diethyl-maleate and Leukemia--Promyelocytic--Acute

The influence of reducing compounds on the formation of DNA--protein cross-links induced by hexavalent chromium was studied in the human cell line HL-60. Analysis of cytoplasmic concentration of ascorbic acid and glutathione by HPLC in these cells showed that ascorbic acid was not detectable (detection limit: 0.1 nmol). The cellular content of glutathione was low (6 nmol/million cells). It could easily be depleted with diethylmaleate. The effect of glutathione, ascorbic acid and ascorbyl palmitate alone, or glutathione in combination with ascorbyl palmitate was investigated. It could be shown that glutathione increased DNA--protein cross-links in HL-60 cells by chromate significantly in a dose dependent manner, while pre-incubation with L-ascorbic acid and L-ascorbic acid-6-hexadecanate (ascorbyl palmitate) did not change the cross-linking activity of chromate significantly. Ascorbyl palmitate counteracted the increasing effect of glutathione on the concentration of DNA--protein cross-links in HL-60 cells after exposure to chromate. As ascorbic acid reacts much faster with hexavalent chromium at physiological pH than glutathione does, this suggests an influence of the reaction velocity of the redox reaction between hexavalent chromium and the reducing compounds on the toxification of Cr(VI) and formation of DNA--protein cross-links.

Topics: Antimutagenic Agents; Ascorbic Acid; Biological Transport; Carcinogens, Environmental; Cell Division; Cell Line; Chromates; Chromium; DNA, Neoplasm; Dose-Response Relationship, Drug; Glutathione; Humans; Kinetics; Leukemia, Promyelocytic, Acute; Maleates; Neoplasm Proteins; Oxidation-Reduction; Tumor Cells, Cultured

We have investigated the effect of redox changes in vivo on the differentiation of two human myeloid cell lines, HL-60 and KG-1. The glutathione-depleting agent diethyl maleate (DEM) prevented the development of differentiated features in response to phorbol esters, including adherence of the cells to plastic surfaces and repression of the myeloperoxidase and CD34 genes. Moreover, DEM abolished phorbol 12-myristate 13-acetate-induced activation of the transcription factors AP-1 and Egr-1, suggesting that inhibition of differentiation may be due, at least in part, to redox modifications of these proteins.

Topics: Antigens, CD; Antigens, CD34; Base Sequence; Cell Adhesion; Cell Differentiation; DNA-Binding Proteins; Early Growth Response Protein 1; Glutathione; Granulocytes; Humans; Immediate-Early Proteins; Leukemia, Erythroblastic, Acute; Leukemia, Promyelocytic, Acute; Maleates; Molecular Sequence Data; Oxidation-Reduction; Peroxidase; Phenotype; Proto-Oncogene Proteins c-jun; RNA, Messenger; Tetradecanoylphorbol Acetate; Transcription Factors; Tumor Cells, Cultured