EFFECTS OF VOMITOXIN (DEOXYNIVALENOL) ON TRANSCRIPTION FACTOR NF-KAPPA-B REL BINDING-ACTIVITY IN MURINE EL-4 THYMOMA AND PRIMARY CD4(+) T-CELLS/

The trichothecene mycotoxin vomitoxin (VT, deoxynivalenol) superinduce s the gene expression of IL-2 and several other cytokines in both cell ular and murine models. Because transcription factor NF-kappa B/Rel ha s been shown to play a crucial role in control of cytokine gene transc ription, we assessed the in vitro effects of VT on NF-kappa B/Rel bind ing activity by electrophoretic mobility shift assay using both cloned (EL-4) and primary (CD4(+)) murine T cells. When EL-4 thymoma cells w ere stimulated with phorbol 12-myristate 13-acetate plus ionomycin in the presence of 500 ng/ml VT, DNA binding activity by NF-kappa B/Rel i n nuclear extracts was increased from 2 to 48 hr when compared to cont rols employing no VT. VT preferentially induced a slower migrating ele ctrophoretic band of the NF-kappa B/Rel complex particularly in later time points (8-48 hr). The band was found to contain a c-Rel/p50 heter odimer by supershift assay using antibodies specific for c-Rel and p50 . NF-kappa B/Rel binding activity was enhanced by VT in a dose-depende nt fashion. As little as 50 ng/ml VT was sufficient to increase NF-kap pa B/Rel binding in a 1-hr EL-4 culture. Using Western blot analysis, effects on EL-4 cells were further related to VT-mediated inhibition o f resynthesis of I kappa B alpha, a cytoplasmic inhibitor of NF-kappa B/Rel. Decreased I kappa B alpha levels were observed with 250-1000 ng /ml VT from 4 to 48 hr. Using primary murine CD4(+) T cell cultures, e levated NF-kappa B/Rel and c-Rel/p50 binding activities were also obse rved at VT of 500 ng/ml from 1 to 72 hr concurrently with decreased I kappa B alpha levels. These data suggest that VT increased NF-kappa B/ Rel binding activity and, in particular, the transactivating form, c-R el. Increased NF-kappa B/Rel binding activity in the later (48 hr) sta ges of cell incubation may be explained, in part, by VT-mediated inhib ition of resynthesis of its cytoplasmic inhibitor I kappa B alpha and by decreases in the inhibitory p50 homodimer. Elevated NF kappa B/Rel binding activity may be involved mechanistically in VT-induced gene ex pression of the cytokines and resultant toxic and autoimmune effects. (C) 1996 Academic Press, Inc.