naphthoquinones and Leukemia-L5178

2-Hydroxy-1,4-naphthoquinone (HNQ; Lawsone; CAS 83-72-7) is the principal natural dye ingredient contained in the leaves of Henna (Lawsonia inermis). Published genotoxicity studies on HNQ suggested it was a weak bacterial mutagen for Salmonella typhimurium strain TA98 or was more clearly mutagenic for strain TA 2637, both in the presence of metabolic activation. HNQ was unable to induce sex-linked recessive lethal mutations in Drosophila melanogaster. However, a small increase in micronucleus frequency was reported in the bone marrow of mice at a single mid-range dose level, 24h after intraperitoneal injection. In view of the wide use of Henna hair dyes it was deemed necessary to conduct a thorough investigation, under Good Laboratory Practice conditions, of the genotoxicity of HNQ. HNQ was non-mutagenic in bacterial (Ames test) or mammalian (V79 hprt) assays. It was borderline positive in a mouse lymphoma tk mutation assay and a chromosome aberration test (CHO cells), results that may reflect a similar clastogenic mechanism. Negative in vivo genotoxicity results were noted in the rat hepatocyte in vivo/in vitro UDS test, in peripheral lymphocytes (chromosome aberrations) of rats receiving repeated oral doses of HNQ at the MTD for 28 days, and in mouse and hamster bone marrow chromosome aberration tests. However small, but statistically significant increases in the incidence of bone marrow micronuclei were observed in two out of five tests at 72 h after dosing, but not at 24 or 48 h. There was evidence of haematotoxicity at 72 h, which may have been enhanced by the vehicle (DMSO) used in the positive tests. As erythropoiesis and administration of haematotoxic agents are known to induce small increases in the frequency of bone marrow micronuclei, typically at delayed sampling times, the data suggest that the positive 72 h response produced by HNQ is consistent with stimulation of haematopoiesis subsequent to haematological toxicity of HNQ, and not due to a DNA-reactive mechanism. Overall, the weight of evidence suggests that Henna and HNQ pose no genotoxic risk to the consumer.

Topics: Animals; Bone Marrow Cells; Cell Transformation, Neoplastic; Coloring Agents; Cricetinae; DNA; Dose-Response Relationship, Drug; Female; Hepatocytes; Leukemia L5178; Male; Mesocricetus; Mice; Micronuclei, Chromosome-Defective; Mutagenicity Tests; Mutagens; Naphthoquinones; Rats; Rats, Inbred Strains; Salmonella typhimurium

The murine L5178Y (LY) lymphoma sublines, LY-R (radiation resistant) and LY-S (radiation sensitive) display a difference in susceptibility to camptothecin (CPT): LY-S cells are less sensitive to killing by this inhibitor of topoisomerase I than LY-R cells. Post-treatment (CPT present until 3 h after irradiation) sensitizes only LY-S cells. In agreement with this, only in LY-S cells is the relative number of DNA-protein cross-links formed after treatment with CPT + X higher than expected for additivity of X-ray and CPT-induced damage. The pattern of changes in the labelling indices and cell cycle distribution in cells that underwent combined treatment is essentially like that seen for single-agent treatment: for LY-S cells like that for radiation, for LY-R cells like that for CPT. We found no direct relation between the patterns of cell cycle distributions and the enhancement of the lethal effect of X-irradiation by CPT post-treatment. The sublines are not markedly differentially sensitive to beta-lapachone, which modifies topoisomerase I activity, and not sensitized to X-rays by post-irradiation treatment with the drug.

Topics: Animals; Antibiotics, Antineoplastic; Camptothecin; Combined Modality Therapy; Drug Screening Assays, Antitumor; Leukemia L5178; Mice; Naphthoquinones; Radiation Tolerance; Radiation-Sensitizing Agents; Topoisomerase I Inhibitors; Tumor Cells, Cultured

Murine L517BY (LY) lymphoma sublines, LY-R (X-radiation resistant) and LY-S (X-radiation sensitive) displayed a difference in susceptibility to camptothecin: susceptibility of LY-S cells to the alkaloid was shifted towards higher concentrations as compared to LY-R cells. A similar difference was observed at the level of genomic DNA when a number of DNA-protein cross-links was determined or single-strand breaks were revealed by the fluorescent nucleoid halo assay. Activities of topoisomerases I and II were the same in both sublines. In turn, a higher resistance to camptothecin was found for the isolated LY-S topoisomerase I in the DNA cleavage test, suggesting that an altered enzyme was responsible for the susceptibility difference observed at the cellular level. In the relaxation test the enzymes from the two sublines showed a different sensitivity to beta-lapachone, an activator of topoisomerase I, but were similarly sensitive to all inhibitors, except camptothecin.

Topics: Animals; Antibiotics, Antineoplastic; Camptothecin; Cell Nucleus; Cell Survival; DNA Topoisomerases, Type I; DNA Topoisomerases, Type II; Kinetics; Leukemia L5178; Mice; Naphthoquinones; Plasmids; Substrate Specificity; Topoisomerase I Inhibitors; Tumor Cells, Cultured; X-Rays

An alkalophilic actinomycete, strain OPC-553 regarded as Nocardiopsis dassonvillei subsp. prasina, produced the cytotoxic substance, TS-1, which showed a marked inhibitory activity against L5178Y mouse leukemic cell in vitro. The cytotoxicity of TS-1 on this cell was very strong and its ID50 was 0.018 micrograms/ml. Through direct comparison of its spectral data with those of an authentic sample, TS-1 was identified as the antifungal antibiotic, kalafungin, already isolated from the culture broth of Streptomyces tanashiensis. However, the isolation of kalafungin from an alkalophilic actinomycete and its cytotoxicity are reported for the first time in this paper.

Topics: Actinomycetales; Animals; Antibiotics, Antineoplastic; Antifungal Agents; Cell Survival; Drug Screening Assays, Antitumor; Leukemia L5178; Mice; Naphthoquinones; Tumor Cells, Cultured

Streptomyces tanashiensis IM8442T was found to produce lactoquinomycin B, a novel antibiotic, together with lactoquinomycin A. Lactoquinomycin B was purified, and the physico-chemical and biological characteristics were studied. Lactoquinomycin B, C24H27NO9, mp 149-152 degrees C (dec), FD-MS m/z 473 (M+), is a basic substance, showing UV lambda MeOHmax (epsilon) 239 (15,100), 287 (3,450) and 369 nm (5,300), and IR nu CHCl3max 1790 (gamma-lactone), and 1700 and 1650 (quinone) cm-1. The structure of lactoquinomycin B was elucidated by 1H NMR and 13C NMR in comparison with those of lactoquinomycin A, indicating that B is a 4a,10a-epoxide derivative of A. Lactoquinomycin B displayed inhibitory activity against bacteria, particularly Gram-positive organisms, and cytotoxicity against human and murine tumor cell lines. LD50 for mice was ca. 40 mg/kg by iv route.

Topics: Animals; Antibiotics, Antineoplastic; Bacteria; Cell Line; Humans; Leukemia L5178; Magnetic Resonance Spectroscopy; Mice; Microbial Sensitivity Tests; Naphthoquinones; Spectrophotometry, Infrared; Streptococcus