Hatter Institute for Cardiovascular Research, University of Cape Town Medical School, Cape Town, South Africa.
J Cell Physiol. 2011 Sep;226(9):2457-68. doi: 10.1002/jcp.22592.
PKCε is central to cardioprotection. Sub-proteome analysis demonstrated co-localization of activated cardiac PKCε (aPKCε) with metabolic, mitochondrial, and cardioprotective modulators like hypoxia-inducible factor 1α (HIF-1α). aPKCε relocates to the mitochondrion, inactivating glycogen synthase kinase 3β (GSK3β) to modulate glycogen metabolism, hypertrophy and HIF-1α. However, there is no established mechanistic link between PKCε, p-GSK3β and HIF1-α. Here we hypothesized that cardiac-restricted aPKCε improves mitochondrial response to hypobaric hypoxia by altered substrate fuel selection via a GSK3β/HIF-1α-dependent mechanism. aPKCε and wild-type (WT) mice were exposed to 14 days of hypobaric hypoxia (45 kPa, 11% O(2)) and cardiac metabolism, functional parameters, p-GSK3β/HIF-1α expression, mitochondrial function and ultrastructure analyzed versus normoxic controls. Mitochondrial ADP-dependent respiration, ATP production and membrane potential were attenuated in hypoxic WT but maintained in hypoxic aPKCε mitochondria (P < 0.005, n = 8). Electron microscopy revealed a hypoxia-associated increase in mitochondrial number with ultrastructural disarray in WT versus aPKCε hearts. Concordantly, left ventricular work was diminished in hypoxic WT but not aPKCε mice (glucose only perfusions). However, addition of palmitate abrogated this (P < 0.05 vs. WT). aPKCε hearts displayed increased glucose utilization at baseline and with hypoxia. In parallel, p-GSK3β and HIF1-α peptide levels were increased in hypoxic aPKCε hearts versus WT. Our study demonstrates that modest, sustained PKCε activation blunts cardiac pathophysiologic responses usually observed in response to chronic hypoxia. Moreover, we propose that preferential glucose utilization by PKCε hearts is orchestrated by a p-GSK3β/HIF-1α-mediated mechanism, playing a crucial role to sustain contractile function in response to chronic hypobaric hypoxia.
PKCε 是心脏保护的核心。亚蛋白组分析表明，激活的心肌 PKCε（aPKCε）与代谢物、线粒体和心脏保护调节剂（如缺氧诱导因子 1α（HIF-1α））共定位。aPKCε 易位到线粒体，使糖原合酶激酶 3β（GSK3β）失活，从而调节糖原代谢、肥大和 HIF-1α。然而，PKCε、p-GSK3β 和 HIF1-α 之间尚未建立明确的机制联系。在这里，我们假设心脏特异性 aPKCε 通过改变底物燃料选择，通过 GSK3β/HIF-1α 依赖性机制改善对低氧的线粒体反应。aPKCε 和野生型（WT）小鼠暴露于 14 天的低压缺氧（45 kPa，11% O2），并与常氧对照组相比分析心脏代谢、功能参数、p-GSK3β/HIF-1α 表达、线粒体功能和超微结构。缺氧 WT 中的线粒体 ADP 依赖性呼吸、ATP 产生和膜电位减弱，但在缺氧 aPKCε 线粒体中保持（P < 0.005，n = 8）。电子显微镜显示，与 WT 心脏相比，缺氧相关的线粒体数量增加，超微结构排列混乱。一致地，左心室工作在缺氧 WT 中减少，但在 aPKCε 小鼠中没有（仅葡萄糖灌注）。然而，添加棕榈酸可消除这种情况（与 WT 相比，P < 0.05）。aPKCε 心脏在基线和缺氧时显示葡萄糖利用率增加。平行地，缺氧 aPKCε 心脏中的 p-GSK3β 和 HIF1-α 肽水平增加。我们的研究表明，适度的、持续的 PKCε 激活可减轻慢性缺氧通常引起的心脏病理生理反应。此外，我们提出，PKCε 心脏的葡萄糖优先利用是由 p-GSK3β/HIF-1α 介导的机制协调的，在应对慢性低氧血症时维持收缩功能发挥关键作用。
