International journal of radiation biology · 2000
Involvement of calcium ion in elevation of mRNA for gamma-glutamylcysteine synthetase (gamma-GCS) induced by low-dose gamma-rays.
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Teshima K, Yamamoto A, Yamaoka K, Honda Y, Honda S, Sasaki T, Kojima S
Аннотация
PURPOSE: To investigate the mechanism of the intracellular glutathione elevation induced by low-dose gamma-radiation.
MATERIALS AND METHODS: RAW 264.7 cells were irradiated with 1-400cGy gamma-rays. Intracellular total glutathione content was determined by DTNB-recycling assay. Expression of mRNA for intracellular glutathione synthesis-related enzymes with or without treatment with various inhibitors of second messengers of gene expression were examined by Northern blot analysis.
RESULTS: Expression of mRNA for gamma-glutamylcysteine synthetase (gamma-GCS), a rate-limiting enzyme of the de novo glutathione synthesis pathway, was elevated much more than that of glutathione reductase (GR) mRNA after exposure to 50cGy gamma-rays. The low-dose gamma-ray-induced gamma-GCS mRNA elevation was abolished by inhibitors of protein kinase C and protein tyrosine kinase, as well as by the calcium ion channel blocker, nifedipine. Calcium-related reagents, such BAPTA/AM and EGTA, chelators of intra- and extracellular Ca2+ respectively, and a Ca2+ ionophore (A23187), also strongly blocked the elevation of gamma-GCS mRNA expression induced by gamma-rays.
CONCLUSIONS: The increase of intracellular glutathione in RAW 264.7 soon after low-dose gamma-ray exposure mainly occurs through the operation of the de novo pathway, following by the induction of gamma-GCS mRNA, for which elevation of intracellular calcium is required.
MATERIALS AND METHODS: RAW 264.7 cells were irradiated with 1-400cGy gamma-rays. Intracellular total glutathione content was determined by DTNB-recycling assay. Expression of mRNA for intracellular glutathione synthesis-related enzymes with or without treatment with various inhibitors of second messengers of gene expression were examined by Northern blot analysis.
RESULTS: Expression of mRNA for gamma-glutamylcysteine synthetase (gamma-GCS), a rate-limiting enzyme of the de novo glutathione synthesis pathway, was elevated much more than that of glutathione reductase (GR) mRNA after exposure to 50cGy gamma-rays. The low-dose gamma-ray-induced gamma-GCS mRNA elevation was abolished by inhibitors of protein kinase C and protein tyrosine kinase, as well as by the calcium ion channel blocker, nifedipine. Calcium-related reagents, such BAPTA/AM and EGTA, chelators of intra- and extracellular Ca2+ respectively, and a Ca2+ ionophore (A23187), also strongly blocked the elevation of gamma-GCS mRNA expression induced by gamma-rays.
CONCLUSIONS: The increase of intracellular glutathione in RAW 264.7 soon after low-dose gamma-ray exposure mainly occurs through the operation of the de novo pathway, following by the induction of gamma-GCS mRNA, for which elevation of intracellular calcium is required.
Предметные рубрики MeSH
AnimalsBlotting, NorthernCalcimycinCalciumCalcium Channel BlockersCell LineChelating AgentsDose-Response Relationship, RadiationEgtazic AcidGamma RaysGlutamate-Cysteine LigaseGlutathioneGlutathione ReductaseIonophoresIonsMacrophagesMiceModels, BiologicalNifedipineProtein Kinase CProtein-Tyrosine KinasesRNA, MessengerSignal TransductionTime Factors