Induction of micronucleated erythrocytes by MEA, AET, WR-2721 and X-rays

Genoprotective Effect of Some Flavonoids against Genotoxic Damage Induced by X-rays In Vivo: Relationship between Structure and Activity

Flavonoids constitute a group of polyphenolic compounds characterized by a common gamma-benzo- pyrone structure considered in numerous biological systems to possess antioxidant capacity. Among the different applications of flavonoids, its genoprotective capacity against damage induced by ionizing radiation stands out, which has been related to antioxidant activity and its chemical structure. In this study, we determined the frequency of appearance of micronucleus in vivo by means of the micronucleus assay. This was conducted in mice treated with different flavonoids before and after exposure to 470 mGy X-rays; thereafter, their bone marrow polychromatophilic erythrocytes were evaluated to establish the structural factors enhancing the observed genoprotective effect. Our results in vivo show that the presence of a monomeric flavan-3-ol type structure, with absence of carbonyl group in position C4 of ring C, absence of conjugation between the carbons bearing the C2 = C3 double bond and the said ring, presence of a catechol group in ring B and characteristic hydroxylation in positions 5 and 7 of ring A are the structural characteristics that determine the highest degree of genoprotection. Additionally, a certain degree of polymerization of this flavonoid monomer, but maintaining significant levels of monomers and dimers, contributes to increasing the degree of genoprotection in the animals studied at both times of their administration (before and after exposure to X-rays).

A core in vitro genotoxicity battery comprising the Ames test plus the in vitro micronucleus test is sufficient to detect rodent carcinogens and in vivo genotoxins

In vitro genotoxicity testing needs to include tests in both bacterial and mammalian cells, and be able to detect gene mutations, chromosomal damage and aneuploidy. This may be achieved by a combination of the Ames test (detects gene mutations) and the in vitro micronucleus test (MNvit), since the latter detects both chromosomal aberrations and aneuploidy. In this paper we therefore present an analysis of an existing database of rodent carcinogens and a new database of in vivo genotoxins in terms of the in vitro genotoxicity tests needed to detect their in vivo activity. Published in vitro data from at least one test system (most were from the Ames test) were available for 557 carcinogens and 405 in vivo genotoxins. Because there are fewer publications on the MNvit than for other mammalian cell tests, and because the concordance between the MNvit and the in vitro chromosomal aberration (CAvit) test is so high for clastogenic activity, positive results in the CAvit test were taken as indicative of a positive result in the MNvit where there were no, or only inadequate data for the latter. Also, because Hprt and Tk loci both detect gene-mutation activity, a positive Hprt test was taken as indicative of a mouse-lymphoma Tk assay (MLA)-positive, where there were no data for the latter. Almost all of the 962 rodent carcinogens and in vivo genotoxins were detected by an in vitro battery comprising Ames+MNvit. An additional 11 carcinogens and six in vivo genotoxins would apparently be detected by the MLA, but many of these had not been tested in the MNvit or CAvit tests. Only four chemicals emerge as potentially being more readily detected in MLA than in Ames+MNvit--benzyl acetate, toluene, morphine and thiabendazole--and none of these are convincing cases to argue for the inclusion of the MLA in addition to Ames+MNvit. Thus, there is no convincing evidence that any genotoxic rodent carcinogens or in vivo genotoxins would remain undetected in an in vitro test battery consisting of Ames+MNvit.

Erythropoietic dynamic equilibrium in rats maintained after microwave irradiation

The aim of study was to define influence of radiofrequency microwave (RF/MW) radiation on erythropoiesis in rats. The kinetics of polychromatic erythrocytes (PCEs) and micronucleated (MN) PCEs in the bone marrow (BM) and peripheral blood (PB) of rats during the intermittent subchronic experiment was followed. Rats were exposed 2h/day, 7 days/week to RF/MW of 2.45 GHz and whole-body specific absorption rate (SAR) of 1.25+/-0.36 W/kg. Control animals were included in the study. Each exposed and control group was killed on the final day of irradiation. Acridine-orange stained BM and blood smears were examined by fluorescence microscope. PCEs were obtained by inspection of 2000 BM and 1000 PB erythrocytes/slides. BMMNs and PBMNs frequency was obtained by observation of 1000 PCEs/slides. BMPCEs were increased on day 8 and 15, and PBPCEs were elevated on days 2 and 8 (p<0.05). The BMMN frequency was increased on experimental day 15, and MNPCEs in the PB was increased on day 8 (p<0.05). Findings of BM and PBPCEs or MNPCEs declined nearly to the control values until the end of the experiment. Such findings are considered to be indicators of radiation effects on BM erythropoiesis consequently reflected in the PB. Rehabilitated dynamic haemopoietc equilibrium in rats by the end of experiment indicates possibility of activation adaptation process in rats to the selected experimental conditions of subchronic RF/MW exposure.

Blood-forming system in rats after whole-body microwave exposure; reference to the lymphocytes

The influence of 2.45 GHz microwave (RF/MW) irradiation on blood-forming cells after whole-body irradiation of rats was investigated. The exposures were conducted with a field power density of 5-10 mW/cm2, and whole-body average specific absorption rate (SAR) of 1-2 W/kg. Four experimental subgroups were created and irradiated 2, 8, 15 or 30 days, for 2 h a day, 7 days a week. Concurrent sham-exposed rats were also included in the study. The cell response was assessed by number and type of the bone marrow nuclear cells and peripheral blood white cells using standard laboratory methods. Significant decrease in lymphoblast count was obtained at 15 and 30th experimental day (P < 0.05), whereas other examined parameters did not significantly differed in comparison to the sham-exposed controls. The findings point out at stress response in blood-forming system in rats after selected microwave exposure, which could be considered rather as sign of adaptation than malfunction.

Erythropoietic changes in rats after 2.45 GHz nonthermal irradiation

The purpose of this study was to observe the erythropoietic changes in rats subchronically exposed to radiofrequency microwave (RF/MW) irradiation at nonthermal level. Adult male Wistar rats (N=40) were exposed to 2.45 GHz continuous RF/MW fields for 2 hours daily, 7 days a week, at 5-10 mW/cm2. Exposed animals were divided into four subgroups (n=10 animals in each subgroup) in order to be irradiated for 2, 8, 15 and 30 days. Animals were sacrified on the final irradiation day of each treated subgroup. Unexposed rats were used as control (N=24). Six animals were included into the each control subgroup. Bone marrow smears were examined to determine absolute counts of anuclear cells and erythropoietic precursor cells. The absolute erythrocyte count, haemoglobin and haematocrit values were observed in the peripheral blood by an automatic cell counter. The bone marrow cytogenetic analysis was accomplished by micronucleus (MN) tests. In the exposed animals erythrocyte count, haemoglobin and haematocrit were increased in peripheral blood on irradiation days 8 and 15. Concurrently, anuclear cells and erythropoietic precursor cells were significantly decreased (p < 0.05) in the bone marrow on day 15, but micronucleated cells' frequency was increased. In the applied experimental condition, RF/MW radiation might cause disturbance in red cell maturation and proliferation, and induce micronucleus formation in erythropoietic cells.

Radioprotective effects in vivo of phenolics extracted from Olea europaea L. leaves against X-ray-induced chromosomal damage: comparative study versus several flavonoids and sulfur-containing compounds

The radioprotective effects of a polyphenolic extract of Olea europaea L. leaves (OL); the flavonoids diosmin and rutin, which are widely used as pharmaceuticals; and the sulfur-containing compounds dimethylsulfoxide (DMSO) and 6-n-propyl-2-thiouracil (PTU) were determined by using the micronucleus test for anticlastogenic activity, evaluating the reduction of the frequency of micronucleated polychromatic erythrocytes (MnPCEs) in bone marrow of mouse before and after X-ray irradiation. With treatment before X-irradiation, the most effective compounds were, in order, rutin > DMSO > OL > PTU > diosmin. These results showed, for the polyphenols studied, a linear correlation (r(2) = 0.965) between anticlastogenic activity and antioxidant capacity. The magnitude of protection with treatment after X-irradiation were lower, and the most effective compounds were, in order, OL > diosmin > rutin; DMSO and PTU lacked radioprotective activity. Therefore, OL is the only substance that showed a significant anticlastogenic activity both before and after X-ray irradiation treatments. Structurally, the free oxygen radicals and lipoperoxyradicals scavenging capacity and, consequently, the anticlastogenic activity of these polyphenolic compounds are based principally on the presence of specific functional groups, mainly catechol groups (rutin, oleuropein, hydroxytyrosol, verbascoside, luteolin), that also increase the stability of the aroxyl-polyphenol radical generated in the above processes.

Radioprotective action of extracellular adenosine on bone marrow cells in mice exposed to gamma rays as assayed by the micronucleus test

The frequency of micronucleated polychromatic erythrocytes (PCEs) in mouse bone marrow was assessed after administration of dipyridamole and/or adenosine monophosphate (AMP) to nonirradiated mice or to mice irradiated 15 min later with a sublethal dose of 6.5 Gy gamma rays. In nonirradiated mice, the administration of the drugs increased the frequency of micronucleated PCEs significantly (by 108%). In contrast, in irradiated mice, the number of radiation-induced micronucleated PCEs was significantly decreased if the mice had been pretreated with dipyridamole or AMP alone (by 24% after administration of each of the compounds) and in particular after administration of the drugs in combination (by 36%).

Effects of GSH and WR-2721 on induction of micronuclei by cyclophosphamide

The frequency of micronucleated polychromatic erythrocytes (MNPCEs) was assessed in the bone marrow and peripheral blood of adult male Swiss mice treated with reduced glutathione (GSH) and/or S-2-/3-aminopropylamino/ethyl phosphorothioic acid (WR-2721), at a dose of 400 mg/kg body weight, and/or with cyclophosphamide (CP), at a dose of 200 mg/kg body weight. GSH was given 60 or 15 min and/or WR-2721 was applied 30 min before CP administration. The number of MNPCEs was determined at 24 h after the drug application. After treatment of mice with CP, the frequency of MNPCEs was distinctly increased. The stronger chemoprotective effect against CP-induced cytotoxicity was obtained following GSH administration than after WR-2721 injection. WR-2721 characterized greater cytotoxicity than GSH. The combination of GSH and WR-2721 given alone, or before CP administration resulted in the most cytotoxic and chemoprotective effects, compared with the respective single-thiol treatment of mice. The most effective protection against CP-induced genotoxicity was observed in the case of treatment of mice with WR-2721and GSH, respectively, 30 and 15 min before CP administration. The most cytotoxic effect of the thiols was found when GSH given 30 min prior to WR-2721 application. The chemoprotection and cytotoxicity caused in the mouse erythroblasts by GSH and WR-2721, as indicated by the number of MNPCEs were dependent on the thiol(s) given, and the time intervals between the drug administration. The modulatory effect of the thiols GSH and WR-2721 on 'delayed apoptosis' induced in the erythropoietic system by cyclophosphamide was shown.