Extracellular adenosine-induced apoptosis in mouse neuroblastoma cells - Studies on involvement of adenosine receptors and adenosine uptake

The induction of apoptosis by adenosine was studied in the mouse neuroblast oma cell line N1E-115. Apoptosis was characterized by fluorescence acid ele ctron microscopy, fluorescence-activated cell sorter (FACS) analysis, and c aspase activity assays. A sixteen-hour exposure to 100 muM of adenosine led to chromatin condensation and caspase activation. However, selective agoni sts for all four adenosine receptors were ineffective. Caspase activation c ould be blocked partially by an inhibitor of the nucleoside transporter, di pyridamole, and completely by uridine, a competing substrate for adenosine transport. 2'-Deoxycoformycin, an inhibitor of adenosine deaminase, enhance d caspase activation by adenosine but had no effect by itself. Caspase acti vation could be blocked by 5'-amino-5'-deoxyadenosine, which inhibits the p hosphorylation of adenosine by adenosine kinase. These results indicate tha t adenosine receptors are not involved in adenosine-induced apoptosis in N1 E-115 cells, but that uptake of adenosine and its subsequent phosphorylatio n is required. (C) 2001 Elsevier Science Inc. All rights reserved.