促发低氧性肺动脉高压的新机制——肺微动脉的血管胰岛素敏感性降低及其信号障碍

A novel pathogenetic mechanism of hypoxic pulmonary hypertension:decreased insulin sensitivity in pulmonary arterial hypertension

目的:观察低氧诱导大鼠肺微血管内皮细胞(PMVEC),是否同样存在肺血管的胰岛素敏感性变化?并探讨潜在的分子机制。方法:采用低压低氧法建立低氧性肺动脉高压(HPH)大鼠模型,14只雄性SD大鼠随机分为:正常对照组和HPH组(低氧4周),每组7只大鼠(n=7)测定两组平均肺动脉压(mPAP)及胰岛素诱导的血管舒张效应。原代培养大鼠PMVEC,分为常氧(21%O2,37℃)和低氧(10%O2,37℃)处理,分别培养6 h、24 h、48 h和96 h收集细胞以Western blot检测Tribbles同源蛋白3(TRB3)、过氧化物酶体增殖物激活受体(PPARγ)及胰岛素的磷脂肌醇3激酶/蛋白激酶B/内皮一氧化氮合酶(PI3K/Akt/eNOS)信号通路蛋白水平,培养基上清检测一氧化氮(NO)生成量。结果:与正常对照组比较,低氧组mPAP明显升高,胰岛素诱导的肺动脉血管舒张作用明显减弱(P<0.05,P<0.01)。PMVEC在含胰岛素的内皮培养基培养不同时间,低氧组与常氧组相比,培养6 h NO量明显升高,培养24 h后有所下降,随低氧时间的延长下降幅度增大(P<0.01);随低氧时间延长,PI3K-p85、p-Akt、p-eNOS表达逐渐下降,低氧时间越长下降幅度越明显,与NO生成相一致,p-ERK1/2随低氧时间延长表达明显升高;随低氧时间延长TRB3表达增加显著,而PPARγ表达减少(P<0.05,P<0.01)。而不同培养时间常氧组间NO量及上述蛋白表达无显著性差异。结论:低氧可诱导大鼠PMVEC内TRB3的过表达从而负性调控PPARγ,引起下游胰岛素信号通路受损,造成肺血管内皮功能异常,进而促进HPH发生。

AIM： To investigate the underlying molecular mechanisms responsible for vascular insulin resistance （VIR） in pulmonary arterial hypertension （PAH）. METHODS： Fourteen male Sprague Dawley rats were randomly divided into two groups： normal group and hypoxic pulmonary hypertension （HPH） group （exposed in hypobarie and hypoxia condition for 4 weeks）. Pulmonary arterial pressure （PAP） and insulin-induced vasodilation effects of pulmonary artery rings were measured. Primary rat pulmonary microvascular endothelial cells （PMVEC） were cultured, respectively, in normal oxygen （21% 02, 37℃） and low oxygen （10% 02, 37℃） incubators. After cultured at 6, 24, 48, 96 h, cells were collected to detect the expression of TRB3, PPAR-Y and insulin signaling proteins by Western blot. Culture supernatant was used to detect generation of nitric oxide （NO）. RESULTS： Comparedwith those in the control group, mPAP was significantly enhanced in the HPH group, whereas insulin induced vasorelaxation reaction was significantly attenuated （ n = 7, P 〈 0. 05 or P 〈 0. 01 ）. Compared with that in the normoxic group, NO level significantly increased after 6 h, declined after 24 h in the HPH group and further decreased with prolonged hypoxia. Such trends of NO changes were consistent with the expressions of PI3K-p85, p-Akt, p-eNOS but contrary to those of p-ERK1/2. In addition, TRB3 was distinctly overexpressed, whereas PPAR-Y expression decreased. CONCLUSION： Hypoxia induces overexpression of TRB3 in rat PMVEC, which negatively regulates balance of insulin signaling pathways and then dysfunction of PMVEC, thus ment of PHP. PPAR-Y, leading to the im contributing to the development of PHP.