ATP-induced apoptosis of thymocytes is mediated by activation of P2X7 receptor and involves de novo ceramide synthesis and mitochondria

Thymocytes were reported to undergo apoptosis in the presence of extracellular ATP through the activation of the purinergic receptors P2X1R, P2X7R or both. We investigated the identity of the P2XR and the signaling pathways involved in ATP-mediated apoptosis. Apoptosis elicited by ATP was prevented by inhibition of P2X7R, or in thymocytes bearing a mutated P2X7R, and reproduced with a P2X7R agonist, but not with a P2X1R agonist. Stimulation of thymocytes with either ATP or a P2X7R agonist was found to stimulate a late de novo ceramide synthesis and mitochondrial alterations. Inhibition of either processes attenuated apoptosis. Interestingly, stimulation with either ATP or a P2X1R agonist induced an early ceramide accumulation and a weak caspases-3/7 activation that did not lead to apoptosis. In conclusion, de novo ceramide generation and mitochondrial alterations, both resulting from P2X7R activation, were implicated in ATP-induced thymocyte apoptosis.