Cardiac-Specific Inhibition of Kinase Activity in Calcium/Calmodulin-Dependent Protein Kinase Kinase-β Leads to Accelerated Left Ventricular Remodeling and Heart Failure after Transverse Aortic Constriction in Mice

BackgroundThe mechanism of cardiac energy production against sustained pressure overload remains to be elucidated.Methods and ResultsWe generated cardiac-specific kinase-dead (kd) calcium/calmodulin-dependent protein kinase kinase-β (CaMKKβ) transgenic (α-MHC CaMKKβkd TG) mice using α-myosin heavy chain (α-MHC) promoter. Although CaMKKβ activity was significantly reduced, these mice had normal cardiac function and morphology at baseline. Here, we show that transverse aortic binding (TAC) in α-MHC CaMKKβkd TG mice led to accelerated death and left ventricular (LV) dilatation and dysfunction, which was accompanied by significant clinical signs of heart failure. CaMKKβ downstream signaling molecules, including adenosine monophosphate-activated protein kinase (AMPK), were also suppressed in α-MHC CaMKKβkd TG mice compared with wild-type (WT) mice. The expression levels of peroxisome proliferator-activated receptor-γ coactivator (PGC)-1α, which is a downstream target of both of CaMKKβ and calcium/calmodulin kinases, were also significantly reduced in α-MHC CaMKKβkd TG mice compared with WT mice after TAC. In accordance with these findings, mitochondrial morphogenesis was damaged and creatine phosphate/β-ATP ratios assessed by magnetic resonance spectroscopy were suppressed in α-MHC CaMKKβkd TG mice compared with WT mice after TAC.ConclusionsThese data indicate that CaMKKβ exerts protective effects on cardiac adaptive energy pooling against pressure-overload possibly through phosphorylation of AMPK and by upregulation of PGC-1α. Thus, CaMKKβ may be a therapeutic target for the treatment of heart failure.研究背景：心脏在持续性压力负荷下的能量产生机制仍有待阐明。研究方法与结果：我们利用α-肌球蛋白重链（α-myosin heavy chain, α-MHC）启动子构建了心脏特异性激酶失活（kinase-dead, kd）钙/钙调蛋白依赖性蛋白激酶激酶-β（calcium/calmodulin-dependent protein kinase kinase-β, CaMKKβ）转基因小鼠（α-MHC CaMKKβkd TG）。尽管CaMKKβ的活性显著降低，但该类小鼠在基线状态下的心脏功能与形态均表现正常。本研究发现，对α-MHC CaMKKβkd TG小鼠施行主动脉弓缩窄（transverse aortic binding, TAC）术后，小鼠死亡率升高，并出现左心室（left ventricular, LV）扩张与功能障碍，同时伴随心力衰竭的典型临床体征。与野生型（wild-type, WT）小鼠相比，α-MHC CaMKKβkd TG小鼠体内的CaMKKβ下游信号分子——包括腺苷单磷酸激活蛋白激酶（adenosine monophosphate-activated protein kinase, AMPK）——的活性亦受到抑制。在TAC术后，α-MHC CaMKKβkd TG小鼠体内过氧化物酶体增殖物激活受体γ辅激活因子（peroxisome proliferator-activated receptor-γ coactivator, PGC）-1α的表达水平相较WT小鼠显著降低，而该因子是CaMKKβ与钙/钙调蛋白激酶的共同下游靶点。与上述实验结果一致，TAC术后α-MHC CaMKKβkd TG小鼠的线粒体形态发生过程受损，且通过磁共振波谱检测得到的磷酸肌酸/β-三磷酸腺苷（creatine phosphate/β-ATP）比值较WT小鼠出现下降。研究结论：上述数据表明，CaMKKβ可能通过磷酸化AMPK并上调PGC-1α，在压力负荷下发挥心脏适应性能量储备的保护作用。因此，CaMKKβ有望成为心力衰竭治疗的潜在靶点。