Cittadini A, Monti M G, Iaccarino G, Di Rella F, Tsichlis P N, Di Gianni A, Strömer H, Sorriento D, Peschle C, Trimarco B, Saccà L, Condorelli G
Department of Clinical Medicine and Cardiovascular Sciences, University 'Federico II', Naples, Italy.
Gene Ther. 2006 Jan;13(1):8-19. doi: 10.1038/sj.gt.3302589.
The serine-threonine kinase Akt/PKB mediates stimuli from different classes of cardiomyocyte receptors, including the growth hormone/insulin like growth factor and the beta-adrenergic receptors. Whereas the growth-promoting and antiapoptotic properties of Akt activation are well established, little is known about the effects of Akt on myocardial contractility, intracellular calcium (Ca(2+)) handling, oxygen consumption, and beta-adrenergic pathway. To this aim, Sprague-Dawley rats were subjected to a wild-type Akt in vivo adenoviral gene transfer using a catheter-based technique combined with aortopulmonary crossclamping. Left ventricular (LV) contractility and intracellular Ca(2+) handling were evaluated in an isolated isovolumic buffer-perfused, aequorin-loaded whole heart preparations 10 days after the surgery. The Ca(2+)-force relationship was obtained under steady-state conditions in tetanized muscles. No significant hypertrophy was detected in adenovirus with wild-type Akt (Ad.Akt) versus controls rats (LV-to-body weight ratio 2.6+/-0.2 versus 2.7+/-0.1 mg/g, controls versus Ad.Akt, P, NS). LV contractility, measured as developed pressure, increased by 41% in Ad.Akt. This was accounted for by both more systolic Ca(2+) available to the contractile machinery (+19% versus controls) and by enhanced myofilament Ca(2+) responsiveness, documented by an increased maximal Ca(2+)-activated pressure (+19% versus controls) and a shift to the left of the Ca(2+)-force relationship. Such increased contractility was paralleled by a slight increase of myocardial oxygen consumption (14%), while titrated dose of dobutamine providing similar inotropic effect augmented oxygen consumption by 39% (P<0.01). Phospholamban, calsequestrin, and ryanodine receptor LV mRNA and protein content were not different among the study groups, while sarcoplasmic reticulum Ca(2+) ATPase protein levels were significantly increased in Ad.Akt rats. beta-Adrenergic receptor density, affinity, kinase-1 levels, and adenylyl cyclase activity were similar in the three animal groups. In conclusion, our results support an important role for Akt/PKB in the regulation of myocardial contractility and mechanoenergetics.
丝氨酸 - 苏氨酸激酶Akt/PKB介导来自不同类型心肌细胞受体的刺激，包括生长激素/胰岛素样生长因子和β - 肾上腺素能受体。虽然Akt激活的促生长和抗凋亡特性已得到充分证实，但关于Akt对心肌收缩力、细胞内钙（Ca(2+)）处理、氧消耗和β - 肾上腺素能途径的影响知之甚少。为此，采用基于导管的技术结合主肺动脉交叉钳夹，对Sprague - Dawley大鼠进行野生型Akt体内腺病毒基因转移。术后10天，在分离的等容缓冲液灌注、装有水母发光蛋白的全心标本中评估左心室（LV）收缩力和细胞内Ca(2+)处理。在强直收缩的肌肉中，在稳态条件下获得Ca(2+) - 力关系。与对照大鼠相比，野生型Akt腺病毒（Ad.Akt）组未检测到明显的心肌肥厚（左心室与体重比：对照组为2.6±0.2，Ad.Akt组为2.7±0.1mg/g；对照组与Ad.Akt组相比，P，无显著性差异）。以舒张期压力衡量的左心室收缩力在Ad.Akt组增加了41%。这是由于收缩装置可利用的收缩期Ca(2+)增加（比对照组增加19%）以及肌丝对Ca(2+)的反应性增强所致，表现为最大Ca(2+)激活压力增加（比对照组增加19%）以及Ca(2+) - 力关系向左移。这种收缩力增加伴随着心肌氧消耗略有增加（14%），而提供相似正性肌力作用的滴定剂量多巴酚丁胺使氧消耗增加39%（P<0.01）。研究组之间受磷蛋白、肌集钙蛋白和兰尼碱受体的左心室mRNA和蛋白含量无差异，而Ad.Akt大鼠的肌浆网Ca(2+)ATP酶蛋白水平显著增加。三组动物的β - 肾上腺素能受体密度、亲和力、激酶 - 1水平和腺苷酸环化酶活性相似。总之，我们的结果支持Akt/PKB在心肌收缩力和机械能量学调节中起重要作用。
