Carbon monoxide protects Neural Stem Cells against iron overload by modulating the crosstalk between Nrf2 and NF-κB Signaling

Abstract Background:It is well CO is an important gas transmitter. Although accumulating evidences have demonstrated pro-survival effects of CO against various insults, the precise mechanism explaining how neural stem cell is protected by CO also remains largely unknown. Methods: After NSCs were challenged by iron overload with or without CO pretreatment, apoptosis of NSCs was tested by Flow cytometry and the level of antioxidant protein was also detected. ROS of NSCs was demonstrated via the fluorescent probe. We applied siRNA to demonstrated role of the protective effect of CO. In invivo experiment, NSCs with or without CO pretreatment were implanted into intracranial hemorrhagic mouse and the survival of NSCs were detected. The significance of the difference among mean values was determined by the Student–Newman–Keuls test or two-way analysis of variance followed by the Bonferroni post hoc test. Results: CO effect on pro-survival was comparable to that obtained with pharmacological inhibitors of ROS. Its effect on pro-survival was accompanied by the inhibition of ROS and subsequent inhibition of NF-κB. Such effect is believed to be mediated through Nrf2, in that siRNA-mediated inhibition of Nrf2 revealed that Nrf2 is required for the pro-survival effect of CO. CO also activated NQO-1, a downstream target of Nrf2, which was inhibited by down-regulating Nrf2. CO-mediated precondition results in Nrf2 stimulation and NF-κB inhibition, suggesting that these two pathways act in an inverse manner to maintain redox homeostasis. The pro-survival effect of CO was also further endorsed by the evidences in mouse hemorrhagic stroke models. Conclusions: Results, by showing that CO attenuates iron overload induced apoptosis by suppressing the NF-κB signaling via Nrf2-mediated anti-oxidant effect, contribute to the understanding of essential cellular pathways. Our findings reveal CO preconditioning as a promising treatment strategy to improve efficacy of NSCs transplantation after HS.