High Glutathione and Glutathione Peroxidase-2 Levels Mediate Cell-Type-Specific DNA Damage Protection in Human Induced Pluripotent Stem Cells

Abstract

SummaryPluripotent stem cells must strictly maintain genomic integrity to prevent transmission of mutations. In human induced pluripotent stem cells (iPSCs), we found that genome surveillance is achieved via two ways, namely, a hypersensitivity to apoptosis and a very low accumulation of DNA lesions. The low apoptosis threshold was mediated by constitutive p53 expression and a marked upregulation of proapoptotic p53 target genes of the BCL-2 family, ensuring the efficient iPSC removal upon genotoxic insults. Intriguingly, despite the elevated apoptosis sensitivity, both mitochondrial and nuclear DNA lesions induced by genotoxins were less frequent in iPSCs compared to fibroblasts. Gene profiling identified that mRNA expression of several antioxidant proteins was considerably upregulated in iPSCs. Knockdown of glutathione peroxidase-2 and depletion of glutathione impaired protection against DNA lesions. Thus, iPSCs ensure genomic integrity through enhanced apoptosis induction and increased antioxidant defense, contributing to protection against DNA damage.

Full biological characterization of human pluripotent stem cells will open the door to translational research

“…This indicates that oxidative DNA damage occurs less frequent rather than it gets more efficiently repaired (Maynard et al 2008). In accordance with this assumption, hiPSC also display less oxidative DNA lesions, but enhanced anti-oxidative defense proteins (induced levels of GSH, GST and glutathione) (Dannenmann et al 2015). Upon topoisomerase-induced DSB, members of the PI3K-related kinases (PI3KKs) are activated.…”

“…Therefore, other mechanisms must prime pluripotent stem cells for rapid induction of apoptosis. It has been shown that hESC and hiPSC display higher mitochondrial readiness for apoptosis than differentiated cells, because the intrinsic balance between anti-apoptotic and pro-apoptotic proteins is more primed toward apoptosis (Dannenmann et al 2015;Liu et al 2013).…”

“…DNA repair mechanisms work in concordance with various apoptosis inducing pathways like p53-dependent apoptosis, mitochondrial priming and BAX pre-activation. Of note, the hESC line H1 and hiPSC do not harbor pre-activated BAX; however, these cells are equally sensitized to DNA damage through other mechanisms (Dannenmann et al 2015;Dumitru et al 2012;Liu et al 2013Liu et al , 2014.…”

pH and glutathione dual-triggered supramolecular assemblies as synergistic and controlled drug release carriers

“…54,55 Aside from normal cells, tumor cells have more reducing power than the extracellular medium or plasma with higher glutathione (GSH) concentrations in the cytosol (GSH levels within cells, roughly 100-5000 times more concentrated than in most extracellular environments, ranging from 1 to 10 mM). 56,57 Therefore, polymers embedded with GSHresponsive cleavable bonds such as disulfide bonds have been extensively utilized for the development of site-targeted drug delivery systems and selective imaging reporters. However, the practicability of using pH and GSH dual responsive nano drug delivery systems exhibiting tunable drug releasing behavior for tumor treatment remains challenging.…”

Novel AKT phosphorylation sites identified in the pluripotency factors OCT4, SOX2 and KLF4

“…For Western blot analysis proteins were transferred onto polyvinylidenedifluoride membranes (Amersham Biosciences). 42,43 Membranes were blocked in PBS containing 4% BSA and 0.05% Tween-20 for 1 h, followed by an overnight incubation with the primary antibodies in Figure 4. AKT phosphorylation sites in OCT4, SOX2 and KLF4.…”