The Mechanism And Effect Of Reactive Oxygen Species (ROS) On Neural Stem Cell Proliferation

It is known that the proliferation of the neural stem cells (NSCs), an attractive therapeutic target for treatment of neurotrauma and neurodegenerative diseases, is influenced by various factors, including reactive oxygen species (ROS). The several studies revealed that the low concentration of ROS without causing oxidative stress can be served as a signal transduction molecule, promoting the proliferation of NSCs. The gene of B-cell-specific moloney leukemia virus insert site 1(Bmil), one of polycomb group genes, plays an important role in proliferation and self-renewal of NSCs by depression of P16 and P19. Moreover, Bmil maintains the intracellular redox homeostasis by regulating mitochondrial function and ROS production. Heterozygous knockout of the Bmi1 gene (Bmil+/-) down-regulates P16 and P19 in NSCs, but does not significantly alter the NSC proliferation, and the underlying mechanism remains unclear. We hypothesized that the down-regulation of Bmi1 mildly increases the endogenous ROS levels, which promotes the proliferation of NSCs and subsequently counteracts the inhibitory effect of cyclin dependent proteins on NSC proliferation.To explore the interaction effect of ROS and Bmi-1 on NSCs proliferation, in the present study, NSCs derived from Bmil+/- and wild-type (WT) mice were cultured, and their intracellular ROS levels were controlled by treatment with different concentrations of H2O2and the anti-oxidant NAC, respectively.The results showed:1) At the basic condition, Bmil+/--NSCs exhibited a normal proliferation capability, but companying a mild increase in intracellular ROS levels, when compared to WT-NSCs.2) The endogenous ROS levels were slightly raised inWT-NSCs following treatment with 1μM H2O2 for 24 h, companied with a mild increase in neurosphere number, high levels of cellular viability and BrdU incorporation ratio, as well as increases in the total antioxidant capacity (T-AOC) and total superoxide disproportionation enzyme (T-SOD) activity, although no obvious change in the neurosphere diamater occurred. Bmi1+/--NSCs had higher levels of the intracellular ROS than WT-NSCs, but decreases in the other parameters above mentioned significantly compared to the baseline control, thus causing a significant difference from WT-NSCs. The intracellular ROS levels increased significantly in Bmil+/--NSCs compared to WT-NSCs after cultured with 10 μM H2O2, however, the above other indexes declined significantly, especially in Bmi1+/--NSCs. Treatment with 100 μM H2O2 for 24 h caused reductions in the intracellular ROS production and the above related indexes in the both gene types of NSCs without difference from each other, but decreases in BrdU incorporation ratio were more obvious in Bmil+/--NSCs than WT controls.3) After cultured with the ROS scavenger NAC at different concentrations (1,5 and 10 mM) for 24 h, both of Bmi1+/--NSCs and WT-NSCs showed concentration dependent deceases in the intracellular ROS levels, neurosphere number and diameter, cellular viability, and BrdU incorporation ratio, as well as T-AOC and T-SOD, and these declines were more obvious for Bmil+/"-NSCs.The above results suggested that mildly increased endogenous ROS caused by low concentration of H2O2 or heterozygous knockout of the Bmil gene improves the NSC proliferation, whereas, the higher ROS levels induced by H2O2 or lower ROS levels induced by NAC inhibits the proliferation and self-renewal of NSCs. The finding will be beneficial for further understanding of the interaction role of Bmil and ROS in regulation of neurogenesis, providing a new idea for the treatment of brain developmental abnormalities and neurodegenerative diseases.