α1-肾上腺素受体激活大鼠心脏腺苷酸活化蛋白激酶

为了验证心脏腺苷酸活化蛋白激酶（AMP-activated protein kinase,AMPK）是否为肾上腺素受体（adrenergic receptor,AR）的下游信号分子,本实验在大鼠心室肌源细胞和大鼠心脏中观察了α-AR对AMPK的激活作用,利用Western blot检测了AMPK-α总蛋白表达量及其172位苏氨酸磷酸化水平。雄性Sprague-Dawley大鼠皮下植入去甲肾上腺素（norepinephrine,NE）,苯肾上腺素（phenylephrine,PE）或者溶剂载体0．01％（W／V）维生素C]的缓释微泵（osmotic minipump）。NE或PE以每小时0．2 mg／kg的速率持续输注,7 d后用AMPK-α抗体免疫沉淀处理样本并测定AMPK的活性。结果显示,在细胞水平,NE引起的AMPK磷酸化水平增高具有时间依赖和剂量依赖特点, NE处理细胞10 min后AMPK磷酸化水平达到最高峰;NE引起的这种效应对β-AR的拮抗剂普萘洛尔（propranolol）不敏感,但是可以被α1-AR拮抗剂哌唑嗪（prazosin）所阻断。结果提示,α1-AR介导AMPK的磷酸化,但β-AR无此作用。AR激动剂持续灌注7 d后,AMPK的活性在NE（7．4倍）和PE（6．0倍）灌注组较对照组显著增高（P〈0．05,H=6）。PE持续灌注组大鼠与对照组相比无明显的心肌肥厚和组织纤维化变化。本文证明α1-AR激动剂可以增强AMPK的活性,揭示了心脏中α1-AR激动在调控AMPK活性方面的重要作用。深入了解α1-AR介导的AMPK激活可能在心衰治疗中具有重要的临床意义。

alpha1-adrenergic receptors activate AMP-activated protein kinase in rat hearts

To test the hypothesis that AMP-activated protein kinase (AMPK) is possibly the downstream signaling molecule of certain subtypes of adrenergic receptor (AR) in the heart, we evaluated AMPK activation mediated by ARs in H9C2 cells, a rat cardiac source cell line, and rat hearts. The AMPK-α subunit and the phosphorylation level of Thr172-AMPK-αt subunit were subjected to Western blot analysis. Osmotic minipumps filled with norepinephrine (NE), phenylephrine (PE) or vehicle 0.01% (W/V) vitamin C solution]were implanted into male Sprague-Dawley rats subcutaneously. The pumps delivered NE or PE continuously at the rate of 0.2 mg/kg per hour. After 7-day infusion, the activity of AMPK was examined following immunoprecipitation with anti-AMPK-α antibody. At the cellular level, we found that NE elevated AMPK phosphorylation level in a dose- and time-dependent manner, with the maximal effect at 10 μmol/L NE after 10-minute treatment. This effect was insensitive to propranolol, a specific β-AR antagonist, but abolished by prazosin, an α1-AR antagonist, suggesting that α1-AR but not β-AR mediated the phosphorylation of AMPK. Moreover, the results from rat models of 7-day-infusion of AR agonists demonstrated that the activity of AMPK was significantly higher in NE (7.4-fold) and PE (6.0-fold) infusion groups than that in the vehicle group (P＜0.05, n=6). On the other hand, no obvious cardiac hypertrophy and tissue fibrosis changes were observed in PE-infused rats. Taken together, our results demonstrate that α1-AR stimulation enhances the activity of AMPK, indicating an important role of α1-AR stimulation in the regulation of AMPK in the heart.Understanding the activation of AMPK mediated by α1-AR might have clinical implications in the therapy of heart failure.