title: Stage-specific expression of TNFα regulates bad/bid-mediated apoptosis and RIP1/ROS-mediated secondary necrosis in Birnavirus-infected fish cells.
abstract: Infectious pancreatic necrosis virus (IPNV) can induce Bad-mediated apoptosis followed by secondary necrosis in fish cells, but it is not known how these two types of cell death are regulated by IPNV. We found that IPNV infection can regulate Bad/Bid-mediated apoptotic and Rip1/ROS-mediated necrotic death pathways via the up-regulation of TNFα in zebrafish ZF4 cells. Using a DNA microarray and quantitative RT-PCR analyses, two major subsets of differentially expressed genes were characterized, including the innate immune response gene TNFα and the pro-apoptotic genes Bad and Bid. In the early replication stage (0-6 h post-infection, or p.i.), we observed that the pro-inflammatory cytokine TNFα underwent a rapid six-fold induction. Then, during the early-middle replication stages (6-12 h p.i.), TNFα level was eight-fold induction and the pro-apoptotic Bcl-2 family members Bad and Bid were up-regulated. Furthermore, specific inhibitors of TNFα expression (AG-126 or TNFα-specific siRNA) were used to block apoptotic and necrotic death signaling during the early or early-middle stages of IPNV infection. Inhibition of TNFα expression dramatically reduced the Bad/Bid-mediated apoptotic and Rip1/ROS-mediated necrotic cell death pathways and rescued host cell viability. Moreover, we used Rip1-specific inhibitors (Nec-1 and Rip1-specific siRNA) to block Rip1 expression. The Rip1/ROS-mediated secondary necrotic pathway appeared to be reduced in IPNV-infected fish cells during the middle-late stage of infection (12-18 h p.i.). Taken together, our results indicate that IPNV triggers two death pathways via up-stream induction of the pro-inflammatory cytokine TNFα, and these results may provide new insights into the pathogenesis of RNA viruses.
authors.affiliation: Institute of Fisheries Science, National Taiwan University, Taipei, Taiwan, Republic of China.
authors.forename: Wei-Lun
authors.initials: WL
authors.lastname: Wang
authors.forename: Jiann-Ruey
authors.initials: JR
authors.lastname: Hong
authors.forename: Gen-Hwa
authors.initials: GH
authors.lastname: Lin
authors.forename: Wangta
authors.initials: W
authors.lastname: Liu
authors.forename: Hong-Yi
authors.initials: HY
authors.lastname: Gong
authors.forename: Ming-Wei
authors.initials: MW
authors.lastname: Lu
authors.forename: Ching-Chun
authors.initials: CC
authors.lastname: Lin
authors.forename: Jen-Leih
authors.initials: JL
authors.lastname: Wu
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000235:genetics* / Q000502:physiology; D051023:BH3 Interacting Domain Death Agonist Protein / Q000235:genetics / Q000502:physiology; D018175:Birnaviridae Infections / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D002478:Cells, Cultured; D004625:Embryo, Nonmammalian; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005393:Fish Diseases / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects / Q000502:physiology; D018061:Infectious pancreatic necrosis virus / Q000502:physiology; D009336:Necrosis / Q000139:chemically induced / Q000235:genetics / Q000378:metabolism; D010544:Peroxidases / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D034741:RNA, Small Interfering / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000009:adverse effects* / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D020032:Tyrphostins / Q000494:pharmacology; D015027:Zebrafish / Q000196:embryology / Q000378:metabolism / Q000502:physiology; D051025:bcl-Associated Death Protein / Q000235:genetics / Q000502:physiology
chemical_list: D051023:BH3 Interacting Domain Death Agonist Protein; D004791:Enzyme Inhibitors; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D014409:Tumor Necrosis Factor-alpha; D020032:Tyrphostins; D051025:bcl-Associated Death Protein; C069028:AG 127; D010544:Peroxidases; C103372:Rip1 peroxidase