The Expression And Detection Of Inflammatory Cytokines In Rat Brain With Diffuse Axonal Injury

Objective:To investigate the expression and accumulation of tumor necrosis factor alpha (TNFα), interleukin-1 (IL-1) and interleukin-2 (IL-2) in injured sites of rats brain after diffuse axonal injury (DAI) and the correlations with that of beta-amyloid precursor protein (β-APP).Methods:30 adult male Sprague-Dawley rats were randomly divided into control group (n=5) and experimental group (n=25).5 injured rats were sacrificed respectively after 3 hours,6 hours,12 hours,24 hours and 48 hours after objected to diffuse axonal injury according to Marmarou's methods. In prepared brain tissues sections, HE and Bielschowsky staining were performed to investigate the histological changes, while immunohistochemical staining to determine the expression and accumulation ofβ-APP, TNFα, IL-1 and IL-2. Rats in control group experienced sham operation without brain injury and the same tissue preparation procedure.Results:Axonal disorder and neuron degeneration in experimental rats brain tissue could be observed as early as 3h after DAI and axonal retraction ball can be detected 12-24h after injury. The integral optical density (IOD) ofβ-APP in neocortex, hippocampus and corpus callosum significantly increased 3h after injury and continued within 48 hours. The expression of TNFαand IL-1 in neocortex, hippocampus and corpus callosum are similar, whose mean optical density elevated significantly at 3h after DAI and peaks at 6-12h, and then gradually decreased but still higher than that in control group at 48h after injury. The mean optical density of IL-2 in the above areas was also higher significantly than that in control group at 3h after injury and decreased during 4-24h. However, it increased again at 48h. Significant correlation was found betweenβ-APP's IOD and TNFαand IL-1's mean optical density, which was not betweenβ-APP and IL-2.Conclusion:After DAI,β-APP gradually accumulated in injured axon within 48 hours. The expression of TNF a and IL-1 also increased in neocortex, hippocampus and corpus callosum and peaks at 6-12h after injury. There are significant correlation betweenβ-APP'accumulation and TNF a and IL-1's expression, suggesting that both cytokines may be involved in the secondary injury of DAI.IL-2 may entered into brain tissue through injured brain-blood barrier at the early phase of DAI and its expression also increase at the later phase.