Abstract 17933: Cardioprotection by GLP-1(28-36) is Mediated by ATP-Dependent Activation of Soluble Adenylyl Cyclase in Coronary Vascular Cells
Introduction: How the incretin glucagon-like peptide-1 (GLP-1) prevents acute myocardial ischemia-reperfusion injury (IRI) as well as chronic myocardial ischemic injury has not been established. We previously described how GLP-1(28-36), a small metabolite of GLP-1, is as protective as the parent peptide in ex vivo isolated heart IRI and in vivo experimental myocardial infarction (MI) models in mice, and that these effects require soluble adenylyl cyclase (sAC), but not the known GLP-1 receptor. Here we define the molecular mechanisms and cell types in which GLP-1(28-36) activates sAC.
Hypothesis: GLP-1(28-36) mediates cardioprotection by a mitochondria-derived ATP-dependent activation of sAC in coronary vascular cells.
Methods & Results: Immunoblots reveal that mouse and human coronary artery smooth muscle cells (caSMC) and human coronary artery endothelial cells (caEC) express sAC, while mouse neonatal ventricular cardiomyocytes (CM), a mouse atrial CM cell line (HL-1), and human embryonic stem cell (ESC)-derived CM do not. Using pharmacological inhibitors of sAC, sAC-null mice and siRNA against sAC, we demonstrate that GLP-1(28-36) causes sAC-dependent increases in cAMP, activation of PKA, and cytoprotection from oxidative stress injury in both mouse and human caSMC. Moreover, GLP-1(28-36) increases cAMP responses in human caEC and probenecid, which blocks the anion (HCO3) entry required for sAC activity, abrogates these effects. By contrast, human ESC-derived CM shows no cAMP or cytoprotection responses to GLP-1(28-36). Next, we show in caSMC that GLP-1(28-36) causes dose-dependent increases in intracellular ATP, a known substrate of sAC. Affinity pull-down experiments using biotinylated-GLP-1(28-36), proteomic analysis with mass spectrometry, and confirmatory immunoblots suggest that GLP-1(28-36) interacts with mitochondrial trifunctional protein alpha (MTPα), an enzyme involved in fatty acid metabolism, and does not directly interact with sAC.
Conclusion: GLP-1(28-36) is a small peptide that targets a novel molecular (MTPα-ATP-sAC) and cellular (caSMC and caEC) mechanisms for the treatment of myocardial ischemic injury
Author Disclosures: M. Siraj: None. D. Mundil: None. T. Afroze: None. E.A. Shikatani: None. G. Keller: None. M. Husain: None.
- © 2016 by American Heart Association, Inc.