title: Superinduction of IL-2 gene expression by vomitoxin (deoxynivalenol) involves increased mRNA stability.
abstract: To better understand molecular mechanisms by which the trichothecene vomitoxin (VT) superinduces cytokine gene expression, we studied the posttranscriptional effects of this mycotoxin on interleukin-2 (IL-2) gene expression in murine EL-4 thymoma cells stimulated with phorbol 12-myristate 13-acetate and ionomycin (PMA + ION). Northern analysis revealed that doses of 50 to 500 ng/ml VT superinduced IL-2 mRNA expression in a dose- and time-dependent manner in a synchronous model where VT was added at onset of PMA + ION stimulation. In accordance with the mRNA levels, IL-2 production was significantly elevated in the presence of 50 to 250 ng/ml VT. Superinduction of IL-2 mRNA was also observed in a delayed synchronous model (VT added 20 hr after PMA + ION stimulation) and an asynchronous model (VT added 20 hr after PMA + ION stimulation and removal). To assess the effects of VT (500 ng/ml) on IL-2 mRNA half-life, three transcriptional inhibitors were used in the delayed synchronous model. Actinomycin D (ActD) had a pronounced stabilizing effect on IL-2 mRNA but not on mRNA for the housekeeping gene GAPDH. VT did not affect IL-2 mRNA levels in ActD-treated cells. Although 5,6-dichloro-beta-D-ribofuranosyl-benzimidazole (DRB) also had a stabilizing effect on IL-2 mRNA, IL-2 mRNA half-life t1/2 in VT-treated cells was three times that of control. In contrast, inclusion of cyclosporin A (CsA) into the cultures specifically arrested IL-2 transcription in EL-4 cells without any stabilizing effect. VT exposure in the presence of CsA markedly prolonged the half-life of IL-2 mRNA in a dose-dependent manner. The t1/2 for IL-2 mRNA in the control culture was 2.1 hr, whereas t1/2 was 3.1, 3.4, 4.2, and 10.5 hr in cultures containing 50, 100, 250, and 500 ng/ml VT, respectively. These results suggest that VT can superinduce IL-2 at both the mRNA and the protein level and that this superinduction can be explained, in part, by posttranscriptional mechanisms such as enhanced mRNA stability.
authors.affiliation: Department of Food Science and Human Nutrition, Michigan State University, East Lansing 48824, USA.
authors.forename: S
authors.initials: S
authors.lastname: Li
authors.forename: Y L
authors.initials: YL
authors.lastname: Ouyang
authors.forename: W
authors.initials: W
authors.lastname: Dong
authors.forename: J J
authors.initials: JJ
authors.lastname: Pestka
mesh_terms: D000818:Animals; D007376:Interleukin-2 / Q000096:biosynthesis* / Q000235:genetics; D051379:Mice; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology*; D012323:RNA Processing, Post-Transcriptional / Q000187:drug effects*; D012333:RNA, Messenger / Q000378:metabolism*; D013601:T-Lymphocytes / Q000187:drug effects* / Q000502:physiology*; D014255:Trichothecenes / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
chemical_list: D007376:Interleukin-2; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D014255:Trichothecenes; C007262:deoxynivalenol