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Background. Tetrapyrrole substrates and products of heme oxygenase are potent inhibitors of hepatitis C virus (HCV) replication. It is not clear whether this occurs through primary induction of type I interferon (IFN), inhibition of viral NS3/4A protease, or a combination of these mechanisms. We studied the antiviral actions of tetrapyrroles and their potential influence on type I IFN induction.Methods. The effects of tetrapyrrole on NS3/4A protease activity and type I IFN induction were assessed in HCV-permissive cells, replicons, or human embryonic kidney (HEK) 293 cells transfected with NS3/4A protease. Activation of innate immune signaling was determined after transfection of double-strand surrogate nucleic acid antigens or infection with defined sequence HCV cell culture (HCVcc) RNA.Results. Tetrapyrroles failed to directly induce IFN expression at concentrations that inhibited HCV replication and NS3/4A protease activity. However, they potently restored IFN induction after attenuation with NS3/4A protease, a process accompanied by preservation of the adapter protein, mitochondrial antiviral signaling protein, nuclear localization of IFN regulatory factor 3, and augmentation of IFN-stimulated gene products.Conclusions. Tetrapyrroles do not directly induce IFN, but they dramatically restore type I IFN signaling pathway after attenuation with NS3/4A protease. They show immunomodulatory as well as antiprotease activity and may be useful for treatment of HCV infection. [ABSTRACT FROM AUTHOR]

Background: Chronic hepatitis C virus (HCV)-induced liver fibrosis involves upregulation of transforming growth factor (TGF)-β and subsequent hepatic stellate cell (HSC) activation. MicroRNAs (miRNAs) regulate HCV infection and HSC activation.Methods: TaqMan miRNA profiling identified 12 miRNA families differentially expressed between chronically HCV-infected human livers and uninfected controls. To identify pathways affected by miRNAs, we developed a new algorithm (pathway analysis of conserved targets), based on the probability of conserved targeting.Results: This analysis suggested a role for miR-29 during HCV infection. Of interest, miR-29 was downregulated in most HCV-infected patients. miR-29 regulates expression of extracellular matrix proteins. In culture, HCV infection downregulated miR-29, and miR-29 overexpression reduced HCV RNA abundance. miR-29 also appears to play a role in HSCs. Hepatocytes and HSCs contribute similar amounts of miR-29 to whole liver. Both activation of primary HSCs and TGF-β treatment of immortalized HSCs downregulated miR-29. miR-29 overexpression in LX-2 cells decreased collagen expression and modestly decreased proliferation. miR-29 downregulation by HCV may derepress extracellular matrix synthesis during HSC activation.Conclusions: HCV infection downregulates miR-29 in hepatocytes and may potentiate collagen synthesis by reducing miR-29 levels in activated HSCs. Treatment with miR-29 mimics in vivo might inhibit HCV while reducing fibrosis. [ABSTRACT FROM AUTHOR]

Antioxidant enzymes, including heme oxygenase (HO)-1, are an important line of defense against oxidant-mediated liver injury. Because hepatitis C virus (HCV) infection appears to increase the production of oxidants, we evaluated levels of antioxidant enzymes and HO-1 in liver-biopsy samples from HCV-infected patients by immunoblot and semiquantitative reverse-transcriptase polymerase chain reaction. In HCV-infected liver samples, levels of immunoreactive HO-1 and HO-1 mRNA were >4-fold lower than levels in control samples, but levels of superoxide dismutase and catalase were unaffected. Immunohistochemical results confirmed the decreased expression of HO-1 in hepatocytes from liver samples from HCV-infected patients but not in those from patients with other chronic liver diseases. The expression of HO-1 was also reduced in cell lines that stably express HCV core protein, which suggests that core gene products are capable of regulating the expression of HO-1. [ABSTRACT FROM AUTHOR]

Monoclonal or affinity-purified antibodies specific to Novikoff hepatoma cytokeratin p39 were employed to study the origin and fate of p39-containing cell types during hepatocarcinogenesis induced with N,N-dimethyl-p(m-tolylazo)aniline. Frozen sections were obtained from the livers of animals autopsied temporally during carcinogen feeding and were assayed immunohistochemically. In normal, untreated liver or in liver from animals fed the hepatotoxin alpha-naphthylisothiocyanate, the localization of p39 was restricted to bile duct epithelial cells while hepatocytes were non-reactive. However, during carcinogen treatment we observed a sequential appearance of immunoreactive cells which were similar morphologically to the classical ‘oval’ cells of hepatocarcinogenesis; eventually these cell types were enriched around the preneoplastic hepatocyte nodules. Occasional transformed hepatocytes within the nodules exhibited strong immunoreactivity. In the later stages of hepatocarcinogenesis, these antibodies stained the epithelial cells in areas of severe adenosis as well as the neoplastic epithelial cells of cholangiomas and some, but not all, hepatocellular carcinomas. Our results document the presence of p39 in the ‘oval’ cells of hepatocarcinogenesis and indicate that some populations of transformed hepatocytes exhibit this cytokeratin after transformation. [ABSTRACT FROM PUBLISHER]

Chromosomal proteins from rat liver have been assessed immunologically for changes in specific cytokeratins or primary tumor nonhistone proteins during treatment with an azo dye hepatocarcinogen (3′-methyl-4-dimethylaminoazobenzene), (3′-Me-DAB) or the hepatotoxin a-naphthyl-iso-thiocyanate (α-NIT). Fisher rats were fed laboratory diets supplemented with either agent and sacrificed sequentially at various intervals. Chromosomal proteins from these livers were electro-phoresed in the presence of sodium dodecyl sulfate, transferred to nitrocellulose sheets and reacted with rabbit antisera to Novikoff hepatoma cytokeratin or 3′-Me-DAB induced primary hepatoma dehistonized chroma tin. Livers from carcinogen-fed animals exhibited distinct, sequential changes in antigenic nonhistone proteins until the immunological specificity characteristic of the hepatoma was achieved concomitant with the induction of neoplasia. No antigenic changes were observed to occur in hepatotoxin-fed animals. The rat carcinoma-specific cytokeratin antigens p39 and p49 in Novikoff hepatoma were observed to appear as early as three weeks after the start of carcinogen feeding and were present maximally in 23 week livers with carcinoma. These cytokeratins were not detected in α-NIT-fed animals. Our results support the concept that the carcinogenic process can be related to temporal changes in the expression of cell-specific cytokeratins in addition to nonhistone chromosomal proteins. Furthermore, these data suggest the expression of these antigenic species to not be the direct result of changes in liver structure and cellular composition associated with carcinogen toxicity; rather, neoplastic transformation is apparently required. [ABSTRACT FROM PUBLISHER]

Presents a letter to the editor about an article by I. Castillo, et al, on seronegative hepatitis C virus infection in individuals with persistently negative results of HCV-antibody tests.