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.
PLoS One. 2013 Aug 20;8(8):e71980. doi: 10.1371/journal.pone.0071980. eCollection 2013.
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.
比索洛尔，第三代β肾上腺素受体（β-AR）拮抗剂（β-阻滞剂），通过诱导一氧化氮（NO）的产生引起血管扩张。比索洛尔诱导 NO 产生的机制尚不清楚，这导致了比索洛尔药理学作用的大部分争议的产生。卡维地洛是另一种诱导 NO 产生的β-阻滞剂。卡维地洛的一个突出的药理学机制是偏向激动作用，它与 Gαs 无关，涉及 G 蛋白偶联受体激酶（GRK）/β-抑制蛋白信号转导，随后激活表皮生长因子受体（EGFR）和细胞外信号调节激酶（ERK）。由于比索洛尔和卡维地洛之间存在药理学相似性，我们假设比索洛尔也是一种 GRK/β-抑制蛋白偏向激动剂。我们利用仅表达β2-AR 的小鼠胚胎成纤维细胞（MEFs）和表达β1-和β2-AR 且无检测到β3-AR 的 HL-1 心肌细胞来测试这一假设。我们证实了之前的报道，即比索洛尔不会显著改变 cAMP 水平，因此不是经典激动剂。此外，在这两种细胞类型中，比索洛尔诱导β-AR 快速内化，表明比索洛尔也不是经典的β-阻滞剂。此外，比索洛尔处理导致 ERK 的时间依赖性磷酸化，与卡维地洛相似，持续时间相似，但幅度不同，与异丙肾上腺素相似。比索洛尔介导的 ERK 磷酸化对普萘洛尔（非选择性β-AR 阻滞剂）和 AG1478（EGFR 抑制剂）敏感，表明信号来自β-AR 并涉及 EGFR。此外，在 MEFs 中，比索洛尔介导的 ERK 磷酸化对 GRK2 的药理学抑制以及β-arrestin 1/2 的 siRNA 敲低均敏感。此外，比索洛尔诱导β-arrestin 2 从弥散染色模式重新分布到更强烈的点状斑点。我们得出结论，比索洛尔是一种β2-AR，可能是β1-AR，GRK/β-抑制蛋白偏向激动剂，这表明比索洛尔的一些独特的临床有益作用可能是由于β1-和/或β2-AR 的偏向激动作用。
