Role of Glutathione in Apoptosis Induced by Radiation as Determined by¹H MR Spectra of Cultured Tumor Cells

Abstract

The relationship between apoptosis induced by gamma radiation and glutathione in cells of two human cancer cell lines, HeLa from cervix carcinoma and MCF-7 from mammary carcinoma, was examined. MCF-7 cells appeared to be more radioresistant than HeLa cells, and radiation-induced apoptosis, which was monitored by assessing phosphatidylserine externalization, was observed in HeLa cells but not in MCF-7 cells. Glutathione levels monitored by (1)H MRS were higher in MCF-7 cells than in HeLa cells, while the opposite was true for the free glu signals. MCF-7 cells became more radiosensitive when treated with 0.1 mM buthionine sulfoximine, which inhibits GSH synthesis through inactivation of gamma-glutamylcysteine synthetase, with the concomitant appearance of radiation-induced apoptosis. We can thus reasonably associate, at least in part, the resistance of MCF-7 cells to apoptosis with a high level of glutathione and probably with a high activity of gamma-glutamylcysteine synthetase. A late decrease in glutathione concentration after irradiation was observed in MCF-7 cells, but not in HeLa cells and to a lesser degree in buthionine sulfoximine-treated MCF-7 cells. This would indicate that the radiation-induced decrease in glutathione concentration is not related to the onset of apoptosis, but it is more likely related to glutathione consumption as a result of detoxification reactions.

Malignancy-associated metabolic profiling of human glioma cell lines using 1H NMR spectroscopy

“…In addition, GSH is particularly vital in protecting cells from radiation damage, which has generated reactive oxygen species. Rosi et al found that a high level of GSH was correlated with radiation-induced apoptosis by MR spectra of cultured tumor cells [31]. Thus, consistently with previous literature [30, 31], the elevated GSH levels observed in our work might be related to enhanced antioxidant mechanisms in glioma cells with high malignant degree.…”

Metabolism of glutathione in tumour cells as evidenced by 1H MRS

“…PCA extracts were prepared as previously described [8]. All reagents were purchased from Sigma (St. Louis, MI, USA).…”

“…1H MRS signals of GSH and of its oxidized form GSSG were assigned to specific chemical groups through 1D and 2D COSY experiments performed in GSH solution and in perchloric acid extracts from tissues [4,7,8].…”

“…In a previous paper [8], we related the intensity of GSH signals of tumour cells to cell tendency to undergo apoptosis by irradiation. In the present study, we examined MRS signal intensity of GSH and of free glu in cultured cells MCF-7 from mammary carcinoma and T98G from malignant glioma, aiming at elucidating to which aspects of GSH metabolism they are related.…”

UPLC-ESI-TOFMS-Based Metabolomics and Gene Expression Dynamics Inspector Self-Organizing Metabolomic Maps as Tools for Understanding the Cellular Response to Ionizing Radiation

“…16,17 At the same time, the metabolomic technologies have contributed to a general understanding of how metabolites and their concentrations change under defined conditions.18 However, in contrast to transcriptomics and proteomics, broadbased metabolomic studies have not been used to analyze the cellular effects of IR. Smallscale, directed approaches using high-sensitivity nuclear magnetic resonance spectroscopy (NMR) [19][20][21][22][23] have been applied to estimate the relative concentration changes of a small subset of metabolites (e.g., reduced glutathione) following IR, but a global metabolomic approach has not yet been reported. The effects of IR include activation of stress responses to reduce reactive oxygen species (ROS), an increase in nucleotide pools for unscheduled DNA repair, and increases in cellular energy intermediates.…”