Clin Sci (Lond). 2014 Apr;126(7):483-95. doi: 10.1042/CS20130235.
Mechanical cyclic stretch of cardiomyocytes causes cardiac hypertrophy through cardiac-restricted gene expression. Leptin induces cardiomyocyte hypertrophy in response to myocardial stress. In the present study, we evaluated the expression of leptin under cyclic stretch and its role in regulating genetic transcription in cardiomyocytes. Cultured rat neonatal cardiomyocytes were subjected to cyclic stretch, and the expression levels of leptin, ROS (reactive oxygen species) and AngII (angiotensin II) were evaluated. Signal transduction inhibitors were used to identify the pathway of leptin expression. EMSAs were used to identify the binding of leptin/STAT3 (signal transducer and activator of transcription 3) and luciferase assays were used to identify the transcription of leptin in cardiomyocytes. The study also used an in vivo model of AV (aortocaval) shunt in rats to investigate leptin, ROS and AngII expression. Leptin and leptin receptor levels increased after cyclic stretch with the earlier expression of AngII and ROS. Leptin expression was suppressed by AngII receptor blockers, an ROS scavenger [NAC (N-acetylcysteine)], an ERK (extracellular-signal-regulated kinase) pathway inhibitor (PD98059) and ERK siRNA. Binding of leptin/STAT3 was identified by EMSAs, and luciferase assays confirmed the transcription of leptin in neonatal cardiomyocytes after cyclic stretch. Increased MHC (myosin heavy chain) expression and [3H]-proline incorporation in cardiomyocytes was detected after cyclic stretch, which were inhibited by leptin siRNA and NAC. The in vivo model of AV shunt also demonstrated increased levels of plasma and myocardial leptin, ROS and AngII expression after cyclic stretch. Mechanical cyclic stretch in cardiomyocytes increased leptin expression mediated by the induction of AngII, ROS and the ERK pathway to cause cardiomyocyte hypertrophy. Myocardial hypertrophy can be identified by increased transcriptional activity and an enhanced hypertrophic phenotype of cardiomyocytes.
机械循环拉伸可通过心脏限制性基因表达引起心肌肥厚。瘦素可诱导心肌细胞肥大以应对心肌应激。本研究评估了循环拉伸下瘦素的表达及其在调节心肌细胞基因转录中的作用。培养的新生大鼠心肌细胞进行循环拉伸，评估瘦素、ROS（活性氧）和 AngII（血管紧张素 II）的表达水平。使用信号转导抑制剂鉴定瘦素表达的途径。EMSA 用于鉴定瘦素/STAT3（信号转导和转录激活因子 3）的结合，荧光素酶测定用于鉴定心肌细胞中瘦素的转录。该研究还使用大鼠 AV（主动脉-腔静脉）分流的体内模型来研究瘦素、ROS 和 AngII 的表达。循环拉伸后，瘦素和瘦素受体水平增加，AngII 和 ROS 较早表达。AngII 受体阻滞剂、ROS 清除剂[NAC（N-乙酰半胱氨酸）]、ERK（细胞外信号调节激酶）通路抑制剂（PD98059）和 ERK siRNA 抑制瘦素表达。EMSA 鉴定了瘦素/STAT3 的结合，荧光素酶测定证实了循环拉伸后心肌细胞中瘦素的转录。循环拉伸后检测到心肌细胞中 MHC（肌球蛋白重链）表达增加和[3H]-脯氨酸掺入增加，瘦素 siRNA 和 NAC 抑制了这些增加。AV 分流的体内模型也表明，循环拉伸后血浆和心肌瘦素、ROS 和 AngII 的表达增加。心肌细胞的机械循环拉伸增加了瘦素的表达，介导途径为 AngII、ROS 和 ERK 通路，导致心肌细胞肥大。心肌肥大可以通过增加心肌细胞的转录活性和增强的肥大表型来识别。
