title: The β-blocker Nebivolol Is a GRK/β-arrestin biased agonist.
abstract: Nebivolol, a third generation β-adrenoceptor (β-AR) antagonist (β-blocker), causes vasodilation by inducing nitric oxide (NO) production. The mechanism via which nebivolol induces NO production remains unknown, resulting in the genesis of much of the controversy regarding the pharmacological action of nebivolol. Carvedilol is another β-blocker that induces NO production. A prominent pharmacological mechanism of carvedilol is biased agonism that is independent of Gαs and involves G protein-coupled receptor kinase (GRK)/β-arrestin signaling with downstream activation of the epidermal growth factor receptor (EGFR) and extracellular signal-regulated kinase (ERK). Due to the pharmacological similarities between nebivolol and carvedilol, we hypothesized that nebivolol is also a GRK/β-arrestin biased agonist. We tested this hypothesis utilizing mouse embryonic fibroblasts (MEFs) that solely express β2-ARs, and HL-1 cardiac myocytes that express β1- and β2-ARs and no detectable β3-ARs. We confirmed previous reports that nebivolol does not significantly alter cAMP levels and thus is not a classical agonist. Moreover, in both cell types, nebivolol induced rapid internalization of β-ARs indicating that nebivolol is also not a classical β-blocker. Furthermore, nebivolol treatment resulted in a time-dependent phosphorylation of ERK that was indistinguishable from carvedilol and similar in duration, but not amplitude, to isoproterenol. Nebivolol-mediated phosphorylation of ERK was sensitive to propranolol (non-selective β-AR-blocker), AG1478 (EGFR inhibitor), indicating that the signaling emanates from β-ARs and involves the EGFR. Furthermore, in MEFs, nebivolol-mediated phosphorylation of ERK was sensitive to pharmacological inhibition of GRK2 as well as siRNA knockdown of β-arrestin 1/2. Additionally, nebivolol induced redistribution of β-arrestin 2 from a diffuse staining pattern into more intense punctate spots. We conclude that nebivolol is a β2-AR, and likely β1-AR, GRK/β-arrestin biased agonist, which suggests that some of the unique clinically beneficial effects of nebivolol may be due to biased agonism at β1- and/or β2-ARs.
authors: Department of Internal Medicine, University of Missouri, Columbia, Missouri, United States of America ; Harry S Truman Memorial Veterans' Hospital, Columbia, Missouri, United States of America.
authors: Catherine E
authors: CE
authors: Erickson
authors: Rukhsana
authors: R
authors: Gul
authors: Christopher P
authors: CP
authors: Blessing
authors: Jenny
authors: J
authors: Nguyen
authors: Tammy
authors: T
authors: Liu
authors: Lakshmi
authors: L
authors: Pulakat
authors: Murat
authors: M
authors: Bastepe
authors: Edwin K
authors: EK
authors: Jackson
authors: Bradley T
authors: BT
authors: Andresen
mesh_terms: D058671:Adrenergic beta-1 Receptor Antagonists / Q000494:pharmacology*; D000818:Animals; D019390:Arrestins / Q000235:genetics / Q000378:metabolism*; D001578:Benzopyrans / Q000494:pharmacology*; D002227:Carbazoles / Q000494:pharmacology; D000077261:Carvedilol; D002460:Cell Line; D066246:ErbB Receptors / Q000378:metabolism; D004983:Ethanolamines / Q000494:pharmacology*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D054769:G-Protein-Coupled Receptor Kinase 2 / Q000378:metabolism*; D020935:MAP Kinase Signaling System; D051379:Mice; D000068577:Nebivolol; D009569:Nitric Oxide / Q000378:metabolism; D010766:Phosphorylation; D011412:Propanolamines / Q000494:pharmacology; D011499:Protein Processing, Post-Translational; D021381:Protein Transport; D018343:Receptors, Adrenergic, beta-2 / Q000378:metabolism; D000071559:beta-Arrestin 1; D000071560:beta-Arrestin 2; D000071557:beta-Arrestins
chemical_list: D058671:Adrenergic beta-1 Receptor Antagonists; C000605255:Arrb1 protein, mouse; C000605258:Arrb2 protein, mouse; D019390:Arrestins; D001578:Benzopyrans; D002227:Carbazoles; D004983:Ethanolamines; D011412:Propanolamines; D018343:Receptors, Adrenergic, beta-2; D000071559:beta-Arrestin 1; D000071560:beta-Arrestin 2; D000071557:beta-Arrestins; D000068577:Nebivolol; D000077261:Carvedilol; D009569:Nitric Oxide; D066246:ErbB Receptors; C496568:GRK2 protein, mouse; D054769:G-Protein-Coupled Receptor Kinase 2; D048049:Extracellular Signal-Regulated MAP Kinases
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