Superinduction of TNF-α and IL-6 in macrophages by vomitoxin (deoxynivalenol) modulated by mRNA stabilization

Vomitoxin (VT or deoxynivalenol), a trichothecene, superinduces proinflammatory cytokine gene expression in vitro and in vivo. To better understand the underlying molecular mechanisms for this observation, post-transcriptional effects of VT on TNF-alpha and IL-6 gene expression were studied in lipopolysaccharide (LPS)-stimulated macrophage RAW 264.7 cells. VT was found to enhance both TNF-alpha and IL-6 protein secretion in the presence of LPS. Upon addition of the transcriptional inhibitor, 5,6-dichloro-1-beta-D-ribofuranosyl benzimidazole (DRB). secretion of both cytokines was inhibited. Using Northern analysis. the mRNA stabilities of TNF-alpha and IL-6 were studied in DRB-treated. cells exposed to VT and LPS in both asynchronous and delayed synchronous modes. In the asynchronous model, cells were first incubated with LPS for 2 h, and then the medium was removed and replaced with medium containing DRB and VT. In the delayed synchronous model, cells were pretreated with LPS for 2 h and then DRB and VT were added to the culture. TNF-alpha and IL-6 mRNA were rapidly stabilized by VT (100 and 250 ng/ml) in both asynchronous and delayed synchronous models. In the asynchronous model, TNF-alpha. mRNA half-life was 25 mill but this was extended in the presence of 100 and 250 ng/ml of VT to > 3 h. VT also extended half-lives of IL-6 mRNA from 60 min to > 3 h. In the delayed synchronous model, the half-lives for TNF-alpha and IL-6 mRNA of 1.3 and 1.5 h, respectively, were extended to > 3 h upon incubation with 100 and 250 ng/ml VT. These results suggest that post-transcriptional control via enhancement of mRNA stability is likely to contribute to proinflammatory cytokine superinduction in macrophages by VT and other trichothecenes. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.