Changes in phosphate metabolism in thymoma cells suggest mechanisms for resistance to dexamethasone-induced apoptosis. A 31P NMR spectroscopic study of call extracts

N. W. Lutz, M. E. Tome, N. R. Aiken, M. M. Briehl

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

Treatment of the mouse thymoma-derived WEHI7.2 cell line with dexamethasone, a synthetic glucocorticoid, causes the cells to undergo apoptosis. Previous studies have shown that WEHI7.2 cell variants with an increased antioxidant defense exhibit increased resistance to dexamethasone-induced apoptosis, suggesting that oxidative stress may play a role in glucocorticoid-induced apoptosis. In this work we compared metabolic profiles of WEHI7.2 parental cells with those of WEHI7.2 variants with an increased antioxidant defense or overexpressing bcl-2, to determine whether bolstering the antioxidant defense results in altered metabolic parameters that could translate into increased resistance to dexamethasone-induced apoptosis. WEHI7.2 parental cells and cells overexpressing catalase, thioredoxin or bcl-2, or selected for resistance to 200 μM H2O2 were cultured in low-glucose DMEM medium supplemented with 10% calf serum, and extracted using chloroform-methanol-water (1:1:1). Metabolites contained in the aqueous and organic phases of the extracts were processed separately and subjected to high-resolution 31P NMR spectroscopy. In most of the steroid-resistant variants, ATP levels and energetic status were decreased compared with the steroid-sensitive parental cell line, while the concentrations of hexose and triose phosphates were increased. Furthermore, the ratio of choline-containing phospholipids to ethanol amine-containing phospholipids was generally reduced in steroid-resistant cells. Phosphatidylethanolamine and its derivatives contain a higher amount of polyunsaturated fatty acids (PUFA) than the choline-containing analogs, and PUFA are readily oxidized by reactive oxygen species. Therefore, an increased initial amount of phosphatidylethanolamine may increase the 'buffering capacity' of this antioxidant and may thus contribute to the steroid resistance of WEHI7.2 variants.

Original languageEnglish (US)
Pages (from-to)356-366
Number of pages11
JournalNMR in biomedicine
Volume15
Issue number5
DOIs
StatePublished - Aug 2002

Keywords

  • Apoptosis
  • Cell extracts
  • Glucocorticoids
  • Metabolism
  • NMR spectroscopy
  • Oxidative stress
  • Thymocytes

ASJC Scopus subject areas

  • Molecular Medicine
  • Radiology Nuclear Medicine and imaging
  • Spectroscopy

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