缬沙坦对大鼠颈动脉血管外膜损伤后收缩功能的影响及其机制探讨

Effect of valsartan on vasoconstriction induced by the chronic injury of the adventitia in the rat collared carotid artery

目的 通过观察缬沙坦对大鼠颈动脉血管外膜损伤后收缩功能的影响,探讨血管紧张素Ⅱ（AngⅡ）及其受体以及p22phox在外膜损伤致血管收缩性增强过程中的作用.方法 雄性Wistar Kyoto大鼠分成3组,空白组（n=6,不作任何处理）,对照组（n=12,蒸馏水1 ml每日1次灌胃）,缬沙坦组（n=12,缬沙坦30 mg/kg每日1次灌胃）.用硅胶管经血管外膜包裹大鼠颈动脉.包管手术前后各给药1周.于术后1周用超声血流量仪检测大鼠双侧颈动脉血流量,并观察血管对局部应用5-羟色胺（5-HT）的反应;苏木素-伊红染色,光镜下观察血管形态学变化;心腔取血,用ELISA法检测大鼠血清AngⅡ浓度;以Western blot方法测血管壁AngⅡ受体及p22phox蛋白的表达.结果 缬沙坦组大鼠包管侧颈动脉管腔面积缩小5%,中膜增厚10%,比对照组[管腔面积缩小44%（P＜0.001）,中膜直径增厚62%]明显改善（P＜0.001）;颈动脉血流量为（4.33±0.84）ml/min显著大于对照组[（2.79±0.22）ml/min]（P＜0.001）;血管对5-HT的反应敏感性改善;循环血AngⅡ浓度为（89.73±20.44）pg/ml,明显高于对照组[（45.21±4.52）pg/ml,P=0.001]及空白组[（19.83±0.54）pg/ml,P＜0.001].对照组血AngⅡ浓度显著高于空白组（P=0.0148）.对照组包管侧颈动脉血管壁AngⅡ1型受体（AT1R）表达是对照侧的2.95倍（P=0.0065）,AngⅡ2型受体（AT2R）表达是其3.37倍（P＜0.001）,p22phox的表达是其4.54倍（P＜0.001）.缬沙坦组与对照组比较包管侧颈动脉血管壁AT1R的表达差异无统计学意义（P=0.4095）,AT2R的表达高了55%（P＜0.001）,p22phox的表达低了51%（P=0.0013）.结论 硅胶管包裹大鼠颈动脉导致血管外膜慢性损伤,慢性激活循环肾素血管紧张素系统及上调血管局部AngⅡ受体,AngⅡ作用于上调的AT1R,通过氧化应激反应介导致血管收缩性增强.缬沙坦通过阻断AT1 R及刺激AT2R的表达预防外膜损伤所致的血管收缩性改变.

Objective Vasoconstriction and vascular hypersensitivity to serotonin were previously shown in animal models of adventitia injury. We investigated the contribution of angiotensin Ⅱ（Ang Ⅱ）/Ang Ⅱ receptors and oxidative stress to vascular contractility and reactivity in this model. Methods Wistar Kyoto rats were divided into 3 groups： normal（n =6, no any intervention, only for measuring the serum Ang d-1）. After one week of treatment, adventitia injury was induced by positioning a silicone collar around the right carotid artery for one week. Blood flow and vascular reactivity to serotonin were determined one week after injury, the blood from left ventricle was taken to measure the serum Ang Ⅱ concentration by ELISA,and carotids were harvested for morphometry and Western blot analysis. Results Adventitia injury induced lumen cross-sectional area reduction（- 44% vs. - 5%）, media diameter increase（62% vs. 10%）,blood flow reduction[（2. 79 ± 0. 22）vs.（4. 33 ± 0. 84）ml/min]were significantly attenuated by valsartar. The increased vascular reactivity sensitivity to serotonin in vehicle group was also significantly reduced in valsartan group. Serum Ang Ⅱ concentration was significantly increased in vehicle group [（45.21 ± 4. 52）pg/ml vs.（19. 83 ± 0. 5）pg/ml in normal rats, P = 0. 0148]and the expression of Ang Ⅱtype 1（AT1）receptor, Ang Ⅱ type 2（AT2）receptor, as well as p22pbox in collared arteries were significantly upregulated. Valsartan did not affect the AT1 receptor expression but further increased serum Ang Ⅱ concentration[（89. 73 ±20. 44）pg/ml vs.（45.21 ±4. 52）pg/ml, P =0. 001], and AT2 receptor expression, while downregulated p22phox expressions. Conclusions Collar-induced adventitia injury resulted in chronic vsoconstriction and vascular hypersensitivity to serotonin via increased serum Ang Ⅱ level,upregulated Ang Ⅱ receptors expression in the vascular well, and activated local oxidative stress. These changes could be blocked by valsartan suggesting a crucial role of Ang Ⅱ/Ang Ⅱ receptors on vascular contractility and reactivity changes in this model.