Cell-cycle analysis and micronuclei frequency reveals G0/G1 blockers as weak micronuclei inducers

Micronuclei (MN) formation is generally attributed to error in DNA synthesis or mitosis, which are represented by the S or G₂/M phase respectively, in the cell-cycle histogram. Interestingly, many of the known anticancer drugs target these cell-cycle phases to elicit cytotoxicity. Here, we attempted to identify whether any correlation exists between the cell-cycle effect and MN induction potential using various treatments. In addition, we tracked down MN in cycling cells to assess its final fate. We treated SiHa cells with various known drugs and correlated their effects on cell-cycle and MN frequency. MN-tracking studies were performed in peripheral mononuclear and siHa cells upon staining with Giemsa and ethidium bromide respectively. We observed MN induction by all the tested drugs irrespective of their basic effect on cell cycle. However, MN induction was more with drugs which interfere with the S or G₂/M than the G₀/G₁ phase. Our results indicate G₀/G₁ blockers to be comparatively safer drugs. Additionally, our results show that expulsion out of cells may be one of the main fates of drug-induced MN.     

灵芝茶抗辐射损伤作用研究

目的：探讨灵芝茶抑制辐射损伤作用。方法：选用小鼠进行灵芝茶抗辐射试验，结果显示，灵芝茶各试验组动物的骨髓微核率明显低于辐射对照组（P＜0．01），12．0g/kg.bw,18.0g/kg.bw灵芝茶试验组动物血中超氧化物歧化酶（SOD）活性的6．0g/kg.bw组动物平均存活时间明显高于辐射对照组（P＜0．01），表明灵芝茶具有一定的抗辐射损伤作用。     

Nutritional,biochemical and cytogenotoxicity studies on wasted fat released from chicken during grilling process

Some physico–chemical properties of fat released from chicken during grilling process were evaluated and the results showed that refractive index and saponification values were not affected by grilling process. However, serious increases in oxidative deterioration parameters and color were noticed. The main objective of this study was to characterize the effect of grilled fat on body weight, liver function, chromosomal aberrations and micronucleus formation in rats. Eight-week-old Swiss male albino rats, weighing approximately 90 g were used in this study. Rats were fed on a diet containing grilled fat for two months showed insignificant decrease in body weight compared to the control except, the eighth week (last weighing). The serum analysis should that aspartate transaminase (AST), cholesterol, creatinine and urea levels increased significantly whereas, alanine transaminase (ALT), and triglyceride levels were not affected. Also, cytogenetic analysis showed various types of chromosomal aberrations, i.e., chromatide breaks, ring chromosome, fragment chromosome, and end to end association chromosomes and insignificant increase in the frequency of micronucleated cells.     

Patulin-induced genotoxicity and modulation of glutathione in HepG2 cells

Patulin (PAT), a mycotoxin produced by certain species of Penicillium, Aspergillus and Byssochlamys, is mainly found in ripe apple and apple products. In our present study, a significant increase of the micronuclei frequency induced by PAT was found in human hepatoma HepG2 cells. To elucidate the role of glutathione (GSH) in the effect, the intracellular GSH level was modulated by pre-treatment with buthionine-(S, R)-sulfoximine (BSO), a specific GSH synthesis inhibitor, and by pre-treatment with N-acetylcysteine (NAC), a GSH precursor. It was found that depletion of GSH in HepG2 cells with BSO dramatically increased the PAT-induced micronuclei frequencies and that when the intracellular GSH content was elevated by NAC, the chromosome damage induced by PAT was significantly prevented in our test concentrations (0.19-0.75 μM). These results indicate that GSH play an important role in cellular defense against PAT-induced genotoxicity.     

达美康的降脂与致突变实验

本文报道了用小白鼠对降血糖药达美康降脂效应的研究结果。实验证明达美康具有非常显著的降脂效应。致突变试验表明,微核试验及Ames试验均为阴性。     

4-Methylbenzophenone and benzophenone are inactive in the micronucleus assay

Many materials in contact with food, including printing inks, the lack of deeper knowledge about possible toxic effects is a problem. Furthermore, some of these substances are not only produced for packaging of foods, they are produced for a variety of purposes and are not meant to come into direct contact with foodstuffs. Two examples on such chemicals in printing inks are benzophenone and 4-methylbenzophenone. Recently, authorities reported that high levels of the photoinitiator 4-methylbenzophenone had been detected in cereal products. Based on this information we have studied 4-methylbenzophenone and the chemically similar benzophenone using the micronucleus assay in vivo and in vitro. To increase the sensitivity we have used the in vivo flow cytomer-based micronucleus assay in mouse.Although doses up to lethality were used and an average of hundred thousand young erythrocytes, polychromatic erythrocytes, analysed from each animal, no genotoxic effect occurred. The 4-methylbenzophenone was also analysed in the in vitro micronucleus assay, using human lymphocytes. The result does not show any dose-related effect.These results show that the occurrence of 4-methylbenzophenone that so far has been detected in foodstuff does not increase the cancer risk through chromosome breaks or mal-distribution of chromosomes.     

Genotoxic evaluation of pirfenidone using erythrocyte rodent micronucleus assay

Pirfenidone is a non-steroidal antifibrotic compound that has been proposed in clinical protocols and experimental studies as a pharmacological treatment for fibroproliferative diseases. The objective of this study was to determine the genotoxicity or cytotoxicity of three doses of pirfenidone using the micronuclei test in peripheral blood erythrocytes of rodent models. Pirfenidone was administered orally to Balb-C mice for 3 days, and also was administered topically to hairless Sprague Dawley rats during the final stage of gestation. Mice were sampled every 24 h over the course of 6 days; pregnant rats were sampled every 24 h during the last 6 days of gestation, and pups were sampled at birth. Blood smears were analyzed and the frequencies of micronucleated erythrocytes (MNEs), micronucleated polychromatic erythrocytes (MNPCEs), and the proportion of polychromatic erythrocytes (PCEs), were recorded in samples from mice, pregnant rats and rat neonates. Increases in MN frequencies (p < 0.03) were noted only in the positive control groups. No genotoxic effects or decreased PCE values were observed neither in newborn rats transplacentally exposed to pirfenidone, or in two adult rodent models when pirfenidone was administered orally or topically.     

宫颈癌放疗细胞遗传学损伤的生物标志物及剂量-反应关系

目的：探讨子宫颈癌患者hprt基因突变率、微核率和姐妹染色单体交换SCE率的自发水平及放疗后变化,评估电离辐射诱发的染色体损伤。方法：取25例宫颈鳞癌患者放疗前与放疗中外周静脉血,多核细胞法测hprt突变率,胞质分裂阻滞法测微核率,姐妹染色单体交换试验测姐妹染色单体交换率。正常对照组共25例,来自健康查体者。结果：（1）子宫颈癌患者自发hprt基因突变率、微核率、姐妹染色单体交换率均高于健康人（P均〈0．05）。（2）hprt突变率在放疗后升高,40Gy时达最高峰,40Gy后稍下降,差别有显著性（P〈O．05）,呈剂量-反应关系（r=0．620,P〈0．01）。（3）微核率在放疔后逐渐升高并呈线性关系（r=0．827,P〈0．01）。（4）各累积剂量组SCE率均高于治疗前,差异有统计学意义（P均〈0．05）,但无明显的线性关系。结论：在一定的放射剂量范围内,外周血淋巴细胞hprt突变率、微核率与姐妹染色单体交换率是评估放射损伤的有效生物指标。     

Evaluation of the in vitro and in vivo genotoxicity of magnolia bark extract

Magnolia bark extract (MBE) is an extract of the dried stem, root, or branch bark of magnolia trees that has been used historically in traditional Chinese and Japanese medicines, and more recently as a component of dietary supplements and cosmetic products. To study the genotoxic potential of MBE, a bacterial reverse mutation assay and an in vivo micronucleus test were conducted. Compositional analysis of the test substance revealed that MBE contains 94% magnolol and 1.5% honokiol. MBE exerted no mutagenic activity in various bacterial strains of Salmonella typhimurium and in Escherichia coli WP2 uvrA, either in the absence or presence of metabolic activation at all doses tested. In the micronucleus test, various doses of MBE did not affect the proportions of immature to total erythrocytes, nor did it increase the number of micronuclei in the immature erythrocytes of Swiss albino mice. The results of these studies demonstrate that MBE is not genotoxic under the conditions of the in vitro bacterial reverse mutation assay and the in vivo micronucleus test, and support the safety of MBE for dietary consumption.     

The cyto- and genotoxicity of organotin compounds is dependent on the cellular uptake capability

Organotin compounds have been widely used as stabilizers and anti-fouling agents with the result that they are ubiquitously distributed in the environment. Organotins accumulate in the food chain and potential effects on human health are disquieting. It is not known as yet whether cell surface adsorption or accumulation within the cell, or indeed both is a prerequisite for the toxicity of organotin compounds. In this study, the alkylated tin derivatives monomethyltin trichloride (MMT), dimethyltin dichloride (DMT), trimethyltin chloride (TMT) and tetramethyltin (TetraMT) were investigated for cyto- and genotoxic effects in CHO-9 cells in relation to the cellular uptake. To identify genotoxic effects, induction of micronuclei (MN), chromosome aberrations (CA) and sister chromatid exchanges (SCE) were analyzed and the nuclear division index (NDI) was calculated. The cellular uptake was assessed using ICP-MS analysis. The toxicity of the tin compounds was also evaluated after forced uptake by electroporation. Our results show that uptake of the organotin compounds was generally low but dose-dependent. Only weak genotoxic effects were observed after exposure of cells to DMT and TMT. MMT and TetraMT were negative in the test systems. After forced uptake by electroporation MMT, DMT and TMT induced significant DNA damage at non-cytotoxic concentrations. The results presented here indicate a considerable toxicological potential of some organotin species but demonstrate clearly that the toxicity is modulated by the cellular uptake capability.