Ujiie Hiroshi, Chaytor Andrew T, Bakker Linda M, Griffith Tudor M
Department of Diagnostic Radiology, Wales Heart Research Institute, University of Wales College of Medicine, Heath Park, Cardiff, UK.
Stroke. 2003 Feb;34(2):544-50. doi: 10.1161/01.str.0000054158.72610.ec.
Direct intercellular communication via gap junctions may play a central role in endothelium-dependent relaxations that are mediated by a conducted hyperpolarization and do not involve the synthesis of NO and prostanoids. In the present study, inhibitory peptides homologous to the Gap27 domain of the second extracellular loop of connexin37/connexin43 and connexin40, designated as 37,43Gap27 and 40Gap27, respectively, were used to evaluate the role of this mechanism in intracerebral arteries.
Isolated rings of rabbit middle cerebral artery were constricted by histamine (10 micromol/L) in the presence of N(G)-nitro-L-arginine methyl ester (300 micromol/L) and indomethacin (10 micromol/L). Concentration-relaxation curves for acetylcholine were constructed in the presence and absence of 37,43Gap27 and 40Gap27. Specific antibodies were used to delineate the distribution of connexin37, connexin40, connexin43, and connexin45 within the arterial wall.
Individually, 37,43Gap27 and 40Gap27 minimally affected endothelium-dependent relaxations to acetylcholine at concentrations of 300 micro mol/L, whereas their combination (at 300 micromol/L each) inhibited the maximal response by approximately 70% and increased the EC50 value for relaxation by approximately 15-fold. In endothelium-denuded rings, this peptide combination did not attenuate responses to sodium nitroprusside, an exogenous source of NO. Gap junction plaques, whose incidence was highest in endothelium, were constructed from connexin40 and connexin43 in the media and connexin37, connexin40, and connexin43 in the endothelium.
The findings confirm that direct communication via gap junctions contributes to agonist-induced relaxations of intracerebral arteries. More than one connexin subtype appears to participate in such responses.
通过缝隙连接进行的直接细胞间通讯可能在由传导性超极化介导且不涉及一氧化氮（NO）和前列腺素合成的内皮依赖性舒张中起核心作用。在本研究中，分别与连接蛋白37/连接蛋白43和连接蛋白40的第二个细胞外环的Gap27结构域同源的抑制性肽，分别命名为37,43Gap27和40Gap27，用于评估该机制在脑动脉中的作用。
在存在N(G)-硝基-L-精氨酸甲酯（300 μmol/L）和吲哚美辛（10 μmol/L）的情况下，用组胺（10 μmol/L）收缩分离的兔大脑中动脉环。在存在和不存在37,43Gap27和40Gap27的情况下构建乙酰胆碱的浓度-舒张曲线。使用特异性抗体描绘连接蛋白37、连接蛋白40、连接蛋白43和连接蛋白45在动脉壁内的分布。
单独使用时，37,43Gap27和40Gap27在300 μmol/L浓度下对乙酰胆碱引起的内皮依赖性舒张影响极小，而它们的组合（各300 μmol/L）使最大反应抑制约70%，并使舒张的半数有效浓度（EC50）值增加约15倍。在去内皮的动脉环中，这种肽组合并未减弱对硝普钠（一种外源性NO来源）的反应。缝隙连接斑在中膜由连接蛋白40和连接蛋白43构成，在内皮由连接蛋白37、连接蛋白40和连接蛋白43构成，其发生率在内皮中最高。
这些发现证实通过缝隙连接的直接通讯有助于激动剂诱导的脑动脉舒张。似乎不止一种连接蛋白亚型参与此类反应。
