Lavrentyev Eduard N, Estes Anne M, Malik Kafait U
Department of Pharmacology, College of Medicine, University of Tennessee Health Science Center, Memphis, TN 38163, USA.
Circ Res. 2007 Aug 31;101(5):455-64. doi: 10.1161/CIRCRESAHA.107.151852. Epub 2007 Jul 12.
Angiotensin II (Ang II), a circulating hormone that can be synthesized locally in the vasculature, has been implicated in diabetes-associated vascular complications. This study was conducted to determine whether high glucose (HG) (approximately 23.1 mmol/L), a diabetic-like condition, stimulates Ang II generation and the underlying mechanism of its production in rat vascular smooth muscle cells. The contribution of various enzymes involved in Ang II generation was investigated by silencing their expression with small interfering RNA in cells exposed to normal glucose (approximately 4.1 mmol/L) and HG. Angiotensin I (Ang I) was generated from angiotensinogen by cathepsin D in the presence of normal glucose or HG. Although HG did not affect the rate of angiotensinogen conversion, it decreased expression of angiotensin-converting enzyme (ACE), downregulated ACE-dependent Ang II generation, and upregulated rat vascular chymase-dependent Ang II generation. The ACE inhibitor captopril reduced Ang II levels in the media by 90% in the presence of normal glucose and 19% in HG, whereas rat vascular chymase silencing reduced Ang II production in cells exposed to HG but not normal glucose. The glucose transporter inhibitor cytochalasin B, the aldose reductase inhibitor alrestatin, and the advanced glycation end product formation inhibitor aminoguanidine attenuated HG-induced Ang II generation. HG caused a transient increase in extracellular signal-regulated kinase (ERK)1/2 phosphorylation, and ERK1/2 inhibitors reduced Ang II accumulation by HG. These data suggest that polyol pathway metabolites and AGE can stimulate rat vascular chymase activity via ERK1/2 activation and increase Ang II production. In addition, decreased Ang II degradation, which, in part, could be attributable to a decrease in angiotensin-converting enzyme 2 expression observed in HG, contributes to increased accumulation of Ang II in vascular smooth muscle cells by HG.
血管紧张素II（Ang II）是一种可在血管系统中局部合成的循环激素，与糖尿病相关的血管并发症有关。本研究旨在确定高糖（HG）（约23.1 mmol/L）这种类似糖尿病的状态是否会刺激大鼠血管平滑肌细胞中Ang II的生成及其产生的潜在机制。通过用小干扰RNA沉默暴露于正常葡萄糖（约4.1 mmol/L）和HG的细胞中参与Ang II生成的各种酶的表达，研究了这些酶的作用。在正常葡萄糖或HG存在的情况下，组织蛋白酶D可从血管紧张素原生成血管紧张素I（Ang I）。虽然HG不影响血管紧张素原的转化速率，但它降低了血管紧张素转换酶（ACE）的表达，下调了ACE依赖性Ang II的生成，并上调了大鼠血管糜酶依赖性Ang II的生成。ACE抑制剂卡托普利在正常葡萄糖存在时可使培养基中Ang II水平降低90%，在HG存在时降低19%，而大鼠血管糜酶沉默可降低暴露于HG而非正常葡萄糖的细胞中Ang II的产生。葡萄糖转运体抑制剂细胞松弛素B、醛糖还原酶抑制剂阿雷司他汀和晚期糖基化终产物形成抑制剂氨基胍可减弱HG诱导的Ang II生成。HG导致细胞外信号调节激酶（ERK）1/2磷酸化短暂增加，ERK1/2抑制剂可减少HG诱导的Ang II积累。这些数据表明，多元醇途径代谢产物和晚期糖基化终产物可通过ERK1/2激活刺激大鼠血管糜酶活性并增加Ang II的产生。此外，Ang II降解减少（部分可归因于HG中观察到的血管紧张素转换酶2表达降低）导致HG使血管平滑肌细胞中Ang II积累增加。
