SHIGA TOXIN TYPE-1 ACTIVATES TUMOR-NECROSIS-FACTOR-ALPHA GENE-TRANSCRIPTION AND NUCLEAR TRANSLOCATION OF THE TRANSCRIPTIONAL ACTIVATORS NUCLEAR FACTOR-KAPPA-B AND ACTIVATOR PROTEIN-1

Shiga toxins (Stxs) produced by Shigella dysenteriae 1 and Escherichia coli have been implicated in the pathogenesis of bloody diarrhea, acu te renal failure, and neurologic abnormalities. The pathologic hallmar k of Stx-mediated tissue damage is the development of vascular lesions in which endothelial cells are swollen and detached from underlying b asement membranes. However, in vitro studies using human vascular endo thelial cells demonstrated minimal Stx-induced cytopathic effects, unl ess the target cells were also incubated with the proinflammatory cyto kines tumor necrosis factor-alpha (TNF-alpha) or interleukin-1 beta (I L-1 beta). These cytokines have been shown to upregulate the expressio n of the Stx-binding membrane glycolipid globotriaosylceramide (Gb(3)) . We show here that purified Stx1 induces TNF secretion by a human mon ocytic cell line, THP-1, in a dose- and time-dependent manner. Treatme nt of cells with both lipopolysaccharides (LPS) and Stx1 results in au gmented TNF production. Treatment with the nontoxic Gb(3)-binding sub unit of Stx1 or with an anti-Gb(3) monoclonal antibody did not trigger TNF production. Northern blot analyses show that Stx1 causes increase d TNF-alpha production through transcriptional activation. Increased l evels of TNF-alpha mRNA are preceded by the nuclear translocation of t he transcriptional activators NF KB and AP 1 and the loss of cytoplasm ic I kappa B-alpha. These data are the first to show that, in addition to direct cytotoxicity, Stxs possess cellular signaling capabilities sufficient to induce the synthesis of cytokines that may be necessary for target cell sensitization and the development of vascular lesions. (C) 1998 by The American Society of Hematology.