Department of Biomedical Sciences, Quillen College of Medicine, East Tennessee State University; and.
Am J Physiol Heart Circ Physiol. 2013 Sep 15;305(6):H821-8. doi: 10.1152/ajpheart.00140.2013. Epub 2013 Jul 19.
Hypoxia-inducible factor-1α (HIF-1α) is a transcription factor that directs many of the cellular responses to hypoxia. In these studies, we have used a mouse model containing a cardiac-specific, oxygen-stabilized, doxycycline (Dox)-off regulated HIF-1α transgene to probe the role of HIF-1α in cardioprotection. Hearts used in these studies were derived from wild-type (WT), noninduced (Non-I), and 2 day (2D) and 6 day (6D) Dox-deprived mice. Whereas HIF-1α protein is undetectable in WT mice, it is present in heart tissue of "noninduced" transgenic mice, presumably because of leakiness of the promoter construct. In mice denied Dox for 2 or 6 days, HIF-1α is overexpressed to a much greater extent than Non-I or WT animals, as expected. WT and HIF-1α-expressing hearts (Non-I, 2D and 6D induced) were subjected to 30 min of ischemia, and functional recovery was measured upon reperfusion. Recovery of preischemic left ventricular developed pressure was 14% for WT, 67% for Non-I hearts, 64% for 2D-induced, and 62% for 6D-induced hearts. 6D-induced HIF hearts have increased preischemic glycogen reserves, higher glycogen synthase protein levels, and significantly higher lactic acid release during ischemia. 6D-induced HIF hearts were also better able to maintain ATP levels during ischemia compared with WT and Non-I hearts. Interestingly, Non-I hearts showed no significant increase in glycogen reserves, glycolytic flux, or greater ATP preservation during ischemia and yet were protected to a similar extent as the 6D-induced hearts. Finally, the mitochondrial membrane potential of isolated adult myocytes was monitored during anoxia or treatments with cyanide and 2-deoxyglucose. HIF-1α expression was shown to protect mitochondrial polarization during both stress treatments. Taken together these data indicate that, while HIF-1α expression in heart does induce increases in compensatory glycolytic capacity, these changes are not necessarily required for cardioprotection, at least in this model of ischemic stress.
缺氧诱导因子-1α（HIF-1α）是一种转录因子，可指导细胞对缺氧的许多反应。在这些研究中，我们使用了一种心脏特异性、氧稳定、强力霉素（Dox）关闭调节的 HIF-1α转基因小鼠模型，来探讨 HIF-1α在心脏保护中的作用。这些研究中使用的心脏来自野生型（WT）、非诱导（Non-I）以及 2 天（2D）和 6 天（6D）强力霉素剥夺的小鼠。虽然 WT 小鼠中无法检测到 HIF-1α 蛋白，但在“非诱导”转基因小鼠的心脏组织中存在 HIF-1α，这可能是由于启动子构建的渗漏。在 2 天或 6 天未给予 Dox 的小鼠中，HIF-1α 的过度表达程度远远超过 Non-I 或 WT 动物，这是预期的。WT 和 HIF-1α 表达的心脏（Non-I、2D 和 6D 诱导）经历 30 分钟的缺血，然后在再灌注时测量功能恢复。WT 心脏的缺血前左心室发展压恢复为 14%，Non-I 心脏为 67%，2D 诱导心脏为 64%，6D 诱导心脏为 62%。6D 诱导的 HIF 心脏具有更高的缺血前糖原储备、更高的糖原合酶蛋白水平，以及在缺血期间释放出更高水平的乳酸。与 WT 和 Non-I 心脏相比，6D 诱导的 HIF 心脏在缺血期间也能够更好地维持 ATP 水平。有趣的是，Non-I 心脏在缺血期间并没有显著增加糖原储备、糖酵解通量或更好地保存 ATP，但它们的保护程度与 6D 诱导的心脏相似。最后，监测了分离的成年心肌细胞在缺氧或氰化物和 2-脱氧葡萄糖处理期间的线粒体膜电位。结果表明，HIF-1α 的表达可在这两种应激处理中保护线粒体极化。这些数据表明，虽然心脏中 HIF-1α 的表达确实会增加代偿性糖酵解能力，但在这种缺血应激模型中，这些变化不一定是心脏保护所必需的。
