Mechanical pressure on endothelial cells mediates remote ischaemic preconditioning‐induced neuroprotection via miR‐126

Remote ischaemic preconditioning (RIPC) uses brief limb ischaemia to protect distant organs, but the mechanism of travel of the protective signal remains unclear. This study investigated whether endothelial cells (ECs) contribute to RIPC-induced neuroprotection and the underlying mechanisms. Ten healthy volunteers (5 men, 5 women) underwent RIPC. Blood velocity was measured by Doppler ultrasound, and vascular wall pressure (VWP) was computed from 3D fluid-structure interaction models based on magnetic resonance imaging data. Human microvascular endothelial cells (HMEC-1) were exposed to cyclic higher pressure (CHP) for five cycles. miR-126 expression and promoter DNA methylation were assessed by real-time PCR and bisulfite sequencing. DNA methyltransferases (DNMTs) and global methylation levels were measured. SH-SY5Y neurons were incubated with exosomes from HMEC-1 culture medium and then subjected to oxygen-glucose deprivation/reperfusion (OGD/R). Neuronal viability and apoptosis were evaluated by MTS assay and flow cytometry, and damage by spectrin and cleaved caspase-3 levels. Dicrotic waves were induced in 9 of the 10 participants following RIPC treatment. VWP transiently increased following RIPC. CHP reduced the expression and activity of DNMTs and induced the hypomethylation of the miR-126 promoter sequence in HMEC-1 cells, leading to an increase in miR-126 levels. Exosomes from CHP-treated HMEC-1 cells decreased SH-SY5Y cell injury under OGD/R. RIPC transiently increased VWP in healthy volunteers. The results of this study indicate that CHP treatment may induce the production of neuroprotective molecules by ECs, which may protect against ischaemia/hypoxia-induced neuronal cell injury in vitro, possibly through a CHP-induced effect involving miR-126.