The role of the large conductance Ca2+-activated K+ channel in adenosine receptor-mediated cytoprotection

The rat embryonic cardiomyoblast-derived H9c2 cell line is increasingly used for studies into cardioprotection, as these cells display similar properties to primary cardiomyocytes. Adenosine receptors are well known mediators of cardioprotection and trigger effectors such as the mitochondrial KATP channel – however, the role of the mitochondrial BKCa channel in adenosine receptor-mediated cardioprotection has not been investigated. GPCR assays provided evidence for functional expression of Gi-coupled adenosine A1 and κ-opioid receptors, Gs-coupled β2 adrenergic receptors and Gq-coupled UTP-binding P2Y purinergic receptors on H9c2 cells. Activation of the adenosine A1 receptor with CPA (N(6)-cyclopentyladenosine) provided significant protection against hypoxia-induced cell death in these cells, as did opening of a BKCa channel with NS1619. The location of this BKCa channel was confirmed to be the mitochondria by the probing of subcellular fractions with BKCa-specific antibodies. Interestingly, CPA-induced protection against hypoxia was blocked by inhibition of the BKCa channel