体外循环对大鼠脑血管内皮细胞功能的影响

Cerebrovascular endothelial cell injury induced by cardiopulmonary bypass in rats

目的探讨不同体外循环转流模式中大鼠脑血管内皮细胞功能变化及其发生机制。方法构建大鼠闭胸体外循环模型常温转流120min、深低温低流量60min、深低温停循环60min和空白对照4组。颈内静脉采血测定血浆一氧化氮和炎症因子浓度变化。取右大脑中动脉观察不同浓度乙酰胆碱对内皮细胞相关的血管舒张反应强度。Werstem免疫印迹技术测定脑血管eNOS蛋白表达。结果体外循环后各组一氧化氮浓度均低于对照组，各组乙酰胆碱诱导血管舒张反应亦明显受损。体外循环后脑血管eNOS蛋白表达明显降低，停循环组降低最为明显。各组体外循环后炎症因子水平均明显高于术前。结论体外循环可以引起脑血管内皮细胞损伤，主要表现为血管舒张功能受损，且在深低温转流后更为严重；损伤的主要原因是全身炎症反应。

Objective Damage to the nervous system remains an inevitable ccanphcation for the clinical application of carttiopbypass（CPB）technique. Experiment studies in animals with cerebral isehemia-reperfusien injury have revealed the association between inflammation and the impaired endothelium-dependent vasodilation in the brain vessels. Few studies have described the effects of CPB on the vascular endothelial cells of the brain, This study is to investigate functional changes, which occurred in the different CPB modes, of the cerebrovascular endothelial cells and the associations between CPB end inflammatory factors. Methods Twenty-four S.D. rats were equally divided into four groups and underwent nonnothermic CPB for 120 min（group A）, deep hypothermic low flow（DHLF） for 60 min （ Group B ）, deep hypothermic circulatory arrest （DHCA） for 60 min （ Group C ） and sham group （Group D） respectively via fight carotid and jugular cannulation. Blood samples from the internal jugular vein were collected before and after bypass to lest the serum levels of nitrogen monoxide （NO） and IL-6. The middle cerebral artery （MCA） in the right side was harvested for the evaluation of the endothelial cell response to acetylcholine at different concentrations. The protein expression of endothelial NO synthase （eNOS） was determined by Western immunoblotting. The ICAM-1 expression in the cerebral vessels was tested with immunohistochemistry staining. Results Bypass in all of the rats were established and removed successfully. Plasma concentrations of NO were reduced in CPB groups as compared with that in the sham group. Plasma NO levels were lower in group B and C than that in group A[（3.94 ± 0.15） mg/L in group B and （2.93 ± 0.33） mg/L in group C vs. （4.33 ±0. 17） mg/L in group A, P = 0.002]. Acetylcholine induced a dose-dependent MCA vasodilation in sham group[ （24.26 ±1.90）% increase in diameter ], that was attenuated in all CPB groups [（9.60± 1.09）% in group A, （5.97±0.68）% in group B end （5.72±0.67）% in group C, P〈0.011. The hypothennic bypass was associated with significantly reduced eNOS expression as compared with that in group A （ P 〈0.01）, and the eNOS expression was even lower in group C than in group B （ P =0.002）. The IL-6 level increased in all of the bypass groups （ P 〈0.05）. ICAM-1 was overexpressed in all of the bypass groups and the amount of ICAM-lexpressiou increased significantly in these groups as compared with that in the control group. Conclusion CPB may induce injury to the cerebrevasctdar endothelial cells, particularly in the DHCA/DHLF bypass modes. The damage to the endothelial cells may be represented mainly as impaired vasedilatatiou and loss of endothelitun-dependent regulatory factors. Endothelial cell injury may be mainly accounted for by the systemic inflammatory response syndrome. Severe damage to the vasedilation function of the endothelial cells in the middle cerebral artery observed in the DHLF and DHCA groups, as compared with that in the normothennie CPB gronp,may be associated with damage to the endothelial cells induced by hypothermia, more severe hypoperfusion status and iscbemia-reperfusion injury.