Adenosine uptake is the major effector of extracellular ATP toxicity in human cervical cancer cells.
Bottom Line: Corroborating these data, blockage or knockdown of P2 × 7 only slightly reduced ATP cytotoxicity.Moreover, ATP-induced apoptosis and signaling-p53 increase, AMPK activation, and PARP cleavage-as well as autophagy induction were also inhibited by dipyridamole.In addition, inhibition of adenosine conversion into AMP also blocked cell death, indicating that metabolization of intracellular adenosine originating from extracellular ATP is responsible for the main effects of the latter in human cervical cancer cells.
Affiliation: Laboratory of Biochemical and Cytological Analysis, Faculty of Pharmacy, Federal University of Rio Grande do Sul, Porto Alegre, RS 90610-000, Brazil.Show MeSH
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Mentions: To investigate which cells are killed by ATP directly, we determined the P2×7 protein levels in cells after treatment with ATP in two ways: 1) cells were treated with 5 mM ATP for 24, 48, and 72 h, and the remaining adherent cells were lysed and tested for P2×7 levels (Figure 5A); and 2) cells were treated with 5 mM ATP for 24, 48, and 72 h, followed by medium removal, two washes with 1× phosphate-buffered saline (PBS), and growth in ATP-free medium for an additional 4 d; adherent cells were then collected, and Western blot analysis was performed (Figure 5B). As shown in Figure 5, A and B, in both treatments, cells that remained adherent showed lower P2×7 protein levels than control, indicating that a subpopulation of cells with higher P2×7 levels was eliminated by ATP, as was also observed in glioma cells (Tamajusuku et al., 2010). Together these results suggest that extracellular ATP per se is responsible for only a small part (∼20%) of the toxicity of extracellular ATP through the P2×7 receptor and that the remaining cytotoxic effect might be through a metabolite derivative.
Affiliation: Laboratory of Biochemical and Cytological Analysis, Faculty of Pharmacy, Federal University of Rio Grande do Sul, Porto Alegre, RS 90610-000, Brazil.