Effect of Glutathione Depletion on Antitumor Drug Toxicity (Apoptosis and Necrosis) in U-937 Human Promonocytic Cells

Abstract

Treatment with the DNA topoisomerase inhibitors etoposide, doxorubicin, and camptothecin, and with the alkylating agents cisplatin and melphalan, caused peroxide accumulation and apoptosis in U-937 human promonocytic cells. Preincubation with the reduced glutathione (GSH) synthesis inhibitor L-buthionine-(S,R)-sulfoximine (BSO) always potentiated peroxide accumulation. However, although GSH depletion potentiated the toxicity of cisplatin and melphalan, occasionally switching the mode of death from apoptosis to necrosis, it did not affect the toxicity of the other antitumor drugs. Hypoxia or preincubation with antioxidant agents attenuated death induction, apoptotic and necrotic, by alkylating drugs. The generation of necrosis by cisplatin could not be mimicked by addition of exogenous H 2 O 2 instead of BSO and was not adequately explained by caspase inactivation nor by a selective fall in ATP content. Treatment with cisplatin and melphalan caused a late decrease in mitochondrial transmembrane potential (⌬⌿m), which was much greater during necrosis than during apoptosis. The administration of the antioxidant agents N-acetyl-L-cysteine and butylated hydroxyanisole after pulse treatment with cisplatin or melphalan did not affect apoptosis but attenuated necrosis. Under these conditions, both antioxidants attenuated the necrosis-associated ⌬⌿m decrease. These results indicate that oxidation-mediated alterations in mitochondrial function regulate the selection between apoptosis and necrosis in alkylating drug-treated human promonocytic cells.

12-O-Tetradecanoylphorbol-13-acetate May Both Potentiate and Decrease the Generation of Apoptosis by the Antileukemic Agent Arsenic Trioxide in Human Promonocytic Cells

“…If this was the case we could predict a similar potentiation of apoptosis when the phorbol ester is used in combination with other GSH-sensitive agents but probably not with GSH-insensitive drugs. Earlier observations indicated that GSH depletion enhanced the toxicity of the heavy metal cadmium (43, 44) but did not affect the toxicity of anti-DNA topoisomerase drugs in myeloid cells (29,45). Hence, we decided to compare the effect of BSO and TPA on U-937 cells treated with cadmium chloride (CdCl 2 , 40 M) and with the antitumor anti-DNA topoisomerase drugs etoposide (0.5 M), camptothecin (50 nM), and doxorubicin (0.5 M).…”

“…Measurement of GSH Levels-The total cellular GSH content was determined by fluorometry after cell loading with monochlorobimane following the previously described procedure (29).…”

Carbonylation of glycolytic proteins is a key response to drug-induced oxidative stress and apoptosis

“…For example VP16, or etoposide, is a topoisomerase II inhibitor; however, there are reports in the literature of VP16-induced cell death being mediated through pathways independent of topoisomerase II inhibition, but dependant on ROS production. 4,6 It is likely that the generation of ROS by cytotoxic drug treatment of cells results in nonenzymatic protein modifications that may play an important role in the early stages of apoptosis.…”

Oxidative Stress Stimulates the Synthesis of the Eosinophil Chemoattractant 5-Oxo-6,8,11,14-eicosatetraenoic Acid by Inflammatory Cells

“…The response to H 2 O 2 was also inhibited by about 50% following culture of U937 cells for 24 h in the presence of BSO (Fig. 2C), which depletes cells of GSH by inhibiting ␥-glutamylcysteine synthetase (32). In contrast, BSO had no effect on the stimulatory effect of PMS on 5-oxo-ETE formation.…”