Figure 3. Lithium at 3 mM rescues proliferating cells in S phase.

A. Propidium iodide (PI) histograms representing the different phases of the cell cycle distribution in sham (black), irradiated (red) and irradiated+3 mM LiCl (purple). B. Quantification of the percentages of cells in G₁ phase of the cell cycle providing additional evidence of irradiation inducing an arrest in this phase at 24 and 48 hours, ****p_{24 hours} < 0.0001, *p_{48 hours} = 0.0007. Lithium at 3 mM was able to reduce the proportion of cells arrested in G₁ after irradiation at 24, 48 and 72 hours **p_{3 mM_24 hours} = 0.0070, ***p_{3 mM_48 hours} = 0.0006 and *p_{3 mM_72 hours} = 0.0121. C. Quantification over time of the proportion of cells in S phase shows that very few events were found in this phase after irradiation, indicating a negative effect on proliferation at any given time, **p_{6 hours} = 0.0012, ****p_{24 hours} < 0.0001, ****p_{48 hours} < 0.0001, **p_{72 hours} = 0.0018. Lithium at 3 mM dose restored the proliferating pool 6 hours after irradiation and this moderate effect was also observed at 24 and 48 hours, *p_{3 mM_6 vhours} = 0.0265, *p_{3 mM_24 hours} = 0.0359, *p_{3 mM_48 hours} = 0.0225. D. Quantification of the distribution of the cells in G₂/M phase over time shows a pattern of accumulation in this cell phase after irradiation, **p_{6 hours} = 0.0074, ****p_{24 hours} < 0.0001, **p_{48 hours} = 0.0012, **p_{72 hours} = 0.0011. Even a more prominent stall in G₂/M phase was observed after irradiation in combination with 3 mM LiCl treatment, **p_{3 mM_24 hours} = 0.0072, ***p_{3 mM_48 hours} = 0.0005, *p_{3 mM_72 hours} = 0.0232. Asterisks in the graph represent significant differences between the irradiated NSPCs and the irradiated NSPCs treated with lithium. Data are presented as mean ± SEM, n = 3–6.