Pyrrolidine dithiocarbamate induces apoptosis by a cytochrome c-dependent mechanism

Pyrrolidine dithiocarbamate (PDTC) is a synthetic antioxidant molecule, whi ch has been recently proposed as an antitumoral agent on the basis of its c apability of inducing apoptosis. We investigated the effect of PDTC on the proliferation and survival of the promyelocitic cell line HL-60. Concentrat ion as low as 10 mu M of PDTC induces a significant reduction of the growth rate and the contemporaneous activation of the apoptotic process. Programm ed cell death was demonstrated by biochemical analyses, including the activ ation of procaspase 3 and the cleavage of poly(ADP-ribose) polymerase (PARP ). PDTC-dependent apoptosis was associated with an early release of cytochr ome c from mitochondria, while the involvement of pathways due to cell deat h receptors engagement was ruled out by detailed time-course analyses of ca spases 3 and 8 activation. Moreover, no up-regulation of p21(CIP1) level, a pivotal cyclin-dependent kinase inhibitor, occurred at PDTC concentration able to induce apoptosis. Finally, in vitro incubation of purified mitochon dria with PDTC demonstrated that the molecule is directly able to induce cy tochrome c release from the intermembrane space, thus confirming that mitoc hondria are a primary cellular target of the molecule. (C) 2000 Academic pr ess.