Studies of the potential genotoxic effects of furoxans: the case of CAS 1609 and of the water-soluble analogue of CHF 2363.

CAS 1609 (compound 1) and CHF 2363 (compound 2) are two furoxan derivatives able to release nitric oxide (NO) under physiological conditions, and display typical NO-dependent vasodilator activity. The potential genotoxic effects of compound 1 and of the water-soluble analogue of CHF 2363 (compound 2a) were investigated. The results show that the two compounds induce genotoxic effects only at concentrations that significantly reduce cell viability. However, in the case of compound 1 this range of concentrations is one order of magnitude higher than the one leading to the beneficial effects, while in the case of compound 2a these ranges partially overlap. In both cases the release of NO plays a key role in the induction of the cytotoxic and genotoxic effects, since the non-NO-donating furazan analogues display a different toxicological profile, and since the effects were reduced in the presence of oxyhaemoglobin, a well-known NO-scavenger.

Chromosomal changes: induction, detection methods and applicability in human biomonitoring.

The objective of this state of the art paper is to review the mechanisms of induction, the fate, the methodology, the sensitivity/specificity and predictivity of two major cytogenetic endpoints applied for genotoxicity studies and biomonitoring purposes: chromosome aberrations and micronuclei. Chromosomal aberrations (CAs) are changes in normal chromosome structure or number that can occur spontaneously or as a result of chemical/radiation treatment. Structural CAs in peripheral blood lymphocytes (PBLs), as assessed by the chromosome aberration (CA) assay, have been used for over 30 years in occupational and environmental settings as a biomarker of early effects of genotoxic carcinogens. A high frequency of structural CAs in lymphocytes (reporter tissue) is predictive of increased cancer risk, irrespective of the cause of the initial CA increase. Micronuclei (MN) are small, extranuclear bodies that arise in dividing cells from acentric chromosome/chromatid fragments or whole chromosomes/chromatids that lag behind in anaphase and are not included in the daughter nuclei in telophase. The cytokinesis-block micronucleus (CBMN) assay is the most extensively used method for measuring MN in human lymphocytes, and can be considered as a "cytome" assay covering cell proliferation, cell death and chromosomal changes. The key advantages of the CBMN assay lie in its ability to detect both clastogenic and aneugenic events and to identify cells which divided once in culture. Evaluation of the mechanistic origin of individual MN by centromere and kinetochore identification contributes to the high sensitivity of the method. A number of findings support the hypothesis of a predictive association between the frequency of MN in cytokinesis-blocked lymphocytes and cancer development. Recent advances in fluorescence in situ hybridization (FISH) and microarray technologies are modifying the nature of cytogenetics, allowing chromosome and gene identification on metaphase as well as in interphase. Automated scoring by flow cytometry and/or image analysis will enhance their applicability.