Beyer Andreas M, Durand Matthew J, Hockenberry Joseph, Gamblin T Clark, Phillips Shane A, Gutterman David D
Department of Medicine, Cardiovascular Center, Medical College of Wisconsin, Milwaukee, Wisconsin;
Department of Surgery, Division of Surgical Oncology, Medical College of Wisconsin, Milwaukee, Wisconsin.
Am J Physiol Heart Circ Physiol. 2014 Dec 1;307(11):H1587-93. doi: 10.1152/ajpheart.00557.2014. Epub 2014 Sep 26.
Endothelial nitric oxide (NO) is the primary mediator of flow-mediated dilation (FMD) in human adipose microvessels. Impaired NO-mediated vasodilation occurs after acute and chronic hypertension, possibly due to excess generation of reactive oxygen species (ROS). The direct role of pressure elevation in this impairment of human arteriolar dilation is not known. We tested the hypothesis that elevation in pressure is sufficient to impair FMD. Arterioles were isolated from human adipose tissue and cannulated, and vasodilation to graded flow gradients was measured before and after exposure to increased intraluminal pressure (IILP; 150 mmHg, 30 min). The mediator of FMD was determined using pharmacological agents to reduce NO [N(G)-nitro-l-arginine methyl ester (l-NAME), 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (c-PTIO)], or H2O2 [polyethylene glycol (PEG)-catalase], and mitochondrial (mt) ROS was quantified using fluorescence microscopy. Exposure to IILP decreased overall FMD (max %dilation: 82.7 ± 4.9 vs. 62 ± 5.6; P < 0.05). This dilation was abolished by treatment with l-NAME prepressure and PEG-catalase after IILP (max %dilation: l-NAME: 23.8 ± 6.1 vs. 74.8 ± 8.6; PEG-catalase: 71.8 ± 5.9 vs. 24.6 ± 10.6). To examine if this change was mediated by mtROS, FMD responses were measured in the presence of the complex I inhibitor rotenone or the mitochondrial antioxidant mitoTempol. Before IILP, FMD was unaffected by either compound; however, both inhibited dilation after IILP. The fluorescence intensity of mitochondria peroxy yellow 1 (MitoPY1), a mitochondria-specific fluorescent probe for H2O2, increased during flow after IILP (%change from static: 12.3 ± 14.5 vs. 127.9 ± 57.7). These results demonstrate a novel compensatory dilator mechanism in humans that is triggered by IILP, inducing a change in the mediator of FMD from NO to mitochondria-derived H2O2.
内皮型一氧化氮（NO）是人体脂肪微血管中血流介导的血管舒张（FMD）的主要介质。急性和慢性高血压后会出现NO介导的血管舒张功能受损，这可能是由于活性氧（ROS）生成过多所致。压力升高在这种人体小动脉舒张功能受损中所起的直接作用尚不清楚。我们检验了压力升高足以损害FMD的假设。从小鼠脂肪组织中分离出小动脉并插管，在暴露于管腔内压力升高（IILP；150 mmHg，30分钟）之前和之后，测量对分级血流梯度的血管舒张情况。使用药理学试剂来降低NO [N（G）-硝基-L-精氨酸甲酯（L-NAME），2-（4-羧基苯基）-4,4,5,5-四甲基咪唑啉-1-氧基-3-氧化物（c-PTIO）] 或H2O2 [聚乙二醇（PEG）-过氧化氢酶] 来确定FMD的介质，并使用荧光显微镜对线粒体（mt）ROS进行定量。暴露于IILP会降低总体FMD（最大舒张百分比：82.7±4.9对62±5.6；P<0.05）。在IILP后用L-NAME预加压和PEG-过氧化氢酶处理可消除这种舒张（最大舒张百分比：L-NAME：23.8±6.1对74.8±8.6；PEG-过氧化氢酶：71.8±5.9对24.6±10.6）。为了研究这种变化是否由mtROS介导，在存在复合物I抑制剂鱼藤酮或线粒体抗氧化剂米托坦的情况下测量FMD反应。在IILP之前，FMD不受任何一种化合物的影响；然而，两者在IILP后均抑制舒张。线粒体过氧黄1（MitoPY1）是一种用于H2O2的线粒体特异性荧光探针，在IILP后的血流过程中线粒体的荧光强度增加（与静态相比的变化百分比：12.3±14.5对127.9±57.7）。这些结果证明了人体中一种新的代偿性舒张机制，该机制由IILP触发，导致FMD的介质从NO转变为线粒体衍生的H2O2。
