Moon Yuseok, Pestka James J
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.
Toxicol Sci. 2002 Oct;69(2):373-82. doi: 10.1093/toxsci/69.2.373.
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.
呕吐毒素（VT）和其他单端孢霉烯族霉菌毒素通过诱导白细胞中炎症相关基因，介导广泛的免疫毒性作用。本研究的目的是验证以下假设：VT诱导巨噬细胞中环氧化酶-2（COX-2）基因表达，且这一过程在丝裂原活化蛋白激酶（MAPK）水平受到调控。将小鼠巨噬细胞系RAW 264.7暴露于50 - 250 ng/ml的VT中24小时，显著增强了前列腺素E2（PGE2）的产生，PGE2是COX-2的主要代谢产物。在VT处理的细胞中，COX-2 mRNA（2小时）和COX-2蛋白（15小时）增加之前，PGE2水平就已升高。VT诱导细胞外信号调节蛋白激酶1和2（ERK1/2）以及p38 MAPK快速（15分钟）且持续（长达240分钟）磷酸化，同时诱导c-Jun氨基末端激酶1和2（JNK1/2）快速（15分钟）但短暂（长达60分钟）磷酸化。ERK抑制剂PD98059和p38抑制剂SB203580抑制VT诱导的PGE2和COX-2蛋白表达，而通过用显性负性（dn）JNK载体瞬时转染损害JNK功能，对COX-2蛋白表达没有影响。相关地，在用COX-2启动子 - 荧光素酶构建体转染的细胞中，PD98059和SB203580处理（而非dnJNK处理）抑制VT诱导的荧光素酶转录。VT还增加了COX-2 mRNA稳定性，这被PD98059抑制，但未被SB203580抑制。综上所述，这些结果表明，VT通过提高转录活性和mRNA稳定性来诱导PGE2产生和COX-2表达。增强的转录活性由ERK和p38信号通路调节，而mRNA稳定性仅由VT激活的p38磷酸化促进。这些数据为VT和其他单端孢霉烯族毒素上调促炎基因并赋予免疫毒性的可能一般机制提供了见解。
