Expression of Toll-like receptor 4 in the brain in a rabbit experimental subarachnoid haemorrhage model

Objective: To investigate the expression of the Toll-like receptor (TLR) 4 in the brain after experimental subarachnoid haemorrhage (SAH) in rabbits. Methods: A total of 52 rabbits were randomly divided into four groups: control group; day 3, day 5, and day 7 groups. Day 3, day 5, and day 7 groups were all SAH groups in which the rabbits were killed on day 3, 5, and 7, respectively. In SAH groups, autologous arterial blood was injected into cisterna magna twice on day 0 and day 2. Immunostaining and immunoblotting experiments were performed to detect the expression of TLR4 protein. Reverse-transcriptase polymerase chain reaction was used to analyze the presence and quantity of TLR4 mRNA. Results: The expressions of TLR4 protein and mRNA were increased remarkably in SAH groups compared with the control group. The immunohistochemical staining demonstrated high level expression of TLR4 was present mainly in the endothelial cells of capillaries in the brain. Conclusion: Our results indicate that TLR4 expression is upregulated in the brain after experimental SAH.