Mild hypoxia (5% O₂) as well as FGFR1-induced activation of phosphatidylinositol-4,5-bisphosphate 3-kinase/protein kinase B (PI3K/AKT) and MAPK signaling pathways markedly support pluripotency in human pluripotent stem cells (hPSCs). This study demonstrates that the pluripotency-promoting PI3K/AKT signaling pathway is surprisingly attenuated in mild hypoxia compared to the 21% O₂ environment. Hypoxia is known to be associated with lower levels of reactive oxygen species (ROS), which are recognized as intracellular second messengers capable of upregulating the PI3K/AKT signaling pathway. Our data denote that ROS downregulation results in pluripotency upregulation and PI3K/AKT attenuation in a hypoxia-inducible factor 1 (HIF-1)-dependent manner in hPSCs. Using specific MAPK inhibitors, we show that the MAPK pathway also downregulates ROS and therefore attenuates the PI3K/AKT signaling—this represents a novel interaction between these signaling pathways. This inhibition of ROS initiated by MEK1/2–ERK1/2 may serve as a negative feedback loop from the MAPK pathway toward FGFR1 and PI3K/AKT activation. We further describe the molecular mechanism resulting in PI3K/AKT upregulation in hPSCs—ROS inhibit the PI3K's primary antagonist PTEN and upregulate FGFR1 phosphorylation. These novel regulatory circuits utilizing ROS as second messengers may contribute to the development of enhanced cultivation and differentiation protocols for hPSCs. Since the PI3K/AKT pathway often undergoes an oncogenic transformation, our data could also provide new insights into the regulation of cancer stem cell signaling.

轻度缺氧（5％O ₂）以及FGFR1诱导的磷脂酰肌醇4,5-双磷酸3激酶/蛋白激酶B（PI3K / AKT）和MAPK信号通路的激活明显支持人多能干细胞（hPSC）的多能性。 。这项研究表明，与21％O ₂相比，在轻度缺氧条件下，促进多能性的PI3K / AKT信号传导途径出人意料地减弱了。环境。已知缺氧与较低水平的活性氧（ROS）有关，后者被认为是能够上调PI3K / AKT信号通路的细胞内第二信使。我们的数据表明，ROS下调导致hPSCs中缺氧诱导因子1（HIF-1）依赖性的多能性上调和PI3K / AKT衰减。使用特定的MAPK抑制剂，我们显示MAPK途径还下调ROS，因此减弱了PI3K / AKT信号传导-这代表了这些信号传导途径之间的新型相互作用。由MEK1 / 2–ERK1 / 2引发的对ROS的抑制作用可能是从MAPK途径向FGFR1和PI3K / AKT激活的负反馈回路。我们进一步描述了导致hPSCs中PI3K / AKT上调的分子机制-ROS抑制PI3K' 的主要拮抗剂PTEN和FGFR1磷酸化上调。这些利用ROS作为第二信使的新型调节电路可能有助于开发hPSC的增强培养和分化方案。由于PI3K / AKT途径经常经历致癌转化，因此我们的数据还可以为癌症干细胞信号传导的调控提供新的见解。