Álvarez-Miguel Inés, Cidad Pilar, Pérez-García M Teresa, López-López José Ramón
Departamento de Bioquímica y Biología Molecular y Fisiología e Instituto de Biología y Genética Molecular (IBGM), Universidad de Valladolid y Consejo Superior de Investigaciones Científicas (CSIC), Valladolid, Spain.
J Physiol. 2017 Mar 1;595(5):1497-1513. doi: 10.1113/JP273327. Epub 2016 Dec 29.
Canonical transient receptor potential (TRPC)3 and TRPC6 channels of vascular smooth muscle cells (VSMCs) mediate stretch- or agonist-induced cationic fluxes, contributing to membrane potential and vascular tone. Native TRPC3/C6 channels can form homo- or heterotetrameric complexes, which can hinder individual TRPC channel properties. The possibility that the differences in their association pattern may change their contribution to vascular tone in hypertension is unexplored. Functional characterization of heterologously expressed channels showed that TRPC6-containing complexes exhibited Pyr3/Pyr10-sensitive currents, whereas TRPC3-mediated currents were blocked by anti-TRPC3 antibodies. VSMCs from hypertensive (blood pressure high; BPH) mice have larger cationic basal currents insensitive to Pyr10 and sensitive to anti-TRPC3 antibodies. Consistently, myography studies showed a larger Pyr3/10-induced vasodilatation in BPN (blood pressure normal) mesenteric arteries. We conclude that the increased TRPC3 channel expression in BPH VSMCs leads to changes in TRPC3/C6 heteromultimeric assembly, with a higher TRPC3 channel contribution favouring depolarization of hypertensive VSMCs.
Increased vascular tone in essential hypertension involves a sustained rise in total peripheral resistance. A model has been proposed in which the combination of membrane depolarization and higher L-type Ca channel activity generates augmented Ca influx into vascular smooth muscle cells (VSMCs), contraction and vasoconstriction. The search for culprit ion channels responsible for membrane depolarization has provided several candidates, including members of the canonical transient receptor potential (TRPC) family. TRPC3 and TRPC6 are diacylglycerol-activated, non-selective cationic channels contributing to stretch- or agonist-induced depolarization. Conflicting information exists regarding changes in TRPC3/TRPC6 functional expression in hypertension. However, although TRPC3-TRPC6 channels can heteromultimerize, the possibility that differences in their association pattern may change their functional contribution to vascular tone is largely unexplored. We probe this hypothesis using a model of essential hypertension (BPH mice; blood pressure high) and its normotensive control (BPN mice; blood pressure normal). First, non-selective cationic currents through homo- and heterotetramers recorded from transfected Chinese hamster ovary cells indicated that TRPC currents were sensitive to the selective antagonist Pyr10 only when TRPC6 was present, whereas intracellular anti-TRPC3 antibody selectively blocked TRPC3-mediated currents. In mesenteric VSMCs, basal and agonist-induced currents were more sensitive to Pyr3 and Pyr10 in BPN cells. Consistently, myography studies showed a larger Pyr3/10-induced vasodilatation in BPN mesenteric arteries. mRNA and protein expression data supported changes in TRPC3 and TRPC6 proportions and assembly, with a higher TRPC3 channel contribution in BPH VSMCs that could favour cell depolarization. These differences in functional and pharmacological properties of TRPC3 and TRPC6 channels, depending on their assembly, could represent novel therapeutical opportunities.
血管平滑肌细胞（VSMC）中的典型瞬时受体电位（TRPC）3和TRPC6通道介导牵张或激动剂诱导的阳离子通量，影响膜电位和血管张力。天然的TRPC3/C6通道可形成同四聚体或异四聚体复合物，这可能会影响单个TRPC通道的特性。它们的缔合模式差异是否会改变其在高血压中对血管张力的作用尚未得到研究。对异源表达通道的功能表征表明，含有TRPC6的复合物表现出对Pyr3/Pyr10敏感的电流，而TRPC3介导的电流被抗TRPC3抗体阻断。来自高血压（血压高；BPH）小鼠的VSMC具有更大的阳离子基础电流，对Pyr10不敏感，但对抗TRPC3抗体敏感。同样，肌动描记法研究表明，在血压正常（BPN）的肠系膜动脉中，Pyr3/10诱导的血管舒张更大。我们得出结论，BPH VSMC中TRPC3通道表达的增加导致TRPC3/C6异源多聚体组装的变化，TRPC3通道的更高贡献有利于高血压VSMC的去极化。
原发性高血压中血管张力增加涉及总外周阻力的持续升高。有人提出了一个模型，其中膜去极化和更高的L型钙通道活性共同作用，使更多的钙流入血管平滑肌细胞（VSMC），导致收缩和血管收缩。对导致膜去极化的罪魁祸首离子通道的研究提供了几个候选通道，包括典型瞬时受体电位（TRPC）家族的成员。TRPC3和TRPC6是二酰基甘油激活的非选择性阳离子通道，参与牵张或激动剂诱导的去极化。关于高血压中TRPC3/TRPC6功能表达的变化存在相互矛盾的信息。然而，尽管TRPC3-TRPC6通道可以异源多聚化，但它们的缔合模式差异是否会改变其对血管张力的功能作用在很大程度上尚未得到研究。我们使用原发性高血压模型（BPH小鼠；血压高）及其血压正常的对照（BPN小鼠；血压正常）来探究这一假设。首先，从转染的中国仓鼠卵巢细胞记录的通过同四聚体和异四聚体的非选择性阳离子电流表明，只有当存在TRPC6时，TRPC电流才对选择性拮抗剂Pyr10敏感，而细胞内抗TRPC3抗体选择性地阻断TRPC3介导的电流。在肠系膜VSMC中，基础电流和激动剂诱导的电流在BPN细胞中对Pyr3和Pyr10更敏感。同样，肌动描记法研究表明，在BPN肠系膜动脉中，Pyr3/10诱导的血管舒张更大。mRNA和蛋白质表达数据支持TRPC3和TRPC6比例及组装的变化，在BPH VSMC中TRPC3通道的贡献更高，这可能有利于细胞去极化。TRPC3和TRPC6通道的功能和药理学特性的这些差异，取决于它们的组装，可能代表新的治疗机会。
