Department of Biological Sciences, Division of Cellular, Developmental and Integrative Biology, Louisiana State University, Baton Rouge, LA 70803, USA.
Cell Tissue Res. 2013 Jan;351(1):99-106. doi: 10.1007/s00441-012-1517-2. Epub 2012 Nov 9.
Induction of HIF-1α by oxygen limitation promotes increased phosphorylation and catalytic depression of mitochondrial pyruvate dehydrogenase (PDH) and an enhanced glycolytic poise in cells. Cobalt chloride and desferrioxamine are widely used as mimics for hypoxia because they increase the levels of HIF-1α. We evaluated the ability of these agents to elicit selected physiological responses to hypoxia as a means to metabolically precondition mammalian cells, but without the detrimental effects of hypoxia. We show that, while CoCl(2) does increase HIF-1α in a dose-dependent manner, it unexpectedly and strikingly decreases PDH phosphorylation at E1α sites 1, 2, and 3 (Ser(293), Ser(300), and Ser(232), respectively) in HepG2 cells. This same effect is also observed for site 1 in mouse NIH/3T3 fibroblasts and J774 macrophages. CoCl(2) unexpectedly decreases the mRNA expression for PDH kinase-2 in HepG2 cells, which likely explains the dephosphorylation of PDH observed. And nor does desferrioxamine promote the expected increase in PDH phosphorylation. Dimethyloxaloylglycine (a prolyl hydroxylase inhibitor) performs better in this regard, but failed to promote the stronger effects seen with hypoxia. Consequently, CoCl(2) and desferrioxamine are unreliable mimics of hypoxia for physiological events downstream of HIF-1α stabilization. Our study demonstrates that mimetic chemicals must be chosen with caution and evaluated thoroughly if bona fide cellular outcomes are to be promoted with fidelity.
氧限制诱导 HIF-1α 的形成，促进了线粒体丙酮酸脱氢酶（PDH）磷酸化和催化活性的降低，以及细胞中糖酵解平衡的增强。氯化钴和去铁胺被广泛用作缺氧的模拟物，因为它们可以增加 HIF-1α 的水平。我们评估了这些试剂引发特定的缺氧生理反应的能力，作为代谢预处理哺乳动物细胞的一种方法，但没有缺氧的有害影响。我们发现，虽然 CoCl2 以剂量依赖的方式增加 HIF-1α，但它出人意料地显著降低了 HepG2 细胞中 PDH 在 E1α 位点 1、2 和 3（分别为 Ser293、Ser300 和 Ser232）的磷酸化。在小鼠 NIH/3T3 成纤维细胞和 J774 巨噬细胞中也观察到同样的效应。CoCl2 出人意料地降低了 HepG2 细胞中 PDH 激酶-2 的 mRNA 表达，这可能解释了观察到的 PDH 去磷酸化。而且，去铁胺也不能促进 PDH 磷酸化的预期增加。二甲基草酰甘氨酸（脯氨酰羟化酶抑制剂）在这方面表现更好，但未能促进与缺氧相关的更强作用。因此，CoCl2 和去铁胺不能可靠地模拟 HIF-1α 稳定后的缺氧生理事件。我们的研究表明，模拟化学物质必须谨慎选择，并进行彻底评估，如果要真实地促进细胞的结果。
