TLR4/PKCα/occludin signaling pathway may be related to blood-brain barrier damage

Abnormal blood-brain barrier (BBB) is a common pathological feature in brain damage. In the present study, a brain microvascular endothelial cell (BMEC) model was established to determine the role of the toll-like receptor 4 (TLR4)/protein kinase C alpha (PKC alpha)/occludin signaling pathway in BBB dysfunction. Three small interfering (si)RNAs directed against PKC alpha were designed to investigate the molecular mechanisms of PKC alpha underlying BBB damage. BMECs were divided into 4 groups: Control group, TAK-242 (a TLR4 inhibitor) group, PKC alpha-siRNA group and TAK-242+PKC alpha-siRNA group. The results indicated that siRNA-3 was the most effective at silencing PKC alpha gene expression. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis indicated no significant difference of TLR4 mRNA expression levels between three different treated groups and the Control group. However, PKC alpha mRNA expression in the PKC alpha-siRNA and TAK-242+PKC alpha-siRNA groups were significantly decreased compared with that in Control and TAK-242 groups. In addition, occludin mRNA expression in PKC alpha-siRNA and TAK-242+PKC alpha-siRNA groups were significantly higher compared with the Control group. Meanwhile, occluding expressions in three treated groups were also significantly higher compared with the Control group. Furthermore, TAK-242 treatment, PKC alpha-siRNA treatment, and TAK-242+PKC alpha-siRNA treatment could promote occludin junctional labeling compared with the Control group. The permeability of PKC alpha-siRNA and TAK-242+PKC alpha-siRNA groups was significantly promoted compared with the control group. The TLR4/PKC alpha/occludin signaling pathway was closely related to BBB damage. The present study will lead to an improved molecular understanding of BBB damage in the future.