title: Oxidative properties of 12-O-tetradecanoylphorbol-13-acetate-stimulated human blood monomorphonuclear leukocytes and their toxicity against a human lung carcinoma cell line.
abstract: Human monomorphonuclear leukocytes (MMNs) stimulated with 12-O-tetradecanoylphorbol-13-acetate (TPA) were found to be toxic towards human A549 lung carcinoma cells which have been desensitized against the direct growth-inhibitory effect of TPA. This toxicity was dependent on the TPA concentration and the ratio of MMNs to A549 cells. Using a TPA concentration of 10(-7) M and an effector:target cell ratio of 30:1, experiments were performed to give clues as to the mechanisms by which TPA-stimulated MMNs cause toxicity. Levels of the endogenous thiol glutathione were reduced by 37% in MMNs exposed to TPA for 24 h, but the glutathione levels in the A549 target cells were not markedly affected by TPA-stimulated MMNs. The supernatant of incubations of MMNs with TPA contained a species which was capable of oxidizing the thiol agent 5-thio-2-nitrobenzoic acid. Within 2 h, 9 nmol of this oxidant were produced by 10(7) MMNs. The oxidant exhibited a half-life of 20 h, and its formation was abolished by adding catalase (150 units/ml), azide (1 mM), or cyanide (1 mM) to the incubations of MMNs with TPA. The addition of superoxide dismutase (100 units/ml) enhanced oxidant formation. These results indicate that its generation was dependent on the myeloperoxidase:H2O2:halide system. Large amounts of an oxidizing species with properties identical to those described here have been characterized recently in polymorphonuclear leukocytes [S. J. Weiss, M. B. Lampert, and S. T. Test. Science (Wash. DC), 222: 625-627, 1983]. The toxicity exerted by TPA-stimulated MMNs was partially inhibited by superoxide dismutase and by retinoic acid (30 microM) but not at all by catalase, azide, or cyanide. Therefore, the 5-thio-2-nitrobenzoic acid oxidant does not appear to be involved in the process which led to cytotoxicity by TPA-stimulated MMNs in A549 cells.
mesh_terms: D002460:Cell Line; D003602:Cytotoxicity, Immunologic / Q000187:drug effects*; D005609:Free Radicals; D005978:Glutathione / Q000378:metabolism; D006801:Humans; D007694:Killer Cells, Natural / Q000187:drug effects; D007962:Leukocytes / Q000187:drug effects* / Q000378:metabolism; D008175:Lung Neoplasms / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D010084:Oxidation-Reduction; D010704:Phorbols / Q000494:pharmacology*; D013438:Sulfhydryl Compounds / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014212:Tretinoin / Q000494:pharmacology
chemical_list: D005609:Free Radicals; D010704:Phorbols; D013438:Sulfhydryl Compounds; D014212:Tretinoin; D005978:Glutathione; D013755:Tetradecanoylphorbol Acetate