Vomitoxin-induced cyclooxygenase-2 gene expression in macrophages mediated by activation of ERK and p38 but not JNK mitogen-activated protein kinases.
Vomitoxin (VT) and other trichothecene mycotoxins mediate a broad range of immunotoxic effects via the induction of inflammation-associated genes in leukocytes. The purpose of this study was to test the hypothesis that VT induces cyclooxygenase-2 (COX-2) gene expression in macrophages and that this is regulated at the level of mitogen-activated protein kinases (MAPKs). Exposure of the murine macrophage cell line RAW 264.7 to 50-250 ng/ml VT for 24 h markedly enhanced the production of prostaglandin E(2) (PGE(2)), a major COX-2 metabolite. PGE(2) elevation was preceded by increases in COX-2 mRNA (2 h) and COX-2 protein (15 h) in VT-treated cells. VT induced rapid (15 min) and persistent (up to 240 min) phosphorylation of extracellular, signal regulated protein kinases 1 and 2 (ERK1/2) and p38 MAPK as well as a rapid (15 min) but transient (up to 60 min) phosphorylation of c-Jun N-terminal kinases 1 and 2 (JNK1/2). The ERK inhibitor PD98059 and p38 inhibitor SB203580 suppressed VT-induced PGE(2) and COX-2 protein expression, whereas impairment of JNK function by transient transfection with a dominant negative (dn) JNK vector had no effect on COX-2 protein expression. Relatedly, in cells transfected with a COX-2 promoter-luciferase construct, PD98059- and SB203580-, but not dnJNK-treatment, suppressed VT-induced luciferase transcription. VT also increased COX-2 mRNA stability, and this was inhibited by PD98059 but not by SB203580. Taken together, these results indicate that VT-induced PGE(2) production and COX-2 expression by elevating transcriptional activity and mRNA stability. Enhanced transcriptional activity was modulated by ERK and p38 signaling pathways, whereas mRNA stability was promoted exclusively by VT-activated p38 phosphorylation. These data provide insight into possible general mechanisms by which VT and other trichlothecenes upregulate proinflammatory genes and impart immunotoxicity.
Moon
Yuseok
Y
Department of Food Science and Human Nutrition, Institute for Environmental Toxicology, Michigan State University, 234 G.M. Trout Bldg., East Lansing, MI 48824-1224, USA.
Pestka
James J
JJ
D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D051546:Cyclooxygenase 2; D015232:Dinoprostone / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004790:Enzyme Induction / Q000187:drug effects; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D007527:Isoenzymes / Q000096:biosynthesis* / Q000235:genetics*; D048031:JNK Mitogen-Activated Protein Kinases; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D048670:MAP Kinase Kinase 4; D008264:Macrophages / Q000187:drug effects / Q000201:enzymology*; D051379:Mice; D020929:Mitogen-Activated Protein Kinase Kinases / Q000502:physiology*; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology*; D010957:Plasmids; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis* / Q000235:genetics*; D012323:RNA Processing, Post-Transcriptional / Q000187:drug effects; D012333:RNA, Messenger / Q000096:biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection; D014255:Trichothecenes / Q000633:toxicity*; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases
D007527:Isoenzymes; D012333:RNA, Messenger; D014255:Trichothecenes; D008156:Luciferases; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases; D001616:beta-Galactosidase; C007262:deoxynivalenol; D015232:Dinoprostone