镁对慢性阻塞性肺疾病大鼠血管钙化和弹力纤维降解的影响及机制

目的探讨镁在慢性阻塞性肺疾病(chronic obstructive pulmonary disease,COPD)大鼠血管钙化和弹力纤维降解中的作用及可能机制。方法SD大鼠40只,随机分为低镁组、高镁组、模型组、对照组各10只。低镁组、高镁组、模型组雾化吸入丙烯醛制备COPD模型,对照组雾化吸入蒸馏水。造模成功后,低镁组给予低镁饮食(镁元素质量构成比0.02%)、高镁组给予高镁饮食(镁元素质量构成比0.20%),对照组和模型组给予正常饮食(镁含量正常),连续14 d。干预结束,检测4组血镁含量;处死大鼠取胸主动脉和肺组织,采用von Kossa染色法检测胸主动脉钙化程度,邻甲酚酞络合酮比色法测定胸主动脉壁钙含量,实时荧光定量PCR法检测肺组织弹力纤维mRNA相对表达量,Western blot法检测肺组织基质金属蛋白酶(matrix metalloproteinase,MMP)-9、MMP-2相对表达量。结果镁干预14 d,高镁组血镁含量[(1.33±0.45)mmol/L]高于低镁组[(0.62±0.24)mmol/L]、模型组[(0.91±0.34)mmol/L]、对照组[(0.91±0.15)mmol/L](P<0.05),且对照组和模型组高于低镁组(P<0.05),模型组与对照组比较差异无统计学意义(P>0.05);低镁组、模型组、高镁组、对照组肺组织弹力纤维mRNA相对表达量(0.14±0.09、0.31±0.05、0.81±0.04、0.95±0.08)依次增高(P<0.05);对照组胸主动脉几乎无钙化,模型组胸主动脉一定程度钙化,低镁组胸主动脉弥漫性钙化,高镁组胸主动脉钙化程度较模型组、低镁组轻;低镁组、模型组、高镁组、对照组胸主动脉壁钙含量[(13.21±0.22)、(8.12±0.55)、(5.21±0.35)、(3.98±0.15)μg/mg]依次降低(P<0.05),肺组织MMP-9相对表达量(6.12±0.15、4.21±0.32、2.21±0.25、1.98±0.05)、MMP-2相对表达量(4.34±0.09、3.21±0.15、1.61±0.21、1.55±0.15)依次降低(P<0.05)。结论镁可通过下调肺组织MMP-9、MMP-2表达,进而抑制COPD大鼠血管钙化及弹力纤维降解。

Influence of magnesium on antagonizing vascular calcification and elastin degradation in rats with chronic obstructive pulmonary disease and its mechanism

Objective To investigate the role of magnesium in antagonizing vascular calcification and elastin degradation in rats with chronic obstructive pulmonary disease(COPD)and its possible mechanism.Methods Forty SD rats were randomly divided into low-magnesium group,high-magnesium group,model group and control group,with 10 rats in each group.Low-magnesium group,high-magnesium group and model group inhaled acrolein to prepare COPD models,and control group inhaled distilled water.After successful modeling,low-magnesium group received low magnesium diet(magnesium mass composition ratio of 0.02%),high-magnesium group received high magnesium diet(magnesium mass composition ratio of 0.20%),and control group and model group were given normal diet(normal magnesium content),totally for 14 days.The blood magnesium content was detected in four groups.All rats were sacrificed to obtain the thoracic aorta and lung tissue.The calcification degree of the thoracic aorta was detected by von Kossa staining,the calcium content in the thoracic aortic wall was measured by pyrophthalein complexone colorimetry,the relative expression of elastic fiber mRNA in the lung tissue was measured by real-time fluorescence quantitative PCR,and the relative expressions of matrix metalloproteinase(MMP)-9 and MMP-2 in the lung tissue were detected by Western blot.Results After 14-day treatment,the blood magnesium content was higher in high-magnesium group((1.33±0.45)mmol/L)than that in low-magnesium group((0.62±0.24)mmol/L),model group((0.91±0.34)mmol/L)and control group((0.91±0.15)mmol/L)(P<0.05),higher in control group and model group than that in low-magnesium group(P<0.05),and showed no significant difference between model group and control group(P>0.05).The relative expression of elastic fiber mRNA increased gradually in turn in low-magnesium group,model group,high-magnesium group and control group(0.14±0.09,0.31±0.05,0.81±0.04,0.95±0.08)(P<0.05).von Kossa staining showed no calcification of the thoracic aorta in control group,some calcification in model group,diffuse calcification in low-magnesium group,and milder calcification in high-magnesium group than model group and low-magnesium group.The content of calcium in the thoracic aortic wall decreased gradually in turn in low-magnesium group,model group,high-magnesium group and control group((13.21±0.22),(8.12±0.55),(5.21±0.35),(3.98±0.15)μg/mg)(P<0.05).The relative expression levels of MMP-9(6.12±0.15,4.21±0.32,2.21±0.25,1.98±0.05)and MMP-2(4.34±0.09,3.21±0.15,1.61±0.21,1.55±0.15)decreased gradually in turn in low-magnesium group,model group,high-magnesium group and control group(P<0.05).Conclusion Magnesium can inhibit vascular calcification and elastic fiber degradation in COPD rats by down-regulating the levels of MMP-9 and MMP-2 in the lung tissue.