孕期炎症刺激对子代大鼠心肌纤维化的影响

Maternal lipopolysaccharides exposure during pregnancy induces myocardiac fibrosis in offspring rats

目的探讨孕期炎症刺激对子代大鼠心肌纤维化的影响。方法 8只SD孕鼠采用随机数字表法完全随机分为:对照组(Con)和脂多糖(lipopolysaccharides,LPS)刺激组,每组4只。分别在孕第8、10、12天腹腔注射0.5 m L生理盐水或LPS(0.79 mg/kg)。仔鼠6、8、10、12、16周龄测尾动脉血压;组织切片Masson染色观察心肌组织纤维化;透射电镜观察心肌显微结构;实时荧光定量PCR检测心肌组织缝隙连接蛋白(Connexin,Cx)43、微管相关蛋白1轻链3B(microtubule-associated protein 1light chain 3B,LC3B)、DNA甲基转移酶-1(DNA methyltransferase 1,DNMT-1)mRNA表达水平;Western blot检测Cx43、LC3B、DNMT-1蛋白表达。结果与Con组子代相比,LPS组子代大鼠6、8、10、12、16周龄时血压均明显升高(P<0.01);心肌组织胶原沉积增多,细胞间缝隙连接减少,自噬小体数量增加;Cx43和DNMT-1 mRNA表达水平显著增加(P<0.05),而LC3B的mRNA表达水平显著下降(P<0.05);Cx43蛋白表达水平较Con组子代明显降低(P<0.05),LC3BⅡ/LC3BⅠ和DNMT-1的蛋白表达水平均明显增加(P<0.05)。结论孕期炎症刺激可导致子代大鼠心肌纤维化。这可能与孕期炎症刺激子代大鼠心肌组织自噬活化及Cx43蛋白表达降低相关。

Objective To explore the effect of maternal exposure to lipopolysaccharides （LPS） during pregnancy on myocardial fibrosis in offspring rats. Methods Eight pregnant rats were randomized into 2 equal groups to receive intraperitoneal injections of saline （control） or LPS （0.79 mg/kg） at the 8th, 10th, and 12th days of gestation. The offspring rats were examined at 6, 8, 10, 12, and 16 weeks after birth for systolic blood pressure using the tail-cuff method, and the ventricular histopathology was observed with Masson staining and transmission electron microscopy. The left ventricular myocardial tissues of the offspring rats were sampled for detecting the mRNA and protein expression levels of connexin （Cx） 43, microtubule-associated protein 1 light chain 3B （LC3B） and DNA methyltransferase 1 （DNMT1） using real-time PCR and Western blotting. Results Compared with those in the control group, the offspring rats in LPS group showed significantly increased systolic blood pressure at 6, 8, 10, 12, and 16 weeks after birth （P〈0.01）. No detectable pathological changes were observed in the offspring rats in the control group, whereas those with maternal LPS exposure presented with obvious myocardial pathologies in the left ventricle characterized by increased collagen deposition, disrupted myofibrils, decreased gap junctions, and an increased number of autophagosomes. The offspring rats with maternal LPS exposure showed significantly increased myocardial expression of Cx43 and DNMT-1 mRNA （P〈0.05） and decreased LC3B mRNA expression （P〈0.05） but with obviously decreased protein expression of Cx43 （P〈0.05） and increased expression of LC3BⅡ/LC3BⅠ and DNMT-1 proteins （P〈0.05）. Conclusion Maternal LPS exposure during pregnancy can cause cardiac fibrosis in offspring rats possibly through a mechanism involving autophagy activation and Cx43 degradation.