Key result
In rat cardiomyocytes during simulated ischaemia, CFTR-dependent bicarbonate entry stimulated ATP release via pannexin 1 through mitochondrial signalling and caspase activation.
Why the study?
CFTR is expressed in the heart, but its function and the identity and regulatory mechanism of the ATP release pore it regulates were unknown.
During simulated ischaemia, CFTR-dependent bicarbonate entry controls cardiomyocyte ATP release via mitochondrial signalling, caspase 3 activation, and pannexin 1 channels.
CFTR pathway inhibition may limit cardiomyocyte ATP release during ischemia; leaves open clinical relevance pending human studies.
AIM: Cystic fibrosis transmembrane conductance regulator (CFTR) is expressed in the heart, but its function there is unclear. CFTR regulates an ATP release pore in many tissues, but the identity and regulatory mechanism of the pore are unknown. We investigated the role of CFTR in ATP release from primary cardiomyocytes and ventricular wall in vivo. METHODS: Proteins involved in the signalling pathway for ATP release during simulated ischaemia (lactic acid treatment) were investigated using inhibitors and siRNA; colocalization was identified by coimmunofluorescence and proximity ligation assays; changes in near-membrane pH and calcium were identified with total internal reflection microscopy; in vivo ATP release was investigated using interstitial microdialysis of rat heart. RESULTS: Lactic acid-induced CFTR-dependent ATP release from cultured cardiomyocytes and left ventricle in vivo. Lactic acid entry elevated near-membrane calcium, which involved Na/H- and Na/Ca-exchangers colocalized with CFTR. Calcium entry-induced CFTR activation, which involved cAMP, protein kinase A, FAK, Pyk2 and Src. Removal of extracellular bicarbonate abolished cardiomyocyte ATP release induced by lactic acid or CFTR activators. Bicarbonate stimulated cytochrome c expression, cytochrome c release and ATP release from isolated cardiomyocyte mitochondria. Pannexin 1 (Panx1) colocalized with CFTR. Lactic acid increased cardiomyocyte caspase activity: caspase inhibitors or Panx1 siRNA abolished cardiomyocyte ATP release, while pannexin inhibition abolished cardiac ATP release in vivo. CONCLUSION: During simulated ischaemia, CFTR-dependent bicarbonate entry stimulated ATP and cytochrome c release from mitochondria; in the cytoplasm, cytochrome c-activated caspase 3, which in turn activated Panx1, and ATP was released through the opened Panx1 channel.
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Wang et al. (2020) studied Simulated ischaemia. Simulated ischaemia (lactic acid treatment) was evaluated on ATP release from primary cardiomyocytes and ventricular wall. In rat cardiomyocytes during simulated ischaemia, CFTR-dependent bicarbonate entry stimulated ATP release via pannexin 1 through mitochondrial signalling and caspase activation.
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