Hypoxia and HIF-2 alpha-dependent A(2A) receptor expression and activation increase proliferation of human lung microvascular endothelial cells (HLMVECs). This study was undertaken to investigate the signaling mechanisms that mediate the proliferative effects of A(2A) receptor. A(2A) receptor-mediated proliferation of HLMVECs was inhibited by intracellular calcium chelation, and by specific inhibitors of ERK1/2 and PI3-kinase (PI3K). The adenosine A(2A) receptor agonist CGS21680 caused intracellular calcium mobilization in controls and, to a greater extent, in A(2A) receptor-overexpressing HLMVECs. Adenoviral-mediated A(2A) receptor overexpression as well as receptor activation by CGS21680 caused increased PI3K activity and Akt phosphorylation. Cells overexpressing A(2A) receptor also manifested enhanced ERK1/2 phosphorylation upon CGS21680 treatment. A(2A) receptor activation also caused enhanced cAMP production. Likewise, treatment with 8Br-cAMP increased PI3K activity. Hence A(2A) receptor-mediated cAMP production and PI3K and Akt phosphotylation are potential mediators of the A(2A)-mediated proliferative response of HLMVECs. Cytosolic calcium mobilization and ERK1/2 phosphorylation are other critical effectors of HLMVEC proliferation and growth. These studies underscore the importance of adenosine A(2A) receptor in activation of survival and proliferative pathways in pulmonary endothelial cells that are mediated through PI3K/Akt and ERK1/2 pathways. (C) 2013 Elsevier Inc. All rights reserved.