Diethyldithiocarbamate-Induced Cytotoxicity and Apoptosis in Leukemia Cell Lines

Diethyldithiocarbamate (DDTC) has been shown to induce cytotoxicity in several different systems. We examined whether the DDTC-induced cytotoxicity was via apoptosis, or in relation to intracellular glutathione (GSH) in various murine and human leukemia cell lines. The cells most sensitive to DDTC-induced cytotoxicity were P388 lymphoid neoplasma cells and NALM-6, a B cell line of acute lymphocytic leukemia (ALL). The next level of susceptible cells included J774.1, having a macrophage function, HL-60 premyelocytic leukemia cells, MOLT-4, an acute lymphoblastic leukemia cell, and Jurkat, a T-cell leukemia. U937 (expressing many monocyte-like characteristics), K562 erythroleukemia and K562/DXR (a multidrug-resistant clone derived from K562) were almost unaffected by DDTC. P388 was also highly susceptible to H2O2, a most useful exogenous reactive oxygen species generator, and was lower in intracellular total GSH content than other leukemia cells. DDTC-induced cytotoxicity was closely related to intracellular GSH, but the level of cellular GSH did not always correlate with H2O2-induced cytotoxicity in this experiment. K562 had a higher intracellular total GSH content and showed lower susceptibility to DDTC and H2O2, but with the combination of DDTC and DL-buthionine-(S,R)-sulfoximine (BSO), cytotoxicity increased significantly. The ratio of GSH/GSSG in P388 was reduced by DDTC or H2O2. H2O2-induced cytotoxicity was completely blocked by catalase (CAT), while it was enhanced by superoxide dismutase (SOD). CAT or SOD did not affect DDTC-induced cytotoxicity. N-Acetylcysteine (NAC: 1 mM), a vanguard substance of GSH, and aurintricarboxylic acid (ATA: 100 μM), an endonuclease inhibitor, ameliorated DDTC-induced cytotoxicity and apoptosis. In conclusion, we suggest that DDTC-induced cytotoxicity was via an oxidative shift in the intracellular redox state, and accompanied the activation of endonuclease through apoptosis in leukemia cell lines.