Genotoxicity of tryptophol in a battery of short-term assays on human white blood cells in vitro.

The genotoxic effects of tryptophol (indole-3-ethanol), an aromatic alcohol and known secondary metabolite of the opportunistic yeast Candida albicans and other Candida spp., were studied using a battery of short-term assays on human white blood cells in vitro. The concentration range of tryptophol tested was 0.25 mM to 2.00 mM. Lymphocyte viability and induction of apoptosis/necrosis were studied by simultaneous use of a fluorescent assay with ethidium bromide and acridine orange. Levels of primary DNA damage and dynamics of DNA repair were evaluated using the alkaline comet assay while the levels and nature of residual DNA damage were assessed by the analysis of structural chromosome aberrations, the sister chromatid exchange test and the cytokinesis-block micronucleus assay. The results obtained suggest cytotoxic, cytostatic and genotoxic effects of the tryptophol treatment in vitro that were mainly dose-dependent. The type and the extent of DNA lesions detected in tryptophol-treated samples indicate the possibility that observed damage is mediated by highly reactive aldehyde metabolite and/or free radicals produced by treatment. The results show that mortality of lymphocytes in tryptophol-treated samples was primarily caused by apoptosis. The generation of additional DNA strand breaks and cytogenetic consequences (chromosome aberrations, sister chromatid exchanges and micronuclei), as observed in this study, sustain the possibility that tryptophol toxicity is mediated by the formation of DNA cross-links and aldehyde-protein adducts. In conclusion, this preliminary study elucidates only a part of tryptophol toxicity to human cells. Because current evidence is not sufficient to obtain information relevant for human risk assessment, further in vitro and in vivo studies are essential in order to clarify remaining issues, especially to elucidate the exact mechanisms and nature of the damage produced following treatment as well to estimate possible interindividual variability in genotoxic responses to the chemical.