Cellular stress by light and rose bengal in human lymphocytes

Toxicogenetic evaluation of metronidazole in the treatment of women infected withTrichomonas vaginalis

Samples of peripheral blood were collected once from non-smoking women who were healthy (controls) and twice (immediately before and immediately after 7 days of treatment with metronidazole at 500 mg/day) from non-smoking women infected with Trichomonas vaginalis. Lymphocyte cultures were prepared and used, in toxicogenetic studies, to determine the frequency of sister-chromatid exchange (SCE), the mitotic index (MI), and the replication index (RI) for each sample. MTZ treatment of the infected women led to an increase in the frequency of SCE (P <0.001), a decrease in the MI (P <0.003), and a modification in the kinetics of cell proliferation, with a decrease in the RI (P <0.0006). The differences seen between the results for the controls and those for the infected women, before and after MTZ treatment, may be attributed to the presence of the parasite, to the treatment itself, and/or to variation in the host's response to infection with T. vaginalis.

Estimation of lipid peroxidation induced by hydrogen peroxide in cultured human lymphocytes

Malondialdehyde (MDA) is used for the estimation of damage by reactive oxygen species. MDA is a major reactive aldehyde resulting from the peroxidation of biological membranes. The most common method used to assess MDA production is the thiobarbituric acid (TBARS) assay. However, the value of this method is curbed by low specificity and has been criticized for its use in human studies. In the present study we have used an alternative method for the estimation of MDA production i.e. reaction of MDA with a chromogenic agent 1-methyl-2-phenylindole at 45°C. The paper describes the method of preparing standards for the estimation of MDA (lipid peroxidation) after the treatment with an oxidative stress inducing agent hydrogen peroxide (H(2)O(2)). In the present study, the treatments of 1, 5, 10, 20, 50, 100, 150 and 200 μM of H(2)O(2) induced significant increase in lipid peroxidation as compared to the untreated ones. The results suggest that the present method can be used to measure the lipid peroxidation in cultured human peripheral blood lymphocytes and is specific for MDA estimation.

Evaluation of differential representative values between Chinese hamster cells and human lymphocytes in mitomycin C-induced cytogenetic assays and caspase-3 activity

Chinese hamster ovary (CHO) cells, its lung fibroblasts (V79), and human lymphocytes are routinely used in in vitro cytogenetic assays, which include micronuclei (MN), sister chromatid exchange (SCE), and chromosome aberration (CA) assays. Mitomycin C (MMC), a DNA cross-link alkylating agent, is both an anticancer medicine and a carcinogen. To study the differential representative values of cell types in MMC-treated cytogenetic assays and its upstream factor, cysteine aspartic acid-specific protease (caspase)-3. Among the chosen cell types, lymphocytes expressed the highest sensitivity in all three MMC-induced assays, whereas CHO and V79 showed varied sensitivity in different assays. In MN assay, the sensitivity of CHO is higher than or equal to V79; in SCE assay, the sensitivity of CHO is the same as V79; and in CA assay, the sensitivity of CHO is higher than V79. In-depth analysis of CA revealed that in chromatid breaks and dicentrics formation, lymphocyte was the most sensitive of all and CHO was more sensitive than V79; and in acentrics and interchanges formation, lymphocyte was much more sensitive than the others. Furthermore, we found caspase-3 activity plays an important role in MMC-induced cytogenetic assays, with MMC-induced caspase-3 activity resulting in more sensitivity in lymphocytes than in CHO and V79. Based on these findings, lymphocyte will make a suitable predictive or representative control reference in cytogenetic assays and caspase-3 activity with its high specificity, positive predictive value, and sensitivity.

Thiocyclam does not induce structural chromosome aberrations in human lymphocytes in vitro

Thiocyclam (trade name Evisect) is a broad-spectrum nereistoxin analogue insecticide used widely for agricultural applications. The aim of this investigation was to determine its genotoxic effects in the chromosome aberration (CA) test and determining of mitotic index (MI), using lymphocytes from peripheral blood samples of healthy human donors. A negative and a positive control (MMC) were also included. Chromosomal analyses of the metaphase plates of the samples treated with 14 different concentrations (from 0.1 to 120 μg/ml) of thiocyclam, indicating the lack effect on chromosomes. Thus thiocyclam is not genotoxic but highly toxic on cell proliferation in human lymphocytes.

Protective effect of ascorbic acid against oxidative damage induced by hydrogen peroxide in cultured human peripheral blood lymphocytes

Hydrogen peroxide is one of the reactive oxygen species for cellular injury. It is overproduced during oxidative stress and is known to damage proteins, nucleic acids and cell membranes. The present study was aimed to study the protective effect of ascorbic acid against the toxic doses of hydrogen peroxide using lipid peroxidation and cytokinesis blocked micronucleus assay. Hydrogen peroxide was studied at 50, 100 and 200μM and was found to increase a dose dependent increase in lipid peroxidation and micronuclei frequency. The treatment of 100 and 200μM of hydrogen peroxide separately along with 20, 40 and 80μM of ascorbic acid showed a dose dependent decrease in the lipid peroxidation and micronuclei frequency. The results suggest a protective effect of ascorbic acid against the hydrogen peroxide induced oxidative damage in cultured human peripheral blood lymphocytes.

Antigenotoxic role of Centella asiatica L. extract against cyproterone acetate induced genotoxic damage in cultured human lymphocytes

The majority of the Indian population use traditional natural preparations derived from plant material for the treatment of various diseases, and for that reason it becomes necessary to assess the mutagenic potential or modulating action of plants extract when associated with other substances. The genotoxicity testing provides human a risk assessment. Earlier in vitro and in vivo studies reveal that the plant extracts from various parts of the plant play a modulating role in xenobiotic effects. Identification and characterization of some active principles may lead to the development of the strategies to reduce the risk for developing cancer in humans. Cyproterone acetate (CPA), a synthetic progestin is not only a genotoxic agent but also a tumor initiating agent. It is used in oral contraceptives formulations and also in the treatment of various sexual and metabolic disorders. In this context, the antigenotoxic effect of Centella asiatica L. extract was studied against the genotoxic effect induced by CPA on human lymphocytes using chromosomal aberrations and sister chromatid exchanges as parameters. The treatment of the two doses of CPA, i.e. 20 and 30 microM was given along with the C. asiatica extract at the dosages of 1.075 x 10(-4), 2.125 x 10(-4), 3.15 x 10(-4) and 4.17 x 0(-4)g/ml of culture medium. A clear dose dependent decrease in the genotoxic damage of CPA was observed, suggesting a protective role of C. asiatica extract during CPA therapy. The results of the present study suggest that the plant extract per se do not have genotoxic potential, but can modulate the genotoxicity of CPA on human lymphocytes in vitro.

Antigenotoxic effect of apigenin against anti-cancerous drugs

Mitomycin C and cyclophosphamide are well known anti-tumor drugs. Their genotoxic effects are well established in various test systems. The genotoxic effects in non-tumor cell are of special significance due to the possibility that they may induce secondary tumors in cancer patients. Apigenin is a well known anti-oxidant and possess number of properties that are beneficial in some way to humans. With this view, the present study deals with the effect of apigenin against the genotoxic doses of mitomycin C and cyclophosphamide using chromosomal aberrations, sister chromatid exchanges and cell cycle kinetics as a parameters. The treatment of apigenin results in a significant, dose dependent decrease in the genotoxic damage, induced by mitomycin C and cyclophosphamide. It is concluded that the apigenin is potent in reducing the genotoxic damage, induced by anti-cancerous drugs, thereby reducing the chances of developing secondary tumors during the therapy.

Anti-genotoxic effect of Ocimum sanctum L. extract against cyproterone acetate induced genotoxic damage in cultured mammalian cells

The anti-genotoxic effect of Ocimum sanctum L. extract was studied against the genotoxic effect induced by a synthetic progestin cyproterone acetate, on human lymphocytes using chromosomal aberrations, mitotic index, sister chromatid exchanges and replication index as a parameters. About 30 microM of cyproterone acetate was treated with O. sanctum L. infusion, at dosages of 1.075 x 10(-4), 2.125 x 10(-4) and 3.15 x 10(-4) g/ml of culture medium. A clear dose-dependent decrease in the genotoxic damage of cyproterone acetate was observed, suggesting a possible modulating role of the plant infusion. The results of the present study suggest that the plant infusion per se does not have genotoxic potential, but can modulate the genotoxicity of cyproterone acetate on human lymphocytes in vitro.

Genotoxic potential of medroxyprogesterone acetate in cultured human peripheral blood lymphocytes

Medroxyprogesterone acetate was studied at three different concentrations (1, 5 and 10 microM), for its genotoxic effects in human peripheral blood lymphocyte culture using chromosomal aberrations and sister chromatid exchanges as parameters. Duplicate peripheral blood cultures were treated with three different concentrations (1, 5 and 10 microM) of medroxyprogesterone acetate. The study was carried out both in the absence as well as in the presence of metabolic activation (S9 mix) with and without NADP. Medroxyprogesterone acetate was found genotoxic at 5 and 10 microM in the presence of S9 mix with NADP. To study the possible mechanism of the genotoxicity of medroxyprogesterone acetate, superoxide dismutase and catalase at different doses were used separately and in combination with 10 microM of medroxyprogesterone at different doses in the presence of S9 mix with NADP. Superoxide dismutase treatment results in an increase of the genotoxic damage but catalase treatment reduce the genotoxic damage of medroxyprogesterone acetate. Catalase treatment in combination with superoxide dismutase also results in the further reduction of the genotoxic damage. The results of the present study reveal that medroxyprogesterone acetate is genotoxic only in the presence of metabolic activation (S9 mix) with NADP. Treatments with superoxide dismutase and catalase suggests the possible generation of reactive oxygen species by redox cycling of various forms of quinones, similar to estrogens, that are the results of aromatic hydroxylation by cytochrome P450s.

Protective effect of nordihydroguaiaretic acid (NDGA) against norgestrel induced genotoxic damage

Nordihydroguaiaretic acid (NDGA) is a phenolic lignan and possesses antioxidant and number of properties potentially useful to man. The effect of NDGA was studied against norgestrel induced genotoxic damage, using sister chromatid exchanges (SCEs), chromosomal aberrations (CAs), mitotic index (MI) and replication index (RI) as parameters. Amounts of 5, 10 and 20 microM of norgestrel was tested for its genotoxic effect in the absence as well as presence of S9 mix, and was found to be genotoxic at 10 and 20 microM in the presence of S9 mix. Again, 10 microM of norgestrel was treated with 0.5 and 1 microM of NDGA, separately, in the presence of S9 mix. Similar treatment was given with 20 microM of norgestrel. Treatments given with NDGA result in the reduction of SCE, CA and increase of MI as well as RI, suggesting its protective action on human lymphocytes in vitro against the norgestrel induced genotoxic damage.

Genotoxic potential of cyproterone acetate: a possible role of reactive oxygen species

The genotoxicity of cyproterone acetate was studied in human lymphocytes using chromosomal aberrations (CAs), mitotic index (MI) and sister chromatid exchanges (SCEs) as a parameter. Cyproterone acetate was found to be genotoxic at 20 and 30 microM. To study the possible mechanism of the genotoxicity of cyproterone acetate, superoxide dismutase (SOD) and catalase (CAT) were used separately and in combination along with the 30 microM of cyproterone acetate at different doses. SOD treatment increases CAs, SCEs and decreases MI as compared to treatment with 30 microM CPA alone, at both of the tested doses. CAT treatment decreases the frequencies of CAs and SCEs and increases MI in both, as compared to treatment with 30 microM CPA alone, separately and in combination with SOD, suggesting a possible role of reactive oxygen species for the genotoxic damage.

Genotoxic potential of ethinylestradiol in cultured mammalian cells

Ethinylestradiol, a steroidal estrogen, is widely used with various progestogens in oral contraceptives formulations. There are sufficient evidences for the carcinogenicity of ethinylestradiol in experimental animals. The reports on the genotoxic potential of ethinylestradiol are contradictory. Here in the present study we have tested the genotoxicity of ethinylestradiol in human lymphocytes using chromosomal aberrations (CAs), mitotic index (MI) and sister chromatid exchanges (SCEs) as a parameter. The study was carried out in the absence, as well as in the presence, of rat liver microsomal fraction, with and without NADP. Ethinylestradiol was studied at three different concentrations (1, 5 and 10 microM) and was found non-genotoxic in the absence of metabolic activation (S9 mix) and in S9 mix without NADP. Ethinylestradiol was found to be genotoxic at 5 and 10 microM in the presence of S9 mix with NADP. To study the possible mechanism of the genotoxicity of ethinylestradiol, superoxide dismutase (SOD) and catalase (CAT) were used separately and in combination along with 10 microM of ethinylestradiol at different doses. SOD treatment increased CAs and SCEs and decreases MI as compared with treatment with 10 microM of ethinylestradiol alone in the presence of S9 mix with NADP at both of the tested doses. CAT treatment decreased the frequencies of CAs and SCEs and increased MI, as compared with treatment with 10 microM of ethinylestradiol alone in the presence of S9 mix with NADP. CAT treatment in combination with SOD also decreased the frequencies of CAs and SCEs and increased MI suggesting a possible role of reactive oxygen species for the genotoxic damage.

Cytogenetic evaluation of two nitroimidazole derivatives

5-Nitroimidazoles are a well-established group of antiprotozoal and antibacterial agents. Thanks to their antimicrobial activity these chemotherapeutic agents inhibit the growth of both anaerobic bacteria and certain anaerobic protozoa such as Trichomonas vaginalis, Entamoeba histolytica and Giardia lamblia. The aim of the present study is to achieve a precise characterization of the genotoxic activity of these compounds and to establish the value of cytogenetic assays in order to determine the effect of these drugs, at therapeutic doses, to settle an improved risk assessment. Two nitroimidazole were studied, metronidazole and ornidazole, at four different concentrations (0.1, 1, 10 and 50 microg/ml of peripheral blood lymphocyte culture). Endpoints analyzed included: mitotic index (MI), replication index (RI), sister chromatid exchange (SCE) and chromosomal aberrations (CA). An analysis of variance test (ANOVA) was performed to evaluate the results. A significant decrease (P<0.0001) in MI as well as an increase in SCE (P<0.0001) and CA (0.0001) frequencies for both drugs was observed. No modifications in RI were found. The results suggest a genotoxic and cytotoxic effect of MTZ and ONZ in human peripheral blood cultures in vitro.

Evaluation of genetic damage induced by a nitroimidazole derivative in human lymphocytes: Tinidazole (TNZ)

One of the useful drugs in the treatment against infestations caused by Trichomonas vaginalis, Entamoeba histolytica and Giardia lamblia is Tinidazole (TNZ) 1-[2-(ethylsulfonyl) ethyl]-2-methyl-5-nitroimidazole) (Gilman R.H., Marquis G.S., Miranda E., Vestegui M., Martinez H., 1988. Rapid reinfection by Giardia lamblia after treatment in a hyperendemic third world community. Lancet i, 343-345). We decided to evaluate the potential genetic damage induced by TNZ using different biological biomarkers such as the mitotic index (MI), sister chromatid exchange (SCE) and cell proliferation kinetics (CPK). We observed a significant decrease (P<0.0005) in the MI as well as an increase (P<0.0005) in SCE frequency and no modifications in the replication index (RI). The results obtained suggest a potential genotoxic and cytotoxic effect of TNZ in human peripheral blood cultures in vitro.

Oxidative stress by visible light irradiation suppresses immunoglobulin production in mouse spleen lymphocytes

In this study, we attempted to induce the oxidative stress in mouse spleen lymphocytes with visible light irradiation and examined the effects of lipid peroxidation on immunoglobulin (Ig) production. The spleen lymphocytes were isolated from 8-week-old male balb/c mice and irradiated with 300 W visible light. When the cells were cultured for 72 hr, Ig contents in culture supernatants were decreased gradually by irradiation for over 30 min. The cell viability was also lowered by the irradiation. Intracellular phosphatidylcholine hydroperoxide (PCOOH) levels and thiobarbituric acid-reactive substances (TBARS) values in culture supernatants were measured as indices of lipid peroxidation and we found that Ig production by mouse spleen lymphocytes was suppressed accompanied with the progress of peroxidation of intracellular phospholipids. Cell membrane fluidity was also significantly decreased, but the intracellular Ig level was not changed in the irradiated cells. These results suggest that the peroxidation of intracellular lipids is a cause of the suppression of Ig production by mouse spleen lymphocytes via lowering cell viability and suppressing Ig synthesis and secretion.

Antioxidant adaptive response of human mononuclear cells to UV-B: effect of lipoic acid

Supplementation of human mononuclear cells with 3 and 6 mM of lipoic acid produces an inhibition of the antioxidant adaptive response triggered by treatment with UV-B light (0.30 W/m2 for 15 min). Supplementation with 1.5 mM of lipoic acid gives no conclusive results. The adaptive response is characterized by an increase in the activities of superoxide dismutase, catalase, glutathione peroxidase and DT-diaphorase. Catalase (5.5 +/- 0.6 pmol/mg prot) increases its activity by up to 22 +/- 3 pmol/mg prot, after irradiation with UV-B. Supplementation with 3 and 6 mM of lipoic acid completely inhibits the adaptive response. The activities of the membrane-bound mitochondrial enzymes succinate dehydrogenase and cytochrome oxidase do not increase after UV-B exposure. Moreover, their activities are found to decrease and the addition of lipoic acid does not prevent this effect. The inhibition of the antioxidant response by lipoic acid in human cells appears as indirect evidence of the existence of oxidative stress in the development of this response. As lipoic acid behaves as an effective antioxidant, it seems that its action decreases the intracellular oxidative signals necessary to develop the adaptive response in human mononuclear cells.

Effects of fluorescent light on growth of bovine retinal pigment epithelial cells in vitro incubated with linoleic acid or linoleic acid hydroperoxide

Light-induced peroxidation of polyunsaturated fatty acids (PUFA) may generate lipid hydroperoxides, which may have toxic effects on retinal pigment epithelial (RPE) cells in vitro. We investigated the effects of cool-white fluorescent light on the RPE cells incubated with linoleic acids (LA) or linoleic acid hydroperoxides (LHP) and the influence of antioxidative enzymes. We measured the bovine RPE cell number after exposure to fluorescent light (610 and 1,200 lux) in the presence of LA or LHP. Furthermore, the effects of superoxide dismutase (SOD) and catalase on LA- or LHP-treated RPE cells were also examined. Both LA and LHP treatment increased RPE cell number under weak illumination (610 lux), but dose-dependently decreased the number of cells exposed to strong illumination (1,200 lux). With exposure to strong illumination, LA caused a greater reduction in RPE cell number than LHP. Multiple linear regression analysis showed that the number of RPE cells was significantly decreased in a manner dependent on the interactions of the illuminance of light and the concentrations of LA or LHP. The antioxidative enzymes significantly ameliorated the damage to RPE cells from LA or LHP and exposure to light. Therefore, the exposure to fluorescent light augmented the cytotoxic effects of LA and LHP on RPE cells, and this effect is likely to be mediated by reactive oxygen species.

Antioxidant adaptive response in human blood mononuclear cells exposed to UVB

Human blood mononuclear cells exposed to UVB radiation develop increased antioxidant enzyme activities. Catalase (5.50 +/- 0.65 pmol (mg protein)-1), CuZn-superoxide dismutase (16.7 +/- 2.1 pmol (mg protein)-1), Mn-superoxide dismutase (11.3 +/- 1.7 pmol (mg protein)-1), Se-dependent glutathione peroxidase (13.2 +/- 1.5 mU (mg protein)-1) and Se-independent glutathione peroxidase (3.30 +/- 0.52 mU (mg protein)-1) activities increase by 1.3-1.5-fold from the control activities after exposure to 0.3 W m-2 of 280-315 nm light for 15 min and a 3 h dark incubation period. DT-diaphorase activity (2.86 +/- 0.21 mumol DCPIP min-1 (mg protein)-1) increases threefold from the indicated control values. In contrast, cytochrome oxidase (0.36 +/- 0.04 min-1 (k') (mg protein)-1) and succinate dehydrogenase (3.06 +/- 0.25 mumol DCPIP min-1 (mg protein)-1) activities remain unchanged during the same irradiation and incubation period. The treatment of cells with cycloheximide prevents the response triggered by UVB exposure. These findings suggest that an inducible antioxidant defence mechanism operates on photo-oxidative stress and that both superoxide dismutase and DT-diaphorase may display a concerted antioxidant role.