Fig. 7. Adora2b signaling in human polymorphonuclear leukocytes (PMNs). Human PMNs were isolated from healthy individuals and activated using formyl-Met-Leu-Phe (fMLP 10 nM). Cells were treated with a specific Adora2b antagonist (PSB 1115, 100 μM, A ) or an Adora2b agonist (BAY 60-6583,1 μM, B ) or vehicle. Tumor necrosis factor α (TNFα) release into the supernatant was measured by enzyme-linked immunosorbent assay (ELISA). Vehicle treatment of PMNs significantly increased TNFα, with a maximal response 30 and 60 min after activation (22.88 ± 4.0 pg/ml and 31.4 ± 5.4 pg/ml, respectively) (A, B ). Pretreatment with an Adora2b antagonist enhances TNFα secretion significantly (24.8 ± 4.8, 42.3 ± 3.2, 48.6 ± 4.0, and 28 ± 4.6 pg/ml at 5, 30, 60, or 120 min, respectively) (A ). Pretreatment with an Adora2b agonist significantly dampens TNFα release (7.89 ± 1.3, 10.70 ± 2.6, 15.9 ± 2.5, and 5.5 ± 0.9 pg/ml at 5, 30, 60, and 120 min, respectively; n = 5 per group) (B ). Proposed role and potential therapeutic intervention: Cardiac ischemia reperfusion injury leads to PMN adhesion to the endothelial cells in the area at risk (AAR) (C, D ). PMNs release TNFα, which further damages the myocardial tissue and enhances reperfusion injury (C ). Pharmacologic treatment upon reperfusion using an Adora2b agonist activates A2B adenosine receptors on PMNs, which inhibits TNFα release and thereby protects the myocardium from additional damage (D ).