vitamin-k-semiquinone-radical and juglone

The breakage/reunion reaction of DNA topoisomerase II (TOP2) can be interrupted by DNA intercalators (e.g., doxorubicin), enzyme binders (e.g., etoposide), or DNA lesions (e.g., abasic sites) to produce TOP2-mediated DNA damage. Here, we demonstrate that thiol alkylation of TOP2 can also produce TOP2-mediated DNA damage. This conclusion is supported by the following observations using purified TOP2: (1) Thiol-reactive quinones were shown to induce TOP2-mediated DNA cleavage. (2) Thiol-reactive compounds such as N-ethylmaleimide (NEM), disulfiram, and organic disulfides [e.g., 2,2'-dithiobis(5-nitropyridine)] were also shown to induce TOP2-mediated DNA cleavage with similar reaction characteristics as thiol-reactive quinones. (3) TOP2-mediated DNA cleavage induced by thiol-reactive quinones was completely abolished using mutant yeast TOP2 with all cysteine residues replaced with alanine (cysteineless TOP2). These results suggest the possibility that cellular DNA damage could occur indirectly through thiolation of a nuclear protein, TOP2. The implications of this reaction in carcinogenesis and apoptotic cell death are discussed.

Topics: Alanine; Alkylation; Animals; Cysteine; DNA Damage; DNA Topoisomerases, Type II; Drosophila; Humans; Intercalating Agents; KB Cells; Mutagenesis, Site-Directed; Naphthoquinones; Quinones; Sulfhydryl Compounds; Tumor Cells, Cultured; Vitamin K

The purpose of this study was to examine the possibility of using Artemia salina as a test organism in the search for compounds having the ability to protect against superoxide-mediated toxicity. The basic procedure for the assay using Artemia salina was performed as described in previous literature, with minor modifications. We found that Artemia salina are extremely sensitive to menadione bisulfite, a compound whose toxicity is probably mediated by intracellular superoxide generation. Desferrioxamine (desferal), a compound with known protective effects, was shown to display dramatic protective activity in our system. We also observed that an inhibitor of endogenous superoxide dismutase (SOD) activity increased the toxicity of menadione toward Artemia salina. In conclusion, this simple, inexpensive, and convenient assay could be a valuable addition to a screening effort in the search for compounds that will be protective against damage by superoxide or other active oxygen species.

Topics: Animals; Artemia; Biological Assay; Deferoxamine; Dimethyl Sulfoxide; Drug Evaluation, Preclinical; Drug Interactions; Hydrogen Peroxide; Naphthoquinones; Paraquat; Potassium Cyanide; Reactive Oxygen Species; Sensitivity and Specificity; Superoxide Dismutase; Superoxides; Ubiquinone; Vitamin K; Vitamin K 3

Several naphthoquinones, except 2-hydroxy-1,4-naphthoquinone, were found to inhibit microsomal cytochrome P-450-linked monooxygenase activities in rabbit liver and human placenta. In particular, 5-hydroxy-1,4-naphthoquinone inhibited placental estrogen biosynthesis more effectively than it did hepatic drug oxidation reactions. There was little contribution by superoxide radicals to these enzyme inhibitions by naphthoquinones. Spectrophotometric studies revealed that naphthoquinones bind to the cytochrome P-450 component of the monooxygenase complex in both microsomal systems, suggesting that the inhibition is caused by direct interaction of these compounds with the heme.

Topics: Androstenedione; Animals; Cytochrome c Group; Cytochrome P-450 Enzyme System; Humans; Microsomes; Microsomes, Liver; Naphthoquinones; Oxygenases; Placenta; Rabbits; Spectrophotometry; Vitamin K

Electron transport from H2, NADPH, NADH and succinate to O2 or ferricytochrome c in respiratory particles isolated from Anacystis nidulans in which hydrogenase had been induced was abolished after extraction of the membranes with n-pentane; oxidation of ascorbate plus NNN'N'-tetramethyl-p-phenylenediamine remained unaffected. Incorporation of authentic ubiquinone-10, plastoquinone-9, menaquinone-7 and phylloquinone (in order of increasing efficiency) restored the electron-transport reactions. ATP-dependent reversed electron flow from NNN'N'-tetramethyl-p-phenylenediamine to NADP+ or, via the membrane-bound hydrogenase, to H+ was likewise abolished by pentane extraction and restored by incorporation of phylloquinone. Participation of the incorporated quinones in the respiratory electron-transport reactions of reconstituted particles was confirmed by measuring the degree of steady-state reduction of the quinones. Isolation and identification of the quinones present in native Anacystis membranes yielded mainly plastoquinone-9 and phylloquinone; neither menaquinone nor alpha-tocopherolquinone could be detected. Together with the results from reconstitution experiments this suggests that phylloquinone might function as the main respiratory quinone in Anacystis nidulans.

Topics: Cell Membrane; Cyanobacteria; Dibromothymoquinone; Electron Transport; Kinetics; NADP; Naphthoquinones; Oxygen Consumption; Quinones; Tetramethylphenylenediamine; Ultraviolet Rays; Vitamin K