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

Abstract

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? (PKC?)/occludin signaling pathway in BBB dysfunction. Three small interfering (si)RNAs directed against PKC? were designed to investigate the molecular mechanisms of PKC? underlying BBB damage. BMECs were divided into 4 groups: Control group, TAK-242 (a TLR4 inhibitor) group, PKC?-siRNA group and TAK-242+PKC?-siRNA group. The results indicated that siRNA-3 was the most effective at silencing PKC? 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? mRNA expression in the PKC?-siRNA and TAK-242+PKC?-siRNA groups were significantly decreased compared with that in Control and TAK-242 groups. In addition, occludin mRNA expression in PKC?-siRNA and TAK-242+PKC?-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?-siRNA treatment, and TAK-242+PKC?-siRNA treatment could promote occludin junctional labeling compared with the Control group. The permeability of PKC?-siRNA and TAK-242+PKC?-siRNA groups was significantly promoted compared with the control group. The TLR4/PKC?/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.