Chromosomes and stress

The present investigation examines genotoxic effects of: prolonged periods of stress; the role of the endocrine system; and the relationship between psychogenic stress and chemical mutagens. Increased levels of both Sister Chromatid Exchanges (SCEs) and Chromosome Aberrations (CAs) were observed in male rats subjected to white noise of either 72 or 240 hrs duration, demonstrating that damage occurs during chronic stress. Rats subjected to foot-shock after having been either hypophysectomized or sham-operated, showed elevation of both SCEs and CAs, indicating that hormones in the hypothalamic-pituitary-adrenal axis do not play a role in genotoxic damage. Rats subjected to foot-shock, and/or the mutagen Mitomycin-C(MMC) showed elevated SCEs, both separately and together. The combined effect was the sum of the individual effects, demonstrating that synergism was not involved. This investigation establishes that psychogenic stress plays a role in genotoxic damage.

Psychogenic stress induces chromosomal and DNA damage

In this investigation, rats subjected to swim stress showed within 24 hours significant increases in both the level of chromosome aberrations and Sister Chromatid Exchanges (SCEs) in bone marrow cells. The generality of cytogenetic damage by behavioral stressors was demonstrated by exposing rats to both cold-and warm-water forced swims, to white noise, and to continuous or intermittent inescapable foot shock stress (IFS). The induction of chromosome aberrations and SCEs, to differing degrees, by stressors that differ both quantitatively and qualitatively, demonstrates that this is a general phenomenon of stress. The use of an additional measure, unscheduled DNA Synthesis (UDS) showed that stress-induced genotoxic damage can occur in a second cell type and on a molecular as well as chromosomal level. These results indicate that there may be a cellular genetic basis for some of the effects of stress.

Protein binding, sister chromatid exchange and expression of oncogene proteins in patients treated with cisplatinum (cisDDP)-based chemotherapy

The aim of this pilot was to evaluate the feasibility of incorporating several complementary biologic markers into a molecular epidemiologic study of chemotherapy patients. Thirty-two cancer patients being treated with cis-DDP-based chemotherapy for the first time were enrolled in the study and donated a baseline sample and at least one post-treatment sample of blood. Sister Chromatid Exchange (SCEs) and plasma protein and hemoglobin binding by cisDDP were significantly increased in samples drawn at various timepoints following treatment. The pattern of nine different oncogene protein products (including those of ras, fes, and myc) remained unchanged in sera of six patients followed over the course of their treatment. However, the levels of ras P21 product were significantly elevated above normal, control levels in all six cancer patients--both prior to and throughout the course of chemotherapy. These results suggest the usefulness of utilizing a battery of markers to evaluate biologic response to cisplatinum-based chemotherapy.

Comparison of DNA adducts and sister chromatid exchange in lung cancer cases and controls

In a molecular epidemiological study of lung cancer cases (n = 81) and noncancer controls (n = 67), polycyclic aromatic hydrocarbon (PAH)-DNA adducts were evaluated in peripheral blood leukocytes from all subjects and in a smaller number of lung tissue specimens collected prior to or at surgery. Sister chromatid exchanges (SCE) in lymphocytes were also studied in a subset of cases and controls. Questionnaire, medical record, or tumor registry data provided a family history of cancer, as well as information on cigarette smoking, dietary and occupational exposure to PAHs, and other factors related to SCEs. In both cases and controls PAH-DNA adducts in leukocytes measured by an enzyme-linked immunosorbent assay were not significantly related to age, sex, ethnicity, amount of cigarette smoking, passive smoking, dietary charcoal, or caffeine consumption. Nor did family history of cancer or histological type of cancer significantly affect adduct levels. However, when subjects were stratified by smoking status (current, former, and nonsmoker), lung cancer cases who were current smokers had significantly higher levels of covalent adducts than current smoker controls. A seasonal variation was observed in PAH-DNA binding, with a peak in adduct levels during July-October. This peak corresponds to that seen in a prior study of aryl hydrocarbon hydroxylase inducibility by other investigators. The finding of significant levels of PAH-DNA adducts in former smokers and non-smokers supports an earlier observation that this marker is not smoking specific but reflects a pervasive and variable "background" exposure to PAH. These results are consistent with a genetically determined enhancement of PAH-DNA adduct formation in leukocytes of lung cancer cases which is evident in current smokers. The results in lung tissue are limited by the small number of samples. Adduct levels were not significantly increased in lung tissue of smokers compared with nonsmokers. An inverse linear correlation was seen between adduct values in lung tissue and age of the donors. SCEs were significantly related to pack years of smoking. However, there was no difference in the frequency of SCE between cases and controls; nor were SCE and DNA adducts significantly correlated in this small sample.

DNA adducts, protein adducts, and sister chromatid exchange in cigarette smokers and nonsmokers

In order to validate markers of internal dose and biologically effective dose of carcinogens, a battery of measurements was made on blood samples from 22 smokers and 24 nonsmokers. The markers included immunoreactivity in an enzyme-linked immunosorbent assay (ELISA) quantified in white blood cells with the use of a polyclonal anti-benzo[a]pyrene diol epoxide-I-DNA antibody, 4-aminobiphenyl hemoglobin (4-ABP-Hb) adducts measured by negative chemical ionization mass spectrometry, sister chromatid exchange (SCE) in cultured lymphocytes, and cotinine in plasma measured by radioimmunoassay. Several blood samples were drawn from each subject. In blood samples 1 and 3 having detectable levels of DNA adducts, mean femtomole-per-microgram levels were consistently higher among smokers compared to nonsmokers. The borderline significance of this difference may be attributable to the small numbers of subjects. Consistently higher adduct levels were seen in females compared to males. In sample 3, adduct levels were significantly correlated with measurements of active smoking in smokers and with passive smoking in nonsmokers. By contrast to the ELISA data, which may reflect cumulative exposure from multiple background sources, the 4-ABP-Hb assay was able to distinguish clearly between smokers and nonsmokers. SCEs were significantly elevated in the smokers compared to nonsmokers. Also observed were significant correlations between 4-ABP-Hb and both cotinine and SCEs, as well as a positive correlation between the 4-ABP-Hb and DNA adduct levels (sample 3) that was highly significant. The correlation between DNA and 4-ABP-Hb adducts was significant in smokers but not nonsmokers (sample 3). These results support the need for batteries of markers to detect and to quantify the carcinogenic dose to humans resulting from both specific and "background" environmental exposures.

Sister chromatid exchanges induced by behavioral stress

Rats subjected to swim stress showed a doubling of sister chromatid exchange (SCE) level. In a second experiment, the generality of SCE induction by behavioral stressors was tested by exposing rats to either swim, white noise, or either continuous or intermittent inescapable footshock stress. The induction of SCEs, although to differing degrees, by qualitatively different stressors, demonstrates that this is a general phenomenon of stress. There may be a cellular genetic basis for some of the effects of stress.

Sister chromatid exchanges and cell cycle kinetics in Alzheimer's disease

Six female outpatients with Alzheimer's disease (AD) along with four female controls of a similar age range were analyzed for sister chromatid exchangers (SCEs), cell cycle kinetics, and sensitivity to mutagens, in lymphocyte cultures. The mean level of SCEs for the AD patients was 11.40 SCEs/metaphase, while that for the controls was 9.12. The difference between the two groups was significant as shown by the Wilcoxon rank-sum test (p = 0.05). Cell cycle was 50% longer both in the AD patients (31.7 hr) and aged controls (31.5 hr) than in normal young adults (21.76 hr). Mitomycin-C (MMC) decreased the mitotic index in AD patients by 35% and in controls by only 12%. MMC also increased the cell cycle duration in AD patients by a greater extent (20%) than it did in the controls (13.5%), and AD cells were more sensitive to the toxic effects of bromodeoxyuridine. What appeared to be chromosomes with prematurely divided centromeres were also observed in AD cells.

Clastogenic effects of heroin in pregnant monkeys and their offspring

Heroin was administered daily i.v. to pregnant Macaca mulatta monkeys, for 3 months, and after birth of their babies, was continued for 3 months post-partum. The dose was gradually increased to as high as 1.5 mg/kg/day. Pregnant control animals were given saline injections following the same design. WBC cultures for analysis of sister-chromatid exchanges (SCEs) and chromosome aberrations were taken from all adult animals, prior to heroin or saline administration, and also after 6 months, at time of sacrifice. Cultures were also done for all babies, and bone marrow analyses of aberrations were done on all animals at sacrifice. Both heroin mothers and babies showed a doubling in SCE level over their respective controls, and the heroin mothers demonstrated an almost 3-fold increase over their initial cultures. Heroin babies had 10 times as many chromosome aberrations in their WBC cultures as did their controls, and an equivalent increase in their bone marrow cells. The heroin mothers' final WBC cultures showed an increase in chromosome aberrations both over that of their initial cultures and those of their controls. The heroin babies demonstrated greater sensitivity to heroin, compared with their mothers, as measured by chromosome aberrations, but a corresponding sensitivity to SCE induction. No correlation in SCE levels was detected between individual pairs of mothers and babies, but there was one between the groups of mothers and babies. The route(s) through which the chromosomal alterations were inflicted in the babies could be transplacental, through the mother's milk, or both. The results of this investigation correspond with those of several previous studies on addict populations, and demonstrate that under these conditions, heroin is a chromosomal mutagen.