³¹P NMR characterization of cellular metabolism during dexamethasone induced apoptosis in human leukemic cell lines

Abstract

31P NMR has been used to study the effects of dexamethasone on phosphorus metabolism in one dexamethasone (dex)-sensitive (CEM-C7) and three different dex-resistant (CEM-C1, CEM-4R4, and CEM-ICR27) human leukemic cell lines. The use of these cell lines, containing widely varying amounts of glucocorticoid receptors, made it possible to evaluate the receptor-mediated contributions to the modes of action of dexamethasone in these cells. To evaluate the effects of dexamethasone without any significant contribution from experimental conditions, all the experiments were done with parallel controls. Results obtained showed: 1) significantly different levels of phosphorylethanolamine (PE) and phosphorylcholine (PC) among cell lines, suggesting significant differences in phospholipid metabolism; 2) the dexamethasone induced reduction of phosphomonoester (PE+PC), ATP, and metabolic rates probably through glucocorticoid receptor mediated mechanisms; 3) the dexamethasone induced stimulation of cellular metabolism in a process which seems to be independent of glucocorticoid receptors; and 4) the dexamethasone induced alkaline shift of intracellular pH in all the cell lines except ICR27. The reduction in PME levels seems to be an earlier step in dexamethasone-induced apoptosis than the reduction in ATP. The degree of alkaline shift was found to correlate with the number of glucocorticoid receptors present. The possible involvement of phospholipid metabolites as second messengers in dexamethasone-induced apoptosis is discussed.

13C-NMR investigation of protein synthesis during apoptosis in human leukemic cell lines

“…Since the CEM-ICR27-4 cells lack functional glucocorticoid receptors, the observed dex-induced stimulation of the CEM-ICR27-4 cells can be attributed to the glucocorticoid receptor-independent mechanism. This result is consistent with the previous 31 P-NMR study (Adebodun and Post, 1994) in which dex-induced stimulation of CEM-ICR27-4 cells was observed. The dex-induced stimulation is probably due to the binding of dex to growth factor receptors (Baker et al, 1978).…”

“…The pellet was resuspended in 100 mL of fresh label-free Iscove's medium and recentrifuged (200g, 4°C, 10 min) in order to wash the cells and remove any residual extracellular 13 C-labeled amino acids. The resulting pellet was used to prepare the NMR sample by suspending the pellet in 1 mL of cold isotonic Iscove's medium supplemented with glucose and HEPES buffer (Adebodun and Post, 1994) to provide sufficient sustenance and buffering capacity during NMR experiments.…”

Early gene therapy–induced apoptotic response in BT4C gliomas by magnetic resonance relaxation contrast T1 in the rotating frame

“…40 Unlike ischemia, or necrosis, apoptotic cell death is an energy requiring process and cell energy levels are reasonably well maintained. 41,42 Nevertheless, the clear mismatch between T 1 , and the conventional relaxation parameters, i.e., T 1 and T 2 , diffusion and spin density changes, directly indicates that the latter MRI variables are sensing different cellular events of advanced apoptotic cell death, i.e., depicting increased tissue water content.…”

Methodological standardization for a multi‐institutional in vivo trial of localized 31P MR spectroscopy in human cancer research. In vitro and normal volunteer studies

“…Our rationale for this evaluation was based on promising preliminary evidence that: (a) tumor levels of the phospholipidrelated phosphomonoesters, phosphoethanolamine (Etn-P) and phosphocholine (Cho-P) measured by 31 P-MRS are elevated in human tumors in vivo; [1][2][3][4] (b) a decrease of Etn-P and Cho-P has been demonstrated to precede cell death of several types of human cancerous cells in vitro; [5][6][7] and (c) pretreatment variations of Etn-P þ Cho-P have been found to predict long-term response to treatment and time to treatment failure, especially when correlated with a well-standardized clinical parameter, the International Prognostic Index, in a small cohort of patients afflicted with non-Hodgkin's lymphomas. 8 These preliminary observations point out the possibility of utilizing clinically the Etn-P and Cho-P changes in tumors in vivo as early indicators of treatment response.…”