Department of Kinesiology, Faculty of Applied Health Sciences, University of Waterloo, Waterloo, Ontario, Canada.
Am J Physiol Heart Circ Physiol. 2010 May;298(5):H1391-405. doi: 10.1152/ajpheart.01233.2009. Epub 2010 Feb 12.
Hypertensive vasomotor dysfunction is defined by endothelium-dependent contractions involving prostaglandins and ROS. Since both thromboxane-prostanoid receptor (TPr) signaling and ROS activate RhoA-Rho kinase (ROCK) in vascular smooth muscle (VSM) preparations, we hypothesized that enhanced endothelium-dependent contraction in the common carotid artery (CCA) of spontaneously hypertensive rats (SHRs) is ROCK mediated. ACh-stimulated contractions were approximately twofold greater in SHRs versus normotensive Wistar-Kyoto (WKY) rats, abolished by endothelial denudation or cyclooxygenase (COX)-1 inhibition, and nearly eliminated by TPr blockade. RhoA but not ROCK-II protein expression was increased ( approximately 50%) in the SHR CCA. Inhibition of ROCK, but not protein kinase C, caused a dose-dependent reduction in endothelium-dependent contractions to ACh across strains, with the highest dose mirroring the effect of high-dose TPr antagonism. Conversely, ROCK inhibition caused dose-dependent and endothelium- and nitric oxide-independent relaxation in CCAs precontracted with the TPr agonist U-46619. Prostacyclin was the predominant prostaglandin produced by ACh-stimulated CCAs, with greater than twofold more prostacyclin released from SHR versus WKY rats, and its production was unaffected by ROCK inhibition. RhoA activation was approximately twofold higher in quiescent SHR CCAs compared with those from WKY rats and was significantly increased by ACh stimulation. Augmentation of chemical superoxide quenching with tiron or inhibition of the NADPH oxidase-derived superoxide-producing pathway with apocynin reduced ACh-stimulated contractile activity in SHR more than in WKY rats, whereas the SOD mimetic tempol amplified the response. Exposure of CCAs to exogenous H(2)O(2) caused contractions, similar to ACh stimulation, that were greater in SHR than in WKY rats, abolished by COX-1 inhibition, and highly attenuated by TPr blockade or ROCK inhibition. These results indicate that RhoA-ROCK may act as a molecular switch, transducing signals from endothelium-derived prostaglandin(s) and ROS, which are overproduced in SHR CCAs, to "turn on" VSM contractile pathways, thus mediating the enhanced endothelium- and endoperoxide-dependent vascular contractions characteristic of hypertension, among other cardiovascular disease states, such as diabetes and aging.
高血压血管舒缩功能障碍定义为涉及前列腺素和活性氧（ROS）的内皮依赖性收缩。由于血栓素 - 前列腺素受体（TPr）信号和 ROS 在血管平滑肌（VSM）制剂中均能激活RhoA- Rho 激酶（ROCK），我们假设自发性高血压大鼠（SHR）颈总动脉（CCA）中增强的内皮依赖性收缩是 ROCK 介导的。与正常血压的 Wistar-Kyoto（WKY）大鼠相比，SHR 中 ACh 刺激的收缩约增加了两倍，内皮细胞剥脱或环氧化酶（COX）-1 抑制可消除收缩，而 TPr 阻断几乎可消除收缩。SHR CCA 中的 RhoA 但不是 ROCK-II 蛋白表达增加（约 50%）。ROCK 抑制而非蛋白激酶 C 抑制导致 ACh 引起的内皮依赖性收缩在各品系中呈剂量依赖性降低，最高剂量与高剂量 TPr 拮抗作用的效果相似。相反，ROCK 抑制可引起 TPr 激动剂 U-46619 预收缩的 CCAs 呈剂量依赖性和内皮非依赖性及一氧化氮依赖性松弛。前列环素是 ACh 刺激的 CCAs 产生的主要前列腺素，SHR 释放的前列环素比 WKY 大鼠多两倍以上，其产生不受 ROCK 抑制的影响。与 WKY 大鼠相比，SHR 静息 CCA 中的 RhoA 激活约增加两倍，并且 ACh 刺激可显著增加其激活。用钛络合物增加化学超氧化物淬灭或用 apocynin 抑制 NADPH 氧化酶衍生的超氧化物产生途径可使 SHR 中 ACh 刺激的收缩活性降低超过 WKY 大鼠，而 SOD 模拟物 tempol 则放大了该反应。向 CCAs 中添加外源性 H2O2 会引起类似于 ACh 刺激的收缩，SHR 中的收缩比 WKY 大鼠中的收缩更强，COX-1 抑制可消除收缩，而 TPr 阻断或 ROCK 抑制可高度减轻收缩。这些结果表明，RhoA-ROCK 可能作为分子开关，将来自 SHR CCA 中超产的内皮衍生前列腺素和 ROS 的信号转导，“开启”VSM 收缩途径，从而介导增强的内皮和内过氧化物依赖性血管收缩，这是高血压等心血管疾病状态的特征，例如糖尿病和衰老。
