Frequency Of Chromosome Damage Research Articles

3-Heptylidene-4,6-Dimethoxy-3H-Isobenzofuran-1-One Is Genotoxic, Increases the Frequency of Cell Death, and Potentiates the Effects of Cyclophosphamide and Cisplatin.

3-heptylidene-4,6-dimethoxy-3H-isobenzofuran-1-one (Phthalide 1) is the precursor of three resorcinol lipids that have been described as potential chemotherapeutic agents and capable of potentiating the effects of cyclophosphamide. In this study, we evaluated the genotoxic potential, cell-killing potential, and interactions with cyclophosphamide and cisplatin of phthalide 1. Twelve groups were created from 120 mice: Negative Control, cyclophosphamide (100 mg/kg), cisplatin (6 mg/kg), Phthalide 1 (5, 10 and 20 mg/kg), and associations of 1 with cyclophosphamide and 1 with cisplatin. The results demonstrate that 1 increases (p < 0.05) the frequency of chromosomal damage, liver and kidney cell death, and splenic phagocytosis. The association of 1 with cyclophosphamide and cisplatin demonstrated a chemopreventive effect and, therefore, a reduction (p < 0.05) in the frequency of chromosomal damage. However, cell death and splenic phagocytosis did not suffer significant variations. As a result of the above, 1 has potential chemotherapeutic application and may be a candidate for developing a new generation of chemotherapeutics. In addition, it has characteristics to be used as a chemotherapy adjuvant in association with cyclophosphamide and cisplatin since it increases the frequency of cell death induced by chemotherapy. We also reported that the chemopreventive effect of 1, in association with cyclophosphamide and cisplatin, can prevent adverse effects (induction of DNA damage in non-tumor cells) without interfering with the mode of action of chemotherapy drugs and, therefore, without reducing the induction of cell death.

Persistence of space radiation induced cytogenetic damage in the blood lymphocytes of astronauts

Cytogenetic damage was assessed in blood lymphocytes from 16 astronauts before and after they participated in long-duration space missions of 3 months or more. The frequency of chromosome damage was measured by fluorescence in situ hybridization (FISH) chromosome painting before flight and at various intervals from a few days to many months after return from the mission. For all individuals, the frequency of chromosome exchanges measured within a month of return from space was higher than their preflight yield. However, some individuals showed a temporal decline in chromosome damage with time after flight. Statistical analysis using combined data for all astronauts indicated a significant overall decreasing trend in total chromosome exchanges with time after flight, although this trend was not seen for all astronauts and the yield of chromosome damage in some individuals actually increased with time after flight. The decreasing trend in total exchanges was slightly more significant when statistical analysis was restricted to data collected more than 220 days after return from flight. When analysis was restricted to data collected within 220 days of return from the mission there was no relationship between total exchanges and time. Translocation yields varied more between astronauts and there was only a slight non-significant decrease with time after flight that was similar for both later and earlier sampling times.

Gene-exposure interaction in occupational and environmental epidemiology: Results from an ongoing study

ABSTRACTA tissue bank is established in our department on a total of 659 persons whereof 341 are included in theNordic data base on somatic chromosome damage in humans. Genotyping of susceptibility genes relevantto the exposures of the cohort is an ongoing undertaking in our laboratory. GST's and mEH have beengenotyped for 80 persons so far, CYP's for 20 persons. When the mean number of chromatide breaks and ofcells with aberrations were related to genotypes no statistical difference could be observed between thegenotypes for either parameter. No difference in cytogenetic damage between exposed and referents orbetween smokers and non-smokers were identified for the two separate occupational studies these 80persons represent. The results of the various cytogenetic endpoints were trichotomized and compared to thegenotype distribution. Although not statistically significant, the observed trend with higher percentage ofpersons with polymorphic GSTp1 in particular, but also for GSTq1 and mEH (exon 4) in the group withhigh frequency of chromosome aberrations will be interesting to follow. For further follow-up studies, anested case-control study within the cohort would give a more rapid and less expensive approach thananalysing each study separately as a traditional case-control study. As high frequency of chromosomaldamage is associated with cancer development, the hypothesis to be tested would be whether genetic polymorphismsfor the most appropriate susceptibility genes could be an explanatory factor for this association.

GST Polymorphisms: Bonassi et al. Respond

We thank Vodicka et al. for drawing attention to a critical issue—the role of genetic polymorphisms in the induction of chromosomal damage. First, we would like to clarify that our study (Rossi et al. 2009) was not designed to evaluate the influence of glutathione S-transferase (GST) polymorphisms on the frequency of chromosomal aberrations (CAs). Instead, we aimed to identify any possible susceptibility alleles that would increase the strength of the relationship between CAs and risk of cancer in subgroups of genetically variant individuals. The specific purpose of this case–control study explains the relative small size: We planned to obtain data on both CAs and enetic polymorphisms in the same individuals, with all subjects at ages appropriate to allow for an informative follow-up. The interesting data reported by Vodicka et al. in their letter confirm the extreme heterogeneity of findings when the frequency of chromosome damage is associated with polymorphisms in genes that influence several pathways. In fact, the lack of association in the whole database described by Vodicka et al. contrasts with the significant results reported in exposure-specific subsets, such as the highest frequency of CAs in GSTT1-null smokers working in the tire industry (Musak et al. 2008). This interpretation is also supported by the study of Iarmarcovai et al. (2008a), who reviewed 72 population studies reporting a significant effect of GSTM1, EPHX (microsomal epoxide hydrolase), and GSTT1 on micronucleus frequency. These authors also reported that the effect observed in specific pathways—such as ALDH2 in connection to chromosome damage due to alcohol consumption, BRCA1 and BRCA2 mutations in breast cancer patients, and MTHFR depending on folate levels—was much more pronounced. A great deal of information about the role of genetic polymorphisms in the induction of chromosomal damage will stem from genome-wide association studies, when enough resources will be available in the field to explore the genetic determinants of chromosome damage using a whole genome scan. Nevertheless, classical association studies are still valid assuming that specific pathways are identified, possibly a priori, linking genotoxic exposure to polymorphisms of genes involved in the correspondent pathway We would also like to address future strategies for exploring the link between the frequency of chromosome damage and the risk of cancer (and other diseases). We fully agree with Vodicka et al.’s recommendation that possible modifying effects of lifestyle, occupational factors, and genetic poly morphisms be taken into account. However, after finding negative results concerning the role of occupational exposure to genotoxic agents and smoking habit (Bonassi et al. 2000), and polymorphisms of metabolic genes (Rossi et al. 2009), we believe that the remaining factor to be investigated is diet. Many studies have reported on the role of various food items and nutrients as modulators of chromosome stability (Fenech 2007); therefore, this parameter now has top priority, although reliable data are difficult to collect retrospectively. The other recommendation from Vodicka et al. seems less promising, because measuring the frequency of chromosome damage in cancer patients (besides the classical discussion about whether the damage is a cause or a consequence of the disease) is possibly more a marker of progression than a predictive marker (Iarmarcovai et al. 2008b).

Nickel potentiates the genotoxic effect of benzo[a]pyrene in Chinese hamster lung V79 cells

The modulating effect of acute exposure to NiCl2 on the induction of chromosome aberrations by a model carcinogen, benzo[a]pyrene (B[a]P), was examined in Chinese hamster V79 lung cells. At concentrations up to 20 microg/ml (84.2 microM), NiCl2 did not significantly increase the frequency of chromosome aberrations in V79 cells when the cells were exposed concomitantly to 0.5 microg/ml B[a]P. Addition of the S15 liver microsomal fraction together with the B[a]P did not alter the results. Addition of NiCl2 2 hr before treatment of cells with 0.5 microg/ml B[a]P also did not result in a significant elevation of the frequency of chromosome aberrations, even at NiCl2 concentrations as high as 20 microg/ml. Contrasting sharply with these findings, when V79 cells were treated with NiCl2 immediately after B[a]P exposure, a significant increase in the frequency of chromosome damage was observed at NiCl2 concentrations as low as 5 microg/ml (21.1 microM). NiCl2-mediated enhancement of chromosome damage was also observed when V79 cells were exposed to the reactive B[a]P intermediate, benzo[a]pyrene-r-7,t-8-dihydrodiol-t-9,10-epoxide (BPDE). In the BPDE-treated cells, the level of NiCl2-mediated enhancement was similar to that observed with the tumor promoter 12-o-tetradecanoylphorbol-13-acetate (TPA, 100 ng/ml). These results are consistent with the view that the effect of nickel (II) on B[a]P-induced genetic damage is dependent on the relative times of exposure to Ni2+ and B[a]P. NiCl2 did not enhance the frequency of chromosome aberrations induced by Chromium (VI), regardless of the order of addition of the chemicals to the V79 cells. These results suggest that nickel may act as a promoter of chemically-induced genetic damage through induction of error-prone repair.

Characterization of Accelerated Iron-Ion-Induced Damage in Gap Junction-Competent and -Incompetent Thyroid Follicular Cells

Early- and late-passage cultures of Fischer rat thyroid cells differ in their growth properties and gap junction competency. Previous studies comparing early- and late-passage cultures exposed to gamma rays and proton beams revealed that differences in growth rate did not influence their responses; however, the presence of connexin 32 gap junctions conferred resistance to gamma radiation. To further assess differences in radiation quality, suspension cultures of early- and late-passage cells were exposed to accelerated iron ions, and their comparative biological responses were measured. The iron-ion-irradiated cells displayed sustained levels of incorporated dUTP, reflecting persistent DNA damage. These results were supported by the frequency of chromosomal damage measured by micronucleus formation. Iron-ion irradiation induced micronuclei at a rate of eight per gray per 100 binucleated cells scored in early-passage cells and nine per gray per 100 binucleated cells scored in late-passage cells. Relative to photons, the calculated radiobiological effectiveness for frequency of micronuclei was 5.7 and 6.4 for the early- and late-passage cultures, respectively (P > 0.05). Levels of apoptosis fluctuated as a function of dose, and modest increases above basal levels persisted throughout the 48-h period. The comparison of retained follicular structures revealed differences in the alpha components of the linear-quadratic dose-response curves (0.60 Gy(-1) for early-passage and 0.71 Gy(-1) for late-passage cultures, P < 0.014). Cell cycle phase redistribution resulted in a G2 arrest (P < 0.001) for both early- and late-passage cultures. In conclusion, the response of thyroid follicular cells to high-LET radiation was not influenced by the presence of gap junctions or the proliferative status of the target cells.

Changes in biomarkers from space radiation may reflect dose not risk

This presentation evaluates differences between radiation biomarkers of dose and risk and demonstrates the consequential problems associated with using biomarkers to do risk calculations following radiation exposures to the complex radiation environment found in deep space. Dose is a physical quantity, while risk is a biological quantity. Dose does not predict risk. This manuscript discusses species sensitivity factors, tissue weighting factors, and radiation quality factors derived from relative biological effectiveness (RBE). These factors are used to modify dose to make it a better predictor of risk. At low doses, where it is not possible to measure changes in risk, biomarkers have been used incorrectly as an intermediate step in predicting risk. Examples of biomarkers that do not predict risk are reviewed. Species sensitivity factors were evaluated using the Syrian hamster and the Wistar rat. Although the frequency of chromosome damage is very similar in these two species, the Wistar rat is very sensitive to radiation-induced lung cancer while the Syrian hamster is very resistant. To illustrate problems involved in using tissue weighting factors, rat trachea and deep lung tissues were compared. The similar level of chromosome damage observed in these two tissues would predict that the risk for cancer induction would be the same. However, even though large numbers of deep lung tumors result from inhaled radon, under the same exposure conditions there has never been a tracheal tumor observed. Finally, the Relative Biological Effectiveness (RBE) used to generate “quality factors” that convert exposure and dose from different types of radiation to a single measure of risk, is discussed. Important risk comparisons are done at very low doses, where the response to the reference radiation has been shown to either increase or decrease as a function of dose. Thus, the RBE and the subsequent risk predicted is more dependent on the background response of the endpoint and the shape of the dose response to the reference radiation than it is on the radiation type of interest.A large study using micronuclei as biomarkers following exposure to different energies of mono-energetic neutrons, x-rays and gamma rays delivered at very low doses (0.0 to 0.10 Gy) is reported. As additional biomarkers of risk involved in critical steps in the carcinogenic process are developed, it may become possible to base risk estimates on biological change rather than the radiation energy deposition or dose.

A study to verify a reported excess of chromosomal aberrations in blood lymphocytes of Namibian uranium miners.

This report describes a study to verify an earlier report of excess chromosomal damage in the blood lymphocytes of uranium miners. Coded blood samples from 10 miners and 10 controls were analyzed conventionally for unstable aberrations and by FISH for translocations. Conventional analysis, scoring 1000 metaphases per subject, showed no significant difference between miners and controls in the frequencies of chromosome- and chromatid-type aberrations. Investigators at two laboratories undertook FISH analyses, each scoring 4000 metaphases per subject. When the data from each laboratory were examined separately, one found slightly more translocations in the miners while the other found fewer. In neither case was the difference significant at the 95% level of confidence. Combining the data likewise showed no significant excess of damage in the miners. This applied to simple one- and two-way translocations and to cells with complex exchanges. There was no correlation between levels of translocations and total lifetime doses from occupational and/or background irradiation. A borderline significant excess of rogue cells was found in the miners. This may be a chance observation, as these rare, highly abnormal cells are considered to be unrelated to radiation exposure and are probably due to a virus. The overall conclusion is that the frequency of chromosomal damage in the miners did not exceed that in the controls. Therefore, the result of the earlier study was not confirmed.

Viral Infections and Chromosome Damage in Bank Vole from Natural and Laboratory Populations

The frequency of chromosome damage was studied in the carriers of virus of the hemorrhagic fever with renal syndrome (Puumala virus) and in noninfected animals from two laboratory colonies and two natural populations of bank vole. In the laboratory colony, where Puumala virus persisted for three years, multiaberrant (“rogue”) cells were found in the bone marrow; the mean frequencies of both structural and numeral chromosome abnormalities were significantly enhanced. In the other laboratory colony, no Puumala virus was detected during all 30 years of its existence, but the mean frequencies of structural chromosome damage were increased to the same degree probably due to the prolonged breeding under laboratory conditions, which resulted in suppression of immunity and DNA repair. The voles from the natural populations were more resistant to the clastogenic viral effect, but they also had multiaberrant cells which served as indicators of viral infection. The data obtained support the hypothesis that viral infections increase mutation rate, contributing thereby to the evolution process.

Modulatory effects of curcumin on the chromosomal damage induced by doxorubicin in Chinese hamster ovary cells.

Curcumin, a natural phenolic compound, is gaining importance as a free radical scavenger. This study was undertaken to investigate the modulatory effects of curcumin on the chromosomal damage induced by the antitumoral doxorubicin (DXR), a known free radical generator, in Chinese hamster ovary cells in culture. Cells were treated with three concentrations of curcumin (2.5, 5, or 10 microg/ml) and then treated with DXR (1.0 microg/ml) during different phases of the cell cycle. The results show that curcumin induces chromosomal damage in CHO at the highest concentration when compared to the untreated control. Neither treatment with curcumin shows a reduction in the clastogenicity of DXR. Instead, a statistically significant increase in the frequency of chromosomal damage was observed when the middle and the highest concentrations of curcumin were associated with DXR during the G1/S, S, and S/G2 phases of the cell cycle. The results clearly indicate the potentiating effect of curcumin on DXR-induced chromosomal damage.

Effect of hydroxyurea and normal plasma on DNA synthesis in lymphocytes from Fanconi anemia patients

Fanconi anemia (FA) is characterized at the cellular level by a high frequency of spontaneous chromosomal aberrations; crosslinking agents cause an abnormal increase in the frequency of chromosomal damage, and semiconservative DNA synthesis is severely inhibited. Deoxyribonucleotides are needed in both semiconservative and repair DNA synthesis. To investigate the involvement of deoxyribonucleotide pools in the inhibition of DNA synthesis in FA, we evaluated the effect on FA lymphocytes of hydroxyurea (HU), an inhibitor of ribonucleotide reductase which is known to alter the intracellular levels of deoxyribonucleotides. To achieve this goal, lymphocyte cultures of 4 FA patients and 4 normal individuals were used. Cultures were treated with HU and/or mitomycin C and normal human plasma. All cultures were processed to detect the number of DNA synthesizing nuclei by autoradiography. Scoring of 2000 nuclei for each kind of culture every 6 h in the last 24 h of incubation showed that, in long incubation periods, DNA synthesis in FA is largely inhibited by HU and this hypersensitivity may be partially decreased by addition of normal human plasma. It is known that recovery from damage induced by HU involves several enzymes such as flavin oxido-reductase, superoxide dismutase and catalase which are involved in the production or scavenging of O 2 radicals; FA cells are deficient in the detoxification of oxygen and this could explain the response of FA cells to HU.

DIFFERENTIAL SENSITIVITY AMONG 3 HUMAN SUBPOPULATIONS IN RESPONSE TO 4-NITROQUINOLINE-1-OXIDE AND TO BLEOMYCIN

An assay employing the UV-mimetic mutagen 4-nitroquinoline-1-oxide (4NQO) to estimate a person's UV-sensitivity was developed. This sensitivity may be translated into an individual's susceptibility to acquire cutaneous malignancies. We used cytogenetic recordings on cultured lymphocytes from 103 normal individuals, 62 melanoma patients, and 71 patients with head and neck cancer. The frequency of chromosome damage (chromatid breaks) caused by exposure to 4NQO was used to measure sensitivity. Preliminary results showed that a significantly higher proportion of melanoma patients was 4NQO sensitive compared to the other two groups, whose 4NQO sensitivity was statistically not different. Although a number of theoretical and technical problems remain to be resolved and a great deal of additional information (especially clinical and epidemiological) is needed, it appears that 4NQO sensitivity may be effectively employed as a biological marker for identification of individuals at risk for melanoma (and possibly other cutaneous neoplasms as well).

No relationship between genetic instability in Bloom's syndrome and DNA hypomethylation of some major repetitive sequences.

Bloom's syndrome (BS) is an autosomal recessive disorder, characterized by a high incidence of cancer at a young age. Cytogenetically, BS cells exhibit a high frequency of chromosomal damage and sister chromatid exchange (SCE). Thus, BS provides a human model of a genetic disorder exhibiting both chromosomal instability and a high incidence of cancer. In addition to its involvement in gene regulation, CpG methylation has recently been suggested to play an important role in the evolution and stability of chromosome structure. We have examined DNA methylation profiles of total DNA and some selected repeated sequences in normal and BS cells. No specific DNA hypomethylation in either total blood or lymphoblastoid cell lines from BS patients has been detected, suggesting that the genomic instability observed in BS is not directly related to a major DNA demethylation of the total CCGG sites, or of Alu or chromosome 1 satellite 2 repeated sequences.

Modulation of the frequency of human cytomegalovirus-induced chromosome aberrations by camptothecin

The effects of selected DNA repair inhibitors on the frequency of human cytomegalovirus (HCMV)-induced chromosome aberrations were evaluated in human peripheral blood lymphocytes (PBLs). Treatment of HCMV-infected PBLs with camptothecin (0.05 to 0.3 μg/ml), an inhibitor of topoisomerase I, for 30 hr resulted in a significant ( P < 0.01) synergistic enhancement of the frequency of HCMV-induced chromosome damage. On the other hand, a significant increase in the frequency of chromosome damage was not noted for infected PBLs treated with either 3-aminobenzamide (3-AB; 3 to 30 μg/ml), an inhibitor of poly(ADP-ribose) polymerase, or novobiocin (3 to 30 μg/ml), an inhibitor of topoisomerase II or excision repair processes, for 30 hr. Chromatid-type breaks and exchanges were the predominant type of chromosome aberrations observed in the HCMV-infected cells treated with camptothecin, suggesting that HCMV infection is associated with the induction of single-strand DNA breaks. Furthermore, these findings suggest that HCMV infection does not inflict direct DNA damage which is repaired through 3-AB- or novobiocin-sensitive pathways.

Comparative mutagenicity of four organophosphorous insecticides in meiotic system of red pepper.

A study has been made of the effects of four organophosphorous insecticides: TARA 909, DDVP, phosphomidon (PMN) and monocrotophos (MCP) on ger-mination, survival and meiotic behaviour in Capsicum annuum. Soaked (24 h) seeds were treated with 0.1, 0.5 and 1.0% of the insecticides for 24h. There was a sig-nificant decline in germination and seedling survival percentage in all insecticidal treatments. All the insecticides were capable of inducing various types of meiotic alterations. Abnormalities consisted of univalents, multivalents, bridges, lagging chromosomes, non-synchronization, multipolar formation, micronuclei, unoriented and unequal disjunction of chromosomes at various divisional stages of PMCs. Stickiness and clumping of chromosomes was a common effect. As a result of these abnormalities, the tetrad formation were highly irregular and caused a high pollen sterility. Chromosomal aberrations and pollen sterility were dose-dependent and there was an apparent relationship between frequency of chromosomal damage and pollen sterility. Among the four insecticides, DDVP and TARA produced greater damage on chromosomes, which also caused significant reduction in ger-mination, survival and pollen viability followed by PMN and MCP.The present study has shown that the insecticides were effective mutagenic agents with radiomimetic action, and point out the need of adequate information concerning plant responses to agricultural chemicals to ensure their safe use.

Combined and individual effects of isoniazid and thiacetazone on human lymphocyte chromosomes in vitro and in vivo.

Genetic effects of the drugs, isoniazid and thiacetazone used for antituberculosis chemotherapy were investigated on human lymphocyte chromosomes in vitro and in vivo. Therapeutic concentrations of these drugs did not induce chromosome aberrations in vitro both in combination and individually during any of the treatment period in 72 h lymphocyte cultures. At higher concentrations both the drugs were found to be cytotoxic. The frequency of chromosome damage was increased significantly in first-division metaphases of the patients, i.e. in vivo during treatment with isoniazid (300 mg) + thiacetazone (150 mg); this could be due to the synergistic action between the metabolites of the two drugs in the body or due to the metabolites of thiacetazone since isoniazid was found to be nonclastogenic in vivo. The frequency of sister chromatid exchanges was not increased in any of the patients except in one, who probably had a higher baseline level. These results suggest that chromosome aberrations and sister chromatid exchanges represent two different lesions. Chromosome damage induced by drugs could lead to congenital malformations, cancer, ageing and therefore contributes to the overall toxicology of the drugs and hazard to human genetic health. Hence drugs like isoniazid and thiacetazone which induce chromosome damage, should be used with caution.

Karyological analysis of Rous sarcoma virus-producing rat-kangaroo cell lines.

Karyological analysis of the PtK 1 cell line and of cell lines derived from it which had been productively infected with Rous sarcoma virus (Schmidt-Ruppin strain) revealed heterogeneity among the various stemlines. The 11-chromosome stemlines of all cell lines were composed of several karyotypic variants. The frequency of chromosomal damage in the Rous sarcoma virus-producing cell lines was not increased above the control level in the noninfected cell line.

Human chromosomes and opiates.

A cytogenic study of 16 opiate addicts receiving methadone hydrochloride compared with a control population revealed an unusual number of chromosome aberrations including dicentric chromosomes and an exchange figure at 72 hours in the addicted group, but no significant increase in chromosome anomalies over the controls at 48 hours. To determine whether methadone was the drug responsible for these chromosome abnormalities an in vitro study was initiated to evaluate the effects of methadone, morphine, and quinine on peripheral blood leukocytes from nonaddicts. Chromosome studies at three times normal, normal, and one third, one sixth, and one twelfth the normal therapeutic concentrations of quinine, morphine, and methadone introduced at 24, 48, and 68 hours into 72-hour leukocyte cultures did not reveal an increased frequency of chromosome damage.