Changes in tumor necrosis factor alpha and myeloper-oxidase in mouse models of local cerebral infarction induced by photochemical method

摘要

BACKGROUND: Lots of evidences have demonstrated that acute inflammatory reaction plays an important role in cerebral ischemia and cerebral ischemia/reperfusion injury. Tumor necrosis factor (TNF), as one of important inflammatory cytokines, also participates in the injury. OBJECTIVE: To observe the changes in TNF-α expression and myeloperoxidase (MPO) activity of mouse models of local cerebral infarction induced by photochemical method, and analyze the correlation of TNF-α expression and MPO activity. DESIGN: Randomized controlled experiment. SETTING: Laboratory of Cerebral Microcirculation, Taishan Medical College. MATERIALS: Sixty involved male adult Kunming mice were provided by the Experimental Animal Center of Shandong University. TNF-α primary antibody, kits for enzyme-linked immunosorbent assay(ELISA) and streptavidin-biotin complex immunohistochemical dyeing kit were purchased from Boster Company(Wuhan). MPO kit was purchased from Jiancheng Bioengineering Institute (Nanjing). Cold light source was developed by Hengfa Co.,Ltd.( LG-150, Xuzhou). METHODS: This experiment was carried out in the Laboratory of Cerebral Microcirculation of Taishan Medical College between July 2004 and July 2005. The involved 60 Kunming mice were randomized into 3 groups: normal control group (n =6), sham-operation group (n =6) and model group (n =48). Mice in the model group were observed at 30 minutes, 1, 3, 6, 12, 24, 48 and 72 hours after illumination, separately, 6 mice at each time point. In the model group, mice models of local cerebral infarction were developed as follows: The mice were anesthetized to expose left skulls. Taking 2 mm left to sagittal suture and 2 mm posterior to coronal suture as center, a field with diameter of 3 mm for illumination was set. The optical fiber detecting head of cold light source was vertically close to exposed skull. The mice were injected with rose Bengal for 5 minutes, and then cold light source was open for 10 minutes. Illumination was omitted in the sham-operation group. Mice in the control group were not modeled. At postoperative 6 hours, TNF-α expression in infracted-side cortex was detected with immunohistochemical method and ELISA, and MPO activity in infracted-side cortex with chromatometry. MPO activity could reflect the infiltration degree of neutrophils in tissue. Stronger activity indicated severer infiltration. Single-factor analysis of variance was used for comparison among groups, q test for pairwise comparison and correlative analysis for detecting the inter-parameter correlation. MAIN OUTCOME MEASURES: Changes in TNF-α expression and MPO activity of left cortex of mice in each group. RESULTS: Sixty mice were involved in the final analysis. After cerebral infarction, TNF-α positive cells were neurons and glial cells mainly, distributing in and around the infarct region. TNF-α expression in cortex of mice of sham-operation group was (615.7±16.1) ng/L, and that of model group increased to (792.2±17.8) ng/L at 3 hours after illumination, and reached peak [(921.9±23.9) ng/L] at 6 hours after illumination, and decreased to (848.0±30.6) ng/L at 12 hours after illumination and recovered to the normal level [(625.3±14.3) ng/L] at 72 hours after illumination. MPO activity of sham-operation group was (7.151±0.433) nkat/g, and that of model group increased to (10.469±0.600) nkat/g at 3 hours after illumination, reached the peak ([15.486±0.650) nkat/g] at 12 hours after illumination, decreased to (11.052±0.617) nkat/g at 24 hours after illumination and recovered to the normal level [(7.418± 0.617) nkat/g] at 72 hours after illumination. Change of MPO activity lagged behind that of TNF-α, andcorrelative analysis showed that the both were positively correlated(r =0.953, P < 0.01). CONCLUSION: In the acute stage of cerebral infarction of mice induced by photochemical method, TNF-α expression in infarcted-side cortex is closely related with infiltration of neutrophils. TNF-α induces inflammatory cells to intrude into ischemic brain tissue, and participates in the inflammatory reaction process at the early stage of cerebral ischemia.