Diminished α1-adrenergic-mediated contraction and translocation of PKC in senescent rat heart
Diminished α1-adrenergic-mediated contraction and translocation of PKC in senescent rat heart
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DOI：
10.1152/ajpheart.2001.281.2.h581
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发表时间：
2001-08-01
影响因子：
4.8
通讯作者：
Lakatta, EG
中科院分区：
文献类型：
--
作者：
Korzick, DH;Holiman, DA;Lakatta, EG
心肌储备功能随着年龄的增长而下降，部分原因是α和β肾上腺素能受体（AR）介导的收缩增强作用减少。尽管已经鉴定了β-AR信号传导中特定的年龄相关缺陷，但尚不知道α（1）-AR信号传导级联的哪些组分，例如，蛋白激酶C（PKC）和相关的锚定蛋白（活化C激酶的受体; RACK）是随着衰老α（1）-AR收缩功能缺陷的基础。因此，我们评估了用苯肾上腺素（PE）最大程度刺激α（1）-AR后，从成年（5个月）和衰老（24个月）Wistar大鼠分离的Langendorff灌注心脏的心脏收缩（dP/dt），并通过Western印迹法测量了PKC α和PKC β及其各自锚定蛋白RACK 1和RACK 2的亚细胞分布。与5月龄相比，24月龄的大鼠对PE（10（-5）M）的最大dP/dt反应显著降低41%（P < 0.01）。PKC阻断剂（白屈菜红碱; 10 M）对在成人心脏中观察到的用PE刺激α（1）-AR后dP/dt的抑制作用在24月龄心脏中不存在（P < 0.01）。在5个月大的心脏中，PE引起可溶性PKC和PKC β水平的降低，同时增加颗粒PKC α和PKC β水平到相似的程度。相比之下，24个月大的心脏中可溶性PKC α和PKC β水平在对PE的反应中增加;颗粒PKC β和PKC α不变或减少，并与颗粒RACK 1和RACK 2的显著减少相关。结果首次表明，在衰老心肌中，响应于α（1）-AR刺激的PKC α和PKC β的选择性易位被破坏。还观察到颗粒RACK 1和RACK 2水平的年龄相关性降低，这提供了PKC锚定蛋白的改变可能有助于老年大鼠心脏中PKC易位受损和α（1）-AR收缩缺陷的证据。
Myocardial reserve function declines with aging due in part to reduced alpha- and beta -adrenergic receptor (AR)-mediated contractile augmentation. Whereas specific age-associated deficits in beta -AR signaling have been identified, it is not known which components of the alpha (1)-AR signaling cascade, e.g., protein kinase C (PKC) and associated anchoring proteins (receptors for activated C kinase; RACKs), underlie deficits in alpha (1)-AR contractile function with aging. We therefore assessed cardiac contraction (dP/dt) in Langendorff perfused hearts isolated from adult (5 mo) and senescent (24 mo) Wistar rats following maximal alpha (1)-AR stimulation with phenylephrine (PE), and we measured the subcellular distribution of PKC alpha and PKC epsilon, and their respective anchoring proteins RACK1 and RACK2 by Western blotting. The maximum dP/dt response to PE (10(-5) M) was significantly reduced by 41% in 24-mo-old vs. 5-mo-old (P < 0.01). Inhibitory effects of PKC blockade (chelerythrine; 10 M) on dP/dt following alpha (1)-AR stimulation with PE observed in adult hearts were absent in 24-mo-old hearts (P < 0.01). In 5-mo-old hearts, PE elicited reductions in soluble PKC and PKC epsilon levels, while increasing particulate PKC alpha and PKC epsilon levels to a similar extent. In contrast, soluble PKC alpha and PKC epsilon levels in 24-mo-old hearts were increased in response to PE; particulate PKC epsilon and PKC alpha were unchanged or reduced and associated with significant reductions in particulate RACK1 and RACK2. The results indicate, for the first time, that selective translocation of PKC alpha and PKC epsilon in response to alpha (1)-AR stimulation is disrupted in the senescent myocardium. That age-related reductions in particulate RACK1 and RACK2 levels were also observed provide evidence that alterations in PKC-anchoring proteins may contribute to impaired PKC translocation and defective alpha (1)-AR contraction in the aged rat heart.