Enriching the drinking water of rats with extracts of Salvia officinalis and Thymus vulgaris increases their resistance to oxidative stress.

Nature is an attractive source of therapeutic compounds. In comparison to the artificial drugs, natural compounds cause less adverse side effects and are suitable for current molecularly oriented approaches to drug development and their mutual combining. Medicinal plants represent one of the most available remedy against various diseases. Proper examples are Salvia officinalis L. and Thymus vulgaris L. which are known aromatic medicinal plants. They are very popular and frequently used in many countries. The molecular mechanism of their biological activity has not yet been fully understood. The aim of this study was to ascertain if liver cells of experimental animals drinking extracts of sage or thyme will manifest increased resistance against oxidative stress. Adult Sprague-Dawley rats were divided into seven groups. They drank sage or thyme extracts for 2 weeks. At the end of the drinking period, blood samples were collected for determination of liver biochemical parameters and hepatocytes were isolated to analyze (i) oxidatively generated DNA damage (conventional and modified comet assay), (ii) activities of antioxidant enzymes [superoxide dismutase (SOD), glutathione peroxidase (GPx)] and (iii) content of glutathione. Intake of sage and thyme had no effect either on the basal level of DNA damage or on the activity of SOD in rat hepatocytes and did not change the biochemical parameters of blood plasma. Simultaneously, the activity of GPx was significantly increased and the level of DNA damage induced by oxidants was decreased. Moreover, sage extract was able to start up the antioxidant protection expressed by increased content of glutathione. Our results indicate that the consumption of S.officinalis and T.vulgaris extracts positively affects resistency of rat liver cells against oxidative stress and may have hepatoprotective potential.

Assessment of antioxidative, chelating, and DNA-protective effects of selected essential oil components (eugenol, carvacrol, thymol, borneol, eucalyptol) of plants and intact Rosmarinus officinalis oil.

Selected components of plant essential oils and intact Rosmarinus officinalis oil (RO) were investigated for their antioxidant, iron-chelating, and DNA-protective effects. Antioxidant activities were assessed using four different techniques. DNA-protective effects on human hepatoma HepG2 cells and plasmid DNA were evaluated with the help of the comet assay and the DNA topology test, respectively. It was observed that whereas eugenol, carvacrol, and thymol showed high antioxidative effectiveness in all assays used, RO manifested only antiradical effect and borneol and eucalyptol did not express antioxidant activity at all. DNA-protective ability against hydrogen peroxide (H2O2)-induced DNA lesions was manifested by two antioxidants (carvacrol and thymol) and two compounds that do not show antioxidant effects (RO and borneol). Borneol was able to preserve not only DNA of HepG2 cells but also plasmid DNA against Fe(2+)-induced damage. This paper evaluates the results in the light of experiences of other scientists.

Effects of Salvia officinalis and Thymus vulgaris on oxidant-induced DNA damage and antioxidant status in HepG2 cells.

Salvia officinalis (SO) and Thymus vulgaris (TV) are medicinal plants well known for their curative powers. However, the molecular mechanisms responsible for these abilities of sage and thyme have not been fully understood yet. In this study we investigated the composition and the quantitative estimation of plant extracts, the protective effects of plant extracts against hydrogen peroxide- and 2,3-dimethoxy-1,4-naphthoquinone-induced DNA damage, and levels of enzymatic and non-enzymatic antioxidants (superoxide dismutase, glutathione peroxidase, glutathione) in human HepG2 cells. To measure antioxidative activity of plant extracts we used three assays: 1,1-diphenyl-2-picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP) and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS). The results showed that the oxidant-induced DNA lesions were significantly reduced in cells pre-treated with the plant extracts studied. The observed DNA-protective activity could be explained by both elevation of GPx activity in cells pre-treated with SO and TV and antioxidant activity of SO and TV.

Comparison of biological processes induced in HepG2 cells by tert-butyl hydroperoxide (t-BHP) and hydroperoxide (H2O2): The influence of carvacrol.

This paper presents comparisons of biological impacts of the oxidants H2O2 and t-BHP on human liver cells, and shows modulation of these effects by the phenolic compound carvacrol. To understand better how these oxidants exert their effect on DNA and on the activity of the enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPx), we measured intracellular antioxidant glutathione (iGSH) and intracellular reactive oxidative species (iROS). DNA lesions corresponded to single-strand DNA breaks, alkali-labile lesions and formamido-pyrimidine-DNA-glycosylase (FPG)-sensitive sites. Pre-treatment of cells with carvacrol substantially decreased the number of H2O2-induced DNA lesions, but the number of t-BHP-induced DNA lesions was not reduced. Activities of both SOD and GPx were stimulated significantly by carvacrol and were reduced by the combined effect of carvacrol and oxidants. H2O2 and t-BHP alone influenced the level of antioxidant enzymes differently. While H2O2 did not markedly change the activity of SOD or GPx, lower concentrations of t-BHP stimulated activity of SOD and mainly GPx. The level of iROS was increased by both oxidants and decreased by carvacrol applied either alone or with oxidants. The level of iGSH was not influenced in any of the treatments tested. Our results show that although both oxidants induced oxidative stress and damaged cellular DNA, their influences on other molecular processes were different. The protective effect of carvacrol against DNA-damaging effects of H2O2 was unambiguous, but reduction by carvacrol of the DNA-damaging effect of t-BHP was not observed. These results suggest that the phenolic compound carvacrol contributes to the defence mechanisms of the human organism, but these beneficial effects are dependent on the origin and source of the actual oxidative stress.

Borneol administration protects primary rat hepatocytes against exogenous oxidative DNA damage.

Experimental evidences suggest that most essential oils possess a wide range of biological and pharmacological activities that may protect tissues against oxidative damage. In this study, we investigated DNA-protective effect of borneol, a component of many essential oils, against oxidative DNA damage induced in primary cultures of rat hepatocytes. Borneol was added to drinking water of Sprague-Dawley rats and DNA resistance against oxidative agents was compared in hepatocytes originated from control and borneol-treated rats. Oxidative stress induced by visible light-excited methylene blue (MB/VL) or 2,3-dimethoxy-1,4-naphthoquionone (DMNQ) resulted in increased levels of DNA lesions measured by the modified single cell gel electrophoresis. Borneol (17 or 34 mg/kg body weight) added to drinking water of rats for 7 days reduced the level of oxidative DNA lesions induced in their hepatocytes by MB/VL or DMNQ. To explain the increased resistance of DNA towards oxidative stress, we measured the base-excision repair (BER) capacity in liver cell extracts of control and borneol-supplemented rats on DNA substrate of HepG2 cells containing oxidative damage. Our results showed that administration of borneol in drinking water had no effect on incision activity of hepatocytes isolated from supplemented rats. The spectrophotometric assessment of enzymatic antioxidants superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities and the flow cytometric assessment of total intracellular glutathione (iGSH) in primary hepatocytes of borneol-supplemented rats showed no changes in SOD and GPx activities but higher iGSH content particularly in hepatocytes of higher borneol dose (34 mg/kg) supplemented rats in comparison to control animals. Despite the fact that borneol had no effect either on BER of oxidative DNA damage or on the levels of antioxidant enzymes and manifested no reducing power and radicals scavenging activity, it increased significantly the level of non-enzymatic antioxidant iGSH which could reduce the oxidative DNA lesions induced by MB/VL or DMNQ.

Carboxymethyl chitin-glucan (CM-CG) protects human HepG2 and HeLa cells against oxidative DNA lesions and stimulates DNA repair of lesions induced by alkylating agents.

A large number of functional foods, including those that contain ß-d-glucans, have been shown to prevent human DNA against genotoxic effects and associated development of cancer and other chronic diseases. In this paper, carboxymethyl chitin-glucan (CM-CG) isolated from Aspergillus niger was investigated from two standpoints: (1) DNA-protective effects against oxidative DNA damage induced by H(2)O(2) and alkylating DNA damage induced by MMS and MNNG, and (2) a potential effect on rejoining of MMS- and MNNG-induced single strand DNA breaks. The results obtained by the comet assay in human cells cultured in vitro showed that CM-CG reduced significantly the level of oxidative DNA lesions induced by H(2)O(2) but did not change the level of alkylating DNA lesions induced by MMS or MNNG. On the other side, the efficiency of DNA-rejoining of single strand DNA breaks induced by MMS and MNNG was significantly higher in HepG2 cells pre-treated with CM-CG. The antioxidative activity of carboxymethyl chitin-glucan was confirmed by the DPPH assay.

Investigation of anti-oxidative, cytotoxic, DNA-damaging and DNA-protective effects of plant volatiles eugenol and borneol in human-derived HepG2, Caco-2 and VH10 cell lines.

Plant volatiles, which can get into the human organism in food, medicines, or cosmetic preparations, frequently manifest antibacterial, antifungal, antiviral and other effects. We studied anti-oxidative, cytotoxic, genotoxic and possible DNA-protective effects of eugenol and borneol. Anti-oxidative activities of aqueous and ethanolic solutions of these two volatile compounds of plants were determined by a spectrophotometric method by the use of the stable DPPH radical. Borneol did not show any anti-oxidative activity even at the highest concentrations soluble in water or ethanol (<1000mM), while eugenol did manifest anti-oxidative activity, and at much lower concentrations (5-100 microM). The cytotoxicity of eugenol and borneol as well as their DNA-damaging effects and their influence on sensitivity of cells against the DNA-damaging effects of H(2)O(2) were investigated in three different cell lines, i.e. malignant HepG2 hepatoma cells, malignant Caco-2 colon cells, and nonmalignant human VH10 fibroblasts. The trypan-blue exclusion assay showed that in the three cell lines the cytotoxicity of eugenol was significantly higher than that of borneol. Single-cell gel electrophoresis revealed that borneol did not cause any DNA strand-breaks at the concentrations studied, but showed that all concentrations of eugenol (<600 microM) significantly increased the level of DNA breaks in human VH10 fibroblasts and to a lower degree in Caco-2 colon cells. The DNA-damaging effects of eugenol were not observed in metabolically active HepG2 hepatoma cells. Borneol and eugenol differed also with respect to their DNA-protective effects. While borneol protected HepG2 and, to a lesser extent, VH10 cells (but not Caco-2) against H(2)O(2)-induced DNA damage, eugenol either did not change the cellular sensitivity to H(2)O(2) (HepG2 cells) or it even increased the sensitivity (Caco-2 and VH10 cells). These results do not indicate any correlation between the DNA-protective and the anti-oxidative capacities of eugenol and borneol.

Evaluation of genotoxic and cytotoxic effects of H2O2 and DMNQ on freshly isolated rat hepatocytes; protective effects of carboxymethyl chitin-glucan.

OBJECTIVES: Utilizing primary rat hepatocytes we investigated the potential antimutagenic and anti-cytotoxic effects of carboxymethyl chitin-glucan (CM-CG) with respect to oxidative stress induced by the model free-radical-generating compounds hydrogen peroxide (H2O2) or 2,3-dimethoxy-1,4-naphthoquinone (DMNQ). Different kinds of CM-CG action were studied by two different treatment protocols: a. pre-incubation of freshly isolated hepatocytes with the potential anti-mutagen followed by exposure to the oxidant or b. simultaneous treatment of hepatocytes with the potential anti-mutagen and the oxidant. METHODS: As a measure of genotoxicity, the percentages of DNA in tails of comets by single cell gel electrophoresis were evaluated. The cytotoxicological endpoints analysed were the cell density (number of cells/cm2), and the percentages of apoptotic and necrotic cells. RESULTS: H2O2 and DMNQ, causing DNA single-strand breaks via the formation of *OH radicals, have been demostrated to induce both genotoxic and cytotoxic effects in primary rat hepatocytes resulting in increased percentages of DNA in tails of comets, and increased frequencies of apoptotic and necrotic cells accompanied by a decreased cell density. Further investigations were therefore focussed on possible modifications of these parameters by CM-CG. The results obtained clearly demonstrate that CM-CG (applied before and during treatment) protects primary rat hepatocytes against the genotoxic and cytotoxic effects of oxidative stress (H2O2 or DMNQ), whereas CM-CG itself has no effect on the endpoints of genotoxicity and cytotoxicity studied. CONCLUSION: Our results indicate that carboxymethyl chitin-glucan represents a natural fungal polysaccharide that can inhibit the genotoxicity and cytotoxicity of experimentally induced oxidative stress in primary rat hepatocytes.

Induction of DNA-lesions in freshly isolated rat hepatocytes by different genotoxins and their reduction by lignin given either as a dietary component or in in vitro conditions.

The aim of our investigation was to verify the protective effect of lignin on DNA in rat hepatocytes damaged by 3 different genotoxins attacking DNA in a different manner. Hydrogen peroxide was used for induction of direct single strand breaks of DNA, visible light-excited methylene blue for induction of oxidized DNA lesions and 1,2-dibromo-3-chloropropane for induction of alkali-labile DNA lesions. Hepatocytes were pre-treated with lignin either immediately after isolation, i.e., in in vitro conditions, or the hepatocytes were isolated from rats fed a lignin enriched diet for 21 days (ex vivo conditions). The protective effect of lignin applied to hepatocytes by the first or by the second approach was tested on the level of DNA using classical and modified single cell gel electrophoresis (SCGE). We found that lignin applied by each way significantly reduced the level of direct DNA strand breaks induced by H2O2, alkali-labile sites of DNA induced by DBCP as well as oxidative DNA lesions induced by visible light-excited methylene blue. These results confirm that lignin represents a very important micronutrient in our vegetable food, protecting DNA against damaging effects of different genotoxicants.

Study of cytotoxic, genotoxic and DNA-protective effects of selected plant essential oils on human cells cultured in vitro.

OBJECTIVES: To investigate cytotoxic, genotoxic and DNA-protective effects of carvacrol and thymol on human hepatoma HepG2 and colonic Caco-2 cells cultured in vitro. METHODS AND RESULTS: Cytotoxicity testing was performed by the trypan blue exclusion technique. Level of DNA lesions induced in human cells with carvacrol, thymol or their combinations with hydrogen peroxide (H(2)O(2)) were measured by alkaline single cell gel electrophoresis (comet assay). The trypan blue exclusion technique showed that though the metabolically more competent human hepatoma HepG2 cells were more sensitive to the toxic effects of carvacrol or thymol than colonic Caco-2 cells, which contained lower levels of metabolizing enzymes, the observed differences were not very expressive. The comet assay technique showed that at concentrations

Effects of dietary intake of a fungal beta-D-glucan derivative on the level of DNA damage induced in primary rat hepatocytes by various carcinogens.

Water-soluble derivative of chitin-glucan complex used in our study, carboxymethyl chitin-glucan (CM-CG), enables oral administration without harmful side-effects, which can occur upon parenteral administration of the insoluble fungal beta-D-glucans. The aim of this study was to determine in ex vivo experiments the effects of dietary CM-CG on the level of DNA lesions in primary rat hepatocytes induced by various indirectly acting carcinogens. Multiorgan carcinogen benzo[a]pyrene (BaP); two hepatocarcinogens, dimethyldibenzocarbazole (diMeDBC) and N-nitrosomorpholine (NMOR); as well as a complex mixture of organic compounds adsorbed on ambient air particles (TP-S) were used for this purpose. The amount of DNA lesions was assessed using the comet assay and the micronucleus test. In addition, the mitotic indexes and the frequencies of necrotic and apoptotic cells were evaluated as well. Our results showed that the diet enriched with CM-CG (200 mg/kg of body weight) during 21 days did not induce any negative effect on DNA nor did the mitotic indexes and the frequencies of necrotic and apoptotic cells differ statistically from the controls. On the other hand, the hepatocytes isolated from CM-CG fed animals were more resistant to the action of all genotoxins used in our study [BaP (5-20 microM), diMeDBC (0.2-2 microM), NMOR (3.4-10.2 mM), TP-S (5-20 microM)]. We can conclude that in addition to the known immunopotentiating activity of beta-D-glucans, they can efficiently inhibit the genotoxicity of carcinogens requiring metabolic activation in rat heptocytes.

Protective effects of ursolic acid and oleanolic acid in leukemic cells.

Ursolic acid (UA) and oleanolic acid (OA) have similar chemical structures but differ in the position of one methyl group on the ring E. We investigated protective effects of these two triterpenoic acids against H(2)O(2)-induced DNA damage in leukemic L1210, K562 and HL-60 cells using single-cell gel electrophoresis (SCGE). We compared their protective effects (antioxidant activities) with respect to the different position of the methyl group in their chemical structures. After 24h pre-treatment of cells both compounds investigated inhibited significantly the incidence of DNA single strand breaks induced by H(2)O(2). The concentration range of UA and OA was in all experiments 2.5-10 micromol/l. The antioxidant activity of OA determined by SCGE was significantly higher compared to UA in L1210 ((+)P<0.05) and K562 cells ((+++)P<0.001). Significant difference of the antioxidant activities of the two compounds was evidently connected with the different position of the methyl group. The protective effect of OA was in HL-60 cells slightly lower compared to the activity of UA, but the difference between the protective effects of UA and OA was not significant. In conclusion we can say that both natural pentacyclic triterpenoic acids investigated, UA and OA, manifested potent antioxidant effects. The different position of one methyl group in their chemical structures caused moderately different biological activities of these compounds on three leukemic cell lines. To explore their mechanisms of action further investigation seems to be therefore worthwhile.

Nature of DNA lesions induced in human hepatoma cells, human colonic cells and human embryonic lung fibroblasts by the antiretroviral drug 3'-azido-3'-deoxythymidine.

This study tried to clarify the question if nuclear genotoxicity played a role in 3'-azido-3'-deoxythymidine (AZT) toxicity. We investigated cytotoxic and DNA-damaging effects of AZT on human hepatoma HepG2 and human colonic CaCo-2 cells as well as on human diploid lung fibroblasts HEL. The amount of induced DNA damage was measured by standard alkaline single cell gel electrophoresis (SCGE). The nature of induced DNA lesions was evaluated (1) by modified SCGE, which includes treatment of lysed cells with DNA repair enzymes Endo III and Fpg and enables to recognize oxidized bases of DNA, and (2) by SCGE processed in parallel at pH 13.0 (standard technique) and pH 12.1, which enables to recognize alkali labile DNA lesions and direct DNA strand breaks. Cytotoxicity of AZT was evaluated by the trypan blue exclusion technique. Our findings showed that 3-h treatment of cells with AZT decreased the viability of all cell lines studied. SCGE performed in the presence of DNA repair enzymes proved that AZT induced oxidative lesions to DNA in all cell types. In hepatoma HepG2 cells and embryonic lung fibroblasts HEL the majority of AZT-induced DNA strand breaks were pH-independent, i.e. they were identified at both pH values (12.1 and 13.0). These DNA lesions represented direct DNA breaks. In colonic Caco-2 cells DNA lesions were converted to DNA strand breaks particularly under strong alkaline conditions (pH>13.0), which is characteristic for alkali-labile sites of DNA. DNA strand break rejoining was investigated by the standard comet assay technique during 48 h of post-AZT-treatment in HepG2 and Caco-2 cells. The kinetics of DNA rejoining, considered an indicator of DNA repair, revealed that AZT-induced DNA breaks were repaired in both cell types slowly, though HepG2 cells seemed to be more repair proficient with respect to AZT-induced DNA lesions.

Comparative evaluation of DNA damage by genotoxicants in primary rat cells applying the comet assay.

Various compounds known to cause DNA damage (hydrogen peroxide, visible light-excited methylene blue, N-nitrosomorpholine and benzo[a]pyrene) were tested with different primary rat cells (lymphocytes, testicular cells, type II pneumocytes and hepatocytes) to determine the range of induced DNA damage applying the comet assay. A dose-dependent increase of DNA breaks was observed after treatment with hydrogen peroxide in all cell types studied. The most prominent effect was observed in lymphocytes, whereas only a slight increase of DNA breaks was observed in hepatocytes. Visible light-excited methylene blue caused significant oxidative DNA damage, which did not significantly differ between the cell types used with the exception of hepatocytes, for which a lower level of DNA damage was observed. N-Nitrosomorpholine and benzo[a]pyrene induced a moderate but significant increase of DNA strand breaks in pneumocytes and hepatocytes while in lymphocytes no effect was observed. Our results clearly demonstrate that due to their differential function which is also expressed by the level of drug metabolizing and/or antioxidant enzymes, freshly isolated rat cells (lymphocytes, testicular cells, type II pneumocytes and hepatocytes) respond differently to the exposure to genotoxic agents as detected by comet assay.

Genotoxicity of environmental air pollution in three European cities: Prague, Kosice and Sofia.

The genotoxic potential of extractable organic matter (EOM) associated with the respirable particulate matter (PM <10 microm) of atmospheric pollution has been determined in three European cities--Prague (Czech Republic, two monitoring sites, Libus and Smíchov), Kosice (Slovak Republic) and Sofia (Bulgaria) using the alkaline single-cell gel electrophoresis (the comet assay). The EOM samples were extracted by dichloromethane from ambient airborne particles collected daily (24 h intervals) during 3-month sampling periods in winter and summer seasons. The human metabolically competent cell line Hep G2 was used as a test system and benzo[a]pyrene (BaP), a known carcinogen, was applied as a positive control (internal standard) in each electrophoretic run. Two-hour exposure of Hep G2 cells to equivalent EOM concentrations ranging from 5 to 150 microg EOM/ml resulted in a linear dose-dependent increase of DNA migration (r > 0.9, P < 0.01). A less significant dose-response (r = 0.61) was only induced by the EOM sample from the locality Prague-Libus (PRG-LB) in the winter. Generally, a 1.5 to four-fold increase of DNA strand breaks over the background control level was determined in EOM-exposed cells. In order to compare the genotoxic potential of individual EOMs, a mathematical model was used to correct the 'real' data. No substantial location- or season-related differences were found in EOM genotoxicity (EOM microg/ml), except for the EOM sample from Sofia, collected in the summer. This EOM sample induced a nearly two-fold lower level of DNA damage in comparison with other EOMs. On the other hand, clear statistically significant location- and season-related differences (P < 0.001) in ambient air genotoxicity were determined when the EOM quantity per cubic meter of air (microg/m3) was taken into account. In that case, the genotoxicity of winter air pollution was six- to 10-fold higher in comparison with summer air. The air pollution genotoxicity in individual localities rose during the winter season in the order: PRG-LB < Kosice < Prague-Smíchov (PRG-SM) < Sofia, while during the summer season the highest ambient air genotoxicity was revealed in the locality Prague-Smíchov and approximately equal air pollution genotoxicity was determined among localities Prague-Libus, Kosice and Sofia (PRG-LB approximately Kosice approximately Sofia < PRG-SM). The greatest overall air pollution genotoxicity was determined in the locality Sofia during the winter season. In a time course study to evaluate the kinetics of DNA strand break rejoining it was shown that the level of DNA strand breaks in EOM-exposed cells has returned to near the background level within 24 h after the treatment.

An investigation of the genotoxic effects of N-nitrosomorpholine in mammalian cells.

N-nitrosomorpholine (NMOR) is a well-known hepatocarcinogen. Since this compound is representative of the group of indirect-acting N-nitrosamines, its metabolic activation should be essential. However, the mechanism of NMOR-induced carcinogenesis is still not completely clear. In this paper we tried to further our understanding of the genotoxic effects of NMOR. The central aim of this study was to elucidate to what extent NMOR requires metabolic activation. For evaluation of the mutagenicity of NMOR, V79 cells were used either in the presence or absence of the microsomal S9 fraction in the mutation assay and formation of reactive oxygen/nitrogen species (ROS/RNS) in Caco-2 cells treated with NMOR was measured by a fluorescent assay. A very weak rise of 6-thioguanine resistant mutations was observed in both NMOR-treated model cells, V79/-S9 and V79/+S9. A significant difference between the level of mutations in V79/-S9 and V79/+S9 cells was recorded on the 7th day of expression only. Data obtained by the fluorescent assay confirmed that NMOR caused generation of ROS/RNS. In summary, the presented results showed that NMOR might induce DNA damage not only indirectly by its activation by drug-metabolizing enzymes but also via direct formation of ROS/RNS.

Cytotoxic and DNA-damaging effects of diterpenoid quinones from the roots of Salvia officinalis L. on colonic and hepatic human cells cultured in vitro.

Three diterpenoid quinones (royleanone- SAR 3, horminone- SAR 26, and acetyl horminone- SAR 43) isolated from the roots of Salvia officinalis L. were tested for their cytotoxic and DNA-damaging activity in human colon carcinoma cells Caco-2 and human hepatoma cells HepG2 cultured in vitro. Cytotoxicity was measured by the trypan blue exclusion technique and induction of apoptosis was evaluated by flow immunofluorocytometry after 30-300 min. exposure of HepG2 and Caco-2 cells to diterpenoid quinones and following 24 hr post-incubation in the culture medium. Induction of DNA breaks was measured after 60 min. exposure of cells to different concentrations of the compounds studied by the alkaline elution of DNA and by the Comet assay. Though all the quinones tested decreased the viability of the cells studied proportionally to the concentration and to the time of treatment (cytotoxicity= 30-60%), the increased level of apoptotic nuclei comparable to the level of apoptotic nuclei induced by a topoisomerase I inhibitor was proved only in HepG2 cells treated with 1x10(-4) mol/l SAR 26 or SAR 43. Either no or marginal increase of the level of apoptotic nuclei was observed in SAR 3-treated HepG2 cells and in SAR 3-, SAR 26- or SAR 43-treated Caco-2 cells. All compounds tested induced creation of DNA strand breaks in both cell types at concentrations >1x10(-7)-1x10(-6) mol/l. The occurrence of DNA strand breaks at different pH values as well as the kinetics of DNA breaks rejoining were evaluated only in colonic cells Caco-2. The Comet assay processed in parallel at pH 13.0 and pH 12.1 showed that strand breaks detected in SARs-treated colonic Caco-2 cells originated from alkali-labile sites, as induced DNA lesions were converted to DNA strand breaks only under strong alkaline conditions. The kinetics of DNA rejoining revealed that SARs-induced DNA breaks were repaired very slowly.

DNA lesions and cytogenetic changes induced by N-nitrosomorpholine in HepG2, V79 and VH10 cells: the protective effects of Vitamins A, C and E.

INTRODUCTION: N-Nitrosomorpholine (NMOR), present in the workplace of tyre chemical factories, is a known hepatocarcinogen. This compound belongs to the group of N-nitrosamines, which are indirect-acting and require metabolic activation. However, the mechanism of its carcinogenic effect is not completely clear. AIMS: The objective of this study was (i) to compare the DNA-damaging and clastogenic effects of NMOR in three cell lines (HepG2, V79 and VH10) with different levels of metabolizing enzymes and (ii) to determine the protective effects of Vitamins A, C and E against deleterious effects of NMOR. METHODS: The exponentially growing cells were pre-treated with Vitamins A, C and E and treated with NMOR. Genotoxic effects of NMOR were evaluated by single-cell gel electrophoresis (SCGE, comet assay), while the chromosomal aberration assay was used for the study of clastogenic effects. KEY RESULTS: NMOR-induced a significant dose-dependent increase of DNA damage as analyzed by SCGE, but the extent of DNA migration in the electric field was unequal in the different cell lines. Although the results obtained by SCGE confirmed the genotoxicity of NMOR in all cell lines studied, the number of chromosomal aberrations was significantly increased only in HepG2 and V79 cells, while no changes were observed in VH10 cells. In HepG2 cells pre-treated with Vitamins A, C and E we found a significant decrease of the percentage of tail DNA induced by NMOR. The reduction of the clastogenic effects of NMOR was observed only after pretreatment with Vitamins A and E; Vitamin C did not alter the frequency of NMOR-induced chromosomal aberrations under the experimental conditions of this study. CONCLUSIONS: The fat-soluble Vitamins A and E, which are dietary constituents, reduce the harmful effects of N-nitrosomorpholine in human hepatoma cells HepG2, which are endowed with the maximal capacity for metabolic activation of several drugs.

Genotoxic effects of a complex mixture adsorbed onto ambient air particles on human cells in vitro; the effects of Vitamins E and C.

Genotoxicity of complex mixtures of organic compounds adsorbed onto ambient air particles (extractable organic matter, EOM) collected in Teplice (Czech Republic) as well as genotoxicity of the indirectly acting carcinogens benzo[a]pyrene (B[a]P) and 5,9-dimethyl-7H-dibenzo[c,g]carbazole (5,9-diMeDBC) was studied in human HepG2 and Caco-2 cells cultured in vitro. The level of DNA breaks was detected by conventional single-cell gel electrophoresis (alkaline comet assay). The level of DNA breaks+oxidative DNA lesions was assessed by modified single-cell gel electrophoresis. The indirectly acting chemical carcinogens studied were able to induce DNA breaks as well as oxidative DNA damage in both cell lines, but stronger DNA-damaging effects were observed in HepG2 cells, which contain a higher level of metabolic enzymes. Treatment of cells with the complex mixtures showed a dose-dependent increase of DNA breaks in HepG2 cells as well as in Caco-2 cells, with seasonal differences. Winter samples of EOM from Teplice (TP-W) were more effective in inducing DNA damage than summer samples (TP-S). Both mixtures caused significant oxidative DNA damage in HepG2 cells. The effect was less evident in cells treated with higher concentrations of TP-W, since the comet assay is limited by saturation at a higher level of DNA damage. Possible reduction of B[a]P-, 5,9-diMeDBC- or EOM-induced DNA damage by Vitamins E and C was evaluated in HepG2 cells only. Pre-treatment of these cells with either one of the vitamins considerably reduced the levels of both DNA breaks and oxidative DNA lesions induced by all compounds investigated.

Protective effects of fungal (1-->3)-beta-D-glucan derivatives against oxidative DNA lesions in V79 hamster lung cells.

beta-Glucans belong to the class of substances known as biological response modifiers with a broad range of activity. We have investigated two types of glucans: (1-->3)-beta-D glucan from the baker's yeast Saccharomyces cerevisiae and beta-glucan-chitin complex from the mycelium of filamentous fungus Aspergillus niger. Since these fibrillar beta-glucans are insoluble in water, their water-soluble derivatives--carboxymethyl glucan (CM-G), sulfoethyl glucan (SE-G), and carboxymethyl chitin-glucan (CM-CG) were prepared and tested. The aim of the present work was to investigate the protective effect of the prepared glucan derivatives against oxidative DNA damage induced by H2O2 and visible light-excited Methylene Blue in V79 hamster lung cells. The level of DNA damage (DNA strand breaks) was measured using the single cell gel electrophoresis, so called comet assay. Our findings demonstrate that all three tested glucans reduce oxidative DNA damage. The ability to reduce genotoxic activity increased in the order: CM-G