海馬における一過性脳虚血誘導性Zn²⁺集積はEAAT3日内変動により制御される

抄録

[AIM] Stroke during sleep shows a worse prognosis than that during wakefulness, but the mechanism is mostly unknown. In ischemic hippocampus, extracellular Zn²⁺ accumulates in neurons, resulting in neuron death. Excitatory amino acid transporter 3 (EAAT3) is involved in Zn²⁺ homeostasis. Here, we investigated whether diurnal variations in ischemic injury is mediated by altered Zn²⁺ accumulation via EAAT3.

[METHODS] Mice (12 weeks old) were subjected to ischemia/reperfusion (I/R) at 09:00 (ZT4) or 23:00 (ZT18). At 72 h after I/R, Zn²⁺ accumulation and neuron death were assessed by the Zn²⁺-specific probe, TSQ, and Fluoro-Jade B (FJB), respectively. Next, mice were subjected to I/R at ZT18 after injection (ICV) with a non-selective EAAT3 inhibitor (TBOA, 12.5 mM, 2 mL) and then Zn²⁺ accumulation and neuron death were evaluated as same as above. EAAT3 expression and glutathione (GSH) level were detected by western blot and GS-NEM, respectively.

[RESULTS] I/R-induced TSQ (+) and FJB (+) cells were less at ZT18 than ZT4. TBOA increased TSQ (+) and FJB (+) cells. Besides, hippocampal EAAT3 expression and GSH level were higher at ZT18 than ZT4.

[CONCLUSION] These results suggest I/R-induced Zn²⁺ accumulation displays temporal changes via diurnal variations in EAAT3 expression, which affects susceptibility to hippocampal ischemic injury.