RESUMO
Nucleotide excision repair (NER) is the most flexible of all known DNA-repair mechanisms, and XPG is a 3'-endonuclease that participates in NER. Mutations in this gene (ERCC5) may result in the human syndrome xeroderma pigmentosum (XP) and, in some cases, in the complex phenotype of Cockayne syndrome (CS). Two Brazilian XP siblings, who were mildly affected, were investigated and classified into the XP-G group. The cells from these patients were highly ultraviolet (UV) sensitive but not sensitive to photosensitized methylene blue, an agent that causes oxidative stress. This phenotype is in contrast to XP-G/CS cells, which are highly sensitive to this oxidative agent. Sequencing revealed a compound heterozygous genotype with two novel missense mutations: c.83C>A (p.Ala28Asp) and c.2904G>C (p.Trp968Cys). The first mutation maps to the catalytic site of the XPG protein, whereas the second may compromise binding to DNA. Functional assays indicated that the mutated alleles were unable to perform the complete repair of UV-irradiated plasmids; however, full correction was observed for oxidatively damaged plasmids. Therefore, the XP phenotype of these patients is caused by novel missense mutations that specifically affect DNA repair for UV- but not oxidative-stress-induced DNA damage, and implications for XP versus XP/CS phenotype are discussed.
Assuntos
Sobrevivência Celular/efeitos da radiação , Reparo do DNA/efeitos da radiação , Proteínas de Ligação a DNA/genética , Endonucleases/genética , Proteínas Nucleares/genética , Fatores de Transcrição/genética , Adolescente , Alelos , Sequência de Aminoácidos , Brasil , Linhagem Celular , Clonagem Molecular , Síndrome de Cockayne/genética , Dano ao DNA/efeitos da radiação , Feminino , Fibroblastos/citologia , Fibroblastos/efeitos da radiação , Heterozigoto , Humanos , Masculino , Dados de Sequência Molecular , Mutação de Sentido Incorreto , Estresse Oxidativo/efeitos da radiação , Fenótipo , Conformação Proteica , Alinhamento de Sequência , Análise de Sequência de DNA , Raios Ultravioleta , Xeroderma Pigmentoso/genética , Adulto JovemRESUMO
The caspase-3-cleaved presence was evaluated in this study in the heart of irradiated rats, during the decline of ventricular function. Female Wistar rats were irradiated with a single dose of radiation (15 Gy) delivered directly to the heart and the molecular, histological and physiological evaluations were performed at thirteen months post-irradiation. The expressions of procollagen type I, TGF-ß1 and caspase-3-cleaved were analyzed using Western blotting. Cardiac structural and functional alterations were investigated by echocardiography and electron microscopy. In the irradiated group, the levels of procollagen type I, TGF-ß1 and caspase-3-cleaved are increased. Significant histological changes (degeneration of heart tissue and collagen deposition) and functional (reduced ejection fraction) were observed. Data suggest that the cardiac function decline after exposure to ionizing radiation is related, in part, to increased collagen and increased caspase-3-cleaved.
Assuntos
Caspase 3/metabolismo , Colágeno Tipo I/metabolismo , Coração/efeitos da radiação , Miocárdio/enzimologia , Fator de Crescimento Transformador beta1/metabolismo , Animais , Western Blotting , Relação Dose-Resposta à Radiação , Ecocardiografia , Ativação Enzimática/efeitos da radiação , Feminino , Microscopia Eletrônica de Transmissão , Miocárdio/ultraestrutura , Ratos , Ratos WistarRESUMO
Lanthanum (La) is a rare-earth metal with applications in agriculture, industry, and medicine. Since lanthanides show a broad spectrum of applications there is an increased risk of contamination for humans. We examined the effects of lanthanum in Jurkat cells and human peripheral lymphocytes (HPL), and we found that it was cytotoxic and genotoxic on both cell lines. Additionally, HPL were more sensitive to La treatment than Jurkat cells and necrosis was the pathway by which La induced cytotoxicity. Vitamin E was able to diminish the DNA strand breaks induced suggesting that oxidative stress may be involved in the genotoxic process.
Assuntos
Carcinógenos/toxicidade , Poluentes Ambientais/toxicidade , Lantânio/toxicidade , Linfócitos/efeitos dos fármacos , Mutagênicos/toxicidade , Sobrevivência Celular/efeitos dos fármacos , Dano ao DNA/efeitos dos fármacos , Relação Dose-Resposta a Droga , Antagonismo de Drogas , Combinação de Medicamentos , Poluentes Ambientais/classificação , Humanos , Células Jurkat , Lantânio/classificação , Linfócitos/patologia , Necrose/induzido quimicamente , Vitamina E/farmacologiaRESUMO
Foi avaliada neste estudo a presença de caspase-3-clivada no coração de ratos irradiados durante o declínio da função ventricular. Ratas Wistar foram irradiadas com uma dose única de radiação (15 Gy) diretamente no coração e as análises molecular, histológica e fisiológica foram realizadas treze meses pós a irradiação dos animais. As expressões de procolágeno tipo I, TGF-ß1 e caspase- 3-clivada foram analisadas usando Western blotting. Alterações cardíacas estruturais e funcionais foram investigadas por meio de ecocardiografia e microscopia eletrônica. No grupo irradiado, os níveis de procolágeno tipo I, TGF-ß1 e caspase-3-clivada estão aumentados Alterações histológicas importantes (degeneração do tecido cardíaco e deposição de colágeno) e funcionais (fração de ejeção reduzida) foram observadas. Dados sugerem que o declínio da função cardíaca após a exposição à radiação ionizante está relacionado, em parte, com aumento do colágeno e da caspase-3-clivada.
RESUMO
Oxyygen free radicals are highly reactive species that damage several cellular macromolecules and organelles, including membrane lipid peroxidation and produce DNA lesions. We have discussed here; i) The mechanism of radiation-induced cellular damage in bacteria through the intermediation of active oxygen species; ii) the cellular inactivation and the role of bacterial SOS and OxyR systems in the repair of lesions induced by H2O2 under low iron condition; iii) the lethal interaction between H2O2 and o-phenanthroline in E. coli; iv) the biological response induced by near-UV radiation mediated by active oxygen species and finally v) the mutagenic potential of popular plant extracts like guaraná (Paullinia cupana), mate (Ilex paraguariensis) and saiao (Kalanchoe brasiliensis), whose effects are eventually mediated by active oxygen species.