Evaluación del daño oxidativo y por metilación del ADN de pintores expuestos ocupacionalmente a solventes orgánicos y pintura / Evaluation of oxidative and methylating DNA damage in painters occupationally exposed to organic solvents and paints

Resumen Introducción. La exposición a solventes orgánicos y pinturas se ha asociado con efectos genotóxicos y mayor riesgo de neoplasias. Sin embargo, aún no se ha caracterizado bien el tipo de daño que esta exposición induce en el ADN humano, ni los mecanismos por los cuales se genera. Uno de los grupos con mayor exposición a dichos solventes y pinturas son los pintores de automóviles del sector informal que trabajan sin adecuadas prácticas de seguridad ocupacional. Objetivo. Determinar el daño oxidativo y por metilación del ADN de linfocitos de pintores de automóviles expuestos a solventes orgánicos y pinturas. Materiales y métodos. Se analizaron linfocitos aislados de sangre periférica de 62 pintores y 62 sujetos no expuestos mediante el ensayo cometa de gran eficiencia acoplado a las enzimas Fpg y AlkA. Las categorías de daño en el ADN evaluadas fueron el daño basal (sin enzimas), el daño oxidativo y el daño por metilación, y el parámetro de medición, el porcentaje de ADN en la cola. Resultados. El porcentaje de ADN en la cola fue mayor en el grupo expuesto con respecto al no expuesto (p<0,05). En el grupo expuesto, dicho porcentaje fue mayor en la categoría de daño oxidativo comparado con la del basal (16,50 Vs. 12,87; p<0,001), en tanto que en el daño por metilación no se encontraron diferencias significativas (14,00 Vs. 12,87; p>0,05). Conclusión. La exposición a solventes orgánicos y pinturas se asoció con el aumento de las lesiones oxidativas del ADN de los linfocitos de pintores de automóviles, tales como la producción de 8-oxo-2'-desoxiguanosina (8-oxodG) y otros productos formamidopirimidina, los cuales se consideran considerablemente mutagénicos.

Abstract Introduction: The exposure to organic solvents and paints has been associated with genotoxicity and a greater risk of neoplasms. However, the type of DNA damage induced in humans by the exposure to these compounds, which would help explain the mechanisms of their genotoxicity, is still not fully characterized. Due to inadequate practices of occupational safety, car painters in the informal sector are a highly exposed group to organic solvents and paints. Objective: To identify the oxidative and methylating damage in the DNA of lymphocytes of car painters exposed to organic solvents and paints. Materials and methods: Isolated peripheral blood lymphocytes from 62 painters and 62 unexposed subjects were analyzed by the modified high-throughput comet assay with the Fpg and AlkA enzymes. The categories used for the evaluation of the DNA damage were basal damage (without enzymes), oxidative and methylating damage. The measurement parameter used to establish the damage was the percentage of DNA in the tail. Results: The percentage of DNA in the tail was higher in the exposed group compared to the unexposed group (p<0.05). In the exposed group, this percentage was higher in the oxidative damage category than the baseline (16.50 vs. 12.87; p<0.001), whereas methylating damage did not show significant differences (14.00 vs. 12.87; p>0.05). Conclusion: In this study, exposure to organic solvents and paints was associated with an increase in oxidative lesions in the DNA of car painters' lymphocytes, such as the production of 8-oxodG and other formamidopyrimidine products which are considered highly mutagenic.

Histological study and DNA changes in the kidneys of rat fetuses maternally treated with Clarithromycin

Introduction: macrolide antibiotics are a class of potent and well established antimicrobials that also possess anti-inflammatory and/or immunomodulatory properties. Because of their size, lower levels of macrolides are able to reach the developing fetuses

Materials and method: the pregnant rats were orally administered with clarithromycin at early and late gestational periods. The 20 day-old fetuses were dissected for excision of the kidney. Half of the kidney was processed and stained with H and E, PAS, Masson's trichrome and Feulgen techniques then followed by morphometric measurements and statistical study. The other half of the kidney was preserved for DNA fragmentation assay.Results: This study revealed that clarithromycin administration to pregnant rats showed different histopathological, histochemical and DNA changes in the kidneys of their fetuses

Conclusion: Administration of the antimicrobial agent; clarithromycin at early and late gestational periods exhibits nephrotoxicity in the developing fetuses

In vitro and In vivo anti-cancer effects of Tillandsia recurvata (Ball Moss) from Jamaica / Efectos Anticancerosos In vitro e In vivo de la Tillandsia recurvata (Bola de Musgo) de Jamaica

OBJECTIVE: Tillandsia recurvata, also commonly known as Ball Moss, is endemic to Jamaica and some parts of the Caribbean and South America. The plant, despite being reported to be used in folk medicine, had not previously been evaluated for its anti-cancer potential. The aim of this study was to evaluate the anti-cancer activity of Ball Moss. METHODS: The anti-proliferation activity of the crude methanolic extract of the T recurvata was evaluated in vitro in five different histogenic cancer cell lines (prostate cancer - PC-3, breast cancer, Kaposi sarcoma, B-16 melanoma and a B-cell lymphoma from a transgenic mouse strain) using the trypan blue assay. The crude extract was also evaluated in vivo in tumour-bearing mice. Immunohistochemistry staining with Apoptag was used for histology and determination of apoptosis. RESULTS: The crude methanolic extract of T recurvata demonstrated anti-proliferation activity against all the cell lines, killing > 50% of the cells at a concentration of 2.5 µg/ml. Kaposi sarcoma xenograft tumours were inhibited by up to 75% compared to control in the in vivo study (p < 0.05). There was evidence of DNA fragmentation and a decrease in cell viability on histological studies. The methanolic extract showed no toxic effect in the mice at a dose of 200 mg/kg. CONCLUSIONS: Our data suggest that T recurvata has great potential as an anti-cancer agent and that one of its mechanisms of cell kill and tumour inhibition is by the induction of apoptosis.

OBJETIVO: La Tillandsia recurvata, también conocida como bola de musgo, es endémica en Jamaica, así como en algunas partes del Caribe y América del sur. Si bien se había reportado su uso como parte de la medicina popular, esta planta no había sido evaluada previamente en relación con su potencial para la lucha contra el cáncer. El objetivo de este estudio fue evaluar la actividad anticancerígena de la bola de musgo. MÉTODOS: La actividad antiproliferativa del extracto metanólico crudo de la T recurvata, fue evaluada in vitro en cinco líneas celulares diferentes de cáncer histogenético (cáncer de próstata - PC-3, cáncer de mama, sarcoma de Kaposi, melanoma B-16 y un linfoma de células B de una cepa de ratón transgénico) usando el ensayo con azul de tripano. El extracto crudo también se evaluó in vivo en ratones portadores de tumor. La tinción inmunohistoquímica con ApopTag fue utilizada para la histología y determinación de la apoptosis. RESULTADOS: El extracto metanólico crudo de T recurvata demostró la actividad proliferativa frente a todas las líneas celulares, matando > 50% de las células a una concentración de 2,5 µg/ml. Los tumores de xenoinjerto de sarcoma de Kaposi fueron inhibidos hasta un 75% en comparación con el control en el estudio in vivo (p < 0.05). Hubo evidencia de fragmentación de DNA y una disminución en la viabilidad celular en los estudios histológicos. El extracto metanólico no mostró ningún efecto tóxico en los ratones a dosis de 200 mg/kg. CONCLUSIONES: Nuestros datos sugieren que la T recurvata tiene gran potencial como agente anticanceroso, y que uno de sus mecanismos de inhibición de tumores y muerte de las células tiene lugar mediante la inducción de la apoptosis.

Effect of vitamin E on sperm parameters and DNA integrity in sodium arsenite-treated rats

Arsenic as an environmental toxicant is able to exert malformations in male reproductive system by inducing oxidative stress. Vitamin E [Vit.E] is known as antioxidant vitamin. The aim of this study was to investigate the harmful effects of sodium arsenite on sperm parameters and the antioxidant effects of Vit.E on sperm anomalies in sodium arsenite treated rats. Adult male rats were divided into 4 groups: control, sodium arsenite [8 mg/kg/day], Vit.E [100 mg/kg/day] and sodium arsenite+Vit.E. Oral treatments were performed till 8 weeks. Body and left testis weight were recorded and then left caudal epididymis was cut in Ham's F10. Released spermatozoa were used to analyze number, motility, viability and abnormalities of the sperm. Sperm chromatin quality was assessed by nuclear staining using acridine orange and aniline blue. Body and testis weight showed no significant change in 4 groups [p>0.05]. A significant decrease in the number, motility, viability and normal sperm morphology was found in sodium arsenite-treated rats compared to the control [p<0.001]. Sodium arsenite had no effect on sperm DNA integrity and histon-protamine replacement [p>0.05]. In sodium arsenite+Vit.E group, Vit.E could significantly compensate the harmful effects of sodium arsenite on sperm number, motility, viability and morphology compared to sodium arsenite group. In addition, sperm viability and motility was significantly increased in rats treated with Vit.E alone compared to the control and sodium arsenite+Vit.E group. Vitamin E could compensate the adverse effects of sodium arsenite on sperm parameters in adult rats

Acute effects of ruta graveolens L. on sperm parameters and DNA integrity in rats

Increase in world population is one of the serious and threatening issues in this century. Therefore, it is vitally important to find safe and effective contraceptive methods, especially for men which already have few choices in this regard. Medicinal plants that were used for contraception in ancient times could be good sources of investigation in this filed. Ruta graveolens L. is one the plants introduced in the Iranian traditional medicine as an oral male contraception to be used before intercourse. In this study we tried to investigate the probable effects of the plant on the spermatozoa of male rats. Ruta graveolens L. aqueous extract [5 g/kg] was administered orally to five groups of male rats and sperm motility was checked after half, one, two, four and six hours later. Moreover, one group of rats served as the control group. Subsequently, viability of cells [Eosin-Nigrosin staining], morphological changes [Diff-Quick staining], DNA status [acridine orange dye] and serum testosterone levels were assessed in the treated groups which had significant immotile spermatozoa. For statistical analysis, Student's t-test and one-way ANOVA with Tukey's post-hoc test were employed for comparison between groups. A significant reduction in sperm motility was seen one hour after administration of the extract in the case groups compared to the controls [36% vs. 68.15%, respectively, p<0.01]. The motility gradually increased afterwards, and by 6 hours, it was the same as the control group [65.43% and 68.15%, respectively]. No significant changes were seen in viability, morphology or DNA structure of spermatozoa in each group. Testosterone levels did not show any significant changes in the treated groups when compared with the controls. Since a significant temporary immobility of spermatozoa without any adverse effects on other sperm characteristics occurred upon the administration of Ruta graveolens L. aqueous extract, it seems that this plant might have the potential to be used for the suggested male contraception

Preferential recognition of methylglyoxal-modified calf thymus DNA by circulating antibodies in cancer patients.

Methylglyoxal (MG) has been implicated in mutagenesis and cancer. Present study probes the antigenicity of MG damaged DNA in cancer patients. Purified calf thymus DNA was damaged by the synergistic action of MG, lysine (Lys) and CuSO4 for 24 h at 37oC. DNA modifications produced single-strand breaks, hyperchromicity in UV spectrum and increased fluorescence intensity. Binding characteristics of auto-antibodies in cancer patients were assessed by direct binding and inhibition ELISA. These antibodies exhibited enhanced binding with the modified DNA, as compared to the native form. The effect was more pronounced when affinity-purified IgG was used in place of the serum. In conclusion, MG-modified DNA presents unique epitopes which are recognized as non-self by the immune system and may, therefore, be one of the factors for the autoantibody induction in cancer patients.

Screening of codeine, dextromethorphan & dextropropoxyphene for their genotoxicity in swiss albino mice.

Background & objectives: It is mandatory for all new drugs to be tested for their potential genotoxicity in addition to general toxicity testing. Some old drugs have not been tested adequately for their genotoxic effects as these were in use before the regulations were enforced. The present study therefore aims to explore the genotoxic potential of some commonly used opioids like codeine, dextromethorphan and dextropropoxyphene in swiss albino mice. Methods: Therapeutic equivalent doses of codeine, dextromethorphan and dextropropoxyphene were given orally. Single dose for acute study and multiple doses (repeated every 24 h for 7 times) in additional groups of mice (n=5 in each) for subacute study. Cyclophosphamide served as positive control while normal saline as negative control. About 0.5 ml of blood was collected by retroorbital sinus for comet assay and later the mice were sacrifi ced to aspirate the femoral bone marrow for micronucleus test. Percentage of micronucleated polychromatic erythrocytes (MnPCE) and comet tail length were calculated in micronucleus assay and comet assay respectively, which served as markers of genotoxicity. Results: Signifi cant Signififi (P<0.001) increase in comet tail length and % MnPCE was observed in both acute and subacute studies of cyclophosphamide group, whereas codeine, dextromethorphan and dextropropoxyphene treated groups did not show any signifi cant changes. Interpretation & conclusion: The results indicated that codeine, dextromethorphan and dextropropoxyphene were devoid of genotoxicity in mice.

Telbivudina / Telbivudina

Es un análogo nucleósido sintético de la timidina, cuyo nombre químico es 1-( 2-deoxy-ß-L-ribofuranosyl)-5metiluracil, y ejerce su acción a través de la inactivación de la ADN polimerasa del virus de la Hepatitis B, mediante la inhibición competitiva de su sustrato natural , el 5-trifosfato timidina. Fue recientemente aprobado por el FDA para el tratamiento de la hepatitis B.

Telbivudine´s chemical name is 1-(2-deoxy-ß-Lribofuranosyl)-5-metiluracil. It is a synthetic nucleoside analogue of timidine with activity against HBV DNA Polymerase by competing with the natural substrate, timidine 5-triphosphate. It was recently approved by the FDA for hepatitis B treatment.

Evaluation of the effectiveness of peracetic acid in the sterilization of dental equipment.

PURPOSE: To evaluate the effectiveness of peracetic acid in the microbiological sterilisation of dental materials. METHODS: Peracetic acid solution was evaluated at concentrations of 800, 1500 and 2500 ppm. At these concentrations, it was determined whether peracetic acid caused corrosion to dental instruments and induced cellular mutagenicity and cytotoxicity. In addition, the minimum inhibitory concentration (MIC), the minimum bactericidal concentration (MBC), agar diffusion and diffusion by well method, were also verified. RESULTS: The corrosion rate, calculated from potentiodynamic assays was 10(-6) cm/year, indicating that the product does not damage equipment. The sterilisation capacity of peracetic acid at 2500 ppm was the best. The comet assay indicated genotoxic activity at 2500 ppm. CONCLUSIONS: This study demonstrated the effectiveness of peracetic acid for sterilizing dental equipment, providing another alternative for the prevention of infections in clinics.

Dietary supplementation of vitamin A, C and E prevents p-dimethylaminoazobenzene induced hepatic DNA damage in rats.

The preventive effect of antioxidant vitamins A, C, E and their analogues against DNA damage induced by a hepatocarcinogen p-dimethylaminoazobenzene (DAB) was assessed by comet assay. For genotoxicity (DNA damage) study, male albino rats were divided into 11 groups, consisting of four rats each. Group I served as control. Group II to VII received 1, 10, 100, 200, 300 and 400 mg per kg body wt of DAB respectively; group VIII to XI received 500 mg/kg body wt of DAB. They were sacrificed by cervical decapitation 3, 6, 12 and 24 h after treatment; livers were excised immediately and subjected to comet assay to measure DNA damage. To study the effect of vitamins, experiments were conducted on a group of 275 rats divided into 3 sets of 25 rats each. First set served as control; second set received 0.06% DAB and third set received 0.06% DAB, along with analogues of vitamins A, C and E. Rats fed with 0.06% DAB were provided water ad libitum for a period of 4 months, followed by a normal (basal) diet for further 2 months. Vitamins A (10,000-50,000 IU), C (75-1000 mg) and E (50-500 mg) and their analogues were given (per kg body wt) to the third set of rats by gavage route once in a week for a period of 6 months. The DAB induced DNA damage only at the highest tested dose of 500 mg/kg body wt. Administration of high doses of vitamin A acid, L-ascorbic acid and vit. E succinate individually prevented the DNA damage. However, administration of a mixture of these vitamins at low doses prevented the DAB-induced DNA damage, which may be due to their synergistic effect. The results indicate that there is a significant advantage in mixed vitamins therapy at low dose over the treatment with individual vitamins.

Effect of chlorpromazine on intact and irradiated aliquot ctdsDNA samples

Chlorpromazine is widely used in human medicine in the therapy of schizophrenia, organic psychosis and the manic phase of manic depressive illness. It expressed a selective cytotoxicity and the results of genotoxicity were positive. This study is designed to explore the effect of chlorpromazine on irradiated and non irradiated calf thymus double strands DNA [ctdsDNA] molecule. Aliquots of irradiated [subjected to UVB light] and non-radiated ctdsDNA samples were incubated with different concentrations of chlorpromazine. Further series of experiments studied the simultaneous effects of chlorpromazine and UVB light on aliquots of ctdsDNA. The changes in optic densities of ctdsDNA aliquots were monitered and recorded by UV-spectrophotometer at 260 nm. Chlorpromazine exerts dual effects on non-radiated ctdsDNA aliquots represented by hyperchromasia and hypochromasia in regard to its concentration. It potentiates the effect of UVB radiation on ctdsDNA molecules. Its effect is differed in respect to the radiation status. Chlorpromazine exerts several effects on aliquot ctdsDNA samples which are related to the nature of DNA molecule as well as to the concentration of chlorpromazine. Also chlorpromazine potentiates the hyperchromatic effect of UVB radiation on aliquot ctdsDNA samples but it produces complete damage of DNA molecule when the aliquot ctdsDNA samples irradiated in presence of chlorpromazine

Alpha-lipoic acid counteracts the promoted oxidative DNA damage in the liver of septic rats

Viral, parasitic infections and chemical carcinogens are among the etiological factors of liver cancer. It seems important to study the initiating and promoting agents to evaluate the etiology and prevention of such life threatening disease. Intestine-derived bacterial product, lipopolysaccharide [LPS], is mainly detoxified by the liver. It has shown to induce a state of oxidative stress in the liver but its capability to induce oxidative DNA damage is not fully investigated. Increased oxidative DNA damage and rate of cell proliferation may initiate or even promote cancer. In the present work, the capability of LPS to induce 8-hydroxydeoxyguanosine [8-HDG], a specific DNA adduct for oxidative DNA damage, in rat livers is tested. Furthermore, a possible protective effect of alpha lipoic acid [ALA] is also assessed. Investigated parameters are liver contents of glutathione [GSH], lipid peroxides [MDA], nitric oxide [NO] and 8-HDG in the liver-extracted DNA. Serum activities of ALT, AST, and GGT as liver-function markers as well as serum IL2 are assessed. Moreover, liver histology is examined. LPS was given in doses of 1,3,5,7 and 9 mg/kg once i.p while, the rat mortality was examined 24hrs later. ALA was given in doses of 50,100 and 200 mg/kg once i.p 3h before LPS. LD50 of LPS is found to be 5 mg/kg. LPS increased the level of 8-HDG, MDA and NO in the liver. It also induced an acute liver necrosis and inflammatory cell infiltration as shown in liver-histopathology and in the significant increase in the activities of ALT, AST and GGT. LPS increased the serum level of IL2 as well. The dose 200 mg/kg of ALA revealed a 100% protection against LPS-induced lethality. It also, prevented the LPS-induced increase in 8-HDG in liver-extracted DNA, the liver contents of MDA and NO. ALA also rescued the LPS-induced GSH depletion. It corrected the liver function as shown by the prevention of the increases in the activity of ALT, AST and GGT with a remarkable improvement in liver histology. Moreover, it prevented the increase in serum level of IL2. These data illustrate that LPS can induce oxidative DNA damage which can be prevented by ALA suggesting a potential role for ALA as an adjuvant therapy in a plethora of liver disorders

Protective effect of the isoflavone equol against DNA damage induced by ultraviolet radiation to hairless mouse skin

Equol, an isoflavonoid metabolite produced from the dietary isoflavone daidzein by the gut microflora in mammals, has been found to protect not only against ultraviolet (UV) radiation-induced cutaneous inflammation and photoimmune suppression, but also have antiphotocarcinogenic properties in mice. Because the state of DNA damage has been correlated with suppression of the immune system and photocarcinogenesis, we have therefore examined the potential of equol to offer protection from solar-simulated UV (SSUV) radiation-induced DNA damage in hairless mice by the immunohistochemical approach using monoclonal antibody specific for cyclobutane pyrimidine dimers (CPDs; H3 antibody). Topical application of 20 micrometer equol lotion, which was applied both before and after SSUV significantly reduced the number of CPDs. This reduction was evident immediately after SSUV exposure, at 1 h after exposure, and at 24 h after exposure, revealing 54%, 50%, and 26% reduction in CPDs, respectively. When the same concentration was applied for 5 consecutive days after SSUV exposure, there was no significant difference in the reduction of CPDs immediately after SSUV irradiation or at 1 hour afterwards, but there were significant reductions of 23% and 42% at 24 and 48 h after SSUV exposure, respectively. Despite apparently reducing the number of CPDs post-SSUV, topically applied equol did not appear to increase the rate of dimer removal. To conclude, equol applied topically prior to SSUV irradiation offers protection against CPD formation in hairless mice, possibly by acting as a suncreen and thus inhibiting DNA photodamage.

The potential roles of p53 tumor suppressor in nucleotide excision repair (NER) and base excision repair (BER)

The p53 tumor suppressor has long been envisaged to preserve genetic stability by the induction of cell cycle checkpoints and apoptosis. More recently, p53 has been implicated to play roles in DNA repair responses to genotoxic stresses. UV-damage and the damage caused by certain chemotherapeutics including cisplatin and nitrogen mustards are known to be repaired by the nucleotide excision repair (NER) pathway which is reportedly regulated by p53 and its downstream genes. There are evidences to suggest that the base excision repair (BER) induced by the base-damaging agent methyl methanesulfonate (MMS) is partially deficient in cells lacking functional p53. This result suggests that the activity of BER might be also dependent on the p53 status. In this review, we discuss the possibilities that p53 regulates BER as well as NER; these are one of the most significant potentials of p53 tumor suppressor for repairing the vast majority of DNA damages that is incurred from various environmental stresses.

Comparative effeicacy and potency of snake venom, mitomycin-C and cyclophosphamide for RNA and DNA inhibition in breast cancer

Anti-proliferating effect of the cobra venom throughh the meassurement of tissue nucleic acids [RNA and DNA] in breast cancerr has been studied and compared to that of cyclophosphamide and mitomycin-C. The venom and other anti-neoplastic were incubated singly as well as in combination for 30 minutes at 37

Emerging antimicrobial resistance, plasmid profile and pulsed-field gel electrophoresis pattern of the endonuclease-digested genomic DNA of Neisseria gonorrhoeae

Resistant gonococci are very prevalent in many countries, particularly in Asia. This study was conducted to determine the trend of resistance, the effect of decreasing the ciprofloxacin susceptibilities of gonococci on the prevalence of penicillinase-producing N. gonorrhoeae (PPNG), and to compare the epidemiology of strains with the previous studies. A total of 602 strains of gonococci were isolated from prostitutes in 1997-1999. Antimicrobial susceptibility was tested by NCCLS disk diffusion and agar dilution methods. For epidemiologic analysis, vplasmid analysis and pulsed-field gel electrophoresis (PFGE) were performed. The proportion of PPNG remained high (79%), and the strains with decreased susceptibility to ciprofloxacin increased significantly from 67% in 1997 to 84% in 1999. Compared to our previous study, the PFGE patterns were similar, while the proportion of strain with the 3.2-MDa plasmid markedly decreased. In conclusion, a rapid increase in ciprofloxacin-nonsusceptible strains may suggest difficulties in the treatment of gonococcal infections in the near future with the drug. The recent decrease of PPNG with the 3.2-MDa plasmid may suggest that there is an epidemiological change in gonococcal infections, and the prevalence of related PFGE patterns suggests the dissemination of a few clones among the high risk populations.

Protective mechanism of glucose against alloxan-induced beta-cell damage: pivotal role of ATP

Glucose prevents the development of diabetes induced by alloxan. In the present study, the protective mechanism of glucose against alloxan-induced beta-cell damage was investigated using HIT-T 15 cell, a Syrian hamster transformed beta-cell line. Alloxan caused beta-cell damages with DNA fragmentation, inhibition of glucose-stimulated insulin release, and decrease of cellular ATP level, but all of these beta-cell damages by alloxan were prevented by the presence of 20 mM glucose. Oligomycin, a specific inhibitor of ATP synthase, completely abolished the protective effects of glucose against alloxan-induced cell damage. Furthermore, treatment of nuclei isolated from HIT-T15 cells with ATP significantly prevented the DNA fragmentation induced by Ca2+. The results indicate that ATP produced during glucose metabolism plays a pivotal role in the protection of glucose against alloxan-induced beta-cell damage.

Radioprotective effects of DNA ligands Hoechst-33342 and 33258 in whole body irradiated mice.

Radioprotective effects of bisbenzimidole derived DNA ligands Hoechst-33342 (H-342) and Hoechst-33258 (H-258) have been investigated in whole body irradiated stain-A and Balb/c mice (Co-60 Gamma-ray, absorbed doses of 2.5 to 10 Gy delivered at dose rates of 0.01 to 0.50 Gy/min). Biodistribution of Hoechst dyes (2 or 5 mg/kg, body wt., i.v.) and their effects on cell cycle kinetics in bone marrow were studied by flow cytometry. Protection against radiation-induced chromosomal aberrations, micronuclei formation, alterations in DNA content dispersion, inhibition of erythropoiesis and animal lethality were investigated. Significant amount of DNA bound Hoechst could be observed in liver, intestine, kidney and brain for more than 14 days after its administration, while in the bone marrow cells, a reduction in the bound Hoechst was noticed after 7 days. H-342 significantly reduced the radiation-induced chromosome aberrations mainly due to a decrease in the frequency of acentrics (nearly 30%), while a marginal decrease (10%) in the dicentrics was observed at all the dose rates studied. Both H-342 and H-258 reduced the radiation-induced micronuclei formation in a dose dependent manner (2-10 mg/kg body wt.) and this protective effect was observed up to 6 days after the administration. Neither of the two compounds induced any cytogenetic damage in the bone marrow cells of unirradiated animals nor induced tumours at the doses used here (< 5 mg/kg, body wt. i.v.). Reduction in cytogenetic damage of bone marrow cells led to a faster recovery of erythropoesis as observed by increased PCE/NCE ratio in the peripheral blood erythrocytes of the animals which received Hoechst before irradiation. H-258 (5 mg/kg body wt.) given 18 hr before irradiation reduced radiation-induced animal death (5-9 Gy), while no significant effect was observed at higher doses (10 Gy). However, H-342, which has a higher cell permeability, even at a lower dose (2 mg/kg body wt.) showed significant protection at 10 Gy. The protective effects could be enhanced further, by combining these DNA binding agents with the glucose analogue, 2-deoxy-D-glucose (2-DG) which has been shown earlier to protect bone marrow cells against radiation damage.