title: Tetrodotoxin-sensitive α-subunits of voltage-gated sodium channels are relevant for inhibition of cardiac sodium currents by local anesthetics.
abstract: The sodium channel α-subunit (Nav) Nav1.5 is regarded as the most prevalent cardiac sodium channel required for generation of action potentials in cardiomyocytes. Accordingly, Nav1.5 seems to be the main target molecule for local anesthetic (LA)-induced cardiotoxicity. However, recent reports demonstrated functional expression of several "neuronal" Nav's in cardiomyocytes being involved in cardiac contractility and rhythmogenesis. In this study, we examined the relevance of neuronal tetrodotoxin (TTX)-sensitive Nav's for inhibition of cardiac sodium channels by the cardiotoxic LAs ropivacaine and bupivacaine. Effects of LAs on recombinant Nav1.2, 1.3, 1.4, and 1.5 expressed in human embryonic kidney cell line 293 (HEK-293) cells, and on sodium currents in murine, cardiomyocytes were investigated by whole-cell patch clamp recordings. Expression analyses were performed by reverse transcription PCR (RT-PCR). Cultured cardiomyocytes from neonatal mice express messenger RNA (mRNA) for Nav1.2, 1.3, 1.5, 1.8, and 1.9 and generate TTX-sensitive sodium currents. Tonic and use-dependent block of sodium currents in cardiomyocytes by ropivacaine and bupivacaine were enhanced by 200 nM TTX. Inhibition of recombinant Nav1.5 channels was similar to that of TTX-resistant currents in cardiomyocytes but stronger as compared to inhibition of total sodium current in cardiomyocytes. Recombinant Nav1.2, 1.3, 1.4, and 1.5 channels displayed significant differences in regard to use-dependent block by ropivacaine. Finally, bupivacaine blocked sodium currents in cardiomyocytes as well as recombinant Nav1.5 currents significantly stronger in comparison to ropivacaine. Our data demonstrate for the first time that cardiac TTX-sensitive sodium channels are relevant for inhibition of cardiac sodium currents by LAs.
authors.affiliation: Department of Anesthesiology and Intensive Care Medicine, Hannover Medical School, Carl-Neuberg Strasse 1, 30625, Hannover, Germany. stoetzer.carsten@mh-hannover.de.
authors.forename: C
authors.initials: C
authors.lastname: Stoetzer
authors.affiliation: Department of Anesthesiology and Intensive Care Medicine, Hannover Medical School, Carl-Neuberg Strasse 1, 30625, Hannover, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Doll
authors.affiliation: Department of Anesthesiology and Intensive Care Medicine, Hannover Medical School, Carl-Neuberg Strasse 1, 30625, Hannover, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Stueber
authors.affiliation: Department of Anesthesiology and Intensive Care Medicine, Hannover Medical School, Carl-Neuberg Strasse 1, 30625, Hannover, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Herzog
authors.affiliation: Department of Anesthesiology and Intensive Care Medicine, Hannover Medical School, Carl-Neuberg Strasse 1, 30625, Hannover, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Echtermeyer
authors.affiliation: Institute of Molecular Biology, Hannover Medical School, Hannover, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Greulich
authors.affiliation: Institute of Molecular Biology, Hannover Medical School, Hannover, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Rudat
authors.affiliation: Institute of Molecular Biology, Hannover Medical School, Hannover, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Kispert
authors.affiliation: Department of Neurology, Hannover Medical School, Hannover, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Wegner
authors.affiliation: Department of Anesthesiology and Intensive Care Medicine, Hannover Medical School, Carl-Neuberg Strasse 1, 30625, Hannover, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Leffler
mesh_terms: D000577:Amides / Q000494:pharmacology*; D000779:Anesthetics, Local / Q000494:pharmacology*; D000818:Animals; D002045:Bupivacaine / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D018507:Gene Expression Regulation, Developmental; D057809:HEK293 Cells; D006801:Humans; D008564:Membrane Potentials; D051379:Mice; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000378:metabolism; D062554:NAV1.5 Voltage-Gated Sodium Channel / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D021122:Protein Subunits; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000187:drug effects / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000077212:Ropivacaine; D013779:Tetrodotoxin / Q000494:pharmacology*; D014162:Transfection; D061567:Voltage-Gated Sodium Channel Blockers / Q000494:pharmacology*
chemical_list: D000577:Amides; D000779:Anesthetics, Local; D062554:NAV1.5 Voltage-Gated Sodium Channel; D021122:Protein Subunits; D012333:RNA, Messenger; D011994:Recombinant Proteins; C568320:SCN5A protein, human; C568321:Scn5a protein, mouse; D061567:Voltage-Gated Sodium Channel Blockers; D013779:Tetrodotoxin; D000077212:Ropivacaine; D002045:Bupivacaine
keywords: Cardiac sodium currents; Local anesthetics; Tetrodotoxin; Voltage-gated sodium channels