RESUMO
Tumor hypoxia may compromise the results of chemotherapy for treating colorectal cancer because it stimulates angiogenesis and the release of tumor growth factors. Hyperbaric oxygen (HBO) supplementation may potentiate the effects of chemotherapy in such cases. This study aimed to assess the effect of HBO therapy combined with chemotherapy on the treatment of colorectal cancer in mice. C57BL6 mice were submitted to the intrarectal instillation of N-methyl-N-nitrosoguanidine (MNNG) and treated with 5-fluorouracil (5FU) and/or HBO therapy. The MNNG group presented the highest dysplastic crypt rate. The 5FU + HBO group presented the highest rate of apoptotic cells per dysplastic crypt. The 5FU group presented the highest expression of hypoxia-inducible factor-1 alpha and CD44. HBO therapy increased the effect of 5FU on the treatment of the experimental colorectal neoplasia in mice.
Assuntos
Neoplasias Colorretais , Fluoruracila , Oxigenoterapia Hiperbárica , Camundongos Endogâmicos C57BL , Animais , Fluoruracila/farmacologia , Camundongos , Neoplasias Colorretais/terapia , Neoplasias Colorretais/patologia , Neoplasias Colorretais/tratamento farmacológico , Masculino , Antimetabólitos Antineoplásicos/farmacologia , Apoptose/efeitos dos fármacos , Subunidade alfa do Fator 1 Induzível por Hipóxia/metabolismo , Receptores de Hialuronatos/metabolismo , Terapia Combinada , Metilnitronitrosoguanidina/farmacologiaRESUMO
Several possible mechanisms have been examined to gain an understanding on the carcinogenic properties of lead, which include among others, mitogenesis, alteration of gene expression, oxidative damage, and inhibition of DNA repair. The aim of the present study was to explore if low concentrations of lead, relevant for human exposure, interfere with Ape1 function, a base excision repair enzyme, and its role in cell transformation in Balb/c-3T3. Lead acetate 5 and 30 µM induced APE1 mRNA and upregulation of protein expression. This increase in mRNA expression is consistent throughout the chronic exposure. Additionally, we also found an impaired function of Ape1 through molecular beacon-based assay. To evaluate the impact of lead on foci formation, a Balb/c-3T3 two-step transformation model was used. Balb/c-3T3 cells were pretreated 1 week with low concentrations of lead before induction of transformation with n-methyl-n-nitrosoguanidine (MNNG) (0.5 µg/mL) and 12-O-tetradecanoylphorbol-13-acetate (TPA) (0.1 µg/mL) (a classical two-step protocol). Morphological cell transformation increased in response to lead pretreatment that was paralleled with an increase in Ape1 mRNA and protein overexpression and an impairment of Ape1 activity and correlating with foci number. In addition, we found that lead pretreatment and MNNG (transformation initiator) increased DNA damage, determined by comet assay. Our data suggest that low lead concentrations (5, 30 µM) could play a facilitating role in cellular transformation, probably through the impaired function of housekeeping genes such as Ape1, leading to DNA damage accumulation and chromosomal instability, one of the most important hallmarks of cancer induced by chronic exposures.
Assuntos
Carcinógenos Ambientais/toxicidade , Transformação Celular Neoplásica/efeitos dos fármacos , Dano ao DNA , DNA Liase (Sítios Apurínicos ou Apirimidínicos)/biossíntese , Chumbo/toxicidade , Modelos Biológicos , Animais , Células 3T3 BALB , Proliferação de Células/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Ensaio Cometa , Expressão Gênica/efeitos dos fármacos , Humanos , Metilnitronitrosoguanidina/farmacologia , Camundongos , Acetato de Tetradecanoilforbol/farmacologiaRESUMO
Xanthophyllomyces dendrorhous (formely Phaffia rhodozyma) is a basidiomycetous yeast-like fungus that produces carotenoids useful for the food industry. Recently, its sexual cycle was reported but little is known about its genetic constitution. To inquire into the ploidy state of X. dendrorhous, biased mutant spectrum, genetic complementation and mitotic recombination analysis were used. A wild-type strain was subjected to N-methyl-N'-nitro-N-nitrosoguanidine mutagenic treatment. Auxotrophic and carotene mutants were forced to revert to the wild-type phenotype. Pigment producing and prototroph revertants behaved as diploid except for adenine less mutants. These results are in agreement with the limited spectrum of auxotrophs obtained in this strain for the ADE1 locus. To analyze the genetic characteristic of the adenine genetic marker of X. dendrorhous, protoplast fusion experiments with several adenine less mutants were performed. The experiments presented in this work suggest that the ATCC 2430 (UDC 67-385) strain of X. dendrorhous is diploid and a heterozygous constitution is proposed for the ADE1 locus.
Assuntos
Basidiomycota/citologia , Basidiomycota/genética , Cromossomos Fúngicos/genética , Diploide , Adenina/biossíntese , Basidiomycota/metabolismo , Teste de Complementação Genética , Metilnitronitrosoguanidina/farmacologia , Mutação , Pigmentos Biológicos/biossíntese , Pigmentos Biológicos/genética , Protoplastos , Recombinação GenéticaRESUMO
A novel mutant isolate of Saccharomyces cerevisiae, sensitive to photoactivated mono- and bi-functional psoralens, to UV at 254 nm (UVC), and to nitrosoguanidine, was found to complement the photoactivated psoralen-sensitivity phenotype conferred by the pso1- pso7 mutations and was therefore named pso8-1. A constructed pso8-1 rad4-4 double mutant was super-sensitive to UVC, thus indicating a synergistic interaction of the two mutant alleles. Molecular cloning via complementation of the pso8 mutant's sensitivity phenotype and genetic studies revealed that pso8 is allelic to RAD6. While a pso8-1 mutant had low mutagen-induced mutability, homoallelic diploids showed nearly wild-type sporulation. Sequence analysis of the mutant allele showed pso8-1 to contain a novel, hitherto undescribed T-->C transition in nucleotide position 191, leading to a substitution by leucine of a highly conserved proline at position 64, Rad6-[P64L], which may have severe consequences for the tertiary structure (and hence binding to Rad18p) of the mutant protein.
Assuntos
Furocumarinas/farmacologia , Genes Fúngicos , Mutação de Sentido Incorreto , Fármacos Fotossensibilizantes/farmacologia , Saccharomyces cerevisiae/genética , Raios Ultravioleta , Alelos , Sequência de Aminoácidos , Sequência Conservada , Metilnitronitrosoguanidina/farmacologia , Dados de Sequência Molecular , Mutagênicos/farmacologia , Fenótipo , Fotoquímica , Filogenia , Saccharomyces cerevisiae/efeitos dos fármacos , Saccharomyces cerevisiae/efeitos da radiação , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo , Homologia de Sequência de AminoácidosRESUMO
We analyzed DNA lesions produced by H2O2 under low iron conditions, the cross adaptive response and the synergistic lethal effect produced by iron chelator-o-phenanthroline, using different Escherichia coli mutants deficient in DNA repair mechanisms. At normal iron levels the lesions produced by H2O2 are repaired mainly by the exonuclease III protein. Under low iron conditions we observed that the Fpg and UvrA proteins as well as SOS and OxyR systems participate in the repair of these lesions. The lethal effect of H2O2 is strengthened by o-phenanthroline if both compounds are added simultaneously to the culture medium. This phenomenon was observed in the wild type cells and in the xthA mutant (hypersensitive to H2O2). E. coli cells treated with low concentrations of H2O2 (micromolar) acquire resistance to different DNA damaging agents. Our results indicate also that pretreatment with high (millimolar) H2O2 concentrations protects cells against killing, by UV and this phenomenon is independent of the SOS system, but dependent on RecA and UvrA proteins. H2O2 induces protection against lethal and mutagenic effects of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). H2O2 also protects the cells against killing by cumene hydroperoxide, possibly with the participation of Ahp protein.
Assuntos
Proteínas de Escherichia coli , Escherichia coli/efeitos dos fármacos , Peróxido de Hidrogênio/farmacologia , Adenosina Trifosfatases/metabolismo , Proteínas de Bactérias/metabolismo , Dano ao DNA , Reparo do DNA , DNA Bacteriano/efeitos dos fármacos , Proteínas de Ligação a DNA/metabolismo , DNA-Formamidopirimidina Glicosilase , Sinergismo Farmacológico , Escherichia coli/genética , Escherichia coli/metabolismo , Ferro/metabolismo , Quelantes de Ferro/farmacologia , Metilnitronitrosoguanidina/farmacologia , N-Glicosil Hidrolases/metabolismo , Fenantrolinas/farmacologia , Proteínas Repressoras/metabolismo , Resposta SOS em Genética , Fatores de Transcrição/metabolismo , Raios UltravioletaRESUMO
It is important to have a rapid and accurate method to detect the toxic action of drugs and chemical compounds used by man. A comparative study with two microbial systems was carried out: one using Salmonella typhimurium and the other using Bacillus subtilis. The 1-8-dihydroxyantraquinone was the tested drug and the N-methyl-N'-nitro-N-nitrosoguanidine and the 2-aminofluorene were used as control substances. These compounds were used as such or after previous transformation by a microsomal system. The results obtained showed that both systems: the S. typhimurium and the B. subtilis work in a similar way, but the latter allows a more direct action of drug on the genetic material. The effect of the solvents: ethanol and dimethylsulfoxide was analysed, because they affected the transformation and reversion processes that were carried out.