Trappanese Danielle M, Liu Yuchuan, McCormick Ryan C, Cannavo Alessandro, Nanayakkara Gayani, Baskharoun Marina M, Jarrett Harish, Woitek Felix J, Tillson D Michael, Dillon A Ray, Recchia Fabio A, Balligand Jean-Luc, Houser Steven R, Koch Walter J, Dell'Italia Louis J, Tsai Emily J
Cardiovascular Research Center, Temple University School of Medicine, 3500 North Broad Street, MERB 1047, Philadelphia, PA, 19140, USA.
Basic Res Cardiol. 2015 Jan;110(1):456. doi: 10.1007/s00395-014-0456-3. Epub 2014 Dec 6.
The β1-adrenergic antagonist metoprolol improves cardiac function in animals and patients with chronic heart failure, isolated mitral regurgitation (MR), and ischemic heart disease, though the molecular mechanisms remain incompletely understood. Metoprolol has been reported to upregulate cardiac expression of β3-adrenergic receptors (β3AR) in animal models. Myocardial β3AR signaling via neuronal nitric oxide synthase (nNOS) activation has recently emerged as a cardioprotective pathway. We tested whether chronic β1-adrenergic blockade with metoprolol enhances myocardial β3AR coupling with nitric oxide-stimulated cyclic guanosine monophosphate (β3AR/NO-cGMP) signaling in the MR-induced, volume-overloaded heart. We compared the expression, distribution, and inducible activation of β3AR/NO-cGMP signaling proteins within myocardial membrane microdomains in dogs (canines) with surgically induced MR, those also treated with metoprolol succinate (MR+βB), and unoperated controls. β3AR mRNA transcripts, normalized to housekeeping gene RPLP1, increased 4.4 × 10(3)- and 3.2 × 10(2)-fold in MR and MR+βB hearts, respectively, compared to Control. Cardiac β3AR expression was increased 1.4- and nearly twofold in MR and MR+βB, respectively, compared to Control. β3AR was detected within caveolae-enriched lipid rafts (Cav3(+)LR) and heavy density, non-lipid raft membrane (NLR) across all groups. However, in vitro selective β3AR stimulation with BRL37344 (BRL) triggered cGMP production within only NLR of MR+βB. BRL induced Ser (1412) phosphorylation of nNOS within NLR of MR+βB, but not Control or MR, consistent with detection of NLR-specific β3AR/NO-cGMP coupling. Treatment with metoprolol prevented MR-associated oxidation of NO biosensor soluble guanylyl cyclase (sGC) within NLR. Metoprolol therapy also prevented MR-induced relocalization of sGCβ1 subunit away from caveolae, suggesting preserved NO-sGC-cGMP signaling, albeit without coupling to β3AR, within MR+βB caveolae. Chronic β1-blockade is associated with myocardial β3AR/NO-cGMP coupling in a microdomain-specific fashion. Our canine study suggests that microdomain-targeted enhancement of myocardial β3AR/NO-cGMP signaling may explain, in part, β1-adrenergic antagonist-mediated preservation of cardiac function in the volume-overloaded heart.
β1肾上腺素能拮抗剂美托洛尔可改善患有慢性心力衰竭、单纯二尖瓣反流（MR）和缺血性心脏病的动物及患者的心脏功能，但其分子机制仍未完全明确。据报道，在动物模型中，美托洛尔可上调心脏β3肾上腺素能受体（β3AR）的表达。心肌β3AR通过神经元型一氧化氮合酶（nNOS）激活的信号传导最近已成为一种心脏保护途径。我们测试了用美托洛尔进行慢性β1肾上腺素能阻断是否能增强MR诱导的容量超负荷心脏中心肌β3AR与一氧化氮刺激的环磷酸鸟苷（β3AR/NO-cGMP）信号的偶联。我们比较了手术诱导MR的犬（犬科动物）、琥珀酸美托洛尔治疗的犬（MR+βB）以及未手术对照犬心肌膜微区中β3AR/NO-cGMP信号蛋白的表达、分布和诱导激活情况。与对照组相比，以看家基因RPLP1标准化后，MR组和MR+βB组心脏中β3AR mRNA转录本分别增加了4.4×10³倍和3.2×10²倍。与对照组相比，MR组和MR+βB组心脏中β3AR的表达分别增加了1.4倍和近两倍。在所有组中，均在富含小窝的脂筏（Cav3(+)LR）和高密度非脂筏膜（NLR）中检测到β3AR。然而，在体外使用BRL37344（BRL）选择性刺激β3AR仅在MR+βB组的NLR中触发了cGMP的产生。BRL诱导MR+βB组NLR中nNOS的Ser（1412）磷酸化，但对照组或MR组未出现，这与检测到的NLR特异性β3AR/NO-cGMP偶联一致。美托洛尔治疗可防止MR相关的NLR中一氧化氮生物传感器可溶性鸟苷酸环化酶（sGC）的氧化。美托洛尔治疗还可防止MR诱导的sGCβ1亚基从小窝重新定位，这表明在MR+βB组的小窝内，尽管未与β3AR偶联，但仍保留了NO-sGC-cGMP信号传导。慢性β1阻断以微区特异性方式与心肌β3AR/NO-cGMP偶联相关。我们的犬类研究表明，微区靶向增强心肌β3AR/NO-cGMP信号传导可能部分解释了β1肾上腺素能拮抗剂介导的容量超负荷心脏中心脏功能的保留。
