Objective To study the regulative effects and mechanism of A2a AR on expression of suppressor of cytokinesignaling-3 (SOCS-3) in hypoxic pulmonary hypertension rats.Methods SpragueDaeley rats were randomly divided into 3 groups:a normal control group,a hypoxia group,and a hypoxia with selective agonists of A2a AR group.Animals in the hypoxia groups were housed in a chamber with 8％-11％ O2 and 1％-3％ CO2 for8 hours (8:00 AM to4:00 PM) daily for 28 days.They were treated intraperitoneally with either 4 ml/kg weight of normal saline or 0.2 mg/kg weight of CGS-21680 30 minutes before exposure to hypoxia.Four weeks later,mean pulmonary artery pressure (mPAP),mean carotid arterial pressure (mCAP) and right ventricular rate [RV/(LV + S)] were measured.The expression of A2aAR and SOCS-3 in pulmonary arterioles was measured by immunohistochemistry.The expression of A2aAR mRNA and SOCS-3 mRNA in lung tissues were measured by real time RT-PCR.The expression of A2aAR protein and SOCS-3 protein in lung tissues were measured by Western blot.Results The mPAP in the hypoxia group was [(20.9 ±3.9)mmHg,1 mmHg =0.133 kPa],significantly higher than the normal control group [(12.6 ±6.6) mmHg] (P ＜ 0.01).The mPAP in CGS-21680 group was [(14.8 ± 3.8) mmHg],significantly lower than the hypoxia group(P ＜ 0.01).RV/(LV + S) in the hypoxia group was [(35.2 ± 2.0) ％],significantly higher than the normal control group [(29.6 ± 2.7) ％] (P ＜ 0.01).RV/(LV + S) in the CGS-21680 group was [(28.3 ± 8.8)％],significantly lower than the hypoxia group (P ＜0.01).WA/TA in the hypoxia group was (73 ± 5,P ＜ 0.01),significantly higher than the normal control group.WA/TA in CGS21680 group was (54 ± 3,P ＜ 0.01),significantly lower than the hypoxia group.A2aAR and SOCS-3 expressions on pulmonary arterioles in the hypoxia group were (0.134 ±0.034) and (0.119 ± 0.011),both significantly higher than the normal group (P ＜ 0.01);and CGS-21680 treatment further increased their expressions.The mRNA expression of both molecules showed a 1.5-fold increase after 28-day hypoxia exposure.A2aAR activation by CGS-21680 treatment in hypoxia-exposed rats further increased the expression levels of A2aAR and SOCS-3 to about 2-fold higher than the normal controls.Furthermore,protein levels of A2aAR and SOCS-3 in the lung tissue were determined using Western blot.A similar increase was observed in hypoxia-induced pulmonary hypertension,and CGS-21680 treatment group showed the highest levels of these 2 proteins.Conclusion A2a AR activation prevents hypoxia-induced pulmonary hypertension,and its mechanisms are related to the activation of A2a AR SOCS-3 signaling pathway.%目的 探讨腺苷A2a受体(A2aAR)对低氧肺动脉高压大鼠肺血管和肺组织细胞因子信号传导抑制蛋白3(SOCS-3)表达的调控作用.方法 SD大鼠30只按照随机数字表法分为3组:对照组,低氧组,低氧+A2aAR激动剂组(激动剂组).低氧组及激动剂组置入常压低氧舱内,氧浓度控制在8％ ～ 11％,CO2浓度维持在1％ ～3％,每天8h(晨8时至16时),每周6d,连续4周,低氧组入舱前腹腔注射生理盐水4 ml/kg,激动剂组入舱前腹腔注射A2aAR激动剂0.2 mg/kg.造模4周后,有心导管法测定各组大鼠平均肺动脉压(mPAP)、平均颈动脉压(mCAP),测定右心室/(左心室+室间隔)厚度[RV/(LV+S)];观察各组肺细小动脉显微结构变化,测定管壁面积/管总面积(WA/TA);用免疫组织化学法测定肺细小动脉管壁A2aAR和SOCS-3含量,实时荧光定量PCR法、Western blot法测定肺组织匀浆A2aAR mRNA、SOCS-3 mRNA和A2aAR蛋白、SOCS-3蛋白含量的变化.结果 低氧组大鼠mPAP为[(20.9±3.9) mmHg,1 mmHg =0.133 kPa],明显高于对照组[(12.6±6.6) mmHg,P＜0.01],激动剂组mPAP为[(14.8±3.8)mmHg],明显低于低氧组(P＜0.01).低氧组RV/(LV+S)为[(35.2±2.0)％],显著高于对照组[(29.6±2.7)％,P＜0.01],激动剂组RV/(LV+S)为[(28.3±8.8)％],显著低于低氧组(P＜0.01).低氧组大鼠WA/TA值为73 ±5,显著高于对照组(48±4,p ＜0.01),激动剂组WA/TA值为54±3,明显低于低氧组(P＜0.01).低氧组大鼠肺血管A2aAR含量为(0.134±0.034),SOCS-3含量为(0.119 ±0.011),两者均高于正常组(P＜0.01),而激动剂组肺血管A2aAR含量(0.201±0.024)和SOCS-3含量(0.136±0.004)较低氧组进一步升高(p＜0.01).与对照组相比,低氧组大鼠肺组织A2aAR mRNA和SOCS-3 mRNA表达增加1.5倍,而激动剂组A2aAR mRNA和SOCS-3 mRNA表达增加2倍.同样,低氧组大鼠肺组织A2aAR蛋白和SOCS-3蛋白表达明显高于对照组,而激动剂组两种蛋白的表达进一步上升.结论A2aAR能够上调低氧肺动脉高压大鼠肺血管和肺组织SOCS-3的表达,该通路可能是其抑制低氧性肺动脉高压和低氧性肺血管重建的重要机制.
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