Subcytocidal attack by staphylococcal alpha-toxin activates NF-kappa B andinduces interleukin-8 production

Formation of transmembrane pores by staphylococcal alpha-toxin can provoke a spectrum of events depending on target cell species and toxin dose, and i n certain cases, repair of the lesions has been observed. Here, we report t hat transcriptional processes are activated as a response of cells to low t oxin doses. Exposure of monocytic (THP-1) or epithelial (ECV304) cells to 4 0 to 160 ng/ml alpha-toxin provoked a drop in cellular ATP level that was f ollowed by secretion of substantial amounts of interleukin-8 (IL-8). Cells transfected with constructs comprising the proximal IL-8 promoter fused to luciferase or to green fluorescent protein cDNA exhibited enhanced reporter gene expression following toxin treatment. Electrophoretic mobility shift and immunofluorescence assays demonstrated that IL-8 secretion was preceded by activation of NF-kappaB. Transfection experiments conducted with p65/p5 0 double-deficient cells showed that activation of the IL-8 promoter/report er by toxin was absolutely dependent on NF-kappaB. In contrast, this transc ription factor was not required for lesion repair. Attack of cells by low d oses of a pore-forming toxin can lead to transcriptional gene activation, w hich is followed by production of mediators that may contribute to the init iation and propagation of inflammatory lesions.