Possible roles for ATP release from RBCs exclude the cAMP-mediated Panxl pathway

摘要

Red blood cell (RBC)-derived adenosine triphosphate (ATP) has been proposed as an integral component in the regulation of oxygen supply to skeletal muscle. In ex vivo settings RBCs have been shown to release ATP in response to a number of stimuli, including stimulation of adrenergic receptors. Further evidence suggested that ATP release from RBCs was dependent on activation of adenylate cyclase (AC)/cyclic adenosine monophosphate (cAMP)-dependent pathways and involved the pannexin 1 (Panxl) channel. Here we show that RBCs express Panxl and confirm its absence in Panxl knockout (-/-) RBCs. However, Panxl-/- mice lack any decrease in exercise performance, challenging the assumptions that Panxl plays an essential role in increased blood perfusion to exercising skeletal muscle and therefore in ATP release from RBCs. We therefore tested the role of Panxl in ATP release from RBCs ex vivo in RBC suspensions. We found that stimulation with hypotonic potassium gluconate buffer resulted in a significant increase in ATP in the supernatant, but this was highly correlated with RBC lysis. Next, we treated RBCs with a stable cAMP analog, which did not induce ATP release from wild-type or Panxl-/- mice. Similarly, multiple pharmacological treatments activating AC in RBCs increased intra-cellular cAMP levels (as measured via mass spectrometry) but did not induce ATP release. The data presented here question the importance of Panxl for exercise performance and dispute the general assumption that ATP release from RBCs via Panxl is regulated via cAMP.