Adenosine A1 receptor activation reduces opening of mitochondrial permeability transition pores in hypoxic cardiomyocytes.

Summary 1. Adenosine A1 receptors (A1R) play an important role in cardioprotection against hypoxic damage and the opening of mitochondrial permeability transition pores (MPTP) is central to the regulation of cell apoptosis and necrosis. However, it is still unclear whether A1R open MPTP in hypoxic cardiomyocytes. 2. The present study used primary cardiomyocyte cultures from neonatal rats to investigate the mechanisms of A1R activation and the effects of A1R on MPTP opening under hypoxic conditions. 3. Hypoxia increased both MPTP opening and the production of reactive oxygen species (ROS), while decreasing cell viability and mitochondrial membrane potential (Δψ). The A1R agonist 2-chloro-N6-cyclopentyladenosine (CCPA; 500 nmol/L) blocked the increase in MPTP opening and ROS production and maintained cell viability and Δψ under hypoxic conditions. 4. The protective effects of CCPA were eliminated by both the protein kinase C (PKC) inhibitor chelerythine (2 μmol/L) and the mitochondrial ATP-sensitive K+ channel (mitoKATP) inhibitor 5-hydroxydecanoate (500 μmol/L). Moreover, CCPA significantly increased the PKC content in both total protein and membrane protein of cardiomyocytes. 5-Hydroxydecanoate did not prevent these CCPA-induced increases in PKC. 5. These results demonstrate that CCPA reduces MPTP opening in hypoxic cardiomyocytes, possibly by activating PKC, stabilizing Δψ and reducing ROS production following the opening of mitoKATP. Consequently, fewer MPTP open.