Estudos in vitro sobre a atividade antioxidante, antimutagenica e potencial de risco da melatonina
Simone Fanan
DISSERTAÇÃO
Português
T/UNICAMP F212e
Campinas, SP : [s.n.], 1999.
98p. : il.
Orientador: Maria Edwiges Hoffmann
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia
Resumo: A melatonina, honnônio produzido pela glândula pineal, apresenta um gr-ande interesse na atualidade, devido à demonstração de sua ação antioxidante tanto in vitro como in vivo. Neste trabalho, foi investigado o potencial de risco genético e toxicológico da melatonina em culturas de células,...
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Resumo: A melatonina, honnônio produzido pela glândula pineal, apresenta um gr-ande interesse na atualidade, devido à demonstração de sua ação antioxidante tanto in vitro como in vivo. Neste trabalho, foi investigado o potencial de risco genético e toxicológico da melatonina em culturas de células, e sua atividade antimutagênica. A mutagenicidade da melatonina foi determinada pelo teste de Ames, na presença e na ausência de ativação metabólica (fração S9), nas linhagens de Salmonella typhimurium TA97, Tal00 e TA102. A exposição das culturas por 30 minutos, à diferentes concentrações de melatonina (29-1160 _g/placa) não induziu nenhum aumento significativo do número de colônias revertentes, tanto na presença como na ausência de ativação metabólica. A melatonina mostrou, também, uma reversão dose-dependente (29 ¿ 232 _g/placa) dos efeitos mutagênicos causados pelo H2O2 (0,5 mM), na linhagem T A1O2. A atividade citotóxica da melatonina para fibroblastos de hamster chinês (linhagem V79) foi determinada pela medida de seus efeitos sobre a viabilidade e proliferação celular. A melatonina não alterou a viabilidade celular, medida pela redução do MTT, na faixa de concentração entre 0,0001 a 1 mM. A exposição das células por 30 minutos a diferentes concentrações de melatonina (0,01 - 5 mM) não causou inibição significativa do crescimento celular, no período de 24 horas subsequente ao tratamento. Entretanto, a exposição das células por 24 horas a concentrações de melatonina entre 0,5 a 5 mM causou inibição significativa do crescimento celular, de fonna dependente da dose. A melatonina mostrou ser um antioxidante altamente eficiente em solução, inibindo a oxidação degradativa da desoxirribose, induzida pelo sistema H2O2/Fe+3/NTA, de forma dependente da dose. Este hormônio foi 10 vezes mais eficiente que a glutationa e 200 vezes mais que o manitol, ao sequestrar os radicais hidroxila. Porém, o trolox foi 15 vezes mais eficaz que a melatonina. Entretanto, ao avaliar crescimento celular em fibroblastos V79, a melatonina (0,001 mM) mostrou uma proteção apenas parcial (50+ 7%) do efeito inibitório induzido por H2_ (50 µM). Contudo, a melatonina não protegeu a membrana mitocondrial de fibroblastos V79 contra os ataques dos oxidantes H2O2 e HPC (2,5 mM), como demonstrado pela ausência de proteção no ensaio do MTT. Já em eritrócitos humanos, ela mostrou ser um antioxidante eficiente contra a peroxidação lipídica, induzida pelo H2O2 (5 mM), apresentando um efeito protetor dose-dependente. Estes resultados indicam que a melatonina não é mutagênica e, além disso, inibe a mutação induzida pela H2O2 . A análise da toxicidade da melatonina pelas células V79 mostrou que a melatonina é citotóxica somente quando presente em altas concentrações e por tempo prolongado. A melatonina mostrou ser um eficiente antioxidante em sistema livre de células, em cultura de fibroblastos V79 apresentou proteção apenas parcial contra os efeitos da H2O2 . Entretanto, em eritrócitos mostrou eficiente proteção contra danos de membrana induzidos por este oxidante
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Abstract: The melatonin, hormone produced 1>y the pineal gland,presents _ great interest at the present time due to the demonstration of its antioxidant action as in vitro as in vivo. In this work, the potential of toxicological risk of the melatonin was investigated in bacterias and in mammal...
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Abstract: The melatonin, hormone produced 1>y the pineal gland,presents _ great interest at the present time due to the demonstration of its antioxidant action as in vitro as in vivo. In this work, the potential of toxicological risk of the melatonin was investigated in bacterias and in mammal cells,and its antioxidant activity was examined in cell tree systems, in human fibroblast V79 and in erythrocyte. The mutagenicity of the melatonin was determined by Ames Test, in the presence and in the absence of metabolic activation (S9-traction), in the strains of Salmonella typhimurium TA97, TA100 and TA102. The exposition of cultures by 30 minutes, to different melatonin concentrations (29 to 1,160 µg/plate) didn't induce any significant increase of the number of reverted colonies, after 48 hours of cultivation, so much in the presence as in the absence of metabolic activation. The melatonin also showed, a dose
dependent reversion (29 to 232 µg/plate) ofthe mutagenics effects caused by the hydrogen peroxide (0.5 mM), in the TA102 straip.. Theçytotmric activity of the melatonin to V79 Chinese hamster fibroblasts was determined by the measure of its effects on proliferation. The melatonin didn't chage the cellular viability mesured by the reduction of MTT, in the concentration range trom 0.0001 to 1 mM. The exposition of the cells for 30 minutes to different melatonin concentrations (0.01 -5 mM) didn't caus_significant iphibitionof the cellular growth, in the period of subsequent 24 hours of treatment. However, the exposition of the cells for 24 hours to increasing melatonin concentrations between 0.5 and 5 mM, caused significant inhibition in the cellular growth, in dependent way of the dose. The .melatonin,showed to be ahighly efficient antioxidant in solution, inhibiting thedegradative oxidation of the deoxyribose, induced by the system H2O2/Fe3+/NTA, in a dependent way to the dose. This honnone was more than 10 times efficient than the glutathione and 200 times more efficient than the manit04 when scaveng the hydroxil radical. Even so, the trolox was more than 15 times effective than the melatonin. However, when evaluating cellular growth in fibroblasts V79, the melatonin just showed a partial protection (50+
7%) ofthe inhibition effect induced by H2O2 (50µM), in _low concentration (0.001 mM). However, the melatonin up to lmM didn't protect the mitochondrional membrane of fibroblasts V79 against the attacks of the hydrogen peroxide and cumene hydroperoxide (2.5 mM), as demonstrated by the absence of protection related to the inhibition of the MTT reduction induced by these oxidizers. Yet in human erythrocytes, it showed to be an efficient antioxidant against lipid peroxidation, induced in the membrane by hydrogen peroxide (5 mM), presenting a dose-dependent protecting effect. These results indicate that melatonin is not mutagenic; besides, it inhibits mutations induced by H2O2 . The analysis of melatonin toxicity through the cells V79 showed that melatonin is citotoxic, on1y when it is present in high concentrations, for a long time. Melatonin showed to be na efficient antioxidant in a cell ftee system, but in cultures of fibroblasts V79 it showed just a partial protection against the effects of H2O2 . However, in erythrocytes, it showed an efficient protection against membrane injuries caused by this oxidant Ver menos
dependent reversion (29 to 232 µg/plate) ofthe mutagenics effects caused by the hydrogen peroxide (0.5 mM), in the TA102 straip.. Theçytotmric activity of the melatonin to V79 Chinese hamster fibroblasts was determined by the measure of its effects on proliferation. The melatonin didn't chage the cellular viability mesured by the reduction of MTT, in the concentration range trom 0.0001 to 1 mM. The exposition of the cells for 30 minutes to different melatonin concentrations (0.01 -5 mM) didn't caus_significant iphibitionof the cellular growth, in the period of subsequent 24 hours of treatment. However, the exposition of the cells for 24 hours to increasing melatonin concentrations between 0.5 and 5 mM, caused significant inhibition in the cellular growth, in dependent way of the dose. The .melatonin,showed to be ahighly efficient antioxidant in solution, inhibiting thedegradative oxidation of the deoxyribose, induced by the system H2O2/Fe3+/NTA, in a dependent way to the dose. This honnone was more than 10 times efficient than the glutathione and 200 times more efficient than the manit04 when scaveng the hydroxil radical. Even so, the trolox was more than 15 times effective than the melatonin. However, when evaluating cellular growth in fibroblasts V79, the melatonin just showed a partial protection (50+
7%) ofthe inhibition effect induced by H2O2 (50µM), in _low concentration (0.001 mM). However, the melatonin up to lmM didn't protect the mitochondrional membrane of fibroblasts V79 against the attacks of the hydrogen peroxide and cumene hydroperoxide (2.5 mM), as demonstrated by the absence of protection related to the inhibition of the MTT reduction induced by these oxidizers. Yet in human erythrocytes, it showed to be an efficient antioxidant against lipid peroxidation, induced in the membrane by hydrogen peroxide (5 mM), presenting a dose-dependent protecting effect. These results indicate that melatonin is not mutagenic; besides, it inhibits mutations induced by H2O2 . The analysis of melatonin toxicity through the cells V79 showed that melatonin is citotoxic, on1y when it is present in high concentrations, for a long time. Melatonin showed to be na efficient antioxidant in a cell ftee system, but in cultures of fibroblasts V79 it showed just a partial protection against the effects of H2O2 . However, in erythrocytes, it showed an efficient protection against membrane injuries caused by this oxidant Ver menos
Estudos in vitro sobre a atividade antioxidante, antimutagenica e potencial de risco da melatonina
Simone Fanan
Estudos in vitro sobre a atividade antioxidante, antimutagenica e potencial de risco da melatonina
Simone Fanan
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