Dissecting the Molecular Response of Human Escs to Iron-Mediated Oxidative Stress by Genetic Silencing of FTH1 Gene

Abstract Background: Embryonic stem cells (ESCs) are pluripotent cells with indefinite self-renewal ability and differentiation properties. As such, to function properly and maintain genomic stability, ESCs need to be endowed with an efficient repair system as well as effective redox homeostasis. In this study, we investigated and characterized different aspects involved in ESCs response to iron accumulation following stable knockdown of ferritin heavy chain (FTH1) gene, encoding for a major iron storage protein with ferroxidase activity. Methods: stable FTH1 knockdown of H9-hES cell line was achieved with the use of shRNA lentiviral particles. Upon FTH1 silencing, we speculated whether hESCs still retained their pluripotency capability were first monitored for their capability the pluripotent status,FTH1 stable knock-down ESCs were obtained using lentiviral vector plasmids. The effect of FTH1 silencing on hESCs pluripotency was evaluated through alkaline phosphatase (AP) staining, immunofluorescence and embryoid bodies (EBs) formation assay. Western blotting and qRT-PCR analysis were performed to assess the involvement of nuclear factor (erythroid-derived-2)-like 2 (Nrf2) and pentose phosphate pathway (PPP) in the antioxidant response. ROS levels and mitochondrial functionality were explored by flow cytometry. Seahorse Analyzer was used to evaluate metabolic and bioenergetic profiles. Results: Our findings clearly show that FTH1 silencing in hESCs does not correlate with increased ROS production nor with redox status strengthening the concept that hESCs are extremely resistant and, to certain extent, even refractory to the pattern of results produced in other cell lines. Collectively, our results demonstrate that FTH1 silencing is accompanied by a significant activation of the nuclear factor (erythroid-derived-2)-like 2 (Nrf2) signaling pathway and pentose phosphate pathway (PPP) which crosstalk in driving hESCs antioxidant cascade events able to antagonize the effects of FTH1 silencing.Conclusion: to our knowledge, this is the first evidence of a crosstalk between FTH1 silencing and Nrf2 pathway activation in hESCs, casting a new light on how human ESCs perform under oxidative stress conditions. Our findings go beyond previous reports, showing how the Nrf2 pathway, in combination with PPP activation, regulates the molecular signature underlying ESCs defence mechanisms against oxidative stress mediated by FTH1 downregulation.