PYRROLIDINE DITHIOCARBAMATE, A POTENT INHIBITOR OF NUCLEAR FACTOR KAPPA-B (NF-KAPPA-B) ACTIVATION, PREVENTS APOPTOSIS IN HUMAN PROMYELOCYTIC LEUKEMIA HL-60 CELLS AND THYMOCYTES

We examined the effect of pyrrolidine dithiocarbamate (PDTC), which po tently blocks the activation of nuclear factor kappa B (NF-kappa B), o n the induction of apoptosis by a variety of agents. Treatment of a hu man promyelocytic leukemia cell line, HL-60, with 10 mu g/mL etoposide or 2 mu M 1-beta-D-arabinofuranosylcytosine induced NF-kappa B activa tion within 1-hr and subsequently caused apoptosis within 3-4hr. The s imultaneous addition of 50-500 mu M PDTC with these agents blocked NF- kappa B activation and completely abrogated both morphologically apopt otic changes and internucleosomal DNA fragmentation for up to 6 hr. Ho wever, PDTC failed to inhibit the endonuclease activity contained in t he whole cell lysates. The inhibitory effect of PDTC was also observed in etoposide- and dexamethasone-induced apoptosis in human thymocytes at a concentration of 1-10 mu M. Since PDTC has both antioxidant and metal-ion chelating activities, we tested the effects of N-acetyl-L-cy steine (NAC) (antioxidant) or o-phenanthroline (OP) (metal-ion chelato r) on the induction of apoptosis. Pretreatment of HL-60 cells or thymo cytes with 100-500 mu M OP for 2 hr, but not 10-60 mM NAC, suppressed subsequent occurrence of apoptosis induced by etoposide. These results suggest that the activation of NF-kappa B plays an important role in the apoptotic process of human hematopoietic cells.