Hydroxytyrosol: lack of clastogenicity in a bone marrow chromosome aberration study in rats.

BACKGROUND: Hydroxytyrosol is naturally found in olives, olive oil and wine, and is consumed as part of a normal diet. The substance may have utility as a preservative in a wide variety of foods due to its antioxidant, antimicrobial and amphipathic properties. The potential for hydroxytyrosol to cause chromosome aberrations in vitro had been tested previously, with positive results at high concentrations. An OECD Guideline 475 study (mammalian bone marrow chromosome aberration test) was conducted in rats with the oral limit dose of 2000 mg/kg bw to determine whether hydroxytyrosol is a clastogen in vivo. RESULTS: The oral limit dose of 2000 mg/kg hydroxytyrosol was well tolerated by most rats; however, some rats exhibited clinical signs that abated within 24 hours. Treatment with hydroxytyrosol did not significantly enhance the number of aberrant cells or the mitotic index 24 or 48 hours post-dose. The positive control (cyclophosphamide) induced the expected increase in chromosomal aberrations and a decrease in the mitotic index, confirming the validity of the assay. CONCLUSION: An oral limit dose of 2000 mg/kg hydroxytyrosol does not induce chromosome aberrations in bone marrow cells of the rat. Accordingly, hydroxytyrosol is not a clastogen in vivo.

Genotoxicity of dried Hoodia parviflora aerial parts.

Hoodia parviflora is being developed commercially for use in weight loss food and dietary supplement products. Its effects are ascribed to a number of glycosides that have been shown to be present in plant extracts from several Hoodia species, the best known of which is H. gordonii. H. parviflora has been identified as an alternative to H. gordonii, and, as part of the process to develop H. parviflora, in vitro genotoxicity tests, as recommended by recent European Food Safety Authority guidance, were conducted on a dried powder preparation of H. parviflora aerial parts. The preparation was tested for reverse mutation at doses up to 5,000µg/plate in Salmonella typhimurium strains TA98, TA100, TA1535, and TA1537, and in Escherichia coli WP2 uvrA TA, both in the presence and in the absence of an exogenous source of metabolic activation (rat liver S9). In addition, the dried powder was evaluated in an in vitro cytotoxicity chromosome aberration assay using human lymphocytes. Test conditions included both a 4 (up to 2500µg/mg) and 44-h exposure period (up to 1000µg/mg) and the incorporation of an exogenous source of metabolic activation (4-h exposure only). H. parviflora dried powder was non-genotoxic in both in vitro assays.

Spontaneous and radiation-induced chromosomal instability and persistence of chromosome aberrations after radiotherapy in lymphocytes from prostate cancer patients.

The aim of the study was to compare the spontaneous and ex vivo radiation-induced chromosomal damage in lymphocytes of untreated prostate cancer patients and age-matched healthy donors, and to evaluate the chromosomal damage, induced by radiotherapy, and its persistence. Blood samples from 102 prostate cancer patients were obtained before radiotherapy to investigate the excess acentric fragments and dicentric chromosomes. In addition, in a subgroup of ten patients, simple exchanges in chromosomes 2 and 4 were evaluated by fluorescent in situ hybridization (FISH), before the onset of therapy, in the middle and at the end of therapy, and 1 year later. Data were compared to blood samples from ten age-matched healthy donors. We found that spontaneous yields of acentric chromosome fragments and simple exchanges were significantly increased in lymphocytes of patients before onset of therapy, indicating chromosomal instability in these patients. Ex vivo radiation-induced aberrations were not significantly increased, indicating proficient repair of radiation-induced DNA double-strand breaks in lymphocytes of these patients. As expected, the yields of dicentric and acentric chromosomes, and the partial yields of simple exchanges, were increased after the onset of therapy. Surprisingly, yields after 1 year were comparable to those directly after radiotherapy, indicating persistence of chromosomal instability over this time. Our results indicate that prostate cancer patients are characterized by increased spontaneous chromosomal instability. This instability seems to result from defects other than a deficient repair of radiation-induced DNA double-strand breaks. Radiotherapy-induced chromosomal damage persists 1 year after treatment.

Genotoxicity studies of PolyGlycopleX (PGX): a novel dietary fiber.

PolyGlycopleX (PGX), a novel dietary fiber, produces no mutagenic effects in bacterial tester strains Salmonella typhimurium TA 98, TA 100, TA 1535, and TA 1537 and Escherichia coli WP2 uvrA at concentrations of 0.316, 1.00, 3.16, 10.0, 31.6, and 100 microg/plate. No biologically relevant increases in revertant colonies of any of the 5 strains are observed at any concentration; however, a reduction at 100 microg/plate in TA 1537 is noted. PGX, analyzed for polychromatic erythrocyte micronuclei induction in mice following a single 1x, 0.5x, and 0.2x maximum tolerable dose intraperitoneal treatment, produces no biologically relevant increase in any dose group. Males at 1x maximum tolerable dose show a reduction of micronuclei-containing cells. High-dose animals show signs of systemic toxicity, including a reduction of spontaneous activity, rough fur, palpebral closure, prone position, and constricted abdomen. These genotoxicity studies show PGX to be nonmutagenic in both the Ames bacterial reverse mutation assay and the mammalian erythrocyte micronucleus test.

Chromosomal instability and delayed apoptosis in long-term T-lymphocyte cultures irradiated with carbon ions and x rays.

In this study, we examined genomic instability induced by 250 kV X rays and 100 MeV/nucleon carbon ions in long-term lymphocyte cultures from two healthy donors. Two biological end points, delayed apoptosis and chromosomal instability, were studied in descendants of cells irradiated with three different doses of the particular radiation up to 22 population doublings. The delayed apoptosis showed no clear dependence on radiation dose, culture time or radiation quality. A persistent significant increase in the rate of apoptosis up to 36 days after X irradiation was observed for a dose of 4 Gy in donor 1 only. For both donors and radiations, de novo aberration yields were significantly increased in comparison to control values up to day 36. For both radiations, chromosome-type aberrations were seen more frequently than chromatid-type aberrations in both donors up to 22 days postirradiation. In both donors, carbon ions were more effective than X rays with respect to the induction of chromosome instability. A dose of 0.25 Gy of carbon ions corresponding to 1.4 ion traversals per cell nucleus was effective in the induction of instability in our cell system.

The effect of wortmannin on radiation-induced chromosome aberration formation in the radioresistant tumor cell line WiDr.

We analyzed the formation of radiation-induced chromosome aberrations in the cells of the radioresistant colon carcinoma cell line WiDr after treatment with wortmannin, an inhibitor of PI-3 kinases, including DNA-PK. Cells irradiated in G0/G1 phase with 200 kV X rays were treated with wortmannin before or after irradiation. Chromosome-type and chromatid-type aberrations were scored in metaphase cells by either Giemsa staining or FISH. Moreover, DNA-PK activity was measured in the absence and presence of wortmannin. In irradiated G0/G1-phase WiDr cells, only chromosome-type aberrations, including simple and complex exchanges and excess acentrics, were observed. After addition of 1 to 20 microM wortmannin, the formation of chromosome-type exchange aberrations was completely suppressed. The irradiated cells displayed exclusively chromatid-type aberrations including simple and complex chromatid exchanges and chromatid/isochromatid breaks. Whether the chromatid-type aberrations arise during G0/G1 as a result of homologous recombination processes coping with damaged DNA or whether DNA damage induced during G0/G1 phase persists until S and G2 phase and is then processed by homologous recombination pathways must be investigated further.