血管紧张素-（1-7）在减轻兔腹主动脉球囊损伤后血管壁胶原合成中的作用

Angiotensin-（1-7） reduced postangioplasty vascular fibrosis in abdominal aorta of rabbits

目的 探讨血管紧张素（ANG）-（1-7）对兔腹主动脉球囊损伤后血管壁胶原合成的影响及转化生长因子（TGF）β/Smad通路在其中的作用.方法 将32只健康新西兰白兔随机分为4组.假手术组不予任何处理,模型组、ANG-（1-7）组和ANG-（1-7）＋A-779组均行腹主动脉球囊扩张术,术后分别通过微泵持续静脉给予生理盐水（2.5 μl/h）、ANG-（1-7）（576 μg·kg^-1·d^-1及ANG-（1-7）＋A-779（576 μg·kg^-1·d^-14周.于术前、术后4周采血,用酶联免疫吸附测定方法测定血浆中ANG Ⅱ的水平.术后4周行腹主动脉造影及苏木精-伊红染色,计算血管腔的内径及新生内膜面积和管腔狭窄率等.以逆转录聚合酶链反应及免疫组织化学法测定血管壁中Ⅰ、Ⅲ型胶原蛋白的含量和表达部位,同时以Western blot方法测定血管组织中TGF-β_1、磷酸化Smad2的表达水平.结果 术后4周,与模型组相比,ANG-（1-7）组和ANG-（1-7）＋A-779组管腔内径较大[（4.11 ±0.10）mm和（3.34±0.1） mm比（2.88 ±0.08）mm,P均〈0.05],新生内膜面积[（0.27±0.09）mm^2和（0.38±0.01）mm^2比（0.41±0.02）mm^2,P均〈0.05],内膜厚度[（208 ±17）μm和（407 ±25）μm比（448 ±15）μm,P均〈0.05]和管腔狭窄率[（28.1 ±2.7）%和（36.8 ±2.2）%比（40.1 ±2.7）%,P均〈0.05]均较小,ANG-（1-7）＋A-779组与ANG-（1-7）组间差异也有统计学意义（P〈0.05）.与假手术组比较,术后4周模型组、ANG-（1-7）组和ANG-（1-7）＋A-779组血管组织中Ⅰ、Ⅲ型胶原蛋白,TGF-β1和磷酸化Smad2的表达水平均较高（P〈0.01或P〈0.05）,ANG-（1-7）组Ⅰ、Ⅲ型胶原蛋白,TGF-β1和磷酸化Smad2的表达均低于模型组（P均〈0.05）,ANG-（1-7）＋A-779组与模型组间Ⅰ、Ⅲ型胶原蛋白,TGF-β1和磷酸化Smad2的表达差异无统计学意义.术后模型组和ANG-（1-7）组血浆中ANG Ⅱ水平均较术前升高（P〈0.05）,但两组差异无统计学意义.结论 ANG-（1-7）可明显减轻兔腹主动脉球囊损伤后的再狭窄及血管壁胶原合成,这可能与调节组织中TGF-β1的表达,间接抑制Smads途径的激活有关.

Objective To explore the effects of Angiotensin （ANG）-（ 1-7 ） on postangioplasty fibrotic remodeling and the involvement of TGF-β/Smad signaling pathway in this process. Methods Thirty two healthy New Zealand white rabbits were randomly divided into 4 groups： sham group, control group,ANG-（1-7） group and ANG-（ 1-7 ） ＋ A-779 group. Rabbits underwent angioplasty in the abdominal aorta or sham surgery. Subsequently, an osmotic minipump was implanted for saline, ANG-（1-7） （576 μg· kg^-1 ·d^-1） or ANG-（1-7） ＋ A-779 （576 μg · kg^-1 · d^-1） delivery. Before and after 4 weeks treatment, the levels of ANG Ⅱ in plasma were measured by ELISA. At week 4, angiography and histomorphometric analysis were performed, mRNA levels of collagen Ⅰ and Ⅲ were assayed by RT-PCR and protein levels of TGF-β1 and Stand2 in local vessel were assayed by Western blot. Results Following 4 weeks treatment,ANG-（ 1-7 ） and ANG-（ 1-7 ） ＋ A-779 group displayed a significant elevation in lumen diameter [ （4. 11±0.10） mm and （3.34 ±0. 11） mm vs. （2.88 ±0.08） mm,P 〈0.05, respectively] and reduction in neointimal thickness [ （208 ± 17） μm and （407±25） μm vs. （448 ± 15） μm, P 〈0. 05, respectively],neointimal area [（0.27 ±0.09） mm^2 and （0.38 ±0.01） mm^2 vs. （0.41 ±0.02） mm^2, P〈0.05,respectively] and restenosis rate [（28. 1 ±2.7）% and （36.8 ±2.2）% vs. （40. 1 ±2.7）% ,P〈0.05,respectively] compared with control group. Collagen Ⅰ , Ⅲ mRNA and TGF-β1 , Smad2 protein levels were significantly elevated in control group,ANG-（1-7） group and ANG-（1-7） ＋ A-779 group compared to sham group （ P 〈 0. 01 or P 〈 0. 05 ） and reduced in ANG- （1-7） group compared to control group （ all P 〈 0. 05）.Co-treatment with A-779 reversed the inhibitory action of ANG-（ 1-7 ） . Plasma levels of ANG Ⅱ postangioplasty were similar in control and ANG-（ 1-7 ） group and both were significantly higher than preoperation levels. Conclusion ANG-（1-7） attenuates postangioplasty collagen synthesis in rabbits possibly through down-regulating the expression of TGF-β1 and inhibiting the activation of Smad2 pathway.