Bailey S R, Mitra S, Flavahan S, Flavahan N A
Davis Heart and Lung Research Institute, R 110E, The Ohio State Univ., 473 West 12th Ave, Columbus, OH 43210, USA.
Am J Physiol Heart Circ Physiol. 2005 Jul;289(1):H243-50. doi: 10.1152/ajpheart.01305.2004. Epub 2005 Mar 11.
Cold constricts cutaneous blood vessels by selectively increasing the activity of smooth muscle alpha2-adrenoceptors (alpha2-ARs). In mouse tail arteries, alpha2-AR constriction is mediated by alpha2A-ARs at 37 degrees C, whereas the cold-induced augmentation in alpha2-AR activity is mediated entirely by alpha2C-ARs. Cold causes translocation of alpha2C-ARs from the trans-Golgi to the plasma membrane, mediated by cold-induced activation of RhoA and Rho kinase. The present experiments analyzed the mechanisms underlying these responses. Mouse tail arteries were studied in a pressure myograph. Cooling the arteries (28 degrees C) caused a rapid increase in reactive oxygen species (ROS) in smooth muscle cells, determined by confocal microscopy of arteries loaded with the ROS-sensitive probes, dichlorodihydrofluorescein or reduced Mitotracker Red. The inhibitor of mitochondrial complex I rotenone (10 micromol/l), the antioxidant N-acetylcysteine (NAC; 20 mmol/l), or the cell-permeable mimic of superoxide dismutase MnTMPyP (50 micromol/l) did not affect vasoconstriction to alpha2-AR stimulation (UK-14304) at 37 degrees C but dramatically inhibited the response at 28 degrees C. Indeed, these ROS inhibitors abolished the cold-induced increase in alpha2-AR constrictor activity. NAC (20 mmol/l) or MnTMPyP (50 micromol/l) also abolished the cold-induced activation of RhoA in human cultured vascular smooth muscle cells and the cold-induced mobilization of alpha2C-ARs to the cell surface in human embryonic kidney 293 cells transfected with the receptor. The combined results suggest that cold-induced constriction is mediated by redox signaling in smooth muscle cells, initiated by mitochondrial generation of ROS, which stimulate RhoA/Rho kinase signaling and the subsequent mobilization of alpha2C-ARs to the cell surface. Altered activity of ROS may contribute to cold-induced vasospasm occurring in Raynaud's phenomenon.
寒冷通过选择性增加平滑肌α2 - 肾上腺素能受体（α2 - ARs）的活性来收缩皮肤血管。在小鼠尾动脉中，α2 - AR收缩在37℃时由α2A - ARs介导，而寒冷诱导的α2 - AR活性增强则完全由α2C - ARs介导。寒冷导致α2C - ARs从反式高尔基体转运到质膜，这是由寒冷诱导的RhoA和Rho激酶激活介导的。本实验分析了这些反应背后的机制。在压力肌动描记仪中研究小鼠尾动脉。通过对装载了ROS敏感探针二氯二氢荧光素或还原型线粒体追踪红的动脉进行共聚焦显微镜检查确定，冷却动脉（28℃）导致平滑肌细胞中活性氧（ROS）迅速增加。线粒体复合物I抑制剂鱼藤酮（10 μmol/l）、抗氧化剂N - 乙酰半胱氨酸（NAC；20 mmol/l）或超氧化物歧化酶MnTMPyP的细胞可渗透模拟物（50 μmol/l）在37℃时不影响对α2 - AR刺激（UK - 14304）的血管收缩，但在28℃时显著抑制该反应。实际上，这些ROS抑制剂消除了寒冷诱导的α2 - AR收缩活性增加。NAC（20 mmol/l）或MnTMPyP（50 μmol/l）也消除了寒冷诱导的人培养血管平滑肌细胞中RhoA的激活以及在转染了该受体的人胚肾293细胞中寒冷诱导的α2C - ARs向细胞表面的转运。综合结果表明，寒冷诱导的收缩由平滑肌细胞中的氧化还原信号介导，由线粒体产生的ROS引发，其刺激RhoA/Rho激酶信号传导以及随后α2C - ARs向细胞表面的转运。ROS活性改变可能导致雷诺现象中发生的寒冷诱导的血管痉挛。
