Purine Uptake and Release in Rat C6 Glioma Cells

Abstract

Adenosine, through activation of membranebound receptors, has been reported to have neuroprotective properties during strokes or seizures. The role of astrocytes in regulating brain interstitial adenosine levels has not been clearly defined. We have determined the nucleoside transporters present in rat C6 glioma cells. RT H]adenine to label adenine nucleotide pools. Tritium release was initiated by inhibiting glycolytic and oxidative ATP generation and thus depleting ATP levels. Our results indicate that during ATP-depleting conditions, AMP catabolism progressed via the reactions AMP 3 IMP 3 inosine 3 hypoxanthine, which accounted for Ͼ90% of the evoked tritium release. It was surprising that adenosine was not released during ATP-depleting conditions unless AMP deaminase and adenosine deaminase were inhibited. Inosine release was enhanced by inhibition of purine nucleoside phosphorylase; ENT2 transporters mediated the release of adenosine or inosine. However, inhibition of AMP deaminase/adenosine deaminase or purine nucleoside phosphorylase during ATP depletion produced release of adenosine or inosine, respectively, via the rENT2 transporter. This indicates that C6 glioma cells possess primarily rENT2 nucleoside transporters that function in adenosine uptake but that intracellular metabolism prevents the release of adenosine from these cells even during ATPdepleting conditions.

[18F]Fludarabine-PET as a promising tool for differentiating CNS lymphoma and glioblastoma: Comparative analysis with [18F]FDG in human xenograft models

“…Therefore, the better inter-model differentiation with [ 18 F]FDB-PET was quite evident. Indeed, the mechanism of incorporation of [ 18 F]FDB into CNSL and GBM should well be similar, as both cells are known to express ENT proteins 46 , 47 . The selective uptake of this radiotracer for CNSL is due to its dCK-related retention mechanism, as the activity of this enzyme is elevated in lymphoid malignancies 23 , 24 .…”

Regulation of Equilibrative Nucleoside Uptake by Protein Kinase Inhibitors

“…This included inhibitors of MEK (PD98059, U0126) and inhibitors of PI-3 kinase (wortmannin, LY294002). However, recent characterization of the effects of Ro-31-6045 and SB203580-iodo on ENT2-dependent transport in Rat C6 glioma cells, a cell line predominantly expressing ENT2, [18] suggests that ENT2 is also inhibited by these compounds with an IC 50 of, 0.52 mM and 0.77 mM respectively (Dr. Min Huang, unpublished observations). For instance, SB202474, an analog of SB203580 that does not inhibit p38 MAPK, also significantly inhibited nucleoside uptake in these cells (65%) suggesting that the effects of these compounds occurred independently of p38 MAP kinase inhibition.…”

ADP-ribose triggers neuronal ferroptosis via metabolic orchestrating

“…These results are similar in some terms with a study made by Perez and colleagues, who demonstrated that the major amount of [3H]-adenosine taken up by rabbit retina cells is converted into adenine nucleotides and, in the presence of a depolarizing stimulus, an increase of purine release is observed, mainly as hypoxanthine, xanthine, and inosine. This release was partially blocked by dipyridamole, an inhibitor of nucleoside transporters( 51-53 ).…”