NF-kappaB activation by triphenyltin triggers apoptosis in HL-60 cells

Trisubstituted organotin pesticides are lethal for different cell types. In this study we investigated whether triphenyltin chloride (TPT) causes apoptosis in HL-60 promyelocytic cells and, if so, by what mechanisms. We report that 5 microM TPT increased intracellular Ca2+ in HL-60 cells within seconds; concomitantly actin depolymerization was detected 30 s and 1 min after the treatment. This was followed 15 min later by NF-kappaB activation, and apoptotic bodies and DNA fragmentation were evident after 3 and 6 h, respectively. At these times TPT also induced the release of tumor necrosis factor-alpha (TNF-alpha). Prior treatment of the cells with a polyclonal antibody to human TNF-alpha abolished TPT-induced DNA fragmentation, which suggests that the ultimate effect of TPT may be mediated by TNF-alpha. Prior treatment of the cells with 100 microM pyrrolidine dithiocarbamate, an antioxidant and potent inhibitor of NF-kappaB activation, prevented actin depolymerization, NF-kappaB activation, and DNA fragmentation, although it did not affect TPT-induced Ca2+ mobilization. These findings suggest that TPT increases intracellular Ca2+, alters actin polymerization and the cytoskeleton, and induces NF-kappaB activation, TNF-alpha synthesis, DNA degradation, and apoptosis. Reactive oxygen species seem to be essential to NF-kappaB activation, TNF-alpha synthesis, and the subsequent steps.