Non-invasive transcranial direct-current stimulation (tDCS) is a safe ischaemic stroke therapy. Cathodal bilateral tDCS (BtDCS) is a modified tDCS approach established by us recently. Because selenium (Se) plays a crucial role in cerebral ischaemic injury, we investigated whether cathodal BtDCS conferred neuroprotection via regulating Se-dependent signalling in rat cerebral ischaemia–reperfusion (I/R) injury. We first showed that the levels of Se and its transport protein selenoprotein P (SEPP1) were reduced in the rat cortical penumbra following I/R, whereas cathodal BtDCS prevented the reduction of Se and SEPP1. Interestingly, direct-current stimulation (DCS) increased SEPP1 level in cultured astrocytes subjected to oxygen-glucose deprivation reoxygenation (OGD/R) but had no effect on SEPP1 level in OGD/R-insulted neurons, indicating that DCS may increase Se in ischaemic neurons by enhancing the synthesis and secretion of SEPP1 in astrocytes. We then revealed that DCS reduced the number of injured mitochondria in OGD/R-insulted neurons cocultured with astrocytes. DCS and BtDCS prevented the reduction of the mitochondrial quality-control signalling, vesicle-associated membrane protein 2 (VAMP2) and syntaxin-4 (STX4), in OGD/R-insulted neurons cocultured with astrocytes and the ischaemic brain respectively. Under the same experimental conditions, downregulation of SEPP1 blocked DCS- and BtDCS-induced upregulation of VAMP2 and STX4. Finally, we demonstrated that cathodal BtDCS increased Se to reduce infract volume following I/R. Together, the present study uncovered a molecular mechanism by which cathodal BtDCS confers neuroprotection through increasing SEPP1 in astrocytes and subsequent upregulation of SEPP1/VAMP2/STX4 signalling in ischaemic neurons after rat cerebral I/R injury.

无创经颅直流电刺激（tDCS）是一种安全的缺血性中风治疗方法。阴极双边 tDCS（BtDCS）是我们最近建立的改良 tDCS 方法。由于硒 (Se) 在脑缺血损伤中起着至关重要的作用，因此我们研究了阴极 BtDCS 是否通过调节 Se 依赖性信号传导对大鼠脑缺血再灌注 (I/R) 损伤提供神经保护。我们首先表明，缺血再灌注后大鼠皮质半暗带中 Se 及其转运蛋白硒蛋白 P (SEPP1) 的水平降低，而阴极 BtDCS 则阻止 Se 和 SEPP1 的降低。有趣的是，直流电刺激（DCS）增加了氧糖剥夺再氧合（OGD/R）培养的星形胶质细胞中的SEPP1水平，但对OGD/R损伤的神经元中的SEPP1水平没有影响，表明DCS可能增加缺血性脑损伤中的Se神经元通过增强星形胶质细胞中 SEPP1 的合成和分泌来发挥作用。然后我们发现，DCS 减少了与星形胶质细胞共培养的 OGD/R 损伤神经元中受损线粒体的数量。DCS 和 BtDCS 分别阻止了与星形胶质细胞和缺血脑共培养的 OGD/R 损伤神经元中线粒体质量控制信号、囊泡相关膜蛋白 2 (VAMP2) 和突触蛋白 4 (STX4) 的减少。在相同的实验条件下，SEPP1 的下调阻断了 DCS 和 BtDCS 诱导的 VAMP2 和 STX4 的上调。最后，我们证明阴极 BtDCS 增加 Se 来减少 I/R 后的梗塞体积。总之，本研究揭示了一种分子机制，在大鼠脑 I/R 损伤后，阴极 BtDCS 通过增加星形胶质细胞中的 SEPP1 以及随后上调缺血神经元中的 SEPP1/VAMP2/STX4 信号传导来提供神经保护。