Liquid-holding experiments with human lymphocytes. III. Experiments with G0 and G1 cells

3-Selenocyanate-indoles as new agents for the treatment of superficial and mucocutaneous infections

The development of resistance to the current antifungal agents is an alarming problem.

In vitro genotoxic and cytotoxic effects of doxepin and escitalopram on human peripheral lymphocytes

Antidepressants are drugs used for the treatment of many psychiatric conditions including depression. There are findings suggesting that these drugs might have genotoxic, carcinogenic, and/or mutagenic effects. Therefore, the present in vitro study is intended to investigate potential genotoxic and cytotoxic effects of the antidepressants escitalopram (selective serotonin reuptake inhibitor) and doxepin (Tricyclic antidepressant) on human peripheral lymphocytes cytokinesis-block micronucleus (CBMN), sister chromatid exchange (SCE), and single cell gel electrophoresis (alkaline comet assay) were used for the purpose of the study. In the study, four different concentrations of both drugs (1, 2.5, 5, and 10 µg/mL) were administered to human peripheral lymphocytes for 24 h. The tested concentrations of both drugs were found to exhibit no cytotoxic and mitotic inhibitory effects. SCE increase caused by 5 and 10 µg/mL of escitalopram was found statistically significant, while no statistically significant increase was observed in DNA damage and micronucleus (MN) formation. Moreover, the increase caused by doxepin in MN formation was not found statistically significant. Besides, 10 µg/mL of doxepin was demonstrated to significantly increase arbitrary unit and SCE formation. These findings suggest that the investigated concentrations of escitalopram and doxepin were non-cytotoxic but potentially genotoxic at higher concentrations.

Evaluation of the genotoxic and antioxidant effects of two novel feed additives (ethoxyquin complexes with flavonoids) by the comet assay and micronucleus test

The complexes of antioxidant ethoxyquin (1,2-dihydro-6-ethoxy-2,2,4-trimethylquinoline; EQ) with rutin or quercetin (EQ-R and EQ-Q, respectively) were studied in human lymphocytes for genotoxic and antioxidant activities with the use of the comet assay and micronucleus test. The study was undertaken to search for new potential antioxidants, and was motivated by reports of unfavourable side-effects observed in animals fed with feeds containing EQ, which is allowed up to 150 mg kg(-1) (0.015%) in complete animal feed. It was shown that EQ-R induced DNA damage in human lymphocytes when used at all the concentrations studied (1-25 microM), while after EQ-Q treatment, the genotoxic effect was observed mainly after higher doses (10 and 25 microM). An increase in the number of micronuclei was observed only for EQ-Q after a dose of 50 microM. The studied compounds decreased the degree of DNA damage induced by hydrogen peroxide (10 microM) in the comet assay. The results obtained in both tests showed that the antioxidant activity of EQ-Q was comparable with that of EQ, so further detailed studies are necessary to estimate its possible usefulness as a feed preservative.

Comparative analysis of cytotoxic, genotoxic and antioxidant effects of 2,2,4,7-tetramethyl-1,2,3,4-tetrahydroquinoline and ethoxyquin on human lymphocytes

2,2,4,7-Tetramethyl-1,2,3,4-tetrahydroquinoline (THQ) is a new synthetic compound with potential antioxidant activity. In this study, cytotoxic, genotoxic and antioxidant activities of THQ were studied on human lymphocytes with the use of the trypan blue exclusion assay, the TUNEL method, the comet assay and the micronucleus test. The activities of THQ were compared with those of a structurally similar compound-ethoxyquin (1,2-dihydro-6-ethoxy-2,2,4-trimethylquinoline, EQ), which is used in animal feeds as a preservative. Cytotoxic effects of THQ were observed after 1-h treatment at the concentration of 500 microM and after 24-h treatments at the concentrations of 250-500 microM. Although the micronucleus test did not reveal a genotoxic effect of THQ, in the comet assay the statistically significant increase in DNA damage was observed as compared with the control. On the other hand, the protection of human lymphocytes against DNA damage induced by hydrogen peroxide suggests an antioxidant activity of THQ. The comparative analysis of THQ and EQ activities performed in these studies revealed that THQ was less cytotoxic and less genotoxic than EQ. Slightly lower antioxidant activity of THQ was also shown in the comet assay when it was used at the lower studied doses (1-5 microM), but for the highest one (10 microM) its efficiency was similar to that of EQ. In the micronucleus assay THQ was more effective than EQ in protecting the cultured lymphocytes from clastogenicity of H2O2. We believe that THQ is worthy of further detailed studies on its antioxidant properties to confirm its usefulness as a preservative.

Determination of genotoxicity of classical swine fever vaccine in vitro by cytogenetic and comet tests

Chromosome damage in lymphocyte cultures induced by live virus vaccine against classical swine fever (CSF) has been observed in previous studies. In vivo cytogenetic tests were made with several doses of vaccines used in Argentina to control the disease. These studies have shown that genotoxic effects increased with dose. In the present study, two different in vitro assays were performed by recording the frequency of cells with chromosome alterations and by assessing the ability of the vaccine to damage DNA, using the single cell gel microelectrophoretic assay (comet test). Frequencies of cells with chromosomal alterations increased significantly when compared with controls and were dose (microl/ml) dependent: 0 = 1.23, 5 = 2.29, 10 = 5.42 and 20 = 11.71%. In the comet assay the variables measured, tail length (TL) and tail moment (TM), also increased. For control cultures TL was 2.32 microm, whereas with concentrations of 20 and 100 microl/ml TL were 12.47 and 42.3 microm, respectively. TM of control cultures was 0.18, whereas with vaccine concentrations of 20 and 100 microl/ml TM were 5.52 and 24.52, respectively. Comet frequency distributions differed significantly among treatments. These results agree with previous in vivo observations. Regarding CSF pathogeny, our results support a direct effect of CSF vaccinal virus on lymphocyte DNA. Genotoxicity of CSF vaccine was corroborated in vitro at the cytogenetic and molecular levels.

In vitro testing for genotoxicity of the herbicide terbutryn: cytogenetic and primary DNA damage

Terbutryn is a widely used preemergence and postemergence s-triazine herbicide. This pesticide is used in agriculture as a control agent for most grasses and many annual broadleaf weeds in cereal and legume fields, and under fruit trees. Unexpectedly, this compound was found to persist in the environment (240 and 180 days in pond and river sediment, respectively) and to have the tendency to move from treated soils to water compartments through water runoff and leaching. However, only scant information is available about the genotoxic properties of terbutryn. In the present in vitro study, we investigated the relationship between cytogenetic damage, as evaluated in the sister-chromatid exchange (SCE) assay and the micronucleus (MN) test, and primary DNA damage (as evaluated by the "comet" assay). Cytogenetic and primary DNA damage were recorded in vitro in freshly isolated human peripheral blood leukocytes. Our results showed that the tested compound failed to produce any significant increases in SCE or MN, neither in the absence nor in the presence of S9-mix. However, terbutryn was found to induce primary DNA damage, more pronounced without S9 mix, even though in the absence of a clear trend for dose-dependence and in the presence of a concomitant mild cytotoxic effect.

In vivo repair during G1 of DNA lesions eliciting sister chromatid exchanges induced by methylnitrosourea or ethylnitrosourea in BrdU substituted or unsubstituted DNA in murine salivary gland cells

The difference in efficiency of methylnitrosourea (MNU) and ethylnitrosourea (ENU) to induce SCE in early or late G1 was determined in synchronized murine salivary gland cells in vivo, as a measure of the capacity of this tissue to repair the lesions involved in SCE formation during G1. The repair during G1 was determined by treating the cells in early or late G1. Treatment was in the first cycle (G1 before incorporation of 5-bromodeoxyuridine (BrdU)) or in G1 of the second cycle (after a single round of BrdU incorporation). It was observed that 50% of the lesions induced by MNU that elicit SCE are repaired during G1. BrdU incorporation into DNA increases the sensitivity of the cell to SCE induction by MNU nearly 40%; however under this circumstance a slightly lower SCE frequency was observed in the cells exposed to MNU at early G1, indicating that during G1 only few lesions are repaired. The ENU-induced DNA-lesions involved in SCE production are nearly 100% persistent along G1; besides, a slight but significantly higher SCE frequency was observed in cells exposed at early G1, suggesting the formation of SCE-inducing lesions during G1. BrdU incorporation to DNA sensitizes the cell to SCE induction by ENU, increasing the SCE frequency to nearly to a 40%, although these additional lesions involved in SCE induction seem to be susceptible to repair during G1.

In vitro genotoxic effects of the insecticide deltamethrin in human peripheral blood leukocytes: DNA damage ('comet' assay) in relation to the induction of sister-chromatid exchanges and micronuclei

Deltamethrin, a synthetic dibromo-pyrethroid insecticide, is extensively used in agriculture, forestry and in household products because of its high activity against a broad spectrum of insect pests (both adults and larvae), its low animal toxicity and its lack of persistence in the environment. Data on the genotoxicity and carcinogenicity of deltamethrin are rather controversial, depending on the genetic system or the assay used. The aim of this study was to further evaluate the potential genotoxic activity of deltamethrin. The in vitro genotoxicity of deltamethrin has been evaluated by assessing the ability of the insecticide to damage DNA (as evaluated using the single-cell microgel-electrophoresis or 'comet' assay) or induce sister-chromatid exchanges (SCE) and micronuclei (MN) in human peripheral blood leukocytes. All treatments were conducted with and without the presence of an external bioactivation source (+/- S9mix). The results indicate that deltamethrin, in the presence of metabolic activation (+ S9mix), is able to induce DNA damage (double- and single-strand breaks, alkali-labile sites and open excision repair sites) as revealed by the increasing tail moment values observed with increasing doses. The frequency of SCE and MN were not statistically increased in deltamethrin-treated cells as compared to controls, both with and without S9mix. However, lower deltamethrin doses were tested, as compared to 'comet' assay, because of cytotoxicity.

Persistence of 4-nitroquinoline-1-oxide induced lesions in human lymphocytes

Liquid holding (LH) recovery was matched with three-way differential staining (TWD) to assess the reduction of damage induced in DNA following treatment with 4-nitroquinoline-1-oxide (4NQO) in resting (GO) lymphocytes. Human peripheral lymphocytes (HPL) from three donors were used to evaluate lesion persistence and individual repair capacity. Our data are in contrast to those for diepoxybutane (Ponzanelli et al., 1995) and suggest that LH recovery is completely inefficient in removing 4NQO induced lesions, which are only partially repaired after one cell cycle.

Use of three-way differential staining and liquid holding for the assessment of individual repair capacity

Many studies on DNA repair mechanisms in mammalian cells have used liquid holding (LH) recovery to evaluate premutational damage repair. We used human peripheral lymphocytes (HPL) to assess damage reduction during the G0 phase. This technique was matched with the three-way differential (TWD) staining that allows identification of sister-chromatid exchanges (SCE) per cell cycle in third metaphases. By adopting this approach, the persistence of diepoxybutane (DEB)-induced lesions during subsequent cycles and individual repair capacity in LH conditions were measured. Our results show that most DEB-induced damage was repaired during the first cell cycle; a large part of lesions were removed during LH recovery, demonstrating G0 HPL repair capacity.

Persistence of SCE-inducing lesions in lymphocytes of mice exposed to diaziquone

Male C57B1/6 mice were injected i.p. with either 1.25 or 5.0 mg/kg diaziquone (AZQ) and killed at various time intervals from 1 to 99 days post treatment for examination of sister chromatid exchange (SCE) persistence in the peripheral blood lymphocytes (PBLs) and splenocytes. SCE frequencies were found to decay steeply during the first week after exposure in both PBLs and splenocytes. This pattern was followed by a slower decline to baseline over the next week. However, high-frequency cell (HFC) analysis indicates that significant numbers of HFCs persist in the PBLs through day 28 and splenocytes at day 99 post exposure. Mathematical modeling of the time-response curves indicates that the average life span of the majority of AZQ-induced SCE-producing lesions in murine PBLs and splenocytes responsive to phytohemagglutinin is between 3 and 5 days.