title: Double-stranded RNA-activated protein kinase mediates induction of interleukin-8 expression by deoxynivalenol, Shiga toxin 1, and ricin in monocytes.
abstract: Translational inhibitors such as the trichothecene mycotoxin deoxynivalenol (DON) and ribosomal inhibitory proteins (RIPs) induce mitogen-activated protein kinase (MAPK)-driven chemokine and cytokine production by a mechanism known as the ribotoxic stress response (RSR). Double-stranded RNA-activated protein kinase (PKR) associates with the ribosome making it uniquely positioned to sense 28S ribosomal RNA damage and initiate the RSR. We have previously shown that PKR mediates DON-induced MAPK phosphorylation in macrophages and monocytes. The purpose of this study was to test the hypothesis that PKR is essential for induction of interleukin (IL)-8 expression in monocytes by DON and two prototypical RIPs, ricin, and Shiga toxin 1 (Stx1). Preincubation of human monocytic U937 cells with the PKR inhibitors C16 and 2-aminopurine (2-AP) blocked DON-induced expression of IL-8 protein and mRNA. Induction of IL-8 expression was similarly impaired in U937 cells stably transfected with a dominant negative PKR plasmid (UK9M) as compared with cells transfected with control plasmid (UK9C). Nuclear factor-kappa B binding, which has been previously shown to be a requisite for DON-induced IL-8 transcription, was markedly reduced in UK9M cells as compared with UK9C cells. As observed for DON, ricin-, and Stx1-induced IL-8 expression was suppressed by the PKR inhibitors C16 and 2-AP as well as impaired in UK9M cells. Taken together, these data indicate that PKR plays a common role in IL-8 induction by DON and the two RIPs, suggesting that this kinase might be a critical factor in RSR.
authors.affiliation: Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA.
authors.forename: Jennifer S
authors.initials: JS
authors.lastname: Gray
authors.forename: Hee Kyong
authors.initials: HK
authors.lastname: Bae
authors.forename: James C B
authors.initials: JC
authors.lastname: Li
authors.forename: Allan S
authors.initials: AS
authors.lastname: Lau
authors.forename: James J
authors.initials: JJ
authors.lastname: Pestka
mesh_terms: D004305:Dose-Response Relationship, Drug; D006801:Humans; D016209:Interleukin-8 / Q000235:genetics / Q000378:metabolism*; D009000:Monocytes / Q000187:drug effects* / Q000201:enzymology / Q000276:immunology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011500:Protein Synthesis Inhibitors / Q000633:toxicity*; D012333:RNA, Messenger / Q000378:metabolism; D012276:Ricin / Q000633:toxicity*; D022622:Shiga Toxin 1 / Q000633:toxicity*; D015398:Signal Transduction / Q000187:drug effects*; D051996:Transcription Factor RelA / Q000378:metabolism; D014162:Transfection; D014255:Trichothecenes / Q000633:toxicity*; D020298:U937 Cells; D015854:Up-Regulation; D019892:eIF-2 Kinase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: C508606:CXCL8 protein, human; D016209:Interleukin-8; D047428:Protein Kinase Inhibitors; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D022622:Shiga Toxin 1; D051996:Transcription Factor RelA; D014255:Trichothecenes; D012276:Ricin; D019892:eIF-2 Kinase; D048051:p38 Mitogen-Activated Protein Kinases; C007262:deoxynivalenol