The Research On Correlation Of The Expression Of IFN-γ And ICAM-1 In Rats With Cerebral Ischemia

Objective: ICAM-1 (CD54) is a transmembrane glycoprotein moleculeof the immunoglobulin superfamily that plays a key role in the tight adhesionbetween leukocytes and vascular endothelium. ICAM-1 interacts with twointegrins, LFA-1 and Mac-1, which are critical for leukocyte extravasation intoinflamed tissue. The expression of ICAM-1 increases in HCEC after focalcerebral ischemia, which allows an influx of neutrophil. Activated neutrophilsappear to be directly involved in tissue injury after focal cerebral ischemia andreperfusion. IFN-γ is a pleiotropic cytokine product of lymphocytes (subtypeTh-1) and natural killer cells, which plays a critical role in a variety ofimmunological functions. Among IFN-γ's many effects are the induction of anumber of antiviral proteins, upregulation of class II MHC expression, B cellmaturation, activation of cells to cytotoxic states, and release of inflammatorymediators. IFN-γ is known to induce the expression of ICAM-1 in a variety ofcell types such as melanoma cell, human lung fibroblasts, colonocytes,endometrium, basal cell carcinoma and so on. The present study is designed toassess the relationship between IFN-γ and ICAM-1 in cerebral ischemia. Methods:36 male Sprague-Dawley rats, weighing 200～250 g, aresubjected to 1 h of ischemia by inserting a suture into the lumen of the internalcarotid artery and occluding the origin of MCA, followed by 1-24 hours ofreperfusion and recovery. 6 groups (n=6) of animals are investigated after1,3,6,9,12,24 hours reperfusion separately. Each group has a control group (n=3)which undergoes a sham-operation. The cerebral tissues are fixed by 4%paraformaldehyde and embedded by paraffin. Antigens are improved by theMicrowave Oven. Endogenous peroxidase activity is blocked by incubation with3% hydrogen peroxide. ABC method is used for immunohistochemical staining.The first layer is unlabeled primary antibody(IFN-γ antibody /ICAM-1antibody). The second layer is biotinylated secondary antibody. The third layeris a complex of Streptavidin-biotin peroxidase. The peroxidase is thendeveloped by the DAB to produce colored end products. Each step incubates in37℃ incubator for one/half hour. Results are the means of ten different highpower fields of the microscope. Results:Both IFN-γand ICAM-1 expression increase at 1, 3, 6, 9, 12, 24hours after cerebral ischemia and reperfusion. IFN-γ positive cells are roundnucleus -dominative lymphocyte. The expression of 1 hour is 3.2+1.3; that of 6hours is 7.0+2.2; that of 24 hours is 14.8+1.8. ICAM-1 positive cells are flatbrain microvessel endothelial cells. The expression of 1 hour is12.1+2.1; that of6 hours is 19.3+3.2; that of 24 hours is 27.6+2.8. Correlation analysis indicatesthe expressions of IFN-γand ICAM-1 are correlated. Conclusion:The expressions of IFN-γand ICAM-1 increase after focalcerebral ischemia and they are significantly positively correlated. It illustratesIFN-γ may be proinflammatory cytokine to enhance the expression of ICAM-1in cerebral ischemia.