高碳酸血症通过赖氨酰氧化酶依赖的胶原蛋白交联影响大鼠缺氧性肺动脉高压

摘要

目的: 通过研究缺氧和/或高碳酸血症时赖氨酰氧化酶(LOX)以及细胞外基质胶原蛋白的交联变化,探讨高碳酸血症对缺氧性肺动脉高压的影响机制.方法: SD大鼠随机均分为4组,分别为常氧对照组、缺氧组、高碳酸血症组以及缺氧+高碳酸血症组.比色法测定胶原蛋白含量,荧光光谱法分析LOX酶活性,免疫组织化学和Western blot法检测肺动脉LOX蛋白含量,实时荧光定量PCR检测肺动脉LOX的mRNA水平.结果: 缺氧组大鼠平均肺动脉压(mPAP)、右心室/(左心室+室间隔)重量比值[RV/(LV+S)]及血管壁面积(WA)/血管总面积(TA)均明显高于常氧对照组;高碳酸血症组与常氧对照组的mPAP、RV/(LV+S)差异无统计学显著性;缺氧+高碳酸血症组大鼠的mPAP及RV/(LV+S)显著低于单纯缺氧组.缺氧组大鼠肺组织的胶原交联程度则明显高于常氧组及高碳酸血症组;高碳酸血症组大鼠肺组织的胶原交联程度与常氧组比较无显著差异;缺氧+高碳酸血症组大鼠肺组织的胶原交联程度显著低于缺氧组.缺氧组大鼠肺动脉LOX的mRNA、蛋白表达量及其酶活性均高于常氧组(P<0.01);缺氧+高碳酸血症组大鼠肺动脉LOX mRNA、蛋白表达以及酶活性均明显低于缺氧组(P<0.01).结论: 缺氧能诱导肺动脉LOX高表达,通过促进胶原合成及交联,参与肺动脉高压的形成.高碳酸血症通过抑制缺氧诱导的LOX表达和胶原交联,延缓缺氧性肺动脉高压的进展.%AIM: To investigate the effect of hypercapnia on hypoxia-induced pulmonary hypertension and the changes of lysyl oxidase (LOX) and extracellular matrix collagen cross-links in the rat.METHODS: Sprague-Dawley rats were randomly divided into 4 groups: normoxia group, hypoxia group, hypercapnia group and hypoxia+hypercapnia group.LOX activity was detected by fluorescence spectrophotometry.LOX protein expression was detected by immunohistochemistry and Western blot.The mRNA expression of LOX in the pulmonary artery was detected by real-time PCR.RESULTS: The levels of mean pulmonary artery pressure (mPAP), RV/(LV+S) and WA/TA in hypoxia group were significantly higher than those in normoxia group (P<0.01).Moreover, the levels of mPAP and RV/(LV+S) in hypoxia+hypercapnia group were significantly lower than those in hypoxia group (P<0.01).However, no significant difference of mPAP and RV/(LV+S) between hypercapnia group and normoxia group was observed.In hypoxia group, the collagen cross-links in the lung tissue was significantly higher than that in normoxia group and hypercapnia group (P<0.01).Importantly, collagen cross-links in the lung tissue of hypoxia+hypercapnia group was significantly lower than that in hypoxia group (P<0.01).There was no significant difference in collagen cross-links between hypercapnia group and normoxia group.The expression of LOX at mRNA and protein levels and its activity in the pulmonary arteries of hypoxia group were significantly increased as compared with normoxia group (P<0.01).Furthermore, the expression of LOX at mRNA and protein levels and its activity in the pulmonary arteries in hypoxia+hypercapnia group were lower than those in hypoxia group (P<0.01).CONCLUSION: Hypoxia not only up-regulates LOX but also promotes collagen cross-linking in the rat lung, which contributes to the development of pulmonary hypertension.Hypercapnia inhibits hypoxia-induced LOX expression and collagen cross-linking, therefore impairing the progress in hypoxia-induced pulmonary hypertension.