title: Inhibitory effect of a triterpenoid compound, with or without alpha interferon, on hepatitis C virus infection.
abstract: A lack of patient response to alpha interferon (α-IFN) plus ribavirin (RBV) treatment is a major problem in eliminating hepatitis C virus (HCV). We screened chemical libraries for compounds that enhanced cellular responses to α-IFN and identified a triterpenoid, toosendanin (TSN). Here, we studied the effects and mechanisms of action of TSN on HCV replication and its effect on α-IFN signaling. We treated HCV genotype 1b replicon-expressing cells and HCV-J6/JFH-infected cells with TSN, with or without α-IFN, and the level of HCV replication was quantified. To study the effects of TSN on α-IFN signaling, we detected components of the interferon-stimulated gene factor 3 (ISGF3), phosphorylated signal transducer and activator of transcription 1 (STAT1), and STAT2 by Western blotting analysis; expression levels of mRNA of interferon regulatory factor 9 using real-time reverse transcription-PCR (RT-PCR); and interferon-stimulated response element reporter activity and measured the expression levels of interferon-inducible genes for 2',5'-oligoadenylate synthetase, MxA, protein kinase R, and p56 using real-time RT-PCR. TSN alone specifically inhibited expression of the HCV replicon (50% effective concentration = 20.6 nM, 50% cytotoxic concentration > 3 μM, selectivity index > 146). Pretreatment with TSN prior to α-IFN treatment was more effective in suppressing HCV replication than treatment with either drug alone. Although TSN alone did not activate the α-IFN pathway, it significantly enhanced the α-IFN-induced increase of phosphorylated STATs, interferon-stimulated response element activation, and interferon-stimulated gene expression. TSN significantly increased baseline expression of interferon regulatory factor 9, a component of interferon-stimulated gene factor 3. Antiviral effects of treatment with α-IFN can be enhanced by pretreatment with TSN. Its mechanisms of action could potentially be important to identify novel molecular targets to treat HCV infection.
authors: Department of Gastroenterology and Hepatology, Tokyo Medical and Dental University, Tokyo, Japan.
authors: Takako
authors: T
authors: Watanabe
authors: Naoya
authors: N
authors: Sakamoto
authors: Mina
authors: M
authors: Nakagawa
authors: Sei
authors: S
authors: Kakinuma
authors: Yasuhiro
authors: Y
authors: Itsui
authors: Yuki
authors: Y
authors: Nishimura-Sakurai
authors: Mayumi
authors: M
authors: Ueyama
authors: Yusuke
authors: Y
authors: Funaoka
authors: Akiko
authors: A
authors: Kitazume
authors: Sayuri
authors: S
authors: Nitta
authors: Kei
authors: K
authors: Kiyohashi
authors: Miyako
authors: M
authors: Murakawa
authors: Seishin
authors: S
authors: Azuma
authors: Kiichiro
authors: K
authors: Tsuchiya
authors: Shinya
authors: S
authors: Oooka
authors: Mamoru
authors: M
authors: Watanabe
mesh_terms: D000998:Antiviral Agents / Q000494:pharmacology*; D045744:Cell Line, Tumor; D004359:Drug Therapy, Combination; D004365:Drugs, Chinese Herbal / Q000494:pharmacology*; D016174:Hepacivirus / Q000187:drug effects* / Q000502:physiology; D006526:Hepatitis C / Q000188:drug therapy; D006801:Humans; D016898:Interferon-alpha / Q000494:pharmacology*; D012367:RNA, Viral / Q000096:biosynthesis; D014779:Virus Replication / Q000187:drug effects; D014315:Triterpenes
chemical_list: D000998:Antiviral Agents; D004365:Drugs, Chinese Herbal; D016898:Interferon-alpha; D012367:RNA, Viral; C036454:toosendanin; D014315:Triterpenes