硫氧还蛋白对氢醌细胞毒性的抑制

目的　氢醌引起细胞凋亡 ,可能是通过降低细胞内巯基水平及升高活性氧水平改变细胞内氧化还原状态。鉴于硫氧还蛋白在维持细胞氧化还原状态平衡上也起着重要作用 ,本研究探讨人硫氧还蛋白(hTRX)对氢醌细胞毒作用有无影响。方法　采用脂质体法 ,将真核表达质粒pVP2 2 hTRX和pVP2 2分别转入人胚肾细胞中 ,并将获得的G4 18抗性单克隆细胞株hTRX12和VP2 2细胞进行Western印迹法分析。分别用荧光探针DCFH DA法、碘化丙啶染色法及MTT法测定活性氧水平、凋亡率及细胞存活率。结果　用不同浓度氢醌处理hTRX12细胞与VP2 2细胞 ,hTRX过度表达可降低氢醌所致的活性氧水平升高 ,降低氢醌诱导的凋亡 ,抑制氢醌的细胞毒性。另外 ,用重组人硫氧还蛋白 (rhTRX)与氢醌同时处理未转染人胚肾细胞 ,也可观察到类似结果。结论硫氧还蛋白可对抗氢醌的细胞毒性 ,其机制可能是通过降低氢醌所致活性氧升高及维持细胞内巯基水平     

Genotoxic effect of substituted phenoxyacetic acids

The potential toxic and mutagenic action of 2,4-dichlorophenoxyacetic acid has been studied in different test systems, and the obtained results range from increased chromosomal damage to no effect at all. We reexamined the effect of this herbicide by simultaneous using three tests based on yeast, transformed hematopoietic, and mouse bone marrow cells. The results obtained demonstrated that 2,4-dichlorophenoxyacetic acid has cytotoxic and mutagenic effects. The positive response of yeast and transformed hematopoietic cells was verified in kinetics and dose-response experiments. The analysis of metaphase chromosomes indicated a statistically proved induction of breaks, deletions, and exchanges after the intraperitoneal administration of 2,4-dichlorophenoxyacetic acid in mice. The study of phenoxyacetic acid and its differently chlorinated derivatives showed that cytotoxicity and mutagenicity are induced by chlorine atoms at position 2 and/or 4 in the benzene ring. The mutagenic effect was abolished by introduction of a third chlorine atom at position 5. Thus 2,4,5-trichlorophenoxyacetic acid was found to have very weak, if any mutagenic effect; however, the herbicide preserved its toxic effect.     

Protective effect of [6]-gingerol on the ethanol-induced teratogenesis of cultured mouse embryos

Excessive ethanol consumption during pregnancy causes fetal alcohol syndrome. We investigated the effect of [6]-gingerol on ethanol-induced embryotoxicity using a whole embryo culture system. The morphological changes of embryos and the gene expression patterns of the antioxidant enzymes cytosolic glutathione peroxidase (cGPx), cytoplasmic Cu/Zn superoxide dismutase (SOD1), and Mn-SOD (SOD2), and SOD activity were examined in the cultured mouse embryos exposed to ethanol (5 μL/3 mL) and/or [6]-gingerol (1×10⁻⁸ or 1×10⁻⁷ μg/mL) for 2 days. In ethanol-exposed embryos, the standard morphological score of embryos was significantly decreased compared with those of the control (vehicle) group. However, cotreatment of embryos with [6]-gingerol and ethanol significantly improved all of the developmental parameters except crownrump length and head length, compared with those of the ethanol alone group. The mRNA expression levels of cGPx and SOD2, not SOD1, were decreased consistently, SOD activity were significantly decreased compared with the control group. However, the decreases in mRNA levels of antioxidant enzymes and SOD activity were significantly restored to the control levels by [6]-gingerol supplement. These results indicate that [6]-gingerol has a protective effect against ethanol-induced teratogenicity during mouse embryogenesis.     

Genotoxic evaluation of letimide with the mouse bone marrow micronucleus test

Letimide, 3[2-(diethylamino)ethyl]-2H-1,3-benzoxazine-2,4(3H)-dione, a new analgesic, is a cyclic derivative of a salicylamide with a higher pharmacological potency than acetylsalicylic acid. In this study we evaluated its clastogenic activity using the micronucleus test in vivo. Our results did not show any clastogenic effect produced by letimide as compared with control mice and animals treated with cyclophosphamide.     

含去痴灵挥发油的大鼠血清对体外培养新生小鼠皮层神经元的营养作用*

目的:研究含去痴灵挥发油的大鼠血清对体外培养新生小鼠皮层神经元的营养作用。方法:采用血清药理学方法,制备含去痴灵挥发油的大鼠血清。体外培养新生小鼠皮层神经元,在无血清培养液中加入含去痴灵挥发油的大鼠血清,使培养基中含药血清的最终体积分数分别为0.1%,0.5%和2.5%,设立空白血清对照组和重组人碱性成纤维细胞生长因子(rhbFGF,终浓度为20 ng.mL-1)阳性对照组。观察培养48 h细胞的形态学改变,定量比较神经元突起数目和长度;用四甲基偶氮唑蓝(MTT)比色法检测培养d 4和d 8神经元存活数;并用RT-PCR测定培养d 4时神经元细胞的微管相关蛋白2(MAP2)的mRNA含量。结果:0.5%和2.5%的含去痴灵挥发油的大鼠血清均能使神经元突起数目和长度增加、不同培养期细胞存活数增加、MAP2基因表达量增加。结论:含去痴灵挥发油的大鼠血清对新生小鼠皮层神经元具有营养作用。     

The effect of oxygen tension on the cytotoxicity of hydroquinone and selected hydroquinone metabolites to isolated rat renal proximal tubular cells

The cytotoxicity of hydroquinone (HQ) and several of its metabolites was studied using freshly isolated proximal tubular (PT) kidney cells from rats. Incubations were conducted for periods of up to 4 h at 37°C, with cytotoxicity measured either as increased leakage of lactate dehydrogenase or as a decreased energy status, as determined by decreased ratios of adenosine triphosphate (ATP) to adenosine diphosphate (ADP). Incubation atmospheres consisted of either 95% O₂/5% CO₂, to promote cell viability in vitro, or 5% O₂/5% CO₂/90% N₂. Preliminary studies with bovine serum albumin (BSA) added to the incubation media indicated a lack of toxicity for HQ or its metabolites. For the tests discussed in this report, incubations were performed without the addition of BSA. Under 95% O₂ atmospheres, PT cells from male Fischer F344 rats were significantly more sensitive to HQ than those from male Sprague-Dawley (SD) rats, with decreases in ATP to ADP ratios seen as early as 0.5 h at a concentration of 0.5 mM. When incubations were performed under a 5% O₂ atmosphere, 2-(cysteine-S-yl)hydroquinone (Cys-HQ) and HQ toxicities were observed later (3–4 h) in the incubation period, occurred at higher concentrations, were similar in magnitude for the two strains, and were greater for Cys-HQ than for HQ. These results show that variations in oxygen tension can dramatically influence the toxicity of HQ and its metabolites. The specific compounds tested that were cytotoxic at a physiologically relevant oxygen tension (5%) were (in decreasing order of potency): Cys-HQ>2-(glutathion-S-yl)hydroquinone>HQ. These results support an association of toxicity with metabolism through the glutathione pathway, with ultimate toxicity associated with the cysteinyl conjugate. Biochemical characteristics of PT cells from these two strains suggest a significantly greater capacity of cells from the SD rat to respond to oxidative stress.     

Genotoxic and cytotoxic effects of doxycycline in cultured human peripheral blood lymphocytes

Doxycycline (DOX) is a broad-spectrum tetracycline antibiotic used in the treatment of many infections. In this study, the genotoxic and cytotoxic effects of DOX in cultured human peripheral blood lymphocytes were investigated by measuring chromosome aberrations (CAs), cytokinesis-block micronucleus (CBMN) assay, mitotic index (MI), and nuclear division index (NDI). Cultures were treated with DOX at three concentrations (2, 4, and 6 μg/mL) for 48 hours. Mitomycin C (MMC) was used as a positive control. All the tested concentrations of DOX for MI and the higher concentrations (4 and 6 μg/mL) for NDI significantly decreased mitotic activity. However, there are no significant differences between negative control and all the tested concentrations of DOX for CA and MN frequencies. In conclusion, our results indicate that DOX has a cytotoxic effect, but not a genotoxic effect, on human peripheral blood lymphocyte cultures. Further detailed studies, especially about the cell-cycle kinetics of DOX, are required to elucidate the decreases in dividing cells and make a possible risk assessment on cells of patients receiving therapy with this drug. Further, if the specific cytostatic and cytotoxic potential of DOX to different types of cancer cells is investigated in detail, it may also have been used as an antitumoral drug.     

Genotoxic and cytotoxic effects of doxycycline in cultured human peripheral blood lymphocytes

Doxycycline (DOX) is a broad-spectrum tetracycline antibiotic used in the treatment of many infections. In this study, the genotoxic and cytotoxic effects of DOX in cultured human peripheral blood lymphocytes were investigated by measuring chromosome aberrations (CAs), cytokinesis-block micronucleus (CBMN) assay, mitotic index (MI), and nuclear division index (NDI). Cultures were treated with DOX at three concentrations (2, 4, and 6 µg/mL) for 48 hours. Mitomycin C (MMC) was used as a positive control. All the tested concentrations of DOX for MI and the higher concentrations (4 and 6 µg/mL) for NDI significantly decreased mitotic activity. However, there are no significant differences between negative control and all the tested concentrations of DOX for CA and MN frequencies. In conclusion, our results indicate that DOX has a cytotoxic effect, but not a genotoxic effect, on human peripheral blood lymphocyte cultures. Further detailed studies, especially about the cell-cycle kinetics of DOX, are required to elucidate the decreases in dividing cells and make a possible risk assessment on cells of patients receiving therapy with this drug. Further, if the specific cytostatic and cytotoxic potential of DOX to different types of cancer cells is investigated in detail, it may also have been used as an antitumoral drug.     

Genotoxic and antiapoptotic effect of nicotine on human gingival fibroblasts.

Growing evidence suggests that nicotine, the addictive component of cigarettes, can have a direct role in tumor development by enhancing cell proliferation and impairing apoptotic process in certain types of human cancer cell lines. Since the correlation between apoptosis and DNA damage is already well documented, we investigated the response of human gingival fibroblasts (HGFs) to nicotine exposure by examining its effect on DNA damage induction and apoptotic process in parallel. To assess the genotoxicity of this drug, the cytokinesis-block micronucleus (CBMN) test was performed. Treatment of HGFs with nicotine, at a concentration of 1 microM, caused a statistically significant increase of micronucleus (MN) frequency at the tested time intervals, while no change was detected in cell growth under the same conditions. Furthermore, we found that preincubation of HGFs with 1 microM nicotine strongly attenuated staurosporine (STP)-induced apoptosis. Finally, we found that cultures exposed to nicotine showed an increase of reactive oxygen species, as determined by increased levels of 2,7-dichlorofluorescein (DCF). When cells were prelabeled with N-acetyl-cysteine (NAC), a substrate for glutathione synthesis, and catalase (CAT), the oxygen free radical scavenger, a significant reduction in cytogenetic damage was observed. Thus, for the first time, we report a concomitant genotoxic and antiapoptotic effect of nicotine in HGFs.     

Lack of clastogenic effects in cultured human lymphocytes treated with hydroquinone.

Hydroquinone (HQ) occurs in the environment as a result of manmade processes as well as in natural products from plants and animals. The compound has been reported to produce chromosomal effects in some in vivo and in vitro animal models. However, its potential to produce similar effects in human lymphocytes is less clear. To obtain more information on the clastogenic potential of HQ in human cells, its ability to induce structural chromosomal aberrations in human lymphocytes in vitro has been examined, both in the absence and presence of exogenous metabolic activation. Moreover, the effect of HQ pre-incubation on peroxide induced clastogenicity was studied, because HQ has putative chemopreventive activity as well. It was found that HQ was cytotoxic, but did not induce chromosomal aberrations in human lymphocytes cultured in vitro. Additionally, it was observed that pre-incubation of lymphocytes with HQ resulted in a concentration dependent reduction of the H2O2 induced chromosomal aberrations (P=0.069). However, this effect was present at 12 mM H2O2 only, because of high cytotoxicity at higher dosages.     

Genotoxic and mutagenic studies of teratogens in developing rat and mouse

In this review, genotoxic and mutagenic effects of teratogenic chemical agents in both rat and mouse have been reviewed. Of these chemicals, 97 are drugs and 33 are pesticides or belong to other groups. Large literature searches were conducted to determine the effects of chemicals on chromosome abnormalities, sister chromatid exchanges, and micronucleus formation in experimental animals such as rats and mice. In addition, studies that include unscheduled DNA synthesis, DNA adduct formations, and gene mutations, which help to determine the genotoxicity or mutagenicity of chemicals, have been reviewed. It has been estimated that 46.87% of teratogenic drugs and 48.48% of teratogenic pesticides are positive in all tests. So, all of the teratogens involved in this group have genotoxic and mutagenic effects. On the other hand, 36.45% of the drugs and 21.21% of the pesticides have been found to give negative results in at least one test, with the majority of the tests giving positive results. However, only 4.16% of the drugs and 18.18% of the pesticides were determined to give negative results in the majority of the tests. Among tests with major negative results, 12.50% of the teratogenic drugs and 12.12% of the teratogenic pesticides were negative in all conducted tests.     

Genotoxic effects of acrylamide and glycidamide in mouse lymphoma cells.

In addition to occupational exposures to acrylamide (AA), concerns about AA health risks for the general population have been recently raised due to the finding of AA in food. In this study, we evaluated the genotoxicity of AA and its metabolite glycidamide (GA) in L5178Y/Tk(+/-) mouse lymphoma cells. The cells were treated with 2-18 mM of AA or 0.125-4 mM of GA for 4 h without metabolic activation. The DNA adducts, mutant frequencies and the types of mutations for the treated cells were examined. Within the dose range tested, GA induced DNA adducts of adenine and guanine [N3-(2-carbamoyl-2-hydroxyethyl)-adenine and N7-(2-carbamoyl-2-hydroxyethyl)-guanine] in a linear dose-dependent manner. The levels of guanine adducts were consistently about 60-fold higher across the dose range than those of adenine. In contrast, no GA-derived DNA adducts were found in the cells treated with any concentrations of AA, consistent with a lack of metabolic conversion of AA to GA. However, the mutant frequency was significantly increased by AA at concentrations of 12 mM and higher. GA was mutagenic starting with the 2mM dose, suggesting that GA is much more mutagenic than AA. The mutant frequencies were increased with increasing concentrations of AA and GA, mainly due to an increase of proportion of small colony mutants. To elucidate the underlying mutagenic mechanism, we examined the loss of heterozygosity (LOH) at four microsatellite loci spanning the entire chromosome 11 for mutants induced by AA or GA. Compared to GA induced mutations, AA induced more mutants whose LOH extended to D11Mit22 and D11Mit74, an alteration of DNA larger than half of the chromosome. Statistical analysis of the mutational spectra revealed a significant difference between the types of mutations induced by AA and GA treatments (P=0.018). These results suggest that although both AA and GA generate mutations through a clastogenic mode of action in mouse lymphoma cells, GA induces mutations via a DNA adduct mechanism whereas AA induces mutations by a mechanism not involving the formation of GA adducts.     

Protective effect of dieckol against chemical hypoxia-induced cytotoxicity in primary cultured mouse hepatocytes

Hepatic ischemic injury is a major complication arising from liver surgery, transplantation, or other ischemic diseases, and both reactive oxygen species (ROS) and pro-inflammatory mediators play the role of key mediators in hepatic ischemic injury. In this study, we examined the effect of dieckol in chemical hypoxia-induced injury in mouse hepatocytes. Cell viability was significantly decreased after treatment with cobalt chloride (CoCl₂), a well-known hypoxia mimetic agent in a time- and dose-dependent manner. Pretreatment with dieckol before exposure to CoCl₂ significantly attenuated the CoCl₂-induced decrease of cell viability. Additionally, pretreatment with dieckol potentiated the CoCl₂-induced decrease of Bcl-2 expression and attenuated the CoCl₂-induced increase in the expression of Bax and caspase-3. Treatment with CoCl₂ resulted in an increased intracellular ROS generation, which is inhibited by dieckol or N-acetyl cysteine (NAC, a ROS scavenger), and p38 MAPK phosphorylation, which is also blocked by dieckol or NAC. In addition, dieckol and SB203580 (p38 MAPK inhibitor) increased the CoCl₂-induced decrease of Bcl-2 expression and decreased the CoCl₂-induced increase of Bax and caspase-3 expressions. CoCl₂-induced decrease of cell viability was attenuated by pretreatment with dieckol, NAC, and SB203580. Furthermore, dieckol attenuated CoCl₂-induced COX-2 expression. Similar to the effect of dieckol, NAC also blocked CoCl₂-induced COX-2 expression. Additionally, CoCl₂-induced decrease of cell viability was attenuated not only by dieckol and NAC but also by NS-398 (a selective COX-2 inhibitor). In conclusion, dieckol protects primary cultured mouse hepatocytes against CoCl₂-induced cell injury through inhibition of ROS-activated p38 MAPK and COX-2 pathway.     

Genotoxic effect of lead nitrate on mice using SCGE (comet assay)

Single stranded DNA breakage induced by lead nitrate in mice has been studied in vivo using alkaline single cell gel electrophoresis (comet assay). Mice were administered orally 0.7, 1.4, 2.8, 5.6, 11. 2, 22.4, 44.8 and 89.6 mg/kg body weight of lead nitrate and the assay was performed on whole blood at 24, 48, 72 h, 1st and 2nd week. Significant increase in mean tail-length of DNA was observed at all time intervals after treatment with lead nitrate when compared to controls. The mean tail-length did not show a dose-related increase and the elevation in the mean tail-length was of a fluctuating type. Increase in mean tail-lengths clearly gives evidence that lead nitrate causes DNA damage effectively. The study indicates that the alkaline comet assay is a sensitive and rapid method to detect DNA damage caused by heavy metals.     

The pro-apoptotic effect of hydroquinone in human neutrophils and eosinophils

Hydroquinone (HQ) is a benzene metabolite that is involved in hematopoiesis via its accumulation into bone marrow. HQ also acts as a toxic agent that influences various immune responses. Both neutrophils and eosinophils function as important leukocytes in immunological regulation and immune diseases. In this study, we examined the toxic effects of HQ on the apoptosis of human neutrophils and eosinophils isolated from the blood of healthy donors. HQ markedly increased the apoptosis of neutrophils and eosinophils in a concentration- and a time-dependent manner. The pro-apoptotic effect is involved in activation of caspase 9 and caspase 3. Reactive oxygen species (ROS) production was enhanced after HQ treatment in a dose-dependent manner. In addition, HQ upregulated the release of IL-8 and MCP-1 from neutrophils and eosinophils, respectively. Taken together, the results of this study demonstrated that HQ strongly induces the apoptosis of neutrophils and eosinophils through the caspase 9/3-dependent pathway and the increased ROS production. HQ exerts a cytotoxic effect in human neutrophils and eosinophils and may impair the regulation of immune responses.     

Characterizing the ovotoxicity of cyclophosphamide metabolites on cultured mouse ovaries.

Cyclophosphamide (CPA) is reported to target dormant primordial ovarian follicles in rodents and humans. However, mechanistic studies are complicated due to the complex ovarian structure. We present here the characterization of the sensitivity of ovaries to CPA metabolites and the timing of morphological alterations induced by phosphoramide mustard (PM) in an in vitro system. Intact mouse ovaries (postnatal-day-4) were cultured in vitro and exposed to multiple breakdown products of CPA on day 0 (d0). Tissues were cultured up to d8, and then follicle counts and immunohistochemistry were performed. 4-Hydroperoxy-CPA (4-HC), a precursor of an activated form of CPA, and PM depleted primordial and primary follicles (> or =1 microM and > or =3 microM, respectively, p < 0.05); acrolein had effects on follicle numbers only under continuous exposure (> =30 microM); carboxycyclophosphamide and 4-ketocyclophosphamide reduced primordial and small primary follicles only at high concentrations (100 microM). PM-induced follicle loss became significant (p < 0.05) by d1 or d2 following exposures to 10 microM or 3 microM PM, respectively, as determined by the numbers of pyknotic or TUNEL-positive follicles. Cellular targets were oocytes in the smallest follicles, but granulosa cells in large primary follicles. TUNEL staining was observed in both cell types, but caspase-3, a marker of apoptosis, was absent from primordial follicles. In addition, a pan-caspase inhibitor could not prevent follicle losses when administered prior to PM. Thus, brief exposures to 4-HC or PM are sufficient to induce permanent follicle loss in ovaries, and PM is likely the ultimate ovotoxicant. Furthermore, the cell death pathway is likely caspase-independent.     

Some effects of lignocaine on cultured mouse peritoneal macrophages

Macrophages were exposed to lignocaine in perifused and non-perifused cultures using media with or without foetal calf serum. Effects on morphology, viability, phagocytosis and the release of enzymes were assessed. During the period of contact with lignocaine there was a selective release of beta-glucuronidase. After washing, enzyme release continued over a period of 7 hours and, in the absence of foetal calf serum, a decrease in the total beta-glucuronidase content was found in non-perifused cultures. Although lignocaine-treated cells phagocytosed particulates the rate of enzyme release was reduced compared with normal cells when subsequently exposed to quartz.     

Genotoxic effect of monocrotophos to sentinel species using comet assay.

Monocrotophos is the single largest selling agrochemical in India. Sensitive biomarkers to study the genotoxic effects caused by monocrotophos in aquatic organisms, especially fish, are lacking. The fish used in this study are Tilapia mossambica, which are edible, commercially valuable and distributed all over India. The objective of this study was to study DNA strand breaks induced by monocrotophos in T. mossambica in vivo using single-cell micro gel electrophoresis/comet assay. Tilapia were treated orally with 0.313, 0.625, 1.25, 1.875, 2.5, 3.125, 3.75 and 4.375 ppm of monocrotophos and the assay was performed on nucleated erythrocytes after 24, 48, 72 and 96 h. A significant increase in mean comet tail-length (5.21-7.46 microM), indicating DNA damage, was observed at all the doses with monocrotophos when compared to controls (3.36 microM). The mean tail-length showed a dose-related increase and time-dependent decrease. The maximum increase in mean comet tail-length was observed at 24 h. Relative to these effects, reductions in mean comet tail-length were seen at 48 and 72 h. By 96 h, values had returned to control levels at all doses, indicating repair of the damaged DNA and/or loss of heavily damaged cells. The study reveals that the comet assay is a sensitive and rapid method to detect genotoxicity of monocrotophos and other environmental pollutants in sentinel species.