Reoxygenation‐Induced ATP Release from Endothelial Cells via Connexin 43 is Regulated by cAMP/PKA Signaling

Background Reperfusion disturbes endothelial barrier function leading to edema formation and impaired recovery of the heart. Recently, we have shown that connexin 43 (Cx43) is essential for reperfusion‐induced ATP release from endothelial cells (EC) stabilizing endothelial barrier function. Here we analyzed the signaling mechanism regulating Cx43‐dependent ATP release during reoxygenation. Methods and Results ATP release, Cx43 content, and phosphorylation of Cx43 were determined in cultured endothelial cells exposed to hypoxia and reoxygenation. Specific involvement of Cx43, but not Pannexin 1 was confirmed by use of pharmacological inhibitors as well as Cx43 silencing by specific siRNA. Activation of the cAMP/PKA signaling pathway at the onset of reoxygenation enhanced reoxygenation‐induced ATP release, which could be abolished by pharmacological and peptide‐based inhibition of PKA. Silencing of Cx43 by siRNA abolished reoxygenation‐induced ATP release and also abolished the effect of PKA activation on ATP release. Conclusion The data of the present study demonstrate for the first time that in endothelial cells reoxygenation‐induced ATP release by Cx43 is cAMP/PKA‐dependent. Strengthening of this endogenous mechanism by direct activation of the cAMP/PKA pathway could represent a new therapeutic strategy to prevent acute endothelial barrier failure during reperfusion‐injury.