Bitopic Sphingosine 1-Phosphate Receptor 3 (S1P3) Antagonist Rescue from Complete Heart Block: Pharmacological and Genetic Evidence for Direct S1P3 Regulation of Mouse Cardiac Conduction

• DOI: 10.1124/mol.115.100222
• Publication Date: 2015-10-23T01:49:51Z
• Authors: M. Germana Sanna; Kevin P. Vincent; Emanuela Repetto; Nhan Nguyen; Steven J. Brown; Lusine Abgaryan; Sean W. Riley; Nora B. Leaf; Stuart M. Cahalan; William B. Kiosses; Yasushi Kohno; Joan Heller Brown; Andrew D. McCulloch; Hugh Rosen; Pedro J. Gonzalez...
• Keywords: Male; Cardiotonic Agents; Knockout; Medical Physiology; 610; Cardiovascular; Inbred C57BL; Mice; 03 medical and health sciences; Heart Rate; Receptors; 2.1 Biological and endogenous factors; Animals; Pharmacology & Pharmacy; Sphingosine-1-Phosphate Receptors; Mice, Knockout; 0303 health sciences; Biomedical and Clinical Sciences; Neurosciences; Pharmacology and Pharmaceutical Sciences; 540; 3. Good health; Mice, Inbred C57BL; Receptors, Lysosphingolipid; Heart Disease; Pharmacology and pharmaceutical sciences; Heart Block; 5.1 Pharmaceuticals; Biochemistry and cell biology; Lysosphingolipid; Biochemistry and Cell Biology

The molecular pharmacology of the G protein-coupled receptors for sphingosine 1-phosphate (S1P) provides important insight into established and new therapeutic targets. A new, potent bitopic S1P3 antagonist, SPM-354, with in vivo activity, has been used, together with S1P3-knockin and S1P3-knockout mice to define the spatial and functional properties of S1P3 in regulating cardiac conduction. We show that S1P3 is a key direct regulator of cardiac rhythm both in vivo and in isolated perfused hearts. 2-Amino-2-[2-(4-octylphenyl)ethyl]propane-1,3-diol in vivo and S1P in isolated hearts induced a spectrum of cardiac effects, ranging from sinus bradycardia to complete heart block, as measured by a surface electrocardiogram in anesthetized mice and in volume-conducted Langendorff preparations. The agonist effects on complete heart block are absent in S1P3-knockout mice and are reversed in wild-type mice with SPM-354, as characterized and described here. Homologous knockin of S1P3-mCherry is fully functional pharmacologically and is strongly expressed by immunohistochemistry confocal microscopy in Hyperpolarization Activated Cyclic Nucleotide Gated Potassium Channel 4 (HCN4)-positive atrioventricular node and His-Purkinje fibers, with relative less expression in the HCN4-positive sinoatrial node. In Langendorff studies, at constant pressure, SPM-354 restored sinus rhythm in S1P-induced complete heart block and fully reversed S1P-mediated bradycardia. S1P3 distribution and function in the mouse ventricular cardiac conduction system suggest a direct mechanism for heart block risk that should be further studied in humans. A richer understanding of receptor and ligand usage in the pacemaker cells of the cardiac system is likely to be useful in understanding ventricular conduction in health, disease, and pharmacology.