Transcranial direct current stimulation combined with swimming exercise improves the learning and memory abilities of vascular dementia rats by regulating microglia through miR-223-3p/PRMT8.

Background: Vascular dementia (VD) is the second most common type of dementia worldwide. Previous studies have proven that transcranial direct current stimulation (tDCS) has potential applications in relieving cognitive impairment in VD animal models. The purpose of this study was to probe the mechanism by which tDCS combined with swimming exercise improves the learning and memory abilities of VD model rats.

Method: The VD rat model was induced using the permanent bilateral common carotid artery occlusion (2-VO) method; tDCS was applied to the rats and then they took part in swimming exercises. Rat memory, platform crossing time, and platform crossing frequency were analyzed via a water maze experiment. Nerve damage in the cortex and hippocampal CA1 area of the rats was observed using Nissl staining. Western blotting, immunohistochemistry, immunofluorescence staining and reverse transcription quantitative polymerase chain reaction (RT - qPCR) were used to determine the expression of related proteins and genes. The levels of oxidative stress were detected by kits.

Results: We demonstrated that VD model rats treated with tDCS combined with swimming exercise exhibited significant improvement in memory, and VD model rats exhibited significantly reduced neuronal loss in the hippocampus, and reduced microglial activation and M1 polarization. tDCS combined with swimming exercise protects VD model rats from oxidative stress through the miR-223-3p/protein arginine methyltransferase 8 (PRMT8) axis and inhibits the activation of the TLR4/NF-κB signaling pathway.

Conclusion: Our results suggest that tDCS combined with swimming exercise improved the learning and memory ability of VD model rats by regulating the expression of PRMT8 through miR-223-3p to affect microglial activation and M1 polarization.