Oxidative stress promotes exit from the stem cell state and spontaneous neuronal differentiation
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Qidong Hu1, Puja Khanna1, Belinda Shu Ee Wong1, Zealyn Shi Lin Heng1, Charannya Sozheesvari Subhramanyam1, Lal Zo Thanga1, Sharon Wui Sing Tan1 and Gyeong Hun Baeg1
1Department of Anatomy, Yong Loo Lin School of Medicine, National University of Singapore, MD 10, Singapore
Qidong Hu, email: [email protected]
Gyeong Hun Baeg, email: [email protected]
Keywords: Ntera2 cell; differenitation; reactive oxygen species; oxidative stress
Received: September 18, 2017 Accepted: December 27, 2017 Published: December 30, 2017
Reactive oxygen species (ROS) play important roles in fundamental cellular processes such as proliferation and survival. Here we investigated the effect of oxidative stress on stem cell maintenance and neuronal differentiation in a human embryonic stem cell (hESC) model, Ntera2 (NT2). CM-H2DCFDA and DHE assays confirmed that the oxidizing agent paraquat could induce a high level of ROS in NT2 cells. Quantitative PCR, Western blotting and immunocytochemistry showed that paraquat-induced oxidative stress suppressed the expression of stemness markers, including NANOG, OCT4 and TDGF1, whereas it enhanced the spontaneous expression of neuronal differentiation markers such as PAX6, NEUROD1, HOXA1, NCAM, GFRA1 and TUJ1. The treated cells even exhibited a strikingly different morphology from control cells, extending out long neurite-like processes. The neurogenic effect of ROS on stem cell behaviour was confirmed by the observations that the expression of neuronal markers in the paraquat-treated cells was suppressed by an antioxidant while further enhanced by knocking down Nrf2, a key transcription factor associated with antioxidant signaling. Lastly, paraquat dose-dependently activated the neurogenic MAPK-ERK1/2, which can be reversed by the MEK1/2 inhibitor SL327. Our study suggests that excessive intracellular ROS can trigger the exit from stem cell state and promote the neuronal differentiation of hESCs, and that MAPK-ERK1/2 signaling may play a proactive role in the ROS-induced neuronal differentiation of hESCs.
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