Effects of Toll-like receptor 4 inhibitor on hypoxic-ischemic hippocampal neurons and dendritic spines in neonatal rats

Abstract

Objective To evaluate the effects of preconditioning with Toll-like receptor 4 (TLR4) inhibitor on hypoxic-ischemic hippocampal neurons and dendritic spines in neonatal rats. Methods Seventy-five neonatal (7-day-old) rats were randomly divided into control group, hypoxia-ischemia group (HI group) and TAK-242 (a TLR4-specific antagonist) group. In the latter 2 groups, rat models of hypoxic-ischemic brain damage (HIBD) were established using the Rice method, and in TAK-242 group, a single dose of TAK-242 (0.5 mg/kg) was intraperitoneally injected 30 min prior to HI. Western blotting was used to detect TLR4 expression in the left hippocampus of the rats 24 h after HI. On day 21 following the modeling, HE staining, Nissl staining and Golgi silver staining were used to assess neuronal loss and the changes in dendritic spine density in the left hippocampus. The expression of N-methyl-D-aspartic acid receptors 2A and 2B (NR2A and NR2B) was detected using Western blotting and immunofluorescence staining. Results The expression of TLR4 in the left hippocampus of the neonatal rats increased significantly at 24 h after HI (P < 0.05), and TAK-242 obviously suppressed the up-regulated expression of TLR4 (P < 0.05). Compared with those in the control group, the number of neurons, dendritic spine density and the expression of NR2A all decreased significantly in the left hippocampus of the rats at 21 d after HI (P < 0.05); pretreatment with TAK-242 obviously alleviated these changes (P < 0.05). Conclusion TLR4 inhibitor can mitigate HI-induced long-term damage of the hippocampal neurons and the dendritic spines.

Keywords

• hypoxic-ischemic injury
• neonate
• brain injuries
• hippocampus
• toll-like receptor 4
• rats