Teratogenesis, carcinogenesis, and mutagenesis最新文献

Thalassaemia is a heterogeneous group of inherited anaemias, characterised by a reduction or total absence of one or more of the globin chains of haemoglobin. Individuals with thalassaemia major require regular blood transfusions in order to maintain their haemoglobin concentration at an appropriate level. An essential treatment in parallel with transfusions is iron chelation therapy to remove excess iron deposited in tissues from the transfused blood. The high iron levels in these patients make free oxygen radicals accessible, for example, through Fenton-type chemistry, and generate superoxide and hydroxyl radicals. Increased oxygen radical capacity is known to be associated with cancer and ageing. In a previous study, it has been shown that peripheral blood lymphocytes isolated from a sickle/beta thal double heterozygote-sickle phenotype thalassaemia patient, who was not undergoing chelation therapy, showed increased sensitivity to the effects of oxygen radicals and iron salts by comparison with lymphocytes from normal controls. Furthermore, in a later study, this patient also showed increased sensitivity to the dietary food mutagen 3-amino-1-methyl-5H-pyridol(4,3-b)indole (Trp-P-2) when compared to the control. The present study, therefore, investigated whether the above observation could be duplicated using different food mutagens in different thalassaemia genotypes. The effect of the food mutagens 2-amino-2-methylimidazolo(4,5-f)quinolone (IQ) and 2-amino-1-methyl-6-phenylimidazol(4,5-b)pyridine (PhIP) on lymphocytes of three different thalassaemia patients, a beta-thalassaemia major, a beta-thalassaemia/Hb E, and an alpha-thalassaemia trait with a 3.7-kb deletion, who were not undergoing chelation therapy were investigated using the Comet assay. All three thalassaemia genotypes showed increased sensitivity to both IQ and PhIP in comparison to the control, although with PhIP at the highest two concentrations (50 and 75 microM) the differences monitored with the alpha-thalassaemia trait were found not to be statistically significant (P > 0.05).

In order to determine differences in repair after treatment with DNA damaging agents, normal and cancer cells were selected for analysis of single strand breaks and DNA crosslinks using the Comet assay. Normal human lymphocytes, human colorectal adenocarcinoma SW620 cells, lung carcinoma A549, and H460 cell lines were exposed to an ethylating agent (ethylmethane sulfonate [EMS]), and a cross-linking agent (mitomycin C [MMC]). Differences in repair profiles of DNA damage demonstrated using the comet assay were observed in human lymphocytes and tumour cell lines with both mutagens. Results were also indicative that MMC repair is concentration-dependent. It was also apparent that normal cells repair DNA damage more readily than tumour cells. Repair also varied between different cell lines. To investigate the mechanistic differences of these two chemicals, flow cytometry studies were undertaken in tumour cells, namely cell cycle analysis and frequency of micronuclei induction (FMN). A G2M phase block was clearly evident following treatment with EMS at all concentrations tested. With MMC, an initial arrest of cells in G2M was accompanied by a build-up in S-phase over longer exposure periods. Also, at the highest mutagen doses there were different patterns of micronuclei induction. Thus, using the mutagens with different mechanisms of action highlighted the differences in repair patterns between normal and tumour cells.

Vitamin C (l-ascorbic acid), an effective free radical scavenger present as ascorbate in most biological systems, is one of the most extensively studied antioxidant vitamins. Vitamin C acts as either a free radical scavenger or a pro-oxidant producing hydrogen peroxide and free radicals. The modulatory effect of L-ascorbic acid (AA) on Mitomycin C (MMC) induced chromosome damage has been evaluated in human peripheral blood lymphocytes in vitro. The effect of L-ascorbic acid, 200 microg/ml as 1- and 2-h pretreatment on the frequencies of the biomarkers micronuclei (MN), sister chromatid exchanges (SCEs), and chromosome aberrations (CA) induced by mitomycin C 0.1 and 0.2 microg/ml has been studied. AA pretreatment caused a statistically significant increase in MMC-induced MN and SCE frequencies for all treatment groups, but did not show an increase in induced chromosome aberrations compared to MMC treatment alone. Cell division delays caused by MMC was reversed in the presence of AA. Interindividual variability in MMC as well as AA plus MMC-induced MN, SCE, and CA frequencies were evident. Ascorbic acid potentiated MMC-induced chromosome damage in human lymphocytes in vitro. The potentiation observed has to be viewed in the light of metal ion catalysed autooxidation of AA in oxygenated media and the existence of an antioxidant system in vivo that inactivates oxyradicals before their interaction with DNA.

We have recently reported that the fluoroquinolone antibacterial DW-116 induces a significant developmental toxicity in rat. The present study was conducted to better understand the teratogenic effects of DW-116 at several developmental toxic doses in rats. DW-116 was orally administered to pregnant rats from gestational day (GD) 6 through 16 at dose levels of 0, 320, 400, and 500 mg/kg/day. All dams were subjected to caesarean section on GD 20 and their fetuses were examined for external, visceral, and skeletal abnormalities. At above 400 mg/kg, severe decreases in maternal body weight gain, food consumption, litter size, fetal weight and placental weight, and severe increases in resorption rate and fetal morphological alterations were observed. At 320 mg/kg, mild decreases in maternal body weight gain, food consumption, fetal weight and placental weight, and mild increases in fetal variations and retardations were observed. These results suggest that DW-116 is embryotoxic at above 320 mg/kg/day and is embryolethal and teratogenic at above 400 mg/kg in pregnant rats and that DW-116 is a selective developmental toxicant in rat conceptuses.

The human diet contains a variety of compounds that exhibit chemopreventive effects towards an array of xenobiotics. In the present study, the antigenotoxic potential of selected dietary constituents including Diallyl sulfide (DAS), Indole-3-carbinol (I3C), Curcumin (CUR), and Black tea polyphenols (BTP) has been evaluated in the Salmonella typhimurium reverse mutation and mammalian in vivo cytogenetic assays. In addition, the anticlastogenic effect of the above dietary constituents was identified towards Benzo(a)pyrene (BaP) and cyclophosphamide- (CP) induced cytogenetic damage in mouse bone marrow cells. The induction of BaP and CP induced chromosomal aberrations, micronuclei formation, and sister chromatid exchanges (SCEs) were found to be inhibited in a dose-dependent manner by DAS, I3C, CUR, and BTP. Thus the study reveals the antimutagenic potential of these dietary compounds towards BaP- and CP-induced genotoxicity in microbial and mammalian test systems.

In girls of adolescent age, primary amenorrhea is a major problem and it is often suspected as Turner syndrome (TS), with complete or partial absence of one of the two X chromosomes. The girls who are unable to menstruate are primarily investigated by the gynecologists with the help of a physical examination, sonogram of the pelvis, endocrinologic tests, and ultimately cytogenetic analysis. Chromosomal analyses have been carried out in 280 such cases that were referred from different parts of the country. The standard protocol for peripheral blood lymphocyte culture was followed for metaphase chromosome preparation and conventional analysis of G-banded chromosomes. A total of 29% cases were found to have some chromosomal abnormality, including TS and testicular feminization syndrome involving sex chromosomes. Amongst those with sex chromosomal anomaly, 34% had evidence of a 46,XY karyotype in phenotypic females and 51% had pure line 45,X or mosaic with normal XX or other aberrations in X. The classification of the TS group further showed the spectrum of variant TS in Indian adolescent girls who suffered from absence or delayed menarche to correspond well with the Belgian, Danish, or Russian population. However, it has been reported that only 1% of the pure line 45,X conception is viable, indicating the necessity of mosaicism with X or Y chromosome. It has been understood that conventional banding analysis is absolutely necessary for segregating the variant nature of TS. In addition, molecular genetic or molecular cytogenetic investigations can determine the nature of mosaicism. The present study further indicated the involvement of autosomes in causing improper sexual development in girls of adolescent age.

DNA microarray is a powerful tool for parallel detection of multiple target genes in biological systems. In this study, a low-density DNA microarray has been custom designed by using Pseudomonas stutzeri strain KC ORFs that are implicated in carbon tetrachloride degradation. PCR amplified strain KC probes of varying lengths were obtained using ORF-specific primers. Purified short probes (80-120 bp) and full-length amplicons were directly immobilized on gamma-aminosilane coated and superaldehyde trade mark glass substrates without any chemical modification. The full-length amplicons exhibited a much higher signal compared to the shorter probes upon hybridization with the Cy5/Cy3-labeled unfragmented cDNA targets. The meager signal with the shorter probes limits the advantage of using the multiple probes of the same genes for enhancing the specificity of hybridization with environmental samples. Nevertheless, expression analysis of strain KC genome, under controlled laboratory conditions, revealed the constitutive expression of at least 11 putative ORFs of the pdt operon. Comparatively weaker hybridization signals with the cDNA from mutant cells suggested a low abundance of mRNA transcripts in the KC 1896 mutant. Similar expression levels of the pdt ORFs I, J, K, M, N, O, P, and fur gene both under iron-limiting conditions and in presence of iron (20 micro M Fe(3+)) suggested metal ion-independent regulation of the pdt operon. The tailor-made array with strain KC gene-specific probes served as a model for demonstrating the utility of cDNA microarray technology in monitoring the expression of environmentally important genes in bacteria.

The results of quantitative structure-activity relationship (QSAR) studies on six series of compounds exhibiting indirect mutagenic activity are reported. These findings demonstrate the importance of frontier orbital energies and, in some cases, frontier orbital electronic populations to overall mutagenicity in diverse polyaromatic hydrocarbons, benzidines and aminobiphenyls, benzonitrofurans, nitrogenous cooked-food mutagens, benzanthracenes, and chrysenes. The correlations between structural parameters and mutagenic potency vary from R=0.81 to R=0.97, and these findings are discussed in the context of possible molecular mechanisms of mutagenicity. In particular, it is generally regarded that cytochrome P450-mediated activation of polyaromatic hydrocarbons and their amino derivatives plays an important role in mutagenic activity. In this respect, it is apparent that enzymes of the cytochrome P4501 (CYP1) family are closely associated with the metabolic activation of polyaromatic mutagens and carcinogens via the generation of reactive intermediates (usually electrophilic in nature) that attack DNA. The findings presented in this study indicate that QSAR analyses on several series of compounds are consistent with the known evidence of procarcinogen activation mechanisms, particularly for polyaromatic hydrocarbons and their heterocyclic/amino derivatives, pointing to the importance of frontier orbital energy values in particular.

The aim of this study was to explore the relationship between local ischaemic preconditioning and the effectiveness of fractionated radiotherapy. The rat serum, bone marrow, and small intestine were examined for oxidative changes induced by total body irradiation with gamma rays with applied local ischaemic preconditioning immediately before irradiation. Serum concentrations of TBA-RS examined 12 hours after the last irradiation did not reveal any differences among the groups of animals analyzed. Twenty-four hours after the last dose of irradiation, the serum concentrations of TBA-RS varied in particular groups (P<0.0001). The concentration of triglycerides in the serum of local preconditioned ischaemia and irradiated animals showed a reversed shape similar to the TBA-RS fluctuation (P<0.003). The level of uric acid in the serum of animals treated only with radiation is slightly higher than the level of this acid in the serum of the local preconditioned ischaemia radiation group (P<0.58). The number of bone marrow polychromatic erythrocytes did not appear to differ substantially in both irradiated groups. At the first 12 hours after irradiation, the frequency of micronucleated polychromatic erythrocytes is significantly different in the bone marrow of both groups either in combination with ischaemic preconditioned radiation or with radiation alone (P<0.0002). In irradiated animals without ischaemic preconditioning, on the 3rd day after irradiation the number of crypts increased and in the next days decreased achieving the level of the control group on the 7th day. Irradiated rats with local ischaemic preconditioning did not reveal an increase in the number of crypts. The difference was statistically significant (P<0.05). These data indicate that the local ischaemic preconditioning modifies the radiation peroxidising effects through inhibition of free radical-dependent lipid peroxidation and, probably, other unrecognized mechanisms.