Abstract 3885: Adenosine A2A and A2B Receptors Work in Concert to Produce a Strong Protection against Reperfusion Injury by Targeting the mPTP via a GSK-3β-Dependent Mechanism
While the role of adenosine A2 receptor activation in modulation of reperfusion injury has been extensively investigated, controversies still exist regarding its exact role (protective or not). We aimed to test if a simultaneous stimulation of A2A and A2B receptors can produce a strong protection against reperfusion injury by targeting mitochondrial permeability transition pore (mPTP) and glycogen synthase kinase 3β (GSK-3β). NECA (100 nM) given at reperfusion reduced infarct size in isolated rat hearts (14.1 ± 1.9 % vs. 37.9 ± 3.1 % of risk zone in control), an effect that was blocked by both the A2A antagonist SCH58261 (36.6 ± 2.4 %) and the A2B antagonist MRS1706 (39.2 ± 2.9 %), indicating that both the receptor subtypes are involved in the anti-infarct effect of NECA. NECA increased GSK-3β phosphorylation at Ser9 and translocated GSK-3β to mitochondria upon reperfusion, an effect that was blocked by both SCH58261 and MRS1706, implying that NECA may protect the heart at reperfusion by targeting GSK-3β and mitochondria through activation of both A2A and A2B receptors. In support of this interpretation, NECA prevented oxidant-induced loss of mitochondrial membrane potential (MMP) in cardiomyocytes (91.2 ± 3.7 % vs. 38.8 ± 5.4 % in control), which was also partially blocked by both SCH58261 and MRS1706, indicating that NECA prevents mPTP opening by stimulating both A2A and A2B receptors. Further experiments showed that a combination of CGS21680 (A2A agonist) and BAY60 – 6583 (A2B agonist) induced a greater protection against the loss of MMP (84.7 ± 1.1 %) than that induced by CGS21680 (55.6 ± 2.9 %) or BAY60 – 6583 (63.7 ± 5.0) alone, corroborating the above observations. In conclusion, these data suggest that A2A and A2B receptors work in concert to prevent reperfusion injury by targeting mPTP through a GSK-3β-dependent mechanism.