Aburto C, Ruminot I, San Martín A
Centro de Estudios Científicos (CECs), 5110466, Valdivia, Chile; Facultad de Ciencias, Universidad Austral de Chile, 5110566, Valdivia, Chile.
Centro de Estudios Científicos (CECs), 5110466, Valdivia, Chile; Facultad de Ciencias para el Cuidado de la Salud, Universidad San Sebastián, 5110773, Valdivia, Chile.
Redox Biol. 2025 Jun 27;85:103740. doi: 10.1016/j.redox.2025.103740.
Oxidative stress reprograms metabolic flux from glycolysis to the pentose phosphate pathway. Recently, it has been proposed that NADPH acts as a key molecule in pentose phosphate pathway regulation by exerting negative feedback through tonic inhibition of glucose-6-phosphate dehydrogenase. Interestingly, recent studies show that NADPH levels remain stable during acute exposure to hydrogen peroxide in the presence of glucose, ruling out NADPH-dependent feedback inhibition. We hypothesize that hydrogen peroxide triggers a feedforward activation mechanism, increasing NADPH production even before any detectable NADPH depletion. To probe this hypothesis, we used a panel of genetically encoded fluorescent indicators to monitor glucose, NADPH, fructose 1,6-bisphosphate and pyruvate in single cells with high temporal resolution. Our results reveal that hydrogen peroxide rapidly activates glucose transport and consumption rates, enabling cells to preserve NADPH steady-state levels during early oxidative stress. Notably, this response precedes NADPH depletion, implying an anticipatory phenomenon that boosts NADPH production prior to its consumption. Furthermore, hydrogen peroxide induced an acute perturbation of fructose 1,6-bisphosphate steady-state and an increase of pyruvate accumulation. The pharmacological inhibition of the PPP's gateway enzymes, glucose-6-phosphate dehydrogenase and transketolase, abolished the hydrogen peroxide-dependent alterations in fructose 1,6-bisphosphate steady-state levels and pyruvate accumulation, respectively. These findings suggest that a substantial fraction of glucose-derived carbon flux is diverted to the pentose phosphate pathway under oxidative stress, underscoring the importance of feedforward control in maintaining redox balance.
氧化应激可使代谢通量从糖酵解重编程为磷酸戊糖途径。最近，有人提出烟酰胺腺嘌呤二核苷酸磷酸（NADPH）通过对葡萄糖-6-磷酸脱氢酶的持续抑制施加负反馈，在磷酸戊糖途径调节中起关键分子的作用。有趣的是，最近的研究表明，在有葡萄糖存在的情况下，急性暴露于过氧化氢期间，NADPH水平保持稳定，排除了NADPH依赖性反馈抑制。我们假设过氧化氢触发了一种前馈激活机制，甚至在任何可检测到的NADPH消耗之前就增加了NADPH的产生。为了探究这一假设，我们使用了一组基因编码的荧光指示剂，以高时间分辨率监测单细胞中的葡萄糖、NADPH、果糖1,6-二磷酸和丙酮酸。我们的结果表明，过氧化氢迅速激活葡萄糖转运和消耗速率，使细胞能够在早期氧化应激期间维持NADPH稳态水平。值得注意的是，这种反应先于NADPH消耗，这意味着一种预期现象，即在NADPH消耗之前增加其产生。此外，过氧化氢引起了果糖1,6-二磷酸稳态的急性扰动和丙酮酸积累的增加。磷酸戊糖途径入口酶葡萄糖-6-磷酸脱氢酶和转酮醇酶的药理学抑制分别消除了过氧化氢依赖性的果糖1,6-二磷酸稳态水平变化和丙酮酸积累。这些发现表明，在氧化应激下，相当一部分源自葡萄糖的碳通量被转移到磷酸戊糖途径，强调了前馈控制在维持氧化还原平衡中的重要性。
