Verotoxin-1 stimulation of macrophage-like THP-1 cells up-regulates tissue factor expression through activation of c-Yes tyrosine kinase: Possible signal transduction in tissue factor up-regulation

Verotoxin (VT)-producing Escherichia coli (E. coli) O157:H7 infections are frequently complicated by thrombotic angiopathy, hemolytic uremic syndrome (HUS) and neurological symptoms. The present data demonstrate that VT-1 (Shiga toxin) stimulation of macrophage-like THP-1 cells up-regulates the activity, antigen and mRNA levels of tissue factor (TF), a key cofactor of the coagulation–inflammation–thrombosis circuit. This up-regulation is accompanied by phosphorylation of phosphatidylinositol 3-kinase (PI3-kinase), IκB kinase β (IKKβ) and extracellular signal-regulated kinase 2 (ERK2). Changes in TF mRNA levels were in parallel with the activation of NF-κB/Rel and Egr-1 activation, but not with AP-1. Inhibition of PI3-kinase attenuated VT-1-induced phosphorylation of IKKβ and ERK2, and the up-regulation of TF mRNA levels. VT-1 stimulation rapidly activated c-Yes tyrosine kinase, a member of the Src family. Treatment of the cells with c-Yes antisense oligos attenuated the VT-1-induced phosphorylation of PI3-kinase, IKKβ and ERK2, activations of NF-κB/Rel and Egr-1, and up-regulation of TF mRNA levels. These results suggest that VT-1-induced macrophage stimulation activates c-Yes, which then up-regulates TF expression through activation of the IKKβ/proteasome/NF-κB/Rel and MEK/ERK2/Egr-1 pathways via activation of PI3-kinase. Induction of macrophage TF expression by VT-1 may play an important role in the acceleration of the coagulation–inflammation–thrombosis circuit during infections by VT-producing E. coli.