Genotoxicity of alcohol is linked to DNA replication-associated damage and homologous recombination repair.

Although alcohol consumption is related to increased cancer risk, its molecular mechanism remains unclear. Here, we demonstrate that an intake of 10% alcohol for 4 weeks in rats is genotoxic due to induction of micronuclei. Acetaldehyde (AA), the first product of ethanol metabolism, is believed to be responsible for DNA damage induced by alcohol. Here, we observe that AA effectively blocks DNA replication elongation in mammalian cells, resulting in DNA double-strand breaks associated with replication. AA-induced DNA damage sites colocalize with the homologous recombination (HR) repair protein RAD51. HR measured in the hypoxhantineguaninefosforibosyltransferase (HPRT) gene is effectively induced by AA and recombination defective mammalian cells are hypersensitive to AA, clearly demonstrating that HR is essential in the repair of AA-induced DNA damage. Altogether, our data indicate that alcohol genotoxicity related to AA produces replication lesions on DNA triggering HR repair.

Sulindac and its metabolites: sulindac sulfide and sulindac sulfone enhance cytotoxic effects of arsenic trioxide on leukemic cell lines.

The effects of arsenic trioxide (ATO) in combination with sulindac (SUL), sulindac sulfide (SS) or sulindac sulfone (SF) on human (Jurkat, HL-60, K562 and HPB-ALL) and mouse (EL-4) leukemic cell lines were investigated. The cells showed different sensitivity to sulindacs (2.5-200 µM) with SS being the most cytotoxic (72 h WST-1 reduction test). The cytotoxicity of ATO was enhanced by combination with sulindacs. The combination of ATO (1 µM) with SS or SF at concentrations over 50 µM induced considerable cytotoxicity in all cell lines. Normal human lymphocytes exposed for 48 h to the combinations showed smaller decrease in viability. Measurements of Jurkat, HL-60 and K562 cells exposed to ATO (1 µM) and sulindacs (100 µM or 200 µM for K562 cells) indicated apoptosis as the main cell death mechanism. The mitochondrial membrane potential measurements (JC-1 probe) indicated an active involvement of mitochondria in the process. The results did not indicate involvement of an inhibitory effect of the combinations on NF-κB activity in Jurkat, HL-60 and K562 cells.

Assessment of the protective effects of selected dietary anticarcinogens against DNA damage and cytogenetic effects induced by benzo[a]pyrene in C57BL/6J mice.

The protective action in C57BL/6J mice from orally administered ellagic acid (EA), benzyl isothiocyanate (BITC), an extract of epigallocatechins (Tegreen®) as well as chlorophyllin (CHL) against benzo[a]pyrene (B[a]P)-induced DNA damage and cytogenetic effects was investigated. In pilot experiment the comet assay indicated protective effects for all compounds, while such activity was confined to EA and CH with respect to B[a]P-DNA adducts and micronuclei. EA and CH were chosen for the main study where the levels of DNA adducts in liver after injection of 30 mg B[a]P/kg b.w. did not differ from those found for animals exposed to B[a]P and treated with the protective substances. In leukocytes no significant protective effect of CHL was detected while a 2-fold increase of adduct concentrations was observed after co-administration of EA. In the comet assay CHL or EA caused a 3-fold decrease of SSB, and a 2-fold decrease of FPG sites in comparison to animals treated with B[a]P. CHL or EA showed a significant protective effect against B[a]P-induced MN in polychromatic erythrocytes in bone marrow. In contrast, flow cytometry measurements in peripheral blood indicated the MN frequency after treatment with CHL or EA almost twice as high as that recorded for B[a]P alone.

Interleukin-1beta and surface marker expression changes induced by tetrachloroplatinate in human monocyte-derived dendritic cells.

BACKGROUND AND AIM: Platinum salts, known occupational respiratory sensitizers, may also induce contact hypersensitivity in animal models. The aim of this study was to determine the effect of potassium tetrachloroplatinate (TCPP) on in vitro cultured human monocyte-derived dendritic cells (MoDCs) and to compare it with a response to nickel sulfate (NiSO4). The expression of CD54, CD86, and HLA-DR surface antigens as well as IL-1beta transcription was investigated. CONCLUSIONS: MoDCs populations generated from three healthy volunteers displayed the phenotype responsive to NiSO4 and non-responsive to sodium dodecyl sulfate (SDS). Clear up-regulation of IL-1beta mRNA as well as CD54, CD86 and HLA-DR expression in response to NiSO4 (250 microM) was detected after 48 hrs of exposure. No up-regulation of evaluated surface antigens was observed following the treatment with SDS (150 microM). TCPP (150 microM) similarly to NiSO4 induced up-regulation of IL-1beta mRNA, CD54, CD86, but not HLA-DR expression. The response to TCPP showed less inter-individual variability, however it was weaker in comparison to the response to NiSO4. The results suggest that platinum salts can induce in MoDCs phenotypical changes characteristic for skin sensitizers.

Carcinogenic effect of arsenate in C57BL/6J/Han mice and its modulation by different dietary selenium status.

In this study, carcinogenic effects of arsenate in female C57BL/6J/Han mice exposed in drinking water to 50, 200 or 500microgAs/L for 24 months were investigated. All animals were fed low-selenium diet, however half of them were supplemented with sodium selenite in drinking water (200microgSe/L) to ensure the normal dietary level of selenium. Glutathione peroxidase activity in erythrocytes and plasma as well as selenium concentration in plasma after 3, 6, 12 and 18 months in satellite groups showed considerable decrease in animals from non-selenium supplemented groups in comparison to supplemented groups. A clear arsenic concentration-dependent increase in the number of malignant lymphoma associated with increase in the risk of death was observed (hazard ratio=0.91, 1.46, and 2.24, for 50, 200 and 500microgAs/L, respectively). No significant influence of selenium dietary status on arsenic carcinogenicity was shown. A significant association between selenium supplementation status and increased risk of death of the animals from causes other than malignant tumors was found (HR=1.79, p=0.04).