ToxSci Advance Access originally published online on July 16, 2007
Toxicological Sciences 2007 99(2):502-511; doi:10.1093/toxsci/kfm182
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Transcriptional Regulation of Deoxynivalenol-Induced IL-8 Expression in Human Monocytes
,
,1
* Department of Microbiology and Molecular Genetics
Center for Integrative Toxicology
Department of Food Science and Human Nutrition, Michigan State University, East Lansing, Michigan 48824-1224
1 To whom correspondence should be addressed at 234 G.M. Trout Building, Michigan State University, East Lansing, MI 48824-1224. Fax: (517) 353-8963. E-mail: pestka{at}msu.edu.
Received June 5, 2007; accepted July 3, 2007
 |
Abstract |
|---|
The trichothecene mycotoxin deoxynivalenol (DON), commonly present in contaminated grains worldwide, induces expression of the chemokine interleukin (IL)-8 in human monocytes. The purpose of this study was to test the hypothesis that DON modulates transcriptional and posttranscriptional regulation of IL-8 expression in the U937 human monocyte model. When U937 cells were transfected with a wild-type IL-8 promoter luciferase construct (–162/+44 IL-8 LUC) and incubated with DON (1 µg/ml) or the positive control, lipopolysaccharide (LPS) (1 µg/ml), there was a significant increase in luciferase expression. Mutation of the nuclear factor-
B (NF-B) binding site significantly impaired both DON- and LPS-induced luciferase expression. In contrast, mutating the activator protein-1 binding site resulted in significantly increased DON- and LPS-induced luciferase expression. CCAAT/enhancer-binding protein ß, octamer-1, or NF-B repressing factor binding site mutations did not affect DON-induced luciferase activity. Consistent with reporter studies, the NF-B inhibitor caffeic acid phenethyl ester completely ablated both DON-induced IL-8 mRNA and protein expression. When NF-B subunit binding to a specific IL-8 promoter probe was evaluated by enzyme-linked immunosorbent assay (ELISA), DON was observed to increase p65 binding by 21-fold, have no effect on p50 binding and decrease p52 binding. DON was not found to stabilize IL-8 mRNA in U937 cells. Taken together, these data suggest that DON-induced IL-8 expression is likely to be mediated at the transcriptional level by NF-B, specifically p65, but does not appear to involve mRNA stabilization.
Key Words: mycotoxin; trichothecene; chemokine; transcription; immunotoxicity.