Maternally acquired genotoxic Escherichia coli alters offspring’s intestinal homeostasis

The neonatal gut is rapidly colonized by a newly dominant group of commensal Escherichia coli strains among which a large proportion produces a genotoxin called colibactin. In order to analyze the short- and long-term effects resulting from such evolution, we developed a rat model mimicking the natural transmission of E. coli from mothers to neonates. Genotoxic and non-genotoxic E. coli strains were equally transmitted to the offspring and stably colonized the gut across generations. DNA damage was only detected in neonates colonized with genotoxic E. coli strains. Signs of genotoxic stress such as anaphase bridges, higher occurrence of crypt fission and accelerated renewal of the mature epithelium were detected at adulthood. In addition, we observed alterations of secretory cell populations and gut epithelial barrier. Our findings illustrate how critical is the genotype of E. coli strains acquired at birth for gut homeostasis at adulthood.     

Radioprotective Effect of Achillea millefolium L Against Genotoxicity Induced by Ionizing Radiation in Human Normal Lymphocytes

The radioprotective effect of Achillea millefolium L (ACM) extract was investigated against genotoxicity induced by ionizing radiation (IR) in human lymphocytes. Peripheral blood samples were collected from human volunteers and incubated with the methanolic extract of ACM at different concentrations (10, 50, 100, and 200 μg/mL) for 2 hours. At each dose point, the whole blood was exposed in vitro to 2.5 Gy of X-ray and then the lymphocytes were cultured with mitogenic stimulation to determine the micronuclei in cytokinesis-blocked binucleated cell. Antioxidant capacity of the extract was determined using free radical-scavenging method. The treatment of lymphocytes with the extract showed a significant decrease in the incidence of micronuclei binucleated cells, as compared with similarly irradiated lymphocytes without any extract treatment. The maximum protection and decrease in frequency of micronuclei were observed at 200 μg/mL of ACM extract which completely protected genotoxicity induced by IR in human lymphocytes. Achillea millefolium extract exhibited concentration-dependent radical-scavenging activity on 1,1-diphenyl-2-picryl hydrazyl free radicals. These data suggest that the methanolic extract of ACM may play an important role in the protection of normal tissues against genetic damage induced by IR.     

Genotoxic and oxidative responses in coelomocytes of Eisenia fetida and Hediste diversicolor exposed to lipid‐coated CdSe/ZnS quantum dots and CdCl2

The emerging of Quantum Dots utilization in industrial or medicinal fields involved a potentially increase of these nanoparticles in environment. In this work, the genotoxic (comet assay) and oxidative effects (SOD activity, TBARS) of functionalized‐QDs and cadmium chloride were investigated on Hediste diversicolor and Eisenia fetida coelomocytes. Results demonstrated that functionalized‐QDs (QDNs) and cadmium chloride induced DNA damages through different mechanisms that depended on the nano‐ or ionic nature of Cd. The minimal genotoxic concentrations for H. diversicolor (<0.001ng/g for QDNs and CdCl₂) were lower than for E. fetida (between 0.01 and 0.1 ng/g for QDNs, and between 0.001 and 0.01 ng/g for CdCl₂). These results showed that H. diversicolor was more sensitive than E. fetida. The two contaminants had a low impact on the oxidative stress markers. © 2014 Wiley Periodicals, Inc. Environ Toxicol 30: 918–926, 2015.     

Single-Dose Toxicity of Individual and Combined Sterigmatocystin and 5-Methoxysterigmatocistin in Rat Lungs

Sterigmatocystin (STC) and 5-methoxysterigmatocystin (5-M-STC) are mycotoxins produced by common damp indoor Aspergilli series Versicolores. Since both STC and 5-M-STC were found in the dust of indoor occupational and living areas, their occupants may be exposed to these mycotoxins, primarily by inhalation. Thus, STC and 5-M-STC were intratracheally instilled in male Wistar rats using doses (0.3 mg STC/kg of lung weight (l.w.); 3.6 mg 5-M-STC/kg l.w.; toxin combination 0.3 + 3.6 mg/kg l.w.) that corresponded to concentrations detected in the dust of damp indoor areas in order to explore cytotoxicity, vascular permeability, immunomodulation and genotoxicity. Single mycotoxins and their combinations insignificantly altered lactate-dehydrogenase activity, albumin, interleukin-6, tumor necrosis factor-α and chemokine macrophage inflammatory protein-1α concentrations, as measured by ELISA in bronchioalveolar lavage fluid upon 24 h of treatment. In an alkaline comet assay, both mycotoxins provoked a similar intensity of DNA damage in rat lungs, while in a neutral comet assay, only 5-M-STC evoked significant DNA damage. Hence, naturally occurring concentrations of individual STC may induce DNA damage in rat lungs, in which single DNA strand breaks prevail, while 5-M-STC was more responsible for double-strand breaks. In both versions of the comet assay treatment with STC + 5-M-STC, less DNA damage intensity occurred compared to single mycotoxin treatment, suggesting an antagonistic genotoxic action.     

益母草碱对胚胎-胎仔发育毒性和遗传毒性的评价

目的 检测益母草碱的发育毒性和遗传毒性。方法 在SD孕鼠妊娠第6~15天经口灌胃给予500、1 000和2 000 mg/kg体重的益母草碱,同时设溶媒对照组,经口灌胃0.5% CMC-Na溶液。妊娠第20天剖杀孕鼠,分析其生殖毒性。分别采用反映基因突变的鼠伤寒沙门菌回复突变试验（Ames试验）、反映染色体畸变的细胞染色体畸变试验（体外培养CHO）和ICR小鼠骨髓微核试验（体内）检测益母草碱的遗传毒性。结果 在500、1 000和2 000 mg/kg剂量益母草碱的作用下孕鼠的增重与对照组相比,差异均无统计学意义;各受试剂量组孕鼠各项指标与对照组相比,差异均无统计学意义;各剂量组胎鼠各类指标与溶媒对照组相比,无明显差异。Ames试验结果提示：在0.5、5、50、500、5 000 μg/皿受试剂量下,在有或无代谢活化S9系统时,与溶媒对照组相比,受试物对组氨酸缺陷型鼠伤寒沙门菌（TA97、TA98、TA100、TA102及TA1535）所诱发的回复突变菌落数均相近。染色体畸变试验结果显示：250、500和1 000 μg/ml 3个剂量的受试物,对有或无代谢活化系统S9培养的CHO细胞的染色体畸变率无明显影响。微核试验显示100、500和2 000 mg/kg各个剂量组对ICR小鼠的微核诱发率与溶媒对照组比较均无显著差异（P>0.05）。结论 益母草碱在500、1 000和2 000 mg/kg剂量下未观察到明显的母体毒性、胚胎毒性、胎儿毒性和致畸作用。益母草碱对鼠伤寒沙门菌无致突变性,对哺乳动物培养细胞的染色体无致畸变作用,对ICR小鼠无诱发骨髓嗜多染红细胞微核的效应。上述结果表明在本试验条件下,益母草碱无发育和遗传毒性。     

Assessment of 5‐fluorouracil and 4‐nitroquinoline‐1‐oxide in vivo genotoxicity with Pig‐a mutation and micronucleus endpoints

Genotoxicity assessments were conducted on male Sprague Dawley rats treated with 5‐fluorouracil (5‐FU) and 4‐nitroquinoline‐1–oxide (4NQO) as part of an international validation trial of the Pig‐a mutant phenotype assay. Rats were orally exposed to 0, 11.5, 23, or 46 mg/kg/day 5‐FU for three consecutive days (Days 1–3); blood was sampled on Days ?1, 4, 15, 29, and 45. Pig‐a mutant phenotype reticulocyte (RET^CD59?) and mutant phenotype erythrocyte (RBC^CD59?) frequencies were determined on Days ?1, 15, 29, and 45, and percent micronucleated reticulocytes (%MN‐RET) were measured on Day 4. Rats were treated with 4NQO for 28 consecutive days by oral gavage, at doses of 1.5, 3, or 6 mg/kg/day. RBC^CD59? and RET^CD59? frequencies were determined on Days ?1, 15, and 29, and MN‐RET were quantified on Day 29. Whereas 5‐FU was found to increase %MN‐RET, no significant increases were observed for RBC^CD59? or RET^CD59? at any of the time points studied. The high dose of 4NQO (6 mg/kg/day) was observed to markedly increase RBC^CD59? and RET^CD59? frequencies, and this same dose level caused a weak but significantly elevated increase in MN‐RET (approximately twofold). Collectively, the results provide additional support for the combination of Pig‐a mutation and MN‐RET into acute and 28‐day repeat‐dose studies. Environ. Mol. Mutagen. 55:735–740, 2014. © 2014 Wiley Periodicals, Inc.     

Nanoscale zerovalent iron particles induce differential cytotoxicity,genotoxicity, oxidative stress and hemolytic responses in human lymphocytes and erythrocytes in vitro

The growing usage of nanoscale zerovalent iron particles (nZVI) in the remediation of soil, ground/surface water has elicited large‐scale environmental release triggering human exposure. The size of nanomaterials is a key regulator of toxicity. However, the effect of a variable size of nZVI on genotoxicity is unexplored in human cells. To the best of our knowledge, in this study, the cytotoxic, genotoxic and hemolytic potential of nZVI‐1 (15 nm) and nZVI‐2 (50 nm) at concentrations of 5, 10 and 20 μg/mL was evaluated for the first time in human lymphocytes and erythrocytes treated for 3 hours. In erythrocytes, spherocytosis and echinocytosis occurred upon exposure to nZVI‐1 and nZVI‐2, respectively, leading to hemolysis. Lymphocytes treated with 20 μg/mL nZVI‐2 and 10 μg/mL nZVI‐1, incurred maximum DNA damage, although nZVI‐2 induced higher cyto‐genotoxicity than nZVI‐1. This can be attributed to higher Fe ion dissolution and time/concentration‐dependent colloidal destabilization (lower zeta potential) of nZVI‐2. Although nZVI‐1 showed higher uptake, its lower genotoxicity can be due to lesser Fe content, Fe ion dissolution and superior colloidal stability (higher zeta potential) compared with nZVI‐2. Substantial accumulation of Ca²⁺, superoxide anions, hydroxyl radicals and H₂O₂ leading to mitochondrial impairment and altered antioxidant enzyme activity was noted at the same concentrations. Pre‐treatment with N‐acetyl‐cysteine modulated these parameters indicating the indirect action of reactive oxygen species in nZVI‐induced DNA damage. The morphology of diffused nuclei implied the possible onset of apoptotic cell death. These results validate the synergistic role of size, ion dissolution, colloidal stability and reactive oxygen species on cyto‐genotoxicity of nZVI and unlock further prospects in its environmental nano‐safety evaluation.     

Induction of hepatocellular carcinoma by in vivo gene targeting

The distinct phenotypic and prognostic subclasses of human hepatocellular carcinoma (HCC) are difficult to reproduce in animal experiments. Here we have used in vivo gene targeting to insert an enhancer-promoter element at an imprinted chromosome 12 locus in mice, thereby converting ～1 in 20,000 normal hepatocytes into a focus of HCC with a single genetic modification. A 300-kb chromosomal domain containing multiple mRNAs, snoRNAs, and microRNAs was activated surrounding the integration site. An identical domain was activated at the syntenic locus in a specific molecular subclass of spontaneous human HCCs with a similar histological phenotype, which was associated with partial loss of DNA methylation. These findings demonstrate the accuracy of in vivo gene targeting in modeling human cancer and suggest future applications in studying various tumors in diverse animal species. In addition, similar insertion events produced by randomly integrating vectors could be a concern for liver-directed human gene therapy.