). A major aim of new management strategies is usually to prevent chronic liver injury from the virus by interference with the viral life cycle and/or hepatic inflammatory injury at critical points. An attractive but unexplored strategy for HCV therapy is usually use of host antioxidant enzymes to reduce chronic inflammation and thus attenuate progressive liver disease. Initial hepatic injury from HCV is likely oxidant-mediated and appears to result from immune mechanisms (7;8). In addition, prooxidant production is also increased by viral proteins such as core and NS5A in host cells (9-15). Collectively, these observations suggest that antioxidant enzymes could be used therapeutically to reduce oxidative injury during chronic HCV contamination. Heme oxygenase (HO) catalyzes the first and rate-limiting step in the catabolism of heme which produces equimolar amounts of biliverdin, carbon monoxide (CO) and free iron. Of the three HO isoenzymes (16), HO-1 has been shown to inhibit inflammation and protect against oxidative damage (17;18). HO-1 is usually highly inducible by hemin and Mouse monoclonal to GABPA various stressors while HO-2 and HO-3 are mainly expressed constitutively (19) Recently, induction or overexpression of HO-1 was shown to inhibit full length replication of viruses such as HIV and influenza (20;21) emphasizing the potential importance of the enzyme as a virucidal agent. We have previously described effects of HCV around the expression MK-0557 of HO-1 in hepatocytes. In liver samples from patients infected with HCV, HO-1 mRNA and protein are decreased (9). The downregulation of HO-1 expression by HCV is usually reproduced in hepatocyte cell lines that express HCV core MK-0557 protein, but not its envelope or non-structural proteins (10). Furthermore, the induction of HO-1 in response to cytotoxins is usually impaired in core-expressing hepatocytes (22), suggesting that a diminished HO-1 response to stressors may be an additional source of injury in HCV contamination. While these data establish that HCV proteins modulate expression of HO-1, it is unknown whether the enzyme impacts viral replication and hepatocellular injury. The focus of the present work was to evaluate these possibilities by examining the effects of HO-1 overexpression and induction on HCV replication and cellular injury. == Materials and Methods == == Materials == TaqDNA polymerase (Perkin-Elmer Cetus, Norwalk, CT), and Maloney murine leukemia virus (MMLV) reverse transcriptase (Gibco/BRL Life Technologies, Gaithersburg, MD) were used in MK-0557 these studies. Tert-butyl-hydroperoxide (tBOOH) was obtained from Sigma Chemical Co. (St. Louis, MO). 27-Dichlorodihydrofluorescein diacetate (DCFH-DA) and 5-carboxyl-27- dichlorodihydrofluorescein diacetate (carboxy-DCFH-DA) were obtained from Molecular Probes, Eugene, OR (catalogue numbers C-399 and C-369, respectively). == Antibodies == Anti-heme oxygenase-1 antibody was obtained from Stressgen (MI) and specificity characterized as described previously (22). Other antibodies included anti-catalase, anti- MnSOD, and anti-CuZnSOD, (kind gifts from Dr. Larry Oberley, University of Iowa), and antiactin (Sigma, MO). Secondary antibodies were purchased from Santa Cruz Biotechnology (Santa Cruz, CA). == Cell lines and cell culture == The human hepatoma cell line (Huh-7) containing stable replication of sub-genomic selectable HCV RNAs (4) was a kind gift of Dr. Volker Lohmann.