抗α1-肾上腺素受体抗体介导大鼠心室重塑的免疫机制

目的观察抗α1-肾上腺素受体自身抗体对大鼠心室重塑的影响并探索其可能机制.方法用α1-肾上腺素受体胞外第二肽段合成肽免疫Wistar大鼠作为模型,设自发性高血压大鼠及正常Wistar大鼠为对照;用尾套法监测收缩压及心率,用酶联免疫吸附试验(ELISA)法检测抗α1-肾上腺素受体抗体滴度,用光镜和电镜观察并计算心脏病理变化;用逆转录多聚合酶链式反应(RT-PCR)、免疫印迹及免疫组织化学的方法检测左心室肌组织的c-jun和/或c-fos、α1-肾上腺素受体的表达.结果在免疫后2周抗α1-肾上腺素受体抗体滴度开始升高,并在整个实验过程中维持在较高水平;在实验过程中,免疫组血压心率与对照组差异无统计学意义,但均显著低于自发性高血压大鼠组;免疫组心脏体重比、左心室心肌细胞截面积、心肌胶原体积比例和心肌血管周围胶原面积与管腔面积比例分别为3.32 mg/g±0.25 mg/g、231 μm2±11 μm2、5.40%±0.66%和1.89±0.62,均显著高于正常对照组(分别为3.06 mg/g±0.25 mg/g、197 μm2±19 μm2、3.22%±0.15%和0.86±0.17), 但低于自发性高血压大鼠组;电镜结果显示心肌细胞肥大、线粒体增多,心肌间质胶原纤维增多,说明免疫组发生心室重塑;在免疫组中,α1A、B-肾上腺素受体及c-fos的表达与正常对照差异无统计学意义,但α1D-肾上腺素受体表达显著降低(免疫组和正常对照组分别为0.55±0.01 和 0.88±0.08,P<0.05),同时心肌细胞及心肌间质成纤维细胞c-jun蛋白及mRNA的表达显著增加.结论抗α1-肾上腺素受体抗体可以通过增加大鼠心肌细胞及心肌间质成纤维细胞c-jun的表达,导致心室重塑,可能是该抗体介导大鼠心室重塑的免疫机制之一.

Immune mechanism of cardiac remodeling induced by antibodies against to the alpha1-adrenergic receptor

OBJECTIVE: To study the effects of autoantibodies against alpha1-adrenergic receptor on the cardiac remodeling and relevant mechanism. METHODS: Four-week-old male Wistar rats were immunized with synthesized second extracellular loop of alpha1-adrenergic receptor and raised for one year, with spontaneously hyperetensive rats (SHRs) and no-immunized Wistar rats of the same age as controls. Every one or two months blood was collected from the caudal vein to detect the level of serum antibodies to alpha1-adrenergic receptor by ELISA and the systolic blood pressure (SBP) and heart rate were measured. One year after the rats were killed and their hearts were taken out. The heart weight/body weight ratio, cardiac muscle cell cross-sectional area (CSA), interstitial collagen volume fraction (CVF) and the ratio of perivascular collagen area to vessel luminal area (PVCA) were calculated, the expression of alpha1-adrenergic receptor, c-fos and c-Jun in heart were measured by RT-PCR, Western blotting and immunohistochemistry. RESULTS: During the experiment the blood pressure of the SHRs were significantly higher than those of the immunization group and normal control group (both P < 0.01) without significant difference between the 2 latter groups. The heart weight/body weight ratio, CSA, CVF and PVCA of the immobilization group were 3.32 mg/g +/- 0.25 mg/g, 231 microm(2) +/- 11 microm(2), 5.40% +/- 0.66% and 1.89 +/- 0.62 respectively, all significantly higher than those of the normal control group (3.06 mg/g +/- 0.25 mg/g, 197 microm(2) +/- 19 microm(2), 3.22% +/- 0.15% and 0.86 +/- 0.17 respectively), but still significantly lower than those of the SHR group. Since the second week after immunization, the titre of antibody against of the immunization group began increase, peaked in the second and third months, and then decreased slowly, and remained at a high level by the end of experiment. The titre of antibody was not correlated with blood pressure. Hypertrophy of cardiac muscle cells and increase of sedimentation of collagen in stroma were seen in the hearts of the immunization group. RT-PCR showed that the expression of alpha1D-adrenergic receptor mRNA of the immunization group was 0.55 +/- 0.01, significantly lower than that of the normal control group (0.88 +/- 0.08, P < 0.05); the expression of c-jun mRNA in the immunization group was 0.82 +/- 0.02, significantly higher than that in the normal control group (0.42 +/- 0.07, P < 0.05); and there were no significant differences in the expressions of heart alpha1A- and alpha1B-afrenergic receptors and c-fos mRNAs between these 2 groups. Western blotting showed that the expression of c-jun protein in the immunization group was 6.24 +/- 2.13, significantly higher than that in the normal control group (2.55 +/- 0.58, P < 0.05); and there were no significant differences in the expressions of c-fos andalpha1A-adrenergic receptor proteins between these 2 groups. CONCLUSION: The antibodies against alpha1-adrenergic receptor up-regulates the expression of c-jun in cardiac muscle cells and interstitial fibroblast, which may be an immunologic mechanism of cardiac remodeling.