Fig. 1.

Schematic of miRNA regulatory blood-brain-barrier (BBB) tight junction (TJs) protein. a miR-181c promotes the destruction of the BBB through the delocalization of actin fibers via the downregulation of 3 phosphoinositide-dependent protein kinase-1 (PDPK1). PDPK1 degradation by miR-181c leads to the downregulation of phosphorylated cofilin and the resultant activated cofilin-induced modulation of actin dynamics [69]. b miR-1258 downregulates MMP-9 and COX-2 protein by directly targeting HPSE, hence protecting the BBB from destruction [40]. c miR-509 negatively regulates the expression of two essential genes for brain metastasis, RhoC and TNF-α, which enhance the permeability of the BBB [121]. d miR-210 directly targets β- Catenin and Occudin to disrupt the integrity of the BBB [37]. e MiR-143 decreases the expression of TJs by directly targeting p53 upregulated modulator of apoptosis (PUMA) and increases the permeability of human brain endothelial cells [35]