Department of Basic Medical Sciences, Physiology Group, Faculty of Medicine & Health Sciences, Ghent University, De Pintelaan 185 (Block B, Room 031), 9000 Ghent, Belgium.
Unité de Chronobiologie Théorique, Faculté des Sciences, Université Libre de Bruxelles (ULB), 1000 Brussels, Belgium.
Cardiovasc Res. 2017 Feb;113(2):195-206. doi: 10.1093/cvr/cvw215. Epub 2016 Sep 27.
Connexins form gap-junctions (GJs) that directly connect cells, thereby coordinating vascular cell function and controlling vessel diameter and blood flow. GJs are composed of two hemichannels contributed by each of the connecting cells. Hemichannels also exist as non-junctional channels that, when open, lead to the entry/loss of ions and the escape of ATP. Here we investigated cross-talk between hemichannels and Ca/purinergic signalling in controlling blood vessel contraction. We hypothesized that hemichannel Caentry and ATP release contributes to smooth muscle cell (SMC) Cadynamics, thereby influencing vessel contractility. We applied several peptide modulators of hemichannel function and inhibitors of Caand ATP signalling to investigate their influence on SMC Cadynamics and vessel contractility.
Confocal Caimaging studies on small mesenteric arteries (SMAs) from rat demonstrated that norepinephrine-induced SMC Ca oscillations were inhibited by blocking IP receptors with xestospongin-C and by interfering with hemichannel function, most notably by the specific Cx43 hemichannel blocking peptide TAT-L2 and by TAT-CT9 that promotes Cx43 hemichannel opening. Evidence for hemichannel involvement in SMC function was supported by the fact that TAT-CT9 significantly increased SMC resting cytoplasmic Caconcentration, indicating it facilitated Caentry, and by the observation that norepinephrine-triggered vessel ATP release was blocked by TAT-L2. Myograph tension measurements on isolated SMAs showed significant inhibition of norepinephrine-triggered contractility by the ATP receptor antagonist suramin, but the strongest effect was observed with TAT-L2 that gave ∼80% inhibition at 37 °C. TAT-L2 inhibition of vessel contraction was significantly reduced in conditional Cx43 knockout animals, indicating the effect was Cx43 hemichannel-dependent. Computational modelling suggested these results could be explained by the opening of a single hemichannel per SMC.
These results indicate that Cx43 hemichannels contribute to SMC Cadynamics and contractility, by facilitating Caentry, ATP release, and purinergic signalling.
连接子形成缝隙连接（GJ），直接连接细胞，从而协调血管细胞功能并控制血管直径和血流。GJ 由连接细胞各自贡献的两个半通道组成。半通道也存在作为非连接通道，当打开时，导致离子的进入/损失和 ATP 的逸出。在这里，我们研究了缝隙连接和钙/嘌呤能信号在控制血管收缩中的串扰。我们假设半通道 Ca 内流和 ATP 释放有助于平滑肌细胞（SMC）Ca 动力学，从而影响血管收缩性。我们应用几种缝隙连接功能的肽调节剂和 Ca 和 ATP 信号转导的抑制剂来研究它们对 SMC Ca 动力学和血管收缩性的影响。
在大鼠的肠系膜小动脉（SMA）上进行共聚焦 Ca 成像研究表明，用 xestospongin-C 阻断 IP 受体和干扰半通道功能，特别是用特异性 Cx43 半通道阻断肽 TAT-L2 和促进 Cx43 半通道开放的 TAT-CT9，可抑制去甲肾上腺素诱导的 SMC Ca 振荡。半通道参与 SMC 功能的证据得到支持，事实是 TAT-CT9 显著增加了 SMC 静息细胞质 Ca 浓度，表明它促进了 Ca 内流，并且观察到去甲肾上腺素触发的血管 ATP 释放被 TAT-L2 阻断。在分离的 SMA 上进行的肌动图张力测量表明，ATP 受体拮抗剂苏拉明对去甲肾上腺素触发的收缩性有显著抑制作用，但 TAT-L2 的作用最强，在 37°C 时抑制率约为 80%。在条件性 Cx43 敲除动物中，TAT-L2 抑制血管收缩的作用显著降低，表明该作用依赖于 Cx43 半通道。计算模型表明，这些结果可以通过每个 SMC 打开一个半通道来解释。
这些结果表明，Cx43 半通道通过促进 Ca 内流、ATP 释放和嘌呤能信号传导，有助于 SMC Ca 动力学和收缩性。
